Fuel cell system

Abstract

The present invention relates to a fuel cell system. A fuel cell system of one embodiment of the present invention may include: a fuel cell stack, which generates electricity using reformed gas; a fuel processing device, which supplies reformed gas to the fuel cell stack; a first gas flow path, which connects the fuel cell stack and the fuel processing device, and supplies the reformed gas discharged from the fuel processing device; a second gas flow path, which connects the fuel cell stack and the fuel processing device, and supplies the anode exhaust gas discharged from the fuel cell stack; a buffer tank, which stores a part of the anode exhaust gas discharged from the fuel cell stack; a first buffer tank flow path, which connects the buffer tank and the second gas flow path; a second buffer tank flow path, which supplies the anode exhaust gas stored in the buffer tank; a gas mixer, which is connected to the second buffer tank flow path, and supplies the anode exhaust gas stored in the buffer tank to the fuel cell stack; and a control unit, which supplies the anode exhaust gas stored in the buffer tank to the fuel cell stack by adjusting the gas mixer to preheat the fuel cell stack or remove the remaining air in the fuel cell stack.

Description

Technical Field

[0001] The present invention relates to a fuel cell system, and more particularly to a fuel cell system that preheats a fuel cell stack when initially entering a power generation operation and removes residual air in the fuel cell stack when the operation is stopped. Background Art

[0002] A fuel cell system is a power generation system that generates electric energy by electrochemically reacting hydrogen and oxygen contained in hydrocarbon substances such as methanol, ethanol, and natural gas.

[0003] Similar to the prior art 1 (Korea Patent Publication No. 10-2012-0071288), a typical fuel cell system includes: a fuel processing device that converts and reforms fuel containing hydrogen atoms into hydrogen; and a stack that generates electric energy using the hydrogen supplied from the fuel processing device. In addition, the fuel cell system may also include a heat exchanger for cooling the stack and recovering heat, cooling water piping, and a power conversion device that converts the generated DC power into AC power.

[0004] On the other hand, in order to remove the residual oxygen in the fuel cell stack after the power generation operation is completed, the prior art 2 (Korean Patent Publication No. 10-2011-0019274) discloses the following scheme: by installing a separate branch valve branching from the hydrogen purge valve on the hydrogen purge line of the fuel supply system that supplies fuel to the fuel cell stack, when the power generation operation is completed, the hydrogen passing through the branch valve is cleared from the cathode electrode part of the fuel cell stack via the air supply line. However, the above scheme has the problem of requiring the additional generation and supply of anode exhaust gas (Anode Off Gas: AOG) for supply to the cathode electrode part.

[0005] Therefore, it is necessary to conduct research on removing the oxygen remaining in the cathode electrode part of the fuel cell stack after the power generation operation is completed to prevent the life of the fuel cell stack from being reduced.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: KR 10-2012-0071288 A

[0009] Patent Document 2: KR 10-2011-0019274 A Summary of the invention

[0010] The present invention is directed to solving the above-referenced problems and other problems.

[0011] Another object of the present invention is to provide a fuel cell system that performs a scavenging operation to remove residual oxygen in a cathode electrode portion of a fuel cell stack after the power generation operation is completed.

[0012] Another object of the present invention is to provide a fuel cell system that performs a stack preheating operation for preheating the stack during power generation operation.

[0013] Another object of the present invention is to provide a fuel cell system that can save maintenance costs of the fuel cell system.

[0014] The purpose of the present invention is not limited to the above-mentioned purpose, and those skilled in the art can clearly understand other purposes not mentioned through the following description.

[0015] In order to solve the above-mentioned problems, a fuel cell system of one embodiment of the present invention may include: a fuel cell stack, which generates electricity using reformed gas; a fuel processing device, which supplies reformed gas to the fuel cell stack; a first gas flow path, which connects the fuel cell stack and the fuel processing device, and allows the reformed gas discharged from the fuel processing device to flow; a second gas flow path, which connects the fuel cell stack and the fuel processing device, and allows the anode exhaust gas (AOG) discharged from the fuel cell stack to flow; a buffer tank, which stores a portion of the anode exhaust gas discharged from the fuel cell stack; a first buffer tank flow path, which connects the buffer tank and the second gas flow path; a second buffer tank flow path, which allows the anode exhaust gas stored in the buffer tank to flow; a gas mixer, which is connected to the second buffer tank flow path, and supplies the anode exhaust gas stored in the buffer tank to the fuel cell stack; and a control unit, which supplies the anode exhaust gas stored in the buffer tank to the fuel cell stack by adjusting the gas mixer to preheat the fuel cell stack or remove residual air in the fuel cell stack.

[0016] A fuel cell system according to an embodiment of the present invention may further include: a buffer tank valve, which is arranged in the first buffer tank flow path and controls the flow of anode exhaust gas supplied to the buffer tank; and a buffer tank compressor, which is located at the front end of the buffer tank valve and compresses the anode exhaust gas supplied to the buffer tank; during power generation operation, the control unit closes the gas mixer and opens the buffer tank valve, and operates the buffer tank compressor, so that a portion of the anode exhaust gas discharged from the fuel cell stack can be compressed and stored in the buffer tank.

[0017] The fuel cell system of one embodiment of the present invention may further include: a pressure sensor, arranged in the buffer tank, measuring the pressure of the anode exhaust gas stored in the buffer tank; when the pressure of the anode exhaust gas stored in the buffer tank measured by the pressure sensor is above a first set pressure, the control unit may close the buffer tank valve and stop the buffer tank compressor.

[0018] The fuel cell system of one embodiment of the present invention may also include: a blower, which supplies air to the fuel cell stack; and an air supply valve, which is arranged between the fuel cell stack and the blower, and regulates the air supplied from the blower to the fuel cell stack; during the purge operation, the control unit can close the air supply valve and open the gas mixer to supply the anode exhaust gas stored in the buffer tank to the fuel cell stack.

[0019] The fuel cell system of one embodiment of the present invention may further include: a pressure sensor, which is arranged in the buffer tank, measuring the pressure of the anode exhaust gas stored in the buffer tank; when the pressure of the anode exhaust gas in the buffer tank measured by the pressure sensor is below the second set pressure, the control unit may close the gas mixer and end the purge operation.

[0020] The fuel cell system of one embodiment of the present invention may further include: a blower, which supplies air to the fuel cell stack; and an air supply valve, which is arranged between the fuel cell stack and the blower, and regulates the air supplied from the blower to the fuel cell stack; when the fuel cell stack is preheating, the control unit may open the gas mixer and the air supply valve and operate the blower so that air and anode exhaust gas are supplied to the fuel cell stack after mixing.

[0021] A fuel cell system according to an embodiment of the present invention may further include: a first gas valve, arranged in the first gas flow path, controlling the flow of reformed gas supplied to the fuel cell stack; a bypass flow path, connecting the first gas flow path and the fuel processing device; and a bypass valve, arranged in the bypass flow path, controlling the flow of reformed gas in the bypass flow path; when the fuel cell stack is preheating, the control unit may close the first gas valve and open the bypass valve to allow the reformed gas discharged from the fuel processing device to flow into the fuel processing device again.

