Improvements in the Method of Burning and Controlling the Combustion of Solid Fuel, and in Hearths or Furnaces therefor.
Year: 1893

page_text: Date of Application, 28th Aug., 1893
Complete Specification Left, 24th May, 1894-Accepted, 28th July, 1894
PROVISIONAL SPECIFICATION.
Improvements in the Method of Burning and Controlling the
Combustion of Solid Fuel, and in Hearths or Furnaces therefor.
I, ROBERT NOBEL, of Getå, Åby, in the Kingdom of Sweden, Gentleman, do
hereby declare the nature of this invention to be as follows :—
With the heretofore usual manner of supplying air for the combustion of solid
fuel, it is in most hearths and furnaces not practicable, except within certain very
Darrow limits, to control the rate of consumption of fuel without impairing the
completeness of the combustion to a very considerable extent.
Now my invention relates to a method by which the rate of consumption of fuel
can be regulated within considerable limits without thereby impairing the com-
pleteness of the combustion. According to my invention the air required for
combustion is supplied to the fuel at two places, viz., partly in the chamber that
contains the fuel, the fuel chamber, and partly in the outlet through which the
gases generated in the said chamber escape and at a point thereof where the
temperature of the gases is still high enough to cause ignition on meeting with
the air. The first supply of air, viz. that admitted to the fuel chamber is such as
to cause only an incomplete combustion in this chamber and by the heat generated
thereby to produce a dry distillation of a part of the fuel whilst the second supply
of air viz. that admitted to the gases generated by the said combustion, at or after
their escape from the fuel chamber, is such as is necessary to effect the complete
combustion of the gases without affecting the rate of consumption of fuel in the
fuel-chamber by the first supply of air.
According to this method, the rate of consumption of fuel will be capable of
being very exactly controlled by increasing or decreasing the first supply of air,
without thereby depriving the gases of any part of the air required for their
complete combustion, which is given to them by the second supply of air.
In the construction of hearth or furnace necessary for the above named purpose,
the fuel-chamber forms a kind of gas generator and the really useful combustion is
effected outside the same at the place of the second supply of air, the location of
which place may in some measure be modified according to requirements. This
construction differs essentially from the arrangements, occasionally to be met
with, in which a small quantity of air is introduced into the furnace flue in
order to consume the combustible gases which may pass off unconsumed from the
hearth.
It is very advantageous, for the completeness of the combustion, to heat the air,
especially the second portion or supply, before admixture with the gases to effect
their complete combustion, the higher the temperature to which the air is heated,
the better. For the purpose of heating the air supply several known arrangements
may be used; for instance, passages formed through the warmer parts of the walls
of the furnace, or tubes arranged to pass through suitably heated parts of the fuel
chamber. An arrangement which has been found to answer well in practice is to
pass the air through hollow grate-bars which open just at the desired point in the
gas outlet from the fuel chamber.
My invention may be applied to furnaces for a great variety of almost all
purposes where heat is required such as for example heating boilers, heating rooms
and the like, boiling food. It may be used with all kinds of solid fuel, but I prefer
to employ combustibles that produce a considerable amount of flame. Two or more
kinds of fuel mixed together may also be employed.

page_text: tees according to my invention that have been found to
give satisfactory results in practice.
Fig. 1 shows a longitudinal vertical section and
Fig. 2 a horizontal section of one construction.
Figs. 3 and 4 show longitudinal and cross sections, and
Fig. 5 a horizontal section, of a modified construction of furnace.
Fig. 6 shows a vertical and Fig. 7 a horizontal section of the lower part of
another arrangement of furnace.
Figs. 8 and 9 show similar sections of a modified construction of the furnace
represented in Figs. 6 and 7.
Figs. 10 and 11 show in longitudinal vertical section and in cross section
respectively and
Figs. 12 and 13 in longitudinal vertical section and in horizontal section
respectively two modifications of a construction of furnace especially adapted
for coal.
