JP2014091843A - Corrosion prevention method for heat exchanger narrow pipe made of copper alloy - Google Patents
Corrosion prevention method for heat exchanger narrow pipe made of copper alloyInfo
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- JP2014091843A JP2014091843A JP2012241906A JP2012241906A JP2014091843A JP 2014091843 A JP2014091843 A JP 2014091843A JP 2012241906 A JP2012241906 A JP 2012241906A JP 2012241906 A JP2012241906 A JP 2012241906A JP 2014091843 A JP2014091843 A JP 2014091843A
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- copper alloy
- heat exchanger
- water
- oxidizing agent
- iron salt
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Links
- 229910000881 Cu alloy Inorganic materials 0.000 title claims abstract description 35
- 238000000034 method Methods 0.000 title claims abstract description 17
- 238000005536 corrosion prevention Methods 0.000 title claims abstract description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 27
- 239000007800 oxidant agent Substances 0.000 claims abstract description 23
- 150000002505 iron Chemical class 0.000 claims abstract description 17
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 12
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000005708 Sodium hypochlorite Substances 0.000 claims abstract description 6
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000000460 chlorine Substances 0.000 claims abstract description 5
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 5
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000004155 Chlorine dioxide Substances 0.000 claims abstract description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 4
- 235000019398 chlorine dioxide Nutrition 0.000 claims abstract description 4
- 238000005259 measurement Methods 0.000 claims abstract description 4
- 239000001301 oxygen Substances 0.000 claims abstract description 4
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 4
- 230000033116 oxidation-reduction process Effects 0.000 claims abstract description 3
- 230000001590 oxidative effect Effects 0.000 claims description 5
- 239000011790 ferrous sulphate Substances 0.000 claims description 4
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 4
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 4
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 4
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 claims description 3
- QDHHCQZDFGDHMP-UHFFFAOYSA-N Chloramine Chemical compound ClN QDHHCQZDFGDHMP-UHFFFAOYSA-N 0.000 claims description 3
- 229910021578 Iron(III) chloride Inorganic materials 0.000 claims description 3
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 3
- FNXLCIKXHOPCKH-UHFFFAOYSA-N bromamine Chemical compound BrN FNXLCIKXHOPCKH-UHFFFAOYSA-N 0.000 claims description 3
- 229960002089 ferrous chloride Drugs 0.000 claims description 3
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 3
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 3
- RUTXIHLAWFEWGM-UHFFFAOYSA-H iron(3+) sulfate Chemical compound [Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RUTXIHLAWFEWGM-UHFFFAOYSA-H 0.000 claims description 3
- 229910000360 iron(III) sulfate Inorganic materials 0.000 claims description 3
- 238000005260 corrosion Methods 0.000 abstract description 15
- 230000007797 corrosion Effects 0.000 abstract description 15
- 230000000694 effects Effects 0.000 abstract description 8
- 230000003647 oxidation Effects 0.000 abstract description 4
- 238000007254 oxidation reaction Methods 0.000 abstract description 4
- 239000013535 sea water Substances 0.000 description 27
- -1 sulfide ions Chemical class 0.000 description 24
- 238000002474 experimental method Methods 0.000 description 18
- 238000012360 testing method Methods 0.000 description 15
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 12
- 239000000126 substance Substances 0.000 description 12
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 10
- 229910052742 iron Inorganic materials 0.000 description 9
- 238000002347 injection Methods 0.000 description 8
- 239000007924 injection Substances 0.000 description 8
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 7
- 239000000498 cooling water Substances 0.000 description 6
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical compound [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 description 5
