Solid oxide fuel cell recirculation system

Abstract

A solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to one embodiment of the present invention comprises: a solid oxide fuel cell which receives ammonia and air to generate electricity through an electrochemical reaction, and discharges a reaction product containing nitrogen, hydrogen, and water vapor, and exhaust gas having reduced oxygen concentration; an ammonia supply unit for supplying the ammonia to the solid oxide fuel cell; an air supply unit for supplying the air to the solid oxide fuel cell; and an electrochemical hydrogen pump for separating only the hydrogen from the reaction product of the solid oxide fuel cell and resupplying the separated hydrogen to the solid oxide fuel cell.

Description

Solid oxide fuel cell recirculation system

[0001] The present invention relates to a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump that uses a proton exchange membrane and operates at a temperature of 100°C or lower, and more specifically, to a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump that separates only hydrogen from a mixed gas of nitrogen and hydrogen produced by decomposing ammonia and selectively recirculates the separated hydrogen, thereby improving the overall efficiency of the system and the concentration of hydrogen in the fuel.

[0002] Recently, research into the production of eco-friendly hydrogen fuel, which produces energy using hydrogen gas, has been increasing.

[0003] While conventional energy sources such as coal and oil contain carbon dioxide, hydrogen gas contains no carbon dioxide at all and is mostly converted to water, so no unnecessary byproducts are created after it is used as an energy source.

[0004] In addition, since hydrogen gas can generate a large amount of energy when converted to water, there is increasing interest in related technologies as it is an environmentally friendly and ideal energy source.

[0005] Meanwhile, among the methods of producing hydrogen gas to use hydrogen as an energy source, a method of using ammonia (NH3) as a hydrogen carrier is attracting attention.

[0006] The solid oxide fuel cell (SOFC) system, one of the various fuel cell systems for using ammonia as fuel for hydrogen, operates in a high temperature range of over 600℃ and is known to have the highest efficiency among various fuel cell systems. Since it can generate power with various fuels such as H2, CH4, CO, and NH series, a lot of research has been conducted recently.

[0007] In general, solid oxide fuel cell systems are structured to have a maximum fuel utilization rate of about 80%, and the remaining 20% ​​or so of fuel is discarded without reacting. When producing hydrogen from ammonia using a solid oxide fuel cell system, the maximum utilization rate is lower than 80%, so in order to improve the efficiency of the system, a structure is required to recirculate the fuel that is discharged without reacting.

[0008] To this end, conventional solid oxide fuel cell systems use a blower to recirculate unreacted fuel that is discharged to produce hydrogen from ammonia.

[0009] However, the method of recirculating fuel using a blower has problems such as low fuel efficiency, as it is difficult to determine the amount of fuel recirculation, and nitrogen and hydrogen cannot be separated, so nitrogen, which is an unnecessary reaction product, is recirculated and reacts with hydrogen, resulting in a decrease in hydrogen yield and a decrease in hydrogen concentration.

[0010] In addition, there is a problem that nitrogen is recirculated with hydrogen, which increases the flow rate in the fuel-flowing pipeline, increases the differential pressure, dilutes the concentration of hydrogen, lowers the performance of the solid oxide fuel cell, and thus reduces the efficiency of the entire system.

[0011] Accordingly, there is a need for a method to prevent unnecessary recirculation of nitrogen and consequent increase in differential pressure in the pipeline, and to improve fuel efficiency by separating hydrogen from nitrogen and then recirculating only the separated hydrogen.

[0012] Based on the technical background described above, the present invention uses a proton exchange membrane in a solid oxide fuel cell system and applies an electrochemical hydrogen pump (EHP) that operates at a temperature of 100°C or lower to separate only hydrogen from a mixture of nitrogen and hydrogen gas generated by decomposing ammonia, and selectively recirculates the separated hydrogen to reduce a differential pressure that may occur in a pipeline due to nitrogen generated unnecessarily, and to increase the concentration of hydrogen in the fuel, thereby increasing the overall efficiency, and provides a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump.

[0013] A solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to one embodiment of the present invention may include: a solid oxide fuel cell that receives ammonia and air and converts them into a reaction product and exhaust gas including nitrogen, hydrogen, and water vapor; an ammonia supply unit that supplies the ammonia to the solid oxide fuel cell; an air supply unit that supplies the air to the solid oxide fuel cell; and an electrochemical hydrogen pump that separates only hydrogen from the reaction product of the solid oxide fuel cell and resupplies the hydrogen to the solid oxide fuel cell.

[0014] As described above, according to the present invention, by applying an electrochemical hydrogen pump (EHP) to a solid oxide fuel cell system, hydrogen is separated from a mixed gas of nitrogen and hydrogen, and only the separated hydrogen is selectively recycled to improve the concentration of hydrogen, and an increase in differential pressure due to unnecessary circulation of nitrogen is prevented, thereby reducing heat exchange loss, thereby improving the capacity of the solid oxide fuel cell and increasing the overall efficiency of the solid oxide fuel cell system.

[0015] FIG. 1 is a schematic diagram showing a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a first embodiment of the present invention.

[0016] FIG. 2 is a schematic diagram showing a process of separating hydrogen from ammonia exhaust gas mixed with nitrogen and hydrogen in a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a first embodiment of the present invention.

[0017] Figure 3 is a schematic diagram showing a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a second embodiment of the present invention.

[0018] FIG. 4 is a schematic diagram showing a process in which external air is introduced into a heating section and heated, and then the heated air is mixed with exhaust gas discharged from a solid oxide fuel cell and heat is exchanged in an air heat exchanger in a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a second embodiment of the present invention.

