JP5017742B2 - Anti-corrosion method for boilers during suspension - Google Patents
Anti-corrosion method for boilers during suspension Download PDFInfo
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- JP5017742B2 JP5017742B2 JP2000322724A JP2000322724A JP5017742B2 JP 5017742 B2 JP5017742 B2 JP 5017742B2 JP 2000322724 A JP2000322724 A JP 2000322724A JP 2000322724 A JP2000322724 A JP 2000322724A JP 5017742 B2 JP5017742 B2 JP 5017742B2
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Classifications
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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
- 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
-
- 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
- C23F11/14—Nitrogen-containing compounds
- C23F11/141—Amines; Quaternary ammonium compounds
-
- 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
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/78—Treatment of water, waste water, or sewage by oxidation with ozone
Description
【０００１】
【発明の属する技術分野】
本発明は休止中にあるボイラの防食方法、特に薬品を含む水でボイラを満水にして保存するボイラの防食方法に関する。
【０００２】
【従来の技術】
ボイラプラントを２週間以上等の比較的長期にわたって休止させる場合、休止中におけるボイラの腐食を防止することが必要とされる。腐食防止に関し、ボイラ水を完全にブローし、シリカゲルなどの乾燥剤をボイラ缶内に配置した状態でボイラ缶内を密閉する、乾燥保存方法が従来より採用されている。
しかし、近年ボイラの構造が複雑になってきており、完全にボイラ水をブローできない場合が増えている。また乾燥保存方法では、休止期間が長期間にわたる場合に乾燥剤を定期的に交換しなければならず、手間がかかる。
【０００３】
完全にボイラ水をブローできない場合においては、純水若しくは軟水にヒドラジンを１００〜１０００ｍｇ／Ｌ添加してボイラを満水保存する方法や、亜硝酸ナトリウムを２００〜５００ｍｇ／Ｌ添加してボイラを満水保存する方法が採用されている。
しかし、ヒドラジンは発癌性に関与している疑いがあるので、その使用が問題視されている。また亜硝酸ナトリウムは固形成分であるため、スーパーヒーターやタービンを有するボイラでは、保缶後に純水による逆流洗浄が可能な場合にしか適用することができない。
【０００４】
【発明が解決しようとする課題】
本発明の課題は、どのようなボイラにも適用可能であり、人体に対する安全性も高く、長期間にわたって高い防食効果を得ることができる休止中のボイラの防食方法を提案することである。
【０００５】
【課題を解決するための手段】
本発明は次の休止中のボイラの防食方法である。
（１） ボイラ水のブロー後、
純水若しくは軟水に中和性アミンを含有させ、ヒドラジンおよび亜硝酸ナトリウムを含有させないｐＨ９．５以上の中和性アミン液でボイラを満水にして、
ボイラ内に存在する酸性物質を中和してボイラ缶水のｐＨを上昇させ、ボイラ缶水をアルカリ性に保つことにより、ボイラの腐食を防止し保存する休止中ボイラの防食方法であって、
前記中和性アミンは、モノエタノールアミン、モノイソプロパノールアミン、シクロヘキシルアミン、２−アミノ−２−メチル−１−プロパノール、ジエチルエタノールアミンおよびモルホリンからなる群より選ばれる少なくとも一種の化合物であることを特徴とする休止中ボイラの防食方法。
（２） 中和性アミン液において、中和性アミンの濃度が５０〜２０００ｍｇ／Ｌｉｔｅｒである上記（１）記載の休止中ボイラの防食方法。
【０００６】
本発明の防食方法は、どのようなボイラにも適用可能であり、具体的には丸ボイラ、水管ボイラ、貫流ボイラ、特殊ボイラ等をあげることができる。これらボイラは低圧、中圧、高圧のいずれのボイラでもよい。また本発明の防食方法はスーパーヒーターやタービンを有するボイラ等において逆流洗浄が不可能なボイラにも適用可能である。
【０００７】
本発明の防食方法は、このようなボイラについて、まずボイラ水をブローする。ブローは、ボイラ内のボイラ水を全ブローするのが好ましい。ただし全ブローができない場合、可能な限りボイラ水を排出した後、ボイラ内や管内に残っているボイラ水を置換するようにしてブローを行う。
【０００８】
ブロー後、純水若しくは軟水に中和性アミンを添加し、ヒドラジンおよび亜硝酸ナトリウムを添加しないｐＨ９．５以上の中和性アミン液でボイラを満水にする。中和性アミンがボイラ内に存在する二酸化炭素、その他の酸性物質を中和してボイラ缶水のｐＨを上昇させ、ボイラ缶水をアルカリ性に保つことにより、ボイラの腐食が長期間にわたって防止される。中和性アミン液は、純水若しくは軟水に予め中和性アミンを混和させることによって得ることができる。ただし、純水若しくは軟水でボイラ内を満水にした後、ボイラ内に中和性アミンを添加してもよい。
