DE112013003846T5 - Blast furnace injection coal, and process for its production - Google Patents

Abstract

In a blast furnace injection coal injected via a tuyere into the interior of a blast furnace main unit of a blast furnace plant, the content of oxygen atoms (on a dry basis) is 10-20 wt%, and the average pore size is 10-50 nm.

Description

Technical area

The present invention relates to a blast furnace injection coal and a process for their preparation.

Previous state of the art

Blast furnace equipment is designed to be capable of producing iron ore pig iron by introducing raw materials such as iron ore, limestone and coke into the blast furnace main aggregate via the gout, and hot air and pulverized coal (PCI coal). as auxiliary fuel are blown over the tuyeres on the lower lateral side.

As such a blast furnace injection coal, there have been proposed coals which are obtained by previously adding an oxidizing agent such as KMnO ₄ , H ₂ O ₂ , KClO ₃ or K ₂ Cr ₂ O ₄ to pulverized coal to thereby improve the combustion efficiency so that generation of unburned carbon (soot) can be suppressed (see, for example, Patent Literature 1 listed below).

In addition, methods have been proposed which include, for example, enriching the oxygen in hot air and blowing the air into the blast furnace main unit via the tuyeres to thereby improve the combustibility of the blast furnace injection coal (for example, see Patent Literature 2 listed below).

List of references

patent literature

• Patent Literature 1: Japanese Patent Application, Publication No. Hei 6-220510
• Patent Literature 2: Japanese Patent Application Publication No. 2003-286511

Summary of the invention

Technical problems

However, the blast furnace injection coal described in the above Patent Literature 1 inevitably requires the addition of the above-mentioned oxidizing agent to pulverized coal, and thus increases the running cost.

Moreover, the method for improving the combustibility described in Patent Literature 2 mentioned above requires operating the blast furnace with a large amount of oxygen continuously added to the hot air, and thus also increases operating costs.

In view of the above, it is an object of the present invention to provide a blast furnace injection coal and a process for producing the same which are capable of improving the combustion efficiency at a low cost and the production of unburned carbon (soot) prevention.

Solution of the problems

The blast furnace injection coal according to a first aspect of the invention for solving the above-mentioned problems is a blast furnace injection coal to be blown via a tuyere into a blast furnace main aggregate of a blast furnace plant, characterized in that the proportion of oxygen atoms (dry basis) is between 10 and 20% by weight, and the 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 the pore volume is between 0.05 and 0.5 cm ³ / 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 the specific surface area is between 1 and 100 m ² / g.

A method for producing blast furnace injection coal according to a fourth aspect of the invention for solving the above-mentioned problems is a method for producing the blast furnace injection coal according to any one of the first to third aspects of the invention, characterized in that the method comprises: a drying step in Form of heating subbituminous coal or lignite to remove moisture; and a pyrolysis step in the form of pyrolyzing the carbon dried in the drying step at a temperature between 460 and 590 ° C.

The method for producing 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 in the form of cooling the coal which has undergone pyrolysis in the pyrolysis step Temperature between 50 and 150 ° C; and a partial oxidation step of partially oxidizing the coal cooled in the cooling step by exposing the carbon to an oxygen-containing atmosphere at a temperature between 50 and 150 ° C to allow chemical adsorption of oxygen to the coal.

Advantageous Effects of the Invention

In the blast furnace carbon blacks according to the present invention, the average pore size is 10 to 50 nm, that is, 10 to 50 nm. H. that tar-producing groups such as oxygen-containing functional groups (for example, carboxyl groups, aldehyde groups, ester groups and hydroxyl groups) desorb and greatly decrease while the content of oxygen atoms (dry basis) is 10 to 20% by weight, that is. H. that decomposition (decrease) of the main scaffolds (combustion components mainly containing C, H and O) is massively suppressed. If such a blast furnace injection coal is injected together with hot air through the tuyere in the blast furnace main unit, the blast furnace Einblaskohle, as numerous oxygen atoms are contained in the main frames and beyond the large pores, a simple propagation of the oxygen contained in the hot air thus allowing the interior to be burnt completely and with virtually no unburned carbon (soot) produced, and also significantly inhibiting the production of tar. Accordingly, it is possible to improve the combustion efficiency at a low cost and to suppress the generation of unburned carbon (soot).

According to the method of producing the blast furnace injection coal according to the present invention, the above-described blast furnace injection blanks can be manufactured inexpensively.

