DESCRIPTION
TITLE OF INVENTION
BURDEN CHARGING APPARATUS FOR BLAST FURNACE, AND BURDEN
CHARGING METHOD USING THE SAME
TECHNICAL FIELD
[0001]
The present invention relates to a bell-less charging apparatus for a blast
furnace, and to a burden charging method using the same. Specifically, the present
invention relates to a burden charging apparatus and a burden charging method using
the same that, when burdens consisting of iron source, a reducing agent, or the like
(collectively referred to as "main burden(s)" hereinafter) as well as a small amount of
burdens of specific type/brand/description (referred to as "specific material(s)"
hereinafter) is charged into a blast furnace from a blast furnace top bunker to form
mixed layers, is capable of forming a mixed layer in which main burdens and specific
materials have a uniform mixing proportion, and that is capable of enhancing the
controllability of the distribution of the charged burdens in the blast furnace.
BACKGROUND ART
[0002]
In blast furnace operations, iron sources such as sintered ore, ore lumps,
pellets, or the like (collectively referred to as "ore" hereinafter), and a reducing agent
such as coke are alternately charged into the blast furnace from a blast furnace top area
so as to be accumulated in layers in an alternate fashion in the furnace. A bell-less
charging apparatus in which top bunkers are disposed in parallel at a blast furnace upper
area (referred to as "parallel bunker bell-less charging apparatus" hereinafter) may be
used to charge ore and the reducing agent from the blast furnace top area.
[0003]
Fig. 1 is a conceptual diagram illustrating an example of the configuration of a
parallel bunker bell-less charging apparatus in the related art. In Fig. 1, blast furnace
burdens such as ore and a reducing agent are classified and stocked in material bins 1
depending on the type/class, particle size or the like, respectively. When burdens are
charged into the blast furnace using the burden charging apparatus, a predetermined
mass of burdens of each type stocked in the bins is extracted to be a group of burdens
onto a charging conveyor belt 2 and transported thereby. Each group of the burdens
which are transported to the blast furnace top by the charging conveyor belt 2 are
brought into a blast furnace top bunker 4 via a switching chute 15 and are temporarily
stored in the top bunker 4.
[0004]
In the burden charging apparatus shown in Fig. 1, two top bunkers 4 are
disposed in parallel, so that each group of burdens which have been transported to the
blast furnace top by the charging conveyor belt 2 are distributed by the switching chute
15, so as to be brought into and stored in a desired one between two top bunkers 4.
The top bunker 4 discharges the stored burdens in the bunker from an outlet 4a at the
bottom thereof, and a flow control valve 5 that controls an amount of flow of burdens is
disposed below the outlet 4a of the top bunker. The aperture of the flow control valve
5 may be changed to adjust an area of an opening 6, so that an amount of flow of
burdens supplied from the top bunker 4 to a distributing chute 8 via a collecting hopper
7 is controlled. The distributing chute 8 charges the supplied burdens into a desired
location inside a blast furnace 9.
[0005]
In the case where such a parallel bunker bell-less charging apparatus is used, an
operation of charging ore from one top bunker and an operation of charging coke from
another top bunker are performed in an alternating manner. As a result, it is possible
to form an ore layer and a coke layer so as to be accumulated in an alternating manner
inside the blast furnace.
[0006]
When burdens charged into the furnace in this manner are processed in a blast
furnace, a region in which a reducing reaction is rapidly developed and a gas-flow
resistance becomes high is produced. This region is referred to as "cohesive zone",
which has a large impact on the overall gas flow in the blast furnace and the
productivity of the blast furnace. Therefore, in order to improve the gas flow in the
cohesive zone and accelerate the reducing reaction, typically preformed are operations
of controlling the mass, layer thickness, particle size distribution, or the like of the
accumulated burdens along a radial direction inside the blast furnace.
[0007]
For example, in case of a parallel bunker bell-less charging apparatus
illustrated in Fig. 1, the distribution of the charged burdens is controlled by charging the
burdens into the furnace while tilting and swirling the distributing chute 8. In this
case, "tilting" refers to as changing an inclination angle formed between the central axis
8a of the distributing chute and the vertical central axis 9a ofthe blast furnace, in a state
where the distributing chute 8 is swirled as indicated by the solid line arrow in Fig. 1.
Typically, the distributing chute is tilted in a manner that the location inside the blast
furnace into which the burdens are charged is shifted from the furnace wall side, to an
intermediate area, and to the central portion, in the order written.
[0008]
In recent years, a method in which a small amount of coke as being separate
from that of a coke layer is mixed into ore to be charged as an ore layer has been
garnering attention as the method to improve the reaction efficiency and gas flow in the
cohesive zone. Through such a method in which a mixed layer (ore and coke) is
formed by mixing a small amount of coke into ore, expected are both an acceleration of
the reducing reaction by virtue of disposing ore and coke at a close distance
therebetween and an improvement of the gas flow by virtue of coke which serves as an
aggregate (a spacer) when ore becomes soft to be cohesive.
[0009]
The method in which a mixed layer of ore and coke is formed includes a type
in which a mixed layer is formed uniformly in a radial direction of furnace, and a type
in which a mixed layer is formed in a specific location where poor reducing reaction
and or poor gas flow, or the like occur. In either type, there are cases where, when
burdens are supplied from the top bunker 4 to the distributing chute 8 via the collecting
hopper 7, the proportion of ore and coke contained in the mixed burdens which are
supplied to the distributing chute 8 changes so that the percentage of coke may decrease
or significantly increase. In these cases, the percentage of coke may be changed in a
circumferential direction or in a radial direction inside the blast furnace, and the
acceleration of the reducing reaction and the improvement of the gas flow are impeded.
Therefore, it is desirable for the mixing proportion of the burdens which are to be
supplied to the distributing chute 8 to change as little as possible over time and to be as
uniform as possible, for forming a mixed layer in burdens inside the blast furnace.
[0010]
In this case, for forming a mixed layer having a uniform mixing proportion, a
technique may be employed in which the mixed layer is formed inside the furnace by
mixing ore and coke in advance and supplying the mixed burdens to the top bunker.
However, in such a technique, segregation occurs during the transport process before
the charging into the blast furnace since the particle sizes, densities, or the like are
different, so that the percentage of coke varies from location to location in the mixed
layer formed in the blast furnace. Accordingly, it is difficult, in the techniques in
which ore and coke are mixed with each other in advance, to maintain a uniform state of
mixing throughout the overall mixed layer.
[0011]
Various types of methods for suppressing segregation and maintaining a
uniform state of mixing when a mixed layer of ore and coke is preferably formed inside
the blast furnace have been proposed, such as those disclosed in fatent Documents 1
through 3. In the burden charging methods disclosed in Patent Document 1 and Patent
Document 2, ore is stored in one of multiple top bunkers, and coke is stored in another
top bunker. In this state, a flow control valve disposed at the bottom of each top
bunker is controlled, and both ore and coke are taken out and supplied to a distributing
chute, so that a mixed layer is formed inside the blast furnace.
[0012]
Since the blast furnace operates at a higher pressure than the atmospheric
pressure, pressure equalization and pressure relief operations are performed inside the
top bunker whenever burdens of one type and another are charged into the blast furnace.
