锌冶炼过程中提取镓的技术研究及其进展

Research and prospect of gallium recovery technology in zinc smelting

  • 摘要: 针对镓从锌冶炼过程中回收占比低的问题,总结分析了锌冶炼过程中镓回收技术研究进展. 在鼓风炉炼锌(ISP)工艺中,镓主要富集在鼓风炉炉渣里,其质量分数通常在0.025%~0.031%,从鼓风炉炉渣中回收镓主要有还原蒸发法、高温氯化挥发法、硫酸浸出法、碱熔–浸出法、还原熔炼–电解法和还原熔炼–熔融造渣法等方法,但这些工艺普遍流程长,回收率低,加工成本偏高,部分工艺环境污染大,难以工业化应用. 传统的湿法炼锌工艺中,大于93.5%的镓富集在浸出渣中,浸出渣处理以火法还原挥发工艺为主,在回转窑挥发浸出渣工艺中90%的镓保留在窑渣中,导致镓的回收流程长且回收率低,湿法处理浸出渣存在镓和铁分离的难题,至今未得到有效解决. 氧压浸出炼锌工艺中,镓主要富集在锌粉置换渣里,锌粉置换渣采用酸性浸出和萃取工艺分离富集镓,最终制备金属镓,镓的综合回收率达到71%. 通过对火法和湿法炼锌中镓回收工艺进行分析,对镓回收工艺中存在的关键问题和分离技术进行了总结,提出萃取分离、乳状液膜和树脂吸附有望成为锌冶炼过程中回收镓的绿色高效短流程关键技术.

     

    Abstract: Gallium is an important dispersive metal with widespread applications in high-tech fields such as semiconductor materials, optoelectronics, and radio technology. Recently, the market demand for gallium metal has grown, given the continuous progress of science and technology. Gallium is primarily recovered as a by-product of aluminum and zinc metallurgy, accounting for approximately 90% and 10% of the total gallium production. The relatively low production share derived from zinc metallurgy is because of the high recovery difficulty. In this study, various technological routes for gallium extraction from zinc metallurgy are summarized with detailed analyses based on technological and economic perspectives. During closed blast furnace zinc smelting, >95% of Ga is enriched in water-quenched slag with an average mass fraction of 0.025%–0.031%. Several methods for extracting Ga from the slag are proposed, including reduction evaporation, chlorination volatilization, sulfuric acid leaching, caustic fusion–leaching, reduction smelting–electrolysis, and reduction smelting–slagging . However, these methods are difficult to obtain industrial applications due to long flow, low recovery, high cost, or severe pollution. During the conventional roasting–leaching–purification–electrowinning process, >93.5% of Ga remains in the leaching residue, closely associated with a ZnFe2O4 phase. Next, the reduction volatilization or hot acid leaching is employed to treat the residue. Only 10% of Ga volatilizes into the crude zinc oxide dust, whereas the other Ga remains in the kiln slag, causing huge Ga loss. Ga and Fe are dissolved into the solution through hot acid leaching, and the Ga and Fe separation is a large technological problem. Compared to roasting–leaching, pressure leaching is considered more suitable for treating the Ga-rich zinc concentrate due to the absence of a roasting procedure. Ga can be leached directly into the solution with a high reaction temperature and strong oxidization atmosphere. Before Fe removal, Ga is successfully enriched in the refining residue, with an average mass grade of >0.25%, through preneutralization and zinc powder replacement. Next, the Ga-enriching residue can be further treated by H2SO4 leaching and subsequent solvent extraction. Finally, Ga with 99% purity is produced using neutralization–sedimentation, alkaline dissolution, and electrowinning. The total recovery for Ga production from zinc concentrate to gallium product is >70%. Based on this technological route, an annual production of 15 t Ga is established in the Danxia smelter. In this research, the gallium distribution behavior among the multiphase during various procedures such as roasting, leaching, replacement, and sedimentation is clarified carefully, and a reasonable technological route for enriching Ga from zinc metallurgy is proposed. Moreover, the methods for separation and enrichment of Ga from the leaching solution are summarized. The development of solvent extraction, emulsion film, and resin adsorption should be the key progress for green and efficient Ga recovery from zinc metallurgy.

     

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