TITLE OF INVENTION: METHOD FOR CHARGING RAW MATERIAL INTO
BELL-LESS BLAST FURNACE
~CHNICALFI ELD
[OOOl]
The present invention relates to a method for charging raw material into a
Bell-less blast fiunace, which is capable of controlling gas flow in the vicinity of a
furnace wall without significantly increasing a reducing material ratio of the blast
furnace.
BACKGROUND ART
[0002]
A bell-less blast fiunace is a blast fiunace which is provided with a bell-less
type charging apparatus having a swivel chute as a raw material charging apparatus
in a furnace top portion.
[0003]
FIG. 1 is a diagram schematically illustrating the apparatus configuration of a
fiunace top portion of a bell-less blast furnace, and a piled-up state of raw material in
the blast furnace. As shown in FIG 1, in the bell-less blast fiunace, iron sources
such as sintered ore, lump ore, pellets, scrap, and reduced iron (hereinafter these are
generically referred to as "ore") and coke, which is a reducing material (ore and coke
are generically referred to as "raw material") are piled up alternately in layers in a
hrnace of a blast furnace 2 by means of a swivel chute 1, and auxiliary fuel such as
pulverized coal is blown into the fiunace along with hot air from a tuyere in a
furnace bottom portion. A charging raw material (charging material) which is the
raw material charged into the blast furnace is heated and reduced by rising hot gas
and the coke in the charging material while gradually descending in the hrnace fiom
the furnace top so that the ore is melted to become pig iron and is discharged fiom a
tap hole in a side wall of a furnace bottom portion.
[0004]
Operation to distribute charging material in the bell-less blast furnace is
performed by turning the swivel chute 1 while being in tilting motion, thereby
charging coke and ore into the furnace, and controlling a fall position of coke and ore
in the direction of a furnace opening radius 4 at a raw material stock level 3. Where,
tilting motion means that an angle formed between a central axis la of the swivel
chute and a central axis 2a in the vertical direction of the blast furnace is changed
during turning. In general, the swivel chute is disposed in a furnace wall side at the
start of charging, and is then actuated to gradually tilt toward a furnace center side.
[OOOS]
In the blast furnace, a series of charging operations to form a coke layer and
an ore layer (which consists mainly of ore, but may include a small or medium lump
coke) are referred to as "charge". Conventionally, one charge of raw material is
charged by continuously charging one batch of coke and one batch of ore
respectively fiom the furnace wall side toward the center side while the swivel chute
is in tilting motion.
[0006]
For stable operation of the blast furnace, it is important to stabilize the descent
of the charging material and the gas flow in the furnace, thereby maintaining good air
permeability. To that end, along with adjustment of condition of air draft from the
tuyere, operation is performed to control the distribution of mass ratio between ore
and coke (hereinafter referred to as "OIC") and particle size distribution of the raw
material to be piled up in the furnace in a furnace radial direction. Since the
average particle size of the coke to be charged into the furnace is larger than that of
the ore, it is possible to control the distribution of gas flow from a h a c e lower
portion toward a furnace upper portion by controlling the OIC distribution and
particle size distribution of the ore and coke in the hate radial direction (that is, by
adjusting the distribution of the charging material).
[0007]
To ensure a stable gas flow, it is preferable to keep the O/C of the central
portion at a low level (that is, to increase the proportion of coke). Further, to
improve the reaction efficiency of the entire furnace, it is preferable to keep the O/C
in a range fiom a furnace intermediate portion (a portion between the region near the
central portion and the region near the furnace wall in the furnace), which occupies a
large proportion of the furnace opening sectional area, to the furnace wall side at a
high level.
[OOOS]
To make such OIC distribution easy to obtain, it is common practice to
separate coke and ore and charge them individually. FIG. 1 shows a piled-up state
5 of one charge of raw material, in which coke and ore are divided into 2 batches
respectively, and a total of 4 batches are charged.