[0019] Figure 5 is a schematic diagram showing a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a third embodiment of the present invention.

[0020] FIG. 6 is a schematic diagram showing a process in which nitrogen or nitrogen and hydrogen discharged from an electrochemical hydrogen pump are introduced into a heating section and heated, and then the heated nitrogen or nitrogen and hydrogen are mixed with exhaust gas discharged from a solid oxide fuel cell and heat is exchanged in an air heat exchanger in a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a third embodiment of the present invention.

[0021] Figure 7 is a schematic diagram showing a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a fourth embodiment of the present invention.

[0022] FIG. 8 is a schematic diagram showing a process in which, in a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a fourth embodiment of the present invention, external air and nitrogen or nitrogen and hydrogen discharged from an electrochemical hydrogen pump are introduced into a heating section, mixed and heated, and then the heated mixed gas is mixed with exhaust gas discharged from a solid oxide fuel cell and heat is exchanged in an air heat exchanger.

[0023] A solid oxide fuel cell recirculation system according to one embodiment of the present invention may include a solid oxide fuel cell that receives ammonia and air, generates electricity through an electrochemical reaction, and discharges a reaction product including nitrogen, hydrogen, and water vapor and an exhaust gas that is air with a reduced oxygen concentration; an ammonia supply unit that supplies the ammonia to the solid oxide fuel cell cell; an air supply unit that supplies the air to the solid oxide fuel cell cell; and an electrochemical hydrogen pump that separates only hydrogen from the reaction product of the solid oxide fuel cell cell and resupplies the hydrogen to the solid oxide fuel cell cell.

[0024] In the present embodiment, the solid oxide fuel cell recirculation system may further include a fuel heat exchanger that heat-exchanges the high-temperature reaction product discharged after reaction in the solid oxide fuel cell with the ammonia supplied to the solid oxide fuel cell; an air heat exchanger that heat-exchanges the high-temperature exhaust gas discharged after reaction in the solid oxide fuel cell with the air supplied to the solid oxide fuel cell; and a condenser that condenses the reaction product heat-exchanged through the fuel heat exchanger.

[0025] In the present embodiment, the condensing unit may include a cooling heat exchanger that condenses the water vapor through heat exchange with the reaction product supplied through the fuel heat exchanger, and a drain unit that discharges the condensed water through the cooling heat exchanger to the outside.

[0026] In the present embodiment, the electrochemical hydrogen pump can separate hydrogen from a mixed gas containing nitrogen and hydrogen, and selectively mix the separated hydrogen with ammonia supplied from the ammonia supply unit to the fuel heat exchanger.

[0027] In this embodiment, the electrochemical hydrogen pump can control the amount of hydrogen separated from the mixed gas by controlling the current load.

[0028] In the present embodiment, the solid oxide fuel cell recirculation system may further include a heating unit that increases the temperature of the air supplied from the air supply unit.

[0029] In this embodiment, the heating unit may be either a burner or a catalytic converter.

[0030] In this embodiment, the heating unit can heat the exhaust gas discharged from the solid oxide fuel cell.

[0031] In this embodiment, the heating unit can heat the outside air by drawing in the outside air, and mix the heated outside air with the exhaust gas to heat the exhaust gas.

[0032] In this embodiment, the heating unit can receive the nitrogen from which the hydrogen has been removed from the electrochemical hydrogen pump.

[0033] In this embodiment, the ammonia supply unit may be provided with a fuel blower on one side for supplying the ammonia to the solid oxide fuel cell.

[0034] In this embodiment, the air supply unit may be provided with an air blower on one side for supplying the air to the solid oxide fuel cell.

[0035] In this embodiment, the electrochemical hydrogen pump can be operated at a temperature of 50°C to 100°C.

[0036] In the present embodiment, the solid oxide fuel cell recirculation system may further include a control unit that controls the operation of the solid oxide fuel cell, the ammonia supply unit, the air supply unit, and the electrochemical hydrogen pump.

[0037] In this embodiment, the control unit can control the amount of hydrogen separated by controlling the amount of current load applied to the electrochemical hydrogen pump.

[0038] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0039] The terminology used herein is merely used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In the present invention, it should be understood that the terms "comprise" or "have" are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0040] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Please note that, where possible, identical components are represented by identical reference numerals throughout the drawings. Furthermore, detailed descriptions of well-known functions and configurations that may obscure the gist of the present invention will be omitted. For the same reason, some components in the attached drawings are exaggerated, omitted, or schematically depicted.

[0041] Hereinafter, a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a first embodiment of the present invention will be described.

[0042] Fig. 1 is a schematic diagram showing a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a first embodiment of the present invention. Fig. 2 is a schematic diagram showing a process of separating hydrogen from ammonia exhaust gas mixed with nitrogen and hydrogen in a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a first embodiment of the present invention.

[0043] Referring to FIG. 1, a solid oxide fuel cell recirculation system (1a) using an electrochemical hydrogen pump according to the present invention may include an ammonia supply unit (10), an air supply unit (20), a solid oxide fuel cell (30), a fuel heat exchanger (40), an air heat exchanger (50), a condenser unit (60), an electrochemical hydrogen pump (70), a piping assembly (not shown), and a control unit (not shown).

[0044] The ammonia supply unit (10) is for supplying ammonia (NH3) as fuel to the solid oxide fuel cell (30), and can be provided at the front end of the solid oxide fuel cell recirculation system (1a) using the electrochemical hydrogen pump according to the present embodiment.

