Note: Descriptions are shown in the official language in which they were submitted.
1~76785
Specification
Title of the Invention
Powder Feeder
Background of the Invention
The present invention relates to a powder feeder
in an apparatus for feeding a powder by means of an air or
a gas.
When a powder ore containing, e.g., a metal
oxide, is pre-reduced and is then reduced at molten state
to manufacture a molten metal, a powder feeder for feeding
powder ore by an air or a gas is required in a powder ore
feeder from a pre-reduction furnace to a smelting reduction
furnace, a dust delivery unit of an exhaust gas combustor
in a rotary kiln process for reduced iron production, or a
sand recovery feeder in a molding sand roasting furnace.
However, a powder feeder used in such a location,
particular, a feeder arranged on a powder ore feeder,
cannot be a mechanical powder feeder, e.g., a rotary feeder
since an object to be fed is at high temperatures around
1,000C. Therefore, demand has arisen for a feeder capable
of feeding a high-temperature powder.
Summary of the Invention
It is a principal object of the present invention
to provide a powder feeder which can reliably and easily
feed a powder in a constant amount even at a very high
temperature.
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In order to achieve the above object, there
i5 provided a powder feeder, comprising: a cylinder body
connected to a gas blow pipe for fluidi~ing a powder at
its bottom portion; a porous plate crossing the lower
portion of the cylinder body above a gas blow hole; partitioning
means for vertically dividing the interior of the cylinder
body into a powder supply side and a delivery side and
for communicating the supply and delivery sides with
each other at its upper portion; a powder supply pipe
connected to the lower portion of the cylinder body at
the supply side to be inclined downward toward a connecting
portion; and a powder delivery pipe connected to the lower
portion of the cylinder body at the delivery side to
be inclined downward in a delivery direction.
Brief description of the Drawings
Fig. 1 is a schematic view showing an entire
smelting reduction apparatus to which a powder feeder
according to an embodiment of the present invention is
applied;
Fig. 2 is a cross-sectional view of a powder
feeder;
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Fig. 3 is a perspective view of the powder feeder
shown in Fig. 2;
Fig. 4 is a graph showing the relationship
between an N2 gas flow rate and a powder ore feed amount;
Figs. 5 and 6 show another embodiment of the
present invention, in which Fig. 5 is a cross-sectional
view of a powder feeder corresponding with Fig. 2, and
Fig. 6 is a perspective view thereof corresponding with
Fig. 3;
Fig. 7 is a cross-sectional view of a powder
feeder according to still another embodiment of the present
invention corresponding with Fig. S; and
Fig. 8 is a cross-sectional view of a waste
combustion fluidized-bed boiler to which the powder feeder
of the present invention is applied.
Description of the Preferred Embodiments
An embodiment of the present invention will now
be described with reference to Figs. 1 to 4.
In this embodiment, a powder feeder according to
the present invention is applied to a smelting reduction
apparatus. Referring to Fig. l, a pre-reduction furnace 2
is coupled to an upper portion of smelting reduction
furnace 1, so that a high-temperature reducing gas is
introduced from the furnace l to the furnace 2. A tuyère 3
formed in the lower portion of the reducing furnace 1 is
connected to a blow pipe 4 for blowing a high-temperature
air. A powder feeder 5 (to be described later in detail)
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is arranged between the pre-reduction furnace 2 and the
blow pipe 4.
The powder feeder 5 comprises a cylinder body 9
consisting of an outer cylinder 6 and an inner cylinder 7
concentrical therewith. The upper and lower ends of the
outer cylinder 6 are closed at the periphery of the inner
cylinder 7. The inner cylinder 7 extends downward from the
outer cylinder 6, and the bottom plate of this extending
portion is connected to a gas blow pipe 9 for supplying N2
gas for fluidizing a powder. Reference numeral 10 denotes
partition plates for partitioning the cylinder body 8 into
a supply side and a delivery side. ~he partition plates 10
divide a cylindrical space between the outer and inner
cylinders 6 and 7 into two sections and extend along almost
the total length of the cylinder body 8 to leave an
appropriate gap between themselves and the upper end of the
outer cylinder 6. A slit 11 for communicating the supply
and delivery sides with each other is formed in the outer
wall of the inner cylinder 7 at the delivery side. A
porous plate 12 having a large number of small holes is
arranged on the lower portion of the inner cylinder 7 at
substantially the same level as the bottom plate of the
outer cylinder 6 to cross the inner cylinder 7. A supply
port 13 and a delivery port 14 are respecti~ely open to
lower portions of an outer wall at the supply and delivery
sides of the outer cylinder 6 of the cylinder body 8 above
the porous plate 12. The supply port 13 is connected to
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the bottom portion of the pre-reduction furnace 2 through a
supply pipe 15 for powder ore. The supply pipe 15 is
inclined through an angle of rest or more, so that the
supply port 13 side is lower. The delivery port 14 and the
blow pipe 4 are coupled through a powder ore delivery pipe
16. The delivery pipe 16 is inclined through an angle of
rest or more, so that the blow pipe 4 side is lower. An
opening 17 for communicating the outer and inner cylinders
6 and 7 with each other is formed in the lower portion of
the inner cylinder 7. The slit 11 extends up to the upper
end of the inner cylinder 7 to have its lower end slightly
higher than the upper end of the delivery port 14.
