Improvements in Furnaces.
Year: 1894

page_text: Date of Application, 29th Oct., 1894
Complete Specification Left, 29th Aug., 1895-Accepted, 5th Oct., 1895
Improvements in Furnaces.
1, ROBERT MARSHALL, of No. 6 Cleveland Terrace Gardens, Kensington, in the
County of London, Engineer, do hereby declare the nature of this invention to be
as follows:-
My invention relates to the combustion chambers of furnaces in which the air
draught whether forced or natural, is made to take place in a downward direction
through the fuel which is fed in at top, in order that the volatile constituents and
smoke given off from the freshly charged upper layers of the fuel are made to pass
down through the incandescent layer of fuel at the bottom of the chamber, so as to
effect the perfect combustion thereof. With this mode of effecting the combustion
of the fuel it is essential for insuring that the whole of the smoke and volatile
constituents shall pass through the incandescent layer of fuel, to form the sides of
the fuel chamber in such manner that they shall offer at least the same amount of
resistance to the passage of the combustible gases as is offered by the fuel at the
centre of the chamber as otherwise the greater part of the gases might escape down
the sides of the chamber without passing through the incandescent fuel.
effect this by making the sides of the fuel chamber, or some of them, inclined
inwards in downward direction, thereby firstly offering a greater amount of wall
surface for a given depth of fuel, and consequently a correspondingly increased
frictional resistance to the gases passing downward between such wall surface and
the fuel, and secondly insuring a closer contact between such fuel and the wall
surface by reason of its pressing thereon with the weight due to the layer of fuel
above it.
The combustion chamber may be variously constructed in carrying out this
invention, thus it may be made of an inverted truncated pyramidal or conical form,
or it may be partly pyramidal or conical and partly rectangular or cylindrical.
In cases where the draught passes away from the lower end of the fuel chamber in
a direction to one side thereof, instead of centrally downwards, the wall of the
chamber on the same side as the discharge opening is by preference made with a
greater inclination than the other walls in order to increase the resistance of the
draught on that side and thus neutralize the tendency that would otherwise exist,
for the draught to pass the shortest way to the exit opening. In this case when the
width of the incandescent fuel layer at bottom is considerable, so that the draught
passing down the side of the combustion chamber opposite that where the exit
opening is situated meets with correspondingly increased resistance in passing
through the fuel towards such opening, the wall of the chamber opposite the
opening may be made perpendicular, so as to reduce the resistance to the downward
draught on that side as much as possible.
When combustion chambers constructed as above described are applied to
furnaces such as reverberatory furnaces for puddling &e. it is essential to insure
that the combustion of the gases coming from the fuel chamber shall continue to a
greater or less extent when they arrive over the hearth of the furnace, in order to
maintain the required heat at that point. In order to insure this, it is necessary to
shorten the length of passage leading from the fuel chamber to the hearth of the
furnace as much as possible and I effect this by arranging the before described
inclined wall of the fuel chamber so as also to constitute the one wall of the flue or
passage leading the flames and combustible gases from the bottom opening of the
fuel chamber to the hearth, the other sides of such passage being carried up

page_text: either "vertical or parallel with such inclined wall, or inclined in the opposite
direction.
With the above described arrangement, slag is liable to accumulate in the said
bottom passage of the fuel,chamber whereby the proper action of the furnace is
gradually impeded.
In order to avoid such detrimental accumulation I provide at the side of the
furnace at the point where such bottom passage is situated a door or doors through
which access can be gained from time to time to such passage for the removal of
the accumulation of the slag and ashes.
Furthermore, in order to insure the regular descent of the fuel in a solid mass
in the fuel chamber as it burns.away, I form in the front end wall of the furnace
a number of small stoppered openings at different levels, through which stoking
tools can be introduced from time to time in order to break up the fuel and prevent
scaffolding.
In order to facilitate this operation, I prefer to make the fuel chamber of only
such moderate width in the longitudinal direction as will enable a moderate sized
-stoking tool to reach right across it while in the transverse direction I make the fuel
chamber.ofiany.desired greater size to afford the chamber the requisite capacity.
The above described construction of combustion chambers is more particularly
adapted for metallurgical purposes.
When applying the invention to the combustion chambers of steam boilers,
there is, as a rule, not sufficient space at the sides of the chamber for providing the
above described side doors for the removal of the slag and ashes. In such cases
.therefore I modify the construction as follows.
Instead of forming the opening at the bottom of the fuel chamber at the inner
side of the chamber, I form it at the outer side, and from such opening I form a
"flue leading first vertically down along the front side of the chamber and then
horizontally along underneath the fuel chamber and into the furnace tube of the
boiler. The part of the front wall of the chamber along which the said flue
descends I form.as a door or doors so that on opening this or these the whole of
the flue is exposed, and as the accumulations of slag in this case take place at the
front end of the fluc, they are readily removed, together with the accumulation of
ashes through such front door or doors.
This construction is applicable not only with fuel chambers with inclined sides
as above described but also with chambers having vertical sides.
The before described small stoking holes are with this construction also formed
in the front door or doors.
The air supply is admitted from an air distributing chamber arranged on the
top of the fuel chamber and having a number of graduated openings leading into
the latter. The fuel is introduced into the combustion chamber through a suitable
hopper at top. When working with ordinary chimney draught, 'the top of the fuel
chainber may be left open.
For the purpose of strengthening the arch forming the top of the before
described flue leading horizontally beneath the combustion chamber, which arch
also forms the bottom of the said chamber, I provide a series of tubes extending
either transversely through or beneath the brick arch, through which tubes
currents of water steam or air may be made to pass so as to keep them from
becoming overheated, such water or air being used on the one hand to feed the
boiler and on the other hand as the air supply to the fuel chamber. Or the
steam from the boiler may be passed through the tubes so as to be superheated.
The tubes may for the above purpose be connected at their ends to boxes
outside the combustion chamber, communicating with the water or steam space of
the boiler. Or the tubes may be made to form part of the water tubes of a water
tube boiler, of which the combustion chamber constitutes the furnace.
Dated this 29th day of October 1894.
ABEL & IMRAY,
.Agents for the Applicant.

