Modern Gasworks Practice

WATER GAS The calorific power of the gas was found to be 720-987 B.Th.U. per cubic foot, and the quantity of tar recovered was 5 1b., its calorific value being assumed the same as that of the petroleum. Therefore the heat recovered was — 1,000 cubic feet of gas X 720-987 = 5 Ib. of tar X 18,500 = . 720,987 B.Th.U. . 92,500 „ Total . . . 813,487 „ On this basis, the heat efficiency amved at is equivalent to 80-76 per cent. MODIFICATIONS OF WATER-GAS PLANT During recent years various modifications of water-gas plant have been intro-duced with the result that in. some cases apparatus of a novel character is to be found. The main development has been in the direction of the complete gasification of coal, which is fully discussed in the next cliapter. Mention may be made liere of the carburetted hydrogen or “ Methane-Hydrogen " plant, which produces a semi-water gas enriched by means of coal tar. Methane-hydrogen gas dillers from ordinary water gas in many respects. It burns with a decided yellow, instead of a blue, flame, this being due to the high per-centage of methane present, whilst the proportion, of CO shows some considerable reduction as compared with “ blue ” gas. The approximate composition of methane-hydrogen gas is as foliows :— Methane .................................... 19 per cent. Carbon monoxide ....... 29 „ Carbon dioxide ..... • 3 „ Hydrogen ...... ■ 42 „ Unsaturated hydroearbons • 1 „ Nitrogen ...... . 5-8 „ Oxygen . 0-2 „ In the plant for the manufacture of this type of gas the depth. of fuel in the generator is nearly double that in the ordinary carburetted water-gas generator, but the lower portion only is raised to mcandescence by the air biast admitted to the base. About midway up generator the prodiicts of the “ blow ” are removed through special ports, thus maintaining the upper portion of the fuel-bed at a moderate heat. During the “ run ” tar is inj eet ed as well as steam, the former being split up into carbon and methane. The carbon is filtered out by the cool upper portion of the bed, and gradually descends into the zone of combustion. C. B. Tully1 has introduced a process for the manufacture of a mixture of hydrogen and carbon monoxide. The plant consists of a fuel-bed shaft placed above a combustion chamber. Around the lower part of the shaft there is a chamber filled with iron ore, and around the upper part a chamber filled with chequer Ibrick. The products resulting from the biasting up of the fuel-bed in the combustion chamber pass first through the iron ore, reducing it to a spongy condition, then 1 B.P. 16932/15.