COAL - Clpdigital.org

cient air over top of coal in oven to aid combustion
and take away the gases. In the meantime, the
coal has been leveled to a uniform depth.
The furious burning process i.s somewhat of a
puzzle at first on account of the checking effect
of an over draught and no under draught what­
ever, but the intense heat of the oven is deflected
back by the dome-shaped top, hence, the coal is
burned, or rather volatilized from the top clown-
wards, some eighteen to twenty-six inches in
depth: that is, the volatile matter is driven off
and not the carbon of the coal. The coal on the
floor of the oven is often but partially carbonized
on account of the oven being drawn before the
heat has gone down thoroughly.
After ihe flame over the coal in the oven has
passed, leaving a clear glow of fire, the oven is
ready to be drawn. A stream of water from a
hose is then turned into the oven of red hot car­
bon or coke, which quenches it sufficiently to be
handled with iron scraper and coke fork. The
action of the water also completes the process by
hardening or crystallizing the carlion. It is then
taken direct from the oven and loaded into the
railroad car for transportation.
ALTERNATE OVENS ARE DRAWN,
leaving an active oven on either side to better
retain the heat in the oven being discharged.
The bee-hive coking process requires 48 to 72
hours, charging and drawing of alternate ovens
continues daily except Sunday, the quantity of
coal in the oven indicating the length of time
to burn off.
Coke represents from 50 per cent, to 73 per cent.
of the original weight of coal, or in other words,
it takes from l'/i to 2 tons of coal to make one
ton of coke, according to the percentage of carbon
in the coal, which total weight of coal, after car­
bonization, leaves S5 per cent, to 90 per cent, fixed
carbon, also 10 per cent, to 15 per cent, ash and
non-combustibles.
To allow an oven to continue to burn longer
than enough to drive off the volatile matter, the
downward deflection of the heat from the top of
the bee-hive oven, would in time consume the
carbon and nothing but ashes would remain;
therefore, the time to discontinue the coking or
baking process and draw the coke, is before the
carbon is affected, or after the flame of volatile
over bed of coal subsides.
The only other method of making coke for com­
mercial purposes, is the retort oven, where the
by-products are reclaimed.
Germany, France and Belgium are the home of
the retort ovens in the carbonization of coal.
While America leads the world in mechanical and
inventive genius; devices for economical perform­
ance of work have not been the only object in view,
THE COAL TRADE BULLETIN. 43
and til is country's inventors are not in tne lead
in economic devices for coke making.
The great incentive to development of economic
methods in the coking fields of continental Europe
lies in tlie fact that their coal supply is limited,
and experience in other resources becoming ex­
hausted, no doubt prompted the invention of the
retort oven for the recovery of by-products.
It has only been during recent years that retort
ovens have been used in this country and the industry
may be considered in ils infancy. First
mention of by-product ovens, however, dates back
to 176S, as installed in Rhineland province of
Germany. Tar was produced at that time.
In the United States this oven commenced about
January, 1892; they are
USUALLY BUILT IN BATTERIES
of thirty or multiples thereof. A single oven is
thirty feet long, four to six feet high and sixteen
to twenty inches wide. Unlike the bee-hive oven.
this one is closed and does away with combustion
there, and heat necessary for coking comes from
the combustion of air and gas in the fines, which
make up the sides and bottom of the ovens.
A by-product oven takes a charge of five to
seven tons of coal similar to the bee-hive pattern,
although in appearance the ovens are very differ­
ent—the interior of the bee-hive oven would re­
semble the top half of an orange flat side down.
while the retort or by-product oven would re­
semble the shape of the modern high grade building
brick of the long slim pattern resting upon
its edge.
The retort oven is charged much the same as
the bee-hive, from hole in top, but it is then
sealed with fire clay. The oven becomes tight'
and the gases pass off to be turned into mains for
treatment in tbe by-product apparatus. The more
volatile matter in the coal, the longer it takes
to coke. While eighteen to twenty hours' time
is sufficient to make coke from coal of low volatile.
Connellsville coal most used in the bee-hive ovens
and requiring forty-eight hours, can be coked in
by-product ovens in twenty-four hours. As high
as 73 per cent, of coke is also claimed for byproduct
as against 67 per cent, by bee-hive ovens
using the same coal; hence, the average out-put
of the retort by-product oven last season was
about 896 tons per oven as compared with 306 tons
for the bee-hive pattern.
The retort oven is heated with a portion of the
gas it produces, it being returned to the walls of
the oven, which are hollow and furnish prompt,
active and intense heat upon the coal to be coked;
hence, the short space of time required for coking
as compared with the bee-hive oven, and the
greater annual capacity.
Finished coke is discharged by automatic steam
or electric ram, which pushes entire contents of