Improvements in Steam-boilers and in Furnaces therefor.
Year: 1893

page_text: Date of Application, 19th May, 1893-Accepted, 19th Aug., 1893
COMPLETE SPECIFICATION.
Improvements in Steam-boilers and in Furnaces therefor.
I, LOUIS SIMON DULAC, of 95 Boulevard Beaumarchais, Paris, in the Republic
of France, 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 :--
This invention is designed to provide a furnace which is so constructed as to
ensure more effectually than heretofore the gradual, complete and smokeless
combustion of the coal, whilst preserving the advantages of durability of the parts
and facility of firing.
The conditions which I have kept before me, and which are, moreover, necessary
in order to obtain this result are the following
1. High temperature of a large combustion chamber.
2. Low temperature of the parts in contact with the fire.
3. Gradual descent of the coal over an inclined plate or surface in front of the
grate.
4. Prevention of back currents of air during the charging of coal onto the
inclined surface which forms the grate.
5. Equal distribution of the fresh coal on the flat surface in front of the grate.
6. The use of a secondary layer of air which just touches the fresh coal and
assists in the burning of the hydrocarbons.
In order to fulfil these several conditions, whilst employing existing steam boilers,
it is necessary to introduce certain novel elements, and to utilize those existing
portions of the boilers which contribute to the economical and smokeless combustion
of the coal.
In order therefore, to demonstrate more clearly the arrangements of my furnace,
it is desirable to show first, with all the details of construction of the various
parts, the application of my furnace to the boiler which possesses the fewest
utilizable parts, viz.:-a horizontal boiler with one or two flue-tubes or furnace-
tubes, and afterwards to show the arrangements which should be made to adapt my
furnace either to a water-tube boiler or to a locomotive boiler.
The accompanying drawings illustrate these various applications.
Figure 1 is a section of my furnace applied to a horizontal boiler with two flue-
tubes or furnace-tubes.
Figure 2 is a longitudinal section, and
Figure 3 a transverse section, showing in detail the frame-work of the grate,
and one of the side-pieces or collectors.
Figure 4 shows a protecting piece or guard.
Figure 5 is an underside view of the terminal bracket of a fire-bar.
Figures 6, 7 and 8 show details of the fire-bars.
Figures 9, 10 and 11 are plans and sections showing steel plates provided with
recesses, serving to connect the terminal brackets of the fire-bars to the side-pieces
or collectors.
Figure 12 shows the application of my furnace to a water-tube boiler.
Figure 13 shows the application of my furnace to a locomotive boiler.
Figure 13 is a longitudinal central section, showing my improved fire-bar as
applied to a locomotive boiler.
Figure 14 shows details of the pieces of refractory material used in the said
furnace for filling the spaces between the tubes 19 forming the screen.
In the first example which I have chosen, the application of my furnace to a
horizontal boiler with one or two flue-tubes or furnace-tubes, the combustion
chamber is small and the walls which are in contact with the water absorb the
•

page_text: heat, this is evidently the most unfavourable case. My furnace has, in this case,
to be provided with all the necessary parts to produce the desired result, so that
it is the entire apparatus which I am about to describe. It is composed of a large
combustion chamber A made of sheet-iron and angle-iron, provided on the inside
with a lining of fire-brick; around this chamber circulates the air for supporting
combustion. As far as is possible, the walls of this chamber are of a curved form;
on the lower portions, close to the fire-bars, which portions are necessarily flattened,
I arrange sheet-iron compensators a which yield immediately under the force due
to expansion, so as to preserve uninjured these flat or slightly curved surfaces.
The front of the combustion chamber is bolted to a casting B to which are
attached the mouth C of the furnace and the rocking feeder D hereinafter
described. The products of combustion rise in the chamber A and pass by one or
more orifices, formed for the purpose, into the flue or flues E of the boiler."
