【Weekly Topic】What should be considered in the anti-corrosion design of chimneys and flues? (8.29-9.05)

This post was last edited by zgj2405 on 2011-9-1 13:28. 1) The original flue duct before the flue gas heat exchanger does not need to have anti-corrosion measures applied. For desulfurization units equipped with flue gas heat exchangers, anti-corrosion measures should be taken in the flue running from the inlet elbow on the raw flue gas side of the heat exchanger to the chimney. Depending on the applicable conditions, scale resin or rubber lining should be used as the anti-corrosion material. For desulfurization units that do not have flue gas heat exchangers, anti-corrosion measures should be applied starting from a distance of at least 5 meters from the inlet of the absorption tower. Technical evaluations have confirmed that, when corrosion-resistant steel is used, anti-corrosion measures may not be necessary for the tops and side walls of the flue in certain sections, but an adequate margin against corrosion should still be considered. 2) The structural design of the anti-corrosion flue should meet the corresponding anti-corrosion requirements, and ensure that the vibration and deformation of the flue body remain within acceptable limits, thereby preventing the anti-corrosion layer from peeling off. 3) A drainage system should be installed in the flue at the lower part of the flue gas heat exchanger. 4) The design temperature of the flue gas for the desulfurization unit should be the flue gas temperature at the exit of the air preheater under the BMCR condition of the coal type specified for the boiler. For newly installed units, an overtemperature of 50°C during short-term operation should be taken into account, but the resulting temperature should not exceed 180°C. The design temperature of the raw flue gas duct downstream of the flue gas heat exchanger should take into account a 30°C overtemperature, while the design temperature of the clean flue gas duct should consider a 20°C overtemperature.

:Is there any anti-corrosion treatment? I noticed that the large chimneys built by our company don’t seem to have any proper anti-corrosion measures; only a layer of paint has been applied on the outside, which might provide some protection against corrosion. Additionally, lightning rods are necessary.

1. The anti-corrosion of chimneys is divided into external and internal anti-corrosion measures. External anti-corrosion typically involves the use of anti-corrosive coatings and paints, as well as safety measures such as lightning protection. Internal corrosion protection primarily addresses dew point corrosion caused by low-temperature dew formation in flue gas. It should also be noted that the flue gas after wet flue gas desulfurization needs to be heated; otherwise, dew formation is likely to occur. In some projects, the flue gas has carried the alkali used for desulfurization into the chimney, resulting in chimney corrosion. For details on the anti-corrosion treatment of flues, see Floor 1.

What the poster is referring to is likely anti-corrosion treatment for the inner walls. It’s very important to choose the right materials for such anti-corrosion treatment; one must opt for qualified products from reputable manufacturers. Moreover, anti-corrosion work is carried out manually, and the construction methods and skills used greatly determine the quality of the work. Therefore, when selecting a construction team, it’s essential to choose a qualified professional team. I work in chimney construction, so I have frequent exposure to this type of work and thus have some understanding of it.

This post was last edited by www.jsycyn.com on 2012-3-14 at 15:30. Hehe, you must be referring to applying aviation markings on the exterior walls; it does indeed have an anti-corrosion effect. Are those red and white color bands? How tall is the chimney, and how many coats were applied? Additionally, lightning rods and lightning conductors also need to be protected against corrosion, as do the steel structures such as ladders and platforms, in order to facilitate maintenance in the future!