[0009]
A first batch of coke (hereafter, referred to as a "first charging batch") 5a is
charged in a range fiom the furnace wall portion to the intermediate portion, and a
second batch of coke (hereafter, referred to as a "second charging batch") 5b is
charged in the vicinity of the center of the furnace so as to have a larger thickness
than that of the first charging batch 5a. A first batch of ore (hereafter, referred to as
a "third charging batch") 5c is charged over the first and second charging batches 5a
and 5b in a range fiom the furnace wall to the furnace intermediate portion, and a
second batch of ore (hereafter, referred to as a "fourth charging batch") 5d is charged
in the furnace wall side. Owing to the relation between the thickness of the coke
layer, which consists of the first and second charging batches 5a and 5b, and the
thickness of the ore layer, which consists of the third and fourth charging batches 5c
and 5d, the OIC of the central portion of the furnace is kept at a low level, thereby
ensuring a stable gas flow, and the OIC in a range fiom the furnace intermediate
portion to the furnace wall side is kept at a high level, thereby improving the reaction
efficiency of the entire furnace.
[OO lo]
Generally, so-called small-and-middle lump coke, which has a particle size
smaller than that of the coke to be charged in the coke batch, is mixed in the ore
batch. This is because it can be expected that the reaction between ore and coke is
facilitated by disposing them in proximity, and the air permeability is improved as a
result of coke serving as an aggregate (spacer) when the ore is softened and fused
together. The particle size of the small-and-middle lump coke has a lower limit of
about 5 mm, and an upper limit of about 35 to 40 mm, although it varies depending
on the particle size of coke to be charged in the coke batch.
[OO 1 11
Meanwhile, in a blast furnace, zinc-containing compounds may solidify and
form deposits on the inner wall of a furnace upper portion, and metallic iron and slag
on the inner wall in a range fiom a furnace belly portion to a furnace lower portion.
If such furnace wall deposits grow excessively, the descent of charging material and
the gas flow may become unstable, thereby hindering stable operation of the blast
furnace. Further, if furnace wall deposits fall off irregularly and descend to the
furnace lower portion, the furnace may lose heat due to the fallen-off deposits,
thereby even causing serious operation troubles such as cool down of furnace etc,
For this reason, to maintain stable operation of the blast furnace, it is important to
suppress the formation of furnace wall deposits.
[OO 121
To suppress the formation of furnace wall deposits, it is generally attempted
to perform operation to distribute charging material to control the OIC of the furnace
wall side to be relatively low. Since such control enhances the gas flow in the
furnace wall side, thereby maintaining the heat level at a high level, the formation of
deposits can be suppressed.
[0013]
On the other hand, however, since the time for reaction between the gas
moving up in the furnace and the charging material decreases as the gas flow
becomes enhanced, a decrease of OIC leads to a decrease in reaction efficiency.
When the charging amount of coke to the furnace wall side is increased for the
purpose of controlling the formation of furnace wall deposits in the conventional raw
material charging method using a swivel chute, it is difficult to independently control
only the OIC in the vicinity of the furnace wall. This is because OIC will decrease
not only in the vicinity of the furnace wall, but also over a wide range including the
fiunace intermediate portion which occupies a large proportion of the furnace
opening sectional area. Since, for this reason, the reaction efficiency as the entire
hrnace decreases, thereby increasing the latent heat of the gas to be discharged fiom
a furnace top to outside of the furnace, the reducing material ratio will increase to
make up for the heat, thus increasing the production cost of pig iron. It is also not
preferable in the viewpoint of reduction of COz emission amount.
[00 141
Therefore, to realize operation at a lower reduction material ratio while
suppressing formation of furnace wall deposits, a technique for independently control
the O/C only in the vicinity of the furnace wall is necessary, and for example, Patent
Literatures 1 to 3 disclose methods therefor.
[OO 1 51
Patent Literature 1 makes it possible to control the O/C in the vicinity of the
furnace wall without requiring a new ancillary facility, by charging small lump coke,
preferably as a mixture with fine particle sintered ore having a particle size of 1 to 5
mm, on the ore layer in a range of 500 mm fiom the furnace wall. However, it is
dBicult to make small lump coke stably pile up on a terrace in a range of 500 mm
fiom the furnace wall.
[OO 161
Patent Literature 2 makes it possible to independently control the O/C in the
vicinity of the furnace wall by charging raw material in a state that a cylindrical
member is placed along a furnace opening outer periphery. However, since control
range is fixed by the placement position of the cylindrical member, the degree of
fieedom in operation is small.
[00 171
Patent Literature 3 makes it possible to independently control the O/C in the
vicinity of the furnace wall by providing a raw material charging system different
fiom a normal route and a supplemental bunker, and discharging coke fiom the
supplemental bunker in conjunction with ore discharge from the normal bunker.
