SU1225827A1 - Method of reprocessing waste water - Google Patents

Description

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The invention relates to the purification of wastewater from ion exchange water treatment plants and can be used in the preparation of water from water treatment plants of combined heat and power plants and boilers for reuse.

The known method of purification of wastewater sodium-cationite filters with a solution of soda, settling and filtering the sodium chloride solution for the purpose of its subsequent use for the regeneration of sodium-cationite filters ij.

The disadvantages of this method are the increased consumption of soda, which increases the cost of purification, and the insufficient decrease in the concentration of magnesium ions, which worsen the regeneration ability of the resulting salt solution.

A known method of purification and reuse of waste mineralized water, including co-calcining, separation of the sediment and subsequent evaporation to dry jZ salts.

The disadvantage of the method is a significant consumption of reagents for wastewater treatment, especially of scarce expensive soda, in addition, the excess amount of acid and alkali in the wastewater after regeneration of ion-exchange filters is not used as cleaning reagents, but. is neutralized and irretrievably lost.

The closest to the invention according to the technical essence is the method of wastewater treatment of ion-exchange water treatment plants, which consists of mixing acidic and alkaline effluents of ion-exchange filters by treating them with flue gases, separating sludge and reusing treated water in circulating water supply systems 3J.

The disadvantage of this method is a large amount of effluent with high salinity after treatment, which dramatically increases the water aggression of circulating systems, and if there is a purge, environmental water bodies are polluted with mineral salts.

In addition, the method has limited application, since it is effective only when processing alkaline wastewater, and in most cases a mixture of regenerated water and hydrogen

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2258271.

. Cation and anion filter has an acid reaction, which requires additional costs of alkaline reagents.

The purpose of the invention is to reduce the amount of wastewater and their mineralization, as well as reducing the consumption of reagents.

The goal is achieved by the fact that when processing wastewater of ion-exchange water treatment plants in a closed circulation circuit, at the beginning, the wastewater of cationic filters of water treatment plants feed the heating network with alkaline waste waters of anion-exchange filters of desalting plants in a ratio of 1: 0.3-1: 0.1 then the mixture is fed to a sludge pit where, in the presence of calcium sulphate precipitate and magnesium oxide hydrate, water is clarified, and the clarified water is mixed with hydrogen wastewater. onite

.., desalting filters up to a calcium concentration of 20-30 mg-eq / kg and directed to loosening and per., the generation of cation-exchange filters of the heating network, and the filtrate is mixed with wastewater anionite filters.

At the same time, the wastewaters of cationite filters of desalted plants are mixed with clarified waters in a ratio of 1: 2-1: 7, and during the regeneration of the 5th walkie-talkie filters of water treatment plants to feed the heat network, the acid is added in a stoichiometric amount to the mixture of clarified water and wastewaters hydrogen-cationic filters every 3-4 cycles of filtration, and the time required for the regeneration solution to pass through the filters of the heating network make-up installations is limited to 8-15 minutes.

PRI me R. The heat and power plant is equipped with a heating network feed system with 80.32 t / h effluent and a desalting installation with 35.21 t / h effluent, of which 15.53 t / h are alkaline anion exchangers and 19.68 t / h cationite filters.

The proposed method is carried out according to the scheme indicated in the drawing.

Used solutions of cation-exchange filters feed the heating network through pipeline 1 is fed to mixer 2, which is fed through pipeline 3 from 30

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Worked regeneration water from the filters of the first 4 and second 5 stages of anion desalting plant.

After mixing, the solution is directed through conduit 6 to the sludge pit 7, where, in the presence of a chemical sludge, calcium sulfate and magnesium oxide hydrate are precipitated.

The resulting clarified solution through pipeline 8 is directed to mixing unit 9, where pipeline 10 receives the waste of the regenerated hydrochloric acid-cationite filters of the first 11 and second I2 cationization stages of the desalting plant.

After mixing, the solution is directed through conduit 13 to regenerate cation-exchange filters of the heating network 14.

If necessary, the water is acidified, dosing concentrated sulfuric acid through conduit 15.

An excess amount of clarified water, equal to the wastewater flow of the desalting plant, is withdrawn from the loop through conduit 16 and is used to compensate for the loss of circulating cooling systems.

Source water is fed for treatment to ion exchange filters through pipelines 17 and 18 to the desalting unit.

Chemically purified water from cationite filters feeds the heating network is directed through conduit 19 to the feedwater supply system, and the filtrate of the desalting plant is directed through conduit 20 to compensate for the losses of the main thermal circuit of the station or boiler house,

Tables 1 and 2 show experimental data on the treatment of wastewater from iontow filters using the proposed method, obtained at the installation of an in-feed heat network with cationite filters regenerated initially with stoichiometric consumption of sulfuric acid.

The change in the quality parameters of the effluent is carried out by varying the flow rates of the effluent from the anionite and cationite filters of the desalting plant;

Wastewater from the filters of the cooling installation of the heating system and anionite filters of the desalting plant are mixed in the ratio

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1: 0.8, 1: 0.3, 1: 0.1, and sent to sludge pits.

