JP3774802B2 - Corrosion prevention method for exhaust heat boiler - Google Patents
Corrosion prevention method for exhaust heat boiler Download PDFInfo
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- JP3774802B2 JP3774802B2 JP09126598A JP9126598A JP3774802B2 JP 3774802 B2 JP3774802 B2 JP 3774802B2 JP 09126598 A JP09126598 A JP 09126598A JP 9126598 A JP9126598 A JP 9126598A JP 3774802 B2 JP3774802 B2 JP 3774802B2
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Description
【０００１】
【発明の属する技術分野】
この発明は、重油を燃料としかつＤＳＳ（Daily Start & Stop）運転を実施するガスタービン発電プラント用排熱ボイラの低温腐食防止方法に関する。
【０００２】
【従来の技術】
従来のガスタービン発電プラントは、燃料として天然ガスや灯油を用いたものであり、また重油（硫黄分を含んでいる）を燃料とするガスタービンもあるが、これは連続運転するのが原則であって、ＤＳＳ運転は後述する硫酸腐食の問題のために殆どなされなかった。
【０００３】
【発明が解決しようとする課題】
発電コストの低減の目的で上記ＤＳＳ運転ガスタービン発電プラントの燃料として重油を用いると、排ガス後流域において、同プラント停止時の温度低下に伴って結露した硫酸によって、排熱ボイラが腐食するという問題がある。
【０００４】
この発明は、重油を燃料とし、ＤＳＳ運転を実施するガスタービン発電プラントにおいて、その排ガス後流域に設置された排ガスボイラの低温腐食の発生を効果的に防止することができる方法を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明による排熱ボイラの腐食防止方法は、発電プラント停止時にボイラの排ガス入口と出口を閉じ、低圧ドラム (5) の圧力が規定値まで下がった時に循環水ポンプを起動して低圧ドラム(5)内のドラム水を低圧節炭器の管群(4)に循環させ、またこれと同時に、保缶用蒸気を低圧蒸発器の降水管に供給して、該降水管を経た後に該保缶用蒸気が低圧ドラムおよび管群に供給されるようにし、また、高圧ドラムの圧力が規定値まで下がった時に保缶用蒸気を高圧蒸発器の降水管に供給して、該降水管を経た後に該保缶用蒸気が高圧ドラムおよび高圧節炭器の管群に供給されるようにすることによって、低圧節炭器、低圧蒸発器、低圧過熱器、高圧節炭器、高圧蒸発器および高圧過熱器の温度を硫酸結露による低温腐食を防止するに必要な温度以上に保持することを特徴とする方法である。
【０００６】
ボイラのケーシング(32)の外皮(33)の内面には耐硫酸塗装を施すことが好ましい。
【０００７】
また、排ガス温度が３５０℃未満の領域でケーシング(32)の内皮(34)を耐硫酸腐食鋼で構成することも好ましい。
【０００８】
【発明の実施の形態】
つぎに、本発明を実施例により具体的に説明する。
【０００９】
朝方、ガスタービン発電プラントの運転開始とともに、図１に示すように、その後流域にある排熱ボイラの排ガス入口ダンパ(1) と出口ダンパ(2) が開かれる。排熱ボイラは、入口から出口に直列状に配された高圧過熱器、高圧蒸発器、高圧節炭器、低圧過熱器、低圧蒸発器および低圧節炭器からなる。入口ダンパ(1) および出口ダンパ(2) はギロチン式、フラッパ式またはルーバー式のものであり、耐熱性・耐硫酸腐食性材料からなる。
【００１０】
脱気器から来る水は低圧給水ポンプ(3) によって低圧節炭器の管群(4) を通され、ついで気水分離用の低圧ドラム(5) へ送られる。低圧ドラム(5) 内の水の一部はボイラ外を通る降水管(6) を流下し、低圧蒸発器の管群(7) を上昇し、気水混合化する。生じた気水混合物は低圧ドラム(5) へ戻される。低圧ドラム(5) 内の低圧蒸気は低圧過熱器の管群(8) を通され、ボイラ外のバルブ(9) を経て低圧タービンまたは脱気器へ送られる。
【００１１】
低圧ドラム(5) 内の水の残部はボイラ外の高圧給水ポンプ(39)を経て高圧節炭器の管群(10)を通され、ついで気水分離用の高圧ドラム(11)へ送られる。
【００１２】
高圧ドラム(11)内の水の一部はボイラ外を通る降水管(12)を流下し、高圧蒸発器の管群(13)を上昇し、気水混合化する。生じた気水混合物は高圧ドラム(11)へ戻される。高圧ドラム(11)内の蒸気は高圧過熱器の管群(23)を通され、ボイラ外のバルブ(14)を経て高圧タービンへ送られる。
【００１３】
夕方、ガスタービン発電プラントの運転が停止されると、これに伴って、排ガス入口ダンパ(1) と出口ダンパ(2) が閉じられ、低圧給水ポンプ(3) が止められる。低圧ドラム(5) の圧力が規定圧まで下がった時、循環水ポンプ(15)が起動され、低圧ドラム(5) 内のドラム水が低圧節炭器の管群(4) に循環させられる。これによって、低圧節炭器の温度が硫酸結露による低温腐食を防止するに必要な温度以上に保持される。
【００１４】
また、低圧ドラム(5) 内の圧力が規定圧に下がった時、バルブ(17)が開かれ、補助ボイラ(18)から低圧蒸発器の降水管(6) へ保缶用蒸気が供給され、低圧蒸発器の降水管(6) を上昇し、低圧ドラム(5) に入り、逆循環力で管群(7) を下降し、降水管(6) を経て低圧ドラム(5) へ戻る。これによって、低圧蒸発器の温度が硫酸結露による低温腐食を防止するに必要な温度以上に保持される。バルブ(17)は保缶用蒸気の供給を制御し、圧力検出装置(16)は低圧ドラム(5) 内の圧力を検出し、この信号によりバルブ(17)が蒸気圧を一定に保つ。低圧蒸気は低圧ドラム(5) から低圧過熱器の管群(8) を経てドレンとしてバルブ(25)から抜き出される。
