Zinc Calcine Immersed Slag Pressure Acid Leaching

The residues from the neutral leaching is a product from zinc calcine after neutral leaching. It mainly includes Zinc ferrite,zinc sulfate,zinc oxide,Zinc sulfide and other Valuable element such as:Pb,Ag,Cu,Cd,In, etc. And there is about 20%-30% Zinc in the residue. Generally, zinc calcine leaching process includes neutral leaching, low acid leaching and high acid leaching. Iron would be dissolved into the solution during process which would make reject of iron difficulty. Meanwhile, lots of problems such as:long process,increases cost and environmental pollution and so on will come out during the process of removing iron.In this paper, by reference a large amount of mature and foresight processes in zinc metallurgy, the current research situation and thermodynamics and kinetics of treatment of neutral leach residue at home and abroad were analyzed and the traditional zinc hydrometallurgical and oxygen pressure leaching were combined. So as to simplify process and save energy.This experimental study is small-scale experimental which carried out oxidizing pressure leaching on neutral leach residue. At first, the influence of oxygen pressure, concentration of sulfuric acid, temperature, leaching time, mineral partical size, liquor/solid ratio and dispersing agent amount on leaching rate of zinc from neutral leach residue was studied. The optimum condition was obtained according to six group comprehensive experiment.The result showed that the optimum condition was as follows:oxygen pressure is 0.8 MPa; the concentration of sulfuric acid is 90g/L;temperature is 150℃; leaching time:80min; mineral partical size:-320 mesh; liquor/solid ratio:3:1; dispersing agent amount:0.15%. Under this condition the leaching rate of zinc from run of mine and grinding ore was 93.33%(The mineral with not grinding process),98.71%(The mineral with grinding 20 min); the leaching rate of iron from run of mine and grinding ore was 36.35%(The mineral with not grinding process),48.89%(The mineral with grinding 20 min). After the optimum condition pressure, the dregs contains the zinc quantity is 1.4%-1.7%(The mineral with not grinding process),0.27%-0.35%(The mineral with grinding 20 min).Slag containing low zinc quantity, so that can reduce the difficulty in depleted tailings.The process of neutral leach residue oxygen pressure leaching was discussed under experiment. Meanwhile, the flow charts of oxygen pressure acid leaching was drew. Oxidizing pressure leaching is not only improving Zn leaching rate and reducing Fe leaching rate but also decreasing production cycle and improving the environment, which is a reference for Semi-industrial and industrial test in future.