EP2940107A1

EP2940107A1 - Method for manufacturing coal briquettes, and apparatus for manufacturing said coal briquettes

Info

Publication number: EP2940107A1
Application number: EP13869240.5A
Authority: EP
Inventors: Nam-Hwan Heo; Jae-Hoon Choi
Original assignee: Posco Co Ltd
Current assignee: Posco Holdings Inc
Priority date: 2012-12-27
Filing date: 2013-12-16
Publication date: 2015-11-04
Anticipated expiration: 2033-12-16
Also published as: WO2014104631A1; EP2940107A4; CN104884588B; KR101405479B1; EP2940107B1; CN104884588A

Abstract

Coal briquettes having excellent hot strength and a manufacturing method thereof are provided. The method for manufacturing coal briquettes includes: i) providing powdered coals; ii) providing graphite suppressing hot differentiation of the coal briquettes; iii) providing a hardening agent and a binder; iv) providing a mixture by mixing the powdered coals, the graphite, the hardening agent, and the binder; and v) providing the coal briquettes by molding the mixture. In the providing of the mixture, a ratio of the amount of graphite to the sum of the amount of powdered coals and the amount of graphite is greater than 0 and 0.3 or less.

Description

[Technical Field]

The present invention relates to a method and an apparatus for manufacturing coal briquettes. More particularly, the present invention relates to a method and an apparatus for manufacturing coal briquettes capable of implementing excellent hot strength by using graphite.

[Background Art]

In a smelting reduction iron-making method, a reducing furnace for reducing iron ore and a melter-gasifier for melting reduced iron ore are used. In the case of melting iron ores in the melter-gasifier, as a heat source to melt iron ores, coal briquettes are charged into the melter-gasifier. Here, reduced iron is melted in the melter-gasifier, transformed to molten iron and slag, and then discharged outside. The coal briquettes charged into the melter-gasifier form a coal-packed bed. After oxygen is injected through a tuyere installed at the melter-gasifier, the coal-packed bed is combusted to generate combustion gas. The combustion gas is transformed into a hot reducing gas while rising through the coal-packed bed. The hot reducing gas is discharged outside the melter-gasifier to be supplied to the reducing furnace as the reducing gas.
In the case of using the coal briquettes, additional control means is necessary to make a process for manufacturing molten iron efficient by increasing yield of molten iron and reducing fuel ratio. To this end, differentiation capacity in the melter-gasifier of the coal briquettes is reduced and thus the coal briquettes in the melter-gasifier need to be maintained with a large grain size. In this case, reaction efficiency and heat-transfer efficiency between materials may increase by ensuring permeability and flow so that gas and liquid smoothly pass through the melter-gasifier. Further, a generation amount of fine powder which is not efficiently used due to differentiation during manufacture of molten iron may be reduced. There is a limitation in reduction of generating amount of fine powers by mixing of various kinds of coals.

[DISCLOSURE]

[Technical Problem]

A method for manufacturing coal briquettes having excellent hot strength is provided. Further, an apparatus for manufacturing coal briquettes having excellent hot strength is provided.

[Technical Solution]

A method for manufacturing coal briquettes according to an exemplary embodiment of the present invention is applied to be charged into a dome part of a melter-gasifier to be rapidly heated in an apparatus for manufacturing molten iron including the melter-gasifier into which reduced iron is charged, and a reducing furnace connected to the melter-gasifier and providing the reduced iron. A method for manufacturing coal briquettes according to an exemplary embodiment of the present invention includes i) providing powdered coals; ii) providing graphite suppressing hot differentiation of the coal briquettes; iii) providing a hardening agent and a binder; iv) providing a mixture by mixing the powdered coals, the graphite, the hardening agent, and the binder; and v) providing the coal briquettes by molding the mixture. In the providing of the mixture, a ratio of the amount of graphite to the sum of the amount of powdered coals and the amount of graphite is greater than 0 and 0.3 or less.
The ratio of the amount of graphite to the sum of the amount of powdered coals and the amount of graphite may be 0.1 to 0.15. The graphite may be crystalline graphite or kish graphite. In the providing of the graphite, the graphite may be pressure-transported with a gas, stored in a graphite storage bin, and then provided. In the providing of the mixture, the graphite may be directly mixed with the hardening agent and the binder while not mixed with the powdered coals in advance. The gas may include nitrogen or a by-product gas.
In the providing of the mixture, the amount of binder may increase as the amount of graphite increases. In the providing of the coal briquettes, the coal briquettes may have an X-ray peak at 26 to 27 degrees when the coal briquettes are under X-ray diffraction analysis.
An apparatus for manufacturing coal briquettes according to an exemplary embodiment of the present invention includes i) a powdered coal storage bin storing powdered coal; ii) a graphite storage bin storing graphite; iii) a graphite transport pipe connected with the graphite storage bin and pressure-transporting the graphite with a gas to the graphite storage bin; iv) a binder storage bin storing a binder; v) a hardening agent storage bin storing a hardening agent; vi) a mixer providing a mixture by mixing the powdered coal supplied from the powdered coal storage bin, the graphite supplied supplied from the graphite storage bin, the binder supplied from the binder storage bin, and the hardening agent supplied from the hardening agent storage bin; and vii) a molding machine receiving the mixture from the mixer to mold the mixture. The graphite storage bin may be directly connected with the mixer.

