Reduced iron producing facility and method

Abstract

The present invention relates to a reduced iron producing facility and method and, more specifically, to a reduced iron producing facility and method for producing reduced iron by reducing a raw material. A reduced iron producing facility according to an embodiment of the present invention comprises: a reduction unit capable of producing reduced iron; a thermal decomposition unit capable of preparing hydrogen gas and solid carbon by thermally decomposing hydrocarbon-containing gas; and a connection unit connecting the reduction unit and the thermal decomposition unit so that at least a portion of exhaust gas discharged from the reduction unit can be supplied to the reduction unit together with the hydrogen gas prepared by the thermal decomposition unit.

Description

Title of the Invention: REDUCED IRON PRODUCING FACILITY AND METHOD TECHNICAL FIELD

[0001] The present invention relates to a reduced iron producing facility and method, and more particularly, to a reduced iron producing facility and method for producing reduced iron by reducing a raw material. BACKGROUND ART

[0002] Generally, melted iron, i.e., molten iron is manufactured through a furnace process. The furnace process is carried out by processing iron ore and coal into a form that is suitable for use, inserting the processed iron ore and coal in a furnace, and blowing hot air into the furnace. Here, the hot air burns the coal, and a carbon monoxide gas generated at this time causes a reduction reaction that removes oxygen from the iron ore. In addition, heat over approximately 1,500°C generated inside the furnace causes a melting reaction that melts the iron ore or iron reduced by the carbon monoxide gas to produce molten iron. In such a furnace process, the reduction reaction and the melting reaction are carried out simultaneously within the furnace by the coal and the carbon monoxide gas generated from the coal.    However, the furnace process has a problem of generating a large amount of carbon dioxide, which causes environmental problems such as global warming, due to the reduction reaction between the carbon monoxide gas and the iron ore.

[0003] As a result, a hydrogen reduced iron-making process technology, which produces molten iron using a hydrogen gas instead of fossil fuels such as coal, is being researched and developed. The fossil fuels such as coal generate carbon dioxide when reacting with the iron ore, but since the hydrogen gas reacts with the iron ore to generate water or steam, the hydrogen reduced iron-making process may innovatively reduce carbon emission in manufacturing of the molten iron.

[0004] Unlike the reduction by the fossil fuels, the hydrogen reduction is a strong endothermic reaction, and thus, in the hydrogen reduced iron-making process, it is required that the hydrogen gas is introduced at a high temperature. In addition, in order to improve a reduction rate of the iron ore during the hydrogen reduction, a large amount of hydrogen gas that exceeds the amount required for the reduction has to be supplied. Thus, there is an urgent need for the development of technology in which a large amount of hydrogen gas is stably introduced in the high-temperature state.

[0005] (PRIOR ART DOCUMENTS)

[0006] Korean Patent Registration No. 10-1699236 DISCLOSURE OF THE INVENTION TECHNICAL PROBLEM

[0007] The present invention provides a reduced iron producing facility and method capable of introducing a reducing gas containing a hydrogen gas in a high-temperature state. TECHNICAL SOLUTION

[0008] A reduced iron producing facility according to an embodiment of the present invention includes: a reduction unit configured to produce reduced iron; a thermal decomposition unit configured to thermally decompose a hydrocarbon-containing gas so as to produce a hydrogen gas and solid carbon; and a connection unit configured to connect the reduction unit to the thermal decomposition unit so that at least a portion of an exhaust gas discharged from the reduction unit is supplied to the reduction unit together with the hydrogen gas produced in the thermal decomposition unit.

[0009] The connection unit may include: a hydrogen gas supply line configured to connect the reduction unit to the thermal decomposition unit so that the hydrogen gas provided in the thermal decomposition unit is supplied to the reduction unit; and an exhaust gas supply line configured to connect the reduction unit to the hydrogen gas supply line so that at least a portion of the exhaust gas discharged from the reduction unit is supplied to the hydrogen gas supply line.

[0010] The reduction unit may include a plurality of reducing furnaces disposed to sequentially reduce the moving raw material, the hydrogen gas supply line may be configured to connect the reducing furnace, which is disposed at the rearmost side among the plurality of reducing furnaces with respect to the moving direction of the raw material, to the thermal decomposition unit, and the exhaust gas supply line may be configured to connect the reducing furnace, which is disposed at the frontmost side among the plurality of reducing furnaces with respect to the moving direction of the raw material, to the hydrogen gas supply line.

[0011] The reduced iron producing facility may further include an exhaust gas branch line configured to connect the exhaust gas supply line to the thermal decomposition unit so that a portion of the exhaust gas moving along the exhaust gas supply line is supplied to the thermal decomposition unit.

[0012] The thermal decomposition unit may include:  a reactor configured to provide a reaction space in which the hydrocarbon containing gas is thermally decomposed; and a first heat exchanger connected to the exhaust gas branch line and installed in the reactor to transfer heat of the exhaust gas supplied from the exhaust gas branch line to the reaction space.

[0013] The thermal decomposition unit may include:  a reactor configured to provide a reaction space in which the hydrocarboncontaining gas is thermally decomposed; a hydrocarbon-containing gas supply unit connected to the reactor to supply the hydrocarbon-containing gas into the reaction space; and a second heat exchanger connected to the exhaust gas branch line and installed in the hydrocarbon-containing gas supply unit to transfer heat of the exhaust gas supplied from the exhaust gas branch line to the hydrocarbon-containing gas.

[0014] The thermal decomposition unit may include: a reactor configured to provide a reaction space in which the hydrocarboncontaining gas is thermally decomposed; a combustion gas supply unit connected to the reactor to supply an oxygen-containing gas and a combustion gas containing a fuel gas to the reaction space; and a third heat exchanger connected to the exhaust gas branch line and installed in the combustion gas supply unit to transfer heat of the exhaust gas supplied from the exhaust gas branch line to at least one of the oxygen-containing gas or the fuel gas.

[0015] The combustion gas supply unit may be connected to the exhaust gas branch line to supply the fuel gas containing the exhaust gas supplied from the exhaust gas branch line.

[0016] The thermal decomposition unit may include: a reactor configured to provide a reaction space in which the hydrocarboncontaining gas is thermally decomposed; a catalyst gas supply unit connected to the reactor to supply a catalyst for promoting the thermal decomposition to the reaction space; and a fourth heat exchanger connected to the exhaust gas branch line and installed in the catalyst supply unit to transfer heat of the exhaust gas supplied from the exhaust gas branch line to the catalyst.

[0017] The reduced iron producing facility may further include: a separation unit installed in the exhaust gas supply line to remove a first by-product from the exhaust gas moving along the exhaust gas supply line; and an extraction unit installed in the exhaust gas supply line to remove a second by-product, which is different from the first by-product, from the exhaust gas moving along the exhaust gas supply line, wherein the separation unit may be installed in the exhaust gas supply line extending between a position, to which the exhaust gas branch line is connected, and the reduction unit, and the extraction unit may be installed in the exhaust gas supply line extending between a position, to which the exhaust gas branch line is connected, and a position, to which the hydrogen gas supply line is connected.

