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THE COAL TRADE BULLETIN. 41
COKE AND THE BY-PRODUCTS.
Who of us have not sat before a bright, blazing
coal fire and noticed, with almost indifference, the
tiny bursts of flame that from time to time shoot
out from what apparently was a dead ember?
Perhaps a certain small flame attracts our in­
terest by the length of time it burns and perhaps
we have been momentarily aroused to wonder at
the large amount of gas that must be confined
in so small a crevice to maintain so bright a
flame for so long a time. Were we to consult
some technical book and look under "Coal," we
would find there are principally two kinds of coal,
anthracite and bituminous. A little reading and
we find the anthracite is the hard, cdean coal,
almost pure carbon, and the bituminous is the
"soft" coal, the character of which is associated
in our minds with great volumes of sooty clouds
which settle on everything and everybody, alto­
gether more conducive to discomfort than any
public nuisance I know of. We read of the
different periods of formation, all of which are
very interesting, and tnen the article merges
into me technical, giving the average analysis of
bituminous coal as follows: Volatile matter. 33.5
per cent; fixed carbon, 59.5 per cent.; ash, 7.0 per
cent.; sulphur, 1.15 per cent. From which we
see that ordinary bituminous coal is two thirds
carbon and ash. and about one-third volatile
matter in the form of gas. In order to understand
the full significance of this, we must im­
agine the coal as being honey-combecl, with thousands
of little pockets, each pocket being filled
with gas, which, of course, is under great pres
sure. Understand, this gas constitutes one-third
of the entire weight of the coal, not volume, therefore,
when disintegration of the coal takes place
through the intense heat which is generated by
its combustion, the gas is liberated and as its
tension has become greater with the increase of
temperature, it forces its way through the walls
of the pockets, the moment they become too thin
to support the pressure, which only increases our
wonderment at the simplicity of nature and her
niechanicai laws.
It is with the sole intention of giving a clear,
plain description of the manufacture of coke and
the recovery of the resultant by-product, that
this paper is written, and is in no sense intended
as a technical pamphlet.
THE ORIGIN OF THE WORD "COKE"
is obscure. When used as a noun, it means what
remains of certain kinds of bituminous coal after
the volatile matter has been driven off.
There is as much authority to use the word
"Paper read before the Monday Night Club, Pittsburgh. Pa..
October in, 1905.
By T. J. Easter, President of the Pittsburgh Fuel & Iron (!o.
"cake" or "cook" as a derivation for coke as any
other words I can find; however, they would not
lie understood commercially as related to what
we now call coke. A coal to be adapted for coke
must, when heated to a certain degree, knit together
or cake, as particles of food are caked.
Some coals leave nothing but powder after the
bitumen or volatile matter has been driven off—
while a good coking coal leaves a hard, brittle,
porous, solid cake, with a steel grey, somewhat
metallic lustre.
Most coking coal is soft and breaks up as
though crushed after exposure to the air. Where
the coal is hard and lumpy when taken from the
mine, it is necessary that it be crushed to the
consistency of slack, if iiossible. before beingplaced
in the o.ven.
The nature of Ihe difference between coking and
non-coking coals has not yet been fully made out.
It is almost always a question of test to determine;
then again some coals will coke when first
taken from the mine, but not if exposed lo the
air any length of lime. One of the principal
requisites in coking coal is that it does not contain
much moisture.
The slack of dry or non-coking coal or anthracite,
which cannot be coked alone, may be con­
verted into coke by mixture with certain grades
of bituminous coal. Experimentally, substances
such as sawdust in connection with gas pitch and
bitumen have produced coke.
Coke is principally valued for the intense heat
which it gives off in combustion and its freedom
from smoke in burning. The process also drives
off a good deal of sulphur, which may be present
in coal, making it better adapted for metallurgical
operations, where intense smokeless combustion
is desired.
Iron pyrites is the most objectionable material
in fuel for melting purposes: hence, a coal high in
this property is looked upon with disfavor by the
coke manufacturer who must sell his coke to the
maker of pig iron.
A good coking coal with the exception of too
much iron pyrites, slate or ash, may be relieved
of the surplus of these objectionable properties,
although not entirely, by what is known as
WA.SIU.NO THE COAL.
This principle, however, is not the same as wash­
ing one's hands or soiled clothing, but a separat­
ing device. It means to crush and float the coal
through a system of jigs or flumes containing
water and as the specific gravity of the impurities
is greater than the coal, they sink, and the coal
passes on to be used in the coke oven. Of the