KR102550359B1 - Fuel cell system - Google Patents

Abstract

The present invention relates to a fuel cell system. A fuel cell system according to an embodiment of the present invention includes a fuel processing device generating reformed gas by reforming fuel gas; a stack generating electricity using the reformed gas; a first passage through which the reformed gas discharged from the fuel processing device flows; a second passage through which anode off gas (AOG) discharged from the stack flows; a third flow path connected to the first flow path and the second flow path; and a valve operable to allow at least a portion of the anode-off gas flowing in the second flow path to flow to the fuel processing device and a remaining portion to flow to the third flow path. Various other embodiments are possible.

Description

Fuel cell system {FUEL CELL SYSTEM}

The present invention relates to a fuel cell system, and more particularly, to a fuel cell system that improves power generation efficiency by using gas discharged from a stack.

A fuel cell system is a power generation system that generates electrical energy by electrochemically reacting hydrogen contained in hydrocarbon-based materials, such as methanol, ethanol, and natural gas, with oxygen.

Similar to Prior Art 1 (Korean Patent Publication No. 10-2012-0071288), a conventional fuel cell system includes a fuel processing device for converting fuel containing hydrogen atoms into hydrogen gas, and a fuel processing device. A stack is provided to generate electric energy using hydrogen gas supplied therefrom. In addition, the fuel cell system may further include a heat exchanger and a cooling water pipe for cooling the stack and recovering heat, a power conversion device for converting DC power generated into AC power, and the like.

On the other hand, in order to achieve the target amount of power generation, a larger amount of hydrogen gas than the minimum required for power generation is supplied to the stack in consideration of the reaction efficiency of the hydrogen gas. Fuel is usually used. At this time, some of the hydrogen gas supplied to the stack is used in the electrochemical reaction for power generation, but some of the hydrogen gas supplied to the stack is discharged as it is without reacting in the stack, so research on recycling the hydrogen gas discharged from the stack has been actively conducted. are losing

Conventionally, by supplying hydrogen gas discharged without reacting from the stack to the burner, combustion efficiency of the burner is increased through recycling of the hydrogen gas. However, even when the hydrogen gas is recycled as a burner fuel, there is still a problem in that the amount of fuel used in the fuel cell system cannot be effectively reduced.

KR 10-2012-0071288 A

The present invention aims to solve the foregoing and other problems.

Another object is to provide a fuel cell system capable of reducing fuel consumption while meeting a target power generation amount by using gas discharged from a stack.

Another object is to provide a fuel cell system capable of improving the power generation efficiency of the stack by reducing the moisture ratio of the reformed gas supplied to the stack.

Another object is to provide a fuel cell system having a structure that properly mixes a reformed gas discharged from a fuel processing device and a gas discharged from a stack.

The tasks of the present invention are not limited to the tasks mentioned above, and other tasks not mentioned will be clearly understood by those skilled in the art from the following description.

To achieve the above object, a fuel cell system according to an embodiment of the present invention includes a fuel processing device generating reformed gas by reforming fuel gas, and a stack generating electricity using the reformed gas, The anode off gas toward the passage through which the reformed gas flows so that the reformed gas discharged from the fuel processor and the anode off gas (AOG) discharged from the stack are mixed and introduced into the stack It may further include a valve that operates to allow at least a portion of the flow.

The fuel cell system may include: a first passage through which the reformed gas discharged from the fuel processing device flows; a second passage through which anode off gas (AOG) discharged from the stack flows; and a third flow path connected to the first flow path and the second flow path, wherein the valve allows at least a portion of the anode-off gas flowing in the second flow path to flow to the fuel processor, and a remaining portion to flow to the fuel processing device. It may operate to flow into the third passage.

The fuel cell system may further include a controller configured to adjust the opening of the valve, and the controller may calculate an amount of electricity generated from the stack and adjust the opening of the valve according to the calculated amount of power. there is.

The control unit controls the opening of the valve so that the flow of the anode off gas to the third flow path is blocked when the amount of power generation is less than the preset minimum amount of power generation, and when the amount of power generation is greater than or equal to the minimum amount of power generation, the anode off An opening degree of the valve may be adjusted such that a portion of the gas flows into the fuel processor and the remaining portion flows into the third passage.

The control unit controls the valve to set a flow rate of the anode off-gas flowing into the fuel processor to be greater than a flow rate of the anode-off gas flowing into the third flow path when the amount of power generation is greater than or equal to the minimum amount of power generation. You can adjust the opening.

The flow rate of the anode off-gas flowing through the second flow path may correspond to the sum of the flow rate of the anode-off gas flowing into the fuel processor and the flow rate of the anode-off gas flowing through the third flow path. .

When the amount of power generation is equal to or greater than the minimum amount of power generation, the control unit may calculate the amount of power generation according to a predetermined period and adjust the opening of the valve based on a change in the amount of power generation calculated according to the predetermined period.

The control unit, when the amount of power generation decreases during the predetermined period, adjusts the opening degree of the valve so that the flow rate of the anode off-gas flowing in the third flow path decreases, and the amount of power generation increases or is maintained during the predetermined period In this case, the opening degree of the valve may be adjusted to increase the flow rate of the anode-off gas flowing in the third passage.

The fuel cell system may further include a gas mixer disposed in the first flow path to mix the reformed gas and the anode-off gas flowing in the third flow path.

The gas mixer may include a main flow path in the form of a venturi tube in which a cross-sectional area decreases and expands in a direction in which the reformed gas flows.

The gas mixer may include: a passage reducing portion through which the reformed gas is introduced and reducing a cross-sectional area of the main passage; a flow path holding unit connected to the flow path reducing unit and maintaining a cross-sectional area of the main flow path; and a flow path extension portion connected to the flow path holding unit and increasing a cross-sectional area of the main flow path, wherein the anode-off gas may be introduced into the flow path holding unit.

A length of the flow path maintaining part may be longer than a length of the flow path expanding part and shorter than a length of the flow path reducing part.

The gas mixer may include a housing including a first inner wall forming the main flow path and a first outer wall formed outside the first inner wall; and a gas supply part disposed between the first inner wall and the first outer wall through which the anode-off gas flows, wherein the anode-off gas flowing into the gas mixer passes through the gas supply part to the main flow path. can be fluid

The gas supply unit may include a second inner wall disposed to contact the first inner wall; a second outer wall formed outside the second inner wall; and a sub-passage disposed between the second inner wall and the second outer wall, through which the anode-off gas flows.

The second inner wall may include a plurality of discharge holes formed to be spaced apart in a spiral direction, and the passage holding part may include a plurality of inlet holes formed to be spaced apart in a spiral direction, corresponding to the plurality of discharge holes, respectively. there is.

The fuel cell system may include: a first moisture removal device disposed between the gas mixer and the stack to remove moisture contained in the reformed gas; and a second moisture removal device disposed between the stack and the valve to remove moisture contained in the anode off-gas.

Details of other embodiments are included in the detailed description and drawings.

According to various embodiments of the present disclosure, the anode off-gas discharged from the stack is configured to be properly supplied back to the stack, so that the amount of fuel used can be reduced while meeting a target amount of power generation.

In addition, according to various embodiments of the present invention, the moisture ratio of the reformed gas supplied to the stack can be reduced by mixing the anode off-gas from which moisture is removed after being discharged from the stack with the reformed gas discharged from the fuel processor, The power generation efficiency of the stack can be improved.

