Fuel cell system

Abstract

The present invention provides a fuel cell system. The fuel cell system according to an embodiment of the present invention includes: a reformer that performs a reforming process of generating hydrogen from gasified fuel; a burner that supplies heat to the reformer; a fuel cell stack that generates an electrochemical reaction using reformed gas discharged from the reformer and air to generate electric power; a first supply pipe that supplies external air to the burner; a second supply pipe that supplies external air to the fuel cell stack; a first storage tank that stores liquid fuel; a second storage tank that supplies gasified fuel to the reformer; and a fuel evaporator that exchanges heat between the liquid fuel discharged from the first storage tank and the air flowing in the first supply pipe or the air flowing in the second supply pipe, and conveys the gasified fuel to the second storage tank.

Description

Technical Field

[0001] The present invention relates to a fuel cell system, and more particularly, to a fuel cell system using a liquid fuel. Background Art

[0002] A fuel cell system is a power generation system that generates electric power by causing an electrochemical reaction between hydrogen and oxygen contained in a hydrocarbon-based substance such as methanol, ethanol, or natural gas.

[0003] The fuel cell can adjust the power generation amount by adjusting the flow rate of air supplied to the stack and the amount of gas reformed by the reformer. The gas supplied to the reformer generates hydrogen by supplying and reforming the vaporized fuel.

[0004] The flow rate of air supplied to the stack can be adjusted using a blower. However, since the flow rate of air adjusted by the blower is limited, when the power generation operating conditions are too high, there is a problem of reduced power generation efficiency due to the difficulty of supplying stable air.

[0005] In addition, when improving the burner for heating the reformer, the density of the reformed gas, etc., the reaction efficiency of the reformer can be improved.

[0006] In Korean Patent No. 10-2116876, a fuel cell system using a liquid fuel is disclosed. However, in the above document, as a structure for directly supplying a liquid fuel to a fuel processing device for reforming the liquid fuel, it cannot utilize the heat supply generated by the phase change of the liquid fuel. Summary of the Invention

[0007] The problem to be solved by the present invention is to provide a fuel cell system that increases the density of air supplied to the burner of the reformer by utilizing the fuel supplied to the reformer.

[0008] Another problem of the present invention is to provide a fuel cell system that increases the density of the reformed gas discharged from the reformer and supplied to the burner by utilizing the fuel supplied to the reformer.

[0009] Still another problem of the present invention is to provide a fuel cell system that increases the density of air supplied to the stack by utilizing the fuel supplied to the reformer.

[0010] The object of the present invention is not limited to the above-mentioned objects, and those skilled in the art can clearly understand other objects not mentioned from the following description.

[0011] The fuel cell system of the present invention includes: a reformer that performs a reforming process of generating hydrogen from gasified fuel; a burner that supplies heat to the reformer; an electric stack that generates an electrochemical reaction using the reformed gas and air discharged from the reformer to generate electric power; a first supply pipe that supplies external air to the burner; and a second supply pipe that supplies external air to the electric stack.

[0012] To solve the above problems, the fuel cell system of the present invention includes: a first storage tank that stores liquid fuel; a second storage tank that supplies gasified fuel to the reformer; and a fuel evaporator that exchanges heat between the liquid fuel discharged from the first storage tank and the air flowing in the first supply pipe or the air flowing in the second supply pipe, and conveys the gasified fuel to the second storage tank. Thus, it is possible to increase the density of the air supplied to the electric stack or the air supplied to the burner by utilizing the temperature difference of the liquid fuel.

[0013] The fuel evaporator includes: a first fuel evaporator that exchanges heat between the liquid fuel discharged from the first storage tank and the air flowing in the first supply pipe; and a second fuel evaporator that exchanges heat between the liquid fuel discharged from the first storage tank and the air flowing in the second supply pipe. Thus, it is possible to cool the air supplied to the electric stack or the air supplied to the burner.

[0014] The fuel cell system of the present invention includes: a first liquid gas supply pipe that connects the first storage tank and the first fuel evaporator; a second liquid gas supply pipe that connects the first storage tank and the second fuel evaporator; a first expansion valve disposed in the first liquid gas supply pipe to open and close the internal flow path of the first liquid gas supply pipe or adjust the opening degree of the first liquid gas supply pipe; and a second expansion valve disposed in the second liquid gas supply pipe to open and close the internal flow path of the second liquid gas supply pipe or adjust the opening degree of the second liquid gas supply pipe. Thus, it is possible to adjust the flow of the liquid fuel according to the operation mode.

[0015] In the preheating mode of preheating the reformer, the first expansion valve expands the internal flow path of the first liquid gas supply pipe, and the second expansion valve closes the internal flow path of the second liquid gas supply pipe. Thus, it is possible to supply liquid fuel to the first fuel evaporator disposed in the first supply pipe through which air flows in the preheating mode.

[0016] In the power generation mode of generating electric power using the electric stack, the first expansion valve expands the opening degree of the internal flow path of the first liquid gas supply pipe, and the second expansion valve expands the internal flow path of the second liquid gas supply pipe. Thus, it is possible to cool both the air supplied to the electric stack and the air supplied to the burner.

[0017] The fuel cell system of the present invention includes: a reformed gas discharge pipe that conveys the reformed gas discharged from the reformer to the burner or to the fuel cell stack. The fuel evaporator includes: a third fuel evaporator disposed in the reformed gas discharge pipe, which exchanges heat between the reformed gas discharged from the reformer and the liquid fuel, thereby being able to cool the high-pressure reformed gas discharged from the reformer.

[0018] The fuel cell system of the present invention includes: a third liquid gas supply pipe connecting the first storage tank and the third fuel evaporator; and a third expansion valve disposed in the third liquid gas supply pipe to open and close the internal flow path of the third liquid gas supply pipe or adjust the opening degree of the third liquid gas supply pipe, thereby being able to supply liquid fuel to the third fuel evaporator according to the operating mode.

[0019] In the reforming mode of increasing the amount of hydrogen contained in the reformed gas discharged from the reformer, the first expansion valve expands the opening degree of the internal flow path of the first liquid gas supply pipe, and the third expansion valve expands the opening degree of the internal flow path of the third liquid gas supply pipe, thereby being able to vaporize the liquid fuel using the gas discharged from the reformer and being able to increase the density of the reformed gas discharged from the reformer.

[0020] In the reforming mode, the opening degree of the third expansion valve is expanded to be larger than the opening degree of the first expansion valve, thereby being able to effectively phase-change the liquid fuel.

[0021] In the power generation mode of generating electric power using the fuel cell stack, the first expansion valve expands the opening degree of the internal flow path of the first liquid gas supply pipe, the second expansion valve expands the opening degree of the internal flow path of the second liquid gas supply pipe, and the third expansion valve expands the opening degree of the internal flow path of the third liquid gas supply pipe, so as to be able to vaporize the liquid fuel using the three fuel evaporators.

[0022] In the power generation mode, the opening degree of the third expansion valve is expanded to be larger than the opening degree of the first expansion valve or the second expansion valve, so as to be able to effectively phase-change the liquid fuel.

[0023] The fuel cell system of the present invention includes: a liquid gas common pipe connecting the fuel processing device and the first liquid gas supply pipe, the second liquid gas supply pipe, or the third liquid gas supply pipe; and a common pipe valve for opening and closing the liquid gas common pipe, thereby being able to stably store the liquid fuel stored in the first storage tank.