【０００９】
本発明において用いられる中和性アミンは、具体的にはモノエタノールアミン、モノイソプロパノールアミン、シクロヘキシルアミン、２−アミノ−２−メチル−１−プロパノール、ジエチルエタノールアミンおよびモルホリンからなる群より選ばれる。これら中和性アミンは、一種のみで用いてもよいが、２種以上を組み合わせて使用してもよい。上記の中和性アミンの中でも、シクロヘキシルアミン、モルホリンおよびジエチルエタノールアミンはＦＤＡ規格のボイラ用添加剤としても使用が認められており、また２−アミノ−２−メチル−１−プロパノールはＦＤＡ規格の間接食品添加物（secondary direct food additives）に記載されており、人体に対する安全性が高い。
【００１０】
中和性アミンは、純水若しくは軟水中に好ましくは５０〜２０００ｍｇ／Ｌｉｔｅｒの割合で添加され、更に好ましくは１００〜１５００ｍｇ／Ｌｉｔｅｒ、特に好ましくは２００〜１０００ｍｇ／Ｌｉｔｅｒであることが望ましい。特に中和性アミンの添加量が１００ｍｇ／Ｌｉｔｅｒ以上であると、十分な防食効果を得ることができ、添加量が増えるほど防食効果が高くなる。なお添加量は前記上限を越してもかまわないが、経済性の点から２０００ｍｇ／Ｌｉｔｅｒ以下であることが好ましい。中和性アミンを添加した水のｐＨは９．５以上、好ましくは１０以上とする。
【００１１】
中和性アミンは、純水若しくは軟水に添加される。本発明において軟水とは、軟水処理を施した水を意味し、具体的には硬度（ＣａＣＯ3）が１ｍｇ／Ｌｉｔｅｒ以下のものであることが好ましい。
【００１２】
ボイラを満水にする純水若しくは軟水には、中和性アミンの他、必要に応じてその他既存のボイラ水処理用添加剤が添加されてもよい。なおヒドラジンや亜硝酸ナトリウムは使用しない。
【００１３】
上記のようにして中和性アミン液で満水にされたボイラの保存が長期にわたる場合には、定期的に点検を行うことが好ましい。例えば月に１〜２回程度中和性アミンの濃度を調査し、中和性アミンの濃度またはｐＨが低下している場合には、中和性アミンをボイラ内に追加注入することが好ましい。
中止期間の終了後、ボイラを再度運転開始させるときには、全ブローして内部を点検したのち、水張りして運転を開始させる。
【００１４】
【００１４】
【発明の効果】
以上の通り、本発明によれば、ボイラ水のブロー後、純水若しくは軟水に中和性アミンを含有させ、ヒドラジンおよび亜硝酸ナトリウムを含有させないｐＨ９．５以上の特定の中和性アミン液でボイラを満水にして、ボイラ内に存在する酸性物質を中和してボイラ缶水のｐＨを上昇させ、ボイラ缶水をアルカリ性に保つことにより、ボイラの腐食を防止し保存するようにしたため、ボイラを中和性アミン液で満水させる方法によって休止中のボイラの腐食を簡単に防止できるので、本発明の防食方法はどのような種類のボイラにも適用可能であり、例えば乾燥保存方法が適用できないボイラや、亜硝酸ナトリウム等の固体の防食剤を用いる満水保存が適用できないボイラであっても、腐食を防止することができる。
さらに本発明のボイラの防食方法を用いると、ボイラが長期間にわたって休止し保管される場合であっても、高い防食効果が維持される。
また本発明で用いられる中和性アミンのうち、米国ＦＤＡ規格に記載されているシクロヘキシルアミン、モルホリンおよびジエチルエタノールアミンは人体に対する安全性が高いので、ボイラ休止後の運転再開後に得られるボイラ水は、人体に有害な物質を含む可能性が低い。
【００１５】
【発明の実施の形態】
以下、具体例によってさらに本発明を説明するが、本発明はこれらに限定されるものではない。
実施例１〜２０
純水に表１に示す薬剤を添加して５００ｍｌにメスアップしたものを容量５００ｍＬのコニカルビーカーに入れ、ここに鋼材性試験片（１ｍｍ×３０ｍｍ×５０ｍｍ）を２枚浸漬し、ビーカー上部にプラスチック製シートで蓋をして室温にて静置した。
表１に示した期間経過後に試験片を引き上げ、脱錆処理して腐食減量を測定し、腐食速度を求めた。結果を表１に示す。
なお、表中のＭＥＡはモノエタノールアミン、ＭＩＰＡはモノイソプロパノールアミン、ＭＯＲはモルホリン、ＤＥＥＡはジエチルエタノールアミン、ＡＭＰは２−アミノ−２−メチル−１−プロパノール、ＣＨＡはシクロヘキシルアミンを示す。
【００１６】
比較例１〜３
比較例１は、防食のための薬剤を添加しない点以外は実施例と同様に試験を行った。比較例２および３は、防食効果を得るための薬剤として中和性アミンの代わりにヒドラジンを用いた点以外は実施例と同様に試験を行った。
【００１７】
【表１】
表１の結果より、実施例１〜２０において比較例のヒドラジンとほぼ同等若しくはそれ以上の防食効果を得られたことがわかる。また、中和性アミンの含有量が多いほど、防食効果が高くなった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an anticorrosion method for a boiler that is at rest, and more particularly to an anticorrosion method for a boiler in which the boiler is filled with water containing chemicals and stored.
[0002]
[Prior art]
When a boiler plant is paused for a relatively long period of time, such as two weeks or longer, it is necessary to prevent boiler corrosion during the pause. For preventing corrosion, a dry storage method has been conventionally employed in which boiler water is completely blown and the inside of the boiler can is sealed with a desiccant such as silica gel placed in the boiler can.
