Improvements in or connected with the Heating of Drying Chambers with which Coke Furnaces are Used.
Year: 1896

page_text: Date of Application, 19th Oct., 1896-Accepted, 9th Jan., 1897
COMPLETE SPECIFICATION.
Improvements in or connected with the Heating of Drying Chambers
with which Coke Furnaces are Used.
I, JOHN THOMAS GODFREY, of 80 Industry Road, Darnall, Yorkshire,*
Engineer, do hereby declare the nature of this invention and in what manner the.
same is to be performed to be particularly described and ascertained in and by the
following statement :-
The objects of this invention are improvements in or connected with the heating.
of drying chambers such as are fired by coke in a grate in or adjoining the drying
chamber.
As ordinarily constructed, the heat in such drying chambers is obtained by the
emission of the gases from the fire, which gases are solely the product of a more or
less complete combustion.
Apart from the fact that these gases do not possess good drying properties, the
fumes are, as is well known, an inconvenience, and deleterious to the operatives.
This invention affords :-
1. A more complete combustion.
2. A greater volume of heat for a given expenditure of fuel, and in a
time.
given
3. The use as a drying medium of highly heated atmospheric air, which absorbs
moisture more readily than fire gases.
4. A better disposition and spreading or circulation of the heat.
5. The minimizing of fumes, saving of fuel and time.
The manner in which this invention is carried into effect is as follows:-
A shaft, the upper part of which forms a vertical mixing chamber, is built up
round the grate in which the coke is burnt, having its outlet opening into the
drying chamber close under the roof.
Air is admitted in the usual way from the ashpit.
On the outer side of the grate, and open to the air, louvre blades are fixed one
above the other from the level of the grate to the top level of the coke charge and
extending the full breadth of the grate, and preferably slanting downwards towards
the coke.
Dampers are placed outside the louvre blades, one above the other, in such a
manner that they can be regulated to ensure air being admitted through, or
through and over, the upper layer of burning coke, and according as the level of
the fire sinks.
.
:
The carbonic oxide gas which burns at the top of the fire, and has a very high
fame temperature but no radiating power, is thus met by a secondary supply of
atmospheric oxygen, part of which passing through the upper layer of the fire
becomes heated and ensures the complete combustion of the carbonic oxide gas
into carbonic acid of intense beat. This having a great radiating power freely
mixes with the remainder of the air passing over the fire, thus imparting its heat
to the over-current and producing a large volume of hot air having good drying
properties. Only sufficient air need pass through the lower layers of coke-be it
through the grate or through the louvre blades-to keep the lower part of the fire
aglow, and a considerably greater quantity of air may be admitted through the
upper layers.
.
The proportion passing over the top layer, compared with that passing through
it, is determined by the heat it is required to produce in the chamber. Thus

