MODULE 7 Liberation

A liberation model for comminution operations can be used effectively when the model is based on the Population Balance approach. Two such models have been implemented in Modsim. The "ljubljana" model and the "beta function model". Both models describe the internal structure of the bivariate breakage function, a.k.a. the Andrews-Mika diagram. The ljubljana model is a clever conceptual model of the A-M diagram. Its main advantage is that it contains a single parameter that can be changed to describe a wide range of textures, and therefore simulate the liberation process. The beta function model on the other hand is based on careful observation of the liberation process in real ores. It contains a number of parameters that can be adjusted to provide an as accurate as possible description of the liberation process under almost all circumstances, including differential and preferential breakage. Both models are currently two-phase models, and one phase is invariably the gangue phase while the other is the phase of interest, the valuable. Although this may be seen as a limitation, it represents a tremendous improvement over assuming that liberation remains constant in comminution circuits.

Simulation of liberation is quite a complex subject. However, and fortunately, the interface implemented in MODSIM greatly facilitates the effective use of this rather advanced technology.

The details of the modeling of simulation and comminution can be found in Chapter 3 of the textbook and in Technical Notes 10


1. Learn how to specify liberation data for a binary ore feed stream in MODSIM.

2. Learn how to simulate the liberation process together with the size reduction process in a Ball Mill using a liberation model.

3. Learn to view and interpret liberation simulation results.

This module contains a single section:

Simulation of a closed continuous grinding circuit with concentration and classification of a Taconite ore.

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