Improvements in and relating to Furnaces for the Prevention of Smoke and the Economization of Fuel.
Year: 1899

page_text: Improvements in and relating to Furnaces for the Prevention of
Smoke and the Economization of Fuel.
A communication from abroad by EMIL OTT, of 11, Kurstrasse, Berlin, Germany,
Engineer to the Kaiserlichen Reichsbank," of Berlin aforesaid.
..
I, ALFRED GEORGE BROOKES, of 55 & 56, Chancery Lane, in the County of
London, Chartered Patent Agent, do hereby declare the nature of this invention
to be as follows:-
-
This invention relates to a furnace which, without the employment of any
secondary currents of air for the complete combustion of gases, burns without
smoke and enables full benefit to be derived from the fuel.
The objects in view, viz. the smokelessness of the furnace and the better utiliza-
tion of the fuel, are obtained by causing a portion of the gases escaping from
the furnace to mix with fresh air, and then once more conducting them under
the fire grates. By such means, while the air supply may be controlled or varied
at will, an active circulation of the furnace gases may be ensured, a result of
the highest importance in so far as it affects the amount of heat yielded up to the
surfaces to be heated.
The heating effect may be materially enhanced in this arrangement by the
admission of steam, the large quantities of gases, or in other words, of air and
smoke-which are available for the absorption of the steam that is to be con-
ducted under the grates, serving to obviate the drawbacks which otherwise
attend the introduction of steam (or water vapour ").
*
The combustion gases produced on the furnace grates pass to and between
and so as to yield up their heat to the steam generating pipes in the well known
manner; and then escape through the flue. In order to facilitate the return of
part of the combustion or furnace gases under the grates, the ash box is con-
nected with the flue through a channel, at the orifice of which, leading into the
ash box, there is arranged an exhaustor or fan, or some equivalent appliance;
such fan or equivalent being driven from a motor-preferably where it is avail-
able a small electro motor.
The channel which serves to place the ash box in communication with the flue
or chimney consists of a suction pipe, a mixing chamber and a fan casing. One
end of the said suction pipe opens into the chimney or flue while its other end
leads into the mixing chamber, into which open air inlet ports.
Owing to this arrangement the fan draws in a fresh supply of air together
with the furnace gases, which air mixes with such furnace gases in the mixing
chamber and is thereby brought to a high temperature.
Dampers serve to regulate the flow of the furnace gases and the relation between
the gases escaping directly through the chimney and the gases drawn in through
the suction pipe.
The fan exhausts furnace gas from the chimney or flue through the suction

page_text: pipe; draws in fresh supplies of air through the air inlets; and then forces the
mixture of gas and air under the grate. Owing to the high temperature of the
air used in sustaining combustion, the temperature at which the combustion takes
place is correspondingly raised.
Inasmuch as the furnace gases are kept in sufficiently active motion without
the necessity of driving excessive quantities of air through the furnace, it is
feasible to utilize the fuel to far better advantage than it could be done before.
In order to enhance the heating effect, a water supply pipe is preferably arranged
below the grate; such pipe being provided with minute perforations, and being
fed from the conduit or service pipe. This water pipe supplies it in a fine spray,
falling below the grate, in a plane parallel to the grate surface. This sprav
is in part conducted into the furnace by the air employed in assisting combustion
and, owing to the production and combustion of water gas serves to develop
uncommonly high temperatures. By reason of the air being actively maintained
in motion, considerable quantities of steam may find their way into the furnace,
without any necessity for the proportion of steam contained in the air, used in
keeping up combustion, to exceed certain narrow limits. Also, in consequence
of the high temperature of the combustion air-mixture, the steam undergoes a
sufficient preparatory heating to be precluded from interfering with combustion
immediately above the grate.
The process of mixing the combustion air with combustion-gases, therefore,
affords a novel means whereby an ordinary furnace may be successfully converted
into a partial water gas furnace.
