Petroleum coke
Encyclopedia
Petroleum coke is a carbonaceous
solid derived from oil refinery
coker unit
s or other cracking
processes. Other coke
has traditionally been derived from coal
.
Marketable coke is coke that is relatively pure carbon
and can be sold for use as fuel
(i.e. fuel grade coke
), or for the manufacture of dry cell
s, electrode
s, etc. (i.e., anode grade coke).
Needle coke, also called acicular coke, is a highly crystalline petroleum coke used in the production of electrodes for the steel
and aluminium
industries and is particularly valuable because the electrodes must be replaced regularly. Needle coke is produced exclusively from either FCC decant oil or coal tar pitch. Catalyst coke is coke that has deposited on the catalysts used in oil refining, such as those in a fluid catalytic cracker. This coke is impure and is only used for fuel.
Fuel Grade Coke is classified as either sponge coke or shot coke morphology. While oil refiners have been producing coke for well over 100 years, the mechanisms that cause sponge coke or shot coke to form are not well understood and cannot be accurately predicted. In general, lower temperatures and higher pressures promote sponge coke formation. Additionally, the amount of heptane insolubles present, and fraction of light components in the coker feed contribute.
Its high heat and low ash
content make it a good fuel for power generation in coal fired boiler
s, but petroleum coke is high in sulfur
and low in volatile
content which pose some environmental and technical problems with its combustion. In order to meet current North American emissions standards some form of sulfur capture is required, a common choice of sulfur recovering unit for burning petroleum coke is the SNOX Flue gas desulphurisation
technology, which is based on the well-known WSA Process. Fluidized bed combustion
is commonly used to burn petroleum coke. Gasification
is increasingly used with this feedstock (often using gasifiers placed in the refineries themselves).
Calcined petroleum coke (CPC) is the product from calcining
petroleum coke. This coke is the product of the coker unit
in a crude oil refinery
. The calcined petroleum coke is used to make anode
s for the aluminium
, steel
and titanium
smelting industry. The green coke
must have sufficiently low metals content in order to be used as anode material. Green coke with this low metals content is referred to as anode grade coke. The green coke with too high metals content will not be calcined and is used for burning. This green coke is called fuel grade coke
.
Traditionally in India the prices of petroleum coke have remained higher than Fuel oil. However due to excess production in the recent past the values have dropped and are currently in the range of Rs. 17,000 / M.T.
Carbonaceous
Carbonaceous is the defining attribute of a substance rich in carbon. Particularly, carbonaceous hydrocarbons are very unsaturated, high-molecular-weight hydrocarbons, having an elevated carbon:hydrogen ratio....
solid derived from oil refinery
Oil refinery
An oil refinery or petroleum refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas...
coker unit
Coker unit
A coker or coker unit is an oil refinery processing unit that converts the residual oil from the vacuum distillation column or the atmospheric distillation column into low molecular weight hydrocarbon gases, naphtha, light and heavy gas oils, and petroleum coke...
s or other cracking
Cracking (chemistry)
In petroleum geology and chemistry, cracking is the process whereby complex organic molecules such as kerogens or heavy hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds in the precursors. The rate of cracking and the end products...
processes. Other coke
Coke (fuel)
Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...
has traditionally been derived from coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
.
Marketable coke is coke that is relatively pure carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
and can be sold for use as fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...
(i.e. fuel grade coke
Coke (fuel)
Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...
), or for the manufacture of dry cell
Dry Cell
-Dry Cell's formation:Part of the band formed in 1998 when guitarist Danny Hartwell and drummer Brandon Brown met at the Ratt Show on the Sunset Strip. They later met up with then-vocalist Judd Gruenbaum. The original name of the band was "Beyond Control"....
s, electrode
Electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
s, etc. (i.e., anode grade coke).
