Improvements in Furnaces for Burning Coal Dust.
Year: 1894

page_text: Date of Application, 6th Sept., 1894-Accepted, 1st Dec., 1894
COMPLETE SPECIFICATION.
Improvements in Furnaces for Burning Coal Dust.
I, CARL WEGENER of No. 14 Gitschiner Strasse, Berlin, Kingdom of Prussia,
German Empire, 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 :-
The improved furnace for burning coal dust, which will be hereinafter explained,
belongs to that class of furnaces in which the air forced into the combustion
chamber by means of a suitable blowing apparatus, or by means of the natural
draught of the chimney, is charged on its way to the combustion chamber with the
fuel or material which is to be burnt.
The main feature of the invention consists in that the feeding of the dust into
the current of air, as shown by the diagram Figure 1, of the accompanying
drawings, takes place whilst the current of air is moving in a vertical direction,
whether it be rising or descending. The dust falls from the feeding apparatus
arranged underneath the storage hopper through a vertical feed pipe b arranged in
the centre of the air passage a, onto a distributing device c also placed centrally
underneath the mouth of this pipe, this distributing device being for instance a
cone or conoid with an upwardly directed point, or another suitably shaped diverting
surface arranged so as to direct the dust outwards, and the latter slides off this
surface through an annular space between the distributing body c and the wall of
the air passage a towards the latter, so that it is taken up in a state of even
distribution by the air passing through the annular space and carried forward with
this air. In order to prevent the speed of the air current being reduced by the
formation of a vortex, a second downwardly directed diverting surface co is
preferably attached to the under side of the diverting surface_c. The movement
of the dust along the distributing or diverting body c may be accelerated, and
ensured, by imparting to this body a rotary motion on its central axis. It 18
preferable to utilise the current of air set in motion by the blast apparatus or by
the draught of the chimney for producing this rotary movement by means of a fan
wheel d (Figures 2 and 3).
Figure 2 shows as an example a form of construction of this improved arrange-
ment, the air current in this case being directed upwards. The admission of the
air, drawn in by the chimney, through the openings of the air pipe a may be
buitably regulated by means of revolving slides or dampers e, or in any other
suitable manner. The air in its course through the pipe a first sets the fan wheel d
in rotation, the spindle of which carries the double conoid c cº, and, on an upper
extension, the feeding device y, it then becomes charged at the level of the
distributing body cc with the fuel, and is carried away at the sides above the
lower opening of the feed pipe b.
In the example shown, the air passage a branches into two pipes a¹ a³, each of
which opens into one of the flues, (which are closed by means of a cover plate i),
of a Cornish boiler k in which the combustion chambers are arranged.
Figure 3 shows a coal dust burning apparatus of the kind hereinbefore described
with the current of air directed downwards. The air drawn in by the draught of
the chimney obtains access, through the openings e" which may be regulated by
means of slides, valves or flaps e, to the annular space formed by the feed pipe b
within the pipe a, and passes the annular fan wheel d, the inner rim do of which
forms a rotating continuation of the feed pipe b. The spindle on which the fan
wheel d is fastened by the spokes d' and the nave d² (the spokes being preferably
formed of sheet metal) has at the top a rotary feeding device g and below it

page_text: cone c,
the double cone c cº. In order to cause the air to encounter the particles of dust
sliding down from off the cone as far as possible in a direction vertical to their way,
the wall of the tube a is tapered inwards and downwards at the level of the counter
cone c and has further a conical casing fastened in the tube a parallel to the
which casing diverts the air, which has passed through the fan wheel d
against the tapering lower parts of the wall of the tube a, so that it assumes the
direction of the same. Small perforations or openings h° are preferably made in
the casing h, which openings allow a portion of the air to pass inwards in proximity
to the double cone c cº. The air charged with the fuel reaches the combustion
chamber Z through the lower opening of the tube a.
