Modern Gasworks Practice

614 MODERN GASWORKS PRACTICE COST Öl' PUBIFICATION BY CaRPBNTER-EvANS PrOCESS Fuel (coke at 42s. ßd. per ton) . Conveying coke and cleaning producers Power ___________________________..... Labour and Chemical supervision Repairs and maintenanoe . Capital charges _____________________.... Pence per 1,000 cubic feet. . 0-2550 . 0-0240 . 0-0129 . 0-1180 . 0-1649 . 0-1967 Total __ -3 Before the war the total Capital expenditare for a large plant was in the neigh-bourhood of £1,500 per million cubic feet per day. As regards efficiency of extraction, the proportionate reduction is somewhat higher when a gas containing a large amount of CS 2 is dealt with. The folio wing results illustrate the average efiect obtained ;— CS2, etc.—Grains per 100 cubic feet of gas. Reduction, per cent. Before After 63-78 10'34 83-8 19-21 5-34 72-2 Other CS 2 Processes Prevailing opinion all goes to show that the problem of removing sulphur Compounds from gas is by no means solved. These compounds consist for the most part of carbon bisulphide, with. a small proportion of thiophen, ethyl and methyl sulphides, and in all probability certain mercaptans. Certainly, the first named may be removed by several known processes, but the difficulty lies in determining a method whereby the more elusive organic compounds may be eliminated. The Carpenter-Evans process marked a great step forward ; but it must be borne in mind that, while it removes some 80 per cent, of the impurities it does not completely elimi-nate thcm. Moreover, very much depends upon the efficiency of the catalytic agent; which appears to fall off to some considerable extent between the periods of regeneration. While, therefore, the method has partly served its purpose it must not be considered as the final word in purification processes of the kind, more particularly as it is still of an intermittent nature, and requires a certain amount of care in operation. The past two years have been particularly productive of newer suggestions for effecting purification, and many of the proposals are of interest in that they indicate the possibility of evolving means which would be scientifically perfect and readily operated without practical complications. Rideal and Taylor,1 for instance, have carried the matter a stage further by causing the carbon bisulphide to react with water vapour instead of with hydrogen as in the Carpenter-Evans process. The desirable effect of this may best be illustrated by considering the reactions occurring. Thus, (1.) Carpenter-Evans : CS2 + 2H2 = 2H2S_+C. (2) Rideal-Taylor: CS2+ 2HaO = 2H2S-|-CO2. 1 B.P. 130C54/18.