A method for synthesizing two different grades of A-type zeolites by utilizing coal ashes

Abstract

The invention relates to a method for synthesizing two different grades of A-type zeolites by utilizing coal ashes. The method is characterized by using the coal ashes as raw material, carrying out pretreatment on the coal ashes, and then, fusing the coal ashes and sodium carbonate under a high temperature; mixing the coal ashes obtained after alkali fusion with water fully to dissolve out sodium silicate, silicon-aluminum ratio in the ingredients of the desiliconized coal ashes being ideal ratio for synthesizing the A-type zeolites; then, mixing and stirring the desiliconized coal ashes and a sodium hydroxide solution to obtain a silica-alumina gel; carrying out hydrothermal crystallization on the silica-alumina gel, carrying out washing till the pH value is neutral after the crystallization, and carrying out drying to obtain a type-I A-type zeolite; adding appropriate amount of sodium aluminate into desiliconized filtrate, wherein the desiliconized filtrate is a solution comprising the sodium silicate; and carrying out hydrothermal crystallization, washing and drying to obtain a type-II A-type zeolite. The method can enable effective constituents of aluminosilicate in the coal ashes to be used completely, and is an effective resource utilization mode.

Description

technical field [0001] The invention relates to zeolite, in particular to a method for synthesizing two types of A-type zeolite products with different grades by using fly ash of industrial waste as raw material, through alkali fusion-desiliconization treatment, and utilizing desiliconized fly ash and desiliconized filtrate. Background technique [0002] my country is one of the few countries in the world that uses coal as the main energy source. More than 75% of the national power supply is supplied by coal-fired power plants. Every year, the national power plants burn more than 400 million tons of coal. Fly ash is the main solid in coal-fired power plants. Waste, the annual output of fly ash is more than 100 million tons, but the utilization rate is less than 50%. At present, its cumulative accumulation has exceeded 2 billion, occupying a large area of ​​cultivated land and causing environmental pollution, seriously affecting human health. Its main components are A1 2 o 3...

AI Technical Summary

Problems solved by technology

[0002] my country is one of the few countries in the world that uses coal as the main energy source. More than 75% of the national power supply is supplied by coal-fired power plants. Every year, the national power plants burn more than 400 million tons of coal. Fly ash is the main solid in coal-fired power plants. Waste, the annual output of fly ash is more than 100 million tons, but the utilization rate is less than 50%. At present, its cumulative accumulation has exceeded 2 billion, occupying a large area of ​​cultivated land and causing environmental pollution, seriously affecting human health

The main technical methods reported at present include one-step method, two-step method, alkali fusion method, seed crystal method, microwave heating method, etc., but there are still disadvantages such as complex composition, low yield, and low utilization efficiency, which are difficult to apply to actual production.

[0004] One-step method is a traditional hydrothermal synthesis method, but it has disadvantages such as long aging time, low yield, and easy by-product formation.

The two-step method is to dissolve the soluble silica-alumina in the fly ash, measure the composition of the filtrate, add the required silica-alumina source accordingly according to the composition ratio of the synthetic zeolite, and then carry out hydrothermal crystallization. Synthetic zeolite has high purity, but the utilization rate of silicon and aluminum in fly ash is very low, so it cannot make full use of fly ash

Although the alkali fusion method can fully activate the fly ash, the synthetic product does not contain quartz and mullite, the utilization efficiency of the fly ash is high, and the corresponding zeolite can be synthesized by adding an aluminum source, but there is still a bottleneck in the purity

In the seed crystal method, sodium hydroxide is used to simultaneously extract silicon and aluminum without adding aluminum source, but it must add a certain amount of seed crystal or template directing agent, which has poor operability and high cost

The microwave heating method is based on the traditional hydrothermal synthesis method. Although the crystallization time of the synthetic zeolite is improved, it still cannot solve the disadvantage of the low conversion rate of the zeolite product.

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