The inlet end of the air pipe a may, in both the forms of construction, be also
connected to an air pipe, if it be desired that the current of air for the combustion
shall be produced by means of a blowing apparatus instead of by the natural
draught of the furnace.
Figures 4 to 7 show a further developed form of a coal dust burning furnace of
the kind of which an example has already been shown in Figure 2.
This is characterised by two improvements, one of which consists of an arrange-
ment for imparting to the air current, which conveys the coal dust to the combustion
chamber, a rotary motion on its axis in addition to the forward one, that is to say,
a spiral movement, such movement being advantageous for maintaining the even
distribution of the dust in the current of air. If the movement of the particles of
air has already been changed into a spiral one before they have become charged
with the coal dust, on their passage over the distributing body, the thorough
admixture of the latter with the air is thereby facilitated, and more particularly
if the direction of rotation of the rotary distributing body is opposite to that of the
current of air. The rotation of the straight-flowing air current is produced by
means of spiral surfaces which project from the wall of the air pipe, and are
preferably not united in the middle but leave an inner space.
The other improvement allows the device for regulating the quantity of air,
which is to be mixed with the dust, to be placed in the exit opening of the air pipe.
This regulation is produced by a gradual diminution of the size of the openings.
For this object rings, in the form of a truncated cone, are arranged one behind
the other within the air pipe, and co-axial with the same, which rings only slightly
diminish the section of the air pipe. These rings may be serially adjusted in the
exit opening and are of such dimensions that the latter is gradually diminished
in size.
Figure 4 shows such a dust consuming furnace partially in vertical section,
partially in elevation.
and
Figures 5 and 6 are horizontal sections through the vertical part of the air pipe,
Figure 7 is a horizontal section through the exit opening.
The spiral surfaces s are arranged in three groups, the first of which s¹ is placed
in front of the distributing or diverting body c, the second behind the same, and
the third in front of the opening into the combustion chamber of the air pipe a.
The diminution of the exit opening, Figures 4 and 7, is, in the example shown in
the drawing, assumed to be from the outside inwards. The mouth of the air pipe a,
which is surrounded with a chamber having one or more inlet nozzles (Figure 4)
serving for supplying additional air into the combustion chamber, is for this purpose
provided with a fixed conical extension 70. Against this latter the tapering ring r
may be adjusted, which in turn may serve as a support for the second ring. The
first ring is fastened with its spokes on a tube u¹ which is guided within the
air tube, in the cross bar v', and which passes through a socket w¹ on the bend of
the air pipe. A knob a¹ on the end of the tube u¹ serves as a handle for adjusting
the ring. The second ring is attached by its spokes to a rod u³ passing
through the tube u', and the outer end of which rod, projecting from this tube, ends
again in a knob x². By pushing in the knob a', both rings are moved towards the
nozzle-shaped projection until the ring r' rests against the same.
The pushing

page_text: in of the knob then brings also the second ring into the position shown in
dotted lines, in which it forms a continuation of the first.
Figures 8 and 9 show front and side views, with some of the parts in vertical
section, of a form of construction of the invention in case the furnace is to be
operated sometimes with natural draught and sometimes with forced draught, as
in the case of marine boilers for instance. The device for regulating the quantity
of air which is to be drawn in for the combustion by the chimney, is here again
placed on the inlet opening of the air pipe a, and also serves for entirely shutting
off this inlet of air when the forced draught is to be used. The air pipe a, which
rests on the feet 45, stands a suitable distance away from the bottom plate 46 and
has an adjustable casing 47, the lower edge of which extends over the air pipe and
is curved round to the outside, so that an annular receiving opening is formed,
The central blast pipe 48,
which, by its shape, favours a noiseless inflow of the air.
which opens in the bottom plate 46, is preferably closed by a cover 49 of such a
form that the air flowing radially inwards may as far as possible unite to a compact
axial current. The lowering of the casing 47 reduces the section of the annular
inlet for the air drawn in by the draught of the chimney. This movement is
brought about by means of a lever 50 which is mounted in a fork 44 attached to
the air pipe a and has a forked part half embracing the air pipe, the outer ends of
which forked part have slots which engage the pins 43 fixed at diametrically
opposite points on the cylindrical sliding casing 47, so that this casing, on the
hand lever being operated, is moved upwards or downwards. If the blast pipe 48
is to be used, the cover 49 is removed and the casing 47 is let down to the bottom
plate 46.
