RU1601938C - Method of boric acid producing - Google Patents

Abstract

FIELD: chemical technology. SUBSTANCE: boric acid is prepared by decomposition of boronsilicate raw with sulfuric acid where 75-95% sulfuric acid is fed for decomposition and its residual portion up to stoichiometric quantity is used for additional decomposition of separated insoluble residue. Additional decomposition is carried out for 50-70 min at the ratio liquid: solid = (2-5):1 following by reprocessing by known schema up to preparing of crystalline boric acid. Invention ensures to increase decomposition degree of raw from 93.1-97.6% to 98.0-99.6%. EFFECT: increased decomposition degree of raw. 3 tbl

Description

 The invention relates to chemical technology, in particular to methods for producing boric acid, which is widely used in chemical, construction and other fields of national economy.

 The aim of the invention is to increase the degree of decomposition of raw materials.

 The essence of the method is as follows. When reducing the consumption of sulfuric acid for decomposition to 75-95% of the stoichiometric amount, the degree of decomposition of the datolite concentrate decreases slightly and amounts to 83.7-95.8%, while silicic acid does not have time to go into a gel state and the pulp retains satisfactory filtration properties. When the solution is separated, silicic acid is separated from the insoluble residue and does not prevent its further decomposition. An insoluble residue is further decomposed by 5-25% sulfuric acid of the stoichiometric amount, while the remaining amounts of boric and silicic acids pass into the solution, but the concentration of silicic acid does not reach a critical value and the resulting pulp retains satisfactory filtration properties.

PRI me R. 54 g of sulfuric acid (monohydrate), constituting 85% of the stoichiometric amount, is diluted with 546 g of a circulating solution with a content of 0.94 wt.% B ₂ O ₃ , 100 g of a datolite concentrate of the composition, wt.%: B ₂ O ₃ acid-soluble (cr) 17.5; SiO ₂ 35.04; CaO 35.8; MgO 0.1; Fe ₂ O ₃ 2.8; . other impurities (pp = 8.76 decomposition was conducted for 30 min at ⁹⁵ ° C, the initial ratio of W: T = 6: 1, and a turbulent mixing regime resulting pulp is separated on a laboratory suction filter..

The cake of the decomposition step is diluted with 370 g of a wash solution containing 0.78 wt.% B ₂ O ₃ and 9 g H ₂ SO ₄ . (15% of stoichiometric amount) and at a ratio of W: T = 4: 1 repulped for 60 minutes at ⁹⁵ ° C, and then the pulp is separated on a laboratory suction filter. The filtrate is sent to dilute sulfuric acid, and the sludge is subjected to a four-stage countercurrent washing with technical water in an amount of 420 g to obtain 112 g of dry sludge composition, wt.%: In ₂ About ₃ K. 0.06; B ₂ O ₃ water-soluble (vp) 0.05; SO ₂ 10.57; 370 g of washing solution, which is sent to the stage of additional decomposition.

Produktcionnyj solution was dried at ³⁰⁰ ° C in a muffle furnace to give 79.51 g of crude product as a dry crumbly powder composition, wt%: H ₃ BO ₃ 39.62;. SiO ₂ 31.69; H ₂ SO ₄ 2.12; Fe ₂ O ₃ 1.02; CaO 1.13; p.p. 0.4; H ₂ O, 24.02.

The resulting intermediate was diluted with 500 g of a mother liquor with a content of 2.8 wt.% In ₂ About ₃ , boric acid was leached for 60 minutes at 80 ^about C and insoluble residue was separated in the form of silicon dioxide. The silica was subjected three-stage countercurrent washing process water in an amount of 100 g at ⁸⁰ ° C, the washings are fed to the dilution of the sulfuric acid, the silica was dried in a muffle furnace at ³⁰⁰ ° C to give 22.3 g of product composition, by weight%:. SiO ₂ 98.6; Fe ₂ O ₃ 0.02; Al ₂ O ₃ 0.002; B ₂ O ₃ 0.4; H ₂ O 0.5; p.p. 0.4. The resulting product complies with GOST 22551-77.

