EP3354712A1

EP3354712A1 - Coal briquettes, method for manufacturing same, apparatus for manufacturing same, and method for manufacturing molten iron

Info

Publication number: EP3354712A1
Application number: EP16848768.4A
Authority: EP
Inventors: Woo Il Park; Sang Hyun Kim; Hong San Kim; Hyun Jong Kim; Moo Eob Choi
Original assignee: Posco Co Ltd
Current assignee: Posco Holdings Inc
Priority date: 2015-09-25
Filing date: 2016-07-01
Publication date: 2018-08-01
Anticipated expiration: 2036-07-01
Also published as: EP3354712A4; CN108138064A; WO2017052042A8; WO2017052042A1; KR101696628B1; EP3354712B1; BR112018005949A2

Abstract

Provided are a coal briquette, a method of manufacturing coal briquettes, and a method of manufacturing molten iron. The coal briquette is inputted into and quickly heated in a dome portion of a melting and gasifying furnace in an apparatus for manufacturing molten iron that includes i) the melting and gasifying furnace into which reduced iron is inputted, and ii) a reducing furnace which is connected to the melting and gasifying furnace and provides the reduced iron. The method of manufacturing coal briquettes includes i) providing powdered coal, ii) mixing the powdered coal with a binder and providing a mixture, iii) providing coal briquettes by molding the mixture, and iv) performing a heat treatment of heating the coal briquettes to improve compressive strength of the coal briquettes.

Description

[Technical Field]

The present invention relates to a coal briquette, a method and an apparatus for manufacturing coal briquettes, and a method of manufacturing molten iron. More particularly, the present invention relates to a coal briquette, a method and an apparatus for manufacturing coal briquettes, and a method of manufacturing molten iron, capable of ensuring compressive strength of the coal briquette having a high moisture content.

[Background Art]

In a direct iron ore smelting reduction process, a reducing furnace for reducing iron ore and a melting and gasifying furnace for melting the reduced iron ore are used. When the iron ore is melted in the melting and gasifying furnace, coal briquettes, as a heat source for melting the iron ore, are inputted into the melting and gasifying furnace. The reduced iron is melted in the melting and gasifying furnace, converted into molten iron and slag, and then discharged to the outside. The coal briquettes inputted into the melting and gasifying furnace form a coal-packed bed. Oxygen is injected through a tuyere installed in the melting and gasifying furnace, and then combusts the coal-packed bed to generate combustion gas. The combustion gas is converted into high-temperature reducing gas while moving upward through the coal-packed bed. The high-temperature reducing gas is discharged to the outside from the melting and gasifying furnace and supplied, as reducing gas, to a reducing furnace.
The coal briquette is manufactured by mixing and then compressing powdered coal and a binder. It is necessary to manufacture the coal briquette with excellent cold strength and excellent hot strength so that the coal briquette is used to manufacture molten iron. Therefore, the coal briquette is manufactured by using a binder, such as molasses, having excellent viscosity.

[DISCLOSURE]

[Technical Problem]

The present invention has been made in an effort to provide a coal briquette having excellent hot strength and cold strength by performing a heat treatment on the coal briquette, which is manufactured by mixing a binder with water or manufactured to include a binder having a high moisture content, in order to improving compressive strength of the coal briquette. The present invention has also been made in an effort to provide a method and an apparatus for manufacturing coal briquettes. The present invention has also been made in an effort to provide a method of manufacturing molten iron including the method of manufacturing coal briquettes.

[Technical Solution]