[0022] On the other hand, in order to solve the above-mentioned problems, a control method of a fuel cell system according to an embodiment of the present invention may include: performing a step of storing the anode exhaust gas discharged from the fuel cell stack in the buffer tank for power generation operation by adjusting a buffer tank valve for controlling the flow of the anode exhaust gas supplied to the buffer tank and a buffer tank compressor for compressing the anode exhaust gas.

[0023] The step of performing the power generation operation may include closing the gas mixer, opening the buffer tank valve, and operating the buffer tank compressor to compress a portion of the anode exhaust gas discharged from the fuel cell stack and store it in the buffer tank.

[0024] The step of storing the anode exhaust gas discharged from the fuel cell stack in the buffer tank may include the step of closing the buffer tank valve and stopping the buffer tank compressor when the pressure measured by the pressure sensor measuring the pressure of the anode exhaust gas stored in the buffer tank is greater than a first set pressure.

[0025] On the other hand, in order to solve the above-mentioned problems, the control method of the fuel cell system of one embodiment of the present invention may also include: performing a cleaning operation to remove residual air in the fuel cell stack by adjusting the air supply valve and the gas mixer for controlling the flow of air to the fuel cell stack.

[0026] The step of performing the purge operation may include closing the air supply valve and opening the gas mixer to supply the anode exhaust gas stored in the buffer tank to the fuel cell stack.

[0027] The step of performing the purge operation may include closing the gas mixer and ending the purge operation when the pressure measured by the pressure sensor measuring the pressure of the anode off-gas stored in the buffer tank is less than a second set pressure.

[0028] On the other hand, in order to solve the above-mentioned problems, the control method of the fuel cell system of one embodiment of the present invention may also include: performing a stack preheating operation step of preheating the stack by adjusting the air supply valve, the gas mixer and the blower for controlling the air flow to the stack.

[0029] The step of performing the stack preheating operation may include opening the gas mixer and the air supply valve, and operating the blower to mix air and anode exhaust gas in the gas mixer and then supply the air and anode exhaust gas to the stack.

[0030] Detailed information regarding other embodiments is included in the detailed description and drawings.

[0031] According to various embodiments of the present invention, after the power generation operation is completed, a purge operation is performed to supply the anode exhaust gas stored in the buffer tank to the stack to remove the oxygen remaining in the stack, thereby preventing the stack life from being shortened due to oxidation of the cathode electrode portion.

[0032] In addition, according to various embodiments of the present invention, the cleaning operation can increase the service life of the fuel cell stack, thereby saving system maintenance costs and ensuring economy.

[0033] In addition, according to various embodiments of the present invention, when the power generation operation is initially started, the anode exhaust gas stored in the buffer tank is supplied to the fuel cell stack, so that the fuel cell stack is quickly preheated, thereby improving the power generation efficiency.

[0034] The effects of the present invention are not limited to the above-mentioned effects, and those skilled in the art can clearly understand other effects not mentioned through the description of the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the structure of a fuel processing device according to an embodiment of the present invention.

[0036] Figure 2 and Figure 3 FIG. 1 is a diagram showing the structure of a fuel cell system according to an embodiment of the present invention.

[0037] Figure 4 The flowchart is about a control method of a fuel cell system according to an embodiment of the present invention.

[0038] Figure 5 It is a flow chart of a control method for preheating operation of a fuel cell stack according to an embodiment of the present invention.

[0039] Figure 6 It is a diagram illustrating the stack preheating operation according to an embodiment of the present invention.

[0040] Figure 7 It is a flow chart of a method for controlling power generation operation according to an embodiment of the present invention.

[0041] Figure 8a and Figure 8b It is a diagram for explaining the power generation operation according to one embodiment of the present invention.

[0042] Fig. 9 The present invention is a flowchart of a method for controlling shutdown according to an embodiment of the present invention.

[0043] Fig.10a and Fig.10b It is a diagram for explaining the shutdown operation of one embodiment of the present invention. DETAILED DESCRIPTION

[0044] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In the accompanying drawings, in order to clearly and briefly describe the present invention, illustrations of parts not related to the description are omitted, and the same reference numerals are used for the same or very similar parts throughout the specification.

[0045] The suffixes "module" and "unit" of the structural elements used in the following description are only given for the convenience of writing this specification, and they themselves do not have a particularly important meaning or function. Therefore, the above-mentioned "module" and "unit" can be used interchangeably.

[0046] In the present application, terms such as "including" or "having" are only used to specify the existence of features, numbers, steps, actions, structural elements, parts or their combinations recorded in the specification, and are not intended to exclude the possibility of the existence or addition of one or more other features or numbers, steps, actions, structural elements, parts or their combinations.

[0047] In addition, in the present specification, the terms "first", "second", etc. may be used to describe various elements, but these elements are not limited by these terms. These terms may be used only to distinguish one element from another element.

[0048] Figure 1 It is a schematic diagram of the structure of a fuel processing device according to an embodiment of the present invention.

[0049] Reference Figure 1 The fuel processing device 10 may include a desulfurizer 110, a burner 120, a steam generator 130, a reformer 140 (reformer), a first reactor 150 and / or a second reactor 160. The fuel processing device 10 may further include at least one mixer 111, 112.

[0050] The desulfurizer 110 may perform a desulfurization process for removing sulfur compounds contained in the fuel gas. For example, an adsorbent may be provided inside the desulfurizer 110. At this time, the sulfur compounds contained in the fuel gas passing through the inside of the desulfurizer 110 may be adsorbed by the adsorbent.

[0051] The adsorbent can be composed of metal oxides, zeolite, activated carbon, etc.

[0052] The desulfurizer 110 may further include a filter for removing impurities contained in the fuel gas.

[0053] The burner 120 may supply heat to the reformer 140 to promote the reforming reaction in the reformer 140. For example, the fuel gas discharged from the desulfurizer 110 and the air flowing in from the outside may be mixed in the first mixer 111 and supplied to the burner 120. At this time, the burner 120 may generate combustion heat by burning the mixed gas formed by mixing the fuel gas and the air. At this time, the internal temperature of the reformer 140 may be maintained at an appropriate temperature (e.g., 800° C.) under the action of the heat provided by the burner 120.

[0054] On the other hand, the exhaust gas generated in the burner 120 by the combustion of the mixed gas may be discharged to the outside of the fuel processing device 10 .

[0055] The steam generator 130 may vaporize water and discharge it as water vapor. For example, the steam generator 130 may vaporize water by absorbing heat from the exhaust gas generated by the burner 120, the first reactor 150, and / or the second reactor 160.

[0056] The steam generator 130 may be disposed adjacent to the first reactor 150 , the second reactor 160 , and / or a pipe through which the exhaust gas exhausted from the burner 120 flows.

[0057] The reformer 140 may perform a reforming process for generating hydrogen from the fuel gas from which the sulfur compounds have been removed using a catalyst. For example, the fuel gas discharged from the desulfurizer 110 and the water vapor discharged from the steam generator 130 may be mixed in the second mixer 112 and supplied to the reformer 140. At this time, when the fuel gas and the water vapor supplied to the reformer 140 undergo a reforming reaction in the reformer 140, hydrogen may be generated.

