SU948891A1 - Method of treating effluents from cation filters in desalination and softening of water - Google Patents

Description

The invention relates to the treatment and desalination of water and can be used in the power industry, chemical, petrochemical and other industries.

A known method for the treatment and reuse of effluents of sodium cation exchange filters, according to which the spent regeneration solution of these filters is treated with sodium hydroxide (or lime) and soda ash, and then acidified with hydrochloric acid. The salt solution thus treated is used for subsequent regenerations [1].

However, this method requires a significant consumption of expensive reagents - soda, hydrochloric acid and 20 not quite enough to prevent environmental pollution.

The closest to the proposed technical essence and the achieved result is a method of treating wastewater of cation exchange filters in the process of desalination and softening of water, including soda liming of effluents of sodium cation exchange filters, mixing 25 “80% of the treated effluent with the source water, and using the remaining 20- 75% For the preparation of a regeneration solution [2].

¹⁰ However, for the deposition of hardness salts, expensive reagent soda ash is used, which increases the cost of the process, as well as the content of sodium ions in softened water. The purpose of the invention is the possibility of obtaining sodium sulfate cation exchange filters from wastewater used to regenerate Na-cation exchange filters and eliminating soda consumption for effluent treatment.

This goal is achieved by the method of treating the effluent of cation exchange filters in the process of desalination and softening of water, namely, that the concentrated part of the effluent of Na-cation exchange filters is subjected to liming, the resulting solution after separation of 5 sediment is mixed with the rest of these effluents and passed through Na - cation exchange filter, after which the softened effluents of Na-cation exchange filters are mixed with the effluents of H-cation exchange filters of the desalination plant I, which are neutral salts of sodium sulfate, and sent for concentration.

In this case, 30-60% of the total effluent of Na-cation exchange filters is subjected to liming by treatment with lime taken in an amount equivalent to the magnesium hardness of the solution, and concentration is carried out in ₂ evaporators or electrodialyzers to obtain a 3-8% sodium sulfate solution.

'The drawing shows a diagram implementing the proposed method. g Source water is fed into clarifier 1 and is subjected to calcareous treatment. Lime water is passed through a sodium cation exchange filter 2. One part of the softened water is sent ₃ , sent to the consumer of softened water, and the other is passed sequentially through an H-cation exchange filter 3. and anion exchange filter 4, and demineralized water is obtained. ₃

The regeneration of the sodium-cation exchange filter 2 is carried out with a 3 “8% sodium sulfate solution at a speed of 6-15 m / h, and a dual-flow countercurrent filter can be used as a filter ₄ . The concentrated portion of the solution (30-60%) is fed from ^- . crystallizer stand 5, | * ud also serves a concentrated part of the spent solution of sodium cation exchange filter 6 and lime is added in an amount equivalent to the magnesium hardness of the solution. After precipitation of the precipitate, the solution is mixed with the remaining 70-40% diluted solution ⁵ 'collected in the tank 7, and through the sodium-cation exchange filter 6 together with the drain of the hydrogen-cation exchange filter 3 is fed to a concentrator 8 (evaporator or electrodialyzer). When organizing separately ^{5 the} production of sulfate and sodium chloride during the regeneration of anion exchange filters, sodium sulfate obtained from the regeneration of the anion exchange filter is also fed to the concentrator 8. This increases the amount of softened water received. A solution of sodium sulfate concentrated to 3 ~ 8% is used for regeneration of sodium-cation exchange filters 2 and 6. If an evaporator is used as a concentrator, the obtained distillate is added to demineralized water, and if an electrodialyzer is used, the resulting diluted solution is added to softened water.

Liming of the source water is desirable, but not required. If the source water is not subjected to lime treatment, then instead of the sodium cation exchange filter 2, a hydrogen-sodium cation exchange filter can also be used.

The proposed processing method in the process of desalination and water softening also eliminates the consumption of imported caustic soda used for the regeneration of anion exchange filters. In this case, a sodium hydroxide solution is obtained by passing a solution or suspension of lime through a sodium cation exchange filter regenerated with a sodium sulfate solution. The concentrated part of the spent solution of sodium cation exchange filters, softening the solution or suspension of lime, is also fed into the clarifier-crystallizer 5, and the diluted part of the solution is fed into the tank 7. The caustic soda solution obtained from the lime solution can be used directly or previously concentrated in electrodialyzers or evaporators. If it is necessary to obtain an additional amount of softened water or sodium hydroxide solution for the regeneration of sodium-cation exchange filters, an additional imported cheap sodium sulfate salt can be used, and the consumption of this salt is equivalent to the amount of additional hardness salts removed from the filter. Anion exchange filters can also be regenerated directly with a solution or suspension of lime, and calcium ions are deposited in a calcium sulfate sump.