The lower end 69 of the feed hopper 68 is formed as a hollow cylindrical valve
in the socket 70 into which the upper end of the tube 6 opens. The hopper is
arranged above the rotating feeding device, which is mounted on the upper end of
the spindle within the tube b, and is maintained in an erect position (in which its
lower opening 72 coincides with the opening of the tube b) by means of a weighted
lever 71 bearing against the socket 70. If the hopper 68 is to be refilled, it is
As it is then disconnected from
turned to the right until its opening 72 is closed.
the tube b containing the feeding device, the renewal of the supply in the hopper
cannot impede the regular action of this feeding device.
In order to again re-establish the uniform suspension of the particles of dust, so
far as this suspension may have been lost, on the entrance of the mixture of air
and dust into the combustion chamber a fixed spiral fan wheel 30 is arranged in
the exit opening of the air pipe a, which fan wheel imparts a whirling motion to the
mixture passing through it.
A device which may be substituted for the fixed spiral fan wheel 30 is shown in
Figures 10 and 11, corresponding to the Figures 8 and 9, which device serves the
same purpose but even more effectively, because it produces within the whole
current a number of smaller vortices travelling side by side. Diverting plates 64
are arranged alternately in opposite directions in the exit opening of the air pipe a
in such a way that they are equally distributed over the whole section of the air
passage. These diverting plates may be held in position in any suitable manner,
for instance, by arranging them on parallel bars 65, which, as shown in Figure 10,
are preferably pivoted in the wall of the air pipe so as to be turned on their
longitudinal axes, and adjusted to any suitable position like louvre boards by means
of lever arms 66 and a draw bar 67 connecting these. The draw bar 67 may be
arranged so as to be directly operated by hand, the links of a chain attached thereto
allowing of its being fixed in any desired position.
A device for regulating the quantity of air passing through the air pipe a, which
device may replace with advantage the one shown in Figure 2, is shown in vertical
A second fau wheel
section in Figure 12, and in horizontal section in Figure 13.
is arranged immovably under the rotary fan wheel d, the vanes 52 of this second fan
wheel being made revoluble in the nave and the rim, and having on the outer ends
eccentric pins 53, which are passed through holes (slots) in the wall of the air pipe a

page_text: and are attached outside to a common ring 54 which is provided with handles 55.
The slots in the wall of the air pipe are of such a form and in such a position
that a rotation of the ring causes a rotation of the fan vanes on their axes so that
the opening between two adjacent vanes may be diminished or increased in order
to regulate the section of the passage. The vanes 52 have an opposite direction to
the vanes of the rotary fan d, so that their surfaces serve as directing surfaces
for the air which operates the wheel d.
Figures 14 and 15 show a vertical section and plan view respectively of the
feeding device g mounted on the upper end of the spindle f, which feeding device is
formed of a disc fitted with cutters or knives. This knife disc is firmly connected
with a ring 9 which prevents the particles of dust passing to the outside over the
edge of the disc, which latter consists preferably of a flat or somewhat concave
sheet metal disc, the separate knives 29 of which may be of any suitable form.
The knives are preferably formed out of the sheet metal disc itself, by this disc
having suitable pieces partly cut out in the desired form, and then bent up. These
knives, which may be of triangular, curved or other suitable form, project upwards
out of the disc, as may be seen in the two partial sections shown in Figure 15.
In place of the rotary knife disc g, feeding devices for coal dust are also, as is
well known, employed in the form of a disc-shaped sieve, or grate, oscillating on
its axis.
