Improvements relating to the Combustion of Fuel in Furnaces and to Apparatus therefor.
Year: 1899

page_text: Date of Application, 2nd May, 1899-Accepted, 24th June, 1899
COMPLETE SPECIFICATION.
Improvements relating to the Combustion of Fuel in Furnaces and to
Apparatus therefor.
I, ADAM HEBERER, of No. 1000, Paru Street, Alameda, in the County of Alameda
and State of California, United States of America, 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 made in burning coal in the furnaces
of steam boilers, and in other similar situations in the arts and manufactures
where heat is to be generated and applied for various useful purposes; and it
relates more especially to a method or process of producing an economical com-
bustion of all the grades of bituminous and lignite coals without the production
of smoke.
This invention is based on the discovery I have made that, in the process of
burning coal of a bituminous character, the escape of the combustible gaseous pro-
ducts in an unconsumed or partially consumed state can be prevented and a
thorough combustion of such products can be effected by excluding or reducing
the draught or current of air from the ash-pit upwards through the body of fuel
to a degree or condition sufficient to retain the volatile and gaseous compounds
in the region of greatest heat when and where they are generated and released
from the solid portion of the fuel, and by delivering and distributing air within
the furnace above the surface of the fuel in sheets or streams downwards against
or in close relation to the combustible products at varying and opposing angles
under sufficient degree of pressure to cause the currents or streams of air to meet
together over the mass of fuel and thereby cover the entire surface of the mass;
the quantity or volume of air so distributed being properly regulated to supply
the required proportion or quantity of oxygen for the complete conversion and
combustion of the combustible products from the bituminous portions of the fuel.
In this process or operation the desired result-that is, the effectual combustion
of the volatile and gaseous compounds without the production of smoke-depends
not only upon supplying air in proper quantity to furnish the necessary volume
of oxygen, but also upon delivering and distributing the air in such intimate
contact with, or relation to these combustible products, when and where they are
set free from the solid portions of the fuel, that the oxygen is compelled to mix
and combine with these combustible compounds before they can decompose, or
precipitate, or condense in the solid form of soot, and thus produce smoke.
And this mixing or mingling of the oxygen with the combustible compounds
must be effected, also, while they are in suitably close relation to the incandescent
fuel or in the region of greatest heat, in order to secure the thorough conversion
of the combustible compounds into carbonic acid gas.
My said invention based on this discovery consists in introducing and distribut-
ing air in sheets or streams downwards against or in close relation to the surface
of the mass of fuel at opposing angles so as to meet together above the surface
of the fuel lying on the grate-surface and entirely cover the same and in regulating

page_text: the upflow of air through the body of fuel: also in delivering and distributing air
under pressure in sheets or streams downwards towards the surface of the fuel
at opposing angles so as to meet together over the surface of the fuel and mingle
with the gaseous compounds while they are retained in the region of greatest
heat, the up-draught of air through the mass of foel being controlled and regulated
in volume or quantity from time to time as required to maintain active combustion
of the solid portions of the fuel and at the same time to avoid forcing the com-
bustible gases away from close proximity to the fuel during the operation.
The invention embraces also a device or apparatus of novel construction for
delivering and distributing air above and beneath the body of fuel on the grate-
surface and for regulating from the outside of the furnner from time to time as
required during the operation the volume or quantity of air so admitted above
and beneath the fuel.
In carrying out this invention exclude or reduce the updraught or flow of
air-currents from beneath the fuel-supporting surface upward through the mass
fuel to an extent or degree sufficient to prevent the too rapid decomposition of
the coal and the too rapid liberation and movement of the volatile and gaseous
elements away from the incandescent mass, thereby holding them in the region of
greatest heat for effective contact and mixture with the oxygen and until there
has been effected a complete combination between these combustible elements and
the oxygen before they escape and are carried over the bridge-wall.
The up-draught should be reduced and regulated to furnish a suitable proportion
of air for maintaining active combustion and an incandescent condition in the
carbonaceous or solid portions of the fuel, and at the same time to avoid such a
degree of upward pressure through the mass of fuel as would tend to force or carry
the gaseous products out of the region of greatest heat while meeting and becoming
mixed with the streams of air descending from above. The quantity of air
admitted under the mass of fuel is determined and regulated by the conditions
existing from time to time in the operation of the furnace, and as these are found
to vary during combustion the supply of air is to be varied to meet the conditions.
