Research On Enhanced Leaching Of Low-grade Vanadium-bearing Stone Coal By Additive

Vanadium-bearing stone coal is a unique vanadium resource in China.Because of its low vanadium grade and complex vanadium occurrence,the vanadium extraction process has some problems such as high energy consumption,high acid consumption and low recovery.It is of great significance for the development of vanadium industry to carry out research on clean and efficient vanadium extraction process.In this paper,based on the technology of full wet extraction of vanadium,the study of vanadium extraction from stone coal in Shaanxi Province was carried out.The optimum leaching scheme was determined by orthogonal test.The control steps were determined by dynamic analysis method.The extraction process parameters of the leaching solution were preliminarily explored.The results are as follows:(1)By comparing the leaching effects of several kinds of leaching additives on the vanadium-bearing stone coal,it is found that Na F can effectively improve the leaching rate of vanadium.The single factor test of enhanced leaching showed that:Leaching temperature,leaching time,sulfuric acid concentration and leaching additive dosage are positively correlated with vanadium leaching rate.The optimum parameters of leaching were obtained by orthogonal test analysis:the leaching rate can reach 92.26%,under the conditions of leaching temperature 90?,leaching time 75 min,sulfuric acid concentration 20%,leaching additive dosage 1.5%of the sample mass.Among the factors,the dosage of leaching aid is the most significant factor.(2)The kinetic study shows that:The initial stage of leaching process(30 min before)was controlled by chemical reaction.This process conformed to1-(1-?)~13=kt+b.The relationship between chemical reaction rate constant and reaction temperature was as follows:ln k=-45.5256/T–4.3030.The apparent activation energy was 45.5 k J/mol.The control model of the middle and late stage of leaching process(after 30 min)was transformed from chemical reaction control to diffusion control or mixing control.(3)The extraction test showed that:The unreduced leaching solution was affected by the content of trivalent iron,which led to obvious co extraction of vanadium and iron.After reduction by reduced iron powder,the extraction rate of iron decreased effectively.The optimum extraction conditions were obtained by:the pH of aqueous phase was 1.6,the ratio of extractant was 20%P204+5%TBP+75%260 solvent oil,the ratio of organic phase to aqueous phase was 1:1,the contact time of single-stage extraction was7 min.Under this condition the extraction rate of vanadium was 99.19%,and the extraction rate of iron was 6.48%.The results of this paper provide basic data and parameters for the development and utilization of the vanadium ore in Shaanxi Province,and have certain reference value for the utilization of low-grade vanadium ore resources.