【００１５】
高圧ドラム(11)内の圧力が規定圧まで下がった時、バルブ(20)が開かれ、補助ボイラ(18)から高圧蒸発器の降水管(12)へ保缶用蒸気が供給され、高圧蒸発器の降水管(12)を上昇し、高圧ドラム(11)に入り、逆循環力で管群(13)を下降し、降水管(12)を経て高圧ドラム(11)へ戻る。これによって、高圧蒸発器の温度が硫酸結露による低温腐食を防止するに必要な温度以上に保持される。バルブ(20)は保缶用蒸気の供給を制御し、圧力検出装置(19)は高圧ドラム(11)内の圧力を検出し、この信号によりバルブ(20)が蒸気圧を一定に保つ。高圧蒸気は高圧ドラム(11)から高圧過熱器の管群(23)を経てドレンとしてバルブ(26)から抜き出される。
【００１６】
低圧ドラム(5) および高圧ドラム(11)に溜まって来るドレンは水位の上昇を 来たすのでブローバルブ(30)(31)で排出し、水位を維持する。
【００１７】
高圧節炭器は低圧蒸発器と高圧蒸発器の間にあるので、高圧節炭器の管群(10)にドラム水または保缶用蒸気の循環を行わなくても、硫酸結露による低温腐食を防止するに必要な温度は保持される。ただし、低圧ドラム(5) 内のドラム水を高圧節炭器の管群(10)にも循環させ、高圧節炭器を積極的に昇温するようにすることもできる。
【００１８】
朝方、ガスタービン発電プラントの運転再開に伴ってボイラの運転も再開するには、まず、空気抜きバルブ(21)(22)(24)(27)が運転再開前に開かれ、過熱器および節炭器内のエアー溜まりが急速に排出される。運転再開前にドレンブローバルブ(28)(29)が開かれて低圧節炭器および高圧節炭器内の水が少量排出されるが、つぎにブローバルブ(37)(38)を開いて同節炭器内の水が新しい水に入れ換えられる。低圧過熱器の管(8) 底部および高圧過熱器の管(23)底部のドレン抜きバルブ(25)(26)は、運転再開前に開かれ、保缶用蒸気のドレンが十分抜け切っていることを確認する。
【００１９】
保缶蒸気の供給によりドラム(5)(11) 内の水位が上昇した時は、バルブ(30)(31)が開かれ、同水位が所定値に保たれる。
【００２０】
ボイラのケーシング(32)は、図３に示すように、外皮(33)と内皮(34)とこれらの間に介在された保温材(35)とからなる。外皮(33)の内面には耐硫酸塗料が膜厚約１００μｍで塗布されている。この塗膜(36)は日本ペイント社製「Silica coating」で形成するのが好ましい。
【００２１】
排ガス温度が３５０℃以上の領域、例えば高圧蒸発器のガス流れ方向中間部から前流側では、ケーシング(32)の内皮(34)は厚さ２ｍｍのＳＵＳ３０４で構成され、他方、排ガス温度が３５０℃未満の領域、例えば高圧蒸発器のガス流れ方向中間部から後流側ではケーシング(32)の内皮(34)は厚さ３．４ｍｍの耐硫酸腐食鋼で構成されている。耐硫酸腐食鋼としては住友金属社製ＣＲＩＡ（１．２Ｃｒ−０．３Ｃｒ−０．０２Ｓ）が好ましい。
【００２２】
【発明の効果】
本発明方法によって、低圧節炭器、低圧蒸発器、低圧過熱器、高圧節炭器、高圧蒸発器および高圧過熱器の温度を硫酸結露による低温腐食を防止するに必要な温度以上に保持することができ、これによって、排ガスボイラの低温腐食の発生を効果的に防止することができる。
【図面の簡単な説明】
【図１】 排熱ボイラの運転状態を示す概略図である。
【図２】 排熱ボイラの保缶状態を示す概略図である。
【図３】 ボイラのケーシング構造を示す断面図である。
【符号の説明】
４：低圧節炭器の管群
５：低圧ドラム
７：低圧蒸発器の管群
１３：高圧蒸発器の管群
３２：ケーシング
３３：外皮
３４：内皮[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for preventing low temperature corrosion of an exhaust heat boiler for a gas turbine power plant that uses heavy oil as fuel and performs DSS (Daily Start & Stop) operation.
[0002]
[Prior art]
Conventional gas turbine power plants use natural gas or kerosene as fuel, and there are gas turbines that use heavy oil (which contains sulfur) as fuel. Thus, the DSS operation was hardly performed due to the problem of sulfuric acid corrosion described later.
[0003]
[Problems to be solved by the invention]
When heavy oil is used as the fuel for the above-mentioned DSS operation gas turbine power plant for the purpose of reducing power generation costs, the exhaust heat boiler corrodes in the wake area of the exhaust gas due to the sulfuric acid that is condensed due to the temperature drop when the plant stops. There is.
[0004]
