TWI548595B - Water treatment method - Google Patents

Description

Water treatment method

The present invention relates to a water treatment method for supplying water to a steam generating device such as a boiler. In particular, the present invention relates to a water treatment method which does not require the use of a strong base or a strong acid, and which does not require the use of a large amount of sodium chloride, which can be drastically reduced compared to the previous soft water supply (blow) The operation of the loss of heat and water. The present invention relates to a water treatment method capable of preventing rusting of a heat transfer surface caused by calcium or magnesium, and also preventing rusting of iron brought in by steam condensate, thereby The heat transfer surface remains clean.

When the operating pressure is low in a steam generating facility such as a boiler, generally, a taper filled with a sodium-type cation exchange resin is used to treat tap water or groundwater such as a city water supply, thereby using calcium and magnesium in the water. The softened water substituted with sodium is used as make-up water. This is to prevent the hardness component such as calcium or magnesium from being introduced into the boiler and rusting on the heat transfer surface to hinder heat transfer, thereby causing energy loss or overheating of the heat transfer surface.

When the steam generating apparatus is operated using demineralized water as the makeup water, there is a problem that a large amount of sodium chloride is used in the regeneration of the cation exchange resin of the softener. The demineralized water obtained by the softener contains a large amount of dissolved salts, so that the concentration of the salt in the boiler water is increased by the concentration of the vapor, and the boiler water and the vapor are likely to cause accompanying soda azealing. Therefore, it is necessary to blow off a relatively large amount of boiler water and it will be thick The magnification is maintained within the specified range. By blowing off the boiler water, the make-up water will increase, and the amount of heat lost with the blowing of water will increase.

In order to reduce the heat lost by blowing, it is known that the following i-iii method is used to treat the supply water of the low-pressure boiler, thereby removing the dissolved matter in the make-up water, thereby reducing the amount of blown water. The following problems exist in each method.

i) A method of removing dissolved ions using a strong salt-based anion exchange resin and a strongly acidic cation exchange resin (Non-Patent Document 1).

In this method, it is necessary to frequently regenerate the ion exchange resin with a strong acid and a strong base.

Ii) A method of removing dissolved salts of water supply by a reverse osmosis membrane apparatus after treatment with a softener (Non-Patent Document 2).

In this method, as in the method of softening by a previous softener, a large amount of sodium chloride is used in the regeneration of the cation exchange resin filled in the softener, and a relatively large amount of concentrated water is discharged in the reverse osmosis membrane treatment. Therefore, the amount of demineralized water used for the reverse osmosis membrane treatment is further increased, whereby the amount of sodium chloride used is further increased. Even if the reduction amount of the blow-off is subtracted, the amount of water used is increased as compared with the case where only the softener is used for the treatment.

Iii) A method of performing treatment by an electrical desalination apparatus in which an ion exchange membrane and a DC power source are combined after being treated by a reverse osmosis membrane device (Non-Patent Document 3).

In this method, the treated water obtained is a water having a very small amount of dissolved matter, but the apparatus is very large in scale and high in price.

The condensed water from the steam generated in the boiler is recovered and reused as a water supply, and heat and water are recovered, and in the case of replenishing the softened water, the dissolved matter brought into the boiler by the self-water supply is reduced. Further energy savings are achieved by the reduction of blown water. The iron eluted from the piping for recovering the condensed water is brought into the boiler, whereby the heat transfer surface in the boiler adheres to the oxidized rust, which lowers the heat transfer efficiency and becomes a corrosion problem in which the lower portion to which the rust adheres is generated. the reason. Therefore, when the iron concentration of the collected condensed water is high, there is a case where it cannot be discharged as a water supply.

The electric double-layer condenser desalination device used in the present invention is applied to the production of pure water, etc., and it is also known to use a liquid-through type electric double-layer capacitor desalination device and an ion exchange device to sequentially perform processing. Desalination method (Patent Document 1).

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2002-210468

Non-patent literature

Non-Patent Document 1: Water Management of Boilers <Knowledge and Application> The first edition of P.146~176 issued by the Japan Boiler Association

Non-Patent Document 2: Water Management of Boilers <Knowledge and Application> Social Welfare Corporation Japan Boiler Association Released P.183

Non-Patent Document 3: Water Management of Boilers <Knowledge and Application> The first edition of P.191~193 issued by the Japan Boiler Association

A first object of the present invention is to provide a water treatment method which improves the problems of the prior art which require a large amount of sodium chloride or a strong acid or a strong alkali, or a large amount of concentrated water in a water supply treatment, and The low pressure boiler can be blown and reduced.