An excess or surplus of upwardly-flowing air-currents through the fuel will
be indicated by the presence of smoky vapors in the furnace, or a dull smoky
appearance of the flame: and on the other hand, the lack of a sufficient quantity
of air admitted under the grate-surface at any time will be indicated by the con-
dition of the fire in the solid portions of the mass. This supply of air from below
should be the least quantity that will supply the solid portions of the fuel with
the proper volume of oxygen for combustion of the solid carbonaceous portions
of the fuel.
Atmospheric air in sufficient volume to supply the required proportions of oxygen
is introduced also and distributed from above the mass of fuel in sheets or streams
downwards toward the surface of the fuel at varying and opposing angles from
opposite directions, so as to meet together over the fuel and cover the surface
from front to rear and from side to side of the furnace.
The air is forced through slits or apertures inclining downwards at the required
angle as before described, and under such degree of pressure above that of the
atmosphere that the streams coming from opposite directions will meet together
over the mass of fuel and be brought in intimate contact with the volatile and
gaseous elements from the bituminous portions of the fuel while they are in close
relation or proximity to the incandescent fuel in what is herein designated as
the region of greatest heat. Ordinarily, a pressure of one ounce to the square
inch above atmospheric pressure will be the greatest that will be required, and
in some cases I have secured excellent results with one-half that pressure.
The best amount or degree of pressure to maintain in the furnace at any time
will be readily ascertained by inspecting the conditions of the combustion going
on in the furnace.
As the volume of volatile and gaseous compounds set free from the fuel is
constantly varying it will be necessary to regulate the pressure and the volume

page_text: of air so distributed above the fire; but as low a degree of pressure must be
employed as will produce the desired effect and will insure the free circulation of
the burning gases and heat-products over the bridge-wall and under the boiler
without a too rapid upward movement of the unconverted or partially consumed
gases away from the surface of the fuel.
I have obtained good results in a furnace of ordinary dimensions having about
twenty (20) square feet of fuel-supporting surface, with air-distributing slits or
apertures extending longitudinally over the fuel from front to rear of the furnace,
set at about eighteen (18) inches apart widthwise of the furnace, and about twelve
(12) inches above the fuel surface, the air being supplied to these outlet-apertures
at between one-half an ounce and one ounce pressure above that of the atmosphere.
The conditions existing in the furnace while the combustion is going on, to be
ascertained by inspection through the furnace-door, are the best guide in regulating
and varying the volume of air to secure effective results.
In the accompanyings drawings I have illustrated a construction of coal-burning
furnace for a return-tubular steam-boiler which is specially adapted for the
combustion of bituminous coal without smoke in accordance with my said process.
Figure 1 is a front-elevation partly in transverse-section of a coal-burning
furnace constructed with two fuel-troughs for burning coal under a horizontal
steam-boiler in accordance with the present invention;
Figure is a side-elevation taken from the left-hand side of Figure 1, with
the outer wall or boiler-setting removed, and with portions of the furnace broken
away to disclose the internal construction;
Figure 3 is a horizontal section on the linee Figure 1;
Figure is a top-view partly in horizontal section of the central standing-
partition in Figure 1, the section being taken on the line y y Figure 1;
Figure 5 is an end-elevation of the metal parts of the central standing-partition:
Figure 6 is a vertical transverse section on an enlarged scale of the upper part
of the standing-partition;
Figures and S illustrate a construction of furnace in which the boiler-water
is caused in circulate through the standing-partitions to protect the metal parts
from injury by heat, Figure 7 being a front-elevation principally in cross-section,
and Figure 8 a longitudinal section.
The device or apparatus as herein illustrated consists first of cast-iron plates a a
bb of peculiar form as hereinafter described, and fire-proof bricks or tiles d d
that when assembled and joined together produce a standing-partition B having
inclosed air-spaces or chambers in the hottom or lower part, and air-channels or
passages running perpendicularly upward from the bottom air-chambers to the
top of the partition and to an air-outlet along its top. Through these passages
the air conducted from the chamber in the bottom to the outlet at the top is
carried and caused to circulate between the cast-iron plates forming the body-
part of the device and the bricks or tiles, and these air-passages are so interposed
between the tile and the metal as to protect the metal from warping or cracking
and incidentally to heat the air before it enters the fuel-chamber."
