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It is a much simpler version of flexi-coking process consisting of a reactor bed and a burner.
It does not consist of a gasifier.
In fluid coking, feed is first preheated to 260oC and then sent to a scrubber unit located above the reactor bed for recovering fine particles of coke from overhead vapors. The fine particles are recycled with heavy compounds and are entered into the reactor bed and the coking process takes place.
The lighter products from the reactor are withdrawn as overhead vapors and the remaining coke at the bottom is separated continuously .
The cold coke at the bottom of the reactor is fed into the burner in a layering manner , and a scrubber is also present there to scrub any heavier hydrocarbons on coke, where it is fluidized with the help of steam. Some part of coke (15-30%) is sent to burner for combustion along with injected air and the coke is heated up and the rest is separated out.
The hot coke is sent back to the reactor bed and combustion of coke in the burner produces flue gases of lower calorific value which is processed with the help of separators, scrubbers etc. and can be used in steam generation , power generation etc.
The pet coke so obtained out of burner is used as cement industry fuel and partial oxidation feed.
So, it can be analyzed that both fluid and flexi-coking processes involve separation of lighter materials from the VDU residue and reduction of coke as plenty of coke is used in heating up the coke.
Therefore, much of the residue is converted to fuel gases during combustion to heat up the coke and lighter fractions at the top of reactor bed and the remaining is left up as pet coke. Also, the amount of coke left in case of flexi-coking is less than that of fluid coking.
