Material selection for atmospheric and vacuum distillation units
Thread Content
Some time ago, I went to a company for technical exchanges and noticed that the materials used in the atmospheric and vacuum distillation units were somewhat different. I wonder what everyone knows about this? Currently, some foreign engineering companies use AL-6XN (N08367) as the cladding for the upper part, while 317L is used for the lower part. Additionally, some domestic engineering companies choose Monel 400 or 2205 as the cladding material for the upper part, with 317L being used for the lower part. As we all know, due to the high acid value of Middle Eastern oil as well as the presence of H2S, the requirements for material selection have become stricter than before. I wonder if there are any friends who can discuss here what you know.
H2S causes corrosion at the top of the tower; ordinary stainless steel is sufficient, but the tray design also needs to be upgraded. Cyclohexanoic acid, the cause of the acid value issue, causes corrosion in the middle and lower sections of the tower; domestic design institutes generally use a composite material of 20# + 316L for this purpose. Personally, I think it should be fine.
Domestic design: 2205+316L (preferably with Mo>2.5%) should work
I’ve never seen anything this complex! ! ! One really needs to think carefully about what composite panels are meant for!
Low-temperature acid corrosion, high-temperature sulfur corrosion, and naphthenic acid corrosion generally occur at pressures from reduced pressure line 2 down to reduced pressure line 4. . . :lol (280–380)
This post was last edited by lijianhuai on 2011-12-3 at 16:11. The corrosion is most severe at the top of the vacuum distillation column, followed by that at the top of the atmospheric distillation column. We use composite 316L.
Below 200 degrees, the corrosive effect of oil is not very strong, so 316L should be sufficient; however, the corrosion increases when the temperature exceeds 200 degrees. Some companies choose 2205, but the operating temperature for 2205 should be below 300 degrees. Could some experienced experts who are familiar with this area tell me what the operating temperature conditions are in these devices?
The low-temperature top used in our unit’s atmospheric pressure tower is 16MnR+Monel； The high-temperature bottom uses 16MnR+316L
There are two reasons for the differences in the design I want to create: 1. Cold reflux and hot reflux; 2. Whether ammonia is to be injected or not