US4721532A — Removal of iron fouling in cooling water systems

Claim 1

Independent Claim 124 words

A method of removing iron fouling from heat transfer surfaces of cooling water systems which comprises (a) contacting said surfaces with an aqueous solution containing an effective amount, totalling at least 0.1 ppm, of at least one compound of the group of alkylene amine carboxyl polyacids consisting of compounds having the formula ##STR5## wherein R 1 , R 2 , and each X may be the same or different and are each selected from the group consisting of hydrogen, methyl and ethyl, wherein each M is selected from the group consisting of hydrogen, sodium or potassium, and wherein n is an integer from 2 to 5; (b) maintaining the solution at a pH of at least about 5, but below about 9 during removal.

Claim 2

Independent Claim 124 words

A method of removing iron fouling from heat transfer surfaces of cooling water systems which comprises (a) contacting said surfaces with an aqueous solution containing an effective amount, totalling at least 0.1 ppm, of at least one compound of the group of alkylene amine carboxyl polyacids consisting of compounds having the formula ##STR5## wherein R 1 , R 2 , and each X may be the same or different and are each selected from the group consisting of hydrogen, methyl and ethyl, wherein each M is selected from the group consisting of hydrogen, sodium or potassium, and wherein n is an integer from 2 to 5; (b) maintaining the solution at a pH of at least about 5, but below about 9 during removal.

Claim 3

Dependent Claim 16 words

Method according to claim 1 in which the iron fouling comprises iron oxide and calcium scale.

Claim 4

Dependent Claim 23 words

Method according to claim 1 in which the compound concentration in the contacting solution is within the range of 1 to 250 ppm.

Claim 5

Dependent Claim 14 words

Method according to claim 1 in which the fouling is removed by on-stream cleaning.

Claim 6

Dependent Claim 19 words

Method according to claim 4 in which the calcium hardness of the cooling water is at least 500 ppm.

Claim 7

Dependent Claim 24 words

Method according to claim 4 in which the cooling water in contact with the surfaces has a temperature between 90° F. and 150° F.

Claim 8

Dependent Claim 35 words

Method according to claim 4 wherein the heat transfer surfaces operate at temperatures of about 180° F. or less and in contact with cooling water having a pH within the range of 5 to 9.

Claim 9

Dependent Claim 19 words

Method according to claim 7 wherein the iron fouling consists predominantly of iron compounds deposited from said cooling water.

Claim 10

Dependent Claim 19 words

The method of claim 1 wherein the cooling water system is an industrial heat exchanger having ferrous metal tubes.

Claim 11

Dependent Claim 15 words

The method of claim 1 wherein the pH is maintained below about 8 during removal.

Claim 12

Dependent Claim 16 words

Method of claim 1 wherein the cooling water system is an internal combustion engine cooling system.

Claim 13

Dependent Claim 21 words

Method according to claim 1 in which the at least one compound comprises N,N-ethylene-bis ((2-hydroxy-4-methyl phenyl) glycine) or a salt thereof.

Claim 14

Dependent Claim 20 words

Method according to claim 1 in which the solution further comprises N,N-di (2-hydroxy-5-sulfonic acid benzyl) glycine or a salt thereof.

Claim 15

Dependent Claim 18 words

Method according to claim 1 in which the solution further comprises diethylenetriamine pentaacetic acid or a salt thereof.

Claim 16

Dependent Claim 22 words

Method according to claim 1 in which the acid and a neutralizing amount of base are added separately to the cooling system.

Claim 17

Dependent Claim 46 words

Method according to claim 1 in which a sufficient quantity of an aqueous solution containing about 25-35 wt. % of the acid as the sodium or potassium salt is added to the cooling water system to provide therein a concentration of about 1 to 250 ppm.

Claim 18

Dependent Claim 20 words

Method according to claim 1 in which the surfaces are contacted with a solution containing a mix of the acids.

Claim 19

Dependent Claim 49 words

Method according to claim 1 in which the contacting solution further contains at least one compound selected from those compounds having the formula ##STR6## wherein each J is selected from the group consisting of hydrosen, ammonium, sodium, or potassium, and wherein q is an integer from 1 to 5.

