Coke is the infusible, solid residue remaining
after the distillation of
certain bituminous coals, or as a by-product of
petroleum distillation. Coke may also be obtained from
petroleum residue, pitch, and
other materials representing the
residue of destructive distillation. Coke will ignite more
quickly than anthracite, but less readily than bituminous. It burns rapidly with
little draft. As a result, all openings or
leaks into the ash pit must be closed
tightly when the coke is being burned.
Since less coke is
burned per hour per
square foot of grate than coal, a larger
grate is required and a deep fire-pot is
necessary to accommodate the
thick bed of coal.
Since coke contains very
little hydrogen, the quick
flaming combustion, which characterizes coal, is not produced, but the fire is
nearer even and regular. The best size of coke recommended for general use, for small fire-pots
where the full depth is not over 20
inches is that which
passes over a one-inch
screen and through a one and a half inch screen. For large fire-pots where the fuel can be fired over 20 inches deep, coke
which passes over a one inch screen and
through a three inch
screen can be used, but a coke of
uniform size is always more satisfactory.