Filters and systems for softening water: marketing stroke or urgent need. Water softening Methods

Technological schemes I. constructive elements Installations of reagent water softening

Thermochemical water softening method

Water softening dialysis

Magnetic treatment of water

Literature

Theoretical foundations of water softening, classification of methods

Under the softening of water implies the process of removing stiffness cations from it, i.e. Calcium and magnesium. In accordance with GOST 2874-82 "Water drinking" the rigidity of water should not exceed 7 mgq / l. Separate species Productions to technological water are presented by the requirements of deep softening it, i.e. up to 0.05.0.01 mg-eq / l. Typically used water sources have rigidity that meets the standards of drinking water, and in softening do not need. Water softening is produced mainly in preparation for technical purposes. Thus, the rigidity of water for nutrition of drum boilers should not exceed 0.005 mg-eq / l. Water softening is carried out by methods: thermal, based on water heating, distillation or freezing; Reagent, in which the ions are in the water CA. ( II. ) I. MG. ( II. ) are associated with different reagents in practically insoluble compounds; ion exchange based on filtering softened water through special materials, exchanging ions in their composition Na. ( I) or n (1) on ions sa (ii) and MG. ( II. ) contained in water dialysis; Combined, representing various combinations of listed methods.

The choice of the water softening method is determined by its quality, the necessary depth of softening and technical and economic considerations. In accordance with the recommendations of SNIPA When softening groundwater, ion exchange methods should be applied; When softening surface waters, when water is also required, a limestone or lime-soda method is required, and with deep softening of water - subsequent cationation. The main characteristics and conditions for the use of water softening methods are given in Table. 20.1.

softening water dialysis thermal

To obtain water for economic and drinking needs, only its some of them are softened, followed by mixing with source water, with the amount of softened water Q y. Determine the formula

(20.1)

where is about. and. - the overall rigidity of the original water, mM-eq / l; F 0. p. - the overall rigidity of water entering the network, mM-eq / l; G 0. y - stiffness of softened water, mM-eq / l.

Methods softened water

Indicator	thermal	reagent	ion exchange	dialysis
Process characteristic	Water is heated to a temperature above 100 ° C, while the carbonate and non-carbonate rigidity is removed (in the form of calcium carbonate, hydroxy-. Da magnesium and gypsum)	Lime, eliminating carbonate and magnesium rigidity, as well as soda, eliminating necarbonate, is added to the water.	Softened water is passed through the cationiso - you filters	Source water is filtered through a semipermeable membrane
Purpose of the method	Elimination of carbonate hardness from water used to feed low-pressure boilers	Shallow softening with simultaneous clarification of water from suspended substances	Deep softening of water containing a minor amount of suspended substances	Deep softening of water
Water consumption for own needs	-	No more than 10%	Up to 30% and more proportional to the rigidity of the source water	10
Conditions effective application: The turbidity of the original water, mg / l	Up to 50	Up to 500.	Not more than 8.	Up to 2.0.
Water rigidity, mM-eq / l	Carbonate rigidity with a predominance of CA (NS03) 2, non-marble rigidity in the form of plaster	5.30	Not higher than 15.	Up to 10.0.
Residual water rigidity, mM-eq / l	Carbonate rigidity to 0.035, CAS04 to 0.70	Up to 0.70.	0.03.0.05 PRF Single-stage and up to 0.01 with two-stage ka - thiona	0.01 and lower
Water temperature, ° С	Up to 270.	Until 90.	Up to 30 (glauconit), up to 60 (sulfouge)	Up to 60.

Thermal water softening method

The thermal water softening method is advisable to apply when using carbonate waters that are powered by low pressure boilers, as well as in combination with reagent water softening methods. It is based on the displacement of carbon dioxide equilibrium when it is heated towards the formation of calcium carbonate, which is described by the reaction

Ca (NS0 3) 2 -\u003e SASI 3 + C0 2 + H 2 0.

Equilibrium is reduced by lowering the solubility of carbon oxide (IV) caused by increasing temperature and pressure. Boiling can be completely removed from carbon oxide (IV) and thereby significantly reduce carbonate calcium rigidity. However, it is not possible to completely eliminate the specified rigidity, since calcium carbonate, albeit slightly (13 mg / l at 18 ° C), but still soluble in water.

In the presence of a magnesium bicarbonate in water, the process of precipitation occurs as follows: at first the relatively well-soluble (110 mg / l at a temperature of 18 ° C) magnesium carbonate

Mg (NSO 3) → MGC0 3 + C0 2 + H 2 0,

which during long-term boiling is hydrolyzed, as a result of which the precipitate of a small-soluble (8.4 mg / l) falls. Magnesium hydroxide

MGC0 3 + H 2 0 → Mg (0h) 2 + C0 2.

Consequently, when boiling water, the rigidity caused by calcium and magnesium bicarbonates is reduced. When water boiling, the rigidity is also reduced, determined by calcium sulfate, the solubility of which drops to 0.65 g / l.

In fig. Figure 1 shows the thermo-softener of the design of a spear, characterized by the relative simplicity of the device and the reliability of work. Pre-fitted in the apparatus processed water goes through the ejector to the foster of the film heater and sprinkles over the vertically placed tubes, and it flows down to towards the hot pair. Then, together with the purge water from the boilers, it enters a culvert with a suspended sediment in a central feed pipe through a hole.

Restracted from the water of carbon dioxide and oxygen together with excess steam is reset into the atmosphere. The calcium and magnesium salts formed in the process of heating water are delayed in a suspended layer. Having passed through a suspended layer, the softened water enters the collection and is discharged outside the device.

The time of water in the thermo-lion is 30.45 minutes, the rate of its ascending movement in the suspended layer 7.10 m / h, and in the holes of the false bottom 0.1.0.25 m / s.

Fig. 1. Thermal imaging of the design of the Copeva.

15 - Reset drainage water; 12 - central feed tube; 13 - false perforated bottoms; 11 - weighted layer; 14 - reset of the sludge; 9 - Collection of softened water; 1, 10 - feeding the initial and disgusting of softened water; 2 - blowing boilers; 3 - Ejector; 4 - Viola; 5 - film heater; 6 - Reset steam; 7 - Ring perforated water removal pipeline to ejector; 8 - inclined separating partitions

Reagent water softening methods

Water softening by reagent methods is based on the processing of its reagents, forming with calcium and magnesium, low-soluble compounds: Mg (OH) 2, CAC0 3, CA 3 (P0 4) 2, Mg 3 (P0 4) 2 and others, followed by their separation in clarifier , thin layer sumps and clarifying filters. Lime, calcined sodium, sodium and barium hydroxides and other substances are used as reagents.

Water softening lime It is used in its high carbonate and low non-margotic stiffness, as well as in the case when it is not necessary to remove salt from the water of necarbonate stiffness. As a reagent, the lime is used that is administered in the form of a solution or suspension (milk) into pre-heated cultivated water. Dissolving, the lime enriches water by ions of it - and Ca 2+, which leads to the binding of the free carbon oxide dissolved in the water (IV) to form carbonate ions and the transition of hydrocarbonate ions to carbonate:

C0 2 + 20N - → 3 + H 2 0, NSO 3 - + it - → CO 3 - + H 2 O.

The increase in the concentration of ions C0 3 2 in the treated water and the presence of C 2+ ions in it, taking into account the lime introduced with lime leads to an increase in the product of solubility and precipitation of a low-soluble calcium carbonate:

Ca 2+ + C0 3 - → CAC0 3.

