WO2021181723A1 - ボイラにおける蒸発管の腐食疲労の抑制方法 - Google Patents
ボイラにおける蒸発管の腐食疲労の抑制方法 Download PDFInfo
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- WO2021181723A1 WO2021181723A1 PCT/JP2020/033205 JP2020033205W WO2021181723A1 WO 2021181723 A1 WO2021181723 A1 WO 2021181723A1 JP 2020033205 W JP2020033205 W JP 2020033205W WO 2021181723 A1 WO2021181723 A1 WO 2021181723A1
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- Prior art keywords
- boiler
- water
- corrosion fatigue
- concentration
- scale
- Prior art date
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- 238000005260 corrosion Methods 0.000 title claims abstract description 64
- 230000007797 corrosion Effects 0.000 title claims abstract description 64
- 238000001704 evaporation Methods 0.000 title claims abstract description 38
- 238000000034 method Methods 0.000 title claims abstract description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 101
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims abstract description 14
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims abstract description 14
- 238000005342 ion exchange Methods 0.000 claims abstract description 7
- 239000012528 membrane Substances 0.000 claims abstract description 7
- 238000001223 reverse osmosis Methods 0.000 claims abstract description 7
- 230000008020 evaporation Effects 0.000 claims description 35
- 239000002270 dispersing agent Substances 0.000 claims description 27
- 150000003839 salts Chemical class 0.000 claims description 18
- 238000011084 recovery Methods 0.000 claims description 9
- 229920002845 Poly(methacrylic acid) Polymers 0.000 claims description 8
- 229920002125 Sokalan® Polymers 0.000 claims description 5
- 239000004584 polyacrylic acid Substances 0.000 claims description 5
- 150000001875 compounds Chemical class 0.000 claims description 4
- 238000011033 desalting Methods 0.000 claims description 2
- 238000009296 electrodeionization Methods 0.000 abstract description 3
- 238000010612 desalination reaction Methods 0.000 abstract 1
- 150000002500 ions Chemical class 0.000 description 21
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 16
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 10
- 229910052760 oxygen Inorganic materials 0.000 description 10
- 239000001301 oxygen Substances 0.000 description 10
- 239000012085 test solution Substances 0.000 description 10
- 239000000377 silicon dioxide Substances 0.000 description 8
- 238000009661 fatigue test Methods 0.000 description 7
- 239000008234 soft water Substances 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 229920001495 poly(sodium acrylate) polymer Polymers 0.000 description 4
- NNMHYFLPFNGQFZ-UHFFFAOYSA-M sodium polyacrylate Chemical compound [Na+].[O-]C(=O)C=C NNMHYFLPFNGQFZ-UHFFFAOYSA-M 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- DZSVIVLGBJKQAP-UHFFFAOYSA-N 1-(2-methyl-5-propan-2-ylcyclohex-2-en-1-yl)propan-1-one Chemical compound CCC(=O)C1CC(C(C)C)CC=C1C DZSVIVLGBJKQAP-UHFFFAOYSA-N 0.000 description 1
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229940123973 Oxygen scavenger Drugs 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000004115 Sodium Silicate Substances 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003002 pH adjusting agent Substances 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 229940085991 phosphate ion Drugs 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229920000193 polymethacrylate Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 235000011121 sodium hydroxide Nutrition 0.000 description 1
- 239000001488 sodium phosphate Substances 0.000 description 1
- 159000000000 sodium salts Chemical class 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 229910052911 sodium silicate Inorganic materials 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 235000019832 sodium triphosphate Nutrition 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 description 1
- 229910000406 trisodium phosphate Inorganic materials 0.000 description 1
- 235000019801 trisodium phosphate Nutrition 0.000 description 1
Images
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
- F22B37/56—Boiler cleaning control devices, e.g. for ascertaining proper duration of boiler blow-down
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/26—Treatment of water, waste water, or sewage by extraction
- C02F1/265—Desalination
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
- B01D61/44—Ion-selective electrodialysis
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F14/00—Inhibiting incrustation in apparatus for heating liquids for physical or chemical purposes
- C23F14/02—Inhibiting incrustation in apparatus for heating liquids for physical or chemical purposes by chemical means
-
- 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
- F22B37/025—Devices and methods for diminishing corrosion, e.g. by preventing cooling beneath the dew point
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/101—Sulfur compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/12—Halogens or halogen-containing compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/19—SO4-S
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/22—O2
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/29—Chlorine compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2303/00—Specific treatment goals
- C02F2303/08—Corrosion inhibition
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2303/00—Specific treatment goals
- C02F2303/22—Eliminating or preventing deposits, scale removal, scale prevention
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
Definitions
- the present invention relates to a method for suppressing corrosion fatigue of an evaporation tube in a boiler. More specifically, the present invention relates to a method of effectively suppressing corrosion fatigue of an evaporator tube in a boiler associated with repeated stresses due to a corrosive environment or the presence of scale.
