U.S. patent application number 14/428553 was filed with the patent office on 2015-10-01 for blow-pipe structure.
This patent application is currently assigned to MITSUBISHI HEAVY INDUSTRIES, LTD.. The applicant listed for this patent is MITSUBISHI HEAVY INDUSTRIES, LTD.. Invention is credited to Tsutomu Hamada, Keiichi Nakagawa, Takeshi Okada, Setsuo Omoto, Masakazu Sakaguchi.
Application Number | 20150275322 14/428553 |
Document ID | / |
Family ID | 50341259 |
Filed Date | 2015-10-01 |
United States Patent
Application |
20150275322 |
Kind Code |
A1 |
Sakaguchi; Masakazu ; et
al. |
October 1, 2015 |
BLOW-PIPE STRUCTURE
Abstract
Provided is a blow-pipe structure for a blast furnace facility
configured so as to be capable of suppressing slag adhesion by
using a simple structure, even if pulverized coal with an
unadjusted softening temperature is used. The blow-pipe structure
is attached to a tuyere in a blast furnace main body that produces
pig iron from iron ore. The blow-pipe structure injects auxiliary
fuel pulverized coal together with hot air and slag from the
pulverized coal containing a component that is melted by the hot
air and/or heat from the combustion of the pulverized coal
combustion heat. The blow-pipe structure has an internal/external
double pipe structure having an internal pipe that continues from a
header pipe that supplies the hot air, to the vicinity of the
tuyere and opens, said internal pipe being provided inside an
external pipe that continues from the header pipe to the
tuyere.
Inventors: |
Sakaguchi; Masakazu; (Tokyo,
JP) ; Hamada; Tsutomu; (Tokyo, JP) ; Okada;
Takeshi; (Tokyo, JP) ; Omoto; Setsuo; (Tokyo,
JP) ; Nakagawa; Keiichi; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI HEAVY INDUSTRIES, LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
MITSUBISHI HEAVY INDUSTRIES,
LTD.
Tokyo
JP
|
Family ID: |
50341259 |
Appl. No.: |
14/428553 |
Filed: |
September 10, 2013 |
PCT Filed: |
September 10, 2013 |
PCT NO: |
PCT/JP2013/074402 |
371 Date: |
March 16, 2015 |
Current U.S.
Class: |
110/182.5 |
Current CPC
Class: |
C21B 7/163 20130101;
C21B 5/003 20130101 |
International
Class: |
C21B 7/16 20060101
C21B007/16; C21B 5/00 20060101 C21B005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 20, 2012 |
JP |
2012-207273 |
Claims
1. A blow-pipe structure attached to a tuyere for a main blast
furnace body that produces pig iron from iron ore, the blow-pipe
structure injecting pulverized coal as an auxiliary fuel along with
hot air, slag from the pulverized coal containing a component that
is melted by the hot air and/or heat from the combustion of the
pulverized coal combustion heat; the structure being an
internal/external double pipe structure in which an internal pipe
that continues from a header pipe, which supplies the hot air, to
the vicinity of a tuyere and opens is provided inside an external
pipe that continues from the header pipe to the tuyere, and a
pulverized coal outlet of an injection lance for introducing the
pulverized coal opens to the interior of the internal pipe.
2. The blow-pipe structure according to claim 1, wherein a flow
path resisting element is provided at a position in a flow path
formed between the external pipe and the internal pipe and near the
outlet of the internal pipe.
3. The blow-pipe structure according to claim 1, wherein a nitrogen
injection pipe for supplying nitrogen to the internal pipe is
provided.
4. The blow-pipe structure according to claim 1, wherein an oxygen
injection pipe for supplying oxygen to the external pipe is
provided.
5. The blow-pipe structure according to claim 2, wherein a nitrogen
injection pipe for supplying nitrogen to the internal pipe is
provided.
6. The blow-pipe structure according to claim 2, wherein an oxygen
injection pipe for supplying oxygen to the external pipe is
provided.
