Coal is a solid hydrocarbon compound that is found in natures with a complex composition.
- Combustible Material, are materials that are combustible or can be oxidized. These materials generally consists of Fixed Carbon, Hydrocarbon compounds, Total Sulphur, Hydrogen Compound and other compounds in small numbers.
Non Combustible Material, are materials that are not combustible or cannot be oxidized. These materials are generally shaped by inorganic compounds (Si02, A1203, Fe203, Ti02, Mn304, CaO, MgO, Na20, K20 and other metal compounds in small numbers) which will form the ashes inside the coal. These non combustible materials are generally unwanted because it will lower its combustion value.
In the coal forming process, with help from physico and natural chemistry, cellulose (C49H7O44) which comes from plants will go through changes to become Lignite (C70H5O25), Subbituminous (C75H5O20), Bituminous (C80H5O15) or Anthracite (C94H3O3).