For sulfate waters (wastewater of some metallurgical and chemical:

plants, waste regeneration water of hydrogen-cation exchange filters and others) the chemical desalination plant can be replaced by a thermal desalination plant. 5 At the same time, the purge water of the distillation unit, which is a 3-8% solution of sodium sulfate, together with a 38% solution of sodium sulfate from a concentrator of effluents <0 of sodium-cation exchange filters is used to regenerate all sodium-cation exchange filters.

Example. Source water with ionic composition, mEq / l: Ca 3.5; fifteen

Md 2.0; Na 1, 5; S0 ₄ 2.1; CE 1.1; HCOj 3, θ, is subjected to coagulation and liming. Lime water with ionic composition, mEq / l; Ca. 2.6;

Md 0.4; Na 1.5; SO4 2.4; CO2 0.7; Μ OH 0.3; CE 1.1 is passed through a sodium-cation exchange filter loaded with KU-2 cation exchanger. The sodium cation filter is regenerated with a 5% sodium sulfate solution with a 25 specific flow rate of 2 g-eq / g-eq. The exchange capacity of cation exchanger is 800 geq / m ^. The volume of the regeneration solution per 1 m ^ of cation exchanger is 2.3 m ³ , the water consumption for washing is 6 m ³ ,

The concentrated part of the spent solution of this filter with a volume of 3.5 together with the spent solution of a sodium cation exchange filter that softens the lime waste water with a volume. 0.9 m ³ with a total concentration of hardness salts

212 mEq / L, collected and subjected to calcareous treatment. After sedimentation, this water with a hardness of 40 mEq / L is mixed with the rest of the diluted part of the spent solution with a volume of 6 m ^ and a hardness of 12 mEq / l. The resulting mixture with a hardness of 24 mEq / l and a total salt content of 1 20.4 mg-eq / l and a volume of 10.4 m ^{3 is} passed through a sodium cation exchange filter, the filtrate is mixed with the spent solution of hydrogen cation exchange filters of a desalination plant with a volume of 7 , 5 m® and salinity of 107.4 mEq / L, regenerated with 4% sulfuric acid solution. The total volume of 17.9 m ³ and a salinity of 115 mEq / L. This solution is concentrated in the evaporator or electrodialyzer 6.1 times,

those. up to 5% ”sodium sulfate solution. The latter, with a volume of 2.9 m ^, is used for the regeneration of sodium cation exchange filters.

The proposed method allows, in comparison with the known method, to eliminate the consumption of soda ash for processing the spent solution, the consumption of imported caustic soda for regeneration of anion exchange filters of the desalination part and significantly reduce the content of sodium ions in softened water. The supply of softened water to the H-cation exchange filters dramatically increases the exchange capacity of cation exchangers.

. The expected technical and economic effect of the implementation of the proposed method with a productivity of the chemical desalination plant of 1000 m ³ / h is 15O thousand rubles. in year

Claims (2)

