How to solve the corrosion problem of ND steel heat pipes in low-temperature, humid flue gas?
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This post was last edited by Wang Wei2 on 2019-9-26 at 10:39. How to address the corrosion problem of ND steel heat pipes in low-temperature, humid flue gas? The image below shows the heat pipes used in a GGH within wet flue gas at low temperatures (60–90°C) in a certain boiler; they were discarded after less than a year of use. ND steel and 09CrCuSb steel are recommended materials for coal-fired boilers, flue pipes, chimneys, boiler air preheaters, and economizers. However, their service life is short due to corrosion in such environments, which limits the use of GGHs. How to address surface corrosion of heat pipes is crucial for enabling GGH to function in flue gas; what are the best methods to use?
It’s been a long-standing issue; it seems it still hasn’t been resolved! Due to differences in coal quality and process control among various power plants, GGHs exhibit distinct characteristics, and specific analysis is necessary ； ND steel is not a one-time solution either. The following points should be noted for practical implementation at present: 1. Under the conditions of 70% H2SO4 at 80°C, the corrosion rate of ND steel in its passivated state is low; the process should be adjusted to match these conditions, avoiding as much as possible the use of 50% concentrated sulfuric acid ； 2. For the low-temperature cold end of the hot flue gas outlet and cold flue gas inlet, composite materials such as plastic coating or spraying should be considered. 3. The design of the heat pipes is also crucial, such as their arrangement and spacing. If there are any new developments, I hope to be able to share them! Good luck!
Should one use coatings or paints with good anti-corrosion properties and excellent thermal conductivity?
Should one use coatings or paints with good anti-corrosion properties and excellent thermal conductivity?
Is the efficiency lower when using a heat pipe at 90°C?
Generally, coatings will affect the heat exchange efficiency, right?
The heat transfer rate of ordinary coatings is indeed lower than that of metals, but if surface corrosion and scale formation on heat pipes can be addressed, the issue of coatings affecting heat exchange efficiency need not be considered. Because, when there is no anti-corrosion coating on the surface of the heat pipe, the thermal resistance of the rust layer and soot layer resulting from corrosion is much greater than that of the coating.
The anti-corrosion treatment for this flue gas is relatively simple; contact ZhiSheng WeiHua’s Tang Engineer for a complete set of solutions and classic application examples
This post was last edited by Wang Wei2 on 2021-9-29 at 20:10. Preventing corrosion and scaling on the surface of heat pipes is a challenging problem; therefore, coatings with a thickness of less than 200 microns are required. The coating is required to be heat-resistant, corrosion-resistant, scale-resistant, wear-resistant, and have good thermal conductivity. Therefore, to date, the method of using coating materials has not provided a satisfactory solution. This requires our corrosion prevention engineers to continuously screen materials, conduct tests, and draw conclusions. By doing it repeatedly, I think there will be a better way to solve this problem. If this issue is resolved, it can be said that the service life of heat pipes in low-temperature, humid flue gas can be increased, which in turn can extend the service life of the GGH in boiler systems. This environmental protection device can meet the requirements regarding exhaust gas temperature over the long term, and GGHs can be used in most thermal power plants, thereby saving a large amount of energy. However, most power plant boilers still do not use GGHs, as the problem of heat pipe corrosion in GGHs has not yet been properly resolved, and the production cost is too high. If anyone is interested, let’s work together to address the issue of corrosion caused by low-temperature, humid flue gases in heat pipes.