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Is there a problem with the material of the equipment? A carbon content test should be conducted. Many of the designs these days use 304 material, and Hualu Hengsheng has been in operation for 5 years now without any widespread cracking occurring. Moreover, the impact of S on 304 should be relatively small. Chloride ions have a significant impact, as does stress corrosion. Please have the design team check the stress conditions of the pipes; in Weihua, stress-induced cracking occurred in the E01 feed gas heat exchangers.

Which company’s equipment, and what kind of materials are used? = =Tell me secretly, haha – I’m also in the process of making purchases right now; be sure not to fall for it.

1. First, check whether there is any issue with the material. 2. It is necessary to check whether there are any issues with the manufacturing of the equipment, and whether the stainless steel has undergone solution treatment. 3. There are no chloride ions in methanol, so corrosion caused by chloride ions can be ruled out. 4. 304 stainless steel is widely used in low-temperature methanol washing environments with high sulfur content, so it should not present any problems.

The absence of chloride ions in methanol does not mean that they will not be introduced from the conversion unit; moreover, who can guarantee that there are no chloride ions at all in the water used for washing and alkali cleaning during the commissioning phase?

The last edit to this post was made by 654262293 on 2010-7-1 at 13:40. Reply to 5# wgonline: After the combined operation of low-temperature methanol washing, the fluid needs to be dried; that’s one point. Additionally, if the chlorine ions come from the shift gas, then how is it that the stainless steel in the shift system does not get corroded under high temperature and pressure in the presence of those chlorine ions? Moreover, why isn’t the cylinder corroded? Why is it only the head that gets corroded? ? ? ?

This post was last edited by wgonline on 2010-7-1 at 14:16. There are many human factors involved in the drying process, and it’s not always possible to achieve complete drying. We have tried this process many times; sometimes the water content in the liquid can still be as high as 10% while the vehicle is in use. There have also been cases where a leak in the steam supply valve of the water separation tower led to the tower becoming filled with water (anything can happen, O(∩_∩)O haha~). The problem may not lie in the previous system, but rather in the ammonia washing solution used at the end of the processing stage. As for why the cylinder does not corrode, I think it is very likely that the methanol flows through the tube side; the internal tubes and the head plates are clearly not of the same manufacturer, so it is possible that the issue lies simply with the quality of the equipment’s materials. Moreover, I really didn’t pay attention earlier; if cracks only appeared at the junction of the end caps and the equipment nozzles, then stress corrosion should be taken seriously, as that was exactly where the cracks appeared in WeiHua E01.

Reply to 7# wgonline: The normal water content level for poor-quality methanol is below 0.5%; a high water content in your case indicates that the methanol-water separation tower is not functioning properly. Our level is around 0.3%. Additionally, the water used in the shift ammonia washing tower is usually low-temperature sealed water (deoxygenated desalinated water), with almost no chloride ions present.

The chloride ion content does not have to be very high; generally, a concentration on the order of PPM is sufficient to damage the passivation film on the surface of stainless steel. Under tensile stress, cracks will form in the areas where the passivation film has been damaged.

I already said it’s due to human factors during drying – in normal production, who wouldn’t keep it below 0.5%? Hehe. The operation was not thorough; drying was inadequate, the water in the dead corners was not completely removed, and nitrogen was not used for purging. It is important to check the quality of the water used for washing, as well as the quality of the water used for ammonia washing; additionally, the quality of the steam needs to be examined. These are all areas where problems may arise. Chemical processing, right? =Anything is possible; if everything can operate according to the set parameters, then what’s the need for skilled operators, analysts, technicians, and engineers? Just use automatic control systems...

Reply to 10# wgonline: Why isn’t the cylinder corroded, while only the head is corroded? ? ? ?