Method for co-producing aluminum oxide and sodium carbonate from coal gangue

The invention relates to a method for co-producing aluminum oxide and sodium carbonate from coal gangue. The method comprises the following steps of: calcining and activating the coal gangue and dissolving the calcined and activated coal gangue in acid to prepare an aluminum chloride acid extract; concentrating and crystallizing the acid extract to prepare crystalline aluminum chloride; calcining and decomposing the crystalline aluminum chloride to prepare crude aluminum oxide; dissolving the crude aluminum oxide in alkali to prepare sodium metaaluminate; performing solid-liquid separation on iron and titanium insoluble substances and other impurities and washing the product to obtain solution of sodium metaaluminate; adding an aluminum hydroxide seed crystal into the solution of sodium metaaluminate to prepare aluminum hydroxide deposit and solution of sodium carbonate; performing solid-liquid separation to obtain an aluminum hydroxide crystal and solution of sodium carbonate; concentrating and crystallizing the aluminum hydroxide crystal and the solution of sodium carbonate to obtain sodium carbonate; and calcining the aluminum hydroxide to prepare metallurgical-grade aluminum oxide. In a production process, sodium hydroxide from a chlorine industry, hydrochloric acid which is a byproduct of a PVC industry and carbon dioxide discharged from a calcium carbide plant in a production place of the coal gangue are fully utilized, so that industry pollution is reduced, a useful product is obtained and comprehensive resource utilization is realized. The method has the advantages of simple production technology, easily-controlled production process, high aluminum oxide extraction ratio, low production cost and stable product quality.