Study on Calcination Catalysis and the Desilication Mechanism for Coal Gangue

Coal gangue is a solid waste discharged during coal mining, which not only occupies large land resources but also brings about certain risks to the environment. The alumina and silica minerals in coal gangue are the major resources and difficult to separate from each other, which hinders the resource utilization of coal gangue. The catalytic effect of various additives on the phase transformation process of coal gangue is studied in this paper to strengthen the separation of silica from alumina minerals and to increase the resource utilization rate of coal gangue. The study results show that the silica-containing minerals in coal gangue can be promoted to transform into mullite by alumina-based additives. The soluble active silica is released during phase transformation in the calcination process, which has a positive effect on the caustic desilication after calcination. The secondary aluminum dross has a positive catalytic effect on the active silica released during calcination. The alumina to silica ratio of the desilication product can be increased from 0.91 to 1.94 and the desilication rate can be increased from 42.99 to 56.16% by 6% secondary aluminum dross addition. The solid slag after desilication can be used to extract an alumina source for the synthesis of molecular sieve products with the silica source obtained by the desilication process so that the high-value resource utilization of coal gangue can be realized.