Evening star., 1912-11-20

coal is entirely burned by the time il
reaches the rear set of wheels. AS the
crate chain passes down over these
wheels 1t dumps the ashes into the ash
PIT and moves on around to bring in q
new load of coal.
Inc front feed stoker consists of a hop
per and a reciprocating pusher which
pushes the coal into the outlying pre-
clhcts OF the furnace. where it comes
upon the CRATES which are built with a
considerable incline and placed so as to
be mechanically moved for passing the
coal down over them and the residue On
TO the ashpit. it being completely con-
verted into ashes by the time the pit is
reached.
1ne underfeed mechanical stoker sends
the coal in beneath the burning material
that has preceded it. In one underfeed
furnace this is accomplished by cone
SNAPPED screw. driven by small steam
engine, which forces the coal in under
the bed of fire. In another it is forced
In heavy charges instead of in a con-
tlnuous supply. This forces the live Goals
Up and outward. and they are caught in
large chamber where thorough combus-
ton is completed.
There are innumerable devices on the
market to promote efficient and non-
m o i n g
1nnumerable Devices hand firing
to Promote Efficiency. a. on1 r,,sst o. 'ns nf
these is the coking furnace, in which
the coal is first deposited at the front
end Of the furnace 9nd gradually pushed
back into the hotter portions as it reach
es the proper heat. The front end of the
furnace has no CRATES in it, but has a
dead plate instead.
The steam jet is a favorite apparatus
by which many hand-fired furnaces are
rendered smOkeless. AS a furnace is fired
a jet of steam is allowed to play upon
the fire and thus thoroughly mix the air
and the gases in the furnace. Some have
asserted that the steam jet is economical,
but the geological survey found in its
experiments that 1t is expensive unless
properly applied. and that even then it
has to take some of the heat that other
wise might be used in heating the boil
ers. The only value of the steam jet is
to. prevent smoke. 1t adds nothing to
the thermal value of the coal, according
to the survey report.
Downdraft furnaces are resorted to in
many plants to avoid the emission of
smoke. Such a furnace has an upper
CRATE, sometimes consisting of water
tubes through which the water going
into the boiler circulates. The fresh coal
Is thrown upon these, whence, after par
tial burning. it falls through this crate
to a regulation CRATE below, where the
process of combustion is completed
The investigation by the bureau of
mines reveals surprising number of
central heating plants. 1t showed "A
such plants In Illinois, II in Indiana. 10
in New York, "a in Ohio and % in Penn
sylvania, with 80 others scattered through
other states. Some of these heating
plants have been in commission for a
quarter Of century, but most of them
have been placed in operation in the
past decade. They range In size from
300 to 10000 horsepower, and the price
of the coal used ranges from $4.6O per
short ton in Montana to 90 cents per
short ton in Illinois. They have success
fully and economically furnished heat
and steam within a radius of a mile.
which. in city would represent some
400 ordinary blocks for each plant.