Fuel gas

Hydrogen and carbon monoxide are readily combustible with high calorific values (–286 and –283 kJ/mol, respectively). Although the name synthesis gas reflects its intended use in subsequent operations for production of other fuels or chemicals, no technical issues prevent use of products of gasification (or partial oxidation or steam reforming) directly as fuels. Such products can be used for domestic heating and cooking, for process heat, or for raising steam in industry. Many countries had, at one time, significant infrastructure for making and distributing fuel gases from coal. Indeed, until the development of syntheses based on CO and H2, in the early decades of the last century, the whole purpose of converting coal to gas was for domestic or industrial heating and illumination. Current interest focuses on use of synthesis gas as fuel in IGCC plants.

Water gas, town gas, illuminating gas, and related fuels made from early coal conversion processes, as well as the products of oxygen-blown gasifiers, have calorific values in the range 11–19 GJ/m3. Table 21.1 compares calorific values of some gases produced from coal with hydrogen, methane, and LPG.

A problem with some of these products is the high toxicity of carbon monoxide. Many gas-fired domestic appliances, such as water heaters or stoves, were equipped with pilot lights, in which a small quantity of gas was always being burned. Then, when the gas was turned on to the main burner or heater, it would be ignited by the pilot light, without a need to find matches. This bit of convenience for the householder, however, meant that if anything should cause the pilot light to go out, a small quantity of gas was now being emitted directly into the home.