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A method for preparing α-type hemihydrate gypsum from desulfurized ash and its product

A technology of hemihydrate gypsum and desulfurization ash, which is applied in the field of preparation of α-type hemihydrate gypsum from desulfurization ash, which can solve problems such as hidden dangers, environmental pollution, and inability to compete, and achieve high strength and high purity

Active Publication Date: 2020-09-08
JIANGSU EFFUL SCIENCE AND TECHNOLOGY CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] Most of my country's steel mills use dry process desulfurization, and the by-products discharged are sintering desulfurization ash, the main component of which is CaSO 3 0.5H 2 O, Ca(OH) 2 and a small amount of CaCO 3 , it is difficult to directly apply
Some scholars have suggested that desulfurization ash can be directly used to prepare plaster or gypsum-based cementitious materials after calcination. On the one hand, the performance of the material is unstable, and on the other hand, the application field is narrow, and it cannot be compared with the existing domestic production of building gypsum powder. Rendering gypsum or gypsum-based cementitious materials competes; some scholars also propose to use desulfurization ash to directly neutralize with sulfuric acid to prepare dihydrate gypsum, but the biggest drawback of this method is that it will produce SO 2 harmful gas
[0004] CN109455752A discloses a method for preparing calcium sulfate by directly reacting desulfurized ash with dilute sulfuric acid. Although the method effectively handles calcium hydroxide and calcium carbonate in desulfurized ash, calcium sulfite can react with sulfuric acid to generate SO 2 Harmful gas requires an additional desulfurization device, which not only increases the investment cost, but also brings hidden dangers of environmental pollution
[0005] CN102912445A discloses a process and device for finally preparing whiskers by using semi-dry desulfurization ash and waste acid. The process includes mixing the semi-dry desulfurization ash with water to obtain a desulfurization ash slurry, and then adjusting the pH to 5-6 with hydrochloric acid. Oxidation to obtain a slurry containing calcium sulfate and calcium chloride, the slurry is swirled and separated, the underflow slurry after the swirled separation is adjusted to obtain a reaction slurry, and the reaction slurry is reacted with sulfuric acid waste acid to obtain hemihydrate gypsum Whiskers; the preparation process of the method described in this scheme produces a large amount of HCl waste gas, which needs to be collected, thereby increasing the cost of the device
Moreover, there are a large amount of Cl ions in the system enriched in gypsum, which cannot be directly applied

Method used

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  • A method for preparing α-type hemihydrate gypsum from desulfurized ash and its product
  • A method for preparing α-type hemihydrate gypsum from desulfurized ash and its product
  • A method for preparing α-type hemihydrate gypsum from desulfurized ash and its product

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Embodiment 1

[0081] The method for preparing α-type hemihydrate gypsum by utilizing desulfurization ash:

[0082] (a) Calcining the desulfurized ash in an air atmosphere at 450° C. for 2 hours to obtain calcined desulfurized ash;

[0083] (b) mixing and stirring the calcined desulfurized ash obtained in step (a) and water according to a mass ratio of 1:5 to form a slurry;

[0084] (c) Heat the slurry obtained in step (b) in a water bath at 40°C, stir at a speed of 300r / min, add a sulfuric acid solution with a concentration of 1mol / L dropwise at a rate of 0.1mL / s, and continue to Stir for 1 h, separate the product from solid and liquid, and wash with water until neutral to obtain a solid product, and the addition of the sulfuric acid makes the pH of the slurry 5;

[0085] (d) mixing the solid product of step (c), water and the crystal-transforming agent, the mass ratio of the solid product to water is 1:1, the mass ratio of the solid product to the crystal-transforming agent is 1:0.001, in...

Embodiment 2

[0094] The method for preparing α-type hemihydrate gypsum by utilizing desulfurization ash:

[0095] (a) Calcining the desulfurized ash in an air atmosphere at 500° C. for 1.5 hours to obtain calcined desulfurized ash;

[0096] (b) mixing and stirring the calcined desulfurized ash obtained in step (a) and water according to a mass ratio of 1:8 to form a slurry;

[0097] (c) Heat the slurry obtained in step (b) in a water bath at 30°C, stir at a speed of 200r / min, add a sulfuric acid solution with a concentration of 5mol / L dropwise at a rate of 0.02mL / s, and continue to Stir for 15 hours, separate the product from solid and liquid, and wash with water until neutral to obtain a solid product. The amount of sulfuric acid added makes the pH of the slurry 3.5;

[0098] (d) mixing the solid product of step (c), water and the crystal-transforming agent, the mass ratio of the solid product to water is 1:3, the mass ratio of the solid product to the crystal-transforming agent is 1:0.0...

Embodiment 3

[0102] The method for preparing α-type hemihydrate gypsum by utilizing desulfurization ash:

[0103] (a) calcining the desulfurized ash in an air atmosphere at 550° C. for 1 hour to obtain calcined desulfurized ash;

[0104] (b) mixing and stirring the calcined desulfurized ash obtained in step (a) and water according to a mass ratio of 1:15 to make a slurry;

[0105] (c) Heat the slurry obtained in step (b) in a water bath at 20°C, stir at a speed of 100r / min, add a sulfuric acid solution with a concentration of 0.1mol / L dropwise at a rate of 1mL / s, and continue to Stir for 5 hours, separate the product from solid and liquid, and wash with water until neutral to obtain a solid product. The sulfuric acid is added in an amount such that the pH of the slurry is 2.5;

[0106] (d) mixing the solid product of step (c), water and the crystal-transforming agent, the mass ratio of the solid product to water is 1:7, the mass ratio of the solid product to the crystal-transforming agent...

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Abstract

The invention relates to a method for preparing alpha-semi-hydrated gypsum by using desulfurized fly ash and a product of the alpha-semi-hydrated gypsum. The method comprises the following steps: calcining desulfurized ash to convert the main component into type-II anhydrous gypsum, CaO and CaCO3, then preparing the desulfurized ash into slurry, carrying out reacting with sulfuric acid to obtain dihydrate gypsum, and carrying out a crystal transformation reaction to obtain the alpha-semi-hydrated gypsum. In the preparation process of the method disclosed by the invention, addition of an excitant of II-type anhydrous gypsum is not needed, and discharge of harmful substances such as SO2 gas and the like is avoided, so that cost is reduced, and environment-friendly requirements are met. In addition, the prepared alpha-semi-hydrated gypsum is high in purity and has relatively high bending strength and compressive strength.

Description

technical field [0001] The invention belongs to the resource utilization field of flue gas desulfurization ash, and in particular relates to a method for preparing α-type hemihydrate gypsum from desulfurization ash and a product thereof. Background technique [0002] Flue gas circulating fluidized bed (CFB) desulfurization technology has been popularized and applied by steel mills in my country because of its advantages such as high desulfurization efficiency, simple process flow, low investment cost, and no desulfurization wastewater discharge. At the same time, a large amount of sintered desulfurization ash is discharged every year, and its main components are calcium sulfite, calcium hydroxide and a small amount of calcium carbonate, which are difficult to directly develop and utilize. Compared with the desulfurization gypsum produced by wet desulfurization, the application of sintered desulfurization ash is more difficult, and has not attracted enough attention from the ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C04B11/26C04B11/032
CPCC04B11/005C04B11/032C04B11/264
Inventor 孟醒刘丽娟刘成龙张婧陈甜甜王姗李山山马红青唐永波万建东
Owner JIANGSU EFFUL SCIENCE AND TECHNOLOGY CO LTD