We are having considerable coke accumulation in the reactor outlet line to the main column. During start-up and unit upsets the coke falls off and causes plugging in the slurry circuit (particularly pump suction strainers).
One consideration is to install LCO quench or something equivalent to reduce coking in the outlet line.
Does anyone have experience with installing this technology? Is the technology open art or is Stone and Webster the only licenser?
We installed the technology on one unit in 2002 and it has worked well. We’ve entered the reactor in a 2008 turnaround and found typical level of coking. This unit did not have a vapor line coking problem to deal with. The design was done by S&W with Amoco technical support.
We used this technology in our RFCC unsuccessfully on an external riser system. Need to ensure excellent atomization (nozzle type and atomization media (steam)) on the LCO or naphtha boiling point range quench material and that the riser piping is lay-out is designed properly so that liquid droplets are not classified. It definetly reduces 1,3 BD and pverall gas make but comes at the risk of coking the gas tube or cyclones especially in a resid unit.
I would not consider LCO quench as a technology that reduces transfer line coking. LCO quench should mainly reduce gas yields in the FCC. Regarding transfer line coke, issues could be related to feed injection (poor atomization, feed too heavy), low velocity and cold spots in the OVHD line.
We had a run with 1 out of 8 feed injectors in a poor shape and we saw lots of coke buildup in the transfer line (none in the riser).
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