高铝粉煤灰伴生资源清洁循环利用技术的构建与研究进展

Construct and research advance in clean and cyclic utilizations of associated resources in high-alumina coal fly ash

我国富含硅锂镓的高铝粉煤灰年排放量高达3 000万t以上,但综合利用率不到30%,是西北大型煤电能源基地重大环境生态瓶颈问题。为实现高铝粉煤灰的大规模高值化利用,提出机械-化学协同活化新思路,开展了高铝粉煤灰协同活化-深度脱硅工艺研究,实现了非晶态二氧化硅的深度分离,进一步提出了脱硅粉煤灰矿相重构制备铝硅系列材料、脱硅粉煤灰两步碱溶提取氧化铝2条技术路线。结果表明,高铝粉煤灰深度脱硅后,铝硅比由1.75提高至2.75以上;1 600℃烧结后,莫来石相含量达到88.33%,产品指标达到行业优级标准;脱硅粉煤灰经过两步水热反应,氧化铝提取率达到94.9%,实现锂、镓伴生资源协同利用,将氧化铝行业拜耳法主流工艺用于高铝粉煤灰提取氧化铝的过程;在此基础上构建了多产业链接循环经济体系,为高铝粉煤灰大规模高值化利用提供了新途径。

High-alumina coal fly ash（ HAFA） with high content of associated Al,Li and Ga is produced at a quantity of 30 Mt/a,however less than 30% of them is comprehensively utilized.It is a great challenge for the environment and ecology in the large coal and electricity production bases.To realize the utilization of HAFA into high value,this paper proposed the mechanical and chemical synergistic activation method to remove amorphous silica from HAFA efficiently.Based on this method,the desilicated HAFA was used to prepare the Al-Si composite,and the extraction of alumina using two-step-alkaline dissolution process was approved.The results shows that the mass ratio of Al2O3 to SiO2 of HAFA increases from 1.75 to 2.75 after deep-desilication.After calcinations at 1 600 ℃ for 2 hours,the mullite phase content reaches up to 88.33%,and the product quality meets the high standard of industry.After the optimization of two-step-alkaline hydrothermal process,the highest extraction efficiency of alumina is 94. 9%. To utilize the associated Li and Ga from HAFA,Bayer process,a classic process applied in alumina industry is introduced in the extraction of alumina from HAFA. Accordingly,a circular economy system with multi industry chains is built,and it provides a new approach to the utilization of HAFA into high value products at a large scale.