[0018]

[0019] In addition, a reduced iron producing method according to an embodiment of the present invention includes: a process of thermally decomposing a hydrocarbon-containing gas to produce a hydrogen gas and solid carbon; a process of allowing the produced hydrogen gas to react with a raw material; a process of collecting an exhaust gas discharged in the process of reacting with the raw material; and a process of supplying at least a portion of the collected exhaust gas together with the produced hydrogen gas to the raw material.

[0020] The process of supplying the exhaust gas together with the hydrogen gas to the raw material may include: a process of mixing the collected exhaust gas with the produced hydrogen gas; and a process of supplying the mixed gas to the raw material.

[0021] The mixing process may include a process of adjusting a flow rate of at least one of the collected exhaust gas or the produced hydrogen gas so that the mixed gas has a set temperature, and the process of supplying the mixed gas to the raw material may include a process of directly supplying the mixed gas to the raw material.

[0022] The mixing process may include a process of adjusting a temperature of the produced hydrogen gas so that the mixed gas has a set temperature, wherein the process of adjusting the temperature of the hydrogen gas may include a process of heating a combustion gas supplied for thermally decomposing the hydrocarbon-containing gas through the produced hydrogen gas.

[0023] The temperature may be set within a range of 700°C to 1,000°C.

[0024] The reduced iron producing method may further include a process of supplying a portion of the collected exhaust gas during the producing of the hydrogen gas and the solid carbon.

[0025] In the supplying process during the producing of the hydrogen gas and the solid carbon, after the portion of the collected exhaust gas is burned, the portion of the collected exhaust gas may be supplied during the producing of the hydrogen gas and the solid carbon.

[0026] The supplying process during the producing of the hydrogen gas and the solid carbon may include a process of heating a reaction space for thermally decomposing the hydrocarbon-containing gas using the portion of the collected exhaust gas.

[0027] The supplying process during the producing of the hydrogen gas and the solid carbon may include a process of heating the hydrocarbon-containing gas using the portion of the collected exhaust gas.

[0028] The supplying process during the producing of the hydrogen gas and the solid carbon may include a process of heating a combustion gas supplied for thermally decomposing the hydrocarbon-containing gas using the portion of the collected exhaust gas.

[0029] The supplying process during the producing of the hydrogen gas and the solid carbon may include a process of heating a catalyst supplied for thermally decomposing the hydrocarbon-containing gas using the portion of the collected exhaust gas.

[0030] The reduced iron producing method may further include a process of heating at least one of the hydrocarbon-containing gas, a combustion gas supplied for thermally decomposing the hydrocarbon-containing gas, or a catalyst supplied for thermally decomposing the hydrocarbon-containing gas using at least a portion of the produced solid carbon. ADVANTAGEOUS EFFECTS

[0031] According to the embodiment of the present invention, the high-temperature hydrogen gas produced by thermally decomposing the hydrocarbon-containing gas may be used to reduce the iron ore to reduce the energy required for the hydrogen reduction reaction.

[0032] In addition, the exhaust gas discharged during the reduction of iron ore may be reused as the reducing gas together with the high-temperature hydrogen gas produced by thermally decomposing the hydrocarbon-containing gas to stably introduce the large amount of hydrogen gas into the reduction space in the high-temperature state.

[0033] In addition, the portion of the exhaust gas discharged during the reduction of iron ore may be used as the energy source for producing the hydrogen gas and the solid carbon by thermally decomposing the hydrocarbon-containing gas to minimize the overall energy required for the production of the reduced iron. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a schematic view of a reduced iron producing facility according to an embodiment of the present invention.

[0035] FIG. 2 is a view illustrating an example of a reducing furnace for melting the producing reduced iron and reduced iron. an electr ic furnace for

[0036] FIG. 3 is a view illustrating a state in which a reaction space of a thermal decomposition unit is heated by an exhaust gas supplied from an exhaust gas branch line.

[0037] FIG. 4 is a view illustrating a state in which a hydrocarbon-containing gas supplied to the thermal decomposition unit is heated by the exhaust gas supplied from the exhaust gas branch line.

[0038] FIG. 5 is a view illustrating a state in which a combustion gas supplied to the thermal decomposition unit is heated by the exhaust gas supplied from the exhaust gas branch line.

[0039] FIG. 6 is a view illustrating a state in which a catalyst supplied to the thermal decomposition unit is heated by the exhaust gas supplied from the exhaust gas branch line.

[0040] FIG. 7 is a schematic view of a reduced iron producing method according to an embodiment of the present invention. MODE FOR CARRYING OUT THE INVENTION

[0041] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. In order to explain the present invention in detail, the drawings may be exaggerated, and the same symbols in the drawings refer to the same elements.

[0042]

[0043] FIG. 1 is a schematic view of a reduced iron producing facility according to an embodiment of the present invention, and FIG. 2 is a view illustrating an example of a reducing furnace for producing reduced iron and an electric furnace for melting the reduced iron. In FIG. 1, an arrow indicated by dotted lines indicates flows of a raw material and reduced iron, and an arrow indicated by solid lines indicates flows of gases.

[0044] Referring to FIGS. 1 and 2, a reduced iron producing facility according to an embodiment of the present invention includes a reduction unit 120 capable of producing reduced iron, a thermal decomposition unit 130 capable of producing a hydrogen gas and solid carbon by thermally decomposing a hydrocarboncontaining gas, and connection units RL and EL connecting the reduction unit 120 to the thermal decomposition unit 130 so that at least a portion of an exhaust gas discharged from the reduction unit 120 is supplied to the reduction unit 120 together with the hydrogen gas produced by the thermal decomposition unit 130. In addition, the reduced iron producing facility according to an embodiment of the present invention may further include a raw material supply unit 110 installed to supply a raw material to the reduction unit 120 and a purge gas supply unit 150 installed to supply a purge gas to the reduction unit 120.

[0045] The raw material supply unit 110 may be installed to supply the raw material to the reduction unit 120. Here, the raw material may include various forms of iron ore. For example, the iron ore may include fine iron ore, i.e., fine iron ore having a particle size of more than 0 mm and less than or equal to 8 mm. However, this is not limited thereto, and it is of course possible to use a molded object molded so that lump iron ore has a particle size of more than 8 mm, or fine iron ore has a particle size of more than 8 mm, for example, pellets, as raw materials. As described above, the raw material supply unit 110 may include a reservoir having a storage space in which the raw material is stored. The raw material may be stored in the storage space of the reservoir for a long time or may be temporarily stored before supplying the raw material to the reduction unit. The reservoir may include, for example, a hopper.