Figs. 14 and 15 show in vertical longitudinal section and in cross section
respectively another construction of furnace according to this invention.
In the several figs. a is the fuel chamber, which is to be closed; b the ash pit,
which is also to be closed; and c the flue leading to the place where the heat is to
be utilized, or to the chimney. d are the outlets for the gases escaping from the
fuel-chamber. e are the inlets for the air supplied to the fuel-chamber and f the
inlets for the air to be mixed the gases escaping through the outlets d. 9 is
the opening through which the fuel is charged or fed: hand i are closely fitting
doors for the fuel-chamber and the ash-pit respectively.
Figs. 1 and 2 represent a furnace to be fed with wood in large pieces or with
mixed fuel. Unsplit logs, branches, and roots may advantageously be used in the
same. In this furnace the fuel-chamber a is shown as provided with only one air-
inlet e, to the closed fuel chamber a though it is obvious that more than one may be
provided. Through the bottom of the fuel chamber a there is formed an outlet d
for the generated gases and into this outlet open four air-inlets f for the final supply
of air to effect complete combustion. This air flows through passages formed in the
brick-work of the furnace as shown and whereby such air is heated. If the
dimensions of the furnace are not very great a smaller number of the said air-
inlets will be sufficient for the purpose.
Figs. 3, 4, and 5 represent a furnace which has proved suitable for purposes
where less heat has been required, for instance for heating a room. In this furnace
the bottom of the fuel-chamber is provided with several slits or perforations d for
the escape of the generated gases. Several air inlets e lead into the fuel chamber a
from a channel or passage & arranged in one of the walls; and in the wall of each
gas-cutlet d there is an air-inlet f issuing from a channel arranged in the
other wall.
Figs. 6 and 7 show a construction of furnace provided with several gas outlets d
in the bottom and three air-inlets e into the fuel-chamber a. The air-inlets fin
the gas-outlets d are here arranged in the bottom of tubes m placed across the said
gas-outlets.
Figs. 8 and 9 represent a similar construction of furnace, which differs from that
represented in Figs. 6 and 7 only in the fact that the air-inlets fare here arranged
in the bottom of a tube m¹ extending across all of the gas-outlets.
Figs. 10 to 13 inclusive represent a construction of furnace or hearth in which
hollow grate-bars n are used, partly for carrying the fuel, and partly for conveying
and heating the portion of the air to be led to the gases escaping from the fuel-
chamber a. These gases are here carried off through an outlet d arranged above
the bottom formed by the grate-bars n. The hearth represented in Figs. 10 and 11
is shown with three air-inlets e and as applied to the flue of a boiler o.
tubular grate-bars n communicate at one end with the open air and at the other.
end with the outlet for the gases generated in the fuel-chamber, and at the latter.
The

page_text: end they are bent upwards in order to compel the air to mix with the escaping
gases. The feed-opening for the fuel is shown arranged in the upper part of the
furnace.
The hearth represented in Figs. 12 and 13, and shown as applied to the heating
of a stove, has two air-inlets e into the fuel-chamber a. The hollow grate-bars n
are straight, but the bottom of the flue in front of their ends is made upwardly
inclined for securing a better mixture of the air with the escaping gases.
The
fire-door is shown placed at the side.
When hollow grate bars are employed the supply of air to the fuel in the fuel
chamber a may be arranged beneath the grate bars, but for the purpose of
rendering these bars more durable it is more advantageous to supply the air from a
point above them as shown in the drawings. The hollow grate-bars may be of
any desired cross section but their inner cross-sectional area must be sufficient for
the supply of enough air to effect complete combustion of the desired amount
of gas.
