Technical Field
The present invention relates to blast furnace
injection coal and a method of manufacturing the same.
Background Art
Blast furnace installations are designed to be
capable of manufacturing pig iron from iron ore by
charging raw materials such as iron ore, limestone, and
coke i n ~ oth e blast furnace main unit through the top
and blowing hot air and pulverized coal ( P C 1 coal) as
auxiliary fuelthroughthetuyeres on the lower lateral
side.
As such blast furnace injection coal, coals have
been proposed which are obtained by adding an oxidant
such for example as KMn04, H202, KC103, or K2Cr204 to
pulverized coal in advance to improve the combustion
efficiency sothat generation of unburned carbon (soot)
can be suppressed (see Patent Literature 1 listed below,
for example).
Moreover, methods have beenproposedwhichinvolve,
for example, enrichingthe oxygen in hot air andblowing
the air into the blast furnace main unit through the
tuyeres to improve the combustibility of the blast
furnace injection coal (see Patent Literature 2 listed
below, for example) .
Citation List
Patent Literatures
Patent Literature 1 : Japanese Patent Application
Publication No. Hei 6-220510
Patent Literature 2 : Japanese Patent Application
Publication No. 2003-286511
Summary of Invention
Technical Problems
However, the blast furnace injection coal
described in Patent Literature 1 listed above
inevitably requires adding the above-mentioned oxidant
to pulverized coal and therefore increases the running
cost.
Moreover, the combustibility improving method
described in Patent Literature 2 listed above requires
operating the blast furnace with a large amount of
oxygen constantly added into the hot air and therefore
increases the running cost as well.
In view of the above, an object of the present
invention is to provide blast furnace injection coal
and amethodofmanufacturingthe same which are capable
of improving the combustion efficiency at a low cost
and suppressing generation of unburned carbon (soot).
Solution to Problems
Blast furnace injection coal according to a first
aspect ofthe invention for solvingthe above-mentioned
problems is blast furnace injection coal to be blown
into a blast furnace main unit of a blast furnace
installation through a tuyere, characterized in that
an oxygen atom content ratio (dry base) is between 10
and 20% by weight, and an average pore size is between
10 and 50 nm.
Blast furnace injection coal according to a second
aspect of the invention is the first aspect of the
invention, characterized in that a pore volume is
between 0.05 and 0.5 cm3/g.
Blast furnace injection coal according to a third
aspect of the invention is the first or second aspect
of the invention, characterized in that a specific
surface area is between 1 and 100 m2/g.
A method of manufacturing blast furnace injection
coal according to a fourth aspect of the invention for
solving the above-mentioned problems is a method of
manufacturing the blast furnace injection coal
according to any one of the first to third aspect of
the invention, characterized in that the method
comprises: a drying step of heating subbituminous coal
or brown coal to remove moisture; and a pyrolysis step
of performing pyrolysis at a temperature between 460
and 5 9 0 " ~on the coal dried in the drying step.
The method of manufacturing blast furnace
injection coal according to a fifth aspect of the
invention is the fourth aspect of the invention,
characterized in that the method further comprises: a
cooling step of cooling the coal subjected to the
pyrolysis in the pyrolysis step to a temperature
between 50 and 150°C; and a partially oxidizing step
of partially oxidizing the coal cooled in the cooling
step by exposing the coal in an oxygen-containing
atmosphere at a temperature between 50 and 150°C to let
the coal chemically adsorb oxygen.
Advantageous Effects of Invention
According to the blast furnace injection coals
according to the present invention, the average pore
size is 10 to 50 nm, that is, tar producing groups such
as oxygen-containing functional groups (such as
carboxyl groups, aldehyde groups, ester groups, and
hydroxylgroups) desorb andgreatlydecrease, while the
oxygen atom content ratio (dry base) is 10 to 20% by
weight, that is, decomposition (decrease) of the main
skeletons (combustion components mainly containing C,
H, and 0) is greatly suppressed. Hence, when such blast
furnace injection coal is blown into the blast furnace
main unit through the tuyere together with hot air, the
blast furnace injection coal can be completely
combusted with almost no unburned carbon (soot)
generated because many oxygen atoms are contained in
the main skeletons and also because the large-sized
pores allow the oxygen in the hot air tobe easily spread
to the inside and also significantly suppresses the
production of tar. Accordingly, it is possible to
improve the combustion efficiency at a low cost and
suppress generation of unburned carbon (soot).
According tothe method ofmanufacturingthe blast
furnace injection coal according to the present
invention, the blast furnace injection coals described
above can be manufactured at a low cost.
