A method for producing xonotlite and alumina by hydrothermal method of fly ash alkali leaching and sintering

Abstract

A method for producing xonotlite and alumina by fly ash alkali leaching and sintering hydrothermal method, comprising the following steps: (1) chemical beneficiation; (2) alkali leaching to produce alumina; (3) preparing raw slurry; 4) Preparation of clinker by sintering; (5) Dissolution of clinker and separation and washing; (6) Preparation of xonotlite precursor original slurry; (7) Preparation of xonotlite precursor by hydrothermal synthesis; (8) Hydrothermal synthesis Synthetic preparation of xonotlite filter cake. The invention effectively solves the problems and defects of large limestone consumption, large energy consumption and large slag volume in the prior art; the comprehensive utilization of fly ash can produce xonotlite and alumina, which not only realizes the replacement of silicon minerals Resources, and achieved the replacement of bauxite resources, but also save resources such as land, and can also achieve large-scale economic production.

Description

technical field [0001] The invention relates to a comprehensive utilization method of fly ash, in particular to a method for producing xonotlite and alumina by a hydrothermal method of alkali leaching and sintering of fly ash. Background technique [0002] Some coal fields in central and western Inner Mongolia and northern Shanxi are rich in high-alumina coal resources, with prospective reserves of nearly 100 billion tons, equivalent to about 15 billion tons of high-alumina fly ash, which is equivalent to the current reserves of bauxite in my country More than 8 times of that, and the alumina content in some fly ash can reach 40~50%. This kind of fly ash is generally called high aluminum fly ash. Fly ash is the main solid waste from the perspective of power generation in power plants, but the alumina content in the high-alumina fly ash produced by the combustion of high-alumina coal can reach 35-45%, some even as high as 50%, and the silicon content is generally 35%. %above....

AI Technical Summary

Problems solved by technology

However, my country's bauxite resources are quite scarce, and bauxite reserves only account for about 5% of the world's total reserves, and most of them are low-grade diaspore-type bauxite that is difficult to handle. Purchasing restriction policy, bauxite resource problem has become the biggest bottleneck for the sustainable development of my country's alumina and aluminum industry

[0005] The traditional process produces xonotlite and its products, and its siliceous raw materials are generally produced by using diatomite or quartz sand and alkali under melting conditions to generate industrial water glass. In the preparation process of raw materials, it is necessary to use a large amount of high-quality silicon ore such as quartz sand and diatomaceous earth to co-melt with soda ash or sodium sulfate in a melting kiln, and then cool, pulverize and dissolve to make it; this makes the selection of silicon raw materials require mining and Consume a large amount of non-renewable silicon mineral resources such as quartz and diatomaceous earth; at the same time, calcareous raw materials generally need to use high-quality fuels such as coke or white coal to separately burn lime and refined milk of lime, which consumes a lot of energy and costs, and is harmful to resources and the environment. Great impact

[0006] Existing various processes for producing aluminum hydroxide or aluminum oxide with high alumina fly ash all produce a large amount of silicon-calcium slag or silicon slag, a large amount of silicon-calcium slag or The large-scale rational utilization of silicon slag has become a huge bottleneck in various processes

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