An exemplary embodiment of the present invention provides a coal briquette which is inputted into and quickly heated in a dome portion of a melting and gasifying furnace in an apparatus for manufacturing molten iron that includes i) the melting and gasifying furnace into which reduced iron is inputted, and ii) a reducing furnace which is connected to the melting and gasifying furnace and provides the reduced iron.
Another exemplary embodiment of the present invention provides a method of manufacturing coal briquettes, the method including: i) providing powdered coal; ii) mixing the powdered coal with a binder and providing a mixture; iii) providing coal briquettes by molding the mixture; and iv) performing a heat treatment of heating the coal briquettes to improve compressive strength of the coal briquettes.
The method of manufacturing coal briquettes according to the exemplary embodiment of the present invention may further include adding water to the mixture and mixing the water and the mixture after the providing of the mixture.
In the providing of the mixture, the binder may be a water-soluble binder.
In the providing of the mixture, the binder may be at least one selected from a cellulose ether compound, PVA, Lignin, and starch.
The cellulose ether compound may include at least one compound selected from a group consisting of methyl cellulose (MC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), hydroxypropylmethyl cellulose (HPMC), and hydroxyethylmethyl cellulose (HEMC).
The cellulose ether compound may include no carboxymethyl cellulose (CMC). The viscosity of the cellulose ether compound may be 4,000 cps to 80,000 cps. The method of manufacturing coal briquettes according to the exemplary embodiment of the present invention may further include drying the mixture after the adding of the water to the mixture and the mixing of the mixture with the water.
In the providing of the coal briquettes, the amount of moisture contained in the coal briquettes may be 8 wt% to 15 wt%.
In the performing of the heat treatment, the coal briquette may be heated at a temperature of 80 to 150°C for 1 to 24 hours.
In the performing of the heat treatment, the coal briquette may be heated so that a moisture content is 5 wt% or less.
In the performing of the heat treatment, the coal briquette may be heated so that compressive strength is 100 kgf or more.
The performing of the heat treatment may include heating the coal briquette by using at least one selected from a hot blast, steam, near infrared rays, and microwaves.
The performing of the heat treatment may include: conveying the coal briquette and inputting the coal briquette into a storage bin; heating the coal briquette by supplying a high-temperature hot blast into the storage bin; and discharging the heat-treated coal briquette from the storage bin.
In the performing of the heat treatment, a temperature of the hot blast being inputted into the storage bin may be 80 to 150°C.
The performing of the heat treatment may further include discharging moisture vapor, which is vaporized from the coal briquette by the high-temperature hot blast, through an upper portion of the storage bin.
Still another exemplary embodiment of the present invention provides an apparatus for manufacturing coal briquettes, the apparatus including: a mixer which mixes raw materials including powdered coal and a water-soluble binder; a briquette machine which manufactures coal briquettes by molding a mixture mixed in the mixer; and a heat treatment unit which improves compressive strength of the coal briquettes by heating the coal briquettes manufactured by the briquette machine.
The apparatus may further include a water supply unit for supplying water to the mixer.
The heat treatment unit may include: a storage bin which is connected to the briquette machine and accommodates the coal briquettes; a hot blast supply pipe which is connected between a lower portion of the storage bin and a heat source and supplies a hot blast into the storage bin; a blower which is installed in a hot blast supply pipe; and a discharge line which is connected to an upper portion of the storage bin and discharges moisture vapor evaporated from the coal briquette.
Yet another exemplary embodiment of the present invention provides a method of manufacturing molten iron, the method including: i) providing the coal briquettes manufactured according to the aforementioned method; ii) providing reduced iron made by reducing iron ore in a reducing furnace; and iii) providing molten iron by inputting the coal briquettes and the reduced iron into a melting and gasifying furnace. In the providing of the reduced iron, the reducing furnace may be a fluidized-bed reducing furnace or a packed-bed reducing furnace.
Still yet another exemplary embodiment of the present invention provides a coal briquette which is inputted into and quickly heated in a dome portion of a melting and gasifying furnace in an apparatus for manufacturing molten iron that includes i) the melting and gasifying furnace into which reduced iron is inputted, and ii) a reducing furnace which is connected to the melting and gasifying furnace and provides the reduced iron. The coal briquette may contain moisture of 5 wt% or less. Compressive strength of the coal briquette may be 100 kgf or more.

[Advantageous Effects]

The compressive strength of the coal briquette is improved by the heat treatment, and as a result, it is possible to greatly improve hot strength and cold strength of the coal briquette even though the coal briquette is manufactured by a water-soluble binder or water.
In addition, the compressive strength of the coal briquette is improved in a short time by the quick and efficient heat treatment, and as a result, it is possible to ensure hot strength and cold strength.
In addition, the storage bin existing in the related art and a heat source in a steel mill are used, and as a result, it is possible to minimize costs and effectively perform the heat treatment on the coal briquette.

