Q.2 (b) Calculate the gross and net calorific value of coal having the following compositions. Carbon=85%, hydrogen=8%, sulphur=1%, nitrogen=2%, ash=4%, and the latent heat of steam is 587 cal/gm.
Best answer
Given: C = 85%, H = 8%, S = 1%, N = 2%, ash = 4%.
Total = 85 + 8 + 1 + 2 + 4 = 100%, so O = 0%. Latent heat of steam = 587 cal/g = 587 kcal/kg.
Dulong's formula (C, H, O, S in %):
\( \text{HCV} = \frac{1}{100}\left[8080\,C + 34500\left(H - \frac{O}{8}\right) + 2240\,S\right] \) kcal/kg
\( \text{LCV} = \text{HCV} - 0.09\,H \times 587 \) kcal/kg (latent heat of steam = 587 kcal/kg)
\( \text{GCV} = \frac{1}{100}\left[8080(85) + 34500\left(8 - \frac{0}{8}\right) + 2240(1)\right] = \frac{1}{100}\left[686800 + 276000 + 2240\right] = \frac{965040}{100} \)
Gross calorific value (HCV) = 9650.4 kcal/kg
\( \text{NCV} = \text{GCV} - 0.09\,H \times 587 = 9650.4 - 0.09 \times 8 \times 587 = 9650.4 - 422.64 \)
Net calorific value (LCV) = 9227.76 kcal/kg
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