7. The blow-pipe structure according to claim 3, wherein an oxygen
injection pipe for supplying oxygen to the external pipe is
provided.
Description
TECHNICAL FIELD
[0001] The present invention relates to a blow-pipe structure for
use with a blast furnace facility, and, in particular, to a
blow-pipe structure that can be advantageously used to blow
pulverized coal obtained by pulverizing low-grade coal into a
furnace as an auxiliary fuel along with hot air.
BACKGROUND ART
[0002] A blast furnace facility is used to produce pig iron from
iron ore by introducing feedstocks such as iron ore, limestone,
coal, and the like into the interior of a main blast furnace body
from the apex thereof, and injecting hot air and pulverized coal
(PCI coal) as an auxiliary fuel through a tuyere located toward the
bottom on a side of the furnace.
[0003] In a blast furnace facility of this sort, if low-grade coal
generally having a low ash melting point of 1,100 to 1,300.degree.
C., such as sub-bituminous coal or lignite, is used as the
pulverized coal during the operation of injecting pulverized coal,
the oxygen contained in the roughly 1,200.degree. C. hot air used
to inject the pulverized coal into the furnace engages in a
combustion reaction with part of the pulverized coal. The
combustion heat generated thereby causes low-melting point ash
("slag") to melt within the injection lance or tuyere.
[0004] The melted slag is rapidly cooled through contact with the
tuyere, which is constantly cooled in order to protect it from the
temperature of the blast furnace. As a result, solid slag adheres
to the tuyere, leading to the problem of blockage in the blow pipe
flow path.
[0005] In order to solve this problem, the softening point
(temperature) of the slag within the pulverized coal is adjusted to
a melting point that is equal to or greater than the temperature
within the blast furnace if the slag has a low softening point,
preventing slag from adhering to tuyeres, as, for example, in the
conventional art disclosed in Patent Document 1 listed below.
[0006] Patent Document 2 listed below discloses an arrangement in
which a divider ring is provided in a hollow section of a tuyere.
The divider ring creates a two-layered pipe structure that divides
the front end of the tuyere into a central region main channel and
a peripheral region secondary channel, and gas supplied from a rear
end of the tuyere is divided into streams passing through the main
channel and the secondary channel, creating a jet in the
furnace.
CITATION LISTS
Patent Literatures
[0007] Patent Document 1: Japanese Unexamined Patent Application
Publication No. H05-156330A
[0008] Patent Document 2: Japanese Unexamined Patent Application
Publication No. H06-235009
SUMMARY OF INVENTION
Technical Problem
[0009] However, attention has been called to the following two
problems in the method according to the method of Patent Document 1
as described above.
[0010] The first problem is that it is difficult to completely
(homogeneously) mix pulverized coal and additives, with the result
that slag formation cannot be prevented at parts where the
proportion of additive in the mixture is less than a predetermined
value.
[0011] The second problem is that a new source of calcium oxide
(CAA), such as limestone or serpentinite, is necessary, creating
excessive costs.
[0012] Meanwhile, there is a region in which a two-layered pipe is
not formed from the outlet of a lance to the divider ring in the
conventional structure disclosed in Patent Document 2, with the
result that at least some pulverized coal inevitably fails to enter
into the divider ring and flows into the secondary channel in the
peripheral region.
[0013] In view of these circumstances, there is a demand for a
blow-pipe structure for use with blast furnace facilities that
allows for the suppression of slag adhesion using a simple
structure without the need for softening point adjustment.
[0014] The present invention was conceived in order to solve the
problems described above, and has an object of providing a blast
furnace facility blow-pipe structure that allows slag adhesion to
be suppressed using a simple structure even if pulverized coal of
an unadjusted softening point is used.
Solution to Problem
[0015] In order to solve the problem described above, the present
invention employs the following means.
