IMPROVED APPARATUS FOR GENERATING HEAT IN STEAM BOILER FURNACES
Year: 1885

page_text: Furnaces.
I, THOMAS CHRISTOPHER LEWIS of 78 Stockwell Park Road in the County of
Surrey, Organ Builder and Bell-founder do hereby declare the nature of my
invention for IMPROVED APPARATUS FOR GENERATING HEAT IN STEAM BOILER
FURNACES, to be as follows:―
This invention has for its object the economising of fuel and boiler space and at
the same time the prevention of smoke, and consists in dividing the necessary air
for the combustion of the fuel, the air being under a moderate pressure, into two
separate volumes, the one entering under the firegrate into a closed ash-pit to
support combustion, and the other, in an artificially heated state entering into the
combustion chamber at the back of the fire-bridge to complete the combustion of
the fuel, the resulting gases then pass off through the flues or tubes to heat the
boiler in the usual manner. As in this arrangement the fire place, as also the flues
and take-ups can be considerably reduced in length, the length of the boiler can be
shortened and still produce the same quantity of steam as a longer boiler and at the
same time, as a limited quantity of air is permitted to mingle with the fuel and
the gases from it are completely burnt, it is evident not only that economy must
result but a colourless vapour only will escape from the chimney.
The arrangement of parts to accomplish this is as follows:-
On the bottom of the fire tube in Lancashire, Cornish or Marine boilers I lay a
hollow platform divided underneath up its centre into two channels, the one'
serving to conduct the necessary air from the main source to an air box at its
further or back extremity and thence to the closed ashpit under the fire bars to
support combustion; the other channel serves to conduct the air, also from the
main source, to another air box behind the fire bridge wall and under the bridge,
thence through a heating apparatus and so further to the combustion chamber
behind the firebridge to burn the gases produced in and coming from the fireplace.
On the air box first mentioned is built up a thin wall of firebricks to form the
back end of the fire place and front part of fire bridge, the continuation of which

page_text: forms the combustion chamber for the gases. The bottom of this combustion
chamber is formed of fire bricks which are laid upon the upper side of the hot air
apparatus, the latter consisting of a shallow flat box provided with partitions to
forin a serpentine channel for the air to pass through on its road from the main to
its exit into the combustion chamber.
It will be understood that pipes can be substituted for heating the air instead of
the flat box, and so can pipes be substituted for the channels under the platform,
but I prefer the plan here described. The fire place is provided with two dead
plates set one above the other, the lower one being the broader.
The ashpit is closed by a hinged door or flap, easily opened or shut, for the
removal of the ashes. This is placed at the inner end of the lower dead-plate, or
close up to the front fire bar bearer. In this door is a smaller door for the purpose
of admitting the stoking irons and removing the scoriæ from the grate bars. Both
these doors work on a hinge attached to the underside of the lower dead plate.
The two dead plates reach quite across the boiler tube or fireplace and are placed a
few inches apart in a vertical direction. The fuel lies partly on both of them, but
the upper one being shorter than the other most lies on the bottom one. . It is thus
possible to push the necessary quantity of fuel for one firing onto the grate without
smoke or gases escaping at the fire door, as there is always a barrier of fuel between
the grate and the fire door.
The fire door is of the usual kind, with the exception that it has a small doorway
within it covered by a sliding door which communicates with the compartment
formed between the two dead plates and through which the fuel is pushed forward
onto the grate. The fuel is shovelled in as usual, the upper dead plate and the
back half of the lower one being always covered with it up to the top of the boiler
tube or arch of the fireplace. The fire bars are placed as deep as practicable below
the fire bridge, without interfering too much with the room in the ashpit, in order
to produce gases as rich as possible in carbonic oxide without creating too much
carbonic acid. A locking arrangement working under the platform between the
air channels is applied for locking the flap door of the ash-pit against the internal
pressure and unlocking it when required, as also one for holding it open whilst the
ashpit is being emptied. The necessary cocks or valves are also introduced for
regulating the supply of air to the ash pit and combustion chamber respectively.
In certain cases I dispense with the flap door to the ash pit and the forced air
under the fire grate together with one air channel and air box, and only utilise the
chimney draught for creating the gases, but retain the forced hot air to burn them
with, as also all other parts of the arrangement as here described.
Of course the whole arrangement is applicable to other boilers besides those
specially named.
Again I sometimes introduce into the ash pit under the fire bars with the air a
small amount of steam from the boiler when the steam from the steam cylinder is
condensed, or from the exhaust when it otherwise would escape into the atmosphere.
This I do partly to keep the grate bars cool, partly to economise the quantity of
forced air necessary and partly to enrich the gases with the hydrogen set free from
the reduction of the steam.
To accomplish this I lead the steam through a small channel under the platform
to the foremost air box, from which it issues alongside the air nozzle which leads
the air under the fire grate.

