Note: Descriptions are shown in the official language in which they were submitted.
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Feeder Apparatus
Field of the Invention.
The present invention relates to a feeder apparatus. In particular, the
present invention
relates to a feeder apparatus for a metallurgical furnace that reduces the
emission of
fugitive gases from the furnace.
Background Art.
In many conventional metallurgical furnaces, fresh feed material is supplied
to the
furnace through a feed port in the furnace roof. Typically, feed material is
supplied to
the furnace on a conveyor which deposits the feed material through an open
port.
However, providing an open port in the furnace allows for the possibility that
fugitive
gases (such as sulphur dioxide) may escape to the atmosphere through the port.
Not
only can the emission of fugitive gases have a detrimental impact on the
environment,
but it can also impact negatively on people living or working in the vicinity
of the
furnace.
In addition, fugitive gases escaping from the furnace may carry fine particles
of the
material being treated, representing a loss of metal recovery.
Thus, there would be an advantage if it were possible to provide a feeder
apparatus
that not only reduces the fugitive gases emitted from a metallurgical furnace,
but also
ensures a consistent and reliable stream of feed material to the furnace.
It will be understood that the term "fugitive gases" may refer to either
gaseous
emissions from the furnace, or a combination of gaseous emissions and
entrained
particulates.
It will be clearly understood that, if a prior art publication is referred to
herein, this
reference does not constitute an admission that the publication forms part of
the
common general knowledge in the art in Australia or in any other country.
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Throughout this specification, the term "comprising" and its grammatical
equivalents
shall be taken to have an inclusive meaning unless the context of use
indicates
otherwise.
Summary of the Invention.
It is an object of the present invention to provide a feeder apparatus which
may
overcome at least some of the abovementioned disadvantages, or provide a
useful or
commercial choice.
In one aspect the invention resides broadly in a feeder apparatus for a
furnace
comprising a vessel for feed material, said vessel being positioned at least
partially
above a feed port of the furnace, and feeding means located at least partially
within
the vessel, said feeding means being adapted to control the rate of feed flow
from the
vessel, through the feed port and into the furnace, said apparatus preventing
escape of
fugitive gases between an exterior of the vessel and the feed port.
The vessel may be of any suitable size, shape or configuration. Preferably,
the vessel
comprises one or more walls defining an internal region in which the feed
material is
retained. The vessel may be of any suitable shape. For instance, the vessel
may be
substantially square or rectangular in cross-section. However, in a preferred
embodiment, the vessel may be substantially circular or oval in cross-section.
Preferably, the vessel comprises a hopper, holding tank or the like adapted.
to retain a
quantity of feed material therein. The exact configuration of the vessel is
not critical,
although a skilled addressee will understand that it would be beneficial if
the vessel
was substantially conical in shape across at least a portion of its height so
as to '
facilitate the flow of feed material through the vessel and to minimise the
amount of
feed material adhering or being caught on the internal walls of the vessel.
Preferably,
the conical portion of the vessel tapers inwardly from an upper portion of the
vessel to
a lower portion of the vessel at or adjacent the feed port of the furnace.
In some embodiments of the invention, the vessel may be substantially conical
across
its entire cross-section. Alternatively, in a preferred embodiment of the
invention, the
vessel may comprise an upper conical portion and a lower throat portion, the
throat
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portion being positioned adjacent the feed port of the furnace. The throat
portion may
be of any suitable shape, although in some embodiments the throat portion may
be
substantially cylindrical.
As previously stated, the vessel is positioned at least partially above the
feed port of
the furnace. In some embodiments the lower section of the vessel is at least
partially
positioned within the feed port of the furnace so as to prevent the fugitive
gases
escaping to atmosphere by flowing out past an exterior surface of the vessel.
The
vessel may be positioned such that a portion of the lower section of the
vessel is at
least surrounded by the feed port. More preferably, the feed port entirely
surrounds the
lower portion of the vessel, with the perimeter matching the feed port
perimeter.
In some embodiments, the feed port entirely surrounds the lower portion of the
vessel
and a seal is achieved between the feed port and the vessel.
Thus, in a preferred embodiment, the lower section of the vessel is adapted to
abut the
edge of the feed port. More preferably, the lower section of the vessel is
adapted to
form a seal with the edge of the feed port. The lower section of the vessel
itself may
form a seal, or sealing means (such as gaskets, 0-rings or the like) may be
provided to
create a seal between the vessel and the feed port.
