Method for subsequent treatment of aluminum sulfate generated in technical process of extracting alumina from fly ash

Abstract

The invention relates to a method for the subsequent treatment of aluminum sulfate generated in the technical process of extracting alumina from fly ash. According to a process for extracting the alumina from the fly ash, when hydrochloric acid is used for dissolving out, the corrosion of equipment is serious, and the continuous production is difficult to realize; and when sulfuric acid is used for dissolving out, the content of crystal water in prepared aluminum salt crystals is high, and the thermal loss of roasting decomposition is relatively high. The method comprises the following steps of: adding a subsequent aluminum chloride lotion or a solution of hydrochloric acid into a solution of aluminum sulfate generated in the technical process or aluminum sulfate crystals obtained after crystallization, diluting, introducing HCl gas into the mixed solution at the temperature of between 30 and 85 DEG C to ensure that the solution is saturated, and precipitating aluminum chloride hexahydrate crystals; and roasting to obtain the alumina. By the method, the problems about equipment corrosion caused by using the hydrochloric acid for dissolving out in the process for extracting the alumina from the fly ash, and overhigh energy consumption caused by roasting aluminum sulfate salt crystals after the sulfuric acid is used for dissolving out are solved; and the HCl gas which is brought into the production process can be obtained from smoke produced by roasting aluminum chloride hexahydrate, and can be recycled without any conversion, so that the cost is effectively reduced.

Description

technical field [0001] The invention relates to a process for treating fly ash, in particular to a subsequent treatment method for aluminum sulfate in the process of extracting alumina from fly ash. Background technique [0002] Fly ash is the fine ash collected from the flue gas after coal combustion, and its main composition is SiO 2 、Al 2 o 3 , FeO, Fe 2 o 3 , CaO, TiO 2 wait. The whole world emits a huge amount of fly ash every year. In 2010, the domestic emission exceeded 300 million tons. Air and water pollution, land desertification, alkalization and other environmental pollution problems caused by its accumulation and loss of land are problems that plague the world. All countries are actively looking for ways to reuse fly ash. [0003] The technical research on extracting alumina from fly ash began in the 1980s. To obtain alumina from fly ash with a higher extraction rate, it is necessary to try to destroy SiO 2 -Al 2 o 3 bond, raise Al 2 o 3 activity. ...

AI Technical Summary

Problems solved by technology

In the process of extracting alumina, if hydrochloric acid is used to dissolve and participate in the reaction, the problem of equipment corrosion will be serious, it will be difficult to realize continuous production, and the investment cost will be high.

And when sulfuric acid is used for stripping (during stripping reaction) in the technological process, although the equipment corrosion problem is solved and the investment cost is lower than the former, the crystal water contained in the obtained aluminum sulfate crystal is higher than that of aluminum chloride crystal, and alumina The content is lower than that of aluminum chloride crystals, and the heat consumption of aluminum sulfate crystals for roasting and decomposition will be much higher than that of aluminum chloride crystals, so the production cost is higher

Images