| Our country is rich in stone coal resources, and consequently vanadium extraction from stone coal is of great economic value. The traditional vanadium extraction processes are of high energy consumption, great greenhouse gases emissions and serious environment pollution. The hydrometallurgical process of vanadium extraction can effectively avoid greenhouse gas emissions and reduce pollution, but at present, the process has its shortcoming, such as small leaching velocity and low recovery. On the other hand, it is increasingly difficult to extract vanadium from stone coal. Therefore, the development of vanadium extraction process with high efficiency and low emission, especially vanadium extraction process from refractory stone coal, are of great significance to environment protection and comprehensive utilization of mineral resources. In this paper, leaching dynamics, strenthening leaching process of refractory stone coal, separation of vanadium from leaching liquid with high iron concentration were studied; and pilot test was conducted on the base of bench experiment. The main experimental results obtained were as follows.Sulfuric acid leaching dynamics research showed that the leaching process was controlled by surface chemical reaction in the early stage, and activation energy was 103.26 kJ/mol. With the leaching process going on, siliceous residues appeared on the surface of stone coal particles. Sulfuric acid need diffuse through siliceous residues to react with internal vanadium compound, and the controling step of the reaction gradually transformed from surface chemical reaction controlled to solid membrane diffusion controlled.Electromagnetic field and additive were used to strengthen vanadium leaching. Research results showed that they can effectively strengthen vanadium leaching from refractory stone coal. The reason of electromagnetic field and additive strengthening vanadium leaching was that they can strengthen the destory of micas in siliceous residues, and vanadium in the micas was easier to be transferred to the solution. A new kind of heating device was designed, this device can generate alternating electromagnetic field when heating, the alternating electromagnetic field enabled vanadium leaching efficiency increase by 2% or so. The economic and reasonable leaching condition was:two stages countercurrent leaching process used, leaching time of each stage 4h, total consumption of acid 55%, fluoride addition 1.9%, temperature 95?, liquid-solid ratio 1:1, vanadium leaching efficiency can reach 83.27%. The leachate contained lots of impurities, such as iron and aluminum.Precipitating-dis solving method was used to purify vanadium leaching solution with high iron concentration. Results showed that:?enriching effect of direct precipitation with sodium carbonated was poor, and the filtration was slow.?precipitation containing 10%vanadium can obtained when reducing-precipitating method used. Leaching efficiency were about 59% and 69% respectively when the precipitate dissolved by sodium carbonated and sodium hydroxide. In a word, vanadium recovery was low when precipitating-dissolving method used.Solvent extraction with P204 can efficiently seperate vanadium from iron containing leaching solution. When phase ratio Vo:VA?1:1, solution electric potential about -100mV, pH 2.2, phase contact time 8 min,99% of vanadium entered organic phase after 4 stage extraction. When 1.5 mol/L sulphuric acid used as the stripping agent, phase ratio Vo: VA= 10:1, contact time 15min, stripping ratio reached 99% after 5 stages. The stripped solution was oxidized by sodium chlorate, adjusted pH value with ammonia solution to 1.5, and agitated at 95?for 3h, ammonium polyvanadate can precipitate, and precipitating ratio was 96.5%. Ion exchange process was used to recover vanadium from the mother liquid after vanadium precipitation, which can increase vanadium recovery.Treatment technology of wastewater generated in the process was studied. The ion exchange raffinate and other waste water containing ammonium can meet the discharge standard or be recyled after neutralization with lime, ammonia stripping and fold point-chlorodizing. While waste water not containing ammonium can meet the discharge standard or be recyled after neutralization with lime. Pilot test was conducted on the base of laboratory experiment. Technics process of the pilot test contained sulfuric acid leaching, solvent extraction, vanadium precipitation with ammonium salt, vanadium recovery with ion exchange process. Vanadium leaching was strengthened with the electromagnetic field and additive. The result showed that when acid consumption 18%, leaching strengthening agent addition 1.5%, total yield of vanadium pentoxide was more than 68%, each index of vanadium pentoxide reached GB3283-87 metallurgy grade 98. Compared with other traditional processes, hydrometallurgical process can reduce environment pollution, especially avoid greenhouse gas emissions. |
PDF Full Text Request