[0045] Here, a valve for supplying ammonia may be installed between the ammonia supply unit (10) and the solid oxide fuel cell (30). The ammonia supply unit (10) may be heated and / or pressurized, and accordingly, ammonia in the ammonia supply unit (10) may be supplied to or stopped from the solid oxide fuel cell (30) by the operation of the valve.

[0046] As an optional embodiment, a fuel blower (11) may be installed between the ammonia supply unit (10) and the solid oxide fuel cell (30) to supply ammonia from the ammonia supply unit (10) to the solid oxide fuel cell (30).

[0047] The air supply unit (20) is for supplying air to the solid oxide fuel cell (30), and can be provided at the front end of the solid oxide fuel cell recirculation system (1a) using the electrochemical hydrogen pump according to the present embodiment.

[0048] Here, the air supplied to the solid oxide fuel cell (30) through the air supply unit (20) refers to air and oxygen, and can react with ammonia supplied through the ammonia supply unit (10) in the solid oxide fuel cell (30) to generate reaction products such as nitrogen, hydrogen, water vapor, and exhaust gas.

[0049] A valve for controlling the air supply operation may be positioned between the air supply unit (20) and the solid oxide fuel cell cell (30). As an optional embodiment, an air blower (21) may be installed between the air supply unit (20) and the solid oxide fuel cell cell (30) to supply air from the air supply unit (20) to the solid oxide fuel cell cell (30).

[0050] A solid oxide fuel cell (SOFC: Solid Oxide Fuel Cell, 30) can receive ammonia and air as fuel from an ammonia supply unit (10) and an air supply unit (20) and generate electricity through an electrochemical reaction. In addition, the supplied ammonia generates nitrogen and hydrogen through reforming, and water vapor can be discharged through the electrochemical reaction of the solid oxide fuel cell (30). In addition, the air supplied from the air supply unit (20) has a reduced oxygen concentration and is discharged from the solid oxide fuel cell (30).

[0051] Hereinafter, nitrogen and hydrogen generated by reforming ammonia and water vapor generated by electrochemical reaction of a solid oxide fuel cell (30) are all referred to as reaction products, and air with reduced oxygen concentration discharged from a solid oxide fuel cell (30) is referred to as exhaust gas.

[0052] Here, the solid oxide fuel cell (30) has a general configuration, so it is briefly described below.

[0053] A solid oxide fuel cell (30) includes an ion conductive membrane (not shown) that allows oxygen ions to move, and an anode electrode (31) and a cathode electrode (33) provided on one side and the other side of the ion conductive membrane, and may be a stack in which the ion conductive membrane, the anode electrode (31), and the cathode electrode (33) are formed in layers.

[0054] Ammonia supplied from the ammonia supply unit (10) is reformed (decomposed) into hydrogen and nitrogen in the solid oxide fuel cell (30) stack, and the decomposed hydrogen can react with oxygen ions at the anode electrode (31) to generate electricity and water vapor.

[0055] Oxygen supplied from the air supply unit (20) moves from the cathode electrode (33) to the anode electrode (31) through the ion conducting membrane, and then reacts with hydrogen decomposed from ammonia to generate electricity and water vapor.

[0056] Meanwhile, the fuel heat exchanger (40) and the air heat exchanger (50) can recover heat from the high-temperature reaction products and exhaust gas generated through the solid oxide fuel cell (30) operating at high temperature.

[0057] The fuel heat exchanger (40) can be connected to the anode electrode (31) side of the solid oxide fuel cell (30), and the air heat exchanger (50) can be connected to the cathode electrode (33) side of the solid oxide fuel cell (30).

[0058] The fuel heat exchanger (40) can recover heat from reaction products such as nitrogen, hydrogen, and water vapor that are discharged after reaction in the solid oxide fuel cell (30) but whose temperature has increased due to the reaction.

[0059] Specifically, the fuel heat exchanger (40) can raise the temperature of ammonia supplied to the solid oxide fuel cell (30) to a predetermined level through heat exchange between the high-temperature reaction product discharged from the solid oxide fuel cell (30) and the ammonia supplied from the ammonia supply unit (10).

[0060] The fuel heat exchanger (40) may be provided between the ammonia supply unit (10) and the solid oxide fuel cell (30), but is not limited thereto.

[0061] The air heat exchanger (50) can recover heat from exhaust gas such as flue gas that is discharged after reaction in the solid oxide fuel cell (30) but whose temperature has increased due to the reaction.

[0062] Specifically, the air heat exchanger (50) can raise the air supplied to the solid oxide fuel cell (30) to a predetermined temperature through heat exchange between the high-temperature exhaust gas discharged from the solid oxide fuel cell (30) and the air supplied from the air supply unit (20).

[0063] An air heat exchanger (50) may be provided between the air supply unit (20) and the solid oxide fuel cell (30), but is not limited thereto.

[0064] The condenser (60) can condense the reaction products whose temperature has dropped after heat exchange through the fuel heat exchanger (40). Since the maximum fuel utilization rate of the solid oxide fuel cell (30) is approximately 80%, the reaction products including nitrogen, hydrogen, and water vapor discharged from the anode electrode (31) can be condensed, and the water generated by the condensation can be recovered and discharged, thereby increasing the partial pressure of hydrogen and nitrogen.

[0065] To this end, the condenser (60) may include a cooling heat exchanger (61) for cooling and condensing the reaction product, and a drainage section (63) for draining and discharging the condensed water through the cooling heat exchanger (61).