The outlet-apertures at the top or in the upper part running horizontally and
longitudinally of the partition intercept the upright air-conducting passages
between the tiles and the metal and extend also in a direction inclined towards
the fuel-supporting surface above which the partition stands, and at an angle
from the horizontal, so as to direct the air in sheets or streams across the trough
or inclosed space between two partitions and also towards the surface of the mass
of fuel on the grate-bars.
In this air-outlet in the upper part of each partition which is a continuous
slit extending practically the whole length of the partition, a valve or damper
for regulating the size of the aperture is connected with means outside the furnace
whereby the valve can be operated at will and the volume or quantity of air applied
above the fuel can be controlled and regulated at this point of discharge while the
process of combustion is going on in the furnace.

page_text: The second portion of the apparatus consists of a box or casing closing in a
space beneath the grate-bars, forming a separate chamber directly under the
bottom of the trough and shutting off the grate-surface from the ash-pit. Inlet-
apertures in the bottom of this casing admit air from the ash-pit to the grate-
surface in quantity or volume that is under control from the outside of the furnace.
being regulated by a slide m on the bottom of the easing, and a hand-lever »
connected with the slide.
The metal parts or members of the standing-partition are constructed of a form
or shape hest adapted to secure the greatest strength with a minimum of weight
and to prevent them from being injured by the irregular heating to which they
are exposed by virtue of their position in the fire.
-
The principal plate is cast with deep ribs on the back and is provided with
for bolts by which two of these plates are secured together back to back
flanges
to produce a standing-partition, and with deep grooves or channels in the front
face or that side which is turned to the fire. Along the top of the channeled
portion a cap-piece & overhangs or extends over the top edge at proper distance
to leave a narrow slit or aperture extending longitudinally and substantially the
whole length of the plate. The top of the cap-piece is practically flat or horizontal,
but the bottom face is inclined downwards, so as to give the outlet-aperture a
pitch or inclination towards the grate-surface.
Along the bottom the standing-plate is cast with a horizontally-projecting
hanger to support the grate-bars and from this support the front face of the plate
extends perpendicularly upwards for a distance about equal to the thickness of
the carrying bar and the grate-bars that go to form the fuel-supporting surface.
That portion of the front face of the partition with which the fuel lies in direct
contact is formed of a separate and detachable plate extending the full length
of the partition and made somewhat thicker than the other metal part a because
of its being in direct contact with the burning fuel and having greater exposure
to the heat. Spurs or knobs are cast on the back of this plate for the two fold
purpose of strengthening the part and giving the currents of air a zig-zag course
in their passage upward between the plate and the channeled surface behind it.
Alove this detachable plate the front wall of the air-passage is formed of fire-
proof tiles or panels that cover the channels and form a close joint with the plate
along the bottom. These tiles extend to the top of the channets and are beveled
on the top edge at about the same angle as the underside of the overhanging cap.
A sheet-metal backing with its bottom flange turned outwardly to rest on the
plate forms a good support for the tiles.
A protecting top-piece of tile or other suitable fire-proof material is placed
on the top off the cap-piece t Both this protecting covering and the panels that
form the sides of the partition above the level of the burning fuel are adapted to
be replaced when cracked or damaged to a suflicient extent to reduce their
efficiency.
The area of the outlet-slit g into which the channels between the cast-iron back
and the front tiles are arranged to deliver the air is contracted or enlarged at
will by a damper C fitting in the slit and movable between the top and bottom
edges of the slit in a vertical direction, so as to reduce the width of the outlet
when raised towards the overhanging cap, or to enlarge it when moved in the
contrary direction. These movements of the damper are produced from the outside
of the furnace by a hand-levers and a system of pivoted levers and connecting
ruds so arranged as to raise or lower the damper with an equal movement for its
entire length and cause it to maintain a parallel position at all times. The
mechanism represented in Figures 1 and 2 provided for this purpose is composed of
The horizontal levers ! pivoted in fixed brackets 2, the upright rods 3 connecting
the damper-plate C with the levers 1, the shaft 4, the bell crank 4' to which the
inner ends of the levers are connected by an upright arm 5, the rod 6 connecting
the bell-crank with the operating lever s outside the furnace. By this means
the air entering the Burnace through the slits is under complete control, and under

page_text: all adjustments of the device the sheets or streams of air are directed at an angle
downward across the fuel-supporting surface.
