WO2014199523A1 - 蒸気発生設備の水処理方法 - Google Patents
蒸気発生設備の水処理方法 Download PDFInfo
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- WO2014199523A1 WO2014199523A1 PCT/JP2013/066521 JP2013066521W WO2014199523A1 WO 2014199523 A1 WO2014199523 A1 WO 2014199523A1 JP 2013066521 W JP2013066521 W JP 2013066521W WO 2014199523 A1 WO2014199523 A1 WO 2014199523A1
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- acid
- salt
- steam generating
- treatment method
- water treatment
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B37/00—Component parts or details of steam boilers
- F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
- F22B37/48—Devices for removing water, salt, or sludge from boilers; Arrangements of cleaning apparatus in boilers; Combinations thereof with boilers
- F22B37/52—Washing-out devices
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
- C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
- C02F5/10—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances
- C02F5/12—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances containing nitrogen
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
- C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
- C02F5/10—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances
- C02F5/14—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances containing phosphorus
Definitions
- 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.
- 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.
- 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.
- 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. Yes.
- Patent Document 1 is an open condition test at a low temperature of 65.6 ° C.
- Patent Document 2 is a batch test (closed condition test) at pH 7 to 9 and 0 to 80 ° C., and the hardness in a high-temperature and high-pressure boiler water system.
- component discharge and scale prevention effects 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.
- an AA / AMPS + HEDP-Zn salt is applied to a boiler water system, it cannot be applied because zinc (Zn) is scaled in the can.
- polyacrylate As a scale inhibitor specialized for boilers, polyacrylate is generally used. 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.
- sulfites are widely used as oxygen scavengers instead of hydrazine.
- sulfite 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.
- 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.
- Patent Document 3 proposes an aqueous oxygen scavenger composition that uses sulfite in combination with an aromatic compound having three or more hydroxyl groups.
- Patent Document 4 proposes an aqueous oxygen scavenger composition that uses sulfite in combination with an aromatic compound having three or more hydroxyl groups.
- 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.
- patent document 4 the stabilizer which uses a sulfite and a chelating agent, sorbic acid, or its salt together is proposed.
- 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.
- sorbate is a potassium salt.
- 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.
- 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.
- the present invention provides the following [1] to [4].
- [1] In a steam generation facility using feed water containing 1 to 50 mg CaCO 3 / L of a hardness component, (a) a scale inhibitor containing the following (a-1) and (a-2) for the feed water; A water treatment method for a steam generating facility, wherein (b) an oxygen scavenger comprising (b-1) below 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
- 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 to the monomer of 2-acrylamido-2-methylpropanesulfonic acid is 90:10 to 50:50.
- the feed of water containing hardness components sufficiently suppresses the adhesion of scale components, efficiently discharges sludge, and in a sulfite aqueous solution.
- the steam generating facility can be operated with high efficiency and stability.
- the water treatment method for a steam generating facility 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 hardness component. Including (a) a step of adding a scale inhibitor, (b-1), and (b-2) or (b-3) below (b) an oxygen scavenger. .
- the object of the water treatment method of the present invention is steam generation equipment such as a boiler.
- the water treatment method for a steam generating facility according to the present invention is intended for a steam generating facility using feed water containing a hardness component of 1 to 50 mg CaCO 3 / L. If the concentration of the hardness component is too high, the scale prevention effect tends to be insufficient, so the hardness component of the feed water 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.
- the operating pressure 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.
- 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.
- the 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
- 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.
- 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.
- 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. Further, acrylic acid and / or 2-acrylamido-2-methylpropanesulfonic acid, which are raw material monomers, are neutralized and used as acrylic acid salt and / or 2-acrylamido-2-methylpropanesulfonic acid salt. AA / AMPS salt may be copolymerized.
- 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.
- neutralizing agents can also be used as neutralizing agents for phosphonic acid, sulfurous acid, erythorbic acid and ascorbic acid described later.
- the phosphonic acid examples 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.
- 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 examples include sodium 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.
- (a-1) is 1 and (a-2) is 1 or less, scale adhesion can be sufficiently suppressed, and (a-1) is 10 and (a-2) is 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.
- 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.
