Fuel cell tail gas recovery system, fuel cell system and control method

Abstract

The invention discloses a fuel cell tail gas recovery system, a fuel cell system and a control method. The fuel cell tail gas recovery system comprises a shunting piece, a water evaporator, an exhaust pipeline and an adjusting assembly. Wherein the flow dividing piece is used for receiving tail gas and dividing the tail gas into at least a first branch flow and a second branch flow; the water evaporator comprises a first heat exchange side and a second heat exchange side, and the first branch communicates with an inlet of the first heat exchange side; one end of the exhaust pipeline is connected to an outlet of the first heat exchange side; the adjusting assembly communicates with the exhaust pipeline and is used for introducing compressed gas into the exhaust pipeline. The introduction amount of the compressed gas can be adjusted according to the operation condition of the fuel cell system, so that temperature shock of the water evaporator can be effectively prevented, and long-term normal operation of the fuel cell system is maintained.

Description

Technical Field

[0001] The present application relates to the field of fuel cell technology, and in particular to a fuel cell tail gas recovery system, a fuel cell system and a control method. Background Art

[0002] In a fuel cell system, a module is usually set up to oxidize the anode tail gas and cathode tail gas emitted by the stack, so as to prevent the residual fuel in the tail gas from being discharged into the environment and causing pollution or combustion and explosion. After oxidation, the anode tail gas and the cathode tail gas will generate high-temperature fuel oxidation tail gas. In order to improve the thermal energy utilization efficiency of the fuel cell, the fuel oxidation tail gas is usually heat recovered, such as passing the fuel oxidation tail gas into a water evaporator and exchanging heat with the liquid water in the water evaporator, so that the liquid water forms high-temperature water vapor. After the high-temperature water vapor is mixed with the fuel, it can return to the anode of the stack to participate in the reaction.

[0003] When the fuel cell system rapidly increases its output power to meet electricity demand, a large amount of liquid water will exchange heat with the high-temperature fuel oxidation exhaust gas. At this time, since the flow rate of the fuel oxidation exhaust gas remains relatively unchanged, the rapid heat exchange reaction of a large amount of liquid water in a short period of time will cause the water evaporator to experience drastic temperature changes. The resulting temperature change rate may even exceed the tolerable range of the water evaporator material. In the long run, it is easy to cause the life and stability of the water evaporator to decrease, thereby affecting the normal operation of the fuel cell system. Summary of the invention

[0004] In order to solve at least one of the above-mentioned technical problems, the present application provides a fuel cell exhaust gas recovery system, a fuel cell system and a control method. By introducing compressed gas into the exhaust pipe connected to the first heat exchange side outlet of the water evaporator, the temperature of the water evaporator can be effectively prevented from changing suddenly. The technical solution adopted is as follows.

[0005] In the first aspect, the present application provides a fuel cell tail gas recovery system, comprising a flow divider, a water evaporator, an exhaust pipe and a regulating component. The flow divider is used to receive the tail gas and divide the tail gas into at least a first branch and a second branch; the water evaporator comprises a first heat exchange side and a second heat exchange side, the first branch is connected to the inlet of the first heat exchange side, and the second heat exchange side is used to pass liquid water; one end of the exhaust pipe is connected to the outlet of the first heat exchange side; the regulating component is connected to the exhaust pipe, and is used to pass compressed gas into the exhaust pipe.

[0006] In certain embodiments of the present application, the intake angle of the compressed gas introduced into the exhaust duct is adjustable.

[0007] In certain embodiments of the present application, the exhaust duct is provided with a preset pressure loss portion, and the preset pressure loss portion can be used to provide a preset pressure loss to the first heat exchange side.

[0008] In certain embodiments of the present application, the fuel cell exhaust gas recovery system further includes a second heat exchanger, and the second branch flow is connected to one of the heat exchange sides of the second heat exchanger.

[0009] The present application provides a fuel cell system in the second aspect, including a fuel cell stack, a fuel oxidizer, and the fuel cell exhaust gas recovery system provided in the first aspect of the present application; wherein the anode outlet and the cathode outlet of the fuel cell stack are both connected to the inlet of the fuel oxidizer, the outlet of the fuel oxidizer is connected to the diverter, the second heat exchanger is an air heat exchanger, and the other heat exchange side of the air heat exchanger is connected to the cathode inlet of the fuel stack.

