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Method for preparing alpha-beta composite semi-hydrated gypsum from phosphogypsum

A technology of hemihydrate gypsum and phosphogypsum, which is applied in the field of construction material preparation, can solve problems such as loose or compact atomic structure ordering, and achieve the effect of solving the bottleneck problem of sustainable development, low production cost, and simple production equipment

Active Publication Date: 2018-05-22
湖北声荣再生资源利用有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Dihydrate gypsum can be converted into hemihydrate gypsum under heating conditions. When dihydrate gypsum is heated in pressurized steam or in a medium with acid and salt, it can be converted into α-hemihydrate gypsum, and heated in a dry environment When dehydrating, β-hemihydrate gypsum is generated, so α and β-type hemihydrate gypsum are two extreme crystal forms of gypsum. Although there is no essential difference in atomic arrangement between the two, the loose or dense arrangement of their atomic structures makes them Makes a huge difference on a macro scale
[0005] However, in the existing α-hemihydrate gypsum preparation method, there is no report of dehydration under subsaturated steam at a temperature <100°C

Method used

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  • Method for preparing alpha-beta composite semi-hydrated gypsum from phosphogypsum

Examples

Experimental program
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Effect test

Embodiment 1

[0029] The phosphogypsum is taken from the phosphogypsum storage yard. After analysis, the attached water content is 10%, and the pH value is 5.0. On a dry basis, take 200kg of this phosphogypsum, and weigh 0.2% of the dry basis mass of the phosphogypsum. 400g of aluminum, 4000g of seed crystals were weighed by 2% by mass, mixed evenly in a horizontal mixer twice, and transferred to the α-hemihydrate gypsum crystal conversion box.

[0030] (1) Preparation of α-β composite hemihydrate gypsum

[0031] Use steam to humidify subsaturated air with a humidity of 90% and a temperature of 80°C to heat up. When the temperature indicated by the crystal conversion box is > 60°C, use atmospheric pressure steam for heating, and maintain the temperature in the crystal conversion box at 100 ℃, humidity 95%, after 8 hours of heat preservation, then use 100 ℃ hot air for pre-drying and dehydration, when the attached water content of the material is less than 5%, transfer it to a drying oven fo...

Embodiment 2

[0035] Phosphogypsum is taken from the phosphoric acid production site. After analysis, its attached water content is 25%, and its pH value is 3.5. On a dry basis, take 200kg of this phosphogypsum, and weigh 0.5% of the dry basis of the phosphogypsum. 1000g, weigh 2000g of seed crystals according to 1% mass, mix them evenly in a horizontal mixer twice, and transfer them to the α-hemihydrate gypsum crystal conversion box.

[0036] (1) Preparation of α-β composite hemihydrate gypsum

[0037]Use steam to humidify subsaturated air with a humidity of 80% and a temperature of 100°C for heating and heating. When the temperature indicated by the crystal conversion box is > 60°C, use atmospheric pressure steam for heating, and maintain the temperature in the crystal conversion box at 85 ℃, humidity 85%, after 12 hours of heat preservation, then use 200 ℃ hot air for pre-drying and dehydration, when the attached water content of the material is less than 5%, transfer it to a drying oven...

Embodiment 3

[0041] Phosphogypsum is taken from the phosphoric acid production site. After analysis, its attached water content is 22%, and its pH value is 2.5. On a dry basis, take 200kg of this phosphogypsum, and weigh 0.3% of the phosphogypsum dry basis. 600g of aluminum, 3000g of seed crystals were weighed according to 1.5% by mass, mixed evenly in a horizontal mixer twice, and transferred to the α-hemihydrate gypsum crystal conversion box.

[0042] (1) Preparation of α-β composite hemihydrate gypsum

[0043] Use steam to humidify subsaturated air with a humidity of 85% and a temperature of 90°C for heating and heating. When the temperature indicated by the crystal conversion box is > 60°C, use atmospheric pressure steam for heating, and maintain the temperature in the crystal conversion box at 90°C ℃, humidity is 90%, after 10 hours of heat preservation, then use hot air at 150 ℃ for pre-drying and dehydration, when the attached water content of the material is less than 5%, transfer ...

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Abstract

The invention relates to a method for preparing alpha-beta composite semi-hydrated gypsum from phosphogypsum. The method comprises the following steps of: (1) mixing the phosphogypsum with crystal modifier and seed crystals fully, then putting the mixture into an alpha-semi-hydrated gypsum crystal transition box, performing preheating by using sub-saturated air, and then introducing normal-pressure steam to maintain the temperature and humidity so as to achieve conversion of partial dihydrate gypsum in the phosphogypsum into alpha-semi-hydrated gypsum; (2) introducing hot air for predrying; and (3) performing further dehydration so as to convert unhydrated dihydrate gypsum into beta-semi-hydrated gypsum which is the alpha-beta composite semi-hydrated gypsum. Compared with traditional beta-semi-hydrated gypsum, the prepared alpha-beta composite semi-hydrated gypsum has small water requirement of normal consistency and high strength, and compared with alpha-semi-hydrated gypsum, no high-pressure dehydration devices and hydrothermal conditions are needed, so that the method has a mild production process, simple devices and low energy consumption; the product can be widely used as building gypsum powder or multiple types of gypsum blocks, and a practical and feasible technical method for resource utilization of the phosphogypsum is provided.

Description

technical field [0001] The invention relates to a method for preparing α-β composite hemihydrate gypsum by using phosphogypsum, belonging to the technical field of building material preparation. Background technique [0002] In the production process of high-concentration phosphate fertilizer, phosphoric acid is generated by the reaction of phosphate rock and sulfuric acid, and the by-product calcium sulfate is usually called phosphogypsum. The appearance of phosphogypsum is yellow-white, light gray-white or black-gray fine powder solid, the main component is CaSO 4 ·nH 2 O, its mass fraction is usually above 85%, similar to natural gypsum; generally contains 20-30% of free water. According to the different wet-process phosphoric acid production processes, the crystallization of phosphogypsum has dihydrate (CaSO 4 ·nH 2 O), hemihydrate (CaSO 4 0.5H 2 O) and other forms. At present, the production of wet-process phosphoric acid is mostly based on the dihydrate process, ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B11/032C04B11/036C04B11/26
CPCC04B11/032C04B11/036C04B11/26
Inventor 夏举佩
Owner 湖北声荣再生资源利用有限公司
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