The present invention provides a method capable of effectively preventing the occurrence of low-temperature corrosion of an exhaust gas boiler installed in the exhaust gas wake area in a gas turbine power plant that uses heavy oil as fuel and performs DSS operation. Objective.
[0005]
[Means for Solving the Problems]
The method for preventing corrosion of a waste heat boiler according to the present invention closes the exhaust gas inlet and outlet of the boiler when the power plant is stopped , starts the circulating water pump when the pressure of the low pressure drum (5) drops to a specified value, and starts the low pressure drum (5 ) Is circulated to the tube group (4) of the low-pressure economizer, and at the same time, the can-carrying steam is supplied to the downcomer of the low-pressure evaporator. Steam is supplied to the low-pressure drum and the tube group, and when the pressure of the high-pressure drum falls to a specified value, the steam for holding can is supplied to the downcomer of the high-pressure evaporator, and after passing through the downcomer by vapor-holding cans to be supplied to the tube bundle of the high-pressure drum and a high-pressure economizer, a low-pressure economizer, a low pressure evaporator, the low-pressure over-heater, a high-pressure economizer, a high pressure evaporator and a high pressure to a temperature above that required to prevent cold corrosion temperature of the over-heater with sulfuric acid dew A method which is characterized in that lifting.
[0006]
It is preferable to apply sulfuric acid resistant coating to the inner surface of the outer shell (33) of the casing (32) of the boiler.
[0007]
It is also preferable that the inner surface (34) of the casing (32) is made of sulfuric acid corrosion resistant steel in a region where the exhaust gas temperature is less than 350 ° C.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be specifically described with reference to examples.
[0009]
In the morning, with the start of operation of the gas turbine power plant, as shown in FIG. 1, the exhaust gas inlet damper (1) and the outlet damper (2) of the exhaust heat boiler in the rear basin are opened. The exhaust heat boiler includes a high-pressure superheater, a high-pressure evaporator, a high-pressure economizer, a low-pressure superheater, a low-pressure evaporator and a low-pressure economizer arranged in series from the inlet to the outlet. The inlet damper (1) and outlet damper (2) are of the guillotine type, flapper type or louver type, and are made of a heat resistant and sulfuric acid corrosion resistant material.