[0010] In certain embodiments of the present application, the fuel cell system also includes a fuel heat exchanger, and the water vapor flowing out from the outlet of the second heat exchange side of the water evaporator is used to mix with the fuel and pass into the third heat exchange side of the fuel heat exchanger, and the inlet of the fourth heat exchange side of the fuel heat exchanger is connected to the anode outlet of the fuel stack, and the anode exhaust gas in the fuel stack is used to heat the third heat exchange side, and the outlet of the third heat exchange side is connected to the anode inlet of the fuel stack, and the outlet of the fourth heat exchange side is connected to the inlet of the fuel oxidizer.

[0011] The present application provides a control method for a fuel cell exhaust gas recovery system in a third aspect, which adopts the fuel cell exhaust gas recovery system provided in the first aspect of the present application and includes: introducing a first branch gas into a first heat exchange side of a water evaporator, and the first branch gas enters the exhaust pipe from the outlet of the first heat exchange side; using a regulating component to supply compressed gas to the exhaust pipe; regulating the amount of compressed gas introduced to change the gas flow rate of the first branch; wherein, when the power output of the fuel cell system increases, the compressed gas input flow rate is reduced; when the power output of the fuel cell system decreases, the compressed gas input flow rate is increased.

[0012] In certain embodiments of the present application, supplying compressed gas to the exhaust duct using the regulating component includes: the regulating component regulating an intake angle of the compressed gas in the exhaust duct.

[0013] In certain embodiments of the present application, regulating the amount of compressed gas introduced to change the gas flow rate of the first branch includes: adjusting the compressed gas introduction flow rate so that when the fuel cell system is in a full-load power generation state and when the fuel cell system is in a heat preservation state, the fluid temperature at the outlet of the first heat exchange side of the water evaporator is maintained within a preset temperature range; or adjusting the compressed gas introduction flow rate so that the fluid temperature change rate at the outlet of the first heat exchange side of the water evaporator does not exceed a preset value.

[0014] In certain embodiments of the present application, adjusting the amount of compressed gas introduced to change the gas flow rate of the first branch includes: when the power output of the fuel cell system increases and the temperature change rate of the fluid at the outlet of the first heat exchange side exceeds a preset value, if the fluid temperature at the outlet of the first heat exchange side rises, the rate of change of the compressed gas flow rate is slowed down; if the fluid temperature at the outlet of the first heat exchange side decreases, the rate of change of the compressed gas flow rate is accelerated; when the power output of the fuel cell system decreases and the temperature change rate of the fluid at the outlet of the first heat exchange side exceeds a preset value, if the fluid temperature at the outlet of the first heat exchange side rises, the rate of change of the compressed gas flow rate is accelerated; if the fluid temperature at the outlet of the first heat exchange side decreases, the rate of change of the compressed gas flow rate is slowed down.

[0015] The embodiments of the present application have at least the following beneficial effects: by introducing compressed gas into the exhaust pipe connected to the outlet of the first heat exchange side of the water evaporator and controlling the flow rate of the compressed gas, the fluid flow resistance of the first heat exchange side of the water evaporator can be adjusted, thereby adjusting the pressure loss of the first heat exchange side of the water evaporator. Since the fuel oxidation tail gas is divided into at least two branches, when the pressure loss of the first heat exchange side of the water evaporator increases or decreases, the pressure loss of the first branch connected to the first heat exchange side also increases or decreases accordingly, so that the flow rate of the fuel oxidation tail gas distributed to the first branch is also reduced or increased accordingly. When the flow rate of liquid water introduced into the water evaporator changes, the flow rate of the fuel oxidation tail gas introduced into the first branch can be matched with the flow rate of liquid water by adjusting the flow rate of the compressed gas introduced, and the temperature sudden change of the water evaporator can be effectively suppressed under the premise of ensuring the liquid water heat exchange demand, the water evaporator is maintained in a stable working state and the service life of the water evaporator is extended, and the long-term normal operation of the fuel cell system is ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present application is further illustrated below in conjunction with the accompanying drawings and embodiments. It should be noted that the embodiments embodied in the following drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0017] Figure 1 A schematic diagram of a fuel cell tail gas recovery system provided in an embodiment of the present application;

[0018] Figure 2 A schematic diagram of an example of a fuel cell system provided in an embodiment of the present application;

[0019] Figure 3 A schematic diagram of another example of a fuel cell system provided in an embodiment of the present application;

[0020] Figure 4 A flowchart of a fuel cell tail gas recovery control method provided in an embodiment of the present application;

[0021] Figure 5A schematic diagram of the intake angle of compressed gas in the exhaust pipe of the fuel cell exhaust recovery system provided in an embodiment of the present application.