Figure 16 shows a vertical section, and
Figure 17, a plan of a device for converting the rotation of the spindle finto the
oscillating movement of such sieve, without necessitating a perforation of the wall
of the tube b, a suitable tight joint being with difficulty obtained at such
perforation.
Figure 18 shows a side view of the devices belonging thereto for regulating the
speed and the extent of the movement of the sieve. The spindle f is provided at
its upper end with a disc 4 with two catch pins 5 which act on a double lever 6-7
arranged within the pipe b. The fork-shaped end 7 of this double lever embraces
a pin 8 which extends downwards from a frame 9 firmly screwed to the sieve 3, so
that the turning of the lever 6-7 produced by the pins 5 causes a movement of
the sieve 3. In order to turn the lever back again, a spring 12 is employed which
acts on the double lever and is adjustable from the outside by means of the screw 10
and the nuts 11. This return movement is limited by the stop 13, the position of
which may be adjusted from the outside, according to a scale and a pointer 16, by
means of the screw 14 and the nuts 15. By the adjustment of the spring 12, the
return movement of the sieve may be made more or less violent according to the
more or less lumpy condition of the dust which is to be disintegrated and supplied
to the current of air. By the adjustment of the stop 13, the extent of the
movement, and thus the quantity of the dust passed through the sieve, may be
regulated.
The circular sieve which oscillates on its axis may be replaced by one moving to
and fro in a straight line. The device for transforming the rotary movement into
a movement to and fro, as well as the regulating devices, may remain the same.
A further device for disintegrating the coal dust and causing it to descend by
gravity, which may be employed to replace the one just described, as well as the
knife disc g, is shown in Figures 19 and 20 in vertical section and plan view
respectively. The chamber filled with dust beneath the supply hopper consists in
the cylinder 17 provided at the bottom with the annalar disc or flat ring 18 and
within with the cone 19. Between the cone 19 and the ring 18 there is an annular
interstice through which scoops or paddles 20 project from the inside to the outside.
These rest on a disc 21 carried by the rotating central spindle f and move, on their
rotation with this spindle, close over the ring 18, so that, by the cam-shaped form
of their edges, they force the dust, which has descended on to the ring 18, towards
the inner edge of this ring, from whence it falls into the passage b. In order to be
able to regulate the quantity of the dust scooped down, a novel arrangement for the
radial adjustment of the scoops or paddles is employed. These are mounted loosely

page_text: on converging guide bars 23, firmly connected to a sleeve 22, which is adjustable
on the spindle but does not revolve with it, each of these guide bars extending
through a radial slot 24 in the disc 21. If the sleeve 22 be raised or lowered by
means of the double lever 25-26, which may be attached to the guide piece 27, the
paddles 20, which rest on the disc 21, are separated or pushed together.
The arrangement of a furnace to be placed in front of the boiler F (hereinafter
called a front furnace) shown in two vertical sections in Figures 21 and 22, forms
the completion of the apparatus shown in Figure 3 which has its air supply from
above. Whilst in Figure 3 it was assumed that the air pipe a opened immediately
into the upper opening of the vertical combustion chamber Z, it is here supposed to
be attached to the cover D of the body of the front furnace. The air for the
combustion in this arrangement only partially passes over the distributing
apparatus e shown in Figure 3, and then, together with the coal dust, through the
opening of the lid D. Another part mingles with this current beneath the cover D
and before it enters into the combustion chamber Z. This second part of the air
for the combustion undergoes a considerable preliminary heating, as, on its course
to the inlet opening, it flows through a chamber between the firebrick chamber in
which the combustion takes place, and an outer casing, the further object of which is to
diminish the loss of heat which takes place through the radiation of the heated fireclay
body, and to avoid some other drawbacks connected with the high temperature of this
latter. The fireclay chamber Z, the horizontal part 2 of which is supposed to open
into the fire flue F of a steam boiler, is connected with the sheet metal casing A in
such a way that two separate chambers B and C are formed, the first of which
surrounds the vertical part 2 of the chamber Z, and the latter the horizontal part z¹.