[0046] The reduction unit 120 may produce reduced iron by reducing the raw material. That is, the reduction unit 120 may receive the iron ore as the raw material from the raw material supply unit 110 and receive a hydrogen gas from the thermal decomposition unit 130 to allow the iron ore to react with the hydrogen gas, thereby producing the reduced iron. The reduction unit 120 may include a reducing furnace having a reducing space capable of producing the reduced iron using the hydrogen gas. Although the reducing furnace is provided as a single furnace, in order to effectively reduce low-grade iron ore or fine iron ore with a low iron content, the reducing furnace may also include a plurality of fluidized reducing furnaces 122, 124, 126, and 128 as illustrated in FIG. 2. Here, the fluidized reducing furnaces 122,  124,  126, and 128 may produce the reduced iron while sequentially moving the raw material. There is no limit to the number of fluidized reducing furnaces 122, 124, 126, and 128, but in order to sufficiently reduce the raw material, and as illustrated in FIG. 2, the reduction unit 120 may include four reducing furnaces including a first fluidized reducing furnace 122, a second fluidized reducing furnace 124, a third fluidized reducing furnace 126, and a fourth fluidized reducing furnace 128. Here, the raw material supply unit 110 may supply the raw material to the first fluidized reducing furnace 510 disposed at the frontmost position with respect to the movement direction of the raw material, and the thermal decomposition unit 130 may supply the reducing gas, i.e., the hydrogen gas to the fourth fluidized reducing furnace 128 disposed at the rearmost position with respect to the movement direction of the raw material. The raw material supplied to the first fluidized reducing furnace 122 may be reduced by sequentially moving through the second fluidized reducing furnace 124, the third fluidized reducing furnace 126, and the fourth fluidized reducing furnace 128 and thus be produced into the reduced iron.

[0047] A large amount of exhaust gas generated during the production of the reduced iron is discharged from the reduction unit 120. The exhaust gas may include a hydrogen gas, steam, a nitrogen gas, etc. In order to improve a reduction rate of the iron ore during the hydrogen reduction, a large amount of hydrogen gas that exceeds the amount required for the reduction has to be supplied. For example, the amount of hydrogen gas required to reduce the iron ore in the reduction unit 120 may be at least two times, but no more than three times the amount required to completely reduce the raw material supplied to the reduction unit 120. Thus, the residual hydrogen gas that does not react with the raw material may be contained in the exhaust gas and then discharged from the reduction unit 120. In addition, in the reduction unit 120, the iron ore and the hydrogen gas may react with each other to produce the reduced iron. Here, an oxygen component of the iron ore and a hydrogen component of the hydrogen gas may react with each other to generate a large amount of steam in the reducing space, and the generated steam may be contained in the exhaust gas and then discharged from the reduction unit 120. In addition, for various reasons such as purging of a pressure gauge, a purge gas, for example, a nitrogen gas may be supplied to the reduction unit 120. As described above, the nitrogen gas supplied for purging may be contained in the exhaust gas and discharged from the reduction unit 120. The exhaust gas may be discharged from the reduction unit 120 at a temperature of 300°C to about 400°C.

[0048] In order to separate the hydrogen gas from the exhaust gas containing the hydrogen gas, the steam, the nitrogen gas, etc., the reduced iron producing facility 10 according to an embodiment of the present invention may further include a separation unit 160 installed in the exhaust gas supply line EL to remove a first by-product, for example, steam, from the exhaust gas flowing along the exhaust gas supply line EL, and an extraction unit 170 installed in the exhaust gas supply line EL to remove a second by-product, for example, a nitrogen gas, which is different from the first by-product, from the exhaust gas flowing along the exhaust gas supply line EL.

[0049] The separation unit 160 may remove the steam from the exhaust gas that moves along the exhaust gas supply line EL. For example, the separation unit 160 may inject water onto the exhaust gas to condense the steam in the exhaust gas and may discharge the condensed steam in a liquid state to remove the steam from the exhaust gas.

[0050] The extraction unit 170 may remove the nitrogen gas from the exhaust gas that moves along the exhaust gas supply line EL. For example, the extraction unit 170 may remove the nitrogen gas from the exhaust gas to extract the hydrogen gas in a pressure swing absorption (PSA) manner. In the pressure swing adsorption manner, a gas may be extracted using an adsorption selectivity of each component for the adsorbent. For example, the extraction unit 170 may adsorb the hydrogen gas to extract the hydrogen gas or may adsorb the nitrogen gas to remove the nitrogen gas, thereby removing the nitrogen gas and extracting the hydrogen gas from the exhaust gas in various manners.

[0051] The thermal decomposition unit 130 may thermally decompose a gas containing hydrocarbon to produce a hydrogen gas and solid carbon. The hydrocarbon-containing gas may include at least one of hydrocarbon compounds such as methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10), ethylene  (C2H4), etc., and may also include a natural gas NG.

[0052] There are various methods for producing the hydrogen gas. Firstly, the hydrogen gas may be produced by electrolyzing water, and the hydrogen gas produced in this manner is referred to as “green” hydrogen. However, the green hydrogen still has the problem of low economic efficiency due to its high production cost.    The hydrogen gas may be produced by allowing the hydrocarbon-containing gas to react with steam at a high temperature and high pressure to convert the hydrocarboncontaining gas into a carbon monoxide gas and hydrogen and then allowing the carbon monoxide gas generated in the reaction to react with steam again to convert the carbon monoxide gas into a hydrogen gas and a carbon dioxide gas. The hydrogen gas produced in this manner is referred to as “gray hydrogen”. Since the gray hydrogen generates a carbon dioxide gas during its production process, it is necessary to capture the generated carbon dioxide gas, thereby minimizing the emission of the carbon dioxide gas. The hydrogen gas produced by capturing the carbon dioxide gas is referred to as “blue hydrogen”. However, the capturing of the carbon dioxide gas may require a large amount of energy, and the captured carbon dioxide gas may also need to be isolated from atmosphere so as to be stored. Since the energy and space available for this purpose are limited, there are many difficulties in realizing these conditions in reality. On the other hand, turquoise hydrogen is produced by thermally decomposing the hydrocarbon-containing gas at a high temperature without separately supplying steam. That is, when the hydrocarbon-containing gas is thermally decomposed at a high temperature, the hydrogen gas and the solid carbon are produced according to the following reaction formula. The hydrogen gas produced as described above is referred to as “turquoise hydrogen”. The turquoise hydrogen has the advantage of low power consumption, and that there is no need to separately capture a carbon dioxide gas because the carbon component of the hydrocarbon-containing gas is discharged as solid carbon. In addition, since the turquoise hydrogen is produced by thermally decomposing the hydrocarbon-containing gas at a high temperature, the hydrogen gas with a high temperature of 500°C to 1,500°C is produced.

