A Furnace adapted for the Combustion of Coal-dust.
Year: 1893

page_text: This Print is in accordance with the Original Specification as it stands after Amend-
ment (under Section 18 of the Patents, &c. Act, 1883) as allowed by the
decision of the Comptroller General of the 29th day of June 1898.
Date of Application, 8th June, 1893 - Accepted, 22nd July, 1893
A Furnace adapted for the Combustion of Coal-dust.
I, GEORG HILLIGER, of No. 4" Breite Strasse, Pankow, near Berlin, Germany,
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 relates to a furnace arranged for the combustion of coal-dust
which, by means of a revolving brush, is conveyed for the purpose into the com-
bustion-chamber; such mechanical introduction and distribution of the fuel in
the condition of dust being, by reason of its simplicity and reliability, far superior
to any of the existing arrangements for the combustion of coal-dust, in which
unlike that which takes place according to the present invention―the pulverulent
fuel is fed to the furnace by means of a blast or by steam, through tuyeres or
injectors.
The invention will be best understood by reference to the accompanying
drawings in which :-
Fig. 1, is a sectional elevation of a boiler-furnace provided with the improved
feeding device operated by means of the available (natural) draught of air;
Fig. 2, shows a similar device, also in section; this involves, however, the
employment of an artificial draught;
Figs. 3 and 4, are, respectively, a section and a front view of a furnace con-
structed in a manner practically corresponding to Fig. 1, but in which the rotating
brush is combined, and adapted to be operated simultaneously, with a vibrating
or shaking arrangement the object of which is to prevent the coal-dust from
agglomerating into clots or lumps, so that it may, without any obstruction, be
conveyed by the revolving brush to the furnace in a continuous and uniform
manner;
Fig. 5, is a partial detail view of the cam and tappet-arm, being accessory
parts of the vibrating plate;
Fig. 6, is a section of a modified construction of the feeding device, in which
the coal-dust, instead of being conducted from the hopper to the revolving brush
direct, is conveyed by a guide-plate to the bottom of the brush-casing whereby
the brush is, as far as possible, protected from obstruction.
Fig. 7, is a section of a simplified arrangement of the furnace, in which the
revolving brush is dispensed with, the coal-dust being distributed and discharged
into the furnace by means of a grooved plate with an arched and inclined
surface; and

page_text: Fig. 8, is a detached view of the grooved plate.
The furnace-chamber A, constructed with fire-brick walls, contains no grate
and is limited at the rear end by a bridge B. As shown in Fig. 1, the fuel-
feeding or charging hopper D is combined with the removable plate C, which
serves to close the furnace at the front. The lower end of the hopper, facing
the furnace A, forms a chamber the walls of which are partly curved in
cylindrical shape. This chamber is connected with the furnace-chamber A by a
discharge orifice a preferably in the shape of a slot; and in the said chamber
is arranged to rotate the conveying brush E, which is preferably made of stiff
but resilient wire. The wire may either cover uniformly the surface of the
roller which constitutes the core or body of the brush and the diameter of which
may vary according to requirements; or it may be arranged upon such roller
spirally, when it is desired that the revolving brush should answer the double
object of distributing the coal-dust and conveying it to the discharge orifice in
the longitudinal direction.
The main purpose of the brush E, however,-while it rotates in the direction
of the arrow with moderate speed is continuously to sweep, as it were, the coal-
dust, which is introduced through the hopper, over the discharge orifice, into the
furnace-chamber.
The arrangement for the admission of air as illustrated in Fig. 1 of the drawings
consists of a grating F, fitted below the discharge orifice, so that through it and
the flue or tube a natural draught is created. By inclining the said grating,
the draught may be deflected in its upward course in such a manner that the
particles of dust, as they are expelled through the orifice, remain in suspension
for a time, and are thus driven a certain distance further forward, before falling
down. This particular action of the draught, however, forms no indispensable
part of the invention, inasmuch as it is sufficient to drive the brush itself with
adequate speed to prevent the coal-dust from descending directly at the front
end of the furnace-chamber.
The closed air chamber J, arranged above, and in front of, the charging hopper,
serves to prevent the partial transmission of heat.
In the form of coal-dust furnace shown in Fig. 2, which in the main corre-
sponds to that which is illustrated in Fig. 1, an arrangement is provided for
producing an artificial draught. The air or blast pipe G, leading from the blast,
conducts the air (by means of connecting pieces indicated in dotted lines) into
two air-chambers J, H, arranged, one (J) above the discharge orifice a, and the
other (H), below that orifice, so that the coal-dust, as it issues from the said
orifice a must pass between two jets of air supplied under pressure, and heated
if necessary, whereby the most favourable conditions of a perfect combustion are
fulfilled. The arrangement shown is such that the chambers J, H, may, along
with the hopper casing and the brush E located therein, be temporarily turned
out of the way, to gain free access to the furnace-chamber, the junction piece G¹
of the blast pipe G in that case forming the required lateral hinge or pivot.
The revolving brush E may be driven by means of the projecting end of its
shaft or spindle, to which motion may be imparted either direct or through the
medium of a belt. The operating mechanism preferred is a steam turbine or
centrifugal machine, which may, if desired form part of the feeding apparatus
of the furnace itself. In the case of large boiler installations, the available
water-pressure may also be utilized in driving the shaft of the rotating brush,
especially when it so happens (as it does while the furnace is being started) that
the pressure existing in the boiler is either insufficient or cannot be used for its
proper purpose.
The modification shown in Figs. 3 and 4, is substantially similar to the form
of apparatus previously described in reference to Fig. 1. The hopper D is here,
however, closed at the back by a movable or hinged plate d which only opens
the passage through the orifice of the hopper when it is slightly moved backward
or turned out of the way.