[0010]
The water coming from the deaerator is passed through the tube group (4) of the low-pressure economizer by the low-pressure feed pump (3), and then sent to the low-pressure drum (5) for separating water. Part of the water in the low-pressure drum (5) flows down the downcomer pipe (6) that passes outside the boiler, rises up the tube group (7) of the low-pressure evaporator, and mixes with water. The resulting air / water mixture is returned to the low pressure drum (5). The low-pressure steam in the low-pressure drum (5) is passed through the tube group (8) of the low-pressure superheater and sent to the low-pressure turbine or deaerator through the valve (9) outside the boiler.
[0011]
The remainder of the water in the low-pressure drum (5) passes through the high-pressure economizer tube group (10) via the high-pressure feed pump (39) outside the boiler, and is then sent to the high-pressure drum (11) for steam-water separation. .
[0012]
A part of the water in the high-pressure drum (11) flows down the downcomer pipe (12) passing outside the boiler, ascends the pipe group (13) of the high-pressure evaporator, and mixes with water. The resulting air / water mixture is returned to the high pressure drum (11). The steam in the high-pressure drum (11) passes through the tube group (23) of the high-pressure superheater, and is sent to the high-pressure turbine through the valve (14) outside the boiler.
[0013]
When the operation of the gas turbine power plant is stopped in the evening, the exhaust gas inlet damper (1) and the outlet damper (2) are closed and the low-pressure feed water pump (3) is stopped. When the pressure of the low-pressure drum (5) drops to the specified pressure, the circulating water pump (15) is activated and the drum water in the low-pressure drum (5) is circulated to the tube group (4) of the low-pressure economizer. As a result, the temperature of the low-pressure economizer is maintained above the temperature required to prevent low-temperature corrosion due to sulfuric acid condensation.
[0014]
When the pressure in the low-pressure drum (5) drops to the specified pressure, the valve (17) is opened, and steam for holding can is supplied from the auxiliary boiler (18) to the downcomer pipe (6) of the low-pressure evaporator, It goes up the downcomer pipe (6) of the low-pressure evaporator, enters the low-pressure drum (5), descends the tube group (7) by reverse circulation, and returns to the low-pressure drum (5) through the downcomer pipe (6). As a result, the temperature of the low-pressure evaporator is maintained at or above the temperature necessary to prevent low-temperature corrosion due to sulfuric acid condensation. The valve (17) controls the supply of steam for holding the can, and the pressure detection device (16) detects the pressure in the low pressure drum (5), and the valve (17) keeps the vapor pressure constant by this signal. The low-pressure steam is extracted from the valve (25) as drainage from the low-pressure drum (5) through the tube group (8) of the low-pressure superheater.
[0015]
When the pressure in the high-pressure drum (11) drops to the specified pressure, the valve (20) is opened, and steam for holding cans is supplied from the auxiliary boiler (18) to the downcomer pipe (12) of the high-pressure evaporator, and high-pressure evaporation Ascend the downcomer pipe (12), enter the high pressure drum (11), descend the pipe group (13) by reverse circulation force, and return to the high pressure drum (11) through the downcomer pipe (12). As a result, the temperature of the high-pressure evaporator is maintained at a temperature higher than that required to prevent low-temperature corrosion due to sulfuric acid condensation. The valve (20) controls the supply of steam for holding the can, and the pressure detector (19) detects the pressure in the high-pressure drum (11), and the valve (20) keeps the vapor pressure constant by this signal. The high-pressure steam is extracted from the valve (26) as a drain from the high-pressure drum (11) through the tube group (23) of the high-pressure superheater.
[0016]
Drain accumulated in the low-pressure drum (5) and high-pressure drum (11) causes the water level to rise, and is discharged by the blow valves (30) and (31) to maintain the water level.
[0017]
Since the high-pressure economizer is located between the low-pressure evaporator and the high-pressure evaporator, low-temperature corrosion due to sulfuric acid condensation can be prevented without circulating drum water or canister steam in the tube group (10) of the high-pressure economizer. The temperature necessary to prevent is maintained. However, it is also possible to circulate the drum water in the low pressure drum (5) also to the tube group (10) of the high pressure economizer to positively increase the temperature of the high pressure economizer.
