Fuel cell system and method of controlling the same

Abstract

The present invention relates to a fuel cell system and a control method thereof. A fuel cell system according to an embodiment of the present invention includes: a stack that generates electric power using an electrochemical reaction of a reforming gas and air; a fuel processing device that generates the reforming gas supplied to the stack; a water supply tank that stores water supplied to the stack; a heat recovery tank that stores hot water; a first heat exchanger that is provided in the fuel processing device to exchange heat between cooling water and exhaust gas discharged from the fuel processing device; and a heat supply valve that supplies the cooling water that has exchanged heat in the first heat exchanger to the water supply tank or the heat recovery tank to heat the water stored in the water supply tank or the water stored in the heat recovery tank. By recovering waste heat of the exhaust gas discharged from the fuel processing device, it is possible to heat the water stored in the water supply tank or the hot water stored in the heat recovery tank.

Description

Technical Field

[0001] This invention relates to fuel cell systems, and more specifically, to a fuel cell system that preheats the fuel cell stack or generates hot water by recovering waste heat from exhaust gases discharged from a fuel processing device. Background Technology

[0002] A fuel cell system is a power generation system that produces electricity by causing an electrochemical reaction between hydrogen and oxygen contained in hydrocarbon substances such as methanol, ethanol, and natural gas.

[0003] Similar to prior art 1 (Korean Patent Publication No. 10-2012-0071288), a typical fuel cell system includes: a fuel processing unit that reforms fuel containing hydrogen atoms into hydrogen gas; and a stack that uses the hydrogen gas supplied from the fuel processing unit to generate electrical energy. Additionally, 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 for converting the generated direct current (DC) power into alternating current (AC) power.

[0004] On the other hand, when a fuel cell system is generating electricity, the rate of the electrochemical reaction of oxygen and hydrogen produced in the stack varies depending on the stack temperature. Therefore, power generation is carried out while maintaining an appropriate temperature according to the type of fuel cell stack. However, in the initial stage of power generation operation, the stack temperature is low, resulting in a problem where power generation cannot proceed smoothly until the stack temperature reaches the specified temperature suitable for power generation. Furthermore, there is a considerable amount of time required for the fuel cell system to generate electricity normally.

[0005] Patent document: KR 10-2012-0071288A Summary of the Invention

[0006] The problem to be solved by the present invention is to provide a fuel cell system that uses waste heat from exhaust gas discharged from a fuel processing device to preheat the fuel cell stack.

[0007] Another objective of this invention is to provide a fuel cell system that uses waste heat from exhaust gases discharged from a fuel processing device to heat hot water supplied to residences or other hot water-using locations.

[0008] The purpose of this invention is not limited to the purposes mentioned above, and those skilled in the art will clearly understand other purposes not mentioned from the following description.

[0009] A fuel cell system according to an embodiment of the present invention for solving the above-mentioned problems may include: a fuel cell stack for generating electricity using an electrochemical reaction of reformed gas and air; a fuel processing device for generating the reformed gas supplied to the fuel cell stack; a water supply tank for storing water supplied to the fuel cell stack; a heat recovery tank for storing hot water; a first heat exchanger disposed in the fuel processing device for exchanging heat between cooling water and exhaust gas discharged from the fuel processing device; and a heat supply valve for supplying cooling water that has undergone heat exchange in the first heat exchanger to the water supply tank or the heat recovery tank to heat the water stored in the water supply tank or the water stored in the heat recovery tank; by recovering the waste heat from the exhaust gas discharged from the fuel processing device, the water stored in the water supply tank or the hot water stored in the heat recovery tank can be heated.

[0010] The fuel cell system of the present invention may include a control unit that adjusts the heat supply valve. In a preheating mode for preheating the fuel processing device, the control unit switches the heat supply valve to the water supply tank side so that cooling water that has undergone heat exchange in the first heat exchanger is supplied to the water supply tank, thereby enabling the water stored in the water supply tank to be preheated in the preheating mode.

[0011] The fuel cell system of the present invention may further include a heat recovery valve, which supplies cooling water discharged from the water supply tank to the first heat exchanger or to the heat supply valve.

[0012] The fuel cell system of the present invention may include a control unit that adjusts the heat supply valve and the heat recovery valve. In the preheating mode of preheating the fuel processing device, the control unit switches the heat recovery valve to the first heat exchanger side so that cooling water discharged from the water supply tank is supplied to the first heat exchanger, thereby enabling the exhaust gas and cooling water to exchange heat in the fuel processing device in the preheating mode.

[0013] The fuel cell system of the present invention may include a first temperature sensor for detecting the temperature of water stored in the water supply tank. When the temperature of the water detected by the first temperature sensor is above a first set temperature, the control unit switches the heat recovery valve to the heat supply valve side and determines that the preheating of the water stored in the water supply tank is completed, thereby interrupting the waste heat recovery in the fuel processing device.

[0014] The fuel cell system of the present invention may include: a first temperature sensor for detecting the temperature of water stored in the water supply tank; a second temperature sensor for detecting the temperature of water discharged from the fuel cell stack; and a control unit for adjusting the heat supply valve; in a power generation mode in which electricity is generated in the fuel cell stack by utilizing the electrochemical reaction of reformed gas and air, when the temperature of the water detected by the first temperature sensor is above a first set temperature and the temperature of the water detected by the second temperature sensor is below a second set temperature, the control unit switches the heat supply valve to the water supply tank side so that cooling water that has undergone heat exchange with exhaust gas in the first heat exchanger is supplied to the water supply tank, thereby heating the water stored in the water supply tank in the early stage of the power generation mode.

[0015] In the power generation mode where the stack generates electricity using the electrochemical reaction of reformed gas and air, when the temperature of the cooling water detected by the second temperature sensor is above the second set temperature, the control unit switches the heat supply valve to the heat recovery tank side so that the cooling water that exchanges heat with the exhaust gas in the first heat exchanger is supplied to the heat recovery tank, thereby enabling the hot water stored in the heat recovery tank to be heated during the power generation mode.

[0016] The first set temperature can be higher than the second set temperature.

[0017] The fuel cell system of the present invention may further include a heat supply pump that forms a cooling water flow circulating through the fuel processing device, the water supply tank, and the heat recovery tank.

[0018] The fuel cell system of the present invention may further include a cooling water pump disposed between the water supply tank and the fuel cell stack, which supplies cooling water stored in the water supply tank to the fuel cell stack.

[0019] The fuel cell system of the present invention may include a control unit that regulates the operation of the cooling water pump. In a power generation mode in which the stack generates electricity using the electrochemical reaction of reformed gas and air, the control unit operates the cooling water pump to supply cooling water to the stack, thereby enabling the stack to be preheated.

[0020] The fuel cell system of the present invention may include: a second heat exchanger disposed in the water supply tank, for exchanging heat between the cooling water that exchanges heat with the exhaust gas in the first heat exchanger and the cooling water stored in the water supply tank; and a third heat exchanger disposed in the heat recovery tank, for exchanging heat between the cooling water that exchanges heat with the exhaust gas in the first heat exchanger and the hot water stored in the heat recovery tank.

[0021] The fuel processing apparatus may further include a burner that supplies the heat energy required to generate the reformed gas, wherein the first heat exchanger is configured adjacent to the outlet side of the burner from which the exhaust gas generated after the combustion reaction of the fuel is discharged.

[0022] Specific details regarding other embodiments are included in the detailed description and accompanying drawings.

[0023] According to various embodiments of the present invention, the waste heat of the exhaust gas discharged from the burner of the fuel processing device is recovered by the cooling water circulating in the waste heat recovery unit. The cooling water in the water supply tank supplied to the fuel cell stack is heated by the cooling water in the waste heat recovery unit and then supplied to the fuel cell stack, so that the fuel cell stack at a low temperature is preheated, thereby improving the power generation efficiency of the fuel cell system.

