Modern Gasworks Practice

 WATER GAS 745 1001b. per square inch., the temperature of the “ blow ” gases at the base of tlie Boiler being approximately 980° C. (1,800° F.). After contact with the water tubes the temperature of the gases is reduced to between 200° and 260° C. In comparison with boilers of the usual type it should be remembered that a waste-heat boiler is entirely self-contained and requires no brickwork setting, flues, or chimney. The männer in which the boiler is connected up to the ordinary Lowe-tvpe plant is shown in Fig. 455. BLAU GAS Blau gas, it should be noted, has no connection with. “ blue ” gas with which it is often confused. Blau gas is the invention of Hermann Blau, a German chemist, and is really a compressed oil gas. Gas oil is led into retorts and is vapoiized and cracked at temperatures between 550° and 600° C. The comparatively low temperature is employed in order to prevent the production of a large proportion of permanent gas. The gas obtained is cooled and purified in the usual männer, and is taken directly from the holder into a compressor, where the hydrocarbons not desired in the final -process are liquefied by compression. The remaining gas is compressed up to 100 .atmospheres, the final product consisting of liquefied hydrocarbons in which perman-.ent hydrocarbons are dissolved. The mixture, in fact, remains liquid under pressure, :and is conducted into steel bottles for transportation. When the pressure is reduced to that of the atmosphere the hydrocarbons immediately volatilize. The gas has a .calorific value of about 1,800 B.Th.U. per cubicfoot, and is mainly employed in dis-tricts (in America and Germany) where there is no town gas supply. The illuminating power of the gas is 80 candles per foot. THERMAL EFFICIENCY OF A WATER-GAS PLANT By means of a series of experiments carried out in America, A. G. Glasgow has ■calculated the efficiency1 of a carburetted water-gas plant. The plant, however, was •operated with anthracite, and not coke, and it was first necessary to ascertain the weights, temperatures, composition, etc., of the raw materials and finished products. With regaid to some of the data obtained, the followiiig list of temperatures will prove interesting to all produceis of water gas :— Gas issuing from superheater Blast gases issuing from superheater Oil leaving preheater Blast entering generator Steam „ „ Ash, etc., withdrawn from generator ö * ~ ~ o o O O O o OO CO CO r|i CO CC O I- CO r-4 H CO 1,450° F. 1,550° „ 235° „ 76° „ 331° „ 1,560° „ The heat absorbed by the apparatus is represented, on a basis of 1,000 cubicfeet of the carburetted gas, first by the amount of fuel fed into tlie generator. This was found to be 23-5 1b. per 1,000 cubic feet, after deducting unconsumed anthracite found with. the ash. Secondly, there is the total heat entering with the steam; 1 For thermal efficiency of various gasmaking processes, see Chap. XXI, p. 759.