In addition, according to various embodiments of the present invention, as the anode off-gas discharged from the stack is discharged to the region where the reformed gas flows through the spiral-shaped passage, a rotational flow may be formed in the region where the anode-off gas is discharged. Therefore, the reformed gas discharged from the fuel processor and the anode-off gas discharged from the stack may be appropriately mixed in the gas mixer.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

1 is a schematic diagram of a configuration of a fuel processing apparatus according to an embodiment of the present invention.
2 is a configuration diagram of a fuel cell system according to an embodiment of the present invention.
FIG. 3 is a diagram showing a part of the configuration of the fuel cell system of FIG. 2 .
4 and 5 are flowcharts illustrating an operating method of a fuel cell system according to an embodiment of the present invention.
6 to 9 are views referenced for description of the operation of the fuel cell system.
10 is a perspective view of a gas mixer according to an embodiment of the present invention.
11 is a perspective view of a gas mixer showing the inside of a gas supply unit according to an embodiment of the present invention.
12 is a side view of a gas mixer according to an embodiment of the present invention.
13 is a perspective view of a housing of a gas mixer according to an embodiment of the present invention.
14 is a side view of a housing of a gas mixer according to an embodiment of the present invention.
15 is a perspective view of a gas supply unit according to an embodiment of the present invention.
16 is a perspective view of a gas supply unit showing a sub-passage according to an embodiment of the present invention.
17 is a front view of a gas supply unit according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings. In the drawings, in order to clearly and concisely describe the present invention, parts not related to the description are omitted, and the same reference numerals are used for the same or extremely similar parts throughout the specification.

The suffixes "module" and "unit" for the components used in the following description are simply given in consideration of ease of writing this specification, and do not themselves give a particularly important meaning or role. Accordingly, the “module” and “unit” may be used interchangeably.

In this application, terms such as "comprise" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Also, in this specification, terms such as first and second may be used to describe various elements, but these elements are not limited by these terms. These terms may only be used to distinguish one element from another.

1 is a schematic diagram of a configuration of a fuel processing apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the fuel processing device 10 includes a desulfurizer 110, a burner 120, a steam generator 130, a reformer 140, a first reactor 150 and/or a second reactor 160. ) may be included. The fuel processing device 10 may further include at least one mixer 111 or 112.

The desulfurizer 110 may perform a desulfurization process to remove sulfur compounds contained in fuel gas. For example, the desulfurizer 110 may have an adsorbent therein. At this time, the sulfur compound included in the fuel gas passing through the desulfurizer 110 may be adsorbed to the adsorbent. The adsorbent may be composed of metal oxide, zeolite, activated carbon, or the like.

The desulfurizer 110 may further include a filter for removing foreign substances included in the fuel gas.

The burner 120 may supply heat to the reformer 140 to promote a reforming reaction in the reformer 140 . For example, fuel gas discharged from the desulfurizer 110 and air introduced from the outside may be mixed in the first mixer 111 and supplied to the burner 120 . At this time, the burner 120 may generate combustion heat by burning a mixture of fuel gas and air, and the internal temperature of the reformer 140 may be increased to an appropriate temperature (eg, 800° C.) by the heat supplied from the burner 120. °C) can be maintained.

Meanwhile, exhaust gas generated in the burner 120 by combustion of a mixture of fuel gas and air may be discharged to the outside of the fuel processing device 10 .

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

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

The reformer 140 may perform a reforming process of generating hydrogen gas from fuel gas from which sulfur compounds are removed by using a catalyst. Here, the catalyst used in the reforming reaction may be a catalyst composed of nickel (Ni), alumina (Al₂O₃), or the like. For example, fuel gas discharged from the desulfurizer 110 and steam discharged from the steam generator 130 may be mixed in the second mixer 112 and supplied to the reformer 140 . In this case, when the fuel gas supplied to the reformer 140 and the water vapor undergo a reforming reaction in the reformer 140, hydrogen gas may be generated.

Meanwhile, the first mixer 111 and/or the second mixer 112 may be implemented as an ejector. For example, the second mixer 112 may be an ejector that uses steam discharged from the steam generator 130 to suck fuel gas discharged from the desulfurizer 110 into the inside.

The first reactor 150 may reduce carbon monoxide generated by a reforming reaction among components included in the gas discharged from the reformer 140 . For example, carbon monoxide included in gas discharged from the reformer 140 may 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 may be lower than the internal temperature of the reformer 140 and higher than room temperature (eg, 200° C.).

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

The second reactor 160 can reduce carbon monoxide remaining among components included in the gas discharged from the first reactor 150 . For example, a selective oxidation (PROX) reaction in which carbon monoxide included in gas discharged from the first reactor 150 reacts with oxygen inside the second reactor 160 may occur.

On the other hand, in the case of the selective oxidation reaction, since a large amount of oxygen is required, additional supply of air is required, and hydrogen is diluted by the additionally supplied air, which reduces the concentration of hydrogen supplied to the stack. Therefore, in order to overcome these disadvantages, a selective methanation reaction in which carbon monoxide and hydrogen react may be utilized.

Meanwhile, gas discharged from the fuel processor 10 via the reformer 140, the first reactor 150, and/or the second reactor 160 may be referred to as a reformed gas.

The stack 20 may generate electrical energy by causing an electrochemical reaction to the reformed gas supplied from the fuel processing device 10 .

The stack 20 may be configured by stacking single cells in which an electrochemical reaction occurs. A single cell may include a membrane electrode assembly (MEA) in which an anode and an air electrode are disposed around an electrolyte membrane, a separator, and the like. At the fuel electrode of the membrane-electrode assembly, hydrogen can be separated into hydrogen ions and electrons by a catalyst to generate electricity, and at the air electrode of the membrane-electrode assembly, hydrogen ions and electrons combine with oxygen to generate water.

The stack 20 may further include a stack heat exchanger (not shown) to dissipate heat generated during the electrochemical reaction. The stack heat exchanger may be a heat exchanger that uses water as a refrigerant. For example, the cooling water supplied to the stack heat exchanger may absorb heat generated in an electrochemical reaction process, and the cooling water whose temperature is raised by the absorbed heat exchanges the stack heat exchanger. It can be discharged to the outside of the group.

FIG. 2 is a configuration diagram of a fuel cell system including a fuel processing device according to an embodiment of the present invention, and FIG. 3 is a diagram showing a part of the configuration of the fuel cell system of FIG. 2 .

Referring to FIGS. 2 and 3 , 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 further include a power conversion unit (not shown) including a power conversion device that converts DC power generated by the power generation unit II into AC power.

The fuel processing unit (I) includes a fuel processing device 10, a fuel valve 30 for controlling the flow of fuel gas supplied to the fuel processing device 10, and a first blower for flowing air to the fuel processing device 10. (71) and the like.

The power generation unit (II) is discharged without reacting in the stacks 20a and 20b, the reformed gas heat exchanger 21 in which heat exchange of the reformed gas discharged from the fuel processing device 10 occurs, and the stacks 20a and 20b. AOG heat exchanger 22 where gas heat exchange occurs, a humidifier 23 which supplies moisture to the air supplied to the stacks 20a and 20b, and a second blower 72 which flows air into the stacks 20a and 20b etc. may be included. Here, the gas discharged from the stacks 20a and 20b without reacting 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 stacks 20a and 20b, but is not limited thereto.

The cooling water circulation unit (III) includes 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), and a fuel processing device (10). ), a water supply valve 39 for controlling the flow of water supplied to the water supply, a cooling water pump 43 for flowing water to the reformed gas heat exchanger 21, and the like.

The heat recovery unit (IV) may include a heat recovery tank 15 for storing water used for heat exchange, a heat recovery pump 48 for flowing water stored in the heat recovery tank 15 to the outside of the heat recovery tank 15, and the like. .

The fuel valve 30 may be disposed in the fuel supply passage 101 through which fuel gas supplied to the fuel processing device 10 flows. Corresponding to the degree of opening of the fuel valve 30, the flow rate of the fuel gas supplied to the fuel processing device 10 may be adjusted. For example, when the fuel valve 30 is closed, the fuel supply passage 101 is blocked, and the supply of fuel gas to the fuel processing device 10 may be stopped.

A first fuel flow meter 51 that detects a flow rate of fuel gas flowing in the fuel supply passage 101 may be disposed in the fuel supply passage 101 .