[0024] The fuel cell system of the present invention includes: a first blower disposed in the first supply pipe for supplying external air to the first supply pipe; and a second blower disposed in the second supply pipe for supplying external air to the second supply pipe. When the first blower operates, the common pipe valve opens, whereby when the fuel cell system operates, the liquid fuel stored in the first storage tank can be discharged.

[0025] The fuel evaporator includes: a housing forming an outer shape; a fuel flow portion disposed inside the housing and formed to allow liquid fuel to flow; and a gas flow portion disposed inside the housing and formed to allow air or reformed gas to flow.

[0026] A plurality of protrusions are respectively formed inside the pipe forming the fuel flow portion and inside the pipe forming the gas flow portion, whereby the heat exchange area can be increased.

[0027] The specific content of other embodiments is included in the detailed description and the drawings.

[0028] The fuel cell system according to the present invention has one or more of the following effects.

[0029] First, by using the heat and cold generated by the phase change of the liquid fuel to increase the density of the air supplied to the burner of the heating reformer, the efficiency of the reforming reaction can be increased.

[0030] Second, by using the heat and cold generated by the phase change of the liquid fuel to increase the density of the air supplied to the fuel cell stack, the reaction efficiency for generating electricity inside the fuel cell stack can also be increased.

[0031] Third, by using the heat and cold generated by the phase change of the liquid fuel to increase the density of the reformed gas discharged from the reformer and supplied to the burner of the heating reformer, the efficiency of the reforming reaction can be increased.

[0032] The effects of the present invention are not limited to the effects mentioned above, and those skilled in the art can more clearly understand other effects not mentioned through the description of the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a configuration diagram of a fuel cell system according to an embodiment of the present invention.

[0034] Figure 2 It is a diagram for explaining a fuel processing device according to an embodiment of the present invention.

[0035] Figure 3 It is a diagram schematically showing a structure for explaining the flow and heat exchange of liquid fuel and vaporized fuel in a fuel cell system according to an embodiment of the present invention.

[0036] Figure 4 It is a schematic diagram of the first storage tank and its related structures for illustrating an embodiment of the present invention.

[0037] Figure 5 It is for illustrating Figure 3 a diagram of the flow of fuel and air in the preheating mode.

[0038] Figure 6 It is for illustrating Figure 3 a diagram of the flow of fuel and air in the reforming mode.

[0039] Figure 7 It is for illustrating Figure 3 a diagram of the flow of fuel and air in the power generation mode.

[0040] Figure 8A and Figure 8B are diagrams for illustrating the structure of the fuel evaporator of the first embodiment, where Figure 8A is a schematic cross-sectional view for illustrating the gas flow portion, Figure 8B is a schematic cross-sectional view for illustrating the fuel flow portion.

[0041] Figure 9A and Figure 9B are diagrams for illustrating the structure of the fuel evaporator of the second embodiment, where Figure 9A is a schematic cross-sectional view for illustrating the gas flow portion, Figure 9B is a schematic cross-sectional view for illustrating the fuel flow portion.

[0042] Figure 10A and Figure 10B are diagrams for illustrating the structure of the fuel evaporator of the third embodiment, where Figure 10A is a schematic cross-sectional view for illustrating the gas flow portion, Figure 10B is a schematic cross-sectional view for illustrating the fuel flow portion.

[0043] Figure 11A and Figure 11B respectively are diagrams showing Figure 10A and Figure 10B the morphological deformation states of the internal tubes in.

[0044] Figure 12 is a perspective view of the fuel evaporator of the fourth embodiment of the present invention.

[0045] Figure 13A and Figure 13B are diagrams for illustrating the structure of the fuel evaporator of the fourth embodiment, where Figure 13A is a schematic cross-sectional view for illustrating the gas flow portion, Figure 13B is a schematic cross-sectional view for illustrating the fuel flow portion.

[0046] Figure 14A and Figure 14B respectively show the diagrams Figure 13A and Figure 13B showing the state of morphological deformation of the internal tubes in

[0047] Description of reference numerals

[0048] 1: Fuel cell system; 10: Fuel processing unit; 20a, 20b: Stack; 71: First blower; 72: Second blower; 140: Reformer; 400: First storage tank; 402: Second storage tank; 410: First fuel evaporator; 412: Second fuel evaporator; 414: Third fuel evaporator; 440: First expansion valve; 442: Second expansion valve; 444: Third expansion valve Detailed description of the preferred embodiments

[0049] The advantages, features, and methods for realizing them of the present invention can be made more apparent by referring to the accompanying drawings and the detailed embodiments described hereinafter. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms. These embodiments are only for more completely disclosing the present invention, and thus more fully indicating the scope of the present invention to those of ordinary skill in the technical field to which the present invention pertains. The present invention is only defined by the scope of the claims. The same reference numerals denote the same structural elements throughout the specification.

[0050] Hereinafter, the present invention will be described by way of embodiments of the present invention with reference to the drawings for explaining a fuel cell system.

[0051] Hereinafter, with reference to Figure 1 and Figure 2 the overall structure of the fuel cell system 1 of the first embodiment will be described.

[0052] With reference to Figure 1 , the fuel cell system 1 may include: a fuel processing unit I, a power generation unit II, a cooling water circulation unit III, and / or a heat recovery unit IV.

[0053] The fuel processing unit I may include a fuel processing device 10, a fuel valve 30 for regulating the flow of fuel gas supplied to the fuel processing device 10, a first blower 71 for causing air to flow to the fuel processing device 10, and the like.

[0054] With reference to Figure 2 , 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.

[0055] The desulfurizer 110 can perform a desulfurization process for removing sulfur compounds contained in the fuel gas. For example, an adsorbent can 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 can be adsorbed onto the adsorbent.

[0056] The adsorbent can be composed of metal oxides, zeolite, activated carbon, etc.

[0057] The desulfurizer 110 can also include a filter for removing impurities contained in the fuel gas.

[0058] The burner 120 can 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 can be mixed in the first mixer 111 and supplied to the burner 120. At this time, the burner 120 can generate combustion heat by burning the mixed gas composed of the fuel gas and the air. At this time, the internal temperature of the reformer 140 can be maintained at an appropriate temperature (e.g., 800 °C) by the heat provided by the burner 120.

[0059] On the other hand, the exhaust gas generated in the burner 120 by the combustion of the mixed gas can be discharged to the outside of the fuel processing device 10.

[0060] The steam generator 130 can vaporize water and discharge it as water vapor. For example, the steam generator 130 can vaporize water by absorbing heat from the exhaust gas generated in the burner 120, the first reactor 150, and / or the second reactor 160.

[0061] The steam generator 130 can be disposed adjacent to the first reactor 150, the second reactor 160, and / or the pipe through which the exhaust gas discharged from the burner 120 flows.

[0062] The reformer 140 can perform a reforming process for generating hydrogen from the fuel gas from which 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 can 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 can be generated.

[0063] The first reactor 150 can reduce carbon monoxide generated by the reforming reaction in 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 room temperature (e.g., 200 °C).

[0064] The first reactor 150 can be referred to as a shift reactor.

[0065] The second reactor 160 can reduce the remaining carbon monoxide in the components contained in the gas discharged from the first reactor 150. For example, the carbon monoxide included in the gas discharged from the first reactor 150 can react with oxygen inside the second reactor 160 to undergo a preferential oxidation (PROX) reaction.

