Note: Descriptions are shown in the official language in which they were submitted.
1060Z71
Tllis al)pllcati.on is a divl.sion of Canadian Patent
~pplica~l.on Serial l~o. 263,87~ filed October 21, 1976.
This invention i5 in the field of pulverulent material
metering and supp].y systcms and is specifically directed in.its
preferred embodiment to a solid fuel metering and delivery
system for providing a metered quantity of comminuted coal or similar
solid particle fuel to a kiln, boiler or similar combustion chamber.
One of the reasons that petroleum based fuels have
achieved widespread acceptance and use is the fact that they can be
fed to a burner assembly at a closely controlled rate for achieving
optimum performance in the particular installation in which they
are used. While solid fuels such as coal have substantial advantages
in terms of dollar costs per BTU, such advantages have been greatly
outweighed by the inability to control flow in small quantities to
the burning area in the accurate manner achieved by petroleum based
systems. This drawback has resulted in the ceramic industry relying
almost totally upon petroleum based fuels such as natural gas for
the fueling of kilns. Projected shortages of natural.gas and the
ever increasing costs of all petroleum based fuels have resulted
in a great need for a fuel delivery and metering system f~r coal
that can provide the high degree of control necessary in many
industrial uses such as the ceramic industry in orde.r to avoid the
high cost and scarcity of petroleum based fuel. In fact, the need
for a satisfactory coal delivery and metering system is particularly
critical in the ceramic industry in which kilns require a large
number of small burners each of which must provide an accurate
temperature control in a finite zone in order to provide a satis-
factory product and the high price and likely inavailability of
petroleum based fuels in the future
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ders the prov-lsion of a satisfactory coal burner system
esscnLial to tllc .survival of the ceramic lndustry.
~ ddlt~onally, many other industries such as the chemical,
pharmaceutical and food product industries require means capable
of providing accurate quantities of powdered or commlnuted materials.
The inability to provide a continuous me~ered flow of such
materials in small quantities frequently results in such industries
having to employ the batch method of mixing compounds in which the
components are weighed and then mixed. The present invention
provides simple means.which can be used to accurately provide a
metered continuous flow of pulverulent or comminuted material in
a continuous mixing process. The terms "pu~verulent" and
"comminuted" are used interchangeably throughout the specification
and claims of this applica~ion in their broadest sense to include
any solid powdery type material that is capable of being free-
flowing. Examples of such materials include finely ground coal,
coke, sand abrasive grits9 pelletized plastics, flour, cornmeal,
pigments, talc, granulated solids such as sugar or salt, organic
compounds and many other materials of like nature which are too
numerous to mention.
The invention according to the parent application referred
to hereinabove may be broadly defined as a method of providing a
metered flow of comminuted material to a desired location, the method
consisting of providing a surface of repose of the comminuted
material oriented at approximately 45~ from horizontal, causing an
ambient air stream to impinge upon the surface of repose to entrain
comminuted material there~rom and convey the material to the desired
location.
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The mcthod of the parent application may be carried out
by the inventlon herein, broadly defined as a pulverulent matcrial
metering and delivery system for feeding mctcrcd quantities of
pulverulent material comprising a sourcc of pulveru]ent particles,
a so~lrce of compressed air, conduit means extending between the
source of pulverulent particlcs and a delivery chclnlber, the source
of pulverulent particlcs including a fecd pipc having a vertical
component of axial orientation and upper and lower ends, a metering
conduit connected to Lhe lowcr end of the feed pipe and having a
horizontal component of axial orientation, tlle feed pipe being full
of pulveru]ent particles whicll flow outwardly into tbe metering
conduit to provide a surface of repose of the pulvcrulen~ particles
in the metering conduit, a venturi housing including a venturi jet,
the venturi housing being connected to tl-e metering conduit at an
end opposite the end conncction of the metering conduit to the feed
pipe and an openillg in the venturi housing for permitting the dis-
charge oI gas and pulverulent particles from the ven~lri housing
into the delivery chamber.
