Mineral Technologies International, Inc.

Modeling and Simulation of Mineral Processing Systems

An online tutorial for learning Modsim

These messages have been compiled from the online courses taught at the University of Utah. You might find some of these relevant to your Modsim trainning. Use the Find function in your browser to search the text below and pinpoint potentially relevant issues.


Message No. 1: posted by Instructor (dddd) on Mon, Dec. 22, 1997, 14:50 Subject: Welcome! 

Welcome to the WebCT Conference tool. Here, students can ask questions, discuss projects, and exchange ideas. You can create any number of private or public discussion groups (i.e. fora). Articles may be listed either by thread or chronologically, include attached files, be searched, and more. If you have any problems, click on the Help button. Have fun!


Message No. 2: posted by Instructor (mete6010) on Tue, Mar. 21, 2000, 13:25 Subject: Course opening 

This course site will be opened for registered students on May 8, 2000. The course commences on May 15. Early opening of the site will allow students ample time to download all the necessary software and other course materials.


Message No. 3: [Branch from no. 2] posted by Temporary Student (pioneer) on Fri, May. 12, 2000, 11:14 Subject: re: Course opening

 Hmmm.... I didn't see it open on the 8th...


Message No. 6: posted by Instructor (mete6010) on Mon, May. 15, 2000, 12:08 Subject: Getting to know you. 

The first day of the course seems to have progressed satisfactorily. Apart from a few difficulties, most attempts to sign on have been successful. One of the advantages of Claudio and I operating in the Mountain Daylight time zone is that we see all the course action for the day when we come in in the morning. Remember that we are 7 hours behind GMT so don't be surprised when you do not get an immediate response to your queries. I think it will be a good idea if we can all get to know each other a little so I have opened this forum. Could I ask each of you to to spare a few minutes and respond with a short note about yourself - your name, where you work and any other snippet of information that will help to flesh out the names in the course list. This will also give you an opportunity to try out the bulletin board. There are quite a few options available to you and you can find these described in the HELP section of the bulletin board. There is no need to delve into these now since the defaults are quite adequate for posting a message. Please let us know if you have any difficulties in accessing any part of the course site. I look forward to a reply from you all.


Message No. 7: [Branch from no. 6] posted by Christian Brown (cbrown) on Mon, May. 15, 2000, 12:47 Subject: re: Getting to know you.

Hello everybody! My name is Christian Brown and I am just finishing up my degree in Metallurgical Engineering from the University of Utah. I am currently employed by Hanson Aggregate West in their Pleasanton California operation which is located near San Francisco California.


Message No. 8: [Branch from no. 6] posted by Michael Snow (mlsnow) on Mon, May. 15, 2000, 14:01 Subject: re: Getting to know you. 

Hello Everyone, This is Mike Snow, I am currently a senior in the undergraduate department of Metallurgical Engineering. I am currently employed by Boart Longyear, and will finish my four year degree in Spring 2001. Mike Snow


Message No. 9: [Branch from no. 6] posted by Ronel Du Plessis (rplessis) on Mon, May. 15, 2000, 14:12 Subject: re: Getting to know you. 

Hi Everyone!! My name is Ronel and I am a graduate student at the University of Utah where my research topic is sulfide mineral flotation chemistry. I am originally from Port Elizabeth (RSA), one of the most beautiful places on earth(and I am not biased :) )


Message No. 10: [Branch from no. 6] posted by Bertil Palsson (bpalsson) on Mon, May. 15, 2000, 14:16 Subject: re: Getting to know you. 

Hej allihop! Greetings from Sweden. My name is Bertil Pålsson and I'm a senior lecturer in Mineral Processing at the University of Technology in Luleå, Northern Sweden. The reason for taking this course is to familiarise myself with MODSIM, and to evaluate it for eventual incorporation in our teaching here. Just a follow-up to the time difference. I'm on GMT+2 making it a 9-hour time difference to Utah.


Message No. 14: [Branch from no. 6] posted by Keila Goncalves (keila) on Tue, May. 16, 2000, 07:49 Subject: re: Getting to know you. 

Hello everyone, This is Keila. I work at the research center of CVRD, a Brazilian mineral company that produces iron ore, gold, manganese, kaolin, bauxite, alumina, alluminum, etc, and is developing a few copper projects. My daily work is related to copper minerals flotation. I am working on the subject "Sulphidizing of secondary copper minerals" for my master degree work. Regards, Keila.


Message No. 21: [Branch from no. 6] posted by Greg Wunderlich (wunder) on Tue, May. 16, 2000, 23:19 Subject: re: Getting to know you. 

Hello Everyone (Guten Tag, Marhaba, Habari), My name is Greg Wunderlich and I work for Rubber Engineering in Salt Lake City, Utah. Rubber Engineering manufactures rubber liners for SAG, FAG, ball, and rod mills mainly for use in the mining industry and in power plants. I am also a graduate student at the University of Utah in the Mechanical Engineering Department. I hope to learn the capabilities of MODSIM and to understand more fully the complete mill circuit design.


Message No. 23: [Branch from no. 6] posted by Dirk Lange (dlange) on Wed, May. 17, 2000, 02:29 Subject: re: Getting to know you. 

Hello Everyone, My name is Dirk Lange and I work for Krupp Foerdertechnik in Essen (Germany) in the field of primary-in-pit-crushing-plant-design. I want to evaluate MODSIM for crushing plant design.


Message No. 25: [Branch from no. 6] posted by David Harding (dharding) on Wed, May. 17, 2000, 08:26 Subject: re: Getting to know you.

 Hello Everyone, My name is David Harding. I am a Junior in the Department of Metallurgy at the University of Utah. I also work here on campus in the Center for Mineral Technologies. Dave


Message No. 30: [Branch from no. 6] posted by Leon Schaeffer (schaeffer) on Wed, May. 17, 2000, 10:32 Subject: re: Getting to know you.

 Hello, my name is Leon Schaeffer known as the RubberMan. I am the VP and General Manager of Rubber Engineering in Salt Lake City. One of our main product lines is rubber mill linings. I hope to gain some additional information from the course on how the variations in a grinding mill affect the grinding mill circuit. This will influence our future mill liner designs.


Message No. 35: [Branch from no. 6] posted by Andrew Wessman (aewessman) on Thu, May. 18, 2000, 14:32 Subject: re: Getting to know you.

 Hello, I'm Andrew Wessman, and I'm a senior at the University of Utah studying Metallurgical Engineering. I also work here at the University on a 3D Mill Simulator, so I'm taking this class to gain some familiarity in the area.


Message No. 44: [Branch from no. 6] posted by Veli Gokdere (szvgok) on Fri, May. 19, 2000, 13:47 Subject: re: Getting to know you. 

Hello Everybody I am Veli Gokdere from Turkey. I am working as Mill Superintendent in a Copper and Zinc producing plant in north eastern part of Turkey. Our plant, located by the Black Sea Coast, Çayeli Bakir Isletmeleri, is a joint venture between INMET Canada and Etiholding of Turkey. We strongly believe that we will get benefit to our operations from MODSIM.


Message No. 45: [Branch from no. 6] posted by Kent Tano (ktano) on Fri, May. 19, 2000, 14:09 Subject: re: Getting to know you. 

Hi everybody, my name is Kent Tano, I'm working at R&D (Mineral Processing) for the Swedish iron ore company LKAB. I hope this course will give me an insight of the benefits that we can reach by using simulation tools in plant optimization. Best wish to all of you.


Message No. 47: [Branch from no. 6] posted by Luis Roman (lroman) on Fri, May. 19, 2000, 20:57 Subject: re: Getting to know you.

 Hello: My name is Luis Roman and I work as metallurgist in cuajone concentrator from Peru - South America. I am undertaking this course because is possible to application in my work. Regards, Luis


Message No. 94: [Branch from no. 6] posted by Robert Braun (rbraun) on Tue, May. 30, 2000, 16:50 Subject: re: Getting to know you.

 Hello Everyone, I'm the late arrival. My name is Robert Braun and I work for Hicom International as a Process Engineer. I use simulation tools similar to MODSIM but have had little formal training in their use. Hopefully this course will rectify this.


Message No. 131: [Branch from no. 6] posted by Reiner Neumann (rneumann) on Thu, Jun. 8, 2000, 14:21 Subject: re: Getting to know you.

 I guess I'm the last, just coming from vacation.... I'm Reiner Neumann, geologist with the Center for Mineral Technology - CETEM in Rio, Brazil, running our mineralogical and technological characterization lab. As we are measuring mineral liberation using image analysis (with a great help from SLC), I decided to learn more about what it is good for. Now excuse me, I've a lot to hold up....


Message No. 11: posted by Instructor (mete6010) on Mon, May. 15, 2000, 15:12 Subject: Phantom assignment 1 

Ronel has pointed out to me that the assignment that is currently in the drop box is meaningless. She is correct. Claudio and I left it lying there after we had tested the dropbox facility a couple of weeks ago. I have now removed it. Sorry if it caused you any inconvenience. Incidently we are not planning any assignments for module 1. This should give every one a chance to find your feet with WebCT during the first week. However please do attempt the exercises and don't be afraid to ask questions.


Message No. 12: posted by Instructor (mete6010) on Mon, May. 15, 2000, 17:50 Subject: New viewlets in MODSIM Trainer 

We added a bunch of new viewlets to the Trainer today and we repaired a few that were not quite correct. If you have already played any viewlets you should refresh or reload the Trainer frame (click on Reload or Refresh in your browser tool bar) to ensure that the new viewlets show up in your list. If you did get some commercial banners served up to your browser when running some of the viewlets we apologize. We had an error in a switch setting when making some of them but we have now rectified this. You should never get any banner other than our departmental logo. If anything else shows up please let us know.


Message No. 13: posted by Edmundo Esguerra (eesguerra) on Mon, May. 15, 2000, 23:19 Subject: MODSIM DOWNLOAD 

Dear Mr. Schneider, I still haven't received the CDROM. What are my options? Please advise. Regards, EDMUNDO P. ESGUERRA ear Edmundo, Go to the General information page, and see the section about software requirements. In the MODSIM paragraph you will find a link to download a sef-extracting executable file with the installation. Can you do me a favor? Post your original message on the bulletin board, with a MODSIM DOWNLOAD subject, so that everybody can see the solution. Thanks, Claudio


Message No. 17: [Branch from no. 13] posted by Instructor (mete6010) on Tue, May. 16, 2000, 11:08 Subject: re: MODSIM DOWNLOAD

 If you haven't received the CDROM, you can go to the General information area and choose Software requirements. In the MODSIM session, you will find a link to a self-extracting executable file that will install MODSIM 3.2 Student edition. This is exactly equal to install from the CDROM. The file is however 22 MBytes large. Alternatively, you may want to download a stripped down version of the Student Edition, without documents, and I've just made this available today. The small self-extracting executable file is 7.6 MBytes, still large, but this maybe small enough for download. This will be useful while you wait for the CD. If this is still too large, you may consider the following options: 1-Look for a friend who have access to a LAN, either at a University, Institution or company, and ask him to help you with the download. 2-Get in contact with your ISP. They are certainly connected to a LAN and may offer help with the download.


Message No. 15: posted by Ayhan Sirkeci (sirkecia) on Tue, May. 16, 2000, 08:20 Subject: Modsim Simulator 

Dear Claudio, I am having some problems with Modsim. I cannot edit or delete annotations. This command does not seem to be working for annotations? I tried restarting the program, it doesn't work. The annotations are in red color. When I uncheck any option on the upper right hand corner of the flowsheet editor (for example, "show unit number") all annotations disappear. What could the problem be? Regards, Ayhan.


Message No. 16: [Branch from no. 15] posted by Instructor (mete6010) on Tue, May. 16, 2000, 10:00 Subject: re: Modsim Simulator 

When you have typed each annotation you must hit the enter key to put the annotation into the data base. When the annotation goes into the data base it changes from red to black. When it is black you can edit it, move it or delete it. If you have some messy annotations on your flowsheet, refresh the flowsheet (1st item in the Edit menu) which will clean the flowsheet up. You can also accept the flowsheet and then re-open it in the graphics editor which will clean it up some more or you can even save the job, close it and then re-open the job. After that you will surely be able to edit or delete any annotations that are not correct.


Message No. 18: [Branch from no. 15] posted by Instructor (mete6010) on Tue, May. 16, 2000, 14:45 Subject: re: Modsim Simulator 

There are several viewlets in the MODSIM Trainer that demonstarte the annotation feature. Add annotations to the flowsheet. Delete annotations. Move an annotation. Edit an annotation.


Message No. 19: posted by Qi Liu (qliu) on Tue, May. 16, 2000, 15:19 Subject: Getting to know you

 Hello, everyone: This is Qi Liu. I am working at the University of Alberta in Canada. I like to learn more about process modeling and simulation and MODSIM because it is becoming such a powerful tool. I had a whole day of meeting yesterday and didn't log in until very late yesterday, but I will catch up. Regards, Qi


Message No. 20: posted by Michael Morey (mmorey) on Tue, May. 16, 2000, 23:13 Subject: Getting to know you 

Hi. I am Mike Morey, a research associate of the Ian Wark Research Institute, University of South Australia. I work in metallurgical consultancy for the Colloids, Surfaces and Mineral Processing research group. This research group specializes in pulp / particle surface chemistry and metallurgy of sulfide minerals. After a PhD examining the lead activation of sphalerite, I have spent the last two years focused on projects related to improving copper sulfide flotation performance in a number of concentrators. I am undertaking this course because my boss decided we needed some 'in-service training'.


Message No. 22: posted by Ayhan Sirkeci (sirkecia) on Wed, May. 17, 2000, 01:42 Subject: Getting to know you 

Hi Everyone, My name is Ayhan, I am working as a lecturer and researcher at the Department of Mining Engr., Istanbul Technical University, Turkey. I have been interested in modeling and simulation in mineral processing for quite a while. Though I am familiar with the Dos version of Modsim, I haven't had the chance to know about the Windows version. I am eventually interested in introducing this software to my class. Therefore, I felt that I should be competent with Modsim before others benefit from me. I wish you all a successful and fruitful course. By the way the time difference with Utah is 9 hours as the Swedish classmate.


Message No. 24: posted by Romina Perusin (rperusin) on Wed, May. 17, 2000, 03:21 Subject: saving flowsheets 

Dear Claudio, There is something I cannot figure out properly about ''saving'' a  flowsheet after editing a new flowsheet I do not see any saving command activated in the pool-down menu FILE... so I say 'accept flowsheet' and 'save as' ... but I cannot retrieve the file later that looks empty also following literally the modsim trainer I cannot save and retrieve... sure I have misunderstood something! second question: where can I read about returning to you the tests/exercises for evaluation? thank you Romina


Message No. 29: [Branch from no. 24] posted by Instructor (mete6010) on Wed, May. 17, 2000, 09:18 Subject: re: saving flowsheets 

Romina: The correct sequence for saving a flowsheet is the following. Draw the flowsheet using the graphics editor. When you have completed the drawing, refresh the flowsheet (use Refresh flowsheet in the Edit menu) and check that it is exactly what you want. Click Accept flowsheet form the File menu. This will place the flowsheet structure in the database for the current job and will take you back to the main menus. Open the main File menu and save the job. You can retrieve the job using Open an existing job in the main File menu. Note that you will get no message to indicate that the job has been retrieved and you should open the flowsheet editor immediately to see the flowsheet. IF YOU WANT THE FLOWSHEET TO OPEN AUTOMATICALLY WHEN YOU OPEN AN EXISTING JOB, select Options from the main File menu and check the box. Note that in the student version this option will not remain set when you exit from MODSIM and will revert to the default when you start it again.


Message No. 31: [Branch from no. 24] posted by Instructor (mete6010) on Wed, May. 17, 2000, 19:35 Subject: re: saving flowsheets 

It is also possible to load just a flowsheet from an existing job. Here's how to do it. Open the main File menu. Select Start a new job. This will open the flowsheet editor with a blank page. Open the File menu. Select Get flowsheet from an existing job. Flowsheet files are displayed with extension .TRN If you have jobs that were saved in early versions of MODSIM you should search for the flowsheet file with extension .TR Open the flowsheet file and it will display on the open page. No other job information is imported - just the flowsheet.


Message No. 26: posted by Ayhan Sirkeci (sirkecia) on Wed, May. 17, 2000, 08:27 Subject: Flow-streams 

Dear Claudio, Is it possible to edit or move flow-streams? Do I have to redraw it if I want to make amends for it? How can I rearrange unit or flow-stream numbers. It seems that they are given in the order of selection. Thanks, Ayhan.


Message No. 27: [Branch from no. 26] posted by Instructor (mete6010) on Wed, May. 17, 2000, 08:39 Subject: re: Flow-streams 

Ayhan You cannot move flow streams on the flowsheet. This feature is not implemented because moving streams is usually not a useful thing to do. You must delete the stream and then redraw it where you need it.


Message No. 28: [Branch from no. 26] posted by Instructor (mete6010) on Wed, May. 17, 2000, 08:45 Subject: re: Flow-streams 

Ayhan STREAM and UNIT NUMBERS You cannot re-allocate numbers to stream or units. MODSIM allocates these numbers in the order that they are drawn on the flowsheet. If you refresh the flowsheet from the Edit menu the streams and units are renumbered. The unit and stream numbers are used internally by MODSIM for a number of purposes but most importantly to organize the order in which the unit models are called during the simulation. For this reason we do not allow the user to change these numbers.