[0066] 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, which dilutes the hydrogen by the additionally supplied air, resulting in the disadvantage that the concentration of hydrogen supplied to the fuel cell stack decreases. Therefore, in order to overcome such a disadvantage, a selective methanation reaction in which carbon monoxide and hydrogen react can be utilized.

[0067] 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 can be referred to as reformed gas.

[0068] The fuel cell stacks 20a, 20b can generate electric energy by electrochemically reacting the reformed gas supplied from the fuel processing device 10.

[0069] The fuel cell stacks 20a, 20b can be composed of a stack of single units that undergo an electrochemical reaction.

[0070] A single unit can be composed of a membrane electrode assembly (MEA) having 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.

[0071] The fuel cells 20a and 20b may further include a fuel cell heat exchanger (not shown) for releasing the heat generated during the electrochemical reaction process. The fuel cell heat exchanger may be a heat exchanger that uses water as a refrigerant. For example, the cooling water supplied to the fuel cell heat exchanger may absorb the heat generated during the electrochemical reaction process, and the cooling water whose temperature has risen due to the absorbed heat may be discharged to the outside of the fuel cell heat exchanger.

[0072] Referring Figure 1 , the fuel processing unit I includes: a first storage tank 400 for storing liquid fuel; a second storage tank 402 for supplying gasified fuel to the reformer 140 of the fuel processing device 10; and fuel evaporators 410, 412, 414 for heat-exchanging with external air to make the liquid fuel discharged from the first storage tank 400 into gasified fuel. The fuel evaporators 410, 412, 414 may include: a first fuel evaporator 410 disposed in the first supply pipe; a second fuel evaporator 412 disposed in the second supply pipe; and a third fuel evaporator 414 disposed in the reformed gas discharge pipe 104a. Hereinafter, the structures and connection relationships of the first storage tank 400, the second storage tank 402, and the fuel evaporators 410, 412, 414 will be specifically described.

[0073] The fuel valve 30 may be disposed in a fuel supply pipe (not shown) that forms a fuel supply flow path 101 for the fuel gas supplied to the fuel processing device 10. The flow rate of the fuel gas supplied to the fuel processing device 10 can be adjusted according to the opening degree of the fuel valve 30. For example, the fuel valve 30 can cut off the fuel supply flow path 101 to interrupt the supply of fuel gas to the fuel processing device 10.

[0074] A first fuel flow meter 51 for detecting the flow rate of the fuel gas flowing in the fuel supply flow path 101 may be disposed in the fuel supply pipe.

[0075] The fuel processing unit I may include: a first supply pipe (not shown) in which a first supply flow path 202 is formed to supply external air to the fuel processing device 10; and a first blower 71 disposed in the first supply pipe to supply external air to the fuel processing device 10.

[0076] The first blower 71 may cause the air flowing in from the outside to flow through the first supply flow path 202 to the fuel processing device 10. The first blower 71 may cause the air flowing in from the outside through the external air inflow flow path 201 to flow to the fuel processing device 10.

[0077] The air flowing into the fuel processing device 10 via the first supply flow path 202 can be supplied to the burner 120 of the fuel processing device 10. For example, the air flowing into the fuel processing device 10 can be mixed with the fuel gas discharged from the desulfurizer 110 in the first mixer 111 and supplied to the burner 120.

[0078] In the external air inlet pipe (not shown) forming the external air inlet flow path 201, a first air filter 91 for removing foreign matters such as dust contained in the air and a first air side check valve 81 for restricting the flow direction of the air can be arranged.

[0079] The fuel processing unit I may include: a first internal gas pipe (not shown) forming a first internal gas flow path 102 for the fuel gas discharged from the desulfurizer 110 to flow to the reformer 140. In the first internal gas pipe, 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 flowmeter 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 restricting the flow direction of the fuel gas flowing in the internal gas flow path 102, and / or a sulfur detection device 94 can be arranged.

[0080] The proportional control valve 31 can regulate the flow rate, pressure, etc. of the fuel gas discharged from the desulfurizer 110 and flowing to the reformer 140 in an electric control mode through internal / external feedback.

[0081] The sulfur detection device 94 can detect the sulfur contained in the fuel gas discharged from the desulfurizer 110. The sulfur detection device 94 may include an indicator that changes color by reacting with the sulfur compound not removed by the adsorbent of the desulfurizer 110. Among them, the indicator may include phenolphthalein, molybdenum compounds, etc.

[0082] The fuel processing unit I may include: a second internal gas pipe (not shown) forming a second internal gas flow path 103 for delivering the fuel gas discharged from the desulfurizer 110 to the burner 120. The burner 120 can burn using the fuel gas flowing in via the second internal gas flow path 103.

[0083] The first internal gas flow path 102 and the second internal gas flow path 103 can communicate with each other.

[0084] The fuel processing device 10 can be connected to a water supply pipe (not shown) forming a water supply flow path 303 for the water flowing out of the water supply tank 13. In the water supply pipe, a water pump 38 for forming the flow of the water flowing in the water supply flow path 303, a water supply valve 39 for regulating the flow of the water, and a water flowmeter 54 for detecting the flow rate of the water flowing in the water supply flow path 303 can be arranged.

[0085] The exhaust gas generated by the burner 120 of the fuel processing device 10 can be discharged from the fuel processing device 10 via the exhaust gas discharge flow path 210.

[0086] The fuel processing device 10 can be connected to a reformed gas discharge pipe (not shown) that forms the reformed gas discharge flow path 104. The reformed gas discharged from the fuel processing device 10 can flow via the reformed gas discharge flow path 104.

[0087] The reformed gas discharge pipe can be connected to a reformed gas heat exchanger 21 that performs heat exchange on the reformed gas. A reformed gas valve 33 for adjusting the flow of the reformed gas flowing into the reformed gas heat exchanger 21 can be arranged in the reformed gas discharge pipe.

[0088] The reformed gas discharge pipe can be connected to a bypass pipe (not shown) that forms a bypass flow path 105 so that the reformed gas discharged from the fuel processing device 10 flows back to the fuel processing device 10. The bypass pipe can be connected to the fuel processing device 10. The reformed gas flowing out of the fuel processing device 10 can be supplied to the burner 120 via the bypass flow path 105. The reformed gas supplied to the burner 120 via the bypass flow path 105 can be used as the combustion fuel for the burner 120. A bypass valve 34 for adjusting the flow of the reformed gas flowing into the fuel processing device 10 can be arranged in the bypass pipe.

[0089] The power generation unit II can include: fuel cells 20a, 20b; a reformed gas heat exchanger 21 for performing heat exchange on the reformed gas discharged from the fuel processing device 10; an AOG heat exchanger 22 for performing heat exchange on the gas that has not reacted in the fuel cells 20a, 20b and is discharged; and a humidifying device 23 for supplying moisture to the air supplied to the fuel cells 20a, 20b.

[0090] It can include a second blower 72 or the like for making air flow to the fuel cells 20a, 20b. Among them, the gas that has not reacted in the fuel cells 20a, 20b and is discharged can be called anode off gas (AOG). In an embodiment of the present invention, the fuel cell system 1 is described as having two fuel cells 20a, 20b, but it is not limited thereto.