Additionally, there may be provided air injection means
in the form a feed air opening over the surface of repose and a
bleed air opening spaced from the feed air opening. The feed air
opening and the bleed air opening are both connected to pipe risers
on which interconnected feed air and bleed air control valves are
mounted. A manually operable inverse adjustment means connects
the feed air valve and the bleed air valve to adjust their degree
of opening in an inverse manner. In other words, when the feed air
- valve is moved toward an open condition, the bleed air valve is
moved toward a closed condition by a li~e or proportional amount.
It is the foregoing inverse operational rcl.~tionship of the feed
air valve and the bleed air valve which enables a highly
accurate metering of the comminuted partic]es.
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I'he downsl-rcam cnd of the metering condui.t is connectcd
to the venturl llousing in whicll an air injector is provlded for
creating a press~re drop through the feed air valve, the bleed air
valve and the meterlng conduit so that ambi.ent air flows through
the feed air valve to engage the surface of repose and entrain
particles therefrolll. The mixture of air and particles is sprayed
by an injector into a kiln or other area. The amount of air injected
by the venturi serves to vary the velocity oE the particle and air
mixture through the injector to vary the depth of penetration in
the chamber and also serves to increase the maximum feed rate
capacity of the system. However, the metering of the particles is
accomplished by the operation of the feed air control valve and the
bleed air controL valve with maximum feed rate occurring when the
bleed air control valve is complete~y closed and the feed air
control valve is completely open. It is then possible to vary the
particles flow in a linear manner by operation of the control
valve.
A better understanding of the manner in which the
preferred embodiment of the invention accomplishes the objects of
the invention will be achieved when the following written discussion
is consioered in conjunction with the appended drawings in which:
Figure 1 is a perspective flow diagram of the preferred
embodiment with portions removed for clarity;
Figure 2 is a bisecting sectional view of the feed
metering portion of the preferred embodiment; and
Figure 3 is a bisecting sectional view of the venturi
and injector portions of the preferred embodiment.
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The preferred embodiment of the invention illustrated
in the drawings is directed to a fuel supply system for a
kiln orthe like and includes a feed hopper lO in which a
supply 11 of pulverized coal is provided. It has been found
that minus 8 mesh coal of less than 3% moisture content
provides highly satisfactory operation with the pulverized
coal flow from the hopper flowing through a ball valve 12
which can be closed by a handle 13 when necessary to discon-
tinue the feed of coal from the hopper for enabling repair
or other maintenance operations on the remainder of the
system.
A vertically extending feed p~pe 14 has its upper
end connected to the ball valve 12 and has its lower end
connected by a smooth welded right angle junction to the
upstream end of a horizontal metering conduit 16. The infeed
pipe 14 and metering conduit 16 are formed of one inch black
iron pipe cut and welded together into a smooth right angle
elbow defining their junction so that gravity causes the
powdered coal to flow into the end of conduit 16 and provide
a stationary surface of repose 17 as shown in Figure 2.
The metering conduit 16 is provided with a feed air
opening 18 positioned in its top surface above the surface of
repose 17 of the coal as also shown in Figure 2. A bleed air
opening 22 is spaced from the feed air opening 18 with the
openings 18 and 22 being respectively communicating with pipe
risers 24 and 26 which are welded to the metering conduit
16. A feed air control valve 28 is mounted on the upper end
of the pipe riser 24 and a bleed air control valve 30 is
mounted on the upper end of the pipe riser 26 with the opposite
sides of the valves 28 and 30 being open to the atmosphere.
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~060271
A manually operable valve interconnection assembly
32 is connected between the valves 28 and 30 for simultaneously
opening and closing the gates 28' and 30' of valves 28 and
30 in an inverse manner. In other words, operation of the
valve interconnection assembly 32 in a direction to open valve
28 will serve to cause closure of valve 30. In like manner,
opening of valve 30 results in the closure of valve member 28.
