NaHSO_(4)焙烧-HCl浸出从白钨矿中提取钨的工艺研究

Tungsten Extraction from Scheelite by NaHSO_(4) Roasting-HCl Leaching

国内普遍采用碱分解-离子交换法处理白钨矿,但存在危废量大、废水量大、生产成本高的问题,严重制约了中国钨冶炼行业的可持续发展。在大量白钨焙烧分解工艺研究的基础上,结合硫酸氢钠焙烧分解白钨的发现,提出白钨矿硫酸氢钠一步焙烧转型的冶炼新思路。结果表明,白钨矿经硫酸氢钠焙烧分解后,产物主要为WO_(3),Na_(2)SO_(4)和CaSO_(4);在NaHSO_(4)·H_(2)O用量为理论用量的2.5倍,焙烧时间为2.5 h,焙烧温度为650℃的条件下,白钨矿中99.5%的CaWO_(4)转型为WO_(3);焙烧产物采用盐酸浸出法,在盐酸浓度为3 mol·L^(-1),浸出时间为60 min,盐酸溶液与焙烧产物液固比15∶1,转速为300 r·min^(-1),浸出温度为90℃的条件下,焙烧产物中的CaSO_(4)脱除率达到98.04%,产物中的WO_(3)由28.95%富集到95.23%,酸浸产物杂质主要为少量SiO_(2)与CaSO_(4);酸浸产物经氨溶、除杂、蒸发结晶后获得合格的零级仲钨酸铵(APT)产品,工艺解决了浮选药剂难题,产生的CaSO_(4)渣无毒无害,无需离子交换,技术经济环保,实现了白钨矿的绿色综合利用。

The alkaline decomposition and ion exchange process was widely used to treat scheelite in China,but there were some problems such as a large amount of hazardous waste,a large amount of waste water and high production cost,which seriously restrict the sustainable development of tungsten metallurgy industry in China.Especially after the"National Catalogue of Hazardous Waste"issued by the Ministry of Environmental Protection of the People's Republic of China in 2016,China's tungsten metallurgy industry was facing the dual pressure of economy and environmental protection.In this background,domestic researchers have developed Na_(2)CO_(3) decomposition-alkaline extraction,phosphorus salt-fluorine salt decomposition of scheelite and sulfur-phosphoric mixed acid decomposition of scheelite and other new processes,have made outstanding contributions to alleviating the production pressure of enterprises in the economic and environmental aspects.However,with the continuous consumption of high-quality tungsten ore,tungsten raw ore grade declined significantly,the amount of flotation reagent input in the beneficiation process increased,resulting in the increase of residual flotation reagent in concentrates,and the traditional alkali pressure decomposition process and the new process are all wet metallurgy process,there are risks to tank spillage,bring inconvenience to production.This paper continued the characteristics of roasting to solve the flotation reagent problem on the basis of a lot of researches on the roasting and decomposition process of scheelite,and put forward a new metallurgy idea of sodium bisulfate scheelite by one-step roasting,which was combined with the advantages of metallurgy slag decomposition of scheelite by sulfur-phosphoric mixed acid,convert CaWO_(4) into WO_(3) and CaSO_(4),and then deal with the roasting product by acid leaching-dissolve in ammonia-purification-evaporative crystallization to produce ammonium paratungstate(APT).In terms of experiments,muffle furnace was used as the roasting experimental equipment to heating the sample which is evenly mixed by scheelite concentrate and NaHSO_(4).After roasting,hydrochloric acid leaching was used to obtain WO_(3) enrichment detection.In terms of detection,X-ray diffraction(XRD)and Mineral Liberation Analyser(MLA),Process Mineralogical Parameter Testing System were used to characterize the roasting product.In addition,hydrogen peroxide-hydrochloric acid mixed solution was used to dissolve the residual CaWO_(4) in the roasting product,and then WO_(3) content in the solid phase was determined by ammonia tungstate burning gravimetric method which was compared with the MLA test results in order to accurately calculate the conversion rate of calcium tungstate in the roasting experiment.The results showed that the roasting products are mainly WO_(3),Na_(2)SO_(4) and CaSO_(4) after roasting and decomposition of scheelite by sodium bisulfate,and WO_(3) was mainly divided into two kinds of occurrence states of granular WO_(3) and micro-granular WO_(3),which were dispersed in the roasted products,and the other phases in the roasted products were mainly CaSO_(4) and Na_(2)SO_(4).A small amount of columnar Na_(2)SO_(4) was mixed in CaSO_(4) aggregate of plate-like crystal,and the gap was filled with Na_(2)SO_(4) and granular WO_(3),Na_(2)SO_(4) and CaSO_(4).The roasting process research showed that the roasting temperature,time and material proportion all had an impact on the decomposition of scheelite by sodium bisulfate roasting.WO_(3) conversion rate increased with the roasting temperature and time,and eventually tended to be stable.However,the amount of sodium bisulfate added should not be too much,because the water of crystal released by excessive NaHSO_(4)·H2O would lead to scheelite agglomeration during mixing,so that scheelite aggregates would form WO_(3) shells during roasting,which hindered the contact between inner CaWO_(4) and outer NaHSO_(4)·H_(2)O,resulting in the decrease of CaWO_(4) conversion rate.Under the condition that the dosage of 2.5 times of NaHSO_(4)·H_(2)O theoretical dosage,roasting time of 2.5 h,and roasting temperature of 650℃,99.5%CaWO_(4) in scheelite have been converted to WO_(3).The roasting products were treated with hydrochloric acid leaching.The hydrochloric acid leaching process showed that the leaching concentration,temperature,time,liquid-solid ratio and rotating speed were all favorable for CaSO_(4) leaching.However,the concentration of hydrochloric acid should not be too high,otherwise,calcium sulfateoccur ion association,tungsten and calcium separation effect would decline.Under the conditions of hydrochloric acid concentration of 3 mol·L^(-1),leaching time of 60 min,liquid-solid ratio of 15∶1,rotation speed of 300 r·min^(-1)and acid leaching temperature of 90℃,the removal rate of CaSO_(4) in the roasting products reached 98.04%.WO_(3) in the product was enriched from 28.95%to 95.23%,and the impurities in the acid leaching product were small amount of CaSO_(4) and SiO_(2).Acid leaching products were obtained qualified APT products after dissolving in ammonia-purification-evaporation crystallization.Compared with the traditional alkali decomposition process and other new wet processes,NaHSO_(4) conversion roasting process of scheelite got rid of the troubles of flotation reagents in the metallurgy process,CaSO_(4) slag was nontoxic and harmless,and could provide a green economy new technological prototype for efficient green utilization of scheelite with no ion-exchange.