[0022] Figure markings: diverter 100, first branch 110, second branch 120, water evaporator 200, first heat exchange side inlet 210, first heat exchange side outlet 220, second heat exchange side inlet 230, second heat exchange side outlet 240, adjustment component 300, exhaust duct 400, air heat exchanger 500, hot side flow path inlet 510, hot side flow path outlet 520, cold side flow path inlet 530, cold side flow path outlet 540, fuel stack 600, anode inlet 610, anode outlet 620, cathode inlet 630, cathode outlet 640, fuel oxidizer 700, fuel oxidizer inlet 710, 720, fuel oxidizer outlet 730, fuel heat exchanger 810, third heat exchange side inlet 811, third heat exchange side outlet 812, fourth heat exchange side inlet 813, fourth heat exchange side outlet 814, pre-reformer 820, anode tail gas diverter 830. DETAILED DESCRIPTION

[0023] The embodiments of the present application are described in detail below in conjunction with the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0024] In the description of the present application, it should be understood that the terms "center", "middle", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0025] In the description of this application, "several" means more than one, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0026] In the description of this application, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0027] In the description of the present application, if the reference terms "as an implementation", "an embodiment", "some instances", "some embodiments", "illustrative embodiment", "example", "specific example", "some examples", etc. appear, it means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0028] See also Figure 1In the first aspect, the present application provides a fuel cell tail gas recovery system, including a diverter 100, a water evaporator 200, an exhaust pipe 400 and a regulating assembly 300. The diverter 100 is used to receive the tail gas and divide the tail gas into at least a first branch 110 and a second branch 120; the water evaporator 200 includes a first heat exchange side and a second heat exchange side, the first branch 110 is connected to the inlet 210 of the first heat exchange side, and the second heat exchange side is used to pass liquid water; one end of the exhaust pipe 400 is connected to the outlet 220 of the first heat exchange side; the regulating assembly 300 is connected to the exhaust pipe 400, and is used to pass compressed gas into the exhaust pipe 400. Specifically, the diverter 100 is used to receive the fuel oxidation tail gas and divert the fuel oxidation tail gas. The outlet 220 of the first heat exchange side of the water evaporator 200 is used to discharge the fuel oxidation tail gas after the heat exchange reaction, while the inlet 230 of the second heat exchange side of the water evaporator 200 is used to pass liquid water, and the outlet 240 of the second heat exchange side is used to discharge the high-temperature water vapor after the heat exchange reaction. By passing compressed gas into the exhaust pipe 400, the fluid flow resistance of the first heat exchange side of the water evaporator 200 can be increased, so that the pressure loss of the first heat exchange side of the water evaporator 200 is increased. Since the fuel oxidation tail gas is divided into at least two branches, when the pressure loss of the first heat exchange side of the water evaporator 200 increases, the pressure loss of the first branch 110 connected to the first heat exchange side will increase, and at this time more fuel oxidation tail gas will flow to the second branch 120, thereby reducing the flow of fuel oxidation tail gas allocated to the first branch 110. Therefore, the amount of compressed gas introduced can be adjusted according to the amount of liquid water introduced into the water evaporator 200, thereby controlling the pressure loss on the first heat exchange side, so that the flow rate of the first branch stream 110 introduced into the water evaporator 200 to participate in the heat exchange reaction can match the amount of liquid water introduced, thereby slowing down the heat exchange reaction of the liquid water in the water evaporator 200 and preventing the temperature of the water evaporator 200 from changing suddenly, thereby maintaining the working stability of the water evaporator 200 and extending the service life of the water evaporator 200, thereby ensuring the long-term normal operation of the fuel cell system.

[0029] Compared with the prior art that uses an actively controlled valve to divert the fuel oxidation tail gas, because the actively controlled valve cannot withstand high temperatures and has a short service life, it is necessary to regularly replace the valve and thus increase the operating cost of the fuel cell system. The fuel cell tail gas recovery system provided in the present application adjusts the gas flow of the first branch 110 by introducing compressed gas, so that the diverter 100 has the function of automatically distributing the tail gas flow of each branch. Therefore, in other examples, the diverter 100 can use a passive device, which can not only withstand high temperatures, but also has a low price, which helps to improve the stability of the operation of the fuel cell system and reduce the operating cost.

[0030] Exemplarily, the compressed gas introduced into the exhaust pipe 400 may be an inert gas or air.

[0031] Optionally, the regulating component 300 can be an air compressor, which is connected to the atmosphere and produces compressed air, and the produced compressed air can be directly supplied to the exhaust pipe 400; or, the regulating component 300 can be a single or multiple gas tanks storing compressed gas, and the compressed gas in the gas tanks is delivered to the exhaust pipe 400 through a valve or an air pump.

