US20120145187A1 - Method for treatment of iron-based metal surface exposed to superheated steam - Google Patents

Method for treatment of iron-based metal surface exposed to superheated steam Download PDF

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Publication number
US20120145187A1
US20120145187A1 US13/377,851 US201013377851A US2012145187A1 US 20120145187 A1 US20120145187 A1 US 20120145187A1 US 201013377851 A US201013377851 A US 201013377851A US 2012145187 A1 US2012145187 A1 US 2012145187A1
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United States
Prior art keywords
treatment
steam
iron
based metal
metal surface
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Abandoned
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US13/377,851
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English (en)
Inventor
Yoshiyuki Abe
Masamichi Miyajima
Kazuo Marugame
Masaki Yoshida
Yuji Shimizu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Chubu Electric Power Co Inc
Naigai Chemical Products Co Ltd
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Chubu Electric Power Co Inc
Naigai Chemical Products Co Ltd
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Application filed by Chubu Electric Power Co Inc, Naigai Chemical Products Co Ltd filed Critical Chubu Electric Power Co Inc
Assigned to NAIGAI CHEMICAL PRODUCTS CO., LTD., CHUBU ELECTRIC POWER CO., INC. reassignment NAIGAI CHEMICAL PRODUCTS CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ABE, YOSHIYUKI, MIYAJIMA, MASAMICHI, MARUGAME, KAZUO, SHIMIZU, YUJI, YOSHIDA, MASAKI
Publication of US20120145187A1 publication Critical patent/US20120145187A1/en
Abandoned legal-status Critical Current

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    • 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
    • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
    • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
    • C23F11/10—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using organic inhibitors
    • 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
    • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
    • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
    • 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

