Extracting Vanadium From Stone Coal By Oxidizing Acid Leaching And Vanadium Residue Comprehensive Utilization

The technology of acid extracting vanadium from stone coal was proposed for theshortage of existing process, which involves low leaching rate and low recovery, toxicsmoke and the environment pollution. The oxidizing acid leaching technology wasadopted to extract vanadium from stone coal. We found that the oxidants of nitrate andnitrite showed a prominent effect for improving leaching rate. Through the study onoptimum conditions of oxidizing acid leaching, ion exchange, sinking vanadium withammonium, we found that the leaching rate and total recovery had greatly improved.The gas pollution produced by roasting process was also solved.The main work and results wre as follows: Main compositions and phases in stonecoal were analyzed in this test. Valence state distribution of vanadium was preliminarydetected. We studied oxidant screening, oxidizing acid leaching, ion exchange andammonium sinking vanadium, including the effect of oxidant dosage, sulfuric acidconcentration, leaching temperature, leaching time and effect of solid-liquid ratio. Theoptimum conditions were obtained by orthogonal experiment. The saturated-staticadsorption capacity of SQD201exchange resin, effect of pH value and flow rate onexchange resin dynamic adsorption, effect of desorption agent concentration, desorptionagent flow rate, desorption agent dosage on desorption were also investigated. When pHwas8.0, the effect of ammonification coefficient (K) on precipitation rate wasdiscussed.The analysis results of stone coal sample composition showed that the minecontains1.2%of vanadium pentoxide and66.54%of silicon dioxide. Vanadium instone coal sample mainly exists in vanadium-containing muscovite. And we found thatit was difficult to extract vanadium from stone coal minerals. Based on the acid leachingtechnique, the synergistic oxidants were added to destroy structures of stone coal andleach vanadium ore. The result demonstrated that the oxidant greatly reduced theamount of sulfuric acid and the leaching rate of vanadium also increased greatly. Theleaching rate of vanadium leaching was affected by oxidant dosage, sulfuric acidconcentration, leaching time, leaching temperature and solid-liquid ratio. The bestleaching conditions of this experiment were as follows: sulfuric acid concentration of20%, nitrate dosage of1.5%, solid-liquid ratio of1:1, leaching temperature of95℃and leaching time of11h. Under these conditions, vanadium leaching rate could reachedto98.4%. when using nitrite as oxidant, the optimum leaching conditions were asfollows: acid dosage of30%, nitrite dosage of1%, solid-liquid ratio of1:0.6, leachingtemperature of100℃and leaching time of12h. And the leaching rate reached to94.9%. The oxidant could coordinated with hydrogen ions to damage the structure ofthe aluminosilicate and to oxidize the low-cost vanadium oxide into high-pricedvanadium. Thus, the leaching rate of vanadium was increased. In this leaching system, we used less oxidant and the leaching acid was reduced by60%. Therefore, it was aneco-friendly and economic leaching system. Five kinds of ion exchange resin D201、D201-7、D301、LF-30、SQD201were used in this experiment, through a selectingexperiments, we found that SQD201resin shows the best adsorption effect under acidicconditions. The best static adsorption capacity of SQD201was up to392mg/g. Whenthe flow rate was2BV/h, pH was2.0, the static saturation adsorption capacity was290mg/g. When NaOH concentration is1.5mol/L, parsing agent flow rate was3BV/h,the ratio of parsing agent volume and resin quality was6, depositing by ammonium salt,the decomposition rate reached to99.2%and the vanadium concentration of eluent wasup to36.5g/L. The processing conditions for ammonium chloride precipitatingvanadium at room temperature were pH of8.0, ammonium coefficient K of2.0, reactiontime of2hours. Under these conditions, this precipitating vanadium rate was99.2%.Calcining analytical solution by ammonium chloride vanadium ammonium at550℃V2O5products were obtained. All the main technical indicators reached ChemicalPowder Vanadium Standard of GB3283-87. Recovery rate of vanadium reached to83.08%. The precipitated silica was prepared by calcining acid leaching residue t750℃. The optimum leaching conditions are as follows: sodium hydroxide concentration of6mol/L, solid-liquid ratio of1:5, leaching temperature of95℃and the reaction timeof4h. The production rate was72.7%and the products coincided with industrystandards.