JPWO2014199523A1 - Water treatment method for steam generating equipment - Google Patents

Abstract

For water supply containing hardness components, the adhesion of scale components is sufficiently suppressed, sludge is efficiently discharged, and deterioration of sulfite in aqueous solution is suppressed, enabling highly efficient and stable steam. Provided is a water treatment method for a steam generation facility that enables the operation of the generation facility. In the steam generation facility using the feed water containing 1 to 50 mg of CaCO 3 / L hardness component, (a) the scale inhibitor containing the following (a-1) and (a-2), and the following (b 1) and (b-2) or (b-3). (B) A water treatment method for a steam generating facility, wherein an oxygen scavenger is added. (A-1) acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer and / or salt thereof (a-2) phosphonic acid and / or salt thereof (b-1) sulfurous acid and / or salt thereof ( b-2) Erythorbic acid and / or salt thereof (b-3) Ascorbic acid and / or salt thereof

Description

  The present invention relates to a water treatment method for steam generating equipment.

Steam generating equipment such as a boiler is a device that generates steam by supplying high-temperature and high-pressure water. When the boiler feed water contains a hardness component such as calcium or magnesium, the hardness component adheres to the heat transfer surface in the boiler can as a scale.
The adhered scale acts as an anticorrosion film in the boiler can, and corrosivity is rarely a problem. However, the adhesion of the scale reduces the boiler's thermal efficiency, resulting in low-efficiency operation, and the scale-adhered part is locally overheated, reducing the mechanical strength of the steel material, leading to accidents such as bulging and rupture. Sometimes.

The techniques of Patent Documents 1 and 2 have been proposed for preventing the scale of the hardness component.
Patent Document 1 discloses a scale prevention method using an acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer (hereinafter sometimes referred to as “AA / AMPS”), and Patent Document 2 describes AA / AMPS. A scale inhibitor containing at least one selected from the group consisting of carboxyphosphonate, hydroxyethylidene disulfonate zinc ion (HEDP-Zn salt) aminotri (methylene sulfonate), hexametaphosphonate salt, polyacrylic acid and the like is disclosed. Yes.

  However, Patent Document 1 is a test of an open condition at a low temperature of 65.6 ° C., Patent Document 2 is a batch test (a test of a closed condition) of pH 7 to 9 and 0 to 80 ° C., and hardness in a high-temperature and high-pressure boiler water system. There are no considerations regarding component discharge and scale prevention effects. For example, under high-temperature and high-pressure conditions assuming the inside of a boiler can, AA / AMPS alone or AA / AMPS + polyacrylic acid cannot sufficiently suppress scale adhesion, and the hardness component discharge effect is insufficient. Moreover, when AA / AMPS + HEDP-Zn salt is applied to a boiler water system, it cannot be applied because zinc (Zn) is scaled in the can.

  In general, polyacrylate has been used as a scale inhibitor specialized for boilers. However, when the water supply contains a hardness component, if the amount of polyacrylate added is small, the scale to the heat transfer surface cannot be sufficiently suppressed, and further, the effect of discharging the hardness component is reduced, and the blow piping is Obstacles such as clogging with sludge of hardness component occur. On the other hand, when the amount of polyacrylate added is increased, the cost for scale prevention increases. For this reason, there is a problem that the amount of polyacrylate that can completely prevent scale is not actually added and the boiler is not operated efficiently.

On the other hand, since the scale acts as an anticorrosion film, it is necessary to prevent corrosion in the boiler can when the scale can be prevented from adhering. For this reason, an oxygen scavenger is added to prevent corrosion in the boiler can.
Conventionally, hydrazine has been used as an oxygen scavenger. However, since hydrazine is a substance having a strong mutagenicity, sulfites and the like have recently been used. The advantages of sulfite are high safety, low price, high reactivity with oxygen at low temperatures, and quick deoxygenation. In addition to sulfites, saccharides, tannic acid, etc. have been developed, but saccharides, tannic acid, etc. are less reactive at low temperatures than sulfite, and chelate corrosion may occur near the injection point, and the price is also low. More expensive than sulfurous acid. For this reason, sulfites are widely used as oxygen scavengers instead of hydrazine.

