GASEOUS FUELS.
The principal kinds of gaseous fuel which are in use at the present time for power producing purposes are natural gas and pro ducer gas. A certain kind of uncarburetted water gas, made by the decomposition of steam in the presence of incandescent-carbon, is also used to a limited extent, but this gas can never play a very important part as a power producer, on account of the large consumption of energy in its production.
The composition, weight and heat value of 1,000 cubic feet of the four types of gases used for power producing and illuminating purposes are as follows: Natural Marsh gas, 92.6 per cent; ni trogen, 3.61 per cent; hydrogen, 2.18 per cent; carbon monoxide, 0.50 per cent; oxygen, 0.34 per cent; olefiant gas, 0.31 per cent; carbon dioxide, 0.26 per cent. Natural gas weighs about 45.6 pounds per 1,000 cubic feet. Its calorific value is 1,100,000 B. T. U. per 1,000 cubic feet.
Coal Gas, or Illuminating Hydro gen, 46.0 per cent; marsh gas, 40.0 per cent; carbon monoxide, 6.0 per cent; olefiant gas, 4.0 per cent; nitrogen, 1.5 per cent; oxygen, 0.5 per cent; carbon dioxide, 0.5 per cent. Coal gas weighs about 32 pounds per 1,000 cubic feet. Its calorific value is 735,000 B. T. U. per 1,000 cubic feet.
Water Hydrogen, 45.0 per cent; car bon monoxide, 45.0 per cent; carbon dioxide, 4.0 per cent; marsh gas, 2.0 per cent; nitrogen, 2.0 per cent ; oxygen, 0.5 per cent. Water gas weighs about 45.6 pounds per 1,000 cubic feet. Its calorific value is 322,000 B. T. U. per 1,000 cubic feet.
Producer Gas (from bituminous coal). nitrogen, 55.3 per cent; carbon monoxide, 27.0 per cent; hydrogen, 12 per cent; marsh gas, 2.5 per cent; carbon dioxide, 2.5 per cent; olefiant gas, 0.4 per cent ; oxygen, 0.3 per cent; Producer gas weighs about 65.9 pounds per 1,000 cubic feet. Its calorific value is 156,900 B. T. U. per 1,000 cubic feet.
This exhibit shows natural gas to be the highest in the order of heat energy, its calor ific power being 50 per cent greater than that of coal gas. This is due to the high percentage of marsh gas given to natural gas by a natural process which cannot be duplicated artificially.
Producer gas has the lowest heat value, yet it is the cheapest artificial fuel gas per unit of heat, as the oxygen for burning the carbon to carbon monoxide is derived principally from the air. It has only one-fifth the heat energy of good illuminating gas per cubic foot, and it is most successfully applied in operations where a con siderable body of gas is burned rather than in small operations where illuminating gas can be used to superior advantage.
Comparison of Gases on a Coal Basis. The theoretical heat value of average anthracite coal is about 14,200 B. T. U.'s per pound, or the power to evaporate about 14.7 pounds of water per pound of coal burned. This theoretical evaporation is never attained in practice, how ever, owing to heat losses sustained in various ways - by improper design of boilers, by radia tion, by improper firing, etc., so that a boiler rarely gives an efficiency equivalent to the evap oration of 12 pounds of water per pound of coal, or the utilization of 80 per cent of the theoretical heat energy of the fuel. The effi ciency usually attained is about 10 pounds of water, or about 67 per cent of the theoretical energy, so that only about 9,500 of the 14,200 heat units in a pound of coal are utilized by the average boiler.
As determined by satisfactory experiments, seven and one-half cubic feet of natural gas burned will evaporate 10 pounds of water; or in other words, about 8,000 heat units in the form of natural gas are equivalent to a pound of good coal burned. Other authorities give the heat value of 1,000 cubic feet of natural gas as equivalent to that of an amount of coal rang ing from 80 to 130 pounds.
Comparison of Illuminating Gas and Pro ducer First-class coal gas, or carhuretted water gas, made with four and one-half gallons of Lima oil per 1,000 feet of gas, contains be tween 730 and 735 heat units per cubic foot, which gives an equivalency of 19 cubic feet of gas to one pound of anthracite coal, or 1,000 cubic feet equal to 59 pounds of coal.