Method for preparing aluminum hydroxide by utilizing high-alumina coal ash

Abstract

The invention relates to a method for preparing aluminum hydroxide by utilizing high-alumina coal ash. By adopting the deep desilicication process and the two-step sub-molten salt dissolution process, not only can the secondary enrichment of the silicon component be realized, but also the aluminum component can be adequately dissolved under the low temperature and low pressure, the operation condition is moderate, the silicon and aluminum can be adequately utilized, and the dissolution rate of the aluminum can reach more than 95 percent. The method comprises the following steps: pretreating the high-alumina coal ash in a deep desilicication way; primarily dissolving; secondarily dissolving; concentrating and crystallizing the dissolution liquid; dissolving hydrated sodium aluminate crystals; performing desilicication on the sodium aluminate coarse liquid; seed precipitating the aluminium hydroxide; and dealkalizing tailings. The obtained desilicication liquid can be used for preparing a liquid controlled process silicon-base product such as white carbon black, and the dealkalized tailings obtained in the process can be used for preparing a solid controlled silicon-base building material such as cement. The raw materials used in the method are wide in source, the price is low, the process is simple, the alkali circulation volume is small, the energy consumption and the water consumption are low, the utilization rate of raw materials is high, and the method is applicable to the industrialized popularization.

Description

technical field [0001] The invention relates to the fields of comprehensive utilization of solid waste resources, materials, chemical industry and metallurgy, in particular to a method for preparing aluminum hydroxide by using high-alumina fly ash. Background technique [0002] High-alumina fly ash is a special type of fly ash discovered in coal-fired power areas such as central and western Inner Mongolia and northern Shanxi in recent years. Its alumina content is much higher than that of ordinary fly ash, which can be as high as 50%. , which is equivalent to the content of alumina in medium-grade bauxite in my country. According to statistics, the annual output of high-aluminum fly ash in the Ordos area alone can reach 30 million tons, and the prospective reserves can reach more than 30 billion tons. [0003] On the other hand, with the substantial increase in the production scale and consumption of my country's alumina industry, my country's bauxite resources will not be a...

AI Technical Summary

Problems solved by technology

[0005] At present, the above-mentioned disclosed acid method and alkali method for extracting alumina from fly ash have certain shortcomings and drawbacks.

The acid method mainly uses a corrosive acid medium, which requires high equipment, and it is difficult to separate impurities, and it is difficult to recycle the acid

Although the sintering method is a more researched process, it still has the disadvantages of high energy consumption, high equipment requirements, and large slag production.

The two-step alkali dissolution process is complicated. The two-step conversion of sodium aluminate not only leads to difficult operation, increased production costs, difficulty in impurity separation, and a large increase in the amount of slag. At the same time, the carbonation decomposition and causticization process will greatly increase the cost. High caustic ratio The eluate will greatly reduce the circulation efficiency of the alkali, thereby increasing energy consumption and water consumption

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