Claim 20

Dependent Claim 27 words

Method according to claim 18 in which the solution contains a mix of acids comprising N,N-di (2-hydroxy-5-sulfonic acid benzyl) glycine, or a sodium or potassium salt thereof.

Claim 21

Dependent Claim 26 words

Method according to claim 18 in which the surfaces are contacted with a solution containing a mix comprising N,N-ethylene-bis ((2-hydroxy-4-methyl phenyl) glycine or a salt thereof.

Claim 22

Dependent Claim 25 words

Method according to claim 20 in which the solution contains a mix comprising N,N-di (2-hydroxy-5-sulfonic acid benzyl) glycine, or a sodium or potassium salt thereof.

Claim 23

Dependent Claim 21 words

Method according to claim 21 in which the mix further comprises diethylenetriamine pentaacetic acid or a sodium or potassium salt thereof.

Claim 24

Dependent Claim 19 words

Method according to claim 1 wherein the heat transfer surfaces operate at temperatures of about 180° F. or less.

Claim 25

Dependent Claim 18 words

Method according to claim 1 wherein the iron fouling consists predominantly of iron compounds deposited from cooling water.

Claim 26

Dependent Claim 17 words

Method according to claim 1 wherein the solution has a calcium hardness of at least 500 ppm.

Claim 27

Independent Claim 239 words

A method for removing iron fouling from heat transfer surfaces of cooling water systems which comprises (a) contacting said surfaces with an aqueous solution having a calcium hardness of at least about 187 ppm as CaCO 3 , and containing an effective amount, totalling at least 0.1 ppm, of at least one compound of the group of alkylene amine carboxyl polyacids consisting of (i) N,N-di (2-hydroxybenzyl)-trimethylenediamine-N,N-diacetic acid and water-soluble potassium and sodium salts thereof; (ii) N-hydroxyethylethylenediamine triacetic acid and water-soluble potassium and sodium salts thereof; (iii) compounds having the formula ##STR7## wherein R 1 , R 2 , and each X may be the same or different and are each selected from the group consisting of hydrogen, methyl and ethyl, wherein each M is selected from the group consisting of hydrogen, sodium or potassium, and wherein n is an integer from 2 to 5; and (iv) compounds having the formula ##STR8## wherein R 3 , R 4 , R 5 and R 6 may be the same or different and are each selected from the group consisting of hydrogen or --CH 2 COOL, at least one of R 3 , R 4 , R 5 and R 6 being --CH 2 COOL, wherein each L is selected from the group consisting of hydrogen, sodium, or potassium, and wherein m is an integer from 1 to 5; and (b) maintaining the solution at a pH of about 6 during removal.

Claim 28

Independent Claim 239 words

A method for removing iron fouling from heat transfer surfaces of cooling water systems which comprises (a) contacting said surfaces with an aqueous solution having a calcium hardness of at least about 187 ppm as CaCO 3 , and containing an effective amount, totalling at least 0.1 ppm, of at least one compound of the group of alkylene amine carboxyl polyacids consisting of (i) N,N-di (2-hydroxybenzyl)-trimethylenediamine-N,N-diacetic acid and water-soluble potassium and sodium salts thereof; (ii) N-hydroxyethylethylenediamine triacetic acid and water-soluble potassium and sodium salts thereof; (iii) compounds having the formula ##STR7## wherein R 1 , R 2 , and each X may be the same or different and are each selected from the group consisting of hydrogen, methyl and ethyl, wherein each M is selected from the group consisting of hydrogen, sodium or potassium, and wherein n is an integer from 2 to 5; and (iv) compounds having the formula ##STR8## wherein R 3 , R 4 , R 5 and R 6 may be the same or different and are each selected from the group consisting of hydrogen or --CH 2 COOL, at least one of R 3 , R 4 , R 5 and R 6 being --CH 2 COOL, wherein each L is selected from the group consisting of hydrogen, sodium, or potassium, and wherein m is an integer from 1 to 5; and (b) maintaining the solution at a pH of about 6 during removal.

Claim 29

Dependent Claim 16 words

Method according to claim 26 in which the iron fouling comprises iron oxide and calcium scale.