[0058] The first reactor 150 can reduce carbon monoxide generated by the reforming reaction among the components contained in the gas discharged from the reformer 140. For example, the carbon monoxide contained in the gas discharged from the reformer 140 can react with water vapor inside the first reactor 150 to generate carbon dioxide and hydrogen. At this time, the internal temperature of the first reactor 150 can be a temperature lower than the internal temperature of the reformer 140 and higher than normal temperature (for example, 200° C.).

[0059] The first reactor 150 may be referred to as a shift reactor.

[0060] The second reactor 160 may reduce carbon monoxide remaining in the gas discharged from the first reactor 150. For example, carbon monoxide included in the gas discharged from the first reactor 150 may react with oxygen inside the second reactor 160 to cause a preferential oxidation (PROX) reaction.

[0061] On the other hand, in the case of the selective oxidation reaction, a large amount of oxygen is required, so additional air needs to be supplied, so that the hydrogen is diluted by the additional air, which has the disadvantage of reducing the concentration of hydrogen supplied to the fuel cell stack. Therefore, in order to overcome such a disadvantage, a selective methanation reaction in which carbon monoxide and hydrogen react can be used.

[0062] On the other hand, the gas discharged from the fuel processing device 10 via the reformer 140, the first reactor 150 and / or the second reactor 160 may be referred to as reformed gas.

[0063] The fuel cell stack 20 may generate electric energy by electrochemically reacting the reformed gas supplied from the fuel processing device 10 .

[0064] The battery stack 20 may be composed of a stack of individual cells in which electrochemical reactions occur.

[0065] A single unit can be composed of a membrane electrode assembly (MEA) with a fuel electrode and an air electrode arranged around an electrolyte membrane, a separator, etc. In the fuel electrode of the membrane electrode assembly, hydrogen can be separated into hydrogen ions and electrons under the action of a catalyst to generate electricity, and in the air electrode of the membrane electrode assembly, hydrogen ions and electrons can combine with oxygen to generate water.

[0066] The stack 20 may further include a stack heat exchanger (not shown) for releasing heat generated during the electrochemical reaction. The stack heat exchanger may be a heat exchanger that uses water as a refrigerant. For example, cooling water supplied to the stack heat exchanger may absorb heat generated during the electrochemical reaction, and the cooling water whose temperature rises due to the absorbed heat may be discharged to the outside of the stack heat exchanger.

[0067] Figure 2 and Figure 3 FIG. 1 is a structural diagram of a fuel cell system including a fuel processing device according to an embodiment of the present invention.

[0068] Reference Figure 2 The fuel cell system 1 may include a fuel processing section I, a power generation section II, a cooling water circulation section III and / or a heat recovery section IV.

[0069] The fuel processing unit 1 may include a fuel processing device 10, a fuel valve 30 that adjusts the flow of fuel gas supplied to the fuel processing device 10, a first blower 71 that allows air to flow toward the fuel processing device 10, and the like.

[0070] The power generation unit II may include: a stack 20a, 20b; a reformed gas heat exchanger 21 for heat exchange of the reformed gas discharged from the fuel processing device 10; an AOG heat exchanger 22 for heat exchange of the gas that has not reacted and discharged in the stack 20a, 20b; a humidifier 23 for supplying moisture to the air supplied to the stack 20a, 20b; and a second blower 72 for flowing air to the stack 20a, 20b. Among them, the gas that has not reacted and discharged in the stack 20a, 20b can be called anode off gas (AOG). In one embodiment of the present invention, it is described that the fuel cell system 1 has two stacks 20a, 20b, but it is not limited to this.

[0071] The cooling water circulation unit III may include: a water supply tank 13, which stores water generated in the fuel cell system 1; a water pump 38, which allows water to flow to the fuel processing device 10; a water supply valve 39, which is used to regulate the flow of water supplied to the fuel processing device 10; and a cooling water pump 43, which allows water to flow to the reforming gas heat exchanger 21.

[0072] The heat recovery unit IV may include a heat recovery tank 15 storing water for heat exchange, and a hot water pump 48 that allows the water stored in the heat recovery tank 15 to flow to the outside of the heat recovery tank 15 .

[0073] The fuel valve 30 may be disposed in the fuel supply flow path 101 through which the fuel gas supplied to the fuel processing device 10 flows. The flow rate of the fuel gas supplied to the fuel processing device 10 may be adjusted according to the degree of opening of the fuel valve 30. For example, the fuel valve 30 may cut off the fuel supply flow path 101 to interrupt the supply of the fuel gas to the fuel processing device 10.

[0074] The fuel supply flow path 101 may be provided with a first fuel flow meter 51 for detecting the flow rate of the fuel gas flowing in the fuel supply flow path 101 .

[0075] The first blower 71 may be connected to the first outside air inflow passage 201 and the fuel side air supply passage 202. The first blower 71 may allow air flowing in from the outside through the first outside air inflow passage 201 to flow toward the fuel processing device 10 through the fuel side air supply passage 202.

[0076] The air flowing into the fuel processing device 10 through the fuel side air supply flow path 202 may be supplied to the burner 120 of the fuel processing device 10. For example, the air flowing into the fuel processing device 10 may be mixed with the fuel gas discharged from the desulfurizer 110 in the first mixer 111 and supplied to the burner 120.

[0077] The first external air inflow passage 201 may be provided with an air filter 91 for removing impurities such as dust contained in the air and / or a first air-side check valve 81 for restricting a flow direction of the air.

[0078] The fuel processing unit 1 may include a first internal gas flow path 102 for the fuel gas discharged from the desulfurizer 110 to flow to the reformer 140. The first internal gas flow path 102 may be provided with a proportional control valve 31, an internal fuel valve 32 for regulating the flow of the fuel gas flowing into the reformer 140, a second fuel flow meter 52 for detecting the flow rate of the fuel gas flowing in the internal gas flow path 102, a fuel-side check valve 83 for limiting the flow direction of the fuel gas flowing in the internal gas flow path 102, and / or a sulfur detection device 94.

[0079] The proportional control valve 31 can adjust the flow rate, pressure, etc. of the fuel gas discharged from the desulfurizer 110 and flowing to the reformer 140 in an electrically controlled manner through internal / external feedback.

[0080] The sulfur detector 94 can detect sulfur contained in the fuel gas discharged from the desulfurizer 110. The sulfur detector 94 can include an indicator that reacts with sulfur compounds that are not removed by the adsorbent of the desulfurizer 110 and changes color. The indicator can include phenolphthalein, molybdenum compounds, and the like.

[0081] The fuel processing unit 1 may include a second internal gas flow path 103 for allowing the fuel gas discharged from the desulfurizer 110 to flow toward the burner 120. The burner 120 may use the fuel gas flowing in through the second internal gas flow path 103 to perform combustion.

[0082] The first inner gas flow path 102 and the second inner gas flow path 103 may communicate with each other.

[0083] The fuel processing device 10 may be connected to a water supply flow path 303 through which water discharged from the water supply tank 13 flows. The water supply flow path 303 may be provided with a water pump 38, a water supply valve 39 for regulating the flow of water, and / or a water flow meter 54 for detecting the flow rate of water flowing in the water supply flow path 303.

[0084] The exhaust gas generated by the burner 120 of the fuel processing device 10 can be discharged from the fuel processing device 10 through the exhaust gas discharge flow path 210 .

[0085] The fuel processing device 10 may be connected to the reformed gas discharge flow path 104. The reformed gas discharged from the fuel processing device 10 may flow through the reformed gas discharge flow path 104.