However, since it is necessary in this method to control the coke discharge fiom the
supplemental bunker in accordance with the ore discharge fiom the normal bunker
and the tilting position of the swivel chute, its control becomes complicated.
CITATION LIST
PATENT LITERATURE
[OO 181
Patent Literature 1: Japanese Patent Application Publication No. 8-239705
Patent Literature 2: Japanese Patent Application Publication No. 2005-3 14771
Patent Literature 3: Japanese Patent Application Publication No. 2009-62576
NON PATENT LITERATURE
[OO 191
Non Patent Literature 1 : Kaoru Nakano, Kohei ~ukharaa,n d Takanobu Inada,
"Advanced Supporting System for Burden Distribution Control at Blast Furnace
Top," ISIJ International, 45(2005), p. 538 to 543.
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0020]
Since if it is attempted to increase the charging amount of coke to the vicinity
of the furnace wall by an ordinary operation to distribute charging material to
suppress the formation of furnace wall deposits, O/C decreases not only in the
vicinity of the furnace wall but also in a wide range including the furnace
intermediate portion, it becomes difficult to concurrently achieve operation at a low
reduction material ratio. To achieve these at the same time, it is necessary to
independently control only the O/C in the vicinity of the furnace wall.
[002 11
Since both the methods according to Patent Literatures 2 and 3 described
above require a new ancillary facility to be installed in an ordinary bell-less charging
apparatus, and are disadvantageous in terms of installation cost and maintenance cost,
a charging method which does not require a new ancillary facility is desirable.
[0022]
Moreover, although, in the method according to Patent Literature 1 described
above, a range of 500 rnm from the furnace wall is specified as a charging range of
small lump coke, the relative position in radial direction in the h a c e of small lump
coke will vary depending on the furnace opening radius of the blast furnace. For
example, although it depends on the furnace volume of the blast furnace and
charging conditions thereof, generally, the width of raw material flow to be charged
via a swivel chute often becomes 500 mm or more at a stock level, and therefore it is
dBicult to make the raw material to be stably piled up on the terrace in a range of
500 mm fiom the furnace wall. Since the raw material is made up of small lump
coke and fine particle sintered ore, if part of the raw material overflows fiom the
terrace and flows into the center side, there is risk that it hinders the gas flow in the
central portion, or causes fluctuation of the gas flow.
[0023]
The present invention has been made in view of the above described
circumstances, and has its object to provide a method for charging raw material into
a bell-less blast furnace, which can independently control OIC only in the vicinity of
the furnace wall without requiring a new ancillary facility.
SOLUTION TO PROBLEM
[0024]
Generally in many blast furnaces, to enhance gas flow in the central portion
for continuing stable operation, it is attempted to reduce the reducing material ratio
by maintaining the OIC in a range fiom the furnace intermediate portion, which
occupies a large proportion of the furnace opening sectional area, to the furnace wall
side at a high level while keeping the OIC of the center side at a low level.
[0025]
On the other hand, under a condition in which furnace wall deposits have
excessively grown and thereby may hinder stable operation of the blast furnace, it is
effective to decrease the OIC in the vicinity of the furnace wall as the method for
suppressing the formation of deposits or removing deposits. However, as described
above, it is difficult to independently control only the OIC in the vicinity of the
furnace wall by an ordinary method of continuously charging raw material fiom the
furnace wall side toward the center side while the swivel chute is in tilting motion,
and the OIC will decrease in a wide range including the furnace intermediate portion.
Therefore, although the formation of furnace wall deposits is suppressed by
enhancing gas flow of the furnace wall side, the reaction efficiency as the entire
furnace decreases, thereby resulting in significant increase in the reduction material
ratio.
[0026]
Therefore, if it is possible to independently control and decrease the OIC only
in the vicinity of the furnace wall without significantly changing ordinary OIC
distribution in the furnace radial direction from the furnace center to the intermediate
portion, it becomes possible to suppress both of formation of furnace wall deposits
and significant increase of the reducing material ratio.
[0027]
Accordingly, the present inventors have conducted various studies on the
method of charging raw material for a bell-less blast furnace, which can
independently control and decrease the OIC in the vicinity of the furnace wall. As a
result of that, they have found a method for charging raw material, which can
independently control only the OIC in the vicinity of the furnace wall without
requiring a new ancillary facility by charging raw material from a chute, thereby
forming a piled-up layer of the raw material having a peak in the furnace
intermediate portion, and taking advantage of a segregation effect by a raw material
slope in a range from that peak (hereafter, referred to as a "piled-up peak") to the
furnace wall.