[Advantageous Effects]

Since the coal briquettes are manufactured by using graphite, cold strength and hot strength of the coal briquettes may be largely improved. That is, it is possible to improve both size and strength of char obtained when the coal briquettes are drastically pyrolyzed in the melter-gasifier by using graphite. Further, it is possible to improve operation efficiency by using the coal briquettes with added graphite in a process for manufacturing molten irons.

[Description of the Drawings]

FIG. 1 is a schematic flowchart of a method for manufacturing coal briquettes according to an exemplary embodiment of the present invention.
FIG. 2 is a schematic diagram of an apparatus for manufacturing coal briquettes according to an exemplary embodiment of the present invention.
FIG. 3 is a schematic diagram of a apparatus for manufacturing molten irons connected to the apparatus for manufacturing coal briquettes of FIG. 2.
FIG. 4 is a schematic diagram of another apparatus for manufacturing molten irons connected to the apparatus for manufacturing coal briquettes of FIG. 2.
FIG. 5 shows a photograph of coal briquettes manufactured according to Experimental Example 5 and a photograph of char obtained by heating the coal briquettes.
FIG. 6 is an X-ray diffraction graph of coal briquettes manufactured according to Experimental Examples 10 to 13 and Comparative Example 1.

[Mode for Invention]

Terms such as first, second, and third are used to illustrate various portions, components, regions, layers, and/or sections, but not to limit them. These terms are used to discriminate the portions, components, regions, layers or sections from the other portions, components, regions, layers, or sections. Therefore, a first portion, component, region, layer, or section as described below may be a second portion, component, region, layer, or section within the scope of the present invention.
It is to be understood that the terminology used therein is only for the purpose of describing particular embodiments and is not intended to be limiting. It must be noted that, as used in the specification and the appended claims, the singular forms include plural references unless the context clearly dictates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated properties, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other properties, regions, integers, steps, operations, elements, and/or components thereof.
Unless it is mentioned otherwise, all terms including technical terms and scientific terms used herein have the same meaning as the meaning generally understood by the person with ordinary skill in the art to which the present invention belongs. The terminologies that are defined previously are further understood to have the meanings that coincide with related technical documents and the contents that are currently disclosed, but are not to be interpreted as the ideal or very official meaning unless it is defined otherwise.
The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are illustrated. 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.
Hereinafter, the term "graphite" means a material that belongs to a hexagonal system, has a plate-like crystal, and has a black color and a metallic luster. Further, it is understood that graphite includes both natural graphite and graphite manufactured artificially.
FIG. 1 schematically illustrates a flowchart of a method for manufacturing coal briquettes according to an exemplary embodiment of the present invention. The method for manufacturing coal briquettes in FIG. 1 is just to exemplify the present invention, and the present invention is not limited thereto. Accordingly, the method for manufacturing coal briquettes may be variously modified.
As illustrated in FIG. 1, the method for manufacturing coal briquettes includes providing powdered coal (S10), providing graphite (S20), providing a hardening agent and a binder (S30), providing a mixture by mixing the powdered coal, the graphite, the hardening agent, and the binder (S40), and providing coal briquettes by molding the mixture (S50). In addition, if necessary, the method for manufacturing coal briquettes may further include other processes.
First, in step S10, the powdered coal is supplied. The powdered coal may be supplied by separating raw coals according to a grain size. For example, raw coal with a grain size of 8mm or less may be supplied as the powdered coal. That is, the raw coals are separated according to a grain size to be sorted into powdered coal having a small grain size and lump coal having a large grain size. Coal briquettes having excellent cold strength may be manufacture by using powdered coal having a small grain size as the raw coal. The lump coal which is raw coal with a grain size of more than 8mm may be directly charged into the melter-gasifier or crushed to be used. Meanwhile, although not illustrated in FIG. 1, in order to improve the quality of molten iron, coal for quality control may be mixed with the powdered coal. Here, as the coal for quality control, coal with reflectance of a predetermined value or more may be used.
Next, in step S20, the graphite is provided. As the graphite, natural graphite, crystalline graphite, kish graphite, and the like may be used. Here, the kish graphite is discharged as a by-product of an iron making process. A grain diameter and strength of char generated by charging coal briquettes into the melter-gasifier are improved by adding the graphite to the coal briquettes. The coal included in the coal briquettes charged into the melter-gasifier is differentiated while a crack is generated by shrinkage and swelling thereof. Accordingly, in order to prevent generation and propagation of the crack, thermally stable graphite is added to the coal briquettes. Since the graphite is thermally stable, it stably exists during swelling and contraction of coals in the coal briquettes. Accordingly, since the graphite plays a role similar to an aggregate used in making concrete or mortar, the coal briquettes may be efficiently prevented from being differentiated at a high temperature by the graphite.
