Plasma-catalyst hybrid hydrogen extraction system

Abstract

Disclosed is a plasma-catalyst hybrid hydrogen extraction system. The plasma-catalyst hybrid hydrogen extraction system of the present invention comprises: a plasma reformer for receiving a feed gas containing biogas to heat the feed gas to a catalytic activation temperature by plasma conversion; a catalyst reformer provided with a catalyst for the catalytic activation temperature, the catalyst reformer receiving the feed gas, heated by the plasma reformer, to generate a synthetic gas containing hydrogen by a reforming reaction; and a pressure swing adsorption (PSA) unit for recovering hydrogen from the synthetic gas generated by the catalyst reformer, wherein the plasma reformer is a direct current (DC) rotating arc plasma device, which receives the feed gas by circulation of the feed gas between a cathode and an anode that are arranged in parallel.

Description

Plasma Catalytic Hybrid Hydrogen Extraction System

[0001] The present invention relates to a plasma catalytic hybrid hydrogen extraction system, and more particularly, to a plasma catalytic hybrid hydrogen extraction system capable of directly reforming biogas to produce hydrogen without a separate methane refinement process by heating biogas to a catalytic activation temperature by plasma formation in a plasma reformer and producing synthesis gas including hydrogen through a reforming reaction in the catalytic reformer.

[0002] As global warming worsens, efforts are being made worldwide to reduce greenhouse gas emissions, and as the 1997 Kyoto Protocol, which obligated developed countries to reduce greenhouse gases, expires in 2020, the 195 parties to the Paris Climate Change Accord, which was adopted at the 21st United Nations Framework Convention on Climate Change held in Paris, France in December 2015 and entered into force in November 2016, are making various efforts with the goal of reducing greenhouse gases.

[0003] Along with this global trend, interest in renewable energy sources such as wind, solar, solar thermal, bioenergy, tidal, and geothermal energy is increasing as clean energy sources that can replace fossil fuels and nuclear power.

[0004] Among them, bioenergy can be used in various ways, such as for heating fuel, automobile fuel, and power generation fuel, and examples include biogas, bioethanol, biodiesel, methanol, and hydrogen, depending on the purpose and form.

[0005] Biogas is a general term for gases produced through biological reactions and usable as fuel. It includes gases produced naturally from organic matter or waste, as well as gases manufactured artificially. Biogas is primarily composed of methane (CH4) and carbon dioxide (CO2).

[0006] As interest in hydrogen fuel as a clean energy source that does not emit carbon dioxide grows, research into hydrogen production methods using biogas is actively underway. Hydrogen extraction methods using biogas include dry reforming and wet reforming.

[0007] Figure 1 schematically illustrates a conventional hydrogen extraction system that extracts hydrogen from biogas using a wet reforming reaction.

[0008] As illustrated in Figure 1, biogas containing methane and carbon dioxide undergoes a purification process in a purification facility. Biogas contains approximately 40 to 80% CH4 and 20 to 60% CO2. However, since a high concentration of unreacted CO2 in a catalytic reformer results in significant heat energy loss, a purification process is used to produce bio-CH4 containing over 95% methane, which is then supplied to the catalytic reformer.

[0009] To maintain the catalytic activity temperature in the catalytic reformer, some of the high-quality biomethane is combusted in a burner to supply heat to the catalytic reformer, where it is converted into synthesis gas containing hydrogen through a hydrogen production reaction under a catalyst.

[0010] Hydrogen is recovered from synthesis gas through the PSA process and off-gas including methane and carbon dioxide is discharged.

[0011] In such hydrogen extraction systems, the CH4 oxidization process requires high pressure, resulting in high process and equipment maintenance costs and CO2 emissions. Furthermore, a significant amount of CO2 is generated when a portion of the oxidized bio-CH4 is burned in a burner to achieve the desired catalytic activity temperature in the catalytic reformer.

[0012] The present invention aims to solve these problems by proposing a system that can produce a large amount of hydrogen while reducing process costs and reducing carbon dioxide emissions without using fossil fuels.

[0013] According to one aspect of the present invention for solving the above-described problem, there is provided a plasma reformer that receives a feed gas and heats it to a catalytic activation temperature by plasma generation;

[0014] A catalytic reformer that is provided with a catalyst having the above catalytic activity temperature and receives the feed gas heated in the plasma reformer to produce a synthesis gas containing hydrogen through a reforming reaction; and

[0015] It includes a PSA (Pressure Swing Adsorption) unit that recovers hydrogen from the synthesis gas generated in the above catalytic reformer.