[0086] The reformed gas discharge flow path 104 may be connected to the reformed gas heat exchanger 21 for heat exchange of the reformed gas. A reformed gas valve 33 for regulating the flow of the reformed gas flowing into the reformed gas heat exchanger 21 may be disposed in the reformed gas discharge flow path 104 .

[0087] The reformed gas discharge flow path 104 may be connected to a bypass flow path 105 for allowing the reformed gas discharged from the fuel processing device 10 to flow to the fuel processing device 10. The bypass flow path 105 may be connected to the fuel processing device 10. The reformed gas flowing into the fuel processing device 10 via the bypass flow path 105 may be used as fuel for combustion of the burner 120. A bypass valve 34 for regulating the flow of the reformed gas flowing into the fuel processing device 10 may be disposed in the bypass flow path 105.

[0088] The reformed gas heat exchanger 21 may be connected to the reformed gas discharge flow path 104 through which the reformed gas discharged from the fuel processing device 10 flows. The reformed gas heat exchanger 21 may be connected to the cooling water supply flow path 304 through which the water discharged from the water supply tank 13 flows. The reformed gas heat exchanger 21 can perform heat exchange between the reformed gas flowing in through the reformed gas discharge flow path 104 and the water supplied through the cooling water supply flow path 304.

[0089] The cooling water supply flow path 304 may be provided with a cooling water pump 43 for flowing water stored in the water supply tank 13 toward the reformed gas heat exchanger 21 and / or a cooling water flow meter 56 for detecting the flow rate of water flowing in the cooling water supply flow path 304 .

[0090] The reformed gas heat exchanger 21 may be connected to the stack gas supply flow path 106. The reformed gas discharged from the reformed gas heat exchanger 21 may flow to the cell stacks 20a and 20b via the stack gas supply flow path 106.

[0091] A reformed gas moisture removal device 61 for adjusting the amount of moisture contained in the reformed gas may be disposed in the stack gas supply flow path 106. The reformed gas flowing into the reformed gas moisture removal device 61 may be discharged from the reformed gas moisture removal device 61 after moisture is removed.

[0092] The condensed water generated in the reformed gas moisture removal device 61 may be discharged from the reformed gas moisture removal device 61 and flow into the first water recovery flow path 309. The first water recovery flow path 309 may be provided with a first water recovery valve 44 for regulating the flow of water.

[0093] The stacks 20a and 20b can generate electric energy by electrochemically reacting the reformed gas flowing in through the stack gas supply flow path 106. In one embodiment, when the fuel cell system 1 has a plurality of stacks 20a and 20b, the reformed gas that has not reacted and discharged in the first stack 20a can be subjected to an additional electrochemical reaction in the second stack 20b.

[0094] The second blower 72 may be connected to the second external air inflow passage 203 and the stack side air inflow passage 204 that are in communication with the first external air inflow passage 201. The second external air inflow passage 203 may be connected to the rear end of the air filter 91. The second blower 72 may allow the air flowing in through the second external air inflow passage 203 to flow toward the stack 20 side through the stack side air inflow passage 204.

[0095] A second air-side check valve 82 for restricting the flow direction of air may be disposed in the second outside air inflow passage 203 .

[0096] An air flow meter 53 for detecting the flow rate of air flowing in the stack-side air inlet flow path 204 may be disposed in the stack-side air inlet flow path 204 .

[0097] The humidifier 23 can supply moisture to the air flowing in through the stack-side air inflow passage 204 , and can discharge the air containing moisture through the stack-side air supply passage 205 .

[0098] The stack-side air supply flow path 205 may be provided with a stack-side air supply valve 36 for adjusting the flow of air supplied to the stack 20 .

[0099] The stack-side air supply flow path 205 may be connected to the individual supply flow paths 206 and 207 corresponding to the stacks 20a and 20b, respectively. The air flowing through the stack-side air supply flow path 205 may be supplied to the stacks 20a and 20b through the individual supply flow paths 206 and 207.

[0100] The plurality of stacks 20a and 20b may be connected to each other via the gas connection flow path 107. The reformed gas that has not reacted and discharged from the first stack 20a may flow into the second stack 20b via the gas connection flow path 107.

[0101] The gas connection flow path 107 may be provided with an additional moisture removal device 62 for removing water generated by condensation of the reformed gas while passing through the first fuel cell stack 20 a .

[0102] The water generated by the additional water removal device 62 may be discharged from the additional water removal device 62 and flow into the second water recovery flow path 310. The second water recovery flow path 310 may be provided with a second water recovery valve 45 for regulating the flow of water. The second water recovery flow path 310 may be connected to the first water recovery flow path 309.

[0103] Anode off-gas (AOG) discharged without reacting in the cell stacks 20 a and 20 b can flow through the stack gas discharge flow path 108 .

[0104] The AOG heat exchanger 22 can be connected to the stack gas discharge flow path 108 through which the anode exhaust gas (AOG) discharged from the stack 20a, 20b flows. The AOG heat exchanger 22 can be connected to the hot water supply flow path 313 through which the water discharged from the heat recovery tank 15 flows. The AOG heat exchanger 22 can perform heat exchange between the anode exhaust gas (AOG) flowing in through the stack gas discharge flow path 108 and the water supplied through the hot water supply flow path 313.

[0105] The hot water supply flow path 313 may be provided with a hot water pump 48 for flowing water stored in the heat recovery tank 15 toward the AOG heat exchanger 22 and / or a hot water flow meter 55 for detecting the flow rate of water flowing in the hot water supply flow path 313 .

[0106] The AOG heat exchanger 22 may be connected to the AOG supply flow path 109, and the anode exhaust gas (AOG) subjected to heat exchange may be discharged through the AOG supply flow path 109. The anode exhaust gas (AOG) discharged from the AOG heat exchanger 22 may flow to the fuel processing device 10 through the AOG supply flow path 109. The anode exhaust gas AOG supplied to the fuel processing device 10 through the AOG supply flow path 109 may be used as a combustion fuel for the burner 120. In addition, the anode exhaust gas (AOG) discharged from the AOG heat exchanger 22 may flow to the buffer tank 230 through the first buffer tank flow path 231. That is, a portion of the anode exhaust gas (AOG) discharged from the AOG heat exchanger 22 may flow to the fuel processing device 10, and the remaining portion may flow to the buffer tank 230.

[0107] The buffer tank 230 can store the anode exhaust gas (AOG) discharged from the battery stack 20. The anode exhaust gas (AOG) stored in the buffer tank 230 can be used in the battery stack preheating operation or shutdown operation (purge operation) described later. The buffer tank 230 can be connected to the AOG supply flow path 109 through the first buffer tank flow path 231. The buffer tank 230 can be connected to the gas mixer 235 through the second buffer tank flow path 234. The buffer tank 230 can be provided with a buffer tank valve 233 for regulating the flow of the anode exhaust gas (AOG) flowing into the buffer tank 230. Specifically, the buffer tank valve 233 can be arranged at the inlet end of the buffer tank 230. The buffer tank 230 can be provided with a pressure sensor 236 for measuring the pressure of the anode exhaust gas (AOG) stored in the buffer tank 230.