[0028]
The present invention has been made based on such a study result, and its gist
is the following method for charging raw material into a bell-less blast furnace.
That is, a method for charging raw material into a bell-less blast furnace such
that a coke layer and an ore layer are alternately piled up, characterized in that
a coke batch, a mixture batch of ore and coke, and an ore batch are charged in
this order with respect to raw material charging from a furnace intermediate portion
to a furnace wall;
the coke batch is piled up such that a coke surface has a piled-up peak in a
range of dimensionless furnace-opening radius of 0.6 to 0.8, and forms a raw
material piled-up slope which is inclined from the piled-up peak to a h a c e center
and to the furnace wall;
the mixture batch of ore and coke is charged such that a fall point of charging is
on the furnace wall side from the piled-up peak of coke; and
the ore batch is charged such that the fall point of charging is in a range of
dimensionless furnace-opening radius of 0.5 to 0.9.
The above described "dimensionless furnace-opening radius" is an index to
represent a position with respect to the furnace center in a raw material charging
plane (raw material stock level), and also an index normalized by dividing a distance
fiom the furnace center to the relevant position by the furnace opening radius. The
furnace center is represented by 0 and the furnace wall by 1.
Moreover, the above described "furnace intermediate portion" here refers to a
range of dimensionless furnace-opening radius of 0.5 to 0.8.
[0029]
In the method for charging raw material into a bell-less blast furnace of the
present invention, it is desirable to take on an embodiment in which charging is
performed such that a charging amount of the above described mixture batch of ore
and coke is less than that of the ore batch, and the fall point of charging of the
mixture batch of ore and coke is on the furnace wall side fiom the piled-up peak
formed by the charging of the coke batch, and in a range of dimensionless furnaceopening
radius of not more than 0.9.
[003 01
Moreover, in the method for charging raw material into a bell-less blast
furnace of the present invention, it is possible to take on an embodiment in which a
batch of coke alone is charged in place of the mixture batch of ore and coke.
ADVANTAGEOUS EFFECTS OF INVENTION
[003 11
According to the method of the present invention for charging raw material
into a bell-less blast furnace, it is possible to independently control and decrease OIC
only in the vicinity of the furnace wall without requiring a new ancillary facility.
This makes it possible to enhance the gas flow of the furnace wall side, thereby
suppressing formation of furnace wall deposits, or removing deposits. Since this
method for charging raw material does not significantly increase the reducing
material ratio of the blast furnace, it can suppress decrease in productivity, increase
in pig iron production cost, and increase in the amount of COz emission.
BRIEF DESCRIPTION OF DRAWINGS
100321
[FIG. 11 FIG. 1 is a schematic view showing apparatus configuration of a furnace top
portion of a bell-less blast furnace and a raw material piled-up state in the blast
furnace.
[FIG. 21 FIG. 2 is a diagram showing a calculation result by a simulation model of
raw material piled-up profile, in which (a) is Comparative Example and (b) is
Inventive Example of the present invention.
[FIG. 31 FIG. 3 is a diagram showing a calculation result by a simulation model of
O/C distribution in the furnace radial direction.
[FIG. 41 FIG. 4 is a diagram showing calculation results by a simulation model of infurnace
distribution of ore and coke in an ore batch according to the method of the
present invention for charging raw material.
[FIG. 51 FIG. 5 is a diagram showing raw material piled-up profiles in a model
experiment, in which (a) is Comparative Example, and (b) is Inventive Example of
the present invention.
[FIG. 61 FIG. 6 is a diagram showing an O/C distribution in the furnace radial
direction in a model experiment.
DESCRIPTION OF EMBODIMENTS
[0033]
The method for charging raw material according to the present invention is
premised on a method for charging raw material in which coke layers and ore layers
are charged to be alternately piled up, which are commonly practiced in a bell-less
blast furnace as described above.
[003 41
In the method for charging raw material according to the present invention,
upon alternately piling up coke layers and ore layers, a coke batch, a mixture batch of
ore and coke, and an ore batch are charged in this order with respect to raw material
charging from the furnace intermediate portion to the h a c e wall. The statement
"with respect to raw material charging from the furnace intermediate portion to the
h a c e wall" intends to focus on raw material charging in an in-furnace region
excluding the center of the furnace and the furnace intermediate portion. For
example, coke can be charged into the vicinity of the center of the furnace as a
second charging batch 5b after being charged into a range fiom the furnace wall
portion to the intermediate portion as a first charging batch 5a as in the past (see FIG.