[0018]
In the morning, in order to resume the operation of the boiler as the gas turbine power plant resumes operation, first, the air vent valves (21), (22), (24), and (27) are opened before the operation is resumed, and the superheater and the economizer are saved. The air reservoir in the chamber is discharged rapidly. Before resuming operation, the drain blow valves (28) and (29) are opened to discharge a small amount of water in the low-pressure and high-pressure economizers.Then, the blow valves (37) and (38) are opened to The water in the economizer is replaced with new water. Low pressure superheater pipe (8) Bottom and high pressure superheater pipe (23) Drain vent valves (25) and (26) at the bottom are opened before resuming operation, and the drainage of the steam for holding cans is sufficiently removed. Make sure.
[0019]
When the water level in the drums (5) and (11) rises due to the supply of canned steam, the valves (30) and (31) are opened, and the water levels are kept at a predetermined value.
[0020]
As shown in FIG. 3, the boiler casing (32) includes an outer skin (33), an inner skin (34), and a heat insulating material (35) interposed therebetween. The inner surface of the outer skin (33) is coated with a sulfuric acid resistant paint with a film thickness of about 100 μm. This coating film (36) is preferably formed by “Silica coating” manufactured by Nippon Paint Co., Ltd.
[0021]
In the region where the exhaust gas temperature is 350 ° C. or higher, for example, from the middle in the gas flow direction of the high-pressure evaporator to the upstream side, the inner skin (34) of the casing (32) is composed of SUS304 with a thickness of 2 mm, while the exhaust gas temperature is 350 In the region below 0 ° C., for example, in the gas flow direction middle portion of the high-pressure evaporator, the inner skin (34) of the casing (32) is made of sulfuric acid corrosion resistant steel having a thickness of 3.4 mm. The sulfuric acid corrosion resistant steel is preferably CRIA (1.2Cr-0.3Cr-0.02S) manufactured by Sumitomo Metals.
[0022]
【The invention's effect】
By the method of the present invention retain the low pressure economizer, a low pressure evaporator, the low-pressure over-heater, a high-pressure economizer, a temperature higher than necessary to prevent a temperature low corrosion by sulfuric acid condensation of high-pressure evaporator and the high pressure over-heater This can effectively prevent the low temperature corrosion of the exhaust gas boiler.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an operating state of a heat exhaust boiler.
FIG. 2 is a schematic view showing a can holding state of a heat exhaust boiler.
FIG. 3 is a cross-sectional view showing a boiler casing structure.
[Explanation of symbols]
4: Low-pressure economizer tube group 5: Low-pressure drum 7: Low-pressure evaporator tube group 13: High-pressure evaporator tube group 32: Casing 33: Outer skin 34: Endothelium
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09126598A JP3774802B2 (en) | 1998-04-03 | 1998-04-03 | Corrosion prevention method for exhaust heat boiler |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09126598A JP3774802B2 (en) | 1998-04-03 | 1998-04-03 | Corrosion prevention method for exhaust heat boiler |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11287401A JPH11287401A (en) | 1999-10-19 |
| JP3774802B2 true JP3774802B2 (en) | 2006-05-17 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP09126598A Expired - Fee Related JP3774802B2 (en) | 1998-04-03 | 1998-04-03 | Corrosion prevention method for exhaust heat boiler |
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| Country | Link |
|---|---|
| JP (1) | JP3774802B2 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006250493A (en) * | 2005-03-14 | 2006-09-21 | Babcock Hitachi Kk | Soot and dust trapping device for exhaust heat recovery boiler |
| JP5613921B2 (en) * | 2010-11-29 | 2014-10-29 | バブコック日立株式会社 | Exhaust heat recovery boiler and method for preventing corrosion in the can |
| CN103353100B (en) * | 2013-07-22 | 2015-10-28 | 清华大学 | A kind of single flow heat-exchanger rig |
| CN103471073B (en) * | 2013-09-06 | 2016-03-23 | 昆山市利昆机电设备有限公司 | There is the waste heat boiler of multiple vertical type module |
| CN105091339A (en) * | 2015-05-12 | 2015-11-25 | 重庆大学 | Flue gas condensation type waste heat recovery heat exchange device for gas water heater |
| CN106958809B (en) * | 2017-05-16 | 2023-05-05 | 中国华电科工集团有限公司 | Low-temperature economizer capable of preventing dust deposit and control method thereof |
-
1998
- 1998-04-03 JP JP09126598A patent/JP3774802B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH11287401A (en) | 1999-10-19 |
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