The air which is introduced beneath the fuel is under like control from the
outside of the furnace. The apertures in the bottom of the casing are fitted with
a slide, or gridiron-valve m, and this is connected with a hand-lever outside by
the rock-shaft carrying arms S S and a rod 9 connecting the rock-shaft with
the operating-lever. Both sets of air-apertures are thus controlled and regulated
in area from time to time during the operation of the furnace, and the air supplied
to both can be taken from the same source, which in the present arrangement
and application of the improvements is the ash-pit beneath the grate. This
space is closed or sealed up for the time being by providing suitably tight doors
and the air is supplied through a trunk or conductor D) to be connected with a
blower or other means for supplying air.
As thus constructed and fitted together the parts forming the standing sides
of the trough extend from the front-plate of the furnace back to the bridge-wall,
thus dividing the grate-surface into two or more separate troughs according to
the size and capacity of the furnace. When one standing-partition is placed in
the middle of the fire-space to produce two troughs it is constructed of the double
form as shown in Figures 1 and 3, with air-inlets and air-outlets on opposite sides
of the longitudinal center-line to supply and distribute the air separately and
independently over each trough, while the remaining standing sides are formed
of single partitions set against the side-walls of the furnace.
All the dampers that control the air-outlets along the top of the partitions are
connected to a common rock-shaft and operated by one-hand lever, and in like
manner all the slides are arranged to be moved and set by a common lever.
In the construction of furnace illustrated in Figures 7 and 8 the standing-
partitions are formed of water-tubes and tiles instead of solid plates and tiles."
For the fuel-supporting surface A, I use either the ordinary grate-bars (rigure 1)
or a flat perforated plate (Figure 7) extending from the front to the bridge-wall W.
This grate-surface is divided into several separate troughs by upright
partitions B B carried from the front of the furnace back to the rear end and
extending perpendicularly upward from the grate-surface. These partitions are
similarly constructed and a detailed description of one will serve or all.
The walls or sides of each partition are constructed of a number of horizontal
water-tubes 10 10 and hollow-heads or box-like ends 12 12, substantially of rect-
angular shape, into which the ends of all the horizontal tubes are fixed. The
top 12 of the box-end is permanently closed and the bottom is fitted with a grid-
iron-valve or plate formed of a stationary slotted plate G, and the gridiron plate Gi
litted to slide in grooves 16 in the sides of the box. By a longitudinal movement
of this plate the area of the inlet-apertures is increased or diminished.
The water-tubes connected together by the box-ends 12 12 are set in two
parallel rows at intervals apart, and the spaces between all the tubes on the same
side are closed by plates or tiles d d laid against the tubes from the outside with
butt-joints covering the outer sides of all the tubes, the plates being drawn up
and held to place by long bolts and nuts 15.
The open space between the two top-tubes is filled by a block or tile 17 with
curved or recessed sides to fit between the tubes.
The hollow space thus inclosed by the plates or tiles between the two tiers
or rows of water-tubes forms an air-chamber into which air is admitted through
the valve G in the bottom, and from this chamber or space outlets g for the air
are made in the sides of the partition by leaving an open space between the top
tube and the next highest tube in the tier on the same side of the partition: the
aperture being made of suitable form to deflect or turn the stream of air at an
angle towards the bottom of the trough.
9
A plate C with a curved edge is set in the top part of the hollow space pro-
jecting through the slit g and inclined downwards, so that its concave side forms
the roof of the air-chamber; this plate is fastened by bolts 13 against the bottom

page_text: of the block. The function of this plate is to deflect the outgoing currents of air
towards the grate-surface, and when properly placed it should give the air such
an angular direction that the currents or streams from the two opposing partitions
will meet together over the bottom of the trough and at all times above the top
line or level of the fire, so as to confine, baffle, or hold the volatile and gaseous
compounds in proximity to the incandescent fuel. The angle or degree of deflection
of such air-currents is regulated by giving this plate a greater or less degree of
curvature.
The outlet-aperture y should also be situated below the line of the opening at the
rear over the bridge-wall, in order to prevent the volatile and gascons products
as they are generated and released from the surface of the fuel from escaping
underneath the streams of air and so passing out over the bridge-wall, and to
compel these combustible gases to mix and effectively combine with the oxygen of
the air while confined between the sides of the trough.