- 230000010287 polarization Effects 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- OMZSGWSJDCOLKM-UHFFFAOYSA-N copper(II) sulfide Chemical compound [S-2].[Cu+2] OMZSGWSJDCOLKM-UHFFFAOYSA-N 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 238000005554 pickling Methods 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 241000894006 Bacteria Species 0.000 description 2
- 229910001369 Brass Inorganic materials 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 239000010951 brass Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- 229940079593 drug Drugs 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 1
- 229910000570 Cupronickel Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000011013 aquamarine Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 235000014413 iron hydroxide Nutrition 0.000 description 1
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000005504 petroleum refining Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 229940048181 sodium sulfide nonahydrate Drugs 0.000 description 1
- PVGBHEUCHKGFQP-UHFFFAOYSA-N sodium;n-[5-amino-2-(4-aminophenyl)sulfonylphenyl]sulfonylacetamide Chemical compound [Na+].CC(=O)NS(=O)(=O)C1=CC(N)=CC=C1S(=O)(=O)C1=CC=C(N)C=C1 PVGBHEUCHKGFQP-UHFFFAOYSA-N 0.000 description 1
- WMDLZMCDBSJMTM-UHFFFAOYSA-M sodium;sulfanide;nonahydrate Chemical compound O.O.O.O.O.O.O.O.O.[Na+].[SH-] WMDLZMCDBSJMTM-UHFFFAOYSA-M 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 210000005239 tubule Anatomy 0.000 description 1
- 239000003643 water by type Substances 0.000 description 1
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- Preventing Corrosion Or Incrustation Of Metals (AREA)
Abstract
Description
本発明は、銅合金製熱交換器細管の防食方法に係り、詳しくは冷却水が導入される冷却管、特に、発電プラント、石油精製プラント、石油化学プラントに設置された熱交換器の冷却管の腐食防止に好適な方法に関する。 The present invention relates to an anticorrosion method for copper alloy heat exchanger capillaries, and more particularly to a cooling pipe into which cooling water is introduced, in particular, a heat exchanger cooling pipe installed in a power plant, an oil refinery plant, and a petrochemical plant. The present invention relates to a method suitable for preventing corrosion.
発電プラント、石油精製プラント、石油化学プラントに設置されたチューブ式熱交換器には、冷却水が流通する細管(冷却管)が取り付けられており、温度の高い気体や液体と冷却水との間で熱交換が行われる。この場合、細管を通る冷却水には、河川、海等から取水された水が利用される。 Tube-type heat exchangers installed in power plants, oil refining plants, and petrochemical plants are equipped with thin tubes (cooling tubes) through which cooling water circulates, and between high-temperature gases and liquids and cooling water. Heat exchange takes place at. In this case, the water taken from the river, the sea, etc. is used for the cooling water passing through the narrow tube.
河川、海等から取水された水は、硫化物イオン(S2-)を含んでいることがあり、銅合金製熱交換器細管の腐食の原因となる。すなわち、細管を流通する水中に硫化物イオンが含まれていると、銅と硫化物イオンとの反応により硫化銅(CuS)の皮膜が細管内面に形成され、この硫化銅皮膜が細管の内面から剥離したり、あるいは硫化銅皮膜と銅との間の電位差により、細管の母材を腐食させる。特に、富栄養化した閉鎖性海域では、水中の硫酸イオンから硫化物イオンを生成させるバクテリア(硫酸イオン還元バクテリア(SRB))によって、水中の硫化物イオンの濃度が高くなり、この水を取水すると、細管の局部腐食が著しく進行する。 Water taken from rivers, seas, etc. may contain sulfide ions (S 2− ), which causes corrosion of copper alloy heat exchanger tubes. That is, if sulfide water is contained in the water flowing through the narrow tube, a copper sulfide (CuS) film is formed on the inner surface of the thin tube by the reaction of copper and sulfide ions, and this copper sulfide film is formed from the inner surface of the thin tube. The base material of the thin tube is corroded by peeling or potential difference between the copper sulfide film and copper. In particular, in eutrophied closed waters, the concentration of sulfide ions in the water is increased by bacteria that produce sulfide ions from sulfate ions in the water (sulfate ion-reducing bacteria (SRB)). In this case, the local corrosion of the tubule proceeds significantly.
細管の腐食を防止するために、細管の内面にあらかじめ酸化鉄皮膜(水酸化鉄皮膜)を形成することが有効である。しかし、冷却水中に硫化物イオンが高濃度で含まれていたり、低濃度であっても長期間に渡って含まれていると、酸化鉄皮膜が還元されて硫化鉄となり、酸化皮膜の防食性能が低下する。 In order to prevent the corrosion of the narrow tube, it is effective to form an iron oxide film (iron hydroxide film) on the inner surface of the narrow tube in advance. However, if the cooling water contains a high concentration of sulfide ions or a low concentration even over a long period of time, the iron oxide film is reduced to iron sulfide and the anticorrosion performance of the oxide film. Decreases.