[0016] A plasma catalytic hybrid hydrogen extraction system is provided, characterized in that the plasma reformer is a DC rotating arc plasma device that receives the feed gas by rotating it between a cathode and an anode arranged in parallel.

[0017] Preferably, the feed gas may be a gas mixed with biogas and steam, including methane and carbon dioxide.

[0018] Preferably, the plasma reformer comprises: an annular anode; a cathode having one end of a flat shape spaced apart and parallel to the anode; and an annular insulator arranged to surround the outer side of the cathode, wherein the diameter of one end of the cathode may be set to be smaller than the outer diameter of the anode.

[0019] Preferably, the feed gas is supplied by swirling into the space between the cathode and the anode, and then ionized by plasma and gathers toward the center of the cathode along the flat cross-section, thereby reducing the gas resistance in the central portion of the cathode and forming an arc point by swirling over a wide area in the center of one end of the flat cathode.

[0020] Preferably, the method may further include a carbon capture unit that captures carbon dioxide by receiving off-gas discharged after hydrogen recovery through the PSA unit.

[0021] Preferably, the method may further include a pretreatment process unit for removing impurities such as hydrogen sulfide, ammonia, and siloxane from biogas and supplying the removed impurities to the plasma reformer.

[0022] The present invention does not require a high-quality facility, so the installation and maintenance costs of the facility can be reduced, and carbon-free operation is possible because a burner is not used, so carbon dioxide emissions can be reduced, and the system configuration can be simplified.

[0023] Additionally, it can produce more hydrogen per unit of biogas than conventional systems, and by providing a flat cathode in the plasma reformer, ionized gas is gathered in the center of the cathode, and the arc point is formed by circulating around a wide area in the center of the cathode, which increases durability against electrode wear.

[0024] Figure 1 schematically illustrates a conventional hydrogen extraction system that extracts hydrogen from biogas using a wet reforming reaction.

[0025] FIG. 2 schematically illustrates a plasma catalytic hybrid hydrogen extraction system according to one embodiment of the present invention.

[0026] FIG. 3 schematically illustrates the structure of a plasma reformer in a plasma catalyst hybrid hydrogen extraction system according to one embodiment of the present invention.

[0027] In order to fully understand the operational advantages of the present invention and the purpose achieved by the practice of the present invention, reference should be made to the attached drawings illustrating preferred embodiments of the present invention and the contents described in the attached drawings.

[0028] Hereinafter, the configuration and operation of a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. Here, when adding reference symbols to components in each drawing, it should be noted that identical components are indicated with the same symbols as much as possible even if they are shown in different drawings.

[0029]

[0030] FIG. 2 schematically illustrates a plasma catalytic hybrid hydrogen extraction system according to one embodiment of the present invention. FIG. 3 schematically illustrates a plasma reformer structure in a plasma catalytic hybrid hydrogen extraction system according to one embodiment of the present invention.

[0031] As illustrated in FIG. 2, the plasma catalytic hybrid hydrogen extraction system of the present embodiment is a system that extracts hydrogen from biogas through a plasma reformer that receives feed gas including biogas and heats it to a catalytic activation temperature by plasma generation, a catalytic reformer that is provided with a catalyst at the catalytic activation temperature and receives feed gas heated in the plasma reformer and generates a synthesis gas including hydrogen through a reforming reaction, and a PSA (Pressure Swing Adsorption) unit that recovers hydrogen from the synthesis gas generated in the catalytic reformer.

[0032] Before being supplied to the plasma reformer, biogas passes through a pretreatment process to remove impurities such as hydrogen sulfide, ammonia, and siloxane.

[0033] Biogas containing methane and carbon dioxide, from which impurities have been removed through a pretreatment process, is mixed with steam without going through a separate purification process, and the feed gas, which is a mixture of biogas and steam, is supplied to the plasma reformer.

[0034] As illustrated in FIG. 3, the plasma reformer (100) is provided as a DC rotating arc plasma device that receives feed gas by rotating it between a cathode and an anode arranged in parallel, and includes an annular anode (120), a cathode (110) having one end of a flat shape spaced apart from the anode and arranged in parallel, and an annular insulator (130) arranged to surround the outside of the cathode. The plasma reformer may be provided with a plurality of electrodes including an anode, a cathode, and an insulator.

