Hydrogen production system and hydrogen production method

Abstract

According to exemplary embodiments of the present invention, it is possible to provide a hydrogen production system and a hydrogen production method which are capable of continuously producing hydrogen from different raw materials by using reduced iron.

Description

Hydrogen production system and hydrogen production method

[0001] The present invention relates to a hydrogen production method and a hydrogen production system.

[0002] Hydrogen is an essential substance in our daily lives and can be said to have been widely used as early as 100 years ago. Major applications of hydrogen include serving as a basic raw material for the production of ammonia, which is a raw material for nitrogen fertilizers; as a basic raw material for methanol, which is used as a solvent or disinfectant; and as a raw material for hydro-cracking to lighten the decomposition of heavy petroleum components. Recently, it has also been used as a raw material for fuel cells. Therefore, if hydrogen can be produced in an environmentally friendly and economical manner, its utilization in various fields, including those mentioned above, will be possible. Furthermore, the widespread use of hydrogen is expected to ultimately contribute to the reduction of environmental pollutants such as carbon dioxide emissions.

[0003] Conventional methods for producing hydrogen include the electrolysis of water, solar electrolysis of water, ammonia reforming using precious metal catalysts such as ruthenium (Ru) supported on an alumina support, direct decomposition of methane using carbon catalysts, and methanol decomposition using catalysts such as copper, gold, or platinum supported on an alumina or zinc oxide support.

[0004] (Patent Document 1) Korean Published Patent Application No. 10-2023-0095308

[0005] The problem that the technical concept of the present invention aims to solve is to provide a hydrogen production method and a hydrogen production system with excellent hydrogen production efficiency.

[0006] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall details of the specification.

[0007] According to exemplary embodiments for solving the problem of the present invention, a hydrogen production system is provided. The hydrogen production system may include: a first hydrogen production device configured to provide hydrogen, a carbon material, and a second reduced iron by contacting a first gas containing methane (CH4) with a first reduced iron; a second hydrogen production device configured to provide hydrogen and a third reduced iron by contacting a second gas containing ammonia with the second reduced iron; and a control unit configured to determine a total hydrogen production amount or the temperature of the first reduced iron based on the energy consumption efficiency of the first hydrogen production device and the second hydrogen production device.

[0008] The above control unit can reduce the total hydrogen production amount if the energy consumption efficiency decreases.

[0009] The control unit may increase the temperature of the first reduced iron when the energy consumption efficiency decreases. At this time, optionally, the control unit may increase the total hydrogen production amount.

[0010] The temperature of the first hydrogen production device can be controlled to 700 to 950°C.

[0011] The temperature of the second hydrogen production device can be controlled to 600 to 800°C.

[0012] The above second reduced iron may contain, in weight percent, carbon: 3 to 40%, the remainder being Fe and unavoidable impurities.

[0013] According to other exemplary embodiments of the present invention, a method for producing hydrogen is provided. The method for producing hydrogen may include the steps of: determining a total hydrogen production amount or a temperature of a first reduced iron based on energy consumption efficiency; contacting the first reduced iron with a first gas containing methane (CH4) to provide hydrogen, a carbon material, and a second reduced iron; and contacting the second reduced iron with a second gas containing ammonia to provide hydrogen and a third reduced iron.

[0014] According to exemplary embodiments of the present invention, a hydrogen production system and a hydrogen production method capable of continuous hydrogen production from different raw materials using reduced iron can be provided.

[0015] The various and beneficial advantages and effects of the present invention are not limited to those described above and will be more easily understood in the process of explaining specific embodiments of the present invention.

[0016] FIG. 1 is a drawing for illustrating a hydrogen production system according to exemplary embodiments.

[0017] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor can appropriately define the concepts of terms to best describe his invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0018] In the following descriptions with reference to the drawings, identical or corresponding components are assigned the same reference numerals, and redundant descriptions thereof will be omitted.

[0019] In the following embodiments, the terms first, second, etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another component.

[0020] In the following embodiments, the singular expression includes the plural expression unless the context clearly indicates otherwise.

[0021] In the following embodiments, terms such as "include" or "have" mean that the features or components described in the specification are present, and do not preclude the possibility that one or more other features or components may be added.

[0022] In the drawings, the size of components may be exaggerated or reduced for convenience of explanation. For example, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, so the present invention is not necessarily limited to what is illustrated.

[0023] Where an embodiment can be implemented differently, a specific process sequence may be performed differently from the order described. For example, two processes described consecutively may be performed substantially simultaneously or proceed in the reverse order of the description.