B r i e f D e s c r i p t i o n of D r a w i n g s
[Fig. 11 Fig. 1is a flowchart showing the procedure
of a first embodiment of amethodofmanufacturingblast
furnace injection coal according to the present
invention.
Fig. 21 Fig. 1is a flowchart showing the procedure
of a second embodiment of the method of manufacturing
blast furnace injection coal according to the present
invention.
[Fig. 31 Fig. 3 is a graph showing the relation
between the temperature of subbituminous coal and the
ratio of content of each of its oxygen-containing
functional groups based on an infrared absorption
spectrum of the subbituminous coal measured with its
temperature is raised under a nitrogen-containing
atmosphere.
[Fig. 41 Fig. 4 is a graph showing the relation
between the ratios of unburned carbon collected after
present invention coal, dried coal, and conventional
coal are combusted, and the concentrations of residual
oxygen (excess oxygen concentrations) in combustion
exhaust gases after the combustion.
[Fig. 51 Fig. 5 is a graph showing the relation
between the excess oxygen ratio and the combustion
temperature of complete combustion of each of the
present invention and the conventional coal.
Description of Embodiments
Embodiments of a blast furnace injection coal and
a method of manufacturing the same according to the
present invention'will be described with reference to
the drawings. However, the present invention is not
limited only to the embodiments to be described below
with reference to the drawings.

A first embodiment of the blast furnace injection
coal and themethod ofmanufacturingthe same according
to the present invention will be described with
reference to Fig. 1.
The blast furnace injection coal according to this
embodiment has an oxygen atom content ratio (dry base)
of 10 to 18% by weight and an average pore size of 10
to 50 nm (nanometer) (preferably 20 to 50 nm
(nanometer) ) .
As shown in Fig. 1, the blast furnace injection
coal according to this embodiment as mentioned above
can be easily manufactured by: drying low-rank coal
(oxygen atom content ratio (dry base) : over 18% by
weight, average pore size: 3 to 4 nm) 11 such as
subbituminous coal or brown coal by heating it (at 110
to 200°C x 0.5 to 1 hour) in a low oxygen atmosphere
(oxygen concentration: 5% by volume or lower) to remove
moisture (drying step S11); performingpyrolysis on the
resultant coal by heating it (at 460 to 5 9 0 " ~
(preferably 500to 550°C) x 0.5to lhour) in alowoxygen
atmosphere (oxygen concentration: 2% by volume or
lower) to remove produced water, carbon dioxide, tar,
and the like as pyrolysis gas and pyrolysis oil
(pyrolysis step S12); cooling the resultant coal (to
5 0 " ~or below) in a low oxygen atmosphere (oxygen
concentration: 2% by volume or lower) (cooling step
S13); andpulverizingthe resultant coal (to a particle
size: 77 pm or smaller (80% pass)) (pulverizing step
S14).
In blast furnace injection coal 12 manufactured
by the manufacturing method according to this
embodiment as described above, the average pore size
is 10 to 50 nm, that is, tar producing groups such as
oxygen-containing functional groups (such as carboxyl
groups, aldehyde groups, ester groups, and hydroxyl
groups) desorb and greatly decrease, while the oxygen
atom content ratio (dry base) is 10 to 18% by weight,
that is, decomposition (decrease) ofthemain skeletons
(combustion components mainly containing C, HI and 0)
is greatly suppressed. Hence, when the blast furnace
injection coal 12 is blown into a blast furnace main
unit through each tuyere together with hot air, the
blast furnace injection coal 12 can be completely
combusted with almost no unburned carbon (soot)
generated because many oxygen atoms are contained in
the main skeletons and also because the large-sized
pores allow the oxygen in the hot air to be easily spread
to the inside and also significantly suppresses the
production of tar.
Hence, the blast furnace i~ljection coal 12
according tothis embodiment can improve the combustion
efficiency and suppress generation of unburned carbon
(soot) without adding an oxidant such as KMn04, H202,
KClO3, or K2Cr204 or enriching the oxygen in the hot air.
Thus, according tothis embodiment, it is possible
to imprsve the combustion efficiency at a low cost and
suppress generation of unburned carbon (soot).
Note that the averagepore size oftheblast furnace
injection coal 12 according to this embodiment needs
to be 10 to 50 nm (preferably 20 to 50 nm). This is
because if the average pore size is smaller than 10 nm,
the spreadability of the oxygen in the hot air to the
inside will be deteriorated and the combustibility will
be accordingly deteriorated, whereas if the average
pore size is larger than 50 nm, the blast furnace
injection coal 12 will easily crack into smaller sizes
due to heat shock and the like, and will therefore crack
into smaller sizes when blown into the blast furnace
main unit, which leads to a situation where the blast
furnace injection coal 12 passes through the inside of
the blast furnace main unit with a gas stream and is
discharged without combustion.