The lower part of the chamber A consists of a very much inclined grate F, and
a series of cast plates G designed to receive the fresh coal. The grate consists of
a variable number of stepped fire-bars ƒ of convenient length. Each fire-bar is
composed of a thin plate having an inclined extension f which is of heavier
section, in contact with the fire, in the centre of the fire-bar is a central tube g
which may be of iron or steel secured in the fire-bars in the casting thereof
(Figure 6); the projecting ends of these tubes (Figure 7) are secured in steel
junction-boxes H, which are provided, in a prolongation of the axis of the tube,
with an orifice for cleaning, and above with a discharging orifice J. Each
junction-box H is provided, perpendicularly to the axis of the tube, with two
brackets h and (Figure 2), having holes and serving to support the tube with the
aid of suitable bolts. The cleaning orifice I is in the form of a truncated cone,
and is closed by a metal washer i in the centre, through which passes the stem of a
bolt, the head of which compresses an elastic washer in the orifice. The
tightening nut rests on an external washer ', threaded upon the bolt; by
operating this nut k, the elastic washer which is placed between the internal
conical washer and the head of the bolt, may be more or less compressed, see
Figure 3.
The fire-bars are secured to the lower surfaces of two square or rectangular
side-pieces or collectors L made of iron, which are placed one on each side of the
grate for this purpose, the said collectors are provided with equidistant holes,
see Figure 2, of the same diameter as the discharge orifices J of the junction-
boxes H. Between these holes formed in the collectors, are rivetted steel plates /
in which are formed recesses M, M', m, m', Fig. 10; two of these recesses M, M
which are of trapezoidal form, are arranged to follow the axis of the collector, and
receive a nut N which completely fills the recess. The other two recesses m, m²
which are arranged in a line at right angles to the first, receive the heads of the
bolts O of a protecting cap or guard o the function of which will be hereinafter
described.
P
Between the end of junction-boxes H of the fire-bars and the lower surfaces of
the side-bars or collectors L, is formed a plastic joint P, see Figure 2, through
which passes a steel tube p, the portion p' of which is bevelled and enters the side-
bar or collector; the exterior of this joint P is protected by a hollow metal ring Q
which is compressible and resisting and which limits the expansion of the plastic
material externally in the same manner that the tube p limits the expansion inside
the joint. In order to attach a fire-bar to the side-bar or collector, the tube is
inserted into the said side-bar, and a bolt r, provided with a powerful spring r, is
passed through the hole in the bracket h or h¹ and screwed into the nut N which
is held in the corresponding recess M of the plate rivetted to the side-bar or
collector. On tightening up both sides, the four springs and the two joints Pare
compressed; then, when the grate is in position, the heads of the bolts are
placed in the side recesses m, m', and on the stems of these bolts, are threaded the
safety-caps o, the central portion of which bears simultaneously on the edges of
the brackets h, h¹ of adjacent fire-bars; the lower nuts S are then tightened and

page_text: in the event of either of the bolts O or breaking, such breakage will not cause
any accident.
This method of construction gives the necessary elasticity to compensate for
expansion and for the relative motion caused by the action of the firing tools on
the fire-bars when the fire is being cleaned.
The clinkers pass into the lower portion of the furnace and, by reason of the
high temperature in the centre, they remain in a plastic or pasty condition which
renders their removal difficult if they unite themselves to the walls. In order to
obviate this disadvantage I close the back of the grate by means of a metal
cylinder T, forming a fire-bridge, which rests on the top of the lower portion of
the side-bars L. The ends of this cylinder project into the air-chamber and are
closed by tubular end-pieces bolted to suitable flanges.
The space allotted to the fuel and cinders, between the lower self-cleaning fire-
bar, which is not provided with an inclined plate f", and the surface of the
cylinder, is of a shape favorable to the discharge of these cinders, this space
gradually increasing towards the ash-pit. By coming into contact with the
bridge T the side-bars L, and the lower self-cleaning fire-bar, which are all
traversed inside by a stream of water, the clinkers set and solidify, thus considerably
facilitating the cleaning of the fires.
The upper fire-bar of the grate serves to support a series of solid flat castings G
placed close together, the upper portion of these plates being provided with a
hook U which engages with an iron cross-bar U₁ supported by two screws Un
whereby the height of the said bar may be varied. This arrangement permits the
adjustment of the upper portions of the plates G towards or away from the lower
edge of the door, which they cover; in this manner an additional or secondary air-
supply may be provided preferably from the heated air-space surrounding the
metallic casing of the furnace, as shown, which secondary air-supply can thus be
controlled at will, and mixes with the gases that slowly distil from the unburnt
coal on the plates in front of the grate, and, combining with the said gases causes
their combustion.
