THE COMPLETE GASIFICATION OF COAL
tion zone through which the cross biast is driven ; (2) a relatively hot coal-car-bonizing zone immediately above the combustion zone; (3) a coal-distilling and tar-condensing zone at the upper end of the column ; and (4) a coke-cooling zone extending from the combustion zone to the bottom of the column. By a careful regulation of the cross biast, the heat-transferring gas, and the passage of the fuel downwardly through the fumace, the temperature in the fuel column may be controlled so that the fuel will enter and leave it in a comparatively cool state. The gases passing upwardly through the fuel column enter and leave the fuel column in a comparatively cool state, and the cross biast air enteis and leaves the heat regenerators comparatively cool. In tliese operations, therefore, heat is always carried towards the hot mid-portion of the fuel column ; the heat being recuperated from the products removed from the fumace, and utilized in the carbonization of coal and the production of gas.
The gases producecl from the fuel and steam, together with the heat-transferring gas which may pass through the fuel column, are removed from the upper end of the fumace into a main and pass into a water condenser (see Fig. 470), whence they
travel into a serubber, then. into a purifier, and finally into a gasholder. A portion of the gas advancing to the holder passes through a valve and is forced by a blower through a water-absorber. The water used in this absorber consists of that which. has been previously heated in the condenser, and flows from it into the upper portion of the absorber. The inereased temperature of the water over that of the incoming gas inereases the temperature of the gas and results in a large amount of water vapour being carried out with the gas. The gas-water-vapour mixture passes into a conduit connected to the generator.