[Description of the Drawings]

FIG. 1 is a schematic view illustrating an apparatus for manufacturing coal briquettes according to an exemplary embodiment of the present invention.
FIG. 2 is a schematic flowchart of a method of manufacturing coal briquettes according to an exemplary embodiment of the present invention.
FIG. 3 is a flowchart schematically illustrating a process of performing a heat treatment on the coal briquettes in accordance with the method of manufacturing coal briquettes according to the exemplary embodiment of the present invention.
FIG. 4 is a schematic view of an apparatus for manufacturing molten iron using the coal briquettes manufactured by the apparatus illustrated in FIG. 1.
FIG. 5 is a schematic view of another device for manufacturing molten iron using the coal briquettes manufactured by the apparatus of FIG. 1.
FIG. 6 is a graph illustrating an experimental result of compressive strength of the coal briquette manufactured in accordance with the present exemplary embodiment.
FIG. 7 is a graph illustrating an experimental result of compressive strength of the coal briquette manufactured in accordance with the present exemplary embodiment.
FIG. 8 is a graph illustrating an experimental result of compressive strength of the coal briquette manufactured in accordance with the present exemplary embodiment.
FIG. 9 is a graph illustrating an experimental result of compressive strength of the coal briquette manufactured in accordance with the present exemplary embodiment.

[Mode for Invention]

