Burning Coal in Power Plants

Coal is the primary fuel for producing Electricity. Some of the characteristics of coal have profound influence on the day to day working and economics of the power plant. This article discus two of the important characteristics – Calorific Value and Moisture.
This is the most important parameter that determines the economics of the power plant operation.

It indicates the amount of heat that is released when the coal is burned. The Calorific Value varies on the geographical age, formation, ranking and location of the coal mines. It is expressed as kJ/kg in the SI unit system. Power plant coals have a Calorific Value in the range of 9500 kJ/kg to 27000 kJ/ kg.
The calorific value is expressed in two different ways on account the moisture in the coal. Coal contains moisture. When coal burns the moisture in coal evaporates taking away some heat of combustion which is not available for our use.

The Heating Value determines how much fuel is required in the power plant. Higher the Calorific Value lesser the amount of the coal required per unit of Electricity. Higher Calorific value also means the cost of the coal is higher but is offset by the lower cost of logistics, storage and ash disposal.

Moisture
The coal when mined contains moisture. The moisture is in two forms. First is the inherent moisture which is entrapped within the structure of the coal. Second is the external moisture that is outside of the coal structure. The amount of moisture depends again on the geographical age, location and condition in the mines. Depending on where and when you determine the moisture, values will be different for the same of coal.

The amount of moisture determines how much of heating is to be done to dry the coal before it is burned in the boiler.