Coal Testing Applications

Coal is technically classified as a sedimentary rock.  It is found in naturally occurring underground seams and composed mainly of organic matter and various mineral aggregates. Coal is formed in a process known as coalification, where dead plant matter first decays into peat and is then converted into coal by the further heat and pressure of deep burial over millions of years.  The coalification process gives rise to different ranks of coal depending upon the length of time the process continues.  The major ranks of coal in increasing order of their maturation are lignite, sub-bituminous, bituminous and anthracite.  The main elemental components of coal are carbon, hydrogen, sulfur, oxygen, and nitrogen; varying in weight basis percentages depending upon the specific rank.  Typical analyses of coal are either presented in the form of a proximate analysis (moisture, ash volatile matter and fixed carbon,) or as an ultimate analysis (ash, carbon, hydrogen, nitrogen, oxygen, and sulfur). Coal also contains various inorganic elemental components depending upon the amount of mineral matter present.  The mineral analyses of coal are typically presented in the elemental oxide basis in ash while trace metal analyses are usually presented in a whole coal basis.


The main use of coal is as a fossil fuel.   Over 60 % of the coal mined around the world is used for the production of electricity.  When coal is burned in the presence of oxygen, heat energy is released.  Thermal coals have high calorific values, which when burned in large industrial boilers, release heat which is used to convert water into steam, which in turn drive large turbines to produce an electric current.

Up to 20 % of coal mined globally is used in the metallurgical industry.  When heated in the absence of air, bituminous coals exhibit a plastic-like nature, which after removing moisture and most of the volatile matter, resolidifies into a porous mass high in carbon content known as coke.  Coke is produced from metallurgical coals which are heated to temperatures of over 1000 °C in large coke ovens.  The resulting cokes are much higher in carbon content than the contributing coals and are used as both fuels and reducing agents in the smelting of irons and ferro alloys and in the forging of steel.

The remaining 20 % of coal is used in various industrial applications, such as in the production of various chemicals, dyes, medicines, insecticides, fertilizers, explosives, synthetic fibers, and even food preservatives.  Coal is also used as a fuel and for drying in the paper, cement and glass industries as well as used in gasification and liquefaction technologies, and in the production of activated carbons.

The world’s leading miners of coal are China, the United States, Australia and India.  Leading consumers of coal are China, United States, India, and Russia.  Of the coal mined in the United States, approximately 85 % is used domestically and 15 % is exported overseas, mainly through ports located on the east and gulf coasts.

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Testing Process

McCreath Laboratories will employ both ASTM and ISO standard methods in the analysis of coals.  The methods are continually verified through the use of certified reference materials.  Typical coal analysis performed are as follows:

TestInstrumentReference Method
Total MoistureAir-Dry OvenASTM D3302
Ash ContentMuffle/TGAASTM D3174/D7582
Volatile Matter ContentFurnace/TGAASTM D3175/D7582
Sulfur ContentLECO SC832ASTM D4239
Calorific ValueLECO AC500ASTM D5865
Carbon, Hydrogen, NitrogenLECO CHN828ASTM D5373
ChlorineISEASTM D4208
FluorineISEASTM D3761
MercuryLECO AMA254ASTM D6722
OxidationSpec 20ASTM D5263
Forms of SulfurThermo ICAPASTM D2492 / D8214
Minerals in AshThermo ICAPASTM D6349
Trace ElementsThermo ICP-MSASTM D6357
Hardgrove Grindability IndexBall MillASTM D409
Free Swelling IndexGas BurnerASTM D720
Bulk DensityPhysicalASTM D291
Sieve AnalysisPhysicalASTM D4749

For more information on the analysis of coals, contact us.