Modern Gasworks Practice

HIGH TEMPERATURE CARBONIZATION OF COAL 427 E1TECT OF STEAMING IN CONTINUOUS VeRTICAL RETORTS Without steam. With steam at 25 Ib. With steam at 40 Ib. Gas, per ton of coal (cubic feet) . 14,989 17,759 21,684 Calorific power (gross B.Th.U.) 503 460 442 Tar, per ton (dehydrated), gallons 17-4 18-2 18-6 Liquor (10 oz.), per ton, gallons . 39-7 42-4 40-3 B.Th.U. (gross) per ton of coal . 7,538,461 8,169,140 9,584,328 Probably the most important work in connection with the process is that which. has been publislied by the Gas Investigation Committee of the Institution of Gas Engineers.1 In considering the results of the tests it sh.ould be remembered th.at the coal used was comparatively poor from the gasification standpoint, so that they do no necessarily represent the maximum results obtainable. Five complete tests were carried out, and the volume of gas per ton of coal increased (as the amount of steam was increased) from 10,384 cubic feet to 21,849 cubic feet. At the same time the gross calorific power of the gas decreased from 544 B.Th.U. per cubic foot with. no steam admitted to 410 B.Th.U. with maximum steaming. The composition of the gas made changed gradually with increasing amounts of steam in such manner that the volume of hydrocarbons per cent, decreased from 2-3 to 1-6, and methane from 28-5 to 14-5 ; while the amounts of carbon dioxide increased from 2-2 to 6-6 per cent., and carbon monoxide from 10-3 to 17-9 per cent.; the hydrogen remained almost constant at 48 to 50 per cent, by volume. The total number of heat units in millions B.Th.U. made in gaseous form per retort; per day increased. from 15-94 gross to 26-70, but in the last test the figure feil to 24-94 since the increase in the amount of potential heat energy per ton in gaseous form was more tlian counterbalanced by the reduction in the amount of coal carbonized per retort per day. One of the most important considerations in connection with. steaming is that of coke yield. Definite figures of the actual amount of coke remaining for sale are particularly difiicult to obtain, but from the Gas Investigation Committee’s results it would appear th.at for each additional 6,570 cubic feet of gas made beyond the yield of straight coal gas 1 cwt. of coke is consumed. As regards the actual weight of coke sold the following figures are extracted from reports made by the engineers of gasworks in various parts of the country where continuous vertical retorts are in use. Coke Sold per Ton of Coal Cabbonized. Steamed Vebtical Retorts Cwts. Coke sold per ton of Coal. 1. Uddingston............................... 8'53 (9-25 cwt. without steaming) 2. Macclesfield 9-50 3. Nelson...................................8-26 4. Helensburgh..............................7’93 (8-8 cwt. without steaming) 1 Proc. I nst. Gas Eng., June, 1920.