Through the grate-bars, which open into the flue, there passes always a current
of air, that increases when the draught becomes stronger in consequence of
increased combustion in the fuel-chamber. This current of air serves to prevent
the destruction of the grate bars. Another cause contributing to protect the grate-
bars, is due to the combustion being comparatively small in the fuel chamber proper,
and that the chief combustion of the fuel takes place after the fuel is brought into
the form of gas and after the gases have escaped from the fuel chamber.
latter fact prevents also the formation of clinker in the fuel chamber, and thus also
contributes to the protection of the grate-bars.
The
In the furnace illustrated in Figs. 14 and 15 the air is introduced under the
bottom of the furna, through one or several channels or conduits p, which may be
provided with dam ers if desired. is a cavity or pocket for collecting ashes that
might otherwise o struct the channel or channels p. This cavity is furnished with
an opening at on side of the furnace only and the mouth is closed by a door. The
ashes on the floor hearth of the furnace are removed through an opening closed
by the door i. The air inlet e to the fuel chamber a may be made in the said door,
and be provid with the necessary air regulator.
Dated
is 28th day of August 1893.
R. NOBEL,
By L. W., per F. B.
COMPLETE SPECIFICATION.
Improvements in the Method of Burning and Controlling the
Combustion of Solid Fuel, and in Hearths or Furnaces therefor.
I, ROBERT NOBEL, of Getå Åby, in the Kingdom of Sweden, Gentleman,
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 :--
With the heretofore usual manner of supplying air for the combustion of solid
fuel, it is in most hearths and furnaces not practicable, except within certain very
narrow limits, to control the rate of consumption of fuel without impairing the
completeness of the combustion to a very considerable extent.
Now my invention relates to a method by which the rate of consumption of fuel
can be regulated within considerable limits without thereby impairing the com-
pleteness of the combustion. According to my invention the air required for
combustion is supplied to the fuel at two places, viz., partly in the chamber that
contains the fuel, the fuel chamber, and partly in the outlet through which the
gases generated in the said chamber escape and at a point thereof where the

page_text: temperature of the gases is still high enough to cause ignition on meeting with
the air. The first supply of air, viz., that admitted to the fuel chamber is such as
to cause only an incomplete combustion in this chamber and by the heat generated
thereby to produce a dry distillation of a part of the fuel whilst the second supply
of air viz., that admitted to the gases generated by the said combustion, at or after
their escape from the fuel chamber, is such as is necessary to effect the complete
combustion of the gases without affecting the rate of consumption of fuel in the
fuel-chamber by the first supply of air.
According to this method, the rate of consumption of fuel will be capable of
being very exactly controlled by increasing or decreasing the first supply of air,
without thereby depriving the gases of any part of the air required for their
complete combustion, which is given to them by the second supply of air.
In the construction of hearth or furnace necessary for the above named purpose,
the fuel-chamber forms a kind of gas generator and the really useful combustion is
effected outside the same at the place of the second supply of air, the location of
which place inay in some measure be modified according to requirements. This
construction differs essentially from the arrangements, occasionally to be met
with, in which a small quantity of air is introduced into the furnace flue in
order to consume the combustible gases which may pass off unconsumed from
the hearth.
It is very advantageous, for the completeness of the combustion, to heat the
air, especially the second portion or supply, before admixture with the gases to
effect their complete combustion, the higher the temperature to which the air is
heated, the better. For the purpose of heating the air supply several known
arrangements may be used; for instance, passages formed through the warmer
parts of the walls of the furnace or tubes arranged to pass through suitably heated
parts of the fuel chamber. An arrangement which has been found to answer well
in practice is to pass the air through hollow grate bars which open just at the
desired point in the gas ontlet from the fuel chamber.
My invention may be applied to furnaces for a great variety of almost all
purposes where heat is required such as for example heating boilers, heating rooms
and the like, boiling food. It may be used with all kinds of solid fuel, but I prefer
to employ combustibles that produce a considerable amount of flame. Two or
more kinds of fuel mixed together may also be employed.
The drawings filed with my Provisional Specification illustrate by way of
example only, several constructions of hearths or furnaces according to my invention
that have been found to give satisfactory results in practice.