[0016] A blow-pipe structure according to an aspect of the present
invention is a blow-pipe structure attached to a tuyere for a main
blast furnace body that produces pig iron from iron ore, the
blow-pipe structure injecting pulverized coal as an auxiliary fuel
along with hot air, slag from the pulverized coal containing a
component that is melted by the hot air and/or heat from the
combustion of the pulverized coal, the structure being an
internal/external double pipe structure in which an internal pipe
that continues from a header pipe, which supplies the hot air, to
the vicinity of a tuyere and opens is provided inside an external
pipe that continues from the header pipe to the tuyere, and a
pulverized coal outlet of an injection lance for introducing the
pulverized coal opens to the interior of the internal pipe.
[0017] In accordance with this blow-pipe structure, an
internal/external double pipe structure is provided in which an
internal pipe that continues from a hot-air supplying header pipe
to the vicinity of a tuyere and opens is provided within an
external pipe that extends from the header pipe to the tuyere, and
a pulverized coal outlet of an injection lance for introducing
pulverized coal opens to the interior of the internal pipe,
allowing the flow of pulverized coal introduced through the
injection lance to be completely segregated from the wall of the
external pipe, i.e., the inner wall of the blow pipe, on the
upstream side of the tuyere. In addition, pulverized coal can be
passed through the tuyere at a distance from the surface of the
tuyere. This impedes the adhesion of pulverized coal slag to the
surface of the tuyere or the inner wall of the blow pipe.
[0018] In the invention described above, it is preferable that a
flow path resisting element be provided at a position in the flow
path formed between the external pipe and the internal pipe and
near the outlet of the internal pipe.
[0019] This allows for a greater flow rate within the internal pipe
than within the external pipe. As a result, hot air flowing out of
the external pipe flows in the direction of the center of the flow
path, thus impeding the flow of the pulverized coal introduced into
the internal pipe in the direction of the external pipe.
[0020] In the invention described above, it is preferable to
provide a nitrogen injection pipe for supplying nitrogen into the
internal pipe.
[0021] This allows the operating conditions of the internal pipe
and the external pipe to be altered. In this case, nitrogen can be
injected into the internal pipe to reduce the temperature of the
hot air. As a result, the temperature of the hot air within the
internal pipe can be adjusted to create an environment in which the
pulverized coal cannot easily combust.
[0022] In the invention described above, it is preferable to
provide an oxygen injection pipe for supplying oxygen into the
external pipe.
[0023] This allows the operating conditions of the internal pipe
and the external pipe to be altered. In this case, oxygen can be
injected into the external pipe in order to allow for rapid
combustion when the gases from the internal and external pipes are
mixed immediately before the tuyere despite the environment
unconducive to the combustion of the pulverized coal within the
internal pipe.
Advantageous Effects of Invention
[0024] In accordance with the blow-pipe structure of the present
invention described above, there is provided an internal/external
double pipe structure in which an internal pipe is provided within
an external pipe that continues from a hot air-supplying header
pipe to a tuyere, and a pulverized coal outlet of an injection
lance for introducing pulverized coal opens to the interior of the
internal pipe, impeding the adhesion of pulverized coal slag to the
surface of the tuyere or the inner wall of the blow pipe. This
allows slag adhesion to be suppressed in the blow-pipe structure
using a simple double pipe structure, even if softening point
adjustment is not performed.
[0025] As a result, even low-grade coals having low ash melting
points of 1,100.degree. C. to 1,300.degree. C., such as
sub-bituminous coal or lignite, can be used as the pulverized coal
constituting the auxiliary fuel by modifying the same for use as
feedstock coal.
BRIEF DESCRIPTION OF DRAWINGS
[0026] FIG. 1 is a longitudinal cross-sectional view of the axial
direction of an embodiment of the blow-pipe structure according to
the present invention.
[0027] FIG. 2 is an illustration of an example arrangement for a
blast furnace facility to which the blow-pipe structure illustrated
in FIG. 1 is applied.