A second object of the present invention is to provide a water treatment method which does not cause energy loss or corrosion trouble caused by rust adhesion, and is recovered from water supply as steam condensate related to energy saving and water saving. Reuse and reuse of heat and water, and energy-saving operation by blowing reduction.

The inventors of the present invention have conducted active research in order to solve the above problems, and as a result, it has been found that a water-soluble polymer having a carboxyl group in a molecule is used as a rust preventive agent by applying a liquid-pass type electric double layer capacitor desalination device. The above problems can be solved.

The present invention has been achieved based on the above findings and is intended to be as follows.

[1] A water treatment method in which raw water obtained by sequentially passing a raw water through a liquid-through type electric double-layer capacitor desalination apparatus and a softener is supplied to a steam generator.

[2] A water treatment method in which a raw material is passed through a through-liquid type electric double layer capacitor desalination apparatus without using a softener in a steam generation apparatus that recovers and reuses steam condensed water as a water supply. The treated water and the recovered water of the vapor condensed water are supplied to the steam generator as a water supply, and a water-soluble polymer having a carboxyl group in the molecule is added to the water supply.

[3] In the water treatment method of [2], with respect to the above steam generator The amount of calcium in the water supply is 1 to 5 times by weight of the above water-soluble polymer having a carboxyl group.

[4] The water treatment method according to [2] or [3], wherein the water-soluble polymer having a carboxyl group is a homopolymer of sodium acrylate.

According to the water treatment method of the present invention, it is not necessary to use a strong base or a strong acid as in the case of using a strong salt-based anion exchange resin and a strongly acidic cation exchange resin, and it is not necessary to use a large amount of chlorination as in the case of treatment using only a softener. Sodium can be used to significantly reduce the loss of heat and water caused by blowing, as compared with the case of the prior softened water treated only with a softener or by treating the softened water with a reverse osmosis membrane device for water supply. The operation. By preventing rusting of the heat transfer surface caused by calcium or magnesium, and also preventing rusting of iron brought in by the steam condensate, water treatment capable of maintaining the heat transfer surface clean can be performed.

In particular, when the steam condensed water is recovered and reused, a water-soluble polymer having a carboxyl group in the molecule can be added to the steam generator in the treated water treated only by the through-liquid type electric double-layer capacitor desalination apparatus. In this case, a softener may not be required, and sodium chloride for simplification of the apparatus and regeneration of the softener may not be required. In this method, rusting of iron brought together with steam condensed water, coexistence with calcium contained in a through-liquid type electric double layer capacitor desalination apparatus, and addition of a water-soluble polymer having a carboxyl group in the molecule Thereby, iron and calcium are not rusted and discharged.

The form of implementation of the present invention will be described in detail below.

A water treatment method according to a first aspect of the present invention is characterized in that the raw water is sequentially supplied to the steam generator by the treated water obtained by sequentially passing through the liquid-through type electric double-layer capacitor desalination apparatus and the softener.

According to the first aspect, the raw water is treated by a through-liquid type electric double layer capacitor desalination device to remove cations such as sodium ions, calcium ions, and magnesium ions in the raw water, and anions such as chloride ions, sulfate ions, and nitrate ions. Therefore, the ions in the raw water can be greatly reduced. Therefore, the ion load of the softener in the subsequent stage can be reduced, and the amount of sodium chloride used in the regeneration of the softener can be greatly reduced. According to the first aspect, the concentration of the salt introduced into the boiler water can be greatly reduced, and the increase in the electrical conductivity caused by the dissolved salts can be greatly reduced, and the blown water can be drastically reduced. According to the first aspect, a strong base or a strong acid as in the case of using an ion exchange resin is not required. The softener replaces calcium ions, magnesium ions, and the like into sodium ions by a cation exchange resin. A thick aqueous solution of sodium chloride is used for the regeneration of the cation exchange resin.

A water treatment method according to a second aspect of the present invention is characterized in that, in a steam generating apparatus that recovers and reuses steam condensed water as a water supply, the raw water is desalted by a liquid-through type electric double layer capacitor without using a softener. The treated water obtained by the apparatus and the recovered water of the vapor condensed water are supplied to the steam generator as a water supply, and a water-soluble polymer having a carboxyl group in the molecule is added to the water supply.