[0024] Furthermore, according to various embodiments of the present invention, the waste heat of the exhaust gas discharged from the burner of the fuel processing device is recovered by the cooling water circulating in the waste heat recovery unit, and the hot water in the heat recovery tank supplied to hot water use places such as residences is heated by the cooling water of the waste heat recovery unit, thereby improving the overall energy efficiency ratio in the fuel cell system.

[0025] The effects of the present invention are not limited to those mentioned above, and those skilled in the art can more clearly understand other effects not mentioned through the description in the claims. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the configuration of a fuel processing device according to an embodiment of the present invention.

[0027] Figure 2 This is a structural diagram of a fuel cell system according to an embodiment of the present invention.

[0028] Figure 3 This is a system diagram illustrating a fuel processing apparatus, fuel cell stack, water supply tank, heat recovery tank, and waste heat recovery unit according to an embodiment of the present invention.

[0029] Figure 4 and Figure 5 This diagram illustrates how, in the preheating mode and / or reforming mode of a fuel cell system according to an embodiment of the present invention, cooling water stored in a water supply tank is preheated by recovering waste heat from the fuel processing device.

[0030] Figure 6 and Figure 7 This diagram illustrates how, in the power generation mode of a fuel cell system according to an embodiment of the present invention, waste heat from a fuel processing device is recovered to heat hot water stored in a heat recovery tank.

[0031] Figure 8 This is a flowchart of a control method for a fuel cell system according to an embodiment of the present invention.

[0032] Explanation of reference numerals in the attached figures

[0033] 1: Fuel cell system; 10: Fuel processing unit

[0034] 13: Water supply tank; 15: Heat recovery tank

[0035] 20: Fuel Cell 400: Waste Heat Recovery Unit

[0036] 410: First heat exchanger; 412: Second heat exchanger

[0037] 414: Third heat exchanger; 422: First-1 heat recovery tube.

[0038] 424: Heat recovery pipe 1-2; 432: Heat recovery pipe 2-1

[0039] 434: Heat recovery pipe 2-2; 440: Heat supply pump

[0040] 452: Heat recovery valve; 462: Heat supply valve

[0041] 472: First thermometer; 474: Second thermometer Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings. In the drawings, for the sake of clarity and brevity, illustrations of parts unrelated to the description have been omitted, and throughout the specification, the same reference numerals are used for the same or very similar parts.

[0043] The suffixes “module” and “section” used for structural elements in the following description are assigned solely for ease of writing this specification and do not inherently possess any particularly important meaning or function. Therefore, the terms “module” and “section” may be used interchangeably.

[0044] In this application, terms such as "comprising" or "having" are used only to specify the presence of features, numbers, steps, actions, structural elements, components or combinations thereof as described in the specification, and are not intended to exclude the possibility of the presence or addition of one or more other features or numbers, steps, actions, structural elements, components or combinations thereof.

[0045] Furthermore, in this specification, terms such as "first" and "second" may be used to describe various elements; however, these elements are not limited by these terms. These terms may be used solely to distinguish one element from another.

[0046] Figure 1 This is a schematic diagram of the configuration of a fuel processing device according to an embodiment of the present invention.

[0047] Reference Figure 1The fuel processing device 10 may include a desulfurizer 110, a burner 120, a steam generator 130, a reformer 140, a first reactor 150, and / or a second reactor 160. The fuel processing device 10 may also include at least one mixer 111 or 112.

[0048] The desulfurizer 110 can perform a desulfurization process to remove sulfur compounds contained in fuel gas. For example, an adsorbent can be placed inside the desulfurizer 110. In this case, sulfur compounds contained in the fuel gas passing through the interior of the desulfurizer 110 can be adsorbed onto the adsorbent.

[0049] Adsorbents can be composed of metal oxides, zeolite, activated carbon, etc.

[0050] The desulfurizer 110 may also include a filter for removing impurities contained in the fuel gas.

[0051] Burner 120 can supply heat to reformer 140 to promote the reforming reaction in reformer 140. For example, fuel gas discharged from desulfurizer 110 and air flowing in from the outside can be mixed in first mixer 111 and supplied to burner 120. At this time, burner 120 can generate combustion heat by burning the mixture of fuel gas and air. At this time, the internal temperature of reformer 140 can be maintained at a suitable temperature (e.g., 800°C) by the heat provided by burner 120.

[0052] 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.

[0053] Steam generator 130 can vaporize water and discharge it as steam. For example, steam generator 130 can vaporize water by absorbing heat from exhaust gas generated in burner 120, first reactor 150 and / or second reactor 160.

[0054] The steam generator 130 may be configured adjacent to the first reactor 150, the second reactor 160 and / or the piping for the flow of exhaust gas from the burner 120.

[0055] Reformer 140 can use a catalyst to perform a reforming process to generate hydrogen from fuel gas from which sulfur compounds have been removed. For example, fuel gas discharged from desulfurizer 110 and water vapor discharged from steam generator 130 can be mixed in a second mixer 112 and supplied to reformer 140. At this point, when the fuel gas and water vapor supplied to reformer 140 undergo a reforming reaction within reformer 140, hydrogen can be generated.

[0056] The first reactor 150 can reduce the amount of carbon monoxide generated by the reforming reaction in the components of the gas discharged from the reformer 140. For example, the carbon monoxide in the gas discharged from the reformer 140 can react with water vapor inside the first reactor 150 to produce carbon dioxide and hydrogen. In this case, the internal temperature of the first reactor 150 can be a temperature lower than the internal temperature of the reformer 140 but higher than room temperature (e.g., 200°C).

[0057] The first reactor 150 can be referred to as a shift reactor.

[0058] The second reactor 160 can reduce the amount of residual carbon monoxide in the components of the gas emitted from the first reactor 150. For example, carbon monoxide in the gas emitted from the first reactor 150 can undergo selective oxidation (PROX) by reacting with oxygen inside the second reactor 160.

[0059] On the other hand, selective oxidation requires a large amount of oxygen, necessitating an additional air supply. This additional air dilutes the hydrogen, resulting in a reduced hydrogen concentration supplied to the fuel cell stack. Therefore, to overcome this drawback, selective methanation, a reaction involving carbon monoxide and hydrogen, can be utilized.

[0060] On the other hand, the gas discharged from the fuel processing unit 10 via the reformer 140, the first reactor 150 and / or the second reactor 160 can be referred to as reformed gas.

[0061] The fuel cell stack 20 can generate electrical energy by electrochemically reacting reforming gas supplied from the fuel processing unit 10.

[0062] The fuel cell stack 20 can be constructed by stacking individual units that undergo electrochemical reactions.

[0063] A single unit can consist of a membrane electrode assembly (MEA) with a fuel electrode and an air electrode arranged around an electrolyte membrane, as well as a separator. In the fuel electrode of the MEA, hydrogen can be separated into hydrogen ions and electrons by a catalyst to generate electricity. In the air electrode of the MEA, hydrogen ions and electrons can combine with oxygen to generate water.

[0064] The fuel cell stack 20 may also include a fuel cell heat exchanger (not shown) for releasing heat generated during the electrochemical reaction. The fuel cell heat exchanger may be a heat exchanger that uses water as a refrigerant. For example, cooling water supplied to the fuel cell 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 fuel cell heat exchanger.

[0065] Figure 2 This is a configuration diagram of a fuel cell system including a fuel processing device according to an embodiment of the present invention.

[0066] Reference Figure 2 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. The fuel cell system 1 may also include a power conversion unit (not shown), which includes a power conversion device for converting the DC power generated by the power generation unit II into AC power.

[0067] The fuel treatment unit I may include a fuel treatment device 10, a fuel valve 30 for regulating the flow of fuel gas supplied to the fuel treatment device 10, a first blower 71 for causing air to flow into the fuel treatment device 10, etc.

