SU1766846A1 - Method of water softening - Google Patents

Abstract

The invention relates to methods of water softening and allows creating a drainless technology by organizing a closed system using process solutions and water. The method of water softening is carried out by passing it through a cationic filter, while the filter is regenerated with salt solution, which is used as a mixture of recycled regeneration solution, part of the washing and purge waters of boilers after its evaporation to the initial concentration by sodium ions in immersion combustion apparatus waste caustic soda to release hardness and gypsum salts and acidified with carbon dioxide and hydrochloric acid. 1 il.

Description

The invention relates to methods of water softening and can be used in water treatment for powering power plants and boilers of small and medium power, having ion exchange filters for cationic absorption of water.

The closest in technical essence and the achieved result to the proposed invention is a method of water softening, including passing it through a cation-exchange filter, regenerating the latter with a solution of potassium chloride and treating the spent regeneration solution together with the purge waters pre-carbonized with flue gases to precipitate and separate hardness salts .

The disadvantages of this method include: incomplete sedimentation of hardness salts and sulfate ions from regeneration solutions, which limits the possibility of multi-cycle use of the latter as a working reagent for regeneration of cationic filters and leads to

pollution of the environment when using these solutions as fertilizers; only partial use of flue gases (their heat).

The purpose of the invention is the creation of drainless technology by organizing a closed system using process solutions and water.

The goal is achieved by using as a salt solution for regeneration a mixture of spent regeneration solution, part of wash water, boiler water after evaporation to its initial concentration by sodium ions in immersion combustion apparatus due to heat of flue gases from boilers, caustic soda treatment pH 11.5 and t 80 ° C to isolate hardness salts and sulfate ions and acidify the resulting solution to pH 5 by passing flue gases and adding hydrochloric acid.

The drawing shows the scheme of implementation of the method.

cl

h about

oh so

& ь

, (

The scheme contains a cation-exchange filter 1, lines for supplying raw water 2 and draining softened water 3 for feeding boilers, lines for supplying waste regeneration solution 4, non-concentrated part of regeneration solutions and wash water 5 and line 6 for concentrated parts of washing water and regenerant - solution, line 7 for supplying BREWING boiler water to mixer 8, line 9 for alkalizing evaporated by regeneration of H brd pacTBopa and 10 for pumping the latter to the submersible combustion apparatus 11, line 12 for supplying flue hectares s and the apparatus 13 for acidification in the averaged regenerant tank 14, slurry supply line 15 with the slurry in a filter press 16, line 17 for withdrawing filtrate regenerant and lines 18 for discharging the sludge.

Example. The initial hard water 2 is passed through the cation-exchange filter 1. The process of water softening proceeds by the reaction:

R

2R-Na + Ca (HCOs)

R

/

Ca + 2HPHSS

After the cation exchanger is saturated with hardness ions, a 10% sodium chloride solution is fed through line 4 for 25-30 minutes. The regeneration process proceeds by the reaction:

R

Ca + 2NaC - 2R-Na + CaCl2

R

The regenerations of the regeneration process and the washing waters are divided into parts, one quarter of which along line 6, containing the highest concentrations of hardness salts CaCl2 and MgCl2, are sent to mixer 8, in which the purge water from boilers 7 and caustic soda the pH of the mixture is adjusted to pH 12. The remaining three quarters of the regeneration solution and wash water 5, which are low in concentration salts, are mixed with the spent regeneration solution 17 and are fed to the regeneration of the cation-exchange filter through line 4. The mixed solution for evaporation, via line 10, enters the submersible combustion apparatus 11, in which the process of evaporation and concentration of hardness salts takes place simultaneously.

The source of carbon dioxide for evaporation and carbonization is spent flue gases of production processes 12. In apparatus 11 the following reactions take place:

2NaOH + C02 - No. 2COz + H20 CaC12 + No. 2COz - CaCO3 + 2№C1 CaC12 + 2 NOHCO3 Ca (NSOz) 2 + 2№С1

MgCl2 + 2NaOH (ОН) 2 + 2№CI CaCl2 + Na2SCM - Са5См + 2№CI Reactions take place at 80-90 ° С due to the heat of flue gases having a temperature of 180-230 ° С. Excess flue gases containing unreacted carbon dioxide are removed via line 13 to pre-acidify to pH 7 of the filtrate.

17c averaged capacity 14. The final acidification to pH 5-6 is made

hydrochloric acid. The results of the experiment showed that at pH 5-6, the exchange capacity of the cation-exchange filter is maximum.

As experiments have shown, the release of gypsum occurs quite fully at the concentration of the solution by Na ions - 69 g / l, pH 11.5 and temperature 80 ° С PH of 11.5 is adjusted for

complete release of magnesium ions, t 80 ° C is established spontaneously after the evaporator, and the concentration of Na ions is kept as high as possible for normal operation of the evaporator

apparatus.

The suspension of one stripped off regeneration solutions from the apparatus 11 through line 15 is pumped to the press filter 16, from which the filtrate through line 17 goes to acidification to the averaging tank 14, and the sludge

18 is removed for further use, for example, in the production of building materials.

Comparative data on the effectiveness of the proposed and known methods are presented in the table.

The proposed method, in comparison with the known, allows completely to refuse the discharge of wastewater and the contents contained therein.

impurities in water bodies or on farmland, and flue gases into the atmosphere, which from an environmental point of view is an important solution to the issue of environmental protection. The use of waste water and flue gases in the technological process makes it possible to refuse additional capital investments in sewage treatment plants, and due to the circulating use of sodium chloride, it is not necessary to replenish it in the process. Finally, a positive economic effect comes from the use of sludges in the production of building materials and the economy of water with the introduction of a closed cycle,

Claims (1)

Invention Formula A method of water softening, including passing it through a cation filter, regenerating the filter with a saline solution, mixing the spent regeneration solution with the purge water of steam boilers, treating the mixture with flue gases to separate hardness ions, in order to create an open-flow technology by organizing closed loop system using process solutions and water, as a salt solution for regeneration of the cation-exchange filter, use a mixture of recycled regeneration solution, part of the washing and purge waters of boilers after its evaporation to the initial concentration by sodium ions in immersion burning apparatus, treated with caustic soda to separate hardness and gypsum salts and acidified with carbon dioxide and hydrochloric acid.