特許文献1には、冷却水として取水される水中に空気を送り込むことによって当該水中の硫化物イオンを低減ないしは除去し、冷却管の腐食を防止する方法が記載されている。しかしながら、空気中の酸素による酸化だけでは硫化物イオンの酸化が十分ではなく、腐食防止効果が十分ではない。 Patent Document 1 describes a method of preventing corrosion of a cooling pipe by reducing or removing sulfide ions in the water by sending air into the water taken as cooling water. However, the oxidation of sulfide ions is not sufficient only by oxidation with oxygen in the air, and the corrosion prevention effect is not sufficient.
本発明は、上記従来技術の問題点を解消し、銅合金製熱交換器細管の腐食防止効果の高い銅合金製熱交換器細管の防食方法を提供することを目的とする。 An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for preventing corrosion of a copper alloy heat exchanger capillary having a high corrosion prevention effect on the copper alloy heat exchanger capillary.
本発明の銅合金製熱交換器細管の防食方法は、水と接触する銅合金製熱交換器細管の防食方法において、該水に、酸素よりも酸化力が強い酸化剤及び/又は鉄塩を添加することを特徴とするものである。 The anticorrosion method for copper alloy heat exchanger capillaries according to the present invention is an anticorrosion method for copper alloy heat exchanger capillaries in contact with water. It is characterized by adding.
酸化剤としては、塩素、次亜塩素酸ナトリウム、二酸化塩素、過酸化水素、クロラミン、ブロマミン、臭化物、過マンガン酸塩、鉄酸塩、オゾンの少なくとも1種が好適である。 As the oxidizing agent, at least one of chlorine, sodium hypochlorite, chlorine dioxide, hydrogen peroxide, chloramine, bromamine, bromide, permanganate, ferrate, and ozone is suitable.
鉄塩としては、硫酸第一鉄、硫酸第二鉄、塩化第一鉄、塩化第二鉄の少なくとも1種が好適である。 As the iron salt, at least one of ferrous sulfate, ferric sulfate, ferrous chloride, and ferric chloride is suitable.
本発明では、水の酸化還元電位又は前記銅合金の自然電極電位を測定し、この測定結果に基づいて酸化剤及び/又は鉄塩の添加量を制御することが好ましい。 In the present invention, it is preferable to measure the redox potential of water or the natural electrode potential of the copper alloy, and to control the addition amount of the oxidizing agent and / or iron salt based on the measurement result.
本発明の銅合金製熱交換器細管の防食方法において、水に酸化剤を添加する場合、この酸化剤の酸化力は酸素よりも強いため、水中の硫化物イオンが硫酸イオンに効率よく酸化され、銅合金製熱交換器細管内面での硫化物皮膜形成が防止され、銅合金製熱交換器細管の腐食が防止される。 In the anticorrosion method for copper alloy heat exchanger capillaries according to the present invention, when an oxidizing agent is added to water, the oxidizing power of this oxidizing agent is stronger than that of oxygen, so that sulfide ions in water are efficiently oxidized to sulfate ions. The formation of a sulfide film on the inner surface of the copper alloy heat exchanger capillary is prevented, and corrosion of the copper alloy heat exchanger capillary is prevented.
本発明において、水に鉄塩を添加した場合、硫化物イオンが鉄イオンと反応して硫化鉄となる。このため、銅合金製熱交換器細管内面の酸化皮膜が還元されて硫化鉄となることが防止され、酸化皮膜の防食性低下が防止される。 In the present invention, when an iron salt is added to water, sulfide ions react with iron ions to form iron sulfide. For this reason, it is prevented that the oxide film on the inner surface of the copper alloy heat exchanger capillary is reduced to iron sulfide, and the corrosion resistance of the oxide film is prevented from being lowered.
