SU1498711A1 - Method of separating fluorine as calcium fluoride from fluorine-bearing solutions - Google Patents

Abstract

The invention relates to the field of chemical technology, in particular, to methods for producing calcium fluoride. Industrial effluent from the production of methane freons, containing hydrofluoric acid from concentrations of 0.015–3.0 g / l, is fed into the stirred reactor, after which 10% calcium hydroxide solution is fed. The reaction mixture is stirred for 5 minutes. The resulting calcium fluoride suspension is sent for separation into a settling tank, settled for 24 hours, the precipitate from the settling tank is fed to a KS dryer. The product contains 99% CAF ₂ , the mother liquor from the settling tank is returned to the site of preparation of calcium hydroxide solution. When the content of fluoride ion in the flow of 0.15-3.0 g / l, the process is carried out at room temperature, with the content of fluorine ion of 0.015-0.15 g / l, the process is carried out when heated to 60-90 ° C. The ratio of ions CA and F ions support equal to (6-8): 1. The invention improves fluorine recovery from 92-99.5% to 100% and shortens the process time. 2 hp f-ly, 2 tab.

Description

The invention relates to the field of chemical technology, in particular to methods for extracting fluorine from solutions in the form of calcium fluoride, used as a mineralizer in the production of cement and other industries.

The purpose of the invention is to increase the degree of extraction of fluorine and reduce the duration of the process.

Waste from the production of methane freons with HF, KF content up to 200 g / l and NaF is used as fluorine-containing solutions.

up to 40 g / l. In order to organize closed-flow production and to obtain high quality calcium fluoride with a high and low degree of fluorine extraction, it is necessary to obtain solutions containing fluoride-ion of 0.015–3.0 g / l.

In production, this is done by mixing process and sewage effluents, where the fluoride ion concentration does not exceed 100–200 mg / l.

C p and meer. Industrial runoff from the production of methane refrigerants, containing hydrofluoric acid with a concentration of 0.15 g / l, in

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the amount of 1 kg / h, served in the reactor while the mixer is running. After that, a 10% solution of calcium hydroxide in the amount of 1.2 kg / h is fed to the reactor. The reaction mixture is stirred in the reactor for 5 minutes at an ambient temperature of IS-ZO C.

The calcium fluoride slurry formed during the process is analyzed for the content of the base material and sent for separation into a settling tank. The precipitate from the settling tank is sent to the KS dryer. The yield of granulated product is 12 kg / h. The finished product contains 99% CaFj and corresponds to TU-02-1165-83. The mother liquor from the sump is returned to the site of preparation of the solution of calcium hydroxide

Table 1 gives examples of the process with various parameters.

When the calcium ion ratio to yogi fluorine is less than six, the duration of the process increases and the degree of fluoride extraction from the solution decreases to the level of the prototype.

When the ratio of calcium ions to fluorine ions is greater than eight, for example, nine quality products are formed, but in this case the degree of contamination of the product with calcium salts from 0.003 to 0.024% increases, which is not economically feasible to do.

In tab. 2 shows a comparative analysis of the known and proposed invention.

The invention makes it possible to increase the degree of fluorine recovery from solutions with a concentration below 0.15 g / l from 92 to tOO% and from solutions with a concentration of 0.15-3.0 g / l with 99.5 D (

100%, reduce the duration of the process: when processing solutions with a concentration below 0.15 g / l, the processing time decreases from 1 day to 10-15 minutes; for solutions with a concentration of 0.15-3.0 g / l, from 30 minutes to 5 -10 min; the sedimentation time of the product decreases, respectively, from 1 day to 2-3 hours and from 6-8 hours to 2-3 hours. A product with a basic substance content of 99% is obtained, the mother liquors are used in the process to prepare a calcium hydroxide solution.

Claims (3)

1. A method of extracting fluorine in the form of calcium fluoride from fluorine-containing solutions, including treatment with a calcium hydroxide solution followed by separation of the product, in order to increase the degree of fluorine recovery. and shortening the process time, the stock solutions are used in an amount that provides a ratio of calcium ions to fluoride ions of 6-8. . 2. A method according to claim 1, characterized in that the content of fluoride ion in the initial solution is maintained at 0.015-3.0 g / l. 3. Method according to paragraphs. 1 and 2, that is, with the fact that when the content of fluoride ion in the initial solution  0.15-3.0 g / l, the treatment is carried out at room temperature, and when the content of fluoride ion is 0.015-0.15 g / l - at 60-9C C. Table 1 Sa (OH  . f PJ-6 5 5 10 20 20 60 20 90 99 99 99 NaF, HF, In dry form or in the form of a 10% solution of Ca (OHHg eleven 20 Initial concentration of fluoride ion, mg F / l Ratio A Amount of fluorine bound in CaF from stoichiometry,% iCapa 720 150-3000 15-150  30 mg P / l; A from 0.3 C 15-150 mg F / l; up to 0.7; With ,, - 720 mg P / l; And from 3.04 to 4.9 Si 30 mg P / l;   С „- 150-3000 mg F / l; t-20; Ch 15-150 mg F / l; CaFft 92; C "-720 mg P / l; t 60-70; DSara 100; t "20; DSARg 99.5 € 150-3000 mg F / l; uCaFj. 100 Continuation of table 1 table 2 NaF, KF,, HF In the form of a 10% solution of Ca (OH) 6-12, Optimally 8-10 For CH, 150-3000 mg F / L; For C nd 150mg F / l t 60 150-3000 15-150   С „- 150-3000 mg F / l; t-20; Ch 15-150 mg F / l; € 150-3000 mg F / l; uCaFj. 100 1498711 Reaction time ff, mg P / l; min, Ca + 2F CaFft 1 day; C 720 mg F / L; t 20; 20 Excess Ca (OH) 2 S |, "30 mg F / l; , 1-f; Cu "720 mg P / l;  f 7Y Cu-720 mg F / l; t "20; t- 6-8 I Where to: the cleared drain In the sewerage received sludge 8 Continuation of table 2 C 15-150 IG F / L; Wed 10-15; Si 150-3000 mg f / l; tTp 5-10 ,9 Ion concentration Ca and F in purified water Ch 15-150 MrF / l; Ch 150-3000 mg F / l; d 10-100 0 15-150 mg F / l; t Sleep  150-3000 mg F / L; t 20; 2-3 In production in production