Definitions

  • the present invention relates to a method for treatment of an iron-based metal surface exposed to superheated steam. More particularly, the invention relates to a surface treatment method for suppressing the formation and growth of steam oxide scale on an iron-based metal surface exposed to superheated steam.
  • the inner surfaces of steam pipes are exposed to superheated steam, which is generated by superheating with superheaters or reheaters, saturated steam produced in boilers. Therefore, the inner surfaces are oxidized and coated with steam oxidation scale during a long period of operation. Since the steam pipe base materials (iron-based metals) are different in thermal expansion coefficient from steam oxide scale, thermal stress occurs between them by change in temperature at the start and the stop of the boilers, thereby exfoliating steam oxide scale from the steam pipe surfaces. Steam oxide scale is believed to be easily exfoliated when it grows more than approximately 200 ⁇ m thick.
  • the exfoliated steam oxide scale can be deposited at U-bent or other portions of the steam pipes to occlude them or can strike against turbine blades to damage them, thereby stopping the power plants irregularly and therefore reducing the generation efficiency or increasing the maintenance and repair costs.
  • the formation and growth of steam oxide scale on the inner surfaces of steam or other pipes can cause problems relating to plant reliability or maintenance.
  • anticorrosion treatment of cooling water pipes' inner surfaces uses anticorrosion by a deposition coating of calcium phosphate, zinc phosphate, calcium carbonate or the like, or electric anticorrosion by using an oxidant such as sodium nitrite, sodium molybdate, sodium chromate, or others.
  • an oxidant such as sodium nitrite, sodium molybdate, sodium chromate, or others.
  • anticorrosion is performed by using a neutralizing amine such as morpholine, cyclohexylamine or a film-forming amine such as octadecylamine, either alone or a combination thereof.
  • Boiler steel pipes having good steam oxidation resistance e.g., Patent Literature 1
  • Patent Literature 2 a method for suppressing oxidation of a steam pipe inner surface by setting the electrical potential within a certain range at the inner surface of the pipe
  • this invention aims to provide a surface treatment method capable of suppressing the formation and growth of steam oxide scale on an iron-based metal surface exposed to superheated steam.
  • the present invention provides a surface treatment method for suppressing the formation and growth of steam oxide scale on an iron-based metal surface exposed to superheated steam, comprising treating said iron-based metal surface with a surface-treatment agent, wherein said surface-treatment agent comprises a polyoxy saturated aliphatic mono- or di-carboxylic acid or a salt thereof and an aliphatic amine represented by the following formula (I):
  • Z represents H, or OH or NH 2 group, and n is an integer of 0-5.
  • the formation and growth of steam oxide scale is suppressed on an iron-based metal surface exposed to superheated steam.
  • a plant a power plant, for example
  • steam oxide scale exfoliation it is possible to reduce the frequencies of irregular stop and chemical cleaning of a plant (a power plant, for example) due to steam oxide scale exfoliation and therefore achieve the improvement in the reliability and operation efficiency and the reduction of the maintenance costs of a plant equipped with pipes carrying superheated steam. It is also possible to reduce the burdens on the environment.
  • FIG. 1 This figure illustrates an experimental system used in order to apply the present method to a test specimen.
  • FIG. 2 This figure illustrates a system evaluating the formation and growth of steam oxide scale on the test specimens treated with the present method and the test specimen in a comparative example.
  • FIG. 3 This figure shows the evaluation results by the evaluation system illustrated in FIG. 2 (the relationship between the time of exposure to superheated steam and the mass gain of the test specimens).
  • the treatment method according to the invention comprises treating an iron-based metal surface exposed to superheated steam with a surface-treatment agent comprising a polyoxy saturated aliphatic mono- or di-carboxylic acid or a salt thereof and an aliphatic amine represented by said formula (I).
  • the present treatment method is considered to suppress the formation and growth of steam oxide scale by high temperature superheated steam on an iron-based metal surface, though the mechanism described below. However, it is not intended to limit the invention by the following theory.
  • Steam oxide scale foams and grows on an iron-based metal surface by contacting and oxidizing it with high temperature superheated steam, as shown in formula (1).
  • the thickness T of steam oxide scale follows the parabola equation is represented as the one-half power of the product of oxidation rate constant Kp and time t, as shown in formula (2).
  • the oxidation rate constant Kp varies depending on materials.
  • iron-based metal refers to iron and alloys comprising iron as a main (50% or more) component such as carbon steels (e.g., STB410 and the like), stainless steels (e.g., SUS321THB and the like), alloy steels (for example, alloy steels with chromium, nickel, molybdenum and/or manganese; e.g., STBA24, STPA24 and the like).
  • carbon steels e.g., STB410 and the like
  • stainless steels e.g., SUS321THB and the like
  • alloy steels for example, alloy steels with chromium, nickel, molybdenum and/or manganese; e.g., STBA24, STPA24 and the like.
  • the iron-based metal surface, to which the present method is applied is an inner surface of a pipe exposed to superheated steam (for example at 450° C., preferably at 450 to 700° C.), and more preferably an inner surface of a main or reheat steam pipe of a power plant (especially a thermal power plant).
  • the surface-treatment agent used in the present treatment method comprises a polyoxy saturated aliphatic mono- or di-carboxylic acid or a salt thereof and an aliphatic amine represented by the following formula (I):
  • n is an integer of 0-5, preferably 0-3.
  • the polyoxy saturated aliphatic mono- or di-carboxylic acid or the salt thereof is preferably selected from the group consisting of C 4 -C 6 polyoxy saturated aliphatic mono- or di-carboxylic acids and salts thereof and more preferably selected from the group consisting of gluconic acid, tartaric acid and salts of aforesaid acids.
  • the polyoxy saturated aliphatic mono- or di-carboxylic acid can be any of the d-, l- and dl-form optical isomers.
  • the salts of polyoxy saturated aliphatic mono- or di-carboxylic acids are preferably alkaline metal salts and more preferably sodium salts.
  • One or more polyoxy saturated aliphatic mono- or di-carboxylic acids or salts thereof may be used, alone or in combination.
  • the concentration of the polyoxy saturated aliphatic mono- or di-carboxylic acid(s) or salt(s) thereof in the surface-treatment agent can range for example from 20 to 6000 mg/L, preferably from 40 to 3000 mg/L, and more preferably from 200 to 600 mg/L.