- the scale inhibitor is preferably added in an amount of 0.1 to 1.0 times, preferably 0.2 to 0.8 times, based on the mass, with respect to the total hardness component of the feed water (calculated as CaCO 3 ). 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 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.
- the scale inhibitor is added to the water supply tank 3, but the added portion of the scale inhibitor may be another location.
- 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.
- 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.
- 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.
- 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
- (B-1) Sulfurous acid and / or its salt is excellent in the initial deoxygenation capacity, but its reactivity with oxygen is too high, so that the deoxygenation capacity tends to decrease over time.
- the combined use of (b-1) sulfite and / or a salt thereof and (b-2) or (b-3) suppresses the rate of decrease in 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.
- the 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%, more preferably 0.1 to 10%, based on mass.
- (b-1), (b-2), and (b-3) are salts, it is preferable that the base acid satisfies the above ratio.
- 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.
- 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.
- the diluted concentration of sulfurous acid in the dissolution (drug injection) tank is preferably 1 to 30% by mass, more preferably 5 to 20% by mass from the viewpoint of deoxygenation and solubility.
- a sulfurous acid salt it is preferable that the sulfurous acid as the base satisfies the above-mentioned concentration.
- sulfurous acid or a salt thereof is preferably added in an amount equal to or more than the equivalent to the dissolved oxygen concentration of the feed water, and more preferably added in an amount of equal to or more than 2 times or less.
- 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.
- a device for measuring the dissolved oxygen concentration of the feed water is connected to the feed water line.
- 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.
- (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.
- the stability of quality may be insufficient. Therefore, it is preferable not to use both as one agent.
- the mass ratio of [scale inhibitor (a) / oxygen absorber (b)] is preferably 0.02 to 500.