page_text: Furnaces.
I THOMAS CHRISTOPHER LEWIS of 78 Stockwell Park Road in the County of
Surrey, Organ Builder and Bell Founder, 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 :-
This invention has for its object the economising of fuel and boiler space, and at
the same time the prevention of smoke, and consists in dividing the necessary air
for the combustion of the fuel, the air being under a moderate pressure, into two
separate volumes, the one entering under the.fire grate into a closed ash pit, to
support combustion, and the other in an heated state entering into the combustion
chamber at the back of the fire bridge, to complete the combustion of the fuel ;-
the resulting gases then pass off through the flues or tubes, to heat the boiler in the
usual manner.
As in this arrangement the fireplace, as also the flues and take-ups, can be
considerably reduced in length, the length of the boiler can be shortened, and still
produce the same quantity of steam as a larger boiler, and at the same time, as a
regulated quantity of air is permitted to mingle with the fuel, and the gases from
it are completely burnt, it is evident, not only that economy must result, but a
colorless vapour only will escape from the chimney.
In the accompanying drawing,
Fig. 1 shews in vertical section, on the line A B of Fig. 3, apparatus comprising
the present invention fixed into a marine boiler tube.
Fig. 2 is a sectional plan on the line C D of Fig. 1.
Fig. 3 is a front view of the apparatus ; and
Fig. 4 is a vertical section of the arrangement as applied to a land boiler.
A is an air main for conveying a forced air current from any suitable blowing
apparatus. a is a branch from the same, connecting it with a channel a a beneath
a platform B constituting the bottom of the ash pit C, which underlies the fire
bars c of the fire place C¹, and is capable of being hermetically closed, save at the
point hereinafter mentioned. a is a similar branch leading the air. to the
channel a a¹, likewise below the platform B, and a² a³ are cut-off cocks in
the branches a a' respectively.
The channels a a and a' al are formed by dividing the hollow space beneath the
platform B longitudinally by means of a partition consisting of parts 6² 63 and 62*,
a small groove or channel b being left between the parts b² and b³ for the purpose to
be presently explained. The channel a a leads from the branch a, under the
platform B, to the air box 6 communicating with the ash pit C through the
slit b¹.
Above the air box b is built a wall of fire brick c², which forms the front of
the fire bridge c¹ and the back of the fire place C¹.
The air box b also carries the after bearing bar c³ of the fire bars c.-The second
channel a¹ a leads from the branch a¹ alongside the channel a a to the entrance of
the air box D, situated at the back of the ash pit C and fire bridge c.-The air
box D is in communication with the air box D₁ through a square hole d¹ on the
left of the boiler (see the plan view Fig. 2).-The air chamber D' is shallow, and
underlies the combustion chamber E at the back of the fire place, and is divided up

