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Chemical cleaning agent for martensitic stainless steel T91 superheater oxide skin and cleaning method

A martensitic stainless steel and cleaning agent technology, which is applied in the field of chemical cleaning agent and cleaning agent for martensitic stainless steel T91 material superheater scale, can solve the problem of low chromium content in the chromium-rich layer, which cannot meet the requirements of inhibiting the secondary growth of scale, conventional The cleaning technology cannot achieve the cleaning effect and other problems, and achieve the effect of efficient removal, reduced risk of secondary peeling, and good solubility

Pending Publication Date: 2021-12-31
XIAN THERMAL POWER RES INST CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Compared with austenitic stainless steel, the chromium content of the chromium-rich layer of T91 material is lower, which cannot meet the requirements of inhibiting the secondary growth of oxide scale, so it should be removed in the chemical cleaning stage
Since the superheater operates under high-temperature and high-pressure steam conditions, the oxide scale formed on the inner wall of the heat exchange tube has the characteristics of large thickness and compact structure, especially the chromium oxide in the chromium-rich layer is difficult to dissolve in acid, resulting in the failure of conventional cleaning techniques. to good cleaning effect

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0017] The first stage cleaning agent is composed of 8% by mass of citric acid, 0.5% malic acid, 0.8% corrosion inhibitor, 0.1% iso-ascorbic acid and demineralized water, and ammonia water is used to adjust the pH of the cleaning agent to 3.8.

[0018] Among them, the corrosion inhibitor is composed of the following mass percentages: hydrazine accounts for 20%, oleic acid-hydroxyethyl imidazoline accounts for 15%, methyl benzotriazole accounts for 15%, hexadecylamine accounts for 20%, Demineralized water accounts for 30%.

[0019] Take 200 mL of the cleaning agent of this embodiment, heat it up to 95 ° C, clean the heat exchange tube of a T91 superheater in a power plant and hang it into a T91 corrosion test piece under airtight conditions, and detect the iron ion concentration in the cleaning solution. After the iron ion concentration no longer changes , the cleaning is over.

[0020] The second-stage cleaning agent is composed of 7.0% citric acid, 0.5% ethylenediaminetetraa...

Embodiment 2

[0024] The first-stage cleaning agent is composed of 10% by mass of glycolic acid, 0.5% of ethylenediaminetetraacetic acid, 1.0% of corrosion inhibitor, 0.2% of acetone oxime and demineralized water, and ammonia water is used to adjust the pH of the cleaning agent to 4.0.

[0025] Among them, the corrosion inhibitor is composed of the following mass percentages: hydrazine accounts for 15%, oleic acid-hydroxyethyl imidazoline accounts for 20%, methyl benzotriazole accounts for 25%, hexadecylamine accounts for 10%, Demineralized water accounts for 30%.

[0026] Take 200mL of the cleaning agent of this embodiment, heat it up to 90°C, clean the heat exchange tube of a T91 superheater in a power plant under airtight conditions, and hang a T91 corrosion test piece to detect the iron ion concentration in the cleaning solution. After the iron ion concentration no longer changes , the cleaning is over.

[0027] The second stage cleaning agent is composed of 7.0% citric acid, 1.0% 2-hy...

Embodiment 3

[0031] The first stage cleaning agent is composed of 8% by mass of acetic acid, 0.3% glycolic acid, 0.5% corrosion inhibitor, 0.1% sodium sulfite and demineralized water, and sodium hydroxide is used to adjust the pH of the cleaning agent to 3.5.

[0032] Among them, the corrosion inhibitor is composed of the following mass percentages: hydrazine accounts for 10%, oleic acid-hydroxyethyl imidazoline accounts for 25%, methyl benzotriazole accounts for 20%, hexadecylamine accounts for 20%, Demineralized water accounts for 25%.

[0033] Take 200 mL of the cleaning agent of this embodiment, heat it up to 95 ° C, clean the heat exchange tube of a T91 superheater in a power plant and hang it into a T91 corrosion test piece under airtight conditions, and detect the iron ion concentration in the cleaning solution. After the iron ion concentration no longer changes , the cleaning is over.

[0034] The second-stage cleaning agent is composed of 6.0% formic acid, 0.5% gluconic acid, 1.0...

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Abstract

The invention discloses a chemical cleaning agent for a martensitic stainless steel T91 superheater oxide skin and a cleaning method. The chemical cleaning agent is prepared from an agent A and an agent B. The agent A is prepared from a descaling agent accounting for 7.0%-10% of the cleaning agent by mass, a cosolvent accounting for 0.1%-0.5%, a corrosion inhibitor accounting for 0.5%-1.0%, a reducing agent accounting for 0.05%-0.5% and demineralized water. The agent B is prepared from the descaling agent accounting for 4.0%-8.0% of the cleaning agent by mass, the cosolvent accounting for 0.5%-2.0%, the corrosion inhibitor accounting for 0.2%-1.0%, the reducing agent accounting for 0.05%-0.5% and the demineralized water. During cleaning, the agent A and the agent B are adopted for two-stage cleaning; the pH value of the cleaning agent is adjusted by a pH adjusting agent, and the cleaning temperature is controlled. The cleaning agent and the cleaning method have good solubility on the T91 superheater oxide skin, a chromium-rich layer in a T91 heat exchange tube can be efficiently removed, and the risk of secondary peeling caused by the residual chromium-rich layer in the T91 heat exchange tube is reduced.

Description

technical field [0001] The invention belongs to the technical field of chemical cleaning of power station equipment, and in particular relates to a chemical cleaning agent for oxide scale of a martensitic stainless steel T91 material superheater and a cleaning method. Background technique [0002] In thermal power units, due to the formation and peeling of superheater oxide scale, the problems of reduced service life of superheater heat exchange tubes, blockage of tubes, main valve jamming and erosion of steam turbine solid particles have become increasingly prominent. The chemical cleaning of the superheater has the advantages of moderate cost, thorough treatment, good removal effect and wide cleaning range. [0003] T91 is a commonly used material for superheaters. The oxide skin produced by T91 is mostly a double-layer structure. The surface layer is an iron oxide layer composed of ferric oxide or ferric oxide, and the inner layer is a metal oxide layer rich in chromium, ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23G1/08C23G1/06
CPCC23G1/088C23G1/063
Inventor 张贵泉姚建涛龙国军
Owner XIAN THERMAL POWER RES INST CO LTD