- 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.
- additive components can be used alone or in combination of two or more.
- the pH of the steam generating part is preferably 9.0 to 12.0 from the viewpoint of preventing corrosion.
- 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.
- the alkali agent include alkali metal hydroxides, alkali metal carbonates, alkali metal phosphates, and neutralizing amines.
- HEDP 1-hydroxyethane-1,1-diphosphonic acid
- PBTC 2-phosphonobutane-1,2,4-tricarboxylic acid
- PAA polyacrylic acid
- AA / “AMPS” indicates a copolymer having acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid as monomer units.
- Examples 1 to 8, Comparative Examples 1 to 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.
- synthetic water adjusted to the conditions in Table 1 using sodium bicarbonate, silicic acid No.
- 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 ⁇ 37 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.
- 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.
- SPCC cold rolled steel plate
- the adhesion amount of the heat transfer surface of the scale is small, the hardness component discharge rate is high, and a synergistic effect by using AA / AMPS and phosphonic acid together can be confirmed. In addition, in Examples 1 to 8, no pitting corrosion occurred. 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.
- 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 absorbers “A to E” in Table 4 refer to oxygen absorbers A to E in Table 3.
- 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.
- 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
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Abstract
Description
付着したスケールは、ボイラ缶内で防食皮膜として作用し、腐食性が問題となることは少ない。しかし、スケールが付着することでボイラの熱効率が低下して低効率運転となるとともに、スケール付着部分が局部的に過熱され、鋼材の機械的強度が低下し、膨出、破裂等の事故につながることがある。
特許文献1は、アクリル酸/2-アクリルアミド-2-メチルプロパンスルホン酸共重合体(以下、「AA/AMPS」と称する場合もある。)によるスケール防止方法、特許文献2は、AA/AMPSと、カルボキシホスホネート、ヒドロキシエチリデンジスルホン酸亜鉛イオン(HEDP-Zn塩)アミノトリ(メチレンスルホン酸)、ヘキサメタホスホネート塩、ポリアクリル酸等からなる群から選ばれる少なくとも一種とを含むスケール防止剤が開示されている。
従来、脱酸素剤にはヒドラジンが用いられてきたが、ヒドラジンは、強度の変異原性を有する物質であるため、最近は亜硫酸塩等が用いられるようになってきている。亜硫酸塩の利点は安全性が高く、価格も安価であり、低温での酸素との反応性が高く速やかに脱酸素が可能である点が挙げられる。亜硫酸塩以外にも糖類やタンニン酸等が開発されているが、糖類やタンニン酸等は、低温での反応性が亜硫酸に劣り、薬注点近傍でキレート腐食を生じる場合があり、また価格が亜硫酸よりも高価である。このため、ヒドラジンに代わる脱酸素剤としては、亜硫酸塩が広く用いられている。