page_text: when the chamber is cold at starting, a less proportion of over-draught is allowed,
as compared with when the chamber is sufficiently hot, at which stage, more over-
draught can be allowed in such proportion as, while not lowering the temperature
in the chamber, will increase the volume of hot air passing through the chamber
as much as possible.
In order to be able easily to get a greater heat during the earlier stages of
warming the chamber, the wall opposite the louvre blades and enclosing the coke
is built tapering inwards towards the bottom, thus giving a greater area of fire
surface in the initiary stages, and proportionately less in the later stages.
The hot air passing up the shaft enters the drying chamber close under the
roof.
On the opposite side of the chamber to that at which the hot air enters, a flue is
built for the air to pass out having its opening inside the chamber near the floor
bottom.
By this means it is ensured that the hot air spreads uniformly over the chamber,
and descends in among the objects to be dried in such a manner that the air which
leaves the chamber is always that which is of the lowest temperature.
.
Except for the openings mentioned the drying chamber is closed up in the
usual way.
The flue through which the air passes out may be provided with a damper to
control the total amount of air passing through the chamber.
In order to control the volume of air passing through the louvre blades at
different heights, a damper is used made partly solid, partly half open, and partly
fully open, which can be lowered according as the level of the fire sinks.
This can be lowered by hand or if no attendant is available, as for instance at
night, the lowering can be effected automatically, such as for instance by a clock
mechanism controlled by a pendulum.
Another method of controlling the volume of air passing through the louvre
blades at different heights, may be by means of hinged dampers, arranged
horizontally one above the other, each capable of being separately opened
more or less, or closed entirely, according to the state of the fire and the heat
in the chamber.
4
If it is desired to add to the charge of fuel, the lowering damper is of course
raised accordingly, or in the case of hinged dampers, the upper ones are opened
and the lower ones closed or nearly closed.
Figure 1 of the accompanying drawings shows a longitudinal section.
Figure 2, a front elevation of the drying chamber and furnace.
Figure 3 represents the damper at a lower stage of the fire than at Figure 2,
and Figure 4 shows it at a lower stage than Figure 3.
A, is the drying chamber, the wall C of which is carried close up to the
roofing D, so that the hot air on entering by the opening E of the mixing
chamber B distributes itself and descends in the drying chamber A and finds an
outlet through the passage F opposite the inlet E and close to the floor G.
H is the furnace with an inclined back wall I. J, J, are louvre blades fitted
in the front of the furnace. K is the charging hole, and L is the charging door
worked by hand lever M. N is the damper made solid at P, P, partly open at Q
and quite open at R, R, and arranged to slide between guides S, S. The lowering
of the damper is controlled by clock gear T in the manner shown, or by any other
means.
When the chamber is cold at starting, this lowering of the damper provides for
a less proportion of overdraught being allowed as compared with when the
chamber is sufficiently hot, at which stage more overdraught is allowed and it
also provides for the draught being gradually increased in the lower layers of
coke.
In practice, the cross bar U is arranged level with the top of the coke in the
furnace, and the damper lowered so that the cross bar U is always level with the
top level of the fuel.

page_text: The damper in Figure 2, is shown in position when the fire is first started, the
fuel then being about level with the top louvre blade so that a full flow of air
goes through the damper into the upper layer of fuel, a half supply through the
middle layer of fuel, the bottom being entirely closed except for that quantity passing
through the bars from the ash pit.
The damper shown in Figure 3, is in position for a full flow of air over the
fire, a full flow of air through the upper part of the fuel and a half supply through
the lower part of the fuel.
The damper shown in Figure 4, is in position for covering the upper part of
the louvre blades, the opening below for a full flow of air over the fire, and a full
flow of air through the fuel which has by this time descended to the bottom of the
furnace.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In connection with a drying chamber and a coke-consuming furnace, the
employment of louvre blades for admitting air into the body of the fire and over
the fire, in combination with a mixing chamber, distinct from the drying chamber,
for the burning of the combustible gases and for mixing the caloric thus obtained
with a large volume of atmospheric air, before its admission into the drying
chamber, substantially in the manner set forth and shown.
2. In connection with a drying chamber and a coke-consuming furnace, a
vertical mixing chamber in which a large volume of atmospheric air is heated in
the manner set forth, in combination with a damper having a lowering action in
proportion to the lowering of the fire due to the combustion of the coke, or a set
of dampers arranged horizontally one above the other, for the purpose of regulating
the position of admission and the proportion of atmospheric air through, or through
and over, the fire at varying levels.
3. In connection with a drying chamber and a coke-consuming furnace, a vertical
mixing chamber in which a large volume of atmospheric air is heated in the
manner set forth, having its opening into the drying chamber at or near the
highest point of the drying chamber, in combination with an outlet flue having its
opening in the drying chamber at or near the lowest point of the drying chamber
for the purpose of allowing of the exit of the air only at its lowest temperature.
Dated this 19th day of October 1896
H. GARDNER,
Patent Agent, 166 Fleet Street, London,
Agent for the said John Thomas Godfrey.