[0053] [Reaction Formula]

[0054] CH4(g)^2H2(g)+C(s)

[0055] In an embodiment of the present invention, the high- temperature hydrogen gas produced by thermally decomposing the hydrocarbon-containing gas is used as a reducing gas for reducing iron ore.    Since the hydrogen reduction is strong endothermic reaction, the hydrogen reduced iron-making process may require that the hydrogen gas is introduced at a high temperature, for example, at temperatures of 700°C or more and 1000°C or less. However, when the high-temperature hydrogen gas produced by thermally decomposing the hydrocarbon-containing gas is used for the reduction, an amount of energy required for the reaction may be minimized. In addition, since the unreacted hydrocarbon may carburize the iron ore and thereby lower the melting point of the resulting reduced iron, the hydrogen gas may be supplied to the reduction unit 120 through the thermal decomposition unit 130 capable of thermally decomposing the hydrocarbon-containing gas, thereby enabling the production of the reduced iron under optimal conditions.

[0056] In addition, in order to improve a reduction rate of the iron ore during the hydrogen reduction, a large amount of hydrogen gas that exceeds the amount required for the reduction has to be supplied. For example, the amount of hydrogen gas required to reduce the iron ore in the reduction unit 120 may be at least twice the amount required to completely reduce the raw material supplied to the reduction unit 120. Thus, in an embodiment of the present invention, at least a portion of the exhaust gas containing the unreacted hydrogen gas discharged from the reduction unit 120 is re-supplied to the reduction unit 120. The exhaust gas may be supplied to the reduction unit 120 together with the hydrogen gas produced in the thermal decomposition unit 130 via the connection units RL and EL.

[0057] The connection units RL and EL may connect the reduction unit 120 to the thermal decomposition unit 130 so that at least a portion of the exhaust gas discharged from the reduction unit 120 is supplied to the reduction unit 120 together with the hydrogen gas produced in the thermal decomposition unit 130. The connection units RL and EL may include a hydrogen gas supply line RL that connects the reduction unit 120 to the thermal decomposition unit 130 to supply the hydrogen gas produced in the thermal decomposition unit 130 to the reduction unit 120, and the exhaust gas supply line EL that connects the reduction unit 120 to the hydrogen gas supply line RL to supply at least a portion of the exhaust gas discharged from the reduction unit 120 to the hydrogen gas supply line RL.

[0058] The hydrogen gas supply line RL connects the reduction unit 120 to the thermal decomposition unit 130 to supply the hydrogen gas produced in the thermal decomposition unit 130 to the reduction unit 120. The hydrogen gas supply line RL may include at least one pipe and at least one valve (not shown) installed in the pipe. For example, as illustrated in FIG. 2, when the reduction unit 120 includes a plurality of reducing furnaces, the hydrogen gas supply line RL may connect the last reducing furnace of the plurality of reducing furnaces, i.e., a fourth fluidized reducing furnace 128 to the thermal decomposition unit 130.

[0059] In addition, the exhaust gas supply line EL connects the reduction unit 120 to the hydrogen gas supply line RL to supply at least a portion of the exhaust gas discharged from the reduction unit 120 to the hydrogen gas supply line RL. As described above, the exhaust gas supply line EL may include at least one pipe and at least one valve (not shown) installed in the pipe. For example, as illustrated in FIG. 2, when the reduction unit 120 includes the plurality of reducing furnaces, the exhaust gas supply line EL may connect the reducing furnace disposed at the frontmost position among the plurality of reducing furnaces with respect to the movement direction of the raw material, i.e., the first fluidized reducing furnace 122 to the hydrogen gas supply line RL.

[0060] For example, the reduced iron producing facility 10 according to an embodiment of the present invention may mix at least a portion of the exhaust gas discharged from the reduction unit 120 with the hydrogen gas produced in the thermal decomposition unit 130 through the connection units RL and EL including the hydrogen gas supply lines RL and the exhaust gas supply lines EL and then supply the mixture to the reduction unit 120. Here, the exhaust gas and the hydrogen gas may be mixed so that the gas obtained after mixing the exhaust gas with the hydrogen gas has a temperature in the range of 700°C to 1,000°C. As described above, the exhaust gas may be discharged from the reduction unit 120 at a temperature of 300°C to 400°C, and the hydrogen gas may be produced at a high temperature of 500°C to 1,500°C. For example, when the hydrogen gas is produced at a temperature exceeding 1,000°C, it may be mixed with the exhaust gas so that the mixed gas has a temperature in the range of 700°C to 1000°C. As described above, when the mixed gas has a temperature in the range of 700°C to 1,000°C, the mixed gas may be directly supplied to the reduction unit 120 without being separately heated.

[0061] In addition, when the hydrogen gas has an excessively high temperature, the hydrogen gas may be heat-exchanged with another element that requires heating to lower the temperature of the hydrogen gas. For example, the hydrogen gas may be heat-exchanged with a combustion gas supplied for thermally decomposing the hydrocarbon-containing gas as described below.

[0062] On the other hand, when the hydrogen gas is produced at a temperature of less than 700°C, even when the hydrogen gas is mixed with the exhaust gas, the mixed gas may not have a temperature within the range of 700°C to 1000°C. Thus, the reduced iron producing facility 10 according to an embodiment of the present invention may further include a heating unit 140 installed in the hydrogen gas supply line RL to heat the mixed gas. The mixed gas may be heated to a temperature within the range of 700°C to 1,000°C through the heating unit 140. Since various structures for directly or indirectly heating the mixed gas may be applied to the heating unit 140, detailed descriptions thereof will be omitted.

[0063] The reduced iron producing facility according to an embodiment of the present invention may further include a purge gas supply unit 150 installed to store a purge gas and supply the purge gas to the reduction unit 120. The reduction unit 120 may have a reducing space capable of producing the reduced iron, and the reducing space may need to be purged for maintenance between processes. In addition, there are cases in which the purge gas needs to be supplied during the process.  For example, when purging the pressure gauge or using the fine iron ore as the raw material, the purge gas may be supplied to increase the fluidity of the fine iron ore, thereby preventing the iron ore from sticking in the reducing space. Thus, the purge gas supply unit 150 may supply the purge gas to the reducing space through a purge gas supply line PL that connects the purge gas supply unit 150 to the reduction unit 120, and an inert gas such as nitrogen may be used as the purge gas.

[0064] In addition, the reduced iron producing facility 10 according to an embodiment of the present invention may use a portion of the exhaust gas moving along the exhaust gas supply line EL as an energy source for the thermal decomposition unit 130 to produce the hydrogen gas and the solid carbon. For this, the reduced iron producing facility 10 according to an embodiment of the present invention may further include an exhaust gas branch line EDL that connects the exhaust gas supply line EL to the thermal decomposition unit 130 to supply a portion of the exhaust gas moving along the exhaust gas supply line EL to the thermal decomposition unit 130. As described above, the structure of supplying a portion of the exhaust gas to the thermal decomposition unit 130 through the exhaust gas branch line EDL may be variously modified and applied depending on the method through which the thermal decomposition unit 130 thermally decomposes the hydrocarbon-containing gas. This will be described in more detail below with reference to FIGS. 3 to 6.