[0066] The cooling heat exchanger (60) can supply cold water having a predetermined temperature from the outside to lower the reaction product, which has been lowered to a predetermined temperature through the fuel heat exchanger (40), to a predetermined temperature again.

[0067] An electrochemical hydrogen pump (EHP: Electrochemical Hydrogen Compressor, 70) can separate and extract only hydrogen from various gas mixtures using electrochemical reactions.

[0068] The electrochemical hydrogen pump (70) can separate only hydrogen from the reaction product of the solid oxide fuel cell (30) and resupply it to the solid oxide fuel cell (30). Specifically, the electrochemical hydrogen pump (70) can separate only hydrogen from a mixed gas containing nitrogen and hydrogen by using a proton exchange membrane. Meanwhile, when the proton exchange membrane is wet with water, it can be conductive and have excellent performance. Therefore, the electrochemical hydrogen pump (70) can be driven at a temperature of 100°C or lower so that water does not vaporize under atmospheric pressure. However, when the operating temperature of the electrochemical hydrogen pump (70) drops below 50°C, the resistance to the movement of hydrogen ions increases, which may reduce the operating efficiency of the electrochemical hydrogen pump (70). Therefore, the operating temperature of the electrochemical hydrogen pump (70) may be 50°C or higher and 100°C or lower. However, under pressure, it can be operated at temperatures higher than 100°C as long as the water does not vaporize.

[0069] The electrochemical hydrogen pump (70) can pump and discharge only hydrogen from a mixed gas of nitrogen and hydrogen through a condenser (60) at low power.

[0070] Here, since the electrochemical hydrogen pump (70) is proportional to the applied current load and the pumping amount of hydrogen, a desired amount of hydrogen can be recycled by controlling the current load, and control can be easier than with a conventional blower (not shown).

[0071] In addition, an immediate response speed can be achieved by controlling the current load, so that the amount of hydrogen separated from a mixture of nitrogen and hydrogen can be quickly controlled.

[0072] Therefore, even if the differential pressure of the pipe changes due to the concentration of ammonia as fuel in the pipeline and nitrogen discharged from the electrochemical hydrogen pump (70), it is possible to easily recirculate a desired amount of hydrogen.

[0073] In this way, the electrochemical hydrogen pump (70) can selectively control the amount of hydrogen separated from a mixed gas of nitrogen and hydrogen by controlling the current load, and can also control the amount of hydrogen recirculation and the recirculation flow rate by controlling the current load.

[0074] The piping assembly may include an eleventh piping line (L11) connecting an ammonia supply unit (10) and a fuel heat exchanger (40), a twelfth piping line (L12) connecting the fuel heat exchanger (40) and a solid oxide fuel cell (30), a thirteenth piping line (L13) connecting the solid oxide fuel cell (30) and the fuel heat exchanger (40), a fourteenth piping line (L14) connecting the fuel heat exchanger (40) and a condenser (50), a fifteenth piping line (L15) connecting the condenser (60) and an electrochemical hydrogen pump (70), a sixteenth piping line (L16) connecting the electrochemical hydrogen pump (70) and the eleventh piping line (L11), and a seventeenth piping line (L17) connected to the electrochemical hydrogen pump (70) to discharge nitrogen.

[0075] Specifically, the 11th pipeline (L11) connects the ammonia supply unit (10) and the fuel heat exchanger (40), and can supply ammonia supplied as fuel from the ammonia supply unit (10) to the fuel heat exchanger (40).

[0076] The 12th pipeline (L12) can connect the fuel heat exchanger (40) and the solid oxide fuel cell (30).

[0077] The 13th pipeline (L13) connects the solid oxide fuel cell (30) and the fuel heat exchanger (40), and can supply the high-temperature reaction product containing nitrogen, hydrogen, and water vapor, which is discharged after reaction in the solid oxide fuel cell (30), to the fuel heat exchanger (40).

[0078] Accordingly, the high-temperature reaction product supplied from the solid oxide fuel cell (30) to the fuel heat exchanger (40) through the 13th pipeline line (L13) and the ammonia supplied from the ammonia supply unit (10) to the fuel heat exchanger (40) through the 11th pipeline line (L11) exchange heat with each other in the fuel heat exchanger (40), and the ammonia whose temperature has increased through the heat exchange can be supplied to the anode electrode (31) of the solid oxide fuel cell (30).

[0079] The 14th pipeline (L14) connects the fuel heat exchanger (40) and the condenser (60), and can supply the reaction product, whose temperature has dropped after heat exchange with ammonia in the fuel heat exchanger (40), to the condenser (60).

[0080] A cooling heat exchanger (61) and a drain section (63) of a condenser section (60) can be installed in the 14th pipeline (L14).

[0081] The 15th pipeline (L15) connects the condenser (60) and the electrochemical hydrogen pump (70), and can supply a mixed gas of nitrogen and hydrogen with moisture removed through the condenser (60) to the electrochemical hydrogen pump (70).

[0082] The 16th pipeline line (L16) connects the electrochemical hydrogen pump (70) and the 11th pipeline line (L11), and can supply hydrogen separated from the electrochemical hydrogen pump (70) to the 11th pipeline line (L11).

[0083] Here, a first mixer (13) can be installed at the connection point of the 11th pipeline line (L11) and the 16th pipeline line (L16), and the first mixer (13) can mix hydrogen supplied from an electrochemical hydrogen pump (70) through the 16th pipeline line (L16) and ammonia supplied from an ammonia supply unit (10) to a solid oxide fuel cell (30) through the 11th pipeline line (L11).

