Study On Technology Of Extracting Vanadium From Stone Coal By Circulating Alkaline Leaching

Abstract:Vanadium-bearing stone coal is a unique vanadium resource in China. Aiming at the shortcomings of large reagent consumption and cumbersome process in traditional vanadium extraction process, this paper presents an efficient process of vanadium extraction. The process includes blank roasting, alkali leaching, vanadium precipitation with Ba(OH)2, hydrochloric acid leaching and refining of coarse product.(1)The results showed that vanadium in stone coal was leached easily when stone coal was milled to45-58μm, and roasted at850-900℃for2h. The leaching rate of vanadium reached87.83%when the calcine was leached by5%alkali solution at120℃for1h with liquid to solid ratio of2:1and stirring speed of300-400r/min. The alkali dosage was10%of ore weight and the alkali consumption was1.33%of ore weight.After extra alkali added, the alkaline leachate was recycled to leach the next batch of calcine. After six times circulatory leaching under the optimum conditions, the concentration of vanadium reached29.00g/L, while the concentration of silicon and phosphor reached37.03g/L and1.31g/L respectively. The average leaching rate of vanadium was80.68%. The average alkali dosage and the average alkali consumption were2.14%and0.44%of ore weight respectively. Compared with single time leaching, the alkali dosage and the alkali consumption was greatly reduced.(2)Ba(OH)2was used to extract vanadium in strong alkaline solution containing high concentration of silicon. With adding0.96times of the theoretical amount of barium hydroxide at90℃for settling time of1.5h, the precipitation rate of vanadium reached93.72%while the precipitation rate of silicon and phosphate were5.17%and56.22%respectively. The precipitation was mainly constituted of Ba3(VO4)2, accounting for93.63%. Adjusting alkali concentration of vanadium-precipitated solution to5%, the solution was recycled to leach calcine. The leaching rate of vanadium was up to83.51%under the optimum conditions obtained in the leaching process, which was close to the average leaching rate of vanadium80.68%during circulatory leaching.(3)The decomposition rate of Ba3(VO4)2was86.75%and the salg contained71.81%V2O5when Ba3(VO4)2was leached at90℃with liquid-solid ratio of2:1and theoretical amount of hydrochloric acid solution. Next, dissolving the coarse product in hydrochloric acid solution and adjusting pH to2.3by ammonia solution, the precipitation efficiency of vanadium reached98.70%at90℃for1h. After calcination of the ammonium polyvanadate, V2O5product with purity of99.20%was obtained.During the process mentioned above,3.29%of vanadium was leached. Therefore, N235was used to extract vanadium from the acid-leaching solution containing4.23g/L V2O5. The results showed that the extraction rate of vanadium reached99.68%using2%N235, pH value of2.5, O/A of1:2at ambient temperature for5mins. Stripping of vanadium reached96.92%with4mol/L NH3H2O, O/A of2:1at ambient temperature for10mins.