page_text: Improvements in Furnaces.
I, ROBERT MARSHALL, of No. 6 Gleveland Terrace Gardens, Kensington, in
the County of London, 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 relates to the combustion chambers of furnaces in which the air
draught whether forced or natural, is made to take place in a downward direction
through the fuel which is fed in at top, in order that the volatile constituents and
smoke given off from the freshly charged upper layers of the fuel are made to pass
down through the incandescent layer of fuel at the bottom of the chamber, so as to
effect the perfect combustion thereof. With this mode of effecting the combustion
of the fuel, it is essential for insuring that the whole of the smoke and volatile
constituents shall pass through the incandescent layer of fuel; to form the sides of
the fuel chamber in such manner that they shall offer at least the same amount of
resistance to the passage of the combustible gases as is offered by the fuel at the
centre of the chamber as otherwise the greater part of the gases might escape down
the sides of the chamber, without passing through the incandescent fuel.
I effect, this by making the sides of the fuel chamber, or some of them, inclined
inwards in downward direction, thereby firstly offering a greater amount of wall
surface, for a given depth of fuel, and consequently a correspondingly increased
frictional resistance to, the gases. passing downward between such wall surface and
the fuel, and, secondly insuring a closer contact between such fuel and the wall
snrface. by reason of its pressing thereon with the weight due to the layer of fuel
above it. The combustion chamber may be variously constructed in carrying out
this invention, thus it may be made of an inverted truncated pyramidal or conical
form, or it may be partly pyramidal or conical and partly rectangular or cylindrical.
In cases where the draught passes away from the lower end of the fuel chamber in
a direction to one side thereof, instead of centrally downwards, the wall of the
chamber on the same side as the discharge opening is by preference' made with a
greater inclination than the other walls in order to increase the resistance of the
draught on that, side and thus neutralize the tendency that would otherwise exist,
for, the draught to pass the shortest way to the exit opening. In this case when
the width of the incandescent fuel layer at bottom is considerable, so that the
draught passing down the side of the combustion chamber opposite that where the
exit opening is situated meets with correspondingly increased resistance in passing
through the fuel towards such opening, the wall of the chamber opposite the
opening may be made perpendicular, so as to reduce the resistance to the downward
draught on that side as much as possible.
When. combustion chambers constructed as above described are applied to
furnaces, such as reverberatory furnaces for puddling &c. it is essential to ensure
that the combustion of the gases coming from the fuel chamber shall continue to a
greater or less extent when they arrive over the hearth of the furnace, in order to
maintain the required heat at that point. In order to ensure this, it is necessary
to shorten the length of passage leading from the fuel chamber to the hearth of the
furnace as much as possible and I effect this by arranging the before described
inclined wall of the fuel chamber so as also to constitute the one wall of the flue or
passage leading the flames and combustible gases from the bottom opening of the
fuel chamber to the hearth, the other sides of such passage being carried up
either vertical or parallel with such inclined wall, or inclined in the opposite
direction.
With the above described arrangement, slag is liable to accumulate in the said

