Producer Gas.
How this remarkable result has been attained we shall consider a little further on, as we briefly examine the construction of a typical [gas engine]. At this point let us note how a gas, suitable for an engine, is manufactured at least cost, the outlay being much less than in the case of illuminating gas which represents but one third of the coal placed in the distilling retorts. Instead of this process of distillation, “producer” gas is due to a modified combustion which gasifies all the fuel. In a producer of standard type, atmospheric oxygen comes into contact with the glowing carbon of the coal or wood, forming carbon dioxide, CO². The heat generated by this union is taken up by the carbon dioxide and the nitrogen of the supplied air. These gases as they rise through the fuel bring it to incandescence so that the carbon dioxide takes up another atom of carbon, becoming carbon monoxide, CO, a highly combustible gas. Were there no impurities in the fuel, were the entering air quite free from moisture, the gases would be in volume 34.7 per cent. carbon monoxide and 65.3 per cent. nitrogen, with a heating value per cubic foot of about 118 British thermal units, a unit being the heat needed to raise a pound of water to 40° Fahr. from 39°, where its density is at the maximum. Gas thus produced is intensely hot; and as usually it contains sulphur, dust, dirt, and other admixtures, their removal by water in a scrubber would involve a waste of about 30 per cent. of the fuel heat. This loss is much diminished by sending into the producer not only air but steam, to be decomposed into oxygen and hydrogen; the oxygen combines with carbon to form more carbon monoxide, while the hydrogen is the most valuable heating ingredient in the emitted stream of gases. Were only air sent through the producer, the outflowing gases would contain nitrogen to the extent of 65 per cent.; with a charge in part air and in part steam, this percentage falls to 52; as nitrogen is useless and wastefully absorbs heat, this reduction of its quantity is gainful. By a duly regulated admission of steam, a producer is kept at a temperature high enough to decompose steam, but not so high as to send forth gases unduly hot to the purifier.
For water-gas the method is to blow steam into the fuel until decomposition ceases; the steam is then shut off, the fire allowed to recover intense heat, when more steam is injected, and so on intermittently.
Taylor gas-producer.
R. D. Wood & Co., Philadelphia.