US3527609A - In-service cleaning of cooling water systems - Google Patents

In-service cleaning of cooling water systems Download PDF

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Publication number
US3527609A
US3527609A US725154A US3527609DA US3527609A US 3527609 A US3527609 A US 3527609A US 725154 A US725154 A US 725154A US 3527609D A US3527609D A US 3527609DA US 3527609 A US3527609 A US 3527609A
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acid
cleaning
stage
cooling water
hardness
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US725154A
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English (en)
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Joseph D Vinso
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Dow Chemical Co
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Dow Chemical Co
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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
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts

Definitions

  • the hardness deposits are removed by adding an alkali metal salt, or ammonium salt, of an amino polycarboxylic acid to the cooling water and adjusting the pH, if necessary, to a value in the range of 7 to about 12, and preferably 8 to about 11, circulating the resulting chelant solution until the hardness is removed; and (2) with or without displacing the chelant solution with make-up Water, adding a mixture of an ammonium salt, or alkali metal salt, of an amino polycarboxylic acid and an acidifying agent to the cooling water system so as to adjust the pH to about 3 to 6, and more preferably about 4 to 5.5, circulating the acidic solution until the iron oxide is removed, and finally displacing the acidic cleaning solution with make-up water.
  • a corrosion inhibitor is employed in the second stage of the cleaning, but may not be necessary in the first stage. Ordinarily, normal water treatment is discontinued during cleaning.
  • the invention relates to a two-stage method of inservice cleaning of a cooling water system having each of (1) iron oxide, and (2) hardness, i.e. carbonates and/or magnesium, deposited on the interior metal surface thereof.
  • a principal object of the invention is to provide a method of in-service cleaning of a cooling water system having each of iron oxide and hardness deposits on the interior metal surfaces thereof.
  • the present method is applicable to in-service cleaning of most any circulating cooling water system, for example, an open system used in connection with an airconditioning system, where displacement of circulating aqueous liquid is economically feasible so that two-stage cleaning is possible as a practical matter, and where removal of both iron oxide and hardness is an important objective.
  • the acidifying agent employed in the second stage may be most any proton-donating substance which provides a substantial concentration of hydrogen ions in aqueous solution sufiicient to provide the pH value desired in the range of about 3 to 6.
  • Such proton-donating substance preferably does not form a precipitate, or not more than a slight amount of easily suspended precipitate, with dissolved salts or dissolved deposits at the concentrations found in the circulating system and is, therefore, compatible with the system.
  • any mineral acid may be used, but sulfuric acid is most preferred of these since chloride or nitrate ions may be harmful to the system.
  • the organic, i.e., carboxylic acids include the di-, trior polycarboxylic acids containing from about 2 to 8 carbon atoms, including the hydroxy polycarboxylic acids all of which are appropriately described as complexing agents.
  • Suitable polycarboxylic acids include citric acid, tartaric acid, oxalocitraconic acid, oxalic acid, malonic acid, succinic acid, malic acid, glutaric acid, adipic acid, pimelic acid. suberic acid, azelaic acid, sebacic acid, diglycolic acid and phthalic acid.
  • citric acid and tartaric acid are preferred.
  • the chelant itself may be used in free acid form, obviating the need for any other acid. In this case, however, it is generally advisable to use both the acid form and the ammonium salt of the chelating agent together.
  • Suitable amino polycarboxylic acid chelating agents for use in the practice of the present invention include the alkylene polyamine polyacetic acids of the formula (HOOCCH N[ (CH N (CH COOH) :lmCHgCOOH,
  • n is an integer from 1 to 4 inclusive and m is a numeral in the range of to 4 inclusive and wherein up to two of the carboxymethyl groups may be replaced with a fi-hydroxyethyl group and one or more of the carboxymethyl groups may be replaced by carboxyethyl groups.
  • acids which are particularly suitable are ethylenediaminetetraacetic acid (EDTA), N- hydroxyethyl ethylenediaminetriacetic acid, nitrolotriacetic acid, N-Z-hydroxyethyliminodiacetic acid, diethylenetriaminepentaacetic acid and mixtures thereof.
  • amino polycarboxylic acid chelating agents are suitably employed, in the first stage cleaning, in the form of one of their alkali metal salts, normally the sodium salt, and preferably the fully neutralized salt since it imparts the greatest alkalinity.