Message No. 32: posted by Instructor (mete6010) on Wed, May. 17, 2000, 22:53 Subject: Modsim download and course info 

As some of you are having to download MODSIM from this site, here is the password to install the self-extracting executable file: mete6010 Interesting fact: mail by curier is not as efficient as downloading the file. Praise the internet! Also, those who registered early were sent the CD by regular mail, and unfortunately you are also the ones who are still waiting. The late registrants were contemplated with express mail, and this seems to work well. I'm starting to think sending CDs is not necessary at all. Some of you posted messages referring specifically to me. I have replied to some postings, but most of them have been responded by Dr. King. There is no way to identify which one of us is responding, as we use the same instructor ID. If you pay attention to detail however, you will soon be able to identify us just by the different styles in writing. Otherwise, we will keep you in the dark as to which one of us is responding. Finally, we have reached 40 registered students today, and I'm still counting, as you may be joined by a few more colleagues in the next few days. And what is more impressing, the variety of countries represented: Brazil, Sweden, Australia, Germany, Philippines, Italy, UK, Canada, Chile, Greece, Turkey, South Africa, Mexico, Finland, Egypt, Peru and the USA. Times are changing fast. Claudio


Message No. 33: posted by Jose Gomez (jgomez) on Thu, May. 18, 2000, 12:55 Subject: CD-ROM 

Dear Claudio: I have many problems because, I don’t have the CD-ROM, What can I do? Regards Jose Angel


Message No. 34: [Branch from no. 33] posted by Instructor (mete6010) on Thu, May. 18, 2000, 13:41 Subject: re: CD-ROM 

Read message 17 in the main Forum about downloading MODSIM. You might want to read message 32 as well.


Message No. 36: posted by Wayne Jacobsen (wjacobsen) on Thu, May. 18, 2000, 19:09 Subject: Hello - 

Greetings My name is Wayne Jacobsen and I will be joining this class, abeit a week late. I'm a mining engineering with Kennecott Minerals Company (Salt Lake City),the US operating company of Rio Tinto. I have little experience in processing, but a lot of experience in GPSSH simulation modeling for mining projects.


Message No. 37: posted by Romina Perusin (rperusin) on Fri, May. 19, 2000, 02:41 Subject: Getting to know you 

Hello everybody! My name is Romina Perusin and I am student of Faculty of Engineering of the University of Trieste (Italy). I will familiarize myself with MODSIM because I think it will provide an excellent simulation engine for my dissertation on flowsheet optimization.


Message No. 74: [Branch from no. 37] posted by Michael Pietrobon (mpietrobon) on Thu, May. 25, 2000, 19:21 Subject: re: Getting to know you

 Ciao Bella! Trieste, A beautiful part of the world indeed. I am familiar with the Veneto region as both my parents are originally from Castelfranco. My last visit was 1994 but i want to come back one day. I live in Adelaide South Australia, it would take me 22hrs to reach the Venice Airport at Maestre. However my Italian writing is terrible, spoken words only in Veneto dialect so i wont embarrass myself in trying to write in Italian. Bye for now.


Message No. 38: posted by Junnikkala Saku (saku) on Fri, May. 19, 2000, 05:33 Subject: Getting to know you 

Hello My name is Saku Junnikkala (Mr) and I work as a research engineer at The Laboratory of Mechanical Process Technology and Recycling, Helsinki University of Technology, Finland. Regards: Saku


Message No. 39: posted by Svetoslav Nikolov (snikolov) on Fri, May. 19, 2000, 07:23 Subject: Svetoslav Nikolov (sveto) 

Hi everybody, My name is Svetoslav, I work at the research center C.T.P. located in Belgium. Mineral processing is a new area for me (i have a background in solid mechanics and micro-mechanics) and I am in charge with the development of new models for fragmentation processes by impact. So that I have to study pretty hard these months. I wish a fruitful work to everybody.


Message No. 40: posted by Instructor (mete6010) on Fri, May. 19, 2000, 11:06 Subject: PROBLEM WITH SAVE JOB AS... 

Romina has reported some difficulty with the "Save job as.." item in the main File menu. This difficulty will be present in all copies of MODSIM released for the course. The Problem: When Save job as is selected the job is saved under the current job name NOT under the jobname specified in the Save dialog. Workaround: Change the job name before you save the job. To change the job name open the main Edit menu and select Change job name. Type the new job name. This is also described in a viewlet called "Change the job name". It is good practice to edit the flowsheet and the system data immediately after a job name change to register the new job name in these data sets. Simply opening the respective editors and clicking Accept immediately will be sufficient.


Message No. 41: posted by Instructor (mete6010) on Fri, May. 19, 2000, 12:52 Subject: PROBLEM WITH REGIONAL SETTINGS

This problem has been reported by Romina and Keila. Modsim will display an error notice with a "Error reading flowsheet" message when opening a saved job. This is because your system's Regional Settings are telling Modsim to save floating point numbers with commas as the decimal symbol and periods as the grouping symbol. To check if you have this problem, open a ".TRN" file that was created when you saved a job with the Notepad or any other ascii editor. If you see commas in this file, you have this problem. Although we had anticipated this could be a problem, the need to make Modsim compatible with Regional Settings other than the ones normally used in the US had never appeared. This problem will be fixed in future versions of MODSIM. The fix for now is to change your regional settings to US like regional settings, with period as the decimal symbol and comma as the grouping symbol.


Message No. 42: posted by Instructor (mete6010) on Fri, May. 19, 2000, 13:21 Subject: Additional instructor Professor 

Saskia Duyvesteyn will join the course as an additional instructor. Saskia is a professor here and her role in the course will be look at the material that we deliver from the student's point of view. In particular she will review modules before they go live on the WebCT site. Sakia will also see all of the e-mail traffic and will add comments and insights as appropriate. Saskia is our most experienced professor in the field of Web-based education and we are grateful to her for giving up her valuable summer break to help make this course a success.


Message No. 43: posted by Instructor (mete6010) on Fri, May. 19, 2000, 13:29 Subject: Getting jobs from the Internet 

Saskia has pointed out to us that we have not provided clear instructions for recovering a job from the Internet. We have accordingly added a viewlet in the MODSIM trainer to do this. Please check this out. If you do not want to spend the time watching the viewlet, here is the method. Start MODSIM or close the job that you are working on. Open the main File menu. Select Get job from the Internet. This will open an FTP browser. In the student version of MODSIM you will not be able to browse but will automatically be connected to our FTP site where you will be able to select the job that you want. This will be loaded and unpacked into MODSIM. You can work on the job at once.


Message No. 46: posted by Qi Liu (qliu) on Fri, May. 19, 2000, 17:25 Subject: "error filling flyouts" 

Dear Claudio: It's quite interesting to play with the drawing features of MODSIM (I used to use Powerpoint to draw the flowsheet before). I have figured out how to do the various things in the exercises, partly by trial & error and partly by reading the Bulletin Board messages. I have only one problem. Whenever I open an exercise and "View" or "Refresh" or "Accept" the flowsheet, I always got the message "error filling flyouts". I know that we are not doing flyouts at this stage but does this message indicate a problem? Thanks. Qi


Message No. 48: [Branch from no. 46] posted by Instructor (mete6010) on Sat, May. 20, 2000, 16:19 Subject: re: "error filling flyouts" 

The flyouts show data from the current simulation on the flowsheet. This message appears whenever you view the flowsheet and there is no current data available from the simulator. Run the simulation, ensure that you get the "Simulation was completed successfully" and the "Data output was completed successfully" messages and view the flowsheet again. If you want to investigate how jobs run, load one of the jobs that were included on your installation disk and run it.


Message No. 50: posted by Ricardo Costa (rvinicius) on Sun, May. 21, 2000, 19:59 Subject: getting to know you 

Hi there, My name is Ricardo and i work for a company in Brazil called Samarco Mineração S/A (www.samarco.com.br). I'm intending to learn more about modeling and would like to make new friends. My occupation at Samarco is process engineer. I'm wanting to learn more about modeling to improve the grinding process within the company. Ricardo.


Message No. 51: posted by Wayne Jacobsen (wjacobsen) on Sun, May. 21, 2000, 23:02 Subject: Download a module 

Is there a way to download the module material so I can get off the net and read/work at my leisure?


Message No. 58: [Branch from no. 51] posted by Instructor (mete6010) on Tue, May. 23, 2000, 16:24 Subject: re: Download a module 

While it is not possible to directly download the Modules, we have developed an intermediate solution that will hopefully meet the needs of those wanting to work off-line. A new page has been added to the homepage - "Compiling modules". This page contains the necessary tools to "download" pages from the modules. There are links to each of the modules (as they become available) that contain all of the pages for that module. You can use the compile tool to combine all the pages within a module into a single document that can be printed or viewed off-line. After clicking the "compile" button, select which module you would like to compile and click "Continue. All the available files for that Module will be displayed. Select the files within the Module that you want to include. You can use the "Mark All" button to mark all the files, which is the recommended method for selecting files. Once you click "Continue," a new browser window will open that contains all the files which have been compiled into 1 long file. At this point you can either print the file out or save it to your hard drive as an HTML file by selecting "Save as" under the "File" menu of your browser. You can then open this HTML file in your browser when you are off-line. Be aware that the links within the compiled file are not active. Please let me know if any of you have problems with this. -Saskia


Message No. 52: posted by Instructor (mete6010) on Mon, May. 22, 2000, 08:43 Subject: Notation in Technical Notes 

Sveto Nikolov has pointed out an inconsistency in the notation used in Technical Notes 1. The symbol F is used for a cumulative distribution in place of P and similarly f is used in place of p. This is a typographical error and is corrected in Technical Notes 2 and the others that are still to come. Throughout the notes P represents a cumulative distribution, p the associated density function and pi the discrete distribution function. The subscript i indicates a particular particle class.


Message No. 53: posted by Ayhan Sirkeci (sirkecia) on Tue, May. 23, 2000, 06:52 Subject: size distribution graphs

 Dear Instructor, I cannot see any graphics when I run the "size distribution function" in the view menu. The message that appears on the bottom left hand side of the graph page is: Running and Input Pending in Metgraph Graphics All I have is a black page.


Message No. 56: [Branch from no. 53] posted by Instructor (mete6010) on Tue, May. 23, 2000, 08:41 Subject: re: size distribution graphs 

You probably have your video display set to 32 bit true color. Metgraph will not display 32 bit color images. Change this setting to 16 bit Hi color or 256 colors. Unless you have a need for true color - doing fancy art work in Photoshop or something like that - you can probably leave your video display set to 16 bit color for the duration of this course without noticing any difference to any of your normal programs.


Message No. 54: posted by Ayhan Sirkeci (sirkecia) on Tue, May. 23, 2000, 07:26 Subject: Answer to the question in exc. 2.3 

Dear Instructor, The decrease in the d50 size from G-class 1 to G-class 3 is due to the increase in the specific gravity. The higher the specific gravity the higher the force centrifugal force effecting the particle. Therefore, of two particles with identical volume the denser one will settle more quickly towards the wall of the cyclone. In other words, the terminal velocity of a quartz particle will be attained by a much finer magnetite particle. On the other hand, the decrease in the d50 size when magnetite is present could be because of the decrease in the % solids by volume.


Message No. 55: [Branch from no. 54] posted by Instructor (mete6010) on Tue, May. 23, 2000, 08:27 Subject: re: Answer to the question in exc. 2.3 

Nice one Ayhan your explanations are correct. This is an example of the kind of critical assessment of the models that you should get into the habit of applying when you undertake any simulation. Any results that appear to be at variance with experience should be examined very carefully. Remember that the simulation is only as good as the models.


Message No. 57: posted by Instructor (mete6010) on Tue, May. 23, 2000, 12:49 Subject: Problems with Loading a job from the Internet

Keila reported problems with the Load a job from the Internet function in Modsim. If you are connected to the Internet either via a Dial Up connection or you are in a LAN this function should work properly. However, complications may arise if you are working in a LAN and using a proxy server, behind a fire wall, as I'm sure is the case with CVRD's system. This is because improved security always implies in less functionality. Nevertheless, you should be able to download the files using Modsim's internet functions, even if you are using a proxy server.

Since we are not using a proxy server at the U of U, it is difficult to diagnose Modsim under these circumstances. All we have to work with is MicroSoft's documentation. Modsim is set to work with your default proxy settings. If Modsim fails to download from the Internet, probability is your settings are incomplete or inaccurate. There are two options here:

  1. Correct your system's proxy settings.
  2. Use the workaround.

Proxy settings

Step 1 - Open your Control Panel window. You can do this by double clicking in My Computer then Control Panel or by choosing Start -> Settings -> Control Panel

Step 2 - Double click on Internet Options.

Step 3 - Click on the Connections tab on top of the window.

Step 4 - Click on LAN Settings... These windows may be different if you are running Windows 95, 98 or NT. If you are running NT, you will need to be Administrator to change settings.

Step 5- You may want to check the Automatically detect settings option and then click on OK. If you know what you are doing, check the Use a proxy server option, then enter and Address and the Port. If you have different servers for different services, Click on Advanced...

Step 6 - Modsim uses FTP to download the files from the Internet. Enter the Proxy address to use for FTP. and the Port (usually ftp uses port 21). You may want to talk to your system administrator about these settings and what values should be used.


The workaround

Use FTP to download the files. The URL for the exercise files is: ftp://ftp.mines.utah.edu/pub/cmt/modsim/ and you should be able to download the Modsim PAK files from there easily. This is however inconvenient since you will have to go to this site every time we add a Modsim PAK file related to an exercise or an assignment.



Message No. 59: posted by Michael Pietrobon (mpietrobon) on Tue, May. 23, 2000, 23:15 Subject: Accepting changes to Sys Data ? 

Hello, When i try "Edit System Data" then go to Ore Characteristics, then Specify Sp.Gr. by Mineral, i cannot get the program to accept and it always defaults back to particle type ? Why is this so ? I have also noticed that in the notes for Exerc 2.2 you mention Cyc U/F should be 71.4%% but my balance is giving 73.3%%. Is this a related problem ? as well as this, when trying to specify the flow rate units in t/h, the program always defaults back to kg/s ? Why is this so ?


Message No. 60: [Branch from no. 59] posted by Instructor (mete6010) on Wed, May. 24, 2000, 00:43 Subject: re: Accepting changes to Sys Data ? 

There are three separate questions here. 1. Reverting to "specify sp.gr. by mineral". You need to specify sp.gr. by mineral only once. As soon as you setup the grade classes MODSIM will calculate the specific gravities of each grade class and enter them on the grade set-up form. Once you accept the data, MODSIM remembers that it has calculated specific gravities for each grade class and uses those rather than make the calculation every time. If you want to change one of the mineral specific gravities, click the "sp.gr. by mineral" button and enter the new value. Click the "Set up grade classes" button to register the change and proceed. 2. 73.3%% solids in the cyclone U/F in exercise 2-1. Your error could be related to an incorrect G-class sp. gr. Check you data carefully against the data in the exercise2-1 job on our internet FTP site. 3. MODSIM works internally in S.I. units exclusively and whenever it displays its data it will do so in SI units. Many people have difficulty with this and we plan to make data conversion within the MODSIM forms possible. This wont happen this summer because it will take a lot of programming. Meanwhile I will post a S.I. unit converter on the site tomorrow which you can download and use to make conversions easily.


Message No. 61: posted by Romina Perusin (rperusin) on Wed, May. 24, 2000, 09:07 Subject: Answer to the question in exercise 2-2 

Dear Instructor, with a larger spigot diameter more water is recovered in underflow and there are more fine particles short-circuiting ! The actual cyclone partition curve moves up and the actual d50 is now lower. Thus there is a finer u'flow and a coarser o'flow. Romina


Message No. 64: [Branch from no. 61] posted by Instructor (mete6010) on Wed, May. 24, 2000, 18:06 Subject: re: Answer to the question in exercise 2-2 

That is the correct explanation. Thanks for submitting it Romina


Message No. 62: posted by Wayne Jacobsen (wjacobsen) on Wed, May. 24, 2000, 14:44 Subject: How to used dropbox 

How do you turn in assignments using the drop box?


Message No. 65: [Branch from no. 62] posted by Instructor (mete6010) on Wed, May. 24, 2000, 18:08 Subject: re: How to used dropbox 

There are 2 viewlets in the "Navigation" section accessed from the "General" information icon on the course home page.


Message No. 63: posted by Wayne Jacobsen (wjacobsen) on Wed, May. 24, 2000, 14:58 Subject: drop box follow up 

when i click on the drop box it's empty.


Message No. 66: [Branch from no. 63] posted by Instructor (mete6010) on Wed, May. 24, 2000, 18:09 Subject: re: drop box follow up 

There are no assignments in modules 1 and 2. The first assignments will appear in the dropbox when Module 3 is activated on Sunday.


Message No. 67: posted by Michael Pietrobon (mpietrobon) on Wed, May. 24, 2000, 21:37 Subject: Technical Notes 


When I go to open Technical Notes, I am asked to supply Username and Password. However these do not work and the message is "The parameter is incorrect"?


