Low-grade High-silicon Oxide Zinc Pressure Leaching Tests

The processes of extracting zinc from zinc-oxide ore in China and overseas are summarized in this article. The processes include pyrometallurgical ones and hydrometallurgical ones. The main object of the study which deals with the low-grade high-silica zinc oxide ore with hydrometallurgical processes is the problem that how to improve the filtrating performance of the slurry produced by the leaching process. Most of the existing hydrometallurgical methods improve the filtrating performance through controlling the rate of adding sulfuric acid and the pH value.The pressure leaching technology has been used in the extraction process of zinc, uranium, molybdenum, copper, nickel, cobalt, manganese, aluminum and vanadium since it was brought forward. The pressure leaching can enhance the reaction velocity, so it makes many metallurgic processes advance though they cannot do under the normal temperature and pressure. Because it has the advantages of simple process, less investment, clean producing process and high metal recovery, it is hopeful to replace the traditional process of zinc producing.A process is expounded in this article. It deals with the low-grade high-silica zinc oxide ore with pressure leaching. It reviewed the effects of the sulfuric acid, leaching pressure, temperature and time on the leaching rate of zinc, silica and the filtrating rate. And it confirmed the best conditions of leaching.The best conditions are as followed, 20～22mL sulfuric acid/100g ore, the pressure is 0.8MPa, the temperature is 150°C, the time is 120min. And the results are as followed, the Zn leaching rate is about 98.5%, the SiO₂ leaching rate is 0.7%, the liquid producing rate isabout 1900 L·m^-2·h^-1, the residue producing rate is 320 kg·m^-2·h^-1.In the waste electrolyte leaching experiment, it obtained results of high Zn leaching rate and good filtrating performance. The results show that the pressure leaching on the low-grade high-silica zinc oxide ore can link up with the existing electrowinning process perfectly.