SU916417A1 - Method for closed-cycle softening of water - Google Patents

Description

The invention relates to the field of water treatment and can be used in heat and power, chemical and petrochemical industries.

There is a method of drainless water softening Ia-cationization, according to which the spent regeneration solution of α-cation filter is softened in a clarifier by co-extracting and partially softened water is directed to evaporators operating under vacuum to evaporate to dry salts [13.

The disadvantages of this method include the use of expensive alloys and heat for evaporation, which increases the cost of the process.

The closest in technical essence and the achieved result to the proposed is a method for smoothing treatment of the make-up water of the heat network, which consists in mixing the source water with the spent 2

A regeneration solution in which hardness ions are partially precipitated, after which water is passed through H-cation-exchange countercurrent filters loaded with multifunctional or weakly catalytic cation exchange resin, regenerated with a stoichiometric amount of sulfuric acid, where only partially the calcium hardness of water is removed.

The spent H-cation filter solution during regeneration is passed, depending on the calcium sulfate content, through the calcium sulfate crystallizer and is collected in a tank, from where it is metered into the softened water during the entire softening cycle so that the concentration of calcium ions in it does not exceed 3 , 5 mEq / l T2).

The disadvantage of this method is the low degree of water purification.

The purpose of the invention is to increase the degree of water purification.

This goal is achieved by the fact that in the method of drainless water softening, including H-cationization of water in countercurrent filters loaded with a polyfunctional cation exchanger, mixing it with the spent regeneration solution, from which the hardness ions are partially precipitated and the latter is regenerated with a stoichiometric amount of sulfuric acid; mixing is carried out before H-cationation, while the spent regeneration solution is pre-softened with lime reduction and 20-50% of softened 55 spent regeneration solution is subjected to mixing with the source water, and 80-50% of the latter is sent to the regeneration stage.

Regeneration of ion-exchange filters is first carried out with an acid solution to become 40–70% of the working exchange capacity of the ion exchangers, and then softened with the spent regeneration solution until the working exchange capacity of the ion exchangers is fully restored. 25

According to the proposed method, the softening of the spent solution after partial precipitation of calcium sulphate, for example, in a crystallizer with co-liming, is carried out either with a veterinarian or with a low plant capacity in the tank, where all hardness salts are removed as insoluble sludge.

When regenerating a cationic filter ~ _{! 3} , an acid solution is first introduced, which easily regenerates the weakly acid part of the cation exchanger together with the strongly acidic one. The amount of acid supplied corresponds to 40-70% of all sorbed cations with softening.

Passing a softened dried solution for regeneration in the amount of 80 ~ 50% of the total volume, which has a weakly alkaline reaction, ensures the displacement of all hydrogen ions retained by the strongly acidic part of the cationite and creates conditions under which the displaced hydrogen ions regenerate the rest of the weakly acidic part of the cationite.

During softening of the initial water, 2050% of the softened spent regeneration solution is uniformly dosed into the water, without increasing its hardness. The depth of the softening in this case is equal to 3 "5 mEq / l, which

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increases the reliability of the heating network. The softened water obtained can be used as feedwater for evaporators and low pressure boilers.

The drawing shows the scheme of the proposed method.

The scheme contains an H-cation filter 1, a mold 2, an apparatus 3 for co-calcining the spent regeneration solution.

The original water, mixed with the softened exhausted regeneration solution that is dispensed into it, is fed into the H-cation filter 1 and after deep softening it is sent to the consumer. After depletion of the cation exchanger, the latter is regenerated first by diluting the acid, and then with a part of the softened spent regeneration

solution of the previous regeneration. In this case, the acid solution can be prepared in softened water or in a softened spent solution. The filter is washed in the same way with softened water. The spent solution containing calcium sulfate, the concentration of which is more than 30–35 μι — eq / l ·, is passed through the crystallizer 2, where. Calcium sulfate precipitates and is removed in solid form. The spent solution, in which the concentration of calcium sulfate is less than 30 ~ 35 mg-sqv / l, bypassing the crystallizer, is mixed with the main stream and sent to the co-calcining apparatus 3. The softened waste solution is metered into the original water before softening and is used for water regeneration.

Example. Source water composition mEq / l: Ca 3; Mg 1.5 ", Ia 1.0; HCO3 3.5; S1L50D2, in the amount of 19.6 l, is mixed with 0.59 l of softened spent solution with a concentration of sodium ions of 48 meq / l and hardness ions 2, 0 mEq / l and passed through a 0.24 l cation exchanger, loaded into the column (1.5 m high) before the hardness breakthrough into the filtrate, 0.10 mEq / l; acid concentration of 400 mEq / l (2%) in the amount of 0.114 l, and then softened with the spent regeneration solution, taken in the amount of 1.37 l. water 0.48 l. Waste solution.

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from which 20 mEq / l of calcium ions are precipitated in the crystallizer, are collected in a tank, where soda and lime are supplied for softening. After sedimentation of the sludge, the spent solution with a concentration of sodium ions and hardness, respectively, 48 and 2 mg-eq / l and in the amount of 1.96 l is used for the next regeneration in the amount of 1.37 l (70%) and mixing with the source water 0 , 59 l (30%).

Comparative data on water softening by the known and proposed methods are given in the table.

Options Famous the way Proposed the way Exchange capacity of cation exchanger, g-eq / l 300 380 Calcium hardness of treated water, mEq / l 0.3 0,003 The total hardness of the treated water, mEq / l 1,800 0,005

As follows from the presented data, the residual stiffness content of the proposed method decreases as compared with the known 360 times, 25. The exchange capacity increases by

1.3 times, the salt content in softened water is 3.5 mEq / l.

Technical and economic effect from the implementation of the proposed method for ₃₀ installations with a capacity of 500 t / h is approximately 250 thousand rubles. in year.

Claims (2)

Claims ³⁵ 1. A method of drainless water softening, including H-cationization of water in countercurrent filters loaded with semi-functional cation resin, mixing with spent regeneration solution, from which hardness ions are partially precipitated, and regeneration of the latter with stoichiometric sulfuric acid, with the increase purification levels, mixing is carried out before H-cationation, while the spent regeneration solution is pre-softened by co-calcining and mixing with the initial water; gayut 20-50% softened spent regenerant, and 80-50% fed to the last stage of regeneration. 2. Method pop.1, characterized by the fact that the regeneration of ion-exchange filters is first carried out with an acid solution until 40–70% of the working exchange capacity of the ion exchangers is restored and then softened with the spent regeneration solution until the working exchange capacity of the ion exchangers is completely restored.