SU1719321A1 - Method of softening sulfate containing water - Google Patents

Abstract

The invention relates to methods for sulphate-containing water softening, simplifies the process and allows utilization of softened water to feed the heating network and regenerate Na-cation-impurity filters. The method involves treating water with sodium sulfate to a single-stage concentration of 1300-1700 mg-eq / l and lime to a concentration of 1100-1300 mg-eq / l, while ensuring that the concentration of Ca2 + and S042- ions is in the limit of Ca24RS04 2. equal to (1, 75-2.0) - 106 (mg-eq.) 2 / l, holding the treated water for at least 60 minutes, separating the precipitate. 1 hp f-ly, 1 tab.

Description

The invention relates to the technology of water preparation, namely, the softening of sulphate-containing waters, and can be used for the treatment of thermal and nuclear power plants, in particular for the treatment of waste regeneration water H-cationite filters.

The purpose of the invention is to simplify the process and the possibility of utilizing softened water to feed the heating network and regenerate Na-cationite filters.

The method of softening sulphate-containing water involves treating the solution with sodium sulphate and lime in one stage, stirring and holding the solution, followed by separating the precipitate, while sodium sulphate is introduced to a concentration of 1300-1700 meq / l and lime to a concentration of 1100-1300 mg-eq / l while ensuring the production of concentrations in the limits of Ca2 + S042l (1.75 - 2.0) - 106 (mg-eq) 2 / l2,

and exposure is carried out for at least 60 minutes.

The significance of the proposed method lies in the fact that the introduction of sodium sulfate and lime within the indicated concentration limits while observing the specified product of ion concentrations ensures optimal conditions for the formation and complete precipitation of hardness salts (calcium-magnesium hardness) from sulfate-containing water in one stage. The effect achieved here is that after the precipitate is separated, the residual concentration of calcium ions in the solution does not exceed 0.05 mgeq / l, and no magnesium ions are detected in the filtrate. The content of sodium ions in the filtrate is at a level that allows it to be used as a regenerating solution of Na-cation-exchange filters of water-preparation heat networks.

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Vfl

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outlets, as well as to feed the heating network.

When added to sulphate-containing water, they are a sulfuric acid solution (200-600 mg-eq / l SCM2) with 5 impurities of hardness salts 3-10 mg-eq / l, sodium sulfate and lime in the concentration limits 1300-1700 and 1100-1300 mg-eq / l, respectively, while observing the product of the concentrations of Ca 10 10 5 Cm21 (1.75-2.0) 106, an optimal supersaturation of the solution over calcium sulfate crystalline hydrate is ensured, allowing practically all calcium ions to transfer to the solid phase 15 exact concentration in the solution is less than 0.05 mEq / l. When treatment of regeneration waters is carried out in compliance with the above conditions, it is possible to achieve a solution pH in the range of 10-12 (20 depending on the initial composition of the regeneration water), which allows for almost complete precipitation of magnesium ions in the form of hydroxide.

The indicated concentration limits 25 and the product of the concentrations of reagent ions in the proposed method are also optimal from the point of view of the kinetics of the heterogeneous gypsum crystallization reaction from the solution and ensure the achievement of both the completeness of the reaction and the formation of solid phase crystals of 10-50 microns in size those. With a system exposure of more than 60 minutes after the introduction of the reagents, not only is the complete formation of the solid phase, but also its almost complete precipitation.

In the case of the introduction of sodium sulfate and lime into the regeneration water to a concentration below 1300 and 1100 mg-eq / l, respectively, and when the product of ion concentrations below 1.75 106 is produced, the oversaturation of the solution in calcium sulfate is lower than the optimum value. At the same time, the required completeness of 45 precipitates of two-water calcium crystalline hydrate and the residual concentration of ions in the solution are higher than 0.5 mEq / L, which does not allow using this water as the supply water in the heat network.

In the case of the introduction of sodium sulfate and lime into regeneration waters to a concentration above 1700 and 1300 mg-eq / l, respectively, and when the product of ion concentrations above 2.0 is reached, the oversaturation of the calcium sulfate solution is above the optimum value. At the same time, an increase in the sediment mass of calcium hydrogen crystal hydrate is not observed, which causes a residual concentration of calcium ions in the solution above 0.5 mEq / L.

When the regeneration water treated with the reagents is kept for less than 60 minutes, the solid phase of the hardness salts is not completely precipitated, even if crystals form completely in the solution.

Example. The experiments were performed on imitate used regeneration water H-cation filter of the following composition, mEq / l:

Acidity97

Stiffness is total 42

Sa

2+

MD2 Na + ZSm2 PH

23

nineteen

25

164

1,3

Sodium sulfate and calcium hydroxide were introduced into the water of the above composition to the required concentrations while observing the specified product of ion concentrations, kept under stirring (R 2000) at room temperature for a specified time. The precipitate was then filtered off and the residual hardness salt content in the filtrate was determined by complexometric titration.

The results of the experiments are presented in the table.

Analysis of the obtained results shows that when sodium sulfate and lime are introduced in an amount below the lower stated concentration limits or the product of ion concentrations (experiments 1, 2), the residual hardness salt content in the filtrate is more than 0.5 mEq / l.

With the introduction of reagents into the regeneration water above the upper limit (experiment 10), the residual concentration of hardness salts is also higher than 0.5 mEq / l,

In the entire claimed range of concentrations and the product of ion concentrations (experiments 3–9), the residual stiffness salts in the filtrate are well below 0.05 mEq / L.

Reducing the exposure time of the system after the introduction of reagents less than 60 minutes (experiment 11) significantly reduces the effectiveness of the proposed method. The increase in the exposure time of the system for more than 60 min (experiment 12) does not impair the effectiveness of the proposed method (experiment 7).

Compared with the prototype of the proposed method provides a reduction in residual. hardness of water in sulfate-containing solutions for one stage of processing. The residual concentration of hardness salts after the first

stages of the reagent treatment of the prototype at the level of 41-42 mEq / l for Ca2 +.

The filtrate according to the proposed process can be used not only to feed the heating network, as meeting the requirements for the hardness salt content, but also to regenerate the Na-cation-exchange filters of water treatment plants, since the content of sodium ions is 1260-1460 mEq / L. this process. Thus, an extension of its use is achieved. In addition, the gypsum obtained after filtration can be used for the manufacture of various construction and decorative products.

Thus, the proposed method provides, in comparison with the prototype, a reduction in both capital costs and operating costs while ensuring unregulated regeneration technology.

H-cationite filters.

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five

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Claims (2)

Claim 1. The method of softening sulphate-containing water, including treatment with sodium sulphate and lime, mixing and aging, followed by separation of the precipitate, characterized in that, in order to simplify the process and the possibility of utilization of softened water to feed the heating network and regenerate the Na-cationite filters, water treatment is carried out in one stage, while sodium sulfate is introduced to a concentration of 1300-1700 mg-eq / l, and lime - to a concentration of 1100 - 1300 mg-eq / l while ensuring the production of the concentration of Ca and S042 ions to Sa21. (5Sm2- equal (1.75-2.0) -106 (mg-eq) 2 / n-. 2. The method according to claim 1 is different in that the exposure to sodium sulfate treated water and lime takes at least 60 minutes.