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Method for producing silicon dioxide and alumina by using fly ash

A technology of silica and fly ash, which is applied in the production of silica, alumina/aluminum hydroxide, cement, etc., can solve the problems of difficulty in realizing industrialization, increase in production cost, and high cost, and improve the extraction utilization rate, The effect of small amount of waste residue and low cost

Inactive Publication Date: 2009-05-27
PINGSHUO INDAL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the Bayer process requires a relatively high aluminum-silicon ratio in the raw ore, which needs to be ≥11. For bauxite ores with an aluminum-silicon ratio of <7, it is uneconomical to directly use the Bayer process to produce alumina, and the silicon-aluminum in the ore must be treated Alkali calcination treatment, resulting in a production cost that is 30-90 US dollars / ton higher than that of the Bayer process
The aluminum-silicon ratio of fly ash is generally less than 1, and it is impossible to directly extract alumina by using the ready-made Bayer process industrial equipment. Even if the improved soda lime or limestone sintering method is used, the cost will inevitably be higher, so it is difficult to realize industrialization

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0028] Take 1t of fly ash, grind it, remove iron by magnetic separation, and then roast it at 350°C for 1.5h to get activated fly ash.

[0029] Move the activated fly ash into the reaction kettle, add 1.7t of 60% NaOH solution, stir and boil at 115°C for 1h, add 2t of water to dilute and filter. The filtrate is moved to the carbon separator, and the CO 2 Gas, stir carbon at 80°C, stop carbon when pH=9, obtain 350kg of silicon dioxide after filtration and separation, the purity is 98.5% after testing.

[0030] According to the prior art, the alkali leaching residue after silica extraction is mixed with CaO and calcined to make clinker, and then the Bayer process is used to directly prepare metallurgical grade alumina, and the residue after aluminum extraction is used to prepare cement.

Embodiment 2

[0032] Take 1t of fly ash, after grinding, magnetic separation to remove iron, in 20% H 2 SO 4 Soak in the solution at room temperature for 100 hours, filter out the soaking solution, and wash the leaching residue until pH = 5 to obtain activated fly ash.

[0033] Move the activated fly ash into the reactor, add 1.5t of 70% NaOH solution, stir and boil at 100°C for 2h, add 2.5t of water to dilute and filter. The filtrate is moved to the carbon separator, and the CO 2 Gas, stir the carbon at 80°C, stop the carbon at pH=9, obtain 400kg of silicon dioxide after filtration and separation, the purity is 98.65% after testing.

[0034] According to the prior art, the alkali leaching residue after silica extraction is mixed with CaO and calcined to make clinker, and then the Bayer process is used to directly prepare metallurgical grade alumina, and the residue after aluminum extraction is used to prepare cement.

Embodiment 3

[0036] Take 1t of fly ash, grind it, remove iron by magnetic separation, soak it in 10% NaOH solution at room temperature for 480 hours, filter out the soaking solution, and obtain activated fly ash.

[0037] Move the activated fly ash into the reaction kettle, add 1.8t of 80% NaOH solution, stir and boil at 115°C for 2.5h, add 3t of water to dilute and filter. The filtrate is moved to the carbon separator, and the CO 2 Gas, stir the carbon at 80°C, stop the carbon at pH=9, obtain 370kg of silicon dioxide after filtration and separation, the purity is 98.2% after testing.

[0038] According to the prior art, the alkali leaching residue after silica extraction is mixed with CaO and calcined to make clinker, and then the Bayer process is used to directly prepare metallurgical grade alumina, and the residue after aluminum extraction is used to prepare cement.

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Abstract

This invention discloses a method for extracting SiO2 and Al2O3 from fly ashes. The method comprises: activating fly ashes, leaching with more than 40 wt. % NaOH solution so that Si is stripped out in the form of sodium cilicate, introducing CO2 to prepare SiO2, adding CaO or CaCO3 into the leaching residue, calcining to obtain a clinker, preparing Al2O3 by Bayer method, and preparing cement from the waste residue. The method extracts Si at first, thus increasing the Al / Si ratio in the leaching residue. Treated leaching residue can be directly subjected to Bayer method to extract Al2O3, which largely simplify Al2O3 extraction process and increase Al2O3 utility. The method has such advantages as simple process, low investment, and high product added value.

Description

technical field [0001] The invention belongs to the refinement and comprehensive utilization of fly ash, and relates to a method for extracting silicon dioxide and alumina from fly ash, in particular to a method for extracting silicon dioxide from fly ash, and then using It is a method for preparing alumina by Er method, and the residue is used for the preparation of cement. Background technique [0002] A large amount of fly ash emitted by coal-fired power plants has caused serious pollution to the surrounding agricultural production and living environment. Comprehensive treatment of fly ash has become an urgent environmental problem that needs to be solved. In my country, the amount of fly ash discharged by coal-fired power plants is as high as hundreds of millions of tons every year, and the stockpiles are large. It is a treasure house of resources with great value for refined comprehensive development and utilization. [0003] Fly ash generally contains Al 2 o 3 About...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B33/113C01F7/02C04B7/24C04B7/26
CPCY02P40/10
Inventor 秦晋国
Owner PINGSHUO INDAL
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