[0068] The power generation unit II may include: fuel cell stacks 20a and 20b; a reformed gas heat exchanger 21 for heat exchange with reformed gas discharged from the fuel processing unit 10; an AOG heat exchanger 22 for heat exchange with gas that has not reacted and is discharged from the fuel cell stacks 20a and 20b; a humidification device 23 for supplying moisture to the air supplied to the fuel cell stacks 20a and 20b; and a second blower 72 for causing air to flow to the fuel cell stacks 20a and 20b. The gas that has not reacted and is discharged from the fuel cell stacks 20a and 20b may be referred to as anode off gas (AOG). In one embodiment of the present invention, the fuel cell system 1 is described as having two fuel cell stacks 20a and 20b, but is not limited thereto.

[0069] The cooling water circulation section III may include: a water supply tank 13 for storing water generated in the fuel cell system 1; a water pump 38 for flowing water to the fuel processing device 10; a water supply valve 39 for regulating the flow of water supplied to the fuel processing device 10; and a cooling water pump 43 for flowing water to the reforming gas heat exchanger 21.

[0070] The heat recovery unit IV may include: a heat recovery tank 15 for storing water for heat exchange; and a hot water pump 48 for flowing the water stored in the heat recovery tank 15 to the outside of the heat recovery tank 15. Alternatively, the water stored in the heat recovery tank 15 may be referred to as hot water. Furthermore, the heat recovery tank 15 may be connected to a hot water usage location (not shown) such as a residence, and supply hot water according to the user's requirements.

[0071] Additionally, the fuel cell system 1 may include a waste heat recovery unit 400, which recovers waste heat from the fuel processing device 10 to heat water stored in the water supply tank 13 or hot water stored in the heat recovery tank 15. The configuration and connection of the waste heat recovery unit 400 will be described in detail later.

[0072] Fuel valve 30 can be configured in fuel supply path 101, which supplies fuel gas to fuel processing device 10. The flow rate of fuel gas supplied to fuel processing device 10 can be adjusted according to the opening degree of fuel valve 30. For example, fuel valve 30 can shut off fuel supply path 101 to interrupt the supply of fuel gas to fuel processing device 10.

[0073] A first fuel flow meter 51 for detecting the flow rate of fuel gas flowing within the fuel supply flow path 101 may be configured in the fuel supply flow path 101.

[0074] The first blower 71 can be connected to the first external air inflow path 201 and the fuel-side air supply path 202. The first blower 71 can cause air flowing in from the outside via the first external air inflow path 201 to flow to the fuel processing device 10 via the fuel-side air supply path 202.

[0075] Air flowing into the fuel processing unit 10 via the fuel-side air supply path 202 can be supplied to the burner 120 of the fuel processing unit 10. For example, the air flowing into the fuel processing unit 10 can be mixed with fuel gas discharged from the desulfurizer 110 in the first mixer 111 and supplied to the burner 120.

[0076] The first external air inflow path 201 may be configured 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 the direction of airflow.

[0077] The fuel processing unit I may include a first internal gas flow path 102 for supplying fuel gas discharged from the desulfurizer 110 to the reformer 140. The first internal gas flow path 102 may be equipped with a proportional control valve 31, an internal fuel valve 32 for regulating the flow of fuel gas into the reformer 140, a second fuel flow meter 52 for detecting the flow rate of fuel gas flowing in the internal gas flow path 102, a fuel-side check valve 83 for restricting the flow direction of fuel gas flowing in the internal gas flow path 102, and / or a sulfur detection device 94.

[0078] The proportional control valve 31 can be electrically controlled to regulate the flow rate, pressure, etc. of the fuel gas discharged from the desulfurizer 110 and flowing into the reformer 140 through internal / external feedback.

[0079] The sulfur detection device 94 can detect 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 sulfur compounds that have not been removed by the adsorbent in the desulfurizer 110. The indicator may include phenolphthalein, molybdenum compounds, etc.

[0080] The fuel processing unit I may include a second internal gas flow path 103 for supplying fuel gas discharged from the desulfurizer 110 to the burner 120. The burner 120 may use the fuel gas flowing in via the second internal gas flow path 103 for combustion.

[0081] The first internal gas flow path 102 and the second internal gas flow path 103 can be connected to each other.

[0082] The fuel processing device 10 can be connected to a water supply path 303 for water flowing from the water supply tank 13. The water supply path 303 can be equipped 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 path 303.

[0083] The exhaust gas generated by the burner 120 of the fuel treatment device 10 can be discharged from the fuel treatment device 10 via the exhaust gas discharge path 210.

[0084] The fuel processing device 10 can be connected to the reformed gas discharge path 104. The reformed gas discharged from the fuel processing device 10 can flow through the reformed gas discharge path 104.

[0085] The reformed gas discharge path 104 can be connected to a reformed gas heat exchanger 21 for heat exchange of reformed gas. A reformed gas valve 33 for regulating the flow of reformed gas into the reformed gas heat exchanger 21 can be configured in the reformed gas discharge path 104.

[0086] The reformed gas discharge path 104 can be connected to a bypass path 105 that supplies reformed gas discharged from the fuel processing unit 10 to flow into the fuel processing unit 10. The bypass path 105 can be connected to the fuel processing unit 10. The reformed gas flowing into the fuel processing unit 10 via the bypass path 105 can be used as fuel for combustion in the burner 120. A bypass valve 34 for regulating the flow of reformed gas into the fuel processing unit 10 can be provided in the bypass path 105.

[0087] The reformed gas heat exchanger 21 can be connected to the reformed gas discharge path 104, which supplies reformed gas discharged from the fuel processing unit 10. The reformed gas heat exchanger 21 can also be connected to the cooling water supply path 304, which supplies water discharged from the water supply tank 13. The reformed gas heat exchanger 21 allows heat exchange between the reformed gas flowing in through the reformed gas discharge path 104 and the water supplied through the cooling water supply path 304.

[0088] The cooling water supply path 304 may be equipped with a cooling water pump 43 for flowing water stored in the water supply tank 13 to the reforming 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 path 304.

[0089] The reforming gas heat exchanger 21 can be connected to the fuel cell stack gas supply path 106. The reforming gas discharged from the reforming gas heat exchanger 21 can flow to the fuel cell stacks 20a and 20b via the fuel cell stack gas supply path 106.

[0090] A reforming gas moisture removal device 61 for adjusting the amount of moisture contained in the reforming gas can be configured in the fuel cell gas supply flow path 106. The reforming gas flowing into the reforming gas moisture removal device 61 can be discharged from the reforming gas moisture removal device 61 after the moisture is removed.

[0091] The condensate generated in the reforming gas moisture removal device 61 can be discharged from the reforming gas moisture removal device 61 and flow into the first water recovery flow path 309. The first water recovery flow path 309 may be equipped with a first water recovery valve 44 for regulating the flow of water.

[0092] The fuel cell stacks 20a and 20b can generate electrical energy by electrochemically reacting reformed gas flowing in through the fuel cell gas supply path 106. In one embodiment, when the fuel cell system 1 has a plurality of fuel cell stacks 20a and 20b, the reformed gas that has not been reacted and discharged from the first fuel cell stack 20a can be additionally electrochemically reacted in the second fuel cell stack 20b.

[0093] The second blower 72 can be connected to the second external air inflow path 203, which is connected to the first external air inflow path 201, and the fuel cell side air inflow path 204. The second external air inflow path 203 can be connected to the rear end of the air filter 91. The second blower 72 can cause the air flowing in through the second external air inflow path 203 to flow towards the fuel cell side 20 via the fuel cell side air inflow path 204.

[0094] A second air-side check valve 82 for restricting the direction of air flow can be configured in the second external air inflow path 203.

