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US 4,666,528 AGranted
Method of removing iron and copper-containing scale from a metal surface
AssigneeHalliburton Company
InventorsStephen T. Arrington, Gary W. Bradley
Life of this patent
Estimating the term…
Abstract
A method of removing iron and copper containing scale from a metal surface by contacting the scale with a composition comprising an admixture of an aminopolycarboxylic acid, such as ethylenediaminetetraacetic acid (EDTA), or the alkali metal salts or ammonium salts or amine salts of the aminopolycarboxylic acid and a phosphonic acid such as aminotrimethylenephosphonic acid (ATMP), or an alkali metal salt or amine salt or ammonium salt of the phosphonic acid. The aminopolycarboxylic acid or salt thereof and phosphonic acid of salt thereof are present in the composition in an amount sufficient to provide a molar ratio of aminopolycarboxylic acid to phosphonic acid in the range of from about 1:9 to about 39:1.
Claims17
A method of removing iron and copper containing scale from a metal surface comprising the steps of:
- (a) contacting said scale containing surface at a temperature of from about 150.degree. F. to about 350.degree. F. with an aqueous scale removing composition having a pH of from about 8.0 to about 10.5 and comprising an admixture of
- (i) an aminopolycarboxylic acid selected from the group consisting of ethylenediamine tetraacetic acid, N-hydroxyethylethylenediaminetriacetic acid, nitrilotriacetic acid, N-2-hydroxyethyliminodiacetic acid, diethylenetriamine pentaacetic acid, N-2-hydroxyethylethylene diaminetriacetic acid, propylene-1,3-diaminetetraacetic acid, propylene-1,2-diaminetetraacetic acid, the alkali metal, amine and ammonium salt of the aminopolycarboxylic acids, and mixtures thereof;
- and
- (ii) a phosphonic acid selected from the group consisting of aminotrimethylenephosphonic acid, ethylenediaminetetra-methylenephosphonic acid, hexamethylenediaminetetra-methylenephosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, the alkali metal, amine and ammonium salt of the phosphonic acid and mixtures thereof;
- (b) maintaining said composition in contact with said scales for a time sufficient to remove said iron containing scale from the metal surface;
- (c) adjusting said pH of said composition to from about 8.0 to about 10.5 when said pH of said composition is outside the range of from about 8.0 to about 10.5 and said temperature to from about 120.degree. F. to about 180.degree. F. when said temperature is outside the range of from about 120.degree. F. to about 180.degree. F. prior to removal of said copper containing scale;
- and,
- (d) contacting said copper containing scales with said composition for a time sufficient to remove said copper containing scales from said surface;
- wherein said aminopolycarboxylic acid and said phosphonic acid are present in said composition in an amount sufficient to produce a molar ratio of aminopolycarboxylic to phosphonic acid in the range of from about 1:9 to about 39:1, wherein the combined weight of the aminocarboxylic acid and phosphonic acid present in said composition is in the range of from about 1.5 percent by weight to about 6.0 percent by weight of the composition, and wherein the composition of step (c) further comprises an oxidizing agent present in an amount sufficient to oxide substantially all the ferrous ions present in said composition to ferric ions and substantially all the copper which is to be removed from said metal surface to cupric ions.
6 more elements
A method of removing iron and copper containing scale from a metal surface comprising the steps of:
- (a) contacting said scale containing surface at a temperature of from about 225.degree. F. to about 275.degree. F. with an aqueous scale removing composition having a pH of from about 8.0 to about 10.5 and comprising
- (i) an aminopolycarboxylic acid selected from the group consisting of ethylenediaminetetraacetic acid, N-hydroxyethylethylenediaminetriacetic acid, nitrilotriacetic acid, N-2-hydroxy-ethyliminodiacetic acid, diethylenetriaminepentaacetic acid, N-2-hydroxyethylethylenediaminetriacetic acid, propylene-1,3-diaminetetraacetic acid, propylene-1,2-diaminetetraacetic acid, the alkali metal, amine and ammonium salt of the aminopolycarboxylic acids, and mixtures thereof;
- and
- (ii) a phosphonic acid selected from the group consisting of aminotri-methylenephosphonic acid, ethylenediaminetetra-methylenephosphonic acid, hexamethylenediaminetetra-methylene-phosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid the alkali metal, amine and ammonium salt of the phosphonic acid and mixtures thereof;
- (b) maintaining said composition in contact with said scales for a time sufficient to remove said iron containing scale from the ferrous metal surface;
- (c) adjusting said pH of said composition to from about 8.0 to about 10.5 when said pH of said composition is outside the range of from about 8.0 to about 10.5 and said temperature to from about 120.degree. F. to about 180.degree. F. when said temperature is outside the range of from about 120.degree. F. to about 180.degree. F. prior to removal of said copper containing scale;
- and,
- (d) contacting said copper containing scales with said composition for a time sufficient to remove said copper containing scales from said surface;
- wherein said aminopolycarboxylic acid and said phosphonic acid are present in said composition in an amount sufficient to produce a molar ratio of aminopolycarboxylic to phosphonic acid of from about 1:9 to about 39:1, wherein the combined weight of the aminocarboxylic acid and phosphonic acid present in said composition is in the range of from about 1.5 percent by weight to about 6.0 percent by weight of the composition, and wherein the composition of step (c) further comprises an oxidizing agent present in an amount sufficient to oxide substantially all the ferrous ions present in said composition to ferric ions and substantially all the copper which is to be removed from said metal surface to cupric ions.
6 more elements
Dependencies are inferred from the claim text.