The terms first, second, third, and the like are used to describe various portions, components, regions, layers, and/or sections, but the present invention is not limited thereto. These terms are used only to distinguish any portion, component, region, layer, or section from other portions, components, regions, layers, or sections. Therefore, a first portion, component, region, layer, or section to be described below may be referred to as a second portion, component, region, layer, or section without departing from the scope of the present invention.
The technical terms used herein are used merely for the purpose of describing a specific exemplary embodiment, and not intended to limit the present invention. Singular expressions used herein include plural expressions unless they have definitely opposite meanings. The terms "comprises" and/or "comprising" used in the specification specify particular features, regions, integers, steps, operations, elements, components, but do not preclude the presence or addition of other features, regions, integers, steps, operations, elements, and/or components thereof.
Unless otherwise defined, all terms used herein including technical or scientific terms have the same meanings as meanings which are generally understood by those skilled in the art. Terms, which are usually used and defined in dictionaries, shall be construed that they have meanings matching those in the context of a related art, and shall not be construed in ideal or excessively formal meanings unless they are clearly defined in the present application.
The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.
FIG. 1 schematically illustrates an apparatus for manufacturing coal briquettes according to an exemplary embodiment of the present invention.
As illustrated in FIG. 1, an apparatus 60 for manufacturing coal briquettes includes a mixer 64 which mixes powdered coal and a binder supplied from a powdered coal hopper 61 that stores powdered coal and a binder hopper 62 that stores a binder, respectively, , a briquette machine 65 which manufactures coal briquettes by molding a mixture mixed by the mixer 64, and a heat treatment unit which heats the coal briquette manufactured by the briquette machine to improve compressive strength of the coal briquette.
The manufacturing apparatus may further include a water supply unit 63 which supplies water to the mixer.
The briquette machine 65 manufactures the coal briquette by compressing the mixture. For example, the briquette machine 65 includes a pair of rollers, and the mixture is inputted and compressed between the rollers, such that the coal briquette may be manufactured in the form of a pocket or a strip.
The heat treatment unit serves to improve compressive strength of the coal briquette by applying energy to the coal briquette, and may have a structure that heats the coal briquette by using a high-temperature hot blast or applying steam, near infrared rays, or microwaves to the coal briquette.
In the present exemplary embodiment, the heat treatment unit includes a storage bin 66 which is connected to the briquette machine 65 and accommodates the coal briquettes, a hot blast supply pipe 68 which is connected between a lower portion of the storage bin 66 and a heat source 67 and supplies a hot blast into the storage bin 66, and a blower 69 which is installed in the hot blast supply pipe.
The storage bin 66 stores the coal briquettes manufactured by and conveyed from the briquette machine 65. The coal briquettes are supplied to an upper portion of the storage bin 66 and discharged through a lower end of the storage bin 66. A discharge device for quantitatively discharging the coal briquettes is installed at the lower end of the storage bin 66. For example, the discharge device constantly discharges the coal briquettes stored in the storage bin at 0 to 50 t/h.
A discharge line 70, which discharges moisture vapor evaporated from the coal briquettes, is installed on the upper portion of the storage bin 66, and a dust collection facility 71 is connected to the discharge line 70. Therefore, the moisture vapor evaporated from the coal briquettes by the heat treatment is discharged to and treated in the dust collection facility 71. In this case, because condensate water may be produced when a temperature is decreased at pressure equal to or higher than saturated vapor pressure, a thermal insulating device (not illustrated) may be further provided to prevent the condensate water from flowing back into the storage bin.
The hot blast supply pipe 68 is installed at one side of the lower portion of the storage bin 66. The hot blast, which is supplied into the storage bin 66 through the hot blast supply pipe 68, heats the coal briquettes while moving upward, thereby evaporating moisture contained in the coal briquettes. The blower 69 forcibly supplies the hot blast, which is heated by the heat source 67, to the hot blast supply pipe.
The heat source 67 may be structured to use commercially available fuel such as LNG or LPG. Otherwise, the heat source 67 may be structured to use by-product gas, such as FOG, COG, or BFG, in a steel mill.
In addition, the heat source 67 may be a direct heating structure such as an electric heater, or may recover and use waste heat, such as slag sensible heat or waste heat generated when powdered reduced iron is oxidized, which is generated in the steel mill.
As described above, the heat treatment is performed on the coal briquettes by utilizing the storage bin that serves as an intermediate buffer in the related art during a process of conveying the coal briquettes, and as a result, it is possible to effectively and sufficiently ensure strength in a short time without investigating separate facilities.
Therefore, even in the case of the coal briquette of which the sufficient strength is not initially ensured because of a high moisture content because the binder and the water are used or the binder itself is water-soluble, cold strength of the coal briquette may be ensured in a short time by heating the coal briquette in a line for manufacturing coal briquettes.
FIG. 2 schematically illustrates a flowchart of a method of manufacturing coal briquettes according to the exemplary embodiment of the present invention. The flowchart of the method of manufacturing coal briquettes as illustrated in FIG. 2 is merely for exemplifying the present invention, and the present invention is not limited thereto. Therefore, the method of manufacturing coal briquettes may be variously modified.