1).
[003 51
First, the coke batch is charged to pile up a coke layer such that the coke layer
surface has a piled-up peak in a range of dimensionless furnace-opening radius of 0.6
to 0.8 at the end of coke charging, and forms a raw material piled-up (coke layer)
slope which is inclined fiom the piled-up peak to a furnace center and to the furnace
wall. Next, a mixture batch of ore and coke is charged such that the fall point of
charging of the mixture batch is on the h a c e wall side fiom the piled-up peak of
the coke layer.
[003 61
The reason why the coke layer is piled up such that the coke layer surface has
a piled-up peak in the predetermined range of dimensionless furnace-opening radius
at the end of coke charging, and forms a raw material piled-up slope which is
inclined fiom the piled-up peak to the furnace center is because it is intended to
enhance central gas flow by facilitating particle size segregation on the slope and
causing raw material having larger particle sizes to be piled up in the furnace center
side. Moreover, the reason why a slope which is inclined fiom the piled-up peak to
the h a c e wall is formed is to cause particles of larger sizes to be piled up in the
vicinity of the furnace wall by taking advantage of a phenomenon of particle size
segregation on the slope.
[0037]
For that reason, it is not preferable that the piled-up peak on the coke layer
surface is formed to be excessively close to the center. Further, it is preferable to
prevent the raw material of the mixture batch of ore and coke to be charged after the
formation of the coke layer from flowing into the center side, and to effectively take
advantage of the particle segregation on the slope fiom the piled-up peak to the
furnace wall. From these viewpoints, the piled-up peak of the coke layer is formed
to be in a range of dimensionless hrnace-opening radius of 0.6 to 0.8. Generally,
small-and-middle lump coke is mixed in the mixture batch of ore and coke. In this
case, ore and coke are separated because of differences in particle size and density so
that coke which has a larger particle size and a lower density with respect to ore is
piled up in the vicinity of the furnace wall. This makes it possible to decrease the
O/C in the vicinity of the furnace wall.
[003 81
Therefore, the charging position of the mixture batch of ore and coke onto the
coke slope is important. This charging position is made to be on the furnace wall
side fiom the piled-up peak of the coke layer. However, since it is not possible to
take advantage of the segregation effect and therefore not possible to decrease the
O/C in the vicinity of the furnace wall if the charging position is too close to the
furnace wall, the charging position is desirably in a range of dimensionless furnaceopening
radius of not more than 0.9 as described below.
[003 91
It is noted that while in the method according to Patent Literature 1 described
above, a mixture of ore and coke is charged onto an ore layer which is formerly
formed, in the method for charging raw material according to the present invention, a
mixture of ore and coke is charged onto a coke layer, for example, as a second batch.
Therefore, in the method for charging raw material according to the present invention,
ore which has a smaller average particle size compared with coke, is more likely to
stay at the fall point of charging in a form to fill a vacant space in the coke layer, and
coke, which has a larger average particle size than that of ore, becomes more likely
to be piled up in the furnace wall side away fiom the fall point due to the segregation
on the slope.
[0040]
Next, an ore batch is charged. This ore batch is charged as usual while a
swivel chute is in tilting motion fiom the fUrnace wall side to the center side such
that the fall point of charging is in a range of dimensionless furnace-opening radius
of 0.5 to 0.9. Since charging raw material of the mixture batch of ore and coke
which is piled up in the furnace wall side acts as a barrier against the ore batch piling
up in the furnace wall side, the O/C in the vicinity of the furnace wall will not
excessively increase, and will be kept at a low level.
COO4 11
In the method for charging raw material according to the present invention, it
is desirable to take on an embodiment in which a charging amount of the above
described mixture batch of ore and coke is less than that of the ore batch, and the f d
point of charging of the mixture batch of ore and coke is on the furnace wall side
from the piled-up peak after completion of charging of coke, and in a range of
dimensionless furnace-opening radius of not more than 0.9.
The reason why the charging amount of the mixture batch of ore and coke is
set to be less than that of the ore batch is to prevent the raw material to be charged in
the mixture batch of ore and coke from flowing over to the furnace center side from
the piled-up peak of the coke layer.
