CA2090736A1 - Method of scavenging oxygen in aqueous systems - Google Patents
Method of scavenging oxygen in aqueous systemsInfo
- Publication number
- CA2090736A1 CA2090736A1 CA 2090736 CA2090736A CA2090736A1 CA 2090736 A1 CA2090736 A1 CA 2090736A1 CA 2090736 CA2090736 CA 2090736 CA 2090736 A CA2090736 A CA 2090736A CA 2090736 A1 CA2090736 A1 CA 2090736A1
- Authority
- CA
- Canada
- Prior art keywords
- oxygen
- ppm
- oxygen scavenger
- corrosion
- range
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Abstract
ABSTRACT OF THE INVENTION
A method for inhibiting or preventing corrosion of metals in contact with an aqueous system containing dissolved oxygen comprising adding to the system an oxygen scavenger having the formula
A method for inhibiting or preventing corrosion of metals in contact with an aqueous system containing dissolved oxygen comprising adding to the system an oxygen scavenger having the formula
Description
2~9~736 FIELD OF THE INVENTION
This invantion relates to the addition of oxygen scavengers to aqueous systems to reduce the corrosion of metals that are in contact with the aqueous system, and more particularly to the use of certain oxygen scavenging compositions which comprise hydroxycarboxylic acids and related compounds.
BACKGROUND OF THE INVENTION
The corrosion of metal surfaces which are in contact with aqueous systems is a common problem. Corrosion may occur in various locations including boiler feedwater lines, heaters, steam lines, process tanks and return lines. Dissolved oxygen in the aqueous system is often a principal factor influencing the formation of the corrosion, particularly where iron and steel are the materials of construction. The corrosion of iron based metals in conventional boiler systems is a well known problem, and controlling the presence of oxygen in boiler systems, particularly in the Eeedwater section has received considerable attention. Oxygen removal may be partially accomplished by either vacuum or thermal deaeration, or both. Complete removal of oxygen cannot be effected by these means, however, and further removal by use of a chemical oxygen scavenging agent, such as sodium sulfite, has been a customary practice.
Recently, the use of low pressure boilers (i.e.
those operating below about 150 psig) has been increasingly supplanted by the use of boilers operating at moderate pressure (i.e. operating between about 150 psig and about 600 psig) and high pressure (i.e.
operating above about 600 psig). As boiler operating temperatures and pressures have increased, there has been particular interest in the performance of chemical oxygen 20~0736 scavengers which are effective at: these operating conditions. The use of sulfites at elevated temperatures and pressures has been known to result in the formation of sulfur dioxide and hydrogen sul~ide, which can be a source of corrosion. Other scavenging agents such as hydra~ine, hydroquinone, and cert;ain hydroxylamines have been found to perform satisfactorily in some circumstances. For example, U.S. Patent No. 4,278,635 to Kerst discloses the use of various dihydroxy, diamino, and amino hydroxy ben2enes and their lower alkyl substituted derivatives, and particularly hydroquinone, as corrosion control agents in boiler systems. U.~.
Patent No. 4,282,111 to Cuiba also relates to the use of hydroquinone to reduce the oxygen content of an aqueous medium. U.S. Patent No. 4,363,734 to Solvinsky discloses the use of hydroquinone as a catalyst in combination with dihydroxy acetone. Japanese Patent Publication No. SHO
51-93741 by Suzuki et al reports synergistic inhibition of metallic corrosion by combinations of dihydroxybenzenes (e.g. hydroquinone and methyl hydroquinone) and various carboxylic acids in boiler water systems. In other circumstances, the efficiency with which the scavenging proceeds has not been optimal.
There is thus a continuing need for alternative oxygen scavengers which can be effectively used at elevated temperatures and pressures.
U.S. Patent No. 2,170,596 to Q~gqle describes oxygen absorbing solutions using catalysts such as various quinones together with reducing agents such as reducing sugars like glucose U.S. Patent No. 1,g88,823 to Winning et al describe rust remover compositions which comprise ammonium salt, an alkali salt of a water soluble organic acid, sugar, and an inhibitor of corrosion such as pyrogallol, hydroquinone, pyridine or quinoline.
209~736 Gluconic acid and its salts have been used for corrosion control. U.S. Patent No. 2,529,178 to Nieland et al discloses the use of gluconates such as sodium gluconate to protect metals, particularly ferrous metals, from corrosion in water systems. This patent describes the formation of a protective layer on the metal surface when certain amounts of the gluconate are added to the water in the system.
U.S. Patent No. 3,589,859 to Foroulis discloses that gluconate salts, particularly when used in combination with a benzoate or a salicylate salt, inhibits the oxidative corrosion in aerated cooling systems. U.S.