With an excess of lime, a magnesium hydroxide falls into the sediment

Mg 2+ + 20n - → MG (OH) 2

To accelerate the removal of dispersed and colloidal impurities and reduce the alkalinity of water simultaneously with the lime, the coagulation of these impurities with iron sulfate (II) is used. Fes0 4 * 7 H 2 0. The residual rigidity of the softened water during decarbonization can be obtained by 0.4.0.8 mG-eq / l more necarboratory rigidity, and alkalinity 0.8.1.2 mG-eq / l. The dose of lime is determined by the ratio of the water concentration in the water of calcium ions and carbonate rigidity: a) at the ratio of [Ca 2+] / 20<Ж к,

(20.2B)

b) at the ratio [CA 2+] / 20\u003e F to,

(20.3)

where [CO 2] is a concentration in water of free carbon oxide (IV), mg / l; [CA 2+] - concentration of calcium ions, mg / l; F to - carbonate rigidity of water, mM-eq / l; D to - the dose of coagulant (FES0 4 or FECL 3 in terms of anhydrous products), mg / l; e K. - equivalent mass of active substance coagulant, mg / mg-eq (for FES0 4 e. K \u003d 76, for FECL 3 E K \u003d 54); 0.5 and 0.3 - excess of lime to ensure greater completeness of the reaction, mM-eq / l.

Water softening dialysis

Magnetic treatment of water

Literature

Theoretical foundations of water softening, classification of methods

Under the softening of water implies the process of removing stiffness cations from it, i.e. Calcium and magnesium. In accordance with GOST 2874-82 "Water drinking" the rigidity of water should not exceed 7 mgq / l. Separate types of production to technological water are presented by the requirements of its deep softening, i.e. up to 0.05.0.01 mg-eq / l. Typically used water sources have rigidity that meets the standards of drinking water, and in softening do not need. Water softening is produced mainly in preparation for technical purposes. Thus, the rigidity of water for nutrition of drum boilers should not exceed 0.005 mg-eq / l. Water softening is carried out by methods: thermal, based on water heating, distillation or freezing; Reagent, in which the ions are in the water CA. ( II. ) I. MG. ( II. ) are associated with different reagents in practically insoluble compounds; ion exchange based on filtering softened water through special materials, exchanging ions in their composition Na. ( I) or n (1) on ions sa (ii) and MG. ( II. ) contained in water dialysis; Combined, representing various combinations of listed methods.

softening water dialysis thermal

To obtain water for economic and drinking needs, only its some of them are softened, followed by mixing with source water, with the amount of softened water Q y. Determine the formula

Methods softened water

Indicator	thermal	reagent	ion exchange	dialysis
Process characteristic	Water is heated to a temperature above 100 ° C, while the carbonate and non-carbonate rigidity is removed (in the form of calcium carbonate, hydroxy-. Da magnesium and gypsum)	Lime, eliminating carbonate and magnesium rigidity, as well as soda, eliminating necarbonate, is added to the water.	Softened water is passed through the cationiso - you filters	Source water is filtered through a semipermeable membrane
Purpose of the method	Elimination of carbonate hardness from water used to feed low-pressure boilers	Shallow softening with simultaneous clarification of water from suspended substances	Deep softening of water containing a minor amount of suspended substances	Deep softening of water
Water consumption for own needs	-	No more than 10%	Up to 30% and more proportional to the rigidity of the source water	10
Conditions for efficient use: the turbidity of the original water, mg / l	Up to 50	Up to 500.	Not more than 8.	Up to 2.0.
Water rigidity, mM-eq / l	Carbonate rigidity with a predominance of CA (NS03) 2, non-marble rigidity in the form of plaster	5.30	Not higher than 15.	Up to 10.0.
Residual water rigidity, mM-eq / l	Carbonate rigidity to 0.035, CAS04 to 0.70	Up to 0.70.	0.03.0.05 PRF Single-stage and up to 0.01 with two-stage ka - thiona	0.01 and lower
Water temperature, ° С	Up to 270.	Until 90.	Up to 30 (glauconit), up to 60 (sulfouge)	Up to 60.

Thermal water softening method

Ca (NS0 3) 2 -\u003e SASI 3 + C0 2 + H 2 0.

In the presence of a magnesium bicarbonate in water, the process of precipitation occurs as follows: at first the relatively well-soluble (110 mg / l at a temperature of 18 ° C) magnesium carbonate

Mg (NSO 3) → MGC0 3 + C0 2 + H 2 0,

which during long-term boiling is hydrolyzed, as a result of which the precipitate of a small-soluble (8.4 mg / l) falls. Magnesium hydroxide

MGC0 3 + H 2 0 → Mg (0h) 2 + C0 2.

The time of water in the thermo-lion is 30.45 minutes, the rate of its ascending movement in the suspended layer 7.10 m / h, and in the holes of the false bottom 0.1.0.25 m / s.

Fig. 1. Thermal imaging of the design of the Copeva.

15 - discharge of drainage water; 12 - central feed tube; 13 - false perforated bottoms; 11 - weighted layer; 14 - reset of the sludge; 9 - Collection of softened water; 1, 10 2 - blowing boilers; 3 - Ejector; 4 - Viola; 5 - film heater; 6 - Reset steam; 7 - Ring perforated water removal pipeline to ejector; 8 - inclined separating partitions

Reagent water softening methods

C0 2 + 20N - → 3 + H 2 0, NSO 3 - + it - → CO 3 - + H 2 O.

Ca 2+ + C0 3 - → CAC0 3.

With an excess of lime, a magnesium hydroxide falls into the sediment

Mg 2+ + 20n - → MG (OH) 2

b) at the ratio [CA 2+] / 20\u003e F to,

Expression D Q / E to take a minus sign if the coagulant is introduced earlier than lime, and with a sign plus, if together or after.

In the absence of experimental data, the coagulant dose is found from the expression

D K \u003d 3 (C) 1/3, (20.4)

where C is the amount of suspension, formed when water softening (in terms of dry substance), mg / l.

In turn, C are determined using addiction

where M and is the content of suspended substances in its original water, mg / l; m. - SAO content in commodity lime,%.

Lime-soda water softening method Describes the following main reactions:

By this method, the residual rigidity can be brought to 0.5.1, and alkalinity from 7 to 0.8.1.2 mG-eq / l.

Doses of lime d and and soda d with (in terms of Na 2 C0 3), mg / l, determined by formulas

(20.7)

where - the content of magnesium water, mg / l; Well. C. - Non-Gonnating Water Stiffness, ME-EQ / L.

With a lime-soda method of water softening, the resulting calcium carbonate and magnesium hydroxide can be loosened and remain in colloid-dispersed state. Their transition to the coarse sludge is long, especially at low temperatures and availability in water organic impuritieswhich act as protective colloids. With a large amount of water, water rigidity at reagent water softening can be reduced by only 15.20%. In such cases, organic impurities with oxidants and coagulants are removed before softening or in the process. With lime-soda method, the process is often carried out in two stages. Originally, organic impurities and a significant part of carbonate rigidity are removed from the water, using aluminum or iron salts with lime, conducting a process when optimal conditions Coagulation. After that, the soda is introduced and the rest of the lime and devaimed water. When the organic impurities are removed simultaneously with the softening of water, only iron salts are used as coagulants, since with a high pH value of the water required to remove magnesium rigidity, aluminum salts do not form sorption-active hydroxide. The dose of coagulant in the absence of experimental data is calculated by formula (20.4). The amount of suspension is determined by the formula

where o is the total rigidity of water, mM-eq / l.

A deeper softening of water can be achieved by heating, by adding an excess of a precipitator reagent and creating a contact of softenable water with previously formed precipitation. When heating water, the solubility of CACO 3 and MG (OH) 2 decreases and the softening reactions are more fully.

From the graph (Fig. 2, a) it can be seen that the residual rigidity close to theoretically possible can only be obtained with a significant heating of water. A significant softening effect is observed at 35.40 ° C, further heating is less effective. Deep softening leads at temperatures above 100 ° C. A large excess of the precipitant reagent during decarbonization is not recommended to be added, since the residual rigidity increases due to unreacted lime or in the presence of magnesium necarbonate rigidity in the water due to the transition to calcium rigidity:

MgS0 4 + SA (OH) 2 \u003d Mg (OH) 2 + CAS0 4

Fig. 2. The effect of temperature (a) and doses of lime (b) to the depth of water softening with a lime-soda and lime method

Sa (0h) 2 + Na 2 C0 3 \u003d CAC0 3 + 2NAOH,

but excess of lime leads to irrational overalling of soda, an increase in the value of water softening and an increase in hydrate alkalinity. Therefore, about 1 mG-eq / l are taken in excess of soda. The rigidity of water as a result of contact with the previous precipitate is reduced by 0.3.0 mM-eq / l. Compared to the process without contact with the sediment.

