Editing Energy value of coal

The '''energy value of [[coal]]''', or '''fuel content''', is the amount of [[potential energy]] coal contains that can be converted into [[Heat of combustion|heat]].<ref>{{Cite journal |last=Vilakazi |first=L |last2=Madyira |first2=D |date=2024 |title=Estimation of gross calorific value of coal: A literature review |url=https://www.tandfonline.com/doi/full/10.1080/19392699.2024.2339340 |journal=International Journal of Coal Preparation and Utilization |language=en |pages=1–15 |doi=10.1080/19392699.2024.2339340 |issn=1939-2699|doi-access=free }}</ref> This value can be calculated and compared with different [[Coal#Types|grade]]s of coal and other combustible materials, which produce different amounts of heat according to their grade.

While [[chemistry]] provides ways of calculating the [[heating value]] of a certain amount of a substance, there is a difference between this [[theoretical]] value and its application to real coal. The grade of a sample of coal does not precisely define its [[chemical composition]], so calculating the coal's actual usefulness as a fuel requires determining its proximate and ultimate analysis (see "Chemical Composition" below).

==Chemical composition==
Chemical composition of the coal is defined in terms of its proximate and ultimate (elemental) analyses. The parameters of proximate analysis are [[moisture]], [[Volatility (chemistry)|volatile]] matter, ash, and fixed carbon. Elemental or ultimate analysis encompasses the quantitative determination of [[carbon]], [[hydrogen]], [[nitrogen]], [[sulfur]] and [[oxygen]] within the coal. Additionally, specific physical and mechanical properties of coal and particular [[coal assay|carbonization]] properties 

The [[calorific value]] ''[[Heat|''Q'']]'' of coal [kJ/kg] is the heat liberated by its complete [[combustion]] with oxygen. ''Q'' is a complex function of the elemental composition of the coal{{cn|date=June 2022}}. ''Q'' can be determined [[experiment]]ally using calorimeters. [[Pierre Louis Dulong|Dulong]] suggests the following approximate formula for ''Q'' when the oxygen content is less than 10%: 

:''Q'' = 337''C'' + 1442(''H'' - ''O''/8) + 93''S'',

where ''C'' is the mass percent of carbon, ''H'' is the mass percent of hydrogen, ''O'' is the mass percent of oxygen, and ''S'' is the mass percent of sulfur in the coal.  With these constants, ''Q'' is given in kilojoules per kilogram.

==See also==
* [[Coal assay|Coal assay techniques]]
* [[Energies per unit mass]]
* [[Heat of combustion]]

==References==
{{Reflist}}
*"Using Charcoal Efficiently."  Food and Agriculture Organization of the United Nations.  Retrieved 10 Nov 2011. [http://www.fao.org/docrep/X5328E/x5328e0b.htm]
*"Combustion Training."  (c)2011 E Instruments International, LLC.{{usurped|1=[https://web.archive.org/web/20110407003846/http://www.e-inst.com/combustion/]}}

{{Coal}}

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[[Category:Coal technology]]
[[Category:Thermodynamic properties]]