Moreover, the oxygen atom content ratio (drybase)
needs to be not smaller than 10% by weight as well. This
is because it will be difficult to achieve complete
combustion without adding an oxidant or enriching the
oxygen in the hot air if the oxygen atom content ratio
(dry base) is smaller than 10% by weight.
Furthermore, the pore volume is preferably 0.05
to 0.5 ~ m ~ / ~ a n d p a r t i c u l a r l y p r e f e r a 0b.l 1yt o 0.2 cm3/g.
This is because the surface area of contact (surface
area of reaction) with the oxygen in the hot air will
be small and the combustibility will possibly be
deteriorated if the pore volume is smaller than 0.05
cm3/g, whereas large amounts of components will
volatilize and the blast furnace injection coal12 will
be so porous that the combustion components may be
excessively reduced if the pore volume is larger than
0.5 cm3/g.
In addition, the specific surface area is
preferably 1 to 100 m2/g and particularly preferably
5to 2 0 m ~ / T~h.is is because the surface area of contact
(surface area of reaction) with the oxygen in the hot
10
air will be small and the combustibility will possibly
be deterioratedifthe specific surface area is smaller
than 1 m2/gr whereas large amounts of components will
volatilize and the blast furnace injection coal12 will
be so porous that the combustion components may be
excessively reduced if the specific surface area is
larger than 100 m2/g.
On the other hand, in the method of manufacturing
the blast furnace injection coal according to this
embodiment, the temperature of the pyrolysis in the
pyrolysis step S12 needs to be 460 to 5 9 0 " ~(p referably
500 to 550°C). This is because, the tar producing groups
such as oxygen-containing functional groups will fail
to be desorbed sufficiently from the low-rank coal 11
and it will be extremely difficult to obtain an average
pore size of 10 to 50 nm if the temperature is lower
than 460°c, whereas the decomposition of the main
skeletons (combustion components mainly containing C,
H, and 0) of the low-rank coal 11 will start to be
remarkable, and large amounts of component will
volatilize, which in turn excessively reduces the
combustion components, if the temperature is higher
than 5 9 0 " ~ .

A second embodiment ofthe blast furnace injection
coal and the method ofmanufacturingthe same according
to the present invention will be described with
reference to Fig. 2. Note that for portions similar to
those in the foregoing embodiment, reference signs
similar to the reference signs used in the description
of the foregoing embodiment will be used, and their
description overlapping the description in the
foregoing embodiment will be omitted.
The blast furnace injection coal according to this
embodiment has an oxygen atom content ratio (dry base)
of 12 to 20% by weight and an average pore size of 10
to 50 nm (preferably >20 to 50 nm) .
As shown in Fig. 2, the blast furnace injection
coal according to this embodiment as mentioned above
can be easilymanufacturedby: dryingthelow-rank coal
(oxygen atom content ratio (dry base) : over 18% by
weight) 11 in a similar way to the foregoing embodiment
(drying step S11); performing pyrolysis on the
resultant coal in a similar way to the foregoing
embodiment (pyrolysis step S12); cooling the resultant
coal (to 50 to 1 5 0 " ~ i)n alow oxygen atmosphere (oxygen
concentration: 2% by volume or lower) (cooling step
S23); partially oxidizing the resultant coal by
exposing it to an oxygen-containing 2tmosphere (oxygen
concentration: 5 to 21% by volume) (at 50 to 1 5 0 " ~x
0.5to10 hours) to let the coalchemicallyadsorboxygen
(partially oxidizing step S25); and pulverizing the
resultant coal in a similar way to the foregoing
embodiment (pulverizing step S14).
In sum, in this embodiment, the coal subjected to
the pyrolysis in the pyrolysis step S12 is cooled to
to 150°c, and the coal is then partially oxidized
by letting the coal chemically adsorb oxygen in the
partially oxidizing step S25, to thereby obtain blast
furnace injection coal22 having an oxygen atom content
ratio (dry base) of 12 to 20% by weight.