[0108] One end of the first buffer tank flow path 231 may be connected to the AOG supply flow path 109 at a position between the AOG valve 35 and the AOG moisture removal device 63. The other end of the first buffer tank flow path 231 may be connected to the buffer tank 230. A buffer tank compressor 232 may be disposed in the first buffer tank flow path 231 to compress the anode exhaust gas (AOG) flowing into the buffer tank 230. The buffer tank compressor 232 may be disposed at the front end of the buffer tank valve 233.

[0109] One end of the second buffer tank flow path 234 may be connected to the buffer tank 230. The other end of the second buffer tank flow path 234 may be connected to a gas mixer 235. A gas mixer 235 for mixing the anode exhaust gas (AOG) discharged from the buffer tank 230 and the air flowing into the stack 20 may be configured in the second buffer tank flow path 234. The gas mixer 235 may be located between the stack-side air supply valve 36 and the stack 20. The gas mixer 235 may adjust the flow of the anode exhaust gas (AOG) discharged from the buffer tank 230. For example, the gas mixer 235 may be a Venturi-type mixer.

[0110] The AOG supply flow path 109 may be provided with an AOG moisture removal device 63 for adjusting the amount of moisture contained in the anode off-gas (AOG) and / or an AOG valve 35 for adjusting the flow of the anode off-gas (AOG) supplied to the fuel processing device 10. The anode off-gas (AOG) flowing into the AOG moisture removal device 63 may be discharged from the AOG moisture removal device 63 after moisture is removed.

[0111] Condensed water generated in the AOG moisture removal device 63 may be discharged from the AOG moisture removal device 63 and flow through the third water recovery flow path 311. The third water recovery flow path 311 may be provided with a third water recovery valve 46 for regulating the flow of water. The third water recovery flow path 311 may be connected to the first water recovery flow path 309.

[0112] The stack-side air discharge flow path 211 can be connected to the individual discharge flow paths 208 and 209 corresponding to the stacks 20a and 20b, respectively. The air discharged from the stacks 20a and 20b can flow to the stack-side air discharge flow path 211 via the individual discharge flow paths 208 and 209. At this time, the air flowing through the stack-side air discharge flow path 211 can contain moisture generated by the electrochemical reaction occurring in the stacks 20a and 20b.

[0113] The stack-side air discharge flow path 211 may be provided with a stack-side air discharge valve 37 for adjusting the flow of air discharged from the cell stack 20 .

[0114] The stack-side air discharge flow path 211 may be connected to the humidifier 23. The humidifier 23 may supply moisture to the air flowing toward the stack 20 using moisture contained in the air supplied via the stack-side air discharge flow path 211. The air supplied to the humidifier 23 via the stack-side air discharge flow path 211 may be discharged to the humidifier discharge flow path 212 through the humidifier 23.

[0115] The water supply tank 13 may be connected to the water inflow passage 301 and may store water supplied via the water inflow passage 301. The water inflow passage 301 may be provided with a first liquid filter 92 for removing impurities contained in water supplied from the outside and / or a water inflow valve 41 for regulating the flow of water flowing into the water supply tank 13.

[0116] The water supply tank 13 may be connected to the water discharge passage 302, and at least a portion of the water stored in the water supply tank 13 may be discharged to the outside through the water discharge passage 302. The water discharge passage 302 may be provided with a water discharge valve 42 for regulating the flow of water discharged from the water supply tank 13.

[0117] The water supply tank 13 may be connected to the water storage flow path 308, and may store water flowing through the water storage flow path 308. For example, water discharged from the reformed gas moisture removal device 61, the additional moisture removal device 62, the AOG moisture removal device 63, and / or the air moisture removal device 64 and flowing through the third water recovery flow path 311 may flow into the water supply tank 13 through the water storage flow path 308. The second liquid filter 93 for removing impurities contained in the water returned to the water supply tank 13 may be arranged in the water storage flow path 308.

[0118] At least a portion of the water stored in the water supply tank 13 can flow to the reformed gas heat exchanger 21 under the action of the cooling water pump 43, and can exchange heat with the reformed gas in the reformed gas heat exchanger 21. The water discharged from the reformed gas heat exchanger 21 can flow into the cell stacks 20a, 20b via the cell stack water supply flow path 305.

[0119] The water flowing into the stacks 20a and 20b through the stack water supply flow path 305 can cool the stacks 20a and 20b. The water flowing into the stacks 20a and 20b can flow along the stack heat exchanger (not shown) included in the stacks 20a and 20b, and can absorb the heat generated by the electrochemical reaction occurring in the stacks 20a and 20b.

[0120] The plurality of cell stacks 20a and 20b may be connected via a water connection flow path 306. Water discharged from the first cell stack 20a may flow into the second cell stack 20b via the water connection flow path 306.

[0121] The water discharged from the cell stacks 20a and 20b can flow into the cooling water heat exchanger 24 via the cell stack water discharge flow path 307. The cooling water heat exchanger 24 can perform heat exchange between the water discharged from the cell stacks 20a and 20b and the water discharged from the heat recovery tank 15. The water discharged from the cell stacks 20a and 20b can flow into the water storage flow path 308 via the cooling water heat exchanger 24.

[0122] The water discharged from the heat recovery tank 15 by the hot water pump 48 may flow into the AOG heat exchanger 22 via the hot water supply flow path 313. The water after heat exchange with the anode off-gas (AOG) in the AOG heat exchanger 22 may be discharged to the first hot water circulation loop 314.

[0123] The air heat exchanger 25 may be connected to the humidifier discharge flow path 212 through which the air discharged from the humidifier 23 flows. The air heat exchanger 25 may be connected to the first hot water circulation circuit 314 through which the water discharged from the AOG heat exchanger 22 flows. The air heat exchanger 25 may perform heat exchange between the air flowing in through the humidifier discharge flow path 212 and the water flowing in through the first hot water circulation circuit 314.

[0124] The air heat-exchanged in the air heat exchanger 25 may be discharged from the air heat exchanger 25 via the air discharge flow path 213. The air discharge flow path 213 may communicate with the exhaust gas discharge flow path 210, and the exhaust gas flowing in the exhaust gas discharge flow path 210 and the air flowing in the air discharge flow path 213 may be mixed.

[0125] The air exhaust passage 213 may be provided with an air moisture removal device 64. The air moisture removal device 64 may adjust the amount of moisture contained in the air exhausted to the outside. The air flowing into the air moisture removal device 64 may be discharged from the air moisture removal device 64 after moisture is removed.

[0126] The condensed water generated in the air moisture removal device 64 may be discharged from the air moisture removal device 64 and flow through the fourth water recovery flow path 312. The fourth water recovery flow path 312 may be provided with a fourth water recovery valve 47 for regulating the flow of water. The fourth water recovery flow path 312 may be connected to the water storage flow path 308.

[0127] The water heat-exchanged in the air heat exchanger 25 may be discharged from the air heat exchanger 25 via the second hot water circulation flow path 315. The water discharged from the air heat exchanger 25 may flow into the cooling water heat exchanger 24 via the second hot water circulation flow path 315.

[0128] The cooling water heat exchanger 24 can perform heat exchange between water flowing in through the stack water discharge flow path 307 and water flowing in through the second hot water circulation flow path 315 .