According to the second aspect, since the softener is not required, sodium chloride for regeneration of the softener is not required. According to the second aspect, the concentration of the salt brought into the boiler is greatly reduced as compared with the case where only the softener is used to treat the raw water. Low, so you can cut off. According to the second aspect, the amount of heat or water and water treatment chemicals discharged is reduced, and the amount of water supplied is reduced, so that the amount of added water treatment chemicals is also reduced.

According to the second aspect, the calcium contained in the treated water of the through-liquid type electric double-layer capacitor desalination apparatus and the water-soluble polymer having a carboxyl group added to the molecule added to the water supply can be prevented from being taken together with the vapor condensed water. The iron that has entered is rusted and can be discharged into the blown water. Therefore, it is preferable that calcium is present in the water supply, and thus the water to be treated is treated without using the softener to treat the treated water of the liquid-through type electric double layer capacitor desalination apparatus.

The liquid-passing type electric double-layer capacitor desalination apparatus has a structure in which two conductor layers having a high specific surface area are interposed between each other, and a collector is disposed outside the conductor layers. By applying a voltage to the collector, ions in the raw water are electrically adsorbed to the conductor layer, and treated water having a reduced concentration of dissolved salts can be obtained. As the above-mentioned high specific surface area conductor, for example, activated carbon is preferable.

In the through-liquid type electric double layer capacitor desalination apparatus, the ionic substance flowing into the water is removed through the processing steps shown below. The treatment mechanism will be described with reference to FIGS. 1 and 2, in the case where the ionic substance contained in the inflow water is sodium chloride and the conductor having the high specific surface area is activated carbon.

As shown in FIG. 1, when a voltage is applied, sodium ions flowing into the water are electrically adsorbed to the activated carbon layer 2 in contact with the collector 1 on the cathode side, and the chloride ions are electrically adsorbed to the collector 3 on the anode side. Activated carbon layer 4. Therefore, the sodium chloride concentration of the treated water obtained from the outlet is greatly lowered. If the water is continuously passed for a long time, the ions of the activated carbon layer 2 and the activated carbon layer 4 are sucked. The saturation is close to the saturation, so that the concentration of sodium chloride in the treated water obtained from the outlet is increased. Therefore, if the anode side and the cathode side are short-circuited or reversed before the adsorption saturation is reached, as shown in FIG. 2, the sodium ions and chloride ions adsorbed on the activated carbon layer 2 and the activated carbon layer 4 are separated, including the inflow water. Sodium chloride concentration The effluent water of a higher concentration of sodium chloride is discharged from the outlet. If the flow rate at this time is delayed, the sodium chloride adsorbed to the activated carbon layer 2 and the activated carbon layer 4 can be discharged with a small amount of flowing water.

In the present invention, the boiler water supply is manufactured using the above-described liquid-through type electric double layer capacitor desalination apparatus.

In the liquid-passing type electric double-layer capacitor desalination apparatus, as described above, since the desalination step and the discharge step are repeated in the electrode portion, the desalination treatment water cannot be obtained in the discharge step. When it is necessary to continuously obtain the treated water, it is only necessary to control the operating period so that a plurality of liquid-through type electric double layer capacitors are provided to secure the necessary amount of treated water.

Examples of the raw water to be treated in the present invention include various types of water such as well water, tap water, river water, industrial water, reclaimed water, and sewage.

Hereinafter, a first aspect of the present invention will be specifically described with reference to Fig. 3 .