Brief description of the drawings

1 FIG. 10 is a flowchart showing the process of a first embodiment of a method of producing a blast furnace injection coal according to the present invention.

2 FIG. 10 is a flowchart showing the process of a second embodiment of the method of producing blast furnace injection coal according to the present invention

3 Fig. 12 is a graph showing the relationship between the temperature of subbituminous coal and the content of each of their oxygen-containing functional groups based on an infrared absorption spectrum of the subbituminous coal taken under a nitrogen-containing atmosphere and increasing temperature.

4 Fig. 10 is a graph showing the relationship between unburned carbon contents collected after combustion of the coal of the present invention, dried coal and conventional coal, and residual oxygen concentrations (excess oxygen concentrations) in combustion exhaust gases after combustion ,

5 Fig. 12 is a graph showing the relationship between the excess oxygen content and the combustion temperature of complete combustion of the coal 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 those embodiments which will be described below with reference to the drawings.

<First Embodiment>

A first embodiment of the blast furnace injection coal and the method for the production thereof according to the present invention will be described with reference to FIG 1 described.

The blast furnace injection coal according to this embodiment has a content of oxygen atoms (dry basis) of 10 to 18 wt%, and an average pore size of 10 to 50 nm (nanometers) (preferably 20 to 50 nm (nanometers)).

As in 1 As shown, the blast furnace injection coal according to this embodiment can be easily produced by: drying low-grade coal 11 (Content of oxygen atoms (dry basis): over 18 wt%, average pore size: 3 to 4 nm), such as subbituminous coal or lignite, by heating them (at 110 to 200 ° C x 0.5 to 1 hour) in an oxygen-poor atmosphere (oxygen concentration: 5 vol% or less) to remove moisture (drying step S11); Pyrolyzing the resulting coal by heating it (at 460 to 590 ° C (preferably 500 to 550 ° C) × 0.5 to 1 hour) in an oxygen-poor atmosphere (oxygen concentration: 2% by volume or less) to produce water, carbon dioxide, To remove tar, and the like as pyrolysis gas and pyrolysis oil (pyrolysis step S12); Cooling the resulting coal (to 50 ° C or below) in an oxygen-poor atmosphere (oxygen concentration: 2% by volume or less) (cooling step S13); and pulverizing the resulting coal (to a particle size of 77 μm or less (80% pass)) (pulverization step S14).

In the blast furnace injection coal 12 produced by the above-described production method according to this embodiment, the average pore size is 10 to 50 nm, ie, desorbing and forming tar-producing groups such as oxygen-containing functional groups (for example, carboxyl groups, aldehyde groups, ester groups, and hydroxyl groups) The content of oxygen atoms (dry basis) is 10 to 18 wt%, that is, decomposition (decrease) of the main skeletons (combustion components mainly containing C, H and O) is massively suppressed. Will the blast furnace injection coal 12 blown into a blast furnace main aggregate together with hot air via each tuyere, so can the blast furnace blow-in coal 12 In addition, since many oxygen atoms are contained in the main skeletons and, moreover, the large pores allow easy propagation of the oxygen contained in the hot air into the interior, therefore burned completely and almost without generation of unburned carbon (soot), and further inhibit the Production of tar in a significant way.

The blast furnace injection coal 12 According to this embodiment, therefore, the combustion efficiency can be improved and the generation of unburned carbon (soot) can be suppressed without adding an oxidizing agent such as KMnO ₄ , H ₂ O ₂ , KClO ₃ or K ₂ Cr ₂ O ₄ , or Hot air containing oxygen is enriched.

Thus, according to this embodiment, it is possible to improve the combustion efficiency at a low cost and to suppress the generation of unburned carbon (soot).

Note that the mean pore size of the blast furnace injection coal 12 According to this embodiment, it must be 10 to 50 nm (preferably 20 to 50 nm). This is because, in the case of an average pore size of less than 10 nm, the spreadability of the oxygen contained in the hot air to the inside deteriorates and, accordingly, the combustibility deteriorates, while in the case of a mean pore size of more than 50 nm, the blast furnace injection coal 12 due to heat shock and the like easily breaks down into smaller sizes, and therefore breaks down into smaller sizes upon blowing into the blast furnace main assembly, resulting in a situation where the blast furnace injection coal 12 passes through the interior of the blast furnace main assembly together with a gas stream and is ejected without combustion.