From table 1 it follows that with an increase in the proportion of wastewater anionic

5 filters above 0.3, the cost-effectiveness of the method is reduced due to an increase in the consumption of hydrogen cations from the regeneration wastewaters of the hydrogen-cation-exchange filters of the desalting unit for neutralization from 20-30 (with an alkalinity of 13.5 mg Sq / kg) to 70-100% (with an alkalinity of 32.0 mg-eq / kg).

Additionally, mixing is carried out.

15 drains in the ratio of 1: 0.05. As a result, the pH of the clarified solution decreases until the residual concentration of magnesium increases to 3.5 mEq / kg, and the degree

20 deposition is only 49 / 92Z. With a decrease in the share of wastewater from anion-exchange filters below 0.1, the solubility of the magnesium oxide hydrate and the degree of precipitation of magnesium sharply increase.

25 decreases.

Thus, the solubility of magnesium oxide gvdrat with a waste water ratio of 1: 0.1 is 0.5 mEq / kg, which corresponds to a deposition rate of magn 30 82-92%, and at a ratio of 1: 0.05 it increases to 3 , 5 mEq / kg, which corresponds to a degree of precipitation of less than 50%.

By mixing wastewater in a ratio of 1: 0.3-1: 0.1, the calcium content is reduced by 80%, and sulfate by 50%.

The effluent of the hydrogen-cationite filters of the desalting plant (Table 2) is mixed with each of the clarified water solutions (Table 1) in a ratio of 0.3: 1; 0.1: 1 (1: 2; 1: 3.3; 1:10) and sent for regeneration of the softening filters.

From Table 2 it follows that with an increase in the pH of mixed drains or an increase in the proportion of clarified water, the amount of hydrogen cations increases, which is lost irretrievably to neutralize the hydroxyl ions of the clarified water.

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So, at a ratio of 3.3: 1, the flow rates of clarified water with a pH of 12.5 and the flow of hydrogen-cationite filters 55 losses are 98.8%, la at

The pH of 11.24 is only 5.42% (respectively, the residual concentration of hydrogen is 0.3 and 23.57 mg-SQV / kg).

With an increase in the ratio to 10: 1 at pH 12.5, the loss of hydrogen cations is 100%, and at pH 11, 24 - 16.29.

From tab. 2 that the indicator for operational control is the concentration of calcium cations, which characterizes the dilution rate of the solution and the efficiency of cation utilization.

With an increase in calcium concentration, the amount of hydrogen cations increases, which is used to regenerate the filtering filters.

So, with a pH of clarified water of 12s1 and a mix ratio of 1: 0.5 (2: 1) with a flow of hydrogen-cation filters, the concentration of calcium is 32.26 mg-eq / kg, while the concentration of hydrogen cations is 27.01 mg eq / kg, which corresponds to 75% of its use for filter regeneration. When the ratio of solutions is 1: 0.3 (3.3: 1), the calcium concentration is 26.98 mEq / kg, the concentration of hydrogen cations is 14.55 mEq / kg, the percentage of use is 58.4%, and when the ratio of solutions is 1 : 0.1 (10: 1) and a calcium concentration of 9.78 mEq / kg, the hydrogen concentration and the percentage of its use become 0.

In order to prevent the calcium sulfate in the cation exchanger and the cation exchanger from plating, the calcium cations are replaced by hydrogen and sodium cation exchangers in the cation exchanger in two steps.

The first stage is combined with the period of loosening and carried out with a weak solution of acid and sodium salts, obtained by mixing clarified waters after the sludge pit. These waters contain sodium salts with waste regeneration waters of hydrogen-cation-exchange filters of the desalting plant, which have an excess of acid (equal to the acid consumption of the regeneration of hydrogen-cation-exchange filters minus the stoichiometric amount of calcium, magnesium and sodium retention during filtration). At the same time, the concentration of calcium after mixing should be equal to 20-30 mg-eq / kg.

The lower limit is determined by the efficiency of using c0

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The wastewater of hydrogen-cation-exchange filters for regeneration of catconite filters to feed the heat network and a decrease in irrecoverable losses for neutralizing hydroxyl ions. So, at a calcium concentration of 18 mEq / kg, the efficiency of use is close to 0%, and at a calcium concentration of 20 mEq / kg, this value averages 40%.

In addition, with increasing dilution of the solution, the efficiency of using the total concentration of reducing cations (sodium and hydrogen) decreases.

So, with a calcium concentration of 15–18 mg-eq / kg, the total concentration of hydrogen and sodium is less than 70% of the stoichiometric concentration spent on restoring the working capacity of the filters, and when the calcium concentration is 18–20 mg-eq / kg, it becomes %

In addition, the concentration of the acid becomes insufficient to undergo the reaction of substitution of hardness cations in the cation resin.