DESCRIPTION OF EMBODIMENTS
[0028] An embodiment of the blow-pipe structure according to the
present invention will now be described with reference to the
drawings.
[0029] The blow-pipe structure according to the embodiment is used
with a blast furnace facility in which pulverized coal of the
low-grade coal constituting the feedstock coal is injected through
a tuyere into a blast furnace along with hot air.
[0030] For example, in a blast furnace facility such as that
illustrated in FIG. 2, feedstock 1 constituted by iron ore,
limestone, and coal or the like is fed from a metered feedstock
feeder 10 via a transport conveyor 11 into a furnace apex hopper 21
provided at the apex of a main blast furnace body 20. A plurality
of tuyeres 22 is provided in a lower side wall of the main blast
furnace body 20 at a roughly uniform pitch in the circumferential
direction. Each of the tuyeres 22 is linked to a downstream end of
a blow pipe 30 for feeding hot air 2 into the interior of the main
blast furnace body 20. The upstream end of each of the blow pipes
30 is connected to a hot air feeder 40 constituting the source of
the hot air 2 supplied to the interior of the main blast furnace
body 20.
[0031] A pulverized coal producing device 50 that performs a
pretreatment (modification) such as evaporating moisture in the
coal out of the feedstock coal (sub-bituminous coal, lignite, or
other low-grade coal), followed by pulverizing the low-grade coal
to produce pulverized coal, is provided near the main blast furnace
body 20.
[0032] Modified pulverized coal (modified coal) 3 produced by the
pulverized coal producing device 50 is conveyed by a carrier gas 4,
such as nitrogen gas, to a cyclone separator 60. The pulverized
coal 3 conveyed by the gas is separated from the carrier gas 4 by
the cyclone separator 60, after which the coal falls into and is
stored in a storage tank 70. This modified pulverized coal 3 is
used as blast furnace injection coal (PCI coal) for the main blast
furnace body 20.
[0033] The pulverized coal 3 within the storage tank 70 is fed into
an injection lance (hereafter, "lance") 31 of the blow pipe 30
described above. The pulverized coal 3 combusts upon being fed into
the hot air flowing through the blow pipe 30, producing a flame at
the end of the blow pipe 30 and forming a raceway. This causes the
coal or the like contained in the feedstock 1 being introduced into
the main blast furnace body 20 to combust. As a result, the iron
ore contained in the feedstock 1 is reduced, becomes pig iron
(molten iron) 5, and is removed through a pig iron outlet 23.
[0034] Preferred properties of the pulverized coal 3 fed from the
lance 31 into the blow pipe 30 as blast furnace injection coal,
that is, of the modified pulverized coal (auxiliary fuel) formed by
modifying and pulverizing low-grade coal, are an oxygen atom
content (dry basis) of 10 to 18 weight %, and an average pore size
of 10 to 50 nanometers (nm). A more preferable average pore size
for the modified pulverized coal is 20 to 50 nanometers (nm).
[0035] In pulverized coal 3 having such properties, there is a
large release of and reduction in tar-forming groups of
oxygen-containing functional groups (carboxyl groups, aldehyde
groups, ester groups, hydroxyl groups, etc.) but breakdown
(reduction) of the main skeleton (the combustible component
primarily formed from carbon, hydrogen, and oxygen) is greatly
suppressed. Thus, when the coal is injected through the tuyeres 22
into the main blast furnace body 20 along with the hot air 2, the
high oxygen atom content of the main skeleton and the large
diameter of the pores not only facilitates dispersion of the oxygen
in the hot air 2 into the coal, but also greatly impedes the
generation of tar, allowing for complete combustion with almost no
uncombusted carbon (soot) being produced.