[0084] The 17th pipeline (L17) is connected to one side of the electrochemical hydrogen pump (70) and can discharge nitrogen separated from the electrochemical hydrogen pump (70).

[0085] Additionally, the 17th pipeline (L17) is connected to one side of an electrochemical hydrogen pump (70) to discharge a mixed gas containing nitrogen and some hydrogen.

[0086] The piping assembly may include a 21st piping line (L21) connecting the air supply unit (20) and the air heat exchanger (50), a 22nd piping line (L22) connecting the air heat exchanger (20) and the solid oxide fuel cell (30), a 23rd piping line (L23) connecting the solid oxide fuel cell (30) and the air heat exchanger (50), and a 24th piping line (L24) connected to the air heat exchanger (50) to discharge the reacted exhaust gas.

[0087] Specifically, the 21st pipeline (L21) connects the air supply unit (20) and the air heat exchanger (50), and can supply air supplied from the air supply unit (20) to the air heat exchanger (50).

[0088] The 22nd pipeline (L22) can connect the air heat exchanger (20) and the solid oxide fuel cell (30).

[0089] The 23rd pipeline (L23) connects the solid oxide fuel cell (30) and the air heat exchanger (50), and can supply the exhaust gas discharged after reaction in the solid oxide fuel cell (30) to the air heat exchanger (50).

[0090] Accordingly, the high-temperature exhaust gas supplied from the solid oxide fuel cell (30) to the air heat exchanger (50) through the 23rd pipeline line (L23) and the air supplied from the air supply unit (20) to the air heat exchanger (50) through the 21st pipeline line (L21) exchange heat with each other in the air heat exchanger (50), and the air whose temperature has increased through the heat exchange can be supplied to the cathode electrode (33) of the solid oxide fuel cell (30).

[0091] The 24th pipeline (L24) is connected to an air heat exchanger (50) and can discharge exhaust gas whose temperature has dropped after heat exchange with the air supplied to the solid oxide fuel cell (30) through the air heat exchanger (50).

[0092] The control unit is connected to the ammonia supply unit (10) and can control the flow rate of ammonia supplied to the solid oxide fuel cell (30) through the ammonia supply unit (10).

[0093] The control unit is connected to the air supply unit (20) and can control the flow rate of air supplied to the solid oxide fuel cell (30) through the air supply unit (20).

[0094] The control unit can be controllably connected to the solid oxide fuel cell (30).

[0095] The control unit can be controllably connected to the electrochemical hydrogen pump (70). Specifically, the control unit can control the amount of current load applied to the electrochemical hydrogen pump (70) to control the amount of hydrogen separated from a mixed gas containing nitrogen and hydrogen through the electrochemical hydrogen pump (70).

[0096] In addition, the control unit can selectively supply hydrogen separated from nitrogen through the electrochemical hydrogen pump (70) to ammonia supplied to the solid oxide fuel cell (30) by controlling the current load applied to the electrochemical hydrogen pump (70).

[0097] The control unit may further include a sensor for measuring the concentration of ammonia supplied as fuel and the concentration of reaction products such as hydrogen, nitrogen, water vapor, and exhaust gas by reacting ammonia. The sensor may be installed in the piping assembly to measure each concentration and then transmit it to the control unit.

[0098] Hereinafter, a process of producing hydrogen from ammonia through a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a first embodiment of the present invention and a process of separating only hydrogen from a mixed gas containing nitrogen and hydrogen and selectively supplying it to fuel will be described with reference to FIG. 2.

[0099] Ammonia is supplied from the ammonia supply unit (10) to the solid oxide fuel cell (30) through the 11th pipeline line (L11) and the 12th pipeline line (L12).

[0100] Here, a fuel blower (11) provided between the ammonia supply unit (10) and the solid oxide fuel cell (30) is driven to supply ammonia from the ammonia supply unit (10) to the solid oxide fuel cell (30).

[0101] Air is supplied to the solid oxide fuel cell (30) through the 21st pipe line (L21) and the 22nd pipe line (L22) from the air supply unit (20).

[0102] Here, the first air blower (21) provided between the air supply unit (20) and the solid oxide fuel cell cell (30) is driven to supply air from the air supply unit (20) to the solid oxide fuel cell cell (30).

[0103] Ammonia and air supplied to the solid oxide fuel cell (30) ionize oxygen at the cathode electrode (33) of the solid oxide fuel cell (30), and the ionized oxygen ions move through an ion conducting membrane and then react with hydrogen reformed from ammonia at the anode electrode (31) to generate reaction products including electricity and water vapor. The reaction products may include hydrogen unreacted with oxygen ions, nitrogen reformed from ammonia, and water vapor generated by the reaction of hydrogen and oxygen ions.

[0104] The reaction product generated at the anode electrode (31) of the solid oxide fuel cell (30) is supplied to the fuel heat exchanger (40) through the 13th pipeline line (L13), and the high-temperature reaction product supplied to the fuel heat exchanger (40) is supplied to the condenser (60) through the 14th pipeline line (L14) after heat exchange with ammonia supplied from the ammonia supply unit (10) to the fuel heat exchanger (40) through the 11th pipeline line (L11).

[0105] Ammonia, whose temperature has increased after heat exchange with the high-temperature reaction product in the fuel heat exchanger (40), is supplied to the solid oxide fuel cell (30) and decomposed into hydrogen and nitrogen.