As illustrated in FIG. 2, the method of manufacturing coal briquettes includes providing powdered coal (S100), providing a mixture by mixing the powdered coal with a binder (S200), providing coal briquettes by molding the mixture (S300), and performing a heat treatment of heating the coal briquette to improve compressive strength of the coal briquette (S400).
In addition, the method of manufacturing coal briquettes according to the exemplary embodiment of the present invention may further include adding water to the mixture of the powdered coal and the binder and mixing the water and the mixture (S210). In addition, the method of manufacturing coal briquettes may further include other steps, as necessary.
First, in step S100, the powdered coal is provided. Raw materials containing carbon, such as bituminous coal, subbituminous coal, anthracite, or cokes, may be used as the powdered coal. A grain size of the powdered coal may be adjusted to 4 mm or less.
Next, in step S200, the powdered coal is mixed with a binder, such that a mixture is provided. That is, the binder is added to the powdered coal, and then the binder and the powdered coal are appropriately stirred to be uniformly mixed.
In the present exemplary embodiment, the binder may be a water-soluble binder. The binder may be at least one selected from a cellulose ether compound, PVA, Lignin, and starch.
The viscosity of the cellulose ether compound may be 4,000 cps to 80,000 cps. The viscosity of the cellulose ether compound means a value obtained by measuring viscosity of an aqueous solution of a cellulose ether compound having concentration of 2% by weight at 20 ± 0.1°C by using DV-II+Pro (spindle HA) manufactured by Brookfield. If the viscosity of the cellulose ether compound is too low, viscosity of a solution containing the cellulose ether compound, for example, viscosity of the aqueous solution is too low, such that coupling force with respect to the powdered coal deteriorates. As a result, strength of the coal briquette may deteriorate. Meanwhile, if the viscosity of the cellulose ether compound is too high, a molecular weight of the cellulose ether compound is too large, such that water solubility deteriorates, and as a result, coupling force with respect to the powdered coal is not sufficient. Therefore, it is preferred to adjust the viscosity of the cellulose ether compound to the aforementioned range.
The cellulose ether compound may include methyl cellulose (MC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), hydroxypropylmethyl cellulose (HPMC), hydroxyethylmethyl cellulose (HEMC), or the like.
The methyl cellulose (MC) has a degree of substitution of a methyl group of 18 to 32 wt%, and the hydroxyethyl cellulose (HEC) has a degree of substitution of a hydroxyethyl group of 20 to 80 wt%. Further, the hydroxypropyl cellulose (HPC) has a degree of substitution of a hydroxypropyl group of 20 to 80 wt%, and the hydroxypropylmethyl cellulose (HPMC) has a degree of substitution of a methyl group of 18 to 32 wt% and a degree of substitution of a hydroxypropyl group of 2 to 14 wt%. In addition, the hydroxyethylmethyl cellulose (HEMC) may have a degree of substitution of a methyl group of 18 to 32 wt% and a degree of substitution of a hydroxyethyl group of 2 to 14 wt%.
Next, in step S210, water may be added to the mixture and the water and the mixture may be mixed.
Meanwhile, although not illustrated in FIG. 2, drying the mixture may be added after step S210. That is, if it is necessary to adjust formability of the mixture of the powdered coal, the powdered cellulose ether compound, and the added water, the mixture may be dried to partially remove moisture. As a result, strength of the coal briquette manufactured during the subsequent processes may be greatly improved.
In step S300, the mixture is molded to provide the coal briquette. The coal briquette in the form of a pocket or a strip may be manufactured by inputting the mixture between a pair of rollers and compressing the mixture.
Here, the amount of moisture contained in the coal briquette manufactured through step S300 may be 8 wt% or more.
As described above, the water-soluble binder is used, or water is used during the process of mixing the powdered coal and the binder, and as a result, the coal briquette manufactured through the molding step does not have sufficient strength because of an excessive moisture content.
Therefore, the coal briquette is heated through the performing of the heat treatment S400, and as a result, sufficient strength of the coal briquette may be ensured even though the coal briquette has a moisture content of 8 wt% or more.
As illustrated in FIG. 3, the performing of the heat treatment (S400) includes conveying the coal briquette and inputting the coal briquette into the storage bin (S410), heating the coal briquette by supplying a high-temperature hot blast into the storage bin (S420), and discharging the heat-treated coal briquette from the storage bin (S430).
In addition, the performing of the heat treatment may further include discharging moisture vapor, which is evaporated from the coal briquette by the high-temperature hot blast, through the upper portion of the storage bin (S440). In addition, the performing of the heat treatment may further include other steps, as necessary.
In step S410, the coal briquette is inputted into the storage bin and fills the storage bin. A level of the coal briquette in the storage bin is maintained to an appropriate level in consideration of heat treatment time or a degree to which the coal briquette is not destroyed by a compressive load caused by the coal briquette in the storage bin.
In step S420, the hot blast is blown into the lower portion of the storage bin. A temperature of the hot blast being inputted into the storage bin may be 80 to 150°C.
If a temperature of the hot blast is lower than 80°C, moisture is not appropriately evaporated from the coal briquette, such that a heat treatment effect deteriorates, and if the temperature thereof is higher than 150°C, the coal briquette may be cracked, and a loss of volatile components may occur.
In the performing of the heat treatment, the coal briquette may be heated at a temperature of 80 to 150°C for 1 to 24 hours. The heat treatment time may be shortened as a temperature at which the coal briquette is heated by the hot blast is high, and a high-temperature hot blast needs to be supplied in order to shorten the heat treatment time within one hour, and as a result, a loss of volatile components of the coal briquette occurs. In addition, only a moisture content of the coal briquette is decreased as the coal briquette is dried at a high temperature, and as a result, compressive strength rather deteriorates. If a temperature at which the coal briquette is heated is lower than 80°C, the time required for the heat treatment exceeds 24 hours, such that productivity deteriorates.