For this reason, in the burden charging methods disclosed in Patent Document 1 and
Patent Document 2, when a small amount of coke (specific materials) are mixed into ore
which is to be charged as a layer of ore, it is necessary to conduct the pressure
equalization and pressure relief operations both in the top bunker that stores the ore and
in the top bunker that stores the coke; and as a result, it takes a long time to complete a
single charge. Three or more top bunkers may be disposed in parallel to eliminate
such charging time implication; however, as the number of top bunkers disposed in
parallel increases, the burden charging apparatus becomes complicated, which is
disadvantageous in terms of equipment costs.
[0013]
In the burden charging apparatus disclosed in Patent Document 3, a bell-less
charging apparatus in which two top bunkers are disposed in a vertical direction and a
distributing chute is disposed directly below an outlet of the lower top bunker (referred
to as "vertical-bunker bell-less charging apparatus" hereinafter) is provided with a
separate specific material bunker, in which the specific material bunker feeds the
materials directly to the distributing chute. In a burden charging method using the
burden charging apparatus disclosed in Patent Document 3, burdens of one type as
being different in either particle size or properties, or in both are stored in the top
bunker and those of another type in the specific material bunker. This enables to
control the change of either the particle size or properties, or both over time for the
burdens which are charged by the distributing chute. Also, it is stated that another
embodiment enables to reduce the charging time by storing burdens of one type having
the same particle size and properties in the top bunker and also in the specific material
bunker.
[0014]
In the burden charging apparatus disclosed in Patent Document 3, in the case
where mixed charging is performed under a certain condition of apertures of the flow
control valves of the top bunker and the specific material bunker, the flow volume of
burdens which are charged into the furnace changes (increases) during the mixed
charging, so that the thickness of the layer of the burdens formed in the furnace also
changes (increases). Therefore, it is necessary to adjust a tilting angle, the rotation
speed, or the like of the distributing chute in order to create a desired burden
distribution state, profile, or the like inside the blast furnace. Alternatively, it is
necessary to perform online control of the aperture of the flow control valves of the top
bunker and the specific material bunker depending on a variety of mixing conditions
(type of burdens, mixing proportion) in order to charge burdens into the furnace at a
constant flow volume during the mixed charging. As described thus far, operations for
creating a desired burden distribution state inside the blast furnace are complicated
e during mixed charging using the burden charging apparatus according to Patent
Document 3.
[0015]
In recent years, in view of the depletion of and increased costs of quality
burdens, it is unavoidable using low-quality but inexpensive burdens in blast furnaces,
and there is a trend toward the diversification of specific materials which are charged
into the furnaces in small amount, including pellets and lump ore in addition to the
above-mentioned coke that is to be mixed with ore~ An important issue, therefore, is
establishing a method for charging these specific materials into the blast furnace at a
proper mixing proportion.
[0016]
Meanwhile, it is known that, in the case where plural types of burdens are
supplied sequentially to a top bunker and are then discharged therefrom after being
stored therein temporarily, the order of discharging the stored burdens does not become
the same as that in supplying them to the top bunker.
[0017]
Fig. 2 is a diagram illustrating the order of supplying plural types of burdens
and the order of discharging them in a top bunker, in which Fig. 2(a) illustrates the
order of supplying the burdens and Fig. 2(b) illustrates the order of discharging?, As
shown in Fig. 2(a), when three subdivided burdens from the above are supplied
sequentially into the top bunker 4, the burdens are accumulated and stored in layers in
the order corresponding to the region 3a, the region 3b, and the region 3c, from a lower
region to an upper region of the top bunker 4. In other words, the burdens as been
supplied first are accumulated and stored in the region 3a, the burdens as been supplied
second are accumulated and stored in the region 3b, and the subdivided burdens as been
supplied last are accumulated and stored in the region 3c. In this manner, burdens 3 as
been supplied to the top bunker are accumulated and stored in the top bunker 4 in the
order of supplying them.
[0018]
When the burdens 3 that are stored in this manner are discharged from the
outlet 4a provided at the bottom of the top bunker 4, however, the burdens will not be
discharged in the same order as that in which the burdens have been supplied to the top
bunker. This is because the portion ofthe burdens that are accumulated in regions near
the inner wall ofthe top bunker is pushed against the inner wall by powder pressure, the
friction therein is increased, and thus it becomes difficult for the burdens in those
regions to be discharged from the top bunker.
[0019]
For example, in the top bunker 4 that has a shape as shown in Fig. 2(b), the
burdens that are accumulated in the region 3d directly above the outlet 4a are discharged
fIrst in discharging burdens from the outlet 4a at the bottom. Next, the burdens
gradually flow out and are discharged from the region 3e, which is in the periphery of
the region 3d as being subjected to fIrst discharging and is somewhat away from the
inner wall of the top bunker, and at last, the burdens remaining in the region 3f in the
vicinity of the inner wall of the top bunker are discharged. The space generated by
fIrst discharging the burdens as been accumulated in the region 3d immediately above
the outlet is referred to as "rat hole", and a phenomenon in which while forming the rat
hole, the burdens in the periphery thereof crumble into the rat hole to be discharged is
referred to as "funnel flow". Hereinafter, the region 3d that is located directly above
the outlet 4a and is subjected to discharging fIrst, or in other words, the region in which
the burdens are discharged in the order of supplying (mass flow) will be referred to as
"rat hole region".
[0020]
Patent Document 4 discloses a method for charging specifIc materials into a
blast furnace at a desired timing using this funnel flow discharge characteristic. The
burden charging method disclosed in Patent Document 4 is a method in which a
plurality of types of burdens are sequentially supplied to a top bunker, loaded and
temporarily stored in layers, and then charged into the blast furnace from the top
bunker. In this method, a relation between a height position to which burdens of
relevant type are loaded and a funnel flow characteristic is grasped in advance, and the
height position of the specifIc materials is then adjusted in accordance with the grasped
relation.
[0021]
It is possible to charge specifIc materials into a desired location by combining
the burden charging method disclosed in Patent Document 4 with tilting angle
adjustment of a distributing chute. However, in the case where burdens of specific
type are supplied to the distributing chute using the burden charging method disclosed
in Patent Document 4, the mixing proportion of specific materials will change
significantly over time. Therefore, for forming a mixed layer of ore and coke, the
burden charging method disclosed in Patent Document 4 is unsuitable for making the
mixing proportion of the burdens uniform when those burdens are discharged from the
top bunker.
CITATION LIST
PATENT LITERATURE
[0022]
PATENT LITERATURE 1: Japanese Patent Application Publication No. 61-243107
PATENT LITERATURE 2: Japanese Patent Application Publication No.2005-264292
PATENT LITERATURE 3: Japanese Patent No. 2782786
PATENT LITERATURE 4: Japanese Patent Application Publication No.2001-192714
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0023]
As described above, in blast furnace operations, a method of forming a mixed
layer where a small amount of coke as specific materials is mixed with ore is garnering
attention as a way of improving the reaction efficiency and gas flow in the cohesive
zone. However, in the case where a mixed layer is formed inside the furnace by
supplying mixed burdens, which have been obtained by mixing ore and coke in
advance, into a top bunker, segregation occurs during the transport process, which
makes it difficult to maintain a uniform state of mixture throughout the mixed layer.
