TECHNICAL FIELD
The present invention relates to a method for producing pig iron and a blast
furnace to be used therefor.
5 BACKGROUND ART
Pig iron is produced from iron ore in a blast furnace by feeding the
materials of iron ore, calcium oxide, and coke into the blast-furnace body from the
top thereof, and blowing in hot air and blast-furnace-injecting coal (pulverized
coal) from a tuyere in a lower portion of the side of the blast-furnace body.
In order to stably operate the blast furnace, it is necessary to suppress
adhesion of blast-furnace-injecting-coal ash to the path of the
blast-furnace-injecting coal into the blast-furnace body and blockage by the
blast-furnace-injecting-coal ash.
For example, it has been proposed that by adding a flux that is a source of
15 CaO such as calcium oxide or serpentine to pulverized coal whose ash has a
melting point of less than 1300°C, the melting point of the ash in the pulverized
coal is adjusted to 1300°C or higher, next only the pulverized coal whose ash has a
melting point of 1300°C or higher is blown to the interior of the blast-furnace body
from the tuyere, thereby improving the combustion properties of the
20 blast-furnace-injecting coal (for example, see Patent Document 1 below).
Also, for example, a method of blowing pulverized coal into a blast furnace
has been proposed in which by further reducing the combustibility by adjusting the
amount of enriching oxygen or the composition or particle size of the pulverized
coal so that the highest temperature reached within the raceway is reduced, it is
possible to improve the ventilation even when blowing a very large quantity of
pulverized coal (for example, see Patent Document 2 below).
CITATION LIST
5 Patent Literature
Patent Document 1 : Japanese Unexamined Patent Application Publication
NO. H05-156330A
(For example, see paragraphs [0014] to [0023], FIG. 1, and the like of the
Specification.)
Patent Document 2: Japanese Unexamined Patent Application Publication
NO. H11-152508A
SUMMARY OF INVENTION
Technical Problem
15 However, with the method of blowing the pulverized coal into the blast
furnace disclosed in Patent Document 1, the flux is added as described above, and
only pulverized coal that has been adjusted so that the ash melting point is 1300°C
or higher is used, so this can increase the running costs.
Also, with the method of blowing pulverized coal into a blast furnace
20 disclosed in Patent Document 2, the blowing quantity of pulverized coal is very
large, and it is necessary to deliberately adjust the composition or particle size of
the pulverized coal, so this can also increase the running costs.
Therefore, the present invention has been devised to solve the above
problems, and it is an object of the present invention to provide a method for
25 producing pig iron and a blast furnace to be used therefor capable of suppressing
3
the adhesion of blast-furnace-injecting-coal ash to the path of
blast-furnace-injecting coal into the blast-furnace body and blockage by the
blast-furnace-injecting-coal ash, and reducing the cost of producing pig iron.
5 Solution to Problem
The method of producing pig iron according to a first invention that solves
the above problem is a pig iron producing method for producing pig iron from
material iron ore by feeding material that includes iron ore and coal into a
blast-furnace body from the top thereof, and blowing hot air and
10 blast-furnace-injecting coal into the blast-furnace body from a tuyere, wherein the
blast-furnace-injecting coal has an oxygen atom content (dry base) of from 10 wt%
to 20 wt% and an average pore diameter of from 10 nm to 50 nm, the melting point
of the ash in the blast-furnace-injecting coal is measured in advance, and the
temperature of the hot air is adjusted to a temperature 100 to 1 50°C lower than the
15 melting point of the ash.
The method of producing pig iron according to a second invention that
solves the above problem is the pig iron producing method according to the first
invention in which the hot air is enriched with oxygen at the tuyere of the
blast-furnace body.
The blast furnace according to a third invention that solves the above
problem includes: a blast-furnace body; material-insertion means for feeding
material that includes iron ore and coal into the blast-furnace body from the top
thereof; hot-air blowing means for blowing hot air into the interior from a tuyere of
the blast-furnace body; and blast-furnace-injecting-coal supply means for blowing
25 blast-furnace-injecting coal into the interior from the tuyere of the blast-furnace
body, wherein the blast-furnace-injecting-coal supply means blows in
blast-furnace-injecting coal with an oxygen atom content (dry base) of 10 to 20
wt% and an average pore diameter of 10 to 50 nm, and the hot-air blowing means
measures the melting point of the ash in the material in advance, and blows in hot
5 air that is 100 to 1 50°C lower than the melting point of the ash.