Fig. 3 is a system diagram showing an embodiment of a first aspect of the present invention. The raw water is first introduced into the liquid-through type electric double layer capacitor desalination apparatus 11 and treated to remove cations such as sodium ions, calcium ions, and magnesium ions, and anions such as chloride ions, sulfate ions, and nitrate ions. By using the liquid-through type electric double-layer capacitor desalination device 11, the ions in the raw water can be removed by at least several tens of%, and then the ion load of the softener 12 can be reduced to several points. One to one tenth. Therefore, the amount of sodium chloride used in the regeneration of the softener 12 can also be reduced to a fraction of a tenth to a few tenths, and the treated water of the water softener 12 is supplied to the boiler 14 via the water supply tank 13, whereby Significantly reducing the concentration of salts brought into the boiler water can also greatly reduce the increase in conductivity caused by the dissolved salts. Therefore, the blowing water can be drastically reduced, the water and heat discharged by the blowing can be reduced, and the amount of water supplied to the boiler for generating the predetermined steam is also reduced. As a result, there is obtained an advantage that the liquid-through type electric double layer capacitor desalination apparatus 11 or the softener 12 can be made smaller in the amount of treated water, and the amount of sodium chloride used in the regeneration of the softener can be further reduced. Further, by reducing the amount of water supplied to the boiler 14, the amount of water treatment chemicals added to the water supply to a predetermined concentration is also reduced. Further, since the concentration of the boiler water is increased by the reduction of the blow-off, the concentration of the water treatment chemicals which can prevent corrosion or rust in the boiler by maintaining a predetermined concentration in the boiler water can be further lowered as compared with the prior art. . In addition, by adding a water-soluble polymer having a carboxyl group in the molecule to the water supply, it is possible to prevent rusting in the boiler in a hardness component which is extremely contained in the water supply, and to suppress heat transfer loss or corrosion of the rust portion. Occurrence of water treatment.

In the first aspect, the water recovery rate of the liquid-through type electric double layer capacitor desalination apparatus is preferably about 80% to 95%, and the removal rate of dissolved salts is about 70% to 90%. If the water recovery rate of the through-liquid type electric double layer capacitor desalination apparatus is too low, the amount of raw water used is increased, and if it is too high, the dissolved salt is not sufficiently removed. If the removal rate of dissolved salts of the through-liquid type electric double layer capacitor desalination apparatus is too low, the ion load of the softener in the latter stage increases, and the frequency of regeneration of the softener increases. Dissolved salt of a liquid-through type electric double layer capacitor desalination device When the removal rate is too high, the economy is lowered by the increase in the use of electric power.

Fig. 4 is a system diagram showing an embodiment of a second aspect of the present invention. The raw water is passed through the liquid-through type electric double-layer capacitor desalination apparatus 21 to reduce the dissolved ions to one-tenth to one-tenth of the treated water, and is directly supplied to the water supply tank 22 without passing through the water softener. The recovered steam condensate (condensed water) is also supplied to the water supply tank 22. In the water of the water supply tank 22, a water-soluble polymer having a carboxyl group in the molecule is added to the boiler in proportion to the flow rate of the treated water of the liquid-through type electric double-layer capacitor desalination device 21. In the present embodiment, the device is simplified because the softener is not used, and sodium chloride for regeneration of the softener is not required. Moreover, the concentration of the salt brought into the boiler is greatly reduced as compared with the case where the raw water is treated only by the softener, so that the blowing can be reduced, the heat or the water, the water treatment chemical component can be reduced, and the water supply can be reduced. The amount of water treatment chemicals added is also reduced. Further, the molten iron from the heat exchanger or the pipe contained in the vapor condensed water recovered as the water supply has the hardness component contained in the treated water of the liquid-through type electric double layer capacitor desalination device 21 and the added intramolecular The effect of the water-soluble polymer of a carboxyl group is effectively discharged by blowing, and rust adhesion of the heat transfer surface due to being brought into the boiler can be effectively suppressed.

In the second aspect, the water recovery rate of the liquid-through type electric double layer capacitor desalination apparatus is preferably about 80% to 95%, and the removal rate of dissolved salts is about 70% to 90%. If the water recovery rate of the through-type electric double-layer capacitor desalination apparatus is too low, the amount of raw water used is increased, and if it is too high, the dissolved salt cannot be sufficiently removed. If the removal rate of the dissolved salt in the through-type electric double-layer capacitor desalination device is too low, the amount of blown water must be increased, but if the flow-through type electric double-layer capacitor When the removal rate of the dissolved salt in the desalination apparatus is too high, the effect of preventing the rust of the iron described above cannot be sufficiently obtained by the calcium in the treated water of the liquid-through type electric double layer capacitor desalination apparatus.

Therefore, it is preferable to adjust the removal rate of dissolved salts of the through-liquid type electric double layer capacitor desalination apparatus by appropriately adjusting the calcium concentration in the boiler water supply to about 0.1 mg to 10 mg-CaCO ₃ /L. .