[0024]
Meanwhile, in the burden charging methods disclosed in Patent Document 1
and Patent Document 2, ore is stored in one top bunker among a plurality of top
bunkers, and coke is stored in another top bunker, so that the ore and coke are mixed
with each other by controlling the flow control valves. In this method, it is necessary
to conduct pressure equalization and pressure relief operations for the two top bunkers,
and thus the charging takes a long time. Although three or more furnace top bunkers
may be disposed in parallel to eliminate such charge time implications, disposing three
or more top bunkers in parallel is disadvantageous in terms of equipment costs.
[0025]
In the vertical-bunker bell-less top charging apparatus disclosed in Patent
Document 3, a specific material bunker is provided separately from the top bunker(s),
and burdens of specific type are directly supplied from the specific material bunker to
the distributing chute. In the case where mixed charging is performed by the burden
charging apparatus disclosed in Patent Document 3 by discharging burdens from the top
bunker and the specific material bunker, it is necessary to adjust a tilting angle, rotation
speed, or the like of the distributing chute, or to perform online control of apertures of
the flow control valves in the top bunker and the specific material bunker, or the like,
which are cumbersome operations.
[0026]
In the burden charging method disclosed in Patent Document 4, specific
materials are charged into the blast furnace at a desired timing using the funnel flow
discharge characteristic. However, in the case where the burdens are supplied to the
distributing chute using the burden charging method disclosed in Patent Document 4,
since the mixing proportion of specific materials will change significantly over time, the
method is unsuitable for forming a uniform mixed layer inside a blast furnace.
[0027]
The present invention is achieved in view of such circumstances, it is an object
of the present invention to provide a burden charging apparatus and a burden charging
method using the same that enable, when main burdens and specific materials are
charged from top bunkers into a blast furnace to form a mixed layer having a uniform
proportion between main burdens and specific materials and to improve the
controllability of the distribution of burdens which have been charged inside the blast
furnace.
SOLUTION TO PROBLEM
[0028]
When blast furnace burdens which have been stored in a top bunker are to be
• g---4
\0
discharged, due to the funnel flow discharge characteristic, the burdens are not
discharged in the same order as in the case when they have been supplied to the top
bunker, as described with reference to Fig. 2. Generally, the burdens that are
accumulated in the region directly above the outlet is discharged first and a rat hole is
formed, the burdens in the periphery of said region where the burdens have been
discharged first (that is, in the periphery of the inner circumferential surface of the rat
hole) crumble from its upper part, flow onto the surface of the burdens in the rat hole
region, and are discharged.
[0029]
Accordingly, in the case where mam burdens and specific materials are
supplied to and stored in a top bunker in the order written and then discharged from the
outlet, a mixing proportion between the main burdens and the specific materials
contained in the discharged burdens will change significantly over time. Therefore, in
the case where after main burdens and specific materials are supplied sequentially into
the top bunker and stored therein, then the stored burdens are to be discharged, it is
difficult to desirably control the proportion between the main burdens and the specific
materials contained in the discharged burdens from the top bunker.
[0030]
Accordingly, inventors of the present invention conducted various experiments
on methods for desirably controlling the proportion between the main burdens and the
specific materials contained in the discharged burdens from the top bunker, and found
after earnest thorough studies, that such control may be realized using the funnel flow
discharge characteristic. A method based on this finding is now described with
reference to the top bunker illustrated in the above-mentioned Fig. 2(b); after a rat hole
is formed while the stored burdens in the region 3d are discharged, detected is the
timing at which the stored burden in the region 3e in the periphery of the region 3d (that
is, in the periphery of the inner circumferential surface of the rat hole) begin to crumble
from its upper part and are mixed with burdens in the rat hole region (that is, burdens
that are accumulated in the lower part of the region 3d), so that the specific materials are
directly fed to an area where this mixing occurs and are mixed with the main burdens
there, and then the mixed burdens are discharged therefrom.
[0031]
-Iff'
II
In order to verify whether or not it is possible to detect the above-mentioned
funnel flow discharge characteristic, an experiment was performed using a parallel
bunker bell-less charging model apparatus of the reduced scale of lI5.6th of an actual
charging apparatus for a blast furnace of 5,370 m3 in volume.
[0032]
Fig. 3 is a diagram illustrating a top bunker in a model apparatus used in an
experiment for detecting how burdens stored in the periphery of the inner
circumferential surface of a rat hole crumble. Fig. 3 illustrates the top bunker 4 that
discharges burdens that are stored therein from the outlet 4a at the bottom thereof, a
level gauge (contactless laser range finder) 10 disposed directly above the outlet 4a, and
burdens 3 that are supplied into and stored in the top bunker 4. In this experiment, a
predetermined mass of main burdens were supplied into and stored in the top bunker 4,
and then the whole of the stored main burdens were discharged from the outlet 4a at the
bottom of the top bunker 4 by setting the aperture of a flow control valve (not shown) to
be constant. At this occasion, a distance from the level gauge 10 to the surface of
burdens in the rat hole region formed directly above the outlet 4a was measured at each
time point after a set period of time by the level gauge 10, so that the height of the
surface of burdens at the rat hole region was measured.
[0033]
In each experiment, the type and an amount (initial burden height) of main
burdens which were supplied into the top bunker were varied and the aperture of the
flow control valve was varied as well.
[0034]
Fig. 4 is a diagram illustrating a relation between an elapsed time (s) after the
startup of discharging burdens and a burden height (mm) at the rat hole, in which Fig.
4(a) illustrates the case where 676 kg of sintered ore is supplied as main burdens, Fig.
4(b) illustrates the case where 473 kg of sintered ore is supplied as main burdens, Fig.
4(c) illustrates the case where 123 kg of coke is supplied as main burdens, and Fig. 4(d)
illustrates the case where 160 kg of coke is supplied as main burdens. The "flow
control valve aperture" in Figs. 4(a) through (d) refers to the aperture of the flow control
valve. As seen from Figs. 4(a) through (d), the speed of decrease of the burden height
at the rat hole is not constant, regardless of the type and the amount of supplied burdens
into the top bunker and the aperture of the flow control valve.
[0035]
Here, it is assumed that the burden height at the rat hole at the time that the
discharging of the burdens is started is defined as Ho(mm), and the burden height at the
rat hole at an elapsed time t(s) after the discharging of the burdens is started is defined
as H(mm), a speed of decrease of the burden height expressed by the following
Equation (1) is defined as VH(mm/s). This speed VH of decrease of burden height (also
referred to as "burden descent speed" hereinafter) is an average speed from the startup
of discharging to the elapsed time t, and the results of the present experiment were
arranged using the burden descent speed.
VH= (Ho- H)/t ...(1)
[0036]
Fig. 5 is a diagram illustrating a relation between an elapsed time (s) after the
startup of discharging burdens and a burden descent speed (mm/s), in which Fig. 5(a)
illustrates the case where 676 kg of sintered ore is supplied as main burdens, Fig. 5(b)
illustrates the case where 473 kg of sintered ore is supplied as main burdens, Fig. 5(c)
illustrates the case where 123 kg of coke is supplied as main burdens, and Fig. 5(d)
illustrates the case where 160 kg of coke is supplied as main burdens. The "flow
control valve aperture" in Figs. 5(a) through (d) refers to the aperture of the flow control
valve.