[0106] As the above process is performed repeatedly, ammonia with an increased temperature is supplied to the solid oxide fuel cell (30), and the reaction product with a decreased temperature is supplied to the condenser (60).

[0107] The reaction product supplied to the condenser (60) is cooled and condensed through the cooling heat exchanger (61), and at this time, the water vapor is condensed into water and discharged through the drain section (63).

[0108] The mixed gas containing nitrogen and hydrogen from which moisture has been discharged through the condenser (60) is supplied to the electrochemical hydrogen pump (70) through the 15th pipeline (L15), and the electrochemical hydrogen pump (70) uses a proton exchange membrane and is operated at a temperature of 50°C to 100°C to separate only hydrogen from the mixed gas.

[0109] The separated hydrogen is supplied to the 11th pipeline line (L11) through the 16th pipeline line (L16), and is supplied to the first mixer (13) provided at the connection between the 11th pipeline line (L11) and the 16th pipeline line (L16). In addition, ammonia supplied from the ammonia supply unit (10) to the solid oxide fuel cell cell (30) is supplied to the first mixer (13). After pure hydrogen and ammonia are mixed in the first mixer (13), heat is exchanged with the high-temperature reaction product in the fuel heat exchanger (40), and the hydrogen and ammonia, whose temperature has increased through the heat exchange, are supplied to the solid oxide fuel cell cell (30) through the 12th pipeline line (L12).

[0110] In this way, by repeatedly mixing hydrogen into ammonia supplied from the ammonia supply unit (10) to the solid oxide fuel cell cell (30), the overall hydrogen concentration can be improved, and as a result, the electrochemical reaction efficiency of the solid oxide fuel cell cell (30) can be improved.

[0111] Nitrogen separated through the electrochemical hydrogen pump (70) is discharged to the outside through the 17th pipeline (L17).

[0112] Meanwhile, the exhaust gas generated at the cathode electrode (33) of the solid oxide fuel cell (30) is supplied to the air heat exchanger (50) through the 23rd pipeline line (L23), and the high-temperature exhaust gas supplied to the air heat exchanger (50) is exhausted (Vent) through the 24th pipeline line (L24) after heat exchange with the air supplied from the air supply unit (20) to the air heat exchanger (50) through the 21st pipeline line (L21).

[0113] In this way, ammonia and air supplied to the solid oxide fuel cell (30) are discharged from the solid oxide fuel cell (30), and are then supplied to the solid oxide fuel cell (30) again after exchanging heat with the reaction products and exhaust gas whose temperature has increased to raise the temperature to a predetermined level, thereby enabling the solid oxide fuel cell (30) to be operated in accordance with temperature conditions under high temperatures.

[0114] Hereinafter, a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a second embodiment of the present invention will be described.

[0115] Fig. 3 is a schematic diagram showing a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a second embodiment of the present invention. Fig. 4 is a schematic diagram showing a process in which external air is introduced into a heating unit and heated, and then the heated air is mixed with exhaust gas discharged from a solid oxide fuel cell and heat is exchanged in an air heat exchanger in a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a second embodiment of the present invention.

[0116] The solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to the second embodiment of the present invention has the same structure as the solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to the first embodiment described above, except for the heating unit and the structure of the heating unit, and therefore, a duplicate description of the same configuration will be omitted.

[0117] Referring to FIGS. 3 and 4, a solid oxide fuel cell recirculation system (1b) using an electrochemical hydrogen pump according to the second embodiment of the present invention may include a heating unit (80).

[0118] The heating unit (80) is intended to further increase the temperature of the high-temperature exhaust gas discharged from the solid oxide fuel cell cell (30). By heating the exhaust gas discharged after reaction in the solid oxide fuel cell cell (30) once again to increase the temperature of the exhaust gas, the temperature of the air supplied from the air supply unit (20) to the air heat exchanger (50) and then exchanged with the exhaust gas can be further increased.

[0119] The heating unit (80) may be either a burner or a catalytic converter and may be connected to an air heat exchanger (50). Specifically, the heating unit (80) may be connected to a 23rd pipe line (L23) connecting a solid oxide fuel cell (30) and an air heat exchanger (50) via a 25th pipe line (L25). Accordingly, the 25th pipe line (L25) may connect the heating unit (80) and the 23rd pipe line (L23).

[0120] The heating unit (80) may be provided with a 26th pipe line (L26) on one side for introducing external air into the heating unit (80).

[0121] At this time, the 26th pipe line (L26) may be equipped with a second air blower (81) for sucking external air into the heating unit (80). Accordingly, the second air blower (81) can forcibly introduce external air into the heating unit (80).

[0122] Here, a second mixer (23) may be installed at the connection between the 23rd pipeline line (L23) and the 25th pipeline line (L25) to mix the exhaust gas flowing into the air heat exchanger (50) from the solid oxide fuel cell (30) through the 23rd pipeline line (L23) and the air heated through the heating unit (80) and then flowing into the air heat exchanger (50) through the 25th pipeline line (L25).

[0123] The second mixer (23) is provided at the connection between the 23rd pipeline line (L23) and the 25th pipeline line (L25), and the mixed gas can be supplied to the air heat exchanger (50) through the second mixer (23).

[0124] Accordingly, the heating unit (80) forcibly sucks in outside air through the second air blower (81) and supplies it into the heating unit (80) through the 26th pipe line (L26), heats the sucked air, and then supplies it to the second mixer (23) through the 25th pipe line (L25) to mix it with the exhaust gas discharged from the solid oxide fuel cell (30) so as to further increase the temperature of the mixed gas supplied to the air heat exchanger (50).