本発明方法では、海水等の酸化還元電位や銅合金の自然電極電位に基づいて薬注制御することにより、薬品の過剰添加や添加不足を防止することが出来る。 In the method of the present invention, chemical addition control based on the oxidation-reduction potential of seawater or the like or the natural electrode potential of a copper alloy can prevent excessive addition or insufficient addition of chemicals.
本発明において、腐食防止対象となる銅合金製熱交換器細管としては、発電プラント、石油精製プラント、石油化学プラントに設置されたチューブ式熱交換器細管などが例示される。 In the present invention, the heat exchanger capillaries made of copper alloy that are subject to corrosion prevention include tube heat exchanger capillaries installed in power plants, petroleum refining plants, and petrochemical plants.
銅合金製熱交換器細管の銅合金としては、JIS H3300−2012記載のC4430、C6870、C6871、C6872などの復水器用黄銅やC7060、C7100、C7150、C7164などの復水器用白銅が例示されるが、これに限定されない。この銅合金製熱交換器細管と接触する水としては、海水、湖沼水、河川水(以下、海水等ということがある。)などが例示される。 Examples of the copper alloy of the copper alloy heat exchanger capillary tube include brass for condensers such as C4430, C6870, C6871, and C6872 described in JIS H3300-2012 and white copper for condensers such as C7060, C7100, C7150, and C7164. However, it is not limited to this. Examples of the water that contacts the copper alloy heat exchanger capillary include seawater, lake water, river water (hereinafter sometimes referred to as seawater), and the like.
この水に対し添加する酸化剤としては、塩素(液体塩素、又は電解塩素)、次亜塩素酸ナトリウム、二酸化塩素、過酸化水素、クロラミン、ブロマミン、臭化物、過マンガン酸塩、鉄酸塩、及びオゾンの少なくとも1種が好適であり、特に次亜塩素酸ナトリウム、過酸化水素が好適である。 The oxidizing agent added to this water includes chlorine (liquid chlorine or electrolytic chlorine), sodium hypochlorite, chlorine dioxide, hydrogen peroxide, chloramine, bromamine, bromide, permanganate, ferrate, and At least one kind of ozone is preferable, and sodium hypochlorite and hydrogen peroxide are particularly preferable.
水に添加する鉄塩としては、硫酸第一鉄又は塩化第一鉄が好適であるが、硫酸第二鉄、塩化第二鉄等も用いることができる。 As the iron salt to be added to water, ferrous sulfate or ferrous chloride is suitable, but ferric sulfate, ferric chloride and the like can also be used.
酸化剤と鉄塩とは、一方のみを添加してもよく、双方を添加してもよい。酸化剤を海水等に添加するに際しては、海水等の酸化還元電位又は銅合金の自然電極電位を測定し、この測定電位が、銅合金製熱交換器細管が清浄な海水等と接触しているときの電位と同等以上となるように添加するのが好ましい。鉄塩を添加する場合には、海水等の酸化還元電位又は銅合金の自然電極電位を測定し、この測定値から推定される硫化物濃度と当量又はそれ以上の量の鉄塩を添加するのが好ましい。 Only one or both of the oxidizing agent and the iron salt may be added. When adding an oxidizing agent to seawater or the like, the redox potential of seawater or the natural electrode potential of the copper alloy is measured, and this measured potential is in contact with the seawater or the like where the copper alloy heat exchanger capillary is clean. It is preferable to add so as to be equal to or higher than the potential at that time. When adding an iron salt, measure the redox potential of seawater or the natural electrode potential of the copper alloy, and add an iron salt equivalent to or greater than the sulfide concentration estimated from this measured value. Is preferred.
酸化剤及び/又は鉄塩の添加による銅合金製熱交換器細管の防食性の評価を行うには、薬注箇所よりも下流域の熱交換器近傍に設置した、仮設の通水試験装置に取り付けられたテスト細管の自然電位および分極抵抗の測定を手動あるいは自動で測定して評価するとともに、一定期間通水後のテスト細管を取り外し、腐食量、付着物量や付着物成分を分析することで評価するのが好ましい。 In order to evaluate the corrosion resistance of copper alloy heat exchanger capillaries by adding oxidizer and / or iron salt, a temporary water flow test device installed near the heat exchanger in the downstream area from the chemical injection point By measuring the self-potential and polarization resistance of the attached test capillary manually or automatically, and removing the test capillary after water has passed for a certain period of time, and analyzing the amount of corrosion, the amount of deposits and deposit components It is preferable to evaluate.
