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Method for producing calcium fluoride, reusing method and recycling method thereof

A technology for calcium fluoride and calcium fluoride production, which is applied in the field of recycling calcium fluoride and recycling calcium fluoride, and can solve the problems of increasing chlorine impurities, excessive secondary aggregation, and decreased hydrogen fluoride yield.

Active Publication Date: 2007-01-31
MORITA CHEMICAL IND CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Recovered calcium fluoride has no particle size or flowability problems, but contains preferably no more than about 3% to 7%, with an average of about 10-15% calcium carbonate, when the recovered calcium fluoride is used as a feedstock for the production of hydrogen fluoride , the calcium carbonate produces a large amount of carbon dioxide gas and water through the reaction represented by equation (1), resulting in the following problems: decreased hydrogen fluoride yield, unstable operation and severe corrosion of equipment
[0022] Recycled calcium chloride obtained from particle-homogenized calcium carbonate or recovered calcium fluoride obtained by crystal growth can be used as a raw material for the production of hydrogen fluoride by combining a certain percentage of the above-mentioned recovered calcium fluoride with It is carried out by mixing fluorite, the raw material for this purpose, but the purity of these recovered calcium fluorides is about 92% to 97%, and the loss on ignition (when heated at 500°C to 600°C for several hours weight loss) and impurities fluctuate widely
Therefore, there are difficulties in analysis and operational management, and a major problem is the added cost of this
[0023] Recycled calcium fluoride usually has the following problems: small average particle size, many secondary aggregations, large specific surface area, low bulk density, high moisture content, large ignition loss, a large amount of impurities such as chlorine, etc.
Therefore, it is difficult to use as a raw material for the production of hydrogen fluoride due to: generation of dust during drying, poor mixing ability with fluorite, high reactivity to sulfuric acid, increased chlorine impurities, etc.

Method used

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  • Method for producing calcium fluoride, reusing method and recycling method thereof
  • Method for producing calcium fluoride, reusing method and recycling method thereof

Examples

Experimental program
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Effect test

Embodiment 1

[0079] 5 liters of hydrochloric acid of 1000 grams of 5% were housed in it was made by Teflon (registered trademark, hereinafter the same) PFA and a reactor equipped with a Teflon stirrer was placed in a water bath whose temperature was set at 50° C., and within 5 hours, Preferably under the balance of the metering pump, drop 1200 grams of 1000 grams of fluoride-containing neutral effluent (containing 21.1% potassium fluoride, 7.2% potassium chloride and 0.4% fluorine) into the stirred solution. NaCl) (totally 7.1% fluoride) and 200 grams of 35% hydrochloric acid mixed solution, drop into 1482 grams of 14% calcium chloride aqueous solution simultaneously. 10 minutes after the dripping was completed, the stirring was stopped, the solution was subjected to suction filtration, and 3520 g of filtrate was recovered. The residue was washed slightly and then dried at 120° C. for 2 hours to recover 134.2 g of calcium fluoride (92% recovery). The purity of calcium fluoride is 99.1%, t...

Embodiment 2

[0081] A 5 liter reactor made of Teflon PFA and equipped with a Teflon stirrer containing 1000 grams of 2% hydrochloric acid is placed in a water bath set at 50° C. and within 5 hours, preferably under metering pump equilibrium, In this stirring solution, drop 1100 grams of a mixed solution consisting of 1000 grams of pH of 9 fluoride-containing alkaline effluent (containing 2.4% sodium fluoride) and 100 grams of 35% hydrochloric acid. 1610 grams of 2% calcium chloride in water. 10 minutes after the dripping was completed, the stirring was stopped, the solution was subjected to suction filtration, and 3650 g of filtrate was recovered. The residue was washed slightly and then dried at 120° C. for 2 hours to recover 15.0 g of calcium fluoride (67% recovery). The purity of calcium fluoride is 99.0%, the average particle size is 9.8 microns, and the loss after burning at 500°C for two hours is 0.23%. The mother liquor contains 1.5% hydrochloric acid and 0.2% calcium fluoride. ...

Embodiment 3

[0083] A 5 liter reactor made of Teflon PFA and equipped with a Teflon stirrer containing 1000 g of 15% hydrochloric acid is placed in a water bath set at 50° C. and within 5 hours, preferably under metering pump equilibrium, 1000 grams of hydrofluoric acid-containing effluent (containing 17.2% hydrofluoric acid and 15.0% hydrochloric acid) was added dropwise to the stirred solution, and 1704 grams of 28% calcium chloride aqueous solution was added dropwise. 10 minutes after the dripping was completed, the stirring was stopped, the solution was subjected to suction filtration, and 3400 g of filtrate was recovered. The residue was washed slightly and then dried at 120° C. for 2 hours to recover 287.6 g of calcium fluoride (86% recovery). The purity of calcium fluoride is 99.3%, the average particle size is 27.3 microns, and the loss after burning at 500°C for two hours is 0.23%. The mother liquor contains 17.9% hydrochloric acid and 1.4% calcium fluoride. mother liquor pH ...

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Abstract

In order to recycle the fluoride, calcium fluoride having a particle size and purity suitable for the production of hydrogen fluoride is recovered from the fluoride-containing effluent or the hydrofluoric acid-containing effluent. The method involves reacting a fluoride-containing effluent or a hydrofluoric acid-containing effluent with an aqueous solution of calcium chloride under acidic conditions formed by hydrochloric acid, under which calcium fluoride has a relatively high solubility. Calcium fluoride can be precipitated with high purity and large particle size. The hydrochloric acid residue from or formed by the reaction reacts with inexpensive calcium compounds such as calcium hydroxide, calcium oxide, and calcium carbonate to produce an aqueous calcium chloride solution that is reused to treat effluents containing hydrofluoric acid . The obtained calcium fluoride can be used as a raw material for producing hydrogen fluoride, and the remaining calcium chloride aqueous solution can be provided for other industrial purposes.

Description

technical field [0001] The present invention relates to a process for the production of calcium fluoride from a fluoride-containing effluent containing little hydrofluoric acid but having a relatively high fluoride concentration, or from a hydrofluoric acid-containing effluent, which has a practical The purity and particle size required for use as a raw material for the production of hydrogen fluoride. In addition, the present invention relates to a method for preparing an aqueous solution of calcium chloride by reacting hydrochloric acid, a by-product of the reaction, with an alkaline calcium salt, and then using the aqueous solution as a calcium source to recover calcium fluoride. The invention also relates to a method for recycling the recovered calcium fluoride. Background technique [0002] In processes for treating fluoride-containing effluents that contain little hydrofluoric acid or hydrofluoric acid-containing effluents, the effluent is typi...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01F11/22C02F1/58B01D9/02B01D9/00C01B7/19C02F1/52
CPCC01F11/22B01D9/0036C02F2303/16C01B7/192C01P2006/82C02F2209/06C02F1/5245C02F1/5236C01P2006/80C01P2004/61C02F2101/14B01D9/005B01D9/0059
Inventor 百田邦堯山本和正井上洋一渡边修一
Owner MORITA CHEMICAL IND CO LTD
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