What Is Meant By Weathering Of Coal?

coal wethering illustration

Coal weathering process

Coal exists in the underground as water saturated and in an oxygen-free environment. This stability hindrance when it is mined and exposed to air. Weathering starts as soon as coal mined. Any physical, chemical change of coal or any other alteration in its properties when it is exposed to a new environment is known as weathering. This includes oxidization, change in moisture content.

Oxidation due to prolonged exposure to air has a greater contribution towards weathering. The oxidization accelerated by humidity, temperature, and O2 partial pressure. Loss of moisture leads to increase porosity, change in volume and also cause spontaneous combustion. Porosity increases oxidization and the volume change cause increase in internal stress.

Properties of coal affected by weathering - Calorific value, moisture content, Density.
Factors that affect weathering - Time elapsed, oxygen partial pressure, rank and grade of coal, particle size.

Effect of weathering of coal

  • Increase moisture content.
  • Decrease in volatile content.
  • The coal surface becomes more hydrophilic.
  • Badly effect on coking properties.
  • The density may change (increase or decrease according to associated mineral matter).
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