In other embodiments of the invention, a chemical sealant (such as resin,
adhesive,
silicone or the like, or a combination thereof), may be used to ensure that a
seal is
formed between the vessel and the feed port that is substantially impermeable
to
gaseous emissions from the furnace. Alternatively, the feed port and the lower
section
of the vessel may be fixed to one another (such as by welding or bolting) to
create a
seal. Alternatively, high tolerance shrouds, adjustable collars or the like
may be used.
In other embodiments, the vessel is positioned above and entirely surrounds
the feed
port. In this embodiment, the vessel may form a seal with the furnace such
that
fugitive gases cannot escape between the vessel and the furnace.
A skilled addressee will understand that the exact nature of the seal is not
critical to
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the invention, provided that there is a sufficient seal formed so as to reduce
or
eliminate the egress of fugitive gases from between the lower section of the
vessel and
the feed port.
The feeding means may be of any suitable form, such as a screw feeder, valve,
door
(or pair of doors), vibratory feeder, pozzalanic feeders or the like that,
when actuated,
cause a flow of feed material to pass from the vessel into the furnace.
Preferably, however, the feeding means is adapted to control the rate of flow
of feed
material between the vessel and the furnace. The control of the rate of flow
of feed
material may be achieved in any suitable manner, however in a preferred
embodiment,
the rate of flow of feed material is controlled by using a variable speed
feeding means.
In this embodiment of the invention, it is preferred that the feeding means
comprises
a screw feeder (and particularly a vertical screw feeder) associated with
drive means
in the form of a variable speed motor or the like. A skilled addressee will
understand
that, typically, a screw feeder comprises a central shaft or post and one or
more helical
screw flights extending outwardly from the shaft.
In the present invention, the length of the screw need only be relatively
short to
control the head of feed material positioned above the screw and to prevent
the feed
material from being delivered in an unreliable manner. The screw may be a
helical
screw.
The feeding means may be positioned at any suitable location. For instance, in
some
embodiments of the invention, the feeding means may be positioned
substantially
within the throat portion of the vessel. Alternatively, the feeding means may
be
located within the conical portion of the vessel. Alternatively, the feeding
means may
be located in both the conical portion and the throat of the vessel.
The apparatus may be provided with cleaning means. In embodiments of the
invention in which the feeding means are located in both the conical portion
and the
throat of the vessel, the shaft of the screw feeder may be provided with
cleaning
means to ensure that the feed port in the furnace is maintained free of any
buildup of
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material to prevent blockages and ensure a reliable supply of feed material to
the
furnace. Any suitable cleaning means may be provided, such as, but not limited
to,
one or more scraper bars, brushes, wedges, blades or the like, or a
combination
thereof. Alternatively, or in addition to the cleaning means located on the
shaft, the
one or more helical screw flights may be provided with reaming flights adapted
to
maintain the feed port clear of any buildup of material. Alternatively the
invention
may incorporate vibration means and controlled blasting methods such as air
blasting
to prevent any buildup of material.
In order to prevent the flow of material past the feeding means when the
feeding
means is not activated, it is preferred that the feeding means is adapted to
be
positioned adjacent, or even abut, an inner wall of the vessel along
substantially the
entire height of the feeding means. For instance, when the feeding means is
located at
least partially in the conical portion of the vessel, the feeding means may
also be
substantially conical in shape such that the outer periphery of the feeding
means lies
substantially parallel to the inner wall of the vessel. In some embodiments of
the
invention the outer periphery of the feeding means may abut the inner wall of
the
vessel such that feed material is unable to flow past the feeding means when
the
feeding means is not operational. However in alternative embodiments of the
invention, the outer periphery of the feeding means may be spaced apart from
the
inner wall of the vessel. In this embodiment, the feed material may be
incapable of
flowing past the feeding means when the feeding means is not operational due
to, for
instance, the angle of repose of the particles in the feed material in the
vessel, and the
angle of the walls of the vessel.
Desirably, material is only fed to the furnace when the feeding means is
operated.
In a preferred embodiment of the invention, the position of the feeding means
within
the vessel may be adjusted as desired. For instance, the feeding means may be
raised
or lowered as required within the vessel (or even lowered at least partially
through the
feed port and into the furnace). Further, the feeding means may be adapted to
be
removed completely from the vessel, such as when maintenance or repair to the
feed
port, vessel or feeding means is required.
