(Session 3)Modelling of an autoclave used for high pressure sulphuric acid/oxygen leaching of first stage leach residue

摘要

Pressure leaching of the first stage leach residue in Base Metal Refinery (BMR) circuits aimsto achieve high base metal dissolution with minimal precious metal leaching. Optimumautoclave operation is challenging because of the complex leaching chemistry, varyingmineralogy of the feed material, and interaction between the different process variables. Thisresearch involved the modelling of the pressure leaching stages with flash recycle cooling at atypical BMR. The steady state solution employed the sequential modular approach inMATLAB, while the dynamic simulation involved the simultaneous solution of a set ofdifferential equations, derived from mass and energy balances, in MATLAB. The model allowsthe prediction of the operating temperature and the slurry composition in the differentautoclave compartments as a function of pressure, feed rates, and the flow rate of the flashrecycle stream. The dynamic response of the temperature and stream compositions to changesin the abovementioned process variables can also be predicted. It has been illustrated howinterdependencies between process variables can be determined and an improvedunderstanding of the process can be developed by means of the process model. The importanceof controlling the relative leaching rates of digenite and covellite to minimise precious metalleaching, for example, was illustrated by modelling the system behaviour at different operationconditions.