[0024] In addition, in describing the present invention, if it is determined that a detailed description of related known components or functions may obscure the essence of the invention, such detailed description is omitted.

[0025] The present invention will be described in detail below through each embodiment. It should be noted that each embodiment described in this specification is not limited to a single embodiment but may also be combined with other embodiments. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0026] The present invention will be described in detail below through examples. However, it should be noted that the following examples are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0027] [Hydrogen Production System]

[0028] FIG. 1 is a drawing for illustrating a hydrogen production system (10) according to exemplary embodiments.

[0029] Referring to FIG. 1, the hydrogen production system (10) includes a first hydrogen production device (100), a second hydrogen production device (200), and a control unit (300).

[0030] The first hydrogen production device (100) is configured to provide hydrogen, carbon material, and a second reduced iron by contacting a first gas containing methane (CH4) with a first reduced iron. In this way, the first hydrogen production device (100) can obtain hydrogen from methane by using the first reduced iron as a catalyst. At this time, the decomposition reaction of methane may follow the following reaction equation 1.

[0031] [Reaction Equation 1]

[0032] CH4 → C + 2H2

[0033] In this way, the decomposition of methane produces not only hydrogen but also carbon materials (C). The carbon materials produced may be materials composed of carbon, such as graphite, carbon nanotubes, or graphene.

[0034] The structure and type of the first hydrogen production device (100) are not particularly limited as long as it can accommodate the first reduced iron inside and provide a space where the first reduced iron and the first gas can come into contact. The first hydrogen production device (100) may be any one of a fluidized bed reactor, a fixed bed reactor, a moving bed reactor, a rotary kiln reactor, a batch reactor, a rotary reactor, and a reactor of a combination thereof.

[0035] According to exemplary embodiments, the temperature of the first hydrogen production device (100) can be controlled to 700 to 950°C. For the thermal decomposition of methane, a sufficient supply of thermal energy from the outside is required. If the temperature of the first hydrogen production device (100) is less than 700°C, the hydrogen production efficiency may decrease. If the temperature of the first hydrogen production device (100) exceeds 950°C, excessive energy is consumed to achieve and maintain the temperature of the first hydrogen production device (100), and thus the energy efficiency may decrease.

[0036] The first gas is a gas mainly containing methane and is a raw gas used to produce hydrogen in the first hydrogen production device (100). The content of methane in the first gas is not particularly limited. As a non-limiting example, the content of methane in the first gas may be 70 to 100% in volume%. As a remainder, the first gas may further include a hydrocarbon composed of carbon and hydrogen (CnHm, where n and m are integers of 2 or more), and natural gas. More preferably in terms of hydrogen production efficiency, the first gas may be composed of methane, but the present invention is not necessarily limited thereto.

[0037] Iron (I) is a metal that acts as a catalyst in the methane decomposition reaction. Generally, precious metals such as ruthenium (Ru) or nickel (Ni) have been used as catalysts for the thermal decomposition of methane. While these materials exhibit high catalytic activity, they are expensive and have limited reserves. Furthermore, the mining and extraction processes generate large amounts of carbon dioxide, resulting in a relatively high Global Warming Potential (GWP). In contrast, iron (Fe) is cheaper than precious metals or nickel catalysts, has abundant reserves, and possesses a low GWP. Therefore, there is a need to utilize iron as a catalyst for hydrogen production.

[0038] According to exemplary embodiments, the first reduced iron may be derived from a steelmaking process. More specifically, the first reduced iron may be derived from one or more of a fluidized bed reduction furnace, a shaft furnace, a rotary kiln, a fixed-bed reactor, a moving-bed reactor, and a combination thereof. These facilities can provide reduced iron by reducing the iron oxide of iron ore in a high-temperature reducing gas atmosphere. Thus, the first reduced iron derived from these facilities (steelmaking process) may contain high-temperature thermal energy. According to exemplary embodiments, the temperature of the first reduced iron may be 500 to 1100°C. By utilizing the first reduced iron at such a high temperature as a catalyst for the methane thermal decomposition reaction, the methane thermal decomposition efficiency can be increased. Additionally, the thermal energy of the first reduced iron itself can be utilized as a heat source to raise the temperature of the first hydrogen production device (100), thereby increasing energy efficiency.

[0039] During the decomposition process of methane, carbonization may occur on the surface or within the crystal lattice of some of the first reduced iron to form a second reduced iron. The second reduced iron is the first reduced iron containing carbon, and may have substantially the same composition as the first reduced iron except for the carbon content. The second reduced iron may be provided to the second hydrogen production device (200) together with the first reduced iron. In this case, or, the second reduced iron may be separated from the first reduced iron and provided to the second hydrogen production device (200). The method of separating the first reduced iron and the second reduced iron is not particularly limited, but as a non-limiting example, it may be performed in various ways such as magnetic separation, flotation, and size separation.

