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Efficient environment-friendly chemical cleaning method

A chemical cleaning and environmental protection technology, applied in the direction of metal material coating process, etc., can solve the problems such as the large influence of residual ion type and concentration, the unsatisfactory passivation effect of hydrogen peroxide, and the not very stable passivation effect, etc., to achieve passivation The effect is stable, the passivation effect is good, and the effect is easy to implement on site

Active Publication Date: 2015-06-24
STATE GRID CORP OF CHINA +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Hydrazine has some defects such as high passivation temperature and complicated post-treatment
Hydrogen peroxide is an environmentally friendly passivating agent that has been used more and more in recent years. Experiments have shown that the passivation effect after rinsing with citric acid is not very stable, and is greatly affected by the type and concentration of residual ions in the rinse solution.
Another disadvantage is that hydrogen peroxide is easy to decompose, and it is easy to cause the air lock of the pickling pump and cause the liquid to overflow. Many reasons cause the passivation effect of hydrogen peroxide to be unsatisfactory.
Sodium nitrite passivation is the passivation agent with the best passivation effect and the most mature passivation process among these agents. However, because its waste liquid pollutes the environment heavily, special agents are required for post-treatment, which has always limited the use of sodium nitrite. usage of

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0031] The present invention is an efficient and environment-friendly chemical cleaning method, the process steps are as follows:

[0032] Pickling: Take 4% sulfamic acid and 0.2% commercially available sulfamic acid corrosion inhibitor, dissolve the above components in an appropriate amount of water according to the above ratio, and put them into the polished pipe sample of the water wall (pickling The ratio of the liquid volume to the surface area of ​​the scale is 22:1), and the descaling rate is 98.7% after soaking statically at 50 degrees for 10 hours.

[0033] Rinse with water after pickling: Rinse the tube sample with desalinated water until the total iron is less than 50mg / l and the pH value is less than 4.5, and the water rinse after pickling is completed;

[0034] Rinsing: Add citric acid corrosion inhibitor to the system, after the circulation is uniform, prepare a citric acid solution with a concentration of 0.1% by mass, adjust the pH value to 3.5 with ammonia wat...

Embodiment 2

[0039] The present invention is an efficient and environment-friendly chemical cleaning method, the process steps are as follows:

[0040] Pickling: the compound acid (90 parts by weight of sulfamic acid and 10 parts by weight of other components) of 7% sulfamic acid as the main detergent in mass fraction, 0.2% commercially available sulfamic acid corrosion inhibitor, the above components Dissolve it in an appropriate amount of water according to the above ratio, put it into the polished tube sample of the water wall (the ratio of the volume of the pickling solution to the surface area of ​​the scale is 22:1), soak it statically at 55 degrees for 7 hours, and the scale removal rate is 99.3%.

[0041]Rinse with water after pickling: Rinse the tube sample with desalinated water until the total iron is less than 50mg / l and the pH value is less than 4.5, and the water rinse after pickling is completed;

[0042] Rinsing: Add citric acid corrosion inhibitor to the system, after the ...

Embodiment 3

[0047] The present invention is an efficient and environment-friendly chemical cleaning method, the process steps are as follows:

[0048] Pickling: the compound acid (90 parts by weight of sulfamic acid and 10 parts by weight of other components) of 10% sulfamic acid as the main cleaning agent in mass fraction, 0.2% commercially available sulfamic acid corrosion inhibitor, the above-mentioned combination Dissolve it in an appropriate amount of water according to the above ratio, put it into the polished tube sample of the water wall (the ratio of the volume of the pickling solution to the surface area of ​​the scale is 22:1), soak it statically at 60 degrees for 4 hours, and the scale removal rate is 99.6%.

[0049] Rinse with water after pickling: Rinse the tube sample with desalinated water until the total iron is less than 50mg / l and the pH value is less than 4.5, and the water rinse after pickling is completed;

[0050] Rinsing: Add citric acid corrosion inhibitor to the ...

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PUM

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Abstract

The invention belongs to the technical field of metal surface chemical cleaning methods, and particularly relates to an efficient environment-friendly chemical cleaning method comprising a surface chemical cleaning method for boilers and other heat exchangers. The efficient environment-friendly chemical cleaning method comprises the processing steps of (1) performing sulfamic acid pickling, (2) performing water washing after pickling, (3) performing citric acid rinsing, (4) performing sodium nitrite passivation and (5) performing liquid waste treatment. The efficient environment-friendly chemical cleaning method utilizes a low-temperature pickling medium which is convenient to transport and facilitates field implementation, and uses a passivation agent with stable and good passivation effect at present to implement passivation. In addition, a passivation liquid used by the efficient environment-friendly chemical cleaning method can react with a pickling agent in a waste liquid pool to generate an innocuous product, so that independent treatment on the passivation liquid is omitted, and the dosage of sodium hydroxide for neutralization is reduced.

Description

technical field [0001] The invention belongs to the technical field of chemical cleaning methods for metal surfaces, and in particular relates to an efficient and environment-friendly chemical cleaning method, including the chemical cleaning method for the surfaces of boilers and other heat exchangers. Background technique [0002] The cleaning of large heat exchange equipment such as boilers and superheaters generally includes pickling, water rinsing after pickling, rinsing and passivation. [0003] Pickling agents mainly include inorganic acids and organic acids, commonly used are hydrochloric acid, citric acid, EDTA, glycolic acid, formic acid, etc. These agents have certain defects in the current use, such as hydrochloric acid cannot be used for austenitic steel and stainless steel, although citric acid and EDTA have a wide range of applications, but the use temperature is relatively high, citric acid 90-95 ℃, EDTA120-140 In this way, there are disadvantages of high hea...

Claims

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Application Information

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IPC IPC(8): C23G1/02C23C22/60
Inventor 沈继军吴南程晓云
Owner STATE GRID CORP OF CHINA
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