Method for producing aluminum oxide from high-alumina fly ash

Abstract

The invention discloses a method for producing aluminum oxide from high-alumina fly ash. The method comprises the following steps: adding concentrated sulfuric acid into fly ash in batches, stirring uniformly, performing acidolysis and curing after adding concentrated sulfuric acid and stirring uniformly each time, then heating to 200-500 DEG C, performing sulfating roasting for 1-4 hours, and obtaining a sulfated roasted product; performing reduction roasting on the sulfated roasted product and a reducing agent at a temperature of 550-900 DEG C, leaching a reduced roasted product with a solution containing sodium hydroxide, performing liquid-solid separation to obtain a sodium aluminate solution and silicon-rich slag, removing silicon from the sodium aluminate solution, performing seed precipitation and calcination to produce aluminum oxide, and returning a seed precipitation mother solution for leaching out the reduced roasted product. The method not only guarantees the activity of aluminum oxide in the reduced roasted product but also cancels a high-energy-consumption process in a conventional sulfuric acid method; the method is simple in process and low in energy consumption, and an aluminum oxide product is good in quality; by adding acid by step in the sulfuric digestion step, the acid utilization ratio is increased, the acidolysis process is convenient to operate, and the reducing agent consumption in subsequent reduction roasting is reduced.

Description

technical field [0001] The invention belongs to the comprehensive utilization of fly ash, and in particular relates to a method for producing alumina from high-alumina fly ash, especially extracting alumina by using an acid-base combined process. Background technique [0002] The coal combustion process produces a large amount of fly ash, except for a small part that is partially utilized for the production of cement building materials, and most of the fly ash is stockpiled, which not only occupies a large amount of land resources, but also seriously pollutes the environment. my country's fly ash is rich in aluminum, with an average alumina content of 27%. The alumina content of fly ash in East China and North China generally exceeds 30%, and the aluminum content in fly ash in some areas is as high as 40-60%. A very important potential bauxite replacement resource. [0003] Because the aluminum-silicon ratio in fly ash is very low, the traditional alumina production process ...

AI Technical Summary

Problems solved by technology

[0008] The purpose of the present invention is to overcome the deficiencies in the existing technology for extracting alumina from fly ash, and to provide a method for extracting alumina from fly ash using an acid-base combination method. In the ash acid treatment process, the problems of high energy consumption of aluminum salt concentration crystallization and pyrolysis, and low purity of alumina products are avoided, while avoiding the defects of large amount of sintered materials, high energy consumption, and large amount of leached slag in the fly ash alkali treatment process

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