The blast furnace according to a fourth invention that solves the above
problem is the blast furnace according to the third invention, further comprising
oxygen enrichment means for enriching the oxygen of the hot air in the tuyere of
the blast-furnace body.
The blast furnace according to a fifth invention that solves the above
problem is the blast furnace according to the fourth invention, wherein the oxygen
enrichment means includes an injection lance to which oxygen flows, and the tip
end of the injection lance is disposed further toward the inside of the blast-furnace
body than the base end side of the tuyere of the blast-furnace body.
15
Advantageous Effects of Invention
According to the method of producing pig iron and the blast furnace to be
used therefor of the present invention, blast-furnace-injecting coal has an oxygen
atom content (dry base) of 10 to 20 wt% and an average pore diameter of 10 to 50
20 nm, in other words, blast-furnace-injecting coal with greatly suppressed
decomposition (reduction) of the main structure (combustible components that
mainly include C, H, and 0) although tar producing groups such as
oxygen-containing groups (carboxyl group, aldehyde group, ester group, hydroxyl
group, or the like) or the like have been separated or greatly reduced is blown into
25 the blast-furnace body together with hot air whose temperature has been adjusted
to 100 to 150°C lower than the melting point of ash in the blast-furnace-injecting
coal, so the temperature of the hot air is lower than the melting point of the ash in
the blast-furnace-injecting coal, and it is possible to suppress adhesion of the
blast-furnace-injecting coal to the path of the blast-furnace-injecting coal into the
5 blast-furnace body and blockage due to the blast-furnace-injecting-coal ash.
Therefore, the blast furnace can be stably operated. Because the
blast-furnace-injecting coal is blown into the blast-furnace body together with the
hot air without melting the ash in the blast-furnace-injecting coal, low cost low
grade coal such as subbituminous coal or lignite or the like can be used as the
10 blast-furnace-injecting coal, and it is possible to reduce the cost of producing pig
iron.
Brief Description of Drawings
FIG. 4. is a schematic view of the configuration of a first embodiment of the
15 blast furnace according to the present invention.
FIG. 2 is a schematic view of the configuration of a second embodiment of
the blast furnace according to the present invention.
FIG. 3 is an enlarged view of a main part of FIG. 2.
20 Description of Embodiments
The following is a description of embodiments of the method for producing
pig iron and the blast furnace to be used therefor according to the present invention
based on the drawings, but the present invention is not limited to only the
embodiments as described below based on the drawings,
First Embodiment
The following is a description of a first embodiment of the method for
producing pig iron and the blast furnace to be used therefor according to the
present invention based on FIG. 1.
5 As illustrated in FIG. 1, a material quantitative supply device 111 that
supplies a fixed quantity of material 1 that includes iron ore and coke is connected
to the upstream side in the feeding direction of a feeding conveyor 112 that
conveys the material 1. The downstream side in the feeding direction of the feeding
conveyor 112 is connected to the top of a furnace top hopper 113 on the top of a
10 blast-furnace body 11 0. A hot air supply device 11 6 that supplies hot air 1 01 is
connected to a blow pipe 1 1 7 provided on a tuyere 11 8 of the blast-furnace body
110.
Also, a supply hopper 120 that supplies blast-furnace-injecting coal 11 is
installed near the blast-furnace body 1 10.
The blast-furnace-injecting coal 11 contains from 10 to 18 wt% of oxygen
atoms (dry base), and has an average pore diameter of from 10 to 50 nm
(preferably from 20 to 50 nm).
The blast-furnace-injecting coal 11 can be easily produced by removing
moisture from low grade coal (atomic oxygen content (dry base): 18 wt% or higher,
20 and average pore diameter: from 3 to 4 nm) such as subbituminous coal, lignite, or
the like, which normally has a low ash melting point (for example, 1200°C) by
heating it (from 110°C to 200°C for 0.5 to 1 hour) in a low oxygen environment
(oxygen content: 5 vol% or less) to dry it, then removing water, carbon dioxide,
and tar as dry distillation gas or dry distillation oil, by carrying out dry distillation
25 in a low oxygen environment (oxygen concentration: 2 vol% or less) by heating
7
(from 460 to 590°C (preferably, from 500 to 550°C) for 0.5 to 1 hour), then cooling
(to 50°C or less) in a low oxygen environment (oxygen content: 2 vol% or less).
