COKE OVEN PROCESS
Coke is the solid residue,consisting chiefly
of carbon,that is left behind when bituminous coal is distilled
in the absence of air. In the production of coke, a process called
" carbonization of coal " or " coking," most
of the volatile matter is removed by heating (baking) the coal in
a closed chamber to retard or prevent burning. Nearly 90% of the
coke produced from coal each year is used by the iron and steel
industry for the production of pig iron.
(c.1620). A beehive oven is a simple firebrick chamber built with
an arched roof so that the shape inside is that of an old-fashioned
beehive. A typical oven is 12 feet in diameter and holds from 5
to 7 tons of coal in a uniform layer between 18 and 24 inches deep
on the floor.
Beehive ovens were usually built in long rows, one
oven beside another with a retaining wall between. Such a row of
ovens is termed a " battery". The batteries often followed
the contours of the hills in the coal fields where they were located.
Railroad tracks for handling the coal to the ovens ran along the
tops; and other tracks for handling the coke cars ran beside the
ovens. Many beehive batteries have been located close to the mines,
so that the freshly mined coal was charged directly into the ovens.
No provision for stocking or mixing the coal is made at a beehive
Coal is charged into an empty oven through the hole
at the apex of the dome. It forms a cone-shaped pile which is levelled
to a uniform layer of 18 to 24 inches by means of a rake passed
through the door. The coking process is started by means of the
heat retained in the walls of the oven from the previous charge
of coal. New ovens are brought up to temperature by heating with
coal or wood before charging.
Almost immediately after charging, gas is evolved (released) from
the coal. The air for combustion is admitted through an opening
at the top of the oven door. By removing or introducing bricks at
the opening, the quanting of air is regulated. The coking time which
depends largely on the depth of the layer of coal, ranges from 48
to 72 hours. As coking proceeds, the volume of gas evolved decreases,
and the size of the opening in the door is correspondingly decreased.
This prevents the entrance of an excessive volume of air, which
otherwise would burn part of the coke and might be sufficient to
cool the oven as well.
When coking is complete, the door is opened and the
white hot charge is quenched by stream of water directed through
the opening. The quenched coke is then raked from the oven by hand
and loaded into train cars for transport. Beehive coking is now
an obsolete process because of the small quantity it manufactured
and the very large amount of pollution it produced.