ducted in the usual manner through coolers, cleaners and scrubbers in order to remove the tar from the gases, and the gases are then conducted into large holders for storage. From the holder the gas is drawn into a three-stage or fourstage compressor, where it is compressed to 100 atmospheres. Under this pressure the oil gas is reduced to 1/400th of its volume, the gas so obtained being of a specific gravity approximately the same as atmospheric air. It has a calorific value of about 1,800 B. t. u.'s per cu. ft., or approximately three times the heat value of ordinary city gas. STPAW GENERATOR FIG. 106. Apparatus for Gas Making by Lowe Process. (From Outlines of Industrial Chemistry, Thorp.) The manufacture of oil-gas by the three processes mentioned is for the purpose of transporting it for the lighting of railway cars or isolated buildings, and also for steel and cast iron welding, brazing, soldering and for all other purposes where a uniform gas with high heat units is essential. About eight gallons of oil are required per 1,000 cu. ft. of gas. By far the greatest consumption of oil in gas manufactured is in the manufacture of carburetted water-gas. The process for the manufacture of carburetted oil-gas was devised by Prof. Lowe in 1874. The Lowe process is carried out as follows: The generator (Fig. 106) is filled with anthracite coal or coke, which is brought to incandescence by a blast of air. The gases from the generator, at this time consisting mainly of carbon monoxide and nitrogen, enter at the top of the carburetor, a circular chamber lined with firebrick, and containing a "checkerwork" of the same material; while passing down through this, the gas is partly burned by an air blast which enters the apparatus near the top, and the checker-work is heated white. hot. The gases pass on to the "superheater," a taller chamber, also filled with checker-work. At the bottom of this an air blast is introduced to complete the burning of the producer gas and to raise the temperature of the checker-work to a very bright red heat. FIG. 107. Charging Floor of Gas-Generating Apparatus in which Oil Is Used for Enrichment. (Courtesy Tide Water Oil Company.) 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, forming illuminating gases which mix with the water-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 order 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 purifying 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. ft. 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 manufacture of the gas increases, and if gas of 600 B. t. u.'s per cu. is required, approximately 3.75 gallons of oil per 1000 cu. ft. are necessary. Generally gas-makers assume a consumption of 32 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. |