Question

Explain higher and lower calorific value of a coal having following composition by mass Carbon 81%,Hydrogen 7%, Oxygen 8%,Nitrogen 2.5%, sulphur 1.5% and remaining is ash

Answer 1

Carbon C = 81% = 0.81

Hydrogen = H2 = 7% = 0.07

Oxygen = O2 = 8% = 0.08

Nitrogen = N = 2.5% = 0.025

Sulphur = S =1.5% = 0.015

Ash = 2.5% = 0.025

Dulong’s formula: H.C.V. of coal

= 33800 C + 144500 ( H2 - O2/8 ) + 9300 S KJ / Kg

=33800 x 0.81 + 144500 (0.07 - 0.08/8) + 9300 x 0.015

H.C.V. of coal = 36187.5 KJ / Kg 

L.C.V. of coal

= H.C.V.- 9H2 x 2442 KJ / Kg

= 36187.5– 9 x 0.07 x 2442

L.C.V. of coal = 34649.04 KJ / Kg