[0129] The exhaust gas heat exchanger 26 may be connected to the exhaust gas discharge flow path 210 through which the exhaust gas flows. The exhaust gas heat exchanger 26 may be connected to the third hot water circulation flow path 316 through which the water discharged from the cooling water heat exchanger 24 flows. The exhaust gas heat exchanger 26 may perform heat exchange between the exhaust gas flowing in through the exhaust gas discharge flow path 210 and the water flowing in through the third hot water circulation flow path 316.

[0130] The exhaust gas that has undergone heat exchange in the exhaust gas heat exchanger 26 can be discharged to the exhaust gas flow path 214 , and the exhaust gas that has flowed in the exhaust gas flow path 214 can be exhausted to the outside.

[0131] The water heat-exchanged in the exhaust gas heat exchanger 26 can be discharged to the hot water recovery flow path 317 , and the water flowing in the hot water recovery flow path 317 can flow into the heat recovery tank 15 .

[0132] On the other hand, the fuel cell system 1 may further include at least one control unit (not shown). The control unit may include at least one processor. Here, the processor may be a common processor such as a CPU (central processing unit). Of course, the processor may be a dedicated device such as an ASIC or other hardware-based processor.

[0133] The control unit can control the overall operation of the fuel cell system 1. The control unit can be connected to each component provided in the fuel cell system 1, and can send and / or receive signals between each component. For example, the control unit can process the signal received from each component provided in the fuel cell system 1, and can send a control signal based on the result of the signal processing to each component provided in the fuel cell system 1.

[0134] Figure 4 The flowchart is about a control method of a fuel cell system according to an embodiment of the present invention. Figure 5 This is a flow chart of a control method for preheating operation of a fuel cell stack. Figure 6 This is the operation diagram of the fuel cell system during stack preheating operation.

[0135] Reference Figure 4 , the fuel cell system 1 can perform a stack preheating operation (S100) to preheat the stack. The stack preheating operation can be performed before the power generation operation described later. Usually, when the power generation operation of the fuel cell system 1 is initially entered, the stack 20 is cooled to the same state as the surrounding atmospheric temperature. Therefore, it is necessary to perform a stack preheating operation to preheat the stack 20 to a specified temperature so that the stack 20 can stably and efficiently perform the power generation operation. Below, refer to Figure 5 and Figure 6 Indicates that the battery stack is preheating.

[0136] Reference Figure 5 and Figure 6 The fuel cell system 1 may maintain an operation standby state for power generation operation (S110). The operation standby state may refer to a series of preparation processes for executing power generation operation, such as supplying power to each component of the fuel cell system 1.

[0137] After step S110, the fuel cell system 1 may perform an operation of preheating the burner 120 of the fuel processing device 10 (S120). For example, combustion heat may be generated by supplying a gas mixed with fuel gas and air to the burner 120. At this time, the internal temperature of the reformer 140 may gradually rise to an appropriate temperature (e.g., 800° C.) for promoting the reforming reaction.

[0138] In addition, during the operation of the preheating burner 120, the fuel cell system 1 can cut off the supply of fuel gas to the reformer 140. For example, the fuel cell system 1 can adjust the proportional control valve 31 so that all the fuel gas discharged from the desulfurizer 110 is supplied to the burner 120, thereby cutting off the supply of fuel gas to the reformer 140.

[0139] For example, during the operation of the preheating burner 120, the fuel cell system 1 may close the reformed gas valve 33, the bypass valve 34, and the AOG valve 35. At this time, the supply of fuel gas to the reformer 140 is cut off, so that no reformed gas is generated in the reformer 140. In addition, the reformed gas or the anode off-gas (AOG) does not flow in the reformed gas discharge flow path 104, the bypass flow path 105, and the AOG supply flow path 109.

[0140] In addition, the fuel cell system 1 may perform a reforming operation for initially generating a reformed gas (S120). For example, when the internal temperature of the reformer 140 rises to an appropriate temperature (e.g., 800° C.) due to preheating of the burner 120, the fuel cell system 1 may start a reforming operation for initially generating a reformed gas. For example, when the internal temperature of the first reactor 150 is above the minimum temperature for removing carbon monoxide (e.g., 160° C.), the fuel cell system 1 may start a reforming operation for initially generating a reformed gas.

[0141] When performing the operation of initially generating the reformed gas, the fuel cell system 1 may adjust the proportional control valve 31 so that part of the fuel gas discharged from the desulfurizer 110 is supplied to the reformer 140 and the rest is supplied to the burner 120 .

[0142] On the other hand, when the operation of initially generating the reformed gas is started, the fuel cell system 1 can drive the water pump 38 to supply water to the steam generator 130 of the fuel processing device 10, so that the water vapor used for the reforming reaction is supplied to the reformer 140. At this time, when the pressure of the water vapor supplied to the reformer 140 is maintained at or above the minimum pressure for the reforming reaction, for example, if a predetermined time has passed after the water pump 38 is driven, the fuel cell system 1 can supply a part of the fuel gas discharged from the desulfurizer 110 to the reformer 140.

[0143] On the other hand, during the operation of initially generating the reformed gas, the ratio of hydrogen in the reformed gas discharged from the fuel processing device 10 may be less than the preset minimum ratio. The preset minimum ratio may refer to the minimum value (for example, 80%) of the ratio of hydrogen in the reformed gas in order to achieve the target power generation. At this time, when the reformed gas with a hydrogen ratio lower than the preset minimum ratio is supplied to the fuel cell stack 20, it is difficult to generate electricity of the target power generation in the fuel cell stack 20, and therefore, the reformed gas discharged from the fuel processing device 10 can be reused as fuel for the burner 120.

[0144] For example, during the operation of initially generating the reformed gas, the fuel cell system 1 may close the reformed gas valve 33 and the AOG valve 35 and open the bypass valve 34. At this time, the reformed gas discharged from the fuel processing device 10 may flow into the fuel processing device 10 again via the reformed gas discharge flow path 104 and the bypass flow path 105, and may be used as a combustion fuel for the burner 120.

[0145] After step S120 , the fuel cell system 1 may open the stack-side air supply valve 36 ( S130 ). Therefore, the air humidified in the humidifying device 23 may be supplied to the gas mixer 235 via the stack-side air supply valve 36 .

[0146] After step S130 , the fuel cell system 1 may open the stack air discharge valve 37 ( S140 ) so that the gas generated by the chemical reaction between the reformed gas and air in the stack 20 may be supplied to the humidifier 23 via the stack air discharge valve 37 and then discharged to the outside.

[0147] After step S140 , the fuel cell system 1 may operate the second blower 72 at a predetermined rotation speed ( S150 ). Therefore, as the second blower 72 operates, air may be pressurized from the outside to the fuel cell stack 20 .

[0148] After step S150, the fuel cell system 1 can open the gas mixer 235 to mix the anode exhaust gas (AOG) stored in the buffer tank 230 with the air (S160). At this time, the buffer tank valve 233 can be closed so that the anode exhaust gas (AOG) stored in the buffer tank 230 flows to the second buffer tank flow path 234. Therefore, the air pressurized from the second blower 72 and the anode exhaust gas (AOG) stored in the buffer tank 230 can be mixed in the gas mixer 235 and supplied to the stack 20, and the stack 20 can be quickly preheated under the action of the exothermic reaction caused by the chemical reaction generated at the cathode inlet end of the stack 20. Among them, the anode exhaust gas (AOG) stored in the buffer tank 230 can be the anode exhaust gas (AOG) stored during the test operation of the fuel cell system 1, or the anode exhaust gas (AOG) remaining after the cleaning operation described later.