page_text: The closing is effected by springs, t, which engage with arms z projecting on the
outside of the hopper-case and carrying tappets v. These arms pass through slots u¹,
provided for the purpose in the corresponding sides or cheeks of the case, within
which they are connected with the vibrating or shaking plate. The said tappets v
are also acted upon by cams q, keyed onto the driving shaft, or the shaft p of the.
revolving brush, and having one or more projections or tappets, so arranged that
when rotation takes place in the direction of the arrow, Fig. 4, the plate d is tempo-
rarily removed from the position in which it closes the passage; when, however,
the tappets v slide off the cam surfaces, the said plate d, under the action of the
springs f instantly swings back to the closing position and in so doing imparts a
shock to the mass of coal-dust contained in the hopper.
The object of this mode of operation, which is illustrated in the detail view
Fig. 5, is to counteract the tendency of the coal-dust to agglomerate and form clots
or lumps, especially under the influence of dampness, so that the revolving brush
may at all times convey into the furnace uniform supplies of pulverulent fuel; the
brush itself, moreover, contributing to separate particles of fuel adhering to each
other. Experiment has actually shown that, with the assistance of the vibrating
device just described, or other similar shaking or rocking arrangement, the brush
more thoroughly takes hold of the material to be conveyed, than it would otherwise
do, and consequently effects a more uniform and reliable feeding action. By thus
combining a shaking device with the improved fuel-conveying brush a further
disadvantage, attending the coal-dust furnaces hitherto known, is also effectually
removed. This disadvantage is, that the coal-dust, forced in by steam or air under
pressure, in the old apparatus of this class, has to go through an elaborate drying
stage before it can be lighted; and that, even in spite of such drying, the hygro-
scopic nature of the material renders the absorption by it of a certain amount of
moisture unavoidable, and therefore its even distribution practically impossible.
In the present arrangement, however, the distribution of the fuel is effected
automatically, no matter whether the fuel is introduced into the hopper in the
condition of dry dust or in lumps.
Fig. 3, shows the air-chamber J, in front of the hopper D, provided with a
damper i, whereby the passage of the air from the said chamber to the upper part
of the furnace may be controlled. The admission of air below the discharge-
orifice a is also controllable in this arrangement, the means of control consisting of
a hinged plate or door k, adjustable on the system of a ventilating valve, and
adapted to open, as required, an opening of greater or less width for the air to pass
through and rise in regulated quantities up to the pulverulent material. Aj
chamber L, formed between the rear-wall of the hopper-casing and the vibrating
plate, is fitted with another damper l, whereby the admission of air into the
brush-case may be controlled, and the case itself protected from undue heating.
In the form of furnace shown in Fig. 6, the coal-dust is conducted from the
hopper D, when the shaking plate d is forced back, not into the top part of the
brush-casing, but over a plate s, curved to suit the periphery of the brush, and
which plate conveys the fuel to the bottom of the brush-case. This is to prevent
the coal-dust from collecting in the brush and impeding its operation by reducing
its elasticity; the coal-dust collecting at the bottom of the brush-case in a loose
heap, fit to be readily swept away by the rotating brush E into the furnace-chamber.
As shown in Figs. 7 and 8, the arrangement of the furnace may be simplified by
entirely dispensing with the brush. The distribution of the coal-dust, uniformly
from the hopper D, is here effected by a vibrating device as described and by a
plate or block W, having an arched or inclined surface, and arranged within the
casing instead of the revolving brush. This plate W is provided with grooves
or channels w leading the coal-dust to the furnace-chamber A, or in other words
to its inlet a. The arrangement for the admission of air, in this form and also
in the modification shown in Fig. 6, is the same as in the construction represented
in Fig. 3, the coal-dust being conducted into the flue by two currents of air directed
towards each other..

page_text: 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 I am aware
that brushes have been before proposed for use in hoppers for assisting in conveying
pulverulent fuel to steam or air injection apparatus and I therefore do not claim
broadly the use of brushes in such hoppers, but what I claim is:
1. A coal-dust furnace characterized by a revolving or roller-shaped brush. (E)
arranged immediately at the outlet of the charging funnel or hopper (D) into the
furnace chamber and consisting of resilient wires or rods, adapted to divide the fuel
into grains or particles and to drive it over the edge of a discharge orifice (a) and
directly into the furnace, substantially as described and shown.
2. In a coal-dust furnace, the vibrating or shaking device adapted to prevent the
agglomeration of the pulverulent fuel into lumps or clots and consisting of a spring-
controlled vibrating plate (d) adapted to open the discharge orifice of the charging
hopper only when, by the action of cams (9) upon the shaft of the brush (p), it is
swung out of the way, when by jerking back to its former position, under the action
of springs (f), it shakes and breaks up the fuel into loose particles, substantially as
described and shown.
3. In a coal-dust furnace with a revolving brush for the conveyance or feeding
of the pulverulent fuel, as claimed by the first claim a guide-plate (s, Fig. 6)
adapted to lead the fuel to the bottom of the brush-casing and to prevent the brush
from being clogged, substantially as described and shown.
4. In a coal-dust furnace with a revolving brush for the conveyance or feeding of
the pulverulent fuel as claimed by the first claim, the air-admitting or air-
circulating arrangement located below the discharge orifice (a) and consisting of a
hinged plate or door, (k) arranged so as to form an air-passage or air-deflecting
surface, directed upwardly and into the furnace, so that, as the air rises it meets
(from below) the coal-dust issuing through the discharge-orifice (a), substantially
as described and shown.
Dated the oth
T..
1000