Method for wet-process extraction of alumina from high-aluminum fly ash

Abstract

The invention provides a method for wet-process extraction of alumina from high-aluminum fly ash, and the method comprises the following steps: 1)silicon pre-removal treatment of the high-aluminum fly ash; 2)low temperature wet dissolution of part of alumina from silicon-pre-removed fly ash; 3)high temperature wet dissolution of the alumina from low temperature dissolution slag; 4)mixing of dissolution solutions of the step 2)and the step 3)and seeded precipitation spent liquor for evaporation concentration crystallization for preparation of hydrated sodium aluminate crystals, or mixing of the dissolution solution of the step 2)and the seeded precipitation spent liquor for evaporation concentration crystallization for preparation of the hydrated sodium aluminate crystals, and returning of the dissolution solution of the step 3)back to the step 2)as a dissolution medium; and 5)dissolving of the hydrated sodium aluminate crystals in a dilute alkali solution, silicon removal and seed decomposition to obtain aluminum hydroxide, and calcination to obtain an alumina product. According to the method, the alumina is step-by-step dissolved, dissolution temperature and dissolution pressure are low, energy consumption is low, requirement of equipment materials is low, process is simple, aluminum and silicon both are effectively utilized, and the method adopts a full-wet process, and is suitable for industrial production.

Description

technical field [0001] The invention relates to the utilization of high-aluminum fly ash, in particular to a method for wet extraction of alumina from high-alumina fly ash. Background technique [0002] my country's alumina output accounts for 1 / 3 of the world, but my country's bauxite resource reserves account for only 3% of the world's total, the resource guarantee period is less than 10 years, and the alumina's external dependence exceeds 50%. Due to the tight mineral export policy, the contradiction between the supply of bauxite resources in my country has become increasingly prominent. [0003] In my country, Inner Mongolia, Shanxi and other places are rich in high-aluminum coal resources, and the amount of resources buried at a depth of more than 500 meters is nearly 50 billion tons. The content of aluminum is 35% to 50%, which is equivalent to the content of alumina in low-grade bauxite in my country. At present, the total amount of high-aluminum fly ash has exceeded ...

AI Technical Summary

Problems solved by technology

Among them, the acid method has disadvantages such as serious corrosion of equipment, difficulty in acid medium recovery, and unreachable product quality; the sintering method has disadvantages such as high sintering temperature, high energy consumption, and large amount of tailings; Disadvantages such as large and large ammonia emissions

Recently, Chinese patent application CN103663516A discloses a method for preparing aluminum hydroxide by using high-alumina fly ash. The process features mainly include two-step desiliconization and two-step high-temperature dissolution reaction. This process can realize the formation of aluminum and silicon in fly ash. However, the process is complicated and the operation is difficult. Two-step desiliconization pretreatment is adopted, and pickling activation is also used. It is difficult to recycle the pickling solution, which is easy to cause environmental pollution. The two-step dissolution reaction conditions are relatively harsh, and the energy consumption larger

Chinese patent application CN104030331A discloses a method for producing alumina by using high-alumina fly ash. The process features mainly include pre-desilication and two alkali dissolutions. The dissolution reaction temperature is still high, and the energy consumption is high. After the decomposed mother liquor is evaporated and concentrated, it returns to an alkali dissolution, and a large amount of aluminum returns to the dissolution process, and the production efficiency of aluminum is low.

Due to the stable structure of mullite, it is generally believed in the industry that the decomposition of mullite in fly ash needs to be carried out at high temperature. Therefore, the reaction temperature for extracting alumina by using fly ash alkali method is at least 160°C, and no lower temperature has been found so far. A report on the dissolution of alumina by using fly ash alkali method

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