The operation of this embodiment with the above
~ arrangement will be described hereinafter.
Powder ore 18, e.g., chromium powder ore, in the
pre-reduction furnace 2 forms a moving bed by its weight,
and moves downward in the supply pipe 15.
In a normal state, a pressure in the smelting
reduction furnace 1 is higher than that in the
pre-reduction furnace 2 by 0.2 to 0.4 kg/cm2, and a gas
flows upward in the moving bed. The powder ore 18 moving
downward in the supply pipe 15 enters the cylinder body 8
from the supply port 13, and is flowed in the lower portion
between the supply side of the outer cylinder 6 and the
inside of the inner cylinder 8 communicating with each
other through the opening 17. At this time, since the N2
gas is supplied from the gas blow pipe 9, it is blown into
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the inner cylinder 7 through the small holes of the porous
plate 12, thus fluidizing the powder ore above the porous
plate 12. In a fluidized state at minimum fluidized gas
flow rate, the upper surface of the fluidized bed of the
S powder ore 18 coincides with the upper end of the opening
17. However, when the N2 gas flow rate is increased, the
height of the fluidized bed is increased. When the height
of the bed exceeds the level of the lower end of the slit
11, the powder ore 18 is overflown to enter a space between
the inner and outer cylinders 6 and 7 at the delivery side.
Then, the powder ore 18 is delivered from the delivery port
14 and slides downward in the delivery pipe 16. In this
case, since high-temperature air flows inside the blow pipe
4, the slid powder ore 18 is blown into the smelting
reduction furnace 1 through the tuyère 3 with the
high-temperature air. Note that the high-temperature air
flows in the reverse direction inside the delivery pipe 16
and reacts with the powder ore 18 to attach it. However,
since the N2 gas is introduced, the powder ore 18 will not
be attached to the pipe 16.
Upon feeding of the powder ore 18, the height and
width of the opening 17 at the supply side, the volume of
the space between the cylinders 6 and 7, the connecting
position OLC the supply pipe 15 to the outer cylinder 6, and
the like are appropriately selected, thus realizing a state
wherein the powder ore 18 at the supply side is fluidized
by the N2 gas flowing into the supply pipe 15 via the
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opening 17 at the supply side, and only the powder ore 18
overflown from the slit 11 at the delivery side is fed.
More specifically, when the N2 gas flow rate is increased,
the height of the fluidized bed is increased, and the
overflow amount from the slit 11 at the delivery side is
increased. In this manner, the feed amount of the powder
ore 18 can be controlled, thus realizing a powder feed
operation.
Fig. 4 is a graph showing the relationship
between an N2 gas flow rate and a powder ore injection rate
upon feeding of the chromium powder ore in the above
embodiment. A fluidizing N2 gas flow rate (Q/min) is
plotted along the abscissa, and the powder ore injection
rate (kg/min) is plotted along the ordinate. In Fig. 4,
marks O and ~ indicate a case wherein a pressure
difference ~P between the furnaces l and 2 is 0.23 kg/cm2,
and marks and ~ indicate a case wherein the pressure
difference ~P is 0.43 kg/cm2. The powder ore used in this
case has an average particle size of 0.2 mm and a bulk
density of 2.5 g/cc, and an angle of repose is 35. It was
confirmed that, after the above-mentioned conditions, e.g.,
the gap between the cylinders 6 and 7 are appropriately
selected, when a gap is formed in the upper portion of each
partition plate 10 to form a gas path between the supply
and delivery sides, even if the pressure difference between
the furnaces 1 and 2 varies within the range of 0.2 to 0.4
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~g/cm2, the feed amount of the powder ore 18 will not be
changed.