[0091] The reformed gas heat exchanger 21 can be connected to a reformed gas discharge pipe (not shown) that forms the reformed gas discharge flow path 104 so that the reformed gas discharged from the fuel processing device 10 flows. The reformed gas heat exchanger 21 can be connected to a cooling water supply pipe (not shown) that forms a cooling water supply flow path 304 so that 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 via the reformed gas discharge flow path 104 and the water supplied via the cooling water supply flow path 304.

[0092] A cooling water pump 43 that allows the water stored in the water supply tank 13 to flow toward the reformed gas heat exchanger 21 and / or a cooling water flowmeter 56 for detecting the flow rate of the water flowing in the cooling water supply flow path 304 may be arranged in the cooling water supply pipe.

[0093] The reformed gas heat exchanger 21 may be connected to a reformed gas supply pipe (not shown) that forms the fuel cell stack gas supply flow path 106. The reformed gas discharged from the reformed gas heat exchanger 21 may flow toward the fuel cell stacks 20a and 20b via the fuel cell stack gas supply flow path 106.

[0094] A reformed gas moisture removal device 61 for adjusting the amount of moisture contained in the reformed gas may be arranged in the reformed gas supply pipe. The reformed gas flowing into the reformed gas moisture removal device 61 may be discharged from the reformed gas moisture removal device 61 after the moisture is removed.

[0095] 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 via the first water recovery flow path 309. A first water recovery valve 44 for adjusting the flow of the water flowing in the first water recovery flow path 309 may be arranged in a first water recovery pipe (not shown) that forms the first water recovery flow path 309.

[0096] The fuel cell stacks 20a and 20b may generate electric power by electrochemically reacting the reformed gas flowing in via the fuel cell stack gas supply flow path 106. In one embodiment, in the case where the fuel cell system 1 has a plurality of fuel cell stacks 20a and 20b, the reformed gas that has not reacted and been discharged in the first fuel cell stack 20a may undergo an additional electrochemical reaction in the second fuel cell stack 20b.

[0097] A second blower 72 may be arranged between a second supply pipe (not shown) that forms the second supply flow path 203 and a fuel cell stack side air inlet pipe (not shown) that forms the fuel cell stack side air inlet flow path 204. The second supply pipe may be arranged downstream of the first air filter 91. The second blower 72 may cause the air flowing in via the second supply flow path 203 to flow toward the fuel cell stacks 20a and 20b side via the fuel cell stack side air inlet flow path 204.

[0098] A second air side check valve 82 for restricting the flow direction of the air flowing in the second supply flow path 203 may be arranged in the second supply pipe.

[0099] An air flowmeter 53 for detecting the flow rate of the air flowing in the fuel cell stack side air inlet flow path 204 may be arranged in the fuel cell stack side air inlet pipe.

[0100] The humidifying device 23 can supply moisture to the air flowing in through the fuel cell side air inflow passage 204, and can discharge the air containing moisture through the fuel cell side air supply passage 205.

[0101] A fuel cell side air supply valve 36 for regulating the flow of the air supplied to the fuel cells 20a, 20b may be disposed in a fuel cell side air supply pipe (not shown) forming the fuel cell side air supply passage 205.

[0102] The fuel cell side air supply pipe may be connected to a separate supply pipe (not shown) forming separate supply passages 206, 207 corresponding to the fuel cells 20a, 20b respectively. The air flowing in the fuel cell side air supply passage 205 may be supplied to the fuel cells 20a, 20b via the separate supply passages 206, 207.

[0103] A plurality of fuel cells 20a, 20b may be connected to each other by a gas connection pipe (not shown) forming a gas connection passage 107. The reformed gas that has not reacted and been discharged in the first fuel cell 20a may flow into the second fuel cell 20b via the gas connection passage 107.

[0104] An additional moisture removal device 62 may be disposed in the gas connection pipe to remove the water generated by the condensation of the reformed gas flowing in the gas connection passage 107 when passing through the first fuel cell 20a.

[0105] The water generated in the additional moisture removal device 62 may be discharged from the additional moisture removal device 62 and flow into the second water recovery passage 310. A second water recovery valve 45 for regulating the flow of water may be disposed in a second water recovery pipe (not shown) forming the second water recovery passage 310. The second water recovery pipe may be connected to the first water recovery pipe.

[0106] The anode off-gas AOG that has not reacted and been discharged in the fuel cells 20a, 20b may flow through the fuel cell gas discharge passage 108.

[0107] The AOG heat exchanger 22 may be connected to a fuel cell gas discharge pipe (not shown) forming the fuel cell gas discharge passage 108 to allow the anode off-gas AOG discharged from the fuel cells 20a, 20b to flow.

[0108] The AOG heat exchanger 22 may be connected to a hot water supply pipe (not shown) forming a hot water supply passage 313 to allow the water discharged from the heat recovery tank 15 to flow. The AOG heat exchanger 22 may exchange heat between the anode off-gas AOG flowing through the fuel cell gas discharge passage 108 and the water flowing through the hot water supply passage 313.

[0109] A hot water pump 48 for causing the water stored in the heat recovery tank 15 to flow to the AOG heat exchanger 22 and a hot water flowmeter 55 for detecting the flow rate of the water flowing in the hot water supply flow path 313 may be arranged in the hot water supply pipe.

[0110] The AOG heat exchanger 22 may be connected to an AOG supply pipe (not shown) forming the AOG supply flow path 109. The AOG heat exchanger 22 may discharge the heat-exchanged anodic off-gas AOG through the AOG supply flow path 109. The anodic off-gas AOG discharged from the AOG heat exchanger 22 may flow to the fuel processing device 10 via the AOG supply flow path 109. The anodic off-gas AOG supplied to the fuel processing device 10 via the AOG supply flow path 109 may be used as combustion fuel for the burner 120.

[0111] An AOG moisture removal device 63 for adjusting the amount of moisture contained in the anodic off-gas AOG and an AOG valve 35 for adjusting the flow of the anodic off-gas AOG supplied to the fuel processing device 10 may be arranged in the AOG supply pipe. The anodic off-gas AOG flowing into the AOG moisture removal device 63 may be discharged from the AOG moisture removal device 63 after the moisture is removed.

[0112] The 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. A third water recovery valve 46 for adjusting the flow of the water flowing in the third water recovery flow path 311 may be arranged in the third water recovery pipe forming the third water recovery flow path 311. The third water recovery pipe may be connected to the first water recovery pipe.

[0113] A stack-side air discharge pipe (not shown) forming the stack-side air discharge flow path 211 may be connected to a separate discharge pipe (not shown) forming separate discharge flow paths 208 and 209 corresponding to the stacks 20a and 20b respectively. A stack-side air discharge valve 37 for adjusting the flow of the air flowing in the air discharge flow path 211 may be arranged in the stack-side air discharge pipe.

[0114] The air discharged from the stacks 20a and 20b may flow to the stack-side air discharge flow path 211 via the separate discharge flow paths 208 and 209. At this time, the air flowing through the stack-side air discharge flow path 211 may contain moisture generated by the electrochemical reaction occurring in the stacks 20a and 20b.

[0115] The air discharge pipe on the stack side can be connected to the humidifying device 23. The humidifying device 23 can supply moisture to the air flowing toward the fuel cells 20a and 20b by using the moisture contained in the air supplied from the air discharge flow path 211 on the stack side. The air that flows in the air discharge flow path 211 on the stack side and is supplied to the humidifying device 23 can be discharged from the humidifying device 23 into the humidifying device discharge flow path 212.