However, since sulfite has a high reactivity with oxygen as a disadvantage of sulfite, it reacts with oxygen in the air when dissolved in a chemical tank during use and exists as an aqueous solution, reducing the concentration of sulfite in the aqueous solution. There is a problem that the deoxygenation effect decreases with time.
In addition, sulfite reacts with oxygen to generate sulfate ions that are corrosive anions. Therefore, when sulfite is injected excessively assuming deterioration of sulfite, sulfate ions in the boiler have a high concentration and may cause severe corrosion.

As techniques for improving the drawbacks of sulfites, the techniques of Patent Documents 3 and 4 have been proposed.
Patent Document 3 proposes an aqueous oxygen scavenger composition that uses sulfite in combination with an aromatic compound having three or more hydroxyl groups. However, the thing of patent document 3 has a problem that a use range is limited because blow water colors with the aromatic compound used together with a sulfite.
In patent document 4, the stabilizer which uses a sulfite and a chelating agent, sorbic acid, or its salt together is proposed. However, if the amount of the chelating agent is insufficient, there is a risk that the corrosiveness further increases in the presence of oxygen. Sorbic acid is poor in workability due to its low solubility, and sorbate is a potassium salt. In the case of having a superheater or a steam turbine, there is a problem that the risk of alkali corrosion due to a small amount of carry-over increases, and in the case of sodium salt, there is a problem that the hygroscopicity is high and the storage stability in powder is poor.

JP 50-86489 A Japanese Patent Laid-Open No. 61-125497 Japanese Patent Publication No. 63-59755 JP-A-9-308824

  The present invention has been made under such circumstances, and sufficiently suppresses the adhesion of scale components to feed water containing hardness components, efficiently discharges sludge, and in an aqueous solution of sulfite. An object of the present invention is to provide a water treatment method for a steam generating facility that can stably and efficiently operate the steam generating facility by suppressing deterioration of the water.

In order to solve the above problems, the present invention provides the following [1] to [4].
[1] In a steam generation facility using water supply containing 1 to 50 mg of CaCO ₃ / L hardness component, (a) a scale inhibitor containing the following (a-1) and (a-2) for the water supply: A water treatment method for a steam generating facility, wherein (b) an oxygen scavenger comprising the following (b-1) and (b-2) or (b-3) is added.
(A-1) Acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer and / or salt thereof (a-2) Phosphonic acid and / or salt thereof (b-1) Sulfurous acid and / or salt thereof b-2) Erythorbic acid and / or salt thereof (b-3) Ascorbic acid and / or salt thereof [2] In the above [1], the phosphonic acid is 1-hydroxyethane-1,1-diphosphonic acid The water treatment method of the steam generation facility as described.
[3] The molar ratio of the acrylic acid of the acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer to the monomer of 2-acrylamido-2-methylpropanesulfonic acid is 90:10 to 50:50. The water treatment method for a steam generating facility according to the above [1] or [2].
[4] The steam generating facility according to any one of [1] to [3], wherein the scale inhibitor is added 0.1 to 1.0 times on a mass basis with respect to all hardness components of the water supply. Water treatment method.

  According to the water treatment method for a steam generation facility of the present invention, the feed of water containing hardness components sufficiently suppresses the adhesion of scale components, efficiently discharges sludge, and in a sulfite aqueous solution. By suppressing the deterioration, the steam generating facility can be operated with high efficiency and stability.

It is a figure which shows one Embodiment of the steam generation equipment for implementing this invention.

The water treatment method for a steam generating facility according to the present invention includes the following (a-1) and (a-2) for the feed water in the steam generating facility using feed water containing 1 to 50 mg CaCO ₃ / L of a hardness component. Including (a) a scale inhibitor, and (b-1) below, and (b-2) or (b-3) including (b) a step of adding an oxygen scavenger. .
(A-1) Acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer and / or salt thereof (a-2) Phosphonic acid and / or salt thereof (b-1) Sulfurous acid and / or salt thereof b-2) Erythorbic acid and / or salt thereof (b-3) Ascorbic acid and / or salt thereof

The object of the water treatment method of the present invention is steam generation equipment such as a boiler. Moreover, the water treatment method for steam generating equipment according to the present invention is intended for steam generating equipment using water supply containing a hardness component of 1 to 50 mg CaCO ₃ / L. In addition, since the scale prevention effect tends to be insufficient if the concentration of the hardness component is too high, the hardness component of the water supply is preferably 1 to ₃₀ mg CaCO ₃ / L.
The concentration of the hardness components in the present invention (unit: mgCaCO ₃ / L) is for magnesium, the hardness components such as calcium and terms of calcium carbonate.

