Improvements. in Boiler and like Furnaces, and in :Self-acting Stokers therefor.
Year: 1895

page_text: Date of Application, 24th July, 1895-Accepted, 24th Aug.,
1895
COMPLETE SPECIFICATION.
Improvements. in Boiler and like Furnaces, and in :Self-acting
Stokers therefor.
I, GUSTAV UNGER, of 10 Friesenstrasse, Magdeburg, in the Empire of 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 improvements in boiler and like furnaces for burning
coal dust or disintegrated fuel, and in self-acting stokers therefor.
Heretofore furnaces for burning coal dust have been defective by reason of their
being built exclusively of a fire proof, grateless chamber, whereby at the beginning
of as well as during the working, gases or even flames pass suddenly through the
air feed holes of the fire chamber toward the outside, and these flames or gases
carry away with them more or less unburnt coal dust or fuel. The cause of these
eruptions which take place under conditions similar to explosions, is due to the fact
that the temperature of the walls of the fire chamber changes continuously and it
can be observed through inspection holes that the said walls are sometimes bright
red sometimes incandescent or glowing and at other times dull red.
This defect is in the construction which forms the object of this invention,
obviated by removing on the oue hand the front part of the base of the fire
chamber and substituting therefor an ordinary grate (plane-grate, inclined grate or
stepped grate) and on the other hand by causing the coal dust or powdered or
disintegrated fuel to fall from above directly into the fire chamber in the form of a
veil or cloud extending over the whole width of the fire chamber.
For starting the fire, ordinary fuel is ignited upon the grate. As soon as the
fire chamber then appears sufficiently hot, the disintegrated fuel for instance coal
dust is fed therein. Above the flame which starts from the grate, another flame
This second
will be observed to pass along below the crown of the fire chaniber.
flame is generated by the particles of coal which by the action of the chimney
draught are drifted along below the crown of the fire chamber. Those particles of
coal or other fuel which fall down toward the front and up to about the middle
of the chamber, will come within the reach of the flame which rises from the grate
and these particles are partly carried forward by the said flame and partly fall
through the flame upon the fire of the grate and are burnt there. Both of the said
flames join and penetrate each other immediately behind the grate, and ignite all
particles of coal or other fuel existing in and between the same and consume the
whole of the smoke still present there; in this manner a complete combustion
is obtained.
When regularly worked, the disintegrated fuel falls upon-the-grate so that the
fire need not or only seldom be re-arranged.
In the accompanying drawing a constructional form of this improved firing
arrangement is illustrated.
As an example a Lancashire boiler has been chosen.
In the said drawing:
Figure 1 is a longitudinal section of the boiler and furnace, and
Figure 2 is a front view of the boiler, one of the furnaces being shown in
section.
The fire chamber a made of fire proof material projects from the furnace tube b.
The base of this projecting portion is formed by an ordinary grate c, below which