Patent No. 3,711,246 to Foroulis is directad to inhibiting oxidative corrosion in an oxygen-containing cooling water system using certain inorganic silicate salts together with certain gluconate salts, optionally with certain polyphosphates.
DETAILED DESCRIPTION
The present invention is directed to a method for inhibiting or preventing corrosion of metal surfaces which are in contact with aqueous systems containing dissolved oxygen and more particularly to the use of corrosion inhibiting oxygen scavengers comprising water-soluble hydroxycarboxylic acids having the general formula:
OH
H--( C ) n COOH
H
wherein n is either 5 or 6, the various lactone derivatives of these acids and the water soluble salts of said acids and lactones.
7 3 ~
The preferred oxygen scaven~ers of this invention are gluconic acid and glucoheptonic acid or their water soluble salts.
The method of this invention comprises adding to an aqueous system which contains dissolved oxygen at least one compound having the above general formula in an amount effective to remove or control the presence of the oxygen in the system.
The oxygen scavengers of this invention are suitable for use in low, moderate or high pressure boiler systems, and may also be utilized in other systems where aqueous solutions containing dissolved air and/or oxygen are in contact with metal surfaces. The precise dosage used in each system may vary somewhat depending on the oxygen content of the water as well as other characteristics of the water system. In general, the dosages range from 0.001 ppm to 500 ppm, and are preferably in the range of from 0.01 ppm to 100 ppm.
The oxygen scavengers of this invention may be used as the sole oxygen scavenger for treating the aqueous system, or other conventional oxygen scavengers such as diethyl hydroxylamine, hydrazine, and the like, may be used in combination therewith. In addition, the oxygen scavengers of this invention may be used in combination with other conventional water treating agents including, but not limited to pH regulators, biocides, dispersants, chelants, corrosion inhibitors, scale inhibitors, polymeric agents, and the like, and mixtures thereof.
Without further elaboration, it is believed that one of ordinary skill in the art, using the preceding detailed description, can utili2e the present invention to its fullest extsnt.
The following exarip-^~ are provided to illustrate the invention in accorc - with the principles of this 2~90~3~
~j invention, but are not to be construed as limiting the invention in any way except as indicated in the appended claims. All parts and percentages are by weight unless otherwise indicated.
Example :L
This example demonstrates the oxygen scavenging activity of the hydroxycarboxylic acids of this invention under boiler sonditions at ~00 psig and 448F. During the test, the boiler feedwater was saturated with dissolved oxygen by continuous aeration. The concentration of dissolved oxygen in the ~eedwater ranged from 8.5 ppm to 9.5 ppm as 2- The boiler steam was condensed through a heat exchanger producing a condensate temperature of 55F. The condensate was then passed through a chamber in which an oxygen probe was inserted to monitor the concentration of dissolved oxygen. A
blank run (i.e. without an oxygen scavenger) was first conducted until a constant oxygen reading was obtained.
once the initial dissolved oxygen reading had been established, the oxygen scavenger being evaluated was fed into the boiler. The reduction o~ the dissolved oxygen in the condensate was then recorded. The boiler feedwater contained 10 ppm total hardness (as CaC03).
Table 1 illustrates the extent of oxygen removal in the stream condensate 30 minutes after the addition of the oxygen scavenger. Sodium sulfite and hydrazine were included in the evaluation for comparison purposes.
2~907~
~ ~ _____ ~
X o ~D ~ ~9 ~D ~r a: I ~
0~ ~1 a ~n co a~ ~D 1-'~
I t~
â ~ ~ _ ~ .,., ~ ~ ~ ~, ~ ~, ~ I
~ ~ O O O O O O ¦ X
0~ __ C~ I
I
.~ .~ l` r~ I~ ~ o~ ~ I
~n ~ .~ ~ ~ ~ ~ ~ ~ I
U~ H ¦ la . I
_ _ I
~a) Oo ~ o o o o o~
__ _ _ ~
~X~
~ ~ h rl ~ ~ ~ ~ ~Q) ~ ~ ~ ~ ~ q:~ ~
~A O O U ;:' 1~ ~ :~ ~ ~ a3 c) ~ ~ ~ ~ ~ ~1 u~
u~ u~ ~ ~ ~ ~ V ~1 ~
N N ~ ~ E~ U~ ,1 .~ S~ ~ rl .,1 ., Q~
_ O O _ _ O O O
., In O
This invantion relates to the addition of oxygen scavengers to aqueous systems to reduce the corrosion of metals that are in contact with the aqueous system, and more particularly to the use of certain oxygen scavenging compositions which comprise hydroxycarboxylic acids and related compounds.
