Method for preparing aluminum oxide through treatment of coal ashes with hydrochloric acid

Abstract

The invention discloses a method for producing aluminum oxide through treatment and utilization of industrial solid wastes and particularly relates to a method for preparing aluminum oxide through treatment of coal ashes with hydrochloric acid. The method comprises the following steps: activating coal ashes; mixing the activated coal ashes with 15%-36% hydrochloric acid, wherein a molar ratio of HCl in the hydrochloric acid to aluminum oxide and iron oxide in the coal ashes is 4-9; feeding mixed serous fluid into a reactor, heating to 90 DEG C-230 DEG C, wherein reaction time is 1 hour-8 hours; carrying out solid-liquid separation after reacting and cooling to obtain aluminum chloride liquid and high-silicon residue, and evaporating, concentrating or drying to obtain crystallized aluminum chloride; decomposing the crystallize aluminum chloride to obtain crude gamma-Al2O3 and a hydrogen chloride gas; and preparing metallurgical-level aluminum oxide by gamma-Al2O3 through a Bayer process, wherein the residue is high-iron residue and can be used as a steelmaking material. According to the method, any auxiliary agent is not added, so that aluminum oxide in the coal ashes can be effectively leached out, and the leaching rate of the aluminum oxide can reach over 85%.

Description

technical field [0001] The invention relates to a method for producing alumina by treating and utilizing industrial solid waste, in particular to a method for preparing alumina by treating fly ash with hydrochloric acid. Background technique [0002] Fly ash is a solid waste from coal-fired power plants. At present, my country's annual discharge of fly ash is hundreds of millions of tons, and the total stockpiles of fly ash in my country are more than one billion tons. The discharge of a large amount of fly ash not only occupies a large amount of land, but also seriously pollutes the environment, which constitutes a double damage to the ecology and the environment. Therefore, the comprehensive utilization of fly ash has great practical and long-term strategic significance. Similarly, my country is a country that is not rich in aluminum resources. It is reported that 45 major minerals in my country can guarantee the demand in 2010. There are 10 minerals that cannot be guar...

AI Technical Summary

Problems solved by technology

However, there are still some problems in the extraction of alumina from fly ash by alkaline method, mainly ① the silicon-calcium slag produced by the sintering method can only be used as cement raw material, and the production of 1 ton of alumina will produce several times the silicon content of fly ash Calcium slag, and cement has its corresponding sales radius, if there is no large-scale cement industry support in the local area, it will cause secondary pollution; ② The sintering method only extracts the alumina in the fly ash, and the use value of its silica is low

③ The sintering method for processing fly ash equipment requires large investment, high energy consumption and high cost

The method reported in the current data is to add fluoride to aid dissolution in the acid leaching reaction, so that silicon and fluorine can be combined to achieve the purpose of releasing alumina in it. However, harmful gases such as HF may be produced during the process of aiding dissolution. During the process, fluorine-containing waste liquid and waste residue will be discharged, which will not only pollute the environment, but also cause safety hazards to operators

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