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Wednesday, October 7, 2015

Q&A - DELAYED COKER

Delayed Coker

Dale:
My coker fractionation tower top pressure surges higher by 5 psi for a few hours. Tower top temperature jumps by 20°F - 40°F. The level in light gas oil pan drops. This occurs every few days. What’s happening?

Norm:

You’re salting-up the top few trays. The top reflux can’t cool off the upper trays. They get hot, and sublime off the salts. A simple way to prevent the problem, is to periodically heat up the top of the tower, maybe for 30 minutes by 30°F, every few days. I’m not too sure about time and temperature factors. Periodic water washing is also possible, but a lot more complicated.

2 comments:

  1. The DCU furnace tube radiation delta pressure is increasing slowly but the skin temperature is not increasing. What could be the possible cause of this?

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  2. It could be that you have only coke formation in a localized area where you are not monitoring skin temperature?
    Perhaps composition of feed has gotten slightly lighter with time and % vaporization is increasing and causing higher delta P?
    Best to be guided by tube color, rather than skin temperature, as coking may be occurring with no skin TI.

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