- Boasts an overwhelming share. Small once-through boilers are often operated in a multi-can installation where multiple boilers are installed, and are operated by repeating start and stop many times depending on the amount of steam required. Further, since the circulation ratio is 2 or less and water is particularly supplied to the lower part of the evaporation pipe, the pH in the vicinity of the lower part is low and the dissolved oxygen is high, so that corrosion is likely to occur. In some cases, this corrosive environment and corrosion fatigue caused by repeated stress caused by temperature fluctuations caused by starting and stopping the boiler cause cracks in the evaporation pipe, leading to water leakage.
- boiler water The pH of the water in the steam generating part of the boiler (hereinafter referred to as boiler water) is maintained at the upper limit of the control reference value.
- boiler water Keep the concentration of oxygen scavenger higher than the control standard value.
- the following measures (1) to (3) can be mentioned as measures to suppress the scale.
- (1) Perform reverse osmosis membrane treatment or softening treatment of boiler feed water.
- (2) A scale dispersant or a boiler compound is added to suppress the formation of scale (for example, Patent Documents 1 and 2).
- (3) Boiler water blow control is performed to eliminate scale components.
- Corrosion fatigue of the evaporation pipe of the boiler could not be sufficiently suppressed by the conventional corrosion suppression method.
- An object of the present invention is to provide a method for effectively suppressing corrosion fatigue of an evaporator tube in a boiler associated with repeated stress due to a corrosive environment or the presence of scale.
- the present inventor has found that by controlling the chloride ion concentration and the sulfate ion concentration of the boiler water to be low, corrosion can be sufficiently suppressed and corrosion fatigue of the evaporation tube can be effectively suppressed. Further, the present inventor has found that the corrosion fatigue of the evaporation tube can be further suppressed by further suppressing the scale adhesion by allowing the scale dispersant to be present in the boiler water.
- the gist of the present invention is as follows.
- a method for suppressing corrosion fatigue of an evaporation tube in a boiler wherein the chloride ion concentration and the sulfate ion concentration of the boiler water are controlled to 10 mg / L or less, respectively.
- the raw water used for supplying water to the boiler is desalted with an ion exchange device, a reverse osmosis membrane device, or an electrodeionizer, or the recovery rate of the boiler recovery water of the boiler is increased to increase the recovery rate of the boiler water.
- the scale dispersant is composed of a polyacrylic acid having a weight average molecular weight of 20,000 to 170,000 and a salt thereof, and a polymethacrylic acid having a weight average molecular weight of 1,000 to 100,000 and a salt thereof.
- the present invention it is possible to effectively suppress the corrosion fatigue of the evaporation pipe of the boiler due to the repeated stress due to the corrosive environment and the presence of the scale, and to extend the life of the boiler.
- FIG. 1 is a schematic view showing the flow of the boiler water system to be tested in Test Example I.
- the method for suppressing corrosion fatigue of the evaporation pipe in the boiler according to the present embodiment is to control the chloride ion concentration and the sulfate ion concentration of the boiler water, that is, the water in the steam generating part of the boiler to 10 mg / L or less, respectively. It is a feature.
