Method for extracting aluminum oxide by quickly heating fly ash

Abstract

The invention discloses a method for extracting aluminum oxide by quickly heating fly ash, which comprises the following steps: 1. grinding and activating fly ash, and meanwhile, grinding ammonium sulfate, 2. carrying out solid-solid uniform mixing on the ground fly ash and ammonium sulfate according to the mol ratio of Al2O3 in the fly ash to (NH4)2SO4 of 1:(3-6); 3. adding a small amount of water into the mixed raw materials, and granulating; 4. roasting the granules formed in the step 3 in a high-frequency or microwave device; 5. dissolving the roasted clinker in water to obtain a solution; 6. filtering the solution formed in the step 5, and separating the filtrate and filter residues; 7. adding ammonia water into the filtrate in the step 6 to obtain an Al(OH)3 precipitate; and 8. calcining the Al(OH)3 precipitate to obtain the Al2O3 product. The high-frequency and microwave heating principle is as follows: an electromagnetic field repeatedly polarizes polar molecules contained in the substance, and the polar molecules vigorously move under the action of the alternating electromagnetic field to generate mutual friction and heat, thereby achieving the goal of heating the material.

Description

technical field [0001] The invention relates to a method for extracting alumina from fly ash, in particular to a method for rapidly heating fly ash to extract alumina. 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 construction and cement industries, and the remaining fly ash needs to be piled up in ash yards, occupying a large amount of land and polluting 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 shortage of domestic bauxite. Therefore, the study of extracting alumina from fly ash is of great significance to the sustainable development of the national alumina industry and the improvement of the...

AI Technical Summary

Problems solved by technology

Compared with the ammonium sulfate method for extracting alumina from fly ash, this method adds additional sodium ions, which has a certain impact on the subsequent process, and the roasting temperature is 620°C-990°C, which is much higher than the ammonium sulfate method. (lower than 450°C), the process is not advanced in terms of energy saving

[0006] In the patent [CN201110208699.7], a method of extracting alumina from fly ash is introduced, which adopts the direct roasting process after mixing ammonium sulfate and fly ash. Melting will occur between 450°C, so that the reactor wall will adhere and bond, and a temperature field with a large gradient will be formed in the reactor, and it will be difficult for the mixed material not on the wall to heat up, resulting in a decrease in the extraction rate of alumina Or the reaction time is prolonged, affecting production efficiency

[0007] The patent [CN201210060558.X] discloses a method for extracting alumina from fly ash based on the ammonium sulfate activation process. The method adopts a two-stage roasting process in a fluidized bed after granulating the fly ash and ammonium sulfate. 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 particles change, resulting in poor fluidization quality, and even particles collide and stick together, unable to fluidize, which will make the production process unable to proceed normally in practice.

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

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