Method for producing aluminum oxide from high-alumina fly ash

A high-aluminum fly ash and alumina technology, applied in the removal of alumina/aluminum hydroxide, solid waste, etc., can solve the problem of high energy consumption for aluminum salt concentration crystallization and pyrolysis, low alumina product purity, and sintering materials. It can reduce the consumption of reducing agent, improve the utilization rate of acid, and reduce energy consumption.

Active Publication Date: 2015-07-22
BEIJING GENERAL RES INST OF MINING & METALLURGY
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Problems solved by technology

[0008] The purpose of the present invention is to overcome the deficiencies in the existing technology for extracting alumina from fly ash, and to provide a method for extracting alumina from fly ash using an acid-base combination method. In the ash acid treatment process, the problems of high energy consumption of aluminum salt concentration crystallization and pyrolysis, and low purity of alumina products are avoided, while avoiding the defects of large amount of sintered materials, high energy consumption, and large amount of leached slag in the fly ash alkali treatment process

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  • Method for producing aluminum oxide from high-alumina fly ash

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Embodiment 1

[0038] Take 100g fly ash, according to Al in fly ash 2 o 3 Take 95% sulfuric acid at 3.5 times the number of moles, and mix it with fly ash for 3 times. After adding acid and mixing well, acidolyze and solidify at 150°C. Sulphate and roast at 320°C for 2 hours, mix the obtained sulfated calcined sand with coal powder at a coal ratio of 8%, and then reduce and roast at 750°C for 7 minutes to obtain the reduced calcined sand.

[0039] Alkali leaching is carried out on the reduced calcine, and the dissolution conditions are: dissolution temperature 100°C, alkali concentration 50g / L, ingredient molecular ratio α k 0.9, time 60min, lime addition 0%. The leaching rate of the obtained aluminum is 85%. The leaching liquid is desiliconized and seeded to obtain an aluminum hydroxide product, which is calcined to prepare a metallurgical grade alumina product, and the seeded mother liquor is returned to the reduced calcined sand for dissolution.

Embodiment 2

[0041] Take 100g fly ash, according to Al in fly ash 2 o 3 Take sulfuric acid with a concentration of 93% which is 4 times the number of moles, and mix it with fly ash in 2 times. After adding acid and mixing well, acidolyze and solidify at 200°C. After the last batch of sulfuric acid is added and mixed well, heat up Sulphate and roast at 320°C for 2 hours, mix the obtained sulfated calcined sand with coal powder at a coal ratio of 10%, and then reduce and roast at 750°C for 7 minutes to obtain the reduced calcined sand.

[0042] Alkali leaching is carried out on the reduced calcine, and the dissolution conditions are: dissolution temperature 90°C, alkali concentration 100g / L, ingredient molecular ratio α k 1.2, time 60min, lime addition 2%. The leaching rate of the obtained aluminum is 89%. The leaching liquid is desiliconized and seeded to obtain aluminum hydroxide products, which are calcined to prepare metallurgical grade alumina products, and the seeded mother liquor i...

Embodiment 3

[0044] Take 100g fly ash, according to Al in fly ash 2 o 3 Take 93% sulfuric acid at 4.5 times the number of moles, and mix it with fly ash in 3 times. After adding acid and mixing well, acidolyze and solidify at 200°C. Sulphate and roast at 350°C for 2 hours, mix the obtained sulfated calcined sand with coal powder at a coal ratio of 10%, and then reduce and roast at 750°C for 7 minutes to obtain the reduced calcined sand.

[0045] Alkali leaching is carried out on the reduced calcine, and the dissolution conditions are: dissolution temperature 150°C, alkali concentration 100g / L, ingredient molecular ratio α k 1.2, time 60min, lime addition 2%. The leaching rate of the obtained aluminum is 90%. The leaching solution is desiliconized and seeded to obtain an aluminum hydroxide product, which is calcined to prepare a metallurgical grade alumina product, and the seeded mother liquor is returned to the reduced calcined sand for dissolution.

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Abstract

The invention discloses a method for producing aluminum oxide from high-alumina fly ash. The method comprises the following steps: adding concentrated sulfuric acid into fly ash in batches, stirring uniformly, performing acidolysis and curing after adding concentrated sulfuric acid and stirring uniformly each time, then heating to 200-500 DEG C, performing sulfating roasting for 1-4 hours, and obtaining a sulfated roasted product; performing reduction roasting on the sulfated roasted product and a reducing agent at a temperature of 550-900 DEG C, leaching a reduced roasted product with a solution containing sodium hydroxide, performing liquid-solid separation to obtain a sodium aluminate solution and silicon-rich slag, removing silicon from the sodium aluminate solution, performing seed precipitation and calcination to produce aluminum oxide, and returning a seed precipitation mother solution for leaching out the reduced roasted product. The method not only guarantees the activity of aluminum oxide in the reduced roasted product but also cancels a high-energy-consumption process in a conventional sulfuric acid method; the method is simple in process and low in energy consumption, and an aluminum oxide product is good in quality; by adding acid by step in the sulfuric digestion step, the acid utilization ratio is increased, the acidolysis process is convenient to operate, and the reducing agent consumption in subsequent reduction roasting is reduced.

Description

technical field [0001] The invention belongs to the comprehensive utilization of fly ash, and in particular relates to a method for producing alumina from high-alumina fly ash, especially extracting alumina by using an acid-base combined process. Background technique [0002] The coal combustion process produces a large amount of fly ash, except for a small part that is partially utilized for the production of cement building materials, and most of the fly ash is stockpiled, which not only occupies a large amount of land resources, but also seriously pollutes the environment. my country's fly ash is rich in aluminum, with an average alumina content of 27%. The alumina content of fly ash in East China and North China generally exceeds 30%, and the aluminum content in fly ash in some areas is as high as 40-60%. A very important potential bauxite replacement resource. [0003] Because the aluminum-silicon ratio in fly ash is very low, the traditional alumina production process ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01F7/02B09B3/00
Inventor 蒋开喜蒋训雄汪胜东范艳青李达张登高蒋伟周立杰冯林永靳冉公王仍坚
Owner BEIJING GENERAL RES INST OF MINING & METALLURGY
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