LIME-CONCENTRATE PROCESS FOR ROASTING OF COPPER-BEARING SULFIDES .2. EFFECT OF SULFIDE - LIME RATIO, AIR-FLOW RATE, PELLET SIZE AND POROSITY ON REACTION-KINETICS

The air-roasting of pellets consisting of copper-iron sulphides and lime has been investigated to explore the possibility of developing a metal-production process that eliminates the emission of sulphur dioxide gas. The effects of pellet porosity, sulphide:lime ratio, air flow rate and pellet size on reaction rates and reaction products were investigated. A thermogravimetric technique was used under air atmosphere and the weight gain of a pelletized sample was used to identify and study the phases present in the reaction products. The experimental results indicate that at 500-degrees-C a completely reacted pellet can be produced in about 50 min with a very low emission of sulphur dioxide. The reaction products are primarily CaSO4, Fe2O3, CuSO4 and CuO.CuSO4, although some CaS may also be produced.