Method of extracting aluminum oxide by leaching flyash with hydrochloric acid

Abstract

The invention discloses a method for extracting alumina by leaching fly ash with hydrochloric acid. By passing hydrogen chloride gas into the leaching solution of fly ash and hydrochloric acid, the aluminum chloride in the leaching solution crystallizes to form aluminum chloride hexahydrate The crystals are precipitated, omitting the complicated iron removal process in the purification process of aluminum chloride and the defects that other impurity ions (sodium, potassium, magnesium, calcium, etc.) cannot be removed, and realize the separation, purification and crystallization of aluminum chloride in one step; at the same time The crystallization process is realized at room temperature, the process is simple, and the energy consumption is low. The impurity metal ions in the residual liquid can be further enriched for recovery. While extracting alumina, other metal salts and silicon oxide in the leaching residue can be recovered. The field of alumina extraction from coal ash has broad application prospects.

Description

technical field [0001] The invention belongs to the field of high-value utilization of fly ash, in particular to a method for preparing alumina by treating fly ash with hydrochloric acid. Background technique [0002] In recent years, the rapid development of my country's coal power industry has brought about a sharp increase in the discharge of solid waste fly ash. At present, the annual discharge of fly ash in my country is over 100 million tons, and the total stockpile of fly ash in my country is more than one billion Ton. 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. According to the current growth rate of alumina production and the wast...

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 amount of residue in the acid process of the prior art is small, and while alumina is effectively extracted, silicon products can be obtained, which can be made into white carbon black and sold after further treatment, but there are also some problems: (1) the corrosion resistance of equipment The requirements are high, and acid-resistant equipment, especially high-pressure acid-resistant equipment, is expensive; (2) Aluminum chloride impurity removal technology is for resin adsorption and iron removal, without removal of other impurity ions (sodium, potassium, magnesium, calcium, etc.); (3) Calcination It is very difficult to decompose aluminum salt hydrates containing a lot of crystal water, and the process of crystallizing aluminum chloride requires high energy consumption; (4) The entire technical impurity removal system is huge and complex

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