Calculating Net and Gross Calorific Value of Coal

Calculating Coal Calorific Value

Calculate the net and gross calorific value of a coal sample with the following composition: C = 82%, H = 8%, O = 5%, N = 1.4%, and ash = 3.5%.

Step 1: Calculate the Gross Calorific Value (GCV)

Dulong's formula is used to calculate the GCV based on the percentages of carbon (C), hydrogen (H), and oxygen (O) in the coal sample. The formula is:

GCV = 1/100 [8080C + 34500(H - O/8) + 2240S]

Assuming no sulfur (S) is present (not listed in the composition):

GCV = 1/100 [8080(82) + 34500(8 - 5/8)]

GCV = 1/100 [662560 + 34500(7.375)]

GCV = 1/100 [662560 + 254437.5]

GCV = 916997.5 / 100

GCV = 9169.975 kcal/kg

Step 2: Calculate the Net Calorific Value (NCV)

The NCV is calculated from the GCV by subtracting the latent heat of condensation of water formed during combustion. The formula is:

NCV = GCV - 0.09 × H × L

Where:

• H is the percentage of hydrogen.
• L is the latent heat of steam (587 kcal/kg).

NCV = 9169.975 - 0.09 × 8 × 587

NCV = 9169.975 - 422.64

NCV = 8747.335 kcal/kg

Final Results

The gross calorific value (GCV) of the coal sample is 9169.975 kcal/kg, and the net calorific value (NCV) is 8747.335 kcal/kg.