Coal is a brownish black sedimentary, organic rock formed from accumulation of plant remains modified by chemical, biological and physical processes during and after burial. The coal property are broadly classified as:
- Physical Property
- Chemical Property
Physical Property
Physical property of coal includes moisture, fixed carbon, volatile matter, ash and heating value. All these parameters are calculated with the help of proximate analysis of coal.
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Moisture
Reduced moisture content of coal increases the efficiency of power plant, decreases transportation costs, decreases ash disposal requirements and decreases power plant emissions.
Typical range of moisture is 0.5 to 10 %
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Volatile Matter
Volatile matter are combustible gases present in coal such as carbon monoxide, methane, hydrocarbons, hydrogen. It also content small amount of incombustible gases like carbon dioxide and nitrogen.
The higher the volatile matter content, the lower the minimum ignition temperature of the coal dust, the easier it is burn and faster spreading of the explosion flame.
Typical range of volatile matter is 20 to 35 %
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Fixed Carbon
Fixed carbon is that portion of coal that remains as residue after volatile matter distills off, after the sum moisture and ash content in the coal is subtracted.
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Ash
Ash represents parts of the original mineral matter in coal that does not combust.
As the ash content increases, the lower burning rate of fuel results in char particle leaving the grate without being fully burned, causing a loss of combustible material and therefore reducing the combustible efficiency.
Typical range of ash is 5 to 40%.
Chemical Property
Chemical property of coal refers to the various elemental chemical constituents such as carbon, hydrogen, oxygen, Sulphur. All these chemical constituents are calculated by ultimate analysis of coal.
- Carbon (50 to 90%)
- Hydrogen (2 to 40 %)
- Oxygen (2 to 4 %)
- Sulphur(0.5 to 3%)
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