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...

Examples

Embodiment approach 1

[0028] Put a certain proportion of fly ash, sodium carbonate, calcium oxide and water into a closed reaction vessel, wherein 500g of fly ash, the molar ratio of sodium carbonate and calcium oxide is 3, the mass ratio of fly ash and calcium oxide is 2, the liquid The solid ratio is 4. After 30 minutes of alkali dissolution at 180°C and 0.9MPa pressure, filter and separate the sodium silicate liquid, desiliconized fly ash and calcium carbonate solid mixture, wash the solid mixture, and dry the desiliconized ash;

[0029] Sodium silicate solution into CO 2 Carbon content, prepared silica, partially desiliconized fly ash and calcium carbonate solid mixture, cement, foaming agent and water to prepare foamed concrete.

[0030] Partially desiliconized fly ash and calcium carbonate solid mixture is prepared by soda lime sintering method to prepare alumina, and the waste residue after preparing alumina by soda lime sintering method is used to prepare cement.

Embodiment approach 2

[0032] Put a certain proportion of fly ash, sodium carbonate, calcium oxide and water into a closed reaction vessel, wherein 500g of fly ash, the molar ratio of sodium carbonate and calcium oxide is 3, the mass ratio of fly ash and calcium oxide is 2, the liquid The solid ratio is 4. After 30 minutes of alkali dissolution at 240°C and 1.2MPa pressure, filter and separate the sodium silicate liquid, desiliconized fly ash and calcium carbonate solid mixture, wash the solid mixture, and dry the desiliconized ash;

[0033] Sodium silicate solution into CO 2 Carbon is prepared to obtain silica, and the mixture of desiliconized fly ash and calcium carbonate solid is prepared by soda lime sintering method to prepare alumina, and the waste residue after preparing alumina by soda lime sintering method is used to prepare foamed concrete blocks.

Embodiment approach 3

[0035] Put a certain proportion of fly ash, sodium carbonate, calcium oxide and water into a closed reaction vessel, wherein 500g of fly ash, the molar ratio of sodium carbonate and calcium oxide is 1, the mass ratio of fly ash and calcium oxide is 4, the liquid The solid ratio is 6, and at 300°C and 7.2MPa pressure, after 50 minutes of alkali dissolution, filter and separate the sodium silicate liquid, desiliconized fly ash and calcium carbonate solid mixture, wash the solid mixture, and dry the desiliconized ash;

[0036] Sodium silicate solution into CO 2 Carbon content, prepared silica, desiliconized fly ash and calcium carbonate solid mixture prepared by soda lime sintering method to prepare alumina, and the waste residue after preparing alumina by soda lime sintering method was used for purification of coal-fired boiler tail gas after beating.

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...

Examples

Embodiment approach 1

[0028] Put a certain proportion of fly ash, sodium carbonate, calcium oxide and water into a closed reaction vessel, wherein 500g of fly ash, the molar ratio of sodium carbonate and calcium oxide is 3, the mass ratio of fly ash and calcium oxide is 2, the liquid The solid ratio is 4. After 30 minutes of alkali dissolution at 180°C and 0.9MPa pressure, filter and separate the sodium silicate liquid, desiliconized fly ash and calcium carbonate solid mixture, wash the solid mixture, and dry the desiliconized ash;

[0029] Sodium silicate solution into CO 2 Carbon content, prepared silica, partially desiliconized fly ash and calcium carbonate solid mixture, cement, foaming agent and water to prepare foamed concrete.

[0030] Partially desiliconized fly ash and calcium carbonate solid mixture is prepared by soda lime sintering method to prepare alumina, and the waste residue after preparing alumina by soda lime sintering method is used to prepare cement.

Embodiment approach 2

[0032] Put a certain proportion of fly ash, sodium carbonate, calcium oxide and water into a closed reaction vessel, wherein 500g of fly ash, the molar ratio of sodium carbonate and calcium oxide is 3, the mass ratio of fly ash and calcium oxide is 2, the liquid The solid ratio is 4. After 30 minutes of alkali dissolution at 240°C and 1.2MPa pressure, filter and separate the sodium silicate liquid, desiliconized fly ash and calcium carbonate solid mixture, wash the solid mixture, and dry the desiliconized ash;

[0033] Sodium silicate solution into CO 2 Carbon is prepared to obtain silica, and the mixture of desiliconized fly ash and calcium carbonate solid is prepared by soda lime sintering method to prepare alumina, and the waste residue after preparing alumina by soda lime sintering method is used to prepare foamed concrete blocks.

Embodiment approach 3

[0035] Put a certain proportion of fly ash, sodium carbonate, calcium oxide and water into a closed reaction vessel, wherein 500g of fly ash, the molar ratio of sodium carbonate and calcium oxide is 1, the mass ratio of fly ash and calcium oxide is 4, the liquid The solid ratio is 6, and at 300°C and 7.2MPa pressure, after 50 minutes of alkali dissolution, filter and separate the sodium silicate liquid, desiliconized fly ash and calcium carbonate solid mixture, wash the solid mixture, and dry the desiliconized ash;

[0036] Sodium silicate solution into CO 2 Carbon content, prepared silica, desiliconized fly ash and calcium carbonate solid mixture prepared by soda lime sintering method to prepare alumina, and the waste residue after preparing alumina by soda lime sintering method was used for purification of coal-fired boiler tail gas after beating.