However, in recent years, the structure of boilers has become complicated, and there are increasing cases in which boiler water cannot be completely blown. In the dry preservation method, when the rest period is long, the desiccant must be periodically replaced, which is troublesome.
[0003]
When boiler water cannot be completely blown, hydrazine is added to pure water or soft water at a rate of 100 to 1000 mg / L, and the boiler is fully stored, or sodium nitrite is added at 200 to 500 mg / L to store the boiler at full The method to do is adopted.
However, since hydrazine is suspected to be involved in carcinogenicity, its use is regarded as a problem. In addition, since sodium nitrite is a solid component, the boiler having a super heater and a turbine can be applied only when backflow cleaning with pure water is possible after holding.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to propose a corrosion prevention method for a boiler that can be applied to any boiler, has high safety to the human body, and can obtain a high anticorrosion effect over a long period of time.
[0005]
[Means for Solving the Problems]
The present invention is the following boiler anticorrosion method.
(1) After blowing boiler water,
Fill the boiler with a neutralizing amine solution having a pH of 9.5 or higher that contains neutralizing amine in pure water or soft water and does not contain hydrazine and sodium nitrite ,
To raise the pH of the boiler water to neutralize the acidic materials present in the boiler, by keeping the boiler water alkalinity, a dormant corrosion process of the boiler to save prevent corrosion of the boiler,
The neutralizing amine is at least one compound selected from the group consisting of monoethanolamine, monoisopropanolamine, cyclohexylamine, 2-amino-2-methyl-1-propanol, diethylethanolamine and morpholine. Corrosion prevention method for boilers during dormancy .
(2) The anticorrosion method for a dormant boiler according to (1) above, wherein the neutralizing amine solution has a neutralizing amine concentration of 50 to 2000 mg / liter.
[0006]
The anticorrosion method of the present invention can be applied to any boiler, and specifically includes a round boiler, a water tube boiler, a once-through boiler, a special boiler, and the like. These boilers may be any of low pressure, medium pressure, and high pressure. The anticorrosion method of the present invention can also be applied to a boiler that cannot be backwashed in a boiler having a super heater or a turbine.
