Improvements in and connected with Furnaces using Coal Dust as Fuel.
Year: 1893

page_text: Date of Application, 4th July, 1893-Accepted, 12th Aug., 1893
COMPLETE SPECIFICATION.
Improvements in and connected with Furnaces using Coal Dust
as Fuel.
We CARL WEGENER and PAUL BAUMERT, both of No. 9 Mohrenstrasse,
Berlin, German Empire, Engineers, 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 relates to improvements in that kind of furnace described in
British Patents No. 22402 of December 22, 1891 and No. 15786 of September 2,
1892, and in which coal dust or the like is used as fuel and the invention consists
in a peculiar kind of internal furnace for steam boilers, in new appliances or
means for the feeding of the fuel (for instance coal dust) as well as in the
arrangement according to which the artificially created current will be replaced
by a current of air caused by the natural draught of the chimney.
These new improvements will now be fully described with the aid of the
accompanying four sheets of drawings.
Figures 1, 2 and 3 on Sheet 1 show a front elevation, a longitudinal vertical
section and a plan view respectively of a furnace of a boiler with the invention
applied to it, whilst Figure 6, on Sheet 2, shows a longitudinal vertical section of
a somewhat modified form of construction.
The combustion chamber (Figure 2) is enclosed or surrounded by a wall b' of
firebrick or other refractory substance and which, as will be seen from the drawing,
is in the form of a hollow cylinder; this wall serves for a lining to the front part
of the fire tube or flue 62, whilst at its rear it forms a bridge ³. This bridge is
of the construction shown in the drawings, that is to say, it leans forward or stands
out projectingly and it thus successfully prevents the passage into the rear part of
the flue of any large and unburnt quantities of the material which may be
employed in the first instance for setting the coal dust alight, besides which, the
bridge will aid or promote the circulation and the whirling motion of the gases in
the combustion chamber . This combustion chamber has at its front end and
around the edge of the flue a suitable plate a and the current of air carrying along
with it the coal dust passes into the furnace through this plate a hereafter called
the furnace front. The other portion of the air, which is necessary for the com-
bustion, is introduced by means of small passages c¹. These small channels or
passages e pass as will be seen from Figure 2, through the wall b', and open out
of and are at right angles to the longitudinal passages or tubes c, the latter c
passing from the space b, enclosed between the furnace front a and the ring a
which is placed at the front face of the wall b¹. The front ends of the passages or
tubes c are, as shown, perforated and thus the air coming from a suitable conduit h,
and a branch conduit m, Figure 1, (provided with a regulating appliance m¹) passes
along the passages e c¹ to the furnace. This air is subjected to considerable
preliminary heating or warming owing to its passage through the circular space b
and especially through the longitudinal passages or tubes c and it is by reason of
this that a complete combustion of the coal dust takes place.
The fire-brick wall encloses further at its lower end a longitudinal passage or
tube c², the rear end of which opens into the flue whilst to its front end, passing
through the ring a' and the circular space b, is fitted a removable cover. By this
means, the flue 2 of the furnace can be cleared of any small ash or soot by means
of a blast of air or steam.
in a
The parts by which the coal dust is blown into the furnace and which for con-
venience of description will be hereinafter referred to as the blast feed may,
similar manner to that described in the above mentioned Patent No. 22402 of 1891,
be so applied to the furnace front a that they can be swung round therefrom, on

page_text: the axis of the vertical conduit / serving for the introduction of the air. The
hopper e³ does not however take part in this movement but is rigidly fixed in any
suitable manner to the boiler. It is therefore only connected with the blast-feed
by means of an easily loosened collar or sleeve f fitted under the feed disc g.
The furnace front a is fitted with a sufficiently large door d, so that, when the
blast feed is turned aside, there will be convenient access to the combustion
chamber. In the normal position of the blast feed it lies tightly against the upper
part of this door which is suitably broken away, whilst there is fitted to the under
part of the door a second and smaller door for preheating and for cleaning the
combination chamber z. Into this latter, air of atmospheric tension can. be let
by means of a register which is fitted to the door l.
The construction of the furnace, shown in Figure 6, Sheet 2, only differs from
the one just described in respect of the ring formed air space b. This is here
projecting from the flue and lined with refractory material in the same manner as
the front part of the flue. Of course either of these forms of air space (that is as
in Figure 2 or as in Figure 6) or a combination of the two may be employed,
according to the space available at the front of the boiler, or the diameter of
the flue.
