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Certain refiners are feeding vacuum residue and FCC slurry oil to the coker unit as part of their strategy for reducing (or eliminating) fuel oil production. To this end, what operational and hardware changes should be made to the vacuum tower and FCC main fractionator?
 
Answers
03/01/2012 A: Saugata Palit, Intercat India Ltd, spalit@intercatinc.com
Feeding Vacuum Residue and FCC slurry oil is not an uncommon practice. This depends on the refinery economics, where the streams need to be routed. Processing these streams in a secondary unit is always profitable than using them in Fuel Oil.
Since these are already products from FCC and VDU, no hardware changes need to be done in the upstream units, but the coker unit needs to be designed for handling these streams. The Coker unit should have High sulfur tolerance if these streams are from HS crudes. Moreover, the CLO from FCC has to have low BS&W (~ 0.05 wt %) as these will tend to corrode Coker heaters. There are processes to reduce BS&W from SO. One good process are the Pall Filters. The Coke chambers must be of sufficient height to tolerate the excess feed CCR which will get manifested in Coke bed height.
As Vineet has already suggested, producing bitumen is a profitable solution from VR. This will require some minor modifications in the Vacuum tower to withdraw vacuum slop oil. For CLO, CBFS is a alternative option.
07/12/2009 A: Vineet Singh, IOCL Barauni, SINGHVK007@GMAIL.COM
Alternatively, you can easily convert vacuum residue to bitumen as a commercial product. Operational changes are required in VDU operation e.g withdrawal of slop oil from (as FCCU feed) VDU column. This may help in reducing the fuel oil production from Coker block.