[0065] As described above, the exhaust gas may be discharged from the reduction unit 120 at a temperature of 300°C to 400 °C. Thus, it may be necessary to increase the temperature of the exhaust gas so that the exhaust gas can be used as an energy source for producing the hydrogen gas and the solid carbon in the thermal decomposition unit 130. In this case, a portion of the exhaust gas supplied to the thermal decomposition unit 130 may be burned by a burner provided in a supply path of the exhaust gas, such as the exhaust gas branch line EDL, thereby increasing the sensible heat of the exhaust gas.

[0066] FIG. 3 is a view illustrating a state in which the reaction space of the thermal decomposition unit is heated by the exhaust gas supplied from the exhaust gas branch line, and FIG. 4 is a view illustrating a state in which the hydrocarboncontaining gas supplied to the thermal decomposition unit is heated by the exhaust gas supplied from the exhaust gas branch line. In addition, FIG. 5 is a view illustrating a state in which the combustion gas supplied to the thermal decomposition unit is heated by the exhaust gas supplied from the exhaust gas branch line, and FIG. 6 is a view illustrating a state in which a catalyst supplied to the thermal decomposition unit is heated by the exhaust gas supplied from the exhaust gas branch line.

[0067] The thermal decomposition unit 130 may thermally decompose the hydrocarbon-containing gas in various manners such as by using plasma to thermally decompose the hydrocarboncontaining gas or by thermally decomposing the hydrocarboncontaining gas through combustion.    However, the thermal decomposition unit 130 may include a reactor 131 that provides the reaction space capable of thermally decomposing the hydrocarbon-containing gas, and a hydrocarbon-containing gas supply unit 132 connected to the reactor 131 to supply the hydrocarbon-containing gas to the reaction space.

[0068] Here, as illustrated in FIG. 3, the reduced iron producing facility 10 according to an embodiment of the present invention may heat the reaction space provided by the reactor 131 through the exhaust gas supplied from the exhaust gas branch line EDL. For this, the thermal decomposition unit 130 may further include a first heat exchanger 136 connected to the exhaust gas branch line EDL and installed in the reactor 131 to transfer the heat of the exhaust gas supplied from the exhaust gas branch line EDL to the reaction space. The first heat exchanger 136 may transfer the heat of the exhaust gas supplied from the exhaust gas branch line EDL to the reaction space in various manners such as direct heat exchange or indirect heat exchange. In addition, the first heat exchanger 136 may be installed inside the reactor 131, i.e., in the reaction space or may be installed outside the reactor 131 to heat a surface of the reactor 131.

[0069] In addition, as illustrated in FIG. 4, the reduced iron producing facility 10 according to an embodiment of the present invention may heat the hydrocarbon-containing gas through the exhaust gas supplied from the exhaust gas branch line EDL. For this, the thermal decomposition unit 130 may further include a second heat exchanger 137 connected to the exhaust gas branch line EDL and installed in the hydrocarbon-containing gas supply unit 132 to transfer the heat of the exhaust gas supplied from the exhaust gas branch line EDL to the hydrocarbon-containing gas. As described above, the second heat exchanger 137 may also heat the hydrocarbon-containing gas supplied to the reactor 131 in various manners such as the direct heat exchange or the indirect heat exchange.

[0070] In addition, as illustrated in FIG. 5, the reduced iron producing facility 10 according to an embodiment of the present invention may heat the combustion gas through the exhaust gas supplied from the exhaust gas branch line EDL. The thermal decomposition unit 130 may thermally decompose the hydrocarboncontaining gas by burning the combustion gas for the combustion. For this, in addition to the reactor 131 and the hydrocarboncontaining gas supply unit 132 described above, the thermal decomposition unit 130 may further include a combustion gas supply unit 133 connected to the reactor 131 to supply an oxygen-containing gas and the combustion gas including a fuel gas to the reaction space. Here, the reduced iron producing facility 10 according to an embodiment of the present invention may heat at least one of the oxygen-containing gas or the fuel gas by using the exhaust gas supplied from the exhaust gas branch line EDL as illustrated in FIG. 5. For this, the thermal decomposition unit 130 may further include a third heat exchanger 138 connected to the exhaust gas branch line EDL and installed in the combustion gas supply unit 133 to transfer the heat of the exhaust gas supplied from the exhaust gas branch line EDL to at least one of the oxygen-containing gas or the fuel gas. As described above, the third heat exchanger 138 may also heat the combustion gas supplied to the reactor 131 in various manners such as the direct heat exchange or the indirect heat exchange.

[0071] The combustion gas supply unit 133 may be connected to the exhaust gas branch line EDL to supply the fuel gas including the exhaust gas supplied from the exhaust gas branch line EDL. As described above, since the exhaust gas contains the hydrogen gas, the combustion gas supply unit 133 may supply the exhaust gas containing the hydrogen gas as fuel to the reaction space from the exhaust gas branch line EDL.

[0072] In addition, as illustrated in FIG. 6, the reduced iron producing facility 10 according to an embodiment of the present invention may heat the catalyst through the exhaust gas supplied from the exhaust gas branch line EDL. The thermal decomposition unit 130 may supply the catalyst to the reaction space and then thermally decompose the hydrocarbon-containing gas to promote thermal decomposition. For this, in addition to the reactor 131 and the hydrocarbon-containing gas supply unit 132 described above, the thermal decomposition unit 130 may further include a catalyst supply unit 134 connected to the reactor 131 to supply the catalyst to the reaction space. Here, the reduced iron producing facility 10 according to an embodiment of the present invention may heat the catalyst supplied to the reaction space through the exhaust gas supplied from the exhaust gas branch line EDL as illustrated in FIG. 6. For this, the thermal decomposition unit 130 may further include a fourth heat exchanger 139 connected to the exhaust gas branch line EDL and installed in the catalyst supply unit 134 to transfer the heat of the exhaust gas supplied from the exhaust gas branch line EDL to the catalyst. As described above, this fourth heat exchanger 139 may also heat the catalyst supplied to the reactor 131 in various manners such as the direct heat exchange or the indirect heat exchange.

