Process method for extracting aluminum oxide in coal ash of pulverized coal furnace by using acid method

The invention relates to a process method for extracting aluminum oxide in coal ash of a pulverized coal furnace by using an acid method. The process method comprises the following steps; adding ammonium sulfate into the coal ash of the pulverized coal furnace for activating, and performing the high-temperature calcination to obtain activated coal ash clinker, adding hydrochloric acid, heating and dissolving out, to obtain aluminum chloride digesting liquor; pumping hydrogen chloride gas into the digesting liquor for crystallizing, performing the solid-liquid separation and washing to obtain high-purity aluminum chloride hexahydrate crystal and waste acid solution, calcining the crystal to generate metallurgy-level aluminum oxide; adding inorganic salt chloride, such as calcium chloride or magnesium chloride, into the waste acid, heating, extractive-distilling and recycling the hydrochloric acid and the hydrogen chloride gas for the dissolving out and crystallization working procedures, performing the absorption-crystallization to tail gas generated in the roasting-calcining activation to generate ammonium sulfate, and realizing the cyclic utilization of materials, wherein the obtained solid residue with abundant silicon dioxide can be used for generating white carbon black or the materials for building. The process method is capable of realizing the reduced recycling of the coal ash of the pulverized coal furnace, and realizing the full cyclic utilization of the materials. The purity of the obtained aluminum oxide product is the first level, the quality of the metallurgy-level aluminum oxide is standard, and the extraction efficiency is up to 84.6%-90.4%.