BACKGROUND OF THE INVENTION
The corrosion of metal surfaces which are in contact with aqueous systems is a common problem. Corrosion may occur in various locations including boiler feedwater lines, heaters, steam lines, process tanks and return lines. Dissolved oxygen in the aqueous system is often a principal factor influencing the formation of the corrosion, particularly where iron and steel are the materials of construction. The corrosion of iron based metals in conventional boiler systems is a well known problem, and controlling the presence of oxygen in boiler systems, particularly in the Eeedwater section has received considerable attention. Oxygen removal may be partially accomplished by either vacuum or thermal deaeration, or both. Complete removal of oxygen cannot be effected by these means, however, and further removal by use of a chemical oxygen scavenging agent, such as sodium sulfite, has been a customary practice.
Recently, the use of low pressure boilers (i.e.
those operating below about 150 psig) has been increasingly supplanted by the use of boilers operating at moderate pressure (i.e. operating between about 150 psig and about 600 psig) and high pressure (i.e.
operating above about 600 psig). As boiler operating temperatures and pressures have increased, there has been particular interest in the performance of chemical oxygen 20~0736 scavengers which are effective at: these operating conditions. The use of sulfites at elevated temperatures and pressures has been known to result in the formation of sulfur dioxide and hydrogen sul~ide, which can be a source of corrosion. Other scavenging agents such as hydra~ine, hydroquinone, and cert;ain hydroxylamines have been found to perform satisfactorily in some circumstances. For example, U.S. Patent No. 4,278,635 to Kerst discloses the use of various dihydroxy, diamino, and amino hydroxy ben2enes and their lower alkyl substituted derivatives, and particularly hydroquinone, as corrosion control agents in boiler systems. U.~.
Patent No. 4,282,111 to Cuiba also relates to the use of hydroquinone to reduce the oxygen content of an aqueous medium. U.S. Patent No. 4,363,734 to Solvinsky discloses the use of hydroquinone as a catalyst in combination with dihydroxy acetone. Japanese Patent Publication No. SHO
51-93741 by Suzuki et al reports synergistic inhibition of metallic corrosion by combinations of dihydroxybenzenes (e.g. hydroquinone and methyl hydroquinone) and various carboxylic acids in boiler water systems. In other circumstances, the efficiency with which the scavenging proceeds has not been optimal.
There is thus a continuing need for alternative oxygen scavengers which can be effectively used at elevated temperatures and pressures.
U.S. Patent No. 2,170,596 to Q~gqle describes oxygen absorbing solutions using catalysts such as various quinones together with reducing agents such as reducing sugars like glucose U.S. Patent No. 1,g88,823 to Winning et al describe rust remover compositions which comprise ammonium salt, an alkali salt of a water soluble organic acid, sugar, and an inhibitor of corrosion such as pyrogallol, hydroquinone, pyridine or quinoline.
209~736 Gluconic acid and its salts have been used for corrosion control. U.S. Patent No. 2,529,178 to Nieland et al discloses the use of gluconates such as sodium gluconate to protect metals, particularly ferrous metals, from corrosion in water systems. This patent describes the formation of a protective layer on the metal surface when certain amounts of the gluconate are added to the water in the system.
U.S. Patent No. 3,589,859 to Foroulis discloses that gluconate salts, particularly when used in combination with a benzoate or a salicylate salt, inhibits the oxidative corrosion in aerated cooling systems. U.S.
Patent No. 3,711,246 to Foroulis is directad to inhibiting oxidative corrosion in an oxygen-containing cooling water system using certain inorganic silicate salts together with certain gluconate salts, optionally with certain polyphosphates.
DETAILED DESCRIPTION
The present invention is directed to a method for inhibiting or preventing corrosion of metal surfaces which are in contact with aqueous systems containing dissolved oxygen and more particularly to the use of corrosion inhibiting oxygen scavengers comprising water-soluble hydroxycarboxylic acids having the general formula:
OH
H--( C ) n COOH
H
wherein n is either 5 or 6, the various lactone derivatives of these acids and the water soluble salts of said acids and lactones.
7 3 ~
The preferred oxygen scaven~ers of this invention are gluconic acid and glucoheptonic acid or their water soluble salts.
The method of this invention comprises adding to an aqueous system which contains dissolved oxygen at least one compound having the above general formula in an amount effective to remove or control the presence of the oxygen in the system.
The oxygen scavengers of this invention are suitable for use in low, moderate or high pressure boiler systems, and may also be utilized in other systems where aqueous solutions containing dissolved air and/or oxygen are in contact with metal surfaces. The precise dosage used in each system may vary somewhat depending on the oxygen content of the water as well as other characteristics of the water system. In general, the dosages range from 0.001 ppm to 500 ppm, and are preferably in the range of from 0.01 ppm to 100 ppm.