[0037]
As seen from Figs. 5(a) through (d), regardless of the type and the supplied
amount of the main burdens into the top bunker and the aperture of the flow control
valve, the burden descent speed at the rat hole increases over time after the startup of
discharging, but decreases from a certain time point. The time point that the burden
descent speed stops increasing and starts decreasing is indicated by solid line arrows in
Figs. 5(a) through (d).
[0038]
The burden descent speed stops increasing and starts decreasing at a certain
time point because, as illustrated in the above-mentioned Fig. 2(b), the burdens that are
stored directly above the outlet are discharged first and a rat hole is formed; and then the
burdens in the periphery of the inner circumferential surface of the rat hole crumble
from its upper part, flow onto the surface of the burdens in the rat hole region, and are
discharged therefrom. In other words, the inventors of the present invention found
that, by calculating the burden descent speed based on the burden height measured by
the level gauge and detecting a time point that the burden descent speed stops increasing
and starts decreasing, it becomes possible to detect the time point that burdens as been
stored in the periphery of the inner circumferential surface of the rat hole crumble from
its upper part and flow onto the surface of the burdens in the rat hole region to thereby
be discharged due to the change in the funnel flow discharge characteristic.
[0039]
Furthermore, in the relation between the elapsed time and the burden descent
speed shown in the above-mentioned Fig. 5, the burden descent speed once again
increases in a later period of discharging. This is because the area of a horizontal
cross-section of the space inside the top bunker illustrated in the above-mentioned Fig.
3 (that is, a region where the burdens are stored) is constant in the vicinity of the outlet
at the bottom and in the upper part of stored burdens, but decreases toward the bottom
of the bunker in other intermediate part in a funnel shape.
[0040]
As may be seen from Figs. 4 and 5, the time point that the burden descent
speed stops increasing and starts decreasing (the burden height) fluctuates depending on
the type and the supplied amount of the burdens (the initial burden height) and the flow
control valve aperture (the discharge flow amount). It goes without saying that the
time point that the burden descent speed stops increasing and starts decreasing also
depends on the shape of the top bunker, the location of the surface apex of the burdens
supplied to and stored in the top bunker (that is, the method for supplying the burdens
into the top bunker), and the moisture content of the burdens. Therefore, for grasping
the funnel flow discharge characteristic of the top bunker, it is preferable to perform
online measurement of the change of the burden height over time at the rat hole during
discharging the burdens.
[0041]
Meanwhile, the change of burden charging conditions occur infrequently
during a steady state of the blast furnace. Thus, as long as the blast furnace is operated
repeatedly under the same conditions, the funnel flow discharge characteristic is grasped
in advance based on the measured data. As a result, using the funnel flow discharge
characteristic grasped and known in advance, it is possible to detect a time point that
burdens stored in the periphery of the inner circumferential surface of the rat hole
crumble from its upper part, flow onto the surface of the burdens located in the rat hole
region, and are discharged therefrom.
[0042]
The present invention has been achieved based on the stated findings, and
summaries thereof reside in burden charging apparatuses for a blast furnace described in
(1) and (2) as below, a first embodiment of a burden charging method into a blast
furnace described in the following (3), and a second embodiment of a burden charging
method into a blast furnace described in the following (4).
[0043]
(1) A burden charging apparatus for a blast furnace, in a bell-less charging
apparatus including; two top bunkers each temporarily storing burden for charging into
the blast furnace, a first supply system that supplies the burden into each of the two top
bunkers; and a distributing chute to which the burden discharged from each of the two
furnace top bunkers are supplied via a collecting hopper and which charges the mixed
burden into the blast furnace, the burden charging apparatus characterized in that: at
least one of the two top bunkers comprises: a level gauge for measuring a burden height
at a rat hole; a specific material bunker for temporarily storing specific materials, a
specific material chute for feeding the specific materials discharged from the specific
material bunker into the rat hole of the top bunker having the level gauge, and a flow
control valve for controlling an amount of flow of specific materials discharged from
the specific material bunker.
[0044]
(2) The burden charging apparatus for a blast furnace according to the above
(I), further characterized by comprising a second supply system that diverges from the
first supply system and supplies specific materials to the specific material bunker.
[0045]
(3) A burden charging method into a blast furnace using the burden charging
apparatus for a blast furnace according to the above (1) or (2), the method characterized
in that: when a mixed burden is discharged from the top bunker having the level gauge,
a burden height at a rat hole formed due to the discharging of the burden is measured, a
speed of decrease of burden height is continuously calculated by the following Equation
(1), a time point is detected where the burden height descent speed stops increasing and
starts decreasing, and the discharging of the materials from the specific material bunker
is started within 15 seconds after the detected time point;
VH = (Ho - H)/t ...(1)
given that:
VH is a burden height descent speed (an average speed from the startup of
discharging to an elapsed time t) (mm/s);
t is an elapsed time from the startup of discharging burden (s);
Hois a burden height at the startup of discharging burden (mm);
H is a burden height after the elapsed time t (mm).
[0046]
(4) A burden charging method into a blast furnace using the burden charging
apparatus for a blast furnace according to the above (1) or (2), the method characterized
in that:
The elapsed time A is grasped in advance, the time A being from the startup of
discharging burden from the top bunker having the level gauge to a time point that the
burden descent speed calculated by the Equation (1) stops increasing and starts
decreasing; and
when a mixed burden is charged from the top bunker having the level gauge
under the same conditions as in the case where said time A is grasped, materials are
started to be discharged from the specific material bunker within 15 seconds before and
up to until the time A as being grasped in advance.
ADVANTAGEOUS EFFECTS OF INVENTION
[0047]
A burden charging apparatus and a burden charging method using the same
according to the present invention enable, when a mixed layer is formed by charging
main burdens such as iron sources, a reducing agent, or the like as well as a small
amount of specific materials into a blast furnace, to form the mixed layer with a uniform
mixing proportion between main burdens and specific materials, to enhance the
controllability on the distribution of the charged burdens inside the blast furnace.
BRIEF DESCRIPTION OF DRAWINGS
[0048]
[Fig. 1] Fig. 1 is a conceptual diagram illustrating an example of the
configuration of a parallel bunker bell-less charging apparatus in the related art.
[Fig. 2] Fig. 2 is a diagram illustrating the order of supplying plural types of
burdens and the order of discharging them in a top bunker, in which Fig. 2(a) illustrates
the order of supplying burdens and Fig. 2(b) illustrates the order of discharging.
[Fig. 3] Fig. 3 is a diagram illustrating a top bunker in a model apparatus used
In an experiment for detecting how burdens stored in the periphery of the inner
circumferential surface of a rat hole crumble.
[Fig. 4] Fig. 4 is a diagram illustrating a relation between an elapsed time after
the startup of discharging burdens and a burden height at a rat hole, in which Fig. 4(a)
illustrates the case where 676 kg of sintered ore is supplied as main burdens, Fig. 4(b)
illustrates the case where 473 kg of sintered ore is supplied as main burdens, Fig. 4(c)
illustrates the case where 123 kg of coke is supplied as main burdens, and Fig. 4(d)
illustrates the case where 160 kg of coke is supplied as main burdens.
