Method for preparing silicon dioxide and aluminum oxide from coal ash

Abstract

The invention relates to a method for preparing silicon dioxide and aluminum oxide, in particular to a method for preparing silicon dioxide and aluminum oxide from coal ash. In the method, the coal ash, sodium carbonate and calcium oxide are used as raw materials, the sodium carbonate is causticized in situ by the calcium oxide, and is dissolved with alkali in a high-temperature high-pressure reaction system to form sodium silicate, calcium carbonate and desiliconized coal ash solid, wherein the sodium silicate solution is carbonated by CO2 to form silicon dioxide; and aluminum oxide and foamconcrete can be prepared from the calcium carbonate and the desiliconized coal ash by a soda lime sintering method. Residues after aluminum oxide preparation can be used as a raw material for preparing a tail gas purification absorbent in cement and chemical plants and coal burning boilers, and the foam concrete. Compared with the prior art, the method has the advantages of weak reacting solutioncorrosion, high desiliconization rate, low metal content of prepared sodium carbonate and high white carbon black quality, high aluminum oxide extraction rate and the like; meanwhile, the raw material source is wide, the process is simple, the production cost is low, and the product additional value is high.

Description

technical field [0001] The invention relates to a method for preparing silica and alumina, in particular to a method for preparing silica and alumina from fly ash. Background technique [0002] Fly ash is the fine particle dispersed residue after pulverized coal combustion. The total accumulation stock of fly ash in my country has exceeded billions of tons, and it is increasing at a rate of 100 million tons per year. The continuous generation of a large amount of solid waste has brought enormous pressure to the normal operation of coal enterprises and the ecological environment, and will also have an important impact on the implementation of the national sustainable development strategy. Therefore, the development and research of comprehensive and effective utilization of fly ash has important economic and social significance for resource utilization and environmental protection. [0003] The main chemical composition of fly ash is Al 2 o 3 and SiO 2 , Al 2 o 3 About 1...

AI Technical Summary

Problems solved by technology

The traditional process characterizes the chemical composition of fly coal, and extracts Al in fly ash by strong acid or strong alkali 2 o 3 or SiO 2 , the process is limited by the chemical composition of fly ash, so it cannot be popularized, and at the same time, it will cause secondary pollution

CN101049935A discloses desiliconization with high-concentration NaOH liquid alkali-soluble fly ash, and desiliconization fly ash prepares CaO and CaCO 3 The method of preparing alumina by Bayer roasting, the high-concentration NaOH solution of this method is highly corrosive, and has high requirements for equipment and operators. The desiliconization rate of the normal temperature and pressure reaction system is low, and the prepared sodium silicate solution has a high metal ion content. , the impurity removal process increases the production cost, and at the same time the desilication fly ash is prepared into CaO and CaCO 3 When the uniformity of solid raw materials cannot be satisfied, the high alkali content of desiliconized fume not only increases the cost of dekalization but also causes waste of caustic alkali