Control the water softening process should be corrected by the pH of the softened water. When it is impossible, it is controlled by the value of hydrate alkalinity, which, during decarbonization, is maintained within 0.1.0.2 mgq / l, with lime-soda softening - 0.3.0.5 mgq / l.

With a sodium-sodium water softening method, it is treated with sodium sodium and hydroxide:

Due to the fact that the soda is formed when sodium hydroxide reactions with hydrocarbonate, necessary for additive to the water dose, it decreases significantly. With a high concentration of hydrocarbonates in water and low non-marble rigidity, the excess of soda can remain in the softened water. Therefore, this method is used only taking into account the relationship between carbonate and non-carbonate rigidity.

Soda-sodium method Usually used for water softening, the carbonate rigidity of which is slightly more nearsbonate. If the carbonate rigidity is approximately equal to non-comboonate, the soda can not be added at all, since its required amount for softening such water is formed as a result of the interaction of hydrocarbonates with caustic sodes. The dose of calcined soda increases as the non-marginal rigidity of water increases.

A coherent method based on the resumption of soda in the process of softening is used in the preparation of water, to power the steam boilers of low pressure

Ca (NS0 3) 2 + Na 2 C0 3 \u003d CAC0 3 + 2NAHC0 3.

Sodium bicarbonate, falling into the boiler with softened water, decomposes under the influence high temperatures

2NHC0 3 \u003d Na 2 C0 3 + H 2 0 + C0 2.

The soda, together with the redundant, introduced first into a water-fuel, is immediately in the boiler, it is hydrolyzed with the formation of sodium hydroxide and carbon oxide (IV), which enters the water-bearing water, which is used to remove calcium and magnesium hydrocarbonate from the softened water. The disadvantage of this method is that the formation of a significant amount of CO 2 in the softening process causes metal corrosion and an increase in the dry residue in boiler water.

Barium water softening method Apply in combination with other methods. Initially, the barium containing reagents in water (VA (OH) 2, Vaso 3, Waa1 2 0 4) are introduced to eliminate sulfate stiffness, then after clarifying the water, it is treated with lime and soda to die. The chemistry of the process is described by reactions:

Due to the high cost of reagents, the barium method is used very rarely. To prepare drinking water due to the toxicity of the barium reagents, it is not suitable. The formed barium sulfate is deposited very slowly, so septic tanks or clarifiers are needed. large sizes. To enter you03, flocculators with mechanical stirrers should be used, because Vaso 3 forms a heavy, fast precipitating suspension.

Required doses of barium salts, mg / l can be found by using expressions: barium hydroxide (product of 100% activity) d B \u003d 1.8 (SO 4 2-), barium aluminate d b \u003d 128zh 0; carbon dioxide d v \u003d 2,07γ (S0 4 2-);

Carbon dioxide applied with lime. By exposure to carbon dioxide, barium bicarbonate is obtained, which doses in softening water. In this case, the dose of carbon dioxide, mg / l, is determined from the expression: D UG. \u003d 0.46 (SO 4 2-); where (S0 4 2-) is the content of sulfate softened water, mg / l; γ \u003d 1,15.1,20 - coefficient taking into account the loss of carbon dioxide barium.

Oxalate water softening method It is based on the use of sodium oxalate and at low solubility in water formed calcium oxalate (6.8 mg / l at 18 ° C)

The method is characterized by simplicity of technological and hardware design, however, due to the high cost of the reagent, it is used to soften the small amounts of water.

Phosphating is used to die water. After the reagent softening of the lime-soda method, the presence of residual stiffness (about 2 mG-eq / l) is inevitable, which phosphate deumenion can be reduced to 0.02-0.03 mgq / l. Such a deep cookie allows in some cases not to resort to cationic water.

Phosphating also achieves a high stability of water, a decrease in its corrosion action on metal pipelines and prevent carbonate deposits on the inner surface of the pipe walls.

Hexametaphos is used as phosphate reagents, triolyphosphate (orthophosphate) sodium, etc.

The phosphate method of softening water when used three - sodium phosphate is the most effective reagent method. The chemistry of the water softening process by trinitium phosphate is described by reactions.

As can be seen from the above reactions, the essence of the method is to form calcium and magnesium salts of phosphoric acid, which have low solubility in water and therefore sufficiently fall out of the precipitate.

Phosphate softening is usually carried out when water heated to 105.150 ° C, reaching its softening to 0.02.0.03 mgq / l. Due to the high cost of the trinitium phosphate, the phosphate method is commonly used to dormit water, pre-softened by lime and soda. Dose of anhydrous trinitrium phosphate (d Φ; mg / l) for adoption can be determined from the expression

D Φ \u003d 54.67 (w OST + 0.18),

where f is the residual stiffness of the softened water before phosphate duity, mM-eq / l.

Ca 3 (P0 4) 2 and Mg 3 (P0 4) 2 formed during phosphate softening (P0 4) 2 and Mg 3 (P0 4) 2 are well adsorbed from softened water organic colloids and silicic acid, which allows you to identify the feasibility of applying this method to prepare feed water for medium and high pressure boilers (58 , 8.98.0 MPa).

The solution for dosing hexamet phosphate or sodium orthophosphate with a concentration of 0.5-3% is prepared in tanks, the number of which should be at least two. Interior surfaces The walls and bottom of the tanks must be coated with a corrosive material. The preparation time of a 3% solution is 3 hours with mandatory stirring with a stirrer or bubble (using compressed air) way.

Technological schemes and constructive elements of reagent water softeners

In the technology of reagent water softening, apparatus for preparation and dosing of reagents, mixers, thin-layer sumps or clarifiers, filters and installations for stabilization water treatment are used. The diagram of the pressure waterfront installation is presented in Fig. 3.

Fig. 3. Water installation with a vortex reactor.

1 - bunker with contact mass; 2 - ejector; 3, 8 - feeding the initial and disgusting of softened water; 4 - vortex reactor; 5 - input reagents; 6 - fast clarifying filter; 9 - relief of contact mass; 7 - Softened water reservoir

In this installation there is no cake formation chamber, since the cereal sediment of calcium carbonate is formed in the contact mass. If necessary, water is brought in front of the reactors.

The optimal construction for softening water with limestone or lime-soda methods is vortex reactor (spider pressure or open) ( Fig. 20.4). The reactor provides a reinforced concrete or steel housing, a narrowed down (angle of tape of 5.20 °) and filled with about half a height of the contact mass. The speed of water in the lower narrow part of the vortex reactor is 0.8.1 m / s; The speed of the ascending flow at the top at the level of the drainage devices is 4.6 mm / s. As a contact mass, sand or marble crumbs with grain size is 0.2.0.3 mm at the rate of 10 kg per 1 m3 of the reactor volume. With a screw ascending flow of water, the contact mass is weighed, the grains are faced with each other and the Saco 3 is intensely crystallized on their surface; Gradually, the grains are turning into the balls of the right shape. The hydraulic resistance of the contact mass is 0.3 m per 1 m height. When the diameter of the balls increases to 1.5.2 mm, the largest most severe contact mass is released from the bottom of the reactor and fit fresh. The vortex reactors do not delay the magnesium hydroxide precipitate, so they should be used in conjunction with the filters installed only in cases where the amount of magnesium hydroxide formed by the resulting precipitate corresponds to the filter dukes.

In the misexacity of sand filters, equal to 1.1.5 kg / m 3, and the filtercycle of 8 h, the permissible amount of magnesium hydroxide is 25.35 g / m 3 (the magnesium content in the starting water should not exceed 10.15 g / m 3). It is possible to use vortex reactors and with greater content of magnesium hydroxide, but after this, after them, it is necessary to install clarifiers to release magnesium hydroxide.

