Q & A > Question Details
What is the relationship between the top temperature of a vacuum tower in a vacuum distillation unit and the rate of corrosion in the overhead condensers?

26/04/2017 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
The motive steam sets the temperature in the inter-condensers. If you have a pre-condenser, remove it.
26/04/2017 A: Yongming Zhang, HQCEC, 13439348666@139.com
The different crude processed, the different temperature adjusted for the overhead condenser. You should control the temperature higher than the acid gas dew point. As the acid gas condensed, the corrosion would be severer.
25/04/2017 A: Dave Collings, Jacobs, dave.collings@jacobs.com
For some refiners, relatively low overhead temperatures (especially below 150degF) can lead to fouling in the overhead system, especially noticed if you have a precondenser. This fouling (assumed to be salts) can lead to corrosion. I have seen this more than once with refiners that process Western Canadian dilbit crudes. Some have found that increasing temperature to say 300degF for a short period of time (approximately 4-8 hours) while living with a a higher vacuum and poorer yields can temporarily remove some of this fouling. To minimize the fouling and subsequent corrosion, you should operate the overhead temperature as high as possible without significantly impacting the vacuum or volume of overhead distillate production. Typically, refiners like to operate this temperature as low as possible to have the best vacuum and minimize overhead distillate make, but lowering this temperature is diminishing returns. You should also consider reviewing your metallurgy.
25/04/2017 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
There is very little relation in a vacuum unit. Corrosion in the overhead condensers is primarily linked to the amount of corrosive contaminants present such as HCl, CO2, and organic acids. What (if anything) is being done for corrosion control and metallurgy also influence corrosion. The OH temperature influences the amount of load on the ejectors (the hotter the temperature the more hydrocarbon that remains in the vapor to the ejectors) and it effects the potential for salt deposition/corrosion in the upper portion of the vacuum tower (lower temperature increases risk of salting/corrosion in the tower).