The oxygen scavengers of this invention may be used as the sole oxygen scavenger for treating the aqueous system, or other conventional oxygen scavengers such as diethyl hydroxylamine, hydrazine, and the like, may be used in combination therewith. In addition, the oxygen scavengers of this invention may be used in combination with other conventional water treating agents including, but not limited to pH regulators, biocides, dispersants, chelants, corrosion inhibitors, scale inhibitors, polymeric agents, and the like, and mixtures thereof.
Without further elaboration, it is believed that one of ordinary skill in the art, using the preceding detailed description, can utili2e the present invention to its fullest extsnt.
The following exarip-^~ are provided to illustrate the invention in accorc - with the principles of this 2~90~3~
~j invention, but are not to be construed as limiting the invention in any way except as indicated in the appended claims. All parts and percentages are by weight unless otherwise indicated.
Example :L
This example demonstrates the oxygen scavenging activity of the hydroxycarboxylic acids of this invention under boiler sonditions at ~00 psig and 448F. During the test, the boiler feedwater was saturated with dissolved oxygen by continuous aeration. The concentration of dissolved oxygen in the ~eedwater ranged from 8.5 ppm to 9.5 ppm as 2- The boiler steam was condensed through a heat exchanger producing a condensate temperature of 55F. The condensate was then passed through a chamber in which an oxygen probe was inserted to monitor the concentration of dissolved oxygen. A
blank run (i.e. without an oxygen scavenger) was first conducted until a constant oxygen reading was obtained.
once the initial dissolved oxygen reading had been established, the oxygen scavenger being evaluated was fed into the boiler. The reduction o~ the dissolved oxygen in the condensate was then recorded. The boiler feedwater contained 10 ppm total hardness (as CaC03).
Table 1 illustrates the extent of oxygen removal in the stream condensate 30 minutes after the addition of the oxygen scavenger. Sodium sulfite and hydrazine were included in the evaluation for comparison purposes.
2~907~
~ ~ _____ ~
X o ~D ~ ~9 ~D ~r a: I ~
0~ ~1 a ~n co a~ ~D 1-'~
I t~
â ~ ~ _ ~ .,., ~ ~ ~ ~, ~ ~, ~ I
~ ~ O O O O O O ¦ X
0~ __ C~ I
I
.~ .~ l` r~ I~ ~ o~ ~ I
~n ~ .~ ~ ~ ~ ~ ~ ~ I
U~ H ¦ la . I
_ _ I
~a) Oo ~ o o o o o~
__ _ _ ~
~X~
~ ~ h rl ~ ~ ~ ~ ~Q) ~ ~ ~ ~ ~ q:~ ~
~A O O U ;:' 1~ ~ :~ ~ ~ a3 c) ~ ~ ~ ~ ~ ~1 u~
u~ u~ ~ ~ ~ ~ V ~1 ~
N N ~ ~ E~ U~ ,1 .~ S~ ~ rl .,1 ., Q~
_ O O _ _ O O O
., In O
Claims (7)
1. A method for inhibiting or preventing corrosion of metals in contact with an aqueous system containing dissolved oxygen comprising adding to the system an oxygen scavenger having the formula wherein n is 5 or 6, lactone derivatives thereof, or its water soluble salts, in an amount effective to substantially remove the dissolved oxygen.
2. A method according to Claim 1 wherein the oxygen scavenger is gluconic acid.
3. A method according to Claim 1 wherein the oxygen scavenger is glucoheptonic acid.
4. a method according to Claim 1 wherein the effective amount of oxygen scavenger added to the system is in the range of from 0.001 ppm to 500 ppm.
5. A method according to Claim 1 wherein the effective amount of oxygen scavenger added to the system is in the range of from 0.01 ppm to 100 ppm.
6. A method according to Claim 1 wherein the aqueous system is a low, moderate or high pressure boiler system.
7. A method according to Claim 6 wherein the boiler system operates at a temperature in the range of from 298°F to 696°F and at a pressure in the range of from 50 psig to 3000 psig.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/844,034 US5244600A (en) | 1992-03-02 | 1992-03-02 | Method of scavenging oxygen in aqueous systems |
| US844,034 | 1992-03-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2090736A1 true CA2090736A1 (en) | 1993-09-03 |
Family
ID=25291622
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2090736 Abandoned CA2090736A1 (en) | 1992-03-02 | 1993-02-24 | Method of scavenging oxygen in aqueous systems |
Country Status (2)
| Country | Link |
|---|---|
| BR (1) | BR9300722A (en) |
| CA (1) | CA2090736A1 (en) |
-
1993
- 1993-02-24 CA CA 2090736 patent/CA2090736A1/en not_active Abandoned
- 1993-03-02 BR BR9300722A patent/BR9300722A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| BR9300722A (en) | 1993-09-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |