Improvements in Smoke Consuming Firebridges for Boilers.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in Smoke Consuming Firebridges for Boilers.
HERBERT WOODVILLE MILLER, of 18, Kensington Court Place, London, W.,
Engineer, do hereby declare the nature of this invention to be as follows:--
My invention has for its object improvements in the design and arrangement
of firebridges fixed in boilers for obtaining better combustion of the furnace
gases and for the consumption of smoke, and specially relates to the following
points (1) preventing the firebridge becoming choked up and inoperative
from the dust and soot from the furnace, (2) to entirely cover up with fire resist-
ing material all metal work forming part of the bridge (3) to make the internal
metal parts of the bridge strong enough to support the whole weight of the bridge
independent of the tubes or parts of the boiler liable to move from expansion or
contraction (4) to provide a sufficient area over and through the bridge for the
gases to pass without spoiling the draught, and to cause thorough mixing of the
gases with the hot air let in through the bridge to promote combustion, (5) to
make the mass and size of the bridge and the air inlets and outlets and passages
for the air through the parts of the bridge of the proper size to suit the class
of coal being burned in the furnace (6) to provide hot air being supplied to the
bridge. The firebridge is placed immediately behind the furnace in the case of
Lancashire, Cornish, or marine boilers, but in water tube boilers such as the
Babcock & Wilcox type of the ordinary standard pattern it is placed on the top
of the flame plate wall which divides the space between the furnace and the
second chamber, so that the flames and gases rising from the furnace pass up
between the water tubes and over the firebridge and then down between the tubes
in the second chamber. In this type of boiler the air box in the centre of the fire
bridge is built up of steel plates and angles and is designed strong enough to carry
the whole weight of the bridge, the ends of the box are built into the side walis
of the boiler. Underneath the box and on top of the flame plate are laid firetiles
or firebricks which thus protect the box from the flames & hot gases. The internal
size of the air box is large enough to carry the volume of hot air required for
completing the combustion of the gases passing over the bridge. The air box
is perforated on the two sides and the top with holes to correspond with the air
passages in the firebrick blocks forming the bridge and the area of these openings
is arranged so as to allow an equal and a proportionate amount of hot air to
pass through each firebrick block. The firebrick blocks are hollowed out so as
to fit over the top and down the two sides of the air box and meet the firetiles
underneath, thus covering the air box and protecting it from the flames.
firebrick blocks are of alternate large and small sizes and are placed side by side
right across the whole length of the air box from side wall to side wall of the
boiler, and are of triangular shape, with the slope of the sides at such an acute
angle as to cause any dust which may fall on them to roll off again and thus
prevent them being choked up.
The
The gases or products of combustion pass over the large blocks and between

page_text: the spaces formed by the small blocks. The outlet holes for the hot air in the
large blocks are perforated through at right angles to the direction of the flow
of the furnace gases and this combined with the outward flow of the hot air
prevents these holes being blocked up by dust or soof.
In order to heat the air which is passed through the firebridge I provide at
the back end of the boiler a number of tubes of metal expanded into a top
and a bottom header or metal box; an inlet pipe is provided to the bottom header
having a door or valve by which the quantity of air entering may be regulated
to suit the amount of smoke to be consumed according to the class of coal used;
at the top header two outlet pipes are provided leading to the two ends of the
firebridge the area of the two outlet pipes being twice that of the inlet pipe to
allow for the increased volume of the air when heated.
The air heater being placed at the back end of the boiler, the air passing up
inside the tubes is heated by the waste gases after they have done their work
in the boiler.
-
HERBERT WOODVILLE MILLER, of 18, Kensington Court Place, London, W.,
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:
-
My invention has for its object improvements in the design and arrangement
of firebridges fixed in boilers for obtaining better combustion of the furnace
gases and for the consumption of smoke, and specially relates to the following
points (1) preventing the firebridge becoming choked up and inoperative
from the dust and soot from the furnace, (2) to entirely cover up with fire resist-
ing material all metal work forming part of the bridge (33) to make the internal
metal parts of the bridge strong enough to support the whole weight of the bridge
independent of the tubes or parts of the boiler liable to move from expansion or
contraction, (4) to provide a sufficient area over and through the bridge for the
gases to pass without spoiling the draught, and to cause thorough mixing of the
gases with the hot air let in through the bridge to promote combustion (5) to
make the mass and size of the bridge, and the air inlets and outlets and passages
for the air through the parts of the bridge of the proper size to suit the class
of coal being burned in the furnace, (6) to provide hot air being supplied to the
bridge.
The firebridge is placed immediately behind the furnace in the case of
Lancashire, Cornish, or marine boilers, but in water tube boilers such as the
Babcock & Wilcox type of the ordinary standard pattern it is placed on the top
of the flame plate wall which divides the space between the furnace and the second
chamber, so that the flames and gases rising from the furnace pass up between
the water tubes and over the firebridge and then down between the tubes in the
second chamber.
In this type of boiler the air box in the centre of the firebridge is built up of
steel plates and angles and is designed strong enough to carry the whole weight
of the bridge; the ends of the box are built into the side walls of the boiler.
Underneath the box and on top of the flame plate are laid fire tiles or fire
bricks which thus protect the box from the flames and hot gases.