[0073] The above-described heat exchangers may be provided in plurality and used in combination in the thermal decomposition unit 130. For example, the exhaust gas supplied from the exhaust gas branch line EDL may be supplied to the first heat exchanger 136 and the second heat exchanger 137 to heat the reaction space and the hydrocarbon-containing gas, respectively, or may be supplied to the third heat exchanger 138 and the fourth heat exchanger 139 to further heat the combustion gas and the catalyst. In addition, since the thermal decomposition unit 130 is used to produce the hydrogen gas and solid carbon by thermally decomposing the hydrocarbons at a high temperature, a hydrogen gas having a high temperature of 500°C to 1,500°C and solid carbon may be produced, and a high-temperature gas may be discharged from the thermal decomposition unit 130. Thus, it is of course possible to supply at least one of the high-temperature hydrogen gas, the high-temperature solid carbon, or the high-temperature combustion exhaust gas, which is produced or discharged from the thermal decomposition unit 130, to the hydrocarbon-containing gas, the reaction space, the combustion gas, and the catalyst to heat the hydrocarbon-containing gas, the reaction space, the combustion gas, and the catalyst. For example, at least a portion of the solid carbon produced by the thermal decomposition unit 130 and having a high temperature of 500°C to 1,500°C may be heat-exchanged with at least one of the hydrocarbon-containing gas, the combustion gas supplied to decompose the hydrocarbon-containing gas, or the catalyst supplied to decompose the hydrocarbon-containing gas, thereby heating at least one of the hydrocarbon-containing gas, the combustion gas, or the catalyst.

[0074] In this manner, when the exhaust gas supplied from the exhaust gas branch line is used as an energy source for producing the hydrogen gas and the solid carbon by the thermal decomposition unit 130, it is possible to prevent a nitrogen gas from being concentrated in the reduction unit 120. As described above, the exhaust gas may contain the nitrogen gas. When a portion of the exhaust gas containing the nitrogen gas is discharged through the exhaust gas branch line EDL so as to be used as the energy source for the thermal decomposition, an amount of nitrogen gas introduced into the reduction unit 120 may be reduced to prevent the concentration of the nitrogen gas within the reduction unit 120. That is, when a portion of the exhaust gas is discharged through the exhaust gas branch line EDL so that the nitrogen gas is introduced into the reduction unit 120 within an allowable range, the extraction unit 170 for removing the nitrogen gas from the exhaust gas may not be installed as described above. On the other hand, even in the case in which a portion of the exhaust gas is discharged through the exhaust gas branch line EDL, when a large amount of nitrogen gas is introduced into the reduction unit 120, the extraction unit 170 may need to be installed in the exhaust gas supply line EL. Since the nitrogen gas in the exhaust gas supplied to the exhaust gas branch line does not need to be removed, in this case, the extraction unit 170 may be installed in the exhaust gas supply line EL that extends between a position at which the exhaust gas branch line EDL is connected to the exhaust gas supply line EL and a position at which the exhaust gas supply line EL is connected to the hydrogen gas supply line RL. Since steam needs to be removed from both the exhaust gas supply line EL and the exhaust gas branch line EDL, the above-described separation unit 160 may be installed in the exhaust gas supply line EL extending between the position, at which the exhaust gas branch line EDL is connected to the exhaust gas supply line EL, and the reduction unit 120.

[0075] As described above, the reduced iron producing facility 10 according to an embodiment of the present invention may produce the reduced iron by moving various gases along each of the above-described pipes. The movement of the various gases may be controlled through valves (not shown) installed in the pipes, and the valves may be installed at various positions to control the flow rate of each gas flowing through the respective pipes.

[0076] The reduced iron produced in the reduced iron producing facility 10 may be supplied to a melting facility 20. As illustrated in FIG. 2, the reduced iron produced through the first fluidized reducing furnace 122, the second fluidized reducing furnace 124, the third fluidized reducing furnace 126, and the fourth fluidized reducing furnace 128 may be discharged from the fluidized reducing furnace 128 and supplied to the melting facility 20. The reduced iron discharged from the fourth fluidized reducing furnace 128 may be directly supplied to the melting facility 20 or may be agglomerated in a hot state in a separate molding device and then supplied to the melting facility 20.

[0077] The melting facility 20 may receive the reduced iron and may melt the received reduced iron by using electric heat. For example, the melting facility 20 may receive the reduced iron from the reduction unit 120 and may heat and melt the received reduced iron by using electrical energy. In addition, the melting facility 20 may receive additional iron scrap in addition to the reduced iron and melt the reduced iron and the iron scrap together. The melting facility 20 may include electric furnaces 21 and 22, each of which has a melting space capable of melting the reduced iron using the electric heat. The above-described electric furnaces 21 and 22 may include an electric furnace main body 21 having a melting space and an electrode rod 22 of which at least a portion is partially disposed in the melting space to generate the electric heat. When the reduced iron is charged into the melting space, the electric furnaces 21 and 22 may apply power to the electrode rod 22 to melt the reduced iron. The reduced iron supplied from the reduced iron producing facility 10 may be melted in the melting facility 20 to produce molten iron, and thus, a molten iron producing facility may include the reduced iron producing facility 10 and the melting facility 20.

[0078]

[0079] Hereinafter, a reduced iron producing method according to an embodiment of the present invention will be described. The reduced iron producing method according to an embodiment of the present invention may be a method for producing reduced iron using the above-described reduced iron producing facility, and thus, since the above-described contents in relation to the reduced iron producing facility is applied as it is, description of duplicated contents will be omitted.

[0080] FIG. 7 is a schematic view of the reduced iron producing method according to an embodiment of the present invention.

[0081] Referring to FIG. 7, the reduced iron producing method according to an embodiment of the present invention includes a process (S100) of thermally decomposing a hydrocarbon-containing gas to produce a hydrogen gas and solid carbon, a process (S200) of allowing the produced hydrogen gas to react with a raw material, a process (S300) of collecting an exhaust gas discharged during the reaction between the raw material and the hydrogen gas, and a process (S400) of supplying at least a portion of the collected exhaust gas together with the produced hydrogen gas to the raw material. Here, since the respective processes are continuously performed to produce reduced iron, the processes may not have a time-series relationship in which one process is performed after another process is completed.

[0082] The process (S100) of producing the hydrogen gas and the solid carbon may be performed in the above-described thermal decomposition unit 130. In the process of producing the hydrogen gas and the solid carbon, the hydrocarbon-containing gas is thermally decomposed at a high temperature to produce a hydrogen gas having a temperature of 500°C to 1,500°C, and the high-temperature hydrogen gas produced by thermally decomposing the hydrocarbon-containing gas in this manner is supplied to a reduction unit 120 to reduce iron ore.

[0083] In the process (S200) of reacting with a raw material, the produced hydrogen gas reacts with the raw material. This may be performed in the reduction unit 120, which receives iron ore as the raw material from a raw material supply unit 110 and receives a hydrogen gas from the thermal decomposition unit 130 to allow the iron ore to react with the hydrogen gas, thereby producing the reduced iron. Here, the raw material may include iron ore in various forms. For example, the iron ore may include fine iron ore having a particle size of more than 0 mm and less than or equal to 8 mm, i.e., fine iron ore or may also include lumpy iron ore having a particle size of more than 8 mm or a molded body (e.g., pellet) obtained by molding the fine iron ore or the lumpy iron ore having a particle size of more than 8 mm.

