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What are the potential problems if feed remains un-vaporized because of heavy tail end of the feed? I know un-vaporized feed leads to increase in coke, which eventually burns in regenerator. Does anybody have any experience about how much portion of un-vaporized feed ends up in coke? Also in case of operating unit how one can figure it out whether feed is fully vaporized or not?
 
Answers
16/08/2010 A: Bob Kalaria, KBR, bhavdip.kalaria@kbr.com
The problem with unvaporized feed is the coke formation. This coke may deposit on your vessel internals hampering the run length of the unit. This will decrease the energy efficiency and mechanical reliability of the unit. We have seen clients who have to bring down the unit frequently to clean up this coke. Also, if your feed does not vaporize completely, you would also loose valuable hydrocarbon products.
If you see increased coke formation in the reactor overhead or cyclones, poor feed vaporization may be a reason.