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Scientific American Supplement, No. 401, September 8, 1883 by Various
page 48 of 136 (35%)

The fuel employed is the coke or char resulting from cannel coal when it
has yielded up its hydrocarbons and other gases during the process of
carbonization in the gas retorts. Being entirely made from Scotch cannel
the coke is very poor in quality, as it contains a large percentage of
mineral matter or ash relatively to its fixed carbon. The retorts are
worked with three-hour charges, but the producer is only charged once in
every six hours For each set of eight retorts the charge of raw cannel
is about 18 cwt., and it is found in practice that the coke drawn from
five of the retorts is quite sufficient to fill up the producer to the
top. Formerly a set of seven retorts fired in the ordinary way from a
furnace underneath, required from 60 to 75 per cent. of the coke made,
but now, with eight retorts in each oven, the quantity has been reduced
to about 30 per cent., or less than one-half of what it formerly was.
Before the retorts are drawn the lid is removed from the top of the
producer, and any fuel still remaining unconsumed is touched up a bit by
way of leveling it on the surface, and as soon as it has been filled up
to the constricted portion a shovelful of soft luting is spread over the
top of the coke, and the lid is laid upon it and driven home, thereby
making a perfectly air-tight joint. The contents of the other three
retorts, as also the contents of the whole of the retorts at each
alternate drawing, are taken to the coke heap in the yard. We have
already spoken of a charge of cannel as being about 18 cwt. for each set
of eight retorts, but in connection with that matter we should mention
that it was formerly about 13 cwt. per oven containing seven retorts,
and that there is every prospect of it being increased without
increasing the length of time occupied in carbonizing the cannel of each
charge.

It may be worth while now to notice briefly what takes place among the
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