WATER GAS
703
manipulated from an. elevated floor, flusli witli the top of the generator, and all valves, levers and gauges are collected at this level. Any risk of the operator moving the wrong levers is obviated by the insertion of a special interlocking valve-gear.
A special feature of the apparatus is the reversal of the “run ” in the generator, so that steam may be admitted either below the coke-bed or above it; it is to enable this to be done that the two-way pipe, previously referred to, is employed.
Experience shows that if steam is continually admitted to the base of the generator, in time the lower portion of the fuel-bed, which has continually to perform the heaviest duty of decomposition, becomes cool and inactive, the steam con-densing instead of being converted into gas. The succeeding “ blow,” therefore,
Fia. 433.—Beckton Plant, showing Levebs fok Hydbaulic Operation.
instead of rekindling the fire, chilis down the lower layers of coke still more. To rectify this, after every few runs the steam is admitted above the fuel and makes its way downwards and thence to the carburettor as usual. The reversal of flow is completely effected in one movement, the valves being controlled by interlocking gear which. renders confusion or mistake impossible. The function. of the washer, which corresponds with the hydraulic main of the coal-gas plant, is to provide a safety seal which precludes the gas from being pushed back into the superheater (by the pressure thrown by the relief holder) during the periods of the “blow.” The washers are well illustrated in Kg. 432. The purpose of the scrubber and the con-densers is to remove the vesicles of tar and oily matter which remain. suspended in the gas, and to cool the gas down to a normal temperature prior to condensation.