[0007]
The anticorrosion method of this invention blows boiler water first about such a boiler. It is preferable to blow all the boiler water in the boiler. However, if full blow is not possible, after discharging boiler water as much as possible, blow is performed so as to replace the boiler water remaining in the boiler or pipe.
[0008]
After blowing, neutralizing amine is added to pure water or soft water, and the boiler is filled with a neutralizing amine solution having a pH of 9.5 or more without adding hydrazine and sodium nitrite . Neutralizing amine neutralizes carbon dioxide and other acidic substances present in the boiler to raise the pH of the boiler can water and keep the boiler can water alkaline so that corrosion of the boiler can be prevented for a long time. The The neutralizing amine solution can be obtained by mixing a neutralizing amine in advance with pure water or soft water. However, the neutralizing amine may be added to the boiler after the boiler is filled with pure water or soft water.
[0009]
The neutralizing amine used in the present invention is specifically selected from the group consisting of monoethanolamine, monoisopropanolamine, cyclohexylamine, 2-amino-2-methyl-1-propanol, diethylethanolamine and morpholine. These neutralizing amines may be used alone or in combination of two or more. Among the above neutralizing amines, cyclohexylamine, morpholine and diethylethanolamine have been approved for use as FDA boiler additives, and 2-amino-2-methyl-1-propanol is FDA standard. It is described in secondary direct food additives and is highly safe for the human body.
[0010]
The neutralizing amine is preferably added to pure water or soft water at a rate of 50 to 2000 mg / liter, more preferably 100 to 1500 mg / liter, and particularly preferably 200 to 1000 mg / liter. In particular, when the addition amount of the neutralizing amine is 100 mg / liter or more, a sufficient anticorrosion effect can be obtained, and the anticorrosion effect increases as the addition amount increases. The amount added may exceed the upper limit, but is preferably 2000 mg / liter or less from the viewpoint of economy. PH of water added neutralizing amine 9.5 or more, preferably shall be the 10 or more.
[0011]
The neutralizing amine is added to pure water or soft water. In the present invention, soft water means water that has been subjected to soft water treatment, and specifically has a hardness (CaCO 3 ) of 1 mg / liter or less.
[0012]
In addition to the neutralizing amine, other existing boiler water treatment additives may be added to the pure water or soft water that fills the boiler . Such your hydrazine and sodium nitrite is not used.
[0013]
When the boiler filled with the neutralizing amine solution as described above is stored for a long period of time, it is preferable to periodically check. For example, the concentration of the neutralizing amine is investigated once or twice a month, and when the neutralizing amine concentration or pH is lowered, it is preferable to additionally inject the neutralizing amine into the boiler.
When the boiler is started again after the stop period is over, the blower is fully blown and the inside is inspected, and then water is filled to start the operation.
[0014]
[0014]
【Effect of the invention】
As described above, according to the present invention, after the boiler water is blown, a specific neutralizing amine solution having a pH of 9.5 or more that contains pure water or soft water and does not contain hydrazine and sodium nitrite. The boiler is filled with water, neutralizes the acidic substances present in the boiler, raises the pH of the boiler can water, and keeps the boiler can water alkaline so that the boiler is prevented from being corroded and stored. Can be easily prevented by the method of filling water with a neutralizing amine solution, the anticorrosion method of the present invention can be applied to any type of boiler, for example, dry storage method is not applicable Corrosion can be prevented even with a boiler or a boiler that is not applicable to full water storage using a solid anticorrosive agent such as sodium nitrite.
Furthermore, when the boiler anticorrosion method of the present invention is used, a high anticorrosion effect is maintained even when the boiler is suspended and stored for a long period of time.
Among the neutralizing amines used in the present invention, cyclohexylamine, morpholine and diethylethanolamine described in US FDA standards are highly safe for human bodies, so the boiler water obtained after resuming operation after boiler shutdown is , It is unlikely to contain substances harmful to the human body.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be further described with reference to specific examples, but the present invention is not limited thereto.
Examples 1-20
Add the chemicals shown in Table 1 to pure water and make up to 500 ml in pure water, put it in a 500 ml conical beaker, immerse two steel specimens (1 mm x 30 mm x 50 mm), and put plastic on the top of the beaker The product was covered with a sheet and allowed to stand at room temperature.