このように、海水等に酸化剤を添加すると、硫化物イオンの硫酸イオンへの酸化が促進され、下流の銅合金製熱交換器細管への硫化物イオンの到達が低減され、硫化物皮膜の形成が防止される。 Thus, when an oxidizing agent is added to seawater or the like, the oxidation of sulfide ions to sulfate ions is promoted, the arrival of sulfide ions to the downstream copper alloy heat exchanger capillary is reduced, and the sulfide film Formation is prevented.
また、海水等に鉄塩を添加すると、海水等に溶存している硫化物イオンが鉄イオンと反応して硫化鉄となる。これにより、銅合金製熱交換器細管表面の酸化鉄皮膜が還元されて硫化鉄となることが防止され、細管の腐食が防止される。 When iron salt is added to seawater or the like, sulfide ions dissolved in seawater or the like react with iron ions to become iron sulfide. Thereby, it is prevented that the iron oxide film on the surface of the copper alloy heat exchanger capillary is reduced to iron sulfide, and corrosion of the capillary is prevented.
図1は本発明方法の一例を説明するフロー図である。取水された海水が配管1から熱交換器2へ流れ、放水口から放水される。薬品タンク3内の薬品(酸化剤又は鉄塩)が薬注装置4によって配管1に添加される。配管1からは検出配管5へ海水の一部が分取され、酸化還元電位及び/又は銅合金の自然電極電位が測定され、この測定結果に基づいて薬注が行われる。また、熱交換器2の直前から海水の一部が配管7へ分取され、評価部8に通水される。この評価部8には、熱交換器2の銅合金製熱交換器細管と同材質のテスト管が設けられている。このテスト管に海水を通水し、電位を測定したり腐食状況を観察し、腐食防止効果を評価する。
FIG. 1 is a flowchart for explaining an example of the method of the present invention. The taken seawater flows from the pipe 1 to the
検出部6にて、海水の酸化還元電位または銅合金の自然電極電位を測定し、電位の卑化が確認された場合には海域から硫化物イオンが流入したものと判断し、薬注装置4を作動させる。 The detection unit 6 measures the redox potential of seawater or the natural electrode potential of copper alloy, and when the potential is confirmed to be reduced, it is determined that sulfide ions have flowed from the sea area, and the chemical injection device 4 Is activated.
酸化剤を添加する場合には、酸化還元電位や銅合金の自然電極電位が、硫化物イオン流入前の清浄海水中での電位と同等以上の電位を示すまで注入を行う。 When the oxidizing agent is added, injection is performed until the redox potential or the natural electrode potential of the copper alloy shows a potential equal to or higher than the potential in the clean seawater before the flow of sulfide ions.
鉄塩を添加する場合には、電位から推定される硫化物イオン濃度又は海水の分析により得た硫化物イオン濃度と当量又はそれ以上(例えば当量の1〜10倍)の量の鉄塩を添加する。 When adding an iron salt, add an amount of iron salt equivalent to or higher than the sulfide ion concentration estimated from the potential or analyzed by analysis of seawater (for example, 1 to 10 times the equivalent). To do.
薬品注入量の増減や抑制効果の確認は、評価部8に設置したテスト管の自然電位および分極抵抗値の推移を手動または自動で測定して行う。また、定期的にテスト管の腐食量、付着物量および付着物成分を測定して薬注効果を評価する。 The increase / decrease and the suppression effect of the chemical injection amount are confirmed manually or automatically by measuring the transition of the natural potential and polarization resistance value of the test tube installed in the evaluation unit 8. Also, periodically measure the amount of corrosion, amount of deposits, and deposit components of the test tube to evaluate the drug injection effect.
以下、本発明の効果を示すための実験例について説明する。 Hereinafter, experimental examples for showing the effects of the present invention will be described.