By these means I attain a smokeless furnace the main feature of which is that
part of the combustion gases, after they have left the fire-chamber, are drawn
in by suitable suction apparatus and mixed with freshly admitted air, whereupon
the resulting mixture is conducted back under the fire grates, for the purpose of
utilizing their heat in subjecting the air, to be used in assisting combustion,
to a preparatory stage of heating, and thereby bringing about the entire com-
bustion of the particles of unburnt fuel contained therein, by repeatedly con-
ducting them through the fire. And further the suction device which draws the
furnace gases with a view to reconducting them under the fire grates, is arranged
between the ash box and a mixing chamber into which open both fhe suction
pipe for drawing in the furnace gases and the air inlets for drawing in fresh
supplies of air to maintain the combustion.
Dated the 15th day of June 1899.
Improvements in and relating to Furnaces for the Prevention of
Smoke and the Economization of Fuel.
A communication from abroad by EMIL OFT, of 11, Kurstrasse, Berlin, Germany,
Engineer to the " Kaiserlichen Reichsbank," of Berlin, aforesaid.'
I, ALFRED GEORGE BROOKES, of 55 & 56, Chancery Lane, in the County of
London, Chartered Patent Agent, 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 in which for the purpose of generating water
gas, steam is sent through the furnace grates.

page_text: In order to obviate the disadvantages attaching to water gas furnaces of this
class, as hitherto constructed-disadvantages mainly arising from the fact that
by the admission of steam in "operative" or "effective" quantities, the glow,
or heat, existing upon the furnace grates, is unduly reduced while at the same
time a coking, instead of a combustion, of the fuel is brought about-the steam
required for the production of water gas is, according to this invention, conducted
through the furnace grates together with a mixture of combustion gases or smoke
and fresh air. As the fresh air, by mixing with the hot combustion gases
enables the gases to move through the furnace chamber very rapidly, without
thereby causing the combustion to take place with a considerable surplus quantity
of air, which would be unsatisfactory in the result, it becomes possible to introduce
somewhat large quantities of steam into the furnace chamber, though the pro-
portion of moisture in the mixture of smoke and air be comparatively small.
And inasmuch as part of the steam which is evolved during the combustion of
the water gas is, together with the combustion gases, reintroduced over and over
again into the furnace chamber and, as it passes through the layer of fuel, is
converted into water gas, the water gas production is greatly facilitated and the
resulting useful effect turns out to be extremely profitable.
In the accompanying drawings a furnace constructed in accordance with this
invention is represented as being applied to a tubular boiler and to a flame tube
boiler.
Figs. 1 to
relate to the tubular boiler furnace, and Figs. 4 to 6, to the flame
tube boiler furnace.
Fig. 1 is a vertical longitudinal section;
Fig. 2 is a horizontal section;
Fig. 3 is a vertical cross section ;
Fig. 4 is a vertical longitudinal section of a flame tube boiler fitted with the
improved furnace;
Fig. 5 is a horizontal cross section with the flame tubes or flues in elevation;
and
Fig. 6 is a vertical cross section on line 6-6 Fig. 5.
In Figs. 1 to 3, relating to the tubular boiler furnace as stated, a designates
the fire grate; b is the furnace chamber; c is the steam boiler, the tubes of which,
as far as is desirable may be built round with tiles or brickwork; d is the draft
flue or chimney; e is the ash box which is connected with the channel or flue f
serving for the escape of the fire gases; y is a screw blast or fan which, as
indicated diagrammatically, is driven by an engine h. Into the space i, which
forms the connection between the ash box e and the fire gas escape flue f, there
open air channels or ports through which fresh air for supporting combustion
is admitted. The fire bridge provided with recesses m and through these
establishes direct communication between the ash box e and the furnace chamber b.
The said recesses or hollow spaces m of the fire bridge open towards the ash
box and communicate therewith through two pipe-shaped ports n, while towards
the furnace chamber they terminate in slots o.
