New HSC Chemistry software from Outotec incorporates a new simulation module that can assist with flotation circuit performance optimisation in flotation plants.
Optimising flotation circuit performance is difficult without addressing factors such as flotation plant operation, throughput, recovery and grade targets, feed mineralogy, metallurgical surveys or gas dispersion in individual flotation cells.
Over the past decade there has been significant advancement 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 the best possible flotation performance.
Flotation circuit benchmarking
There are several ways to do this:
- Mineralogical assessment of flotation streams: Determine the ore mineralogy, degree of liberation, mineral associations and locking at different particle sizes
- Metallurgical assessment of performance: Perform plant surveys to determine grades and recoveries of streams around the circuit in addition to froth carry rates, concentrate lip loadings and flotation cell residence times
- Comparison of plant to laboratory performance: Determine the maximum attainable recovery from the ore and compare this to current plant recovery
- Gas dispersion in each flotation cell: Determine the bubble size distribution, air hold-up, superficial gas velocity and bubble surface area flux
- Froth phase performance: Determine the recovery across the froth phase, froth stability and froth transport distances
Modelling and simulating flotation performance
The results from these studies are 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, entrainment and water recovery to the concentrate.
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.
The latest version of HSC Chemistry software, HSC Sim 7.0 includes further optimisations of existing tools such as a steady state process simulator and flowsheet capabilities.
HSC Sim 7.0 Capabilities
Stage 1: Flowsheet Design
The first stage of any flotation optimisation process is drawing the flowsheet, 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.
Stage 2 & 3: Mass Balancing and Calibration
For mass balancing the experimental data during 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 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, stream tables and mass balance reports
After determining the model parameters, calibration is done and includes elements such as global mineralogy and feed streams. The simulator element of optimisation is ready to run now.
Stage 4: Simulation
HSC Chemistry 7.0 has a mineralogical database consisting of over 4,500 different species and 13,000 different minerals.
One can, in simulation select the best matching mineral or add one’s own minerals into the database. HSC can be set up to enable each person at a site to use and share the same database on the local network. A versatile tool is also provided 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. With HSC, one 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 such as size, specific gravity and composition, and each unit uses these particle properties to determine what to do with each particle.
A structure based on particles allows users to load their liberation data from an MLA (Mineral Liberation Analyser) into the simulator and simulate the process with true particles.
In the highest level, i.e. with true particles, one can have very detailed information on specific process losses and impurities.
At particle level one can simulate scenarios such as:
- 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 some of the minerals are rejected/ accepted?
HSC Sim was used to design the flowsheet of the Esperanza copper-gold deposit in Chile. One particular task of the software was to understand specific benefits, if any that would result from the inclusion of a SkimAir flash flotation cell in the process cyclone underflows.
Using client laboratory testwork, the resulting elemental data was converted to minerals, and their pilot testwork data was mass balanced with models built using both laboratory flotation tests.
The simulation was established on a ‘mineral-by-size by floatability type’ level. Several different scenarios were simulated including circuit with and without SkimAir, number and type of rougher cells, flash cleaning, varying head grades and ore types as well as differing feed rates.
The use of software tools for the simulation of the flotation circuit is a major advance in flotation modelling and optimisation. Steady-state simulators can be used for tasks including circuit diagnosis, process bottle-neck identification, ascertaining the effect of various parameters on metallurgical performance and sizing process units properly.
Some of the more advanced simulation tools such as Outotec’s HSC Sim enable users 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 having measured liberation (MLA) data.
Additionally, experimental data can be collected, elemental assays converted to mineral grades, circuits mass balanced and data reconciled in mineral-by-size level. Different scenarios can be run with the process simulation, saving hundreds of man hours and preventing human errors in the process.