Improvements in or relating to Furnaces for Pulverulent and Fine-grained Fuel.
Year: 1893

page_text: Date of Application. 19th Sept., 1393--Accepted, 1st Sept., 1894
COMPLETE specificATION.
Improvements in or relating to Furnaces for Pulverulent and
Fine-grained Fuel.
1, HERMANN KLUEPFEL, of 6 Carolinenstrasse Barmen in the Kingdom of
Prussia, Manufacturer, 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 furnaces for burning pulverulent or finely divided
fuel, as coal dust, and aims to provide certain improvements in devices of this
character.
To this end, in carrying out the invention in its preferred form, I provide a
receiver for the fuel, a conveyor, communicating with said receiver for carrying the
fuel to the point of delivery, an air blast for conveying the fuel to the point of
combustion, means for controlling said blast, a valve for controlling the supply of
fuel, and preferably a movable frame or plate carrying said parts and serving as
the front plate of the furnace and movable upwardly above the furnace to give
access to the interior thereof, and a movable grate within the furnace for use
previously to the ignition of the powdered fuel and removable therefrom beneath
said plate when the latter has been raised.
In the accompanying drawings:-
Figure 1 is a vertical axial section of a flame tube boiler to which the preferred
form of my improvement is applied.
Figure 2 is a front elevation thereof, the fuel feeding apparatus being in vertical
section.
Figure 3 shows in axial section and in three end views three different shapes of
removable mouth pieces for fuel conveyors.
Figure 4 is a section of such a mouth piece having a swinging throttle valve.
Figure 5 is a vertical axial section of a mouth piece of the construction shown in
Figure 1 but having an axial longitudinally adjustable cone throttle valve within
the fuel conveying pipe.
Referring to the drawings let B represent the receiver for the fuel, bars
carrying the receiver, P a plate engaging said bars, closing the flame tube at front
of the boiler, the air supplying tubes which are carried by said plate, F the ash-
pit doors provided with the usual dampers and carried by said plate, k conveying
pipes connected to, and communicating with the receiver at top and opening into
the tubes at bottom, M nuts fixed to the plate P, S screw spindles engaging these
nuts, Ha hand wheel for operating the screws S, T bevel gears between the
screws and hand wheel, Z the grate frames, and the grate bars. is a valve
for controlling the flow of fuel, c (Fig. 5) a similar valve for a like purpose,
fa valve for controlling the air supply, ando a peep aperture in the latter
valve.
The receiver B may be of any suitable construction, and may have one or more
fuel conveying pipes communicating with its under side and leading to the air
current pipes 7. A suitable valve is provided for controlling the flow of fuel from
the receiver. Preferably a valve d arranged axially of the discharge mouth of
each pipe k, and disposed within the air pipe is provided, which valve can be
moved toward or from the pipe & to control the area of the annular discharge space
between the mouth of this pipe and the valve, and thereby determine the feed of
the fuel. If desired, however, as shown in Fig. 5 a valve c within the pipe k may
be used, either alone or in conjunction with the valve d for controlling the speed of
supply of the fuel.
k

page_text: According to one feature of my invention I construct the internal walls of the
receiver, the fuel conveying pipes, and the external walls of the valve or valves d
and c, at an angle of inclination relatively to the horizontal which is steeper thau
the natural angle of slope of the fuel. This is an important feature, for the reason
that pulverulent or finely divided material will not move under the action of
gravitation over an inclined plane the inclination of which is less than the natural
angle of slope of the fuel, but will in such a case adhere to or rest upon the wall or
plane and eventually prevent the passage of subsequent fuel thereover. With my
invention I construct the walls with such steep inclinations that none of the
powdered fuel will adhere thereto, it all passing freely thereover under the action
of gravitation. I also construct the walls of the valves d and c with like
inclinations preferably the reverse of the inclination of the walls of the pipes k.
The receiver B, bars s, and plate P, coustitute essentially a movable frame
carrying the fuel feeding and draft controlling apparatus. This frame is manipu
lated to open or close the flame tube of the boiler by means of the screws S or in
any other suitable manner.
According to another feature of my invention the powdered fuel is discharged
into a gaseous current or blast, preferably an air current induced by the usual
draught of the furnace, and this current serves to convey the fuel into the flame
tube of the boiler, suitably subdividing the fuel and intermixing the air or gas with
it, and I provide means for controlling this current. Preferably this is accom-
plished by providing an air pipe carried by the plate P, and opening into the flame
tube, and an air valve at the outer open end of this pipe movable to open or close
the same for controlling the flow of current therethrough.
Another feature of the invention consists in providing a removable grate frame Z
carrying the grate bars, which frame rides into the flame tube on rollers X
engaging tracks Y therein, and is enclosed therein by the plate P when the latter
is down. This frame can be withdrawn from the furnace, when combustion of the
powdered fuel is well under way, or preferably when the furnace is sufficiently
heated to ignite the powdered fuel when the latter is fed thereto, by raising the
plate P and drawing out the grate frame. The grate frame is usually loaded with
ordinary fuel, which is ignited and burned in the flame tube until the requisite
heat has been generated therein to ignite the powdered fuel, whereupon the frame
may be withdrawn and the powdered fuel fed to the furnace.
In operation the powdered fuel is placed in the receiver B, the valve for con-
trolling the discharge through the pipes kis closed, the temperature of the flame
tube is raised by ordinary fuel on the grate frame Z, the plate P and feeding
apparatus are then raised and the grate frame withdrawn, the plate and feeding
apparatus are then restored, the valve controlling the feed properly adjusted, and
the operation of burning the powdered fuel then commences. In this operation the
conveying pipes & discharge preferably an annular stream of powdered fuel into the
air pipe and the current through the latter takes up the powdered fuel, sub-
divides it, mixes with it, and carries it into the combustion chamber or flame tube,
where it is ignited either by the heat already generated therein as before described,
or in any suitable manner. A continuous and regular flow of powdered fuel
follows, which may be controlled by adjusting either the fuel valve d or cor both.
The air current may be controlled by the air valve. The operation may
be observed through the aperture o. The draft may be controlled by the doors F.
Preferably the apparatus is constructed with one receiver B having three
conveying pipes k, each having a separate air pipe and the flame tube is partly
lined internally with fire brick, or other refractory material, up to heyond the
fire bridge, in order to protect the walls of the boiler against projecting jets of
Hame.
It will be seen that my invention provides an improved furnace in which
powdered fuel can be readily and conveniently utilized, and it will be under-
stood that the invention is not limited to the precise details of construction and
arrangement set forth in its preferred form, as it may be availed of according