The reason why the mixture batch of ore and coke is charged is for the
purpose of bringing ore and coke into contact not as layers but as grains (that is, by
disposing ore and coke in proximity), thereby facilitating reaction, and also making
the coke function as an aggregate (spacer), thereby enhancing the gas flow in the
furnace wall side and more effectively suppressing the formation of furnace wall
deposits. The above described effect can be equally obtained in both cases where
the coke to be mixed with ore in the mixture of ore and coke is small-and-middle
lump coke and large lump coke (coke having a particle size which is charged in an
ordinary coke batch).
Moreover, since charging a mixture of ore and coke makes it possible to
control the OIC in the vicinity of the furnace wall by adjusting the amount of coke,
the degree of freedom in operation is ensured as well.
The reason why the mixture batch of ore and coke is charged with its fall
point of charging being on the furnace wall side from the piled-up peak after
completion of coke charging, and in a range of dimensionless furnace-opening radius
of not more than 0.9 is because if the charging position in the furnace of the mixture
batch of ore and coke is too close to the furnace wall, segregation effect on the coke
slope cannot be obtained, and ore as well as coke is piled up in the vicinity of the
furnace wall, thereby increasing the OIC.
[0046]
Moreover, in the method for charging raw material into a bell-less blast
furnace according to the present invention, it is possible to take on an embodiment in
which a batch made up of coke alone is charged in place of the mixture batch of ore
and coke.
[0047]
In this case, since there is no need to take consideration of the separation of
ore and coke by particle size segregation effect on the piled-up slope when charging
the mixture batch of ore and coke, charging can be performed with relative ease, and
further can be made to concentrate in the vicinity of the furnace wall. The
controllability of the OIC in the vicinity of the furnace wall and the degree of
freedom in operation based thereon can be equally maintained as in the case where
the mixture batch of ore and coke is charged.
[0048]
Moreover, since only coke is charged, the effect of facilitating reaction by
disposing ore and coke in proximity cannot be expected, but the effect of suppressing
the formation of furnace wall deposits by the enhancement of gas flow in the furnace
wall side, or immediate effect of removing the deposits can be expected.
[0049]
As so far described, according to the method for charging raw material of the
present invention, it is possible to independently control and decrease the OIC in the
vicinity of the fiunace wall without requiring installment of new facility and
maintenance cost associated therewith. Decrease of the OIC in the vicinity of the
furnace wall makes it possible to enhance the gas flow in the furnace wall side,
thereby suppressing the formation of furnace wall deposits or removing the deposits.
Further, since it becomes possible to decrease the OC only in the vicinity of the
furnace wall, there is no need to significantly increase the reducing material ratio of
the blast furnace, and therefore it is possible to suppress decrease in productivity,
increase in pig iron production cost, and increase in the amount of C02 emission.
EXAMPLES
[0050]
The advantageous effects of the method for charging raw material according
to the present invention was verified by using a simulation model for charging
material distribution of a bell-less blast furnace according to Non Patent Literature 1
described above, and a bell-less charging model apparatus.
[005 11
(Example 1)
[Charging material distribution simulation]
The subject blast furnace was a bell-less blast furnace having a furnace
volume of 5,370 m3, and one charge was made up of a total of 4 batches including 2
batches of coke and 2 batches of ore based on charging record of a real furnace.
The charging amount per one charge was assumed to be 25.7 ton in total of coke
batch, and 140.7 ton in total of ore batch including 4.1 ton of coke (of a particle size
of 6 to 50 mm). One batch out of the two batches of coke corresponds to a coke
batch ("first charging batch 5a" of FIG. 2 to be described below, hereafter referred to
by this term) to be charged in a range fiom the furnace intermediate portion to the
furnace wall. Moreover, 2 batches of ore were the mixture batch of ore and coke
(hereafter, referred to as "third charging batch 5c") and an ore batch (hereafter,
referred to as "fourth charging batch 5d"). The mass ratio between the third
charging batch 5c and the fourth charging batch 5d in Example of the present
invention was assumed to be 10:90.
[0052]
FIG. 2 is a diagram showing calculation results of a simulation model of raw
material piled-up profile. Where, (a) is Comparative Example in which raw
material charging was conducted by an ordinary operation, and (b) is Inventive
Example of the present invention in which raw material charging was conducted by
the above described method of the present invention. FIG. 2 shows one charge of
raw material piled-up profile (that is, first and second charging batches 5% 5b of
coke, and third and fourth charging batches 5c, 5d of ore, where the third charging
batch 5c includes coke).