The grain diameter of char of the coal briquettes increases by adding graphite. The increasing of the grain diameter of char means that the hot strength of the coal briquettes is improved because the coal briquettes are not differentiated well in the melter-gasifier. The graphite is composed of carbon, and in the graphite, a hexagonal benzene-ring structure is very well developed as compared with other coal. That is, as a polycyclic carbon structure close to the graphite is developed, a capacity to transfer electrons or heat in the coal briquettes rapidly increases by the polycyclic carbon structure in a plane. Heat conductivity of the coal increases as the degree of coalification increases. For example, heat conductivity (λ: W·m^-1·K^-1) of bituminous coal which is used mainly for iron making is 1 or slightly higher than 1. In contrast, heat conductivity of graphite has several tens of times higher value than that of bituminous coal. That is, the graphite has a very high heat transfer rate. The coal briquettes are differentiated at a high temperature by a heat transfer characteristic. That is, when a reaction in which the coal briquettes are pyrolyzed to generate char is divided into many steps, in the coal briquettes at room temperature charged into the hot melter-gasifier, a heat transfer phenomenon from the surface to the inside thereof occurs. Accordingly, even in the case where a surface portion of coal briquettes reaches a high temperature of 1000°C, the inside of the coal briquettes exists at a temperature much lower than 1000°C. A difference in temperature between the inside and the outside of the coal briquettes causes a difference in contraction ratio, and cracks occur due to the difference in contraction ratio for each portion of the coal briquettes. Accordingly, finally, char having a small grain diameter is manufactured. That is, as a temperature difference increases, a differentiation phenomenon increases.
When a graphite with high heat conductivity and a very low thermal expansion rate is added to the coal briquettes, a temperature difference in the coal briquettes is reduced. That is, when the graphite is added, the temperature of the entire coal briquettes is further uniformalized. Accordingly, since the cracks may be suppressed according to a change in a contraction rate due to the temperature difference of the coal briquettes, the coal briquettes are not differentiated into small pieces but exist with a large grain diameter. Further, even if the crack occurs in the char, thermally stable graphite suppresses the crack from being propagated. Accordingly, even when the coal briquettes are drastically heated, the coal briquettes are differentiated into large grains or char maintaining the shape of the coal briquettes as it is can be manufactured. In the case of manufacturing the coal briquettes by adding graphite according to the aforementioned principle, the grain diameter of char obtained from the coal briquettes which are drastically pyrolyzed is great and the strength thereof is also high.
Meanwhile, the graphite is pressure-transported by a gas and may be stored in a graphite storage bin. Here, in order to prevent the ignition of the graphite, nitrogen or a by-product gas may be used as the gas. When the coal briquettes are manufactured, the graphite stored in the graphite storage bin may be sent out to be used.
Next, in step S30, the hardening agent and the binder are provided. As the hardening agent, quicklime, slaked lime, a metal oxide, fly ash, clay, a surface active agent, a cationic resin, an accelerator, fiber, phosphate, sludge, waste plastics, waste lubricating oil, and the like may be used. Further, as the binder, molasses, starch, sugar, a polymer resin, pitch, tar, bitumen, oil, cement, asphalt, water glass, or the like may be used. For example, when the coal briquettes are manufactured by using molasses as the binder and quicklime as the hardening agent, the cold strength of coal briquettes may be largely increased by a saccharate bond.
Next, in step S40, the mixture is provided by mixing the powdered coal, the graphite, the hardening agent, and the binder. Here, the powdered coal, the graphite, the hardening agent, and the binder may be mixed in a random order or specific materials among those may be first mixed. For example, after the powdered coals and the graphite are first mixed, the binder may be mixed and then the hardening agent may be mixed. Alternatively, the graphite may be directly mixed with the hardening agent and the binder while being not mixed with the powdered coals in advance. That is, since dried coke dust in the graphite does not need to be mixed with the powdered coal in advance by controlling a water amount included therein, the graphite may be directly mixed with the hardening agent and the binder.
When a large amount of graphite is added to the coal briquettes, a usage amount of molasses or bitumen as the binder needs to increase in order to bind the graphite and the powdered coal. That is, as the amount of graphite increases, the amount of binder needs to increase. In the case of adding the graphite while the amount of binder is small, it is difficult to mold the coal briquettes and the room-temperature strength of the coal briquettes is lowered. Accordingly, when the coal briquettes are transported or stored, the coal briquettes are differentiated. That is, when the amount of the binder is too little or too great, the cold strength of the coal briquettes deteriorates. Accordingly, the amount of the binder included in the mixture is controlled in the aforementioned range. For example, the amount of the binder included in the mixture may be controlled to 8.5wt% to 9wt%.