[Fig. 5] Fig. 5 is a diagram illustrating a relation between an elapsed time after
the startup of discharging burdens and a burden descent speed, in which Fig. 5(a)
illustrates the case where 676 kg of sintered ore is supplied as main burdens, Fig. 5(b)
illustrates the case where 473 kg of sintered ore is supplied as main burdens, Fig. 5(c)
illustrates the case where 123 kg of coke is supplied as main burdens, and Fig. 5(d)
illustrates the case where 160 kg of coke is supplied as main burdens.
[Fig. 6] Fig. 6 is a conceptual diagram illustrating a parallel bunker bell-less
charging apparatus to which the present invention is applied.
[Fig. 7] Fig. 7 is a diagram illustrating a state of burdens which are supplied
into a top bunker according to a comparative example in embodiments of the present
invention.
[Fig. 8] Fig. 8 is a diagram illustrating a relation between an elapsed time and
a coke content percentage, according to a comparative example in embodiments of the
present invention.
.10'
17-
II [Fig. 9] Fig. 9 is a diagram illustrating a relation between an elapsed time and
a coke content percentage, according to a first example of the present invention and a
second example ofthe present invention in embodiments ofthe present invention.
DESCRIPTION OF EMBODIMENTS
[0049]
Hereinafter, a burden charging apparatus for a blast furnace and a burden
charging method using the same according to the present invention will be described
with reference to the drawings.
[0050]
Fig. 6 is a conceptual diagram illustrating a parallel bunker bell-less charging
apparatus to which the present invention is applied. The burden charging apparatus
illustrated in Fig. 6 has the same basic configuration as the burden charging apparatus
illustrated in the above-mentioned Fig. 1; however, the material bins I, charging
conveyor belt 2, and switching chute 15 disposed in the top area of the top bunker are
not shown in Fig. 6. In the burden charging apparatus illustrated in Fig. 6, the
followings are added to the burden charging apparatus illustrated in the
above-mentioned Fig. 1: a level gauge 10 disposed directly above the outlet of the top
bunker 4, a specific material bunker 12 for temporarily storing specific materials 13, a
specific material chute 16 for feeding the specific materials, as being discharged from
the specific material bunker 12, into a rat hole in the top bunker 4, and a flow control
valve 11 for controlling an amount of flow of the specific materials to be discharged
from the specific material bunker 12.
[0051 ]
A burden charging apparatus according to the present invention may employ an
embodiment such that; in a bell-less charging apparatus including two top bunkers 4
each of which temporarily stores the burden to be charged into the blast furnace, a first
supply system that supplies the burden into one of two top bunkers 4 and those of
another type into other bunker, and a distributing chute 8 to which the discharged
burden from two top bunkers 4 are supplied via a collecting hopper 7 and which charges
the mixed burden into the blast furnace; at least one of two top bunkers 4 has a level
gauge 10 for measuring a burden height at a rat hole, a specific material bunker 12 for
II temporarily storing specific materials, a specific material chute 16 for feeding the
specific materials, as being discharged from the specific material bunker 12, into the rat
hole of the top bunker 4 having the level gauge 10, and a flow control valve 11 for
controlling an amount of flow of the specific materials discharged from the specific
material bunker 12.
[0052]
As described above using Fig. 4 and Fig. 5, the top bunker 4 having the level
gauge 10 that measures the burden height at the rat hole enables to calculate a burden
descent speed based on the measured burden height when the burdens are discharged
from the top bunker 4 and charged into the blast furnace, so it becomes possible to
detect a time point that the burden descent speed stops increasing and starts decreasing.
In other words, it is possible to detect a time point that the burdens, which are stored in
the periphery of the inner circumferential surface of the rat hole, crumble from its upper
part due to the change of the funnel flow discharge characteristic, flow onto the surface
of the burdens located in the rat hole region, and are discharged therefrom.
[0053]
In the burden charging apparatus according to the pre.sent invention, the top
bunker 4 that has the level gauge 10 for measuring the burden height at the rat hole
further includes: the specific material bunker 12 for temporarily storing the specific
material, the specific material chute 16 for feeding the materials into the rat hole in the
top bunker 4, and the flow control valve 11 for controlling an amount of flow of the
specific materials. Accordingly, a desired amount of flow of the specific materials
may be supplied to the rat hole in the top bunker 4. For supplying the specific
materials to the rat hole in the top bunker 4, when the specific materials are started to be
supplied based on the change of the funnel flow discharge characteristic, which has
been detected using the level gauge 10; the percentage of the specific materials
contained in the mixed burdens discharged from the top bunker 4 may be desirably
controlled.
[0054]
In the burden charging apparatus according to the present invention, while a
small amount of coke as specific materials are stored in the specific material bunker 12;
out of two top bunkers 4, ore is stored in one top bunker 4 into which the specific
materials are fed from the specific material bunker 12, and another coke as main
burdens is stored in the other top bunker 4; whereby burdens are charged into the blast
furnace. As a result, a coke layer and a mixed layer may be formed in an alternating
manner, thereby allowing burdens to be desirably laid inside the blast furnace.
Accordingly, the burden charging apparatus according to the present invention is
capable of forming a coke layer and a mixed layer in an alternating manner and causing
the burdens to be accumulated inside the blast furnace using two furnace top bunkers,
without increasing the number of the top bunkers.
[0055]
The first supply system that supplies burdens of relevant types into two top
bunkers 4 may employ the same configuration as in the burden charging apparatus
illustrated in the above-mentioned Fig. 1. Specifically, the first supply system may be
configured by the multiple material bins 1, the charging conveyor belt 2, and the
switching chute 15 that is disposed at the top of the top bunker to distribute the burdens
which have been transported by the charging conveyor belt 2 into either of the top
bunkers.
[0056]
It is preferable for the burden charging apparatus according to the present
invention to include a second supply system that diverges from the first supply system
to supply materials to the specific material bunker 12. Specifically, in the case where
the first supply system is configured by the multiple material bins 1, the charging
conveyor belt 2, and the switching chute 15 as described above, it is preferable to add a
channel (the second supply system) that supplies a materials from the switching chute to
the specific material bunker in such a manner that the supply destination of the materials
may be switched to either of two furnace top bunkers or the specific material bunker by
operating the switching chute. As a result, the first supply system may be used to
supply a relevant materials to the specific material bunker, which in tum suppresses
equipment costs.
[0057]
The burden charging apparatus according to the present invention is not limited
to the embodiment as illustrated in the above-mentioned Fig. 6; in which one of two top
bunkers 4 includes: the level gauge 10, the specific material bunker 12 for temporarily
,19'
?O
storing specific materials, the specific material chute 16 for feeding the specific
materials, as being discharged from the specific material bunker 12, into the rat hole in a
top bunker 4 having the level gauge 10, and the flow control valve 11 for controlling an
amount of flow of the specific materials discharged from the specific material bunker
12.
