Modern Gasworks Practice

740 MODERN GASWORKS PRACTICE Water-Gas Tak (sp. gr, 1-05Ö) Free carbon, 0-2 per cent. Water Benzol Toluol Solvent naphtha Heavy naphtha . Creosote Naphthalene Tar aoids . Heavy oil . Anthracene (40 per cent.) Pitch (medium) . Yield per 1,000 gallons of tar. . 40 gallons. • 5 • 10 • 6 ,, • 65 . 500 trace • 180 gallons, trace 1 ton 6 owt. WATER. GAS FROM COAL As enrichment by means of oil islikely to drop out entirely in future gasworks practice, it is possible that a solution of the enrichment problem may be found in the utilization of the hydrocarbons evolved from coal. In other words, some means may be found for employing a coal and coke mixture in existing water-gas plant, so that the gas produced and used as a combustible diluent would have a calorific power of some 400 B.Th.U. per cubic foot, as against 300 B.Th.U. given by “ blue ” gas, and 430 B.Th.U. as found with the semi-carburetted gas which is generally made to-day. The primary objection to the use of coal in the water-gas plant of ordinaiy con-struction is the loss of the greater proportion of the secondary by-products, tar and ammonia, which are recovered when the coal is treated in the retort. Again, during the “ blow ” a serious loss of valuable hydrocarbons is involvecl. Anthracite coal' is used very largely in America for water-gas production, but many difficulties arise when coals of the bituminous type are employed. That sott coals can be utilizedfor the purpose,however,has been shown by American experience, as an instance of which the two following examples may be quoted. At Danville (111.) a coal containing 34-5 per cent, of volatile matter has been used with. success, while the same type of coal has been employed by the Union Gas and Electric Company of Bloomington (111.) and gave little trouble from the beginning. An exact comparison between. conditions in that town and those in this country at the present time cannot, perhaps, be made, for the Bloomington undertaking is compelled to supply gas with a calorific power of 565 B.Th.U. Thus, in spite of using coal in lien of coke, it was still found necessary to carburate with oil. The main consideration, however, is that when the change from coke to coal was eflected a considerable reduction. in the quantity of oil used was found to be possible withont any drop in gas quality. In this instance, in faet, the uncarburetted gas had a calorific power of 355 B.Th.U. per cubic foot. The question of employing coal for water-gas manufacture has been very fully considered by the United States Bureau of Mines, while a special study of the matter has been made by R. B. Harper, of the Chicago gas undertaking. The main points which have been established are that when coal is used there is very mueh more