Method for extracting alumina through coal ash

Abstract

The invention particularly discloses a method for extracting alumina through coal ash. The method comprises the following steps of: (1) respectively finely grinding and activating the coal ash and finely grinding ammonium sulfate in order to increase the superficial area; (2) carrying out solid-to-solid mixing on the finely ground coal ash and the ammonium sulfate (on the basis of Al2O3: (NH4)2SO4=1: 3 to 6 (molar ratio) in the coal ash) until reaching the consistency; (3) adding a certain rate of water to the mixed and consistent raw materials in the step (2), which is a mixture of the coal ash and the ammonium sulfate, and granulating; (4) placing the particles in the step (3) into roasting equipment to roast, wherein a two-section temperature control method is carried out in the roasting process; (5) adding the roasted clinker to the water to dissolve into solution; (6) filtering the solution prepared in the step (5), and respectively collecting the filter residue and the filtrate; (7) adding ammonia water to the filtrate in the step (6) to obtain Al(OH3) sediment; and (8) roasting Al(OH3)3 to obtain the Al2O3 product.

Description

Technical field [0001] The invention belongs to the field of comprehensive utilization of fly ash, and particularly relates to a method for producing alumina using fly ash as a raw material. Background technique [0002] China's thermal power generation produces a large amount of fly ash every year, a small part of which is used in the construction and cement industries. The remaining fly ash needs to be accumulated in an ash yard, which takes up a lot of land and pollutes the environment. The composition of fly ash contains Al 2 O 3 20%~50%, SiO 2 20%~60%, the rest has a small amount of Fe 2 O 3 , MgO, Na 2 O, K 2 O and other compounds. At the same time, with the continuous development of my country's economy and society, a large amount of bauxite is imported every year to make up for the lack of domestic bauxite. Therefore, research on the extraction of alumina from fly ash is of great significance to the sustainable development of the national alumina industry and to improve ...

AI Technical Summary

Problems solved by technology

The disadvantages of the existing ammonium sulfate method are long roasting time, high energy consumption for recrystallization of ammonium aluminum sulfate, and the need to add acid during the dissolution process.

[0004] The patent [CN201110208699.7] discloses a method for extracting alumina from fly ash, but this method uses ammonium sulfate and fly ash mixed and then directly roasted. Due to the inherent thermal properties of ammonium sulfate, the Melting will occur between 450°C, which will cause the mixture of ammonium sulfate and fly ash to adhere and bond to the reactor wall, thereby forming a temperature field with a large gradient in the reactor, and the mixture not on the wall It is difficult to raise the temperature of the material, and the result is that the extraction rate of alumina is reduced or the reaction time is prolonged, which affects the production efficiency

[0005] In the patent [CN201210060558.X], a method for extracting alumina from fly ash based on the ammonium sulfate activation process is disclosed. The method adopts a two-stage roasting process in a fluidized bed after the fly ash and ammonium sulfate are granulated. The patent claims to have solved technical problems such as material melting, agglomeration, and ring formation. However, considering the principle of fluidization, particles made of a mixture of fly ash and ammonium sulfate will always release H during the fluidization roasting process. 2 O, NH 3 , SO 2 and SO 3 Such as gas, the shape and density of the particles will change, which will lead to the deterioration of the fluidization quality, and even the phenomenon that the particles will collide and stick together, making it impossible to fluidize. In practice, the production process will not be able to proceed normally.

In addition, this method uses dilute sulfuric acid to dissolve clinker, which has a certain impact on environmental protection.

Images