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In a further embodiment of the invention, the feeding means and the vessel may
be
removed together from the roof of the furnace. In this embodiment the contents
of the
vessel would remain undisturbed while the feeding means and vessel were
removed as
one combined unit. In some embodiments of the invention the removal of the
feeding
means and the vessel may be integrated with the structure and motion of the
upstream
equipment: i.e. the feed transfer means.
To achieve the raising and lowering of the feeding means, it is preferred that
the
feeding means is associated with one or more moveable support members. The
moveable support members may be of any suitable form, such as a boom member
capable of being raised or lowered, a retractable or telescoping member, a
folding
member or the like, or a combination thereof. Preferably, the one or more
moveable
support members are adapted for attachment to a support frame that may be
raised and
lowered as desired, or even retracted when the feeding apparatus is removed
for
maintenance. The support frame may comprise one or more frame members (for
instance, one or more vertical members and/or one or more horizontal members),
including one or more retractable or telescoping members as required. A
skilled
addressee will understand that the exact construction of the support frame is
not
critical.
Alternatively, the feeding means may be lowered using other techniques, such
as a
pulley arrangement, hydraulics, forklift, crane or the like.
The feeding means may be raised or lowered using automated or manual
techniques.
It will be understood, however, that providing the feeding means with a
conical
section is not required in some situations. For instance, in situations in
which it may
be desired to lower the feeding means into the throat or even into the
furnace, it may
not be necessary to provide the feeding means with a conical section which may
otherwise prevent the desired lowering of the feeding means.
The feeder apparatus may further comprise feed transfer means adapted to
transfer
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feed material into the vessel. Any suitable feed transfer means may be
provided, such
as, but not limited to, one or more elevators, chutes, conveyors, pipes or the
like.
Alternatively, feed material may be transferred to the vessel directly from a
truck,
loader, or similar vehicle, or may be manually transferred to the vessel, such
as by a
worker using a spade or shovel.
Thus, the vessel may be provided with no upper wall, or may be provided with
only a
partial upper wall. Alternatively, an upper wall may be provided on the vessel
and the
feed transfer means may be adapted to transfer feed material into the vessel
through an
opening or port in the upper wall.
Preferably, the rate at which feed material is transferred into the vessel is
substantially
the same as the rate at which feed material is fed from the vessel into the
furnace. In
this way, the volume of feed material in the vessel is maintained at a
substantially
constant level. This substantially constant level of material may be achieved
using
any suitable technique. For instance, the feeding apparatus may be provided
with one
or more sensing means to determine the level of feed material within the
vessel. Any
suitable sensing means may be provided, including one or more load sensors,
contact
sensors, level sensors, one or more cameras for monitoring the level and so
on.
Alternatively, the level may be monitored manually.
Preferably, the one or more sensing means may relay signals regarding the
level of the
feed material in the vessel (or the rate of change of the level of the feed
material in the
vessel) to any suitable receiving means, such as a DCS, PLC, computer or other
means using non stationary receiving means such as PDA, mobile telephones and
so
on. Once received, it is envisaged that the receiving means may then take the
appropriate action to ensure that the level of feed material is maintained at
a
substantially constant level. For instance, if the level of feed material in
the vessel
begins to drop below a desired level, a signal may be sent (automatically by
an expert
control system, DCS or the like) to increase the rate at which the feed
transfer means
transfers feed material into the vessel. Similarly, if the level of feed
material in the
vessel begins to rise above a desired level, a signal may be sent to decrease
the rate at
which the feed transfer means transfers feed material into the vessel. This
system may
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be operated with aural signals and/or visual signals such as sirens, flashing
lights or
the like to alert workers in the area if required.
While it is envisaged that much of the adjustment of feed rates may be
achieved
through automated control systems, it is also envisaged that an aural signal
(a siren or
the like) or a visual signal (such as a flashing light) may be used to alert a
worker to
the need to manually adjust the rate at which the feed transfer means
transfers feed
material into the vessel.
In situations in which adjustment of the feed transfer means is not possible
(for
instance if the feed transfer means is operating at its fastest setting), it
is envisaged
that adjustments to the speed of the feeding means may be made to control the
level of
feed material in the vessel. However, a skilled addressee will understand
that, in a
preferred embodiment of the invention, the level of feed material in the
vessel is
maintained through a combination of adjustments in the speeds of both the
feeding
means and the feed transfer means.
The person skilled in the art will appreciate that any control strategy
implemented
with the present invention should ensure safe and reliable operation of the
furnace to
obtain the highest possible safety standards and consistent yield and quality
from the
furnace.
