Char is the solid material that remains after light gases (e.g.
coal gas) and
tar
Tar is a dark brown or black viscous liquid of hydrocarbons and free carbon, obtained from a wide variety of organic materials through destructive distillation. Tar can be produced from coal, wood, petroleum, or peat. "a dark brown or black bit ...
have been driven out or released from a
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
aceous material during the initial stage of
combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...
, which is known as
carbonization
Carbonization is the conversion of organic matters like plants and dead animal remains into carbon through destructive distillation.
Complexity in carbonization
Carbonization is a pyrolytic reaction, therefore, is considered a complex process ...
,
charring Charring is a chemical process of incomplete combustion of certain solids when subjected to high heat. Heat distillation removes water vapour and volatile organic compounds ( syngas) from the matrix. The residual black carbon material is char, as ...
, devolatilization or
pyrolysis
The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements ''py ...
.
Further stages of efficient combustion (with or without char deposits) are known as
gasification reactions, ending quickly when the
reversible gas phase of the
water gas shift reaction
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a s ...
is reached.
See also
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Biochar
Biochar is the lightweight black residue, made of carbon and
ashes, remaining after the pyrolysis of biomass. Biochar is defined by the International Biochar Initiative as "the solid material obtained from the thermochemical conversion of ...
*
Charcoal
Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, cal ...
*
Coke (fuel)
Coke is a grey, hard, and porous coal-based fuel with a high carbon content and few impurities, made by heating coal or oil in the absence of air—a destructive distillation process. It is an important industrial product, used mainly in iro ...
*
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 ...
*
Shale oil extraction
Shale oil extraction is an industrial process for unconventional oil production. This process converts kerogen in oil shale into shale oil by pyrolysis, hydrogenation, or thermal dissolution. The resultant shale oil is used as fuel oil or up ...
*
Spent shale
Spent shale or spent oil shale (also known as retorted shale) is a solid residue from the shale oil extraction process of producing synthetic shale oil from oil shale. It consists of inorganic compounds (minerals) and remaining organic matter kno ...
Oil shale
Coal
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