A method for preparing alumina by treating fly ash with hydrochloric acid

Abstract

The invention discloses a method for preparing aluminum oxide by using hydrochloric acid treatment coal ash. The method comprises the steps: activating coal ash; mixing the activated coal ash with hydrochloric acid with the concentration of 5-10 percent; feeding mixed slurries into a heat exchanger to be heated to be between 90 and 200 DEG C; feeding the heated slurries into a reactor; adding hydrogen chloride gas into the reactor and reacting for 1-8 hours; separating solid from the liquid after reaction is finished and the temperature is reduced to obtain aluminum chloride and ferric chloride solution and high silicon slag; evaporating and condensing or drying to obtain crystallized aluminum chloride and ferric chloride; heating and decomposing the crystallized aluminum chloride to obtain coarse gamma-Al2O3 containing a large number of impurities and hydrogen chloride gas; and treating coarse gamma-Al2O3 by using the Bayer process to prepare metallurgical-level aluminum oxide, wherein residual slag is high iron slag and can be used an iron-making raw material. According to the method, the problem of severe corrosion of the equipment can be avoided, aluminum oxide in the coal ash is effectively leached, and the produced aluminum oxide can meet the industrial requirement of electrolytic aluminum.

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 guara...

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

[0005]The hydrochloric acid method for leaching alumina in fly ash requires heating the mixed slurry of hydrochloric acid and fly ash to 130~180°C, and the concentration of hydrochloric acid must be relatively high High to ensure the leaching rate of alumina in fly ash, under the condition of high concentration hydrochloric acid, the heating process equipment corrosion is serious, seriously restricting the development and application of hydrochloric acid method

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