[0035] The diameter of one end of the cathode (110) parallel to the anode (120) may be provided to be smaller than the outer diameter of the anode and equal to or similar to the inner diameter of the anode. The annular insulator (130) surrounds the outer side of the cathode, and one end of the insulator is joined to one flat end of the cathode without a step, so that one end of the cathode and one end of the insulator form a flat circular cross-section, and a space is formed between the circular cross-section and the anode.

[0036] The feed gas is supplied by swirling into the space between the cathode and anode.

[0037] Direct current (DC) is applied to the plasma reformer, and feed gas is swirled and supplied to the separation space. The feed gas, swirled into the separation space between the cathode and anode, is converted to plasma by the arc discharge, decomposing some of the biogas into synthesis gas.

[0038] However, plasma devices using arc discharge have a problem in that the electrode life is short due to electrode wear caused by the high temperature generated during discharge.

[0039] However, in the plasma reformer of this embodiment, the initial discharge starts between the cathode tip and the anode, indicated by A in Fig. 3. However, due to the flat cathode structure, ionized gas gathers along the flat cross-section toward the central portion of the cathode, reducing the gas resistance in the central portion. Consequently, the arc point in the plasma reformer forms by circulating over a wide area of ​​the central portion of the cathode, thereby enhancing durability against electrode wear.

[0040] Feed gas heated to the catalytic activation temperature by plasma treatment is supplied to a catalytic reformer, where a synthesis gas containing hydrogen is generated through a reforming reaction under a reforming catalyst.

[0041] Synthetic gas generated from the catalytic reformer is supplied to a pressure swing adsorption (PSA) unit, where hydrogen is adsorbed and recovered through an adsorption process. The system of this embodiment can increase hydrogen production per unit of biogas compared to conventional systems.

[0042] The off-gas emitted after hydrogen recovery through the PSA unit includes methane, unrecovered hydrogen, carbon monoxide, and carbon dioxide. Carbon dioxide emissions can be reduced by capturing carbon dioxide in the off-gas through a carbon capture unit downstream of the PSA unit. In conventional systems, carbon dioxide is also emitted from the purification equipment, burner, etc., so at least three carbon capture systems had to be configured to reduce carbon dioxide emissions, which was problematic because the process was complicated. However, this system does not require purification equipment or burners, enables carbon-free operation, and only requires one carbon capture unit on the off-gas exhaust side after hydrogen recovery in the PSA unit, making it easy to reduce carbon dioxide emissions, simplifying the entire process and reducing costs.

[0043]

[0044] It is obvious to a person skilled in the art that the present invention is not limited to the above embodiments, and that various modifications or changes can be made without departing from the technical spirit of the present invention.

Claims

1. A plasma reformer that receives feed gas containing biogas and heats it to a catalytic activation temperature through plasma generation; A catalytic reformer that is provided with a catalyst having the above catalytic activity temperature and receives the feed gas heated in the plasma reformer to produce a synthesis gas containing hydrogen through a reforming reaction; and It includes a PSA (Pressure Swing Adsorption) unit that recovers hydrogen from the synthesis gas generated in the above catalytic reformer. A plasma catalytic hybrid hydrogen extraction system characterized in that the plasma reformer is a DC rotating arc plasma device that receives the feed gas by rotating it between a cathode and an anode arranged in parallel.

2. In paragraph 1, A plasma catalytic hybrid hydrogen extraction system characterized in that the feed gas is a gas mixed with biogas and steam, including methane and carbon dioxide.

3. In the second paragraph, the plasma reformer, annular anode; A cathode having one end of a flat shape spaced apart from the anode in a parallel manner; and A ring-shaped insulator is provided to surround the outer side of the above cathode, A plasma catalyst hybrid hydrogen extraction system, characterized in that the diameter of one end of the cathode is set smaller than the outer diameter of the anode.

4. In paragraph 3, A plasma catalytic hybrid hydrogen extraction system characterized in that the feed gas is supplied by swirling into the space between the cathode and the anode, and then is ionized by plasma and gathers toward the center of the cathode along the flat cross-section, thereby reducing the gas resistance in the central portion of the cathode and forming an arc point by swirling around a wide area in the center of one end of the flat cathode.

5. In paragraph 4, A plasma catalyst hybrid hydrogen extraction system further comprising a carbon capture unit that captures carbon dioxide by receiving off-gas discharged after hydrogen recovery through the above PSA unit.

6. In any one of paragraphs 1 to 5, A plasma catalytic hybrid hydrogen extraction system further comprising a pretreatment process unit for removing impurities such as hydrogen sulfide, ammonia, and siloxane from biogas and supplying the removed impurities to the plasma reformer.

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