- corrosive ions by controlling the concentrations of corrosive chloride ions and sulfate ions (hereinafter, these may be referred to as “corrosive ions”) to 10 mg / L or less, respectively, corrosion fatigue can be prevented. Corrosion of the evaporation pipe, which is the starting point, can be suppressed and corrosion fatigue can be suppressed.
- the raw water used for boiler water supply should be an ion exchange device (ion exchange device such as multi-bed tower system, mixed bed tower system, etc.), reverse osmosis membrane device, or electrodeionization.
- ion exchange device such as multi-bed tower system, mixed bed tower system, etc.
- reverse osmosis membrane device or electrodeionization.
- a method such as desalting with an apparatus or increasing the recovery rate of the boiler recovery water of the boiler can be adopted. You may adopt these two or more methods in combination.
- the corrosive ion concentration of the boiler water may be controlled, for example, by adjusting the corrosive ion concentration of the boiler feed water to be equal to or less than the upper limit of the corrosive ion concentration of the boiler water by using the above method.
- controlling the silica concentration as well as the corrosive ion concentration of the boiler water to be below the upper limit of the corrosive ion concentration of the boiler water suppresses the formation of scale. It is preferable to more reliably suppress the corrosion fatigue of the evaporation tube.
- the silica concentration can also be reduced by treatment with an ion exchange device, a reverse osmosis membrane device, or an electrodeionization device, or by controlling the recovery rate of condensate.
- the scale dispersant is present in the boiler water to suppress the scale adhesion in the evaporation pipe, so that the corrosion is more effectively performed. Fatigue can be suppressed.
- the scale dispersant suppresses the scaling of the hardness component brought into the water system and removes the scale that has already adhered.
- Scale dispersants include phosphates such as trisodium phosphate and sodium tripolyphosphate, polyacrylic acid / or salts thereof, polymethacrylic acid and / or salts thereof, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid. Polymers such as copolymers with and / or salts thereof.
- the scale dispersant preferably contains polyacrylic acid having a weight average molecular weight of 20,000 to 170,000 and / or a salt thereof, polymethacrylic acid having a weight average molecular weight of 1,000 to 100,000 and / or a salt thereof, and the like.
- the weight average molecular weight of the polyacrylic acid and / or a salt thereof is more preferably more than 20,000 and not more than 170,000, still more preferably more than 50,000 million and not more than 120,000.
- the weight average molecular weight of the polymethacrylic acid and / or a salt thereof is more preferably more than 1,000 and 100,000 or less, further preferably more than 5,000 and 80,000 or less.
- the scale dispersant may be contained in the boiler water, and the place where the scale dispersant is added is not particularly limited.
- the scale dispersant may be added to at least one place in the boiler water system including the boiler water supply system (water supply line), the make-up water system (make-up water line), the boiler water, and the condensate system (condensate line).
- the scale dispersant may be added to any of, for example, a boiler water supply pipe, a water supply tank, a make-up water pipe, a make-up water tank, a condensate pipe, and a condensate tank, and may be added at two or more of these locations.
- the amount of the scale dispersant added is not particularly limited, and varies depending on the water quality of the boiler feed water (dissolved oxygen concentration, corrosive salt concentration), the scaling tendency depending on the operating conditions of the boiler, and the like. From the viewpoint of obtaining a sufficient scale suppressing effect while suppressing the chemical cost, for example, in the case of a polymer-based scale dispersant, the concentration in the boiler feed water is 1 to 1,000 mg / L, particularly 10 to 500 mg / L. It is preferable to add in such an amount.
- the water quality of the ion-exchanged water is preferably 1 mS / m or less, particularly 0.5 mS / m or less, particularly 0.1 mS / m or less in terms of electrical conductivity. If salts are removed so that the electrical conductivity is equal to or less than the above upper limit, corrosion in the evaporation tube can be more reliably suppressed and the effect of suppressing corrosion fatigue can be enhanced.
- soft water obtained by softening raw water with a softener may be used for boiler water supply in order to suppress scale.