The valves 28 and 30 are gate valves with non-rising valve
stems and are of identical construction. A reducer 34 is !~l
mounted on the end of metering conduit 16 opposite its junc-
ture with the vertical infeed pipe 14 with a flexible hose 36
being connected by means of an adapter 38 to the metering
conduit in an obvious manner.
The opposite end of the hose 36 is connected to a ven-
turi housing 40 in which a venturi jet 42 is provided as shown
in Figure 3. Venturi jet 42 is connected by a hose 44 to a
source of compressed air consisting of a blower air header
46 connected to a butterfly valve 48 and pipe 50 to the hose
member 44. All flexible hose connections are made by means
of an adapter identical to adapter 38 in an obvious manner.
Air injected by the venturi 42 lowers the pressure in the
housing 40 in a well-known manner and induces ambient air flow
through valve 28 and 30 into conduit 16. The jet from venturi
42 and coal powder from the surface 17 and induced air are
directed into the upstream end of an injector lance 52
mounted in a lance holder 54 in a wall 56 of a kiln with second-
ary combustion air being supplied to the holder by hose 61.
The lance holder 54 is in the form of a straight pipe closed
at the back end except for an axial opening through which the
injector lance is inserted. The axial opening serves as a
rear support for the lance while a small section of pipe 63
mounted by
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a spider arrangement 65 downstream in the lance holder provides
the forward support to keep the lance centered. An opening is
provided near the rear of the lance holder at approximately 90
to the axis of the lance and intersecting the lance holder at its
periphery. The purpose of this opening is to receive secondary
combustion air from hose 61 which air flows around the lance into
the combustion chamber ln a swirling motion and also keeps the
lance and lance holder cool.
The compressed air supply system can be a blower or an
air compressor depending upon the feed requirements of the particular
installation. In the preferred embodiment, the system works
quite well with the blower capable of providing pressure no
greater than 55 inches of water column downstream of the butterfly
valve 48 with satisfactory operation at a pressure as low as 10
ounces per square inch being possible.
The employment of the flexible hose members 36 and 44 is
not essential to the operation of the device; however, the
flexibility provided by the hose members permits the injector
lance 52 to be positioned as desired in one of several openings
in the kiln wall and to also be easily positioned axially with
respect to the kiln wall.
The injector lance 52 must be of sufficient length as to
be capable of carrying the fuel mixture through the wall of the
kiln to the desired point of in~ection into the combustion chamber.
The lance should be made of material having sufficient resistance
to heat to withstand the high temperatures generated in the
combustion chamber in which it is used. Standard iron, stainless
steel, or ceramic tubing are suitable materials for the lance in
most operations.
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In operation, motive air is provided from the header
46 to valve 48, conduit 50 and hose 44 to the venturi nozzle
42 from which it is ejected into the lance member 52. Opera-
tion of nozzle 42 creates a lowered pressure in the venturi
housing 40 which draws air through the valves 28 and 30,
metering conduit 16 and hose 36 into housing 40.
The air induced through the feed air opening 18 onto
the surface of repose 17 of the coal engages the minute coal
particles and entrains them in the air stream at the left end
of the metering conduit 16. The powdered coal is contin-
uously replenished downwardly through the infeed pipe 14 so
that the surface 17 essentially remains in the same position
at all times so as to be impinged upon,by the air flowing through
the opening 18. Additional air is induced through the bleed
air hole 22 with the bleed air mixing with the air and coal
particles and flowing through the hose 36 into the venturi
housing 40 in an obvious manner. It should be understood
that the total amount of air induced through the valves 28
and 30 is constant with the only variation being in the ratio
of the amount provided by each of the individual valve members.
Maximum fuel flow is achieved when the valve 30 is closed and
all of the air is induced via the valve member 28. Minimum
flow is obtained when valve 28 is closed and the air is
induced through the valve 30. Consequently, by manually ad-
justing the valve interconnecting member 32 or by the use of
automatic controls, the amount of fuel fed to the injector
lance 52 can be varied accurately in accordance with the par-
ticular operation being performed.