[0036] In order to produce (modify) this pulverized coal 3, a
drying step of heating (at 110 to 200.degree. C. for 0.5 to 1
hours) and drying the sub-bituminous coal, lignite, or other
low-grade coal (dry-basis oxygen atom content: greater than 18
weight %; average pore size: 3 to 4 nm) constituting the feedstock
coal in a low-oxygen atmosphere having an oxygen concentration of 5
vol % or less is performed in the pulverized coal producing device
50.
[0037] After moisture is removed in the drying step described
above, a dry distillation step in which the feedstock coal is
reheated (at 460 to 590.degree. C., preferably 500 to 550.degree.
C., for 0.5 to 1 hours) in a low-oxygen ambient atmosphere (oxygen
concentration: 2 vol % or less) is performed. Dry distilling the
feedstock coal in this dry distillation step removes generated
water, carbon dioxide, and tar in the form of dry distillation gas
or dry distillation oil.
[0038] The feedstock coal then proceeds to a cooling step in which
the coal is cooled (to 50.degree. C. or less) in a low-oxygen
atmosphere having an oxygen concentration of 2 vol % or less, then
pulverized (particle diameter: 77 .mu.m or less (80% pass)) in a
pulverization step.
[0039] In the embodiment, as illustrated, for example, in FIG. 1,
the structure described hereinafter has been adopted for a blow
pipe 30 that is attached to a tuyere 22 of a main blast furnace
body 20 for producing pig iron from iron ore and injects pulverized
coal 3 as an auxiliary fuel along with hot air 2, slag from the
pulverized coal 3 containing a component that is melted by the hot
air 2 and/or the heat from the combustion of the pulverized coal
3.
[0040] Specifically, the blow pipe 30 illustrated in the drawing
has an internal/external double pipe structure. This
internal/external double pipe structure continues from a header
pipe 41, which is connected to a hot air feeder 40 and supplies hot
air 2, to the tuyere 22 and features an internal pipe 30b provided
within an external pipe 30a.
[0041] Specifically, the external pipe 30a of the blow pipe 30
branches from the header pipe 41 and is connected to the tuyere 22.
By contrast, the internal pipe 30b of the blow pipe 30 branches
from the header pipe 41, like the external pipe 30a, and has a
downstream internal pipe outlet 30c which opens near an inlet of
the tuyere 22.
[0042] The blow pipe 30 thus has an internal/external double pipe
structure in which the internal pipe 30b, which continues from the
hot air 2-supplying header pipe 41 to near the tuyere 22 where an
internal pipe outlet 30c opens, is provided within the external
pipe 30a which continues from the header pipe 41 to the tuyere
22.
[0043] In other words, the blow pipe 30 has an internal/external
double pipe structure in which an internal pipe 30b for introducing
pulverized coal 3 is concentrically provided within the external
pipe 30a constituting the main body of the blow pipe, segregating
the flow paths.
[0044] The external pipe 30a and internal pipe 30b of the blow pipe
30 preferably have a cross-sectional area ratio of approximately
1:1. To give a specific example, if, for example, the inner
diameter of the tuyere 22 is 160 mm, the inner diameter of the
external pipe 30a is 210 mm, and the inner diameter of the internal
pipe 30b is 140 mm.
[0045] In addition, the lance 31 for introducing the pulverized
coal 3 into the blow pipe 30 passes through the external pipe 30a
and the internal pipe 30b and has a pulverized coal outlet 31a that
opens to the interior of the internal pipe 30b.
[0046] In a blow pipe 30 having an internal/external double pipe
structure of this sort, pulverized coal 3 is introduced by the
lance 31 into the interior of the internal pipe 30b, allowing the
flow of pulverized coal 3 to be completely segregated from the
surface of the wall of the external pipe 30a on the upstream side
of the tuyere 22. That is, the flow of pulverized coal 3 is
completely segregated from the surface of the inner wall of the
blow pipe 30, and, at the tuyere 22, the flow of pulverized coal 3
can be passed through at a distance from the surface of the tuyere
22.