The annular space B is closed above by the cover plate D placed on the casing A,
through the central opening of which plate the mixture of fuel and air flows down-
wards. The second part of the air, the quantity of which may be regulated by
means of slides b', passes through the openings 60 into the lower part of the annular
space B, and leaves the latter through the annular opening between the upper edge
of the vertical part of the fireclay chamber Z and the cover D in order to
descend into the combustion chamber together with the mixture of air and dust
which descends through the opening in the cover. The chamber or space C is fed
with air through openings g, which may also be regulated by means of slides or
dampers q', and the air quits the same through the annular interstice which
is left between the mouth of the horizontal part and the entrance of the fire flue F
by the mouth of the casing A, resting against the front of the boiler, being carried
somewhat beyond the mouth of the horizontal part ¹. This third part of the air
then becomes mixed with the current of the fire gases on the latter passing out of
the fireclay chamber into the fire flue and completes the combustion of the same.
The vertical part of the fireclay chamber is, as shown in the drawing,
preferably formed of separate sections, to which a great firmness may be given by
means of rings.
If a blast apparatus be employed for conveying the fuel through the opening of
the cover plate D, it may be necessary to connect the air inlet openings 6° 9° with
the blast pipe. If two boilers or furnaces placed side by side are to be heated with
one apparatus, the body of the front furnace has two horizontal parts in which the
fire gases branch.
If the combustion is not to take place in a separate front furnace, the front part
of the fire flue may be arranged as shown in Figure 23 in longitudinal section, and
in Figure 24 in a front view.
Figure 23 shows the fire tube or flue F coated with a lining 56 of refractory
material, and closed in front by a cover plate through which the pipe a for
conveying the mixture of air and coal dust opens into the flue. The upper part of
the lining 56 stands a little away from the wall of the fire tube or flue, and has
perforations or openings 58 through which the fire gases may directly impinge on
the wall of the flue. In this manner, a boiler surface in contact with the fire is
already formed in the front part of the fire tube or flue without its being necessary

page_text: to dispense with the refractory lining which is important for furnaces fired with coal
dust.
In order to supply previously heated air to the mixture of air and coal dust on
its entrance into the combustion chamber, the expanding mouth of the passage a,
which supplies the mixture of air and dust, is surrounded with a cylindrical casing 60
so that an annular nozzle is formed. This annular passage may be shut off from
the outer air where it passes through the cover plate by means of a register 61
which also serves for regulating the quantity of air. A conical mouthpiece 62
facilitates the access of the air to the valve or slide 61. If the annular space
surrounded by the mouthpiece 62 be closed by means of an annular front plate, and
the pipe sorket 63 be connected with an air pipe, a blowing apparatus may be used
for supplying air instead of the draught of the chimney.
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:
-
1. In a coal dust burning furnace, the arrangement, for mixing the coal dust with
air and for conveying the mixture into the combustion chamber by the draught of the
chimney or by forced draught, consisting in the combination of air pipe a, coal dust
supply-pipe and distributing device placed before the discharge end of the coal
dust supply-pipe, substantially as and for the purpose described.
2. In a coal dust burning furnace of the kind as claimed in the first claiming
clause, the arrangement of imparting to the distributing device a rotary movement
on its central axis, substantially as and for the purpose described.
3. In a coal dust burning furnace of the kind as claimed in the preceding
claiming clauses, an arrangement for obtaining the rotation of the distributing
device, consisting in a fan wheel mounted on the same spindle as the distributing
cone and disposed according to the direction of the current of air either above or
beneath the distributing cone, substantially as and for the purpose described.
4. In a coal dust burning furnace of the kind as claimed in the first claiming
clause, the arrangement, in the air pipe, before the distributing device or behind
the same, or before and behind the same, of internal spiral surfaces or ridges (s', s
and 3) which leave a central core free, and impart to the current of air, or the
mixture of air and dust, a whirling motion, substantially as described with reference
to Figures 4, 5 and 6 of the drawings.