[0040] The second reduced iron may contain, in weight percent, carbon: 3 to 40%, the remainder being Fe and unavoidable impurities.

[0041] Carbon can increase the hardness and strength of the second reduced iron, and in particular, carbon in the form of Fe3C provided on the surface of the second reduced iron can contribute to the ammonia decomposition reaction as a catalyst. If the carbon content is excessively high, it can increase the brittleness of the second reduced iron and degrade catalytic performance by transforming the crystal structure of the second reduced iron in high-temperature environments.

[0042] According to exemplary embodiments, the temperature of the second reduced iron may be 700 to 950°C. More specifically, the temperature of the second reduced iron may be substantially the same as the maintenance temperature in the first hydrogen production device (100). In this way, the thermal energy from the preceding process can be utilized in the subsequent process through the second reduced iron, thereby further improving the energy efficiency of the hydrogen production system (10).

[0043] According to exemplary embodiments, the second hydrogen production device (200) is configured to provide hydrogen and a third reduced iron by contacting the second gas containing ammonia with the second reduced iron. At this time, the decomposition reaction of the ammonia may follow the following reaction equation 2. In this way, the hydrogen production system (10) can increase the hydrogen production efficiency by producing hydrogen using various raw materials from a single catalyst stream.

[0044] [Reaction Equation 2]

[0045] NH3 → 0.5N2 + 1.5H2

[0046] The structure and type of the second hydrogen production device (200) are not particularly limited, provided that it can accommodate the second reduced iron inside and provide a space for the second reduced iron and the second gas to come into contact. The second hydrogen production device (200) may be any one of a fluidized bed reactor, a moving bed reactor, a fixed bed reactor, a rotary kiln reactor, a batch reactor, a rotary reactor, and a reactor of a combination thereof.

[0047] According to exemplary embodiments, the temperature of the second hydrogen production device (200) can be controlled to 600 to 800°C. More specifically, the temperature of the second hydrogen production device (200) may be lower than the temperature of the second reduced iron provided by the first hydrogen production device (100). As a result, ammonia can be decomposed using the natural heat of the second reduced iron without separate heating. If the temperature of the second hydrogen production device (200) is excessively low, it may be difficult to secure sufficient ammonia decomposition efficiency. If the temperature of the second hydrogen production device (200) is excessively high, problems with equipment stability may occur, and a large amount of energy is required to maintain the temperature, which may reduce hydrogen production efficiency.

[0048] The second gas is a gas mainly containing ammonia and is a raw gas used to produce hydrogen in the second hydrogen production device (200). The content of ammonia in the second gas is not particularly limited. As a non-limiting example, the content of ammonia in the second gas may be 70 to 100% in volume%. As a remainder, the second gas may further contain impurities (e.g., nitrogen, moisture, etc.) generated during the ammonia production, storage, and transport processes. More preferably in terms of hydrogen production efficiency, the second gas may consist of ammonia, but the present invention is not necessarily limited thereto.

[0049] During the ammonia decomposition process, nitridation may occur on the surface or within the crystal lattice of some of the second reduced iron, thereby forming third reduced iron. At this time, the iron carbide (Fe3C) of the second reduced iron may be nitrided and replaced with iron nitride (e.g., Fe4N), or the iron (Fe) within the second reduced iron may be directly nitrided to form iron nitride. In this way, the third reduced iron is a second reduced iron in which some carbon is replaced with nitrogen or nitrogen is dissolved, and may have a composition substantially identical to that of the second reduced iron, except for the content of carbon and nitrogen.

[0050] According to exemplary embodiments, an electric melting furnace configured to produce molten iron using a third reduced iron may be further included. In this case, a second reduced iron that is not nitrided may also be provided and utilized as a raw material for producing molten iron. Therefore, when these are used as raw materials for steelmaking, the energy efficiency of the steel manufacturing process can be increased.

[0051] According to exemplary embodiments, hydrogen produced in the first hydrogen production device (100) and the second hydrogen production device (200) can be provided to create a reducing atmosphere in the steelmaking process. As a result, the hydrogen production system (10) can be linked with the steelmaking process to increase the efficiency of the steelmaking process.