[0095] An air flow meter 53 for detecting the flow rate of air flowing within the fuel cell side air inlet path 204 may be configured in the fuel cell side air inlet path 204.

[0096] The humidifier 23 can supply moisture to the air flowing in through the fuel cell side air inflow path 204, and can discharge moisture-containing air through the fuel cell side air supply path 205.

[0097] The fuel cell side air supply path 205 may be equipped with a fuel cell side air supply valve 36 for regulating the flow of air supplied to the fuel cell 20.

[0098] The fuel cell side air supply path 205 can be connected to separate supply paths 206 and 207 corresponding to fuel cell stacks 20a and 20b, respectively. Air flowing through the fuel cell side air supply path 205 can be supplied to fuel cell stacks 20a and 20b via separate supply paths 206 and 207.

[0099] Multiple fuel cell stacks 20a and 20b can be connected to each other via gas connection path 107. Reformed gas that has not reacted and is discharged from the first fuel cell stack 20a can flow into the second fuel cell stack 20b via gas connection path 107.

[0100] An additional moisture removal device 62 may be configured in the gas connection flow path 107 for removing water generated by condensation of reformed gas during its passage through the first fuel cell 20a.

[0101] Water generated by the additional moisture removal device 62 can be discharged from the additional moisture removal device 62 and flow into the second water recovery flow path 310. The second water recovery flow path 310 may be equipped 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.

[0102] The anode exhaust gas AOG that has not reacted and been discharged in the fuel cell stacks 20a and 20b can flow through the fuel cell gas discharge path 108.

[0103] The AOG heat exchanger 22 can be connected to the fuel cell gas discharge path 108, which supplies the anode exhaust gas (AOG) from the fuel cell stacks 20a and 20b. The AOG heat exchanger 22 can also be connected to the hot water supply path 313, which supplies the water discharged from the heat recovery tank 15. The AOG heat exchanger 22 allows heat exchange between the anode exhaust gas (AOG) flowing in through the fuel cell gas discharge path 108 and the water supplied through the hot water supply path 313.

[0104] The hot water supply path 313 may be equipped with a hot water pump 48 that causes water stored in the heat recovery tank 15 to flow to 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 path 313.

[0105] The AOG heat exchanger 22 can be connected to the AOG supply path 109, through which the AOG anode exhaust gas is discharged. The AOG discharged from the AOG heat exchanger 22 can flow to the fuel processing unit 10 via the AOG supply path 109. The AOG supplied to the fuel processing unit 10 via the AOG supply path 109 can be used as combustion fuel for the burner 120.

[0106] An AOG moisture removal device 63 for regulating the amount of moisture contained in the AOG and / or an AOG valve 35 for regulating the flow of the AOG supplied to the fuel treatment unit 10 can be configured in the AOG supply flow path 109. The AOG flowing into the AOG moisture removal device 63 can be discharged from the AOG moisture removal device 63 after the moisture has been removed.

[0107] The condensate generated in the AOG moisture removal device 63 can 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 regulating the water flow can be configured in the third water recovery flow path 311. The third water recovery flow path 311 can be connected to the first water recovery flow path 309.

[0108] The fuel cell side air discharge path 211 can be connected to separate discharge paths 208 and 209 corresponding to fuel cells 20a and 20b, respectively. Air discharged from fuel cells 20a and 20b can flow into the fuel cell side air discharge path 211 via separate discharge paths 208 and 209. At this time, the air flowing through the fuel cell side air discharge path 211 can contain moisture generated by the electrochemical reactions occurring in fuel cells 20a and 20b.

[0109] The fuel cell side air discharge path 211 can be connected to the humidifier 23. The humidifier 23 can use the moisture contained in the air supplied via the fuel cell side air discharge path 211 to supply moisture to the air flowing toward the fuel cell 20. The air supplied to the humidifier 23 via the fuel cell side air discharge path 211 can be discharged from the humidifier 23 to the humidifier discharge path 212.

[0110] The fuel cell side air discharge path 211 may be equipped with a fuel cell side air discharge valve 37 for regulating the flow of air discharged from the fuel cell stacks 20a and 20b and flowing into the humidification device 23.

[0111] Water supply tank 13 can be connected to water inlet flow path 301 and can store water supplied via water inlet flow path 301. Water inlet flow path 301 can be configured with a first liquid filter 92 for removing impurities contained in water supplied from the outside and / or a water inlet valve 41 for regulating the flow of water into water supply tank 13.

[0112] The water supply tank 13 can be connected to the water discharge passage 302, through which at least a portion of the water stored in the water supply tank 13 can be discharged to the outside. The water discharge passage 302 can be equipped with a water discharge valve 42 for regulating the flow of water discharged from the water supply tank 13.

[0113] Water supply tank 13 can be connected to water storage flow path 308 and can store water flowing through water storage flow path 308. For example, water discharged from reformed gas moisture removal device 61, additional moisture removal device 62, AOG moisture removal device 63 and / or air moisture removal device 64 and flowing through third water recovery flow path 311 can flow into water supply tank 13 through water storage flow path 308. A second liquid filter 93 for removing impurities contained in the water returned to water supply tank 13 can be configured in water storage flow path 308.

[0114] At least a portion of the water stored in the water supply tank 13 can flow to the reformer heat exchanger 21 under the action of the cooling water pump 43, and can exchange heat with the reformer gas in the reformer heat exchanger 21. The water discharged from the reformer heat exchanger 21 can flow into the fuel cell stacks 20a and 20b through the fuel cell stack water supply path 305.

[0115] Water flowing into fuel cells 20a and 20b via fuel cell supply water flow path 305 can cool fuel cells 20a and 20b. The water flowing into fuel cells 20a and 20b can flow along the fuel cell heat exchangers (not shown) included in fuel cells 20a and 20b, and can absorb the heat generated by the electrochemical reactions occurring in fuel cells 20a and 20b.

[0116] Multiple fuel cell stacks 20a and 20b can be connected by a water connection channel 306. Water discharged from the first fuel cell stack 20a can flow into the second fuel cell stack 20b via the water connection channel 306.

[0117] Water discharged from fuel cells 20a and 20b can flow into cooling water heat exchanger 24 via fuel cell water discharge path 307. Cooling water heat exchanger 24 allows heat exchange between the water discharged from fuel cells 20a and 20b and the water discharged from heat recovery tank 15. Water discharged from fuel cells 20a and 20b can flow to water storage path 308 via cooling water heat exchanger 24.

[0118] Water discharged from heat recovery tank 15 by hot water pump 48 can flow into AOG heat exchanger 22 via hot water supply path 313. Water that has undergone heat exchange with anode exhaust gas AOG in AOG heat exchanger 22 can be discharged into first hot water circulation loop 314.

[0119] The air heat exchanger 25 can be connected to the humidifier discharge path 212, which supplies airflow from the humidifier 23. The air heat exchanger 25 can also be connected to the first hot water circulation loop 314, which supplies waterflow from the AOG heat exchanger 22. The air heat exchanger 25 allows heat exchange between the air flowing in through the humidifier discharge path 212 and the water flowing in through the first hot water circulation loop 314.

[0120] The air that has undergone heat exchange in the air heat exchanger 25 can be discharged from the air heat exchanger 25 via the air discharge path 213. The air discharge path 213 can be connected to the exhaust gas discharge path 210, and the exhaust gas flowing in the exhaust gas discharge path 210 and the air flowing in the air discharge path 213 can be mixed.

[0121] An air moisture removal device 64 may be configured in the air discharge path 213. 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.

[0122] The condensate generated in 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 regulating the water flow can be configured in the fourth water recovery flow path 312. The fourth water recovery flow path 312 can be connected to the water storage flow path 308.

[0123] The water that has been heat-exchanged in the air heat exchanger 25 can be discharged from the air heat exchanger 25 through the second hot water circulation path 315. The water discharged from the air heat exchanger 25 can flow into the cooling water heat exchanger 24 through the second hot water circulation path 315.