[0125] Here, the temperature of the external air heated through the heating unit (80) can be formed higher than the temperature of the exhaust gas discharged from the solid oxide fuel cell (30).

[0126] Meanwhile, nitrogen from which hydrogen has been separated through an electrochemical hydrogen pump (70) can be discharged to the outside through the 17th pipeline (L17).

[0127] Hereinafter, a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a third embodiment of the present invention will be described.

[0128] Fig. 5 is a schematic diagram showing a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a third embodiment of the present invention. Fig. 6 is a schematic diagram showing a process in which nitrogen or nitrogen and hydrogen discharged from an electrochemical hydrogen pump are introduced into a heating unit and heated, and then the heated nitrogen or nitrogen and hydrogen are mixed with the exhaust gas discharged from the solid oxide fuel cell and heat is exchanged in an air heat exchanger in a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a third embodiment of the present invention.

[0129] The solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to the third embodiment of the present invention has the same structure as the solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to the second embodiment described above, except for the structure in which the electrochemical hydrogen pump is connected to the heating unit, and therefore, a duplicate description of the same configuration will be omitted.

[0130] Referring to FIGS. 5 and 6, the heating unit (80) of the solid oxide fuel cell recirculation system (1c) using an electrochemical hydrogen pump according to the third embodiment of the present invention has one side connected to the 17th piping line (L17) of the electrochemical hydrogen pump (70) so as to receive nitrogen from which hydrogen has been removed from the electrochemical hydrogen pump (70).

[0131] In addition, the heating unit (80) is connected to one side of the 17th pipeline (L17) connected to the electrochemical hydrogen pump (70) to discharge nitrogen from the electrochemical hydrogen pump (70), so that a mixed gas containing nitrogen and hydrogen can be supplied from the electrochemical hydrogen pump (70).

[0132] In this way, the heating unit (80) receives nitrogen from which hydrogen has been removed or a mixed gas containing nitrogen and hydrogen from an electrochemical hydrogen pump (70), heats it, and then supplies the heated nitrogen or nitrogen and hydrogen to a second mixer (23), and after being mixed with the exhaust gas supplied from the solid oxide fuel cell (30) through the second mixer (23), it can be supplied to an air heat exchanger (50).

[0133] Hereinafter, a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a fourth embodiment of the present invention will be described.

[0134] Fig. 7 is a schematic diagram showing a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a fourth embodiment of the present invention. Fig. 8 is a schematic diagram showing a process in which external air and nitrogen or nitrogen and hydrogen discharged from an electrochemical hydrogen pump are introduced into a heating unit, mixed and heated, and then the heated mixed gas is mixed with the exhaust gas discharged from a solid oxide fuel cell and heat is exchanged in an air heat exchanger in a solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to a fourth embodiment of the present invention.

[0135] The solid oxide fuel cell recirculation system using an electrochemical hydrogen pump according to the fourth embodiment of the present invention is configured to include the second and third embodiments, and a duplicate description of the same configuration will be omitted.

[0136] Referring to FIGS. 7 and 8, the heating unit (80) of the solid oxide fuel cell recirculation system (1d) using an electrochemical hydrogen pump according to the fourth embodiment of the present invention receives external air through the 26th pipe line (L26), receives nitrogen from which hydrogen has been removed from the electrochemical hydrogen pump (70) through the 17th pipe line (L17), and then heats the supplied gas by mixing it with external air, and then supplies the heated gas to the second mixer (23), and then mixes it with the exhaust gas supplied from the solid oxide fuel cell (30) through the second mixer (23), and then supplies it to the air heat exchanger (50).

[0137] At this time, the second air blower (81) can be driven to forcibly suck and supply nitrogen or a mixed gas containing nitrogen and hydrogen from the electrochemical hydrogen pump (70) to the heating unit.

[0138] Additionally, the second air blower (81) can be driven to forcibly suck in outside air and supply it into the heating unit (80) through the 26th pipe line (L26).

[0139] In this way, the heating unit (80) receives external air and mixes and heats a gas containing nitrogen or nitrogen and hydrogen discharged through an electrochemical hydrogen pump (70), and then mixes the mixture with the exhaust gas discharged from the solid oxide fuel cell (30) and supplies the mixture to the air heat exchanger (50).

[0140] Therefore, by significantly increasing the temperature of the air supplied from the air supply unit (20) to the solid oxide fuel cell (30) compared to the conventional method, the solid oxide fuel cell (30) can be operated to meet the temperature conditions under high temperatures.

[0141] Meanwhile, depending on the needs of the site, the supply of gas or air to the heater can be selectively controlled, such as by supplying nitrogen or nitrogen and hydrogen to the heater (80) through an electrochemical hydrogen pump (70), heating it, and then supplying it to the air heat exchanger (50), or by sucking in external air, supplying it to the heater (80), heating it, and then supplying it to the air heat exchanger (50).

[0142] If external air is sucked in, supplied to a heater (80), heated, and supplied to an air heat exchanger (50), nitrogen from which hydrogen is separated through an electrochemical hydrogen pump (70) before or after heating the air can be discharged to the outside through the 17th pipeline (L17). That is, nitrogen separated from the mixed gas can be discharged through the 17th pipeline (L17) from the electrochemical hydrogen pump (70), and through a heater (80) connected to the 17th pipeline (L17) and a 26th pipeline (L26) connected to the heater (80).