The fire-door C is cast in one piece, the curved sides thereof being so made that
they resist the variations in temperature without fracture. The width of the
opening of the fire door is equal to the whole width of the grate; in the event of
this width being too great, several fire-doors are employed which are separated by
a hollow pillar, the upper end whereof serves as a spring for the brick arches that
protect the cast front plate. Through this pillar descends the air-supply. The
lower part e (Figure 12) of the fire-door extends into the furnace and covers the
upper part of the closed plates or "dead-plates." The charger or feeder D, which
turns on two horizontal trunnions d extends into the interior of the fire-door in
such a manner that when turned back, the prolongation thereof (Figure 12) is of
sufficient height to close the orifice of the fire-door and prevent the entrance of air.
By reason of this prolongation, the charger or feeder D is balanced on its trunnions
and can be easily manipulated. The movement of the charger or feeder is limited
by a chain d' which can be unhooked when it is desired to turn down the charger
or feeder and leave the orifice of the fire-door entirely free. The whole mass of
ignited fuel can thus be removed when it is desired to draw the fires.
The bridge T is attached to the bearers or side-bars by a series of cast iron
plates V, hooked at their upper end to a sheet iron casing v which surmounts the
bridge, and the lower portion of which rests on a cast iron seating v² separating
the ash-pit from the air-chamber. This cast-iron seating supports the lower
portion of the side-bars L.
The liquid employed for cooling the parts in contact with the fire is drawn from
the boiler at that part where the ebullition is least active, the supply pipe 1 extends
to the cover which closes one end of the bridge T. Another pipe (which is not
visible in Figure 1) conducts the water from the opposite lower end of the bridge
to one of the side-bars or collectors L; the liquid reascends in this side-bar and
enters all the fire-bars and passes thence into the opposite side-bar whence it

page_text: re-enters that portion of the boiler where the ebullition is most active through a
suitable pipe (not shown in Figure 1). In order to release any steam which may
accumulate either in the upper part of the bridge or in the upper part of the first
side-bar, the pipes 2 of small diameter, which I term escape-pipes, connect these
points with that portion of the system where the liquid has the least density.
Finally a pipe, which I term a blow-off pipe and which is closed by a cock, is
attached to the lower part of the second side-bar for removing any solid matter
that may be deposited therein.
A large ash-pit 4 is provided under the grate. The air necessary for combustion,
after having passed around the metallic casing of the furnace passes laterally into
the ash-pit on both sides. The door 5 placed below the fire-door, is only opened
when the fire is to be cleaned; a trap-door 3 situated in the front plate of the
furnace permits the removal of the clinkers, and ashes accumulated in the ash-pit,
by means of a concave rake. Ports 31 provided in the upper part of the fire-door
facilitate the examination of the fire.
The above is the arrangement of my furnace, which may be applied to boilers of
various kinds. This arrangement may be somewhat modified where it is desired to
utilize the existing fittings of the boiler, without interfering with the result
obtained.
As an example of these modifications I will now describe the application of my
furnace to a water-tube boiler, as illustrated in Figure 12. In this case, the
vertical collectors 6 which counect the water-tubes 7, 7, form a screen which
protects the fireman against the radiation from the fire, and a portion of the metallic
casing of the combustion-chamber can therefore be dispensed with, the portion
above the bridge 8 alone being thus closed in, the brickwork being supported
laterally by castings 8' which separate the side-bars from the brick-work; for this
purpose an angle-iron of large section may be used for uniting it to the sheet-
metal casing which surmounts the bridge. It is then only necessary to provide an
opening 9 in the front plate of the furnace of sufficient size to receive the fire-door
and the charger or feeder. Air enters the ash-pit by the door 10 in front and the
trap-door 11 permits the emptying of the ash-pit. The other parts of the furnace
are constructed substantially as above described and are lettered similarly to those
in Figure 1.