The water-spaces in the standing partitions are connected into the circulating
system of the boiler by a supply-pipe R carried from the feed-water-pipe neross
the rear of the furnace behind the bridge-wall and connected to the hollow end
of each partition by a short pipe or coupling 14 through which the water is made
to circulate through the lower ones of the horizontal water-tubes to the front end
and return through the upper ones to the rear box or end of the partition, at
which end an outlet-pipe 14 connects the water-space of each partition with a
pipe leading into the upper part of the water-space of the boiler. Instead of con-
meeting the water-spaces in the hollow end 12 of the troughs with the feed-water
pipe they can be connected into the feed-space of the boiler by carrying a pipe I
from the lowest part of the water-space downward behind and through the bridge
wall and coupling the inlet-pipe 14 to it, a check-valve R being placed in the
pipe R. This arrangement of tubes for carrying the circulation of the boiler.
water through the water-jackets of the troughs is shown in Figure S.
A horizontal partition 18 in the hollow end of the partition above the water-
inlet divides the hollow space into an inlet-side and an outlet-side, and in this
manner a circulation of water is maintained through the water-spaces of the stund
ing sides of the troughs from end to end. A suitable valve R is placed in the
water-pipe for regulating the supply of water.
To the same hand-lever N that operates the slide-valves G that control the air-
inlets in the bottom of the standing partitions are connected the gridiron-valves m
by a common rock-shaft II having an arm 24 in the middle from which a connect-
ing-rod 25 is carried to the hand-lever N. Each slide m is connected by a link 26 to a
separate arm 27 on the shaft II. and the slides G are connected to separate arms 28
on the same shaft by a connecting-rod 29 composed of two sections united by a
turn-buckle 30, so that the lead of the slide can be regulated to vary the area
of the inlet-openings Gover that of the lower slide m controlling the admission
of air into the box D.
By one movement of the hand-lever both valves are moved and set to increase
or reduce the area of the two air-inlets, and by adjusting the points of connection
between the rod 25 and the lever N up or down with respect to the fulerum N
of the lever the length of throw of the slides is varied as cirenmistances are found
to require a greater or less increase in the quantity of air introduced.
The air being introduced first into the ash-pit is thus admitted for distribution
into the air-boxes D under the grate-surface and also into the standing-partitions
through the inlets G. The supply of air under required pressure is maintained
by connecting the air-space in the ash-pit with an air-blower or other suitable
apparatus, such as a pressure-fan, hy means of an air-pipe D carried through the
side of the furnace.
The fire-chamber is divided in this manner into as many separate fuel-troughs
as the area of the grate-surface may be found to require; and the number is

page_text: governed by the width of the grate-surface between the standing partitions that
can be covered by the sheets of air delivered from the opposite sides of the trough.
The lower the pressure and volume of air at the outlet-apertures consistent with
the proper covering of the fuel-surface and the thorough mingling of the gaseous
products and the air while in close relation to the surface of the burning fuel
the better the results attained.
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 1 claim
is-
1 The improvement in the combustion of coal which consists in delivering
and distributing air in sheets at varying angles downwards over the mass of fuel
and in close relation to the surface thereof and so as to cover the surface and in
regulating the flow of air upwards through the fuel-supporting surface as required.
2:The improvement in the combustion of coal which consists in delivering
air under pressure in sheets at varying angles over the mass of fuel and in close
relation to the surface thereof so as to meet together and cover the entire mass of
fuel and in regulating the flow of air from beneath upwards through the fuel.
3: In a furnace for burning coal the combination with a fuel-supporting
surface of means for delivering air in sheets at varying angles downward from
opposite directions over the surface of the fuel so as to meet together and cover
the entire surface of the mass of fuel means for introducing air beneath the fuel-
supporting surface and means for regulating and varying at will from the outside
of the furnace during the operation the quantity of air so distributed above and
beneath the mass of fuel.
4: In a furnace for burning coal the combination of a fuel-supporting surface
hollow standing partitions dividing the fuel-surface into fuel-troughs air-inlets in
the standing-partitions connected with a source of supply outside the furnace
air-outlets in the sides of the standing-partitions situated above the surface of
the mass of fuel having inclined throats adapted to deliver the air in sheets at
angles across the trough and towards the surface of the fuel as described so as to
cover the surface thereof air-outlets beneath the hottom of the fuel-supporting
surface valves adapted to control the air-delivering apertures above and beneath
the fuel-supporting surface and means for regulating said valves at will from the
outside of the furnace as required.
11
1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, Loudon, W.C.,
Agents for the Applicant.