Fresh contact consumption added with ejector, is determined by the formula G. = 0,045 q, where G. - the number of added contact mass, kg / day; J. - Water rigidity removed in the reactor, mM-eq / l; Q - installation performance, m 3 / h.

Fig. 4. Vortex reactor.

1,8 - Feeding the original and removal of softened water: 5 - samplers; 4 - contact mass; 6 - reset air; 7 - hatch for the loading of the contact mass; 3 - input reagents; 2 - removal of spent contact mass

In technological schemes of reagent softening of water with clarifiers instead of vortex reactors, vertical mixers are used (Fig. 5). In the clarifiers, a constant temperature should be maintained, not allowing oscillations more than 1 ° C, for an hour, as convection currents arise, climbing the precipitate and its removal.

Such technology is used to soften the turbid waters containing a large number of Magnesium salts. In this case, the mixers are loaded with contact mass. When using decorators of design E.F. Kurgayev, faucets and chambers Flap formation are not provided, since the mixture of reagents with water and the formation of sediment flakes occur in the clarifier themselves.

A significant height with a small amount of precipostelators allows them to be used to soften the water without heating, as well as when the water is escalating with caustic magnesite. The distribution of the initial water by nozzles causes its rotational movement at the bottom of the device, which increases the stability of the suspended layer during fluctuations in temperature and water supply. Mixed with reagents The water passes horizontal and vertical mixing partitions and enters the zone of sorption separation and adjustment of the precipitate structure, which is achieved by changing the sedimentation conditions at the height of the suspended layer, creating the prerequisites for obtaining its optimal structure that improves the effect of softening and lightening water. Design the clarifiers in the same way as for the usual lightening of water.

With the cost of softened water to 1000 m 3 / day, a water treatment plant type "jet" can be applied. The processed water with the reagents added to it enters the thin-layer sump, then to the filter.

At the Institute of Mining, the Siberian Branch of the Russian Academy of Sciences has developed an unhappy electrochemical technology of water softening. Using the appointment phenomenon at the anode and acidification at the cathode when passing a permanent electric current Through the water system, it is possible to present the reaction of the discharge of water with the following equation:

2H 2 0 + 2e 1 → 20n - + H 2,

where E 1 is a sign indicating the ability of stiffness salts to dissociate into Ca (II) and MG (II) cations.

As a result of this reaction, the concentration of hydroxyl ions increases, which causes the binding of Mg (II) and Ca (II) ions into insoluble compounds. From the anode chamber of the diaphragm (diaphragm from the tissue of the lining type) of the electrolyzer, these ions are moving into the cathode due to the potential difference between the electrodes and the presence of an electric field between them.

In fig. 6 shows the technological scheme of the installation for water softening with an electrochemical way.

Production installation It was mounted in the district boiler room, the tests of which lasted for about two months. The mode of electrochemical processing was stable, the precipitate in cathode chambers was not observed.

The voltage on the supply tires was 16 V, the total current of 1600 A. The overall performance of the installation is 5 m3 / h, the speed of water movement in the anode chambers 0.31 H-0.42 m / min, in the gap between the diaphragm and cathode 0.12- 0.18 m / min.

Fig. 5. Installation of the Nzvestkovo-soda softening of water.1 ,8 - feeding the initial and disgusting of softened water; 2 - Ejector; 3 - bunker with contact mass; 5 Entering reagents; 6 - clarifier with a layer of suspended sediment; 7 - Lightening fast filter; 4 - vortex reactor

Fig. 6. Scheme of the installation of electrochemical softening of water I - rectifier VAKG-3200-18; 2 - a diaphragm electrolyzer; 3, 4 - analyte and catalytes; 5 - pump; 6 - pH-meter; 7 - clarifier with a layer of suspended sediment; 8 - Lightening fast filter; 9 - reset to the sewer; 10, 11 - disgust softened and feeding the source water; 12 - flow meter; 13 - Exhaust umbrella

It has been established that from the water with z o \u003d 14.5-16.7 mG-eq / l, anolyte with rigidity of 1.1 - 1.5 mg-eq / l with pH \u003d 2.5-3 and catholic with rigidity 0 , 6-1 mM-eq / l at pH \u003d 10.5-11. After mixing the filtered anolyte and Catholyte, the indicators of the softened water were as follows: the total rigidity is 0.8-1.2 mg-eq / l, pH \u003d 8-8.5. Electricity costs amounted to 3.8 kW * h / m 3.

Chemical, x-ray structural, IR spectroscopic and spectral analyzes found that the CAC0 3, Mg (OH) 2 and partially Fe 2 0 3 * H 2 0 is mainly contained. This suggests that the binding of MG (II) ions occurs for The score of hydroxyl ions during the discharge of water molecules on the cathode.

Electrochemical processing of water before feeding to cationic filters allows significantly (15-20 times) to increase their working cycle.

Thermochemical water softening method

Thermochemical softening is used exclusively in the preparation of water for steam boilers, Since in this case the heat is most rational, spent on heating water. This method is usually softened by water, "at a water temperature above 100 ° C. More intensive water softening with its heating promotes the formation of severe and large sediment flakes, the fastest deposition of it due to a decrease in the viscosity of water when heated is also reduced, the lime consumption is also reduced, as the free carbon oxide is also reduced (Iv) It is removed when heated to the introduction of reagents. The thermochemical method is used with the addition of coagulant and without it, since a large sediment density eliminates the need for weighting during deposition. In addition to the coagulant, it is used to lime and soda with the addition of phosphates and less frequent sodium hydroxide and soda. Application of hydroxide Sodium instead of lime several simplifies the technology of preparation and dosing reagent, but economically such a replacement is not justified in connection with its high cost.

To ensure the removal of non-marble rigidity of water, the soda is added with excess. In fig. 7 shows the effect of excess soda on the residual calcium and total rigidity of water during its thermochemical softening. As can be seen from the graphs, with an excess of soda 0.8 mG-eq / l calcium rigidity can be reduced to 0.2, and the total - to 0.23 mg / eq-l. With the further addition of soda, the rigidity is even more reduced. The residual magnesium content in water can be reduced to 0.05.01 mM-eq / l with an excess of lime (hydrate alkalinity) 0.1 mM-eq / l. In fig. 20.8 The installation of thermochemical softening of water is shown.

Lime-dolomite method Use for simultaneous softening and explosion of water at a temperature of 120 ° C. This method of softening the alkalinity of water treated with lime or lime and soda (without excess) can be reduced to 0.3 mgq / l at a residual calcium concentration of 1.5 mg -Ex / l and up to 0.5 mM-eq / l with a residual calcium concentration of 0.4 mg-eq / l. The starting water is treated with lime-dolomite milk and brightened in the pressure clarifier. It then passes through the pressure anthracite and Na-cationic filters of the first and second steps.

In the clarifiers, the height of the clarification zone is taken equal to 1.5 m, the speed of the ascending flow during lime is not more than 2 mm / s. The time of water stay in the culpes from 0.75 to 1.5 hours, depending on the type of contamination of the removal. The coagulant of the salt of iron (III) is recommended to be added in an amount of 0.4 mgq / l.

Fig. 7. The effect of excess soda per residual calcium (a) and general (b) Water rigidity during its thermochemical softening

Fig. 8. Installation of lime-soda softening of water with phosphate duity: 1 - Resetting the sludge from the drive 2,3 - collection of softened water; 4 - Entering lime and soda; 5, 11 - feeding the initial and disgusting of softened water; 6 - input steam; 7, 8 - Thermoreactor of the first and second stage; 9 - input trinitium phosphate; 10 - Lightening fast filter

Method high temperature water softening Apply practically for its complete softening. Installations of thermochemical water softening are usually more compact. They consist of reagent dispensers, heaters of thin-layer sumps or clarifier and filters. Doses of lime d and and soda d s, mg / l, with thermochemical softening of water

where C and and C C is, respectively, the content of CAO and Na 2 C0 3 in the technical product,%.