[0032] Optionally, the regulating assembly 300 may be disposed on the side wall of the exhaust pipe 400. In this case, the compressed gas passes through the connection between the regulating assembly 300 and the exhaust pipe 400 and enters the exhaust pipe 400 in a direction that is at a certain angle to the exhaust pipe 400. The specific location of the regulating assembly 300 on the side wall of the exhaust pipe 400 is not limited. In addition, the regulating assembly 300 may also be directly connected to the pipe opening of the exhaust pipe 400 away from the first heat exchange side outlet 220. In this case, the compressed gas enters the exhaust pipe 400 in a direction parallel to the exhaust pipe 400.

[0033] Optionally, to improve the energy utilization efficiency of the fuel cell system, the second branch 120 can be connected to other heat exchangers for heat exchange reaction, and the diverter 100 can also divide the fuel oxidation exhaust gas into multiple branches according to the actual use requirements of the fuel cell system.

[0034] Optionally, the regulating component 300 is further provided with a flow valve, through which the flow of compressed gas entering the exhaust pipe 400 can be controlled.

[0035] Optionally, a temperature sensor is further provided at the outlet 220 of the first heat exchange side, and the temperature sensor can monitor the temperature of the fluid discharged from the outlet 220 of the first heat exchange side. The flow rate of compressed gas input into the exhaust pipe 400 can be controlled according to the monitored temperature data.

[0036] In some embodiments, the intake angle of the compressed gas introduced into the exhaust pipe 400 is adjustable. It is understandable that when the angle between the intake direction of the compressed gas and the axis of the exhaust pipe 400 is large, the compressed gas will experience strong turbulence, resulting in increased pressure loss, and when the angle between the intake direction of the compressed gas and the axis of the exhaust pipe 400 is small, the flow of the compressed gas will be smoother, causing less pressure loss. By adjusting the intake angle of the compressed gas in the exhaust pipe 400, the effect of the compressed gas on the pressure loss of the first heat exchange side can be adjusted, so that the pressure loss of the first heat exchange side can be fine-tuned without changing the flow rate of the compressed gas, thereby achieving fine-tuning of the flow rate of the fuel oxidation exhaust gas entering the water evaporator 200.

[0037] Optionally, an air intake valve is provided at the connection between the regulating component 300 and the exhaust pipe 400, and the air intake angle of the compressed gas can be adjusted by adjusting the setting angle between the air intake valve and the exhaust pipe 400; or, a gas guide plate is provided at the connection between the regulating component 300 and the exhaust pipe 400, and the air intake angle of the compressed gas can be adjusted by setting the angle of the guide plate. The regulating component 300 can also be connected to the exhaust pipe 400 through a structure such as a three-way joint, and the air intake angle of the regulating component 300 can be adjusted by selecting a joint structure with different angle specifications.

[0038] In some embodiments, the exhaust pipe 400 is provided with a preset pressure loss portion, and the preset pressure loss portion can be used to provide a preset pressure loss to the first heat exchange side. By providing the exhaust pipe 400 with a preset pressure loss portion, a preset flow resistance can be provided for the fluid in the exhaust pipe 400, thereby providing a preset pressure loss for the first heat exchange side, effectively reducing excessive fluctuations of the fluid on the first heat exchange side, maintaining the relative stability of the fluid on the first heat exchange side, and making the state change of the fluid more controllable. When the fluid on the first heat exchange side maintains a relatively stable flow state, compressed gas can be introduced into the exhaust pipe 400 to increase the pressure loss of the first heat exchange side, so that the fuel oxidation exhaust gas flow rate allocated to the first branch 110 can be reduced to a flow rate that matches the liquid water input amount, thereby slowing down the heat exchange reaction of the liquid water in the water evaporator 200. Therefore, by providing a preset pressure loss portion, the process of using compressed gas to adjust the fuel oxidation exhaust gas flow rate can be made more accurate.

[0039] Optionally, the preset pressure loss portion includes a bending portion. The bending portion is formed by bending a portion of the exhaust pipe 400. When the fluid at the first heat exchange side outlet 220 passes through the pipe of the bent portion, the contact surface between the fluid and the pipe increases, so that the flow resistance of the fluid increases, thereby providing a preset pressure loss for the first heat exchange side. By adjusting the bending degree of the pipe or the length of the bent portion of the pipe, the preset pressure loss of the first heat exchange side can be further adjusted.