Message No. 75: [Branch from no. 67] posted by Instructor (mete6010) on Thu, May. 25, 2000, 20:03 Subject: re: Technical Notes 

You should use your global ID and you "MyWebCT" password.


Message No. 77: [Branch from no. 75] posted by Michael Pietrobon (mpietrobon) on Thu, May. 25, 2000, 21:39 Subject: re: Technical Notes

 I did try this but it did not work. In the end i found it was due to the download program that i was using. Disabling it then allowed the downloads through.


Message No. 68: posted by Michael Pietrobon (mpietrobon) on Thu, May. 25, 2000, 02:07 Subject: Getting to know you 

Greetings from Australia. (I like sunsets and walking on the beach....oops wrong website) I am currently working as a Research Associate at the Ian Wark Research Institute, University of South Australia, based in Adelaide. I work as a metallurgical consultant for the Colloids, Surfaces and Mineral Processing Group. Specializing in pulp/particle surface chemistry and flotation systems mainly. However we are definitely interested in all aspects of mineral processing. The reason i have selected this course is enhance my skills with interpretation of flotation data gathered during my many site visits to base metals concentrators. I currently travel to Ontario, Canada at least twice a year working on projects with Falconbridge. contact michael.pietrobon@unisa.edu.au


Message No. 69: posted by Instructor (mete6010) on Thu, May. 25, 2000, 10:37 Subject: Importing flowsheet drawings into MSWord documents.

 This problem was raised today and is likely to effect most participants. Here are the options. Firstly some background. Modsim uses the Metgraph graph plotting package for all graphic output. I would use a standard commercial package but that would add a considerable royalty fee to the cost of MODSIM or would require users to purchase another package both of which are unattractive alternatives. In addition, no commercial package can do the special tasks required by Modsim (flowsheet editing, special coordinate system for graphs, mineral liberation plots) without a lot of tweeking. I wrote Metgraph in the 1970s for use on the old IBM mainframes and have simply allowed it to evolve as the technology has developed but it does still reflect some of the inherited limitations. Secondly, since I have to be very concious of the time involved in doing programming, I necessarily limit the scope of supported systems. In particular I support WordPerfect as the preferred reporting vehicle for Modsim. Two reasons for this. We use WordPerfect here for a good historical reason. WP Corporation used to be a Utah corporation and we like to support good products from the state and WP Corporation was started by a U of U graduate. Secondly we find WP significantly more productive for technical documents than MSWord (because of WP's better editing facility). So if you are using WordPerfect stick with it and you will find pretty well seamless transfers between Modsim and WP. You can import PostScript, encapsulated PostScript and Windows metafiles into WordPerfect without difficulty. To limit the scope of my programming effort I support only one specific graphic output format - PostScript. I made the decision to do this in the 1980's because PostScript is the only platform-independent format that can deliver publication-quality graphics every time any where. If you have a PostScript printer you will get excellent results with graphic output from Modsim. Having said that I do program according to Microsoft published standards for general Windows functions and mostly that works satisfactorily for output but, as in this particular situation, the ways of Microsoft are mysterious indeed. IMPORTING FLOWSHEETS INTO MSWORD - easy fix. So back to the issue. How to get a flowsheet into MSWord. When you view the flowsheet export the file as a Windows metafile and save it in a convenient location. Open your document in MSWord. Insert a picture from file. Select your previuosly saved graphic. This produces a mysterious blank (that's right no indication of anything!) on the page. Don't despair your graphic is there but you have to find it. No doubt MSWord has a function to display graphic boxes but I don't know it. Can anyone help out?. I simply poke around with the cursor until the apparently empty box outline appears. Here is the trick. Right click on the box to edit it and immediately click on "Reset picture boundary". This brings the wayward graphic into its correct place and you can close the picture which will take you back to the MSword page with the graphic neatly in place and you can continue with your editing. This will produce a result that is adequate but not up to my standard but that is the best easy fix that we can recommend at present. If anyone can improve on this I would be very pleased to hear from you. IMPORTING FLOWSHEETS INTO MSWORD- using Ghostview. If you are prepared to take a little more trouble here is a better fix. If you do not already have it, get a copy of Ghostview. It is available from its author at http://www.cs.wisc.edu/~ghost/cd.html Ghostview is a useful utility that allows you to view any PostScript image on your screen and manipulate it. Export the flowsheet from Modsim as a PostScript file. Open this file in Ghostview and make any changes that you want (for example you may want to crop it using the bounding box feature). Convert the PS image to EPS (encapsulated PostScript) and add a windows metafile preview (or any of the others offered if you prefer) and save the file. This image should insert nicely into your MSWord document. However since MSWord will not send the PostScript to any printer, not even a PostScript printer, only the preview image is printed. This is pretty good quality on almost any printer that is supported by Windows and should satisfy even the most demanding editor.


Message No. 70: [Branch from no. 69] posted by Instructor (mete6010) on Thu, May. 25, 2000, 14:05 Subject: re: Importing flowsheet drawings into MSWord documents.

 I have put a new viewlet into the Trainer that demonstrates the procedure to insert a flowsheet image into MSWord.


Message No. 71: [Branch from no. 69] posted by Bertil Palsson (bpalsson) on Thu, May. 25, 2000, 14:06 Subject: re: Importing flowsheet drawings into MSWord documents. 

Thanks for the information. I stumbled on this one a few evenings before, and came up with a somewhat different solution. I suggest that you export the graph or flowsheet as a Windows Meta File to a catalogue on your hard disc. Then you import it into to any freeware graphics viewer, where you may convert to TIF format, which is easier handled by MS Word. I use Ulead´s PhotoImpact Viewer ver 4 (www.ulead.com). /bertil


Message No. 72: [Branch from no. 71] posted by Instructor (mete6010) on Thu, May. 25, 2000, 14:28 Subject: re: Importing flowsheet drawings into MSWord documents.

 Thanks Bertil, that's a good way to go. Here is another option that may be acceptable for some reporting and even preferable for some report functions. When you are viewing the flowsheet, hit Alt-PrintScreen on your keyboard. This will copy a bit map of the Modsim window to your clip board. Open your MSWord (or any other document) and simply paste the image.


Message No. 78: [Branch from no. 71] posted by Instructor (mete6010) on Fri, May. 26, 2000, 08:16 Subject: re: Importing flowsheet drawings into MSWord documents.

Just a follow up on GhostView. The software is part of the GNU general public license. You can either buy a CDROM or download it (under GNU's license) at
for Windows. It is good software indeed and you might want to try it out.


Message No. 80: [Branch from no. 71] posted by Instructor (mete6010) on Sat, May. 27, 2000, 15:47 Subject: re: Importing flowsheet drawings into MSWord documents.


Here is a really good option if you use CorelDraw as your graphics package. Any PostScript file (files with extension .ps) produced by Modsim will import perfectly into CorelDraw. From CorelDraw you can export the image in any of many formats that will import into just about anything including MSWord. CorelDraw is equipped with a large array of graphic output filters that allow you to configure your graphics to fit your particular needs perfectly. I have attached an MSWord document that shows two examples of imported graphics. One was destined for an HTML document on the course site and was exported from CorelDraw as a GIF file 464 pixels wide at 75dpi while the other was exported as a Windows metafile to demonstrate the scaling capabilities of PostScript and metafiles. Download this file and print it to see what can be achieved.


Message No. 73: posted by Andrew Wessman (aewessman) on Thu, May. 25, 2000, 14:34 Subject: Problem 2-3 two pointer 

Just thought I'd take a stab at the extra credit here. The reason the D50's get smaller is that the density of the particles increases, and thus their terminal settling velocities increases. This causes the particles to settle to the outside of the hydrocyclone and end up in the underflow, and the D50 will be smaller. I'm not quite as clear on why the silica particle D50 is smaller, but I'm guessing that this is do to the particles having a greater tendency to be pushed outward by the denser magnetite particles. Andrew Wessman


Message No. 76: [Branch from no. 73] posted by Instructor (mete6010) on Thu, May. 25, 2000, 20:08 Subject: re: Problem 2-3 two pointer 

Good try Andrew but I think Ayhan has the better answer See bulletin board posting No.51.


Message No. 79: posted by Instructor (mete6010) on Sat, May. 27, 2000, 14:36 Subject: Some things to watch when running MODSIM jobs The following points have emerged during testing of Module 3 exercises. They are worth bearing in mind. 1 When starting a new job always close the previous job first from the main File menu. MODSIM does not support multiple jobs. If you want to run two jobs side by side open an additional instance of MODSIM. 2 When a job is closed the workspace is cleared but the new job can sometimes inherit the stream names from the previous job . If these are appropriate to the new job you can use them otherwise you must change them in the system data editor. 3 When you generate a Rosin-Rammler feed size distribution, you must click the Clear button to generate the distribution. Do not accept feed stream data while the Rosin-Rammler box is checked on the form. 4 The report file for the screen model SCRN can sometimes give an incorrect value of the oversize factor and therefore of the screen area that is required for the simulated duty. You can check this easily. If the oversize fraction is reported as 0.914 it is probably incorrect. Run the simulation again without any data changes and the correct value should be reported. The calculated values of the stream flows and size distributions are not affected by this error so the simulations are all valid. These difficulties were all uncovered by Saskia who did some really careful checking.


Message No. 81: posted by Diana Drinkwater (drinkwater) on Sun, May. 28, 2000, 22:14 Subject: Getting to know you 

Hi Everybody My name is Diana Drinkwater and I work at the JKMRC in Brisbane, Australia (GMT +10, so I'll be accessing this site when most of you are asleep!). I do a lot of comminution circuit design and optimization work using various modeling tools, and would like to add MODSIM to my list. I also do some teaching for an undergraduate plant design course.


Message No. 82: posted by Instructor (mete6010) on Mon, May. 29, 2000, 12:18 Subject: Grading Policy for Assignments and Exercises

 The grading policy for assignments and exercises will depend on whether you are taking the course for credit or not. Assignments from all for-credit students will be graded and these grades will counted toward the final grade for the course. Assignments from not-for-credit students will be graded on the same numerical scale and the grades posted so that you can check your achievements against our expectations for for-credit students. Assignments should be submitted by dropping in the dropbox. We expect not-for-credit students to submit about half of the assignments but when issuing certificates of completion at the end of the course we will be happy to substitute submitted exercises for assignments. Assignments typically require significantly more time to complete than the exercises and we are concious that all of you are busy at your jobs and do not have unlimited time to work on assignments. All students can submit exercises for evaluation and or checking. These can be submitted as attachments to course e-mails. All assignments submitted before 5pm MDT July 14, 2000 will be graded for credit. This will give us some time to post interesting assignment solutions (with students' approval of course) that we receive before the end of the course. Assignments submitted before this time will be graded soon after submission so that you can check your own progress.


Message No. 99: [Branch from no. 82] posted by Qi Liu (qliu) on Wed, May. 31, 2000, 16:04 Subject: re: Grading Policy for Assignments and Exercises 

Ex2-2.PAK  Ex2-3.PAK  Ex3-1.PAK  Ex3-2.PAK  Ex3-3.PAK  Ex3-4.PAK  Ex3-5.PAK

Dear Instructor: I am a not-for-credit student but I'd like to have a certificate at the completion of the course. I attached the five exercises of this module for evaluation. I also attached two exercises for Module 2 but please ignore them if they are considered overdue. Thanks. Qi Liu


Message No. 100: [Branch from no. 99] posted by Instructor (mete6010) on Wed, May. 31, 2000, 18:25 Subject: re: Grading Policy for Assignments and Exercises 

No problem. You can submit anything up to 5pm July 14 and we will evaluate it.


Message No. 101: [Branch from no. 82] posted by Ricardo Costa (rvinicius) on Thu, Jun. 1, 2000, 11:38 Subject: re: Grading Policy for Assignments and Exercises

 Dear Instructor, I'm a not-for-credit student and I'd like to have a certificate at the completion of the course but I'm doubt about the exercises and assignments. If I send the exercises, will they have same value of an assignment? How can a submitted exercise substitute an assignment? Thanks, Ricardo.


Message No. 134: [Branch from no. 101] posted by Instructor (mete6010) on Fri, Jun. 9, 2000, 08:39 Subject: re: Grading Policy for Assignments and Exercises

 You will qualify for a certificate of completion if you submit a working job for each exercise. You do not need to submit any assignments to qualify. Jobs should be submitted by attaching to course e-mails after the job has been packed using "Pack this job" from the main File menu.


Message No. 136: [Branch from no. 82] posted by Instructor (mete6010) on Fri, Jun. 9, 2000, 10:02 Subject: re: Grading Policy for Assignments and Exercises 

You can check your record of submissions of exercise jobs and assignment grades by clicking on the student profile icon on the course home page.


Message No. 137: [Branch from no. 136] posted by Instructor (mete6010) on Fri, Jun. 9, 2000, 10:15 Subject: re: Grading Policy for Assignments and Exercises 

You can submit assignments as WordPerfect, MSWord, Excel, Quatro Pro, or PDF files. HTML would also work but that is for the really brave.


Message No. 83: posted by Instructor (mete6010) on Mon, May. 29, 2000, 12:27 Subject: Assignments 1 & 2 

Assignments 1 and 2 were deposited in the dropbox today. See bulletin board posting number 82 for more information.


Message No. 84: [Branch from no. 83] posted by Bertil Palsson (bpalsson) on Mon, May. 29, 2000, 13:41 Subject: re: Assignments 1 & 2 

Dear Instructor, I just checked the assignment dropbox and encountered a few technical difficulties. I can read the content of the file "Assignment 3.1.html", but I can't print it directly from my browser. If I try to download it only the text comes down not the drawings. For your information, I'm using IE5.01 English. And then, did I see the unit "inches" ---? :-) /bertil


Message No. 85: [Branch from no. 84] posted by Instructor (mete6010) on Mon, May. 29, 2000, 17:49 Subject: re: Assignments 1 & 2

 Indeed if you download the HTML file the pictures will not download along with it. I've just added the 4 GIF files so that you can print the assignment after you've downloaded all files. Just make sure the GIFs and the HTML files are in the same directory, and open the HTML file with your browser using File, then Open... in I.E. or File, then Open Page... in Netscape.


Message No. 86: posted by Le Huynh (lehuynh) on Mon, May. 29, 2000, 20:00 Subject: Exercise 3-3, 3-4 and 3-5 

Instuctor:  In exercise 3-3, 1200 t/h of feed was specified but the simulation results were for a 1500 t/h feed. In exercises 3-4 and 3-5, is the simulation results (attached to the bottom of the exercise based on a screen with 45 mm mesh, rather than 24 mm mesh as specified in the exercise? Otherwise the solids flowrate in the screen oversize will not be 819.1 t/h but 956.2 t/h Le


Message No. 87: [Branch from no. 86] posted by Instructor (mete6010) on Mon, May. 29, 2000, 23:18 Subject: re: Exercise 3-3, 3-4 and 3-5

 You are correct on both queries. Exercise 3-3 was run at 1500 tonnes/hr when the posted report file was made. You can ignore it. Use a mesh size of 45 mm on the secondary screen in exercises 3-4 and 3-5. Thanks for pointing this out Le


Message No. 88: posted by Instructor (mete6010) on Tue, May. 30, 2000, 13:09 Subject: Adding a mixer- Error in User Manual 

Adrian has pointed out that the user manual specifies a right click when identifying the stream that must be broken to insert a mixer. This is incorrect. Use a left click instead. The viewlet does not make it clear either and we will modify the viewlet sometime today.


Message No. 89: [Branch from no. 88] posted by Instructor (mete6010) on Tue, May. 30, 2000, 13:22 Subject: re: Adding a mixer- Error in User Manual 

I have just checked this out. You can use either a left or right click to identify the stream. Either one will work. Remember to identify the stream immediately after selecting the mixer. If you do anything else after selecting the mixer, Modsim will assume that you are drawing a free-standing mixer and will not automatically connect the streams.


Message No. 90: posted by Instructor (mete6010) on Tue, May. 30, 2000, 13:56 Subject: Changing Icon size 

While checking the User Manual for the last posting another error caught my eye. In paragraph 3.3 on page 9 under the heading Changing Icon Size or Orientation, the User Manual instructs you to use the pointer gauge on the flowsheet. I removed the pointer gauge some while ago because it cluttered the flowsheet. You can specify the icon size in the pop-up text box as shown in the viewlet called "Set icon size".


Message No. 91: posted by Veli Gokdere (szvgok) on Tue, May. 30, 2000, 14:08 Subject: Exercise 3.1 and 3.2 

Dear Instructor I had different simulation outputs for both exercises. I have followed the instructions as you described and repeated several times. When editing sytstem data, you described as this "Use 20 mesh sizes in the feed size distribution data." My understanding from this is to change default value of 25 to 20. This is what I did exactly. In that window there are mesh sizes and % passings next to them. I have accepted default values since you did not specify any where can I make mistake. Regards.