[0058]
In other words, a burden charging apparatus according to the present invention
may employ an embodiment, in which each of two top bunkers includes the
above-mentioned level gauge, the above-mentioned specific material bunker, the
above-mentioned specific material chute, and the above-mentioned flow control valve.
This enables to form a mixed layer using either of the top bunkers, and to change the
top bunker that stores ore. Accordingly, a single charging cycle of forming a coke
layer and a mixed layer in an alternating manner inside the blast furnace may be
configured by, for example, two-divided charges of coke and one charge of ore; and this
configuration may also cope with a case where the top bunker used in ore charging is
switched every charging cycle in order to form a mixed layer.
[0059]
Note that, from the standpoint of equipment costs, it is preferable for a burden
charging apparatus according to the present invention to employ an embodiment in
which either of two top bunkers includes the level gauge or the like.
[0060]
Next, a burden charging method according to the present invention using such
a burden charging apparatus according to the present invention will be described. A
first embodiment of the burden charging method according to the present invention is a
burden charging method into a blast furnace using the above-mentioned burden
charging apparatus according to the present invention, including: when a burden is
discharged from the top bunker having the level gauge, a burden height at a rat hole
formed due to the discharge of the burden is measured, a speed of decrease of burden
height defined by the above Equation (1) (a burden descent speed) is continuously
calculated, a time point is detected where the burden descent speed stops increasing and
starts decreasing, and discharging the material from the specific material bunker is
started within 15 seconds after the detected time point.
2((
2/
[0061]
In a burden charging method in the related art for charging burden into a top
bunker sequentially, when the burdens are discharged from the top bunker in a state
where main burdens and specific materials have been supplied into the top bunker in the
order written, the proportion between the main burdens and the specific materials
contained in the mixed burdens to be discharged from the top bunker will change
significantly over time. In this case, as will be described later related to an
embodiment using Fig. 8, the specific materials are not discharged in the initial period
of discharging and only the main burdens are discharged; the percentage of the specific
materials increases and reaches a peak in the intermediate period of discharging, but
gradually decreases from the intermediate period of discharging toward a later period of
discharging, and then once again increases at the later period of the discharging.
[0062]
Meanwhile, in the first embodiment of the burden charging method according
to the present invention, the burden height is measured at the rat hole formed in
association with the charging of the burdens after the startup of discharging the burdens
from the top bunker; the burden descent speed is continuously calculated; and a time
point that the burden descent speed stops increasing and starts decreasing is detected.
In other words, detected is a time point that the burdens, which are stored in the
periphery of the inner circumferential surface of the rat hole, crumble from its upper
part due to the change of the funnel flow discharge characteristic, flow onto the surface
ofthe burdens located in the rat hole region, and are discharged therefrom.
[0063]
The discharging of materials from the specific material bunker 12 is started
corresponding to such a change of the funnel flow discharge characteristic. As a
result, most of the specific materials, which have been supplied into a top bunker, is
mixed with the burdens in the rat hole region, and the burdens that crumble from the
periphery of the inner circumferential surface of the rat hole and flow onto the surface
of the burdens located in the rat hole region, or the like; and are then discharged from
the outlet.. Therefore, the first embodiment of the burden charging method according
to the present invention enables to have an uniform proportion of the specific materials
contained in the mixed burdens to be discharged from the top bunker from the middle to
later period of discharging as described in an embodiment described later as to a first
example ofthe present invention shown in Fig. 9.
[0064]
Therefore, when burdens are charged into a blast furnace according to the first
embodiment of the burden charging method of the present invention, a mixed layer
having a uniform proportion between the main burdens and the specific materials may
be formed and the controllability of the distribution of the charged burdens inside the
blast furnace may be enhanced. Furthermore, in the first embodiment of the burden
charging method according to the present invention, online measurement of the burden
height is performed using the level gauge to continuously calculate the burden descent
speed. Accordingly, even in the case where a time point that the burden descent speed
stops increasing and starts decreasing fluctuates due to the change in the type of the
burdens, the amount of supplied burdens, the change in the moisture content of the
burdens caused by climate change, and/or the like; a mixed layer having a uniform
proportion between the main burdens and the specific materials may be formed inside
the blast furnace.
[0065]
In the first embodiment of the burden charging method according to the present
invention, it is preferable, from the standpoint of accelerating the formation of the
mixed layers having a uniform proportion between the main burdens and the specific
materials inside the blast furnace and improving the reaction efficiency and gas flow in
the cohesive zone, to rapidly (simultaneously) start discharging the materials from the
specific material bunker after the detection of a time point that the burden descent speed
stops increasing and starts decreasing. Meanwhile, since the mixed layer may not
sufficiently be formed inside the blast furnace if the startup of discharging the materials
from the specific material bunker is too late, in the first embodiment of the burden
charging method according to the present invention, the discharging of the materials
from the specific material bunker is started within 15 seconds after the detection of the
time point that the burden descent speed stops increasing and starts decreasing.
[0066]
.A second embodiment of the burden charging method according to the present
invention is a burden charging method into a blast furnace using the above-described
burden charging apparatus, the method is characterized in that: an elapsed time A is
grasped and known in advance, the elapsed time A being from the startup ofdischarging
the burden out of the top bunker having the level gauge to a time point that a burden
height descend speed as being calculated by the above Equation (1) stops increasing and
starts decreasing; and when a mixed burden are charged from the top bunker having the
level gauge under the same conditions as the case where the time A is grasped, the
discharging of the materials from the specific material bunker is started within 15
seconds before and up to the time A as being grasped and known in advance.
[0067]
The time A from the startup of discharging the burdens to the time point that
the burden descent speed stops increasing and starts decreasing may be grasped and
known using the level gauge by measuring the height of. the burden at the rat hole
formed inside the top bunker at each time point after a set period of time and calculating
the burden descent speed, when main burdens, which have been supplied into a top
bunker under predetermined operating conditions, are discharged.
[0068]
As described above, the time point that the burden descent speed stops
increasing and starts decreasing fluctuates depending on the type of the burdens, the
amount of the charged burdens, and the aperture of the flow control valve provided in
the top bunker. The time point that the burden descent speed stops increasing and
starts decreasing fluctuates also depending on the shape of the top bunker, the position
of the surface apex of the burdens that are supplied to and stored in the top bunker, the
moisture content of burdens, or the like. Meanwhile, as long as these conditions are
the same, the time point that the burden descent speed stops increasing and starts
decreasing is within a certain range. Therefore, in the second embodiment of the
burden charging method according to the present invention, the conditions under which
burdens are charged from the top bunker while the specific materials are fed to the top
bunker are set to be the same as the conditions under which the time A is grasped in
advance.
[0069]
In the second embodiment of the burden charging method according to the
present invention, for charging burdens from top bunkers, the discharging of the
materials from the specific material bunker is started within 15 seconds before and up to
the time A as "been grasped and known in advance. As will be described in an
embodiment described later, the proportion between main burdens and specific
materials contained in the mixed burdens to be discharged from the top bunker may be
controlled in a desired manner and in a uniform manner, even in the case where the
discharging of the materials from the specific material bunker is started earlier than 15
seconds before the time A. Meanwhile, in the case where the discharging of the
materials from the specific material bunker is started earlier than 15 seconds before the
time A as grasped and known in advance, a phenomenon occurs where the proportion of
the specific materials contained in the mixed burden to be discharged from the top
bunker significantly temporarily changes (increases).