Fig. 1 shows a longitudinal vertical section and
Fig. 2 a horizontal section of one construction.
Figs. 3 and 4 show longitudinal and cross sections, and
Fig. 5 a horizontal section, of a modified construction of furnace.
Fig. 6 shows a vertical and Fig. 7 a horizontal section of the lower part of
another arrangement of furnace.
Figs. 8 and 9 show similar sections of a modified construction of the furnace
represented in Figs. 6 and 7.
Figs. 10 and 11 show in longitudinal vertical section and in cross section
respectively and
Figs. 12 and 13 in longitudinal vertical section and in horizontal section
respectively two modifications of a construction of furnace especially adapted
for coal.
Figs. 14 and 15 show in vertical longitudinal section and in cross section
respectively another construction of furnace according to this invention.
In the several figs. a is the fuel chamber, which is to be closed; 6 the ash pit,
which is also to be closed; and c the flue leading to the place where the heat is to
be utilized, or to the chimney. d are the outlets for the gases escaping from the
fuel-chamber. e are the inlets for the air supplied to the fuel-chamber and f the

page_text: inlets for the air to be mixed with the gases escaping through the outlets d. 9 iş
the opening through which the fuel is charged or fed. h and i are closely fitting
doors for the fuel-chamber and the ash-pit respectively.
Figs. 1 and 2 represent a furnace to be fed with wood in large pieces or with
mixed fuel. Unsplit logs, branches, and roots may advantageously be used in the
same. In this furnace the fuel chamber a is shown as provided with only one air-
inlet e, to the closed fuel chamber a though it is obvious that more than one may
be provided. Through the bottom of the fuel chamber a there is formed an
outlet d for the generated gases and into this outlet open four air-inlets f for the
final supply of air to effect complete combustion. This air flows through passages
formed in the brick-work of the furnace as shown and whereby such air is heated.
If the dimensions of the furnace are not very great a smaller number of the said
air-inlets will be sufficient for the purpose.
Figs. 3, 4 and 5 represent a furnace which has proved suitable for purposes
where less heat has been required, for instance for heating a room. In this furnace
the bottom of the fuel chamber is provided with several slits or perforations d for
the escape of the generated gases. Several air inlets e lead into the fuel chamber a
from a channel or passage k arranged in one of the walls; and in the wall of each.
gas-outlet there is an air-inlet f issuing from a channel arranged in the
other wall.
Figs. 6 and 7 show a construction of furnace provided with several gas outlets d
in the bottom and three air-inlets e into the fuel-chamber a. The air-inlets f in the
gas outlets d are here arranged in the bottom of tubes m placed across the said gas
outlets.
Figs. 8 and 9 represent a similar construction of furnace, which differs from that
represented in Figs. 6 and 7 only in the fact that the air-inlets fare here arranged.
in the bottom of a tube m' extending across all of the gas outlets.
Figs. 10 to 13 inclusive represent a construction of furnace or hearth in which
hollow grate-bars n are used, partly for carrying the fuel, and partly for conveying
and heating the portion of the air to be led to the gases escaping from the fuel-
chamber a.
These gases are here carried off through an outlet d arranged above.
the bottom formed by the grate-bars n. The hearth represented in Figs. 10 and 11
is shown with three air-inlets e and as applied to the flue of a boiler o.
tubular grate-bars n communicate at one end with the open air and at the other
end with the outlet for the gases generated in the fuel chamber, and at the latter
end they are bent upwards in order to compel the air to mix with the escaping
gases. The feed-opening for the fuel is shown arranged in the upper part of the
furnace.
The
The hearth represented in Figs. 12 and 13, and shown as applied to the heating:
of a stove, has two air-inlets e into the fuel-chamber a. The hollow grate-bars n
are straight, but the bottom of the flue in front of their ends is made upwardly
inclined for securing a better mixture of the air with the escaping gases. The
fire-door is shown placed at the side.