[0084] In the process (S200) of reacting with the raw material, a large amount of exhaust gas is discharged from the reduction unit 120. As described above, the exhaust gas may include a hydrogen gas, steam, a nitrogen gas, etc., and may be discharged from the reduction unit 120 at a temperature of 300°C to 400°C. As described above, the exhaust gas discharged from the reduction unit 120 is collected in the process (S300) of collecting the exhaust gas, and at least a portion of the collected exhaust gas is re-supplied to the raw material together with the hydrogen gas produced in the process (S100) of producing the hydrogen gas and the solid carbon.

[0085] In the process (S400) of supplying the raw material together with the hydrogen gas, at least a portion of the exhaust gas collected in the process (S300) of collecting the exhaust gas is supplied together with the hydrogen gas produced in the process (S100) of producing the hydrogen gas and the solid carbon to the raw material in the reduction unit 120. The process (S400) of supplying the collected exhaust gas together with the hydrogen gas to the raw material may include a process of mixing the collected exhaust gas with the produced hydrogen gas and a process of supplying the mixed gas to the raw material.

[0086] The process of mixing with the hydrogen gas may include a process of adjusting a flow rate of at least one of the collected exhaust gas or the produced hydrogen gas so that the gas obtained after mixing the exhaust gas and the hydrogen gas has a set temperature. For example, in the process of mixing with the hydrogen gas, the exhaust gas and the hydrogen gas may be mixed so that the resulting gas has a temperature within the range of 700°C to 1,000°C. The exhaust gas may be discharged from the reduction unit 120 at a temperature of 300°C to 400°C, and the hydrogen gas may be produced at a high temperature of 500°C to 1,500°C. For example, when the hydrogen gas is produced at a temperature exceeding 1,000°C, the flow rate of each of the exhaust gas and the hydrogen gas may be adjusted so that the mixed gas has a temperature in the range of 700°C to 1,000°C.

[0087] In addition, the process of mixing with the hydrogen gas may include a process of adjusting the temperature of the hydrogen gas produced so that the gas obtained after mixing the exhaust gas with the hydrogen gas has a set temperature, and the process of adjusting the temperature of the hydrogen gas may include a process of heating a combustion gas supplied for thermally decomposing the hydrocarbon-containing gas through the produced hydrogen gas. That is, when the hydrogen gas mixed with the exhaust gas has an excessively high temperature, the hydrogen gas may be heat-exchanged with another element that requires heating in order to lower the temperature of the hydrogen gas.    For example, the hydrogen gas may be heat- exchanged with the combustion gas supplied for thermally decomposing the hydrocarbon-containing gas.

[0088] The reduced iron producing method according to an embodiment of the present invention may further include a process of supplying a portion of the collected exhaust gas during the producing of the hydrogen gas and the solid carbon. That is, in the reduced iron producing method according to an embodiment of the present invention, as described above, a portion of the exhaust gas moving along the exhaust gas supply line EL may be used as the energy source for the thermal decomposition unit 130 to produce the hydrogen gas and the solid carbon.

[0089] Here, the process of supplying during the production of the hydrogen gas and the solid carbon may be performed by burning a portion of the collected exhaust gas and then supplying the hydrogen gas and the solid carbon. The exhaust gas may be discharged from the reduction unit 120 at a temperature of 300°C to 400°C. However, in order to use the exhaust gas as the energy source for producing the hydrogen gas and the solid carbon by the thermal decomposition unit 130, it may be necessary to increase in temperature of the exhaust gas. In this case, a portion of the exhaust gas supplied to the thermal decomposition unit 130 may be burned through a burner provided in a supply path of the exhaust gas, for example, an exhaust gas branch line EDL, and then, the hydrogen gas and the solid carbon may be produced.

[0090] The process of supplying the hydrogen gas and the solid carbon during the production may include a process of heating the reaction space for thermally decomposing the hydrocarboncontaining gas using a portion of the collected exhaust gas, as described above in relation to FIG. 3 or may include a process of heating the hydrocarbon-containing gas using a portion of the collected exhaust gas, as described above in relation to FIG. 4. In addition, the process of supplying the hydrogen gas and the solid carbon may include a process of heating the combustion gas supplied to thermally decompose the hydrocarbon-containing gas through a portion of the collected exhaust gas, as described above in relation to FIG. 5 or may include a process of heating a catalyst supplied to thermally decompose the hydrocarboncontaining gas through a portion of the collected exhaust gas, as described above in relation to FIG. 6.

[0091] As described above, a portion of the collected exhaust gas is supplied during the production of the hydrogen gas and the solid carbon. Thus, with regard to the specific contents in which a portion of the exhaust gas is used as the energy source for the thermal decomposition unit 130 to produce the hydrogen gas and the solid carbon, the same descriptions given above with reference to FIGS. 4 to 6 may be applied, and thus, duplicated descriptions thereof will be omitted.

[0092] The reduced iron producing method according to an embodiment of the present invention may further include a process of heating at least one of the hydrocarbon-containing gas, the combustion gas supplied to thermally decompose the hydrocarbon-containing gas, or the catalyst supplied to thermally decompose the hydrocarbon-containing gas by using at least a portion of the produced solid carbon. That is, in the process of producing the hydrogen gas and the solid carbon, not only the high-temperature hydrogen gas but also the solid carbon having a high temperature of 500°C to 1,500°C may be produced from the thermal decomposition unit 130. Thus, at least a portion of the high-temperature solid carbon may be supplied to the hydrocarbon-containing gas, the reaction space, the combustion gas, and the catalyst to heat the hydrocarboncontaining gas, the reaction space, the combustion gas, and the catalyst. In addition, at least a portion of the high-temperature combustion exhaust gas generated during the process of producing the hydrogen gas and the solid carbon may also be re-supplied to the hydrocarbon-containing gas, the reaction space, the combustion gas, and the catalyst to heat the hydrocarbon-containing gas, the reaction space, the combustion gas, and the catalyst.

[0093]

[0094] Although the specific embodiments are described and illustrated by using specific terms, the terms are merely examples for clearly explaining the embodiments, and thus, it is obvious to those skilled in the art that the embodiments and technical terms can be carried out in other specific forms and changes without changing the technical idea or essential features.    Therefore, it should be understood that simple modifications in accordance with the embodiments of the present invention may belong to the technical spirit of the present invention.

Claims

1. A reduced iron producing facility comprising:a reduction unit configured to produce reduced iron;a thermal decomposition unit configured to thermally decompose a hydrocarbon-containing gas so as to produce a hydrogen gas and solid carbon; anda connection unit configured to connect the reduction unit to the thermal decomposition unit so that at least a portion of an exhaust gas discharged from the reduction unit is supplied to the reduction unit together with the hydrogen gas produced in the thermal decomposition unit.