The first blower 71 may be connected to the first external air inlet passage 201 and the fuel side air supply passage 202 . The first blower 71 may flow air introduced from the outside through the first external air inlet passage 201 to the fuel processing device 10 through the fuel side air supply passage 202 .

Air introduced into the fuel processing device 10 through the fuel-side air supply passage 202 may be supplied to the burner 120 of the fuel processing device 10 . For example, air introduced into the fuel processor 10 may be mixed with fuel gas discharged from the desulfurizer 110 in the first mixer 111 and supplied to the burner 120 .

An air filter 91 that removes foreign substances such as dust contained in the air and/or a first air-side check valve 81 that restricts the flow direction of air may be disposed in the first external air inflow passage 201 . there is.

The fuel processing unit (I) may include a first internal gas flow path 102 through which the fuel gas discharged from the desulfurizer 110 flows to the reformer 140 . In the first internal gas passage 102, a proportional control valve 31, an internal fuel valve 32 for controlling the flow of fuel gas flowing into the reformer 140, and a control valve for fuel gas flowing in the internal gas passage 102 A second fuel flow meter 52 for detecting the flow rate, a fuel side check valve 83 for limiting the flow direction of the fuel gas flowing in the internal gas flow path 102, and/or a sulfur detection device 94 may be disposed. there is.

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

The sulfur detection device 94 may detect sulfur included in the fuel gas discharged from the desulfurizer 110 . The sulfur detection device 94 may include an indicator that changes color in response to sulfur compounds not removed by the adsorbent of the desulfurizer 110 . Here, the indicator may include phenolphthalein, a molybdenum compound, and the like.

The fuel processing unit (I) may include a second internal gas flow path 103 through which the fuel gas discharged from the desulfurizer 110 flows to the burner 120 . The burner 120 may use fuel gas introduced through the second internal gas passage 103 for combustion.

The first internal gas passage 102 and the second internal gas passage 103 may be connected to each other.

The fuel processing device 10 may be connected to the water supply passage 303 through which water discharged from the water supply tank 13 flows. In the water supply passage 303, a water pump 38, a water supply valve 39 for controlling the flow of water, and/or a water flow meter 54 for detecting the flow rate of water flowing in the water supply passage 303 are disposed. can

Exhaust gas generated by the burner 120 of the fuel processing device 10 may be discharged from the fuel processing device 10 through the exhaust gas discharge passage 210 .

The fuel processing device 10 may be connected to the reformed gas discharge passage 104 . The reformed gas discharged from the fuel processing device 10 may flow through the reformed gas discharge passage 104 .

The reformed gas discharge passage 104 may be connected to the reformed gas heat exchanger 21 in which heat exchange of reformed gas occurs. A reformed gas valve 33 and/or a gas mixer 95 may be disposed in the reformed gas discharge passage 104 to control the flow of the reformed gas flowing into the reformed gas heat exchanger 21 .

The gas mixer 95 provides reformed gas discharged from the fuel processing device 10 and flowing into the reformed gas discharge passage 104, and an anode off discharged from the stacks 20a and 20b and flowing into the AOG supply passage 109. Gas (AOG) can be mixed. The gas mixed and discharged in the gas mixer 95 may flow into the reformed gas heat exchanger 21 . Details of the configuration of the gas mixer 95 will be described later with reference to FIGS. 10 to 17 .

The reformed gas discharge passage 104 may be connected to the bypass passage 105 through which the reformed gas discharged from the fuel processor 10 flows to the fuel processor 10 . The bypass passage 105 may be connected to the fuel processing device 10 . The reformed gas introduced into the fuel processing device 10 through the bypass passage 105 may be used as fuel for combustion in the burner 120 . A bypass valve 34 may be disposed in the bypass passage 105 to control the flow of the reformed gas flowing into the fuel processing device 10 .

The reformed gas heat exchanger 21 may be connected to the reformed gas discharge passage 104 through which the reformed gas discharged from the fuel processing device 10 flows. The reformed gas heat exchanger 21 may be connected to the cooling water supply passage 304 through which water discharged from the water supply tank 13 flows. The reformed gas heat exchanger 21 may heat-exchange the reformed gas introduced through the reformed gas discharge passage 104 and the water supplied through the cooling water supply passage 304 . At this time, the reformed gas flowing into the reformed gas heat exchanger 21 may be a reformed gas mixed with an anode-off gas (AOG) in the gas mixer 95 .

In the cooling water supply passage 304, the cooling water pump 43 for flowing the water stored in the water supply tank 13 to the reformed gas heat exchanger 21 and/or detecting the flow rate of the water flowing in the cooling water supply passage 304 A cooling water flow meter 56 may be disposed.

The reformed gas heat exchanger 21 may be connected to the stack gas supply passage 106. The reformed gas discharged from the reformed gas heat exchanger 21 passes through the stack gas supply passage 106 to the stacks 20a and 20b. can be fluid

The reformed gas discharge passage 104 and the stack gas supply passage 106 through which the reformed gas discharged from the fuel processor 10 flows toward the stacks 20a and 20b may be referred to as reformed gas passages. In this case, the reformed gas discharge passage 104 may be referred to as a front end of the reformed gas passage, and the stack gas supply passage 106 may be referred to as a rear end of the reformed gas passage.

A reformed gas moisture removing device 61 may be disposed in the stack gas supply passage 106 to adjust the amount of moisture included in the reformed gas. The reformed gas introduced into the reformed gas moisture removal device 61 may be discharged from the reformed gas moisture removal device 61 after the moisture is removed.

Condensed water generated in the reformed gas moisture removal device 61 may be discharged from the reformed gas moisture removal device 61 and flow into the first water recovery passage 309 . A first water recovery valve 44 for controlling the flow of water may be disposed in the first water recovery passage 309 .

The stacks 20a and 20b may generate electrical energy by causing an electrochemical reaction to the reformed gas introduced through the stack gas supply passage 106 . In one embodiment, when the fuel cell system 1 includes a plurality of stacks 20a and 20b, the reformed gas discharged without reacting in the first stack 20a is additionally electrochemically discharged from the second stack 20b. can cause a reaction.

The second blower 72 may be connected to the second external air introduction passage 203 connected to the first external air introduction passage 201 and the stack-side air introduction passage 204 . The second external air introduction passage 203 may be connected to a rear end of the air filter 91 . The second blower 72 may flow air introduced through the second external air inlet passage 203 toward the stack 20 through the stack-side air inlet passage 204 .

A second air-side check valve 82 may be disposed in the second external air inlet passage 203 to restrict the flow direction of air.

An air flow meter 53 for detecting a flow rate of air flowing in the stack-side air inlet passage 204 may be disposed in the stack-side air inlet passage 204 .

The humidifier 23 can supply moisture to the air introduced through the stack-side air inlet passage 204 and discharge air containing moisture through the stack-side air supply passage 205 .

A stack-side air supply valve 36 may be disposed in the stack-side air supply passage 205 to control the flow of air supplied to the stack 20 .

The stack-side air supply passage 205 may be connected to individual supply passages 206 and 207 respectively corresponding to the stacks 20a and 20b. Air flowing through the stack-side air supply passage 205 may be supplied to the stacks 20a and 20b through the individual supply passages 206 and 207 .

The plurality of stacks 20a and 20b may be connected to each other by a gas connection passage 107 . The reformed gas discharged without reacting in the first stack 20a may flow into the second stack 20b through the gas connection passage 107 .

An additional water removal device 62 may be disposed in the gas connection passage 107 to remove water produced by condensation while the reformed gas passes through the first stack 20a.

Water generated in the additional water removal device 62 may be discharged from the additional water removal device 62 and flow into the second water recovery passage 310 . A second water recovery valve 45 for controlling the flow of water may be disposed in the second water recovery passage 310 . The second water recovery passage 310 may be connected to the first water recovery passage 309 .

