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Heat exchanger electrochemically-induced film formation method in circulating cooling water micro-alkalifying transition period

A technology of circulating cooling water and film forming method, which is applied in the field of combining cathodic protection and oxidant passivation to achieve great social and economic benefits, reduce thermal resistance, and protect metal substrates

Active Publication Date: 2015-06-10
浙江常山利盛新材料有限公司 +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Carry out chemical cleaning and pre-membrane in this way, realize the method for the smooth transition of micro-alkaliization process, have not yet been reported

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] Off-line chemical cleaning for new construction systems with brass heat exchangers or for older systems during overhaul. Choose 500mm×500mm×10mm zinc plate or aluminum plate as sacrificial anode and immerse in circulating cooling water, use 12mm 2 Thick copper wires connect the anode to both ends of the heat exchanger, forming the primary cell. Then use hydrochloric acid, sulfuric acid or a solution with a ratio of 1:1 to citric acid to adjust the circulating water to acidity, pH=2~4, and circulate for 24 hours. During the cleaning process, measure Cu once every 2 hours. 2+ Content, and check the pH, if the pH rises, then replenish the acid in time. Draw the concentration versus time curve, the curve rises to the highest point, stop pickling.

[0019] Add NaOH, Na 2 CO 3 , NaHCO 3 One or more combinations of them are made into a carbonate buffer solution, the pH of the circulating water is adjusted to 8~9, and then hydrogen peroxide is added to make the H in the ci...

Embodiment 2

[0022] For new construction systems with carbon steel heat exchangers or older systems during overhaul, use the method in Example 1 for off-line chemical cleaning.

[0023] After cleaning, add FeSO 4 , Fe(NO 3 ) 2 or FeCl 2 A ferrous salt in the circulating water makes Fe 2+ The ion content is 1mmol / L~10mmol / L, Fe 2+ The ions move to the cathode under the action of the electric field of the primary battery, are adsorbed on the surface of the heat exchanger, and are reduced to iron atoms to form a pre-membrane of the same material as the matrix, which can effectively cover the surface dirt or corrosion points and prevent the alkaline oxidation environment. Localized accelerated corrosion occurs.

[0024] Then use the same steps as Example 1 to carry out alkalization and passivation, and finally form a dense iron oxide film on the surface of carbon steel, and realize self-renewal and leakage repair in a stable alkaline buffer solution, and control the corrosion rate of carb...

Embodiment 3

[0026] For old systems that require uninterrupted operation, online chemical cleaning is used. Adopt the cathodic protection scheme in Example 1, add strong acid and citric acid in a ratio of 1:1, adjust the pH of the system to 3~4, and monitor the metal ions and pH in the circulating water every day, add cleaning acid in time, and run for about 15 days , Complete in-line chemical cleaning.

[0027] For copper heat exchangers, directly use the method of example 1 to alkalinize and oxidize to obtain an oxide pre-film and complete the slight alkalization transition. For carbon steel heat exchangers, use Example 2 to perform ferrous iron adsorption and reduction pre-film first, and then use the alkalization oxidation method in Example 1 to obtain oxide pre-film to complete the transition.

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Abstract

The invention relates to a heat exchanger electrochemically-induced film formation method in a circulating cooling water micro-alkalifying transition period. The method comprises the following steps: connecting a circulating cooling water system heat exchanger with an active metal zinc block to constitute a primary cell, regulating the pH value of circulating water to 2-4, monitoring the metal ion content of the circulating water in the operation process, and after 2-3 days, finishing cleaning when the rise trend slows down; as for a brass heat exchanger, regulating the system to alkality, adding an oxidizer, and forming a Cu2O passivating film on the surface after some time, wherein after the cathode protection is removed, the Cu2O passivating film is gradually converted into a stable CuO passivating film, and afterwards, the brass corrosion rate is less than 0.005 mm / a; and as for the a carbon steel heat exchanger, adding Fe<2+> at one time, circulating for some time, regulating the solution to alkality, adding an oxidizer, removing cathode protection after some time, and forming a compact ferric oxide passivating film on the surface, wherein the corrosion rate is less than 0.01mm / a. The method prevents local corrosion and completes the circulating cooling water micro-alkalifying transition period.

Description

technical field [0001] The invention relates to a method for chemical cleaning and corrosion control of heat exchanger metals in the transitional stage of micro-alkaline conditioning and tempering of circulating cooling water, especially the combination of cathodic protection and oxidant passivation to produce uniform passivation on the surface of brass and carbon steel membrane method. Background technique [0002] The existing chemical cleaning and pre-film technology for heat exchangers in circulating cooling water systems is to use corrosion and scale inhibitors to achieve the dual purpose of not only removing dirt on metal surfaces, but also reducing the erosion of acidic media on metal substrates during cleaning. The technology is divided into two categories, one is off-line cleaning, and the other is on-line cleaning. The principle of the two is the same, that is, adding dilute strong acid or complex weak acid, and adding corrosion and scale inhibitors, the agent cir...

Claims

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Application Information

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IPC IPC(8): C23F17/00
Inventor 曾惠明吕亮程慎玉沈晓莉范蕊
Owner 浙江常山利盛新材料有限公司
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