5. In a coal dust burning furnace, conical shaped rings of gradually diminishing
diameter arranged within the air pipe at the opening of the same into the com-
bustion chamber and adjustable in the direction of the axis of the air pipe,
substantially as described with reference to Figure 7 of the drawings.
6. In a coal dust burning furnace alternately operated by forced and natural
draught, a device for regulating and shutting off the supply of air, consisting of a
cylindrical slide 47 surrounding the air pipe a and which, by means of an outwardly
bent edge, works against a flat surface 46, whilst the central blast pipe 48 opening
towards the air pipe may be closed by means of a cover tapering in the direction of
the inflowing air, substantially as described with reference to Figures 8 and 9
of the drawings.
7. In a coal dust burning furnace, a feed hopper 68 for the coal dust, which
hopper has a hinged connection with the supply pipe b, the mouth end 69 resting
as a hollow cylindrical valve in a socket 70 at the upper end of the feed pipe,
substantially as described with reference to Figures 8 and 9 of the drawings.
8. In a coal dust burning furnace, the arrangement of fixed spiral vanes 30 or a
series of diverting plates 64 in the passage a conveying the mixture of air and coal
dust into the combustion chamber, substantially as described with reference to
Figures 8, 9, 10 and 11 of the drawings.
9. In a coal dust burning furnace, the arrangement of an immovable fan wheel 52
in the air passage beneath the fan wheel d, the vanes of which fan wheel 52 may be
adjusted like louvre boards and form, by reason of their direction, a directing wheel

page_text: '
which guides the air to the driving wheel d, substantially as described with reference
to Figures 12 and 13 of the drawings.
10. In a coal dust burning furnace, a knife disc g mounted on a vertical spindle f
in the upper end of the feed pipe, the knives 29 of which disc may be formed by
bending upwards partially cut out parts of the disc itself, substantially as described
with reference to Figures 14 and 15 of the drawings.
11. In a coal dust burning furnace, in which a sieve with oscillating or
reciprocating motion is disposed in the upper part of the feed pipe, the arrange-
ment, substantially as described with reference to Figures 16, 17 and 18 of the
drawings, for converting the rotary motion of the spindle into the oscillating or
reciprocating motion.
12. In a coal dust burning furnace, the coal dust feeding arrangement, consisting
of radially adjustable scoops or paddles in combination with an annular horizontal
disc, substantially as described with reference to Figures 19 and 20 of the
drawings.
13. In a coal dust burning furnace in which the current of air is conveyed in a
downward direction, a front furnace with vertical combustion chamber in which,
by means of an outer casing A, an annular chamber B is formed for heating the air
which passes in at the bottom and out at the top in order to unite with the mixture
of air and coal dust descending from the air pipe into the bottom of the front
furnace, substantially as described with reference to Figures 21 and 22 of the
drawings.
14. In a coal dust burning furnace with front furnace as claimed in the preceding
claiming clause, the arrangement of the casing A in such a way that a second air
heating chamber C is formed, from which heated air is mixed with the fire gases
escaping from the horizontal part of the front furnace, substantially as described
with reference to Figures 21 and 22 of the drawing.
15. In a coal dust burning furnace combined with a flue 57 of a steam boiler
lined with refractory material, the arrangement of a space between the upper part
of the refractory lining 57 and the flue, which space is connected by openings in
the refractory material with the combustion chamber, substantially as described
with reference to Figure 23 of the drawing.
16. In a coal dust burning furnace combined with a flue of a steam boiler, the
arrangement of an annular passage 60 surrounding the mouth of the pipe a for the
upply of the mixture of coal dust and air to the combustion chamber, through
which annular passage an additional quantity of air may be supplied to the
ombustion chamber, substantially as described with reference to Figures 23 and 24
of the drawing.
21
antomban 1904
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.