water softening, consisting in that a concentrated part of the effluent of Na-cation-exchange filters is subjected to liming to precipitate hardness salt after separation of the precipitate is mixed with the rest of these effluents and passed through the Na-cation-exchanger filter, after which the Na-cationite effluent is softened The filters are mixed with the effluent of the H-cation resin filters of the desalting plant, represented by. neutral salts of sodium sulfate, and sent for concentration. In this case, liming is subjected to 30-60% of the total volume of effluent of Na-cation-exchange filters by treating them with lime, taken in an amount equivalent to the magnesium hardness of the solution, and the concentration is carried out in evaporators or electrodialyzers until a sodium sulfate solution is obtained. . The drawing shows the scheme carrying out the proposed method. The source water is fed to clarifier 1 and subjected to lime treatment. The limed water is passed through a sodium-cation-exchange filter 2. One part of the softened water is sent to the consumer of the softened water, and the other part is passed through the H-cation-exchange filter 3. and the anionic filter and get demineralized water. The sodium cation-exchange filter 2 is regenerated with 3-8 | -a sodium sulfate solution at a speed of 6-15 m / h, and a double-flow counter-current filter can be used as a filter. The concentrated part of the solution (30-60%) is fed to: Stoic-mold 5, muda also serves the concentrated part of the developed sodium-cation-exchange filter 6 solution and add lime in an amount equivalent to the magnesium hardness of the solution. After sedimentation, the solution is mixed with the remaining 70–40% of the diluted solution collected in tank 7, and through the sodium cation filter 6 together with the drain of the hydrogen cation filter 3 is fed to the concentrator 8 (evaporator or electrodialyzer). In organizing the separate production of sulfate and sodium chloride in the process of regenerating anion-exchange filters, sodium sulfate, obtained from the regeneration of the anion-exchange filter, is also fed to the concentrator 8. This increases the amount of untreated water produced. The sodium sulfate solution, concentrated to 3-8%, is used to regenerate sodium-cation-exchange filters 2 and 6. If an evaporator is used as a concentrator, the distillate obtained is added to desalted water, and if an electrodialyzer is used, the resulting diluted solution is added to gchennoy water. Liming the source water is desirable, but not necessary. If the source water is not subjected to lime treatment, then instead of the sodium-cation filter 2, you can also use a hydrogen-sodium-cation filter. The proposed method of treatment in the process of desalting and water softening also makes it possible to eliminate the consumption of imported caustic soda used to regenerate anionite filters. The sodium hydroxide solution is obtained by passing a solution or a slurry of lime through a sodium cation-exchange filter regenerated with a sodium sulfate solution. The concentrated part of the spent sodium-cation-exchange filter solution, which softens the solution or suspension of lime, is also fed to the settling tank 5, and the diluted part of the solution is fed to the tank 7. The caustic soda solution obtained from the lime solution can be used directly or preconcentrated in electrodialyzers or vaporizers x. If it is necessary to obtain an additional amount of softened water or sodium hydroxide solution, additional imported cheap sodium salt can be used to regenerate sodium-cation-exchange filters, and the consumption of this salt is equivalent to the amount of hardness salts additionally removed from the filter. Anionite filters can also be regenerated directly with a solution or suspension of lime, and calcium ions are precipitated in a calcium sulphate crystallization sump. For sulphate waters (waste waters of some metallurgical and chemical plants, spent regeneration waters of hydrogen-cation filters and others), the chemical salinization unit can be replaced by a thermal desalting plant. At the same time, the purge water of the distillation unit, which is a sodium sulphate solution together with a sodium sulphate solution from the effluent concentrator sodium cationite filters, is used to regenerate all sodium cation exchanger filters. Example .. Source water with ionic composition, mEq / l: Ca 3.5, Md 2.0; Na 1.5; S04 2.1; C8 1.1; HCOj 3.8, coagulated and spilled. Lime water with ionic composition, mEq / l; Ca 2.6; MD 0 Na 1.5; 804 2, k; COj 0.7; OH 0.3; CE 1,1, is passed through a sodium-cation resin filter loaded with cation exchanger KU-2. The sodium cation exchanger filter is regenerated by a 5-1 m sodium sulfate solution with a specific flow rate of 2 g-equiv / g-equiv. The exchange capacity of the cation exchanger is Zoe g-equiv / m. The volume of the regeneration solution per 1 m of cation exchanger is 2.3 m, the water consumption for washing is 6 m. The concentrated part of the spent solution of this filter with a volume of 3.5 m, together with the spent solution of a sodium-cation-exchange filter, softening the calcified waste water with a volume of 0.9 m and a total concentration of hardness salts of 212 mg-eq / l, is collected and subjected to lime treatment. After separation of the precipitates, this water with a hardness of 40 mEq / l is mixed with the rest of the diluted part of the spent solution with a volume of 6 m and a hardness of 12 mEq / l. The resulting mixture with a hardness of 2k mg-eq / l and a total salt content of 1 20, j mg-eq and a volume of 10, m is passed through a sodium-cation filter, the filtrate is mixed with a spent solution of hydrogen-cation-exchange filters of a desalting plant with a volume of 7.5 m and the salt content of 107, mEq / l, re-generated by the%% solution of sulfuric acid. The total volume is 17.9 m, and the salt content is 115 mEq / L. This solution is concentrated 6.1 times in the evaporator or electrodialyzer, i.e. to sulphate solution on ri. The latter, with a volume of 2.9 m, is used to regenerate sodium cation-exchange filters. The proposed method allows, in comparison with the known method, to eliminate the consumption of soda ash for the treatment of the spent solution, the consumption of caustic soda in order to regenerate anionite filters of the desalting part and significantly reduce the content of sodium ions in softened water. The supply of softened water to H-cation-exchange filters dramatically increases the exchange capacity of cation exchangers. The expected technical and economic effect from the implementation of the proposed method with the capacity of the 1000 chemical desalting unit is 150 thousand r. per year 1. Claim treatment method of cation-exchange filters in the process of desalting and water softening, including the stage of liming for sedimentation of hardness salts, characterized in that, in order to ensure the possibility of obtaining sodium sulfate, used to regenerate Na-cation resin filters and eliminate the soda consumption for wastewater treatment, liming is subjected to a concentrated part of the effluent of Na-cationite filters, the resulting solution after separating the precipitate is mixed with the rest of these effluents and skipping After that, the softened effluent of the Na-cation-exchange filters is mixed with the effluent of the H-cation-containing filters of the desalting plant and sent to concentration. 2. The method according to claim 1, characterized in that 30-60% of the total volume of the Na-cation-exchange filters are torn off to lime by treating them with lime, taken in a quantity equivalent to magnesium hardness of the filtrate. 3. Method pop. 1 and 2, characterized in that the concentration is carried out in evaporators or electrodialyzers to obtain 3-8% sodium sulfate solution. Sources of information taken into account in the examination 1. US patent 3,977,968, cl. 210.32. 1978 2. USSR author's certificate If 776990, cl. C 02 F, 1979 (prototype).