A coker or coker unit is an
oil refinery
An oil refinery or petroleum refinery is an industrial process plant where petroleum (crude oil) is transformed and refined into useful products such as gasoline (petrol), diesel fuel, asphalt base, fuel oils, heating oil, kerosene, lique ...
processing unit that converts the residual oil from the
vacuum distillation column into low molecular weight
hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...
gas
Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma).
A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
es,
naphtha
Naphtha ( or ) is a flammable liquid hydrocarbon mixture.
Mixtures labelled ''naphtha'' have been produced from natural gas condensates, petroleum distillates, and the distillation of coal tar and peat. In different industries and regions ''n ...
, light and heavy
gas oil
Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma).
A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), ...
s, and
petroleum coke
Petroleum coke, abbreviated coke or petcoke, is a final carbon-rich solid material that derives from oil refining, and is one type of the group of fuels referred to as cokes. Petcoke is the coke that, in particular, derives from a final cracki ...
. The process thermally
cracks the long chain hydrocarbon molecules in the residual oil feed into shorter chain molecules leaving behind the excess carbon in the form of petroleum coke.
This petroleum coke can either be fuel grade (high in sulphur and metals) or anode grade (low in sulphur and metals). The raw coke from the coker is often referred to as
green coke Green coke (raw coke) is the primary solid carbonization product from high boiling hydrocarbon fractions obtained at temperatures below 900 K. It contains a fraction of matter that can be released as volatiles during subsequent heat treatment at tem ...
. In this context, "green" means unprocessed. The further processing of green coke by
calcining
Calcination refers to thermal treatment of a solid chemical compound (e.g. mixed carbonate ores) whereby the compound is raised to high temperature without melting under restricted supply of ambient oxygen (i.e. gaseous O2 fraction of air), genera ...
in a
rotary kiln
A rotary kiln is a pyroprocessing device used to raise materials to a high temperature (calcination) in a continuous process. Materials produced using rotary kilns include:
* Cement
* Lime
* Refractories
* Metakaolin
* Titanium dioxide
* Alum ...
removes residual volatile hydrocarbons from the coke. The
calcined petroleum coke can be further processed in an anode baking oven in order to produce anode coke of the desired shape and physical properties. The anodes are mainly used in the
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
and
steel
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
industry.
Types of coker units
There are three types of cokers used in oil refineries:
Delayed coker
A delayed coker is a type of coker whose process consists of heating a residual oil feed to its thermal cracking temperature in a furnace with multiple parallel passes. This cracks the heavy, long chain hydrocarbon molecules of the residual oil i ...
,
Fluid coker and
Flexicoker.
The one that is by far the most commonly used is the delayed coker.
The schematic flow diagram below depicts a typical delayed coker:
See also
*
Delayed coker
A delayed coker is a type of coker whose process consists of heating a residual oil feed to its thermal cracking temperature in a furnace with multiple parallel passes. This cracks the heavy, long chain hydrocarbon molecules of the residual oil i ...
*
Shukhov cracking process
The Shukhov cracking process is a thermal cracking process invented by Vladimir Shukhov and Sergei Gavrilov. Shukhov designed and built the first thermal cracking device for the petrochemical industry. His patent (Shukhov cracking process – p ...
*
Burton process The Burton process is a thermal cracking process invented by William Merriam Burton and Robert E. Humphreys, each of whom held a PhD in chemistry from Johns Hopkins University. The process they developed is often called the Burton process. More fai ...
*
Petroleum coke
Petroleum coke, abbreviated coke or petcoke, is a final carbon-rich solid material that derives from oil refining, and is one type of the group of fuels referred to as cokes. Petcoke is the coke that, in particular, derives from a final cracki ...
References
External links
Detailed description of cokers and related topicsQuality specifications for petroleum cokes
{{Petroleum refining
Oil refineries
Chemical equipment
Petroleum production