As a matter of course, if the amount of the N2
gas supplied is set below the minimum fluidizing gas flow
rate, the powder ore 18 is left in the inner cylinder 7 so
as not to be fed therefrom. Therefore, the feed operation
of the powder ore 18 can be started and stopped even though
no valve is provided to the delivery pipe. A structure and
method which can maintain a constant feed amount can be
realized regardless of the pressure difference between both
the furnaces.
Figs. 5 and 6 are a cross-sectional view and a
perspective view of a powder feeder according to another
embodiment of the present invention, in correspondence with
Figs. 2 and 3. In this embodiment, the inner cylinder 7 in
the above embodiment is omitted, and only a partition plate
lOA is provided. Since other arrangements are the same as
those in the above embodiment, the same reference numerals
denote the same parts as in the above embodiment and a
detailed description thereof will be omitted. More
specifically, the partition plate lOA divides tlle outer
cylinder 6 into the supply and delivery sides, and a slit
llA for communicating the supply and delivery sides is
formed in an upper half portion of the plate lOA.
With this arrangement, powder ore flowing from
the supply pipe 15 into the outer cylinder 6 is overflown
by the N2 gas supplied from the gas supply tube 9, thus
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realizing a powder feed operation as in the above
embodiment.
In the above embodiments, as shown in Fig. 7, if
a guide plate 19 for coupling the lower end of the delivery
port 14 to the lower edge of the slit llA to shield the
space is pr~vided, the powder ore can be easily guided to
the delivery pipe 16.
In the abovè embodiments, as shown in Fig. 7, if
a gas blow hole 20 is arranged midway along the delivery
pipe 16 to blow a gas, the powder ore can be smoothly
delivered.
In the above embodiments, the case has been
exemplified wherein the present invention is applied to a
powder ore feeder between the pre-reduction furnace and the
smelting reduction furnace. However, the present invention
can be applied to any feeders, e.g., a dust delivery unit
of an exhaust gas combustor in a rotary kiln process for
reduced iron production, or a sand recovery feeder in a
molding sand roasting furnace, which feeds a powder by an
air or a gas.
Fig. 8 shows a case wherein the powder feeder of
the present invention is applied to a waste combustion
fluidized-bed boiler system, and schematically shows the
entire system. In Fig. 8, a powder feeder 5 described in
detail in the above embodiments is arranged between a
fluidized bed combustor 30 and a converter 41. A waste
fuel, e.g., garbage, is fed to the lower portion of the
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converter 41 by a feeder 42. A volatile is gassified by
sand at a high temperature (540C~ fluidized by air
supplied from a lower nozzle 43, and is fed into a bed from
an exit nozzle 44 through a pipe 33 to be combusted. A
solid carbon component is fed into the bed by an air feeder
45 together with the sand from a nozzle 34 to be combusted.
The fluidized bed combustor 30 is divided into three
chambers by air distributors 31 and 31'. Air enters from a
nozzle 32, passes through the distributor 31, causes sand
39 to be fluidized, and causes the volatile and carbon fed
from the converter 41 to be combusted. Then, the air
passes through the distributor 31' to fluidize limestone
40, causes Sx in a flue gas to be adsorbed, and is then
exhausted from an exit port 37. In this case, the
limestone 40 fed onto the distributor 31' can be delivered
through a spent line 36. Combustion heat is transmitted to
water through a heat transfer pipe 38 to generate steam.
Sand at a high temperature (950C) is constantly fed to the
converter 41 by the powder feeder 5 according to the
present invention to keep its temperature. The sand has a
particle size of 0.4 to 1.5 mm. Although the pressure in
the converter 41 is higher than that in the combustor 30 by
0.05 to 0.1 kg/cm2, since a moving bed is fed to the
entrance side pipe of the powder feeder and provides a
material seal therefor, the reverse flow of a gas can be
prevented and a powder feed operation is allowed at the
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same time. The operation of the powder feeder is the same
as in the above embodiments.
As can be seen from the above description, in a
powder feeder of the present invention, supply and delivery
pipes are respectively connected to lower portions of a
cylinder body, on the supply and delivery sides, which is
divided by a partition plate having a communication slit,
and a porous plate crossing the lower portion of the
cylinder body and a gas blow pipe for fluidizing a powder
connected therebelow are provided. With this arrangement,
the amount of powder to be fed can be adjusted by simply
adjusting a gas flow rate, and a powder can be accurately
fed in a constant rate. Therefore, a constant rate of
powder can be reliably and easily fed even at a very high
temperature without requiring a feed amount adjusting
valve, e.g., a rotary valve.
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