Method for preparing alumina by using fly ash

Abstract

The invention discloses a method for producing alumina by disposing and utilizing industrial solid wastes, in particular to a method for preparing alumina by fly ash, comprising the steps as follows: the fly ash is mechanically activated; the activated fly ash, water and concentrated sulfuric acid react in a reaction kettle under the conditions of heating and pressurizing; the solid is separated from the liquid after the temperature of the reaction is reduced so as to gain aluminium sulfate liquid; the aluminium sulfate liquid is evaporated, concentrated and cooled so as to precipitate aluminium sulphate crystals; the aluminium sulphate crystals are dehydrated and decomposed to gain gama-Al2O3 and SO3; coarse gama-Al2O3 is dissolved in alkaline solution; after the solid is separated from the liquid, the pure sodium aluminate solution is gained; aluminum hydroxide crystal seed is added to the sodium aluminate solution so as to precipitate the aluminum hydroxide; the coarse gama-Al2O3 can be prepared by circularly dissolving the seed-precipitated alkaline solution after vaporization-concentration; the metallurgical alumina can be gained by baking the prepared aluminum hydroxide. The method adds no additive, can lead the alumina in the fly ash to be effectively leached out with the leaching rate more than 90% and saves the energy resource.

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 using fly ash. 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 guaranteed, including bauxite. ...

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 calcium-silicate slag produced by 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, while cement has its corresponding sales radius, if there is no large-scale cement industry support in the local area, it will cause secondary pollution; ②The 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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