The anode off-gas (AOG) discharged from the stacks 20a and 20b without reacting may flow through the AOG discharge passage 108 .

The AOG heat exchanger 22 may be connected to the AOG discharge passage 108 through which the anode off gas (AOG) discharged from the stacks 20a and 20b flows. The AOG heat exchanger 22 may be connected to the hot water supply passage 313 through which water discharged from the heat recovery tank 15 flows. The AOG heat exchanger 22 may heat exchange the anode off gas (AOG) introduced through the AOG discharge passage 108 and water supplied through the hot water supply passage 313 .

In the hot water supply passage 313, a hot water pump 48 for flowing the water stored in the heat recovery tank 15 to the AOG heat exchanger 22 and/or a hot water flow meter for detecting the flow rate of the water flowing in the hot water supply passage 313 (55) can be placed.

The AOG heat exchanger 22 may be connected to the AOG supply passage 109 and may discharge heat-exchanged anode off-gas (AOG) through the AOG supply passage 109 . The anode off-gas (AOG) discharged from the AOG heat exchanger 22 may flow to the fuel processing device 10 through the AOG supply passage 109 . The anode off-gas (AOG) supplied to the fuel processing device 10 through the AOG supply passage 109 may be used as fuel for combustion of the burner 120 .

The AOG discharge passage 108 and the AOG supply passage 109 through which the anode off-gas discharged from the stacks 20a and 20b flows toward the fuel processor 10 may be referred to as AOG passages. In this case, the AOG discharge passage 108 may be referred to as a front end of the AOG passage, and the AOG supply passage 109 may be referred to as a rear end of the AOG passage.

In the AOG supply passage 109, the flow of the anode off gas (AOG) supplied to the AOG water removal device 63 and / or the fuel processing device 10 for adjusting the amount of water contained in the anode off gas (AOG) An AOG valve 35 for adjusting the may be disposed. The anode off-gas (AOG) introduced into the AOG moisture removal device 63 may be discharged from the AOG moisture removal device 63 after the moisture is removed.

The AOG valve 35 may operate such that at least a portion of the anode off-gas (AOG) flowing in the AOG supply passage 109 is supplied to the fuel processing device 10 and the remaining portion is supplied to the gas mixer 95. there is. For example, when the AOG valve 35 is fully opened, all of the anode off-gas (AOG) flowing in the AOG supply passage 109 can be supplied to the fuel processing device 10, and the AOG valve 35 When completely closed, all of the anode off-gas (AOG) flowing through the AOG supply passage 109 may be supplied to the gas mixer 95 .

The AOG valve 35 may be configured as a 3-way valve. The first discharge end of the AOG valve 35 through which the anode off gas (AOG) is discharged is connected to the AOG supply passage 109, and the second discharge end of the AOG valve 35 is connected to the AOG bypass passage 214. can The AOG bypass passage 214 may be connected to the gas mixer 95, and the anode off gas (AOG) discharged from the AOG valve 35 may be introduced into the gas mixer 95 through the AOG bypass passage 214. can

The condensed water generated in the AOG water removal device 63 may be discharged from the AOG water removal device 63 and flow through the third water recovery passage 311 . A third water recovery valve 46 for controlling the flow of water may be disposed in the third water recovery passage 311 . The third water recovery passage 311 may be connected to the first water recovery passage 309 .

The stack-side air discharge passage 211 may be connected to individual discharge passages 208 and 209 respectively corresponding to the stacks 20a and 20b. Air discharged from the stacks 20a and 20b may flow to the stack-side air discharge passage 211 through the individual discharge passages 208 and 209 . At this time, air flowing through the stack-side air discharge passage 211 may include moisture generated by an electrochemical reaction occurring in the stacks 20a and 20b.

The stack-side air discharge passage 211 may be connected to the humidifier 23 . The humidifier 23 may supply moisture to air flowing into the stack 20 by using moisture included in air supplied through the stack-side air discharge passage 211 . Air supplied to the humidifier 23 through the stack-side air discharge passage 211 may pass through the humidifier 23 and be discharged to the humidifier discharge passage 212 .

A stack-side air discharge valve 37 may be disposed in the stack-side air discharge passage 211 to control the flow of air discharged from the stacks 20a and 20b and introduced into the humidifier 23 .

The water supply tank 13 may be connected to the water inflow passage 301 and may store water supplied through the water inflow passage 301 . In the water inlet passage 301, a first liquid filter 92 for removing foreign substances contained in water supplied from the outside and/or a water inlet valve 41 for controlling the flow of water flowing into the water supply tank 13 can be placed.

The water supply tank 13 may be connected to the water discharge passage 302 and may discharge at least a part of the water stored in the water supply tank 13 to the outside through the water discharge passage 302 . A water discharge valve 42 may be disposed in the water discharge passage 302 to control the flow of water discharged from the water supply tank 13 .

The water supply tank 13 may be connected to the water storage passage 308 and may store water flowing through the water storage passage 308 . For example, it is 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 to form the third water recovery passage 311. Water flowing through may be introduced into the water supply tank 13 via the water storage passage 308 . A second liquid filter 93 may be disposed in the water storage passage 308 to remove foreign substances included in the water returned to the water supply tank 13 .

At least some of the water stored in the water supply tank 13 may flow to the reformed gas heat exchanger 21 by the cooling water pump 43 and may exchange heat with the reformed gas in the reformed gas heat exchanger 21 . Water discharged from the reformed gas heat exchanger 21 may flow into the stacks 20a and 20b through the stack water supply passage 305 .

Water introduced into the stacks 20a and 20b through the stack water supply passage 305 may cool the stacks 20a and 20b. Water introduced into the stacks 20a and 20b may flow along a stack heat exchanger (not shown) included in the stacks 20a and 20b, and the water generated by the electrochemical reaction occurring in the stacks 20a and 20b can absorb heat.

The plurality of stacks 20a and 20b may be connected by a water connection passage 306 . Water discharged from the first stack 20a may flow into the second stack 20b through the water connection passage 306 .

Water discharged from the stacks 20a and 20b may flow into the cooling water heat exchanger 24 through the stack water discharge passage 307 . The cooling water heat exchanger 24 may perform heat exchange between the water discharged from the stacks 20a and 20b and the water discharged from the heat recovery tank 15 . Water discharged from the stacks 20a and 20b may flow to the water storage passage 308 via the cooling water heat exchanger 24 .

Water discharged from the heat recovery tank 15 by the hot water pump 48 may flow into the AOG heat exchanger 22 via the hot water supply passage 313 . The water heat-exchanged with the anode off-gas (AOG) in the AOG heat exchanger 22 may be discharged to the first hot water circulation circuit 314 .

The air heat exchanger 25 may be connected to the humidifier discharge passage 212 through which air discharged from the humidifier 23 flows. The air heat exchanger 25 may be connected to the first hot water circulation circuit 314 through which water discharged from the AOG heat exchanger 22 flows. The air heat exchanger 25 may heat exchange air introduced through the humidifier discharge passage 212 and water introduced through the first hot water circulation circuit 314 .

Air heat-exchanged in the air heat exchanger 25 may be discharged from the air heat exchanger 25 through the air discharge passage 213 . The air discharge passage 213 may be connected to the exhaust gas discharge passage 210 , and exhaust gas flowing in the exhaust gas discharge passage 210 and air flowing in the air discharge passage 213 may be mixed.

An air moisture removing device 64 may be disposed in the air discharge passage 213 . The air moisture removing device 64 may adjust the amount of moisture contained in the air discharged to the outside. The air introduced into the air moisture removal device 64 may be discharged from the air moisture removal device 64 after the moisture is removed.

Condensed water generated in the air moisture removal device 64 may be discharged from the air moisture removal device 64 and flow through the fourth water recovery passage 312 . A fourth water recovery valve 47 for controlling the flow of water may be disposed in the fourth water recovery passage 312 . The fourth water recovery passage 312 may be connected to the water storage passage 308 .