[0116] The cooling water circulation section III can include: a water supply tank 13 that stores the water generated in the fuel cell system 1; a water pump 38 that causes water to flow toward the fuel processing device 10; a water supply valve 39 that regulates the flow of the water supplied to the fuel processing device 10; and a cooling water pump 43 that causes water to flow toward the reformed gas heat exchanger 21.

[0117] The heat recovery section IV can include: a heat recovery tank 15 that stores the water for heat exchange; and a heat recovery pump 48 that causes the water stored in the heat recovery tank 15 to flow outside the heat recovery tank 15.

[0118] The water supply tank 13 can be connected to a water inflow pipe (not shown) that forms a water inflow flow path 301. The water supply tank 13 can store the water supplied via the water inflow flow path 301. A first liquid filter 92 for removing foreign substances contained in the water supplied from the outside and a water inflow valve 41 for regulating the flow of the water flowing into the water supply tank 13 can be arranged in the water inflow pipe.

[0119] The water supply tank 13 can be connected to a water discharge pipe (not shown) that forms a water discharge flow path 302. The water supply tank 13 can discharge at least a part of the water stored in the water supply tank 13 to the outside via the water discharge flow path 302. A water discharge valve 42 for regulating the flow of the water discharged from the water supply tank 13 can be arranged in the water discharge pipe.

[0120] The water supply tank 13 can be connected to a water storage pipe (not shown) that forms a water storage flow path 308. The water supply tank 13 can store the water flowing via the water storage flow path 308. For example, the 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 via the third water recovery flow path 311 can flow into the water supply tank 13 via the water storage flow path 308. A second liquid filter 93 for removing foreign substances contained in the water recovered to the water supply tank 13 can be arranged in the water storage pipe.

[0121] At least a part of the water stored in the water supply tank 13 can flow toward 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 fuel cells 20a and 20b via the stack water supply flow path 305.

[0122] The water flowing into the fuel cells 20a and 20b via the fuel cell water supply passage 305 can cool the fuel cells 20a and 20b. The water flowing into the fuel cells 20a and 20b can flow along the fuel cell heat exchangers (not shown) included in the fuel cells 20a and 20b, and can absorb the heat generated by the electrochemical reactions occurring in the fuel cells 20a and 20b.

[0123] A plurality of fuel cells 20a and 20b can be connected by water connection pipes (not shown) forming a water connection passage 306. The water discharged from the first fuel cell 20a can flow into the second fuel cell 20b via the water connection passage 306.

[0124] The water discharged from the fuel cells 20a and 20b can flow into the cooling water heat exchanger 24 via the fuel cell water discharge passage 307. The cooling water heat exchanger 24 can exchange heat between the water discharged from the fuel cells 20a and 20b and the water discharged from the heat recovery tank 15. The water discharged from the fuel cells 20a and 20b can flow toward the water storage passage 308 via the cooling water heat exchanger 24.

[0125] The water discharged from the heat recovery tank 15 by the hot water pump 48 can flow into the AOG heat exchanger 22 via the hot water supply passage 313. The water that has exchanged heat with the anodic off-gas AOG in the AOG heat exchanger 22 can be discharged into the first hot water circulation loop 314.

[0126] The air heat exchanger 25 can be connected to a humidifying device discharge pipe (not shown) forming a humidifying device discharge passage 212 to allow the air discharged from the humidifying device 23 to flow. The air heat exchanger 25 can be connected to the first hot water circulation loop 314 through which the water discharged from the AOG heat exchanger 22 flows. The air heat exchanger 25 can exchange heat between the air flowing in via the humidifying device discharge passage 212 and the water flowing in via the first hot water circulation loop 314.

[0127] The air that has exchanged heat in the air heat exchanger 25 can be discharged from the air heat exchanger 25 via the air discharge passage 213. An air discharge pipe (not shown) forming the air discharge passage 213 can be connected to an exhaust gas discharge pipe (not shown) forming an exhaust gas discharge passage 210. The exhaust gas flowing in the exhaust gas discharge passage 210 and the air flowing in the air discharge passage 213 can be mixed.

[0128] An air moisture removal device 64 can be arranged in the air discharge pipe. The air moisture removal device 64 can adjust the amount of moisture contained in the air discharged to the outside. The air flowing into the air moisture removal device 64 can be discharged from the air moisture removal device 64 after the moisture has been removed.

[0129] The condensed water generated by the air moisture removal device 64 can be discharged from the air moisture removal device 64 and flow through the fourth water recovery flow path 312. A fourth water recovery valve 47 for adjusting the flow of water can be arranged in a fourth water recovery pipe (not shown) forming the fourth water recovery flow path 312. The fourth water recovery pipe can be connected to a water storage pipe.

[0130] The water heat-exchanged in the air heat exchanger 25 can 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 can flow into the cooling water heat exchanger 24 via the second hot water circulation flow path 315.

[0131] The cooling water heat exchanger 24 can heat-exchange the water flowing in via the stack water discharge flow path 307 and the water flowing in via the second hot water circulation flow path 315.

[0132] The exhaust gas heat exchanger 26 can be connected to an exhaust gas discharge pipe forming an exhaust gas discharge flow path 210 for the exhaust gas to flow. The exhaust gas heat exchanger 26 can be connected to a third hot water circulation pipe (not shown) forming a third hot water circulation flow path 316 to allow the water discharged from the cooling water heat exchanger 24 to flow. The exhaust gas heat exchanger 26 can heat-exchange the exhaust gas flowing in via the exhaust gas discharge flow path 210 and the water flowing in via the third hot water circulation flow path 316.

[0133] The exhaust gas heat-exchanged in the exhaust gas heat exchanger 26 can be discharged into the exhaust gas flow path 213, and the exhaust gas flowing in the exhaust gas flow path 213 can be discharged to the outside.

[0134] The water heat-exchanged in the exhaust gas heat exchanger 26 can be discharged into 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.

[0135] Hereinafter, with reference to Figure 3 and Figure 4 describe the structure related to the flow of the liquid gas and the gaseous gas flowing into the reformer 140.

[0136] With reference to Figure 3 , the fuel cell system 1 includes: a first storage tank 400 for storing liquid gas; a second storage tank 402 for supplying gasified fuel to the reformer 140; and fuel evaporators 410, 412, 414 for gasifying the liquid fuel by heat-exchanging the liquid fuel discharged from the first storage tank 400 with external air.

[0137] The fuel evaporators 410, 412, 414 include: a first fuel evaporator 410 arranged in the first supply pipe; a second fuel evaporator 412 arranged in the second supply pipe; and a third fuel evaporator 414 arranged in the reformed gas discharge pipe 104a.

[0138] The fuel cell system 1 includes: a first liquid gas supply pipe 420 connecting the first storage tank 400 and the first fuel evaporator 410; a second liquid gas supply pipe 422 connecting the first storage tank 400 and the second fuel evaporator 412; and a third liquid gas supply pipe 424 connecting the first storage tank 400 and the third fuel evaporator 414.

[0139] The fuel cell system 1 includes: a first gaseous gas supply pipe 430 connecting the first fuel evaporator 410 and the second storage tank 402; a second gaseous gas supply pipe 432 connecting the second fuel evaporator 412 and the second storage tank 402; and a third gaseous gas supply pipe 434 connecting the third fuel evaporator 414 and the second storage tank 402.