[0053]
In the raw material piled-up profile of Comparative Example shown in FIG.
2(a), the OIC in a range fiom the furnace intermediate portion to the furnace wall
side was kept at a high level while keeping the OIC in the center portion at a low
level to aim at stabilizing the central gas flow and improving reaction efficiency in a
range fiom the furnace intermediate portion to the furnace wall side.
[0054]
In contrast to this, in Inventive Example of the present invention shown in
FIG. 2(b), the coke layer was piled up such that the coke layer (first charging batch
5a), which was formed before the charging of ore, had a piled-up peak 6 at a
dimensionless furnace-opening radius of 0.7, and formed a raw material slope which
was inclined fiom the piled-up peak to the furnace center and to the furnace wall.
The raw material of the third charging batch 5c to be charged after the formation of
the coke layer was assumed to be a mixture of ore and coke, and fiom the viewpoint
of preventing the raw material of the aforementioned batch fiom flowing to the
center portion, the tilting angle of the swivel chute was adjusted such that the raw
material supplied fiom the swivel chute was charged at a position of a dimensionless
furnace-opening radius of 0.9 which was on the furnace wall side from the piled-up
peak of the coke layer. Adopting such a charging method would result in that ore
and coke were separated due to particle segregation on the slope of the coke layer in
a range fiom the piled-up peak in the furnace intermediate portion to the furnace wall,
and coke was piled up in the vicinity of the furnace wall.
[0055]
Then, the fourth charging batch 5d to be charged next was charged with the
fall point of charging being in a range of dimensionless furnace-opening radius of
about 0.6 to 0.8, while the swivel chute is in tilting motion from the furnace wall side
to the furnace intermediate portion. Since the raw material of the third charging
batch 5c which was piled up in the furnace wall side would act as a barrier against
the raw material of the fourth charging batch 5d being piled up in the furnace wall
side, the OIC in the vicinity of the furnace wall was kept a low level.
[0056]
FIG. 3 is a diagram showing calculation results by the simulation model of the
OIC distribution in the furnace radial direction, in which the radial distribution of
OIC of a furnace top portion of the blast furnace by the method for charging raw
material in an ordinary operation (Comparative Example) as shown in FIG. 2(a) is
compared with the radial distribution of OIC by the method for charging raw material
according to the present invention shown in FIG. 2(b). FIG. 3 reveals that in the
method for charging raw material according to the present invention in which the
piled-up peak position of the coke layer was at a dimensionless furnace-opening
radius of 0.7, and the raw material charging position of the third charging batch was
at a dimensionless furnace-opening radius of 0.9, the OIC fiom the furnace center to
the furnace intermediate portion did not change significantly compared with the case
of the method for charging raw material in an ordinary operation, and thus the OIC in
the vicinity of the furnace wall decreased, thus realizing a desired OIC distribution
state.
[0057]
FIG. 4 is a diagram showing calculation results by a simulation model of infurnace
distribution of ore and coke in an ore batch in the method for charging raw
material according to the present invention, in which the piled-up peak position of
the coke layer was at a dimensionless furnace-opening radius of 0.7, and the infurnace
charging position of the third charging batch was at a dimensionless furnaceopening
radius of 0.9. This figure reveals that a large amount of coke was piled up
in the vicinity of the furnace wall as a result of particle size segregation on the coke
slope.
[0058]
The results of above described verification using the simulation model for
charging material distribution of a bell-less blast furnace confirmed advantageous
effects (that is, effects that the OIC in the vicinity of the furnace wall can be
controlled independently) of the method for charging raw material according to the
present invention.
[0059]
(Example 2)
[Bell-less charging model experiment]
The effects of the method for charging raw material according to the present
invention was verified by using a bell-less charging model apparatus which is a 1/56
scale model of a furnace volume of 5,370 m3.
[0060]
The particle size of the raw material used in the experiment was about 1/56 of
the real furnace particle size, and the charging amount per one charge was
determined according to the similarity rule as: 146 kg in total of coke batches (the
first and second charging batches) and 801 kg in total of ore batches (the third and
fourth charging batches) including 23 kg of coke (of a particle size of 1 to 10 mm).
