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Method for preparing cryolite by using phosphoric acid industry waste gas

A technology of industrial waste gas and cryolite, applied in the directions of aluminum fluoride, silicon dioxide, aluminum halide, etc., can solve the problems of waste residue and/or waste liquid pollution, and achieve the effect of reducing consumption and non-toxic raw materials

Inactive Publication Date: 2019-04-23
杨先平
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AI Technical Summary

Problems solved by technology

Although this avoids the pollution of fluorine-containing gas to the atmosphere, it also produces waste residue and / or waste liquid pollution

Method used

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Examples

Experimental program
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Embodiment 1

[0030] By 2.5% (volume ratio) HF and 1.7% (volume ratio) SiF4 and the fluorine-containing waste gas that air forms adopt ceramic Raschig ring packing tower, absorb with 5% sodium bicarbonate solution. Control the reflux ratio=5, make the pH of the absorbing liquid=7.5, the exhaust gas contains 0.023% of HF and 0.028% of SiF4 after detection, that is to say, the absorption rate of HF reaches 99.1%, and the absorption rate of SiF4 reaches 98.4%. Raise the temperature of the absorption solution to 90°C, add polyacrylamide with 0.05% of the total amount of precipitates into the solution as a flocculant, keep it warm for 2 hours, cool to 30°C at a cooling rate of 15°C / h and filter, and wash the filter residue twice with water , and then dried at 110°C for 2h, and calcined at 250°C for 3h to obtain white carbon black with a specific surface area of ​​147m2 / g. Then the theoretical amount of 95% aluminum hydroxide is reacted with 20% sodium hydroxide solution to obtain 28% sodium meta...

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Abstract

The invention relates to a method for preparing cryolite by using phosphoric acid industry waste gas. According to the method, fluorine-containing waste gas generated in a phosphoric acid preparationprocess using acid dissolving of phosphate rock is absorbed with a sodium bicarbonate solution, such that the hydrogen fluoride in the fluorine-containing gas reacts with the sodium bicarbonate to generate sodium fluoride, the SiF4 in the fluorine-containing gas reacts with the sodium bicarbonate to generate sodium fluoride and silica gel, and the silica gel is precipitated as hydrated silica; after filtering drying and calcination are performed, high specific surface active silica (white carbon black) can be prepared; after the filtrate (sodium fluoride solution) is mixed with a sodium metaaluminate solution, high molecular ratio sodium fluoroaluminate is obtained by introducing carbon dioxide gas; and filtering and drying are performed to obtain the product cryolite, wherein the step isa crystallization step, and the sodium bicarbonate solution generated in the step can return to the absorption step to repeatedly absorb the fluorine-containing gas. According to the present invention, with the method, the high added value product cryolite can be prepared by using the fluorine-containing waste gas.

Description

Technical field: [0001] The invention is a production method for comprehensively utilizing fluorine-containing waste gas in the production process of phosphoric acid to prepare high molecular ratio cryolite and by-product white carbon black, which belongs to the field of inorganic chemical industry. Background technique: [0002] Phosphoric acid is obtained by metathesis reaction of phosphate rock with strong inorganic acids (such as sulfuric acid and hydrochloric acid). The main component of phosphate rock is fluoroapatite (Ca5F(PO4)3). The fluorine element in phosphate rock will be released in the form of HF gas during the acid hydrolysis process, and some of it will be dissolved in the liquid phase. The HF in the liquid phase reacts with the SiO2 in the phosphate rock to form SiF4, and SiF4 will also be digested in the form of gas during the subsequent phosphoric acid concentration process. Therefore, a large amount of waste gas containing HF and SiF4 will be produced in...

Claims

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Application Information

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IPC IPC(8): C01F7/54C01B33/18
CPCC01F7/54C01B33/18
Inventor 杨先平
Owner 杨先平
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