In the blast furnace injection coal 22
manufactured by the manufacturing method according to
this enbodiment as mentioned above, like the foregoing
embodiment, the average pore size is 10 to 50 nm, that
is, tar producing groups such as oxygen-containing
functional groups (such as carboxyl groups, aldehyde
groups, ester groups, and hydroxyl groups) desorb and
greatly decrease, while the oxygen atom content ratio
(drybase) is12to 20% byweight, that is, decomposition
(decrease) of the main skeletons (combustion
components mainly containing C, H I and 0) is greatly
suppressed, and more oxygen atoms have chemically
adsorbed. Hence, when the blast furnace injection coal
22 is blown into the blast furnace main unit through
the tuyere together with hot air, the blast furnace
injection coal22 can be completely combustedwithless
unburned carbon (soot) generatedthan in the foregoing
enbodiment because the main skeletons contains more
oxygen atoms than in the foregoing embodiment and also
because the large-sized pores allow the oxygen in the
hot air to be easily spread to the inside and also
significantly suppresses the production of tar like the
foregoing embodiment.
Hence, the blast furnace injection coal 22
according tothis embodiment can improve the combustion
efficiencyto a greater extent and suppress generation
of unburned carbon (soot) more reliably than in the
foregoing embodiment without adding an oxidant such as
KMn04, H202, KC103, or K2Cr204 or enriching the oxygen
in the hot air.
Thus, according to this embodiment, it is possible
to further improve the combustion efficiency at a low
cost and suppress generation of unburned carbon (soot)
more reliably than in the foregoing embodiment.
Note that the oxygen atom content ratio (dry base)
ofthe blast furnace injection coal22 according tothis
embodiment needs to be 20% by weight or lower. This is
because the oxygen content will be excessively large
and the amount of heat generation will be excessively
reduced if the oxygen atom content ratio (dry base) is
smaller than 20% by weight.
On the other hand, in the method of manufacturing
the blast furnace injection coal according to this
embodiment, the temperature of the process in the
partially oxidiz2ng step S25 is preferably 50 to 150'~.
This is because it will be difficult to advance the
partial oxidation process even in an air (oxygen
concentration: 21% by volume) atmosphere if the
temperature is lower than 5 0 ° c , whereas large amounts
of carbon monoxide and carbon dioxide will possibly be
generated by the combustion reaction even in an
atmosphere where the oxygen concentration is about 5%
by volume if the temperature is higher than 1 5 0 " ~ .
[Examples]
Examples carried out forthe purpose of confirming
the advantageous effects oftheblast furnace injection
coal and themethod ofmanufacturingthe same according
to the present invention will be described below.
~oweber, the present invention is not limited only to
the examples to be described below based on various
kinds of data.
-
A composition analysis (ultimate analysis) was
performed on the blast furnace injection coal 12
obtained by the manufacturing method according to the
first embodiment described above (present invention
coal). Moreover, for comparison, a composition
analysis was performed also on conventional blast
furnace injection coal (PC1 coal: conventional coal),
and on coal obtained by omittingthe pyrolysis step S12
in the first embodiment (dried coal). Table 1 given
below shows the results. Note that the values are all
on the dry base.
[Table 11
As can be seen from Table 1 given above, the oxygen
(0) ratio of the present invention coal is smaller than
that of the dried coal and significantly larger than
C (wt. % )
H (wt.%)
0 (wt. % )
N (wt.%)
S (wt.%)
Calorific Value
(kcal/kg)
that of the conventional coal, while the carbon (C)
ratio is larger than that of the dried coal and smaller
than that ofthe conventional coal. Thus, the calorific
value ofthe present invention coal is largerthanthat
of the dried c ~ a l and smaller than that of the
conventional coal.

Surface states (average pore size, pore volume,
specific surface area) of the above present invention
coal were measured. Moreover, for comparison, the
surface states ofthe above conventional coal and dried
coal were measured as well. Table 2 given below shows
the results.
Present Invention
Coal
73.8
3.2
14.4
1.1
0.3
6700
Conventional
Coal
84.5
3.8
2.9
1.7
0.5
Dried
Coal
71.0
3.6
18.5
1.0
0.5
[Table 21
As canbe seen fromTable 2 given above, the average
pore size of the present invention coal is
significantly larger than those of the conventional
coal and the dried coal.

An infrared absorption spectrum of subbituminous
coal (PRB coal fromthe United States) wasmeasuredwith
its temperature raised (lOOc/min) under a
nitrogen-containing atmosphere to find the ratio ofthe
content of each of oxygen-containing functional groups
(hydroxyl groups (OH), carboxyl groups (COOH) ,
aldehyde groups (COH), ester groups (COO)) at given
temperatures. Fig. 3 shows the result. Note that the
horizontal axis represents the temperature, and the
vertical axis represents the ratio of the peak area of
each oxygen-containing functional group to the whole
peak area of the oxygen-containing functional groups
at 1 1 0 " ~ .