In the fire gas outlet towards the chimney there is provided an adjustable
damper p, while the width of the channel or passage through which the fire gases
are conducted to the ash box may be varied by means of an adjustable valve or
door g
A pipe which extends into the ash box and is provided with perfora-
tions at the part enclosed within such ash box, serves to admit water or steam
for the production of water gas.
The method of operation of the furnace is as follows:-Upon the grate a
fuel is burnt in the usual way. When the screw blast is set in rotary motion,
with the dampers or valve doors p and q wholly or partly open, the combustion
gases will in part escape through the chimney or flue d, while a portion of them
will be drawn into the ash box e by the suction of the screw blast or fan.
Together with the combustion gases, the screw fan will draw in air through the
air inlets k, which air, upon encountering the fire gases in the space or chamber i,

page_text: will mix with such gases, so that a close mixture of fire gases and air will be
forced into the ash box e by the said screw fan or blast. This mixture of gases
and air, before it passes through the interstices of the grate, and as it comes in'
contact with the water or steam issuing through the perforations of the pipe r,
takes up a certain amount of steam which upon touching the red hot fuel, is
decomposed and causes water gas to be generated.
Through the admixture of fire gases to the fresh air admitted to support com-
bustion, such air is intensely heated, whereby the production of water gas is
facilitated, while the air, on the other hand, cools down the combustion gases
and, by so doing, prevents the screw fan, drawing in the gases, from being injuri-
ously affected by an unduly raised temperature. The water gas is burnt in the
furnace chamber, water being at the same time separated in the form of steam.
The steam so evolved is carried off together with the fire gases, so that these
gases, when they find their way under the grate upon having been mixed with
fresh air, already contain a substantial proportion of steam, and therefore need
absorb but little more water when they come in contact with the steam issuing
from the pipe r. By the proper adjustment of the damper p and the valve or
door 9, the quantity of mixture of smoke and air forced into the ash box by the
screw blast may be regulated at will.
By converting this furnace into a partial gas furnace a flame of far greater
length and more intense heat, and a proportionate increase in the useful effect
or working capacity of the furnace, as compared with an ordinary coal furnace,
will be secured, besides, the permanent filling of the furnace chamber with a
gas burning with a flame, affords the possibility of almost entirely burning the
minute particles of coal, which otherwise-and especially at the time of refilling
the furnace with fuel-would escape in the form of black smoke. Hence the
furnace operates not only economically, but practically without smoke.
A portion of the mixture of combustion gases and air forced into the ash chamber
by the screw blast enters the hollow fire bridge through the pipes n without
passing through the grate bar spaces; and then pass through the slots in the
upper part of the said bridge-it being optional to provide one connected slot
instead of a series-and enter the fire chamber in the direction opposite to that
in which the combustion gases escape; and as, at this stage a portion of the
particles of coal suspended in the said fire chamber are burnt, it will be seen
that this arrangement assists perfect combustion and helps to ensure greater
freedom from smoke.
The furnace represented in Figs. 4 to 6 as being applied to a fire tube boiler,
in no way differs from the tubular boiler furnace just described in so far as its
operation is concerned.
Instead of a single fire chamber, two such chambers b, are provided in this
case, they being formed by the fire tubes or flues of the boiler. The grates a
are fitted within these tubes or flues. The screw blast or fan g, which serves
to draw in the fire gases and the air required to promote combustion, and which
is driven by a motor engine h, is arranged within the fire gas escape flue or
chimney f. In front of the forward orifice of this escape flue there is built a
box or chamber s, which serves to connect the said flue with the ash box or
boxes (as the case may be) e. The pipes serve to admit water or steam into
the said ash boxes e. Air holes or ports admit fresh air, to maintain com-
bustion, into the fire gas escape flue for into the mixing chamber behind the
screw fan g, as the case may be. By the hollow fire bridge 1, a direct communica-
tion is established between the ash chamber e and the furnace chamber b. A
damper p enables the volumes of gases flowing towards the flue or chimney d
to be suitably controlled.