  The steam generation facility preferably has an operating pressure of 4.0 MPa or less. By setting the operating pressure to 4.0 MPa or less, the decomposition of sulfite can be suppressed and the thermal stability of the scale inhibitor can be easily improved.

FIG. 1 is a diagram showing an embodiment of a steam generation facility for carrying out the present invention.
FIG. 1 shows a condensate tank 1, a condensate line 11, a makeup water tank 2, a makeup water line 21, a water supply tank 3, a water supply line 31, a chemical injection tank 4, a chemical injection pipe 41, and a steam generator (boiler can) 5. 1 shows a circulation type steam generation facility 6 having a steam supply line 51 and a drain recovery line 52. Although not shown, it is preferable that a device for measuring the total hardness component concentration of the water supply system is connected to the water supply tank 3 or the water supply line 31.

[Scale inhibitor]
A scale inhibitor contains the following (a-1) and (a-2).
(A-1) Acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer and / or salt thereof (a-2) Phosphonic acid and / or salt thereof

<(A-1) Acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer and / or salt thereof>
The acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer (AA / AMPS) is a copolymer having acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid as monomer units.
The weight average molecular weight of AA / AMPS is preferably 2,000 to 80,000, and more preferably 3,000 to 70,000. By setting the weight average molecular weight to 2,000 or more and 80,000 or less, a higher scale prevention effect can be obtained.

  The molar ratio of acrylic acid to 2-acrylamido-2-methylpropanesulfonic acid monomer in AA / AMPS is preferably 99: 1 to 5:95, and 90:10 to 50:50. It is more preferable. By setting the molar ratio of AA and AMPS within the above range, a higher scale prevention effect can be obtained.

The salt of AA / AMPS contains acrylate and / or 2-acrylamido-2-methylpropanesulfonate in at least a part of the structural unit of AA / AMPS. That is, in the present invention, the salt of AA / AMPS includes not only a completely neutralized product of AA / AMPS but also a partially neutralized product of AA / AMPS.
Examples of the AA / AMPS salt include alkali metal salts such as the above-mentioned AA / AMPS sodium salts and potassium salts, alkaline earth metal salts such as magnesium salts and calcium salts, ammonium salts, and amine salts. Among these AA / AMPS salts, a sodium salt is preferable from the viewpoint of economy.
The AA / AMPS salt is preferably such that the base AA / AMPS satisfies the above weight average molecular weight.

AA / AMPS salt can be obtained, for example, by neutralizing AA / AMPS. Moreover, the acrylic acid and / or 2-acrylamido-2-methylpropane sulfonic acid which are raw material monomers are neutralized, and these are used as acrylate and / or 2-acrylamido-2-methylpropane sulfonate. AA / AMPS salt may be copolymerized.
As a neutralizing agent for AA / AMPS or a raw material monomer thereof, magnesium hydroxide in addition to alkali metal neutralizing agents such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, potassium phosphate, etc. , Calcium carbonate, ammonia, ammonium carbonate, morpholine, diethylethanolamine and the like. These neutralizing agents can also be used as neutralizing agents for phosphonic acid, sulfurous acid, erythorbic acid and ascorbic acid described later.

<(A-2) Phosphonic acid and / or salt thereof>
Examples of the phosphonic acid include 1-hydroxyethane-1,1-diphosphonic acid (hereinafter sometimes referred to as “HEDP”), 2-phosphonobutane-1,2,4-tricarboxylic acid (hereinafter referred to as “PBTC”). In some cases), aminotrimethylenephosphonic acid, hydroxyphosphonoacetic acid and the like. Among these phosphonic acids, they are described in US FDA standard boiler additives, and HEDP is preferable from the viewpoint of safety.

Examples of the phosphonic acid salt include alkali metal salts such as sodium salt and potassium salt of phosphonic acid, alkaline earth metal salts such as magnesium salt and calcium salt, ammonium salt and amine salt. Among these phosphonic acid salts, sodium salts are preferred from the viewpoint of economy.
The salt of phosphonic acid can be obtained by neutralizing the phosphonic acid exemplified above.

  The mass ratio of the above (a-1) and (a-2) is preferably 1: 1 to 10: 1, and more preferably 2: 1 to 8: 1. By making (a-1) 1 or less with respect to 1 (a-1), scale adhesion can be sufficiently suppressed, and (a-1) with respect to 10 and (a-2) being 1 or more. By doing so, the hardness component can be effectively discharged.

