Experiment On The Vanadium Extraction Process By Interim Product With Sulfuric Acid Leaching From Ash Of Stone Coal

Vanadium has got the extensive application in national defense, metallurgy, chemical and medicine, which leads to the rapid progress of vanadium products price and rapid development of vanadium metallurgy. However, the overseas vanadium throughout is restricted by the resource and technology, the output of vanadium products cannot get greatly raised. As for home market, the output is restricted by the output of iron product. Stone coal is another important mineral resource of vanadium in china..But it is difficult to get full use of the low grade stone coal. In order to fulfill the market demand of vanadium products, it is necessary to develop new technique to extract vanadium from stone coal.There have been so many process for vanadium extraction from stone coal. Due to environment pollution, low recovery rate and serious waste of the resource, clean and efficient process seldom appeared. Comparing and analyzing these existed vanadium extraction process, we propose a new process to extract vanadium from low grade stone coal:vanadium extraction by interim product with sulfuric acid leaching from ash of stone coal. It contains:acid leaching by sulfuric acid, aluminum ammonium sulfate crystallizing from leachate, interim product crystallizing, interim product dissolved by water, solvent extraction, back extraction, vanadium precipitation by ammonia and pyrogenation to be vanadium pentoxide.In the leaching phase, high concentration sulfuric acid is used to be leaching solution. The optimal operation conditions are as followed:the concentration of sulfuric acid is 6 mol/L, the leaching temperature is 115℃, the leaching time is 4 hours and the ratio of L/S is 3:1. With these conditions, leaching efficiency is 85.52%. The leaching kinetics of vanadium pentoxide is approached. The result shows that the diffusion through the solid film is the main limited step. Vanadium leaching efficiency is affected by temperature greatly. Aluminum ammonium sulfate crystallization method is proposed to remove the voluminous Al3+ in leachate. The optimal operation conditions are as followed:the concentration of aluminum sulfate is between 150 and 200 g/L, the molar ratio of ammonium to aluminum is about 1.2, cooling rate is about 15℃/h and the crystallization temperature is about 5℃。With the optimal operation conditions, the crystallization efficiency of aluminum ammonium sulfate is 89.52%, the concentration of aluminum sulfate in leachate is just about 5 g/L.In this research, interim product crystallizing method is proposed to extract vanadium from high concentration sulfuric acid. The optimal operation conditions are as followed:crystallizing temperature is 140℃, sulfuric acid concentration is over 9 mol/L, addictive is C, and the coefficient is 0.3. With the optimal operation conditions, interim product crystallization efficiency is 96.72%. The concentration of vanadium pentoxide in the filtrate is just 0.37g/L. The filtrate is named back acid and it goes back to the leaching phase. The dosage of sulfuric acid can be reduced by 49%. The content of vanadium pentoxide in interim product contains is between 4% and 6%, as 3to 5 times of ash.Interim product crystal can be dissolved by water easily. The optimal operation conditions are as followed:temperature is 95℃, L/S is 3:1, dissolving time is 4 hours. With the optimal operation conditions, the dissolution efficiency is 99.63%. The solution of dissolving interim product is deoxidized and neutralized. After that, the solution is extracted by organic solvent. The next phase is back-extraction, oxidization, precipitation and pyrogenation. The purity of vanadium penoxide is 99.34%.The interim product process of vanadium extraction succeeds in lab scale experiment study. Totally recovery rate of vanadium is 82.80%. To check the rationality of operation conditions conclude from lab experiment and applicability of the process, pilot-scale experiment is presecuted after the lab scale experiment.700kg ash was leached in the pilot-scale experiment, operation conditions of pilot-scale experiment is the same as lab scale experiment. Pilot-scale experiment is divided into three phases:sulfuric acid leaching experiment, back-acid leaching experiment and from interim dissolution to pyrogenation experiment. Each phase lasts over 48 hours.2530.7g vanadium penoxide is the main product of Pilot-scale experiment. Technical achievement is comparative to the lab scale experiment. Totally recovery rate of vanadium penoxide is 81.46%. Results of pilot-scale experiment show that operation conditions of lab scale experiment are feasible for large scale experiment. It provide dependable reference to the industry manufacture.In this research, interim product is researched by chemical analyze, SEM-EDS analyze, XPS analyze, XRD analyze and etc. for its chemical composition and phase composition. Result of all kinds of analyze show that the phase composition of interim product are K1.11V3O8, (NH4)(FexV1-x)(SO4)2, (NH4)Al(SO4)2, (NH4)Al(SO4)212H2O. Quantification analyzes shows that the content of K1.11V3O8 in the interim product is just 1.23%. So, interim product is named by complicated ammonium salt of kinds of metal. Structural formula of it is (NH4)(AlxFeyVz)(SO4)2·nH2O, which the sum of x, y, z is land n is Oor 12. With the predigestion and hypothesis of chemical reaction of interim product, Chemical equation of interim product was proposed based on the result of all kinds of analyze. By means of empirical equation, thermodynamic parameters of interim product are estimated. Chemical reaction of K1.11V3O8, (NH4)(FexV1-x)(SO4)2 are calculated in the light of thermodynamic function of state Gibbs Free Energy.