The water-soluble polymer having a carboxyl group in the molecule used in the present invention may, for example, be acrylic acid and/or a salt thereof, maleic acid and/or a salt thereof, itaconic acid and/or a salt thereof, methacrylic acid and/or a homopolymer, a copolymer, or a terpolymer of a carboxylic acid and/or a salt thereof, such as a salt; 2-hydroxy-3-allyloxypropanesulfonic acid and/or a salt thereof, and the above carboxylic acid and/or a salt thereof a copolymer; a copolymer of 2-propenylamine-2-methylpropanesulfonic acid and/or a salt thereof with the above carboxylic acid and/or a salt thereof; bis(poly-2-carboxyethyl)phosphonic acid and/or Its salt; carboxymethyl cellulose and the like. In addition, examples of the salt of the carboxylic acid, the sulfonic acid, and the phosphonic acid include alkali metal salts such as a sodium salt and a potassium salt.

As the water-soluble polymer having a carboxyl group in the molecule, a homopolymer of sodium acrylate is preferred.

The weight average molecular weight of the water-soluble polymer having a carboxyl group in the molecule is preferably from 1,000 to 100,000, particularly preferably from 1,500 to 50,000. If the molecular weight is too large, a gelation is formed by bonding with calcium, and a strainer or the like is blocked. If the molecular weight is too small, a sufficient effect may not be exhibited.

The amount of the water-soluble polymer having a carboxyl group in the molecule should be adjusted to be 0.5 to 10 times the concentration of the calcium in the boiler water supply, and more preferably It is 1 to 5 times the concentration. When the concentration of the water-soluble polymer added is more than the above upper limit, the effect of dispersing iron brought in from the recovery line of the vapor-condensed water is lowered, and the amount of adhesion of rust is increased. When the concentration of the water-soluble polymer to be added is less than the above lower limit, the effect of the hardness component contained in the treated water of the liquid-through type electric double layer capacitor desalination apparatus on the rust adhesion in the boiler is insufficient.

In the present invention, in addition to the above water-soluble polymer, an alkali agent (NaOH, KOH, K ₂ CO ₃ , Na ₂ CO _{3 ,} etc.) or a deoxidizer (tantalum, tannin, etc.) generally used as a water treatment chemical may be used in combination. Tannic acid and/or its salt, isoascorbic acid and/or its salt, ascorbic acid and/or its salt, glucose, etc., corrosion inhibitor (gluconic acid and/or its salt, glucoheptonic acid and/or its salt, Succinic acid and/or a salt thereof, citric acid and/or a salt thereof, tartaric acid and/or a salt thereof, phosphoric acid and/or a salt thereof, a polymerized phosphoric acid and/or a salt thereof, a phosphonic acid and/or a salt thereof.

[Example]

The invention will be more specifically described below by way of examples and comparative examples.

In addition, the raw water to be treated in the following examples and comparative examples is the tap water of Noki-cho, Tochigi Prefecture, Japan, which has the following water quality.

<Original water quality>

Conductivity: 25mS/m

M alkalinity: 23mg-CaCO ₃ /L

Ceria: 18mg/L

Ca hardness: 30mg-CaCO ₃ /L

Mg Hardness: 15mg-CaCO ₃ / L

[Comparative Example 1]

The treatment water obtained by the Nojima water was passed through a softener of a cation exchange resin amount of 18 L to a water supply tank, and 30 mg/L of sodium erythorbate as a deoxidizing agent for water treatment chemicals was added thereto, and 27 mg/ NaOH as an alkali agent of L, the P alkalinity of the NaOH boiler water is 1.7 times the concentration of cerium oxide, and is supplied to the experimental boiler at 0.450 m ³ /h, and the boiler water is at a pressure of 0.7 MPa. The electric conductivity was 300 mS/m, and it was operated for 10 days while being blown off.

At this time, the purge rate averaged 13.5% and the evaporation amount was 0.39 ton/h. Further, the softener was regenerated six times during the test period, and the sodium chloride used for the regeneration was 13.8 kg.