In addition, the proportion of oxygen atoms (dry basis) may not be less than 10 wt .-%. This is because in the case of a content of oxygen atoms (dry basis) of less than 10% by weight, it is difficult to achieve complete combustion without adding an oxidizing agent or enriching the oxygen contained in the hot air.

Furthermore, the pore volume is preferably 0.05 to 0.5 cm ³ / g, and particularly preferably 0.1 to 0.2 cm ³ / g. This is because that in the case of a pore volume of less than 0.05 cm ³ / g a small contact surface (reaction surface) is present with the water contained in the hot air oxygen and the combustibility may deteriorate, while in the case of a pore volume of more than 0.5 cm to ³ / g volatilize large quantities of components and the blast furnace injection coal 12 so porous is that an excessive reduction of the combustion components can result.

In addition, the specific surface area is preferably 1 to 100 m ² / g, and more preferably 5 to 20 m ² / g. This is because in the case of a specific surface area of less than 1 m ² / g, there is a small contact surface (reaction surface) with the oxygen contained in the hot air, and the combustibility possibly deteriorates, while in the case of a specific surface area of more than 100 m ² / g volatilize large amounts of components and the blast furnace injection coal 12 so porous is that an excessive reduction of the combustion components can result.

On the other hand, in the method for producing the blast furnace injection coal according to this embodiment, the pyrolysis temperature in the pyrolysis step S12 must be 460 to 590 ° C (preferably 500 to 550 ° C). This is because, in the case of a temperature of less than 460 ° C, the tar-producing groups, such as oxygen-containing functional groups, are inadequately affected by the low-grade coal 11 and that it is extremely difficult to obtain a mean pore size of 10 to 50 nm, while in the case of a temperature of more than 590 ° C considerable degradation of the main scaffolds (combustion components mainly containing C, H and O) of the low rank coal 11 used and volatilize large amounts of components, which in turn leads to an excessive reduction of the combustion components.

<Second Embodiment>

A second embodiment of the blast furnace injection coal and the method for its production according to the present invention will be described with reference to FIG 2 described. Note that, for portions similar to those of the previous embodiment, reference numerals similar to those used in the description of the previous embodiment are used, and the description thereof overlapping with the description in the preceding embodiment will be omitted ,

The blast furnace injection coal according to this embodiment has a content of oxygen atoms (dry basis) of 12 to 20% by weight and an average pore size of 10 to 50 nm (preferably 20 to 50 nm).

As in 2 As shown, the blast furnace injection coal according to this embodiment can be easily produced by: drying the inferior coal 11 (Content of oxygen atoms (dry basis): over 18 wt%) in a similar manner as in the previous embodiment (drying step S11); Pyrolyzing the resulting coal in a similar manner as in the previous embodiment (pyrolysis step S12); Cooling the resulting coal (to 50 to 150 ° C) in an oxygen-poor atmosphere (oxygen concentration: 2 vol% or less) (cooling step S23); partially oxidizing the resulting coal by exposing it to an oxygen-containing atmosphere (oxygen concentration: 5 to 21% by volume) (at 50 to 150 ° C x 0.5 to 10 hours) to allow chemical adsorption of oxygen to the coal (partial oxidation step S25); and pulverizing the resulting coal in a similar manner as in the previous embodiment (pulverization step S14).

As a result, in this embodiment, the coal subjected to pyrolysis in the pyrolysis step S12 is cooled to 50 to 150 ° C, and the coal is then partially oxidized in the partial oxidation step S25 by permitting a chemical adsorption of oxygen to the coal, thereby blast furnace injection 22 with a content of oxygen atoms (dry basis) of 12 to 20 wt .-% to obtain.

In the blast furnace injection coal 22 produced by the above-mentioned manufacturing method according to this embodiment is, as in the previous embodiment, the average pore size 10 to 50 nm, that is, that tar-producing groups such as oxygen-containing functional groups (for example, carboxyl groups, aldehyde groups, ester groups, and hydroxyl groups) desorb and greatly reduce, while the content of oxygen atoms (dry basis) is 12 to 20% by weight. ie, a decomposition (decrease) of the main skeletons (combustion components mainly containing C, H and O) is massively suppressed and more oxygen atoms are chemically adsorbed. Will the blast furnace injection coal 22 blown together with hot air through the tuyere into the blast furnace main unit, so can the blast furnace injection coal 22 since the main skeletons contain more oxygen atoms than in the previous embodiment, and moreover, the large pores allow easy diffusion of the oxygen contained in the hot air into the interior, therefore, completely and to produce a smaller amount of unburned carbon (soot) than in the previous one Embodiment burns, moreover, and it prevents, like the previous embodiment, the production of tar in a significant way.