Water heat-exchanged in the air heat exchanger 25 may be discharged from the air heat exchanger 25 through the second hot water circulation passage 315 . Water discharged from the air heat exchanger 25 may flow into the cooling water heat exchanger 24 through the second hot water circulation passage 315 .

The cooling water heat exchanger 24 may heat exchange water introduced through the stack water discharge passage 307 and water introduced through the second hot water circulation passage 315 .

The exhaust heat exchanger 26 may be connected to the exhaust gas discharge passage 210 through which exhaust gas flows. The exhaust heat exchanger 26 may be connected to the third hot water circulation passage 316 through which the water discharged from the cooling water heat exchanger 24 flows. The exhaust heat exchanger 26 may heat-exchange the exhaust gas introduced through the exhaust gas outlet passage 210 and the water introduced through the third hot water circulation passage 316 .

Exhaust gas heat-exchanged in the exhaust heat exchanger 26 may be discharged to the exhaust passage 213, and exhaust gas flowing in the exhaust passage 213 may be discharged to the outside.

Water heat-exchanged in the exhaust heat exchanger 26 may be discharged to the hot water recovery passage 317 , and water flowing in the hot water recovery passage 317 may flow into the heat recovery tank 15 .

The fuel cell system 1 may further include a thermometer for detecting temperature and/or a pressure gauge for detecting pressure. For example, the fuel cell system 1 includes a thermometer for detecting the temperature of the burner 120, a thermometer for detecting the temperature of water flowing in the hot water recovery passage 317, and discharged from the stacks 20a and 20b to discharge AOG. A thermometer for sensing the temperature of the anode off gas (AOG) flowing in the flow path 108 may be included. For example, the fuel cell system 1 includes a pressure gauge for detecting the pressure of the reformed gas flowing into the stacks 20a and 20b, and a pressure gauge for detecting the pressure of the anode-off gas (AOG) discharged to the stacks 20a and 20b. A pressure gauge may be included.

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

The controller may control overall operations of the fuel cell system 1 . The control unit may be connected to each component provided in the fuel cell system 1 and may transmit and/or receive signals between each component. The controller may process signals received from each component included in the fuel cell system 1 and transmit a control signal according to a result of processing the signal to each component included in the fuel cell system 1. . For example, the control unit may adjust the opening degree of each valve provided in the fuel cell system 1 .

4 and 5 are flowcharts illustrating an operating method of a fuel cell system according to an embodiment of the present invention.

Referring to FIG. 4 , the fuel cell system 1 may perform an operation of preheating the burner 120 of the fuel processor 10 in operation S410 . For example, the fuel cell system 1 may generate combustion heat by supplying a mixture of fuel gas and air to the burner 120 when power generation is started. At this time, the internal temperature of the reformer 140 may gradually increase to an appropriate temperature (eg, 800° C.) at which the reforming reaction is promoted.

Also, the fuel cell system 1 may cut off the supply of fuel gas to the reformer 140 while preheating the burner 120 . For example, in the fuel cell system 1, the proportional control valve 31 is adjusted so that all of the fuel gas discharged from the desulfurizer 110 is supplied to the burner 120, so that the amount of fuel gas for the reformer 140 is reduced. supply can be cut off.

Meanwhile, referring to FIG. 6 , the fuel cell system 1 turns off the reformed gas valve 33, the bypass valve 34, and the AOG valve 35 while preheating the burner 120. can be closed At this time, since the supply of fuel gas to the reformer 140 is cut off, reformed gas is not generated in the reformer 140 . In the reformed gas discharge passage 104, the bypass passage 105, and the AOG supply passage 109, neither the reformed gas nor the anode-off gas flows.

In operation S420, the fuel cell system 1 may perform an operation of initially generating reformed gas. For example, when the internal temperature of the reformer 140 increases to an appropriate temperature (eg, 800° C.) due to the preheating of the butter 120, the fuel cell system 1 starts an operation to initially generate reformed gas. can For example, when the internal temperature of the first reactor 150 is equal to or higher than the minimum temperature for removing carbon monoxide (eg, 160° C.), the fuel cell system 1 may start an operation of initially generating reformed gas. .

When the fuel cell system 1 performs an operation of initially generating reformed gas, a part of the fuel gas discharged from the desulfurizer 110 is supplied to the reformer 140 and the remaining part is supplied to the burner 120. It is possible to adjust the proportional control valve 31 so that it is supplied.

Meanwhile, the fuel cell system 1 drives the water pump 38 so that steam used in the reforming reaction is supplied to the reformer 140 when an operation for initially generating reformed gas is started, so that the fuel processing device 10 ) It is possible to supply water to the steam generator 130. At this time, in the fuel cell system 1, when the pressure of steam supplied to the reformer 140 is maintained above the minimum pressure for the reforming reaction, for example, when a predetermined time elapses after the water pump 38 is driven, Some of the fuel gas discharged from the desulfurizer 110 may be supplied to the reformer 140 .

Meanwhile, while the operation for initially generating the reformed gas is performed, the ratio of the hydrogen gas among the reformed gases discharged from the fuel processor 10 may be lower than the preset minimum ratio. Here, the preset minimum ratio may mean a minimum value (eg, 80%) of a ratio occupied by hydrogen gas among reformed gases capable of achieving a target amount of power generation. At this time, when the reformed gas having a ratio of hydrogen gas lower than the preset minimum ratio is supplied to the stack 20, it is difficult to generate electricity as much as the target power generation amount in the stack 20, so that the fuel discharged from the fuel processor 10 The reformed gas may be reused as fuel for the burner 120 .

Referring to FIG. 7 , the fuel cell system 1 closes the reformed gas valve 33 and the AOG valve 35 and opens the bypass valve 34 while performing an operation for initially generating reformed gas. can do. At this time, the reformed gas discharged from the fuel processing device 10 may be introduced into the fuel processing device 10 again through the reformed gas discharge flow path 104 and the bypass flow path 105, and the burner 20 may burn. can be used as a fuel for

The fuel cell system 1 may perform a generation operation of generating electricity in the stack 20 in operation S430. For example, the fuel cell system 1 may start power generation operation when the ratio of hydrogen gas in the reformed gas is equal to or greater than a preset minimum ratio. For example, the fuel cell system 1 may start power generation operation when a predetermined time has elapsed from when fuel gas is supplied to the reformer 140 .

Referring to FIG. 8 , the fuel cell system 1 opens the reformed gas valve 33 so that the reformed gas discharged from the fuel processor 10 is supplied to the stack 20 when performing power generation operation. , the bypass valve 34 can be closed. The fuel cell system 1 may supply air used in an electrochemical reaction for generating electricity to the stack 20 by driving the second blower 72 .

Meanwhile, when the power generation operation is performed, the anode-off gas may be discharged from the stack 20 . At this time, the fuel cell system 1 may completely open the AOG valve 35 so that the anode off-gas discharged from the stack 20 flows into the fuel processing device 10 . The anode off-gas flowing into the fuel processing device 10 may be used as fuel for combustion of the burner 20 .

In operation S440 , the fuel cell system 1 may perform a highly efficient power generation operation that reduces the amount of fuel used for power generation while satisfying the target power generation amount. For example, the fuel cell system 1 can perform high-efficiency power generation operation when the amount of electricity generated in the stack 20 maintains a certain amount of power for a certain amount of time. Here, the predetermined amount of power generation may be greater than or equal to the amount of power generation targeted by the fuel cell system 1 . In this regard, it will be described with reference to FIG. 5 . For convenience of description of the present invention, the generation operation in operation S430 may be referred to as a general generation operation, and the high-efficiency generation operation performed in operation S440 may be referred to as a high-efficiency generation operation.

Referring to FIG. 5 , the fuel cell system 1 may adjust the opening degree of the AOG valve 35 according to a preset opening amount when the high-efficiency power generation operation is started in operation S510 .