  • the ammonium salt may be used if desired.
  • any of these same amino polycarboxylic acid chelating agents, or a mixture thereof, are suitably employed in the second stage cleaning in the form of the ammonium salt, preferably the fully neutralized salt, unless the free acid form is used to obtain the desired acidity.
  • the alkali metal salt may also be used if desired.
  • amino polycarboxylic acid chelating agents are conveniently employed in the form of an aqueous solution in which they are normally supplied commercially, typically, a 38 percent by Weight aqueous solution.
  • a corrosion inhibitor is generally not needed during the first stage cleaning unless the cooling system contains or is suspected to contain copper or copper bearing portions in contact with the circulating liquid.
  • an inhibitor such as sodium mercaptobenzothiazol is preferably employed at a concentration of about 0.1 to about 0.5 percent by weight.
  • an inhibitor to completely eliminate and reduce still further the relatively low level attack upon the metal substrate that occurs when using the present cleaning solution in the second stage.
  • a suitable inhibitor used at a concentration of about 0.05 to 1 percent by weight is a commercial product sold by Armour and Company under the name Armohib 31. This inhibitor is a compounded formulation that includes polyethoxylated fatty acids and similar materials, and is more thoroughly described in Chemical Abstracts, volume 62, Column 7448d (1965), the same being incorporated herein by reference.
  • a more preferred inhibitor which can be used in the second stage of cleaning at a concentration in the range of about 0.05 to 1 percent by weight consists of the combination of (1) organic sulfur compound having the sulfur present in the form of -S or 8:, e.g., N-alkylthiourea, with (2) the reaction product of dehydroabietylamine, acetophenone, paraformaldehyde and formic acid or, more generally stated, the reaction product of a nitrogen compound containing at least one active hydrogen attached to the nitrogen atom per molecule with a ketone having at least one hydrogen atom attached to the carbon atom alpha to the carbonyl group, an aldehyde, and a fatty acid, preferably prepared in the presence of an acid catalyst, at a temperature of from about 150 to about 250 F. for from 1 to about 24 hours, the same being more fully described in the copending application of William W. Bakke and Billy D. Oakes, entitled Inhibited Metal Cleaning Composition, filed even date herewith, the disclosure thereof being incorporated here
  • the solution of chelating agent is allowed to circulate for at least several hours or sometimes a day or more, or until successive samples of the system taken at least 15 minutes apart and examined by chemical analysis show that there is some unspent chelating agent in the system and the degree of spentness does not change substantially during the time between samples. If the chelating agent is entirely spent or is substantially spent and the degree of spentness is still increasing, an additional quantity of chelating agent in the form of the sodium salt is preferably injected in order to complete the removal of hardness, and circulation of the cleaning solution is desirably continued until substantially complete removal of hardness has been indicated, as by additional sampling and analysis for unspent chelating agent.
  • the cleaning solution is ordinarily displaced gradually and as rapidly as facilities permit by the addition of make-up water and concurrent blow down of a corresponding amount of circulating liquid.
  • Sufiicient displacement should be carried out to remove enough of the spent cleaning solution to bring the pH of the circulating system back to approximately the pH of the make-up water, i.e., approximate neutrality, so that acid requirements are reduced in the second stage, and also so that dissolved and chelated calcium ion does not become dissociated and precipitated when the pH is lowered below about pH 5.
  • amino polycarboxylic acid chelating agent preferably as the ammonium salt, though the alkali metal salt may be used, and, an acidifying agent are added to the system with or without prior mixing in a manner similar to the injection of chelating agent during the first stage.
  • the material added by injection must bring the pH of the system down to a value in the range of about 3-6, and more preferably to a pH of about 4 to 5.5.
  • the quantity of mixture of acidifying agent and chelating agent is an amount calculated to be sufiicient to dissolve and complex or chelate the iron in the iron oxide deposits in the system.
  • a complexing agent such as the nitrogen-free polycarboxylic acids described, or 3.8 pounds of chelating agent, on a dry basis, are each sutficient to dissolve and tie up about one pound of iron oxide.