[0052] According to exemplary embodiments, the control unit (300) may be configured to determine the total hydrogen production volume or the temperature of the first reduced iron based on the energy consumption efficiency in the first hydrogen production device (100) and the second hydrogen production device (200). The energy consumption efficiency can be determined based on the energy (kWh) consumed to produce 1 kg of hydrogen. More specifically, the energy consumed to produce 1 kg of hydrogen can be determined based on the value converted into the amount of CO2 generated per unit of electricity. If the energy consumption efficiency of the hydrogen production system (10) is higher than 8 kWh / kg-H2, it can be determined that the energy consumption efficiency has decreased. In this way, by controlling the hydrogen production system (10) based on the energy consumption efficiency, the amount of carbon dioxide generated during the energy supply and demand stage can be reduced. As a result, an environmentally friendly hydrogen production system (10) can be provided.

[0053] According to exemplary embodiments, the control unit (300) can improve energy consumption efficiency by reducing the total hydrogen production amount when energy consumption efficiency decreases. The total hydrogen production amount refers to the total amount of hydrogen produced in the first hydrogen production device (100) and the second hydrogen production device (200). The total hydrogen production amount can be controlled by controlling one or more of the first gas amount supplied to the first hydrogen production device (100), the contact time between the first gas and the second reduced iron, and the second gas amount supplied to the second hydrogen production device (200). In this way, energy consumption efficiency can be increased by reducing the total hydrogen production amount.

[0054] According to exemplary embodiments, the control unit (300) may increase the temperature of the first reduced iron when energy efficiency decreases. In this case, the first reduced iron may be derived from a steelmaking process. The temperature of the first reduced iron can be controlled by controlling the DRI time transferred from the steelmaking process to the first hydrogen production device (100). Additionally, the temperature of the first reduced iron can be controlled by controlling the temperature of the steelmaking process. Furthermore, in this case, the control unit (300) may increase the total hydrogen production. As a result, energy consumption efficiency can be improved while hydrogen production efficiency can be increased.

[0055] As a non-limiting example, the control unit (300) may be a programmable logic controller (PLC) device configured to collect energy consumption efficiency data of the hydrogen production system (100) and to control the hydrogen production efficiency of each process facility and the temperature of the first reduced iron. The control unit (300) may be connected to the first hydrogen production device (100) and the second hydrogen production device (200) via wired or wireless connection to exchange relevant data. Furthermore, the control unit (300) may be connected to the preceding steelmaking process via wired or wireless connection.

[0056] [Hydrogen Production Methods]

[0057] According to exemplary embodiments, the method comprises the steps of determining the total hydrogen production amount or the temperature of the first reduced iron based on energy consumption efficiency; contacting the first reduced iron with a first gas containing methane (CH4) to provide hydrogen, a carbon material, and a second reduced iron; and contacting the second reduced iron with a second gas containing ammonia to provide hydrogen and a third reduced iron. As a result, the energy efficiency of hydrogen production can be increased, and hydrogen can be produced from various raw materials using a single catalyst in the hydrogen production stream.

[0058] The step of determining the total hydrogen production amount or the temperature of the first reduced iron based on energy consumption efficiency may refer to the description of the control unit (300) described above. If the energy consumption efficiency decreases, the total hydrogen production amount may be lowered. Alternatively, the temperature of the first reduced iron may be increased. In this case, the total hydrogen production amount may also be increased. As a result, energy efficiency can be improved.

[0059] For the first hydrogen production step, refer to the description of the first hydrogen production device (100). The first hydrogen production step can be performed at 700 to 950°C.

[0060] According to exemplary embodiments, the temperature of the first reduced iron may be 500 to 1100°C. As a result, hydrogen can be produced using the natural heat of the first reduced iron. Alternatively, hydrogen can be produced by adding a small amount of energy. The first reduced iron may be derived from an ironmaking process.

[0061] For the second hydrogen production step, refer to the description of the second hydrogen production device (200). The second hydrogen production step can be performed at 600 to 800°C. Hydrogen can be produced using the thermal energy of the second reduced iron, and the second reduced iron can be appropriately cooled.

[0062] In addition, regarding matters that overlap with the hydrogen production system (10) described above, the same can be applied to the hydrogen production method, so a detailed explanation is omitted.

[0063] In addition, the two processes described above as the methane and ammonia decomposition processes, respectively, may be performed substantially simultaneously or proceed in the reverse order of the described order.

[0064] [Test Example]

[0065] (Process Configuration 1)

[0066] A process configuration was assumed in which a first hydrogen production device and a second hydrogen production device are linked. At this time, it was assumed that a first reduced iron of approximately 750°C is provided from the steelmaking process.