The upper limit of the hardness concentration of 30 mEq / kg is limited by a sharp decrease in the chemical induction period, i.e. a time during which the formation of the solid phase of calcium sulfate does not occur. As a result of exceeding the established limit, the deposition of gypsum occurs in the layer of cation exchanger, which is unacceptable.

To obtain a hard concentration within the established limits, the ratio of the flows of acidic, effluent of hydrogen-cation-exchange filters and clarified water when mixed should be in the range of 1: 2-1: 7. To prevent the gypsum on the cationite (gypsum) grains and improve the efficiency of the regeneration process, the contact time of the regeneration solution with the cation exchanger is limited to 8-15 minutes, i.e., the allowable upper and lower limits for the passage of individual portions of the solution through the filter are set.

With an increase in the CBbmie time of 15 minutes, gypsum-Vschie is noted, evidenced by the decrease in the concentration of sulfate ions in the filtrate of the regeneration solution. Thus, it was found that with increasing contact up to 18 minutes

sulphate ion concentration decreases by 1-2% compared to baseline

As a result of plastering, the absorption capacity of the cation exchanger decreases, the consumption of reagents and water increases to restore the efficiency of the filters. Moreover, a decrease in the absorption capacity at non-observance of the established limit results in almost complete loss of the efficiency of the cation exchanger after 15–20 filter cycles.

Reducing the time for the solution to pass through the filter below 8 minutes reduces the efficiency of using hydrogen and sodium cations to restore the working capacity, which will require additional consumption of reagents.

In addition, the failure to comply with the lower limit (8 min), which corresponds to the permissible limit of loosening intensity commonly used in water treatment of filter materials, leads to their removal.

The technical and economic efficiency of the proposed invention is achieved due to the complete cessation of discharges of ion-exchange plants for heating networks, precipitating calcium cations and the equivalent amount of sulphate ions, as well as magnesium cations retained during the ion exchange, without chemical reagents.

Treatment of wastewater by a known method gives the amount of discharged water in the circulating system 115.3 t / h.

Components g-eq / kg: calcium Ca

2+

Mapnius Mg Sodium Na Hydrogen H

Alkalinity, mEq / kg

2

78.21 6.33 A0.3 0.3

43.45 60.16 71.1 5.2 15.1 15.0 3.52 4.87 5.75 O, 0.1 0.5 138.87 84.11 63.05 49.26 84, eleven

80.0835.42 18.25 7.01

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which is 80.3 t / h more than the proposed.

The amount of salts discharged by the proposed method averages 177 kg / h, and by the known more than 1046 kg / h, while to obtain in a treated effluent according to a known method, a stiffness concentration equal to the rigidity concentration of the proposed one needs to be spent 2 , 5 g of 106% caustic soda for each ton of effluent.

In addition, as a result of the regeneration of cation-exchange filters to feed the heat network with wastewater having a residual acidity and a high concentration of sodium, the depth of regeneration of the cation exchanger increases to 20–25% and, due to this, the specific acid consumption. The acid is added to the mixture of clarified water and wastewater of hydrogen-cation-exchange filters in a stoichiometric amount every 3-4 filtration cycles.

The proposed method in the processing of wastewater from ion-exchange plants of the heat and power plant, which has a water treatment plant for feeding a heat network with a capacity of 1000 tons per hour, the source of water supply for which is city water, reduces the amount of waste water by 120 tons per hour, and the consumption of acid by 2 tons per day. Compared to the known method, the consumption of alkaline reagents for wastewater treatment is completely reduced.

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Claims (4)

1. METHOD FOR WASTE WATER TREATMENT of ion-exchange water treatment plants, including mixing alkaline and acidic waters, concentration with subsequent clarification, characterized in that, in order to reduce the amount of wastewater and their mineralization, as well as reduce the consumption of reagents, wastewater is mixed in a closed loop water of cation exchange filters of water treatment plants of a heating system with alkaline wastewater of anion exchange filters of desalination plants in a ratio of 1: 0.3-1: 0.1, then the mixture is fed to the sludge a test basin, where, in the presence of a precipitate of calcium sulfate and magnesium oxide hydrate, water is clarified, and clarified water is mixed with wastewater of hydrogen cationite filters of a desalination plant to a calcium concentration of 2030 mEq / kg and sent to loosening and regeneration of cationite filters for heating system heating, and the filtrate is mixed with sewage anion exchange filters. 2. The method according to claim 1, characterized in that the wastewater of cation exchange filters of desalination plants is mixed with clarified water in a ratio of 1: 2 - 1: 7. 3. The method according to claim 1, characterized in that during the regeneration of the filters of the water treatment plants, the heating system is added with acid in a stoichiometric amount to the mixture of clarified water and wastewater of hydrogen-cation exchange filters every 3-4 filtering cycles. 4. The method of pop. 1, distinguishing with the fact that time passes. The regeneration solution within the filters of the heating system recharge installations is limited to 8-15 minutes. SU ,,, 1225827>