Oil Processing: Delayed Coking

What is the best way to deal with accumulated coke in the fractionator bottom sump?

Heavy Coke drum vapor is quenched at the coke drum outlet and partially condensed in the bottom section of the coker fractionator. Entrained coke particles are a major source of solids entering the coker fractionator. Conventional technology attempts to control coke build-up by filtering a small portion (~25%) of fractionator bottom liquid to mitigate downstream furnace tube fouling and providing an internal standpipe to allow coke accumulation in the fractionator bottom up to the level where feed pump flow is interrupted.

ThruPlus® technology employs a proprietary Flash Zone Gas Oil (FZGO) system to trap and filter coke fines from the coke drum vapor stream, thus protecting the downstream furnace tubes and minimizing coke build-up in the fractionator bottom liquid sump.

Flash Zone system description

The entire coke drum outlet vapor stream is washed with a curtain of heavy gas oil spray nozzles (refer to process schematic<put a link to Figure 2>) Combined heat and mass transfer condenses natural recycle oil and de-entrains particulate coke on the sloped surface of our Flash Zone Gas Oil tray. FZGO liquid strainer removes larger particles. A mixture of FZGO liquid and preheated residual feed forms the furnace liquid inlet stream. Trapping the incoming particulate coke also inhibits coke growth (thermal cracking) in the fractionator bottom liquid sump. Suspended small diameter particulates pass through the furnace charge pumps and coker furnaces en route to the coke drums.