As can be seen from Fig. 3, the above
Average Pore Size (nm)
Pore Volume ( ~ m ~ / ~ )
Specific Surface Area
(m2/g)
Conventional
Coal
1.5
0.08
0.23
Present Invention
Coal
2 0
0.13
10.4
Dried
Coal
3.5
0.14
15
oxygen-containing functional groups, i.e. the tar
producing groups are confirmed to mostly disappear at
460°C and completely disappear at 500'~.

The relation between the ratio of residual
unburned carbon resulting from combustion of the above
present invention coal with air at 1500"~,an d the flow
rate ofthe fed air was found. Moreover, for comparison,
the relation was found also for the above conventional
coal and dried coal. Fig. 4 shows the results. Note that
in Fig. 4, the horizontal axis represents the
concentration of residual oxygen in combustion exhaust
gas after the combustion ofthe coal, i.e. excess oxygen
concentration, and the vertical axis represents the
ratio of unburned carbon collected after the combustion
of the coal.
As can be seen from Fig. 4, in the cases of the
conventional coal and the dried coal, the amount of
unburned carbon gradually increases as the excess
oxygen concentration decreases. In contrast, in the
case of the present invention coal, the amount of
unburned carbon does not increase even when the excess
oxygen concentration decreases. Thus, the present
invention coal is confirmed to be capable of
substantially complete combustion.

The relation between the excess oxygen ratio and
the combustion temperature of 100% complete combustion
of the above present invention coal under the
conditions given below was found. Moreover, for
comparison, the relation was found also for the above
conventional coal. Fig. 5 shows the results. Note that
an excess oxygen ratio 0s is a value defined by the
formula (1) given below.
* Combustion Formulas
C + 0 2 + C02
H2 + 1/202 4 H20
* Combustion Conditions
Temperature of fed air: 1 2 0 0 " ~
Concentration of oxygen in air: 21 vole%
Temperature of fed coal: 2 5 " ~
Moisture Content: 2%
Excess oxygen ratio
0s = (Oa + Oc/2) / (Cc + Hc/4) (1)
where Oa is the molar flow rate of the oxygen gas
(molecules) in the fed air, Oc is the molar flow rate
of the oxygen atoms in the fed coal, Cc is the molar
flow rate of the carbon atoms in the fed coal, and Hc
is the molar flow rate of the hydrogen atoms in the fed
coal.
As can be seen from Fig 5, although the calorific
value ofthe present invention coal is smallerthanthat
of the conventional coal, the combustion temperature
is confirmed to be higher than that ofthe conventional
coal in a case where the excess oxygen ratio is the same
as that of the conventional coal. This is because the
present invention coal has a larger oxygen content
ratio than the conventional coal does, and therefore
only requires a smaller amount of fed air than the
conventional coal does on conditicn that the excess
oxygen ratio is the same as that of the conventional
coal.
Industrial Applicability
The blast furnace injection coals and the methods
of manufacturing the same according to the present
invention can be utilized significantly beneficially
in the coal industry, steel industry, and the like.
We Claim:
1. Blast furnace injection coal to be blown into a
blast furnace main unit of a blast furnace
installation through a tuyere, characterized in
that
an oxygen atom content ratio (dry base) is
between 10 and 20% by weight, and
an average pore size is between 10 and 50 nm.
2. The blast furnace injection coal according to claim
1, characterized in that a pore volume is between
0.05 and 0.5 cm3/g.
3 . The blast furnace injection coal according to claim
1 OF 2, characterized in that a specific surface
area is between 1 and 100 m2/g.
4. A method of manufacturing the blast furnace
injection coal according to any one of claims 1 to
3, characterized in that the method comprises:
a drying step of heating subbituminous coal
or brown coal to remove moisture; and
a pyrolysis step of performing pyrolysis at
a temperature between 460 and 5 9 0 " ~on the coal
dried in the drying step.
5. The method of manufacturing the blast furnace
injection coal according to claim 4, characterized
in that the method further comprises:
a cooling step of cooling the coal subjected
to the pyrolysis in the pyrolysis step to a
temperature between 50 and 1 5 0 " ~ ;a nd
a partially oxidizing step of partially
oxidizing the coal cooled in the cooling step by
exposing the coal in an oxygen-containing
atmosphere at a temperature between 50 and 150°C
to let the coal chemically adsorb oxygen.