Modern Gasworks Practice

774 MODERN GASWORKS PRACTICE up to the desired temperature, whilst the products, in passing through the regenerators, give up a further quantity of heat, so that the latter are maintamed at a considerable temperature. The gases leaving the lower generators and passing through the nostrils contain, on an average, about 10 per cent, of carbon monoxide, and this is further burned to CO2 by the admission of secondary air at the points shown in the sectional figure. The blow in this way usually coutinues for rather more than a minute. At the end of this time, the blast having been shut off and the stack valves closed, steam is admitted at the top of the regenerator on one side only. Passing downwards around the heated chequer work, it is partly split up and tlien travels first through one coke bed and finally through the second. In this way long contact with the fuel and thorough reducing is assured. Leaving the second fuel-bed, the water gas already produced does not pass through the nostrils (the snift valve being closed), but forces its way through the cool core of fuel in the D-shaped pouch. It then passes into the special hydraulic main and, finally, through the scrubber. One of the chief advantages of passing the hot gas through the incoming coke in this way is that the greater part of the moisture is driven off from tlie fuel; and, moreover, the outgoing gas is tlioroughly filtered. In the cycle just described no mention lias been made as to how carburation is effected, if this is desired. For this purpose air from a compressor is admitted to the surface of the oil in a storage receiver, when the oil is forced out at a pressme of from 30 to 40 1b. per square inch, through a special regulating spray and into the top of the regenerator. Each regenerator is fitted with such a spray, but the oil is only admitted to that one surrounding the top of the generator through which the gas is finally passing. The oil gas is accordingly forced downwards by its pres-sure, passes through the nostrils, and meets the upgoing stream of “ blue ” water gas. The two are then thoroughly intermixed during their passage through the cooler coke core. With regard to the duration of runs and blows, it is usual, after a one-minute blow, to admit steam for five minutes. After the following blow the direction of the steam is reversed. When the plant is used for carbonizing coal and gasifying the resultant coke it is fitted with two automatic feed hoppers which are regulated to provide what practically amounts to a continuous charge. Düring the five-minutes’ run the hot gas evolved from the lower portion of the bed passes up through the cooler zone and partly carbonizes the coal. The latter gradually works its way down the upper portion of tlie generator, undergoing more and more complete carbonization during its travel. In general, it is said to be reduced to the state of ordinary coke by the time it has passed two-thirds the way down the D-shaped portions of the generator. Thus during the run water gas is being evolved from the coke and coal gas fromi the coal, the two intermixing and passing out at the top of the generator. In this way, by the complete gasification of both coal and coke, about 50,000 to 60,000 cubic feet of gas having a calorific power of 370 B.Th.U. per cubic foot may be obtained from a ton of coal.