Experimental and theoretical evaluation of zinc recovery from zinc oxide ore: process optimization and simulation using Aspen Plus software

In the present study, the production process of zinc sulfate from the zinc oxide ore was experimentally investigated. The effect of main operating condition such as weight ratio of sulfuric acid to zinc content of ore (H2SO4/zinc), leaching temperature (degrees C), stirring speed (rpm), leaching time (min), particle size (mm), solid to liquid ratio (pulp density, wt. %), additives amount (kg/m(3)) and leaching pH on dissolution process of zinc oxide ore in H2SO4 solution were evaluated. Taguchi method and Aspen Plus software were used to determine the optimum condition and simulate the production process of zinc sulfate. Also, Aspen Plus software was used to determine the efficiency of zinc sulfate production. The experimental factors and their levels were as follows: 0.937-1.875 for the weight ratio of sulfuric acid to zinc content of ore, 50-80 degrees C for the leaching temperature, 100-400 rpm for stirring speed, 30-120 min for leaching time, 0.01-10 mm for particle size, 10-40 wt% for pulp density, 10-50 kg/m(3) for additives amount and 1.4-2 for solution pH. The optimum condition was found to be H2SO4/Zinc ratio, 1.25; temperature, 70 degrees C; agitation rate, 200 rpm; leaching time, 30 min; particle size, 1 mm; pulp density, 10 wt%; additives amount, 30 kg/m(3) and pH, 1.8. The most effective factors for maximizing the dissolution of ZnO in H2SO4 was the leaching pH. The predicted results by Aspen Plus simulation indicated that the total efficiency of zinc recovery at optimum condition is more than 97%.