Delayed coker

From there, it is pumped, along with some injected steam, into the fuel-fired furnace and heated to its thermal cracking temperature of about 480 °C.

The injected steam helps to minimize the deposition of coke within the furnace tubes.

Pumping the incoming residual oil into the bottom of the main fractionator, rather than directly into the furnace, preheats the residual oil by having it contact the hot vapors in the bottom of the fractionator.

As cracking takes place in the drum, gas oil and lighter components are generated in vapor phase and separate from the liquid and solids.

The stills were heated by wood or coal fires built underneath them, which over-heated and coked the oil near the bottom.

After the distillation was completed, the still was allowed to cool and workmen could then dig out the coke and tar.

A 4-drum delayed coking unit in a petroleum refinery
A delayed coking unit. A schematic flow diagram of such a unit, where residual oil enters the process at the lower left (see → ), proceeds via pumps to the main fractionator (tall column at right), the residue of which, shown in green, is pumped via a furnace into the coke drums (two columns left and center) where the final carbonization takes place, at high temperature and pressure, in the presence of steam.