[0047] As a result, the amount of pulverized coal 3 passing over
the surface of the tuyere 22 and the surface of the inner wall of
the external pipe 30a constituting the main body of the blow pipe
(i.e., the surface of the inner wall of the blow pipe 30) is either
eliminated or greatly reduced compared to a conventional structure
not possessing an internal pipe 30b, allowing for dramatic
suppression of pulverized coal 3 slag adhesion.
[0048] In the blow-pipe structure according to the embodiment
described above, it is preferable to provide a flow path resisting
element 80 for reducing the cross-sectional area of the flow path
in an outer circumferential flow path 30d formed between the
external pipe 30a and the internal pipe 30b and at a position near
the outlet of the internal pipe 30b. This flow path resisting
element 80 allows for a greater flow rate within the internal pipe
30b, where the flow path resistance is low, than within the
external pipe.
[0049] As a result, hot air 2 flowing out of the external pipe 30a
flows in the direction of the axial center of the internal pipe
30b, i.e., in the direction of the center of the flow path of the
blow pipe 30, thus impeding the flow of the pulverized coal 3
introduced into the internal pipe 30b in the direction of the
external pipe 30a, where it is desirable to prevent slag
adhesion.
[0050] The flow path resisting element 80 described above is a
member that projects from the surface of the inner wall of the
external pipe 30a or the outer wall of the internal pipe 30b, or,
alternatively, from the surfaces of both the inner wall of the
external pipe 30a and the outer wall of the internal pipe 30b,
thereby reducing the cross-sectional area of the flow path. There
is no particular limitation upon the cross-sectional shape thereof.
However, if a wedge-shaped projecting member, such as, for example,
a flow path resisting element 80 comprising a slanted surface 81
that reduces the cross-sectional area of the flow path from the
upstream side of the flow direction toward the downstream side, is
provided on the surface of the inner wall of the external pipe 30a,
the slanted surface 81 will direct hot air 2 flowing through the
outer circumferential flow path 30d in the direction of the center
of the tuyere 22, thereby directing the flow of pulverized coal 3
in the direction of the center of tuyere 22, and thus further
suppressing the adhesion of slag from the pulverized coal 3.
[0051] The blow-pipe structure described above is preferably
provided with a nitrogen injection pipe 90 for supplying nitrogen
into the interior of the internal pipe 30b. This nitrogen injection
pipe 90 is used to introduce nitrogen gas into the hot air 2
flowing through the internal pipe 30b as necessary, such as when it
is desirable to alter the operating conditions of the internal pipe
30b and the external pipe 30a.
[0052] Accordingly, introducing nitrogen into the internal pipe 30b
reduces the temperature of the hot air, thus allowing the
temperature of the hot air 2 to be reduced to or below the slag
melting point. In other words, the nitrogen injection pipe 90
allows the temperature of the hot air with the internal pipe 30b to
be adjusted and the oxygen concentration to be reduced through the
injection of nitrogen, thereby allowing for adjustment to an
environment in which the pulverized coal 3 cannot easily
combust.
[0053] The blow-pipe structure described above is preferably
provided with an oxygen injection pipe 91 for supplying oxygen into
the external pipe 30a, i.e., into the outer circumferential flow
path 30d. This oxygen injection pipe 91 is used to introduce oxygen
into the hot air 2 flowing through the external pipe 30a as
necessary, such as when it is desirable to alter the operating
conditions of the internal pipe 30b and the external pipe 30a.
[0054] Accordingly, hot air 2, the oxygen concentration of which
has been increased by injecting oxygen into the external pipe 30a,
is mixed with the pulverized coal 3 introduced into the internal
pipe 30b near the inlet of the tuyere 22, thereby allowing for
rapid combustion of the pulverized coal 3. Accelerating combustion
in this way increases the temperature of the hot air 2, thus
further accelerating the combustion of the pulverized coal 3.
[0055] The process of adjusting the oxygen concentration of the hot
air 2 will now be specifically described using an example.
