Recovery of tar: the coke oven gas coming out from ovens is passed through a tower where liquid ammonia is sprayed. The tar and dust are removed and then recovered.
Recover of NH3: the gases are then passed through a tower in which water is sprayed. It is removed as ammonia hydroxide.
NH3 + H2O NH4OH
Instead Of Water, If Sulphuric Acid Is Sprayed, It forms Ammonium Sulphate Which Can Be Recovered.
2NH4OH + H2SO4 (NH4)2SO4 + 2H2O.
Recovery of Naphthalene: after removal of nh3, the gases are passed through a cooling tower where water at low temperature is sprayed. Naphthalene and some condensed gases are recovered.
Recovery of benzene: it can be recovered by passing the gas through chamber where petroleum is sprayed.
Recovery of H2S : the gas is passed through chamber containing moist Fe2O3, where it is recovered
Fe2O3 + 3H2S Fe2S3 + 3H2O
Fe2O3 can be regenerated by treating Fe2S3 with air
Fe2S3 + 4O2 2FeO + 3SO2
4FeO + O2 2Fe2O3
The coal gas is recovered and collected in a gas holder after passing through various chambers to removed the by- products. The calorific value of the gas is 5000 kcal/m3.