USES OF COAL
Coal is among the most important of all minerals. It furnishes power and heat, and its distillation yields a great number of useful materials, such as gas for lighting and fuel, explosives, ammonia, aniline dyes, etc. Coke, which is bituminous coal with the more volatile constituents removed by distillation, is used for smelting metallic ores; and thus the contiguity of fields of high-grade coking coal and of iron ore determined the location of the centers of steel industry, which are the very main-springs of our modern machine-made civilization. Near such coal districts, other manufactures of all kinds naturally developed, the coal being cheaply available for power and constituting practically the only source of power in regions where cheap hydro-electric power is not available. About 66 per cent. of the coal mined goes to the production of power, including transportation; about 12 per cent. to coking and the by-products; and about 22 per cent. to the heating of buildings.
Commercial coal is of three varieties: (1) anthracite (Pennsylvania anthracite is popularly termed hard coal), and semi-anthracite containing a high percentage of fixed carbon and a relatively low percentage of the volatile constituents (3 to 12 per cent.); (2) bituminous (ambiguously termed “soft coal” in the United States), containing less fixed carbon and more volatile matter (12 to 40 per cent.); and (3) lignite, containing a still smaller proportion of fixed carbon and a large proportion of water. Of the bituminous coals, some coke satisfactorily, but many do not, so that good coking coals are highly prized. Anthracite, because it makes no smoke, is in great demand for house heating; whereas bituminous coal is chiefly used for power production, including locomotive and steamship firing. Lignites as a rule are used only where the better grades of coal are not available.
Coal was first used for heating before steam power came into use, and iron was smelted with charcoal instead of with coke as at present.
Ship bunkering calls for the best grades of bituminous coal, low in ash and preferably high in fixed carbon, because the use of low-grade coals would require carrying larger amounts, leaving less space for cargo. However, no country that has enough coal to bunker ships, need be dependent on foreign supplies; the low grade of coal would simply reduce efficiency and thus increase expense.
Substitutes.
—The proportion of coal used for power, as distinct from that used for heat and coal products, is increasing, and is now two-thirds of the total. As a source of power there is really no complete substitute for coal. All the great industrial nations, like England, Germany and the United States, have developed their industries on the basis of large coal supplies. Some countries make large use of hydro-electric power, but for most it is an insufficient substitute. Wood and other fuels are rarely sufficient to maintain an industry built up on a supply of coal. Oil is being successfully substituted in some industries, notably in shipping, but the importance of coaling stations will no doubt persist.