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Basic Study on Extraction Green Technology of Vanadium from Stone Coal

Author: WangNa
Tutor: DuJun
School: Chongqing University
Course: Chemistry
Keywords: Stone Coal Microwave-roasting Compound Additive Chemical Precipitation Green Vanadium Recovery Process
CLC: TF841.3
Type: Master's thesis
Year: 2010
Downloads: 244
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Abstract

Vanadium is the development of modern industry,modern science and technology of modern national defense and essential materials. Vanadium is an important strategic resource, has abroad application prospcets. China is a big country vanadium resourecs,mainly vanadium V(Ⅲ)andV(IV) occur in the form of stone coal, the traditional method of using sodium chloride roasting stone coal extracted from vanadium pentoxide,this process with a large quantity of emissions harmful gases C12 and HCl,serious pollution of the environment,while vanadium recovery rate of less than 50%, and a new technology to replace the traditional process, reduce pollutional and iomprove the utilization rate of resource is of great significance.Stone coal in Chongqing Xiushan is taken as the research object .vanadium recove- ry process from stone coal has been studied in detail by single-factor conditional experiment. According to its characteristics, the main process is determined as microwave-assisted roasting with additive– acid leaching- impurity removal by chemical precipitation-depositing vanadium with ammonium.This research is mainly focused on roasting, leaching, impurity removal and depositing vanadium.1.Technological research on roasting(1) SEM method and XRD method were used in analyzing the reaction mechanism of roasting progress. Comparison tests of microwave roasting and conventional roasting for stone coal were carried out to investigate the effects of roasting temperature, roasting time and amount and ratio of additives on vanadium extraction.The best preparation technology were: microwave roasting temperature is 750℃, roasting time is 3 h, the mixture of Na2CO3 and K2CO3(mass ratio of Na2CO3 /K2CO3=7:3) uses as the additive, vanadium leaching rate is 90.2%.(2) The size analysis indicates that the size fraction of <0.074 mm particles increases more than 10.0% after the sample is roasted by microwave for 3 h.。Vanadium ore can dilate and be liberated more sufficiently after absorbing microwave compared with the traditional method of using sodium chloride conventional roasting, using the method of microwave-assisted roasting with compound additives not only solve the problem of air pollution, but also synthesize to make use of resourced. And this method has an advantage of lower cost and less poliution.2. Technological research on leaching (1) Potential-pH equilibrium diagram of vanadium in aqueous solution was figured, and existence state and solubility of vanadium in aqueous solution was studied. Existence state of vanadium in aqueous solution is extremely perplexing, and under the condition of high potential and low pH, vanadium exists on the form VO2+ or VO2+ in aqueous solution.(2) Calcine is leached in solution of sulfuric acid solution and optimization of leaching condition has been confirmed as: liquid-solid ratio is 3:1, amount of sulfuric acid solution is 2 mol/L, leaching time is 7h,leaching temperature is 100℃, the leaching rate could reach 90.32%.3. The efficiency of the removal rate for harmful impurity ions in acid leachi ng solution was studied by experiment which used hydrogen peroxide and cupferron were used as screening agent and agent for removing impurities. The results indicate that when the hydrogen peroxide and the vanadium in the solution are in a mass ratio of fifteen,cupferron(1g/L)and the acid leaching solution are in a volumetric ratio of 1:8 and the pH of the solution is 7, a relatively thorough removal of harmful impurities can be realized,with the vanadium loss being only 16.82%,satisfying the requirement of the down stream vanadium extraction.4. The precipitation of vanadiumAmmonium polyvanadium ployvanadate can be directly precipitated through adding ammonium chloride. In the 25g/L of vanadium solution, the optimum technological condition of precipitating vanadium were determines to be: pH=5, coeffcient of ammonification K=2.5, temperature 90℃temperature 80℃and time 120min. The precipitation rate of vanadium was 99.22% and retrieving rate was higher than 80% .After roasted, the purity rate of products was 98.5% and they were achieved national standard(GB3283-87).

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