Method for producing alumina by using high-alumina fly ash

Abstract

The invention provides a method for producing alumina by using high-alumina fly ash. The method comprises adopting the high-alumina fly ash to be reacted with a sodium hydroxide solution to conduct desilicication in advance to obtain coal ash filter cakes and desilicication liquid firstly; and adding the desilicication coal ash filter cakes in slurry of the limestone and sodium carbonate to mix to form raw material slurry, then roasting the raw material slurry to form ripe materials, considering a liquid phase dissolved from the ripe materials as sodium aluminate coarse liquid, conducting carbon separation on the obtained sodium aluminate coarse liquid, and then conducting Bayer process dissolving, dilution desilicication, kind separation and roasting. Tedious desilicication processes of a first section and a second section are removed, equipment, such as high-pressure desilicication groove and deep desilicication groove which are difficult to operate is reduced, equipment cost and operation difficulties are reduced, and high-purity alumina products can be obtained simultaneously.

Description

technical field [0001] The invention relates to a method for utilizing fly ash, in particular to a method for producing alumina from high-aluminum fly ash. Background technique [0002] Alumina is the main raw material for the production of aluminum ingots. More than 95% of the world's alumina is produced through bauxite. my country is the world's largest producer of alumina, and currently produces more than 30 million tons of alumina per year. But at the same time, my country's bauxite resources are relatively scarce, and bauxite reserves only account for about 7% of the world's total reserves, and most of them are difficult-to-handle diaspore mines. Due to insufficient bauxite resources, currently about 60% of bauxite mines are dependent on imports from abroad. [0003] However, the reserves of high-aluminum fly ash produced by coal power generation in central and western Inner Mongolia and northern Shanxi in my country are abundant. The potential reserves of high-alumin...

AI Technical Summary

Problems solved by technology

In recent years, various colleges and universities and research institutes in my country have actively carried out research on new processes for extracting alumina from high-alumina fly ash. Bayer method, limestone sintering-low temperature Bayer method, etc. Among them, the acid method is difficult to realize large-scale industrial production due to serious corrosion of equipment materials and high impurity content in the product, and it is difficult to produce metallurgical grade alumina. Ammonium sulfate sintering method has slag phase flow There are no industrial examples for the disadvantages of large size and difficulty in recycling ammonia gas. The limestone sintering method is similar to the soda-limestone sintering method, but the amount of slag is larger, the energy consumption is higher, and the recovery rate is slightly lower than that of the soda-limestone sintering method. The desiliconization-soda lime sintering method is currently the only process method that realizes industrial production and has achieved success. Patent CN201110117710 discloses the technical characteristics of this process

[0004] However, CN201110117710 adopts a lengthy one-stage and two-stage desiliconization process, which requires difficult-to-operate equipment such as high-pressure desiliconization tanks and deep desiliconization tanks, and the equipment costs are high and the operation is complicated.