Message No. 92: [Branch from no. 91] posted by Instructor (mete6010) on Tue, May. 30, 2000, 16:18 Subject: re: Exercise 3.1 and 3.2 


You are changing data in the wrong box. The correct box is shown on the attached image. (Click on "Attachments" above to see it) You should not use the default size distribution. Generate your own Rosin-Rammler distribution by checking the box in the form shown in the attachment, specify the d63.2 size and the value for lambda. If you are unsure about the significance of the parameters of the Rosin-Rammler distribution, you can find details in Technical Notes 2 page 2-4


Message No. 93: posted by Instructor (mete6010) on Tue, May. 30, 2000, 16:40 Subject: Relation between the exercises and real operation

 Bertil asked whether the cyclone set up in exercise 2-2 was representative of North American practice. The answer is no. That exercise was structured to introduce you to various aspects of data specification in Modsim and to show you how you can see the output and what the output might mean. For example Bertil noted the high underflow discharge rate and the low pressure drop. If you want to see what the Plitt cyclone model will do under more-or-less realistic operating conditions, go back to exercise 2-2, reset the cyclone geometry to the default (click Default in the "Data set" box on the CYCL parameter specification form and change the cyclone diameter to a more realistic value for this flowrate. I used the Warman cyclone selection chart to find that they would recommend a 15 inch (38 cm) cyclone for this duty. You should also change the %% solids in the feed to say 45%%. (If anyone does not know how to make any of these changes please send an e-mail for assistance). Try this and check the underflow rate, the water recovery to underflow and the pressure drop. These will all be at much more normal values.


Message No. 95: posted by Ayhan Sirkeci (sirkecia) on Wed, May. 31, 2000, 05:40 Subject: inconsistent results

 Dear Instructor, In Exercises 3.1 and 3.2 I can never get the same feed size distribution as you specified in your example. I have run it over and over again, however, the result is always the same. Naturally, depending on the feed size distribution all other results are different. For example the distribution for the first 4 size fraction is: 99.86;98.63; 94.09 and 84.53. I cannot figure out where I make the mistake. Ayhan.


Message No. 97: [Branch from no. 95] posted by Instructor (mete6010) on Wed, May. 31, 2000, 10:16 Subject: re: inconsistent results 


The best thing to do under these circumstances is to pack the job, attach it to a course e-mail and send it to us. We can diagnose most problems fairly easily when we are looking at your data. Packed jobs have extension .PAK and only one file needs to be sent. Here are some things to try meanwhile. Remember to click the Clear button as soon as you have selected the D63.2 and lambda values for the Rosin-Rammler distribution. This is the action that generates the distribution. Make sure that you have specified the correct units for the size. See the attached file for details. Also watch the viewlet "Specify size distributions and flowrate in feed streams"


Message No. 96: posted by Ayhan Sirkeci (sirkecia) on Wed, May. 31, 2000, 09:51 Subject: problems in exercise3-3 

Dear Instructor, I could not possibly run simulation in exercise3-3. When I attempt simulation it either gives an error message or shuts Modsim down. Ayhan.


Message No. 98: [Branch from no. 96] posted by Instructor (mete6010) on Wed, May. 31, 2000, 10:41 Subject: re: problems in exercise3-3

 Almost certainly there is an error in your system data or unit model parameter. Pack the JOB and send the file to us now for review.


Message No. 102: posted by Instructor (mete6010) on Thu, Jun. 1, 2000, 11:51 Subject: Getting size distributions in tabular form. assign3-1format.gif    assign3-1format2.gif

Mike Snow asked how to get the size distribution of the combined product stream in Flowsheet A in Assignment 3-1. There are three ways to get size distributions from a Modsim simulation: 1. View the size distribution graph. This will give the size distribution in graphical form for any stream or streams in the flowsheet. 2. To get the size distribution in tabular form there are two options: 2.1 The report files for many units will report the size distributions in all associated streams. However this is not so in this case because there is no report file for the stockpile. 2.2 You can get the size distribution for any stream by checking the "Display size distribution of selected streams" box in the output format editor (select "edit output format" from the main edit menu). Double click to select your streams and accept the form. The size distribution can be seen from "View data output file" on the main View menu. See the attached gif files for the details. You can cut and paste from the output data file if you want to use the size distributions in a spread sheet or report.


Message No. 103: posted by Instructor (mete6010) on Fri, Jun. 2, 2000, 08:56 Subject: Printing flowsheets on a white background. 

Elias asked the following: Is it possible to change the color of the flowsheet background from grey to white while printing? It takes more time and ink. Answer: If you use "Print" from the "File" menu when you are viewing the flowsheet, or from the flowsheet editor, the flowsheet will print on a white background. Exporting the flowsheet as PostScript file or as Windows metafile will also produce blank lines and text without a background when these are imported into a document. The only way to get a grey background is to do a screen dump using the "Print screen" key on the keyboard and then paste the image from the clipboard into another document before printing.


Message No. 105: [Branch from no. 103] posted by Instructor (mete6010) on Sat, Jun. 3, 2000, 01:11 Subject: re: Printing flowsheets on a white background. 

Typo error in message number 103: Second last paragraph, 2nd line: read black not blank.


Message No. 104: posted by Adrian Hinde (adrianh) on Fri, Jun. 2, 2000, 09:26 Subject: Hi Everyone

 Hi Everyone I'm Adrian from Mintek in South Africa. I am a specialist consultant in Mintek's Minerals Processing Division. We do lots of laboratory and pilot scale testing covering all ore types and unit operations. Although this is the first time I have used Modsim you might be interested to know that one of Prof. King's ex students (Merrill Ford), who is now a manager at Mintek, wrote some of the early code for Modsim. Needless to say, many of us at Mintek have had a long association with Peter since the 1970s. I have no doubt that we are all going to learn a lot from this course. Enjoy.


Message No. 106: posted by Bertil Palsson (bpalsson) on Sun, Jun. 4, 2000, 14:12 Subject: Exercise 3-5 tertiary stage

 I looked at (and ran) this exercise, which is a good example of the problem with circulating loads. However, I have one remark regarding the last what-if scenario. If one puts the the short head crusher before the screen, the risk of choke-feeding the crusher becomes imminent. It is not clear to me if the crusher simulation warns for such conditions. I know that it can work if you ar lucky, but since a concentrator is a running proof of Murphy's law I wouldn't dare to use such a circuit lay-out. Any more opinions? /bertil


Message No. 108: [Branch from no. 106] posted by Instructor (mete6010) on Mon, Jun. 5, 2000, 09:55 Subject: re: Exercise 3-5 tertiary stage CHOKE FEEDING OF CRUSHERS

 None of the crusher models in MODSIM will detect whether a crusher is under choke feeding conditions. The reason is that there are no models for this phenomenon in the literature. We rely on the generic crusher capacity tables in the Technical Notes when doing preliminary simulations. If you want to simulate an existing crusher or a specific model that is under consideration you have to work with the technical staff of the crusher manufacturer- or at least with the technical information that was supplied with the crusher. The combination of MODSIM output for the entire circuit and manufacturer's data for the individual equipment will enable you to solve most operating and design problems. Don't be afraid to ask equipment manufacturers to specify which of the major plant simulation systems have models for their equipment.


Message No. 107: posted by Le Huynh (lehuynh) on Sun, Jun. 4, 2000, 22:24 Subject: Exercise 4-1 

Dear Instructor My simulation results for Exercise 4-1 is different to those in the excel spreadsheet (I have tried many times!). It is extremely frustrating to keep trying, because as I'm working, there is usually not enough time to spend on the course. Furthermore, the errors can be caused by something very minor but it's often not obvious. I find that the best way to check my results is to download your job from the internet (after I have carried out my own simulations) so that I can check if I've entered all the correct data or at least find where the differences lie. I see that Exercises for Module 4 are not available for downloading. I was wondering if exercises for Module 4 and beyond will be available? Otherwise, I can see myself packing a lot of jobs to send to you for checking! Le


Message No. 110: [Branch from no. 107] posted by Instructor (mete6010) on Mon, Jun. 5, 2000, 10:44 Subject: re: Exercise 4-1 

The first thing to remember here is that there is never any one "correct" answer to a simulation problem. Also remember that the information that is posted is meant to give you some idea how you should go about doing the exercise and should never be taken too literally. In fact we want to encourage you to 'do things your way' so do not get discouraged if you notice differences with the information that is posted. DO NOT HESITATE TO SEND PACKED JOBS with your queries. This is by far the quickest way to get help and to locate the reasons for any differences. We can comfortably deal with several dozen packed jobs each day so don't hesitate to send them. We will be posting packed versions of Module 4 jobs during the week. We do not want to post them too early and we will welcome suggestions for the best day of the week to post exercise jobs. You are probably all realizing by now that, although the exercises are carefully designed to demonstrate various aspects of simulation, these tasks are by no means trivial. Feel free to pace your work to meet your own schedules.


Message No. 109: posted by Instructor (mete6010) on Mon, Jun. 5, 2000, 10:16 Subject: Saving PostScript and Encapsulated PostScript images of size distribution graphs 

Bertil would like to save .PS and .EPS files on a different hard drive. In this way he can keep his simulation jobs well organized. This can be done as follows Modsim regards .PS and .EPS files as internal files and therefore saves them in the working space which normally will be on drive C. To save these files in any directory on any disk you need to follow this procedure. When the graph is showing, press F3 to generate an EPSI file and/or SPACE BAR to generate a .PS file. Close the graph display and choose "Export as a PostScript" or "Export as an Ecapsulated PostScript" from the "File" menu on "Plot size distributions" form. This will give you the chance to save these files under your choice of name on your data disk. See the viewlet entitled "Save a graph as a PostScript file" to see a demonstration of this procedure. Here is the location of the File menu



Message No. 111: posted by William Bruck (wbruck) on Tue, Jun. 6, 2000, 06:39 Subject: Getting to know you 

Hello Everyone, I'm Bill and I work in the Quarry industry in Pennsylvania. I make little rocks out of big rocks; specifically a sand and gravel operation - processed sand. I'm involved mainly with crushing, screening and classification (classifying tanks and hydrocyclones). I'm looking forward to applying the MODSIM simulator to my operations.


Message No. 112: posted by Gustavo Meyer (gmeyer) on Tue, Jun. 6, 2000, 14:59 Subject: Problems with Exercise 3-1 and 3-2. 

Have followed instructions and somehow cannot get the same size distributions and underflow tonnages. When I check the data for the feed I notice the Rosin-Rammler d63.2=4cm has different number and results don't coincide with those of the exercise.


Message No. 113: posted by Gustavo Meyer (gmeyer) on Tue, Jun. 6, 2000, 15:55 Subject: Exercise 3-1 and 3-2

 I realized that I needed to clear to activate the r-r distribution. I am now getting the correct distributions , however I still have a problem when I view the graphs I don't get all three product distributions, only 2 of them and also get a window with: M6202 : MATH-)-log: SING error. I cant find what is wrong .Help!!!!!


Message No. 114: [Branch from no. 113] posted by Instructor (mete6010) on Tue, Jun. 6, 2000, 17:22 Subject: re: Exercise 3-1 and 3-2

 Dear Gustavo, There is an error in your data. The best way for us to help is for you to pack the job (Use "Pack this job" from the main File menu) and attach the packed job to a mail message to the instructor. We will look at it here and we will find the error for you. Peter King


Message No. 129: [Branch from no. 114] posted by Instructor (mete6010) on Thu, Jun. 8, 2000, 12:47 Subject: re: Exercise 3-1 and 3-2

 My apologies for taking so long to get back to you Gustavo. I did not notice immediately that you had posted your packed jobs as attachments to the bulletin board. The FORTRAN code hit the singularity because you were trying to plot a size distribution that had no values, only zeros, on a log scale. The log of 0.0 does not exist so FORTRAN regards this as a singularity hence the error message that you saw. If you have experimental size distributions in intermediate or product streams and you want these to appear on the particle size distribution graphs, you can enter the experimental size distributions as part of the Sytem data attached to that stream. HOWEVER IF YOU DO NOT HAVE PARTICLE SIZE DISTRIBUTION DATA YOU MUST LEAVE THE NUMBER OF SIZE FRACTIONS ON THOSE FORMS AS 1.


The form should look like this. Note that Gustavo has used this form to specify a name for the stream.



Message No. 115: posted by Gustavo Meyer (gmeyer) on Wed, Jun. 7, 2000, 09:17 Subject: Exercise 3-1, 3-2

Exercise 3-1.PAK    Exercise 3-2.PAK

I am enclosing exercises for your review. Thank you Gustavo


Message No. 116: posted by Instructor (mete6010) on Wed, Jun. 7, 2000, 10:08 Subject: Assignment 3 release dates 

Assignment 3 was inadvertently posted with a one-day release. It is now available in the dropbox. Thanks to Romina for pointing this out.


Message No. 117: posted by Instructor (mete6010) on Wed, Jun. 7, 2000, 12:07 Subject: Models for impact crushers 

Sveto sent the following comment by e-mail. "I have read about the models for crushers implemented in MODSIM but didn't find a specific model for impact crushers. Is the standard model CRSH suitable for these crushers? I'll be grateful if you could give me some tips in the recent scientific literature about the modeling of impact crushing." Because of its general interest I will respond here. Several people have asked in recent months for a good model for the impact crusher. We are not aware of one in the literature but if anyone does have some information on a good model please let us know. We would like to put a model into MODSIM. The existing model CRSH is not a good model for the impact crusher since CRSH is based on Bill Whiten's crusher zone and classification structure. That is obviously not what happens in impact crushers. Because of the increasing popularity of impact crushing we will rectify this omission as soon as we have enough data to justify the development of a model.


Message No. 119: [Branch from no. 117] posted by Instructor (mete6010) on Wed, Jun. 7, 2000, 13:13 Subject: re: Models for impact crushers

 Here is another comment from Sveto that will interest many of you. "Another question is about the cumulative breakage function used by Whiten (eq. 5.11). It looks like the sum of two probability densities (but it is not) and can be replaced by the sum of two Weibull distributions with different 'shape' parameters. I checked this with Mathcad software and the shape parameters are not far from the powers used in (5.11). Thus, one can compute the Bij coef. from true probability densities as in the formalism of tech notes 2 and not as the difference (5.12). Because the Weibull distribution is widely used in fracture mechanics, and because the R-R distribution is a particular case of the Weibull distribution, it seems to me worthy to try to use this in the development of crushing models." Yes, Weibull and R-R distributions make good models for breakage functions but they must be properly truncated at the parent size because the progeny population from a breakage event can never include particles that are larger than the parent particle. Truncated log-normal and truncated logistic distributions are also good. Sums of truncated log-normal distributions have been used by German researchers for many years and are well represented in the literature. You can read about truncated distributions in Technical Notes 2 section 2.2.2 The application of truncated distributions for breakage function models will be discussed in Technical Notes 8 in Module 6. This will include application to JKMRC's t10 procedure. Watch for it!


Message No. 118: posted by William Bruck (wbruck) on Wed, Jun. 7, 2000, 12:24 Subject: Exercises 3.1 - 3.5

Exercise 3-1.PAK Exercise 3-2.PAK Exercise 3-3.PAK Exercise 3-4.PAK Exercise 3-5.PAK

Attached are exercises for your review. In exercise 3.5 my tonnage to be processed is quite a bit higher than what you show. Thanks Bill


Message No. 122: [Branch from no. 118] posted by Instructor (mete6010) on Wed, Jun. 7, 2000, 15:13 Subject: re: Exercises 3.1 - 3.5 

Replied by course e-mail


Message No. 120: posted by Instructor (mete6010) on Wed, Jun. 7, 2000, 14:06 Subject: Liberation distribution in exercise 2-3 

Romina sent the following comment. "I also have a general question about exercise 2.3 that may be relevant to my future work: We defined a feed size distribution and an overall composition in term of G classe -i.e weight fraction of pure A, weight fraction of pure B and weight fraction of middlings A&B- So all the D classes have the same grade distribution and as a consequence A) the 3 G classes have the same size distribution B) all the D classes have same grade Frequently the fines are more liberated that coarser sizes. Thus the D classes have different grade distribution. In one fine D class we may have only liberated particles and no middlings... and complicated cases when there is some sort of selective breakage. Is modsim so flexible to allow this type of feed definition?" The data in exercise 2.3 was chosen to introduce the concept of liberation in the simplest possible way. The simple A,A-B,B model that was used does have the characteristics that you mention: the grade classes all have the same size distribution and the size classes all have the same grade distribution and therefore the same average grade. This is not often realistic in practice where you always find variations of average grade with size and you always find variation of liberation (and therefore grade distribution) with particle size. Finer particles are usually, though not always, more liberated than coarser particles. (There is a 2-point grade bonus for any for-credit student who can post a definition of a valid condition under which finer particles are less liberated than coarser particles) Modsim is indeed flexible enough to accommodate completely realistic grade distributions that are measured by image analysis. In addition Modsim mill models can simulate liberation during grinding including the effects of selective breakage, preferential breakage, differential breakage, grain boundary fracture and boundary region fracture. You will have an opportunity to explore some of these effects in Module 7.