  • the aliphatic amine represented by the formula (I) includes ethylamine, ethylenediamine, monoethanolamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine (TEPA) and the like. Among them, more preferable are mono ethanolamine and TEPA, and still more preferable is TEPA.
  • a single amine may be used alone, or two or more amines may be used in combination.
  • the concentration of the aliphatic amine represented by the formula (I) in the surface-treatment agent may range for example from 3 to 15000 mg/L, preferably from 6 to 7500 mg/L, and more preferably from 30 to 1500 mg/L.
  • the ratio by weight of said carboxylic acid(s) or salt(s) thereof to said aliphatic amine in the surface-treatment agent may range for example from 1:800 to 2000:1, preferably from 1:200 to 500:1, and more preferably from 1:8 to 20:1.
  • the surface-treatment agent may comprise an additional component such as an alkaline metal hydroxide, such as sodium hydroxide and potassium hydroxide, and an aliphatic cyclic amine (or non-aromatic cyclic amine), such as morpholine and cyclohexyl amine.
  • the additional component may be present in the surface-treatment agent at for example 5 to 5000 mg/L, preferably 10 to 2500 mg/L, and more preferably 50 to 500 mg/L.
  • the surface-treatment agent can be an aqueous solution.
  • Water as a solvent may be demineralized water, soft water, tap water, industrial water, groundwater or the like. Demineralized water is preferable, in which less causal components of corrosion and scale remain.
  • the present method is more effective if it applies to an iron-based metal surface when it is clean (e.g., before initial use or after removal of steam oxide scale (at the time of performing regular maintenance, for example)).
  • the treatment of an iron-based metal surface with the surface-treatment agent can be carried out at a temperature of 120° C. to 380° C. for example. In view of costs, efficiency and easiness, it is preferably carried out at a temperature of 120° C. to 250° C.
  • the surface-treatment agent can be heated directly by e.g. an electric heater, or indirectly via heating of the iron-based metal to be treated by e.g. an electric heater or steam.
  • the treatment time is not limited specifically, but the lower limit may be for example 10 hours or more, preferably 24 hours or more and the upper limit may be for example 100 hours in view of costs and efficiency.
  • the treatment of the iron-based metal surface with the surface-treatment agent can be carried out by contacting the agent with the surface. If the iron-based metal surface to be treated is an inner surface of a pipe, it is preferable to circulate the surface-treatment agent into a pipe so as to make the reaction conditions constant.
  • the present invention provides a surface treatment method for suppressing the formation and growth of steam oxide scale on an inner surface of a main or reheat steam pipe of a power plant, comprising treating said inner surface with a surface-treatment agent at a temperature of 120° C. to 250° C. for 10 to 100 hours, wherein said surface-treatment agent comprises gluconic acid, tartaric acid or a salt of aforesaid acids and tetraethylenepentamine and said inner surface is an iron-based metal surface exposed to superheated steam.
  • a pipe alloy steel STPA24 (chromium-molybdenum steel) was cut into pieces of 7 ⁇ 100 ⁇ 1 mm, which were used as (iron-based metal) test specimens after polishing with a coated abrasives up to number 400 and defatting with acetone.
  • test specimens were treated under the above-listed conditions 1-4 as Examples 1-4 respectively.
  • the surface treatments were carried out in the autoclave illustrated in FIG. 1 .
  • a surface-treatment agent 5 in which a test specimen 6 attached to the front end of the rotating shaft of a stirrer 2 was immersed and surface-treated while rotating at 100 rpm.
  • the surface-treatment agent 5 was heated and maintained at a predetermined temperature by an electric heater 3 fit on the outer wall of the vessel 1 .
  • the temperature was monitored with a thermocouple 4 .
  • boiler water actually used in a thermal power plant was introduced into a steam generator 11 (which was actually the autoclave illustrated in FIG. 1 ) and heated to 250° C. to generate saturated steam.
  • the generated saturated steam was feed to an electric superheater furnace 12 and further superheated into superheated steam at a temperature of 550° C.
  • the superheated steam at 550° C. was feed from the electric superheater furnace to a specimen-holder tube 15 , in which a test specimen 17 had been previously held and was exposed to the superheated steam.
  • the evaluation system is a closed circulatory system, wherein a cycle of water->saturated steam->superheated steam->water was repeated.
  • the test specimen 17 was brought into contact with the superheated steam for a predetermined period of time (830, 3,830, 7,680 or 10,000 hours) and the mass was then measured.
  • the oxidation rate constant Kp was calculated from the mass gain.
  • the thickness of steam oxide scale follows the parabola equation represented by the above-described formula (2), and the thickness [in ⁇ m] of steam oxidation scale is 0.75 times of the mass gain [in g/m 2 ] of the test specimen based on the relationship of the oxidation mass gain with the scale thickness described in “A study on steam oxidation behavior of Cr—Mo steel pipe for boilers” (Sumitomo Metal Industries, Ltd., Catalogue No. JB04806).
  • test specimen After 10,000 hours, the appearance of the test specimen was also inspected.
  • the mass gain by contact with superheated steam was suppressed in the test specimens of Examples 1-4 as compared to the test specimen of Comparative Example. Since the mass gain is due to oxidation of the test specimen surface, it is considered that the formation and growth of steam oxide scale on the surfaces of the test specimens of Examples 1-4 was suppressed by applying the present method to the specimens.
  • the oxidation rate constants, Kp values, which are calculated from the mass gains, of the test specimens of Examples 1-4 are found to be half or less of that of the test specimen of Comparative Example. Therefore, one can understand that the growth rate of steam oxide scale in an iron-based metal surface treated by the present method is half or less of that in an untreated surface and therefore after the treatment by the present method, the interval of chemical cleanings to remove steam oxide scales is around two times longer than the interval after the conventional surface treatment.
  • the treatment method according to the present invention can suppress the formation and growth of steam oxide scale on an iron-based metal surface by superheated steam.
  • the present treatment method is especially suitable for the application to a piping system, such as a superheated steam piping system of a power plant, which cannot frequently be cleaned (in particular, by chemical cleaning) and in which an anti-corrosion agent or the like cannot be constantly circulated, and therefore can contribute to the improvement in reliability and operating efficiency and the reduction in administrative and maintenance costs of a plant equipped with such a piping system.
  • a piping system such as a superheated steam piping system of a power plant, which cannot frequently be cleaned (in particular, by chemical cleaning) and in which an anti-corrosion agent or the like cannot be constantly circulated

