Help: Issue with the high-pressure water cooling material in our hydrogenation unit?
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Hello, experts. The plant I work at is equipped with a diesel hydrotreating unit with a capacity of 300,000 tons per year. In April this year, the high-pressure water-cooling tubes in that unit leaked twice, which is really frustrating. I checked the drawings and confirmed that the material used for this high-pressure water-cooled system is 20# steel! Its single tube is 25*2.5, which means the wall thickness of that single tube is 2.5 millimeters. My doubt is whether 20# steel is not suitable for use in high-pressure hydrogen cooling Also, isn’t a wall thickness of 2.5 millimeters a bit thin? ? I called a few competitors and most of them don’t have high-pressure water cooling – only air cooling! I wonder if any expert can answer my question! I would like to thank everyone first! ～～～
Reply to 1# rzg548: What is the hydrogenation pressure rating for your diesel and gasoline, in MP? Is there air cooling? What is the temperature of the water inlet cooler? It goes without saying that in the design of air coolers for hydroprocessing gasoline and diesel, carbon steel is generally used ； The cause of the leakage needs to be carefully analyzed – is it a leak in the weld? Is it caused by circulating water corrosion? Is it a quality issue with the heat exchange tubes? It is inappropriate to use austenitic stainless steel for this application due to the high chloride content in this area ； However, the constraints can be addressed through anti-corrosion treatment to avoid corrosion by circulating water ； At a normal cooling water temperature of below 80 degrees, the rate of sulfur corrosion at low temperatures is very low; therefore, it is no problem to use carbon steel for lines handling low-temperature acidic gases ；
Exactly how high is the pressure you are referring to, and what is the corrosivity of the medium? Based on what you said, it’s not possible to draw a conclusion at the moment.
Just wrote down the advice from the two experts above! Especially the second floor. It confirmed some of my judgments! Our current water injection rate is around 2.5–3.0 tons per hour ； There is no issue with the circulating water quality, and this heat exchanger has been treated to prevent corrosion! If the material is fine, then it’s possible that the issue stems from defects in the manufacturing of this heat exchanger! Of course, I also cannot rule out the possibility that certain changes in the raw materials have led to an increase in corrosion! Thank you again to the two people above; I’ve learned a lot from you! ! ~