Research On Calcium And Vanadium Recycling From Vanadium Bearing Steel Slag

Due to high content of calcium and iron, low content and complex occurrence of vanadium, it is very difficult to recycle vanadium from vanadium bearing steel slag. During the traditional sodium-roasting vanadium extraction process, calcium and vanadium can generate calcium vanadate which is water-insoluble. When it comes to the vanadium extraction process of direct acid leaching, calcium and iron react with acid, which will increase acid consumption. In order to solve the above problems, this paper study on the calcium and vanadium extraction process by ammonium leaching and acid leaching from vanadium bearing steel slag. In the ammonium salt leaching calcium process, leaching agent of ammonium chloride can be recycled, which produce benefit in economy and environment. Leached calcium can be made into high purity of calcium carbonate by the method of precipitation, achieving the effective reclaim for calcium. In acid leaching vanadium extraction process, the roasting process is eliminated, so the pollution problem caused by the traditional sodium roasting is addressed. What is more, the new type leaching agent used in acid leaching can reduce the impurities content in the leaching solution for its high selectivity and the acid consumption.The ammonium salt leaching calcium experimental results show that:(1) It is more reasonable to use one-stage leaching process.(2) It comes to the appropriate conditions:CHN4Cl=30%, T=95℃,t=2h, L/S=4, particle size rang:48-74μm, stirring speed:200rpm.(3) Calcium carbonate is maded by precipitation method and its purity is99.826%, compared with the magnesium oxide plate its whiteness is95.7, and the average particle size is30.92μm, so it belongs to the ordinary light calcium carbonate. In the precipitation process, calcium conversion rate is94.91%.(4) In the experiment, leaching agent of ammonium chloride can be recycled. Not only saves the cost, but also alleviates the environmental pollution.Acid leaching vanadium extraction experimental results show that:(1) When a leaching agent A is used leaching, one-stage leaching process is more reasonable.(2) It comes to the appropriate conditions:pH=2.5, T=65℃, t=60min, L/S=4, particle size rang:48-74μm, stirring speed:300rpm.Results of ferric vanadate recipitation experiment show that:(1) In order to prepare ferric vanadate, the excess iron in acid leaching solution should be removed at first. The appropriate conditions for one-stage of removing iron are:pH=3.5～4.0, T=95℃, t=30min, stirring speed being100rpm. Under these conditions, iron precipitation rate can amount to60.74%, and vanadium loss rate is1.79%.(2) The appropriate conditions for two-stage of removing iron are:pH=4.5-5.0, T=25℃, t=10min, stirring speed being100rpm. Iron precipitation rate can amount to76.68%, and vanadium loss rate is5.57%.(3) Appropriate conditions for ferric vanadate precipitation are:pH=5.0～5.5, T=85℃,t=20min, stirring speed being100rpm. The final product contains ferric vanadate, irons hydroxide and vanadium oxide, which is similar to industrial ferric vanadate in composition.