The means for introducing the coal dust are also shown in Figures 1 to 3. The
lower extremity of the supply hopper e³ which is provided with the feed disc g is
of a knee shape so that the disintegrating and feed appliance i, Figure 4, situated
below the collar or sleeve receives only a slight and uniform pressure independent
of the amount of coal dust which may happen to be in the hopper.
Further there is shown an appliance to cause the disintegrated or powdered fuel
to be evenly discharged into the current of air. The sloping channel e', into
which enters the powdered fuel coming from the funnel e², arranged under the
disintegrating and distributing appliance, terminates for this purpose in a number
of narrow gutters e, arranged in form of a comb with intervening spaces. The
current of air passing between these gutters e carries along with it the powdered
fuel in an uniform and regular manner.
Figures 4 and 5 show views of the disintegrating or powdering and distributing
appliances which, in the main are similar to those described in the aforesaid
Patent No. 224021 consisting of the sieve i moved to and fro on a vertical axis by
means of a pin ².
The layer of coal dust lying on the sieve or grating i tends to partake of the to
and fro motion of the said sieve, whereby the disintegrating and sieving effect is
impaired. To avoid this, strips k are fastened radially and vertically to the ring k¹
which lies between the hopper e² and the above collar or sleeve f so that it can be
easily removed on the blast feed being turned sideways. It is further connected
with a nave 3 by means of webs k2, a cap k being provided on the nave k³,
which will then serve as a guide for the vertical axis of the grating or sieve i.
Figures 7 to 16 (Sheets 3 and 4) show the arrangements by means of which the
natural chimney draught may be employed for the introduction of the coal dust
instead of the artificially produced draught.
Figures 7 to 9 show the new "natural" fuel feed in its application to a front
furnace as described in the aforesaid prior Patent 22402, whilst Figures 10 and 11
show it in its application to a furnace arranged within or underneath the boiler.
Figures 12 to 14 show a modification of this firing arrangement,
Figures 15 and 16 show a modification of the natural fuel feed for both kinds of
arrangements.
The combustion chamber z shown in Figure 7 in longitudinal vertical section
differs only from the one described in the aforementioned Patent No. 22402 in that
the fire bridge in the present instance is built into the walls and hangs forward or
stands out projectingly as above mentioned. The coal dust feed is so applied to the
front opening or mouth of the chamber z that the channel e¹ which forms a prolonga-
tion of the funnel e² situated under the grating or sieve i passes through the annular
space w whereby the gutters e lie within the entrance to the combustion
air

page_text: chamber. There is a small circular wall or mouthpiece o arranged at this entrance
which presents on its rear end a number of superposed and upwardly sloping
plates p. These impart an upward motion to the current of air which is drawn in
from the chimney through the mouthpiece o, so that it takes up the coal dust from
the gutters e ard carries the same so much further into the almost horizontal com-
bustion chamber z.
In order that the swinging motion of the grating or sieve may be produced
without the aid of a special motor, a fan wheel r is inserted with its framework q
into the mouthpiece o and is further supported at p¹. When the framework or
ring q is taken out the fan wheel can be easily removed.
For converting the rotary motion of the fan into the swinging motion of the
sieve plate i, the nave of the wheel r is provided with a stud which by means of
a system of levers o¹, o³, o³, s engaging the peg or stud of the sieve plate i, sets
the sieve in motion in the one direction, whilst its return motion, the extent of
which can be regulated by screw s', is brought about by the spring s², Figure 9.
The regulation of the amount of air to be introduced, is effected by two semi-
circular dampers which are fitted to the front of the ring.g and can be secured at
any desired angle of opening by means of the crown or stirrup t'. In the position
of the parts shown in Figure 7, it is supposed that only a portion of the air
requisite for supporting the combustion passes the fan and the mouthpiece o, as the
circular space w receives the air through openings in its exterior wall. In
Figure 7 on the contrary it is supposed that the entire amount of air passes
through the fan r, mouthpiece o and plates p and is then divided to pass partly
through the gutters e and partly through the circular air chamber w¹ into the
furnace.
In the form of the invention shown in Figures 10 and 11, the mouthpiece o is
fitted to a doorway o* which bears the coal dust funnel e with its allied parts e¹, e,
and which doorway ox is adapted to the furnace front a closing the flue. The
motion of the sieve plate i is brought about by means of a system of levers similar
to that shown in Figures 7 to 9.