[0070]
In this second embodiment of the burden charging method according to the
present invention, the discharging of the materials from the specific material bunker is
started within 15 seconds before and up to the time A. Accordingly, the proportion
between the main burdens and the specific materials contained in the mixed burdens to
be charged from the top bunker may be controlled in a desired manner and in a
uniformed manner over a longer period of time than in the first embodiment of the
burden charging method according to the present invention.
[0071]
According to the burden charging method of the present invention, conditions
such as the type of burdens, the mixing proportion between the main burdens and the
specific materials, operations for the flow control valves provided in the top bunker or
the specific material bunker, operations for tilting the distributing chute, and the like
may be selected and adjusted as desired, so as to cope with various charging conditions
that vary depending on the operating state of the blast furnace.
[0072]
For example, the burden charging method according to the present invention
may be applied even in the case where ore is the main burdens, coke is the specific
materials, and the formation of a mixed layer of ore and coke is undesirable in the
central area of the furnace (the case where a layer of single ore is formed on a furnace
wall side and the central area of the furnace, and a mixed layer is formed in an
intennediate area of the furnace), when the distributing chute is operated so as to charge
the burdens into the furnace wall side, the intennediate area, and'he central area of the
blast furnace in the order written.
[0073]
In this case, supplying coke from the specific material bunker to the bunker is
completed earlier than the case where the discharging of ore' from the furnace top
bunker completes. Specifically, this may be accomplished only by reducing the
amount of coke to be supplied to the specific material bunker, without changing the
aperture of the flow control valve provided in the specific material bunker. In
addition, this may be accomplished only by increasing the aperture of the flow control
valve provided in the specific material bunker, without changing the amount of coke to
be supplied into the specific material bunker.
[0074]
Alternatively, the burden charging method according to the present invention
may be applied even in the case where main burden is iron ore, specific material is coke,
and where it is desired for a mixed layer of iron ore and coke to be fonned on a location
closer to the furnace wall on the furnace wall side, when the distributing chute is
operated to charge the burden into the furnace wall side, the middle area, and the central
area inside the blast furnace in the order written.
[0075]
In this case, by increasing the aperture of the flow control valve provided in the
top bunker, it is possible to reduce the amount of time elapsed from the startup of
discharging the burden into the top bunker to the time point that the burden descent
speed stops increasing and starts decreasing. As a result, the discharging of coke from
the specific material bunker may be started earlier, which makes it possible to fonn a
mixed layer on a location closer to the furnace wall on the furnace wall side of the blast
furnace where burdens are charged.
[0076]
At present, in blast furnace operations, approximately 10 to 20 percent in the
total amount of coke to be charged into the furnace is mixed with ore and charged
thereinto. Accordingly, it is preferable for the burden charging apparatus according to
the present invention to set the ratio of the volume of a specific material bunker relative
to that of a top bunker (quotient of specific material bunker volume divided by top
bunker volume) to be 0.1 or more. However, if the volume of the specific material
bunker is too large, the size of a burden charging equipment mainly including the
burden charging apparatus increase and the equipment becomes expensive, which is
disadvantageous in terms of equipment costs. Therefore, it is preferable for the ratio of
the volume of the specific material bunker relative to that of the furnace top bunker to
be 0.5 or less.
[0077]
Note that the present invention is not limited to the parallel bunker bell-less
charging apparatus described with reference to the embodiments, and may also be
applied to a vertical-bunker bell-less charging apparatus. Furthermore, in the case
where a top bunker provided in the burden charging apparatus has a shape shown in the
above-mentioned Fig. 6, since the rat hole is formed directly above the outlet, the level
gauge is disposed directly above the outlet and the specific material chute is disposed so
that the specific material is charged directly above the outlet. Typically, the rat hole is
formed directly above the outlet ofthe top bunker, but may be formed in other locations
depending on the shape ofthe top bunker. As long as the location where the rat hole is
formed is grasped and known in advance, the present invention may be applied in such
cases as well.
EXAMPLES
[0078]
The following experiments were performed in order to verify the effects of a
burden Charging apparatus and a burden charging method using the same according to
the present invention.
[0079]
[Method of Experiments]
In the present experiments, used is a parallel-bunker bell-less charging model
apparatus of a reduced scale of lIS.6th of the actual unit disposed in a blast furnace of
5,370 m3 in volume. The shape of a top bunker in the bell-less charging model
apparatus was the same as that shown in the above-mentioned Fig. 3. Similarly to the
burden charging apparatus shown in the above-mentioned Fig. 6, this bell-less charging
model apparatus was provided with: a level gauge (contactless laser range finder)
disposed directly above an outlet in the top bunker; a specific material bunker for
temporarily storing specific materials; a specific material chute for feeding the specific
materials from the specific material bunker into a rat hole in the top bunker; and a flow
control valve for controlling the flow amount of the specific materials to be discharged
from the specific material bunker. Sintered ore of 676 kg as main burdens was
supplied into the top bunker, and coke of 20 kg as specific materials was supplied into
the specific material bunker 12.
[0080]
In this state, in a first example of the present invention, the flow control valve
provided in the top bunker was opened while its aperture was kept constant, and the
discharging ofthe burdens from the top bunker was started. At that time, the height of
the burdens at the rat hole formed directly above the outlet was measured every second
by the level gauge, and the burden descent speed was continuously calculated by the
above-mentioned Equation (1).
[0081 ]
In the first example of the present invention, at the same time as the time point
that the burden descent speed stopped increasing and started decreasing was detected,
the flow control valve provided in the specific material bunker was opened and kept at a
constant aperture, and the specific materials were discharged from the specific material
bunker toward the center of the rat hole in the top bunker.
[0082]
In a second example of the present invention, the discharging of materials from
the specific material bunker was started using the time A from the startup of discharging
the burdens from the furnace top bunker to the time point that the burden descent speed
stopped increasing and started decreasing, which was grasped according to the first
example of the present invention. In this case, in the first example of the present
invention, the time A from the startup of discharging burdens from the top bunker to the
time point that the burden descent speed stopped increasing and started decreasing was
35 seconds.
[0083]
In the second example of the present invention, in a state where burdens of
relevant types had been charged into the top bunker and the specific material bunker
under the same conditions as in the first example of the present invention, the flow
control valve provided in the top bunker was opened and kept at a constant aperture, and
then the discharging of the burdens from the top bunker was started. Then, after the
discharging of the burdens from the top bunker was started, the flow control valve
provided in the specific material bunker was opened and kept at a constant aperture, and
the specific materials were discharged from the specific material bunker toward the
center ofthe rat hole in the top bunker, at 15 seconds before the time A as being grasped
in advance (at a time point that 20 seconds have passed after the discharging of the
burdens from the top bunker was started).
[0084]
In both the first and second examples of the present invention, the aperture of
the flow control valve provided in the specific material bunker was set so that the time
when the discharging of all ore from the furnace top bunker completed was the same as
that when the discharging of all coke from the specific material bunker completed.
[0085]
In a comparative example, coke as the specific materials was charged after ore
as the main burdens was charged into the top bunker.