Meanwhile, although not illustrated in FIG. 1, the raw coal is manufactured by mixing the powdered coal and the graphite in advance and then may be mixed with the hardening agent and the binder. The manufactured raw coals may be separated into coals with a predetermined grain size or more. In addition, the grain size of the raw coal may be controlled to be suitable for manufacturing the coal briquettes by crushing the sorted raw coals. That is, the powdered coals and the graphite are crushed to be provided as the raw coal.
A ratio of the amount of graphite to the sum of the amount of powdered coal and the amount of graphite may be greater than 0 and 0.3 or less. When the amount of graphite is too great, the cold strength of the coal briquettes is lowered. Accordingly, the amount of graphite is controlled in the aforementioned range. More preferably, the ratio of the amount of graphite to the sum of the amount of powdered coals and the amount of graphite may be 0.1 to 0.15.
Finally, in step S50, the coal briquettes are provided by molding the mixture. For example, the coal briquettes may be manufactured by continuously compacting the mixture by using a molding machine including a pair of rollers.
The coal briquettes include carbons. Accordingly, when an X-ray diffraction analysis of the coal briquettes is performed, the coal briquettes have X-ray peak 2θ at 26° to 27°. Preferably, the coal briquettes have X-ray peak 2θ at 26.6°.
Generally, a method of improving the hot strength of the coal briquettes by using the binder such as bitumen has been attempted. However, since the coal briquettes are differentiated at a high temperature, efficient means and methods capable of increasing the grain diameter and the strength of the char are required. Further, even though coal is changed in its type, it is difficult to improve the hot strength of the coal briquettes.
FIG. 2 schematically illustrates a apparatus for manufacturing coal briquettes 100 according to another exemplary embodiment of the present invention. The apparatus for manufacturing coal briquettes 100 in FIG. 2 is just to exemplify the present invention, and the present invention is not limited thereto. Accordingly, a structure of the apparatus for manufacturing coal briquettes 100 may be variously modified.
As illustrated in FIG. 2, the apparatus for manufacturing coal briquettes 100 includes a powdered coal storage bin 10, a coal for quality control storage bin 20, a graphite storage bin 30, a binder storage bin 40, a hardening agent storage bin 50, a mixer 60, and a molding machine 70. In addition, the apparatus for manufacturing coal briquettes 100 further includes a crusher 80, a mixed coal storage bin 92, a collected coal storage bin 94, a graphite transport pipe 303, a graphite carrying device 305, and separators 801, 803, and 805. If necessary, the apparatus for manufacturing coal briquettes 100 may further include other devices. Since a detailed structure and an operation method of respective devices included in the apparatus for manufacturing coal briquettes 100 of FIG. 2 can be easily understood by those skilled in the art, the detailed description is omitted.
The powdered coal is stored in the powdered coal storage bin 10. In addition, the coal for quality control may be used in order to improve the quality of the coal briquettes and are stored in the coal for quality control storage bin 20. The coal passes through the separator 801 to be divided into lump coal and powdered coal, and then the powdered coal may be stored in the powdered coal storage bin 10. For example, coal with a grain size of 8 mm or less may be used as powdered coal. Meanwhile, the lump coal separated by the separator 801 may be directly charged into a melter-gasifier 210 (illustrated in FIG. 3).
As illustrated in FIG. 2, the graphite storage bin 30 stores the graphite supplied from the graphite carrying device 305 through the graphite transport pipe 303. For example, a tank lorry and the like may be used as the graphite carrying device 305. The graphite is pressure-transported by a gas and stored to be supplied in the graphite storage bin 30 from the graphite carrying device 305. In this case, nitrogen or a by-product gas is used as the gas to prevent ignition of the graphite. The by-product gas is a gas generated during a process in a steel mill. The graphite is directly mixed with the hardening agent and the binder without being mixed with the powdered coal in advance.
Meanwhile, in order to prevent abrasion by the graphite during transport, the graphite transport pipe 303 may be used by manufacturing the pipe itself with a specific material or coating an inner side of the pipe with basalt or the like. Since the graphite is stored and transported in a large sack, it is preferred that the graphite is loaded for being used in the graphite carrying device 305, but the graphite may be stored in the graphite storage bin 30 by directly removing the sack.
The mixed coal is separated in the separator 803 and the mixed coal with a predetermined grain size or more is crushed by the crusher 80. The crushed mixed coal and the mixed coal with less than a predetermined grain size are stored in the mixed coal storage bin 92. The mixed coal stored in the mixed coal storage bin 92 is provided to the mixer 60.
As illustrated in FIG. 2, the binder is stored in the binder storage bin 40. The binder binds the powdered coal and the graphite to each other to be made into a state suitable for manufacturing the coal briquettes. The binder storage bin 40 is connected with the mixer 60 to provide the binder thereto.
Meanwhile, the hardening agent is stored in the hardening agent storage bin 50. The hardening agent is coupled with the powdered coal, the graphite, and the binder to harden the coal briquettes and thus the strength of coal briquettes may be optimized. The hardening agent storage bin 50 is connected with the mixer 60 to provide the hardening agent to the mixer 60.
