Illustration-I

In coke-making, it is often required to calculate the amount of coke, coke oven gas and tar produced per ton of coal. This can be done by performing elemental balance. For this purpose ash, C, N, H and O balance can be done to obtain the require information. This is illustrated by the following problem

1. By product coke ovens are surrounded by air. There may occur leakage of air in the oven. Consider a coke- oven surrounded by moist air, (The air is at 750 mm Hg pressure and  temperature) . The relative humidity of air is 40%. It carbonizes coal of the composition (Wt%)  C 76.1, H 4.6, N 2.3, S 1.9,O 2.5,  6.3 and ash 6.3. The following product and by products are produced:

Product : Coke (Wt %) C 85.2, H 1.9, O 2.2, N 0.8, S 1.2 and Ash 8.7
By –product :

(a) Coke oven gas (vol % dry basis)
      and  C₆H₆ 1.1,C₂H₄ 2.7,CH₄ 4.4, CO 1.7, CO₂ 1.3, H₂ 36.5, N₂ 6.9, O₂ 2, H₂S 2.1 and NH₃ 1.3

(b) Tar (40 kg/ton of coal) analysis (Wt %)
      C=89.4, H 4.5, N 1.1.and incombustibles Rest.

Required per ton of Coal

1. Amount of coke /ton of coal
2. Amount of coke-oven gas
3. fraction of S in coke and coke oven gas
4. Amount of air leakage: The vapor pressure of moisture in air at saturation is 25.21 mmHg.
5. Calorific value in coke and coke oven gas in terms of fraction of calorific value of Coal.