The bottom of the supply hopper 120 is connected to the base end side of a
belt conveyor 121 that transports the blast-furnace-injecting coal 11 from within
5 the supply hopper 120. The tip end side of the belt conveyor 121 is connected to
the top of a receiving hopper 122 that receives the blast-furnace-injecting coal 11.
The bottom of the receiving hopper 122 is connected to an inlet at the top of
a coal mill 123 that pulverizes the blast-furnace-injecting coal 11 from the
receiving hopper 122 to a predetermined diameter size (for example, 80 pm or less).
10 A nitrogen gas supply source 124 that supplies inert nitrogen gas 102 is connected
to the lower portion of the side of the coal mill 123. The base end side of a
transport line 125 that gaseously transports the pulverized blast-furnace-injecting
coal 1 1 by the nitrogen gas 102 is connected to the top of the coal mill 1 23.
The tip end side of the transport line 125 is connected to a cyclone separator
15 (or bag filter) 126 that separates the blast-furnace-injecting coal 11 and the
nitrogen gas 102. The bottom of the cyclone separator 126 is connected to the top
of a storage hopper 127 that stores the blast-furnace-injecting coal 1 1. The bottom
of the storage hopper 127 is connected to the top of an injection tank 128.
The nitrogen gas supply source 124 is connected to the lower part of the
20 side of the injection tank 128. The top of the injection tank 128 is connected to an
injection lance 129 that is connected to the blow pipe 117, and by supplying the
nitrogen gas 102 from the nitrogen gas supply source 124 into the injection tank
128, the blast-furnace-injecting coal 11 that has been supplied into the injection
tank 128 is gaseously transported and supplied into the blow pipe I17 from the
25 injection lance 129.
8
A hot air temperature control device 115 is connected to the hot air supply
device 116. A hot air supply source 114 is connected to the hot air temperature
control device 115. The hot air temperature control device 115 adjusts the hot air
supplied from the hot air supply source 114 to a temperature 100 to 150°C lower
5 than the melting point of the ash, based on the melting point of the ash
(blast-furnace-injecting-coal ash) of the blast-furnace-injecting coal 11 obtained by
measuring in advance the melting point of the ash (blast-furnace-injecting-coal
ash) of the blast-furnace-injecting coal 1%T. he hot air temperature control device
115 adjusts the hot air to, for example, from 1050 to llOO°C when the melting
10 point of the ash (blast-furnace-injecting-coal ash) of the blast-furnace-injecting
coal 11 is 1200°C.
In FIG. 1, 1 10a is a taphole for extracting the molten pig iron (hot metal) 2,
In this embodiment as described above, material-insertion means is
configured from the material quantitative supply device 11 1, the feeding conveyor
15 112, the furnace top hopper 113, and the like, hot-air blowing means is configured
from the hot air supply source 114, the hot air temperature control device 115, the
hot air supply device 6 the blow pipe 117, and the like, and
blast-furnace-injecting-coal supply means is configured from the supply hopper
120, the belt conveyor 121, the receiving hopper 122, the coal mill 123, the
20 nitrogen gas supply source 124, the transport line 125, the cyclone separator 126,
the storage hopper 127, the injection tank 128, the injection lance 129, the blow
pipe 117, and the like. Hot air temperature control means is configured from the
hot air temperature control device 11 5, and the like.
Next, the method of producing the pig iron using the blast furnace 100 as
25 described above is described.
9
The melting point of the ash (blast-furnace-injecting-coal ash) of the
blast-furnace-injecting coal 1 1 is measured in advance.
When a fixed quantity of the material 1 is supplied from the material
quantitative supply device 111, the material 1 is supplied into the furnace top
hopper 113 by the feeding conveyor 112 and fed into the blast-furnace body 110.
In addition, when the blast-furnace-injecting coal I1 is fed into the supply
hopper 120, the blast-furnace-injecting coal 11 is supplied to the receiving hopper
122 via the belt conveyor 121, and pulverized to a predetermined diameter size (for
example, 80 ym or less) by the coal mill 123.
