From the top of the superheater, the waste gases escape into a hood leading into the open air. When both the carburetor and superheater have reached the desired temperature, the air blasts are cut off, and the steam is introduced into the generator, where it is decomposed by the incandescent fuel, according to the reactions. The water-gas thus formed passes into the carburetor, while a small stream of oil is being introduced through a pipe at the top. The oil is decomposed by contact with the hot checker-work, form ing illuminating gases which mix with the watec-gas, and, passing into the superheater, are completely fixed as non-condensable gases.
It is customary to run the air blast for some eight minutes, when the fuel reaches a temperature of about 1100° C. The steam, superheated before entering the generator, is run about six minutes, until the temperature of the generator and carburetor has fallen below the point at which decomposition occurs. In or der to economize heat, the hot carburetted gas is passed through a pipe surrounded by a jacket, within which the oil is circulating, thus heating it before it enters the carburetor. The lower end of
the pipe leading from the superheater is closed by a water seal to prevent any backward rush of the gas during the operation of the air blast. It is customary to lead the gas from the superheater into a storage holder, from which it is drawn through the purify ing apparatus. In this process, the blowing of air and of steam are intermittent, but the actual formation of gas is accomplished in one operation. The impurities in the water-gas are essentially the same as those in coal gas, and the method of washing and purifying are the same.
- In the making of carburetted water-gas of 535 B. t. u.'s per cu. ft. about three gallons of gas oil are required. As the B. t. u.'s per cu. ft. increase the amount of oil necessary for the man ufacture of the gas increases, and if gas of 600 B. t. u.'s per cu. ft. is required, approximately 3.75 gallons of oil per 1000 cu. ft. are necessary. Generally gas-makers assume a consumption of 3Y2 gallons per 1000 cu. ft. of carburetted water-gas. Fig. 107 shows the charging floor of a gas generating apparatus in which oil is used for. enrichment.