The level of feed material maintained in the vessel may be any suitable level.
However, it is preferred that the level of feed material is maintained at such
a level
that the feed material forms a substantially gas impermeable plug or barrier
in order to
reduce (or eliminate) fugitive gases escaping from the furnace. A skilled
addressee
will understand that the exact volume of feed material required to form a
substantially
gas impermeable plug or barrier will depend on a number of properties of the
feed
material, including density, porosity, moisture content and the like. Thus,
the volume
of feed material required to form a substantially gas impermeable plug or
barrier will
vary depending on the feed material being used.
In addition to reducing the egress of fugitive gases, forming a gas
impermeable plug
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or barrier of feed material also reduces (or eliminates) the flow of unwanted
gases into
the furnace. The flow of gases into a furnace generally results in localized
cooling
within the furnace, which, in turn, reduces the efficiency of operation of the
furnace.
By providing a gas impermeable plug or barrier of feed material, this effect
may be
substantially reduced or even eliminated.
The feeder apparatus may be used in a wide variety of furnaces known to a
person
skilled in the art. The feeder apparatus may be used in any suitable furnace,
such as,
but not limited to, bath-type furnaces (including vertical furnaces), electric
furnaces,
top submerged lance furnaces, blast furnaces, furnaces with top feed ports or
the like.
In one embodiment, the feeder apparatus is used with a top submerged lance
furnace,
although it will be appreciated that the invention is not limited to use only
with this
type of furnace.
In another aspect, the invention resides broadly in a feeder apparatus for a
metallurgical furnace comprising a vessel for feed material, said vessel being
positioned at least partially above a feed port of the furnace so as to
prevent the escape
of fugitive gases between an exterior of the vessel and he feed port, a
vertical screw
feeder positioned at least partially within the vessel, and drive means for
driving the
vertical screw feeder, wherein the flow of feed material from the vessel into
the
furnace is controlled to ensure that a sufficient quantity of feed material is
retained in
the vessel to reduce the egress of fugitive gases from the furnace through the
feed
port.
In a further aspect there is provided an apparatus for reducing emissions from
a
metallurgical furnace comprising a vessel for feed material, said vessel being
positioned at least partially above a feed port of the furnace so as to
prevent the escape
of fugitive gases between an exterior of the vessel and he feed port, feed
transfer
means for transferring feed material into the vessel and feeding means located
at least
partially within the vessel and adapted to control the rate of feed flow from
the vessel
into the furnace, wherein the rate of flow of feed material from the vessel
into the
furnace is substantially the same as the rate of flow of feed material from
the feed
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transfer means into the vessel so as to ensure that a sufficient quantity of
feed material
is retained in the vessel to reduce the egress of fugitive gases from the
furnace through
the feed port.
Brief Description of the Drawings.
An embodiment of the invention will be described with reference to the
following
drawings in which:
Figure 1 illustrates a schematic view of a feeder apparatus according to an
embodiment of the present invention;
Figure 2 illustrates a schematic view of a portion of a feeder apparatus
according
to an embodiment of the present invention; and
Figure 3 illustrates a schematic view of a portion of a feeder apparatus
according
to an embodiment of the present invention.
Detailed Description of the Drawings.
It will be appreciated that the drawings have been provided for the purposes
of
illustrating preferred embodiments of the present invention and that the
invention
should not be considered to be limited solely to the features as shown in the
drawings.
In Figure 1 there is illustrated a feeder apparatus 10 according to an
embodiment of
the present invention. The feeder apparatus 10 comprises a vessel 11
positioned at
least partially above a feed port 12 of a metallurgical furnace 13. The lower
section of
the vessel 11 is positioned within the feed port 12 such that a seal is formed
at the
point at which the feed port 12 and vessel 11 abut. The formation of this seal
prevents
fugitive gases from escaping from the furnace 13 through gaps between the feed
port
12 and the vessel 11.
The apparatus 10 comprises feeding means in the form of a screw feeder 14. The
screw feeder 14 comprises a drive shaft 15 and a screw flight 16 positioned
within the
vessel 11. The vessel 11 is supplied with feed material 17 (such a mineral
concentrate) which may then be feed into the furnace 13 on actuation of the
feeder
apparatus 10.
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In Figure 1, it may be seen that the angle and positioning of the screw flight
16
substantially prevents the feed material 17 from entering the furnace 13 while
the
screw feeder 14 is not operational. This effect may also be aided by the
nature of the
feed material 17, its moisture content, angle of repose and so on. While in
this
position, the feed material 17 effectively forms a solid plug of material that
prevents
emissions (gases, particulates etc) from escaping to the atmosphere through
the feed
port 12 of the furnace 13.