After separation of the silica, the production solution is neutralized with CaCO ₃ to pH 4.9, the solid residue is filtered off, control filtration is carried out, the solution is acidified to pH 2.6 and boric acid is crystallized, crystals are separated, mother liquors are sent to leach the intermediate product, the boric acid crystals are washed , dried, and 29.9 g of boric acid are obtained. The quality of the boric acid obtained meets the requirements of GOST 18704-78 grade B.

 The dependence of the degree of decomposition of raw materials on the amount of sulfuric acid supplied for decomposition and additional decomposition is shown in Table 1.

It follows from Table 1 that during dorazlozheniya using 2% of the stoichiometric amount of sulfuric acid, the total degree of decomposition of B ₂ O ₃ is 97.1, but using 5% is 98%, i.e., the degree of decomposition increases by 0.9%, therefore, the consumption of sulfuric acid 95% of the stoichiometric amount is accepted as the upper limit for the consumption of sulfuric acid for decomposition. During the process of additional decomposition of 30% of the stoichiometric amount of sulfuric acid, the total degree of decomposition of В ₂ О ₃ drops to 92.4%, moreover, under such operating conditions, the filtration properties of the pulp deteriorate (the filtration rate drops to 1.0-1.3 m ³ / m ² ˙ h); therefore, the consumption of 75% of the stoichiometric amount is selected as the lower limit of the rate of consumption of sulfuric acid for decomposition.

 The dependence of the degree of decomposition on the ratio of solid and liquid phases and the duration of decomposition at the stage of additional decomposition are given in Table 2.

From table 2 it follows that at a time of additional decomposition of 40 minutes and the ratio W: T = 2-6: 1, the total degree of decomposition is not more than 97.6%, an increase in the time of additional decomposition to 50 minutes leads to an increase in the degree of decomposition by 0.6- 1.8%, therefore, the time limit of 50 minutes was taken as the lower limit of the time of additional decomposition. When carrying out additional decomposition with the ratio W: T = 1: 1, the filtration properties of the pulp sharply deteriorate (the filtration rate is less than 0.1 m ³ / m ² ˙ h), therefore, the lower limit of the W: T ratio is 2: 1. At the same time, when the solid is diluted to the ratio W: T = 6: 1, the process of additional decomposition proceeds slowly and the degree of decomposition reaches 98.2% in 80 minutes, moreover, an increase in the amount of washings negatively affects the water balance of the circuit and contributes to an increase in losses ₂ O ₃ , so the upper limit of the liquid to solid ratio is 5: 1, and the decomposition time is limited to 70 minutes.

 In the table. 3 shows comparative data on the degree of decomposition, the yield of boric acid and silicon dioxide by this method and prototype.

 Thus, the proposed method allows to increase the degree of decomposition from 93.1 - 97.6% to 98.0 - 99.6%, while the yield of boric acid increases by 0.3-3.1%, and the yield of silicon dioxide by 7.0-10.9%.

Claims (1)

 METHOD FOR PRODUCING BORIC ACID, including decomposition of borosilicate raw materials with sulfuric acid diluted with working solutions, separating the insoluble residue, washing it, drying the solution, leaching boric acid from the dried mixture, separating the solution from silicon dioxide, washing and drying it, neutralizing the solution, vacuum crystallization boric acid, the separation of crystals and their drying, the return of the mother liquor to a process, characterized in that, in order to increase the degree of decomposition of the raw material, sulfuric acid is supplied for decomposition in the amount of 75 - 95% of the stoichiometrically necessary, and the rest of it is directed to the further decomposition of the separated insoluble residue, which is carried out for 50 - 70 minutes with a ratio of liquid and solid phases equal to 2 - 5: 1.

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