Heats of formation of some hydrocarbons are:

Hydrocarbons  (1 atm, 298K)kcal/kgmol CH4 17.89x103 C2H2 54.19x103 C2H4 12.5x103 C2H6 20.24x103 C3H8 24.82x103

To note





Consider an example of gaseous fuel of the following composition:









Let us calculate CV of this fuel
In 1 kg mole of gaseous fuel:

Heat of combustion of Methane

CH4(g)  + 2  (g) =

By substituting the values of heat of formation one obtains heat of combustion of methane equals .

Similarly, combustion equations for  and   can be written and heat of combustion value can be calculated.

Heat of combustion of  and of  is

 when reference state of POC is vapour. Thus net calorific value (NCV) of natural gas is



of natural gas

(1 atm and 273K)