Page:International Library of Technology, Volume 93.djvu/119

 and the gas that the scrubber contains can be used when the engine is again started.

Producer plants consume only a very small amount of coal while the engine is shut down, and can be put in operation at full capacity in a very few minutes, on account of the heavy bed of burning coal carried at all times.

78. The chemical actions involved in generating gas are practically the same for both the suction and the pressure producer, the essential difference between the two types being in their mode of operation. In the former case, the gas is sucked from the generating apparatus by the action of the engine itself; and in the latter case, steam and air are forced into the producer by a pressure blower using steam from a small auxiliary boiler. This blower supplies the power necessary to overcome the resistance encountered by the gas in passing through the generator and the cleaning apparatus on its way to the gasometer, and also introduces the steam.

79. While, as yet, anthracite is the only fuel that has proved entirely satisfactory in the suction producer, almost any fuel containing carbon and volatile hydrocarbons can be employed in the pressure producer, and any of the gases capable of forming a combustible mixture with air can be employed for generating power in a properly designed gas engine. For plants of over 75 or 100 horsepower, pressure producers are sometimes used.

TABLE XI AVERAGE ANALYSIS OF PRODUCER GAS Constituents Gas From Bituminous Coal Gas From Anthracite Nitrogen, N Carbon monoxide, CO Hydrogen, H Carbon dioxide, CO2 Methane, CH4 56.5 27.0 12.0 2.0 2.5 57.3 27.0 12.0 2.5 1.2