2. The reduced iron producing facility of claim 1, wherein the connection unit comprises:a hydrogen gas supply line configured to connect the reduction unit to the thermal decomposition unit so that the hydrogen gas provided in the thermal decomposition unit is supplied to the reduction unit; andan exhaust gas supply line configured to connect the reduction unit to the hydrogen gas supply line so that at least a portion of the exhaust gas discharged from the reduction unit is supplied to the hydrogen gas supply line.

3. The reduced iron producing facility of claim 2, wherein the reduction unit comprises a plurality of reducing furnaces disposed to sequentially reduce the moving raw material,the hydrogen gas supply line is configured to connect the reducing furnace, which is disposed at the rearmost side among the plurality of reducing furnaces with respect to the movingdirection of the raw material, to the thermal decomposition unit, andthe exhaust gas supply line is configured to connect the reducing furnace, which is disposed at the frontmost side among the plurality of reducing furnaces with respect to the moving direction of the raw material, to the hydrogen gas supply line.

4. The reduced iron producing facility of claim 2, further comprising an exhaust gas branch line configured to connect the exhaust gas supply line to the thermal decomposition unit so that a portion of the exhaust gas moving along the exhaust gas supply line is supplied to the thermal decomposition unit.

5. The reduced iron producing facility of claim 4, wherein the thermal decomposition unit comprises:a reactor configured to provide a reaction space in which the hydrocarbon-containing gas is thermally decomposed; anda first heat exchanger connected to the exhaust gas branch line and installed in the reactor to transfer heat of the exhaust gas supplied from the exhaust gas branch line to the reaction space.

6. The reduced iron producing facility of claim 4, wherein the thermal decomposition unit comprises:a reactor configured to provide a reaction space in which the hydrocarbon-containing gas is thermally decomposed;a hydrocarbon-containing gas supply unit connected to the reactor to supply the hydrocarbon-containing gas into the reaction space; anda second heat exchanger connected to the exhaust gas branch line and installed in the hydrocarbon-containing gas supply unitto transfer heat of the exhaust gas supplied from the exhaust gas branch line to the hydrocarbon-containing gas.

7. The reduced iron producing facility of claim 4, wherein the thermal decomposition unit comprises:a reactor configured to provide a reaction space in which the hydrocarbon-containing gas is thermally decomposed;a combustion gas supply unit connected to the reactor to supply an oxygen-containing gas and a combustion gas containing a fuel gas to the reaction space; anda third heat exchanger connected to the exhaust gas branch line and installed in the combustion gas supply unit to transfer heat of the exhaust gas supplied from the exhaust gas branch line to at least one of the oxygen-containing gas or the fuel gas.

8. The reduced iron producing facility of claim 7, wherein the combustion gas supply unit is connected to the exhaust gas branch line to supply the fuel gas containing the exhaust gas supplied from the exhaust gas branch line.

9. The reduced iron producing facility of claim 4, wherein the thermal decomposition unit comprises:a reactor configured to provide a reaction space in which the hydrocarbon-containing gas is thermally decomposed;a catalyst gas supply unit connected to the reactor to supply a catalyst for promoting the thermal decomposition to the reaction space; anda fourth heat exchanger connected to the exhaust gas branchline and installed in the catalyst supply unit to transfer heatof the exhaust gas supplied from the exhaust gas branch line to the catalyst.

10. The reduced iron producing facility of claim 4, further comprising:a separation unit installed in the exhaust gas supply line to remove a first by-product from the exhaust gas moving along the exhaust gas supply line; andan extraction unit installed in the exhaust gas supply line to remove a second by-product, which is different from the first by-product, from the exhaust gas moving along the exhaust gas supply line,wherein the separation unit is installed in the exhaust gas supply line extending between a position, to which the exhaust gas branch line is connected, and the reduction unit, andthe extraction unit is installed in the exhaust gas supply line extending between a position, to which the exhaust gas branch line is connected, and a position, to which the hydrogen gas supply line is connected.

11. A reduced iron producing method comprising:a process of thermally decomposing a hydrocarbon-containing gas to produce a hydrogen gas and solid carbon;a process of allowing the produced hydrogen gas to react with a raw material;a process of collecting an exhaust gas discharged in the process of reacting with the raw material; anda process of supplying at least a portion of the collected exhaust gas together with the produced hydrogen gas to the raw material.

12. The reduced iron producing method of claim 11, wherein the process of supplying the exhaust gas together with the hydrogen gas to the raw material comprises:a process of mixing the collected exhaust gas with the produced hydrogen gas; anda process of supplying the mixed gas to the raw material.

13. The reduced iron producing method of claim 12, wherein the mixing process comprises a process of adjusting a flow rate of at least one of the collected exhaust gas or the produced hydrogen gas so that the mixed gas has a set temperature, andthe process of supplying the mixed gas to the raw material comprises a process of directly supplying the mixed gas to the raw material.

14. The reduced iron producing method of claim 12, wherein the mixing process comprises a process of adjusting a temperature of the produced hydrogen gas so that the mixed gas has a set temperature,wherein the process of adjusting the temperature of the hydrogen gas comprises a process of heating a combustion gas supplied for thermally decomposing the hydrocarbon-containing gas through the produced hydrogen gas.

15. The reduced iron producing method of claim 13 or 14, wherein the temperature is set within a range of 700°C to 1,000°C.

16. The reduced iron producing method of claim 11, further comprising a process of supplying a portion of the collected exhaust gas during the producing of the hydrogen gas and the solid carbon.

17. The reduced iron producing method of claim 16, wherein, in the supplying process during the producing of the hydrogen gas and the solid carbon, after the portion of the collected exhaust gas is burned, the portion of the collected exhaust gas is supplied during the producing of the hydrogen gas and the solid carbon.

18. The reduced iron producing method of claim 16, wherein the supplying process during the producing of the hydrogen gas and the solid carbon comprises a process of heating a reaction space for thermally decomposing the hydrocarbon-containing gas using the portion of the collected exhaust gas.

19. The reduced iron producing method of claim 16, wherein the supplying process during the producing of the hydrogen gas and the solid carbon comprises a process of heating the hydrocarboncontaining gas using the portion of the collected exhaust gas.

20. The reduced iron producing method of claim 16, wherein the supplying process during the producing of the hydrogen gas and the solid carbon comprises a process of heating a combustion gas supplied for thermally decomposing the hydrocarbon-containing gas using the portion of the collected exhaust gas.

21. The reduced iron producing method of claim 16, wherein the supplying process during the producing of the hydrogen gas and the solid carbon comprises a process of heating a catalyst supplied for thermally decomposing the hydrocarbon-containing gas using the portion of the collected exhaust gas.

22. The reduced iron producing method of claim 11, further comprising a process of heating at least one of the hydrocarboncontaining gas, a combustion gas supplied for thermally decomposing the hydrocarbon-containing gas, or a catalyst supplied for thermally decomposing the hydrocarbon-containing gas using at least a portion of the produced solid carbon.

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