[0067] (Process Configuration 2)

[0068] A process configuration was assumed to produce hydrogen solely through the process of thermally decomposing methane at approximately 1000°C.

[0069] (Process Configuration 3)

[0070] A process configuration was assumed to produce hydrogen solely through a process of decomposing ammonia at approximately 600°C.

[0071] To calculate energy consumption efficiency, the CO2 generation per kWh was assumed to be 0.4666 kg. The conversion rate of each raw material (methane and ammonia) in each process was assumed to be 100%. The energy consumed in each process was calculated as the sum of the energy consumed to heat the raw materials to the target temperature and the energy required for the decomposition reaction.

[0072] Assuming a total hydrogen production of approximately 240 kg-H2 / hr, the energy consumption efficiency of each process configuration was calculated and is shown in Table 1.

[0073] Classification Process Configuration 1 Process Configuration 2 Process Configuration 3 Raw Material Heating Energy (kWh) 4.2 4.6 4.7 Reaction Energy (kWh) 5.8 5.7 6.3 Iron Novel Reduction Cooling Energy (kWh) -2.5 -- Total Energy (kWh / kg-H2) 7.5 10.3 11 CO2 Generation (kg-CO2 / kg-H2) 3.5 4.8 5.1

[0074] As such, it can be seen that in the case of process configuration 1 proposed in the present invention, the thermal energy of the first reduced iron can be utilized, resulting in excellent energy consumption efficiency. In contrast, it can be seen that in the case of process configurations 2 and 3, which cannot utilize the thermal energy of the first reduced iron, the energy consumption efficiency is low.

[0075] Subsequently, based on process configuration 1, the energy consumption efficiency was calculated by controlling the total hydrogen production and the temperature of the first reduced iron and is shown in Table 2 below.

[0076] (Process Configuration 4)

[0077] Except for changing the total hydrogen production to 200 kg-H2 / hr, the process was assumed to be the same as process configuration 1.

[0078] (Process Configuration 5)

[0079] Except for changing the temperature of the first reduced iron to 850℃ and the total hydrogen production to 350kg-H2 / hr, the process was assumed to be the same as process configuration 1.

[0080] Classification Process Configuration 4 Process Configuration 5 Raw Material Heating Energy (kWh) 4.4 3.3 Reaction Energy (kWh) 5.8 6.6 Iron-No. 1 Reduced Cooling Energy (kWh) -3 4.4 Total Energy (kWh / kg-H2) 7.2 5.5 CO2 Generation (kg-CO2 / kg-H2) 3.4 2.6

[0081] In this way, it was confirmed that energy consumption efficiency can be further improved by controlling the total hydrogen production and the temperature of the first reduced iron.

[0082] Although the invention has been described with reference to the above embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as described in the following claims.

[0083] (Explanation of symbols)

[0084] 10: Hydrogen Production System

[0085] 100: First hydrogen production unit

[0086] 200: Second hydrogen production unit

[0087] 300: Control unit

Claims

1. A first hydrogen production device configured to provide hydrogen, a carbon material, and a second reduced iron by contacting a first gas containing methane (CH4) with a first reduced iron; A second hydrogen production device configured to provide hydrogen and a third reduced iron by contacting a second gas containing ammonia with the second reduced iron; and A hydrogen production system comprising: a control unit configured to determine the total hydrogen production amount or the temperature of the first reduced iron based on the energy consumption efficiency in the first hydrogen production device and the second hydrogen production device.

2. In Paragraph 1, The above control unit is a hydrogen production system that reduces the total hydrogen production when the energy consumption efficiency decreases.

3. In Paragraph 1, The above control unit is a hydrogen production system that increases the temperature of the first reduced iron when the energy consumption efficiency decreases.

4. In Paragraph 3, The above control unit is a hydrogen production system that increases the total hydrogen production amount.

5. In Paragraph 1, A hydrogen production system in which the temperature of the first hydrogen production device is controlled to 700~950℃.

6. In Paragraph 1, A hydrogen production system in which the temperature of the second hydrogen production device is controlled to 600~800℃.

7. In Paragraph 1, The above-mentioned second reduced iron is a hydrogen production system comprising, in weight %, carbon: 3~40%, the remainder Fe and unavoidable impurities.

8. A step of determining the total hydrogen production or the temperature of the first reduced iron based on energy consumption efficiency: A step of contacting a first gas containing methane (CH4) with the first reduced iron to provide hydrogen, a carbon material, and a second reduced iron; and A method for producing hydrogen comprising the step of contacting a second gas containing ammonia with the second reduced iron to provide hydrogen and a third reduced iron.

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