The mass ratio between the third charging batch and the fourth charging batch in
Example of the present invention was set to be 10:90.
[0061]
In the model experiment, when performing raw material charging according
to the method of the present invention, the piled-up peak position of the coke layer
was at a dimensionless furnace-opening radius of 0.7, and the raw material charging
position of the third charging batch was at a dimensionless furnace-opening radius of
0.9 as in Example 1.
[0062]
FIG. 5 is a diagram showing raw material piled-up profiles in the model
experiment. Where, (a) shows Comparative Example in which raw material
charging was conducted by an ordinary operation, and (b) shows Inventive Example
of the present invention in which raw material charging was conducted by the above
described method of the present invention. The raw material piled-up profile in the
furnace was continuousl; measured by using a laser range meter. It is noted that
FIG. 5 shows a raw material piled-up profile of one charge.
[0063]
FIG. 5 reveals that in both of the case (Comparative Example) in which raw
material charging was conducted by an ordinary operation, and the case in which raw
material charging was conducted by the method of the present invention, the raw
material piled-up profiles were substantially the same as those of the calculation
results by the above described simulation model for charging material distribution.
[0064]
FIG. 6 is a diagram showing the O/C distribution in the furnace radial
direction in the model experiment, in which the radial distribution of O/C of a
fumace top portion of the blast furnace by the method for charging raw material in an
ordinary operation (Comparative Example) as shown in (a) of FIG. 5 is compared
with the radial distribution of O/C by the method for charging raw material according
to the present invention as shown in (b). FIG. 6 reveals that when raw material
charging was conducted by the method for charging raw material according to the
present invention, the O/C from the furnace center to the furnace intermediate
portion did not change significantly compared with the case of the method for
charging raw material by an ordinary operation, and the O/C in the vicinity of the
furnace wall decreased as in the calculation results by the simulation model (see FIG.
3 1.
[0065]
The results of above described verification by using the bell-less charging
model apparatus confirmed advantageous effects (that is, effects that the O/C in the
vicinity of the furnace wall can be controlled independently) of the method for
charging raw material according to the present invention.
INDUSTRIAL APPLICABILITY
[0066]
According to the method of the present invention for charging raw material to
a bell-less blast furnace, it is possible to independently control and decrease the O/C
only in the vicinity of the furnace wall. Further, since this method can prevent the
formation of furnace wall deposits without significantly increasing the reducing
material ratio of the blast furnace, it is possible to suppress decrease in productivity,
increase in pig iron production cost, and the like. Therefore, the present invention
can be effectively used at the time of raw material charging into a bell-less blast
h a c e .
REFERENCE SIGNS LIST
[0067]
1 : Swivel chute, 1 a: Central axis of swivel chute,
2: Blast furnace, 2a: Central axis of blast furnace,
3: Raw material stock level, 4: Furnace opening radius,
5: One charge of raw material, 5a: First charging batch,
5b: Second charging batch, 5c: Third charging batch,
5d: Fourth charging batch,
6: Piled-up peak of coke layer

We claim:-

1. A method for charging raw material into a bell-less blast furnace such that a
coke layer and an ore layer are alternately piled up, characterized in that
a coke batch, a mixture batch of ore and coke, and an ore batch are charged in
this order with respect to raw material charging from a furnace intermediate portion
to a furnace wall;
the coke batch is piled up such that a coke surface has a piled-up peak in a
range of dimensionless furnace-opening radius of 0.6 to 0.8, and forms a raw
material piled-up slope which is inclined from the piled-up peak to a furnace center
and to the furnace wall;
the mixture batch of ore and coke is charged such that a fall point of charging
is on the furnace wall side from the piled-up peak of coke; and
the ore batch is charged such that the fall point of charging is in a range of
dimensionless furnace-opening radius of 0.5 to 0.9.
2. The method for charging raw material into a bell-less blast furnace as
claimed in claim 1, characterized in that charging is performed such that
a charging amount of the mixture batch of ore and coke is less than that of the
ore batch, and
the fall point of charging of the mixture batch of ore and coke is on the
furnace wall side from the piled-up peak formed by the charging of the coke batch,
and in a range of dimensionless furnace-opening radius of not more than 0.9.
3. The method for charging raw material into a bell-less blast furnace as
claimed in claim 1 or 2, characterized in that
a batch of coke alone is charged in place of the mixture. batch of ore and coke.
Dated this 2nd day of December, 20 14.