- the softening treatment alone only removes the cation component, but cannot remove the corrosive salts, and the effect of suppressing the corrosion fatigue of the evaporation tube is not sufficient.
- the boiler to which the present invention is applied is not particularly limited, but a boiler having a vapor pressure of 4 MPa or less is preferable, and a low-pressure boiler having a vapor pressure of 2 MPa or less is more preferable from the viewpoint that corrosion fatigue of the evaporation pipe is likely to occur.
- a typical low-pressure boiler is a small once-through boiler.
- the vapor pressure of the small once-through boiler is, for example, 1 MPa or less.
- a round can body is a can body having a combustion chamber in the center and a burner in the upper part.
- a square can body is a can body that does not have a combustion chamber and has a gas burner arranged adjacent to the side surface of a water pipe.
- Corrosion fatigue of the evaporation tube is more likely to occur in the square can body than in the round can body.
- corrosion fatigue of the evaporation pipe can be sufficiently suppressed even in a small square once-through boiler. Can be suppressed.
- Example 1 The effect of salts on corrosion fatigue was evaluated by a corrosion fatigue test.
- the test solution was assumed to be soft water and had a water quality containing chloride ions, sulfate ions, and silica.
- a test piece of material STB340 was processed for an arcuate fatigue test. Specifically, it was processed into a shape having a parallel portion and an R portion (arc portion), and the parallel portion and the R portion were polished by # 800.
- the stress corresponding to the maximum load in the elastic region was determined to be 220 MPa. This value was set as the maximum stress in the corrosion fatigue test.
- test piece was placed on the shaft of the corrosion fatigue test device, and 1 L of the test solution was poured into a beaker fixed so that the test piece was immersed so that the test piece was completely immersed.
- the test solution was adjusted to the following test solution composition and pH by using special grade reagents sodium chloride, sodium sulfate, 48% caustic soda, and sodium silicate No. 3 in ion-exchanged water.
- the temperature of the test solution was adjusted to 85 ° C.
- oxygen gas is continuously supplied into the beaker so that the dissolved oxygen concentration in the beaker becomes the value shown in Table 1, and the dissolved oxygen concentration is constant while observing the dissolved oxygen meter installed on the circulation line.
- the amount of gas supplied was controlled so as to be.
- the maximum stress was set to 220 MPa with a target of 96 hours of test time, and the test was carried out with a corrosion fatigue test apparatus.
- the test conditions are as follows.
- Test piece Arc-shaped fatigue test piece made from STB340 (reference to ASTM E466-96) Pretreatment of test piece: Finish parallel part and R part # 800
- Control Load control Waveform: Sine wave Maximum stress: 220MPa Frequency: 4.0Hz
- Test period Maximum 96 hours
- Test solution temperature 85 ° C
- Test solution composition Chloride ion, sulfate ion and silica concentrations are as shown in Table 1. No. In No. 1, when each substance was set to 10 mg / L in soft water supply, it was assumed that each substance was concentrated 10 times in the steam generator, and each was set to 100 mg / L. No. In No. In No.
- the water obtained by treating the raw water with the ion exchange device or the softener 1 is supplied to the boiler 4 via the water supply tank 2, and the condensate generated in the boiler 4 is returned to the water supply tank 2.
- the dissolved oxygen concentration was measured immediately after the outlet of the water supply tank 2.
- a scale dispersant and a caustic pH adjuster were injected into the water supply line in front of the boiler 3.
- Target boiler Small once-through boiler Operating pressure: 1.0 MPa or less
- Water supply type Soft water, soft water + condensate, ion-exchanged water, ion-exchanged water + condensate.
- Electrical conductivity 50-400 mS / m
- Scale dispersant The following sodium polyacrylate (PANa), sodium polymethacrylate (PMNa) or orthophosphate was used.
- Example I-1 having a low corrosive ion concentration of 1 mg / L was compared with Comparative Example I-1 having a high corrosive ion concentration of 80 to 100 mg / L. It is presumed that corrosion was suppressed, tensile stress was unlikely to increase, and the occurrence of corrosion fatigue was suppressed.
