IMPROVED APPARATUS FOR EFFECTING THE COMBUSTION OF SMOKE AND UNBURNT GASES IN THE TUBES OF STEAM BOILERS
Year: 1884

page_text: I, JOHN TOBIN of 183 Brunswick Road Poplar London E. in the County of
Middlesex Engineer do hereby declare the nature of my invention for IMPROVED
APPARATUS FOR EFFECTING THE COMBUSTION OF SMOKE AND UNBURNT GASES IN
THE TUBES OF STEAM BOILERS to be as follows:-
-
Within the smoke box of boiler is fitted an air-tight casing communicating with
the exterior atmosphere by suitable openings to arrange the amount of air supply
the area of casing shall be fully equal to that portion of tube plate that is per-
forated for tubes. The front and back plates shall be a certain distance apart and
shall be each perforated to pass small air tubes in such a position that the said air
tubes shall rest on bottom of boiler tubes and shall be of sufficient length to go
within a certain distance of the fire-box tube plate this end of air tube to be fitted
with a conical cover secured to end of tube and passing over a small portion of its
length having its point towards the fire-box and of such a diameter at its base as
to give an annular space between it and air tubes equal in area to the bore of the
air tubes; the other end of air tube to be stopped and to have openings of sufficient
area in that portion of tubes within air casing.
The Conical Cover is intended to divert the current of incoming heated air into
the same line as that of the gasses coming from furnace and intimately mixing
with them and by this means setting up a secondary combustion within the tubes
of the boiler resulting in consumption of smoke, economy of fuel and increased
efficiency of boiler.

page_text: I JOHN TOBIN of 183 Brunswick Road, Poplar, London E. Middlesex, Engineer
do hereby declare the nature of said invention for "IMPROVED APPARATUS FOR
EFFECTING THE COMBUSTION OF SMOKE AND UNBURNT GASES IN THE TUBES OF
STEAM BOILERS " and in what manner the same is to be performed to be par-
ticularly described and ascertained in and by the following statement :-
In the ordinary forms of boilers constructed with flues or tubes passing longi-
tudinally through the boiler whether it be the so called multi-tubular boilers of
locomotive type and similar types, or of the return tube or flue boiler such as the
ordinary marine boiler types or of the Lancashire or Cornish boiler types it is
a well ascertained fact that by far the greatest amount of heat is developed and
given out in the fire box and over and immediately beyond the bridge, all the air
for combustion being supplied in these parts of the boiler. As a consequence
a great and sudden lowering of the temperature of the gases takes place imme-
diately beyond the bridge or fire box and the large calorimeter usually existing
there tends to further diffuse and cool the gases, causing smoke and checking
materially the further or complete burning and utilization of the gases. Various
attempts have been made for mitigating these defects, and appliances have been
proposed for introducing air from front of boiler to the tubular flue or flues beyond
the bridge or firebox but such appliances are generally inconveniently in the way
in that part of the boiler besides having other disadvantages.
Now according to my invention I introduce highly heated air to the gases in the
tubes or tubular flue or flues beyond the bridge or firebox and by this means I set
up a secondary or completing combustion within such tubes or tubular flues or
flue of the boiler the heated air being induced by the draught or current of the
gases, (and not checking or being checked by or flowing counter to it as has been
the effect in previous attempts to introduce heated air from beyond the bridge).
The air admission to the fuel on the grate may at the same time advantageouly
be diminished, the consequence of which is that more carbonic oxide and less carbon
dioxide is produced over the grate and in the parts beyond it, while the carbonic
oxide will finally by the further hot air supply be formed into carbon dioxide.
In the smoke box of the boiler or in some flue situated at the end of the boiler,
whether it be the sinoke box or back end uptake of a locomotive type boiler, or
the back end flue of a Cornish or Lancashire type boiler or the smoke box or front
uptake of a marine type boiler I provide one or more wholly or fairly airtight casings
chambers tubes or nest of tubes or the like which shall offer a heating surface for
the gases to play on, such chamber or chambers, tube or tubes communicating with
the exterior atmosphere by a suitable opening or openings according to the air
supply required, a valve or valves being provided for adjusting the supply of cold
air. From this air supply chamber or chambers I carry one or more tubes into
each tube or tubular flue (or if the boiler is fitted with a number of small tubes
into each of them or into as many of them as may be found desirable). Each such
air tube is carried along for some distance therein but so far that the temperature