Claim 30

Dependent Claim 23 words

Method according to claim 26 in which the compound concentration in the contacting solution is within the range of 1 to 250 ppm.

Claim 31

Dependent Claim 14 words

Method according to claim 26 in which the fouling is removed by on-stream cleaning.

Claim 32

Dependent Claim 19 words

Method according to claim 29 in which the calcium hardness of the cooling water is at least 500 ppm.

Claim 33

Dependent Claim 24 words

Method according to claim 29 in which the cooling water in contact with the surfaces has a temperature between 90° F. and 150° F.

Claim 34

Dependent Claim 33 words

Method according to claim 29 wherein the heat transfer surfaces operate at temperatures of about 180° F. or less and in contact with cooling water having a pH of at least about 5.

Claim 35

Dependent Claim 19 words

Method according to claim 32 wherein the iron fouling consists predominantly of iron compounds deposited from said cooling water.

Claim 36

Dependent Claim 19 words

The method of claim 26 wherein the cooling water system is an industrial heat exchanger having ferrous metal tubes.

Claim 37

Dependent Claim 16 words

Method of claim 26 wherein the cooling water system is an internal combustion engine cooling system.

Claim 38

Dependent Claim 20 words

Method according to claim 26 in which the at least one compound comprises N,N-di (2-hydroxybenzyl)-trimethylene-diamine-N,N-diacetic acid or a salt thereof.

Claim 39

Dependent Claim 20 words

Method according to claim 26 in which the at least one compound is N-hydroxyethylethylenediamine triacetic acid or a salt thereof.

Claim 40

Dependent Claim 20 words

Method according to claim 26 in which the at least one compound is diethylenetriamine pentaacetic acid or a salt thereof.

Claim 41

Dependent Claim 22 words

Method according to claim 26 in which the at least one compound comprises a compound selected from those of paragraph (a) (iv).

Claim 42

Dependent Claim 22 words

Method according to claim 26 in which the acid and a neutralizing amount of base are added separately to the cooling system.

Claim 43

Dependent Claim 46 words

Method according to claim 26 in which a sufficient quantity of an aqueous solution containing about 25-35 wt. % of the acid as the sodium or potassium salt is added to the cooling water system to provide therein a concentration of about 1 to 250 ppm.

Claim 44

Dependent Claim 20 words

Method according to claim 26 in which the surfaces are contacted with a solution containing a mix of the acids.

Claim 45

Dependent Claim 49 words

Method according to claim 26 in which the contacting solution further contains at least one compound selected from those compounds having the formula ##STR9## wherein each J is selected from the group consisting of hydrogen, ammonium, sodium, or potassium, and wherein q is an integer from 1 to 5.

Claim 46

Dependent Claim 19 words

Method according to claim 43 in which the solution comprises N,N-di (2-hydroxy-5-sulfonic acid benzyl) glycine or a salt thereof.

Claim 47

Dependent Claim 22 words

Method according to claim 43 in which the at least one compound comprises a compound selected from those of paragraph (a) (iv).

Claim 48

Dependent Claim 25 words

Method according to claim 45 in which the solution contains a mix comprising N,N-di (2-hydroxy-5-sulfonic acid benzyl) glycine, or a sodium or potassium salt thereof.

Claim 49

Dependent Claim 24 words

Method according to claim 46 in which the compound from paragraph (a) (iv) is diethylenetriamine pentaacetic acid or a sodium or potassium salt thereof.

Claim 50

Dependent Claim 19 words

Method according to claim 26 wherein the heat transfer surfaces operate at temperatures of about 180° F. or less.

Claim 51

Dependent Claim 18 words

Method according to claim 26 wherein the iron fouling consists predominantly of iron compounds deposited from cooling water.

Claim 52

Dependent Claim 17 words

Method according to claim 26 wherein the solution has a calcium hardness of at least 500 ppm.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1991-01-25	1991-07-27	1992-01-26	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1995-01-25	1995-07-27	1996-01-26	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1999-01-25	1999-07-27	2000-01-26	$7700.00	Window Closed / Lapsed

Removal of iron fouling in cooling water systems

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag