THE COMPLETE GASIFICATION OF COAL
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the tar vapours in the gas, but this was soon given up because the tars were themselves of valne and because the results could not be called good. Carbonizing processes left the coal still smoky when the blow began; and it was found that the heat must be developed inside the coal. For this purpose the biast was directed from the middle of the producer downwards, and also from the bottom upwards, so that the zone between distillation and gasification was quite hot, and the water gas from the lower part of the producer was so hot that it effectively distilled the coal above as it passed through it. The temperatures of this distillation were, however, relatively low, so that therc was a good yield of. ammonia, and the tars obtained were low-temperature tars, free from naphthalene. Instead of decomposing the
Fig. 463.—Dellwik-Fleischbb “ Tri-Gas ” Plant.
tars, as had at first been attempted, the new process preserved the tars from over-heating. The first successful experiments were made in Vienna, where a producer of a capacity of 2,800 to 5,250 cubic feet per hour gave gas of 281 B.Th.U. per cubic foot, Ostrau coal gave gas of 338 to 394, and Bosnian brown coal a gas of 336 B.Th.U. per cubic foot. The Stinnes collieries, after seeing the Vienna experi-ments, built three special producers of a capacity of 28,000 to 52,000 cubic feet per hour, with. rotary hearths. The coal was of a very caking quality; but the difficulties were overcome. The first of the three producers began continuoiis working on April 6, 1918, and continued it for five months without a break and without any overhauling. On September 6,1918, the producer was stopped for a short time, in order to deal with slag which had begun to accumulate. After that the working of all three producers was continuous for six months.
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