Water softening dialysis

Dialysis is a method of separating dissolved substances that are significantly characterized by molecular weights. It is based on different rates of diffusion of these substances through a semipermeable membrane separating concentrated and diluted solutions. Under the action of the concentration gradient (according to the law of the active mass) solutes with various speeds Diffund through the membrane toward the dilute solution. The solvent (water) diffuses in the opposite direction, reducing the rate of transfer of dissolved substances. Dialysis is carried out in membrane apparatus with nitro and acetatecellulose film membranes. The effectiveness of the semi-permeable membrane for water softening is determined by the high values \u200b\u200bof selectivity and the water permeability, which it should remain for a long time. The membrane selectivity can be expressed as follows:

(W and - zh) / g and (20.11)

where f is the concentration of the initial solution (rigidity); Well and - stiffness of softened water.

In practice, the coefficient of reducing saline is often used - content C and / with arr. It most fully reflects changes in the work of the membrane associated with its manufacture or with the effects of external factors.

There are several hypothetical models of the action of semi-permeable membranes.

Hypothesis hyperfiltration It implies existence in a semi-permeable pore membrane, transmitting water molecules and hydrated salts ions. The basis of theoretical developments was the provision that water and dissolved salts dissolved in it are penetrated by diffusion and threads through the pores through the half-permeable membrane.

Sorption model permeability is based on the background, according to which on the surface of the membrane and in its Piathers The layer is adsorbed related waterhaving a reduced solventful ability. The membranes will be semi-permeable if they, at least in the surface layer, have pores, not exceeding the doubted thickness of the liner layer in size.

Diffusion model It comes from the assumption that the components of the system dissolve in the material of the membrane and diffuse through it. The membrane selectivity is explained by the difference in diffusion coefficients and solubility of the system components in its material.

Electrostatic theory is as follows. When the initial water is moved in the chamber on one side of the selective (cationic) membrane, and the brine on the other, sodium ions in the case when the brine is prepared from the solution of the table salt, migrate to the membrane and further to the base water, and calcium ions in the opposite direction, T .. Of the rigid water in the brine. Thus, the removal of calcium ions from the source water and replacing them with non-sodium sodium ions. Simultaneously in the chambers there are side processes associated with the main process of dialysis: osmotic transfers of water, the transfer of the same name ions, the diffusion of electrolyte. These processes depend on the quality of the membrane.

The exchange equation between ions contained in the original water and ions in the membrane is

where X, H. - Other ions contained in solution and membrane.

Equilibrium constant

The exchange equation is written only for calcium ion, but in fact it is necessary to consider calcium and magnesium ions. Equilibrium between brine and membrane has the form:

If k1 + k 2, then

where n is an indicator of a degree depending on which ions are included in the solution.

From the last expression, it can be concluded that if the equilibrium ratio of sodium ions in brine and rigid source water is equal to, for example, 10, then the rigidity in the original water will be approximately 100 times less than in the brine. Area, m 2, membrane surface

where M is the amount of substance passed through the membrane; ΔC cf - driving force process, T e. The difference in the concentration of the substance on both sides of the membrane; K d - mass transfer coefficient, usually determined experimentally or approximately from expression

β 1 and β 2 are the corresponding coefficients of the transfer rate of the substance in the concentrated solution to the membrane and from it in the diluted; b - the thickness of the membrane; D. - diffusion coefficient of the dissolved substance.

Stiffness of softened water after dialysis:

where s d and s p is the concentration of salts at the beginning of the apparatus, respectively, in dialysis and in brine, mM-eq / l; and Q P. - The performance of the apparatus, respectively, according to dialysat and brine, M 3 / h; F and p - stiffness of dialyzate and brine at the beginning of the apparatus, mM-eq / l; a - constant determined by the properties of membranes and solutions ;; L. - the length of the solution path in dialyzat and brine chambers of the device, m; υ d - the speed of the movement of dialyzate in the chamber, m / s.

Experimental verification of equation (20.13) At the Kationy membranes, the ICC showed good convergence of results. Analysis of formula (20.13) shows that a decrease in the speed of the dialysate movement in the chambers of the device increases the soften effect, the reduction of the stiffness of the softened water is directly proportional to the brine concentration.

Magnetic treatment of water

Recently, magnetic treatment of water is successfully used in domestic and foreign practice to combat scale formation and inlaid. Exposure mechanism magnetic field on water And its impurities are completely unclear, there are a number of hypotheses that E.F. Tebenchinic Classified into three groups: the first, combining most of the hypotheses, binds the effect of the magnetic field on the ions of salts dissolved in water. Under the influence of the magnetic field Polarization and deformation of ions occur, accompanied by a decrease in their hydration that increases the likelihood of their convergence, and Ultimately education crystallization centers; the second implies the effect of the magnetic field on colloid water impurities; The third group combines ideas about the possible effect of the magnetic field on the water structure. it Impact, on the one hand, can cause changes in the aggregation of water molecules, on the other, to disrupt the orientation of the nuclear spins of hydrogen in its molecules.

Water treatment in a magnetic field is common to combat scale formation. The essence of the method is that with the intersection of the magnetic power lines with water, the acidifiers are not released on the heating surface, but in the mass of water. The resulting loose precipitation (sludge) is removed when purging. The method is effective in the processing of water calcium-carbonate, which make up about 80% of the water of all ponds of our country and cover about 85% of its territory.

Water treatment with a magnetic field received wide application To combat scale formation in capacitors steam turbines, in low pressure and low performance steam generators, in thermal networks and hot water and various networks heat exchangerswhere the use of other methods of water treatment is economically inappropriate. In comparison with water softening, the main advantages of its magnetic processing are simplicity, cheapness, safety and almost complete lack of operating costs.

Magnetic treatment of natural waters (both fresh and mineralized) leads to a decrease in the intensity of the formation of scale on the heating surfaces only under the condition of them as a carbonate and calcium sulfate at the time of the magnetic field exposure and provided that the concentration of free carbon oxide (IV) Less than its equilibrium concentration. The anti-fiber effect E causes the presence of iron oxides in water and other impurities:

where M n and m m - the mass of scale formed on the surface of heating when boiling in same conditions The same amount of water, respectively, unprocessed and treated with a magnetic field,

The anti-fiber effect depends on the composition of water, the tension of the magnetic field, the speed of water movement and the duration of its stay in the magnetic field and from other factors. In practice, magnetic devices with permanent steel or ferrito-barium magnets and electromagnets are used (Fig. 9). The devices with permanent magnets are constructively easier and do not require power from the mains. In the devices with an electromagnet on the core (core) coils coils that create a magnetic field are wound.

The magnetic device is mounted to pipelines in a vertical or horizontal position using transient couplings. The speed of water in the gap should not exceed 1 m / s. The process of the operation of the devices may be accompanied by the contamination of the gap mechanical mainly ferromagnetic impurities. Therefore, the devices with permanent magnets must be periodically disassembled and cleaned. Iron oxides from devices with electromagnetic are removed by turning off them from the network.

The results of the research MGSU (G.I. Nikadze, V.B. Vikulin) showed that for water with carbonate rigidity 6.7 μg-eq / l, oxidation of 5.6 mg02 / l and the salt-containing 385.420 mg / l, the optimal magnetic field strength was (10.12.8) * 19 4 a / m, which corresponds to the strength of the current 7.8 A.

The installation scheme for the magnetic processing of the added nutrient water of heating steam boilers is shown in Fig. 20.10.

Recently, devices spread with external magnetizing coils. For Ocagination large masses Waters created devices with layers in its processing.

In addition to preventing scale formation Magnetic processing , According to P.P. Rogging, can be used to intensify the coagulation and crystallization process, accelerate the dissolution of reagents, increase the efficiency of using ion exchange resins, improve the bactericidal action of disinfectants.

Fig. 9. Electromagnetic apparatus for anti-blocking water treatment SCB WTI: 1,8 - feeding the initial and diversion of the ochased water; 2 - grid; 3 is a working gap for the passage of the stubble water; 4 - casing; 5 - Magnetizing coil; 6 - core; 7 - body; 9 - cap; 10 - Terminals

When designing magnetic apparatus for water treatment, such data are set: the type of machine, its performance, induction of the magnetic field in the working gap or the magnetic field strength corresponding to it, the water velocity rate, the time of the active zone of the apparatus, the genus and its voltage for the electromagnetic device or magnetic alloy and magnet size for hard-magnet devices.