[0086]
Fig. 7 is a diagram illustrating a state of burdens which are supplied into a
furnace top bunker according to the comparative example. As shown in Fig. 7, in the
comparative example, a layer 13 formed by coke was formed onto a layer 14 formed by
ore inside the furnace top bunker. In a state where the burdens were supplied into the
top bunker in this manner, in the comparative example, the flow control valve provided
in the furnace top bunker was opened and kept at a constant aperture, and the
discharging of the burdens from the top bunker was started, so that all of the burdens
inside the top bunker were discharged.
[0087]
[Evaluation Criteria]
Samples of 4 to 6 kg were collected from the burdens discharged from the top
bunker approximately every 6 seconds during a period from the startup of discharging
the burdens from the top bunker to the end of the experiment, for both examples of the
present invention and the comparative example. From the collected samples, coke was
separated through magnetic separation and visual observation and the mass thereof was
measured, so as to calculate the coke content percentage (mass %) in the burdens.
[0088]
[Experiment Results]
Fig. 8 is a diagram illustrating a relation between an elapsed time and a coke
content percentage according to the comparative example. The elapsed time shown in
Fig. 8 is a relative value, in which a time point that the discharging of the burdens from
the top bunker was started is defined as 0 and a time point that the discharging of the
burdens from the top bunker is ended (a time point when all the burdens was
discharged) is defined as 1.
[0089]
As seen from Fig. 8, in the comparative example, Since ore which is
accumulated directly above the outlet was discharged and a rat hole was formed in the
initial period of discharging, only ore was discharged until the elapsed time becomes
near 0.3 after the startup of discharging, with no coke being discharged. In the
intermediate period of discharging, since coke that was accumulated in the periphery of
the inner circumferential surface of the rat hole crumbled and flew onto the surface of
the burdens in the rat hole region, in addition to the coke that was accumulated directly
above the outlet; the coke content percentage increased and reached a peak near an
elapsed time of 0.5. Although the coke content percentage gradually decreased from
the intermediate period to the later period of discharging, the coke content percentage
once again increased in the later period of discharging since the coke that was
accumulated near the bunker side wall was discharged.
[0090]
Fig. 9 is a diagram illustrating a relation between an elapsed time and a coke
content percentage according to a first example of the present invention and a second
example of the present invention. As in the above-mentioned Fig. 8, the elapsed time
shown in Fig. 9 is a relative value, in which a time point that the discharging of the
burdens from the top bunker is started is defined as 0 and a time point that the
discharging of the burdens from the top bunker ends (a time point that all ofthe burdens
were discharged) is defined as 1.
[0091]
The coke content percentage was approximately 4 to 7% after an elapsed time
of approximately 0.6 in the first example of the present invention and approximately 5
to 7% after an elapsed time of approximately 0.5 in the second example of the present
invention, which was essentially constant; and it was thus confirmed that the mixing
proportion of the burdens discharged from the top bunker was made uniform, at which
the present invention aims.
[0092]
In this case, in the second example of the present invention, as the timing when
the discharging of coke from the specific material bunker is started was set earlier, the
pattern became closer to the pattern in the related art having a large peak as shown in
Fig. 8. Accordingly, in the second embodiment of the burden charging method
according to the present invention, the discharging of the materials from the specific
material bunker is started within 15 seconds before and up to the specific time as being
grasped in advance when the burden descent speed stops increasing and starts
decreasing.
INDUSTRIAL APPLICATBILITY
[0093]
A burden charging apparatus and a burden charging method using the same
according to the present invention enable, when a mixed layer is formed by charging
iron sources, a reducing agent, or the like as well as a small amount of specific materials
into a blast furnace, to form a mixed layer having a uniform mixing proportion between
main burdens and the specific materials, so that the controllability of the distribution of
the charged burdens inside the blast furnace is enhanced.
[0094]
Therefore, in blast furnace operations, by forming a mixed layer of ore and
coke inside the furnace by means of the burden charging apparatus and the burden
charging method using the same according to the present invention, a reducing reaction
may be accelerated and the gas flow may be improved in the cohesive zone, which
significantly contributes to an improvement of the productivity of the blast furnace.
REFERENCE SIGNS LIST
[0095]
1: material bin
2: charging conveyor belt
3: charged burdens
4: top bunker
4a: outlet
5: top bunker flow control valve
6: opening
7: collecting hopper
8: distributing chute
8a: center axis of distributing chute
9: blast furnace
9a: central axis of blast furnace
10: level gauge
11: flow control valve for specific material bunker
12: specific material bunker
13: specific materials
14: main burdens (ore)
15: switching chute
16: specific material chute

We claim:
1. A burden charging apparatus for a blast furnace, in a bell-less charging
apparatus including: two furnace top bunkers each of which temporarily stores the
burden to be charged into the blast furnace; a first supply system that supplies the
burden into each of the top bunkers; and a distributing chute to which the burden
discharged from each of the two furnace top bunkers are supplied via a collecting
hopper and that charges the mixed burden into the blast furnace, the burden charging
apparatus characterized in that:
at least one of the two furnace top bunkers comprises: a level gauge for
measuring a burden height at a rat hole; a specific material bunker for temporarily
storing specific materials; a specific material chute for feeding the specific materials, as
being discharged from the specific material bunker, into the rat hole of the top bunker
having the level gauge; and a flow control valve for controlling an amount of flow of
the specific materials discharged from the specific material bunker.
2. The burden charging apparatus for a blast furnace according to claim 1, further
characterized by a second supply system that diverges from the first supply system and
supplies the specific materials to the specific material bunker.
3. A burden charging method into a blast furnace using the burden charging
apparatus for a blast furnace according to anyone of claims 1 and 2, the method
characterized in that:
when a mixed burden is discharged from a furnace top bunker having the level
gauge, a burden height at a rat hole formed by discharging the burden is measured, a
speed of decrease of burden height is continuously calculated by the following Equation
(1), a time point that the burden height descent speed stops increasing and starts
decreasing is detected, and the discharging of the materials from the specific material
bunker is started within 15 seconds after the detected time point;
VH = (Ho - H)/t ...(1)
given that:
VH is a burden descent speed (an average speed from the startup of discharging
to an elapsed time t) (mm/s);
......32'" ;3
t is an elapsed time from the startup ofdischarging burden (s);
Ho is a burden height at the startup ofdischarging burden (mm);
H is a burden height after the elapsed time t (mm).
4. A burden charging method into a blast furnace using the burden charging
apparatus for a blast furnace according to anyone of claims 1 and 2, the method
characterized in that:
the elapsed time A is grasped in advance, the time A being from the startup of
discharging the burden from the top bunker having the level gauge to a time point that
the burden descent speed calculated by the Equation (1) stops increasing and starts
decreasing; and
when a mixed burden is charged from the top bunker having the level gauge
under the same conditions as the conditions for which the time A is grasped, the
discharging of the materials from the specific material bunker is started within 15
seconds before and up to until the time A that has been grasped in advance.
Dated this 29th day of April, 2013.
Nippon Steel & Sumitomo Metal Corporation
~~
(Varon Sharma)
of Amarchand & Mangaldas &
Suresh A. Shroff & Co.
Attorneys for the Applicant