Message No. 124: [Branch from no. 120] posted by Dirk Lange (dlange) on Thu, Jun. 8, 2000, 01:29 Subject: re: Liberation distribution in exercise 2-3 

Theoretical it is possible to get a higher value mineral share in coarser particle fractions if: -we have very different crystal properties -we have mainly grain border cracks at big value mineral crystal (with high internal fracture resistance ) borders compared to the useless (fine) matrix (with small fracture resistance). example: If we have "porphyry" mineralogical texture with big value mineral crystals (with high internal fracture resistance) in a fine crystaline matrix (with small fracture resistance). But in magmatic rocks with low porosity intra-crystalite cracks are dominating in practice and coarse crystallite mineral structures have a smaller fracture resistance compared with fine crystalite structures (without view at different mineral properties)


Message No. 126: [Branch from no. 124] posted by Instructor (mete6010) on Thu, Jun. 8, 2000, 09:51 Subject: re: Liberation distribution in exercise 2-3 

Good explanation Dirk. These nonrandom fracture patterns seem to be quite common in real mineral systems. Selective breakage of the different mineral phases seems to be the rule rather than the exception. Whenever there is a greater tendency for fracturing to occur in the region of the phase boundaries, you can expect to see unliberated particles in the small size fractions. Of course, if the phase boundaries are so weak that the mineral grains are detached from the matrix, the majority of liberated mineral particles will be found in the size classes close to the original mineral 'grain' size.


Message No. 121: posted by Wayne Jacobsen (wjacobsen) on Wed, Jun. 7, 2000, 15:00 Subject: module 4 

Need compiling for module 4 lesson


Message No. 123: [Branch from no. 121] posted by Instructor (mete6010) on Wed, Jun. 7, 2000, 16:27 Subject: re: module 4 

We've just added the relevant files in Module 4 to a path so you can compile them now.


Message No. 125: posted by Instructor (mete6010) on Thu, Jun. 8, 2000, 09:30 Subject: Stratification profiles in a jig.

 Sveto has asked why he cannot see stratification profiles for the Batac jig in exercise 4.3. "When I run the simulation for Ex. 4-3, then enter View menu/Flowsheet and right click on the jig icon, I see the usual Report-Cancel choice. I click on the report and cannot see any graphs. How can I visualize the stratification profiles?" This is because Sveto is using the model BATJ for the jig. This model is based on the 'classical' partition function approach and uses the Gottfried-Jacobsen model to allow for the effect of the particle size distribution. It does not calculate the stratification profile so therefore it cannot display this profile. To see the stratification profile use the model SJIG instead


This model is based on the modern approach to the modeling of autogenous gravity separators like jigs and is far preferable for simulation work. You should experiment with the two parameters of this model. The relative height of the cut in the stratified bed simulates the variation in the height of the weir position as a fraction of the total bed height. The specific stratification constant defines the efficiency of the jigging motion - higher values represent better jigging and vice-versa.


After running the simulation, right click on the jig icon and choose "Stratification profile" to see the graph.


Message No. 127: posted by Wayne Jacobsen (wjacobsen) on Thu, Jun. 8, 2000, 10:30 Subject: feeder?

 In Assignment 3-1a, do we use a conveyor to move material from the stockpile to the DD screen and from the bin to the cone crusher? or, do we use a stream from the gyro to the DD screen and the bin to the cone crusher?


Message No. 128: [Branch from no. 127] posted by Instructor (mete6010) on Thu, Jun. 8, 2000, 12:23 Subject: re: feeder?

In practice you would use a conveyor and that is recommended for the simulation. This will allow you to check that the conveyor can handle the duty required (Use model CONV)


Message No. 130: posted by Gordon Ziesing (gfziesing) on Thu, Jun. 8, 2000, 13:05 Subject: Run time error 380 

I retrieved Flowsheet A (for assignment 3-1) and found that the flyouts were missing. I re-attached them and hit Refresh flowsheet. Got a run time error 380 and program shut down. What am I doing wrong?


Message No. 132: [Branch from no. 130] posted by Instructor (mete6010) on Fri, Jun. 9, 2000, 00:21 Subject: re: Run time error 380

 There is not sufficient information to diagnose this problem. Please pack the job and attach it to an e-mail message.


Message No. 133: posted by Instructor (mete6010) on Fri, Jun. 9, 2000, 01:25 Subject: Slot positions on the Reichert cone 

Qi Liu sent this message today which will be of general interest. "I didn't have any problem with Exercise 4-4. I observed that increasing the slot sizes (from 1 to 9) seemed to produce a higher-grade concentrate. This probably indicates that a "1" setting means that the bullnose is at the upmost position whereas a "9" setting the lowest position. Therefore, at setting "1" we have higher recovery but lower grade because more materials run into the concentrate, and vice versa at setting "9". This should have some implications in the rougher-cleaner-scavenger arrangement since in Roughers we usually emphasis on recovery whereas in Cleaners we emphasis on grade. I tried a Rougher-Cleaner combination and used setting "2" in the Rougher and setting "8" in the Cleaner and found that it worked well (with all the recycles)." This is the correct interpretation of the action of the slot settings on the cone.


Message No. 135: posted by Instructor (mete6010) on Fri, Jun. 9, 2000, 09:11 Subject: Error in data for model DSC1 

Ronel has found the following error in the parameter input form for the double deck screen model DSC1. The screen width value is not converted to SI units when the data is accepted. If you use meters for the unit of size for this model the data will be correct since no conversion is necessary. (This is the recommended workaround). Even if you do use non SI units your simulations will still be correct. The only thing to worry about is the screen width and therefore the screen area will be incorrectly calculated on the report file. Either way you can safely use model DSC1 for all simulations and the simulations will be accurate.



Message No. 138: posted by Instructor (mete6010) on Mon, Jun. 12, 2000, 18:31 Subject: Packed exercise jobs for modules 4 & 5

 Packed exercise jobs for modules 4 and 5 have been posted on our FTP site. You can access them through the Internet connection in MODSIM.


Message No. 139: posted by Instructor (mete6010) on Tue, Jun. 13, 2000, 09:06 Subject: D80,D20 and D50 sizes for process streams.

 Robert made the following comment today: "I am probably missing something right in front of my nose, but is there a built in way to determine the D20, D50 and D80 etc's of a simulated product stream from the MODSIM results? Or do we have to download the results file and interpolate the values externally? I cannot see one and it would make Assignment 3-2 much easier." Unfortunately there is no convenient way to get the D20, D50 and D80 sizes for a process stream out of Modsim at the moment. Although Modsim has excellent internal codes to do these interpolations, we have not provided a convenient way to access them from the user interface. We intend to implement Bertil's earlier suggestion that these values be made available through a more flexible choice of values for display in the stream flyouts. We hope to have that excellent suggestion implemented in the next release of Modsim which will be made available for downloading before the course ends. Your best bet at the moment is to read the values off the size distribution graphs.


Message No. 140: posted by Instructor (mete6010) on Wed, Jun. 14, 2000, 15:28 Subject: Standard dimensions for woven wire mesh screens

 Several people have needed to vary wire diameters as screen mesh sizes vary. You can access a table of standard (US standard) wire mesh dimensions from here. These tables are useful with the Karra screen model and they will help you to get realistic simulations of industrial screening operations.


Message No. 141: posted by Instructor (mete6010) on Wed, Jun. 14, 2000, 16:20 Subject: Limitations of Flotation Models 

Qi Liu commented as follows: "I particularly like the 3rd exercise because the rate constants can be changed in different stages. I understand that in this model (FLTN), we classified the particles into 3 grade classes and each grade class is further divided into a "floatable" and a "non-floatable" fraction. The rate constant for each "floatable" fraction must have lumped together the effects of all the factors such as particle size, reagent scheme and hydrodynamic conditions in the flotation cell. I wonder if finer division of the rate constants for each grade class is possible? For example, for the "floatable" part of chalcopyrite, each size fraction may be assigned a different rate constant (assume the flotation conditions such as reagents types and dosages are the same). In this way, when a regrind is used, the feed size to the subsequent flotation cells can be re-specified to represent the realistic operation. Furthermore, the rate constants in each size fraction may be further distributed among different operating conditions such as types and dosages of reagents, air flux and agitation, etc." Any comments?


Message No. 205: [Branch from no. 141] posted by Bertil Palsson (bpalsson) on Sun, Jul. 9, 2000, 13:21 Subject: re: Limitations of Flotation Models 

I will take this up, although it's three weeks late. Qi Liu is in one way correct that a more detailed specification of model parameters would give us a better simulation tool. However, at the same time it is very difficult to make the right estimation of parameters. For example, do you want to estimate kinetic constants from overall plant flow data, individual cell data, or batch data, and how to take into account different reagent schemes? The result is very much dependent on the way the kinetic data is collected. Although, detailed data can be collected from laboratory batch data, it is not easy to get the same data quality from plant data, mainly due to sampling errors. These errors can to some extent be cancelled out by advanced materials balancing and error distribution but then you may introduce additional difficulties. So, from a practical point of view I believe that Peters model is probably good enough. Then there is a theoretical difficulty. Nearly all the flotation models used are non-linear, which make it hard to do a statistically correct estimate of model parameters. As soon as you start to add more than three-four parameters you often find that the error estimates for the individual parameters rises to +-50%% relative errors. Any such parameter is useless. I do not have the exact formula for Peters or Davids models at hand, but I tried to change the feed particle size to half its original value, and the circuit in Ex5-3 responded in a reasonable way. It gave better recovery and lower concentrate grade, so particle size is included at least in the FLTN model. I presume that some consideration of hydrodynamics can come from the solids hold-up. That leaves us with the change of flotation kinetics with flotation chemistry. Well, I would say that we have a very vague understanding about ultimate flotation kinetics as a result of reagent type, surface oxidation, and general pulp liquid chemistry. We know that a non-xanthate regime gives us a better selectivity against the disulfides, but we do not KNOW why. There are several plausible theories ---, at least one pro research group! Here, we are left with doing comparative tests under different pulp chemistry regimes to establish relative flotation kinetics for the minerals. So my general comment is that, although we can add more parameters, it is seldom useful since we can not estimate them correctly. It is a delicate balance here, and I (the simulation heretic) prefer to use simpler models if I then, because of their simplicity, can update them more often. /bertil


Message No. 142: posted by Wayne Jacobsen (wjacobsen) on Thu, Jun. 15, 2000, 12:13 Subject: Error in your example 4-1 

There is an error in example 4-1 dense medium cyclone. In grade class 3 10.15%% should not be an input. The transposition mistake is easy to spot. The lesson say's the target grade should be <= 2%% CaO and <= 3.5%% SiO2. Why is the target SG of separation not about 3.0 instead of the 2.75 in your example? 3.01 gets you 2.87%% SiO2


Message No. 143: [Branch from no. 142] posted by Wayne Jacobsen (wjacobsen) on Thu, Jun. 15, 2000, 13:59 Subject: re: Error in your example 4-1 

A follow up to my comment. If the data is calculated correctly then my spreadsheet shows the densities do not decline. For classes 1-6, they go 2.873,2.875,2.941,2.939,2.91,2.986 I this OK?


Message No. 144: posted by Le Huynh (lehuynh) on Thu, Jun. 15, 2000, 19:48 Subject: Submitting exercises

 Dear Instructor What is the best way to submit exercises (not the assignments)? I know that we should send them as packed jobs but what do you mean by send it as a course email? Also, for non-credit students, does it mean that ALL exercises from every module has to be submitted if no assignments are to be submitted? This is likely the case for myself (and probably my colleagues here at the Ian Wark Research Institute) due to the demands of work. :-(! Thanks! Le


Message No. 145: [Branch from no. 144] posted by Instructor (mete6010) on Fri, Jun. 16, 2000, 00:15 Subject: re: Submitting exercises 

To send a packed job do the following. When you are ready to pack a job and send it, select "Pack this job" from the main file menu. This opens a dialog box which allows you to choose the directory in which to save the job. Open the mail tool by clicking on the the Private mail icon. Compose your message and attach the packed job. Click send when you are ready to send it. You should try to work through all the exercises to get maximum benefit from the course. At least you should be able to construct one working simulation for each exercise even if you do not have time to try all the suggested variations. Just pack and send one simulation per exercise and that will qualify you for a certificate of completion. That will also give you an idea of the potential of simulation as a working tool.


Message No. 146: [Branch from no. 145] posted by Instructor (mete6010) on Fri, Jun. 16, 2000, 09:29 Subject: re: Submitting exercises 

I should have indicated in the previous posting (No 145) that packed jobs have the file extension .PAK This information is needed so you know which file to attach to an e-mail.


Message No. 147: posted by Instructor (mete6010) on Fri, Jun. 16, 2000, 11:15 Subject: Understanding the Reichert cone 

Romina sent this interesting e-mail today and suggests that we share it with the class. 

"Prof. King I have some questions for the interpretation of the Assignment 4.1 (on which I have been working for a couple of days) that are probably of general interest. I work with 4DSV units for all the 3 stages (R-S-C) as suggested. Each unit has 4 adjustable parameters (the slot setting). I understand that with a low values of the slot setting (say 1) the gap is very open and one obtains low values of concentration but high weight recovery. I also expected the first parameter (of the group of 4 ) to be the gap of the top DSV (of the stack of 4 that you show on the right inside of Figure 4 of your paper) and thus the concentrate determining variable. However it is not so; [5 1 1 1 ] does not generate the same concentrate as [5 9 9 9] ! I also understand that the 3 DSV that follow the top one produce the middlings and that when the middling are not taken out all them contribute to the concentrate (i.e. conc. and middlings go together) and the tailings do not change. This seems confirmed by the simulations. Where do I mistake to interpret the meaning of the 4 parameters? I was also expecting a sensible thing to establish some sort of trend in the 4 setting of each unit in such a way to push the concentration in the top DVS and the recovery in the following 3 like in a cleaner operation [high low low low] (say [7 6 5 4] ) or vice-versa push the recovery on the top as in a scavenger operation [ low lower lower lower] (like [4 3 2 1]). It seems that I am wrong and I think that all has to do with my mis-interpretation of the meaning of the setting variables Indeed there are 4 adjustable variables for each unit. Each variable has 9 possible levels. Thus the number of combinations are 9^4 (for one unit!) . So 9^(4x3) adjustable variables for the 3 units plus configuration variables!. Thus there is the need to establish rules that can narrow down the number of simulations. I hope my question will be of general interest and I thank you for your comments."


There are two major issues here. 

1 Interpretation of the effects of the slot positions. Romina is correct in her interpretation. She just slipped in specifying the parameters for the cone. Each cone has an additional parameter that specifies how many of the internal cone concentrates go to the concentrate stream. To confirm her understanding of the role of the top cone she expected to see the same concentrate values for a 5 1 1 1 configuration as for a 5 9 9 9 configuration. That will happen but the cone MUST BE SET TO SEND THE LOWER 3 CONCENTRATES TO MIDDLING IN EACH CASE. The results of such a test are shown below



When the parameters are changed to 5 9 9 9 the results for the concentrate remain unchanged but the middlings and tails change as expected. 


2 Rational optimization strategies. Yes there are an astronomically large number of combinations and permutations to check for an optimum even in a simple RSC circuit. We need some good methods to make optimization calculations in this situation. That is why it is a good area for Romina to be researching. To handle plants like this I still use the old-fashioned grade recovery curves and use intuitive search strategies to find the best ones. That is what I did in the IMPC paper. I'm sure there is a better way. Romina, her advisor Prof Gianni Schena and I will be discusing this in Rome in July and we will explore the possibility of using some of the more advanced facilities that are available in the professional version of MODSIM to automate the task. When the plant has a parallel structure with no recycle, the optimization problem is amenable to a more analytic approach. These methods have been developed most extensively for coal cleaning plants by people like Dr Geoff Lyman at JKMRC. The role that a simulator like MODSIM can play in these methods is described in a paper that I published in Coal Preparation some years ago. You can link to it from here if you are interested.


Message No. 148: posted by Instructor (mete6010) on Sun, Jun. 18, 2000, 12:00 Subject: Delay in posting Module 6 Module 6 will be posted at 18:00 MDT today Sunday June 18. Apologies for any inconvenience caused by this delay.


Message No. 149: posted by Reiner Neumann (rneumann) on Mon, Jun. 19, 2000, 15:27 Subject: Exercise 3.1


 I've run this exercise, but the screen area is different from the calculated by the instructor. All the data are the same, so I can't see the reason for this important difference. The packed job is attached.


Message No. 154: [Branch from no. 149] posted by Instructor (mete6010) on Thu, Jun. 22, 2000, 09:40 Subject: re: Exercise 3.1 

This is a problem with the Modsim report file for the screen. See bulletin board posting No. 76 item 4 in the main forum. The calculations are all correct.


Message No. 150: posted by Gustavo Meyer (gmeyer) on Tue, Jun. 20, 2000, 15:05 Subject: Exercise 4-1 and 4-2 

Exercise 4-1.PAK  Exercise 4-2.PAK

I seem to be setting wrong data into these exercise 4-1 and first part of 4-2. Can you tell me what I am doing wrong? Thanks, Gustavo


Message No. 153: [Branch from no. 150] posted by Instructor (mete6010) on Thu, Jun. 22, 2000, 09:39 Subject: re: Exercise 4-1 and 4-2 

This is the same problem that Michael reported. See bulletin board postings number 151 and 152 in the Course People forum. See bulletin board postings 59 and 60 also. These should clear up the problem.


