Research On Extracting Vanadium From Stone Coal By Hydrometallurgy Method

Leaching Vanadium from stone coal by roasting with sodium salt in the traditional process would produce large quantity of Cl2, HCl, SO2 and other toxic gases that pollute the environment. What is more, the recovery of vanadium is low (about 40%). In this paper we focus on reducing pollution in the process and launched a salt-free roasting experiment, roasting stone coal with less polluting additives experiment and acid extraction experiment.Salt-free roasting experiment shows that the salt-free roasting-acid extraction method is not applicable to the Yiyang TAOJIANG stone coal. Optimal conditions is the temperature:750°C, roasting time:2 hours, the grain size:120 mesh, the extraction time:4 hours, the ratio of liquid to solid:5:1, the extraction rate could only reach 30%. Roasting with less polluting additives experiments show that the optimal conditions is adding 15% of the lime mud, roasting for 2 hours under 850°C, then mill the sample to 120 mesh, leaching vanadium by 5% sulfuric acid under the ratio of liquid to solid of 3:1 for 3 hours. The extraction rate can reach 51%. Stone Coal acid leaching experiment results show that the best condition is mill the ore to 120 mesh, leaching vanadium by 15% sulfuric acid for 2 hours under the temperature of 90℃, the extraction rate could exceed 50%.In the experiment of extraction vanadium(Ⅳ), By using P204-sulfonated kerosene under 6# mixture ratio, the optimal conditions is the ratio of oil to aqua:1:4,pH:2.5±0.1,time:10 min, extraction rate is 75%, vanadium extraction rate can also be greatly enhanced by using multiple extraction method, after extrating for 3 times, extraction rate can reach 98% or higher levels. Stripping rate can reach 99% by using 10% sulfuric acid solution under the ratio of oil to aqua of 5:1.After the extraction-stripping process, we can precipite vanadium in the form of poly-ammonium vandate by adding NH4VO3 to the solution. The best technology parameter were obtained by tests as follows:original concetration:18~21g/L,pH=5,K (ammonium coefficient) = 250,temperature:90°C, time:120min.Under these conditions the precipitaion rate is more than 97%, and the purity of the product is more than 98% which meets the state standards.