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
US13/377,851 2009-07-06 2010-07-01 Method for treatment of iron-based metal surface exposed to superheated steam Abandoned US20120145187A1 (en)

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JP2009159887A JP5363893B2 (ja) 2009-07-06 2009-07-06 過熱水蒸気に曝される鉄系金属表面の処理方法
JP2009-159887 2009-07-06
PCT/JP2010/061264 WO2011004763A1 (ja) 2009-07-06 2010-07-01 過熱水蒸気に曝される鉄系金属表面の処理方法

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9239282B2 (en) 2011-11-01 2016-01-19 Naigai Chemical Products Co., Ltd. Metal pipe corrosion monitoring device and use thereof
US9670796B2 (en) 2012-11-07 2017-06-06 General Electric Company Compressor bellmouth with a wash door
US9759131B2 (en) 2013-12-06 2017-09-12 General Electric Company Gas turbine engine systems and methods for imparting corrosion resistance to gas turbine engines
US10272475B2 (en) 2012-11-07 2019-04-30 General, Electric Company Offline compressor wash systems and methods

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JP6762010B2 (ja) * 2016-08-17 2020-09-30 株式会社片山化学工業研究所 ボイラの水処理剤およびそれを用いるボイラの水処理方法

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US3000829A (en) * 1958-06-12 1961-09-19 Purex Corp Ltd Composition and process for descaling metal parts
US3095380A (en) * 1958-07-14 1963-06-25 Purex Corp Ltd Composition for removal of heat scale and carbon deposits
US3025189A (en) * 1958-12-10 1962-03-13 Purex Corp Ltd Composition and process for removing heat scale from metal parts
US3072502A (en) * 1961-02-14 1963-01-08 Pfizer & Co C Process for removing copper-containing iron oxide scale from metal surfaces
US3510351A (en) * 1964-11-27 1970-05-05 Paul Van Dillen Method for etching and cleaning of objects and plants,particularly tube systems and boiler plants,consisting of iron or steel
US3907578A (en) * 1972-04-18 1975-09-23 Raffinage Cie Francaise Compositions for inhibiting the corrosion of metals
US3996062A (en) * 1975-08-28 1976-12-07 Halliburton Company Method for removing scale from metallic substrates
US4032460A (en) * 1975-10-28 1977-06-28 Union Oil Company Of California Inhibition of scale deposition in high temperature wells
US20040149310A1 (en) * 2001-06-20 2004-08-05 Dominion Engineering, Inc. Scale conditioning agents and treatment method
US20070001150A1 (en) * 2005-06-29 2007-01-04 Hudgens Roy D Corrosion-inhibiting composition and method of use
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9239282B2 (en) 2011-11-01 2016-01-19 Naigai Chemical Products Co., Ltd. Metal pipe corrosion monitoring device and use thereof
US9670796B2 (en) 2012-11-07 2017-06-06 General Electric Company Compressor bellmouth with a wash door
US10272475B2 (en) 2012-11-07 2019-04-30 General, Electric Company Offline compressor wash systems and methods
US9759131B2 (en) 2013-12-06 2017-09-12 General Electric Company Gas turbine engine systems and methods for imparting corrosion resistance to gas turbine engines

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WO2011004763A1 (ja) 2011-01-13
EP2455514A4 (en) 2018-01-10
JP2011012333A (ja) 2011-01-20
JP5363893B2 (ja) 2013-12-11
EP2455514A1 (en) 2012-05-23

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