page_text: to such modifications as circumstances or the judgment of those skilled in the
art may dictate, without departing from the essential features of the invention.
Preferably the mouth pieces or conveying pipes k are removable so that different
sizes and forms can be employed. Several formns are shown in Figure 3. To
facilitate the removal of the mouth pieces they are constructed at their lower ends
to fit corresponding sockets in the tops of the air pipes, and the discharge outlets
from the receiver are adapted to pass into the upper ends of the pipes k and are
screw threaded above these ends and carry a nut screwing down on the pipes to
hold them in position, as shown in Figure 1. Preferably a threaded hand wheel
engages the screw threaded stem of the valve d and is carried at the under side of
the air tube for adjusting this valve. A similar adjusting device is provided
above the valve c and carried by a frame thereover. With each of these adjusting
devices a suitably arranged mark or graduation may be provided to indicate the
quantity of fuel fed through the valve in a given unit of time.
In the arrangement shown in Figure 4 :-The throttle valve is fixed to the
pin e which is prolonged on the outside and provided with a lever-arm terminating
in a pointer i, moving to and fro against a scale attached to the outside of the
nozzle. The pointer is moved by a hand-wheel and screwed spindle turning in
a nut m pivotted to the lower end of the lever arm. Each division of the scale is
calculated to correspond with a regulated area of openings of the throttle-valve,
and consequently to the admission or supply of a given quantity of fuel in the time
unit.
:-
In the arrangement shown in Figure 4 y -The throttle valve is arranged and
operated in precisely the same manner as in the preceding case (Figure 4), but
the scale is marked on a fixed disc on which a pointer attached to the
hand-wheel h moves to and fro showing in similar manner the sectioual area of
the opening and the corresponding proportionate supply of fuel in the time-unit.
The air current will be regulated according to the quantity of fuel used and the
purpose for which the combustion is required. Ordinarily cold air may be
employed, but for some purposes, especially for melting processes, it will be
desirable to first heat the air.
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 furnace for burning finely divided fuel, the combination with the
combustion chamber of a receiver for the fuel a discharge outlet for said receiver
a plurality of mouth-pieces for said outlet and air tube opening into said chamber
and having a socket at top said mouth pieces each fitting said socket in said tube
at their lower ends and each fitting said discharge outlet from said receiver at
their upper ends and constituting removable pipes communicating between said
receiver and said air tube whereby one can be substituted for another substantially
as and for the purpose set forth.
2. In a furnace for burning finely divided fuel, the combination with a combustion
chamber of a front plate P therefor an air tube carried by said plate a receiver B
or the fuel above said plate a conveying pipe leading from said receiver into said
tube for discharging the fuel therein and a frames carrying said plate and receiver
and movable vertically to raise and lower said parts to give access to said chamber
substantially as and for the purpose set forth.
3. In a furnace for burning finely divided fuel a combustion chamber and a fuel
feeding apparatus in combination with a movable front plate for said chamber
carrying said apparatus and a removable grate frame in said chamber opposite said
plate whereby ordinary fuel can be ignited on said grate frame to heat said
chamber to a temperature necessary to ignite the finely divided fuel, and thereafter
sid grate frame can be removed and the finely divided fuel fed to said chamber
where it will be ignited by the heat thereof.
4. In a furnace for burning finely divided fuel a combustion chamber in

page_text: combination with apparatus for feeding the finely divided fuel thereto a front
plate for said chamber carrying said apparatus and movable vertically relatively
to said chamber to open and close it and a removable grate in said chamber for
retaining the ordinary fuel requisite to initially heat it whereby when said front
plate is moved from said chamber said grate can be withdrawn therefrom
substantially as and for the purpose set forth.
5. In a furnace for burning finely divided fuel the combination with the
combustion chamber of a receiver for the finely divided fuel a conveying pipe & for
discharging the fuel therefrom and an air supplying tube receiving the discharged
fuel and opening into said chamber the inner walls of said conveying pipe
constructed with an inclination steeper than the natural angle of slope of said fuel
and a valve for controlling the discharge through said conveying pipe and
constructed with walls of like but reversed inclination to those of said conveying
pipe.
6. In a furnace for burning finely divided fuel a combustion chamber in
combination with a conveying pipe k for feeding the finely divided fuel to said
chamber said pipe having inclined inner walls and a valve within said pipe
arranged axially thereof movable in vertical direction for controlling the flow
therethrough and constructed in the form of a cone the outer walls of which are
of the same but reversed inclination to those of said pipe.
Dated this 19th day of September 1893.
W. P. THOMPSON & BOULT,
Agents for the Applicant.