  The scale inhibitor may contain components other than the above (a-1) and (a-2) as long as the effects of the present invention are not impaired. However, the total amount of (a-1) and (a-2) is preferably 90% by mass or more, more preferably 95% by mass or more, and more preferably 100% by mass with respect to the total solid content of the scale inhibitor. More preferably.

<Addition amount and location>
The scale inhibitor is preferably added in an amount of 0.1 to 1.0 times, and preferably 0.2 to 0.8 times, based on mass with respect to the total hardness component (CaCO ₃ conversion) of the water supply. Further, it is more preferable to add 0.3 to 0.6 times. For example, when the concentration of all hardness components of the feed water is 20 mg CaCO ₃ / L, it is preferable to add the scale inhibitor so that the effective component concentration thereof is 2 to 20 mg / L.
By adding the scale inhibitor 0.1 times or more with respect to the total hardness component, the scale prevention effect can be sufficiently obtained. By adding 1.0 times or less, the cost is reduced, and AA / AMPS Can be prevented from gelling.

  In FIG. 1, the scale inhibitor is added to the water supply tank 3, but the addition location of the scale inhibitor may be another location. Specifically, the scale inhibitor is preferably added at any location selected from a makeup water tank, a makeup water line, a feed water tank, a feed water line, a condensate tank, and a condensate line. It is more preferable to add at any one of the locations.

<Dosage form of scale inhibitor>
The scale inhibitor is preferably in the form of an aqueous solution, but may be a powder or a pellet-like solid. In the case of a solid, it is preferable to use it in the form of an aqueous solution by dissolving it in a dissolution tank (chemical injection tank) immediately before use.
In addition, AA / AMPS and / or a salt thereof and phosphonic acid and / or a salt thereof may be independent dosage forms, or may be a dosage form obtained by mixing both. In the case of a single dosage form, the storage space is small, which is preferable in that the labor of mixing can be saved.

[Oxygen scavenger]
The oxygen scavenger used in the present invention contains the following (b-1) and (b-2) or (b-3).
(B-1) Sulfurous acid and / or salt thereof (b-2) Erythorbic acid and / or salt thereof (b-3) Ascorbic acid and / or salt thereof

  The sulfurous acid and / or salt thereof of (b-1) is excellent in the initial deoxygenation capacity, but has a tendency to decrease the deoxygenation capacity over time because the reactivity with oxygen is too high. In the present invention, the combined use of (b-1) sulfite and / or a salt thereof and (b-2) or (b-3) suppresses the rate of decrease of sulfite or a salt thereof over time. The stage and subsequent deoxygenation capacity can be made good, and thus the corrosion resistance can be made good.

  Sulfurous acid salts, erythorbic acid salts, ascorbic acid salts include alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as magnesium salts and calcium salts, ammonium salts and amine salts. Can be mentioned. Among these salts, a potassium salt or a sodium salt is preferable from the viewpoints of economy and stability during preparation. Sulfurous acid salts, erythorbic acid salts, and ascorbic acid salts can be obtained by neutralizing sulfurous acid, erythorbic acid, and ascorbic acid.

  Content ratio of (b-2) and / or (b-3) in the above (b-1) to (b-3) [(b-2) + (b-3) / (b-1) + ( b-2) + (b-3)] × 100 is preferably 0.02 to 20% and more preferably 0.1 to 10% on a mass basis. When (b-1), (b-2), and (b-3) are salts, it is preferable that the base acid satisfies the above ratio. By making the content ratio of (b-2) and / or (b-3) 0.02% or more, it is possible to effectively prevent a decrease in the concentration of sulfurous acid, and by making it 20% or less, good stability of the aqueous solution Sex is obtained.

  The oxygen scavenger may contain components other than the above (b-1), (b-2) and (b-3) as long as the effects of the present invention are not impaired. However, the total amount of (b-1), (b-2) and (b-3) is preferably 90% by mass or more, more preferably 95% by mass or more, based on the total solid content of the oxygen scavenger. Preferably, it is more preferably 100% by mass.

<Addition amount and location>
From the viewpoint of deoxygenation and solubility, the diluted concentration of sulfurous acid in the dissolution (drug injection) tank is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass. In the case of a sulfurous acid salt, it is preferable that the sulfurous acid as the base satisfies the above-mentioned concentration.
In addition, sulfurous acid or a salt thereof is preferably added in an amount equal to or greater than the dissolved oxygen concentration of the feed water, and more preferably equal to or greater than 2 equivalents.

Although the addition location of the oxygen scavenger is not limited, it is preferable to add the oxygen scavenger to a water supply line without re-dissolution of dissolved oxygen from the viewpoint of preventing corrosion in the boiler can.
In addition, in order to add an oxygen scavenger more than the equivalent of the dissolved oxygen concentration in feed water, it is preferable that a device for measuring the dissolved oxygen concentration of the feed water is connected to the feed water line.

<Form of oxygen scavenger>
The oxygen scavenger is preferably in the form of an aqueous solution, but may be a powder or a pellet-like solid. In the case of a solid, it is preferable to use it in the form of an aqueous solution by dissolving it in a dissolution tank (chemical injection tank) immediately before use.
In addition, (b-1), (b-2) and (b-3) may each be an independent dosage form, or may be a mixed dosage form. In the case of a single dosage form, the storage space is small, which is preferable in that the labor of mixing can be saved. In addition, it is preferable to use the aqueous solution which diluted the sulfurous acid within 7 days.
Moreover, when the scale inhibitor and the oxygen scavenger are mixed at a high concentration, the stability of quality may be insufficient. Therefore, it is preferable not to use both as one agent.

<Ratio of scale inhibitor (a) and oxygen scavenger (b)>
In the present invention, the mass ratio of [scale inhibitor (a) / oxygen scavenger (b)] is preferably 0.02 to 500.

<Optional components>
In the present invention, as long as the purpose of the present invention is not impaired, various additive components, for example, a canning agent and a condensate treatment agent are added at any point in the system of the steam generation facility as necessary. An effective amount can be added. These additive components can be used alone or in combination of two or more.

Moreover, in this invention, it is preferable to make pH of a steam generation part into 9.0-12.0 from a viewpoint of corrosion prevention. The pH of the steam generating part can be adjusted by adding an alkali agent and increasing / decreasing the amount of blow and / or the amount of water supply. From the viewpoint of ease of pH adjustment, means for adding an alkaline agent is preferable.
Examples of the alkali agent include alkali metal hydroxides, alkali metal carbonates, alkali metal phosphates, and neutralizing amines.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. In the examples, “HEDP” is 1-hydroxyethane-1,1-diphosphonic acid, “PBTC” is 2-phosphonobutane-1,2,4-tricarboxylic acid, “PAA” is polyacrylic acid, “AA / “AMPS” indicates a copolymer having acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid as monomer units.

[Examples 1-8, Comparative Examples 1-4]
The following tests were conducted by adding the scale inhibitors and oxygen scavengers of Examples 1 to 8 and Comparative Examples 1 to 4 having the compositions shown in Table 2 to the concentrations shown in Table 2 in the feed water. The results are shown in Table 2.
(Test equipment)
Using a stainless steel electric test boiler simulating the water circulation of an actual water tube boiler, the amount of scale adhered to the heat transfer surface and the rate of discharge of hardness components were evaluated.
The test boiler operating conditions were a pressure of 2.0 MPa, an evaporation amount of 8 L / h, and a concentration factor of 10 times. For water supply, synthetic water adjusted to the conditions in Table 1 using sodium bicarbonate, silicic acid No. 3, sodium chloride, hydrochloric acid, sodium sulfate, calcium chloride, magnesium sulfate (reagent, manufactured by Kishida Chemical) is used. It was. In addition, the test was performed while the supply water temperature was kept at 30 ° C. with a heater and air was aerated in the supply water tank so that the dissolved oxygen concentration was saturated (7.5 mg O ₂ / L). The test period was 18 hours after the start of heating. In addition, the scale inhibitor and the oxygen scavenger were injected into the water supply line of the test boiler using a plunger pump so as to have the addition concentrations shown in Table 2 in conjunction with the water supply pump.

(Scale adhesion)
The amount of scale attached was evaluated by the amount of scale attached to the test tube. Specifically, in order to reproduce the heat transfer surface of the boiler, a test tube made of stainless steel (heat transfer surface area φ37 mm × 250 mm) in which an electric heater was inserted was used. The test tube was taken out after the test was completed, dried, scraped with a stainless steel metal piece, and the weight was measured.