In practice, while the furnace is in use, the fire gases, as usual in flame tube
boilers, flow towards the chimney in the direction of the arrows. When the
screw fan g is in operation it will attract by suction a portion of the gases and
force them, after they have mixed with the air drawn in at the same time through

page_text: the channels k, through the interior of the box s, into the ash boxes e. Here
the mixture of smoke and air, as it comes in contact with the steam discharged
from the pipes r, takes up a certain amount of water.
The mixture of air and gases, thus charged with steam, then passes through the
interstices of the grate and penetrates the layer of red hot fuel, at which juncture
the steam becomes dissociated and water gas is produced. In the furnace chamber,
the water gas is burnt, and reforms steam during its combustion, which steam
is carried off by the fire gases preparatory to being readmitted under the grate
and to partly escaping through the chimney. The mixture of gases and air
admitted through the hollow fire bridge direct into the furnace assists a more
perfect combustion of smoke in the same manner as has been stated in reference
to the tubular boiler furnace.
The furnace hereinabove described may be variously modified without any
departure from the principle of the invention. For example, instead of charging
the mixture of gas and air, itself, with steam, immediately before its passage
through the grate spaces, an opportunity may be afforded to the constituents of
such mixture, i.e. to the combustion gases on the one hand and to the fresh air
used in keeping up combustion, on the other, to absorb adequate quantities of
steam separately, or before they become mixed. Also, it would suffice to mix
water in a finely divided condition either with the fire gases alone, or only with
the air used to support combustion. The arrangement exemplified in the draw-
ings, however, has proved to be particularly advantageous.
Again, instead of drawing in the fire gases at so early a stage as that at which
they flow towards the chimney flue, they may first be allowed to enter such flue,
though the comparative disadvantage which this method would entail lies in the
fact that more powerful suction would in that case be necessary.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. The method of utilizing a mixture of fire gases and fresh air as a vehicle for
the introduction of steam into the fire grates of furnaces in order to effect the
prevention of smoke and the economisation of fuel therein, substantially as
described.
2. In a furnace the combination of a chamber connecting the ash pit (e) and
the channel (f) which leads the fire gases to the chimney, air conduits (k) opening
into that chamber, means adapted to draw fire gases and fresh air through that
chamber and to force same through the fire grates and means to mix water in
a finely divided state with air and fire gases before passing through the grate,
substantially as and for the purpose described.
3. The construction and use of an improved furnace embodying the combination
of a chamber connecting the ash pit and the channel which leads the fire gases
to the chimney, air pipes (k) opening into that chamber, a fan (g) in that chamber
adapted to draw fire gases and fresh air into that chamber and to force the mixture
of same into the ash pit (e), a water pipe (7) located in the ash pit provided with
fine holes adapted to distribute water in a finely divided state, substantially as
and for the purpose described.
4. The construction and use of an improved furnace embodying the combination
of a hollow fire bridge (2) forming a free passage from the ash pit (e) to the fire
place or chamber (6) means for producing a mixture of fire gases, fresh air and
water in a finely divided state in the ash pit, and means to force part of same
through the fire grates, substantially as and for the purpose described.
5. In a new and improved furnace for flame tube boilers the combination
with fire places in the flame tubes of a casing (s) connecting the ash pit (e)
with the channel (f) leading the fire gases to the smoke flue, means to force a
mixture of fire gases and air through said casing into the ash pit and means

page_text: to mix or combine said gases and air with water in a finely divided state before
entering the slits of the grate (a), substantially as and for the purpose described..
6. The construction and use of an improved furnace for the prevention of
smoke and the economization of fuel whereby greater relative quantities of steam
are enabled to be introduced into the furnace chamber without inconvenient:
increase in proportion of moisture present in the mixture of smoke and air, all
substantially as and for the purpose set forth.
Dated the 16th day of December 1899
WM. BROOKES & SON,
55 & 56, Chancery Lane, London,
Agents for the Applicant.