page_text: The internal size of the air box is large enough to carry the volume of hot air
required for completing the combustion of the gases passing over the bridge.
The air box is perforated on the two sides and the top with holes to correspond
with the air passages in the firebrick blocks forming the bridge and the area of
these openings is arranged so as to allow an equal and a proportionate amount of
hot air to pass through each firebrick block.
The firebrick blocks are hollowed out so as to fit over the top and down the
two sides of the air box and meet the firetiles underneath, thus covering the
air box and protecting it from the flames. The firebrick blocks are of alternate
large and small sizes and are placed side by side right across the whole length
of the air box from side wall to side wall of the boiler, and are of triangular
shape, with the slope of the sides at such an acute angle as to cause any dust
that may fall on them to roll off again and thus prevent them being choked up.
The gases or products of combustion pass over the large blocks and between
the spaces formed by the small blocks.
The outlet holes for the hot air in the large blocks are perforated through at
right angles to the direction of flow of the furnace gases, and this combined with
the outward flow of the hot air prevents these holes being blocked up by dust
or soot.
In order to heat the air which is passed through the firebridge I provide at
the back end of the boiler a number of tubes of metal expanded into a top
and a bottom header or metal box, an inlet pipe is provided to the bottom header,
having a door or valve by which the quantity of air entering may be regulated
to suit the amount of smoke to be consumed according to the class of coal used;
at the top header two outlet pipes are provided leading to the two ends of the
firebridge, the area of the two outlet pipes being twice that of the inlet pipe to
allow for the increased volume of the air when heated.
This air heater being placed at the back end of the boiler, the air passing up
inside the tubes is heated by the waste gases after they have done their work
in the boiler.
In the accompanying drawings Figure 1 shews an end view elevation of a water
tube boiler with the air heater A at the back of the boiler, having the air inlet
door B in the bottom box or header, at the top are two metal boxes or pipes C
for carrying the heated air through the side brick walls of the boiler to the metal
box inside the bridge. The firebrick blocks E are shewn in position, the
vertical boiler tubes F being removed to enable the bridge to be seen.
Figure 2 is a plan view on top of the horizontal tubes of the boiler, shewing
the firebrick blocks in position, the blocks being alternately large and small,
the air boxes ('are also shewn.
Figure 3 shews a side view elevation of the boiler with the bridge in position;
the air heater and the air boxes C, also the holes in the large blocks through
which the hot air escapes to mix with the furnace gases.
Figure 4 shews enlarged views of the firebrick blocks, E being the large one
and the smaller block.
The lower portion of both blocks have spaces G cut away so as to fit over and
rest on the metal bridge D. The large block E is shewn divided into 3 parts
through the lines H H H. for convenience of manufacture, the upper part when
placed in position locks the two lower portions together.
The large block E only is provided with internal air passages for carrying the
hot air from the bridge 1) to the round outlet holes I.
Figure 5 shews a part of one side of the metal bridge D. with round air outlet
holes corresponding with the lowest air passage and outlet hole I in the large
block E, both sides of the bridge D are alike; at the end of the bridge D) is shewn
the junction with the hot air box ('.
Figure 6 shews a part of the top of the metal bridge with square air outlet
holes K, which allow the air to pass into the middle and upper air passages to
the outlet holes I in the large blocks E.

page_text: 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―
A smoke consuming firebridge, consisting of a strong perforated metal air
box supplied with air heated by the waste gases, surrounded with a large mass
of fire resisting material shaped to prevent accumulation of dust or soot, and
to allow the furnace gases to pass freely over and between the bridge blocks, and
hot air to escape from the blocks, substantially as and for the purpose herein
described.