[0124] The cooling water heat exchanger 24 can exchange heat between the water flowing in through the fuel cell water discharge path 307 and the water flowing in through the second hot water circulation path 315.

[0125] The exhaust gas heat exchanger 26 can be connected to the exhaust gas discharge path 210 for supplying exhaust gas. The exhaust gas heat exchanger 26 can also be connected to the third hot water circulation path 316 for supplying water discharged from the cooling water heat exchanger 24. The exhaust gas heat exchanger 26 enables heat exchange between the exhaust gas flowing in through the exhaust gas discharge path 210 and the water flowing in through the third hot water circulation path 316.

[0126] The exhaust gas that has been heat-exchanged in the exhaust gas heat exchanger 26 can be discharged into the exhaust gas flow path 214, and the exhaust gas flowing in the exhaust gas flow path 214 can be discharged to the outside.

[0127] The water that has been 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.

[0128] The fuel cell system 1 may also include a thermometer (or temperature sensor) for detecting temperature. For example, the fuel cell system 1 may include: a first thermometer 472 for detecting the temperature of cooling water stored in a water supply tank; and a second thermometer 474 for detecting the temperature of water discharged from the fuel cell stacks 20a and 20b. As an example, the first thermometer 472 may be configured in the cooling water supply path 304 to detect the temperature of water discharged from the water supply tank 13 and flowing within the cooling water supply path 304. As another example, the first thermometer 472 may be configured in the water supply tank 13 to detect the temperature of water stored in the water supply tank 13. The second thermometer 474 may be configured in the fuel cell stack water discharge path 307 to detect the temperature of water discharged from the fuel cell stack 20 and flowing within the fuel cell stack water discharge path 307.

[0129] Additionally, the fuel cell system 1 may also include at least one control unit (not shown). The control unit may include at least one processor. Here, the processor may be a general-purpose processor such as a CPU (central processing unit). Of course, the processor may be a dedicated device such as an ASIC or a processor based on other hardware.

[0130] The control unit can control the overall operation of the fuel cell system 1. The control unit can be connected to each component installed in the fuel cell system 1, and can send and / or receive signals with each component.

[0131] The control unit can process signals received from each component installed in the fuel cell system 1, and can send control signals based on the processed signals to each component installed in the fuel cell system 1. For example, the control unit can adjust the opening degree of each valve installed in the fuel cell system 1. In addition, the control unit can switch each valve installed in the fuel cell system 1.

[0132] Figure 3 This is a system diagram showing the fuel processing device 10, the fuel stack 20, the water supply tank 13, the heat recovery tank 15, and the waste heat recovery unit 400 in a fuel cell system 1 according to an embodiment of the present invention.

[0133] The following is for reference Figure 2 and Figure 3Explain the composition of the waste heat recovery unit 400.

[0134] Reference Figure 2 and Figure 3 The fuel cell system 1 may include a waste heat recovery unit 400.

[0135] The waste heat recovery unit 400 can recover waste heat from the exhaust gas discharged from the fuel processing unit 10 using cooling water flowing along the cooling water flow path. The waste heat recovery unit 400 can be connected to the fuel processing unit 10, the water supply tank 13, and the heat recovery tank 15, respectively. The waste heat recovery unit 400 can form a cooling water flow path that recirculates the fuel processing unit 10, the water supply tank 13, and the heat recovery tank 15.

[0136] The waste heat recovery unit 400 may include a plurality of heat exchangers 410, 412, and 414 respectively disposed in the fuel processing unit 10, the water supply tank 13, and the heat recovery tank 15. The waste heat recovery unit 400 may include a first heat exchanger 410 disposed in the fuel processing unit 10, a second heat exchanger 412 disposed in the water supply tank 13, and a third heat exchanger 414 disposed in the third heat exchanger 414.

[0137] In the first heat exchanger 410, exhaust gas discharged from the fuel processing unit 10 can exchange heat with cooling water supplied from the water supply tank 13 or the heat recovery tank 15. Specifically, the first heat exchanger 410 can be configured close to the exhaust gas outlet side of the burner 120.

[0138] In the second heat exchanger 412, the cooling water that undergoes heat exchange in the first heat exchanger 410 can exchange heat with the water stored in the water supply tank 13.

[0139] In the third heat exchanger 414, the cooling water that undergoes heat exchange in the first heat exchanger 410 can exchange heat with the hot water stored in the heat recovery tank 15.

[0140] The waste heat recovery unit 400 may include: first heat recovery pipes 422 and 424, which form cooling water flow paths and connect the first heat exchanger 410 and the second heat exchanger 412; and second heat recovery pipes 432 and 434, which form cooling water flow paths and connect the first heat exchanger 410 and the third heat exchanger 414.

[0141] The first heat recovery pipes 422 and 424 may include a first-first heat recovery pipe 422 connecting the outlet end of the second heat exchanger 412 and the inlet end of the first heat exchanger 410. Cooling water that exchanges heat with water stored in the water supply tank 13 may flow in the first-first heat recovery pipe 422.

[0142] The first heat recovery pipes 422 and 424 may include a first-second heat recovery pipe 424 connecting the inlet end of the second heat exchanger 412 and the outlet end of the second heat exchanger 410. Cooling water that exchanges heat with the exhaust gas of the fuel treatment device 10 may flow in the first-second heat recovery pipes 424.

[0143] On the other hand, a heat supply pump 440 for forming a circulating cooling water flow path can be configured in the first-second heat recovery pipe 424.

[0144] Additionally, the waste heat recovery unit 400 may also include a bypass pipe 466 for supplying cooling water to bypass the first heat exchanger 410. The bypass pipe 466 may be disposed on the side of the first heat exchanger 410. The bypass pipe 466 may be connected to the inlet end 422 and the outlet end 424 of the first heat exchanger 410.

[0145] The second heat recovery pipes 432 and 434 may include a second-first heat recovery pipe 432 connecting the outlet of the third heat exchanger 414 and the inlet of the first heat exchanger 410. Specifically, the second-first heat recovery pipe 432 may merge with the first-first heat recovery pipe 422 and connect to the inlet of the first heat exchanger 410. Therefore, cooling water that exchanges heat with the hot water stored in the heat recovery tank 15 may flow through the second-first heat recovery pipe 432.

[0146] The second heat recovery pipes 432 and 434 may include a second-second heat recovery pipe 434 connecting the inlet end of the third heat exchanger 414 and the outlet end of the first heat exchanger 410. Specifically, the second-second heat recovery pipe 434 may branch off from the first-second heat recovery pipe 424 and connect to the outlet end of the first heat exchanger 410. Therefore, cooling water that exchanges heat with the exhaust gas of the fuel processing device 10 may flow in the second-second heat recovery pipe 434.

[0147] The waste heat recovery unit 400 may include a heat recovery valve 452 that supplies cooling water discharged from the water supply tank 13 or the heat recovery tank 15 to the fuel processing unit 10. The heat recovery valve 452 may operate to supply cooling water discharged from the second heat exchanger 412 to the first heat exchanger 410 or to bypass cooling water discharged from the second heat exchanger 412 to the first heat exchanger 410. The heat recovery valve 452 may also operate to supply cooling water discharged from the third heat exchanger 412 to the first heat exchanger 410 or to bypass cooling water discharged from the third heat exchanger 412 to the first heat exchanger 410.

[0148] A heat recovery valve 452 can be configured in the first-first heat recovery pipe 422. The heat recovery valve 452 can be a three-way valve. The inlet end of the heat recovery valve 452 can be connected upstream of the first-first heat recovery pipe 422. The first outlet end of the heat recovery valve 452 can be connected downstream of the first-first heat recovery pipe 422. The second outlet end of the heat recovery valve 452 can be connected to a bypass pipe 466.

