US20150176096A1

US20150176096A1 - Method for producing pig iron, and blast furnace to be used therefor

Info

Publication number: US20150176096A1
Application number: US14/413,879
Authority: US
Inventors: Setsuo Omoto; Keiichi Nakagawa; Tsutomu Hamada; Masakazu Sakaguchi
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2012-08-13
Filing date: 2013-04-25
Publication date: 2015-06-25
Also published as: JP2014037559A; KR101648683B1; CN104411837B; IN2015DN00505A; WO2014027481A1; KR20150020248A; CN104411837A; JP5958935B2

Abstract

A blast furnace (100) is equipped with: a blast-furnace body (110); material-insertion means (111-113) for inserting a material (1) containing iron ore and coal into the interior of the blast-furnace body from the top section thereof; hot-air blowing means (114, 115) for blowing hot air (101) into the interior of the blast-furnace body through the tuyere thereof; and blast-furnace-blowing-coal supply means (120-129) for blowing blast-furnace-blowing coal (11) into the interior of the blast-furnace body through the tuyere thereof. Therein, the blast-furnace-blowing-coal supply means blow a blast-furnace-blowing coal having the proportion of oxygen atoms contained therein (dry base) set to 10-20 wt %, and the average pore diameter set to 10-50 nm, while the hot-air blowing means measures the melting point of the ash in the material in advance, and blows hot air which is 100-150° C. lower than the melting point of the ash.

Description

TECHNICAL FIELD

The present invention relates to a method for producing pig iron and a blast furnace to be used therefor.

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 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 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

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

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 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 producing pig iron and a blast furnace to be used therefor 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 by the blast-furnace-injecting-coal ash, and reducing the cost of producing pig iron.

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 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 150° C. lower than the 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 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 air that is 100 to 150° 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.

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 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 O) 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 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 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 blast-furnace-injecting coal, and it is possible to reduce the cost of producing pig iron.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of the configuration of a first embodiment of the 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.

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.
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 blast-furnace body 110. A hot air supply device 116 that supplies hot air 101 is connected to a blow pipe 117 provided on a tuyere 118 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 110.
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, 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 in a low oxygen environment (oxygen concentration: 2 vol % or less) by heating (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 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 μm or less). 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 11 by the nitrogen gas 102 is connected to the top of the coal mill 123.
The tip end side of the transport line 125 is connected to a cyclone separator (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 11. 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 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 117 from the injection lance 129.
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 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 11. The hot air temperature control device 115 adjusts the hot air to, for example, from 1050 to 1100° C. when the melting point of the ash (blast-furnace-injecting-coal ash) of the blast-furnace-injecting coal 11 is 1200° C.
In FIG. 1, 110 a 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 111, the feeding conveyor 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 116, 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 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 115, and the like.
Next, the method of producing the pig iron using the blast furnace 100 as described above is described.
The melting point of the ash (blast-furnace-injecting-coal ash) of the blast-furnace-injecting coal 11 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 11 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 μm 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 11 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 116 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 117 and combustion in the raceway, reacting with the coke and the like in the material 1 within the blast-furnace body 110 and generating a reducing gas. In this way, the iron ore in the material 1 is reduced to pig iron (hot metal) 2 and extracted from the taphole 110 a. The oxygen gas concentration of the hot air 101 is adjusted to, for example, 28%.
Here, the blast-furnace-injecting coal 11 as described above has an average 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 containing mainly C, H, and O) 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 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 (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 118. 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 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 grade coal such as subbituminous coal, lignite, or the like as the 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.
It is necessary that the blast-furnace-injecting coal 11 has an average pore 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 110, 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 containing the oxidizing agent or oxygen enrichment of the hot air.
Also, when producing the blast-furnace-injecting coal 11, 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 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, H, and O) 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. For 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 213. The oxygen gas supply device 213 is connected to an oxygen gas temperature control device 212. The oxygen gas temperature control device 212 is connected to an oxygen gas supply source 211
The tip end 214 a of the injection lance 214 for oxygen enrichment is located further toward the inside of the blast-furnace body 110 than the base end 118 a of the tuyere 118 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 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 211, the oxygen gas temperature control device 212, the oxygen gas supply device 213, 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 of the ash (blast-furnace-injecting-coal ash) of the blast-furnace-injecting coal 11 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 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 114 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 11 by the hot air temperature control device 115, and supplied to the blow pipe 117 by the hot air supply device 116 at, for example, a gas flow velocity of 240 m/s, oxygen gas 103 from the oxygen gas supply source 211 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 117 via the injection lance 214 for oxygen enrichment by the oxygen gas supply device 213. In this way, the blast-furnace-injecting coal 11 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 110 a. 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 117, so the ash (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 118. 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 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 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 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 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 117, so compared with the embodiment as described above in which hot air 101 only is supplied to the blow pipe 117, 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 11. Therefore, it is possible to more reliably 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.

INDUSTRIAL APPLICABILITY

The method for producing pig iron and the blast furnace to be used therefor 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.

Reference Signs List

1 Material
2 Pig iron (hot metal)
11 Blast-furnace-injecting coal
100, 200 Blast furnace
101 Hot air
102 Nitrogen gas
103 Oxygen gas
110 Blast-furnace body
110 a Taphole
110 b Outer wall
110 c Thermal insulation
111 Material quantitative supply device
112 Feeding conveyor
113 Furnace top hopper
114 Hot air supply source
115 Hot air temperature control device
116 Hot air supply device
117 Blow pipe
118 Tuyere
118 a Base end
120 Supply hopper
121 Belt conveyor
122 Receiving hopper
123 Coal mill
124 Nitrogen gas supply source
125 Transport line
126 Cyclone separator
127 Storage hopper
128 Injection tank
129 Injection lance
211 Oxygen gas supply source
212 Oxygen gas temperature control device
213 Oxygen gas supply device
214 Injection lance for oxygen enrichment
214 a Tip end

Claims

1. 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.

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 150° C. lower than the melting point of the ash.

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.

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.