The amount of air injected by the nozzle 42 remains
constant but can be increased or decreased in order to adjust
the feed range of the entire assembly.
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There is a linear relationship between the degree of
opening of valve 28 and the air being induced by the feed air
opening 18 and the resultant rate at which the fuel is con-
veyed away frcmthe surface of repose 17.
Any increase in the flow of motive air through the
venturi 42 increases the maximum feed rate capability of the
system and simultaneously increases the exit velocity of the
gas and solid fuel particles from the injector lance 52.
Such an increase in the motive air flow through the venturi
does not have any effect whatsoever on the ability of the
solid fuel feeder assembly associated with the metering con-
duit 16 to control the amount of solid fuel from a maximum
feed rate to a minumum flow rate in a linear manner by opera-
tion of the valves28 a~d 30 as previously discussed.
It is desirable that the opening 22 be relatively close
to the opening 18 in order to prevent the occurrence of a
buildup or mound of powdered coal between these two openings
under low flow conditions. Moreover, a close positioning of
the bleed air opening 22 to the fuel air opening 18 also
provides greater linearity in the flow rate variation and
valve opening under low flow conditions. In a typical appli-
cation, pipe 14 and conduit 16 are one inch pipe with the
spaces between the openings 18 and 22 being 4 inches. The
risers are approximately 1 1/2 inches tall and are 3/4 inch
size as are the gate valves 28 and 30. The hose members are
3/4 inch size and the nozzle member 42 consists of a stainless
steel pipe having a 3/8 inch outside diameter and a .035 inch
thick wall.
Pipe 50 is 3/4 inch size and the air pressure can be
varied to any desired level. In the preferred embodiment
using
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turbo blower air, the air pressure can be varied from zero to 24
ounces. When operating with ~ero air pressure, a zero amount of
fuel would be fed to the injector 52 with the device being capable
of feeding up to 40 pounds of coal per hour when operating at 24
ounces of pressure. Higher pressures in the same system result
in a much higher maximum feed rate. l90 pounds per hour can be
fed with 12 psi compressor air. It should be understood that the
dimensions of the parts and the operating pressures can vary
considerably and it would be possible to provide compressed air
to the inlets of the valve members 28 and 30 if desired. The
dimensional and operating variations would depend upon the desired
flow rates, the quality of coal being used and the nature of the
particular operation. In any event, the inventive device
provides a uniquely simple and effective means for varying the
flow of powdered coal to a combustion chamber so as to permit
the use of such fuel in low capacity fuel injection units in
operations previously limited to the use of petroleum based fuels.
Consequently, the present invention meets a long-standing
need of the brick and ceramic industry for means capable of burn-
ing coal under close control by the use of a large number of smallvolume fuel delivery devices each having a wide range of operation
while being easily controlled to provide a metered fuel flow at
its particular location. In addition, use of the metering and
delivery system is not limited to burner operations since the
syætem can be used for feeding practically any pulverulent material
in metered quantities for mixing or other purposes.
A particular advantage of the invention is that it
is economical to fabricate and maintain since it does not require
special equipment and can be completely fabricated from off the
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shelf components. Advantages of operation of the preferred
embodiment used as a burner include the fact that the exit velocity
of the solid fuel from the injector lance can be varied to vary
the fuel penetration into the combustion chamber. Another
advantage of the inventive preferred embodiments resides in the
fact that the solid fuel feed rate into the combustion chamber
can be varied over a wide range without affecting the total carry-
ing air used to deliver the fuel or the exit velocity of the fuel
into the combustion chamber. The device is capable of providing
a wide range of fuel feed rates while operating under low pressure
air supply of between 10 to 24 ounces per square inch which makes
it possible to operate by use of a turbo blower air supply as
opposed to an expensive compressor system. However, the device
can be used for high pressure operation if desired. -
While numerous modifications of the subject inventionwill undoubtedly occur to those of skill in the art, it should be
understood that the spirit and scope of the invention is to be
limited solely by the appended claims.
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