- Examples I-2 to 5 in which the scale dispersants were used at each corrosive ion concentration of 1 mg / L, there was almost no scale adhesion and few cracks were generated. It is presumed that this was because the tensile stress due to scale adhesion was suppressed to a low level and the environment was such that fatigue due to corrosion was unlikely to occur or progress due to the low salt concentration.
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Abstract
Description
(1) ボイラの蒸気発生部内の水(以降、ボイラ水)のpHを管理基準値の上限に保持する。
(2) 脱酸素剤の濃度を管理基準値の高めに保持する。
(3) 缶底ブローは運転終了直後ではなく起動直前に行い高濃度の酸素の混入や低pH化を抑制する。
(1) ボイラ給水の逆浸透膜処理又は軟化処理を行う。
(2) スケールの生成を抑制するためにスケール分散剤や清缶剤を添加する(例えば特許文献1,2)。
(3) スケール成分の排除のためのボイラ水のブロー管理を行う。
腐食疲労試験によって塩類が腐食疲労に及ぼす影響を評価した。試験液は軟水を想定し、塩化物イオン、硫酸イオン、シリカを含む水質とした。
まず用いた試験片での破断条件を求めるため、以下の準備を行った。
材質STB340の試験片を円弧状疲労試験用に加工した。具体的には、平行部とR部(円弧部)とを有する形状に加工し、平行部及びR部を#800研磨した。
この試験片を使用して大気中における引張試験を実施したところ、弾性域最大荷重に対応する応力は220MPaと求められた。この値を腐食疲労試験の最大応力として設定した。
試験液はイオン交換水に、特級試薬の塩化物ナトリウム、硫酸ナトリウム及び、48%苛性ソーダ、3号ケイ酸ナトリウムを用いて、下記試験液組成及びpHとなるように調整した。試験液の温度は85℃に調整した。
溶存酸素濃度が一定になったら、試験時間96時間を目標に最大応力を220MPaに設定し、腐食疲労試験装置にて試験を実施した。
試験条件は以下の通りである。
試験片:STB340より作製した円弧状疲労試験片(ASTM E466-96参考)
試験片の前処理:平行部およびR部を#800仕上げ
制御:荷重制御
波形:正弦波
最大応力:220MPa
周波数:4.0Hz
試験期間:最大96時間
試験液温度:85℃
試験液組成:塩化物イオン、硫酸イオン及びシリカ濃度は表1の通りとした。
No.1では、軟水給水で各物質をそれぞれ10mg/Lとしたとき、蒸気発生器内で10倍濃縮したと想定し、それぞれ100mg/Lとした。
No.2では、軟水給水で復水回収率が90%以上と高い場合に想定される水質とした。
No.3では、イオン交換水の給水で、濃縮50倍以上を想定される水質とした。イオン交換水では、塩類よりもシリカは微量リークしやすいためシリカ濃度のみ10mg/Lとした。
試験液pH:11.0
試験液溶存酸素濃度:8.0mg/L
試験液量:1L
結果を表1に示す。
表1より次のことが分かる。
腐食性イオン濃度が低くなるに従って、試験片の破断に至るまでの引張回数が上がり、各腐食性イオン濃度が10mg/L以下では、試験片が破断し難いことが確認された。特に各腐食性イオン濃度が1mg/L以下では破断が発生しないことが確認された。
これは腐食性イオン濃度が低くなると、試験片の表面での腐食が発生し難くなり、あるいは微小亀裂内での腐食の進行が抑制されたことによると推定された。
<実施例I-1~5、比較例I-1~3>
図1に示すボイラ水系において、ボイラ給水の腐食性イオン濃度及びスケール分散剤の添加の有無と蒸発管の腐食疲労の状況との相関を調べた。
対象ボイラ:小型貫流ボイラ
運転圧力:1.0MPa以下
給水種類:軟水、軟水+復水、イオン交換水、イオン交換水+復水のいずれか。
ボイラ水水質:pH=11.0~11.8
電気伝導率=50~400mS/m
溶存酸素濃度=8.0mg/L
塩化物イオン、硫酸イオン、及びシリカ濃度は表2に示す通りである。
スケール分散剤:下記のポリアクリル酸ナトリウム(PANa)、ポリメタクリル酸ナトリウム(PMNa)又は正リン酸塩を使用した。添加量はボイラ水中でポリマーは純分として30mg/L、正リン酸塩はリン酸イオンとして30mg/Lとした。