Then, when the nitrogen gas 102 is supplied from the nitrogen gas supply
source 124, the nitrogen gas 102 gaseously transports the pulverized
blast-furnace-injecting coal 11 into the cyclone separator 126 via the transport line
125, and after separation from the blast-furnace-injecting coal 1% is discharged to
the outside the system.
After storage in the storage hopper 127, the blast-furnace-injecting coal 11
that is separated in the cyclone separator 126 is supplied into the injection tank 128,
and is gaseously transported to the injection lance 129 by the nitrogen gas 102
from the nitrogen gas supply source 124, and supplied into the blow pipe 117.
Then, the hot air 101 which has been adjusted to a temperature of 100 to
150°C lower than the melting point of the ash (blast-furnace-injecting-coal ash) of
the blast-furnace-injecting coal 11 is supplied at a gas flow velocity of, for
example, 240 m/s from the hot air supply device 9 16 to the blow pipe 117, so the
blast-furnace-injecting coal 11 is preheated and ignites, generating flames at the tip
of the blow pipe 11 7 and combustion in the raceway, reacting with the coke and the
like in the material 1 within the blast-furnace body 11 0 and generating a reducing
10
gas. In this way, the iron ore in the material 1 is reduced to pig iron (hot metal) 2
and extracted from the taphole 110a. The oxygen gas concentration of the hot air
101 is adjusted to, for example, 28%.
Here, the blast-furnace-injecting coal 1% as described above has an average
5 pore diameter of from 10 to 50 nm, in other words, even though tar generating
groups such as oxygen-containing functional groups (carboxyl group, aldehyde
group, ester group, hydroxyl group, and the like) are separated or greatly reduced,
the atomic oxygen content (dry base) is from 10 to 18 wt%, in other words,
decomposition (reduction) of the main structure (combustion components
10 containing mainly C, H, and 0) has been greatly suppressed.
In this way, when the blast-furnace-injecting coal 11 as described above is
blown together with the hot air 101 into the blast-furnace body 110, not only are
there many oxygen atoms in the main structure and the oxygen of the hot air 101
can easily diffuse into the interior due to the large diameter pores, but also it is
15 very difficult for tar to be generated, so complete combustion is enabled while
generating virtually no uncombusted carbon (soot).
Also, the melting point of the ash in the blast-furnace-injecting coal 11 is
measured in advance, and the hot air 101 100 to 150°C lower than the melting
point of the ash is supplied to the blow pipe 117, so the ash
20 (blast-furnace-injecting-coal ash) of the blast-furnace-injecting coal 11 does not
melt and adhere to the inner surfaces of the injection lance 129 and the tuyere 11 8.
In other words, it is possible to suppress adhesion of the
blast-furnace-injecting-coal ash to the path of the blast-furnace-injecting coal 11
into the blast-furnace body 110 and blockage due to the
blast-furnace-injecting-coal ash. Therefore, the blast furnace 100 can be stably
operated.
Therefore, it is possible to suppress adhesion of blast-furnace-injecting-coal
ash to the path of the blast-furnace-injecting coal into the blast-furnace body and
5 blockage due to the blast-furnace-injecting-coal ash, without only using pulverized
coal that has been processed to adjust the melting point of the ash to 1300°C or
higher, or adjusting the composition or the particle size of the pulverized coal
when the blowing quantity of pulverized coal is very high.
Therefore, according to this embodiment, it is possible to use low cost low
10 grade coal such as subbituminous coal, lignite, or the like as the
blast-furnace-injecting coal 1 1, so it is not necessary to use expensive bituminous
coal or the like as the blast-furnace-injecting coal, so it is possible to reduce the
cost of producing the pig iron 2.
It is necessary that the blast-furnace-injecting coal 11 has an average pore
15 diameter of from 10 to 50 nm (preferably, from 20 to 50 nm). This is because if the
diameter is less than 10 nm, the ease of diffusion of the oxygen of the hot air 101
into the interior is reduced, which causes the combustibility to be reduced, and if
the diameter exceeds 50 nm, the coal can easily become split fine particulate, and
if it becomes split fine particulate when it is blown into the blast-furnace body 11 0,
20 it passes through the interior of the blast-furnace body 110 on the gas flow without
being burned, and is discharged.
Also, in the blast-furnace-injecting coal 11, it is necessary that the atomic
oxygen content (dry base) be 10 wt% or higher. This is because if the oxygen
content is less than 10 wt%, it is difficult to obtain complete combustion without
25 containing the oxidizing agent or oxygen enrichment of the hot air.