After the elapse of the period shown in Table 1, the test piece was pulled up, derusted and subjected to corrosion weight loss measurement to determine the corrosion rate. The results are shown in Table 1.
In the table, MEA is monoethanolamine, MIPA is monoisopropanolamine, MOR is morpholine, DEEA is diethylethanolamine, AMP is 2-amino-2-methyl-1-propanol, and CHA is cyclohexylamine.
[0016]
Comparative Examples 1-3
Comparative Example 1 was tested in the same manner as in the Examples except that no anticorrosive agent was added. Comparative Examples 2 and 3 were tested in the same manner as in the Examples except that hydrazine was used in place of the neutralizing amine as a drug for obtaining an anticorrosive effect.
[0017]
[Table 1]
From the results of Table 1, it can be seen that in Examples 1 to 20, the anticorrosive effect almost equal to or higher than that of the hydrazine of the comparative example was obtained. Moreover, the anti-corrosion effect became high, so that there was much content of neutralizing amine.
Claims (2)
純水若しくは軟水に中和性アミンを含有させ、ヒドラジンおよび亜硝酸ナトリウムを含有させないｐＨ９．５以上の中和性アミン液でボイラを満水にして、
ボイラ内に存在する酸性物質を中和してボイラ缶水のｐＨを上昇させ、ボイラ缶水をアルカリ性に保つことにより、ボイラの腐食を防止し保存する休止中ボイラの防食方法であって、
前記中和性アミンは、モノエタノールアミン、モノイソプロパノールアミン、シクロヘキシルアミン、２−アミノ−２−メチル−１−プロパノール、ジエチルエタノールアミンおよびモルホリンからなる群より選ばれる少なくとも一種の化合物であることを特徴とする休止中ボイラの防食方法。After blowing boiler water
Fill the boiler with a neutralizing amine solution having a pH of 9.5 or higher that contains neutralizing amine in pure water or soft water and does not contain hydrazine and sodium nitrite ,
To raise the pH of the boiler water to neutralize the acidic materials present in the boiler, by keeping the boiler water alkalinity, a dormant corrosion process of the boiler to save prevent corrosion of the boiler,
The neutralizing amine is at least one compound selected from the group consisting of monoethanolamine, monoisopropanolamine, cyclohexylamine, 2-amino-2-methyl-1-propanol, diethylethanolamine and morpholine. Corrosion prevention method for boilers during dormancy .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000322724A JP5017742B2 (en) | 2000-10-23 | 2000-10-23 | Anti-corrosion method for boilers during suspension |
Applications Claiming Priority (1)
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| ATE293155T1 (en) * | 2001-09-27 | 2005-04-15 | Kurita Europ Gmbh | METHOD FOR PREVENTING POLLUTION AND CORROSION CAUSED BY AMMONIUM CHLORIDE AND AMMONIUM SULFATE |
| JP3962919B2 (en) * | 2002-11-12 | 2007-08-22 | 栗田工業株式会社 | Metal anticorrosive, metal anticorrosion method, hydrogen chloride generation inhibitor and method for preventing hydrogen chloride generation in crude oil atmospheric distillation equipment |
| JP3855961B2 (en) * | 2003-04-28 | 2006-12-13 | 栗田工業株式会社 | Oxygen absorber and deoxygenation method |
| JP4710561B2 (en) * | 2005-11-16 | 2011-06-29 | 栗田工業株式会社 | Anti-corrosion method for boilers during suspension |
| JP5691134B2 (en) * | 2009-03-31 | 2015-04-01 | 栗田工業株式会社 | How to treat boilers that are not operating |
| JP5849409B2 (en) * | 2011-03-08 | 2016-01-27 | 栗田工業株式会社 | Boiler water treatment agent and boiler water treatment method |
| JP7150594B2 (en) * | 2018-12-27 | 2022-10-11 | 三菱重工業株式会社 | Boiler plant cleaning storage method and cleaning storage device |
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| JPH04110505A (en) * | 1990-08-28 | 1992-04-13 | Takuma Co Ltd | Corrosion preventing method of boiler |
| JPH09323083A (en) * | 1996-06-06 | 1997-12-16 | Kurita Water Ind Ltd | Device for treating boiler feed water |
| JPH11323579A (en) * | 1998-05-18 | 1999-11-26 | Toshiba Corp | Humidity controlling method in clean room |
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