page_text: bottom passage of the fuel chamber whereby the proper action of the furnace is
gradually impeded.
In order to avoid such detrimental accumulation I provide at the side of the
furnace at the point where such bottom passage is situated a door or doors through
which access can he gained from time to time to such passage for the removal of
the accumulation of the slag and ashes.
Furthermore, in order to ensure the regular descent of the fuel in a solid mass
in the fuel chamber as it burns away, I form in the front end wall of the furnace
a number of small stoppered openings at different levels, through which stoking
tools can be introduced from time to time in order to break up the fuel and prevent
scaffolding.
In order to facilitate this operation, I prefer to make the fuel chamber of only
such moderate width in the longitudinal direction as will enable a moderate sized
stoking tool to reach right across it while in the transverse direction I make the
fuel chamber of any desired greater size to afford the chamber the requisite
capacity.
The above described construction of combustion chambers is more particularly
adapted for metallurgical purposes.
When applying the invention to the combustion chambers of steam boilers, there
is, as a rule, not sufficient space at the sides of the chamber for providing the above
described side doors for the removal of the slag and ashes. In such cases therefore
I modify the construction as follows.
Instead of forming the opening at the bottom of the fuel chamber at the inner
side of the chamber, I form it at the outer side, and from such opening I form a
flue leading first vertically down along the front side of the chamber and then
horizontally along underneath the fuel chamber and into the furnace tube of the
boiler. The part of the front wall of the chamber along which the said flue
descends I form as a door or doors so that on opening this or these the whole of
the flue is exposed, and as the accumulations of slag in this case take place at the
front end of the flue, they are readily removed, together with the accumulation of
ashes through such front door or doors.
This construction is applicable not only with fuel chambers with inclined sides as
above described but also with chambers having vertical sides.
The before described small stoking holes are with this construction also formed
in the front door or doors.
The air supply is admitted from an air distributing chamber arranged on the
top of the fuel chamber and having a number of graduated openings leading into
the latter. The fuel is introduced into the combustion chamber through a suitable
hopper at top. When working with ordinary chimney draught, the top of
the fuel chamber may be left open. For the purpose of strengthening the arch
forming the top of the before described flue leading horizontally beneath the
combustion chamber, which arch also forms the bottom of the said chamber, I
provide a series of tubes extending either transversely through or beneath the
brick arch, through which tubes currents of water steam or air may be made to
pass so as to keep them from becoming overheated, such water or air being used
on the one hand to feed the boiler and on the other hand as the air supply to the
fuel chamber. Or the steam from the boiler may be passed through the tubes so
as to be superheated.
The tubes may for the above purpose be connected at their ends to boxes outside
the combustion chamber, communicating with the water or steam space of the
boiler. Or the tubes may be made to form part of the water tubes of a water
tube boiler, of which the combustion chamber constitutes the furnace.
Figs. 1 and 2 of the accompanying drawings shew respectively a longitudinal
section and cross section of one arrangement of my above described combustion
chamber. The chamber A is formed with a sloping side a leading up to the firing
door B, and the opposite side is formed with a sloping part a'.
The air supply which is supposed to be forced enters from a box C through

page_text: perforations in the top plate, and the draught after passing down through the fuel
passes first through the horizontal side flue D in a direction away from the boiler G
then down through the opening E and into the horizontal flue F formed below the
bottom a of the fuel chamber and leading to the boiler G.
The front part at H of the chamber is formed as a door, so that on opening this.
both the flue D and the flue F are accessible for clearing them of deposit. The
bottom a' is formed as an arch, as shewn at Fig. 2.
Figs. 3 and 4 shew respectively a transverse section and a plan of another
modification.
The combustion chamber A is in this case open at top, being worked by induced
draught. The sloping side a as also the bottom a² are supported by a series of
pipes II, which are connected together and with the water space of the boiler G
as shewn, so as to effect a circulation of the water through them in the direction
shewn by the arrows. The flue D, opening E and flue F are arranged in a
similar manner to that described with reference to Figs. 1 and 2; in this case, two
doors H H are provided in the front of the casing serving respectively for gaining
access to the flues D and F.
The ends of the pipes II are carried through the casing of the chamber and are
closed by plugs, so that they are free to expand and contract without straining the
combustion chamber.
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 combustion chambers of furnaces in which the air supply is made to pass
downwards through the fuel, constructing one or more sides of the fuel chamber of
an inward sloping form in the downward direction, substantially as and for the
purposes described.
2. In combustion chambers of furnaces such as are referred to in the first claim,
making the side wall in which the discharge opening for the flames and gases is
situated with a greater inclination than that of the other side wall or walls,
substantially as and for the purposes described.
3. In combustion chambers of furnaces in which the air supply is made to pass
downwards through the fuel, constructing the flue for the flames and gases leading
from the bottom of the combustion chamber to the furnace hearth or boiler, so as
first to extend horizontally outwards away from the furnace or boiler, then to bend
downwards and then to pass horizontally or with more or less inclination in the
direction towards the furnace, the outer wall of the combustion chamber facing the
bend of the flue being formed as a door or doors for gaining access to the flue for
clearing it of deposit, substantially as described.
4. In combustion chambers of furnaces operating with downward draught, such
as described in the third claim, constructing the bottom of the combustion chamber
as an arch below which is formed the horizontal flue leading to the furnace, hearth
or boiler, substantially as described with reference to Figs. 1 and 2 of the drawings.
5. In combustion chambers of furnaces operating with downward draught, such
as described in the third claim, supporting the sloping side or sides and the bottom
of the chamber by means of tubes through which water steam or air is made to
circulate, in order both to prevent the tubes from becoming overheated, and to
effect the heating of a supply of water, or air or steam, substantially as described
with reference to Figs. 3 and 4 of the drawings.
Dated this 29th day of August 1895.
ABEL & IMRAY,
Agents for the Applicant.