The mixer 60 mixes the powdered coal, the graphite, the binder, the hardening agent, and the like with each other to provide the mixture for manufacturing the coal briquettes. Meanwhile, the graphite storage bin 30 is directly connected with the mixer 60 to provide the graphite to the mixer 60. Since the water and the grain size of the graphite are controlled, the graphite may be immediately used in the mixer 60.
As illustrated in FIG. 2, the molding machine 70 includes a pair of rolls that rotate in opposite direction to each other. The mixture is compacted by the pair of rolls by providing the mixture therebetween to manufacture the coal briquettes. Meanwhile, the powdered coal is stored in the collected coal storage bin 94 by separating the manufactured coal briquettes through the separator 805 again. The powdered coal stored in the collected coal storage bin 94 is re-supplied to the mixer 60 again to be used as a raw material of the coal briquettes. As a result, use efficiency of the powdered coal may be improved.
FIG. 3 schematically illustrates an apparatus for manufacturing molten iron 200 which is connected to the apparatus for manufacturing coal briquettes 100 of FIG. 2 and uses the coal briquettes obtained by the apparatus for manufacturing coal briquettes 100. A structure of the apparatus for manufacturing molten iron 200 in FIG. 3 is just to exemplify the present invention, and the present invention is not limited thereto. Accordingly, the apparatus for manufacturing molten iron 200 in FIG. 3 may be modified in various shapes.
The apparatus for manufacturing molten iron 200 in FIG. 3 includes a melter-gasifier 210 and a reducing furnace 220. In addition, if necessary, the apparatus for manufacturing molten iron 200 may include other devices. Iron ore is charged into and reduced in the reducing furnace 220. The iron ore charged into the reducing furnace 220 is dried in advance and then prepared as reduced iron while passing through the reducing furnace 220. The reducing furnace 220 with a packed bed type, receives the reducing gas from the melter-gasifier 210 to form a coal-packed bed therein.
Since the coal briquettes manufactured by the apparatus for manufacturing coal briquettes 100 of FIG. 2 are charged into the melter-gasifier 210 of FIG. 3, a coal-packed bed is formed in the melter-gasifier 210. A dome part 2101 is formed in an upper portion of the melter-gasifier 210. That is, in the dome part 2101 having a wider space than another part of the melter-gasifier 210, hot reducing gas exists. The coal briquettes are charged into the dome part 2101 of the melter-gasifier 210 and then rapidly heated to fall down to the lower portion of the melter-gasifier 210. Char generated by a pyrolysis reaction of the coal briquettes moves to the lower portion of the melter-gasifier 210 to exothermic-react with oxygen supplied through a tuyere 230. As a result, the coal briquettes may be used as a heat source which keeps the melter-gasifier 210 at a high temperature. Meanwhile, since the char provides permeability, a large amount of gas generated from the lower portion of the melter-gasifier 210 and reduced iron supplied from the reducing furnace 220 may more easily and uniformly pass through the coal-packed bed in the melter-gasifier 210.
In addition to the aforementioned coal briquettes, if necessary, lump carbon ash or coke may be charged into the melter-gasifier 210. The tuyere 230 is installed at an outer wall of the melter-gasifier 210 to inject oxygen. Oxygen is injected into the coal-packed bed to form a raceway. The coal briquettes are combusted in the raceway to generate a reducing gas.
FIG. 4 schematically illustrates another apparatus for manufacturing molten irons 300 which is connected to the apparatus for manufacturing coal briquettes 100 of FIG. 2 and uses the coal briquettes manufactured by the apparatus for manufacturing coal briquettes 100. A structure of the apparatus for manufacturing molten iron 300 in FIG. 4 is just to exemplify the present invention, and the present invention is not limited thereto. Accordingly, the apparatus for manufacturing molten iron 300 in FIG. 4 may be modified in various shapes. Since the structure of the apparatus for manufacturing molten iron 300 in FIG. 4 is similar to the structure of the apparatus for manufacturing molten iron 200 in FIG. 3, like reference numerals are used in like parts, and the detailed description thereof is omitted.
As illustrated in FIG. 4, the apparatus for manufacturing molten iron 300 includes a melter-gasifier 210, a reducing furnace 310, a device for compacting reduced iron 320, and a compacted reduced iron storage bin 330. The compacted reduced iron storage bin 330 may be omitted.
The manufactured coal briquettes are charged into the melting gasifier 210. Here, the coal briquettes generate reducing gas in the melter-gasifier 210 and the generated reducing gas is supplied to the fluidized-bed reducing furnace 310. Fine iron ore is supplied to the fluidized-bed reducing furnace 310 and manufactured to reduced iron while fludizing by the reducing gas supplied to the fluidized-bed reducing furnace 310 from the melter-gasifier 210. The reduced iron is compacted by the device for compacting reduced iron 320 and stored in the compacted reduced iron storage bin 330. The compacted reduced iron is supplied from the compacted reduced iron storage bin 330 to the melter-gasifier 210 to be melted therein. Since the coal briquettes are supplied to the melter-gasifier 210 to be transformed to char having permeability, a large amount of gas generated from the lower portion of the melter-gasifier 210 and the compacted reduced iron more easily and uniformly pass through the coal-packed bed in the melter-gasifier 210 to manufacture molten iron with good quality. Meanwhile, oxygen is supplied through the tuyere 230 to combust the coal briquettes.
Hereinafter, the present invention will be described in more detail through experimental examples. The experimental examples are just to exemplify the present invention, and the present invention is not limited thereto.