page_text: i
is arranged an ash pit provided with a flap door d and above which an ordinary
fire door g is provided in the front wall of the fire-chamber. Between the front
grate-carrier and the fire door a slit his left, which can be closed by means of a
slide or damper i. Above the front extremity of the grate lies the mouth of the
feed channel traversing the top cover of the fire chamber; this feed channel
serves for introducing the coal dust or other fuel, and extends over the whole width
or nearly the whole width of the fire chamber as is shown in dotted lines in
Figure 2. The said channel can be more or less or entirely closed by means of a
flap or door l. Below the place where the feed channel k has its outlet orifice into
the fire chamber a, a transverse slit m passes through the front wall of the
chamber (see also Figure 2, left hand) which slit can likewise be closed by means
of a slide or damper n.
For feeding the coal dust or the like various arrangements may be employed.
The device which is shown as an example, is arranged in the following manner.
9.
The top or cover of the fire chamber carries above the feed channel k a box
shaped receptacle o, the cover or lid of which is provided with a tubular feet
socket, which communicates through a leather hose or pipe, with a feed chaunel
In the box o a second receptacle is movably suspended from one or several pins
or pivots or by other suitable means. The bottom of the receptacle has
a tapering portion t, in which a lateral slit u is left, which can be narrowed by
means of a slide v. The lowermost edge of the movably suspended receptacle
presents itself slightly above a feed roller w provided with suitable longitudinal
grooves, which roller, like the receptacle r extends over the whole width of the
fire chamber. This roller which, instead of being provided with grooves, may
also be simply roughened at its surface--for instance like an undressed cast metal
cylinder is driven from outside. The roller has several projections z arranged
at equal distances apart, which, when the roller is rotated will set the receptacle
in a rocking motion and thereby cause the whole contents of the receptacle up to
its uppermost layers to slip down gradually. Thus coal dust or like disintegrated
fuel drops out of the receptacler through the slit u upon the periphery of the roller,
the rotary speed of which-amounting to about 20 revolutions per minute-also
permits of the actuation by hand and is dependent upon the quality of the fuel
used. In order that the roller may not carry away too much of the disintegrated
fuel a sheet plate acting as a scraper is movably suspended above the roller in front
of the slit u, which scraper plate is by means of counterweights always forced
back into its initial or resting position, and which moreover has the obvious
advantage of overcoming without obstruction any irregularities in the action,
caused by a comparatively coarse sort of fuel and other admixtures, the action
being such that the scraper plate simply rises thus allowing of the coarser particles of
fuel being forced into the fire chamber by the energetic and steady action of the
roller. During its rotary motion the roller spreads the powdered fuel resting
thereon down in the feed channel with such a speed that the fuel passes the said
chaunel k in form of a veil or cloud and also enters the fire chamber in this form.
In case where the fuel is moist or wet, further scraping devices of any suitable
kind may be arranged at the place where the material leaves the roller.
Before the fuel feeding device is set in movement, the fire-chaniber must be
first heated by arranging and keeping a fire upon the ordinary grate c.
This
having been done the fuel is fed down and then the before described process will
take place. Owing to the fact that the fuel freely falls down in the shape of a
thin veil or cloud the said fuel is intimately mixed with air whereby one principal
condition for securing a complete combustion is fulfilled. On the other hand the
cooling down of the walls of the fire chamber which under other conditions occurs
frequently, is prevented owing to the fact that the fire on the grate will always
give off a uniform heat.
Owing to the absolute combustion of all particles of fuel introduced, obtained in
this manner, the explosions, hereiubefore mentioned, are entirely avoided.
Through inspection-holes arranged in the front wall of the chamber it can be

page_text: ascertained whether the combustion takes place in a regular manner. If it is
observed that for obtaining a complete combustion, a larger amount of air is
required than enters at the bottom through the slits between the grate and from
above together with the disintegrated fuel through the feed channel k, one opens
the slit in front of the grate and the slit m in the front wall of the fire chamber
to a greater or less extent accordingly. On further observing that the veil or
cloud of coal-dust or other fuel supplied is too thick for being completely burnt,
then the feed passage or slit u of the receptacle is narrowed. Finally by adjusting
the flap in the feed channel k it is given in one's command to more or less
deviate the veil or cloud of coal dust that is to say to impart to it the most
suitable direction for the purpose.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is :-
1. A furnace for burning powdered or disintegrated fuel, in which furnace the
escape of gases, flames and burnt or unburnt fuel from the fire chamber under
explosive action is prevented by constructing the front part of the base of the fire
chamber in the form of an ordinary grate and by feeding the fuel-from above in
the shape of a veil or cloud which latter extends over the whole width or nearly
the whole width of the fire chamber-directly and freely into the fire chamber, and
intimately mixed with air.
2. A furnace of the kind described in the first claim, in which adjustable air
inlet openings (h, m) are provided in front of the grate and in the front wall of the
fire-chamber, for the purpose of introducing air according to requirements.
3. A furnace of the kind described in the first claim, in which the feed-channel k
for the fuel can be more or less narrowed by a slide or flap (!) in order to impart
the most suitable direction to the fuel when passing down the feed-channel.
4. In combination with a furnace of the kind described in the first claim a fuel
feed-device having the characteristic features that the fuel is-by the medium of a
roughened roller (w) or by one provided with appropriate recesses-taken from a
receptacle (r) set in rocking motion by the said roller and is spread into the feed
channel k and into the fire chamber, while scraping devices are or may be provided
at suitable places in order to act upon the feed roller.
Dated this 24th day of July 1895.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.