粉煤灰中铝、镓、锂回收技术研究进展

Research progress of aluminum,gallium and lithium recovery technologies for fly ash

粉煤灰是燃煤电厂产生的主要固废,除了富含Al元素,还含有Ga、Li等有价元素,是铝、镓、锂等有价金属的潜在性提取资源。各种粉煤灰回收铝工艺中,传统碱法工艺、碱溶工艺、酸法工艺等还不能达到低能耗、低试剂消耗、低排放、高回收率的要求,其他新型工艺,如水化学法、真空热还原法、碳热氯化法等,具有产渣量少和绿色环保的优点,但仍处于实验室小试研究阶段;粉煤灰中镓和锂的含量相对较低,回收工艺一般采用沉淀法、溶剂萃取法和树脂吸附法,树脂吸附法具有选择性好、环境污染小的优点,但主要用于碱性体系;铝、镓和锂等多元素协同回收是实现粉煤灰资源化利用的重要途径。“一步酸溶法”工艺技术以氧化铝提取为主线,以镓、锂提取和硅铝基材料制备为副线,是目前粉煤灰资源化利用工艺中最具应用前景的工艺。未来,在粉煤灰中有价金属综合回收方面还需要加强以下几方面研究:研发新型的烧结技术,开发硅钙渣的综合性利用途径,彻底解决碱法工艺能耗高和废渣量大的问题;加大无机非金属材料改性的研发力度,解决酸法工艺的设备腐蚀问题;研发廉价的萃取剂和吸附树脂,或开发更加高效的除杂工艺,从而降低酸法工艺的投资成本。

Coal fly ash is the main solid waste produced by coal-fired power plants.Besides rich in aluminum,fly ash also contains valuable elements such as gallium and lithium,which is a potential extraction resource of valuable metals such as aluminum,gallium and lithium.The traditional alkaline process,alkaline solution process and acid process can not meet the requirements of low energy consumption,low reagent consumption,low emission and high recovery.Other new processes,such as hydrochemistry,vacuum thermal reduction and carbothermic chlorination,have the advantages of less slag production and environmental protection,but are still in the stage of small laboratory trials.The content of gallium and lithium in fly ash is relatively low,the recovery process generally includes precipitation,solvent extraction and resin adsorption.Resin adsorption has the advantages of good selectivity and small environmental pollution,but it is mainly used in alkaline system.The cooperative recovery of aluminum,gallium and lithium is an important way to realize the resource utilization of fly ash.The“one-step acid dissolution”process is the most promising technology in the utilization of fly ash resources,with the extraction of alumina as the main line and the extraction of gallium and lithium and the preparation of silical-aluminum based materials as the secondary lines.In the future,the recovery of valuable metals in fly ash needs to be strengthened in the following aspects:developing new sintering technology and comprehensive utilization of silicon calcium slag,to completely solve the problem of high energy consumption and large amount of waste slag in alkali process;increasing the research and development of inorganic non-metallic material modification,to solve the problem of equipment corrosion in acid process;developing inexpensive extractants and adsorbent resins,or developing more efficient impurity removal processes,to reduce the investment cost of acid processes.