Advantages: 

• Easy to handle
• Ash less
• Good Combustion

Calorific Value (hereafter CV):

Calorific value (CV) is the potential energy in the fuel and refers to the amount of heat released on complete combustion of 1 kg of coal at the reference state of products of combustion (POC hereafter). Its knowledge is required to perform heat balance in the furnaces and to determine the combustion efficiency of coal (combustion efficiency is the fraction of heat released on combustion).

For a hydrocarbon fuel containing C,H and S, products of complete combustion are , and SO₂. Reference state of POC is

So GCV > NCV by an amount equal to latent heat of condensation.

CV can be expressed as cal/g, kcal/kg, kJ/kg, Btu/lb or cal/gmol, kcal/kgmol, kJ/kgmol, Btu/lbmol

Some conversion factors:

Determination of CV of Gaseous Fuel

CV can be determined experimentally or from theoretical considerations. In laboratory,

Bomb calorimeter is used where 1 g coal is combusted at constant volume and rise in temperature is noted^1,2) .
Theoretically, CV of coal can be determined from the heat of formation of products of complete combustion at 298K and 1 atm. pressure.

In terms of % of elements:

(9)

(10)

NCV = GCV – Heat of vaporization of water

(11)

(12)

Equations 9 to 12 are Dulong’s formula

Assumptions:

• Heat of formation of coal is zero.
• Coal contains H and O. Therefore, available H for combustion with gaseous oxygen
• CV of coal is sum of CV of heat of formation of complete combustion products.
• Heat of vaporization of water at (975 Btu/lb); whereas at 25^oC it is 584 kcal/kg (1050 Btu/lb).