[Comparative Example 2]

In Comparative Example 1, after the Noki-machi water was treated with a softener, the water was recovered by a reverse osmosis membrane apparatus at a water recovery rate of 80% (the average removal rate of dissolved salts at this time was 98%), and the reverse was saturated. The treated water of the membrane device is supplied to the water supply tank, and 30 mg/L of sodium erythorbate as a deoxidizing agent for water treatment chemicals and 19 mg/L of NaOH as an alkali agent are added to one side of the membrane, and the NaOH boiler water The conductivity was 11.5 and the conductivity calculated at a blow rate of 3.0% was 300 mS/m, and was supplied to an experimental boiler and operated at a pressure of 0.7 MPa for 10 days.

The evaporation amount at this time was 0.39 t/h. The water supply to the boiler was 0.401 m ³ /h, and the raw water flow rate was 0.501 m ³ /h on average. During the test period, the softener was regenerated 7 times, and the sodium chloride used in the regeneration was 16.1 kg.

[Example 1]

The wild wood water is passed through a liquid-liquid double-layer capacitor desalination device and operated at a water recovery rate of 90% (the average removal rate of dissolved salts at this time is 80%), the treated water of the liquid-through type electric double-layer capacitor desalination apparatus was supplied to the water supply tank by the treated water obtained by the softener in the same manner as in Comparative Example 1, and 30 mg/L was added as a water treatment chemical on one side. The deoxidizer sodium erythorbate and 17 mg/L NaOH as an alkali agent, the P alkalinity of the NaOH boiler water is 1.7 times the concentration of cerium oxide, and is supplied to the experimental boiler at a pressure of 0.7. The boiler water has a conductivity of 300 mS/m at MPa and is blown off and operated for 10 days.

The blow rate at this time was 3.0% on average, and the evaporation amount was 0.39 t/h. The water supply to the boiler was 0.401 m ³ /h, and the raw water flow rate was 0.446 m ³ /h on average. During the test period, the softener was regenerated once, and the sodium chloride used in the regeneration was 2.3 kg.

The results of Comparative Example 1, Comparative Example 2, and Example 1 described above are as follows.

That is, in the example 1 which was treated by the through-liquid type electric double layer capacitor desalination apparatus and the softener, the amount of water used was reduced by about 1 m ³ and chlorinated as compared with the comparative example 1 which was treated only by the softener. The use of sodium was reduced by 11.5 (=13.8-2.3) kg, and the use of fuel A diesel was also reduced by 2.5%. Further, in Example 1, the amount of water used was reduced by 132 (= (0.501 - 0.446) × 24 × 10) m ³ compared with Comparative Example 2 which was treated by the softener and the reverse osmosis membrane device, and sodium chloride was used. The usage was reduced by 13.8 (=16.1-2.3) kg. The amount of fuel used is the same.

[Example 2 to Example 7]

The wild wood water is passed through a liquid-liquid double-layer capacitor desalination device and operated at a water recovery rate of 90% (the average removal rate of dissolved salts at this time is 80%), the treated water of the liquid-through type electric double-layer capacitor desalination device was passed through a softener to pass water, and Ca ions and Mg ions in the water were replaced with Na ions, and then supplied to a water supply tank having a capacity of 10 L. Further, in the water supply tank, the recovered water of the steam condensate to the water supply tank is simulated, and the elution of iron in the recovery line is assumed in pure water heated to 90 ° C, and chlorine is added in such a manner that the iron concentration is 2 mg/L. The water obtained by the iron is supplied at 4 L/h. In the water supply from the water supply tank, 10 mg/L of succinic acid as a corrosion inhibitor of water treatment chemicals was added, and the water-soluble polymer shown in Table 1 was added at the added concentration shown in Table 1, And adding 13 mg/L of NaOH as an alkali agent, the P alkalinity of the NaOH boiler water is 1.7 times the concentration of cerium oxide, and is supplied to a stainless steel test boiler having a capacity of 5 L, at a pressure of 0.7 MPa, and evaporated. The amount is 8 L/h and the blowing rate is 5%.

After one continuous operation, the heat transfer tube (stainless steel, surface area: 200 cm ² × 3) was taken out, and it was confirmed that a large amount of reddish brown rust adhered. Therefore, the amount of adhesion was measured after removal. The results are shown in Table 1.

[Example 8 to Example 19]

In Example 2, the softener was removed, and the water-soluble polymer shown in Table 1 as a water-soluble polymer was added at the added concentration shown in Table 1, except that it was operated under the same conditions, and was similarly continuous. The amount of adhesion of the heat transfer tubes after one week of operation was measured. The results are shown in Table 1.

