粉煤灰提取氧化铝技术研究现状及工业化进展

Research status and industrialization progress of extracting Al_2O_3 from fly ash

我国铝土矿资源不足,铝矾土需求量不断增加,从粉煤灰尤其是高铝粉煤灰中提取Al2O3可有效补充我国铝资源量。分析了不同粉煤灰提取Al_2O_3工艺(酸法提铝、碱法提铝、碱烧结-酸浸出联合提铝技术)的特点、不足及工业化发展现状,探讨了粉煤灰提铝需解决的关键问题,并指出未来发展方向。酸法提铝工艺具有流程简单、能同时溶出Si、Al及其他元素等优点,但存在对提铝设备要求较高,废酸产量大、溶出率低等问题;碱法提取Al_2O_3工艺相对成熟,但存在硅钙渣产量大、能耗较高、成本高等问题,严重制约了其工业化发展;碱烧结-酸浸出联合提铝工艺可实现Al_2O_3的高效提取,但存在工艺复杂,强酸、强碱消耗大,Al_2O_3与Fe、Ti等杂质离子的分离较为困难等缺点。未来应优化完善现有提铝工艺,重视高附加值硅产品协同开发,重视粉煤灰中微量元素的提取和高附加值利用。低能耗、低成本、高效率、无二次污染产生是粉煤灰提铝技术的重要发展方向。

In view of the shortage of bauxite resources in China and the increasing demand for bauxite,the extraction of Al2O3 from fly ash,especially from high alumina fly ash,can effectively supplement the amount of aluminum resources in China.In this paper,the characteristics,deficiency and industrial development of different processes of extracting Al2O3 from fly ash（ acid extraction technology,alkaline extraction technology,alkaline sintering-acid dissolution combined extraction） were analyzed.The key problems to solve aluminum extraction from fly ash were discussed,and the development trend in the future was pointed out.Acidne extraction process of aluminum has advantage,such as simple process,dissolving Si,Al and other elements simultaneously,whereas there are some problems such as high requirements for equipment,large output of waste acid and low extraction rate.Alkaline extraction process of aluminum is relatively mature,but large output of calcium silicate slag,high energy consumption and high cost seriously restrict the industrialization development.High efficiency extraction of Al2O3 can be realized by using alkaline sintering-acid dissolution combined process,but there are also some disadvantages,such as complex process,large consumption of strong acid and strong alkali,difficult separation of Al2O3 with multiple ions.In the future,the existing aluminum extraction process should be optimized and improved,and the cooperative development of high value-added silicon products and extraction of trace elements and so on should be taken seriously. Low energy consumption,low cost,high efficiency and no secondary pollution are the important development direction of aluminum extraction technology from fly ash.