Fig. 10. The layout of the magnetic installation for processing boiler water without preliminary cleaning.

1,8 - Original and feed water; 2 - electromagnetic devices; 3, 4 - heaters I and II steps; 5 - Deaerator; 6 - intermediate tank; 7 - PUBLIC PUMP

Literature

1. Alekseev L.S., Gladkov V.A. Improving the quality of soft waters. M.,

2. Stroyzdat, 1994

3. Alferova L.A., Nechaev A.P. Closed water management systems industrial enterprises, complexes and districts. M., 1984.

4. Ayukaev R.I., Melzer V.Z. Production and use of filtering materials for water purification. L., 1985.

5. Wezer Yu.M., Miitz D.M. High molecular weight flocculants in water purification processes. M., 1984.

6. Egorov A.I. Hydraulics of pressure tubular systems in plumbing treatment facilities. M., 1984.

7. Zhurb M.G. Water purification on granular filters. Lviv, 1980.

Basic methods of water softening

Thermochemical water softening method

Water softening dialysis

Magnetic treatment of water

Literature

Theoretical foundations of water softening, classification of methods

Under the softening of water implies the process of removing stiffness cations from it, i.e. Calcium and magnesium. In accordance with GOST 2874-82 "Water drinking" the rigidity of water should not exceed 7 mgq / l. Separate types of production to technological water are presented by the requirements of its deep softening, i.e. up to 0.05.0.01 mg-eq / l. Typically used water sources have rigidity that meets the standards of drinking water, and in softening do not need. Water softening is produced mainly in preparation for technical purposes. Thus, the rigidity of water for nutrition of drum boilers should not exceed 0.005 mg-eq / l. Water softening is carried out by methods: thermal, based on water heating, distillation or freezing; reagent, under which the water in water Ca (II) and Mg (II) are associated with different reagents in almost insoluble compounds; ion exchange based on filtering softened water through special materials that are exchanged in their composition Na (I) or H (1) on Ca (II) and MG (II) ions contained in water dialysis; Combined, representing various combinations of listed methods.

The choice of the water softening method is determined by its quality, the necessary depth of softening and technical and economic considerations. In accordance with the recommendations of the SNIVA when the groundwater is softening, ion exchange methods should be applied; When softening surface waters, when water is also required, a limestone or lime-soda method is required, and with deep softening of water - subsequent cationation. The main characteristics and conditions for the use of water softening methods are given in Table. 20.1.

softening water dialysis thermal

To obtain water for economic and drinking needs, only its some part is usually softened, with subsequent mixing with source water, while the amount of softened water q y is determined by the formula

where is about. and. - the overall rigidity of the original water, mM-eq / l; F 0. p. - the overall rigidity of water entering the network, mM-eq / l; G 0. y. - stiffness of softened water, mM-eq / l.

Methods softened water

Indicator	thermal	reagent	ion exchange	dialysis
Process characteristic	Water is heated to a temperature above 100 ° C, while the carbonate and non-carbonate rigidity is removed (in the form of calcium carbonate, hydroxy-. Da magnesium and gypsum)	Lime, eliminating carbonate and magnesium rigidity, as well as soda, eliminating necarbonate, is added to the water.	Softened water is passed through the cationiso - you filters	Source water is filtered through a semipermeable membrane
Purpose of the method	Elimination of carbonate hardness from water used to feed low-pressure boilers	Shallow softening with simultaneous clarification of water from suspended substances	Deep softening of water containing a minor amount of suspended substances	Deep softening of water
Water consumption for own needs	-	No more than 10%	Up to 30% and more proportional to the rigidity of the source water	10
Conditions for efficient use: the turbidity of the original water, mg / l	Up to 50	Up to 500.	Not more than 8.	Up to 2.0.
Water rigidity, mM-eq / l	Carbonate rigidity with a predominance of CA (NS03) 2, non-marble rigidity in the form of plaster	5.30	Not higher than 15.	Up to 10.0.
Residual water rigidity, mM-eq / l	Carbonate rigidity to 0.035, CAS04 to 0.70	Up to 0.70.	0.03.0.05 PRF Single-stage and up to 0.01 with two-stage ka - thiona	0.01 and lower
Water temperature, ° С	Up to 270.	Until 90.	Up to 30 (glauconit), up to 60 (sulfouge)	Up to 60.

Thermal water softening method

Ca (NS0 3) 2 -\u003e SASI 3 + C0 2 + H 2 0.

In the presence of a magnesium bicarbonate in water, the process of precipitation occurs as follows: at first the relatively well-soluble (110 mg / l at a temperature of 18 ° C) magnesium carbonate

Mg (NSO 3) → MGC0 3 + C0 2 + H 2 0,

which during long-term boiling is hydrolyzed, as a result of which the precipitate of a small-soluble (8.4 mg / l) falls. Magnesium hydroxide

MGC0 3 + H 2 0 → Mg (0h) 2 + C0 2.

The time of water in the thermo-lion is 30.45 minutes, the rate of its ascending movement in the suspended layer 7.10 m / h, and in the holes of the false bottom 0.1.0.25 m / s.

Fig. 1. Thermal imaging of the design of the Copeva.

15 - Reset drainage water; 12 - central feed pipe; 13 - false perforated bottoms; 11 - weighted layer; 14 - relief of the sludge; 9 - Collection of softened water; 1, 10 - feeding the initial and removal of softened water; 2 - blowing boilers; 3 - Ejector; 4 - Viopa; 5 - film heater; 6 - Reset steam; 7 - Ring perforated water removal pipeline to ejector; 8 - inclined separating partitions

Reagent water softening methods

The softening of water with lime is used in its high carbonate and low non-commissioned stiffness, as well as in the case when it does not need to be removed from the water of salt of necarbonate rigidity. As a reagent, the lime is used that is administered in the form of a solution or suspension (milk) into pre-heated cultivated water. Dissolving, the lime enriches water by ions of it - and Ca 2+, which leads to the binding of the free carbon oxide dissolved in the water (IV) to form carbonate ions and the transition of hydrocarbonate ions to carbonate:

C0 2 + 20N - → 3 + H 2 0, NSO 3 - + it - → CO 3 - + H 2 O.

Ca 2+ + C0 3 - → CAC0 3.

With an excess of lime, a magnesium hydroxide falls into the sediment

Mg 2+ + 20n - → MG (OH) 2

b) at the ratio [CA 2+] / 20\u003e F to,

where [CO 2] is a concentration in water of free carbon oxide (IV), mg / l; [CA 2+] - concentration of calcium ions, mg / l; F to - carbonate rigidity of water, mM-eq / l; D to - the dose of coagulant (FES0 4 or FECL 3 in terms of anhydrous products), mg / l; E K is an equivalent mass of the active substance of coagulant, mg / mg-eq (for FES0 4 E K \u003d 76, for FECL 3 E K \u003d 54); 0.5 and 0.3 - excess of lime to ensure greater completeness of the reaction, mM-eq / l.

Expression D Q / E to take a minus sign if the coagulant is introduced earlier than lime, and with a sign plus, if together or after.

In the absence of experimental data, the coagulant dose is found from the expression

D K \u003d 3 (C) 1/3, (20.4)

where C is the amount of suspension, formed when water softening (in terms of dry substance), mg / l.

In turn, C are determined using addiction

The lime-soda method of water softening is described by the following main reactions:

By this method, the residual rigidity can be brought to 0.5.1, and alkalinity from 7 to 0.8.1.2 mG-eq / l.

Doses of lime d and and soda d with (in terms of Na 2 C0 3), mg / l, determined by formulas

(20.7)

where - the content of magnesium water, mg / l; Well. C. - Non-Gonnating Water Stiffness, ME-EQ / L.