[0140] In addition, the fuel cell system 1 includes a plurality of expansion valves 440, 442, 444 that supply liquid fuel to at least one of the first fuel evaporator 410, the second fuel evaporator 412, and the third fuel evaporator 414. The fuel cell system 1 includes: a first expansion valve 440 disposed in the first liquid gas supply pipe 420 to open and close the internal flow path of the first liquid gas supply pipe 420 or adjust the opening degree; a second expansion valve 442 disposed in the second liquid gas supply pipe 422 to open and close the internal flow path of the second liquid gas supply pipe 422 or adjust the opening degree; and a third expansion valve 444 disposed in the third liquid gas supply pipe 424 to open and close the internal flow path of the third liquid gas supply pipe 424 or adjust the opening degree.

[0141] The fuel cell system 1 may include: a liquid gas common pipe 426 connecting the fuel processing device 10 and the first liquid gas supply pipe 420, the second liquid gas supply pipe 422, or the third liquid gas supply pipe 424; and a common pipe valve 446 that opens and closes the liquid gas common pipe 426.

[0142] The first storage tank 400 may store liquid fuel. The first storage tank 400 may be in the form of a pressure tank to store the fuel in a liquid state. The first storage tank 400 may be composed of a double - structured tank body (not shown) and a heat insulation part (not shown).

[0143] Refer to Figure 4 , a re - liquefaction device 450 for re - liquefying the fuel discharged from the first storage tank 400 and a pump 454 for supplying the fuel discharged from the re - liquefaction device 450 to the fuel evaporators 410, 412, 414 may be disposed between the first storage tank 400 and the fuel evaporators 410, 412, 414. In addition, expansion valves 440, 442, 444 for expanding the liquid fuel flowing to the fuel evaporators 410, 412, 414 may be disposed between the first storage tank 400 and the fuel evaporators 410, 412, 414.

[0144] The reliquefaction device 450 can reliquefy the refrigerant flowing to an additional heat pump (not shown) and the vaporized fuel discharged from and evaporated by the first storage tank 400. The reliquefaction device 450 can liquefy the vaporized fuel by the evaporation of the refrigerant.

[0145] The first storage tank 400 and the reliquefaction device 450 can be connected by a first pipe 456a for the liquid fuel in the first storage tank 400 to flow and a second pipe 456b for the vaporized fuel in the first storage tank 400 to flow. The first pipe 456a is connected to the lower part of the first storage tank 400 and can allow the liquefied fuel stored in the first storage tank 400 to flow.

[0146] The second pipe 456b is connected to the upper part of the first storage tank 400 and can allow the vaporized gaseous gas in the first storage tank 400 to flow. A compressor 452 for compressing the gaseous gas discharged from the first storage tank 400 can be arranged in the second pipe 456b.

[0147] The reliquefaction device 450 can discharge the liquid fuel by mixing the liquid fuel flowing in the first pipe 456a and the vaporized fuel flowing in the second pipe 456b and cooling them. A pump 454 can be arranged to supply the liquid fuel that has passed through the reliquefaction device 450 to the fuel evaporators 410, 412, 414.

[0148] A third pipe 456c is arranged between the reliquefaction device 450 and the fuel evaporators 410, 412, 414 and can supply the liquid fuel discharged from the reliquefaction device 450 to the fuel evaporators 410, 412, 414. A pump 454 can be arranged in the third pipe 456c. In addition, expansion valves 440, 442, 444 for expanding the liquid fuel flowing to the fuel evaporators 410, 412, 414 can be arranged in the third pipe 456c. A fourth pipe 456d can branch from the third pipe 456c and supply the liquid fuel inside the pipe to the first storage tank.

[0149] The first storage tank 400 can temporarily store the vaporized fuel flowing out from the fuel evaporators 410, 412, 414. The vaporized fuel stored in the first storage tank 400 can be supplied to the reformer 140 via the fuel supply flow path 101.

[0150] The liquid gas common pipe 426 is respectively connected to the first liquid gas supply pipe 420, the second liquid gas supply pipe 422 and the third liquid gas supply pipe 424. A filter 428 for preventing foreign matters from flowing in, a common pipe valve 446 for regulating the flow of the liquid gas discharged from the first storage tank 400 and blocking the high-pressure gas in the case of system non-use and emergencies, and a pressure sensor 429 for detecting the pressure of the liquid gas can be arranged in the liquid gas common pipe 426.

[0151] <Operation Mode>

[0152] Hereinafter, with reference to Figures 5 to 7 the operation of the fuel cell system 1 will be described.

[0153] The fuel cell system 1 can operate in a preheating mode WM of the preheating system, a reforming mode RM for ensuring the production amount of reformed gas, and a power generation mode PM for generating electricity using the fuel cells 20a and 20b.

[0154] In the preheating mode WM, the first blower 71 operates to supply outside air to the reformer 140. In the preheating mode WM, by burning the mixed gas formed by the fuel gas and air using the burner 120 of the fuel processing device 10, combustion heat is generated, whereby the fuel processing device 10 can be preheated.

[0155] With reference to Figure 5 , in the preheating mode WM, the common pipe valve 446 is opened and the first expansion valve 440 increases its opening degree, so that the liquid fuel is supplied to the first fuel evaporator 410. In the first fuel evaporator 410, the liquid fuel can be phase-changed into vaporized fuel, and the air flowing in from the outside and flowing inside can be supplied to the burner 120 in a state where its temperature has decreased. The vaporized fuel discharged from the first fuel evaporator 410 can flow toward the second storage tank 402.

[0156] When the gas generated in the second storage tank 402 reaches a specified pressure through the above operation, the gaseous gas in the second storage tank 402 is supplied to the fuel processing device 10. Inside the fuel processing device 10, reformed gas can be generated by reforming the vaporized fuel discharged from the second storage tank 402.

[0157] As the burner 120 operates, the temperature and pressure of the air on the outlet side will both rise compared to the inlet side of the first blower 71. Therefore, the high-temperature / high-pressure air flows into the first fuel evaporator 410. The air flowing into the first fuel evaporator 410 supplies heat to vaporize the liquid fuel discharged from the first storage tank 400. After that, the air discharged from the first fuel evaporator 410 is supplied to the burner 120 in a low-temperature and high-pressure state. Since the density of the low-temperature and high-pressure air is lower, a larger amount of air can be supplied into the same volume of the fuel processing device 10. In addition, since more mixed gas can be mixed with the gas inside the fuel processing device 10 and flow in during combustion, the combustion time required to reach the target temperature can be shortened.

[0158] When supplying the low-temperature and high-pressure air and the low-temperature vaporized fuel to the burner of the fuel processing device 10 using the above-described first fuel evaporator 410, more mixed gas can be supplied to the burner. In addition, compared with the prior art, by supplying more mixed gas, the preheating operation time can be shortened.

[0159] In the reforming mode RM, by re-supplying the reformed gas generated by the reformer 140 to the reformer 140, the reformed hydrogen amount can be ensured. In the reforming mode RM, the reformer 140 generates high-temperature reformed gas based on the gasified fuel, and before the power generation mode PM, all of the generated reformed gas is used for combustion by the bypass valve 34.