12
Also, when producing the blast-furnace-injecting coal 1 1, it is necessary
that the dry distillation temperature be from 460 to 590°C (preferably, from 500 to
550°C). This is because when the temperature is less than 460°C, it is not possible
to sufficiently separate tar generating groups such as oxygen-containing functional
5 groups from the low grade coal, and it is very difficult to obtain an average pore
diameter of from 10 to 50 nm, and if the temperature exceeds 590°C, the main
structure of the low grade coal (combustion components containing mainly C, M,
and 0) start to decompose significantly, and the combustible components are
reduced too much.
Second Embodiment
The following is a description of a second embodiment of the blast furnace
to be used for the method of producing pig iron according to the present invention,
based on FIGS. 2 and 3. FOP parts that are the same as in the embodiment as
described above, the same reference numerals as were used in the description of
the embodiment as described above are applied, and duplication of the explanation
provided in the embodiment as described above is omitted.
A blast furnace 200 according to this embodiment includes an injection
lance 214 for oxygen enrichment provided connected to the blow pipe 117. The
base end of the injection lance 214 for oxygen enrichment is connected to an
oxygen gas supply device 21 3. The oxygen gas supply device 21 3 is connected to
an oxygen gas temperature control device 212. The oxygen gas temperature control
device 2 12 is connected to an oxygen gas supply source 2 11.
The tip end 2 14a of the injection lance 214 for oxygen enrichment is located
further toward the inside of the blast-furnace body 11 0 than the base end 1 I8a of
13
the tuyere 1 18 of the blast-furnace body 110. In this way, the hot air 101 near to the
tuyere 118 of the blast-furnace body 110 can be enriched with oxygen, and it is
possible to delay the time for commencement of combustion of the
blast-furnace-injecting coal 11. In other words, it is possible to suppress adhesion
5 of blast-furnace-injecting-coal ash due to combustion of the blast-furnace-injecting
coal 11 and blockage due to the blast-furnace-injecting-coal ash within the blow
pipe 117.
In this embodiment, oxygen enrichment means is configured from the
oxygen gas supply source 2 11, the oxygen gas temperature control device 2 12, the
10 oxygen gas supply device 2 13, the injection lance 214 for oxygen enrichment, and
the like.
Next, the method of producing the pig iron using the blast furnace 200 as
described above is described.
The melting point sf the ash (blast-furnace-injecting-coal ash) of the
15 blast-furnace-injecting coal 1 1 is measured in advance.
The blast-furnace-injecting coal 11 is supplied to the injection tank 128 via
the supply hopper 120, the belt conveyor 121 the receiving hopper 122, the coal
mill 123, the cyclone separator 126, and the storage hopper 127, in the same way
as described in the embodiment previously described, and is gaseously transported
20 to the injection lance 129 by the nitrogen gas 102 from the nitrogen gas supply
source 124, and supplied into the blow pipe 117.
Then, the hot air 101 from the hot air supply source 1 14 is adjusted to a
temperature 100 to 150°C lower than the melting point of the ash
(blast-furnace-injecting-coal ash) of the blast-furnace-injecting coal 1 1 by the hot
25 air temperature control device 11 5, and supplied to the blow pipe 1 % 7 by the hot air
14
supply device 11 6 at, for example, a gas flow velocity of 240 mls, oxygen gas 103
from the oxygen gas supply source 21 1 is adjusted to the same temperature as the
hot air 101 by the oxygen gas temperature control device 212, and supplied to the
blow pipe 1 17 via the injection lance 2 14 for oxygen enrichment by the oxygen gas
5 supply device 2 13. In this way, the blast-furnace-injecting coal 1 1 is preheated
and ignited, flames occur at the tip of the blow pipe 117, combustion occurs within
the raceway, a reaction occurs with the coke and the like in the material 1 within
the blast-furnace body 110, and reducing gas is generated. In this way, the iron ore
in the material 1 is reduced to pig iron (hot metal) 2 and extracted from the taphole
10 110a, The total of the oxygen concentration of the hot air 101 and the oxygen
concentration of the oxygen gas is adjusted to, for example, 28%-
Also, the melting point of the ash in the blast-furnace-injecting coal 11 is
measured in advance, and the hot air 101 100 to 150°C lower than the melting
point of the ash is supplied to the blow pipe 1 so the ash
15 (blast-furnace-injecting-coal ash) of the blast-furnace-injecting coal 11 does not
melt and adhere to the inner surfaces of the injection lance 129 and the tuyere 11 8.