Needle coke, also called acicular coke, is a highly crystalline petroleum coke used in the production of electrodes for the steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
and aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
industries and is particularly valuable because the electrodes must be replaced regularly. Needle coke is produced exclusively from either FCC decant oil or coal tar pitch. Catalyst coke is coke that has deposited on the catalysts used in oil refining, such as those in a fluid catalytic cracker. This coke is impure and is only used for fuel.
Fuel Grade Coke is classified as either sponge coke or shot coke morphology. While oil refiners have been producing coke for well over 100 years, the mechanisms that cause sponge coke or shot coke to form are not well understood and cannot be accurately predicted. In general, lower temperatures and higher pressures promote sponge coke formation. Additionally, the amount of heptane insolubles present, and fraction of light components in the coker feed contribute.
Its high heat and low ash
Fly ash
Fly ash is one of the residues generated in combustion, and comprises the fine particles that rise with the flue gases. Ash which does not rise is termed bottom ash. In an industrial context, fly ash usually refers to ash produced during combustion of coal...
content make it a good fuel for power generation in coal fired boiler
Boiler
A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.-Materials:...
s, but petroleum coke is high in sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
and low in volatile
Volatile organic compound
Volatile organic compounds are organic chemicals that have a high vapor pressure at ordinary, room-temperature conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and...
content which pose some environmental and technical problems with its combustion. In order to meet current North American emissions standards some form of sulfur capture is required, a common choice of sulfur recovering unit for burning petroleum coke is the SNOX Flue gas desulphurisation
SNOX Flue gas desulphurisation
The SNOX process is a process which removes sulfur dioxide, nitrogen oxides and particulates from flue gases. The sulfur is recovered as concentrated sulfuric acid and the nitrogen oxides are reduced to free nitrogen...
technology, which is based on the well-known WSA Process. Fluidized bed combustion
Fluidized bed combustion
Fluidized bed combustion is a combustion technology used in power plants. Fluidized beds suspend solid fuels on upward-blowing jets of air during the combustion process. The result is a turbulent mixing of gas and solids. The tumbling action, much like a bubbling fluid, provides more effective...
is commonly used to burn petroleum coke. Gasification
Gasification
Gasification is a process that converts organic or fossil based carbonaceous materials into carbon monoxide, hydrogen, carbon dioxide and methane. This is achieved by reacting the material at high temperatures , without combustion, with a controlled amount of oxygen and/or steam...
is increasingly used with this feedstock (often using gasifiers placed in the refineries themselves).
Calcined petroleum coke (CPC) is the product from calcining
Calcination
Calcination is a thermal treatment process applied to ores and other solid materials to bring about a thermal decomposition, phase transition, or removal of a volatile fraction. The calcination process normally takes place at temperatures below the melting point of the product materials...
petroleum coke. This coke is the product of the coker unit
Coker unit
A coker or coker unit is an oil refinery processing unit that converts the residual oil from the vacuum distillation column or the atmospheric distillation column into low molecular weight hydrocarbon gases, naphtha, light and heavy gas oils, and petroleum coke...
in a crude oil refinery
Oil refinery
An oil refinery or petroleum refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas...
. The calcined petroleum coke is used to make anode
Anode
An anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID ....
s for the aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
and titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
smelting industry. The green coke
Green coke
Green 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 temperatures up to approximately 1600 K...
must have sufficiently low metals content in order to be used as anode material. Green coke with this low metals content is referred to as anode grade coke. The green coke with too high metals content will not be calcined and is used for burning. This green coke is called fuel grade coke
Coke (fuel)
Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...
.
Traditionally in India the prices of petroleum coke have remained higher than Fuel oil. However due to excess production in the recent past the values have dropped and are currently in the range of Rs. 17,000 / M.T.
See also
- Delayed cokerDelayed cokerA 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 into coker gas oil and petroleum coke...
- TarTarTar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest...
- List of CO2 emitted per million Btu of energy from various fuels
External links
- IUPAC definition of various forms of solid carbonCarbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
. - BP info on how calcined petroleum coke is produced