Probe into the Reasons for the Comprehensive Utilization of High Aluminum Fly Ash

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Where to coal as an energy source direct combustion process, will produce fly ash. In a thermal power plant, in the process of high-temperature combustion of pulverized coal, the volatiles such as carbon, sulfur, phosphorus and nitrogen are mostly discharged into the atmosphere in the form of gas. Most of the inorganic minerals are melted and polymerized to form pulverized coal. The ash particles are collected as fly ash as the flue gas enters the dust collection device. Fly ash generally accounts for 80% to 90% of the total ash content of power plants. In recent years, a technique called "high aluminum fly" Fly attention. The A12O3+SiO2+Fe2O3 in this fly ash is ≥80%, which is characterized by high A12O3, generally ≥38%, and even higher than 50%, which is equivalent to the A12O3 content of the foreign gibbsite. This fly ash is mainly produced in the central and northern parts of Shanxi Province and the vast areas of Inner Mongolia. The A12O3 content in fly ash in Shanxi's Zhangzhou and Inner Mongolia areas is significantly higher than the domestic average and is much higher than the rest of the world. The coal in these areas is rich in A12O3. The above-mentioned regions have extremely rich reserves of coal resources, and they are concentrated areas of thermal power plants. They can produce a large amount of high-aluminum fly ash every year, and the output is increasing year by year.

China is a big country for bauxite consumption. With the rapid depletion of domestic bauxite resources, the recycling of high-aluminum fly ash has attracted more and more attention. Make full use of this important resource with huge reserves and good prospects, and use high-aluminum fly ash as an important substitute for bauxite. The prospect is considerable and significant.

Bauxite generally refers to aluminum minerals with A12O3 ≥ 40%. From the point of view of A12O3 content, high alumina fly ash has completely possessed the characteristics of bauxite. However, high alumina fly ash contains much higher silicon than bauxite. Therefore, in order to become a substitute resource for bauxite in the true sense, high-aluminum fly ash must first remove SiO2 from it.

Magnesium aluminum Shenyang Design Institute proposed method of treating fly ash to produce an ammonia-alumina, comprises the following steps: mixing the fly ash with ammonium sulfate, grinding raw meal, wherein the ammonium sulfate and fly ash The weight ratio of alumina is 4.5 to 8:1; the raw material is heated to 230-600 ° C, the firing time is controlled at 0.5 to 5 h, and the clinker containing ammonium aluminum sulfate and ammonia gas are prepared; the cooked clinker is heated with hot water. Dissolution, dissolution time 0.1~2h, aluminum enters the solution in the form of ammonium aluminum sulfate, silicon remains in the residue to form high silicon slag; ammonia or ammonia water is added to the ammonium aluminum sulfate solution to obtain crude aluminum hydroxide and ammonium sulfate containing impurities solution; the crude aluminum hydroxide is treated with a low temperature Bayer cycle alkali solution, wherein the removal of iron, calcium impurities, to obtain metallurgical grade alumina and high iron slag.

Chenzhou City, Shanxi Province produces a large amount of high-aluminum fly ash every year, with a quantity of up to 4 million tons. In order to make full use of these resources, Hunan Zhongda Metallurgical Design Co., Ltd. designed a comprehensive utilization project of fly ash for China Coal Pingyu Coal Industry Group. The project uses the latest technology to produce high-quality silica and metallurgical grade alumina products, and its SiO2 extraction rate has reached a relatively high level. This work of Pingyi Coal Industry Group also realized the utilization of aluminum and silicon in high-aluminum fly ash, which provided useful experience for the comprehensive utilization of high-alumina fly ash.

In short, high-aluminum fly ash is a unique high-aluminum resource in China, with abundant reserves and great potential for utilization. How to make good use of this resource to make up for the shortage of bauxite resources in China is a very important issue.

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