The heat treatment condition may be mitigated or strengthened in accordance with a moisture content of the coal briquette to be inputted into the storage bin.
The coal briquette is heated by the hot blast through step S420, and moisture is evaporated.
In step S430, the heat-treated coal briquette is discharged through the lower end of the storage bin. The moisture vapor, which is evaporated from the coal briquette through the heat treatment, is discharged to and treated in the dust collection facility through step S440. In this case, it is possible to prevent the production of condensate water by adjusting a flow rate and a temperature of the hot blast.
The coal briquette manufactured by the aforementioned method contains moisture of 5wt% or less. In addition, because the moisture content is decreased, the coal briquette manufactured by the aforementioned method has compressive strength of 100 kgf or higher.
FIG. 4 schematically illustrates an apparatus 100 for manufacturing molten iron using the coal briquette manufactured in accordance with the present exemplary embodiment. A structure of the apparatus 100 for manufacturing molten iron, which is illustrated in FIG. 4, is merely for exemplifying the present invention, and the present invention is not limited thereto. Therefore, the apparatus 100 for manufacturing molten iron, which is illustrated in FIG. 4, may be modified to various forms.
The apparatus 100 for manufacturing molten iron, which is illustrated in FIG. 4, includes a melting and gasifying furnace 10 and a packed-bed reducing furnace 20. Other devices may be included in addition to the furnaces, as necessary. Iron ore is inputted into and reduced in the packed-bed reducing furnace 20. The iron ore inputted into the packed-bed reducing furnace 20 is dried in advance, and then manufactured as reduced iron while passing through the packed-bed reducing furnace 20. The packed-bed reducing furnace 20 is a packed-bed reducing furnace that forms a packed bed therein by being supplied with reducing gas from the melting and gasifying furnace 10.
Since the coal briquette manufactured in accordance with the present exemplary embodiment is inputted into the melting and gasifying furnace 10, a coal-packed bed is formed in the melting and gasifying furnace 10. A dome portion 101 is formed at an upper side of the melting and gasifying furnace 10. That is, the dome portion 101 has a space wider than the remaining portion of the melting and gasifying furnace 10, and high-temperature reducing gas is present in this space. Therefore, the coal briquette inputted into the dome portion 101 is converted into char by the high-temperature reducing gas by a thermal decomposition reaction. The char generated by the thermal decomposition reaction of the coal briquette is moved to the lower side of the melting and gasifying furnace 10 and exothermically reacts with oxygen supplied through a tuyere 30. As a result, the coal briquette may be used as a heat source for maintaining the melting and gasifying furnace 10 at a high temperature. Meanwhile, the char provides breathability, and as a result, a large amount of gas generated at the lower side of the melting and gasifying furnace 10 and the reduced iron supplied from the packed-bed reducing furnace 20 may more easily and uniformly pass through the coal-packed bed in the melting and gasifying furnace 10.
In addition to the coal briquette, a lump carbon material or cokes may be inputted into the melting and gasifying furnace 10, as necessary. The tuyere 30 is installed in an outer wall of the melting and gasifying furnace 10, and oxygen is injected through the tuyere 30. The oxygen is injected to the coal-packed bed, and a combustion zone is formed. The coal briquette may be combusted in the combustion zone to generate reducing gas.
FIG. 5 schematically illustrates an apparatus 200 for manufacturing molten iron using the coal briquette manufactured in accordance with the present exemplary embodiment. A structure of the apparatus 200 for manufacturing molten iron, which is illustrated in FIG. 5, is merely for exemplifying the present invention, and the present invention is not limited thereto. Therefore, the apparatus 200 for manufacturing molten iron, which is illustrated in FIG. 5, may be modified to various forms. Because the structure of the apparatus 200 for manufacturing molten iron, which is illustrated in FIG. 5, is similar to the structure of the apparatus 100 for manufacturing molten iron, which is illustrated in FIG. 2, the same constituent elements are designated by the same reference numerals, and a detailed description thereof will be omitted.
As illustrated in FIG. 5, the apparatus 200 for manufacturing molten iron includes a melting and gasifying furnace 10, a fluidized-bed reducing furnace 22, a reduced iron compression device 40, and a compressed reduced iron storage tank 50. Here, the compressed reduced iron storage tank 50 may be omitted.
The manufactured coal briquette is inputted into the melting and gasifying furnace 10. Here, the coal briquette generates reducing gas in the melting and gasifying furnace 10, and the generated reducing gas is supplied to the fluidized-bed reducing furnace 22. Fine iron ore is supplied to the plurality of reducing furnaces 22 having fluidized beds, and flows by reducing gas supplied to the fluidized-bed reducing furnace 22 from the melting and gasifying furnace 10, such that the reduced iron is manufactured. The reduced iron is compressed by the reduced iron compression device 40, and then stored in the compressed reduced iron storage tank 50. The compressed reduced iron, together with the coal briquettes, is inputted into the melting and gasifying furnace 10 from the compressed reduced iron storage tank 50 and melted in the melting and gasifying furnace 10. The coal briquette is supplied to the melting and gasifying furnace 10 and converted into char having breathability, and as a result, a large amount of gas generated at a lower side of the melting and gasifying furnace 10 and the compressed reduced iron more easily and uniformly pass through a coal-packed bed in the melting and gasifying furnace 10, such that molten iron with high quality may be provided.
Hereinafter, the present invention will be described in more detail with reference to experimental examples. These experimental examples are merely for exemplifying the present invention, and the present invention is not limited thereto.