[0143] In addition, if there is no need to raise the temperature of the air exchanger (50) above the temperature of the exhaust gas discharged from the solid oxide fuel cell (30) depending on the on-site situation, the heater (80) can be kept in the OFF state and the nitrogen separated through the electrochemical hydrogen pump (70) can be discharged to the outside while sequentially passing through the 17th pipeline (L17), the heater (80), and the 26th pipeline (L26).

[0144] At this time, the heater (80) can serve as a passage for discharging nitrogen to the outside.

[0145] In addition, the second air blower (81) can forcibly suck nitrogen discharged from the electrochemical hydrogen pump (70) through the 17th pipe line (L17) into the heater (80) and then discharge the nitrogen to the outside through the 26th pipe line (L26).

[0146] Here, the pipeline according to the present invention may be provided with at least one valve (not shown) for controlling the flow rate of the fluid.

[0147] Meanwhile, the solid oxide fuel cell recirculation system (1a, 1b, 1c, 1d) using an electrochemical hydrogen pump according to the present invention can utilize existing solid oxide fuel cell cells whose durability and performance have been reduced to a certain extent due to use for a certain period of time, thereby reducing the overall device cost.

[0148] That is, the reason why performance degradation and loss occur in solid oxide fuel cell is mostly due to oxygen reduction reaction, but the electrochemical hydrogen pump (70) applied to the solid oxide fuel cell recirculation system (1a, 1b, 1c, 1d) using an electrochemical hydrogen pump according to an embodiment of the present invention does not require oxygen reduction reaction because oxygen does not participate in the reaction, and thus, the use of existing solid oxide fuel cell in which performance degradation and loss occur due to the oxygen reduction reaction is possible.

[0149] Above, one embodiment of the present invention has been described, but a person having ordinary skill in the art will be able to modify and change the present invention in various ways by adding, changing, deleting or adding components, etc., within the scope that does not depart from the spirit of the present invention described in the claims, and this will also be considered to be included within the scope of the rights of the present invention.

Claims

1. A solid oxide fuel cell cell that receives ammonia and air, generates electricity through an electrochemical reaction, and discharges reaction products containing nitrogen, hydrogen, and water vapor and exhaust gas containing air with a reduced oxygen concentration; An ammonia supply unit for supplying the above ammonia to the solid oxide fuel cell cell; An air supply unit for supplying the air to the solid oxide fuel cell; and A solid oxide fuel cell recirculation system including an electrochemical hydrogen pump that separates only hydrogen from the reaction product of the solid oxide fuel cell and resupplies it to the solid oxide fuel cell.

2. In paragraph 1, The above solid oxide fuel cell recirculation system is, A fuel heat exchanger that exchanges heat between the high temperature reaction product discharged after reaction in the solid oxide fuel cell and the ammonia supplied to the solid oxide fuel cell; An air heat exchanger that exchanges heat between the high-temperature exhaust gas discharged after reaction in the solid oxide fuel cell and the air supplied to the solid oxide fuel cell; and A solid oxide fuel cell recirculation system further comprising a condenser for condensing the reaction product heat-exchanged through the fuel heat exchanger.

3. In paragraph 2, A solid oxide fuel cell recirculation system, wherein the condensing unit includes a cooling heat exchanger that condenses the water vapor through heat exchange with the reaction product supplied through the fuel heat exchanger, and a drain unit that discharges the condensed water through the cooling heat exchanger to the outside.

4. In paragraph 2, The above electrochemical hydrogen pump is a solid oxide fuel cell recirculation system that separates hydrogen from a mixed gas containing nitrogen and hydrogen, and selectively mixes the separated hydrogen with ammonia supplied from the ammonia supply unit to the fuel heat exchanger.

5. In paragraph 4, The above electrochemical hydrogen pump is a solid oxide fuel cell recirculation system that controls the amount of hydrogen separated from the mixed gas by controlling the current load.

6. In paragraph 2, The solid oxide fuel cell recirculation system further includes a heating unit that increases the temperature of the air supplied from the air supply unit.

7. In paragraph 6, A solid oxide fuel cell recirculation system wherein the heating unit is either a burner or a catalytic converter.

8. In paragraph 6, The above heating unit is a solid oxide fuel cell recirculation system that heats the exhaust gas discharged from the solid oxide fuel cell.

9. In paragraph 8, A solid oxide fuel cell recirculation system in which the heating unit draws in outside air, heats it, and mixes the heated outside air with the exhaust gas to heat the exhaust gas.

10. In paragraph 6, The above heating unit is a solid oxide fuel cell recirculation system that receives the nitrogen from which the hydrogen has been removed from the electrochemical hydrogen pump.

11. In paragraph 1, A solid oxide fuel cell recirculation system in which the ammonia supply unit is equipped with a fuel blower on one side for supplying the ammonia to the solid oxide fuel cell cell.

12. In paragraph 1, A solid oxide fuel cell recirculation system in which the air supply unit is equipped with an air blower on one side for supplying the air to the solid oxide fuel cell cell.

13. In paragraph 1, The above electrochemical hydrogen pump is a solid oxide fuel cell recirculation system that operates at a temperature of 50°C to 100°C.

14. In paragraph 1, The above solid oxide fuel cell recirculation system is a solid oxide fuel cell recirculation system further including a control unit that controls the operations of the solid oxide fuel cell, the ammonia supply unit, the air supply unit, and the electrochemical hydrogen pump.

15. In paragraph 14, The above control unit is a solid oxide fuel cell recirculation system that controls the amount of hydrogen separated by controlling the amount of current load applied to the electrochemical hydrogen pump.

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