Modern Gasworks Practice

NAPHTHALENE IN COAL GAS 473 cent, of the original quantity used. The temperature at which the oil mist is in-jected is of some importance, a degree or two above that of the gas in the mains being most satisfactory. It may be mentioned that the quantity of solvent given above was that employed at a time when coal gas was of a very rauch richer nature than at present, and when, therefore; the proportion of natural carriers was very much higher. With present-day gas, accordingly, it will usually be found necessary to add at least 10 gallons of the solvent per million cubic feet. C. Wood, at Bradford gasworks, employs a spray of the for-m shown in Fig. 287, the solvent being supplied to the spray at a pressure of 70 to 80 1b. per square inch. The solvent used is paraffin, having a boiling-point of 165° C. About 10 per cent, of the total oil injected is deposited, the condensate having a boiling-point of from 174° to 179° C. Colson adopted the practice of washing the gas in a Livesey washer with an oil specially pre-pared from tar. The distillate used had an average specific gravity of 0'996 and was ob-tained at temperatures between 170° and 215° C., being of the nature of creosote. It was Fig. 287.— Spkay i or Naphthalene Solvent. not necessary to fill the washer completely with the solvent, and a depth of a few inch.es on the surface of the liquor was found to be sufficient. Leather made use of creosote oil for eliminating naphthalene, but took the precaution to pre-benzo-lize it. Once saturated with naphthalene the oil may be distilled, when the bennene and toluene are recovered with the light oils. The naphthalene is then eliminated by means of live steam, and the residue remixed with the benzene distillate and returned to the washer. R. de la Boulaye experimented with a number of substances, ranging from methyl and ethyl alcohol to heavy oils, in Order to determine their relative merits as solvents for naphthalene. Finally he concluded that the best remedy for naphthalene was abrupt condensation and the ultimate use of a benzol or heavy oil spray in the mains before the gas left for the district. The practice adopted by Ferguson Bell is somewhat uncommon. The gas whilst in ~a warm state is washed with warm tar, and at the outlet of the washers and scrub-bers it is further treated with a naphtha oil. Cäbburation with Solvents Carburation of the gas with. spirits or low-boiling solvents is not now effected to the same extent as formerly owing to the present high cost of suitable liquids. The advantage of using such, spirits as benzol is that they have a comparatively high