Experimental Example

Experiment for measuring size of char of coal briquettes

A mixture was manufactured by mixing coal and graphite. Molasses was mixed in the mixture at 8.5 parts by weight based on 100 parts by weight of the mixture to manufacture coal briquettes. In addition, in order to evaluate the coal briquettes charged through a hot dome part of a melter-gasifier, 1000g of coal briquettes were charged into a reaction tube maintained at 1000 °C and heat-treated for 60 minutes while rotating at 10 rotations per minute. In addition, the coal briquettes obtained by heat treatment were separated. A hot strength index of coal briquettes was evaluated by representing a percentage of a weight of char passed through a sieve opening of 10mm or more with respect to a weight of the entire char. The experimental result is represented in the following Table 1.

Experimental Example 1

Coal briquettes were manufactured by using coal A which was weak coking coal without coking force. An amount of volatile matter of coal A was 35%. When the coal briquettes were manufactured by adding graphite of 10wt%, a grain diameter of char of the coal briquettes increased. That is, a ratio of the char of the coal briquettes with a grain diameter of char of the coal briquettes of 10 mm or more rapidly increased to 77.7%.

Experimental Example 2

Coal briquettes were manufactured by using coal A which was weak coking coal without coking force. An amount of volatile matter of coal A was 35%. When the coal briquettes were manufactured by adding graphite of 15wt%, a grain diameter of char of the coal briquettes increased. That is, a ratio of the char of the coal briquettes with a grain diameter of char of the coal briquettes of 10 mm or more rapidly increased to 91.2%.

Experimental Example 3

Coal briquettes were manufactured by using coal A which was weak coking coal without coking force. An amount of volatile matter of coal A was 35%. When the coal briquettes were manufactured by adding graphite of 30wt%, a grain diameter of char of the coal briquettes slightly increased. That is, a ratio of the char of the coal briquettes with a grain diameter of char of the coal briquettes of 10mm or more rapidly increased to 89%.

Experimental Example 4

Coal briquettes were manufactured by using coal B which was coking coal having a large coking force. An amount of volatile matter of coal B was 25%. When the coal briquettes were manufactured by adding graphite at 10wt%, a grain diameter of char of the coal briquettes increased. That is, a ratio of the char of the coal briquettes with a grain diameter of char of the coal briquettes of 10mm or more rapidly increased to 72.9%.

Experimental Example 5

Coal briquettes were manufactured by using coal B which was coking coal having a large coking force. An amount of volatile matter of coal B was 35%. When the coal briquettes were manufactured by adding graphite at 15wt%, a grain diameter of char of the coal briquettes increased. That is, a ratio of the char of the coal briquettes with a grain diameter of char of the coal briquettes of 10 mm or more rapidly increased to 93.2%.
FIG. 5(a) is a photograph of coal briquettes manufactured according to Experimental Example 5, and FIG. 5(b) is a photograph of char obtained by heat-treating the coal briquettes of FIG. 5 (a).
As illustrated in FIG. 5, the char in which the shape of the coal briquettes was almost left as it is was manufactured. That is, a ratio of char of the coal briquettes with a grain diameter of 10 mm was 93.2%, and the grain diameter of the char was maintained almost the same as the grain diameter of the coal briquettes before heat treatment.

Comparative Example 1

For comparison with the experimental examples, coal briquettes were manufactured by only coal A without adding graphite. The experimental processes were the same as those of the aforementioned Experimental Example 1. In this case, in the size of the char of the obtained coal briquettes, since a ratio of large grains of 10 mm or more was very low at 12.3%, it could be seen that the coal briquettes were rapidly pyrolyzed to be differentiated into small pieces.

Comparative Example 2

Coal briquettes were manufactured by using coal A which was weak coking coal without coking force. An amount of volatile matter of coal A was 35%. When the coal briquettes were manufactured by adding graphite at 40wt%, a grain diameter of char of the coal briquettes was slightly decreased. That is, a ratio of char of the coal briquettes with a grain diameter of the char of the coal briquettes of 10 mm or more as 83.8 % was reduced as compared with a ratio of char of coal briquettes of Experimental Examples 1 to 5. Accordingly, it could be seen that an adding effect of graphite was deteriorated. The aforementioned Experimental Examples 1 to 5 are represented in the following Table 1 by comparing them with Comparative Examples 1 and 2.