page_text: by five vertical partitions d²-ds forming a serpentine passage along which_air
may pass and be heated by contact with the bottom of the combustion chamber E.-
The passage finally leads into the box d' extending across the combustion chamber E,
and in direct connection with it through the opening e.
In land boilers, return pipes may sometimes be used instead of the serpentine
heating passage above described, and common pipes may be substituted for the
passages beneath the platform B.
F is a space between two dead plates f and f¹, situated at the front of the fire
place, one above the other, and extending quite across it. The lower one f projects
into the fire place considerably further than the upper one f¹, so that the fuel
thrown, in the usual way, through the door f6 in the frame f, will lie upon both
dead plates in the manner shewn in Fig. 1, and will completely seal the opening to
the fire place C¹, and prevent the indraught of cool air, at the same time becoming
heated and ready for use. A shallow opening f4, covered by a sliding door f', is
provided in the fire door f6, to allow of the fuel being pushed from the dead plate f
onto the fire, without the possibility of any smoke escaping from the funnel. G is
an air-tight flap door to the ash pit C, hanging upon hinges ggg working on a
hinge rod g, which is fixed to a plate fastened to the lower dead plate f. The
edges of the door G are so arranged that a packing of asbestos tape or cloth may
be inserted to secure air-tight fitting.-H is another flap door placed above the
door G, but also hinged upon the rod g¹. Through this door the irons may be
inserted for stoking the fire or clearing the bars. Both doors G and H are by
preference placed close up to the front tire bar bearer c¹.
I is a strong bar running across the boiler tube under the dead plate f, to which
it is attached. It serves as a fulcrum for the stoking tools, and also to hold a
bolt i, or a hook for holding the door G up out of the way whilst the ashes are
being removed from the ash pit C.-K is a lever bolt which locks and unlocks the
door G when requisite. This is necessary because of the internal pressure in the
ash pit C, caused by the forced air. The lever end comes to the front of the boiler,
and can be worked by the foot.-It lies out of danger of derangement in a small
groove or channel 6* before mentioned.-L is a small channel which runs alongside
the channel a a, and comes into the air box b, but separated from the air also
coming into that box. This channel is a conduit for a small amount of steam,
which is drawn from the boiler into it at l, at the front of the platform B, and
which is discharged into the ash pit C at 7 alongside the nozzle b'.-The object in
employing here a small amount of steam is partly to economize the quantity of
forced air required, partly to keep the fire bars cool, and partly to enrich the gases
by the hydrogen set free by the reduction of the steam.
The manner of working the above described arrangement of parts is as
follows:
The fire is lit and made up in the usual manner whilst the door G is constantly
kept open by the bolt i. The dead plates f and flare charged with as much fuel
as can be placed upon them, and as the fire gradually burns up, the fuel is pushed
forward through the small opening f'in the main fire door f onto the fire place C',
until the top of the fire or incandescent mass of fuel becomes level or nearly so
with the fire bridge c¹. At this point, the fire bars c c c can be cleaned if requisite,
and the ash pit C cleaned out, the door G let down and closed tight by the locking
bolt K, the small door H being also closed. Now, air from the main A may be
gradually let in through the branch a and channel a a by opening the valve a²,
when it will emerge in the ash pit C through the nozzle b¹ of the air box b, and
on meeting the incandescent fuel on the grate C¹, will, with the fuel, be converted
into carbonic acid, which, whilst passing up through the thick bed of hot fuel, will
be reduced to carbonic oxide principally, and flow over the fire bridge c¹ into the
combustion chamber E.-At this juncture the valve a³ may be gradually opened,
and the air, after passing through the branch a¹, the channel a¹ a¹, the box D, and
the heating serpentine passage. D¹, will emerge in a heated state through the slit e
of the box d' into the combustion chamber E, there to mingle with the hot gases'

page_text: from the fire place C', and give the necessary high temperature demanded for the
consumption of the smoke.
The remaining products of combustion passing on under the boiler, and through
the flues, consist mainly of carbonic acid and steam. At intervals of some hours,
the door G is opened for the removal of the ashes from the ash pit C, at which
time the admission of air must be slackened or shut off, as found expedient, at
both valves a² and a³, but while stoking the fire through the door H, it is not
necessary to shut off or slacken the blast. By admitting either more or less air to
either the fire place or the combustion chamber, any degree of evenly distributed
heat may be maintained from front to back of the fire tube.
Not more than a good half of the fuel lying on the dead plate f should be fed
onto the fire each time of firing, so that sufficient may remain to always seal the
opening F.-The top of the fire C¹ should be maintained as level all over as
practicable, and kept up to the level of the fire bridge c¹, or nearly so. The fire
bars ccc are placed very near together, so that scarcely anything but ash descends
into the ash pit C.
In the arrangement Fig. 4, the air entering the box D at d, collects in the
compartment D³, whence it passes out through the pipe D, and flows to tho
extreme back end of the boiler tube, and so round to the return pipe D¹, and into
the compartment D³ of the box D, and emerges at e into the combustion chamber E
at the back of the fire bridge c.-M is a thin wall of fire bricks, of which there are
two or more in the length between the fire bridge and the end of the boiler
(though only one is shewn on the drawing). These walls not only serve as supports
to the hot air pipes D¹ and D¹¹, but also for the purpose of keeping the hot gases
in constant contact with the crown of the fire tube.
In certain cases, though not so economical, one blast of artificially heated air is
einployed for burning the gases in the combustion chamber E, and for the creation
of gases in the fire place C¹, the available chimney draught alone is relied upon.
Of course, in that case, the branch a, channel a a, box b, and nozzle b¹, as well as
the doors G and H, are not required, but in all other respects the arrangement
remains just as described.-But in all and every case, the fire bars c c c are placed
as low as may be below the top of the fire bridge c¹ towards the platform B,
without reducing the room in the ash pit C to an inconvenient extent.-This is in
order to procure the gases as rich as is attainable in carbonic oxide.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed, as communicated to
me by my Foreign Correspondent, I declare that what I claim is
1. The means above described for presenting a regulated divided blast to the
furnace, one part of such blast being delivered to a closed ash pit, for the purpose
of supporting combustion, and the other part being delivered in a heated state to
the combustion chamber, for the purpose of ensuring the burning of the smoke and
gases passing from the fire chamber.
2. The means above described for delivering a column of heated air under
pressure to the combustion chamber, for the purpose above set forth.
3. The arrangement above described for facilitating the stoking of the furnace
with heated fuel, and preventing the indraught of cooling air, or the escape of
unconsumed smoke.
4. The application to the ash pit door of the locking device above described.