Message No. 151: posted by Michael Pietrobon (mpietrobon) on Wed, Jun. 21, 2000, 02:38 Subject: Ex 4.1 


Claudio, I am experiencing similar problems to those encountered in my Ex 3.5. In this case the H-M cyclone produces reverse values for solids in the O/F (92 tph) and U/F(8 tph). Could you please check my attempt. Does this have anything to do with the fact that i am running the program in the Southern Hemisphere ?


Message No. 152: [Branch from no. 151] posted by Instructor (mete6010) on Wed, Jun. 21, 2000, 18:37 Subject: re: Ex 4.1 

The densities of the different particle types have been specified incorrectly. This probably happened because the G-classes were incorrectly set up at first and then subsequently changed.


MODSIM reverts to specification of sp. gr. by particle type once it has calculated the densities from the mineral densities the first time. IT IS NECESSARY TO CHOOSE "Sp. gr. by minerals" to get a new calculation of the particle densities done.


Go back the "Setup g-classes to see this.

 Once this change has been made, the simulation looks fine. Should be OK in the southern hemisphere also!


Message No. 155: posted by Ayhan Sirkeci (sirkecia) on Fri, Jun. 23, 2000, 04:49 Subject: exercise4.3 

Dear instructor, When I try to see stratification profile in exercise4-3, Modsim produces an error message saying "program terminated with exit code 1". Is there anything wrong with the data I specify?


Message No. 156: [Branch from no. 155] posted by Instructor (mete6010) on Fri, Jun. 23, 2000, 14:33 Subject: re: exercise4.3 

Ayhan, You are probably running with your display set to true color. METGRAPH will display graphs only at 16 bit color or less. Try changing your display settings. If that does not solve the problem, attach the packed job to an e-mail message and I will check the data for you.


Message No. 157: [Branch from no. 156] posted by Ayhan Sirkeci (sirkecia) on Mon, Jun. 26, 2000, 07:51 Subject: re: exercise4.3


I still have problems when I attempt to see the stratification in exercise4-3. I am sending the exercise as packed file.


Message No. 158: [Branch from no. 157] posted by Instructor (mete6010) on Mon, Jun. 26, 2000, 11:20 Subject: re: exercise4.3


The packed job indicated that you had chosen model BATJ for the jig. This model is based on the partition function method and therefore does not calculate any stratification profiles. When I changed the model to SJIG, the profiles were calculated and displayed as expected.


I have attached the amended packed job. When you unpack this job you will probably have to re-specify the sink Sp. Gr. on the washability form because this data is not included in a packed job.


Message No. 159: posted by Ayhan Sirkeci (sirkecia) on Tue, Jun. 27, 2000, 02:57 Subject: exercise4-3


Dear Instructor, I made all changes in exercise4-3 and specified sjig as the unit parameter. I still cannot see the stratification, however, the model seems to be working all right. Furthermore, I cannot pack a job under a directory I desire instead it saves to the directory the file originates. I am again sending exercise4-3 as packed file after modifications.


Message No. 161: [Branch from no. 159] posted by Instructor (mete6010) on Tue, Jun. 27, 2000, 09:46 Subject: re: exercise4-3 

When I opened your packed job it indicated that you had not yet specified a model nor parameters for the jig. Please ensure that you in fact have specified the model SJIG before you ran the simulation. Next follow these diagnostic steps. Run the simulation with model SJIG selected. View the flowsheet. Right click the jig icon. Do you see this or this ?

If the former you have the correct model. If the latter, you are using the incorrect model. If you are using the correct model, click on Stratification profiles. If the Metgraph window appears but is black like this


then you are running your display with 32-bit color. Change your display properties to 16-bit color or 256 colors. If anything else happens describe it precisely and convert a screen dump to a GIF image and attach it to an e-mail and send it and we will try to help.


Message No. 160: posted by Ayhan Sirkeci (sirkecia) on Tue, Jun. 27, 2000, 08:07 Subject: Exercise5-2


Dear Instructor, Why do I get different results in Exercise5-2 than yours?


Message No. 162: [Branch from no. 160] posted by Instructor (mete6010) on Tue, Jun. 27, 2000, 10:11 Subject: re: Exercise5-2 

You are simulating a 10 cubic meter cell in the cleaner. I am simulating a 2 cubic meter cell in the cleaner. It would be difficult to run this plant with such a large cleaner cell. Check the calculated residence time in the report file for the cell.


Message No. 163: posted by Jose Gomez (jgomez) on Tue, Jun. 27, 2000, 17:08 Subject: Exercise 4-3

display.doc  Exercise 4-3.PAK

Dear instructor: I have the problem with the exercise 4-3, I see the post 159 y 161 and mead the changes but I still have the seam problem, I attach the exercise. Thank You Jose Angel


Message No. 164: posted by Ayhan Sirkeci (sirkecia) on Wed, Jun. 28, 2000, 03:07 Subject: exercise4-3. 

Dear Instructor, I had had specified SJIG as the unit parameter in the packed job I sent to you. However, I checked my data again and specified SJIG as the unit parameter and it didn't work. I even ran simulation using your data loaded from internet. My results are exactly like yours yet I cannot still see the stratification profile, the message "Program Terminated with Exit Code 1, Exit Window?" appears on top of the blank graph window. Do you have any idea as to the cause of the problem? I wouldn't fuss about that much if I had the wrong results.


Message No. 166: [Branch from no. 164] posted by Instructor (mete6010) on Wed, Jun. 28, 2000, 22:25 Subject: re: exercise4-3. 

Dear Ayhan Please check the color settings on your video display. If you do not know how to do this check under hardware requirements when you click the "General" icon on the main course home page.  

What happens when you try to view particle size distribution graphs when you run any of the exercises in Module 3?


Message No. 167: [Branch from no. 166] posted by Ayhan Sirkeci (sirkecia) on Thu, Jun. 29, 2000, 02:31 Subject: re: exercise4-3. 

Dear Instructor, Color settings are all OK. I have never had problems with seeing the particle size distribution graph under 16 bit or 256 color setting. However, I cannot see the stratification in exercise5-2 under any circumstances. Changing the color setting does not solve the problem.


Message No. 172: [Branch from no. 167] posted by Instructor (mete6010) on Thu, Jun. 29, 2000, 09:33 Subject: re: exercise4-3. 

We are temporarily stumped on this. I will post a notice to see if anyone else is having similar problems.


Message No. 165: posted by Ayhan Sirkeci (sirkecia) on Wed, Jun. 28, 2000, 03:17 Subject: exercise5-2

 Dear Instructor, In exercise5-2 I did specified 2m3 for the cleaner cell, however, it was your error that you specified 98%% ultimate recovery in the cleaner circuit for chalcopyrite though it was instructed 90%% in the exercise. When I chose 98%% as the ultimate recovery my results exactly matched yours. Furthermore, the maximum particle size seems to be 5 mm in your packed example, which is too coarse for flotation. Though particle size is not taken into consideration in the model, running simulation fails when max. particle size is chosen 5 mm.


Message No. 168: posted by Ayhan Sirkeci (sirkecia) on Thu, Jun. 29, 2000, 07:42 Subject: Assignment 2

 In assignment 2 how come the OSS of the primary jaw crusher is 90 mm while the max. particle size in the feed is around 300mm ? Are we supposed to obtain the work index for the building aggregate? What about the other parameters?


Message No. 171: [Branch from no. 168] posted by Instructor (mete6010) on Thu, Jun. 29, 2000, 09:32 Subject: re: Assignment 2

 See response to posting 169


Message No. 169: posted by Ayhan Sirkeci (sirkecia) on Thu, Jun. 29, 2000, 07:57 Subject: assignment 2 

Dear Instructor, 

Sorry for the question regarding OSS in assignment2. It was just my misjudgement. However, I still don't know the answer for the parameters


Message No. 170: [Branch from no. 169] posted by Instructor (mete6010) on Thu, Jun. 29, 2000, 09:31 Subject: re: assignment 2 

In all exercises for this course you can use default values for any parameters that are not specifically specified. MODSIM always supplies default values. In practice however you need to be exceedingly careful in your selection of parameter values if you wish to do valid simulations. The subject of parameter estimation has been raised by a number of participants and unfortunately we will not be able to cover this important topic in this course. Maybe next year we will offer in course on this topic. When selecting parameter values for the exercises we encourage you to explore the response of the simulation to variations in many of the parameters. The values that we specify should serve only as a guide to likely values for the conditions that are specified. These should get you started at a reasonable operating point from which you can explore many other possibilities.


Message No. 173: posted by Instructor (mete6010) on Thu, Jun. 29, 2000, 09:53 Subject: HELP Viewing stratification profile graphs 

Ayhan has experienced difficulty with viewing stratification profiles when using model SJIG. See bulletin board posting threads beginning at numbers 125, 155, 159 and 169 for a record of this saga. HAS ANYONE ELSE EXPERIENCED SIMILAR PROBLEMS? Has anyone else successfully displayed these profiles for either the jig or Reichert cone? We cannot reproduce his problem here so would like to know if this is more general than a specific machine problem.


Message No. 176: [Branch from no. 173] posted by Bertil Palsson (bpalsson) on Sun, Jul. 2, 2000, 12:16 Subject: re: HELP Viewing stratification profile graphs


 Dear Ayhan and Instructor, I can confirm the problem with the stratification profile. When I try to see the profile in Ex 4.3, I get an empty window (ModelGRP) and an error message "Program Terminated with exit code -1. Exit Window?" This happens both on my home PC and the office PC. My home PC is a Dell Latitude with 8 MB video memory (ATI Mobility), uses colour depth 16 bit and runs Windows 98 SE English. I tried reducing to 256 colors and got the same error. Also, after a clean reboot and not loading any other software. The office PC (Dell Optiplex GX1) has 8 MB video memory (ATI Rage Pro), uses color depth 16 bit and runs Windows NT4 Workstation SP5 English. The only reason to the problem I can think of is that I am not (and probably Ayhan too) using US English operating systems. So, what about those in the Australia and South America? I'm attaching a .PAK file with the troublesome flowsheet. On a second thought, has anyone else run MODSIM on Dell PC's with ATI graphics? /bertil


Message No. 177: [Branch from no. 176] posted by Instructor (mete6010) on Sun, Jul. 2, 2000, 12:36 Subject: re: HELP Viewing stratification profile graphs 

Thanks for this posting Bertil. Your attached job runs fine on my home machine and the stratification profiles plot properly. I'm running on a Dell Dimension XPS with 32MB NVIDIA geFORCE 4X AGP graphic card. Could you confirm that the particle size distributions display correctly. We have tried to reproduce this problem on a variety of machines here but have been unable to do so except for our one machine that runs Windows NT. We will keep at it but any other suggestions will be appreciated.


Message No. 178: [Branch from no. 177] posted by Bertil Palsson (bpalsson) on Sun, Jul. 2, 2000, 15:50 Subject: re: HELP Viewing stratification profile graphs 


Peter, Particle size distributions do not plot. I'm getting an error message "Unable to plot size distribution for stream 1" and then for the other streams. This results in a white screen with only the red text in the upper left corner "Space bar: continue F3: create ESPI file". If I then press the space bar I get a program failure (illegal operation), and the OPGRAPH routine shuts down. See attached error dump. /bertil


Message No. 179: [Branch from no. 178] posted by Instructor (mete6010) on Sun, Jul. 2, 2000, 18:03 Subject: re: HELP Viewing stratification profile graphs 

This is an unrelated problem. You were probably trying to plot size distributions when the number of size classes was set to 1. This was the case with your job 4-3. Even so OPGRAPH should have shut down gracefully without an access violation. It normally does under these circumstances. Could you try this again and let us know what happens.


Message No. 182: [Branch from no. 179] posted by Bertil Palsson (bpalsson) on Mon, Jul. 3, 2000, 04:28 Subject: re: HELP Viewing stratification profile graphs 

Peter, I have again tried to plot the size distributions. Same problems; no stratification plot or particle size distributions. Come to think about it, you seem to imply that the failure to plot the particle size distributions is a desirable error condition, but the program exits with the wrong error code? I checked on my office PC, and there it informs me that it is unable to plot, and when I continue it closes down without any error dump. I noted that when I opened the .PAK file on my office PC and went into the editing routines I got the message "An error has occurred when loading washability data". Also, the first time I try to edit Unit model parameters there is no unit found. It reappears after saving the job. So, there is something odd with using one size class and washability data. Just to make sure, I installed MODSIM on an old stand-alone HP Vectra with 1 MB video-memory running Win95a, and got the same errors. I leave it for now, and continue with the other Exercises in Module 4 and 5. Am I the only one having problem catching up with the work-load? /bertil


Message No. 187: [Branch from no. 182] posted by Instructor (mete6010) on Mon, Jul. 3, 2000, 13:01 Subject: re: HELP Viewing stratification profile graphs

 Exercise 4-3 was set up for simplicity without any size distribution in the feed. The number of size classes is set equal to 1 on the main system data a form. Consequently there is no size distribution data to plot. Modsim correctly informs you of this and shows just a blank sheet with no graph. It can not even plot axes because there is no size range available. You can just exit from this screen or hit the space key which will generate the normal exit code message. If you open a packed job that contains model SJIG, Modsim will not find the data for the jig model and you will get a message asking to specify model parameters if you run the job immediately. You will see that Modsim has lost the data because it will default to the BATJ model. This is a known bug which has been fixed for the next release. We have confirmed that this is not connected at all with the stratification graph problem. You are not alone in struggling keep up with the workload. In fact in submissions of assignments you are up there with the leaders. We would welcome any suggestions relating to making the workload more manageable. Have we specified too many exercises? We have tried to be careful to cover all the main types of unit operation. Remember that the course site will remain open for participants for 2 months after the end of the course and you will be able to use MODSIM for a long time into the future.


Message No. 183: [Branch from no. 177] posted by Keila Goncalves (keila) on Mon, Jul. 3, 2000, 06:08 Subject: re: HELP Viewing stratification profile graphs 

Dear instructor, I had the same problem with the exercise 4.3, I couldn't see the stratification profile, but the exercise 4.4, the Reichert cone, worked perfectly. I suppose it could be some problem with the entry of data, maybe we should try to start the exercise again, start a new job and so on. I happened to me in the exercise 7.1 and after doing the job again I could see all the curves. As soon as I have time today, I will do it and let you know if it worked. Regards, Keila.


Message No. 186: [Branch from no. 183] posted by Instructor (mete6010) on Mon, Jul. 3, 2000, 12:34 Subject: re: HELP Viewing stratification profile graphs 

Thanks for the posting Keila. Could you confirm that you saw the stratification profiles when running the Reichert cone job.


Message No. 180: [Branch from no. 173] posted by Le Huynh (lehuynh) on Sun, Jul. 2, 2000, 22:07 Subject: re: HELP Viewing stratification profile graphs 

Dear Instructor I have revisited exercise 4-3 and realised that I'm also experiencing the same problems, i.e. I cannot plot the stratification profiles and the particle size distributions do not plot. The error messages are the same as those described by Bertil. As far as I know, I have not had any problems with plotting in other exercises. Furthermore, my simulation results do not look anything like yours. I checked that all the entered information and values were the same. I get the same error messages in trying to open the stratification profile when I run your exercise downloaded from the internet. In a previous email, I have sent you my exercises. Could you please check to see if you're experiencing the same difficulties as I have described. Thanks! Le


Message No. 174: posted by Instructor (mete6010) on Thu, Jun. 29, 2000, 10:29 Subject: Module 7 exercises

 I've just added a couple of exercises in Module 7. These should be simple to complete and are designed to help you understand one of the important aspects of liberation simulation: texture.


Message No. 175: posted by Instructor (mete6010) on Thu, Jun. 29, 2000, 17:15 Subject: Parameters for grinding mills. Bond work index. 

Qi Liu sent the following message today which will be of general interest. "I used to use the Rowland's method to do rod and ball mill sizing. I wondered why in Exercises 6-1, 6-3 and 6-5 we used the Rowland's factor for open circuit ball mill when the actual circuit is closed? I used an open-circuit inefficiency factor of 1.2, assuming that the control sizes were the 80%% passing sizes. Also, could you tell me where we would find the model parameters, such as zeta, Beta, Gamma, delta, etc., for different types of ores? "


The use of the open circuit correction factor for the Bond calculation is not very useful in practice. It should indicate the power that would be required to produce the ball mill product ( which is coarser than the circuit product) in an open circuit configuration. Modsim does not calculate the closed circuit power requirement because it has no access to any data other than the unit feed and product when it writes the report file. The user must perform the Bond calculation for the closed circuit externally. The Herbst-Fuerstenau method has a distinct advantage in this respect because that model calculates the size reduction that is achieved with a given power input. The parameters for the selection and breakage functions must be estimated from lab batch milling tests using parameter estimation techniques. In the case of the Austin model these parameters must be scaled up according to his recipes while the parameters remain invariant with scale in the Herbst-Fuerstenau model provided that the ball size distribution does not change. Modsim provides good models that incorporates these scale-up features. See models HFSU and GMSU for ball mills.