(Hardness component discharge rate)
The boiler water discharged from the continuous blow of the test boiler is collected one hour before the end of the test, hydrochloric acid is added to the collected boiler water, and the hardness component is dissolved by boiling. After dissolving the hardness component, the calcium concentration and magnesium concentration in the boiler water are measured by atomic absorption analysis, and the concentration in terms of calcium carbonate is calculated. Furthermore, the theoretical concentration was calculated from the total hardness component in feed water and the concentration factor, and the hardness component discharge rate was determined by the formula [calcium carbonate equivalent concentration / theoretical concentration] × 100.

(Corrosion test)
A sensitized cold rolled steel plate (SPCC) test piece (1 mm × 15 mm × 50 mm) was installed in the vicinity of the water supply point in the test boiler, and the number of pitting corrosion generated on the test piece was visually evaluated. Sensitization of the test piece was performed by immersing the degreased test piece in nitric acid, thoroughly washing with water, and quickly drying.

In Examples 1-8, the heat transfer surface adhesion amount of a scale is small, the hardness component discharge rate is also high, and a synergistic effect by using AA / AMPS and phosphonic acid in combination can be confirmed. Moreover, the thing of Examples 1-8 did not generate | occur | produce pitting corrosion.
On the other hand, in the comparative example, the heat transfer surface adhesion amount of the scale was large, and the hardness component discharge rate was also smaller than in the example.

[Examples 9 to 16, Comparative Examples 5 to 6]
(Sulfurous acid residual rate)
The oxygen scavengers A to E having the composition shown in Table 3 were diluted with pure water to 10 mass%, 5 mass%, and 2 mass%. The diluted solution was stored for 7 days at room temperature in a container simulating a 1 L polypropylene dissolution tank with a 5 mm diameter hole in the lid. After storage for 7 days, the concentration of sulfite in the diluted solution was measured, and the residual ratio relative to the initial concentration of sulfite was calculated. The results are shown in Table 3.

  From Table 3, it can be confirmed that when sodium erythorbate or sodium ascorbate is used in addition to sodium sulfite, the residual ratio of sulfite can be improved.

The scale inhibitor and oxygen scavenger shown in Table 4 were added so as to have the concentrations shown in Table 4 in the feed water, and the amount of scale adhesion and the corrosivity were evaluated. The test boiler, boiler operating conditions, and water supply were the same as in Example 4, and the operating time was 72 hours after the start of heating. The results are shown in Table 4.
The types of oxygen scavengers “A to E” in Table 4 refer to the oxygen scavengers A to E in Table 3. For example, in Example 9, a 10% diluted solution of oxygen scavenger A in Table 3 is added so that the sulfurous acid concentration is 45 mg / L in the feed water.

  As apparent from Table 4, in Examples 9 to 16, no pitting corrosion was observed on the test pieces. From this result, it can be confirmed that by adding erythorbic acid (salt) or ascorbic acid (salt) in addition to sulfurous acid (salt), deterioration of sulfite is prevented and corrosion of the boiler is prevented.

DESCRIPTION OF SYMBOLS 1: Condensate tank 11: Condensate line 2: Supply water tank 21: Supply water line 3: Supply water tank 31: Supply water line 4: Chemical injection tank 41: Chemical injection piping 5: Steam generation part (boiler can) 51: Steam Supply line 52: Drain recovery line 6: Steam generation equipment

Claims (4)

In the steam generation facility using the feed water containing 1 to 50 mg of CaCO ₃ / L hardness component, (a) a scale inhibitor containing the following (a-1) and (a-2), and the following ( (b-1) A water treatment method for a steam generating facility, wherein (b) an oxygen scavenger comprising (b-2) or (b-3) is added.
(A-1) Acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer and / or salt thereof (a-2) Phosphonic acid and / or salt thereof (b-1) Sulfurous acid and / or salt thereof b-2) Erythorbic acid and / or salt thereof (b-3) Ascorbic acid and / or salt thereof   The water treatment method for steam generating equipment according to claim 1, wherein the phosphonic acid is 1-hydroxyethane-1,1-diphosphonic acid.   The molar ratio of the acrylic acid of the acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer and the monomer of 2-acrylamido-2-methylpropanesulfonic acid is 90:10 to 50:50. The water treatment method of the steam generation facility according to claim 1 or 2.   The water treatment method for a steam generating facility according to any one of claims 1 to 3, wherein the scale inhibitor is added in an amount of 0.1 to 1.0 times on a mass basis with respect to all hardness components of the water supply.

Images