Another example is given in the locomotive boiler shown in Figures 13, 13
and 14.
The furnace of this boiler operates by forced draught and notwithstanding the
water-jacketted walls of the fire-box the volume of gas generated is such that the
temperature at the centre is sufficient for perfect combustion. Further, the side-
bars are not required and are replaced by an iron frame or ring 12 which serves to
connect the fire-box 13 to the outer shell 14. As the omission of the side-bars
prevents the provision for the circulation of the water as above described, I obtain
a downward circulation by forming a small orifice 13 in one side of the iron frame
or ring, and an upward circulation by perforating the opposite side of the said
frame or ring with a large orifice 14', as shown in Figure 13. Since the fire-
box 13 is entirely surrounded by water, which prevents the adhesion of clinkers,
the bridge above described is unnecessary, and the ash-pit is advantageously
replaced by a pivoted grating 15 called a "jette-feu which has been in use for
some time on locomotives. The high temperature of the gases would act injuriously
on the tube-plates 16 near the furnace end of the tubes 17. It is therefore necessary
to protect these tubes against the radiant heat. This is effected by means of a
screen 18 partially permeable by the gases. This screen is formed of water-
tubes 19 fixed to the side walls 13 of the fire-box. These tubes project into the
water-space; the projection 20, which is cut on the bevel, is made on the upper
edges of the tubes on the side where the water enters and on the diametrically
opposite edges on the side where the water leaves the tubes. Pieces of fire-clay 21
arranged as shown more clearly in Figure 14, are provided in the spaces between
the tubes 19 and allow only a small volume of gas to pass between them. A series
:

page_text: of pieces 22 of fire-brick or other refractory material of triangular form, is arranged
between the water-space below the tubes and the adjacent tube 19 in such a manner as
to complete the screen. The body of gas which cannot pass through the screen, goes
around the same, meanwhile becoming intimately mixed, and then enters the tubes 17.
The opening of the fire-door is of the same width as the fire-box in order that the
lower and side walls may be continued to the raised edge of the external shell, to
which they are securely rivetted. The frame which carries the charger or feeder
extends into the fire-box and protects the framing against radiation from the
furnace and against back currents of air.
The secondary or auxiliary air supply enters the furnace by the aperture 23
which is provided with a cover plate 24 thus permitting regulation of the amount
of air admitted, the dead-plates in front of the furnace being hooked to the cross-
bar 25.
The space below the fire-bars is accessible by means of the curved door 26 which
closes the space below the front end of the fire-box, the lower portion of the
said door resting on the floor 27 of the fireman's cab.
From the above description it follows that my furnace is provided with all the
factors necessary to secure gradual combustion, without the production of smoke,
whilst obtaining the maximum duty from the coal; in some cases, moreover,
certain elements of my furnace may be replaced by certain arrangements already
existing in the boilers without prejudicing the results obtained.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is ;-
First. In a furnace for the gradual, complete and smokeless combustion of coal,
a grate, the steps or stepped bars of which are provided with central tubes com-
municating at their extremities with two side-bars or collectors by means of junction-
boxes, the connection between the boxes and the side-bars or collectors being made
by means of a plastic joint protected against injury by an external compressible
metal band and by a central tube, the connections between the several steps or
stepped bars being made by means of elastic couplings consisting of strong springs
mounted concentrically on tightening screws and bearing on the terminal brackets
of each stepped bar, the fastening being completed by a safety-cap bearing on
two adjacent stepped bars simultaneously, the system comprising the central tubes
and the two side-bars or collectors being traversed by a stream of water from the
fire-bridge.
Second. In a furnace for the gradual, complete and smokeless combustion of coal,
the combination with the grate above described, of inclined flat plates or "dead-
plates" placed close together, and prolonging the upper end of the grate, for the
purpose of preparing the unburnt coal at its entrance to the said grate, these plates
being terminated at their upper portions by hooks which engage with a cross-bar
supported on two screws whereby the height of the said plates may be varied in
such a manner as to regulate the volume of the secondary or auxiliary air-supply
which mixes with the gases in the furnace.