  • the so-prepared acidic cleaning solution is circulated for at least several hours, or sometimes a day or more, or until successive samples drawn from the systern at intervals at least minutes apart indicate that dissolution of iron oxide is substantially complete. If the cleaning materials are entirely spent or if they are substantially spent and analysis indicates iron oxide is still being taken up, one or more small additions of the mixture of acidifying agent and chelating agent are made, if desired, to complete removal of iron oxide.
  • the cleaning operation is completed upon displacing the cleaning solution from the circulating system by addition of make-up water whereby the pH of the circulating system is brought back to a normal operating value close to pH 7.
  • a corrosion inhibitor is employed in each stage of the cleaning.
  • Such corrosion inhibitor is conveniently dissolved in the aqueous solution chelating agent prior to injection.
  • the cleaning solution is not displaced after first stage treatment to dissolve hardness but second stage cleaning is commenced simply by dropping the pH with an acidifying agent and adding additional chelating agent, preferably as the ammonium salt, or the alkali metal salt, or as the free aminopolycarboxylic acid.
  • additional chelating agent preferably as the ammonium salt, or the alkali metal salt, or as the free aminopolycarboxylic acid.
  • Example 1 An open-recirculating cooling water system containing heat exchange equipment holds 84,000 gallons of water with a recirculation rate of 24,000 gallons per minute. The make-up rate of water is 1100- 1200 gallons per minute.
  • the system contains both iron and calcium-bearing deposits primarily in the forms of Fe O and Ca (OH) (PO
  • the total estimated scale is 11,781 pounds with 7,028 pounds of Ca (OH) (PO and 4,753 pounds of Fe O
  • Total estimated material requirements to dissolve this scale in two stages is: 66,903 pounds of 38% aqueous solution of tetra sodium EDTA, 47,530 pounds of aqueous solution of tetra ammonium EDTA (38% by weight concentration of EDTA), 8,802 pounds of anhydrous citric acid, and 84 gallons of inhibitor.
  • the cooling tower Prior to any chemical injection, the cooling tower is blown down to establish one to one and one-half cycles cycles of concentration of dissolved mineral content.
  • the system exhibits a pH of 6.8.
  • the aqueous solution of inhibited tetra sodium EDTA is steadily injected into the system through a convenient point in the circulating system just ahead of the pump.
  • the pH is adjusted to the preferred range of 10-11 by caustic soda.
  • the chelating material circulates throughout the system until hardness tests shows it has stopped spending, i.e., has stopped dissolving and complexing hardness.
  • This solution is then removed from the system by periodic displacement using the systems make-up water supply. This step is completed when the pH of the circulating water is that of the make-up water, ie., about 7.
  • tetra ammonium EDTA, citric acid, and inhibitor are mixed and added to the system in the same manner as the tetrasodium EDTA was added.
  • the inhibitor consists of a mixture of (1) nonyl phenol condensed with moles of ethylene oxide, (2) 1-hexyn-3ol, (3) 1-alkyl-2-thiourea, and (4) the reaction product of dehydroabietylamine, paraformaldehyde, formic acid, and acetophenone.
  • the material added by injection brings the pH to 5.6. This material circulates until spending has ceased, as shown by analysis, indicating that iron oxide is substantially all dissolved.
  • the second stage cleaning solution is then removed from the system by steady displacement using the system make-up water supply.
  • the cleaning operation is completed when the pH of the circulating water again becomes that of the make-up water, i.e., about 6.8.
  • the cooling water system is successfully cleaned while in service by the foregoing recited steps as shown by the temperature of water returning from the cooling tower being below about F. Further, operating experience after cleaning shows subsequent cleaning is not needed again until 5 months later.
  • Example 2 The method of Example 1 is repeated on a similar cooling water system except that the amount of hardness and scale are greater than estimated, as shown by analysis for the spentness of the chelating material at each stage, indicating that chelant is entirely spent.
  • a two stage method of in-service cleaning of a cooling water system having each of iron oxide and hardness deposited on the interior metal surfaces thereof which comprises:
  • the acidifying agent is a proton-donating substance selected from the group consisting of sulfuric acid; and monocarboxylic acids, dicarboxylic acids, tricarboxylic acids and polycarboxylic acids having up to about 8 carbon atoms.
  • the acidifying agent employed is a member of the group consisting of sulfuric acid, citric acid, tartaric acid, formic acid, and acetic acid.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
US725154A 1968-04-29 1968-04-29 In-service cleaning of cooling water systems Expired - Lifetime US3527609A (en)