page_text: of the gases shall still be above that of ignition its end being fitted with a conical
cover, hood, shield box or deflecting appliance of any suitable form but so as to
divert the current of the air (which becomes highly heated by its passage through
the aforesaid chamber and then through the air tube or tubes) and turn it (the
effluent heated air) into the same direction as the flow of the gases from the fire
box; the gases will thus by the induced current action assist the efflux of the hot
air, and the air will be thoroughly mixed with the gases and set up the aforesaid
secondary or further or complete combustion, thus preventing the formation of
smoke economizing the fuel and increasing the efficiency of the boiler, the evapo-
ration in which will also be more equalized.
In the accompanying drawings I have illustrated some typical modes in which
my invention may be carried into effect, Figs 1 to 6 as applied to a locomotive
type boiler or return tube marine boiler and Figs 7 to 11 as applied to a Cornish
or Lancashire boiler.
Fig 1 is a longitudinal section of a locomotive or portable engine boiler and
Fig 2 a vertical transverse section. Fig 3 is a longitudinal section and Fig 4 á
transverse section of a boiler tube with its air tube. Fig 5 is a longitudinal section
and Fig 6 a transverse section of a boiler tube with its air tube, the latter being
steadied in position.
The air is taken from the outside by say two lateral openings o through the
smoke box a and carried into the casing or chamber p and thence by the air
tubes into the boiler tubes c. Each air tube is provided with a cap d, so con-
structed that it causes the air to be deflected and to escape in the same direction
as the flame or gases coming from the fire-box, and the position of these caps d
should be in such a part of the boiler tubes where the temperature of the gases
is not below that of ignition.
In the detail views Figs 3 and 4 the end of the air tube simply rests on the
bottom of the tube c, but in Figs 5 and 6 it is steadied in position by means of
the hoop d².
When the smoke box door e is opened the whole of the apparatus p b d can be
withdrawn to facilitate cleaning. Or the cleaning may be effected by admitting
steam jets into the tubes b instead of air. The openings o may be fitted with
bellmouth pipes (especially in case of a boiler for a locomotive engine) and
the bellmouth may be turned in the required direction for catching the air
or wind.
Fig 7 is a longitudinal sectional elevation of an ordinary Cornish boiler fitted or
provided with my improvements and Fig 8 a part plan. The air from without
enters the chamber p by the pipe o and thence passes into the three pipes b which
terminate in the cover, box, or hood d from which the air is distributed in a thin
stream or streams in the same manner as already described.
I sometimes make two or more outlets for the heated air each provided with
a cover or deflector of such construction as to give the air the same direction as
the flame.
Fig 9 is a longitudinal section of a Cornish boiler fitted with another form of
my apparatus. Fig 10 is a vertical transverse section of the saine and Fig 11
shows a plan.
The air is taken from without through the tube o to the smoke box from which
it is carried through a single large tube b or it might be two or more smaller tubes
to an air distributor or hood or box d, which is provided with one or more upright
tubes d perforated in such a way as to cause the heated air to escape in the same
direction as the flame coming from the fire-box and intimately mixing with the
gases. These tubes which have the same function as the above described caps d
can also be made in the shape of a circle or any other form. In fact it is obvious
that the form of the apparatus as a whole and in its details may be modified in
many different ways. It is immaterial in what part of the tube or flue of the
boiler this air distributor d and its tubes b are situated, provided that the tem-
perature of the gases is not below that of ignition. The parts exposed to the

page_text: greatest heat may be made of fireclay, plumbago, or other suitable fire resisting
material.
As applied to a return tube boiler such as an ordinary marine boiler an apparatus
constructed on the principle of Figs 1 to 6 would be fitted to the front uptake, but
where such return tube boilers are long or the draught in them is insufficient
I apply the form of apparatus described with reference to Figs 7 to 11 behind the
bridge.
I sometimes carry the air tube or tubes o over the roof of the boiler house or up
above the deck and provide it with a wide bellmouth which can be directed against
the wind, thus causing a better supply of air. I also provide the tube o with a
valve by which to regulate the air supply.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed I declare that what
I claim is
First: The application of hot air supply from beyond the fire box of a steam
boiler such bot air being induced by the How of gases of combustion to flow in the
same direction as these and to commingle therewith for effecting a more complete
combustion of the said gases in the tubes or flues substantially as here set forth
and described.
Second: The cap, hood, shield or deflecting appliance d in combination with
a tube or tubes chamber or chambers for supplying heated air thereto from
beyond the firebox substantially as described with reference to the accompanying
drawings.