Additives for heat exchanger deposit removal in a wet layup condition
View Patent ↗This invention relates to compositions and methods for the at least partial dissolution, disruption and/or removal of deposits, such as scale and other deposits, from heat exchanger components. The heat exchanger components can include pressurized water reactor steam generators. The pressurized water reactor steam generators can be in a wet layup condition. The compositions include elemental metal and complexing agent selected from the group consisting of sequestering agent, chelating agent, dispersant, and mixtures thereof. The methods include introducing the compositions into the heat exchanger components.
1. A composition for at least partial disruption or removal of oxide scale, consisting of:
water at ambient temperature having a pH from about 9.0 to about 12.5;
from about 0.001 M to about 0.5 M based on the composition, of at least one elemental metal additive to the water, selected from the group consisting of zinc, beryllium, aluminum, magnesium, iron, lithium, and mixtures thereof, in particulate or colloid form being effective to release one or more electrons to interact with the scale and to result in release of one or more dissociated ions from the scale;
a complexing agent additive to the water, selected from the group consisting of sequestering agent, chelating agent, and mixtures thereof;
optionally a dispersant;
optionally an oxygen scavenger;
optionally a pH control agent; and
optionally a reducing agent,
wherein, the oxide scale is deposited on a surface of a secondary side, internal part of a steam generator in a pressurized water reactor.
2. The composition of claim 1 , wherein the elemental metal is zinc.
3. The composition of claim 1 , wherein the colloid form is selected from the group consisting of micron-sized particles, nano-sized particles, and combinations thereof.
4. The composition of claim 1 , wherein the sequestering agent is selected from the group consisting of acids and salts of orthophosphates, polyphosphates, 1-hydroxyethylidene-1,1-diphosphonic acid, and mixtures thereof.
5. The composition of claim 1 , wherein the chelating agent is selected from the group consisting of ethylenediamine tetraacetic acid, hydroxyethyl ethylenediamine triacetic acid, lauryl substituted ethylenediamine tetraacetic acid, polyaspartic acid, oxalic acid, glutamic acid diacetic acid, ethylenediamine-N,N′-disuccinic acid, gluconic acid, glucoheptonic acid, N,N′-ethylenebis-[2-(o-hydroxyphenyl)]-glycine, pyridine dicarboxcylic acid, nitrilotriacetic acid, acids and salts thereof, and mixtures thereof.
6. The composition of claim 1 , wherein the dispersant is selected from the group consisting of polyacrylic acid, polyacrylamide, polymethacrylate and mixtures thereof.
7. The composition of claim 1 , wherein the elemental metal and complexing agent are together present in an amount of from about 0.025 weight percent to about 6.0 weight percent.
8. The composition of claim 1 , further comprising a reducing agent or oxygen scavenger.
9. The composition of claim 8 , wherein the reducing agent can be selected from the group consisting of ascorbic acid, citric acid, hydrazine, carbohydrazide, catalyzed hydrazine, hydroquinone, m ethylethylketoxime, diethylhydroxylamine, erythorbate, and mixtures thereof.
10. A composition for at least partial disruption or removal of oxide scale, consisting of:
water at ambient temperature having a pH from about 9.0 to about 12.5;
from about 0.001 M to about 0.5 M based on the composition, of at least one elemental metal additive to the water, selected from the group consisting of zinc, beryllium, aluminum, magnesium, iron, lithium, and mixtures thereof, in particulate or colloid form being effective to release one or more electrons to interact with the scale and to result in release of one or more dissociated ions from the scale;
a chelating agent;
optionally a dispersant;
optionally an oxygen scavenger;
optionally a pH control agent; and
optionally a reducing agent,
wherein, the oxide scale is deposited on a surface of a secondary side, internal part of a steam generator in a pressurized water reactor.
11. The composition of claim 1 , wherein the complexing agent additive constitutes from about 0.025 weight percent to about 2.5 weight percent based on total weight of the composition.
12. The composition of claim 10 , wherein the chelating agent constitutes from about 0.025 weight percent to about 2.5 weight percent based on total weight of the composition.