[0149] The waste heat recovery unit 400 may include a heat supply valve 462 that supplies cooling water discharged from the fuel processing unit 10 to the water supply tank 13 or the heat recovery tank 15. The heat supply valve 462 may operate to supply cooling water discharged from the first heat exchanger 410 to the second heat exchanger 412 or the third heat exchanger 414, or to supply cooling water bypassing the first heat exchanger 410 to the second heat exchanger 412 or the third heat exchanger 414.

[0150] A heat supply valve 462 can be configured in the first-second heat recovery pipe 424. The heat supply valve 462 can be a three-way valve. The inlet end of the heat supply valve 462 can be connected upstream of the first-second heat recovery pipe 424. The first outlet end of the heat supply valve 462 can be connected downstream of the first-second heat recovery pipe 424. The second outlet end of the heat supply valve 462 can be connected to the second-second heat recovery pipe 434.

[0151] Therefore, the waste heat recovery unit 400 can recover the waste heat of the exhaust gas by exchanging heat between the cooling water flowing along the cooling water flow paths 422, 424, 432, 434 and the exhaust gas discharged from the fuel processing device 10. Furthermore, by supplying the cooled water that has undergone heat exchange to the water supply tank 13, it can heat the water stored in the water supply tank 13, or by supplying the cooled water that has undergone heat exchange to the heat recovery tank 15, it can heat the hot water stored in the heat recovery tank 15.

[0152] Figure 4 and Figure 5 This is a system diagram showing the operation of the waste heat recovery unit 400 in the preheating mode WM and / or reforming mode RM of the fuel cell system 1.

[0153] The fuel cell system 1 can operate in a preheating mode WM, in which the fuel processing unit 10 is preheated to a temperature suitable for reforming. Specifically, the reformer 140 of the fuel processing unit 10 is preheated using the burner 120. Alternatively, the fuel cell system 1 can operate in a reforming mode RM, in which the reformed gas is recirculated in the burner and repeatedly reformed to achieve a hydrogen and carbon monoxide concentration in the reformed gas that is suitable for power generation.

[0154] In preheating mode WM, fuel cell system 1 can close reforming gas valve 33, bypass valve 34, and AOG valve 35. At this time, the fuel gas supply to reformer 140 is cut off, therefore no reforming gas is generated in reformer 140. Furthermore, reforming gas or anode exhaust gas (AOG) will not flow in reforming gas discharge path 104, bypass path 105, and AOG supply path 109. (Ref) Figure 2 )

[0155] In reforming mode (RM), fuel cell system 1 can close reforming gas valve 33 and AOG valve 35 and bypass valve 34. At this time, the reformed gas discharged from fuel processing unit 10 can flow back into fuel processing unit 10 via reformed gas discharge path 104 and bypass path 105, and can be used as combustion fuel for burner 120. (Ref) Figure 2 )

[0156] In preheating mode WM and / or reforming mode RM, the fuel cell system 1 can generate cooling water flow in circulating cooling water paths 422, 424, and 466 by operating the heat supply pump 440.

[0157] The flow of cooling water in the circulating cooling water path for recovering waste heat from the exhaust gas discharged from the fuel processing unit 10 will be described below.

[0158] Reference Figure 4 Cooling water discharged from the second heat exchanger 412 can flow upstream of the first-1 heat recovery pipe 422 and be supplied to the heat recovery valve 452. At this time, the heat recovery valve 452 can be switched to the first heat exchanger 410 side to connect downstream of the first-1 heat recovery pipe 422, and the cooling water supplied to the heat recovery valve 452 can flow downstream of the first-1 heat recovery pipe 422 and be supplied to the first heat exchanger 410.

[0159] The cooling water supplied to the first heat exchanger 410 can exchange heat with the exhaust gas discharged after combustion with the burner 140 and then flow upstream of the first-second heat recovery pipe 424, and is supplied to the heat supply valve 462 via the heat supply pump 440. At this time, the heat supply valve 462 can be switched to the second heat exchanger 412 side to connect downstream of the first-second heat recovery pipe 424, and the cooling water supplied to the heat supply valve 462 can flow downstream of the first-second heat recovery pipe 424 and be supplied to the second heat exchanger 412.

[0160] The cooling water supplied to the second heat exchanger 412 can be discharged after heat exchange with the water stored in the water supply tank 13, and the cooling water discharged from the second heat exchanger 412 can be discharged along the aforementioned circulating cooling water flow path.

[0161] Thus, in preheating mode WM and / or reforming mode RM, the water stored in the water supply tank 13 can be heated by exchanging heat with the cooling water that recovers the discarded waste heat from the exhaust gas using the first heat exchanger 410.

[0162] The following describes the flow of cooling water circulating in the cooling water path at the end of the waste heat recovery of the exhaust gas discharged from the fuel processing unit 10.

[0163] Reference Figure 5 Cooling water discharged from the second heat exchanger 412 can flow upstream of the first-1 heat recovery pipe 422 and be supplied to the heat recovery valve 452. At this time, the fuel cell system 1 can use the first thermometer 472 to detect the temperature of the water stored in the water supply tank 13. If the water temperature detected by the first thermometer 472 is above the first set temperature, the heat recovery valve 452 can be switched to connect to the bypass pipe 466. The first set temperature refers to the water temperature suitable for fully preheating the fuel cell stack 20 in the power generation mode PM, and can be a value pre-stored in the memory of the control unit.

[0164] Cooling water supplied to heat recovery valve 452 can flow downstream of bypass pipe 466 and the first-second heat recovery pipe 424, and can also be supplied to heat supply valve 462 by heat supply pump 440. At this time, heat supply valve 462 can switch to the second heat exchanger 412 side to connect downstream of the first-second heat recovery pipe 424, and the cooling water supplied to heat supply valve 462 can flow downstream of the first-second heat recovery pipe 424 and be supplied to the second heat exchanger 412.

[0165] The cooling water supplied to the second heat exchanger 412 can be discharged after heat exchange with the water stored in the water supply tank 13, and the cooling water discharged from the second heat exchanger 412 can repeat the above-described cycle process in the same way.

[0166] Therefore, when the temperature of the water stored in the water supply tank 13 is sufficiently heated, the waste heat recovery of the fuel processing unit 10 is completed by the cooling water supplied to the fuel processing unit 10 through the bypass, and the temperature of the water stored in the water supply tank 13 can be maintained at a set temperature suitable for preheating the fuel stack.

[0167] Figure 6 and Figure 7 This is a system diagram related to the operation of fuel cell system 1 under the power generation mode PM of fuel cell system 1.

[0168] The fuel cell system 1 can operate in power generation mode PM, which utilizes the electrochemical reaction of air and reformed gas to generate electricity in the stacks 20a and 20b.

[0169] In power generation mode (PM), fuel cell system 1 can open reforming gas valve 33 and close bypass valve 34 to supply reforming gas discharged from fuel processing unit 10 to fuel cell stack 20. Fuel cell system 1 can supply air used in the electrochemical reaction for generating electricity to fuel cell stack 20 by driving second blower 72. (Ref) Figure 2 )

[0170] In power generation mode PM, the fuel cell system 1 can generate cooling water flow through circulating cooling water paths 422, 424, 432, and 434 by operating the heat supply pump 440.

[0171] In power generation mode PM, the fuel cell system 1 can generate water flow by operating the cooling water pump 43 to supply water stored in the water supply tank 13 to the fuel cell stack 20.

[0172] The following describes the flow of cooling water used to preheat the fuel cell stack 20 during the initial stage of power generation mode PM.

[0173] Reference Figure 6 Cooling water discharged from the second heat exchanger 412 can flow upstream of the first-1 heat recovery pipe 422 and be supplied to the heat recovery valve 452. At this time, the heat recovery valve 452 can be switched to the first heat exchanger 410 side to connect downstream of the first-1 heat recovery pipe 422, and the cooling water supplied to the heat recovery valve 452 can flow downstream of the first-1 heat recovery pipe 422 and be supplied to the first heat exchanger 410.

[0174] The cooling water supplied to the first heat exchanger 410 can exchange heat with the exhaust gas discharged after combustion with the burner 140 and then flow upstream of the first-second heat recovery pipe 424, and is supplied to the heat supply valve 462 via the heat supply pump 440. At this time, the heat supply valve 462 can be switched to the second heat exchanger 412 side to connect downstream of the first-second heat recovery pipe 424, and the cooling water supplied to the heat supply valve 462 can flow downstream of the first-second heat recovery pipe 424 and be supplied to the second heat exchanger 412.

[0175] Therefore, the water stored in the water supply tank 13 can be heated by exchanging heat with the cooling water that has recovered waste heat from the exhaust gas through the first heat exchanger 410 in the second heat exchanger 410. The heated water stored in the water supply tank 13 is then supplied to the fuel cell stack 20 by the operation of the cooling water pump 43, thereby rapidly preheating the fuel cell stack 20 to a suitable temperature for power generation in the initial stage of the power generation mode PM. As a result, the power generation efficiency of the fuel cell stack 20 can be improved.

[0176] In power generation mode PM, the fuel cell system 1 can use a second thermometer 474 to detect the temperature of the water discharged from the fuel cell stack 20. If the water temperature detected by the second thermometer 474 is above a second set temperature, it can be determined that the preheating of the fuel cell stack 20 is complete. The second set temperature refers to the temperature at which the fuel cell stack 20 is fully preheated and can operate normally for power generation in power generation mode PM, and it can be a value pre-stored in the memory of the control unit.

[0177] The following describes the flow of cooling water during the PM generation mode after the preheating of the fuel cell stack 20 is completed.

[0178] Reference Figure 7 Cooling water discharged from the third heat exchanger 414 can flow along the second-first heat recovery pipe 432 and be supplied to the heat recovery valve 452. At this time, the heat recovery valve 452 can be switched to the first heat exchanger 410 side to connect downstream of the first-first heat recovery pipe 422, and the cooling water supplied to the heat recovery valve 452 can flow downstream of the first-first heat recovery pipe 422 and be supplied to the first heat exchanger 410.

[0179] The cooling water supplied to the first heat exchanger 410 can exchange heat with the exhaust gas discharged after combustion with the burner 140 and then flow upstream of the first-second heat recovery pipe 424, and is supplied to the heat supply valve 462 via the heat supply pump 440. At this time, the heat supply valve 462 can be switched to the third heat exchanger 414 side to connect with the second-second heat recovery pipe 434, and the cooling water supplied to the heat supply valve 462 can flow along the second-second heat recovery pipe 434 and be supplied to the third heat exchanger 414.

[0180] Therefore, after the fuel cell stack 20 has been preheated, the hot water stored in the heat recovery tank 15 can be heated by exchanging heat with the cooling water that has recovered the waste heat from the exhaust gas through the first heat exchanger 410 in the third heat exchanger 414. The hot water stored in the heat recovery tank 15 can be supplied to hot water usage locations such as residences according to user requirements. As a result, the amount of waste heat recovered by the fuel processing device 10 can be increased, and the overall energy efficiency of the fuel cell system 1 can be improved.

[0181] In addition, in power generation mode PM, fuel cell system 1 can operate hot water pump 48 to use cooling water heat exchanger 24 to exchange heat between water discharged from stack 20 and hot water in circulating heat recovery tank 15.

[0182] Figure 8 This is a flowchart of a control method for a fuel cell system 1 according to an embodiment of the present invention.

[0183] Reference Figure 8The control unit can start the operation of the fuel cell system 1 (S100). After the operation of the fuel cell system 1 is started, the fuel cell system 1 can perform preheating operation WM, reforming operation RM and / or power generation operation PM.

[0184] After S100, the control unit can determine the current operating mode of the fuel cell system 1 (S110).

[0185] When the current operating mode of the fuel cell system 1 is preheating mode WM or reforming mode RM, the control unit can operate the heat supply pump 440 (S210). As a result, a cooling water flow can be formed that circulates along the cooling water flow path of the waste heat recovery unit 400.

[0186] After S210, the control unit can switch the heat supply valve 462 to the water supply tank 13 side, so that the cooling water that has exchanged heat with the exhaust gas in the first heat exchanger 410 can be supplied to the second heat exchanger 412 (S220). At this time, the control unit can switch the heat recovery valve 452 to the fuel processing device 10 side, so that the cooling water discharged from the second heat exchanger 412 can be supplied to the first heat exchanger 410. Therefore, the cooling water circulating in the cooling water flow path can be supplied to the second heat exchanger 412 after recovering the waste heat of the exhaust gas in the first heat exchanger 410, and the cooling water supplied to the second heat exchanger 412 can exchange heat with the water stored in the water supply tank 13, so that the water stored in the water supply tank 13 is heated.

[0187] After S220, the control unit can determine whether the preheating of the water stored in the water supply tank 13 is complete (S230). Specifically, the control unit can use the first thermometer 472 to detect the temperature of the water stored in the water supply tank 13. If the water temperature detected by the first thermometer 472 is above the first set temperature, it can be determined that the preheating of the water stored in the water supply tank 13 is complete. The first set temperature can be set to a water temperature suitable for fully preheating the fuel cell stack 20 in the power generation mode PM.

[0188] When the preheating of the water stored in the water supply tank 13 is not completed (No in S230), the control unit can switch the heat recovery valve 452 to the inlet end 422 of the fuel processing device 10 so that the cooling water discharged from the second heat exchanger 412 is supplied to the first heat exchanger 410 (S240). Therefore, the cooling water circulating in the cooling water flow path can recover the waste heat of the exhaust gas in the first heat exchanger 410 until the temperature of the water stored in the water supply tank 13 reaches the first set temperature.

[0189] When the preheating of the water stored in the water supply tank 13 is completed (Yes in S230), the control unit can switch the heat recovery valve 452 to the outlet end 424 of the fuel processing device 10, so that the cooling water discharged from the second heat exchanger 412 bypasses the first heat exchanger 410 (S250). Therefore, the cooling water in the circulating cooling water path will no longer recover the waste heat of the exhaust gas from the first heat exchanger 410, and the temperature of the water stored in the water supply tank 13 will be maintained.

[0190] After S240 and S250, the control unit returns to S110 and can once again determine the current operating mode of the fuel cell system 1.

[0191] When the current operating mode of the fuel cell system 1 is power generation mode PM, the control unit can determine whether power generation mode PM is in the initial state (S310). For example, the control unit can determine whether power generation mode PM is in the initial state based on whether the preheating of the fuel cell stack 20 is complete. Specifically, the control unit can use a second thermometer 474 to detect the temperature of the water discharged from the fuel cell stack 20. If the water temperature detected by the second thermometer 474 is above a second set temperature, it can be determined that the preheating of the fuel cell stack 20 is complete, and the current power generation mode PM corresponds to the intermediate state. The second set temperature can be set to the temperature at which the fuel cell stack 20 is sufficiently preheated and can operate normally for power generation under power generation mode PM.

[0192] When the power generation mode PM is in the initial state (Yes in S310), the control unit can determine whether the preheating of the water stored in the water supply tank 13 is complete (S320). Specifically, the control unit can use the first thermometer 472 to detect the temperature of the water stored in the water supply tank 13. If the water temperature detected by the first thermometer 472 is above the first set temperature, it can be determined that the preheating of the water stored in the water supply tank 13 is complete.

[0193] When the preheating of the water stored in the water supply tank 13 is not completed (No in S320), the control unit can operate the heat supply pump 440 (S330). As a result, a cooling water flow can be formed that circulates along the cooling water flow path of the waste heat recovery unit 400.

[0194] After S330, the control unit can switch the heat supply valve 462 to the water supply tank 13 side, so that the cooling water that has exchanged heat with the exhaust gas in the first heat exchanger 410 can be supplied to the second heat exchanger 412 (S340). At this time, the control unit can switch the heat recovery valve 452 to the fuel processing device 10 side, so that the cooling water discharged from the second heat exchanger 412 can be supplied to the first heat exchanger 410. Therefore, the cooling water circulating in the cooling water flow path can be supplied to the second heat exchanger 412 after recovering the waste heat of the exhaust gas in the first heat exchanger 410, and the cooling water supplied to the second heat exchanger 412 can exchange heat with the water stored in the water supply tank 13, so that the water stored in the water supply tank 13 is heated.

[0195] After S340, the control unit can operate the cooling water pump 43 (S350). Additionally, the control unit can stop the hot water pump 48 or keep it in a stopped state (S350). Therefore, in the initial stage of the power generation mode PM, when the water supplied to the water tank 13 of the fuel cell stack 20 is not sufficiently heated, the fuel cell stack 20 can be preheated by concentrating the waste heat from the exhaust gas recovered by the fuel processing unit 10 on the water tank 13 side and simultaneously supplying water from the water tank 13 to the fuel cell stack 20, without supplying it to the heat recovery tank 15 side.

[0196] When the preheating of the water stored in the water supply tank 13 is completed (Yes in S320), the control unit can perform the S360 operation described later.

[0197] When the power generation mode PM is in the intermediate state (No in S310), the control unit can operate the heat supply pump 440 (S360). As a result, a cooling water flow can be formed that circulates along the cooling water flow path of the waste heat recovery unit 400.

[0198] After S360, the control unit can switch the heat supply valve 462 to the heat recovery tank 15 side, so that the cooling water that has exchanged heat with the exhaust gas in the first heat exchanger 410 can be supplied to the third heat exchanger 412 (S370). At this time, the control unit can switch the heat recovery valve 452 to the fuel processing device 10 side, so that the cooling water discharged from the third heat exchanger 414 can be supplied to the first heat exchanger 410. Therefore, the cooling water circulating in the cooling water flow path can be supplied to the third heat exchanger 414 after recovering the waste heat of the exhaust gas in the first heat exchanger 410, and the cooling water supplied to the third heat exchanger 414 can exchange heat with the hot water stored in the heat recovery tank 15, so that the hot water stored in the heat recovery tank 15 is heated.

[0199] After S370, the control unit can operate the cooling water pump 43 (S380). Additionally, the control unit can operate or maintain the operation of the hot water pump 48 (S380). Therefore, during the middle of the power generation mode PM, when the fuel cell stack 20 is sufficiently preheated, as the waste heat from the exhaust gas recovered in the fuel processing unit 10 is supplied to the heat recovery tank 15, the hot water stored in the heat recovery tank 15 is heated, and the hot water stored in the heat recovery tank 15 can be supplied to residential and other hot water usage locations according to user requirements.

[0200] The accompanying drawings are provided to facilitate understanding of the embodiments disclosed in this specification. The technical ideas disclosed in this specification are not limited to the drawings. This invention includes all modifications, equivalents, and substitutions made within the technical ideas and scope of this invention.

[0201] Similarly, the actions are described in a specific order in the accompanying drawings, but this should not be construed as meaning that the actions must be performed in that specific order or sequentially to obtain the preferred result, or that all of the actions shown must be performed. In certain situations, multitasking and parallel processing may be advantageous.

[0202] Furthermore, the preferred embodiments of the present invention have been shown and described above, but the present invention is not limited to the specific embodiments described above. Obviously, those skilled in the art can make various modifications and implementations without departing from the spirit of the present invention as claimed in the claims. Such modified embodiments should not be understood separately from the technical concept or prospect of the present invention.

Claims

1. A fuel cell system, in, include: A fuel cell stack generates electricity through the electrochemical reaction of reformed gases and air. A fuel processing unit generates the reforming gas to be supplied to the fuel cell stack; Water supply tank, storing water supplied to the fuel cell stack; Heat recovery tanks store hot water; A first heat exchanger is configured in the fuel processing unit for heat exchange between cooling water and exhaust gas discharged from the fuel processing unit. A heat supply valve supplies cooling water that has undergone heat exchange in the first heat exchanger to the water supply tank or heat recovery tank to heat the water stored in the water supply tank or the hot water stored in the heat recovery tank. A first temperature sensor detects the temperature of the water stored in the water supply tank; A second temperature sensor detects the temperature of the water discharged from the fuel cell stack; and The control unit adjusts the heat supply valve; In the power generation mode of generating electricity by utilizing the electrochemical reaction of reformed gas and air in the fuel cell stack, if the water temperature detected by the first temperature sensor is above a first set temperature and the water temperature detected by the second temperature sensor is below a second set temperature, the control unit switches the heat supply valve to the water supply tank side so that the cooling water after heat exchange with the exhaust gas in the first heat exchanger is supplied to the water supply tank. The first set temperature is greater than the second set temperature.

2. The fuel cell system according to claim 1, in, include: The control unit adjusts the heat supply valve; In the preheating mode of the fuel processing device, the control unit switches the heat supply valve to the water supply tank side so that the cooling water after heat exchange in the first heat exchanger is supplied to the water supply tank.

3. The fuel cell system according to claim 1, wherein, Also includes: The heat recovery valve supplies cooling water discharged from the water supply tank to the first heat exchanger or to the heat supply valve.

4. The fuel cell system according to claim 3, in, include: The control unit adjusts the heat supply valve and the heat recovery valve; In the preheating mode of the fuel processing device, the control unit switches the heat recovery valve to the first heat exchanger side so that cooling water discharged from the water supply tank is supplied to the first heat exchanger.

5. The fuel cell system according to claim 4, in, include: A first temperature sensor detects the temperature of the water stored in the water supply tank; If the water temperature detected by the first temperature sensor is above the first set temperature, the control unit switches the heat recovery valve to the heat supply valve side.

6. The fuel cell system according to claim 1, wherein, In the power generation mode where the stack generates electricity using the electrochemical reaction of reformed gas and air, if the temperature of the cooling water detected by the second temperature sensor is above the second set temperature, the control unit switches the heat supply valve to the heat recovery tank side so that the cooling water after heat exchange with the exhaust gas in the first heat exchanger is supplied to the heat recovery tank.

7. The fuel cell system according to claim 1, wherein, Also includes: A heat supply pump forms a circulating flow of cooling water between the fuel processing unit, the water supply tank, and the heat recovery tank.

8. The fuel cell system according to claim 1, wherein, Also includes: A cooling water pump, configured between the water supply tank and the fuel cell stack, supplies cooling water stored in the water supply tank to the fuel cell stack.

9. The fuel cell system according to claim 8, in, include: The control unit regulates the operation of the cooling water pump; In the power generation mode where the stack generates electricity using the electrochemical reaction of reformed gas and air, the control unit operates the cooling water pump to supply cooling water to the stack.

10. The fuel cell system according to claim 1, in, include: A second heat exchanger is disposed in the water supply tank, supplying heat to the cooling water after heat exchange with the exhaust gas in the first heat exchanger and the cooling water stored in the water supply tank; and A third heat exchanger is configured in the heat recovery tank to exchange heat between the cooling water after heat exchange with the exhaust gas in the first heat exchanger and the hot water stored in the heat recovery tank.

11. The fuel cell system according to claim 10, wherein, The fuel processing device further includes: The burner supplies the heat energy required to generate the reformed gas; The first heat exchanger is arranged adjacent to the outlet side of the burner from which the exhaust gas generated after the combustion reaction of the fuel is discharged.

Images