Method for producing metallurgical-grade aluminum oxide by coal ash

Abstract

The invention discloses a method for producing metallurgical-grade aluminum oxide by coal ash, comprising the following steps: mechanically activating the coal ash, adding water for performing flotation to remove the black which is not completely burnt; removing ferric oxide by magnetic separation; adding concentrated sulphuric acid in raffinate of the coal ash to perform reaction under high temperature and high pressure for 1-6h; after reaction, adding water, heating up and boiling, filtering, obtaining aluminum sulfate raw liquor, evaporating and concentrating the raw liquor, cooling, and obtaining concentrated solution of aluminum sulfate; adding organic alcohol, filtering; adding water for dissolving filter cake, adding the organic alcohol, dissolving ferric sulfate, separating out aluminum sulfate, filtering, and obtaining aluminum sulfate filter cake, drying at 70-100 DEG C, burning at a temperature more than 800-1200 DEG C, and obtaining the metallurgical grade Al2O3 of which content of Fe2O3 is less than 0.02%. The method avoids that secondary intermediates gamma-Al2O3 must be obtained by burning and purified by Bayer circulation, the method is simple in technology, easy to control, high in extraction rate of the aluminum oxide, low in production cost, low in product impurity content and steady in quality.

Description

technical field [0001] The present invention relates to a process method for resource utilization and comprehensive utilization of fly ash, specifically a method for producing metallurgical grade alumina from fly ash, which is to use a certain concentration of sulfuric acid to heat and pressurize to leaching aluminum sulfate, and after concentration, use a certain concentration A wide range of organic alcohol solutions remove iron from aluminum sulfate to prepare high-purity industrial grade aluminum sulfate with a Fe content of less than 20ppm. Aluminum sulfate is directly calcined to obtain metallurgical grade α-Al with an iron oxide content of less than 0.02%. 2 o 3 . Background technique [0002] Fly ash is the solid residue left after coal combustion in coal-fired boilers. It mainly comes from by-products of coal-fired power plants. For every ton of coal burned, 230kg of fly ash will be produced. According to incomplete statistics, the national fly ash accumulation am...

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Problems solved by technology

[0004] In the aforementioned invention patent applications, metallurgical grade alumina must pass through the intermediate γ-Al 2 o 3 The purification process of the company is handled by the Bayer method, that is, the aluminum sulfate crystal is calcined once to obtain the intermediate γ-Al 2 o 3 , and then through alkali dissolution, sorting, filtration, washing, and secondary calcination to obtain metallurgical grade α-Al 2 o 3 The complex purification process has the disadvantages of complicated process, many process links, large energy consumption and resource consumption, and high production cost, so it is difficult to be popularized and applied.

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