PANa(4,000):重量平均分子量4,000のポリアクリル酸ナトリウム
PANa(60,000):重量平均分子量60,000のポリアクリル酸ナトリウム
PMNa(10,000):重量平均分子量10,000のポリメタクリル酸ナトリウム
正リン酸塩:正リン酸のナトリウム塩
調査対象のボイラ缶数:559缶
運転期間は8年間とした。8年間の運転期間内の蒸発管の亀裂発生数と亀裂発生割合とを調べた。結果を表2に示す。
表2より次のことが分かる。
腐食疲労の発生は、腐食性イオン濃度が高く、さらにスケール分散剤が使用されない場合(比較例I-1)が最も多かった。
本出願は、2020年3月12日付で出願された日本特許出願2020-043295に基づいており、その全体が引用により援用される。
2 給水タンク
3 ボイラ
Claims (6)
- ボイラの蒸発管の腐食疲労を抑制する方法において、該ボイラ水の塩化物イオン濃度及び硫酸イオン濃度を、それぞれ10mg/L以下に管理する、ボイラにおける蒸発管の腐食疲労の抑制方法。
- 前記ボイラ給水に用いる原水をイオン交換装置、逆浸透膜装置又は電気脱イオン装置で脱塩処理するか、或いは、前記ボイラのボイラ復水の回収率を上げることにより、前記ボイラ水の塩化物イオン濃度及び硫酸イオン濃度を管理する、請求項1に記載のボイラにおける蒸発管の腐食疲労の抑制方法。
- 前記ボイラ水にスケール分散剤を存在させる、請求項1又は2に記載のボイラにおける蒸発管の腐食疲労の抑制方法。
- 前記スケール分散剤が、重量平均分子量20,000~170,000のポリアクリル酸及びその塩、並びに、重量平均分子量1,000~100,000のポリメタクリル酸及びその塩からなる群より選ばれる少なくとも一種のポリ(メタ)アクリル酸化合物である、請求項3に記載のボイラにおける蒸発管の腐食疲労の抑制方法。
- 前記ボイラ水における前記スケール分散剤の濃度が1~1,000mg/Lである、請求項3又は4に記載のボイラにおける蒸発管の腐食疲労の抑制方法。
- 前記ボイラが小型貫流ボイラである、請求項1ないし5のいずれか1項に記載のボイラにおける蒸発管の腐食疲労の抑制方法。
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US17/909,986 US20230094476A1 (en) | 2020-03-12 | 2020-09-02 | Method for reducing corrosion fatigue of evaporating tube in boiler |
CN202080098390.4A CN115280068A (zh) | 2020-03-12 | 2020-09-02 | 锅炉中的蒸发管的腐蚀疲劳的抑制方法 |
BR112022017247A BR112022017247A2 (pt) | 2020-03-12 | 2020-09-02 | Método para reduzir fadiga por corrosão de tubo de evaporação em caldeira |
CA3169757A CA3169757C (en) | 2020-03-12 | 2020-09-02 | Method for reducing corrosion fatigue of evaporating tube in boiler |
EP20923759.3A EP4119843A4 (en) | 2020-03-12 | 2020-09-02 | METHOD FOR REDUCING CORROSION FATIGUE OF AN EVAPORATOR TUBE IN A BOILER |
KR1020227029795A KR20220150293A (ko) | 2020-03-12 | 2020-09-02 | 보일러에 있어서의 증발관의 부식 피로의 억제 방법 |
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EP4119843A4 (en) | 2023-10-11 |
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EP4119843A1 (en) | 2023-01-18 |
JP2021143793A (ja) | 2021-09-24 |
JP7050840B2 (ja) | 2022-04-08 |
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