In other words, it is possible to suppress adhesion of the
blast-furnace-injecting-coal ash to the path of the blast-furnace-injecting coal 11
into the blast-furnace body 110 and blockage due to the
20 blast-furnace-injecting-coal ash. Therefore, the blast furnace 200 can be operated
stably.
Therefore, it is possible to suppress adhesion of blast-furnace-injecting-coal
ash to the path of the blast-furnace-injecting coal into the blast-furnace body and
blockage due to the blast-furnace-injecting-coal ash, without only using pulverized
25 coal that has been processed to adjust the melting point of the ash to 1300°C or
15
higher, or adjusting the composition or the particle size of the pulverized coal
when the quantity of pulverized coal is very high.
Therefore, according to this embodiment, it is possible to use low cost low
grade coal such as subbituminous coal, lignite, or the like as the
5 blast-furnace-injecting coal 11, so it is not necessary to use expensive bituminous
coal or the like as the blast-furnace-injecting coal, so it is possible to reduce the
cost of producing the pig iron 2.
In addition, the injection lance 214 for oxygen enrichment is provided in the
blow pipe 1 17, so compared with the embodiment as described above in which hot
10 air 10 1 only is supplied to the blow pipe 1 17, the oxygen concentration of the hot
air 101 is lower, and it is possible to enrich the oxygen by that amount by the
injection lance 214 for oxygen enrichment, so it is possible to delay the start of
combustion of the blast-furnace-injecting coal 1 I. Therefore, it is possible to more
reliably suppress adhesion of blast-furnace-injecting-coal ash to the path of the
15 blast-furnace-injecting coal into the blast-furnace body and blockage due to the
blast-furnace-injecting-coal ash.
%mdustsiaAl pplicability
The method for producing pig iron and the blast furnace to be used therefor
20 according to the present invention are capable of suppressing the adhesion of
blast-furnace-injecting-coal ash to the path of blast-furnace-injecting coal into the
blast-furnace body and blockage due to the blast-furnace-injecting-coal ash, and
reducing the cost of producing pig iron, so they are extremely useful in iron
manufacturing industry.
We Claim:
A pig iron producing method for producing pig iron from material iron ore by
feeding material that includes iron ore and coal into a blast-furnace body from
a top of the blast-furnace body, and blowing hot air and
blast-furnace-injecting coal into the blast-furnace body from a tuyere;
the blast-furnace-injecting coal having
from 10 wt% to 20 wt% of oxygen atoms (dry base); and
an average pore diameter of from 10 nm to 50 nm;
a melting point of ash in the blast-furnace-injecting coal being
measured in advance; and
a temperature of the hot air being adjusted to a temperature 100 to
150°C lower than the melting point of the ash.
15 2. The pig iron producing method according to claim 1, wherein
the hot air is enriched with oxygen at the tuyere of the blast-furnace
body.
3. A blast furnace, comprising:
a blast-furnace body;
material-insertion means for feeding material that includes iron ore
and coal into the blast-furnace body from a top of the blast-furnace body;
hot-air blowing means for blowing hot air into an interior from a
tuyere of the blast-furnace body; and
blast-furnace-injecting-coal supply means for blowing
blast-furnace-injecting coal into the interior from the tuyere of the
blast-furnace body;
the blast-furnace-injecting-coal supply means
blowing in blast-furnace-injecting coal having an oxygen atom content
(dry base) of 10 to 20 wt% and an average pore diameter of 10 to 50 nm; and
the hot-air blowing means
measuring a melting point of ash in the material in advance, and
blowing in hot air that is 100 to 1 50°C lower than the melting point of the ash.
10
4. The blast furnace according to claim 3, further comprising oxygen
enrichment means for enriching oxygen of the hot air in the tuyere of the
blast- furnace body.
15 5. The blast furnace according to claim 4, wherein
the oxygen enrichment means includes an injection lance to which
oxygen flows, and
a tip end of the injection lance is disposed further toward an inside of
the blast-furnace body than a base end side of the tuyere of the blast-furnace
body.