Modern Gasworks Practice

778 MODERN GASWORKS PRACTICE column is blown inter-mittently, and the direction of the blow gas is generally reversed in successive-blowing operations. In. the gas-making operation, the air-blast is cut off ; the regenerator exhaust pipes ara closed ; and a heat-transferring gas (generally a combustible gasv together with steam) is led into the furnace through an inlet near the bottom of the fuel column, and passes-upwardly through it, counter-cuTrent to movement of the fueL The gas enteis the column in a compara-tively cool condition, absorbs heat from the coal in the lower portion, and carries it to-wards the hot mid-portion. After the gas has- passed through, the hot mid-portion, it imparts heat to the fuel in the upper portion and leaves the column in a com-paratively cool state. By means of the intermitten! cross blast and the intermit-tent circulation of gas upwardly through the fuel column, four distinct zones are maintained in a column of fuel containing coal, viz. : (1) the hot mid-zone or combus- Generator. Fig. 469.