Experiment for measuring strength of char of coal briquettes

A mixture was manufactured by mixing coals and graphite. Molasses was mixed in the mixture at 8.5 parts by weight based on 100 weights of the mixture to manufacture coal briquettes. In addition, when coal briquettes charged through a hot dome part of a melter-gasifier were transformed to char, an experiment was performed in order to verify whether the strength of char was deteriorated according to an increase in size of the char. The strength of the char was evaluated under the same conditions as a hot strength (CSR) measuring method of coke for metallurgy used in a blast furnace. The char was put in an I-type drum for measuring the hot strength (CSR) of coke and rotated 600 times at 20rpm, and then the content of the remaining char with a size of 10mm or more was measured. Here, a length of the I-type drum was 600mm. The experimental result is represented in the following Table 1. In the case of Comparative Example 1 without adding graphite, the char strength was 75%, but in Experimental Examples 1 to 5 with added graphite, the char strengths were increased to 80% or more.

(Table 1)

Experimental Example	Coal kind	Mixing ratio of coal briquettes		Hot strength index (+10 mm, %)	Char strength (I⁶⁰⁰,+10 mm %)
Experimental Example	Coal kind	Coals	Graphite	Hot strength index (+10 mm, %)	Char strength (I⁶⁰⁰,+10 mm %)
Experimental Example 1	Coal A	90	10	77.7	84
Experimental Example 2	Coal A	8592	15	91.2	85
Experimental Example 3	Coal A	70	30	89.0	80
Experimental Example 4	Coal B	90	10	72.9	85
Experimental Example 5	Coal B	85	15	93.2	86
Comparative Example 1	Coal A	100	0	12.3	75
Comparative Example 2	Coal A	60	40	83.8	68

Experiment for measuring hot strength of coal briquettes according to graphite type

Coal briquettes were manufactured by using kish graphite and crystalline graphite. In addition, the hot strength of the coal briquettes was measured.

Experimental Example 6

Coal briquettes were manufactured by using kish graphite that is a by-product of an iron making process. Since the kish graphite was generated by precipitating a carbon component dissolved in molten iron, purity and crystallinity thereof were excellent. The coal briquettes manufactured by adding kish graphite at 10wt% to coal A was transformed to char. In this case, a hot strength index of the char of the coal briquettes was 82.7%. Further, an I-drum strength index representing the char strength was relatively high at 86%.

Experimental Example 7

Coal briquettes were manufactured by using crystalline graphite. The coal briquettes manufactured by adding crystalline graphite at 10wt% to coal A was transformed to char. In this case, the hot strength index of the char of the coal briquettes at 77.7% was slightly lower than the hot strength index of the char of the coal briquettes of Experimental Example 6. Further, the I-drum strength index representing the char strength as 84% was similar to the char strength of the coal briquettes of Experimental Example 6.

(Table 2)

Experimental Example	Coal kind	Mixing ratio of coal briquettes (%)			Hot strength index (+10 mm, %)	Char strength (I⁶⁰⁰, +10 mm %)
Experimental Example	Coal kind	Coals	Crystalline graphite	Kish graphite	Hot strength index (+10 mm, %)	Char strength (I⁶⁰⁰, +10 mm %)
Experimental Example 6	Coal A	90	10	0	77.7	86
Experimental Example 7	Coal A	90	0	10	82.7	84

Operation experiment of melter-gasifier of coal briquettes

As described above, results verified in an experimental room were directly applied to a melter-gasifier for manufacturing molten iron. Accordingly, an effect according to application of the melter-gasifier was verified. The results are represented in the following Table 3.

Experimental Example 8

Coal briquettes including graphite at 2 wt% and using molasses as a binder was manufactured. An operation was observed by charging the coal briquettes in the melter-gasifier. The operation was continuously performed and a coal kind and a usage condition of molasses were equally maintained for a continuous operation period. In addition, the hot strength of the coal briquettes, and a yield of molten iron and fuel cost of the melter-gasifier, were summarized by average values for the operation period. The hot strength was represented based on +16 mm, the hot strength was largely increased by adding the graphite, the yield of molten iron largely increased by improving permeability and flowage, and the fuel cost was reduced.

Experimental Example 9

Coal briquettes including graphite at 3 wt% and using molasses as a binder was manufactured. The rest of the experimental processes were the same as those of the aforementioned Experimental Example 8. As an experimental result, when the graphite was added, the hot strength largely increased, the yield of molten irons was largely increased, and the fuel cost was reduced.

Comparative Example 3

Coal briquettes using molasses as a binder without adding graphite were manufactured. The rest of the experimental processes were the same as those of the aforementioned Experimental Example 8. As an experimental result, as compared with Experimental Examples 2 and 3, it could be seen that the hot strength index of the coal briquettes and the yield of molten iron were low.