When the fuel cell system 1 starts the high-efficiency power generation operation, the opening degree of the AOG valve 35 is closed by a predetermined percentage (eg, 20%) of the total opening amount in the state in which the AOG valve 35 is fully open. can be adjusted. At this time, according to the opening degree of the AOG valve 35, a portion (eg, 80%) of the anode off-gas discharged from the stack 20 and flowing into the AOG discharge passage 108 may flow into the fuel processing device 10. and the remaining part (eg, 20%) may flow into the gas mixer 95 through the AOG bypass flow path 214.

On the other hand, the sum of the flow rate of the anode off-gas flowing into the fuel processing device 10 and the flow rate of the anode off-gas flowing through the AOG bypass passage 214 is the AOG valve 35 through the AOG discharge passage 108 It may correspond to the flow rate of the anode off-gas flowing into.

Referring to FIG. 9 , a state in which the reformed gas valve 33 is open and the bypass valve 34 is closed may be maintained while the high-efficiency power generation operation is performed. At this time, the reformed gas discharged from the fuel processing device 10 may flow into the gas mixer 95 through the reformed gas discharge passage 104 .

Moisture may be removed from the anode off-gas discharged from the stack 20 through the AOG moisture removal device 63, and the anode off-gas from which the moisture has been removed may flow into the AOG valve 35. Here, according to the opening degree of the AOG valve 35, some of the anode off-gas from which water is removed in the AOG water removal device 63 may flow into the fuel processing device 10, and the remaining part may flow into the AOG bypass flow path ( 214) may flow into the gas mixer 95. At this time, as the opening amount of the AOG valve 35 increases, the flow rate of the anode off-gas flowing into the fuel processing device 10 increases, and as the opening amount of the AOG valve 35 decreases, the anode off-gas flowing into the gas mixer 95 flow rate may increase.

In the gas mixer 95, the reforming gas and the anode-off gas may be mixed with each other. At this time, since the anode off-gas from which moisture has been removed and the reformed gas are mixed and discharged in the gas mixer 95, as a result, the amount of moisture included in the reformed gas supplied to the stack 20 in high-efficiency power generation operation is reduced in normal power generation operation. The amount of moisture included in the reformed gas supplied to the stack 20 may be less.

In addition, since the anode off-gas discharged from the stack 20 is mixed with the reformed gas discharged from the fuel processor 10 and reused for the electrochemical reaction of the stack 20, the reformed gas discharged from the fuel processor 10 Even if the amount of the anode off gas is reduced corresponding to the amount of reused anode off-gas, hydrogen gas above a certain level may be continuously supplied to the stack 20 . Therefore, the fuel cell system 1 reduces the amount of fuel gas supplied to the fuel processor 10 to generate reformed gas while performing the high-efficiency power generation operation compared to the general power generation operation, while the fuel cell system ( 1) can meet the target generation amount.

In operation S520 and operation S530 , the fuel cell system 1 may calculate the amount of electricity generated by the stack 20 and determine whether or not the amount of power generated by the stack 20 decreases. For example, the fuel cell system 1 may calculate the amount of power generation of the stack 20 when a predetermined time elapses from the time point when the high-efficiency power generation operation starts, and the calculated amount of power generation of the stack 20 and the high-efficiency power generation operation It is possible to determine whether or not the amount of power generation of the stack 20 decreases while a predetermined time elapses by comparing the predetermined amount of power generation, which is the amount of power generation of the stack 20 corresponding to the starting time point.

In operation S540 , when the amount of power generation of the stack 20 does not decrease, the fuel cell system 1 may determine whether the current opening amount of the AOG valve 35 is greater than a preset minimum value. At this time, the preset minimum value may be greater than 50% of the total opening degree of the AOG valve 35. That is, in the fuel cell system 1, while performing high-efficiency power generation operation, the flow rate of the anode off-gas flowing into the fuel processor 10 is higher than the flow rate of the anode-off gas flowing through the AOG bypass passage 214. The opening degree of the AOG valve 35 can be adjusted as much as possible.

In the fuel cell system 1, in operation S550, when the current opening degree of the AOG valve 35 is greater than a preset minimum value, the flow rate of the anode off-gas flowing into the burner 120 decreases, and the gas mixer 95 The opening of the AOG valve 35 may be adjusted to increase the flow rate of the introduced anode-off gas. For example, when the current opening amount of the AOG valve 35 is greater than a preset minimum value, the fuel cell system 1 closes the AOG valve 35 by a first ratio (eg, 5%) of the total opening amount. , the opening degree of the AOG valve 35 can be adjusted.

At this time, when the opening amount of the AOG valve 35 is less than the preset minimum value as the AOG valve 35 is closed by a first ratio (eg, 5%) of the total opening amount, the fuel cell system 1 operates the AOG The opening amount of the valve 35 may be reduced to a predetermined minimum value.

Meanwhile, the fuel cell system 1 may maintain the current opening amount of the AOG valve 35 when the current opening amount of the AOG valve 35 is equal to or less than a preset minimum value.

In the fuel cell system 1, in operation S560, when the amount of power generation of the stack 20 decreases, the flow rate of the anode off-gas flowing into the burner 120 increases, and the flow rate of the anode-off gas flowing into the gas mixer 95 increases. The opening of the AOG valve 35 may be adjusted so that the flow rate decreases. For example, in the fuel cell system 1, when the amount of power generation of the stack 20 decreases, the AOG valve 35 is opened by a second ratio (eg, 3%) of the total opening amount. opening can be adjusted. At this time, the first ratio corresponding to the closing of the AOG valve 35 may be set to a larger value than the second ratio corresponding to the opening of the AOG valve 35 .

The fuel cell system 1 may determine whether the operation of the fuel cell system 1 is terminated in operation S570.

When the operation of the fuel cell system 1 is not finished, the fuel cell system 1 calculates the amount of power generation of the stack 20 and adjusts the opening of the AOG valve 35 according to the calculated amount of power generation. can be done by That is, the fuel cell system 1 calculates the amount of power generation of the stack 20 according to a predetermined period until the operation is completed, and based on the change in the amount of power generation calculated according to the predetermined period, the AOG valve 35 You can adjust the opening. Through this, while the high-efficiency power generation operation is performed, the amount of fuel used for power generation may be reduced while the target power generation amount of the fuel cell system 1 is satisfied.

Hereinafter, a configuration of a gas mixer according to an embodiment of the present invention will be described with reference to FIGS. 10 to 17 .

10 and 13, the gas mixer 95 includes a housing 460 forming a main flow path 480 through which the reformed gas flows, and a gas disposed inside the housing 460 through which the anode-off gas flows. A supply unit 620 may be included.

The housing 460 may include a first inner wall 520 forming the main flow path 480 and a first outer wall 500 spaced apart from the first inner wall 520 in a radially outward direction.

A gas supply unit 620 may be disposed between the first inner wall 520 and the first outer wall 500 . A space in which the gas supply unit 620 is disposed may be formed between the first inner wall 520 and the first outer wall 500 .

The main flow path 480 may be formed in the form of a venturi tube in which a cross-sectional area decreases and expands in a direction in which the reformed gas flows.

The first inner wall 520 is disposed downstream of the flow path reducing portion 540 in which the cross-sectional area of the main flow path 480 decreases, and the flow path in which the cross-sectional area of the main flow path 480 is maintained. The holding part 560 and the passage extending part 600 disposed downstream of the passage holding part 560 and extending the cross-sectional area of the main passage 480 may be formed.

The flow path reducing unit 540 may be connected to the reformed gas discharge channel 104 , and reformed gas flowing into the reformed gas discharge channel 104 may be introduced. The flow path reducing portion 540 may be formed to decrease the cross-sectional area of the flow path in the flow direction of the reformed gas. At this time, the pressure of the reformed gas flowing in the flow path reducing unit 540 may be reduced.