[0160] Refer to Figure 6 , in the reforming mode RM, the opening degrees of each of the first expansion valve 440 and the third expansion valve 444 can be ensured. Therefore, the liquid fuel discharged from the first storage tank 400 can flow to the first fuel evaporator 410 and the third fuel evaporator 414. At this time, by increasing the opening degree of the third expansion valve 444, the amount of the liquid fuel flowing to the third fuel evaporator 414 can be made more than the amount of the liquid fuel flowing to the first fuel evaporator 410. The temperature of the reformed gas flowing in the third fuel evaporator 414 is higher than the temperature of the air flowing in the first fuel evaporator 410. Compared with the first fuel evaporator 410, the phase change of the liquid fuel can occur better in the third fuel evaporator 414, so that the amount of the liquid fuel flowing to the third fuel evaporator 414 can be increased.

[0161] During the operation in the reforming mode RM, the reformer 140 uses the gaseous gas stored in the second storage tank 402 to generate reformed gas. At this time, since the temperature of the reformed gas discharged from the reformer 140 reaches about 90 degrees or more, liquid fuel is supplied to the third fuel evaporator 414 to utilize the waste heat of the reformed gas discharged from the reformer 140.

[0162] The liquid gas supplied to the first fuel evaporator 410 and the third fuel evaporator 414 is vaporized by heat exchange with the high-temperature reformed gas or the air flowing in the first supply pipe 202a and supplied to the second storage tank 402. By using the vaporized fuel generated by the first fuel evaporator 410 and the third fuel evaporator 414 in this way, more gas can be generated than when only the first fuel evaporator 410 is used. As described above, as the gas generation amount increases, the reformer will consume more gas and generate reformed gas, and will make preparations for entering the power generation mode operation.

[0163] The high-temperature reformed gas discharged from the reformer 140 can be changed into low-temperature reformed gas by heat exchange with the liquid fuel using the third fuel evaporator 414. The low-temperature reformed gas is supplied to the burner 120 via the bypass valve 34 to improve the combustion efficiency. The low-temperature reformed gas also has its density reduced due to the temperature change, so that a larger amount can be supplied to the burner 120. In addition, as the reformed gas with a high hydrogen content is burned together in the burner 120, the combustion reaction and efficiency can be improved.

[0164] In the power generation mode PM, electricity can be generated by the electrochemical reaction of oxygen and hydrogen inside the fuel cells 20a and 20b using the reformed gas discharged from the reformer 140 and the air flowing in from the outside.

[0165] In the power generation mode PM, as the first blower 71 operates, outside air can flow toward the fuel processing device 10, and as the second blower 72 operates, outside air can be supplied to the fuel cells 20a and 20b.

[0166] In addition, as the reformer 140 operates, the reformed gas discharged from the reformer 140 can be supplied to the fuel cells 20a and 20b.

[0167] Refer to Figure 7 , when operating in the power generation mode PM, the liquid fuel discharged from the first storage tank 400 can be supplied to the first fuel evaporator 410, the second fuel evaporator 412, and the third fuel evaporator 414, respectively.

[0168] In the power generation mode PM, the first expansion valve 440, the second expansion valve 442, and the third expansion valve 444 can all be opened. In the power generation mode, the opening degree can be set such that the amount of liquid fuel flowing through the third expansion valve 444 is more than the amount of liquid fuel flowing through the first expansion valve 440 or the second expansion valve 442.

[0169] When operating in the power generation mode PM, the second blower 72 operates, and the temperature and pressure of the air discharged from the second blower 72 both increase compared to the air flowing into the second blower 72, which is the same as the operation of the first blower 71.

[0170] The second fuel evaporator 412 disposed in the second supply pipe 203a exchanges heat with the liquid fuel discharged from the first storage tank 400, so that the low-temperature and high-pressure air is discharged from the first fuel evaporator 410. The low-temperature and high-pressure air discharged from the second fuel evaporator 412 is supplied to the fuel cells 20a and 20b, reacts with the reformed gas to generate electricity, and then is discharged.

[0171] In addition, the reformed gas generated in the reformer 140 is supplied to the fuel cells 20a and 20b via the third fuel evaporator 414, and the unreacted hydrogen AOG that is not used for power generation in the fuel cells 20a and 20b and is discharged is supplied to the burner 120 again to improve the combustion efficiency. At this time, the temperature of the reformed gas supplied to the fuel cells 20a and 20b is reduced by the action of the third fuel evaporator 414, so that more reformed gas can be supplied within a predetermined volume, thereby improving the reaction efficiency for power generation.

[0172] As described above, by lowering the temperature of the air and reformed gas supplied to the fuel cells 20a and 20b, their density will be significantly reduced compared to when at a high temperature. Since the reaction area of the air and reformed gas inside the fuel cells 20a and 20b is very limited, when the density is small, more reactions can be promoted. Therefore, by reducing the density of the air and reformed gas, the power generation efficiency inside the fuel cell can be improved.

[0173] Hereinafter, with reference to Figures 8A to 14B Various embodiments of the fuel evaporators 410, 412, and 414 that can be used as the first fuel evaporator 410, the second fuel evaporator 412, or the third fuel evaporator 414 will be described.

[0174] The fuel evaporators 410, 412, and 414 include a housing that forms an outer shape, and inside the housing, a fuel flow portion for liquid fuel to flow and a gas flow portion for air or reformed gas to flow are formed.

[0175] A plurality of the fuel flow portion and the gas flow portion may be arranged in a cross - crossing manner. Protrusions that can increase the contact area of the liquid fuel or air may be formed inside the tube forming the fuel flow portion and inside the tube forming the gas flow portion, respectively. The fuel flow portion and the gas flow portion may be formed in various shapes.

[0176] With reference to Figure 8A and Figure 8B , the fuel evaporator of the first embodiment may have a structure in which a fuel flow portion 470a and a gas flow portion 462a are formed inside a cylindrical housing 460a.

[0177] The gas flow portion 462a may be composed of a plurality of straight - shaped thin - diameter tubes 463a. The fuel flow portion 470a may exchange heat with the gas flow portion 462a through a flow that bends in the vertical direction in the space between the plurality of thin - diameter tubes 463a. The first inlet end 464a and the first outlet end 466a of the gas flow portion 462a may open in a direction parallel to the plurality of thin - diameter tubes. The second inlet end 472a and the second outlet end 474a of the fuel flow portion 470a may open in a direction perpendicular to the first inlet end 464a and the first outlet end 466a of the gas flow portion 462a. The fuel flow portion 470a may include a guide member 471a that is formed in a direction perpendicular to the plurality of thin - diameter tubes 463a of the gas flow portion 462a and causes the flow of the fuel to form in the vertical direction to increase the flow area for heat exchange.

[0178] With reference to Figure 9A and Figure 9B , the housing 460b of the fuel evaporator of the second embodiment may have a structure in which a U - shaped tube is arranged inside it.

[0179] The gas flow portion 462b includes: a plurality of thin-diameter tubes 463b formed in the vertical direction; and a U-shaped bent tube 463b1 bent upward from the thin-diameter tubes 463b. The first inlet end 464b and the first discharge end 466b of the gas flow portion 462b may open in opposite directions in the arrangement direction of the bent tube 463b1.

[0180] The fuel flow portion 470b may have a structure that allows the fuel flowing between the plurality of thin-diameter tubes 463b in the left-right direction to flow through the guide member. The second inlet end 472b and the second discharge end 474b of the fuel flow portion 470b may have a structure that protrudes in the circumferential direction of the housing 460b.

[0181] Refer to Figure 10A and Figure 10B As shown in FIGS. and, the housing 460c of the fuel evaporator of the third embodiment is cylindrical, and a fuel flow portion 470c and a gas flow portion 462c are formed inside the housing 460c.