Experiment on Measurement of Compressive Strength of Coal briquette

Experimental Example

A binder and powdered coal for a coal briquette having average properties, which is used for molten reduced iron, were prepared and mixed. The powdered coal has a grain size of 4 mm or less. The powdered coal was additionally mixed with a carbon source additive. A Ferrobine ™ binder manufactured by Samsung Fine Chemical was used as the binder. The binder of 1 part by weight and the water of 7 parts by weight were added to and uniformly mixed with the powdered coal of 100 parts by weight. Further, the manufactured mixture was inputted and compressed between the pair of rolls, such that the coal briquette having a size of 52 ml was manufactured. Because the detailed remaining processes of manufacturing the coal briquette can be easily understood by those skilled in the art to which the present invention pertains, a detailed description thereof will be omitted.
The manufactured coal briquette was subjected to the heat treatment in a well-ventilated heat treatment oven, thereby evaporating moisture.

Experimental Example 1

A coal briquette with an initial moisture content of 8.8 wt% and compressive strength of 39.5 kgf was subjected to the heat treatment in a heat treatment oven at a temperature of 80°C.

Experimental Example 2

A coal briquette with an initial moisture content of 10.148 wt% and compressive strength of 50.85 kgf was subjected to the heat treatment in the heat treatment oven at a temperature of 100°C.

Experimental Example 3

A coal briquette with an initial moisture content of 9.63 wt% and compressive strength of 52.21 kgf was subjected to the heat treatment in the heat treatment oven at a temperature of 120°C.

Experimental Example 4

A coal briquette with an initial moisture content of 9.21 wt% and compressive strength of 51.36 kgf was subjected to the heat treatment in the heat treatment oven at a temperature of 150°C.

Comparative Example 1

A coal briquette manufactured by the method identical to the method of the exemplary embodiment was stored for 24 hours at room temperature.

Comparative Example 2

A coal briquette manufactured by the method identical to the method of the exemplary embodiment was subjected to the heat treatment at 60°C.

Comparative Example 3

A coal briquette manufactured by the method identical to the method of the exemplary embodiment was subjected to the heat treatment at 200°C.

Experiment Result

Moisture and compressive strength of the coal briquettes manufactured in accordance with Experimental Examples 1 to 4 and the Comparative Examples were measured. Compressive strength was measured by using 30 coal briquettes manufactured in the Experimental Examples and the Comparative Examples. A compressive load of the coal briquette was measured from a maximum load until the coal briquette is destroyed by applying pressure at a constant rate to an upper portion of the coal briquette placed on a measurement device. An average value in respect to 30 coal briquette samples was obtained.
According to the experimental results, in the case of Comparative Example 1 in which the coal briquette was not subjected to the heat treatment, the compressive strength of the coal briquette was 40 kgf at the initial time, and the compressive strength thereof was about 70 kgf after 24 hours had passed at room temperature, and as a result, there was no effect of sufficiently improving strength. In the case of Comparative Example 2 in which the coal briquette was subjected to the heat treatment at 60°C, sufficient compressive strength was not obtained. Even in the case of Comparative Example 3 in which the coal briquette was subjected to the heat treatment at a high temperature of 200°C, a crack occurred and an external shape of the coal briquette was not maintained.
In contrast, in the case of the experimental examples, as illustrated in FIGS. 6 to 9, the coal briquettes were subjected to the heat treatment for 1 to 24 hours at a temperature of 80 to 150°C, and as a result, the coal briquettes had an excellent compressive load. Therefore, it could be seen that it was preferred to adjust the heat treatment condition for the coal briquette to the aforementioned range. In contrast, it could be seen that the compressive loads of the coal briquettes manufactured in accordance with the Comparative Examples were much smaller than the compressive loads of the coal briquettes manufactured in accordance with the experimental examples. Therefore, it could be seen that the coal briquette, which was manufactured by being subjected to the heat treatment as in the exemplary embodiments, was much better in terms of a compressive load than the coal briquette which was manufactured without being subjected to the heat treatment.
While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

