Method for recrystallizing and purifying desulphurized gypsum

A desulfurization gypsum and recrystallization technology, applied in the direction of calcium/strontium/barium sulfate, etc., can solve the problems of complex impurities, serious accumulation of desulfurization gypsum, low whiteness, etc., to reduce the burden on enterprises, good environmental benefits and social benefits , the effect of increasing corporate income

Inactive Publication Date: 2010-10-27
SHANGHAI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] At present, there is no effective method to remove impurities in desulfurized gypsum, resulting in serious accumulation of desulfurized gypsum. How to make reasonable use of desulfurized gypsum has become an urgent problem to be solved
The impurities in desulfurized gypsum are complex, not only soluble ions, but also some water-insoluble ash, resulting in too low whiteness, reducing the hydration performance of gypsum, and seriously affecting the application of industrial by-product gypsum

Method used

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  • Method for recrystallizing and purifying desulphurized gypsum

Examples

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Effect test

Embodiment 1

[0013] Example 1: Crush the desulfurized gypsum from a coal-fired power plant, sieve it through an 80-mesh sieve, add 100.00 g of the crushed desulfurized gypsum to a 1000 mL beaker at the same time as 1000 mL of 1 mol / L nitric acid solution, and stir for 4 hours , to remove the impurities reacting with nitric acid in the raw material, then dry the filter cake in a 60°C blast drying oven for 12 hours, then crush it, weigh 35.00g of the above acid-washed and dried desulfurized gypsum, and mix it with 500mL, 2mol / L nitric acid Add the solution together into a 1000mL flask, immerse more than two-thirds of the volume in a 95°C constant temperature water bath, keep the temperature constant and stir for 4 hours. Put it into a 1000mL beaker, place it in a constant temperature water bath at 15°C for cooling and crystallization for 18h. After the crystallization is complete, filter with suction, transfer the filter cake to a 1000mL beaker for water washing, and then dry the filter cake...

Embodiment 2

[0014] Example 2: Recycle 500mL of the filtrate in Example 1, add 35.01g of acid-washed desulfurized gypsum into a 1000mL flask at the same time, then immerse more than two-thirds of the volume of the flask in a 95°C constant temperature water bath, keep the temperature constant and stir 4h. After the reaction is complete, suction filter while hot to remove solid residues not dissolved in the nitric acid solution, transfer the filtrate to a 1000mL beaker, and place it in a constant temperature water bath at 15°C for cooling and crystallization for 18h. After the crystallization is complete, filter with suction, transfer the filter cake to a 1000mL beaker for water washing, and then dry the filter cake in an oven at 60°C for 12 hours to obtain 15.55g of high-purity gypsum product. The whiteness after purification is 92.4%. The composition analysis of the product is shown in Table 1.

Embodiment 3

[0015] Example 3: Weigh 35.00 g of the recrystallized and purified desulfurized gypsum prepared in the steps of Example 1 to carry out secondary recrystallization and purification of desulfurized gypsum, and then add it to 1000 mL at the same time as the 2 mol / L nitric acid solution with a fixed volume of 500 mL in advance In the flask, more than two-thirds of the volume of the flask was immersed in a 95°C constant temperature water bath, and the temperature was kept constant and stirred for 4 hours. After the reaction was completed, suction filtered while it was hot, and the filtrate was transferred to a 1000mL beaker, and placed in a constant temperature water bath at 15°C for cooling and crystallization for 18h. After the crystallization is complete, filter with suction, transfer the filter cake to a 1000mL beaker for water washing, and then dry the filter cake in an oven at 60°C for 12 hours to obtain 17.42g of high-purity gypsum product. The whiteness of the primary recry...

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Abstract

The invention provides a method for recrystallizing and purifying desulphurized gypsum, which mainly comprises the four steps of acid-washing, dissolution, crystallization and washing, and specifically comprises the following steps of: removing impurities, reacted with acids, in the desulphurized gypsum by the aid-washing, dissolving calcium sulphate in the desulphurized gypsum into the acid solution at a relatively higher temperature by utilizing the characteristic that the solubility of the calcium sulphate in the specific acid solution is remarkably changed with the temperature, performing solid-liquid separation to remove undissolved solid-phase impurities at the high temperature, performing cooling recrystallization and the solid-liquid separation on a liquid phase at a relatively lower temperature, and washing and drying a filter cake to obtain high-purity gypsum, wherein the liquid phase in the dissolution and recrystallization processes can be reused. Through the method provided by the invention, the gypsum with relatively higher purity and whiteness can be prepared by selecting a proper solid-to-liquid ratio, proper temperatures and proper acid concentration and performing dissolution and crystallization for a certain time, and the performance of the desulphurized gypsum is remarkably improved.

Description

technical field [0001] The invention relates to a method for recrystallizing and purifying desulfurized gypsum, which belongs to the technical field of preparing high-purity gypsum. Background technique [0002] Desulfurization gypsum includes by-products produced during the flue gas desulfurization (FGD) process, in which the content of calcium sulfate is higher (above 70%) and the whiteness is lower (about 44% whiteness). Because these gypsums are by-products in the industrial process, the limitations of industrial conditions make them complex in impurity components, high in water content, fine in particle size and concentrated in particle size, poor in gradation, and low in whiteness, which is a problem for resource utilization of desulfurized gypsum. obstacles. Although the content of natural gypsum is large in China, natural gypsum resources are scarce in the Yangtze River Delta and Pearl River Delta regions where the industry is more developed, and the sulfur dioxide ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01F11/46
Inventor 施利毅王钢领冯欣钱明汤庆利杨文文
Owner SHANGHAI UNIV
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