[0182] The gas flow portion 462c may be composed of a plurality of thin-diameter tubes in a linear form. The fuel flow portion 470c may exchange heat with the gas flow portion 462c by flowing through the space between the plurality of thin-diameter tubes. The first inlet end 464c and the first discharge end 466c of the gas flow portion 462c may open in a direction parallel to the plurality of thin-diameter tubes. The first inlet end 464c and the first discharge end 466c of the fuel flow portion 470c may open in a direction perpendicular to the second inlet end 472c and the second discharge end 474c of the gas flow portion 462c.

[0183] In the fuel evaporator of the third embodiment, the inside or outside of the tubes of the fuel flow portion 470c or the gas flow portion 462c may be formed in a flat shape as shown in FIG., or may be formed in a shape with protrusions protruding as shown in FIG.. Figures 10A to 10B as shown in Figures 11A to 11B FIG., or may be formed in a shape with protrusions protruding as shown in FIG..

[0184] Refer to Figures 12 to 14B As shown in FIGS. and, the fuel evaporator of the fourth embodiment may use a plate-type heat exchanger. The housing 460d of the fuel evaporator of the fourth embodiment may be in a plate shape, and a fuel flow portion 470d and a gas flow portion 462d may be formed inside the housing 460d.

[0185] The first inlet end 464d and the first discharge end 466d of the gas flow portion 462d are arranged at a diagonal distance on one side surface of the housing 460d. Refer to Figure 13A and Figure 14A, the gas flow portion 462d has a plurality of flow paths connecting a first inlet end 464d and a first outlet end 466d inside the housing 460d. The gas flow portion 462d is formed with a plurality of flow paths in a direction perpendicular to the first inlet end 464d and the first outlet end 466d. The plurality of flow paths formed in the gas flow portion 462d may be formed in a shape with a flat interior of the tube as shown in Figure 13A , or may be formed in a shape with a protrusion protruding inside the tube as shown in Figure 14A .

[0186] The second inlet end 472d and the second outlet end 474d of the fuel flow portion 470d are arranged at a diagonal distance on one side surface of the housing 460d. Referring to Figure 13B and Figure 14B , the fuel flow portion 470d has a plurality of flow paths connecting the second inlet end 472d and the second outlet end 474d inside the housing 460d. The fuel flow portion 470d is formed with a plurality of flow paths in a direction perpendicular to the second inlet end 472d and the second outlet end 474d. The plurality of flow paths formed in the fuel flow portion 470d may be formed in a shape with a flat interior of the tube as shown in Figure 13B , or may be formed in a shape with a protrusion protruding inside the tube as shown in Figure 14B .

[0187] The preferred embodiments of the present invention have been illustrated and described above. However, the present invention is not limited to the specific embodiments described above. Within the scope not departing from the technical idea of the present invention claimed in the claims, those of ordinary skill in the art can perform various modifications. Such modified implementations should not be understood separately from the technical idea or prospect of the present invention.

Claims

1. A fuel cell system ， Wherein, Comprising: A reformer that performs a reforming process to generate hydrogen from gasified fuel; A burner that supplies heat to the reformer; A fuel cell stack that uses reformed gas and air discharged from the reformer to generate an electrochemical reaction to generate electric power; A first supply pipe that supplies external air to the burner; A second supply pipe that supplies external air to the fuel cell stack; A first storage tank that stores liquid fuel; A second storage tank that supplies gasified fuel to the reformer; A reformed gas discharge pipe that conveys the reformed gas discharged from the reformer to the burner or to the fuel cell stack; and A third fuel evaporator disposed in the reformed gas discharge pipe to effect heat exchange between the reformed gas discharged from the reformer and liquid fuel.

2. The fuel cell system according to claim 1, Wherein, Comprising: A first fuel evaporator that effects heat exchange between the liquid fuel discharged from the first storage tank and the air flowing in the first supply pipe; And A second fuel evaporator that effects heat exchange between the liquid fuel discharged from the first storage tank and the air flowing in the second supply pipe.

3. The fuel cell system according to claim 2 ， Wherein, Comprising: A first liquid gas supply pipe connecting the first storage tank and the first fuel evaporator; A second liquid gas supply pipe connecting the first storage tank and the second fuel evaporator; A first expansion valve disposed in the first liquid gas supply pipe to open and close the internal flow path of the first liquid gas supply pipe or to adjust the opening degree of the first liquid gas supply pipe; and A second expansion valve disposed in the second liquid gas supply pipe to open and close the internal flow path of the second liquid gas supply pipe or to adjust the opening degree of the second liquid gas supply pipe.

4. The fuel cell system according to claim 3, Wherein, In a preheating mode for preheating the reformer, the first expansion valve expands the internal flow path of the first liquid gas supply pipe, and the second expansion valve closes the internal flow path of the second liquid gas supply pipe.

5. The fuel cell system according to claim 3, Wherein, In a power generation mode for generating electric power using the fuel cell stack, the first expansion valve expands the opening degree of the internal flow path of the first liquid gas supply pipe, and the second expansion valve expands the opening degree of the internal flow path of the second liquid gas supply pipe.

6. The fuel cell system according to claim 3 ， Wherein, Comprising: A third liquid gas supply pipe connecting the first storage tank and the third fuel evaporator; and A third expansion valve disposed in the third liquid gas supply pipe to open and close the internal flow path of the third liquid gas supply pipe or to adjust the opening degree of the third liquid gas supply pipe.

7. The fuel cell system according to claim 6, Wherein, In a reforming mode for increasing the amount of hydrogen contained in the reformed gas discharged from the reformer, the first expansion valve expands the opening degree of the internal flow path of the first liquid gas supply pipe, and the third expansion valve expands the opening degree of the internal flow path of the third liquid gas supply pipe.

8. The fuel cell system according to claim 7, Wherein, In the reforming mode, the opening degree of the third expansion valve is expanded to be larger than that of the first expansion valve.

9. The fuel cell system according to claim 6, wherein, In the power generation mode of generating power using the fuel cell stack, the first expansion valve expands the opening degree of the internal flow path of the first liquid gas supply pipe, the second expansion valve expands the opening degree of the internal flow path of the second liquid gas supply pipe, and the third expansion valve expands the opening degree of the internal flow path of the third liquid gas supply pipe.

10. The fuel cell system according to claim 9, wherein, In the power generation mode, the opening degree of the third expansion valve is expanded to be larger than that of the first expansion valve or the second expansion valve.

11. The fuel cell system according to claim 6 ， wherein, comprising: A liquid gas common pipe connecting the first storage tank and the first liquid gas supply pipe, the second liquid gas supply pipe, or the third liquid gas supply pipe; and A common pipe valve for opening and closing the liquid gas common pipe.

12. The fuel cell system according to claim 11 ， wherein, comprising: A first blower arranged in the first supply pipe for supplying external air to the first supply pipe; and A second blower arranged in the second supply pipe for supplying external air to the second supply pipe, When the first blower operates, the common pipe valve is opened.

13. The fuel cell system according to claim 1, wherein, The third fuel evaporator includes: A housing forming the outer shape; A fuel flow part arranged inside the housing and formed for liquid fuel to flow; and A gas flow part arranged inside the housing and formed for air or reformed gas to flow.

14. The fuel cell system according to claim 13, wherein, A plurality of protrusions are respectively formed inside the pipe forming the fuel flow part and inside the pipe forming the gas flow part.

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