Discussion on the corrosion issue of transformation systems
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How to avoid and prevent corrosion of equipment and pipelines in conversion systems is a challenge for those involved in gas purification. As a result, many manufacturers encounter production safety issues. In plants that use sulfur-resistant shift technology, especially full-low-temperature shift, which areas are subject to severe corrosion, and how is monitoring carried out during regular operations? I hope everyone will express their opinions enthusiastically.
Corrosion mainly occurs in the gas inlet pipelines of the saturated hot water tower, the heat exchangers before and after it, and the water heaters. To reduce corrosion, existing manufacturers use a full low-variation process with unsaturated hot water towers. Routine inspections mainly include checking the thickness of gas pipes, elbows, as well as conducting pressure tests and leak checks on heat exchangers.
The part where corrosion is most severe in our system is the steam mixer. There are frequent repairs; this time, the steam mixer is planned to be replaced during the maintenance.
Transformation corrosion is primarily dew point corrosion; it is best to use 304 material for equipment and pipelines in the transformation gas system. Corrosion is severe along the cold transfer lines, and it is best for all heat exchangers in this area to be made of 304 material, as these are the areas most prone to leaks. It is necessary to strengthen drainage systems and regularly measure the thickness of equipment and pipelines
This post was last edited by Luo Hu 15185080221 on 2010-6-2 at 11:47. Corrosion resulting from transformation generally includes chloride ion corrosion, corrosion caused by weak acids formed by carbon dioxide, hydrogen sulfide, and sulfur dioxide, as well as stress corrosion due to manufacturing stresses in the equipment. Solutions to chloride ion corrosion include using deionized water for adding steam (or soft water) ； Corrosion due to weak acid dew points: The manufacturing process should be designed to keep away from dew points, and equipment located in areas near dew points should be made of corrosion-resistant materials ； Stress corrosion in equipment manufacturing: Stress should be relieved through tempering during production; the arrangement of heat exchange tubes in the heat exchanger must be reasonable, and the connection method between the heat exchange tubes and the tube sheet should also be appropriate.
What concentration range of chloride ions in the condensed water is considered safe?
For stress corrosion caused by wet H2S, there is nothing else to do but to enhance monitoring.
Personally, I believe that corrosion (especially total low-temperature corrosion) is caused by the alkali metals, which are the active components in low-temperature catalysts.
The corrosion caused by the loss of alkali metals in the conversion catalyst is severe; it is necessary to control the temperature properly to prevent the catalyst from being exposed to water, and catalysts with a low rate of alkali metal loss should be used
Heat exchangers corrode relatively quickly, as the outlet temperature of the fully low-temperature saturation tower is relatively low, which facilitates the formation of dew point corrosion.
I think it’s also related to the material; water gas reduces the oxide protective film at high temperatures