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Method for producing aluminum oxide by using fly ash

A technology of fly ash and alumina, applied in alumina/aluminum hydroxide and other directions, can solve the problems of small silicon content index of crude products, complicated batching process, low alumina recovery rate, etc., to achieve scientific and reasonable process design, material Simple treatment method and great effect of solid waste

Active Publication Date: 2015-04-22
DATANG INT POWER GENERATION +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Compared with the alkaline process, these methods are characterized by the ability to reduce the amount of waste slag discharge, but the above-mentioned acid processes all have a low recovery rate of alumina, and all of them will make other useful resources in the fly ash, especially gallium, enter the tail slag, resulting in a waste of resources; in addition, under the conditions of high temperature and high pressure, the corrosion of the equipment by acid is very serious, especially the concentrated hydrochloric acid leaching method
Therefore, the acid method reported in the literature has relatively high requirements for equipment, and the discharge of waste residue also has the potential threat of secondary pollution.
[0005] Alkali method is currently a relatively in-depth research method in the comprehensive treatment of fly ash. The representative methods are pre-desilication-soda lime sintering method and limestone sintering method, but both of them have high roasting temperature (>1200°C) , large amount of tailings, and requires precise control of Na / Al ratio and Ca / Si ratio in the system, resulting in complex batching process
In addition, because the eluate is alkaline, part of the silicon oxide is dissolved with the alumina, and the silicon content index of the crude product is small, and further desiliconization is required to meet the requirements of metallurgical grade, resulting in a low overall recovery rate of alumina

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0044] Example 1: Pre-desilication of fly ash

[0045] The raw material is fly ash from a thermal power plant in Inner Mongolia, and its main chemical composition is shown in Table 1 below.

[0046] Table 1 Chemical composition of fly ash samples

[0047] Element

Al 2 o 3

SiO 2

total iron oxide

TiO 2

CaO

Loss on ignition

the sum

Content (%)

48.45

40.55

1.92

1.54

3.64

1.31

97.41

[0048]Mix 200g of fly ash with a sodium hydroxide solution with a mass fraction of about 16.7% (the solution contains 600mL of water and 120g of sodium hydroxide solid), and then place it in a sealed reactor at a pressure of 2atm and a temperature of 150°C After stirring for 1 hour under sealing, cool to below 50°C, filter to obtain desiliconized fly ash and filtrate;

[0049] The desiliconized coal ash obtained by the above filtration was dried at 120° C. and weighed to obtain 164.6 g of dried desiliconized coal...

Embodiment 2

[0052] Example 2: Pre-desilication of fly ash

[0053] The chemical composition of the fly ash is the same as in Example 1.

[0054] Mix 100g of fly ash with a sodium hydroxide solution with a mass fraction of about 18.37% (the solution contains 400mL of water and 90g of sodium hydroxide solid), and then place it in a sealed reactor. After the pressure is 2atm and the temperature is 140°C, it is sealed and stirred for 1 hour, cooled to below 50°C, and filtered to obtain desiliconized fly ash and filtrate;

[0055] The desiliconized coal ash obtained by the above filtration was dried at 120° C. and weighed to obtain 81.9 g of dried desiliconized coal ash;

[0056] Wash 81.9g of the dried desiliconized fly ash once with 200mL of hot water, combine the filtered washing liquid with the above filtrate (that is, desiliconization liquid), and set the volume to 1000mL;

[0057] Silicon molybdenum blue was used to measure the concentration of silicon in the desiliconization solution,...

Embodiment 3

[0058] Embodiment 3: reclaim Al2O3 from desiliconization fly ash

[0059] 100g of dried desiliconized fly ash obtained in Example 1 and 80g of sodium carbonate are mixed and ground to a particle size of 180 mesh mixed material, then the ground mixed material is placed in a corundum crucible, and roasted at 950°C for 3h Make roasted clinker; take it out, cool to room temperature, wash with water, filter, combine the collected filtrate, heat and evaporate water, recover sodium carbonate, and recycle it for roasting with desiliconized fly ash;

[0060] Wash the roasted clinker with 1000 mL of sulfuric acid with a concentration of 5 mol / L, dissolve it under stirring for 1.5 h, and collect the eluate by filtration. Wash the filter residue with water for 1-2 times, combine the washing liquid and the stripping filtrate after filtration, heat and concentrate to 300mL, and cool to below 10°C until aluminum salt crystals (Al 2 (SO 4 ) 3 18H 2 O) The precipitation is complete. Alumi...

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Abstract

The invention provides a method for producing aluminum oxide by using fly ash. The method comprises the following steps of: 1) performing predesilicification on the fly ash to obtain desiliconized fly ash; 2) mixing the desiliconized fly ash and sodium carbonate, and roasting to obtain clinker; 3) dissolving the clinker into acid, filtering, and collecting the solution; 4) concentrating the solution to precipitate aluminum salt crystal; and 5) preparing the aluminum oxide product from the aluminum salt crystal. The method for producing the aluminum oxide by using the fly ash has the advantages of low production energy consumption, low waste slag discharge and high product purity.

Description

technical field [0001] The invention relates to a method for producing alumina by utilizing fly ash, which belongs to the field of comprehensive utilization of fly ash. Background technique [0002] At present, in the fly ash produced by thermal power generation in areas such as Inner Mongolia and Shanxi, the content of alumina reaches 40% to 55%, and the content of gallium exceeds 80ppm. Fly ash not only contains huge aluminum resources, but also There are gallium resources with high economic value. Therefore, the development of fly ash is an effective way to protect the environment and fully recycle resources. [0003] The methods of extracting alumina from fly ash can generally be divided into acid method and alkali method: [0004] The acid method refers to the method of directly treating fly ash with hydrochloric acid or sulfuric acid to dissolve part of the alumina. For example, concentrated acid leaching method under high temperature and high pressure, ammonium sulf...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01F7/02
Inventor 张毅陈刚孙俊民孙振斌闫绍勇孟繁逵张战军王振根张生王毅公彦兵刘鑫平王利娟
Owner DATANG INT POWER GENERATION
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