Third. In a furnace for the gradual, complete and smokeless combustion of coal,
the combination with the grate and the "dead-plates" above described, of a fire-
bridge consisting of a hollow metal cylinder which rests on the lower portions of the
side-bars or collectors, and which is traversed by a stream of water proceeding from
the boiler at the part thereof where the ebullition is the least active, the said fire-
bridge being secured upon the side-bars or collectors by a series of cast-iron plates,
whose upper portions are hooked to a sheet-metal casing surmounting the fire
bridge, and whose lower portions rest on a seating which also supports the side-bars
or collectors.
Fourth. In a furnace for the gradual, complete and smokeless combustion of coal,
the combination with the grate, the preparing or "dead-plates" and the fire-bridge
above described, of a charger or feeder of the same width as the grate, and turning

page_text: on two horizontal trunnions, the said charger or feeder extending into, the interior
of the fire-door opening, in such a manner that, when the said charger or feeder is
turned back, the prolongation thereof will be of sufficient height to close the fire-
door opening and check any back currents of air.
Fifth. In a furnace for the gradual, complete and smokeless combustion o" coal,
the combination with the grate, the preparing or "dead-plates," the fire-bridge and
the charger or feeder above described, of a sheet and angle-iron combustion
chamber lined inside with fire-brick and around which circulates the air for
supporting combustion, the walls of the said chamber being, as far as practicable,
of a curved form, and the flattened portions which connect this chamber to the
grate being provided with sheet metal compensators designed to prevent the
distortion of the said flattened portions.
Sixth. In a furnace for the gradual, complete and smokeless combustion of coal,
the combination with the parts or elements above described, of a circulation of
liquid maintained in such a manner that the water taken from the boiler at the point
where the ebullition is the least active passes through the fire-bridge and thence
through one of the side-bars or collectors, and returns by the other side-bar or
collector, after having passed through all the central tubes of the stepped fire-
bars, and afterward ascends by a pipe to that part of the boiler where the ebullition
is the most active, the steam which may accumulate in the various parts of the
system traversed by the water, being returned to that portion of the boiler where
the liquid has the least density, and the system being completed by a blow-off cock,
situated at the lower end of the second side-bar or collector, for the purpose of
removing any solid matter which may be deposited therein.
Seventh. In a furnace for the gradual, complete and smokeless combustion of
coal, the combination of the parts above described and a large ash-pit or ash-box
communicating with the combustion-chamber by a separate orifice between the last
stepped fire-bar of the grate and the fire-bridge, the same being so formed as to
facilitate the discharge of the ashes, which may be removed by means of an orifice
provided for the purpose below the fire-door.
Eighth. The application to all boilers, of the improved furnace for the gradual,
complete and smokeless combustion of coal, comprising the parts above specified,
portions of which may be modified, omitted or replaced by parts of the particular
boiler under conversion in order to obtain the same result.
Ninth. In the application of my furnace to locomotive boilers, the substitution of
a grating called a "jette-feu" for the ash-box, the omission of the side-bars or
collectors for carrying the stepped fire-bars which are replaced by the shell
enclosing the water-space of the boiler, the circulation of the liquid in the fire-bars
being provided for by means of orifices of different cross-sectional area formed in
the frame or ring at the bottom of the said water-space, the combination of the
stepped fire-bars of the grate with the said frame or ring of the fire-box, and with a
frame provided with a rocking charger or feeder, these two parts closing the wide
orifice formed in the front of the fire-box, the omission of the fire-bridge, the use of
a screen for the purpose of protecting the tubes next the furnace, the said screen
consisting of water-tubes fixed in the lateral walls of the fire-box, the said water-
tubes having their ends cut off in a plane oblique to their axis, in such a manner as
to control the circulation of water therein, and perforated pieces of fire-brick
arranged in the spaces between the tubes.
Tenth. In the application of my furnace to water-tube boilers, the omission of
the metal casing enclosing the combustion chamber, this casing being only provided
below the fire-bridge; the brickwork being supported by castings or angle-irons
which separate the side-bars or collectors from the brickwork.
May 1893.
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.
Dated the 19th day of May 1893.
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.