OIL IN GAS-MAKING William Murdock of London, first employed coal gas for illuminating houses, and his system was introduced for lighting the streets of London in 1812 and for lighting the streets of Paris in 1815. Since the introduction of Murdock's system, gas lighting has developed remarkably.
The gas produced during the carbonization of coal is a mix ture of fixed gases, vapors of various kinds, and at times also globules of liquids held in suspension and carried forward by the gas. Water-gas is produced by the action of steam on incandes cent carbon and is composed chiefly of hydrogen and carbon mon oxide. Water-gas is not luminous, but has a high heat value. The luminosity of a gas depends upon the• presence of hydrocarbons, and in order to render water-gas luminous it is carbureted with gases derived from oil which are rich in illuminants. Illuminating water-gas can be made by two general methods : (1) The carburetted gas is made in one operation.
(2) Non-luminous gas is prepared and then carburetted by a second process.
There are several systems for making oil-gas which are dis tinguished from those known as carburetted water-gas systems. Among these may be mentioned the Pintsch, the Blaugas, and the Peebles procesg. In all of these the oil gas is made by cracking the oil in retorts. In the Pintsch process a transverse partition divides the retort into an upper and lower chamber. In the upper chamber the oil is cracked and vaporized, the vapor passing into the lower compartment, which is heated to nearly 1000 C., where permanent gases are formed. In the Peebles process the oil is only partly cracked, and only the very volatile hydrocarbons leave the apparatus. In the Blaitgas process gas-oil is conducted into the retorts just as it is in the manufacture of Pintsch and other oil gases and is vaporized and decomposes in this retort under the temperature of about 550 to 600 degrees C., this low temperature being employed to prevent the production of a large percentage of fixed gases. After the oil has thus been distilled the gas is con
ducted in the usual manner through coolers, cleaners and scrub bers 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 four stage 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.
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 re quired per 1,000 cu. ft. of gas.
By far the greatest consumption of oil in gas manufactured is in the manufacture of carburetted 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 "checker work" 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 intro duced to complete the burning of the producer gas and to raise the temperature of the checker-work to a very bright red heat.