The blast furnace injection coal 22 Therefore, according to this embodiment, the combustion efficiency can be improved to a greater extent and the generation of unburned carbon (soot) more reliably prevented than the previous embodiment without using an oxidizing agent such as KMnO ₄ , H ₂ O ₂ , KClO ₃ or K ₂ Cr ₂ O ₄ , added or the oxygen contained in the hot air is enriched.

Thus, according to this embodiment, it is possible to further improve the combustion efficiency at low cost and to more reliably suppress the generation of unburned carbon (soot) than in the previous embodiment.

Note that the content of oxygen atoms (dry basis) in the blast furnace injection coal 22 According to this embodiment, it must be 20% by weight or less. This is because in the case of a content of oxygen atoms (dry basis) of less than 20% by weight, the oxygen content is excessively large and the amount of heat generated excessively decreases.

On the other hand, in the method of producing the blast furnace injection coal of this embodiment, the temperature of the process in the partial oxidation step S25 is preferably 50 to 150 ° C. This is because in the case of a temperature of less than 50 ° C, even in an air atmosphere (oxygen concentration: 21% by volume), it is difficult to promote the partial oxidation process, while in the case of a temperature higher than 150 ° C, even in one Atmosphere in which the oxygen concentration is about 5 vol .-%, may be generated in the combustion reaction may be large amounts of carbon monoxide and carbon dioxide.

[Examples]

Examples performed to confirm the beneficial effects of the blast furnace carbon black and the method of making the same according to the present invention are described below. However, the present invention is not limited to those examples which will be described below based on various types of data.

<No. 1: Composition analysis>

It was a compositional analysis (elemental analysis) of the blast furnace injection coal 12 obtained by the above-described production method according to the first embodiment (coal of the present invention). Moreover, for comparative purposes, a compositional analysis of a conventional blast furnace injection coal (PCI coal: conventional coal) and a coal obtained by omitting the pyrolysis step S12 of the first embodiment (dried coal) was also conducted. The following Table 1 shows the results. Note that the values are all dry. [Table 1] Coal of the present invention conventional coal dried coal C (% by weight) 73.8 84.5 71.0 H (% by weight) 3.2 3.8 3.6 O (% by weight) 14.4 2.9 18.5 N (% by weight) 1.1 1.7 1.0 S (% by weight) 0.3 0.5 0.5 Calorific value (kcal / kg) 6700 8020 6300

As is apparent from the above-mentioned Table 1, the content of oxygen (O) in the coal of the present invention is lower than that in the dried coal and significantly larger than that in the conventional coal, while the content of carbon is larger than that in the dried coal and lower than that in the conventional coal. Thus, the calorific value of the coal of the present invention is larger than that of the dried coal and smaller than that of the conventional coal.

<No. 2: Surface states>

Surface conditions (average pore size, pore volume, specific surface area) of the above-mentioned carbon of the present invention were measured. In addition, for the purpose of comparison, the surface states of the above-mentioned conventional coal and the dried coal were also measured. Table 2 below shows the results. [Table 2] Coal of the present invention conventional coal dried coal average pore size (nm) 20 1.5 3.5 Pore volume (cm ³ / g) 12:13 12:08 12:14 specific surface area (m ² / g) 10.4 12:23 15

As apparent from the above-mentioned Table 2, the average pore size of the coal of the present invention is significantly larger than that of the conventional coal and the dried coal.

<No. 3: Amounts of oxygen-containing functional groups>

Under a nitrogen-containing atmosphere and increasing temperature (10 ° C / min), an infrared absorption spectrum of subbituminous coal (United States PRB coal) was recorded to reduce the proportion of all oxygen-containing functional groups (hydroxyl groups (OH), carboxyl groups (COOH ), Aldehyde groups (COH), ester groups (COO)) at given temperatures. 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 total peak area of the oxygen-containing functional groups at 110 ° C.

How out 3 can be seen, it is confirmed that the above-mentioned oxygen-containing functional groups, ie the tar-producing groups, largely disappear at 460 ° C, and completely disappear at 500 ° C.