Message No. 181: posted by Romina Perusin (rperusin) on Mon, Jul. 3, 2000, 03:11 Subject: Exercise 6-5 


 Dear Instructor, I have some problems with the exercise 6-5 (only with it). I have seen the solutions for the exercises for module 6 that you have sent on monday. I cannot reproduce your solution and all the data seems Ok. My simulation does not complete successfully and MODSIM writes: "Allowable number of iteration exceeded". I have attached the file. The run is successful if a put larger cyclone (100 cm instead of 76). Thank you Romina


Message No. 202: [Branch from no. 181] posted by Instructor (mete6010) on Wed, Jul. 5, 2000, 21:47 Subject: re: Exercise 6-5 

This simulation does indeed converge slowly but inspection of the DLL diagnostic file reveals that it is converging. Allowing more iterations - achieved simply by starting the simulation again from the previous end point - allows it to converge to the required tolerance. Anyone can download Romina's attachment to try this.


Message No. 184: posted by Svetoslav Nikolov (snikolov) on Mon, Jul. 3, 2000, 07:24 Subject: Selection, breakage f-s for bauxite

 Hi everyone, I'm looking for the parameters of the selection and the breakage functions for bauxite used in the MILL models. If someone has the refs for such data, I'll be grateful if he(she) let me know. Sveto


Message No. 185: [Branch from no. 184] posted by Instructor (mete6010) on Mon, Jul. 3, 2000, 12:31 Subject: re: Selection, breakage f-s for bauxite 

It would be nice if someone has access to selection and breakage parameter values for bauxite. However if anyone has any data from the milling of bauxite let us know and we may be able to get some preliminary estimate of the parameters for Sveto. Data could be from laboratory batch tests or even some operating plant data.


Message No. 188: posted by Instructor (mete6010) on Mon, Jul. 3, 2000, 14:57 Subject: Viewing Stratification Graphs - PROBLEM RESOLUTION 

We have tracked this down. The problem arose with a misunderstanding between Claudio and I about which executables should be included in the software version for this course. The version that was actually included in the course distribution does no have the code segment to plot the stratification profile for the jig which certainly explains the problem that everyone has been having! Our apologies for that. 


 Our recommendation is that you do nothing at this time. You will not be able to see the stratification profiles for the jig but you can generate them for the Reichert cone. The jig profiles are in the description of exercise 4-3 for reference. The new release of MODSIM for participants will be available in 2 weeks and the correct executables will be included together with all the other fixes that we have implemented during the past seven weeks. If anyone is desperate to see the profiles now, let us know and we will send you a patch to fix the problem. Thanks to all who worked on this and posted messages about your experiences.


Message No. 189: posted by Romina Perusin (rperusin) on Tue, Jul. 4, 2000, 06:32 Subject: Exercise 8-1 

exercise8-1a.PAK  exercise8-1b.PAK

Dear Instructor, I have some problems with exercise 8-1. I think that the error is in the estimated parameter for the rod mill you provided: I have simulated in the attached file exercise 8-1a the behavior for the rod mill isolating it from the BM-CY closed circuit. The simulation completed not successfully and MODSIM writes "There was an unbalanced material flow around at least one unit". I have tried to change the value of the parameter mu; if mu is equal to 10 mm (exercise 8-1b) the solution completed successfully but (of course) the size distributions line does not fit well the points of the experimental data. Thank you Romina


Message No. 198: [Branch from no. 189] posted by Instructor (mete6010) on Wed, Jul. 5, 2000, 15:34 Subject: re: Exercise 8-1 

Several people have reported this problem. A new bulletin will be posted today. Romina's attempts at solving the problem were logical and this is a good example of how to try to diagnose problems. See the bulletin board for the solution


Message No. 190: posted by Ayhan Sirkeci (sirkecia) on Tue, Jul. 4, 2000, 07:35 Subject: exercises6-5, 6.6 

Dear Instructor, Why do exercises 6.5 and 6.6 give such different results from each other? If I obtain 1480 kW power draw in exercise 6.5 and use it in exercise 6.6 in Herbst-Fuerstenau model aren't I supposed to get similar results. The cyclone feed is, for example, 690 and 274 t/h respectively.


Message No. 201: [Branch from no. 190] posted by Instructor (mete6010) on Wed, Jul. 5, 2000, 18:34 Subject: re: exercises6-5, 6.6 

The weak point in this argument is the Bond formula to estimate the power drawn by a mill. It is not good enough to calculate any mill circuit that does not meet Bond's original specification of an 8ft ball mill operating with a 250%% circulating load. There has always been some doubt about the open circuit correction factors and how they should be applied. In addition there are the differences between the Austin model and the Herbst-Fuerstenau model. The parameters for these models must be estimated carefully from separate batch experimental data. Usually only one model is used but in recent years we have started to do both estimates from each experiment. The torque on the batch mill must be measured for the H-F model and this was not usually done in earlier research work. Unfortunately most of Prof Austin's data did not record the energy drawn by the mill so retroactive fitting of his data to H-F parameters is not possible. All of this again emphasizes the need for careful parameter estimates any time that you want to do real simulation work.


Message No. 191: posted by Keila Goncalves (keila) on Tue, Jul. 4, 2000, 13:17 Subject: Exercise 8-1 


Dear instructor, I had the same problem as Romina with the exercise 8-1. The simulation did not complete successfully and MODSIM returned the message: "There was an unbalanced material flow around at least one unit". I have tried the change of the parameter mu to 10 just as Romina did, but the simulation still did not complete and the message was the same as above. I have attached the exercise, so that you can help me to find my error. Thank you, Keila.


Message No. 199: [Branch from no. 191] posted by Instructor (mete6010) on Wed, Jul. 5, 2000, 15:38 Subject: re: Exercise 8-1 

Thanks for the posting Keila. I will post the solution on the bulletin board.


Message No. 192: posted by Instructor (mete6010) on Wed, Jul. 5, 2000, 08:12 Subject: Fourth of July holiday Yesterday was a big holiday here so we took a day off from responding to messages. Many participants were hard at work and we will try to clear the backlog of messages today.


Message No. 193: posted by Instructor (mete6010) on Wed, Jul. 5, 2000, 08:41 Subject: Showing experimental data on size distribution graphs

 Sveto ask the following. "I wonder whether there is a way to plot not only the experimental size distribution for the feed stream but also the data for the products of interest in order to compare the simulation with the experiment for both the feed and the products." Yes it is possible to display experimental size distributions on the same graphs as the simulated distributions. This is useful when trying to calibrate the models against your plant data. To do this double click on the stream number in the main system data form and enter the experimental size distribution data.


Enter the experimental data on the next form that displays.


This is covered in the exercise in module 8. It is important to understand that MODSIM makes no use of this information during the simulation calculation but merely displays it on the graphs.


Message No. 194: posted by Instructor (mete6010) on Wed, Jul. 5, 2000, 09:01 Subject: Water balance in gravity separation units 

Bertil sent the following comment. " All wet gravity units operate within rather narrow optimal volumetric solid concentrations. Despite that I see no consideration for the feed solids concentration in the models or any possibility to specify wt%% solids in the concentrate streams. I understand that a full simulation of the internal water balance is a huge undertaking. However, the possibility to specify wt%% solids in the concentrate streams, together with a simple water balance would improve the overall result. It is especially important in wet gravity circuits, where one often needs to dilute the concentrate streams to get them flowing, and most of the feed water goes with the tailings. If we then have several units linked together, one stage can really upset another. This is something I stress in the teaching of mineral processes. A good simulation makes it easier for the students to grasp the consequences of indiscriminate water addition." This is indeed a weakness in the modeling that MODSIM is currently using for gravity separators. The reason is that there is not much data available in the literature on the effect of pulp dilution on the unit performance and the disposition of the water in concentrate and tailings - or at least I am not familiar with it. It would not be difficult to incorporate this in the various models that have been included. Keeping track of the medium concentration in the medium recycle in dense-media plants can be a bit tricky. This issue is important for the reasons that Bertil mentions. This would make a good project for modules 9 and/or 10 if anyone is interested in developing some modeling ideas for the water balance in any gravity separator.


Message No. 195: posted by Instructor (mete6010) on Wed, Jul. 5, 2000, 10:09 Subject: Simple models in MODSIM 

Here is another suggestion from Bertil and we would like some opinions. "This is maybe a blasphemy in this course, but often I find that very simple models with fixed recoveries (splitters) give reasonable results in multi-unit simulations. It is in my opinion more important to get a correct water balance and circulation ratio, than to simulate a unit very accurately. So, if possible it would be fine to have the opportunity to select simpler models as a first step when setting up a circuit." 


 MODSIM used to have a number of simple models of the kind suggested by Bertil but I have taken these out over the years because they sometimes get abused. Users specify recoveries arbitrarily and then forget that they have done so and later simulations give misleading indications. This can be quite serious depending on the situation. Of course there are arbitrary features built into all the models that are used but I try to make the models evolve to reflect the best techniques that are currently available. The Academic and Professional versions of MODSIM do allow users to insert their own models into the black box icon. There is an example of a simple concentrator that is often used in the black box in section 10.7 of the User Manual.


Message No. 196: [Branch from no. 195] posted by Svetoslav Nikolov (snikolov) on Wed, Jul. 5, 2000, 11:26 Subject: re: Simple models in MODSIM

 In my opinion, Bertil is right and I have a very recent experience with that using MODSIM. Setting simple models for the complex units allows to calibrate the mass and flow balances and fix the parameters of the rest of the units as a first approximation. Once this is done, it is desirable to replace the simple models with more sophisticated ones. Using complex models everywhere and at once in a complex circuit with many parameters you don't know often leads to a simulation which don't work. Sveto


Message No. 197: [Branch from no. 195] posted by Keila Goncalves (keila) on Wed, Jul. 5, 2000, 13:37 Subject: re: Simple models in MODSIM

 I agree with Bertil, once the complexity of the models used depend on the phase of the project or even the objective of the simulation. At the beginning of a project, the only thing we have is the ore characterization. Simpler models would be very welcome to help us to get some idea about the dimension of the equipments needed to get the desired recovery, and the cost of the Unit. Keila.


Message No. 208: [Branch from no. 195] posted by Instructor (mete6010) on Mon, Jul. 10, 2000, 12:17 Subject: re: Simple models in MODSIM  


Bertil has submitted the attached document as an example of a situation in which a simple model would be useful in Modsim. We would be very interested in any comments on this application. Bertil's document is in MSWord format.


Message No. 209: [Branch from no. 208] posted by Ayhan Sirkeci (sirkecia) on Tue, Jul. 11, 2000, 02:32 Subject: re: Simple models in MODSIM

 The incorporation of such models in Modsim will be particulary useful when one wants to asses the performance of an operating plant or circuit without simulation using measurable data.


Message No. 211: [Branch from no. 209] posted by Instructor (mete6010) on Tue, Jul. 11, 2000, 11:27 Subject: re: Simple models in MODSIM

 There seems to be some support for simple models. Let's focus the debate a little bit. Can anyone offer a definition or description of a "simple model". Bertil's case might be a good example to illustrate your definition.


Message No. 212: [Branch from no. 211] posted by Ayhan Sirkeci (sirkecia) on Wed, Jul. 12, 2000, 05:07 Subject: re: Simple models in MODSIM 

*-A simple model should require as few parameters as possible 

*-The parameters must be easily measurable and definable.

 *-Simple models should provide results which are indisputable.


Message No. 213: [Branch from no. 195] posted by Svetoslav Nikolov (snikolov) on Wed, Jul. 12, 2000, 07:18 Subject: re: Simple models in MODSIM 

Let me cite the first comment in MODSIM user manual for the MILL model 'This is the simplest model for the ball mill using the selection and breakage functions'. I'm pretty sure that Prof. King didn't have in mind an academic definition for simple models when he wrote this comment. But nevertheless he and the reader intuitively know the meaning of this word. The MILL model is 'simpler' than the RODM model (it has 1 parameter less) but cannot reproduce the grinding with rod mills as accurately as the RODM model. In some sense, RODM model is the simplest 'good' model. Let us not enter in definitions requiring sophisticated speculations. Can you easily define beauty or intelligence? But nevertheless anyone uses these notions and 'knows' what they mean. Sveto


Message No. 200: posted by Instructor (mete6010) on Wed, Jul. 5, 2000, 15:47 Subject: Missing parameter for rod mill in exercise 8-1 

Romina (bulletin 189), Keila (bulletin 191), Sveto and Le (both by private e-mail) have pointed out that a parameter is incorrect in exercise 8-1. The offending parameter is the index that governs the decrease in transport velocity with particle size in the rod mill. Everyone is using the MODSIM default which in this case is too large (1.0). (The default has been reset in the next release). The value should have been specified in the data and is 0.11 for this rod mill. The data input form is shown below. 


As always, our apologies for the inconvenience.


Message No. 203: posted by Michael Pietrobon (mpietrobon) on Thu, Jul. 6, 2000, 03:03 Subject: ex44 crashing Modsim


I have attached ex44. I cannot run this file. It constantly causes the Modsim program to crash ? Other exercises have not done this up to now. I believe I have specified some parameter incorrectly, but which one ?


Message No. 204: [Branch from no. 203] posted by Instructor (mete6010) on Thu, Jul. 6, 2000, 17:38 Subject: re: ex44 crashing Modsim 

It certainly does crash! I have traced this to an error in a sorting algorithm in the code that solves the differential equations that describe stratification. Michael hit this because he inverted the order of the two minerals in the system data form.


This error has now been fixed for the next release. Meanwhile, if you are using the Reichert cone model, please enter the minerals in the order from least dense to most dense. This will avoid the troublesome algorithm. Thanks for drawing this to my attention.


Message No. 206: posted by Ayhan Sirkeci (sirkecia) on Mon, Jul. 10, 2000, 02:28 Subject: Different feed rates 

Dear Instructor, The flowsheets in assignment 1 contains two different flow regimes via a stockpile. Can Modsim handle two or three different feed rates in a single flowsheet? In assignment1-b, for example, while the crusher capacity is 1400 t/h, the rest of the plant treats 893 t/h material. Can we specify feeders to deliver material from a hopper so that different feed rates are possible?


Message No. 207: [Branch from no. 206] posted by Instructor (mete6010) on Mon, Jul. 10, 2000, 08:30 Subject: re: Different feed rates

 No Modsim cannot handle directly reducing total flowrates in the same plant. However there is a simple trick that can be used in the crusher flowsheets. Insert a stream splitter at the point at which the flowrate decreases and split out the required fraction of the flow. This serves the purposes well. Of course if the flowrate increases there is no problem since Modsim can easily handle additional feed streams. For every simulation Modsim finds a complete material balance.


Message No. 210: posted by Instructor (mete6010) on Tue, Jul. 11, 2000, 09:07 Subject: Singularity error when plotting graphs 

Several participants have hit a singularity error message when plotting graphs in Modsim. The error message is shown here.  

This happens if you try to plot a distribution with a zero size in the data. Remember that the logarithm of zero does not exist. The most common cause is a mismatch between the experimental data and the number of mesh sizes that are specified as on the form below.


The number of sizes specified must match the data. 15 in this case.


Message No. 214: posted by Instructor (mete6010) on Wed, Jul. 12, 2000, 11:24 Subject: Changing metal displayed in flyout

 The following query was submitted today. It will be of general interest. "I also have a question regarding the output format of minerals and metals in a flowsheet. In exercise 4-2 I would like to show silica grade in my flyout streams but cannot change/remove the existing CaO settings (from exercise 4-1). What is the correct procedure of removing existing settings to show the data for another mineral/metal or to include information on several metals/minerals?" The metal to display in the flyouts is specified on the output format form. The first column of the mineral-metal matrix is used.


Insert the metal that you want in column 1. All other columns that are filled will display in the output data.



Message No. 215: posted by Instructor (mete6010) on Wed, Jul. 12, 2000, 13:32 Subject: Taconite liberation simulation 

Romina had a go at the Taconite liberation simulation, and this exercise really sprung up some thinking on her. This is what it was meant to do in the first place. We had a good discussion about the problem afterwards and some of you may be thinking along these lines as well, so I decided to post this with Romina's permission of course. Here is the transcript, with Romina's comments in Italic (as appropriate in her case) I've read your assessment and I have some important comments. 

One can observe on the plot of the washability curve (liberation distribution graphs) of the cyclone u’flow that 25% of the material sent back to milling is made up of liberated valuable taconite (magnetite). This is undesirable but one cannot conclude that the circuit does not perform efficiently. Indeed if the magnetite misplaced is very fine there is little to do for its high specific gravity with respect the gangue. This information requires liberation plots size by size that is not available in my student version.  

Yes, one can only detect the presence of fine-liberated magnetite in the underflow stream by looking at the liberation plots in a size-by-size basis. In a future implementation, we plan to include 3-D graphs, such as the Andrews-Mika graph in mills, for each stream, making detailed liberation information literally graphic. 

I have tried to increase the size separation of the cyclone closing the circuit in order to recover more taconite to the o’flow. The sensitivity of taconite grade and recovery with respect to the cyclone d50 shows that at d50=200 (123) micron we can have a recovery of 85 (81) and a grade of 79 (83). Is this lower grade acceptable for down stream processing?  

This is the very essence of simulation. Only the engineers at the plant can make the economical assessment of grade/recovery changes in the grinding circuit and the impact of these changes in the bottom-line of the plant, given the current market value of the final product.

  However there is still a 20%% of liberated taconite to the underflow. This is because of the water recovery (short circuit) that keeps high the partition curve also for very fine sizes and the taconite is there in the fine sizes 70/120 microns.