[0149] Figure 7 This is a flow chart of a control method for power generation operation. Figure 8a and Figure 8b This is the operation diagram of the fuel cell system during power generation operation. Specifically, Figure 8a This is an operation diagram of a fuel cell system that stores anode off-gas (AOG) in a buffer tank during power generation operation. Figure 8b This is an operation diagram of the fuel cell system after the anode off-gas (AOG) is stored in the buffer tank during power generation operation.

[0150] Refer again Figure 4 The fuel cell system 1 may perform a power generation operation (S200) of generating electricity in the stack by chemical reaction of the reformed gas and air. When performing the power generation operation, the fuel cell system 1 may perform a step of storing the anode exhaust gas (AOG) discharged from the stack 20 in the buffer tank 230. Figure 7 8 and 8 illustrate the power generation operation.

[0151] Reference Figure 7 8 , the fuel cell system 1 may shut down the gas mixer 235 ( S210 ). Therefore, the anode off-gas (AOG) stored in the buffer tank 230 may be shut off from being supplied to the gas mixer 235 during the power generation operation.

[0152] After step S210 , the fuel cell system 1 may adjust the number of revolutions of the second blower 72 according to the target power generation ( S220 ). At this time, the stack side air supply valve 36 may be opened, thereby supplying external air to the stack 20 via the humidifier 23 and the gas mixer 235 .

[0153] On the other hand, the fuel cell system 1 can adjust the reformer 140 of the fuel processing device 10 according to the target power generation (S220). At this time, the fuel cell system 1 can open the reformed gas valve 33 and close the bypass valve 34 to supply the reformed gas discharged from the fuel processing device 10 to the stack 20. In addition, the fuel cell system 1 can open the AOG valve 35 so that part of the anode exhaust gas (AOG) discharged from the stack 20 is supplied to the fuel processing device 10 again.

[0154] After step S220, the fuel cell system 1 may open the buffer tank valve 233 (S230). After step S230, the fuel cell system 1 may drive the buffer tank compressor 232 (S240). Therefore, as the buffer tank compressor 232 is driven, the rest of the anode exhaust gas (AOG) discharged from the stack 20 may be compressed and supplied to the buffer tank 230.

[0155] After step S240 , the fuel cell system 1 may detect the pressure Pbt of the anode off-gas (AOG) stored in the buffer tank 230 using the pressure sensor 236 disposed in the buffer tank 230 ( S250 ).

[0156] After step S250, the fuel cell system 1 can determine whether the storage of the anode exhaust gas (AOG) in the buffer tank 230 has been completed (step S260). For example, the fuel cell system 1 can determine whether the pressure Pbt of the buffer tank 230 detected by the pressure sensor 236 in the step S250 action is above the first set pressure Pa. The first set pressure Pa refers to the pressure value of the anode exhaust gas (AOG) corresponding to 100% of the total storage amount of the anode exhaust gas (AOG) that can be stored in the buffer tank 230, which can indicate that the storage of the anode exhaust gas (AOG) in the buffer tank 230 has been completed.

[0157] When the pressure Pbt of the buffer tank 230 is less than the first set pressure Pa ("No" in S260), the fuel cell system 1 determines that the storage of the anode exhaust gas (AOG) in the buffer tank 230 is not completed, and returns to step S250 to act, and can continue to detect the pressure Pbt of the buffer tank 230 until the storage of the anode exhaust gas (AOG) in the buffer tank 230 is completed, and the pressure Pbt of the buffer tank 230 can be compared with the first set pressure Pa.

[0158] When the pressure Pbt of the buffer tank 230 is above the first set pressure ("Yes" in S260), the fuel cell system 1 can close the buffer tank valve 233 (S270). After step S270, the fuel cell system 1 can stop the buffer tank compressor 232 (S280). Therefore, the fuel cell system 1 can cut off the anode exhaust gas (AOG) discharged from the stack 20 from flowing into the buffer tank 230, and can supply all the anode exhaust gas (AOG) discharged from the stack 20 to the fuel processing device 10.

[0159] Fig. 9 This is a flowchart of a control method for stopping operation. Fig.10a and Fig.10b This is an operation diagram of the fuel cell system during shutdown (purge operation). Specifically, Fig.10a is the operation diagram of the fuel cell system in shutdown. Fig.10b This is an operation diagram of the fuel cell system after the shutdown operation is completed.

[0160] Refer again Figure 4 , the fuel cell system 1 can terminate the power generation of the cell stack 20 and execute a shutdown operation (purge operation) (S300) for removing the residual oxygen in the cell stack 20. When the power generation operation of the fuel cell system is terminated, there is usually a problem that the cathode electrode part is oxidized by the residual oxygen after the chemical reaction in the cell stack 20, which reduces the life of the cell stack 20. Therefore, after the power generation operation of the fuel cell system 1 is terminated, it is necessary to execute a shutdown operation (purge operation) for removing the residual oxygen in the cell stack. Below, refer to Fig. 9 , Fig.10a and Fig.10b Instructions to stop operation (clear operation).

[0161] Reference Fig. 9 , Fig.10a and Fig.10b , when the user ends the power generation operation or the power generation operation is ended due to an error in the system, the fuel cell system 1 can perform post-heat operation to gradually reduce the power generation of the stack (S310). Among them, post-heat operation can refer to the operation of reducing the output in stages and stopping the operation to prevent reliability problems caused by the reformer temperature and the sharp output changes in the stack. For example, the fuel cell system 1 can reduce the flow of air and reforming gas supplied to the stack 20 in stages by adjusting the second blower 72 and the fuel processing device 10.

[0162] After step S310 , the fuel cell system 1 may close the stack-side air supply valve 36 ( S320 ). Thus, the fuel cell system 1 may cut off the air supply to the stack 20 .

[0163] After step S320, the fuel cell system 1 can open the stack side air discharge valve 37 (S330). After step S330, the fuel cell system 1 can open the gas mixer 235 (S340). At this time, the fuel cell system 1 can close the buffer tank valve 233 to supply the anode exhaust gas (AOG) stored in the buffer tank 230 to the gas mixer 235. Therefore, the anode exhaust gas (AOG) supplied to the gas mixer 235 is supplied to the stack 20, so that the oxygen remaining in the cathode (Cathode) electrode part can be discharged to the outside of the stack. Thus, after the power generation operation is completed, the oxygen remaining in the cathode (Cathode) electrode part is removed, thereby preventing the oxidation of the cathode (Cathode) electrode part.

[0164] After step S340 , the fuel cell system 1 may detect the pressure Pbt of the anode off-gas (AOG) stored in the buffer tank 230 using the pressure sensor 236 disposed in the buffer tank 230 ( S350 ).

[0165] After step S350, the fuel cell system 1 may determine whether the oxygen remaining in the stack is removed (step S360). For example, the fuel cell system 1 may determine whether the pressure Pbt of the buffer tank 230 detected by the pressure sensor 236 in the step S350 is greater than the second set pressure Pb. The second set pressure Pb may refer to the pressure value of the anode exhaust gas (AOG) corresponding to 50% of the total storage amount of the anode exhaust gas (AOG) that can be stored in the buffer tank 230.