<No. 4: flammability>

The relationship between the proportion of residual unburned carbon resulting from combustion of the above-mentioned coal of the present invention with air at 1500 ° C and the flow rate of the supplied air was determined. In addition, for comparative purposes, the relationship was also established for the above-mentioned conventional coal and the dried coal. 4 shows the results. Note that in 4 the horizontal axis represents the concentration of residual oxygen in the combustion exhaust gas after combustion of the coal, ie the concentration of excess oxygen, and the vertical axis represents the fraction of unburned carbon collected after the combustion of the coal.

How out 4 As can be seen, in the cases of conventional coal and dried coal, the amount of unburned carbon increases gradually as the concentration of excess oxygen decreases. In contrast, in the case of the coal of the present invention, the amount of unburned carbon does not increase even if the concentration of excess oxygen decreases. Thus, it is confirmed that the coal of the present invention can be substantially completely burned.

<No. 5: combustion temperature>

• * Verbrennungsformeln C + O₂ → CO₂ H₂ + 1/2O₂ → H₂O
• * Verbrennungsbedingungen
• • Temperatur der zugeführten Luft: 1200°C
• • Konzentration an Sauerstoff in der Luft: 21 Vol.-%
• • Temperatur der zugeführten Kohle: 25°C
• • Feuchtigkeitsgehalt: 2%

The relationship between the excess oxygen content and the combustion temperature of 100% completed combustion of the above-mentioned coal of the present invention was determined under the following conditions. In addition, for comparative purposes, the relationship for the above-mentioned conventional coal was also determined. 5 shows the results. Note that the content of excess oxygen Os represents a value defined by the following formula (1).

• * Combustion formulas C + O ₂ → CO ₂ H ₂ + 1 / 2O ₂ → H ₂ O
• * Combustion conditions
• • Temperature of the supplied air: 1200 ° C
• • concentration of oxygen in the air: 21 vol.%
• • Temperature of the supplied coal: 25 ° C
• • moisture content: 2%

Proportion of excess oxygen

• Os = (Oa + Oc / 2) / (Cc + Hc / 4) (1) where Oa represents the molar flow rate of the oxygen gas (molecules) in the feed air, Oc represents the molar flow rate of oxygen atoms in the feed coal, Cc represents the molar flow rate of carbon atoms in the feed coal, and Hc represents the molar flow rate of the hydrogen atoms in the feed Represents coal.

Although the heating value of the coal of the present invention is lower than that of the conventional coal, it is confirmed that the combustion temperature is higher than that of the conventional coal in a case where the excess oxygen content is the same as the conventional coal. like out 5 is apparent. This is because the coal of the present invention has a higher proportion of oxygen than the conventional coal, and therefore, under the condition that the content of excess oxygen is the same as in the conventional coal, a smaller amount of supplied air than the conventional one Coal needed.

Industrial applicability

The blast furnace carbon blanks, as well as the processes for their preparation according to the present invention, can be used with considerable benefit in the coal industry, steel industry, and the like.

LIST OF REFERENCE NUMBERS

11

MINIMUM CARBON (SUBBITUMINOUS COAL OR BROWN COAL)

12, 22

Blast furnace injection

S11

DRYING STEP

S12

pyrolysis

S13, S23

COOLING STEP

S14

pulverization

S25

partially oxidizing

Claims (5)

Blast furnace injection coal to be injected via a tuyere into a blast furnace main unit of a blast furnace plant, characterized in that the proportion of oxygen atoms (dry basis) is between 10 and 20 wt .-%, and the average pore size between 10 and 50 nm , Blast furnace injection coal according to claim 1, characterized in that the pore volume is between 0.05 and 0.5 cm ³ / g. Blast furnace injection coal according to claim 1 or 2, characterized in that the specific surface area is between 1 and 100 m ² / g. A method of producing 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 sub-bituminous coal or brown coal to remove moisture; and a pyrolysis step in the form of pyrolyzing the carbon dried in the drying step at a temperature between 460 and 590 ° C. A method of producing the blast furnace injection coal according to claim 4, characterized in that the method further comprises: a cooling step in the form of cooling the coal subjected to pyrolysis in the pyrolysis step to a temperature between 50 and 150 ° C; and a partial oxidation step of partially oxidizing the coal cooled in the cooling step by exposing the carbon to an oxygen-containing atmosphere at a temperature between 50 and 150 ° C to allow chemical adsorption of oxygen to the coal.

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