Coke-oven gas is a fuel gas having a medium calorific value that is produced during the manufacture of metallurgical coke by heating bituminous coal to temperatures of 900°C to 1000°C in a chamber from which air is excluded. The main constituents are, by volume, about 50% hydrogen, 30% methane and 3% higher hydrocarbons, 7% carbon monoxide, 3% carbon dioxide and 7% nitrogen. The gas has a heating value of about 20,000 kJ/m3.
Typically, coke-oven gas is obtained from a battery comprising a number of narrow, vertical chambers, or ovens (0.5m wide, 5m high and 12m long) built of silica brick that are separated by heating ducts, such that heat is transmitted to the coal through both sides of the chamber walls. The ovens are slightly tapered so that one end is wider than the other to facilitate the horizontal discharge of the coke. Crushed coal is charged from overhead bunkers into the ovens, which are sealed at each end by refractory-lined sheet doors and heated for about 24 hours. The hot coke is then discharged. About 12%, by weight, of the coal is converted into gas. The hot gases evolved from the coal pass through a gas space at the top of the oven and into a collecting main prior to quenching and treatment to remove dust, tar and oil, and gaseous impurities such as ammonia and hydrogen sulphide.
Himus, G. W. (1972) The Elements of Fuel Technology Leonard Hill London.
Gas Making and Natural Gas BP Trading Ltd.