When hollow grate bars are employed the supply of air to the fuel in the fuel
chamber a may be arranged beneath the grate bars, but for the purpose of rendering
these bars more durable it is more advantageous to supply the air from a point
above them as shown in the drawings. The hollow grate-bars may be of any
desired cross section but their inner cross-sectional area must be sufficient for
the supply of enough air to effect complete combustion of the desired amount of gas..
Through the grate-bars, which open into the flue, there passes always a current
of air, that increases when the draught becomes stronger in consequence of
increased combustion in the fuel-chamber. This current of air serves to prevent.
the destruction of the grate-bars. Another cause contributing to protect the
grate-bars, is due to the combustion being comparatively small in the fuel chamber
proper, and that the chief combustion of the fuel takes place after the fuel is
brought into the form of gas and after the gases have escaped from the fuel

page_text: chamber. The latter fact prevents also the formation of clinker in the fuel
chamber, and thus also contributes to the protection of the grate-bars.
In the furnace illustrated in Figs. 14 and 15 the air is introduced under the
bottom of the furnace through one or several channels or conduits p, which may be
provided with dampers if desired. 9 is a cavity or pocket for collecting ashes that
might otherwise obstruct the channel or channels p. This cavity is furnished with
an opening at one side of the furnace only and the mouth is closed by a door. The
ashes on the floor or hearth of the furnace are removed through an opening closed
by the door i. The air inlet e to the fuel chamber a may be made in the said door,
and be provided with the necessary air regulator.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
--
1. The herein before described method of producing a complete and at the same
time controllable combustion of solid fuel, by supplying a controllable amount of
air to the fuel whilst in a closed fuel-chamber and supplying a sufficient amount of
(preferably heated) air to the generated gases escaping from the fuel-chamber, at a
place where the temperature of these gases is still sufficiently high to cause their
ignition by contact with such air, so that by means of the first and ordinarily
smaller supply of air, the rate of consumption of fuel can be regulated and by the
second and greater supply of air a complete combustion of the combustible gases
escaping from the fuel-chamber can be effected without increasing the rate of
ccmbustion in the fuel-chamber proper by the said second supply of air, as set forth.
2. A hearth or furnace comprising a closed fuel-chamber, having one or more
controllable air-inlets in the lower part thereof, one or more outlets for the gases
generated in the fuel-chamber, these outlets being located in the lower part, it
may be in the bottom, of the said fuel-chamber, and one or more additional, and it
may be controllable, air inlets opening into the above mentioned gas outlets at a
point where the gases still have a sufficiently high temperature to cause their
ignition by contact with the additional supply of air, the arrangement being such
that by the first mentioned air inlet or inlets a quantity of air can be admitted to
the fuel chamber such as will cause incomplete combustion and dry distillation of
the fuel, the rate of combustion being capable of regulation by varying the supply
of air through the said opening or openings, and that by the secondly mentioned
air inlet or inlets a sufficient amount of air can be admitted to the gases escaping
from the fuel chamber to effect their complete combustion without thereby
increasing the rate of combustion in the fuel-chamber, substantially as herein
described.
3. A hearth or furnace for the combustion of solid fuel according to the method
specified in Claim 1, in which the bottom of the fuel-chamber is formed of hollow
grate-bars each of which communicates at one end with the open air and at the
other end with the flue, into which the gases escaping from the fuel chamber pass
substantially as and for the purposes hereinbefore described.
4. My improved hearths or furnaces constructed and arranged substantially as
herein before described with reference respectively to and shown in Figs. 1 & 2; in
Figs. 3, 4, & 5; in Figs. 6 & 7; in Figs. 8 & 9; in Figs. 10 & 11; in Figs. 12
12, and in Figs 14 & 15 of the drawings
&
Dated this 24th day of May 1894.
For the Applicant,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.