以下の実施例では、実機熱交換器で使用されたアルミニウム黄銅管の引抜管を切断して作成した酸化鉄皮膜付きの試験片(以下、鉄皮膜形成管ということがある。)と、この試験片を塩酸で洗浄して酸化鉄皮膜を除去した酸洗試験片(以下、酸洗管ということがある。)を用いた。 In the following examples, a test piece with an iron oxide film (hereinafter sometimes referred to as an iron film forming tube) prepared by cutting a drawn tube of an aluminum brass tube used in an actual heat exchanger, and this test. A pickling test piece (hereinafter sometimes referred to as a pickling tube) in which the piece was washed with hydrochloric acid to remove the iron oxide film was used.
模擬海水としては、人工海水(八洲薬品株式会社製金属腐食試験用アクアマリン)(実験1)又はこの人工海水に硫化ナトリウム9水和物を硫化物イオンとして100mg/Lになるように溶解したもの(実験2〜6)を用いた。 As simulated seawater, artificial seawater (Aquamarine for metal corrosion test manufactured by Yasu Pharmaceutical Co., Ltd.) (Experiment 1) or sodium sulfide nonahydrate was dissolved in this artificial seawater as sulfide ions to 100 mg / L. The ones (Experiments 2-6) were used.
実験1,2では、模擬海水に薬剤(酸化剤、鉄塩)は添加しなかった。
実験3,4では模擬海水に次亜塩素酸ナトリウム又は過酸化水素を酸化還元電位が200mV以上になるように添加した。
実験5,6では、模擬海水に鉄イオンとして100mg/L(実験5)又は1000mg/L(実験6)となるように硫酸第一鉄を添加した。
In
In Experiments 3 and 4, sodium hypochlorite or hydrogen peroxide was added to simulated seawater so that the redox potential was 200 mV or higher.
In
各模擬海水(0.5L,25℃)に上記試験片を24時間浸漬し、模擬海水の酸化還元電位及び試験片の自然電極電位を測定した。結果を図2に示す。 The test piece was immersed in each simulated seawater (0.5 L, 25 ° C.) for 24 hours, and the redox potential of the simulated seawater and the natural electrode potential of the test piece were measured. The results are shown in FIG.
また、24時間後、各試験片を各模擬海水から引き上げ、薬剤が添加されていない前述の人工海水で洗浄し、ポテンショスタットにて−100mV陰分極した場合での電流密度からオームの法則で分極抵抗値を求めた。結果を図3に示す。 After 24 hours, each test piece was pulled up from each simulated seawater, washed with the above-mentioned artificial seawater to which no chemical was added, and polarized according to the Ohm's law from the current density when negatively polarized with a potentiostat at −100 mV. The resistance value was determined. The results are shown in FIG.
図2の実験1,2の結果を対比すると、実験2では硫化物イオンを添加していない実験1と比べて酸化還元電位及び自然電極電位が卑な電位を示しており、硫化物イオンの存在を電位により確認することができることが認められた。
Compared to the results of
また、酸化剤を添加した実験3,4では自然電極電位が実験2に比べて高くなっている。従って、酸化剤により硫化物イオンが酸化されることが認められた。
In Experiments 3 and 4 in which an oxidizing agent was added, the natural electrode potential was higher than that in
図3に示すように、酸化剤を添加した実験3および実験4では実験2と比べ酸洗管および鉄皮膜形成管のいずれにおいても分極抵抗値の低下が抑制された。鉄イオンを添加した実験5および実験6を無添加の実験2と比べると、酸洗管では殆ど分極抵抗の抑制効果は無かったが、鉄皮膜形成管では分極抵抗値の低下を抑制する効果が認められた。
As shown in FIG. 3, in Experiment 3 and Experiment 4 in which an oxidizing agent was added, a decrease in polarization resistance value was suppressed in both the pickling tube and the iron film forming tube as compared with
なお、硫化物皮膜は黒色であるが、各試験片の外観を観察したところ、実験2以外では黒色の付着物は認められず、酸化剤又は鉄塩の添加により硫化物皮膜の形成が抑制されることが認められた。
The sulfide film was black, but when the appearance of each test piece was observed, no black deposit was observed except in
1 配管
2 熱交換器
3 薬品タンク
4 薬注装置
6 検出部
8 評価部
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