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RE: Pros and Cons of coking process

Home Forums Coking Technical Fractionation & Process Process Pros and Cons of coking process RE: Pros and Cons of coking process


Mitchell Moloney

There are three coking processes in use in the industry:
(1) Delayed Coking (DLK) – Process resid flows into the bottom of the Main Fractionator mixing with recycled heavy oil and is pumped through a furnace (900-940F) into a coke drum, which cycles with another sister coke drum (or, in rare instances, two sister coke drums) when the drum is deemed full of coke.  The product vapors are fractionated in Main Fractionator.  Coke removal is accomplished with a variety of equipment for steam stripping, quenching, coke drum head operations, coke cutting, drum heating.
(2) Fluid Coking (FBK, ExxonMobil licensed)- In this process the resid enters a fluid reactor (similar to a Gas Oil Fluid Cat Cracker) via injection nozzles located at various levels in the wall of the reactor.  The resid sprays on to small pellets of coke (similar to FCC catalyst in function, but larger in size); reactor temperature is 930 – 950F.  The cracked products are separated from the coke using cyclones (just like in the FCC).  The product vapors flow to a Scrubber vessel which removes heavy oils and recycles them (Analogous to the bottom the DLK Main Frac).  Vapors leave the Scrubber and enter a Main Fractionator.  Product processing is essentially identical to DLK coke is partially combusted in the burner vessel (analogous to the FCC regenerator) and returned to the reactor.  The combustion gases typically flow to a CO Boiler and are scrubbed (analogous to the FCC) or treated.
(3) Flexi Coking (FXK, ExxonMobil licensed) – This is basically a Fluid Coker with an additional vessel, the Gasifier, which completely combusts the coke to low-BTU gas (120 BTU/SCF).  The gas is treated in a special amine (Flexsorb) scrubber.  Typically the entire plant must be configured to burn the large amount of low-BTU gas generated.  The overall investment is high and best justified in locations with little natural gas available or very high gas prices.
Regards – Mitch Moloney ExxonMobil Resid Specialist

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