The flow path reducing portion 540 includes a first flow path reducing portion 540a connected to the reformed gas discharge flow path 104, extending from a downstream end of the first flow path reducing portion 540a, and a flow path holding unit 560 and A second flow path reducing portion 540b connected thereto may be included.

A plurality of inlet holes 580 through which the anode off-gas flows into the main flow path 480 may be formed in the flow path holding part 560 . In the inner housing 640 , a plurality of discharge holes 720 through which the anode-off gas is discharged from the sub-passage 70 to the outside may be formed. The plurality of inlet holes 580 and the plurality of discharge holes 720 may correspond to each other.

In one embodiment, when the sub-passage 700 is formed in a spiral shape, the plurality of discharge holes 720 may be formed along the sub-passage 700 at regular intervals in a spiral direction. In this case, the plurality of inlet holes 580 may be formed to be spaced apart from each other at regular intervals in a spiral direction on the first inner wall 520 . In addition, positions where the plurality of inlet holes 580 are formed in the first inner wall 520 may correspond to positions of the plurality of discharge holes 720 formed in the inner housing 640 .

In one embodiment, the plurality of inlet holes 580 may be formed at intervals of 120 degrees along the circumferential direction of the first inner wall 520 . Since the plurality of inlet holes 580 are formed corresponding to the position of the spiral sub-passage 700, a plurality of inlet holes 580 may be spaced apart from each other along the flow direction of the reformed gas in the same phase.

In the flow path maintaining unit 560 , the reformed gas flowing from the flow path reducing unit 540 and the anode off gas flowing through the plurality of inlet holes 580 may be mixed. When the plurality of inlet holes 580 are formed along the spiral direction, the anode-off gas introduced through the plurality of inlet holes 580 forms a rotary flow in the reformed gas, so that the reformed gas and the anode-off gas are easily mixed. It can be. Hereinafter, the gas in which the reformed gas and the anode-off gas are mixed may be referred to as a mixed gas.

Mixed gas may flow in the passage expansion part 600 . The passage expansion part 600 may be formed to increase the cross-sectional area of the passage along the flow direction of the mixed gas. At this time, since the cross-sectional area of the passage of the passage extension 600 increases along the flow direction of the mixed gas, the pressure of the mixture gas flowing through the passage extension 600 may increase along the flow direction.

The gas supply unit 620 includes an inner housing 640 in which a sub-passage 700 through which an anode-off gas flows is formed, and a first outer wall 500 of the housing 460 at one side of the inner housing 640. It may include a connection pipe 740 that extends long toward. The connection pipe 740 may extend from the first outer wall 500 to the outside of the housing 460 .

The connection pipe 740 may be connected to the AOG bypass flow path 214 . The anode off-gas flowing in the AOG bypass flow path 214 may flow into the gas flow path 760 formed in the connection pipe 740 and may flow into the main flow path 480 via the sub flow path 700. .

The inner housing 640 may be disposed on an outer circumference of the flow path holding part 560 inside the housing 460 . The inner housing 640 may be spaced apart from the inlet end 570 of the flow path holding part 560 by a predetermined interval. Through this, it is possible to prevent the anode-off gas flowing in the inner housing 640 from flowing backward due to the pressure formed by the reformed gas flowing into the flow path holding unit 560, thereby preventing the anode-off gas flowing into the gas supply unit 620 from flowing backward. Gas can be stably supplied to the main flow path 480 . In addition, when the inner housing 640 is spaced apart from the inlet end 570 of the flow path holding part 560 by a predetermined interval, the increase in pressure caused by the inflow of the anode-off gas is alleviated, and the anode-off gas can be easily introduced into the main flow path 480.

The distance L1 at which the inner housing 640 is separated from the inlet end 570 of the flow path holding part 560 is the diameter 560D of the cross-sectional area of the inflow end 570 of the flow path holding part 560 (FIG. 14). It may be formed in a length of 0.2 to 0.3 times.

Referring to FIG. 14 , in the flow path reducing unit 540, the rate at which the cross-sectional area is reduced along the flow direction of the reformed gas in the first flow path reducing unit 540a is reduced in the second flow path reducing unit 540b. It can be formed to be smaller than the ratio. The flow path reducing unit 540 is configured such that the rate at which the pressure of the reformed gas flowing through the first flow path reducing unit 540a decreases is smaller than the rate at which the pressure of the reformed gas flowing through the second flow path reducing unit 540b decreases. can be formed In this case, the pressure of the reformed gas flowing through the second flow path reducing portion 540b may decrease faster than that of the reformed gas flowing through the first flow path reducing portion 540a.

The diameter 560D of the cross-sectional area of the inlet end 570 of the flow path holding part 560 is 0.5 to 0.6 times the diameter 540D of the cross-sectional area of the inlet end 550 of the flow path reducing part 540. It can be. The pressure of the reformed gas flowing through the passage holding unit 560 may be lower than the pressure of the anode off gas flowing through the AOG bypass passage 214 through the AOG valve 35 .

The diameter 600D of the cross-sectional area of the discharge end 610 of the passage expansion part 600 is 0.8 to 0.9 times the diameter 540D of the cross-sectional area of the inlet end 550 of the passage reduction part 540. It can be.

Only the reformed gas is introduced into the flow path reducing unit 540, but the reformed gas and the anode off gas are mixed and flowed in the flow path extending unit 600, so the amount of fluid flowing through the flow path extending unit 600 is reduced by the flow path reducing unit 540. ) may be greater than the amount of flowing fluid. At this time, when the diameter 600D of the cross-sectional area of the discharge end 610 of the passage expansion part 600 and the diameter 540D of the cross-sectional area of the inflow end 550 of the passage reduction part 540 are formed to be the same, the passage expansion The pressure at the discharge end 610 of the portion 600 may be greater than the pressure at the inlet end 550 of the flow path reducing portion 540 . Therefore, the pressure at the discharge end 610 of the flow path expansion unit 600 is similar to the pressure at the inlet end 550 of the flow path reduction unit 540. The diameter 600D of the cross-sectional area may be smaller than the diameter 540D of the cross-sectional area of the inlet end 550 of the flow path reducing portion 540 .

The flow path holding part 560 may be formed long in the flow direction of the reformed gas. The length 560L of the passage holding part 560 formed in the flow direction of the reformed gas may be longer than the diameter 560D of the passage section of the passage holding part 560 . The flow path holding part 560 has a length (560L) formed in the flow direction of the reformed gas that is longer than the length (600L) of the flow path extension part 600 formed in the flow direction of the reformed gas, and the flow path reducing part 540 may be formed to be shorter than the length 540L formed in the flow direction of the reformed gas.

The length 600D of the cross-sectional area of the discharge end 610 of the flow path expansion unit 600 may be 0.9 to 1 times the length 540D of the cross-sectional area of the inlet end 540 of the flow path reduction unit 540. .

The flow path extension part 600 includes a first flow path extension part 600a extending from the flow path holding part 560 and a second flow path extension part 600b extending from the downstream end of the first flow path extension part 600a. can include In the flow path extension part 600, the ratio of the expansion of the cross-sectional area along the flow direction of the mixed gas in the first flow path extension part 600a is the expansion of the cross-sectional area along the flow direction of the mixed gas in the second flow path extension part 600b. It can be formed to be larger than the ratio. The flow path extension part 600 is configured so that the pressure increase rate of the mixed gas flowing through the first flow path extension part 600a is greater than the pressure increase rate of the mixed gas flowing through the second flow path extension part 600b. can be formed The pressure of the mixed gas flowing through the first flow passage extension 600a may increase faster than that of the mixed gas flowing through the second flow passage extension 600b.

15 to 17 , the inner housing 640 may have a cylindrical shape. The inner housing 640 may include a sub-passage 700 spirally formed therein. The inner housing 640 has a second outer wall 660 having a cylindrical shape, spaced apart from the second outer wall 660 in the radial direction, and disposed in contact with the first inner wall 520 of the housing 460. A second inner wall 680 may be included.