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Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3956164A (en) * 1974-09-23 1976-05-11 Calgon Corporation Chelating agents
US4192744A (en) * 1976-11-02 1980-03-11 Ciba-Geigy Corporation Treatment of aqueous systems
US4430128A (en) 1980-12-05 1984-02-07 The Dow Chemical Company Aqueous acid composition and method of use
US4454046A (en) * 1982-09-07 1984-06-12 The Dow Chemical Company Boiler scale prevention employing an organic chelant
US4623399A (en) * 1985-02-04 1986-11-18 Dowell Schlumberger Incorporated Solvent for removing iron oxide deposits
US4636327A (en) * 1980-12-05 1987-01-13 Dowell Schlumberger Incorporated Aqueous acid composition and method of use
US4721532A (en) * 1985-08-05 1988-01-26 W. R. Grace & Co. Removal of iron fouling in cooling water systems
US4778655A (en) * 1985-10-29 1988-10-18 W. R. Grace & Co. Treatment of aqueous systems
US4802990A (en) * 1987-07-30 1989-02-07 Inskeep Jr Eugene L Solution and method for dissolving minerals
US4940493A (en) * 1988-09-30 1990-07-10 Fred Neidiffer Aluminum cleaning composition and process
US4959105A (en) * 1988-09-30 1990-09-25 Fred Neidiffer Aluminium cleaning composition and process
US5151196A (en) * 1991-09-27 1992-09-29 Mobil Oil Corporation Method for regenerating scale solvent
US5183573A (en) * 1991-07-22 1993-02-02 W. R. Grace & Co.-Conn. Multipurpose scale preventer/remover
US5360488A (en) * 1993-03-23 1994-11-01 H.E.R.C. Products Incorporated Method of cleaning and maintaining water distribution pipe systems
US5413168A (en) * 1993-08-13 1995-05-09 Westinghouse Electric Corporation Cleaning method for heat exchangers
US5527395A (en) * 1991-05-16 1996-06-18 H.E.R.C. Products Incorporated Method of cleaning and maintaining potable water distribution pipe systems with a heated cleaning solution
US5800629A (en) * 1997-03-06 1998-09-01 H.E.R.C. Products Incorporated Pipe system cleaning and in-line treatment of spent cleaning solution
US5885364A (en) * 1991-05-16 1999-03-23 H.E.R.C. Products Incorporated Method of cleaning and maintaining potable water distribution pipe systems
US6076536A (en) * 1998-10-07 2000-06-20 H.E.R.C. Products Incorporated Cleaning and passivating water distribution systems
WO2003106735A3 (fr) * 2002-06-17 2004-04-01 Basf Corp Procede de detartrage
US20100288301A1 (en) * 2009-05-15 2010-11-18 Hui Hwang Kee Removing contaminants from an electroless nickel plated surface
US20120073597A1 (en) * 2010-09-28 2012-03-29 Soonchunhyang University Industry Academy Cooperation Foundation Method for removing deposited sludge