また、亜硫酸塩は酸素と反応することで腐食性アニオンである硫酸イオンが生成する。したがって、亜硫酸塩の劣化を想定して過剰に亜硫酸を注入した場合には、ボイラ中の硫酸イオンが高濃度となり、激しい腐食を生じることがある。
特許文献3では、亜硫酸塩と、3個以上の水酸基を有する芳香族化合物とを併用する水性脱酸素剤組成物が提案されている。しかし、特許文献3のものは、亜硫酸塩と併用する芳香族化合物によりブロー水が着色するため使用範囲が限定される問題がある。
特許文献4では、亜硫酸塩と、キレート剤、ソルビン酸又はその塩を併用する安定剤が提案されている。しかし、キレート剤は添加量が万一不足となったときに酸素共存下においては腐食性がさらに増すリスクがあり、ソルビン酸は溶解性が低いため作業性が悪く、ソルビン酸塩は、カリウム塩の場合、過熱器や蒸気タービンを有する場合の微量のキャリーオーバによるアルカリ腐食のリスクが高くなる問題があり、ナトリウム塩の場合、吸湿性が高く粉末での保存性が悪い問題がある。
[1]硬度成分を1~50mgCaCO3/L含む給水を用いる蒸気発生設備において、給水に対して、下記の(a-1)と(a-2)とを含む(a)スケール防止剤と、下記の(b-1)と、(b-2)又は(b-3)とを含む(b)脱酸素剤を添加する、蒸気発生設備の水処理方法。
(a-1)アクリル酸/2-アクリルアミド-2-メチルプロパンスルホン酸共重合体及び/又はその塩
(a-2)ホスホン酸及び/又はその塩
(b-1)亜硫酸及び/又はその塩
(b-2)エリソルビン酸及び/又はその塩
(b-3)アスコルビン酸及び/又はその塩
[2]前記ホスホン酸が、1-ヒドロキシエタン-1,1-ジホスホン酸である、上記[1]に記載の蒸気発生設備の水処理方法。
[3]前記アクリル酸/2-アクリルアミド-2-メチルプロパンスルホン酸共重合体のアクリル酸と、2-アクリルアミド-2-メチルプロパンスルホン酸とのモノマーのモル比が、90:10~50:50である、上記[1]又は[2]に記載の蒸気発生設備の水処理方法。
[4]給水の全硬度成分に対して、質量基準で、前記スケール防止剤を0.1~1.0倍添加する、上記[1]~[3]の何れかに記載の蒸気発生設備の水処理方法。
(a-1)アクリル酸/2-アクリルアミド-2-メチルプロパンスルホン酸共重合体及び/又はその塩
(a-2)ホスホン酸及び/又はその塩
(b-1)亜硫酸及び/又はその塩
(b-2)エリソルビン酸及び/又はその塩
(b-3)アスコルビン酸及び/又はその塩
なお、本発明における硬度成分の濃度(単位:mgCaCO3/L)は、マグネシウム、カルシウム等の硬度成分を炭酸カルシウム換算したものである。
図1は、復水タンク1、復水ライン11、補給水タンク2、補給水ライン21、給水タンク3、給水ライン31、薬注タンク4、薬注配管41、蒸気発生部(ボイラ缶)5、蒸気供給ライン51及びドレン回収ライン52を有する、循環式の蒸気発生設備6を示している。なお、図示しないが、給水タンク3又は給水ライン31には、給水系の全硬度成分濃度を測定する機器が接続されていることが好ましい。
スケール防止剤は、下記の(a-1)と(a-2)とを含むものである。
(a-1)アクリル酸/2-アクリルアミド-2-メチルプロパンスルホン酸共重合体及び/又はその塩
(a-2)ホスホン酸及び/又はその塩
アクリル酸/2-アクリルアミド-2-メチルプロパンスルホン酸共重合体(AA/AMPS)は、モノマー単位として、アクリル酸と、2-アクリルアミド-2-メチルプロパンスルホン酸とを有する共重合体である。
AA/AMPSの重量平均分子量は2,000~80,000であることが好ましく、3,000~70,000であることがより好ましい。重量平均分子量を2,000以上80,000以下とすることにより、より高いスケール防止効果を得られる。
AA/AMPSの塩は、上記AA/AMPSのナトリウム塩、カリウム塩等のアルカリ金属塩、マグネシウム塩、カルシウム塩等のアルカリ土類金属塩、アンモニウム塩、アミン塩等が挙げられる。これらAA/AMPSの塩の中でも、経済性の観点からナトリウム塩が好適である。
AA/AMPSの塩は、そのベースとなるAA/AMPSが上記の重量平均分子量を満たすことが好ましい。
AA/AMPS又はその原料モノマーの中和剤としては、水酸化ナトリウム、水酸化カリウム、炭酸ナトリウム、炭酸カリウム、リン酸ナトリウム、リン酸カリウム等のアルカリ金属系の中和剤の他、水酸化マグネシウム、炭酸カルシウム、アンモニア、炭酸アンモニウム、モルフォリン、ジエチルエタノールアミン等が挙げられる。これら中和剤は、後述するホスホン酸、亜硫酸、エリソルビン酸、アスコルビン酸の中和剤としても用いることができる。
ホスホン酸としては、1-ヒドロキシエタン-1,1-ジホスホン酸(以下、「HEDP」と称する場合もある。)、2-ホスホノブタン-1,2,4-トリカルボン酸(以下、「PBTC」と称する場合もある。)、アミノトリメチレンホスホン酸、ヒドロキシホスホノ酢酸等が挙げられる。これらのホスホン酸の中でも、米国FDA規格ボイラ用添加物に記載されており、安全性の観点からHEDPが好適である。
ホスホン酸の塩は、上記例示したホスホン酸を中和することにより得ることができる。
スケール防止剤は、給水の全硬度成分(CaCO3換算)に対して、質量基準で、0.1~1.0倍添加することが好ましく、0.2~0.8倍添加することが好ましく、0.3~0.6倍添加することがさらに好ましい。例えば、給水の全硬度成分の濃度が20mgCaCO3/Lの場合、スケール防止剤はその有効成分濃度が2~20mg/Lとなるように添加することが好ましい。
全硬度成分に対してスケール防止剤を0.1倍以上添加することにより、スケール防止効果を十分に得ることができ、1.0倍以下添加することにより、コストを抑え、また、AA/AMPSがゲル化することを防止できる。
スケール防止剤は、水溶液の剤型が好ましいが、粉末やペレット状の固体でもよい。固体の場合は使用直前に溶解タンク(薬注タンク)にて溶解して水溶液状にして使用するのが好ましい。
また、AA/AMPS及び/又はその塩と、ホスホン酸及び/又はその塩とは、各々独立した剤型でもよく、両者を混合して一剤化した剤型でもよい。一剤化した剤型の場合、保管スペースが小さくて済み、混合する手間を省くことができる点で好適である。
本発明で用いる脱酸素剤は、下記の(b-1)と、(b-2)又は(b-3)とを含有してなるものである。
(b-1)亜硫酸及び/又はその塩
(b-2)エリソルビン酸及び/又はその塩
(b-3)アスコルビン酸及び/又はその塩
溶解(薬注)タンクでの亜硫酸の希釈濃度は、脱酸素及び溶解度の観点から、1~30質量%であることが好ましく、5~20質量%であることがより好ましい。亜硫酸の塩の場合、そのベースとなる亜硫酸が上記の濃度を満たすことが好ましい。
また、亜硫酸又はその塩は、給水の溶存酸素濃度に対して、当量以上の量を添加することが好ましく、当量以上~2倍量以下を添加することがより好ましい。
なお、脱酸素剤を給水中の溶存酸素濃度の当量以上添加するために、給水ラインには、給水の溶存酸素濃度を測定する機器が接続されていることが好ましい。
脱酸素剤は、水溶液の剤型が好ましいが、粉末やペレット状の固体でもよい。固体の場合は使用直前に溶解タンク(薬注タンク)にて溶解して水溶液状にして使用するのが好ましい。
また、(b-1)、(b-2)及び(b-3)は、各々独立した剤型でもよく、混合して一剤化した剤型でもよい。一剤化した剤型の場合、保管スペースが小さくて済み、混合する手間を省くことができる点で好適である。なお、亜硫酸を希釈した水溶液は、7日以内に使用することが好ましい。
また、スケール防止剤と脱酸素剤とを高濃度で混合すると、品質の安定性が不十分となる可能性があることから、両者は一剤としないことが好ましい。
本発明では、[スケール防止剤(a)/脱酸素剤(b)]の質量比が0.02~500であることが好ましい。
本発明においては、本発明の目的が損なわれない範囲で、必要に応じて、蒸気発生設備の系内の何れかの箇所で、各種の添加成分、例えば、清缶剤、復水処理剤を有効量添加することできる。これらの添加成分は一種単独で又は二種以上を組み合わせて用いることができる。
アルカリ剤としては、例えばアルカリ金属水酸化物、アルカリ金属炭酸塩、アルカリ金属リン酸塩、中和性アミン等が挙げられる。
表2の組成からなる実施例1~8及び比較例1~4のスケール防止剤及び脱酸素剤を、給水中で表2の濃度になるように添加して、以下の試験を行った。結果を表2に示す。
(試験装置)
実機水管ボイラの水循環を模擬したステンレス製電気式テストボイラを用いて、伝熱面へのスケール付着量及び硬度成分の排出率の評価を行った。
テストボイラの運転条件は、圧力2.0MPa、蒸発量8L/h、濃縮倍率10倍とした。また、給水には、重炭酸ナトリウム、ケイ酸3号、塩化ナトリウム、塩酸、硫酸ナトリウム、塩化カルシウム、硫酸マグネシウム(試薬、キシダ化学製)を用いて、表1の条件に調整した合成水を用いた。また、給水温度をヒーターで30℃に保ち、溶存酸素濃度が飽和(7.5mgO2/L)になるように空気を給水タンク内で曝気しながら試験を行った。試験期間は加熱開始後18時間とした。なお、スケール防止剤及び脱酸素剤は、テストボイラの給水ラインにプランジャーポンプを用いて、給水ポンプと連動で表2の添加濃度となるように注入した。
スケール付着量の評価は、テストチューブへのスケール付着量で評価した。具体的には、テストチューブとして、ボイラの伝熱面を再現するために、内部に電気ヒーターが挿入されたステンレス製のテストチューブ(伝熱面面積φ37mm×250mm)を用いた。該テストチューブを試験終了後に取り出し、乾燥させた後、ステンレス製の金属片で掻き取り、重量を測定した。
テストボイラの連続ブローから排出されるボイラ水を試験終了1時間前に採取し、採取したボイラ水に塩酸を添加し、煮沸して硬度成分を溶解する。硬度成分を溶解した後、ボイラ水中のカルシウム濃度及びマグネシウム濃度を原子吸光分析により測定し、炭酸カルシウム換算した濃度を算出する。さらに、給水中の全硬度成分と濃縮倍数から理論濃度を算出し、[炭酸カルシウム換算濃度/理論濃度]×100の式により、硬度成分の排出率を決定した。
鋭敏化した冷間圧延鋼板(SPCC)製のテストピース(1mm×15mm×50mm)をテストボイラ内の給水点近傍に設置し、テストピースに発生した孔食数を目視で評価した。テストピースの鋭敏化は脱脂したテストピースを硝酸に浸漬した後、水で十分に洗浄し、すばやく乾燥させて行った。
一方、比較例においては、スケールの伝熱面付着量が多く、硬度成分排出率も実施例よりも小さくなった。
(亜硫酸の残留率)
表3に示す配合からなる脱酸素剤A~Eを純水で10質量%、5質量%、2質量%に希釈した。希釈液を、蓋に直径5mmの穴を開けた容積1Lのポリプロピレン製の溶解タンクを模擬した容器内で、室温で7日間保管した。7日間保管後に希釈液の亜硫酸濃度を測定し、初期の亜硫酸濃度に対する残留率を算出した。結果を表3に示す。
なお、表4の脱酸素剤の種類「A~E」は、表3の脱酸素剤A~Eを指す。例えば、実施例9では、表3の脱酸素剤Aの10%希釈液を、給水中で亜硫酸濃度が45mg/Lとなるように添加している。
2:補給水タンク 21:補給水ライン
3:給水タンク 31:給水ライン
4:薬注タンク 41:薬注配管
5:蒸気発生部(ボイラ缶)51:蒸気供給ライン 52:ドレン回収ライン
6:蒸気発生設備
Claims (4)
- 硬度成分を1~50mgCaCO3/L含む給水を用いる蒸気発生設備において、給水に対して、下記の(a-1)と(a-2)とを含む(a)スケール防止剤と、下記の(b-1)と、(b-2)又は(b-3)とを含む(b)脱酸素剤を添加する、蒸気発生設備の水処理方法。
(a-1)アクリル酸/2-アクリルアミド-2-メチルプロパンスルホン酸共重合体及び/又はその塩
(a-2)ホスホン酸及び/又はその塩
(b-1)亜硫酸及び/又はその塩
(b-2)エリソルビン酸及び/又はその塩
(b-3)アスコルビン酸及び/又はその塩 - 前記ホスホン酸が、1-ヒドロキシエタン-1,1-ジホスホン酸である、請求項1に記載の蒸気発生設備の水処理方法。
- 前記アクリル酸/2-アクリルアミド-2-メチルプロパンスルホン酸共重合体のアクリル酸と、2-アクリルアミド-2-メチルプロパンスルホン酸とのモノマーのモル比が、90:10~50:50である、請求項1又は2に記載の蒸気発生設備の水処理方法。
- 給水の全硬度成分に対して、質量基準で、前記スケール防止剤を0.1~1.0倍添加する、請求項1~3の何れかに記載の蒸気発生設備の水処理方法。
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JP2018149462A (ja) * | 2017-03-09 | 2018-09-27 | アクアス株式会社 | スケール除去剤、および、スケール除去方法 |
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JPS61125497A (ja) * | 1983-03-07 | 1986-06-13 | カルゴン コ−ポレ−シヨン | アクリル酸/2−アクリルアミド−2−メチルプロピルスルホン酸ポリマ−を含有する腐食抑制用組成物 |
JPH054096A (ja) * | 1990-09-03 | 1993-01-14 | Katayama Chem Works Co Ltd | カルシウム系スケール防止剤 |
JPH07188953A (ja) * | 1993-12-27 | 1995-07-25 | Asahi Breweries Ltd | ボイラ水処理管理方法及びボイラ水処理剤 |
JP2010058079A (ja) * | 2008-09-05 | 2010-03-18 | Kurita Water Ind Ltd | 水処理剤及び水処理方法 |
JP2012071273A (ja) * | 2010-09-29 | 2012-04-12 | Kurita Water Ind Ltd | 酸素除去方法及び酸素除去剤 |
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JPS577225A (en) * | 1980-06-13 | 1982-01-14 | Katayama Chem Works Co Ltd | Stable aqueous deoxigenating agent |
JP2006274427A (ja) * | 2005-03-30 | 2006-10-12 | Miura Co Ltd | 水処理剤および水処理方法 |
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JPS61125497A (ja) * | 1983-03-07 | 1986-06-13 | カルゴン コ−ポレ−シヨン | アクリル酸/2−アクリルアミド−2−メチルプロピルスルホン酸ポリマ−を含有する腐食抑制用組成物 |
JPH054096A (ja) * | 1990-09-03 | 1993-01-14 | Katayama Chem Works Co Ltd | カルシウム系スケール防止剤 |
JPH07188953A (ja) * | 1993-12-27 | 1995-07-25 | Asahi Breweries Ltd | ボイラ水処理管理方法及びボイラ水処理剤 |
JP2010058079A (ja) * | 2008-09-05 | 2010-03-18 | Kurita Water Ind Ltd | 水処理剤及び水処理方法 |
JP2012071273A (ja) * | 2010-09-29 | 2012-04-12 | Kurita Water Ind Ltd | 酸素除去方法及び酸素除去剤 |
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JP2017006853A (ja) * | 2015-06-19 | 2017-01-12 | 三浦工業株式会社 | 脱酸素剤及び脱酸素方法 |
JP2018149462A (ja) * | 2017-03-09 | 2018-09-27 | アクアス株式会社 | スケール除去剤、および、スケール除去方法 |
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