Thursday, January 2, 2014

What are inherent moisture (IM) and total moisture(TM.) in coal?

When coal is traded in its specifications two types of moisture values are mentioned.  This is very important as it affects the cost of fuel per unit of power generated or per kg of steam produced by the boiler. i.e. it affects the boiler efficiency.

The moisture in Coal consists of two parts.

Profit is in moisture than coal for mine owners
  1. One is the moisture held within the molecular structure of the coal called “inherent moisture.” Removal takes place only at temperatures greater than 100 deg C.

  1. The second part is the moisture that is on the surface of the coal. This is normally due to the conditions and locations of the mines. This moisture can evaporate in exposed atmospheric conditions. How much evaporates depends on
    • The time of exposure,
    • Atmospheric contact because of spreading,
    • Ambient temperature and humidity.
The Moisture in the Coal is both these put together and is the “Total Moisture.”

     TM – IM  is the surface moisture, which is not liked by boiler engineers.