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2396938A (en) * 1944-01-22 1946-03-19 Martin Dennis Company Method of treating boilers
US2774694A (en) * 1953-10-15 1956-12-18 Wiggins Leslie Frederick Process for the descaling of sugar factory evaporators and other heat transfer equipment
US2802788A (en) * 1957-08-13 Cleaning composition for automotive
US3033214A (en) * 1955-01-20 1962-05-08 Dow Chemical Co Recovery and reuse of complexing agents from spent solutions
US3067070A (en) * 1961-02-01 1962-12-04 Charles M Loucks Cleaning method for industrial systems

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2802788A (en) * 1957-08-13 Cleaning composition for automotive
US2396938A (en) * 1944-01-22 1946-03-19 Martin Dennis Company Method of treating boilers
US2774694A (en) * 1953-10-15 1956-12-18 Wiggins Leslie Frederick Process for the descaling of sugar factory evaporators and other heat transfer equipment
US3033214A (en) * 1955-01-20 1962-05-08 Dow Chemical Co Recovery and reuse of complexing agents from spent solutions
US3067070A (en) * 1961-02-01 1962-12-04 Charles M Loucks Cleaning method for industrial systems

Cited By (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3956164A (en) * 1974-09-23 1976-05-11 Calgon Corporation Chelating agents
US4192744A (en) * 1976-11-02 1980-03-11 Ciba-Geigy Corporation Treatment of aqueous systems
US4430128A (en) 1980-12-05 1984-02-07 The Dow Chemical Company Aqueous acid composition and method of use
US4636327A (en) * 1980-12-05 1987-01-13 Dowell Schlumberger Incorporated Aqueous acid composition and method of use
US4454046A (en) * 1982-09-07 1984-06-12 The Dow Chemical Company Boiler scale prevention employing an organic chelant
US4623399A (en) * 1985-02-04 1986-11-18 Dowell Schlumberger Incorporated Solvent for removing iron oxide deposits
US4721532A (en) * 1985-08-05 1988-01-26 W. R. Grace & Co. Removal of iron fouling in cooling water systems
US4778655A (en) * 1985-10-29 1988-10-18 W. R. Grace & Co. Treatment of aqueous systems
US4802990A (en) * 1987-07-30 1989-02-07 Inskeep Jr Eugene L Solution and method for dissolving minerals
US4940493A (en) * 1988-09-30 1990-07-10 Fred Neidiffer Aluminum cleaning composition and process
US4959105A (en) * 1988-09-30 1990-09-25 Fred Neidiffer Aluminium cleaning composition and process
US5885364A (en) * 1991-05-16 1999-03-23 H.E.R.C. Products Incorporated Method of cleaning and maintaining potable water distribution pipe systems
US5527395A (en) * 1991-05-16 1996-06-18 H.E.R.C. Products Incorporated Method of cleaning and maintaining potable water distribution pipe systems with a heated cleaning solution
US5183573A (en) * 1991-07-22 1993-02-02 W. R. Grace & Co.-Conn. Multipurpose scale preventer/remover
WO1993006047A1 (fr) * 1991-09-27 1993-04-01 Mobil Oil Corporation Procede de regeneration de solvants pour tartre
US5151196A (en) * 1991-09-27 1992-09-29 Mobil Oil Corporation Method for regenerating scale solvent
US5360488A (en) * 1993-03-23 1994-11-01 H.E.R.C. Products Incorporated Method of cleaning and maintaining water distribution pipe systems
US5413168A (en) * 1993-08-13 1995-05-09 Westinghouse Electric Corporation Cleaning method for heat exchangers
US5601657A (en) * 1993-08-13 1997-02-11 Westinghouse Electric Corporation Two-step chemical cleaning process
US5800629A (en) * 1997-03-06 1998-09-01 H.E.R.C. Products Incorporated Pipe system cleaning and in-line treatment of spent cleaning solution
US6076536A (en) * 1998-10-07 2000-06-20 H.E.R.C. Products Incorporated Cleaning and passivating water distribution systems
US6345632B1 (en) 1998-10-07 2002-02-12 H.E.R.C. Products Incorporated Method of cleaning and passivating a fire protection system
WO2003106735A3 (fr) * 2002-06-17 2004-04-01 Basf Corp Procede de detartrage
US20100288301A1 (en) * 2009-05-15 2010-11-18 Hui Hwang Kee Removing contaminants from an electroless nickel plated surface
US20120073597A1 (en) * 2010-09-28 2012-03-29 Soonchunhyang University Industry Academy Cooperation Foundation Method for removing deposited sludge

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