How to prevent sulfuric acid dew point corrosion in refining equipment
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Drawing on the various cases of sulfuric acid dew point corrosion in refining equipment discussed earlier, preventive measures can be taken in the following areas: operational and process control – strictly controlling the sulfur content in fuels, and using low-oxygen combustion techniques to reduce excess oxygen and thereby inhibit the conversion of SO₂ to SO₃； By means of hot air recirculation and the installation of heaters, the wall temperature of the equipment is raised to 110–150°C, above the dew point of sulfuric acid, to prevent the acid from condensing. Design optimization: Low-temperature flue gas is directed into the convection zone to achieve heat recovery, thereby avoiding direct heat exchange in the radiation zone ； An external insulation layer is added to the equipment casing to prevent localized supercooling and dew formation, while the spacing between the heat exchange tubes is increased appropriately to avoid erosion caused by high flue gas flow rates. Appropriate material selection: Steel materials resistant to sulfuric acid dew point corrosion, such as ND steel (09CrCuSb), should be given priority; materials like 316L and 20G can also be used. For special operating conditions, ceramic or enamel components can be employed, or specialized high-temperature resistant anti-corrosion coatings such as ZS-711 can be applied. Auxiliary protection measures involve adding neutralizing agents to the flue gas to consume SO3 and reduce the formation of sulfuric acid vapor ； At the same time, regularly test the sulfur content in equipment deposits to identify potential corrosion risks in advance.
This topic post is quite comprehensive, covering the key points in both terms of manufacturing processes and design optimization. I would like to add some practical experience: in addition to controlling the sulfur content in the fuel and wall temperature, routine inspections should also focus on corrosion in areas with low temperatures (such as flue bends and economizer inlets), as these are the places most likely to develop problems first. Furthermore, if the sulfur content in the fuel fluctuates significantly, it is recommended to install an online dew point monitoring device, as this allows for more reliable real-time adjustment of operating conditions. Have you encountered any other tricky situations in actual operations? We can think about it together. Of course, the specific plan still needs to be determined based on the recommendations of the equipment manufacturer and the actual operating conditions.