The form of apparatus shown in Figures 12 to 14 has also the above described
arrangement of coal dust funnel on a doorway ox fitted between the furnace front a
and the mouthpiece o which in this case is curved round so that the fan r lies in the
horizontal plane. The axis of the fan will therefore pass up vertically through the
wall of the curved mouthpiece o and has an eccentric peg or pin r¹ at its upper end
which again in conjunction with a spring and a system of levers imparts a to and
fro motion to the sieve plate i.
Since the entire parts are seated on the furnace front a, this furnace front can be
just as well applied to the door frame of a furnace arranged within the boiler as of
one arranged underneath the same. The arrangement shown in Figures 15 and 16,
is applicable to all three cases since it differs from the foregoing only in the
horizontal position of the mouthpiece o and in the disposition of. the levers for
driving the sieve plate.
In order to kindle the fire in the coal dust furnace, a small fire is first lit in
the combustion chamber, and then in case of artificial draught air is allowed to
enter in the air pipe h whereby the wheel arranged therein at is put in motion,
and in case of natural draught the air is admitted in the mouthpiece o to move
the wheel r. Thereby the coal dust is blown into the combustion chamber, the
temperature of which in a few minutes attains the normal degree of heat requisite
to insure perfect smokeless combustion.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. An internal furnace for steam boilers consisting of a fire brick cylinder (b¹)
5 arranged within the fore part of the flue and forming the combustion chamber, a
furnace front (a) closing the entrance of the combustion chamber, an annular air

page_text: chamber (6) fed with compressed air and connected with air conduits (c c¹) leading
through the walls of the said cylinder into the combustion chamber and means for
blowing the coal dust through the furnace front (a) into the combustion chamber,
substantially as shown and described.
2. In an internal furnace of the kind specified in Claim 1, for the purpose of
rendering the combustion chamber accessible, the arrangement of a door (d) hinged
to the furnace front (a) and provided with the necessary openings for the blast feed
and a special door (1) allowing the cleaning of the combustion chamber, the blast
feed being connected to the fixed hopper (e") by means of a collar or sleeve (f)
so that, by loosening the same, it may be swung round on the axis of the air
tube (h) so as to free the door (d) and allow it to be opened, substantially as
shown and described.
3. In an internal furnace of the kind specified in Claim 1, the arrangement of a
passage or tube (2) traversing the lower part of the annular air space and the fire-
brick lining or wall in the direction of the boiler, and by means of which passage
or tube any small ash or soot can be exhausted or blown out of the flue, substantially
as shown and described.
4. The arrangement of a forwardly projecting or sloping fire bridge (c) at the
rear end of the combustion chamber () for the object of retaining any large and
unburnt pieces of fuel and promoting the circulating or whirling motion of the gases
in the combustion space, substantially as shown and described.
5. The arrangement of the supply hopper (e³) placed above the fuel feed
appliance () with a lower angular extension for the purpose of lessening the
pressure weighing on the feed appliance and of maintaining this pressure in as
constant and even a condition or state as possible, substantially as shown and
described.
6. In combination with a feed grating or sieve (i), swinging round vertical
axis, the arrangement of a frame fitted immovably over the grating or sieve and
having radially and vertically arranged strips, with the object of preventing the
conjoint motion of the dust lying on the grating or sieve (i), substantially as shown
and described.
7. The arrangement of a dust channel (e¹) directed slopingly downwards to the
combustion chamber, and underneath the feed appliance (i), which channel (e¹)
terminates in gutters (e), projecting into the entrance of the combustion chamber (*)
and out of which gutters (e) the dust falling down is caught and carried away in an
uniform state of distribution by means of the current of air circulating or passing
between the said gutters, substantially as shown and described.
8. The arrangement of a furnace without a blast feed, characterised by the coal
dust being introduced into a mouth piece or passage (o) opening into and lying close
before the combustion chamber (2), so that the coal dust is carried into the com-
bustion chamber by means of a current of air which is exhausted from the chimney
through this mouth piece, substantially as shown and described.
9. In a furnace without a blast feed of the kind specified in Claim 8, the arrange-
ment of a vertical grating in the mouth piece (o) in front of the place where the
coal dust enters, the bars (p) of which run in a horizontal and sloping direction
so as to divert the current of air upwards, by which means the dust is carried
further into the combustion chamber (=), substantially as shown and described.
10. In a furnace without a blast feed of the kind specified in Claim 8, for the
object of driving the appliances or means for feeding the coal dust, the arrange-
ment of a fan wheel (r) in the mouth piece (o) rotated by a current of air which
is exhausted from the chimney through the mouth piece, substantially as shown
and described.'
I
WM. P..THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicants.