Study On Flash Reduction Roastingprocess Of Zinc Calcine

In conventional zinc hydrometallurgical process, zinc ferrite is unavoidably produced during the process of roasting zinc sulfide concentrate and hard to be dissolved in low acid leaching. Large amounts of leaching residues are not only a loss of resource but also do harms to the environment. This study used the flash reduction roasting process for zinc calcine, made the material inside the flash calciner, so that its heat transfer from a traditional gas-solid-state heat transfer transformed into the suspended gas-solid heat transfer, and its suspended state gas-solid contact surface area greatly increased. By this way, material quickly gained high energies and calcination reaction completed in a short time, get the product of high rates of soluble zinc and low ferrous content. This provided protection for the subsequent leaching process to achieve selective leaching, so as to achieve separation of iron and zinc.The project was supported by the National High Technology Research and Development Program of China (2011AA061001). The zinc calcine reduction roasting system was thermodynamically analyzed, then studies on flash reduction roasting process were conducted by using the zinc cacline.The results showed:At the temperature range of1073Kto1373K, the reduction reaction of zinc ferrite can be carried out at a relatively weaker reducing atmosphere. When the system temperature reaches1223K, and the content of CO2is of30%, only0.023%～1.5%CO needs to make zinc ferrite reduction reaction occur and generate Fe3O4. To achieve the reduction magnetic roasting of Zinc ferrite and afford the product Fe3O4+ZnO, the most important point is to control a suitable reducing atmosphere that is the partial pressure ratio of CO2/CO, which values between20and1300. The reduction reaction of zinc oxide must be carried out at a relatively stronger reducing atmosphere, when the temperature is1473K, the partial pressure ratio of CO2/CO is3.23, when1373K, the partial pressure ratio of CO2/CO is9.77, when1273K, the partial pressure ratio of CO2/CO is35.48, and when1173K, the partial pressure ratio of CO2/CO is147.91. It shows that the reduction temperature which required decrease with increasing temperature. Gas-based reducing agent is conducive to flash reduction roasting, increased furnace temperature is c beneficial to reductive decomposition of zinc ferrite.The Decomposition rate of zinc ferrite reaches81.3%after roasted at furnace temperature1050℃, reaction tower temperature1200℃, top aerate CO concentration13%.Lower the furnace O2concentration is conducive to reduction of zinc calcine,it was required very low concentration of CO can gain the soluble zinc rate more than95%in the O2concentration0.5%.Top aerate adding some CO gas can be added the reducing atmosphere, the soluble zinc rate of roasting product reaches99.45%and after roasted at furnace temperature1000℃, reaction tower temperature1200℃, top aerate CO concentration13%.The furnace temperature was the most important influence factor for soluble zinc rate and Fe2+content of flash reduction roasting product,the reaction tower temperaturewas minimal impact on the soluble zinc rate,the influence of top aerate CO concentration was equal with the furnace CO concentration.The soluble zinc rate of roasting product reaches99.66%and Fe2+/TFe0.316after roasted at furnace temperature950℃, reaction tower temperature100℃, furnace CO concentration2500ppm, top aerate CO concentration7%. The number of figures28, the number of tables20, the number of references95.