(Table 3)

	Graphite mixing ratio (%)	Operation period (day)	Hot strength index of coal briquettes (+16 mm, %)	Yield of molten iron (t-molten iron/day)	Fuel cost (kg/t-molten iron)
Experimental Example 8	2	21	80.9	2526	737
Experimental Example 9	3	7	85.9	2429	714
Comparative Example 3	0	6	67.2	2345	777

X-ray diffraction measurement experiment of graphite-added coal briquettes

Hot quality of coal briquettes manufactured by adding crystalline graphite and kish graphite was excellent. Coal briquettes manufactured by adding graphite were different from coal briquettes without adding graphite in terms of carbon crystallinity. This could be seen through an X-ray diffractometry result. That is, 2θ value of carbon included in coal was exhibited at approximately 21 degrees, and as the degree of coalification is increased, the 2θ value is finely increased.
However, in the coal briquettes adding graphite, a peak was exhibited around 26.6 degrees. A characteristic of the coal briquettes manufactured according to experimental examples of the present invention by using a crystal characteristic of the graphite could be seen. In this case, since SiO₂ among minerals configuring coal had a peak in a range close to the graphite, in order to observe the peak of only the graphite, impurities included in the coal briquettes were removed by pre-processing. A sample of the coal briquettes which are ground to 63µm or less were eluted at 50 °C for 3 hours and then washed using distilled water. Next, in order to remove SiO₂, the coal briquettes was secondarily acid-treated for 3 hours again in a hydrofluoric acid (HF) solution at 48% heated at 50°C, washed using distilled water, and then dried to manufacture a sample for analysis. In addition, an X-ray diffraction analysis was performed by using a copper (CU) target at a speed of 1 degree/min with an acceleration voltage of 20kV at 100mA.

Experimental Example 10

Coal briquettes including graphite of 5wt% were manufactured. The rest of the experimental processes were the same as those of the aforementioned Experimental Example 1. A sample for analysis was extracted according to the aforementioned method.

Experimental Example 11

Coal briquettes including graphite at 10wt% were manufactured. The rest of the experimental processes were the same as those of the aforementioned Experimental Example 1. A sample for analysis was extracted according to the aforementioned method.

Experimental Example 12

Coal briquettes including graphite are 15wt% were manufactured. The rest of the experimental processes were the same as those of the aforementioned Experimental Example 1. A sample for analysis was extracted according to the aforementioned method.

Experimental Example 13

Coal briquettes including graphite of 20wt% were manufactured. The rest of the experimental processes were the same as those of the aforementioned Experimental Example 1. A sample for analysis was extracted according to the aforementioned method.
FIG. 6 illustrates an X-ray diffraction graph of coal briquettes manufactured according to Experimental Examples 10 to 13 and Comparative Example 1.
As illustrated in FIG. 6, as the X-ray diffraction analysis results of the coal briquettes, in the case of Comparative Example 1, at a 2θ value, there was no peak at 26.6 degrees. On the contrary, in Experimental Examples 10 to 13, the peak was exhibited at 26.6 degrees. Further, as the mixing ratio of graphite increased, the strength of the peak clearly increased.
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.

Claims

A method for manufacturing coal briquettes which are charged into a dome part of a melter-gasifier to be rapidly heated in a apparatus for manufacturing molten iron including the melter-gasifier into which reduced iron is charged, and a reducing furnace connected to the melter-gasifier and providing the reduced iron, the method comprising:
providing powdered coals;

providing graphite suppressing hot differentiation of the coal briquettes;

providing a hardening agent and a binder;

providing a mixture by mixing the powdered coals, the graphite, the hardening agent, and the binder; and

providing the coal briquettes by molding the mixture,

wherein in the providing of the mixture, a ratio of the amount of graphite to the sum of the amount of powdered coals and the amount of graphite is greater than 0 and 0.3 or less.
The method of claim 1, wherein the ratio of the amount of graphite to the sum of the amount of powdered coals and the amount of graphite is 0.1 to 0.15.
The method of claim 1, wherein the graphite is crystalline graphite or kish graphite.
The method of claim 1, wherein in the providing of the graphite, the graphite is pressure-transported with a gas, stored in a graphite storage bin, and then provided.
The method of claim 4, wherein in the providing of the mixture, the graphite is directly mixed with the hardening agent and the binder while not mixed with the powdered coals in advance.
The method of claim 4, wherein the gas includes nitrogen or a by-product gas.
The method of claim 1, wherein in the providing of the mixture, the amount of binder increases as the amount of graphite increases.
The method of claim 1, wherein in the providing of the coal briquettes, the coal briquettes have an X-ray peak at 26 to 27 degrees when the coal briquettes are under X-ray diffraction analysis.
An apparatus for manufacturing coal briquettes, comprising:
a powdered coal storage bin storing powdered coal;

a graphite storage bin storing graphite;

a graphite transport pipe connected with the graphite storage bin and pressure-transporting the graphite with a gas to the graphite storage bin;

a binder storage bin storing a binder;

a hardening agent storage bin storing a hardening agent;

a mixer providing a mixture by mixing the powdered coal supplied from the powdered coal storage bin, the graphite supplied supplied from the graphite storage bin, the binder supplied from the binder storage bin, and the hardening agent supplied from the hardening agent storage bin; and

a molding machine receiving the mixture from the mixer to mold the mixture.
The apparatus of claim 9, wherein the graphite storage bin is directly connected with the mixer.