[0166] When the pressure Pbt of the buffer tank 230 is greater than the second set pressure Pb ("No" in S360), the fuel cell system 1 determines that the removal of the residual oxygen in the battery stack 20 is not completed, and returns to step S350 to act, and can continue to detect the pressure Pbt of the buffer tank 230 until the removal of the residual oxygen in the battery stack 20 is completed, and at the same time, the pressure Pbt of the buffer tank 230 can be compared with the second set pressure Pb.

[0167] When the pressure Pbt of the buffer tank 230 is lower than the second set pressure Pb (Yes in S360 ), the fuel cell system 1 may shut down the gas mixer 235 ( S370 ). Therefore, the anode off-gas (AOG) stored in the buffer tank 230 may be cut off from being supplied to the gas mixer 235 .

[0168] The accompanying drawings are only provided to facilitate understanding of the embodiments disclosed in this specification. The technical ideas disclosed in this specification are not limited to the accompanying drawings. The present invention includes all changes, equivalents and substitutes made within the technical ideas and technical scope of the present invention.

[0169] Similarly, the actions are described in a particular order in the drawings, but it should not be understood that in order to obtain the preferred results, such actions must be performed in the particular order shown or in sequence, or all the actions shown must be performed. In certain situations, multitasking and parallel processing may be advantageous.

[0170] In addition, the preferred embodiments of the present invention are shown and described above, but the present invention is not limited to the above-mentioned specific embodiments. Obviously, a person skilled in the art can make various modified implementations without departing from the main purpose of the present invention as claimed in the claims, and such modified embodiments should not be understood separately from the technical ideas or prospects of the present invention.

Claims

1. A fuel cell system, in, include: The fuel cell stack generates electricity using reformed gas; a fuel processing device for supplying reformed gas to the fuel cell stack; a first gas flow path connecting the fuel cell stack and the fuel processing device and allowing the reformed gas discharged from the fuel processing device to flow; a second gas flow path, connecting the fuel cell stack and the fuel processing device, through which the anode exhaust gas discharged from the fuel cell stack flows; A buffer tank storing a portion of the anode exhaust gas discharged from the fuel cell stack; a first buffer tank flow path connecting the buffer tank and the second gas flow path; a second buffer tank flow path for the anode exhaust gas stored in the buffer tank to flow; a gas mixer connected to the flow path of the second buffer tank and supplying the anode exhaust gas stored in the buffer tank to the fuel cell stack; as well as a control unit, which supplies the anode exhaust gas stored in the buffer tank to the fuel cell stack by adjusting the gas mixer to preheat the fuel cell stack or remove residual air in the fuel cell stack; The fuel cell system further comprises: a blower for supplying air to the fuel cell stack; and an air supply valve, disposed between the battery stack and the blower, to adjust the air supplied from the blower to the battery stack; During the stack warm-up operation, the control unit opens the gas mixer and the air supply valve and operates the blower so that air and anode exhaust gas are mixed and supplied to the stack.

2. The fuel cell system according to claim 1, in, Also includes: a buffer tank valve, disposed in the first buffer tank flow path and controlling the flow of anode exhaust gas supplied to the buffer tank; as well as A buffer tank compressor, located at the front end of the buffer tank valve, compresses the anode exhaust gas supplied to the buffer tank; During power generation operation, the control unit closes the gas mixer, opens the buffer tank valve, and operates the buffer tank compressor to compress a portion of the anode off-gas discharged from the cell stack and store the compressed gas in the buffer tank.

3. The fuel cell system according to claim 2, in, Also includes: A pressure sensor, disposed in the buffer tank, for measuring the pressure of the anode exhaust gas stored in the buffer tank; The control unit closes the buffer tank valve and stops the buffer tank compressor when the pressure of the anode off-gas stored in the buffer tank measured by the pressure sensor is equal to or higher than a first set pressure.

4. The fuel cell system according to claim 1, in, During the purge operation, the control unit closes the air supply valve and opens the gas mixer to supply the anode off-gas stored in the buffer tank to the fuel cell stack.

5. The fuel cell system according to claim 4, in, Also includes: A pressure sensor, disposed in the buffer tank, for measuring the pressure of the anode exhaust gas stored in the buffer tank; The control unit closes the gas mixer and ends the purge operation when the pressure of the anode off-gas in the buffer tank measured by the pressure sensor is equal to or lower than a second set pressure.

6. The fuel cell system according to claim 1, in, Also includes: a first gas valve, disposed in the first gas flow path, to control the flow of reformed gas supplied to the fuel cell stack; a bypass flow path connecting the first gas flow path and the fuel processing device; and a bypass valve, disposed in the bypass flow path, and controlling the flow of the reformed gas in the bypass flow path; During stack warm-up operation, the control unit closes the first gas valve and opens the bypass valve to allow the reformed gas discharged from the fuel processing device to flow into the fuel processing device again.

7. A control method for a fuel cell system, in, The fuel cell system comprises: Battery stack; A blower, supplying air to the fuel cell stack; a fuel processing device for supplying reformed gas to the fuel cell stack; a buffer tank for storing a portion of anode exhaust gas discharged from the fuel cell stack; and a gas mixer for mixing the anode exhaust gas and the air; The control method of the fuel cell system comprises: The step of performing a power generation operation of storing the anode exhaust gas discharged from the stack in the buffer tank by adjusting a buffer tank valve for controlling the flow of the anode exhaust gas supplied to the buffer tank and a buffer tank compressor for compressing the anode exhaust gas; and A stack preheating operation for preheating the stack is performed by adjusting an air supply valve for controlling the flow of air to the stack, the gas mixer, and the blower.

8. The control method of the fuel cell system according to claim 7, in, The steps of performing the power generation operation include: The gas mixer is closed, the buffer tank valve is opened, and the buffer tank compressor is operated to compress a part of the anode exhaust gas discharged from the stack and store it in the buffer tank.

9. The control method of the fuel cell system according to claim 8, in, The step of storing the anode exhaust gas discharged from the fuel cell stack in the buffer tank comprises: A step of closing the buffer tank valve and stopping the buffer tank compressor when the pressure measured by the pressure sensor measuring the pressure of the anode off-gas stored in the buffer tank is equal to or higher than a first set pressure.

10. The control method of the fuel cell system according to claim 7, in, Also includes: The step of performing a purge operation to remove air remaining in the stack is performed by adjusting the air supply valve and the gas mixer.

11. The control method of the fuel cell system according to claim 10, in, The steps of performing the cleaning operation include: The step of closing the air supply valve and opening the gas mixer to supply the anode exhaust gas stored in the buffer tank to the fuel cell stack.

12. The control method of the fuel cell system according to claim 11, in, The steps of performing the cleaning operation include: The step of closing the gas mixer and terminating the purge operation when the pressure measured by the pressure sensor measuring the pressure of the anode off-gas stored in the buffer tank is equal to or lower than a second set pressure.

13. The control method of the fuel cell system according to claim 7, in, The steps of performing the stack preheating operation include: The gas mixer and the air supply valve are opened, and the blower is operated so that air and anode exhaust gas are mixed in the gas mixer and then supplied to the fuel cell stack.

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