[0056] Hot air 2 supplied from the header pipe 41 is set, for
example, to an oxygen concentration of 21 vol %. In order to ensure
combustion after convergence with the pulverized coal 3, oxygen is
injected into the external pipe 30a from the oxygen injection pipe
91 to enrich the oxygen concentration to 25 to 50 vol %, preferably
30 to 35 vol %.
[0057] As a result, the combustion rate of the pulverized coal 3 is
reduced within the internal pipe 30b, where the oxygen
concentration is relatively lower than in the external pipe 30a,
allowing slag adhesion in the internal pipe 30b to be suppressed.
The hot air 2 and pulverized coal 3 flowing within the internal
pipe 30b then converge with the oxygen-enriched hot air 2 flowing
in from the external pipe 30a, thereby increasing the combustion
rate of the pulverized coal 3 due to the increase in the oxygen
concentration, and allowing for complete combustion of the
pulverized coal 3 constituting the coal being injected into the
main blast furnace body 20 within the raceway.
[0058] In addition to the adjustment of the oxygen concentration in
this way, nitrogen may concurrently be introduced into the internal
pipe 30b to adjust the temperature of the hot air within the
internal pipe 30b to or below the ash melting point according to
the form of the pulverized coal 3.
[0059] Thus, in accordance with the blow-pipe structure of the
embodiment described above, there is provided an internal/external
double pipe structure in which the internal pipe 30b is provided
within the external pipe 30a continuing from the header pipe 41 to
the tuyere 22, and the pulverized coal outlet 31a of the lance 31
for introducing pulverized coal 3 opens to the interior of the
internal pipe 30b, thereby separating the flow of pulverized coal 3
from the surface of the tuyere 22 and the inner wall of the blow
pipe 30, impeding the adhesion of slag from the pulverized coal
3.
[0060] This allows slag adhesion to be suppressed in the blow-pipe
structure using a simple internal/external double pipe structure,
even if the softening point of the pulverized coal 3 is not
adjusted. As a result, the maintenance interval of the blow pipe 30
can be extended, for example, to the wear lifespan of the tuyere
22.
[0061] The component that is contained in the slag produced by the
pulverized coal 3 described above and is melted by the hot air 2 or
the heat produced by the combustion of the pulverized coal 3, i.e.
the low-melting point slag component, has an ash melting point of
roughly 1,100 to 1,300.degree. C. when hot air 2 of roughly
1,200.degree. C. is used. A low-melting point slag component of
this sort is also contained in modified coal produced by modifying
low-grade coal, such as sub-bituminous coal or lignite, used as the
feedstock coal for the pulverized coal 3 via drying, dry
distillation, or the like, but, by using the blow-pipe structure of
the embodiment, pulverized coal 3 produced by modifying a low-grade
feedstock coal can be used as an auxiliary fuel.
[0062] The present invention is not limited to the embodiment
described above, and various modifications may be made thereto, as
appropriate, within the scope of the invention.
REFERENCE SIGNS LIST
[0063] 1 Feedstock [0064] 2 Hot air [0065] 3 Pulverized coal
(modified coal) [0066] 4 Carrier gas [0067] 5 Pig iron (molten
iron) [0068] 10 Metered feedstock feeder [0069] 20 Main blast
furnace body [0070] 21 Furnace apex hopper [0071] 22 Tuyere [0072]
30 Blow pipe [0073] 30a External pipe [0074] 30b Internal pipe
[0075] 30c Internal pipe outlet [0076] 30d Outer circumferential
flow path [0077] 31 Injection lance (lance) [0078] 31a Pulverized
coal outlet [0079] 40 Hot air feeder [0080] 41 Header pipe [0081]
50 Pulverized coal producing device [0082] 60 Cyclone separator
[0083] 70 Storage tank [0084] 80 Flow path resisting element [0085]
81 Slanted surface [0086] 90 Nitrogen injection pipe [0087] 91
Oxygen injection pipe
* * * * *