One end of the drive shaft 15 is connected to drive means, such as a motor 18
which,
when actuated, rotates the drive shaft 15 in the direction indicated by arrow
19.
Actuation of the drive shaft 15 cause rotation of the screw flight 16 which,
in turn, .
causes feed material 17 to be fed into the furnace 13 through the feed port
12. When
the motor 18 is actuated, it is desirable to maintain a substantially constant
level of
feed material 17 in the vessel 11. If the level of feed material 17 gets too
low, the
effectiveness with which emissions are prevented from leaving the furnace 13
through
the feed port 12 will be reduced. Feed material 17 may be provided to the
vessel 11
using any suitable technique such as a conveyor or elevator, or by feeding
material
into the vessel 11 from a truck, loader, filter or the like.
On occasion, it will be desired to inspect the screw feeder 14 (for instance,
for wear or
damage) or to gain access to the screw feeder 14 for the purposes of
maintenance. To
this end, the feeder apparatus 10 may be provided with a support frame
including a
horizontal member 19 and a vertical member 20. In the embodiment of the
invention
shown in Figure 1, the vertical member is provided as a telescopic or
retractable
member that is associated with a base member 21. The base member 21 is bolted
or
otherwise attached to the floor or ground, or other suitable support.
Providing the
vertical member 20 as a telescopic member enables the vertical member 20 to be
raised when removing the screw feeder 14 from the vessel 11 and lowered when
positioning the screw feeder 14 within the vessel 11. This may be of use not
just
when maintenance of the screw feeder 14 is required, but when adjustments to
the
feeder apparatus 10 or process (such as adjustments to the flow rate of feed
material
17 into the furnace 13) are required.
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Once the screw feeder 14 has been raised clear of the vessel 11 by the action
of the
vertical member 20, the horizontal member 19 may then be used to displace the
screw
feeder 14 from the vessel 11 in a horizontal direction. For instance, the
horizontal
member 19 may also be a telescoping or retractable member that enables the
screw
feeder 14 to be moved away from the vessel 11 in a horizontal direction.
Alternatively, the vertical member 20 may be adapted to pivot about its
longitudinal
axis so that the screw feeder may be pivoted away from the vessel 11.
In Figure 2, a schematic view of a portion of a feeder apparatus 10 according
to an
embodiment of the invention is shown. In this embodiment, the vessel 11 is
positioned entirely above the feed port 12 of the furnace 13. The vessel 11 is
provided
with a pair of flanges 22 that allow the vessel 11 to be connected to the roof
of the
furnace 13, for instance by bolting or welding.
The connection of the flanges 22 to the furnace13 forms a seal that prevents
the
escape of fugitive gases from the furnace 13 through gaps between the feed
port 12
and the vessel 11.
Turning now to Figure 3, a schematic view of a portion of a feeder apparatus
10
according to an embodiment of the invention is shown. In this embodiment, the
vessel 11 is positioned entirely above the feed port 12 of the furnace 13 and
entirely
surrounds the feed port 12. The vessel 11 may either abut the roof of the
furnace 13
or may be retained in position using any suitable fastening technique.
The positioning of the vessel 11 forms a seal that prevents the escape of
fugitive gases
from the furnace 13 through gaps between the feed port 12 and the vessel 11.
The advantages of the feeder apparatus 10 of the present invention are
numerous.
Firstly, the feeder apparatus 10 provides the ability to reduce or even
eliminate the
escape of fugitive gases from a furnace through the feed port. This represents
a
significant advantage, environmentally and from a health and safety point of
view. In
addition; the ability to prevent the emission. of fugitive gases from a
furnace with
minimal additional infrastructure represents an efficient and cost effective
way to
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reduce emissions for new furnaces as well as retrofitting of existing
furnaces. In
addition it prevents the ingress of cooler gases into the furnace that
produces cold
spots within the furnace. Further, the feeder apparatus of the present
invention
achieves these advantages while ensuring a constant and reliable feed of
material to
the furnace. Thus, minimal or no impact on operational effectiveness is
envisaged
when the present invention is in use.
Those skilled in the art will appreciate that the present invention may be
susceptible to
variations and modifications other than those specifically described. It will
be
understood that the present invention encompasses all such variations and
modifications that fall within its spirit and scope.