A spiral sub-passage 700 may be formed between the second inner wall 680 and the second outer wall 660 . The second inner wall 680 may be disposed in contact with an outer circumference of the first inner wall 520 of the housing 460 . A plurality of discharge holes 720 may be formed in the second inner wall 680 . The plurality of discharge holes 720 may be spaced apart at regular intervals along the sub-passage 700 formed inside the inner housing 640 . The plurality of discharge holes 720 may be disposed at positions corresponding to the plurality of inlet holes 580 .

In one embodiment, the plurality of discharge holes 720 may be formed to be spaced apart from each other with a phase difference of 120 degrees along the sub-passage 700 . In various embodiments of the present invention, the plurality of discharge holes 720 may be disposed at different positions while having a phase difference in the range of 90 degrees to 130 degrees.

The anode off-gas flowing along the sub-passage 700 may be supplied to the main passage 480 formed inside the housing 460 through the discharge hole 720 and the inlet hole 580 . Since the pressure of the anode-off gas flowing through the sub-passage 700 is greater than the pressure of the reformed gas flowing through the flow-through holding part 560, the anode-off gas flowing through the sub-passage 700 is formed inside the housing 460. It can flow to the main flow path 480.

A connection pipe 740 may be formed on one side of the second outer wall 660 . A gas flow path 760 through which an anode-off gas flows may be formed inside the connection pipe 740 . The gas passage 760 formed inside the connection pipe 740 may be connected to the sub passage 700 formed inside the inner housing 640 .

As described above, according to various embodiments of the present invention, the anode off-gas discharged from the stack 20 is configured to be properly supplied back to the stack 20, so that the amount of fuel used can be reduced while meeting the target power generation amount.

In addition, according to various embodiments of the present invention, the anode off-gas from which moisture is removed after being discharged from the stack 20 is mixed with the reformed gas discharged from the fuel processor 10, thereby reforming the fuel supplied to the stack 20. It is possible to reduce the moisture ratio of the gas, so that the power generation efficiency of the stack 20 can be improved.

In addition, according to various embodiments of the present invention, as the anode off-gas discharged from the stack 20 is discharged to the region where the reformed gas flows through the spiral-shaped passage, a rotational flow can be formed in the region, The reformed gas discharged from the fuel processor 10 and the anode-off gas discharged from the stack 20 may be appropriately mixed in the gas mixer 95 .

The accompanying drawings are only for easy understanding of the embodiments disclosed in this specification, and the technical idea disclosed in this specification is not limited by the accompanying drawings, and all changes and equivalents included in the spirit and technical scope of the present invention It should be understood to include water or substitutes.

Similarly, while operations are depicted in the drawings in a particular order, it should not be understood that all illustrated operations must be performed, or that those operations must be performed in the specific order shown or in sequential order to obtain desired results. can In certain cases, multitasking and parallel processing can be advantageous.

In addition, although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific embodiments described above, and the technical field to which the present invention belongs without departing from the gist of the present invention claimed in the claims. Of course, various modifications are possible by those skilled in the art, and these modifications should not be individually understood from the technical spirit or perspective of the present invention.

10: fuel processing device 20: stack
21: reformed gas heat exchanger 22: AOG heat exchanger
33: reformed gas valve 34: bypass valve
35: AOG valve 61: reformed gas moisture removal device
63: AOG moisture removal device 95: gas mixer
104: reformed gas outlet flow path 105: bypass flow path
106: stack gas supply passage 108: AOG discharge passage
109: AOG supply passage 214: AOG bypass passage

Claims (15)

a fuel processing device that reforms fuel gas to generate reformed gas;
a stack generating electricity using the reformed gas;
a first passage through which the reformed gas discharged from the fuel processing device flows;
a second passage through which anode off gas (AOG) discharged from the stack flows;
a third flow path connected to the first flow path and the second flow path; and
and a valve operable to allow at least a portion of the anode off-gas flowing in the second flow path to flow to the fuel processing device and a remaining portion to flow to the third flow path. According to claim 1,
the control unit,
Calculate the amount of electricity generated from the stack,
The fuel cell system, characterized in that the opening degree of the valve is adjusted according to the calculated power generation amount. According to claim 2,
The control unit,
Adjusting the opening of the valve so that the flow of the anode off-gas to the third flow path is blocked when the amount of power generation is less than the preset minimum amount of power generation;
When the amount of power generation is greater than or equal to the minimum amount of power generation, the opening degree of the valve is adjusted such that a portion of the anode off-gas flows into the fuel processing device and the remaining portion flows into the third flow path. According to claim 3,
The control unit,
Adjusting the opening degree of the valve so that the flow rate of the anode off-gas flowing into the fuel processor is greater than the flow rate of the anode off-gas flowing in the third flow path when the power generation amount is greater than or equal to the minimum power generation amount A fuel cell system, characterized in that. According to claim 4,
A sum of the flow rate of the anode off-gas flowing into the fuel processor and the flow rate of the anode-off gas flowing in the third flow path corresponds to the flow rate of the anode off-gas flowing in the second flow path. A fuel cell system with According to claim 3,
The control unit,
When the amount of power generation is greater than or equal to the minimum amount of power generation, calculating the amount of power generation according to a predetermined cycle;
The fuel cell system characterized in that the opening degree of the valve is adjusted based on the change in the amount of power generation calculated according to the predetermined period. According to claim 6,
The control unit,
When the amount of power generation decreases during the predetermined period, the opening degree of the valve is adjusted so that the flow rate of the anode off-gas flowing in the third flow path decreases,
The fuel cell system of claim 1 , wherein an opening degree of the valve is adjusted so that a flow rate of the anode-off gas flowing in the third flow path increases when the amount of power generation increases or is maintained during the predetermined period. According to claim 1,
and a gas mixer disposed in the first flow path to mix the reformed gas and the anode-off gas flowing in the third flow path. According to claim 8,
The gas mixer,
A fuel cell system comprising a main flow path in the form of a venturi tube whose sectional area decreases and expands in a direction in which the reformed gas flows. According to claim 9,
The gas mixer,
a flow path reducing unit through which the reformed gas is introduced and a cross-sectional area of the main flow path is reduced;
a flow path holding unit connected to the flow path reducing unit and maintaining a cross-sectional area of the main flow path; and
A flow path extension connected to the flow path holding unit and increasing the cross-sectional area of the main flow path;
The fuel cell system according to claim 1 , wherein the anode off-gas flows into the flow path holding part. According to claim 10,
The fuel cell system according to claim 1 , wherein a length of the flow path maintaining part is longer than a length of the flow path expanding part and shorter than a length of the flow path reducing part. According to claim 10,
The gas mixer,
a housing including a first inner wall forming the main flow path and a first outer wall formed outside the first inner wall; and
A gas supply unit disposed between the first inner wall and the first outer wall through which the anode-off gas flows;
The fuel cell system of claim 1 , wherein the anode off-gas flowing into the gas mixer flows into the main flow path via the gas supply unit. According to claim 12,
The gas supply unit,
a second inner wall disposed to contact the first inner wall;
a second outer wall formed outside the second inner wall; and
and a sub-passage disposed between the second inner wall and the second outer wall and through which the anode-off gas flows. According to claim 13,
The second inner wall includes a plurality of discharge holes formed spaced apart in a spiral direction,
The fuel cell system according to claim 1 , wherein the passage holding part includes a plurality of inlet holes formed to be spaced apart in a spiral direction, corresponding to the plurality of discharge holes, respectively. According to claim 8,
a first moisture removal device disposed between the gas mixer and the stack to remove moisture contained in the reformed gas; and
and at least one of second moisture removal devices disposed between the stack and the valve to remove moisture contained in the anode off-gas.

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