With a lime-soda method of water softening, the resulting calcium carbonate and magnesium hydroxide can be loosened and remain in colloid-dispersed state. Their transition to the coarse sludge is long, especially at low temperatures and the existence of organic impurities in water, which act as protective colloids. With a large amount of water, water rigidity at reagent water softening can be reduced by only 15.20%. In such cases, organic impurities with oxidants and coagulants are removed before softening or in the process. With lime-soda method, the process is often carried out in two stages. Originally, organic impurities and a significant part of carbonate rigidity are removed from the water, using aluminum or iron salts with lime, conducting a process under optimal coagulation conditions. After that, the soda is introduced and the rest of the lime and devaimed water. When the organic impurities are removed simultaneously with the softening of water, only iron salts are used as coagulants, since with a high pH value of the water required to remove magnesium rigidity, aluminum salts do not form sorption-active hydroxide. The dose of coagulant in the absence of experimental data is calculated by formula (20.4). The amount of suspension is determined by the formula

where o is the total rigidity of water, mM-eq / l.

MgS0 4 + SA (OH) 2 \u003d Mg (OH) 2 + CAS0 4

Fig. 2. The effect of temperature (a) and doses of lime (b) to the depth of water softening with a lime-soda and lime method

Sa (0h) 2 + Na 2 C0 3 \u003d CAC0 3 + 2NAOH,

With a sodium-sodium water softening method, it is treated with sodium sodium and hydroxide:

The soda-sodium method is commonly used to soften the water, the carbonate stiffness of which is slightly more nearsbonate. If the carbonate rigidity is approximately equal to non-comboonate, the soda can not be added at all, since its required amount for softening such water is formed as a result of the interaction of hydrocarbonates with caustic sodes. The dose of calcined soda increases as the non-marginal rigidity of water increases.

A coherent method based on the resumption of soda in the process of softening is used in the preparation of water, to power the steam boilers of low pressure

Ca (NS0 3) 2 + Na 2 C0 3 \u003d CAC0 3 + 2NAHC0 3.

Sodium bicarbonate, falling into a boiler with softened water, decomposes under the influence of high temperature

2NHC0 3 \u003d Na 2 C0 3 + H 2 0 + C0 2.

The barium method of softening water is used in combination with other methods. Initially, the barium containing reagents in water (VA (OH) 2, Vaso 3, Waa1 2 0 4) are introduced to eliminate sulfate stiffness, then after clarifying the water, it is treated with lime and soda to die. The chemistry of the process is described by reactions:

Due to the high cost of reagents, the barium method is used very rarely. To prepare drinking water due to the toxicity of the barium reagents, it is not suitable. The resulting barium sulfate is precipitated very slowly, so sumps or large-sized clarifiers are necessary. To enter you03, flocculators with mechanical stirrers should be used, because Vaso 3 forms a heavy, fast precipitating suspension.

Oxalate method of water softening is based on the use of sodium oxalate and at low solubility in the water formed oxalate calcium (6.8 mg / l at 18 ° C)

The method is characterized by simplicity of technological and hardware design, however, due to the high cost of the reagent, it is used to soften the small amounts of water.

Phosphating is used to die water. After the reagent softening of the lime-soda method, the presence of residual stiffness (about 2 mG-eq / l) is inevitable, which phosphate deumenion can be reduced to 0.02-0.03 mgq / l. Such a deep cookie allows in some cases not to resort to cationic water.

Phosphating also achieves a high stability of water, a decrease in its corrosion action on metal pipelines and prevent carbonate deposits on the inner surface of the pipe walls.

Hexametaphos is used as phosphate reagents, triolyphosphate (orthophosphate) sodium, etc.

D Φ \u003d 54.67 (w OST + 0.18),

where f is the residual stiffness of the softened water before phosphate duity, mM-eq / l.

The solution for dosing hexamet phosphate or sodium orthophosphate with a concentration of 0.5-3% is prepared in tanks, the number of which should be at least two. The inner surfaces of the walls and the bottom of the tanks must be coated with a corrosive material. The preparation time of a 3% solution is 3 hours with mandatory stirring with a stirrer or bubble (using compressed air) in the manner.

Technological schemes and constructive elements of reagent water softeners

Fig. 3. Water installation with a vortex reactor.

1 - bunker with contact mass; 2 - Ejector; 3, 8 - feeding the original and diversion of softened water; 4 - vortex reactor; 5 - input reagents; 6 - fast clarifying filter; 9 - relief of contact mass; 7 - Softened water reservoir

In this installation there is no cake formation chamber, since the cereal sediment of calcium carbonate is formed in the contact mass. If necessary, water is brought in front of the reactors.

The optimal construction for softening water with limestone or lime-soda methods is a vortex reactor (spiractor pressure or open) (Fig. 20.4). The reactor provides a reinforced concrete or steel housing, a narrowed down (angle of tape of 5.20 °) and filled with about half a height of the contact mass. The speed of water in the lower narrow part of the vortex reactor is 0.8.1 m / s; The speed of the ascending flow at the top at the level of the drainage devices is 4.6 mm / s. As a contact mass, sand or marble crumbs with grain size is 0.2.0.3 mm at the rate of 10 kg per 1 m3 of the reactor volume. With a screw ascending flow of water, the contact mass is weighed, the grains are faced with each other and the Saco 3 is intensely crystallized on their surface; Gradually, the grains are turning into the balls of the right shape. The hydraulic resistance of the contact mass is 0.3 m per 1 m height. When the diameter of the balls increases to 1.5.2 mm, the largest most severe contact mass is released from the bottom of the reactor and fit fresh. The vortex reactors do not delay the magnesium hydroxide precipitate, so they should be used in conjunction with the filters installed only in cases where the amount of magnesium hydroxide formed by the resulting precipitate corresponds to the filter dukes.

The consumption of fresh contact mass added by ejector is determined by the formula G \u003d 0.045q, where G is the amount of the added contact mass, kg / day; Well - removed in the reactor rigidity of water, mM-eq / l; Q - installation performance, m 3 / h.

Fig. 4. Vortex reactor.

1.8 - Submission of the original and diversion of softened water: 5 - samplers; 4 - contact mass; 6 - reset air; 7 - hatch for the loading of the contact mass; 3 - input reagents; 2 - Removal of the spent contact mass

Such technology is used to soften the turbid waters containing a large number of magnesium salts. In this case, the mixers are loaded with contact mass. When using decorators of design E.F. Kurgayev, faucets and chambers Flap formation are not provided, since the mixture of reagents with water and the formation of sediment flakes occur in the clarifier themselves.

With the cost of softened water to 1000 m 3 / day, a water treatment plant type "jet" can be applied. The processed water with the reagents added to it enters the thin-layer sump, then to the filter.

At the Institute of Mining, the Siberian Branch of the Russian Academy of Sciences has developed an unhappy electrochemical technology of water softening. Using the phenomenon of the alkalization of the anode and acidification at the cathode by passing a constant electric current through the water system, the reaction of water discharge can be submitted by the following equation:

2H 2 0 + 2e 1 → 20n - + H 2,

where E 1 is a sign indicating the ability of stiffness salts to dissociate into Ca (II) and MG (II) cations.

In fig. 6 shows the technological scheme of the installation for water softening with an electrochemical way.

The production unit was mounted in the district boiler room, the tests of which lasted for about two months. The mode of electrochemical processing was stable, the precipitate in cathode chambers was not observed.

Fig. 5. Installation of the nzvestkovo-soda softening of water. 2 - Ejector; 3 - bunker with contact mass; 5 Entering reagents; 6 - clarifier with a layer of suspended sediment; 7 - Lightening fast filter; 4 - vortex reactor

Fig. 6. Scheme of the installation of electrochemical softening of water I - rectifier VAKG-3200-18; 2 - a diaphragm electrolyzer; 3, 4 - analyte and catalytes; 5 - pump; 6 - pH-meter; 7 - clarifier with a layer of suspended sediment; 8 - Lightening fast filter; 9 - discharge into the sewer; 10, 11 - the removal of softened and supply of the source water; 12 - flow meter; 13 - exhaust umbrella

Chemical, X-ray structural, IR spectroscopic and spectral analyzes have been established that the CAC0 3, Mg (OH) 2 and partially Fe 2 0 3 * H 2 is mainly contained in sediment.