  I do not believe short-circuit to underflow is significant here. In fact, I have never seen much short-circuit to underflow in any of the hydrocyclones that I have studied so far. On the other hand, short-circuit to the overflow stream is always significant.

  I have studied the possibility to substitute the cyclone with a screen: so that also the fine taconite will be recovered in the u’size that goes to further processing ! I have done so by setting to a low value the water recovery (short circuit to u’flow) and imposing a sharp classification (SI=1) and no variation of d50 with particle density. I have found that one can lower to 18% (down from the original 25%%) the amount of taconite to u’flow. 

That is the right conclusion. However a cyclone will always show a variation of d50 with particle density, and the cyclone you tested above only exists in the realm of simulation. This behaves much like a screen... 

However screening at circa 123 micron or so is a very risky process in plant practice and requires huge screening area. 

Right, but not impossible. One of the plants in Minnesota have converted one of their lines to screens instead of hydrocyclones, and reported an actual improvement in performance higher than what we saw in the simulation. (Their Taconite probably has different texture than the one studied here). This was possible because the Taconite industry has inherently a lot of practical experience with high-throughput, fine screening. Screens can be stacked in many layers, reducing the area required for the operation, and new mesh materials also require less maintenance. Nevertheless, they have changed only one line because on lack of space in the plant for more screen stacks. 

Probably two-stage cycloning (the u’flow of the first to the second and the 2 overflow together will do a better job but require another pump) and a very diluted slurry can do more or less the same. 

Here simulation is the right tool to help you understand the processes. We have tested this possibility, and quickly concluded that any combination of cyclones in series will make things worse. This is because the overall sharpness of the separation curve in a series of cyclones is higher than the one in a single cut. Here, the improved separation sharpness is with respect to both size and density. Screening remains the only alternative. Now that you understand this problem, here is a question for you to consider: Hydrocyclone separation by density is a problem restricted to the Taconite industry only?


Message No. 219: [Branch from no. 215] posted by Bertil Palsson (bpalsson) on Thu, Jul. 13, 2000, 10:59 Subject: re: Taconite liberation simulation 

Our instructor posted a question at the end of the comments on taconite liberation simulation. It was "Hydrocyclone separation by density is a problem restricted to the Taconite industry only?" No it isn't. In Sweden we have several plants that have included wet gravity units (Reichert cones, spirals, shaking tables) on the hydrocyclone underflow to bleed out fine size heavy minerals. The major minerals concerned are electrum (AuAg alloy) and Au-tellurides. They are recovered in a wet gravity concentrate together with pyrite and some galena. In this case, the hydrocyclone is a sort of pre-concentrator. Otherwise, the hydrocyclone density effect is well known in complex sulphide processing. We may have d50-values for sulphides around 70-100 micron and 150-200 for gangue minerals. This is, however, not necessarily a bad thing. It is then possible to get rid of gangue at a fairly coarse size, provided of course that we do not have fine intergrowths between sulphides and gangue. /bertil


Message No. 216: posted by Instructor (mete6010) on Wed, Jul. 12, 2000, 14:41 Subject: Error in Report File for Model SCR2 

Ayhan has pointed out an error in the report file for model SCR2. The area utilization factor is not reported correctly if more that one screen is used in parallel. The factor shown should be divided by the number of screens in parallel. The error is only in the report file and does not impact the simulation calculations which allow correctly for the parallel screens. The mass flows reported in the stream flyouts and the data file are correct. This error is fixed in the release of Modsim that is due next week.


Message No. 217: posted by Michael Pietrobon (mpietrobon) on Thu, Jul. 13, 2000, 01:39 Subject: Submit Ex 4

Ex41.pak  Ex42.pak  Ex43.pak  Ex444.PAK

please find attached my Ex 4 efforts. Thanks


Message No. 218: posted by Wayne Jacobsen (wjacobsen) on Thu, Jul. 13, 2000, 09:08 Subject: FYI Module 8 

At the end of Module 8, reference by a URL link is made for "project description". The link does not work. Regards


Message No. 220: posted by Michael Pietrobon (mpietrobon) on Thu, Jul. 13, 2000, 20:04 Subject: submit Ex 5 

ex51.PAK  ex52.PAK   ex53.PAK

My Ex 5 efforts.


Message No. 221: posted by Michael Pietrobon (mpietrobon) on Tue, Jul. 25, 2000, 02:42 Subject: Ex6.1 


In the notes, %solids values are specified for Ball mill and cyclone. I can't see where these are entered ?


Message No. 222: [Branch from no. 221] posted by Bertil Palsson (bpalsson) on Tue, Jul. 25, 2000, 06:13 Subject: re: Ex6.1 

Dear Michael, I take the liberty to answer your question since we are in the same time zone, and I know that Prof. King is very busy for the moment. You give the values for %%solids in a unit by specifying, either the water addition rate, or the %%solids for the water addition stream to said unit under the menu "Edit system data". Bertil Pålsson


Message No. 225: [Branch from no. 222] posted by Instructor (mete6010) on Wed, Jul. 26, 2000, 11:19 Subject: re: Ex6.1 

Thanks Bertil, you just saved me some precious time. I would like to appoint you as the official TA for the course. Claudio


Message No. 223: posted by Le Huynh (lehuynh) on Tue, Jul. 25, 2000, 22:14 Subject: Exercise 8-1 

Dear all Has anybody managed to get the 'correct' solids and water balance (as that specified) for exercise 8-1? If so, what value was entered for the water stream to the mixer and what was the cyclone geometry used. I have been stuck for the past few weeks with this. Any help anybody can provide will be greatly appreciated. Cheers Le


Message No. 226: [Branch from no. 223] posted by Instructor (mete6010) on Wed, Jul. 26, 2000, 11:42 Subject: re: Exercise 8-1 

Dear Le, Exercise 8-1 was derived from the ICRA 1995 meeting which contained a number of simulation challenges. I remember working this particular problem out but I used plenty of optimization techniques to get the best set of parameters. Getting parameters by trial and error, as suggested in the exercise is difficult, if you are just guessing. Try to be sly about it. Prof. King usually gets good parameters, wich are meaningful, much before I can finish my optimizations. Of course, the optimized parameters will generate an almost exact fit on the distributions that are being optimized, but sometimes with odd values for the parameters. In your place, I would try and vary the three calibration factors in the Plitt model for the cyclone, particularly the third factor has to do with flow split, thus regulating the amount of water in the underflow. Make sure all other geometry and operational parameters are in agreement with the specifications provided before you try this.


Message No. 228: [Branch from no. 223] posted by Bertil Palsson (bpalsson) on Wed, Jul. 26, 2000, 16:02 Subject: re: Exercise 8-1


 Dear Le and Claudio, I have also got the same problem. If I use the suggested parameters, I get a too low circulating load. It is of course, as Claudio pointed out, possible to tweak the calibration parameters to get the appropriate solution. Before I did that I took a close look at the data, and became a bit suspicious of the %%solid values. To my experience, they are on the high side if you are treating ores or rock materials with densities around 2.7. I therefore changed the ore density to 4.8. That in my opinion does better fit with the overall picture of the circuit. To my astonishment, the simulation produced exactly the same result as for the lower ore density. What I can see is that the hydrocyclone does not take into account the changed density of feed stream. The hydrocyclone model appears to work with a fixed density at 2700 kg/m^3. So, am I right in that the ore density should be in the range of 4.5 to 5.0? And is there something wrong with the hydrocyclone model? I'm attaching a simulation for density 4800 kg/m^3. /bertil


Message No. 229: [Branch from no. 228] posted by Instructor (mete6010) on Thu, Jul. 27, 2000, 13:22 Subject: re: Exercise 8-1 


Dear Bertil, I've checked your job and you are still running at 2.7 even though you've specified 4.8 g/cc and the data file shows 4.8 g/cc as the specific gravity of the phase. This problem had been detected before in module 4. When the density is changed to 4.8, the volume fraction of solids is reduced to .297. The resulting D50 falls to 125.3 microns, as expected, from 469.7 microns at 2.7 g/cc. To test this I've used Modsim 3.3 which is still in the oven. Maybe I should release a Modsim 3.3 alpha and make it available so that you , and your colleagues can contribute in debugging this swiftly. What do you think? Also, if you are interested in cyclones, there is a paper that we've submitted to the IMPC being presented in the poster section right this moment. If you read this you will understand the significance of the parameters in the bottom of the CYCL model form and that are derived from an extensive research program. I'm attaching a PDF of the paper.


Message No. 230: [Branch from no. 229] posted by Bertil Palsson (bpalsson) on Thu, Jul. 27, 2000, 14:45 Subject: re: Exercise 8-1 


Dear Instructor, Thank you for the .PDF-file with cyclone data, and the clarification that something is not quite right with the hydrocyclone model. As for the testing of Modsim 3.3 alpha, I would like to wait with it until I have had the chance to suggest a few more additions. My questioning of the ore density comes from my experience with hydrocylone sampling in complex sulphide circuits, and from our test station for small hydrocyclones. In none of these cases I have seen a properly working hydrocyclone with more than approx. 42 vol-%% solids in the underflow. With the given data, and for ore density 2.7, we get an underflow pulp density of 56 vol-%% solids. Using the supplied data, I estimate that d50c is about 270 micron, cf. the attached Excel-file with a hydrocyclone calculation. The calculated values are far off  from the simulated ones. It is possible to tweak the result from the simulation, so that simulated values coincide with the measured data. I would like to know, however, if we are supposed to use 2.7 for the ore density. /bertil


Message No. 231: [Branch from no. 230] posted by Instructor (mete6010) on Thu, Jul. 27, 2000, 15:39 Subject: re: Exercise 8-1

 Dear Bertil, The nominal density for the ore in exercise 8.1 is 3.3 g/cc. I see the data sheet in Module 8 doesn't contain this information, sorry about that. As for the testing of Modsim 3.3 alpha, I would like to wait with it until I have had the chance to suggest a few more additions. The time to make your suggestions is right now. I'm trying to get version 3.3 out before the end of next week, and this will be the final version made available in this session of the course. Also, I don't see major changes/implementations in version 3.3, since that type of work would generate a brand new set of bugs, requiring another round of testing and time does not allow for such undertaking at the moment.


Message No. 233: [Branch from no. 223] posted by Bertil Palsson (bpalsson) on Sat, Jul. 29, 2000, 03:33 Subject: re: Exercise 8-1 

Dear Le, There have been some postings about this, but none really answered your question. After looking at the basic data and doing a hydrocyclone calculation, I found that the cyclones were operating with a d50c (ca. 270 microns) much lower than the simulated one (ca 470). Therefore, if one enters a value of about 0.6 for the d50 calibration factor, we get a balance that is similar to the one set forth in the exercise. Some additional tweaking can get you even closer. /bertil


Message No. 224: posted by Jose Gomez (jgomez) on Wed, Jul. 26, 2000, 09:41 Subject: I need help......

Hi, everybody: I´m working in mining in mexico and I need to do the dense-liquid fractionation experiment for magnetite ore. I don't now which kind of liquid I can used, I need one with so high density around 3 - 4 g/cm3. I really appreciate if someone can tell me which liquid I can use. Thank you so much Jose Angel


Message No. 227: [Branch from no. 224] posted by Instructor (mete6010) on Wed, Jul. 26, 2000, 11:59 Subject: re: I need help...... 

Dear Jose, This is the very reason why image analysis is used instead of fraction. If you want to avoid image analysis at all costs, here is an alternative: there is a company called Geoliquids that offer colloidal solutions which they claim can reach very high densities. My experience with this has been disastrous, and we could not keep the solution stable long enough to get meaningful results. You may want to try it out anyway. Another alternative: diodomethane can be used for density separation up to 3.3 g/cc. It is expensive and very toxic. Barry Wills also mentions Clerici solution (thallium formate-thallium malonate solution) for densities up to 4.2, or even 5.0 g/cc at higher temperature, but I would much better use image analysis instead of these, since I'm not quite ready to sacrifice everything in the name of science. Claudio


Message No. 232: posted by Bertil Palsson (bpalsson) on Thu, Jul. 27, 2000, 17:03 Subject: Wish list and a bug report

 Dear Instructor, I begin a new subject here, since it not just related to Ex 8-1. I have earlier suggested that a simple separation model in the form of component splitters to be included in MODSIM. Along the same line it would be fine to have a very simple energy-related grinding model in MODSIM. It should be of the form W = constant*(Dp^-n - Df^-n), where Dp and Df are characteristic sizes of product and feed respectively, and n an exponent. One should have the opportunity to select the characteristic sizes as any Dxx, and give n-values in the range 0 to 2. The reason I want this is that in fine grinding of industrial minerals, the energy demand is closely related to the inverse of the median size, or really the increase in specific surface area. Also, the slope of the resulting particle size distribution needs to be entered. I have seen a few oddities in the handling of graphic output. We now know that it is possible circumvent the default storage of .ps file in the MODSIM program directory by pressing space and then doing a manual save to whatever directory and file we choose. Here, I would like to have the possibility to define a default temporary directory when installing MODSIM for the first time. On a second thought, it could be set up in an environmental variable. It is an important modification if one wants to run MODSIM in a PC-lab, and have the program itself residing on the server. I have encountered what I believe is a bug in the generation of EPSI-files. When we are plotting selection functions, stratification profiles etc., the resulting file gets the name Epsi0001. This is supposed to contain an EPS preview picture. Simultaneously a PostScript file with the name Psfile01 appears in the program directory. Both files have the same graphic information. But it is only possible to print out an EPS-preview generated by GhostView from the PostScript-file. The MODSIM EPSI-file causes our Postscript-printers (LaserJet 5M) to skip to the end of the document! The preview is shown correctly on the screen. I have noticed that the MODSIM EPSI-file is smaller than the GhostView-generated EPS-file. Has anyone else seen this? /bertil


Message No. 234: posted by Jose Gomez (jgomez) on Mon, Jul. 31, 2000, 12:01 Subject: my own project 

Simulacion 1.PAK

Hi everyone: This is my circuit of magnetite ore, This mine is on Colima Mexico, I have been Problems with the magnetic separation, I don't Know how I can find the correct parameter for simulate this operation, Could you tell me how I can get this parameters. I really appreciate this information. Thanks All Jose Angel


Message No. 235: posted by Instructor (mete6010) on Tue, Aug. 1, 2000, 19:47 Subject: Modsim 3.3 Beta 

I've just made available Modsim 3.3 Beta for download from the Software icon on the home page. This is still a beta version for several reasons: 1- It hasn't been tested thoroughly as any new release should be. 2- The manual is still the version 3.2 manual. 3- Some of the bugs, such as the problem with regional settings remain. As I won't have time to complete the full release before traveling (I'll be in Brazil for about 5 weeks, and am leaving 8/05) and since the remaining issues can only be addressed by Prof. King (still in Europe), the full release may be made available only during the second half of September. There is also a possibility that this will be the final release for registered students in this session, so I won't recommend anybody wait 'till September to get it. Also, bug reports for Version 3.3 will be much appreciated. Finally, I'll still be somewhat active and responsive to course issues during my stay in Brazil. (Thanks to the internet) Claudio


Message No. 237: [Branch from no. 235] posted by Bertil Palsson (bpalsson) on Thu, Aug. 3, 2000, 13:49 Subject: re: Modsim 3.3 Beta 

Thanks for the Beta version. I really like the possibility to get more information about a stream by clicking on it. May I ask for some more? It would be fine to also have the calculated solid density and pulp density of the stream. They are there already indirectly, through the vol-%% solids and pulp volumes, but a direct measure is always handy. /bertil


Message No. 236: posted by Bertil Palsson (bpalsson) on Wed, Aug. 2, 2000, 03:31 Subject: Module 9


 Dear all, As part of my own project I've tried to simulate a rod mill - pebble mill circuit, but I cannot get it to work. What I've found so far is that the problem seems to be in the FAGM model I use to model the pebble mill. To try understand this model I created a circuit with only the pebble mill, but it still doesn't work. Check the attached PAK-file. Since I don't have any breakage data for this ore, I've used the default values. What I changed was the residence time in the mill (18 min), the grate opening (2 mm), and the attrition size (1 mm). /bertil


Message No. 238: posted by Bertil Palsson (bpalsson) on Sat, Aug. 5, 2000, 04:18 Subject: Bug report MODSIM 3.3 Beta

 When outputting a PostScript file from "View - Size distribution graphs" only the first curve is plotted correctly. The others seem to be scaled off the plot with a factor two at least. The on-screen graph is OK. Postscript files generated from "View - Liberation distribution graphs", selection plots, bed stratification plots are not affected. Has anyone else seen this? /bertil


Message No. 239: posted by Wayne Jacobsen (wjacobsen) on Thu, Aug. 17, 2000, 09:53 Subject: My Project for Lesson 9 

A consulting firm has studied our existing Greens Creek Mill in Alaska for processing massive sulfide (pb,zn,ag,au), and recommended changes to the screens and cyclones, among other things, to increase throughput rate from 1600 tpd to 2400 tpd. I'm going to attempt to simulate the existing SAG, BM, Sieve Bend and Cyclone circuit, then simulate the proposed changes. I'll keep you posted.



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