Preparation method of alumina

Abstract

The process of preparing alumina includes: the reaction of flyash from circular fluidizing bed and acid to obtain aluminum chloride solution, eliminating silicon impurity, concentrating to crystallize and heating to decompose and to obtain crude alumina product; reaction of crude alumina product and hot alkali solution to obtain sodium aluminate solution; eliminating iron, titanium and other impurity, adding aluminum hydroxide crystal seed into sodium aluminate solution for seed separating decomposition to obtain aluminum hydroxide precipitate; and final calcining aluminum hydroxide to obtain metallurgical alumina. The normal pressure process has no any cosolvent added, and the alumina product has Al2O3 content up to 98 %. The process has small sodium hydroxide consumption, reuse of most of sodium hydroxide, simple operation, low cost, low power consumption, capacity of reducing flyash pollution and other advantages.

Description

Technical field: [0001] The invention relates to a method for producing alumina, in particular to a method for producing alumina by using circulating fluidized bed fly ash as raw material. Background technique: [0002] Fly ash is a waste discharged from thermal power plants. my country uses coal as the main energy source. The fly ash discharged from power plants is as high as hundreds of millions of tons every year, which brings great harm to the ecological environment. How to deal with and utilize fly ash is a very important question. Extracting alumina from fly ash is an effective way to comprehensively utilize fly ash, and has good social and economic benefits. [0003] At present, the methods of extracting alumina from fly ash can be divided into two categories: alkali method and acid method. But all there are some problems in existing technological method. The process of extracting alumina by alkaline method is complicated, consumes a lot of energy, and produces a la...

AI Technical Summary

Problems solved by technology

Alkaline extraction of alumina is a complex process with high energy consumption and a large amount of waste residue

Although the method of extracting alumina by the acid method has the advantages of simple process, low energy consumption, and less waste residue, but because the aluminum in the fly ash of the traditional pulverized coal furnace mainly exists in amorphous glass, it is difficult to dissolve directly by acid solution, and it must be added Fluoride is used as a co-solvent, which is harmful to the environment and the human body, and is not conducive to clean production, and the alumina products prepared by acid method contain many impurities such as iron and titanium, which are difficult to remove

Images