Simulation optimisation

Over the past decade there has been a significant advance in flotation circuit optimisation through performance benchmarking using metallurgical modelling and steady-state computer simulation.

This benchmarking includes tradi­tional measures, such as grade and recovery, as well as new flotation measures, such as ore floatability, bubble surface area flux and froth recovery.

Such circuit optimisation is a powerful tool in achieving flotation performance.

To further this optimisation, Outotec has released its HSC Chemistry soft­ware with simulation modules.

There are several ways to bench­mark your flotation circuit, includ­ing mineralogical assessment; metallurgical assessment of performance and performing plant surveys; froth carry rates, concentrate lip loadings and flotation cell residence times can also be determined.

The results from these studies can then be used to calibrate a floatabil­ity component model of the circuit.

The flotation model developed by the AMIRA P9 Project, of which Outotec is a sponsor, is regarded by industry as the most suitable flota­tion model to use for circuit optimi­sation.

This model incorporates ore floata­bility with flotation cell pulp and froth parameters, residence time, ntrain
ment and water recovery.

Once the model is calibrated, it can be set-up in a flotation circuit simulator, such as Outotec’s HSC Sim
7.0.

The simulator is then able to predict the performance of the flotation circuit under various hypothetical changes to the operation of the circuit.

This can include changes to feed properties, flotation cell operating properties, and circuit configura­tion.

The latest version of HSC Chem­istry software, 7.0, includes further optimisations of existing tools such
as a steady state process simulator and flowsheet capabilities, along with further additions.

HSC Sim works in a number of stages, firstly through a flowsheet design, which is done graphically by
the user.

HSC also includes “check for error” tools to ensure various streams are properly connected to the units 
and the process has input and output streams.

The next stage is mass balancing the experimental data for the devel­opment of the model.

HSC Sim has a new experimental mode, which can collate, organise and visualise survey or laboratory data.

A “Mass Balancing and Data Reconciliation” module is included and has the following features: Indi­vidual sampling error for each stream and general or individual error model for each measurement 1D (unsized), 1.5D (sized but no assays) and 2D (size-by-size assays) mass balancing; various regression options such as least-squares regression; versatile visu­alisation tools such as parity charts and stream tables and mass balance reports.

Calibration comes next and includes elements such as global mineralogy and feed streams (grades and flowrates).

The simulator element of optimi­sation is then ready to run.

In simulation you can select the best matching mineral or add your own minerals into the database.

It is possible to set-up HSC so that each person at a site uses and shares the same database on the local network.

It even has a versatile tool for auto­matically converting elemental assays to mineral grades.

As mineral processes do not treat minerals, but particles of different sizes and different compositions, it is important the software is designed on that basis.

An operator can select 5 different minerals in 5 size fractions, with 3 different behaviour types for each
mineral, and HSC will create 75 parti­cles (mineral x size x types).

Particles have global properties like size, specific gravity and compo­sition and each unit uses these parti­
cle properties to determine what to do with each particle.

A structure based on particles allows you to load your liberation data from a mineral liberation analyser
(MLA) into the simulator and simu­late the process with true (measured) particles.

In the highest level, i.e. with true particles, you can have very detailed information on your process losses
and impurities.

At particle level you can simulate scenarios like:

• How will the change in grind influ­ence the metallurgical performance of the plant?
• How will change in liberation influ­ence the metallurgical performance of the plant?
• How will the concentrate quality change if we target to reject/accept some of the minerals?

Steady-state simulators can be used for tasks including circuit diag­nosis, process bottle-neck identifica­
tion, ascertaining the effect of various parameters on metallurgical perform­ance and sizing process units prop­erly.

Outotec’s HSC Sim enables you to simulate mineral processes in differ­ent levels, from comminution circuits with sizes and no composition, through to flotation processes with minerals by size by floatability components, to full processes with true particles with MLA data.

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