<Description of symbols>

10: Melting and gasifying furnace	20: Packed-bed reducing furnace
22: Fluidized-bed reducing furnace	30: Tuyere
40: Reduced iron compression device
50: Compressed reduced iron storage tank
60: Apparatus for manufacturing coal briquettes
61: Powdered coal hopper
62: Binder hopper	63: Water supply unit
64: Mixer	65: Briquette machine
66: Storage bin	67: Heat source
68: Hot blast supply pipe	69: Blower
70: Discharge line	71: Dust collection facility

Claims

A method of manufacturing coal briquettes which are inputted into and quickly heated in a dome portion of a melting and gasifying furnace in an apparatus for manufacturing molten iron that includes the melting and gasifying furnace into which reduced iron is inputted, and a reducing furnace which is connected to the melting and gasifying furnace and provides the reduced iron, the method comprising:
i) providing powdered coal;

ii) mixing the powdered coal with a powdered binder and providing a mixture;

iii) adding water to the mixture;

iv) providing coal briquettes by compressing and molding the mixture to which the water is added; and

v) performing a heat treatment of heating the coal briquettes to improve compressive strength of the coal briquettes,
wherein the powdered binder includes at least one compound selected from a group consisting of methyl cellulose (MC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), hydroxypropylmethyl cellulose (HPMC), and hydroxyethylmethyl cellulose (HEMC).
The method of claim 1, further comprising:
drying the mixture to which the water is added after the adding of the water to the mixture.
The method of claim 1, wherein:
in the providing of the coal briquettes, the amount of moisture contained in the coal briquettes is 8 wt% to 15 wt%.
The method of claim 1, wherein:
in the performing of the heat treatment, the coal briquette is heated at a temperature of 80 to 150°C for 1 to 24 hours.
The method of claim 4, wherein:
in the performing of the heat treatment, the coal briquette is heated so that a moisture content is 5 wt% or less.
The method of claim 5, wherein:
in performing of the heat treatment, the coal briquette is heated so that compressive strength is 100 kgf or more.
The method of claim 1, wherein:
the performing of the heat treatment includes heating the coal briquette by using at least one selected from a hot blast, steam, near infrared rays, and microwaves.
The method of claim 1, wherein:
the performing of the heat treatment includes:
conveying the coal briquette and inputting the coal briquette into a storage bin;

heating the coal briquette by supplying a high-temperature hot blast into the storage bin; and

discharging the heat-treated coal briquette from the storage bin.
The method of claim 8, wherein:
the performing of the heat treatment further includes discharging moisture vapor, which is evaporated from the coal briquette by the high-temperature hot blast, through an upper portion of the storage bin.
An apparatus of manufacturing coal briquettes which are inputted into and quickly heated in a dome portion of a melting and gasifying furnace in an apparatus for manufacturing molten iron that includes the melting and gasifying furnace into which reduced iron is inputted, and a reducing furnace which is connected to the melting and gasifying furnace and provides the reduced iron, the apparatus comprising:
a mixer which mixes raw materials including powdered coal and a binder;

a water supply unit which supplies water to the mixer;

a briquette machine which manufactures coal briquettes by molding a mixture mixed in the mixer; and

a heat treatment unit which improves compressive strength of the coal briquettes by heating the coal briquettes manufactured by the briquette machine.
The apparatus of claim 10, wherein:
the heat treatment unit includes a storage bin which is connected to the briquette machine and accommodates the coal briquettes, a hot blast supply pipe which is connected between a lower portion of the storage bin and a heat source and supplies a hot blast into the storage bin, a blower which is installed in a hot blast supply pipe, and a discharge line which is connected to an upper portion of the storage bin and discharges moisture vapor evaporated from the coal briquette.
A method of manufacturing molten iron, the method comprising:
providing the coal briquettes manufactured according to claim 1;

providing reduced iron made by reducing iron ore in a reducing furnace; and

providing molten iron by inputting the coal briquettes and the reduced iron into a melting and gasifying furnace.
The method of claim 12, wherein:
in the providing of the reduced iron, the reducing furnace is a fluidized-bed reducing furnace or a packed-bed reducing furnace.
A coal briquette which is inputted into and quickly heated in a dome portion of a melting and gasifying furnace in an apparatus for manufacturing molten iron that includes the melting and gasifying furnace into which reduced iron is inputted, and a reducing furnace which is connected to the melting and gasifying furnace and provides the reduced iron,
wherein the coal briquette contains moisture of 5 wt% or less.
The coal briquette of claim 14, wherein:
compressive strength of the coal briquette is 100 kgf or more.