In Examples 1 to 17, the calcium concentration in the treated water of the liquid-through type electric double-layer capacitor desalination device is 6 mg-CaCO ₃ /L, and the treated water of the through-type electric double-layer capacitor desalination device is further softened. After the treatment, in the example 2 to the example 7 of the boiler water supply together with the simulated water of the condensed water recovered, the calcium concentration of the boiler water supply is less than 0.1 mg-CaCO ₃ /L. Further, in the case of the boiler water supply, the treated water of the liquid-through type electric double-layer capacitor desalination apparatus is treated without using the softener and the simulated water of the condensed water recovered as the boiler water supply. The calcium concentration is 3 mg-CaCO ₃ /L.

The polymer addition concentrations of the calcium concentrations of Examples 2 to 19 relative to the boiler water supply are shown in Table 1.

According to the results of Examples 2 to 19 of Table 1, it is understood that when the vapor condensed water is recovered and reused, the softener is not used, and only a predetermined amount of molecules are added by the through-liquid type electric double layer capacitor desalination device. A water-soluble polymer of a carboxyl group, thereby preventing rust defects and continuing stable operation.

The present invention has been described in detail with reference to the specific embodiments of the invention.

In addition, the present application is based on a Japanese patent application (Japanese Patent Application No. 2011-201947) filed on Sep.

1‧‧‧ Collector on the cathode side

2, 4‧‧‧active carbon layer

3‧‧‧ Collector on the anode side

11, 21‧‧‧ desalination device

12‧‧‧Softener

13, 22‧‧‧ water supply tank

14, 23‧‧ ‧ boiler

Fig. 1 is a schematic view showing the principle of a softener, and shows a case where a voltage (desalting) is applied.

Fig. 2 is a schematic view showing the principle of a softener, and shows a short circuit (discharge).

3 is a system diagram showing an example of an embodiment of a water treatment method according to a first aspect of the present invention.

Fig. 4 is a system diagram showing an example of an embodiment of a water treatment method according to a second aspect of the present invention.

1‧‧‧ Collector on the cathode side

2, 4‧‧‧active carbon layer

3‧‧‧ Collector on the anode side

Claims (6)

A water treatment method for treating water obtained by passing a raw water through a liquid-through type electric double layer capacitor desalination apparatus without using a softener in a steam generation apparatus that recovers and reuses steam condensed water as a water supply The recovered water of the steam condensed water is supplied to the steam generator as the water supply, and the water-soluble polymer having a carboxyl group in the molecule is added in an amount of 1 to 5 times by weight with respect to the amount of calcium in the water supply. It is characterized in that the removal rate of dissolved salts of the liquid-pass type electric double layer capacitor desalination device is adjusted so that the concentration of calcium supplied to the steam generator is 0.1 mg-CaCO ₃ /L 10 mg-CaCO ₃ / The way L makes calcium residue. The water treatment method according to claim 1, wherein the water-soluble polymer having a carboxyl group is at least one selected from the group consisting of acrylic acid and/or a salt thereof, maleic acid and/or a homopolymer, a copolymer, or a trimer of a carboxylic acid and/or a salt thereof, or a salt thereof, itaconic acid and/or a salt thereof, methacrylic acid and/or a salt thereof; 2-hydroxy-3-ene a copolymer of propoxypropanesulfonic acid and/or a salt thereof and the above carboxylic acid and/or a salt thereof; 2-propenylamine-2-methylpropanesulfonic acid and/or a salt thereof and the above carboxylic acid and/or a copolymer of a salt; bis(poly-2-carboxyethyl)phosphonic acid and/or a salt thereof; carboxymethylcellulose. The water treatment method according to claim 1, wherein the water-soluble polymer having a carboxyl group is a homopolymer of sodium acrylate. The water treatment method according to claim 1, wherein the water-soluble polymer having a carboxyl group is polyacrylic acid sodium 2-hydroxy-3-allyloxypropane sulfonate or polyacrylic acid-2-acrylamide -2-methylpropanesulfonic acid Sodium, poly(poly-2-carboxyethyl)phosphonate, carboxymethylcellulose. The water treatment method according to claim 1, wherein the raw water is well water, tap water, or river water. The water treatment method according to claim 1, wherein the removal rate of dissolved salts of the liquid-through type electric double layer capacitor desalination device is 70% to 90%.