Water - a forced and expensive event, which is a rather complicated problem associated with a large variety of pollutants and the appearance of new compounds in their composition. Waters cleaning meters can be divided into 2 large groups: destructive and regenerative. The basis of destructive methods is the processes of destruction of pollutants. The resulting decomposition products are removed ...

It is performed through the average and upper team-distribution devices due to the direction of a part of the spent regeneration solution or supply of the initial water along the recycling contour. 1. Types of filters and the features of their structure ionic filters are classified depending on the principle of operation, as well as on the goals pursued during the passage of water through them. 1.1 Fip Filters, ...

Know the degree of rigidity of the water used necessarily. From the record of stiffness of drinking water depends a lot of aspects of our lives: how much to use washing powderWhether measures are needed to soften rigid water, how many aquarium fish will live in water, whether the introduction of polyphosphates in reverse osmosis, etc.

There are many ways to determine hardness:

by the number of formed foam of detergent;
in the area;
by the amount of scale on the heating elements;
on the taste properties of water;
with the help of reagents and special devices

What is stiffness?

In the water there are main cations: calcium, magnesium, manganese, iron, strontium. The last three cations affect the rigidity of water. There is still a trivalent cation of aluminum and iron, which at a certain pH form limestone flare.

Stiffness can be of different types:

total rigidity - the total content of magnesium and calcium ions;
carbonate rigidity- The content of hydrocarbonates and carbonates at the pH is greater than 8.3. They are easy to remove through boiling: during heating decompose on coalic acid and precipitate;
non-gonna rigidity - Calcium and magnesium salts strong acids; You can not remove with boiling.

There are several water rigidity units: mole / m 3, mM-eq / l, DH, D⁰, F⁰, PPM CaCo 3.

Why does water have rigidity? Alkaline earth metal ions are in all mineralized waters. They are taken from the deposits of dolomites, plaster and limestone. Water sources may have rigidity in different ranges. There are several stiffness systems. Abroad, it is suitable more "harsh". For example, we are considered soft with a rigidity of 0-4 mM-eq / l, and in the USA - 0-1.5 mg-eq / l; Very rigid water in Russia - over 12 mg / l, and in the United States - over 6 mgq / l.

The rigidity of low-mineralized water by 80% is due to calcium ions. With increasing mineralization, the share of calcium ions is sharply reduced, and magnesium ions increase.

Most often, surface waters have less rigidity than underground. Also stiffness depends on the season: during melting of the snow, it decreases.

The rigidity of drinking water changes its taste. Sensitivity threshold for calcium ion - from 2 to 6 mg-eq / l depends on the anions. Water becomes bitter and poorly affects the process of digestion. WHO does not give any recommendations on water hardness, as there is no accurate evidence of its influence on the human body.

Restriction of stiffness is necessary for heating devices. For example, in boilers - up to 0.1 mM-eq / l. Soft water has low alkalinity and causes corrosion of plumbing communications. Communal services use special processing to find a compromise between the raid and corrosion.

There are three groups of water softening methods:

physical;
chemical;
extrasessor.

Reagent water softening methods

Ion exchange

Chemical methods are based on ion exchange. The filtering mass is ion exchange resin. It is long molecules that collected in balls yellow color. From the balls are small processes with sodium ions.

During filtration, water impresses all resin, and its salts become sodium. Sodium itself is carried out with water. Due to the difference of charge charges, the ions are washed 2 times more salts than settled. Over time, salts are all replaced and resin ceases to work. Period of work for each resin is yours.

The ion exchange resin can be in cartridges or pumped into a long bologna - column. Cartridges are small and used only to reduce drinking water stiffness. Ideal for softening water at home. Ion exchange column is used to soften water in an apartment or small production. In addition to the high cost of the column, it should be periodically loaded with a reduced filtering mass.

If sodium ions remained in the cartridge resin, it is simply replaced with a new one, and the old one is thrown away. When using ion exchange colone, the resin is restored in a special tank with brine. To do this, dissolve salt tableting. The saline solution regenerates the ability of the resin to the exchange of ions.

The opposite side is the additional water ability to remove the iron. It clogs the resin and leads it to complete unsuitability. You should make water analysis in time!

Use of other chemical reagents

There are a number of less popular, but effective ways Water softening:

calcined soda or lime;
polyphosphates;
anti-Calants - compounds against the formation of scale.

Softening lime and soda

Softening water soda

The method of softening water using lime is called lime. Use hawed lime. The content of carbonates is reduced.

A mixture of soda and lime most effectively. For clarity of water softening at home, you can add a calcined soda to the water for washing. On bucket take 1-2 teaspoons. Well stirred and wait for precipitation. A similar method used women in Ancient GreeceUsing oven ash.

Water after lime and soda is not suitable for food purposes!

Softening polyphosphates

Polyphosphates are able to bind the salts of rigidity. They are large white crystals. Water passes through the filter and dissolves polyphosphates, tying salt.

The disadvantage is the danger of polyphosphates for living organisms, including a person. They are a fertilizer: after entering the water, an active growth of algae is observed.

Polyphosphates are also unsuitable for softening drinking water!

Physical water softening method

Physical methods are struggling with the effects of high rigidity - scale. This is a non-deceptible water purification. When it is used, there is no decrease in salt concentration, but simply prevents damage to pipes and heating elements. Water becomes soft or for greater understanding - softened.

The following physical methods are distinguished:

using a magnetic field;
using an electric field;
ultrasonic processing;
thermal method;
the use of minor current pulses.

A magnetic field

A negligent water softening with a magnetic field has many nuances. Efficiency is achieved only subject to certain rules:

defined water flow rate;
selected field strength;
a certain ionic and molecular composition of water;
the temperature of the incoming and outgoing water;
time of processing;
atmosphere pressure;
water pressure, etc.

Changing any parameter requires full reconfiguration of the entire system. The reaction must be immediate. Despite the complexity of control of parameters, the magnetic softening of water is used in boiler rooms.

But for the softening of water at home with the help of a magnetic field is almost impossible. When desire to purchase a magnet on a pipeline, think how you pick up and will provide the necessary parameters.

Using ultrasound

Ultrasound leads to cavitation - the formation of gas bubbles. The likelihood of a magnesium and calcium ions encouragement. Crystallization centers appear not on the surface of the pipes, but in the thickness of the water.

When softening hot water The ultrasound of the crystals do not reach the size required for precipitation - the scale is not formed on heat exchange surfaces.

Additionally, high-frequency oscillations occur, which prevent the formation of plaque: repel the crystals from the surface.

Flexible fluctuations are detrimental for the formed layer of scale. She begins to dig in pieces that can clog the channels. Before using ultrasound, clean the surfaces from scale.

Electromagnetic impulses

Current water softeners based on electromagnetic pulses change the method of crystallization of salts. Dynamic electrical impulses with different characteristics are created. They go along the wire-winding on the pipe. Crystals acquire the shape of long shelves, which is difficult to fix on the surface of the heat exchange.

During the processing process, carbon dioxide is distinguished, which fights with an existing lime bloom and forms protective film on metal surfaces.

Thermomeness

Someone hears about this method for the first time. But in fact it uses every since childhood. This is familiar to us boiling water.

Everyone noticed that after boiling water, a precipitate from stiffery salts is formed. Coffee or tea makes softer water than plumbing.

And how much should you boil? Everything is simple: with increasing temperature and its effects of stiffness salts are less soluble and more falls out of the sediment. In the process of heating, carbon dioxide is released. The faster it disappears, the more the limestone flare is formed. Tight closed cover Prevents the removal of carbon dioxide, and liquid evaporates in an open container.

When using thermoemium, leaving the lid in the tank slightly open. You should also provide the maximum deposition area of \u200b\u200bsalts to accelerate the softening of drinking water.

With stiffness up to 4 mg-eq / l, thermal softening is not necessary: \u200b\u200bSalts will settle more slowly than water evaporates. The remaining water will be an increased concentration of many impurities.