coking

(chemical engineering) Destructive distillation of coal to make coke A process for thermally converting the heavy residual bottoms of crude oil entirely to lower-boiling petroleum products and by-product petroleum coke.

In the petroleum industry, a process for converting nondistillable fractions (residua) of crude oil to lower-boiling-point products and coke. Coking is often used in preference to catalytic cracking because of the presence of metals and nitrogen components that poison catalysts. See also Cracking.

The liquid products from the coker, after cleanup via commercially available hydrodesulfurization technology, can provide large quantities of low-sulfur liquid fuels (less than 0.2 wt% sulfur). Another major application for the processes is upgrading heavy low-value crude oils into lighter products.

Petroleum coke is used principally as a fuel or, after calcining, for carbon electrodes. The feedstock from which the coke is produced controls the coke properties, especially in terms of sulfur, nitrogen, and metals content. A concentration effect tends to deposit the majority of the sulfur, nitrogen, and metals in the coke. Cokes exceeding around 2.5% sulfur content and 200 parts per million vanadium are mainly used, environmental regulations permitting, for fuel or fuel additives. The properties of coke for nonfuel use include low sulfur, metals, and ash as well as a definable physical structure.