[0040] Optionally, the preset pressure loss portion includes a contraction portion. The contraction portion is formed by reducing the diameter of a portion of the exhaust pipe 400. When the fluid flows from a pipe with a normal diameter to the narrowed pipe, the flow resistance increases, thereby providing a preset pressure loss for the first heat exchange side. By adjusting the diameter and length of the contraction portion, the preset pressure loss of the first heat exchange side can be further adjusted.

[0041] Optionally, the preset pressure loss portion is arranged at one end of the exhaust pipe 400 away from the first heat exchange side outlet 220 , or may be arranged in the middle of the exhaust pipe 400 , or may be arranged at one end of the exhaust pipe 400 close to the first heat exchange side outlet 220 .

[0042] Optionally, the regulating assembly 300 is disposed between the preset pressure loss portion and the first heat exchange side outlet 220 .

[0043] Optionally, one end of the exhaust pipe 400 away from the first heat exchange side outlet 220 can be connected to a recovery filter, and the fluid discharged from the first heat exchange side outlet 220 passes through the recovery filter, and some impurities that are likely to cause air pollution are filtered out before being discharged into the atmosphere. Optionally, the recovery filter can be further connected to a compressed gas recovery device, and the compressed gas recovery device can recover the inert gas or air in the filtered fluid, so as to produce compressed gas again.

[0044] In some embodiments, the fuel cell exhaust gas recovery system further includes a second heat exchanger, and the second branch 120 is connected to one of the heat exchange sides of the second heat exchanger. After passing through the diverter 100, the fuel oxidation exhaust gas is divided into a first branch 110 and a second branch 120, wherein the first branch 110 is passed into the water evaporator 200 for heat exchange reaction and the liquid water passed into the water evaporator 200 forms high-temperature water vapor, and the second branch 120 is passed into one of the heat exchange sides of the second heat exchanger for heat exchange reaction, so as to further recover and utilize the heat in the fuel oxidation exhaust gas. Specifically, the second heat exchanger has a hot side flow path and a cold side flow path, wherein the second branch 120 of the fuel oxidation exhaust gas enters the second heat exchanger through the inlet 510 of the hot side flow path to participate in heat exchange.

[0045] Optionally, the second heat exchanger is an air heat exchanger 500, and fresh air enters the air heat exchanger 500 through the inlet 530 of the cold side flow path, and undergoes heat exchange reaction with the fuel oxidation exhaust gas entering through the inlet 510 of the hot side flow path. The high-temperature air after heat exchange is discharged through the cold side flow path outlet 540, and the cooled exhaust gas after heat exchange is discharged and recovered through the outlet 520 of the hot side flow path.

[0046] Optionally, the second heat exchanger is a coolant heat exchanger, and the coolant enters the heat exchanger through the inlet 530 of the cold side flow path, undergoes heat exchange reaction with the fuel oxidation exhaust gas entering through the inlet 510 of the hot side flow path, and takes away the heat of the fuel oxidation exhaust gas to maintain the thermal balance of the fuel cell system and prevent the power output efficiency from being affected due to excessive temperature of the fuel system. The coolant and exhaust gas after heat exchange are discharged and recovered through the cold side flow path outlet 540 and the hot side flow path outlet 520 respectively.

[0047] Optionally, the flow divider 100 can divide the fuel oxidation exhaust gas into multiple branches, and correspondingly multiple heat exchangers can be provided to connect with the multiple branches to recover and utilize the heat in the fuel oxidation exhaust gas of each branch.

[0048] See also Figure 2In the second aspect, the present application provides a fuel cell system, comprising a stack 600, a fuel oxidizer 700, and a fuel cell tail gas recovery system provided in the first aspect of the present application; wherein the anode outlet 620 of the stack 600 is connected to one of the inlets 710 of the fuel oxidizer, the cathode outlet 640 is connected to the other inlet 720 of the fuel oxidizer, the outlet 730 of the fuel oxidizer is connected to the diverter 100, and the second heat exchanger is an air heat exchanger 500, and the other heat exchange side of the air heat exchanger 500 is connected to the cathode inlet 630 of the stack 600. By applying the tail gas recovery system provided in the first aspect of the present application to the fuel cell system, the fuel oxidation tail gas can be effectively recovered and processed while preventing the water evaporator 200 from being degraded due to sudden temperature changes, thereby affecting the normal operation of the fuel cell system. Specifically, after the stack 600 performs the redox reaction, tail gas will be generated at the anode and cathode respectively. Since the anode outlet 620 of the stack 600 is connected to one of the inlets 710 of the fuel oxidizer, and the cathode outlet 640 is connected to the other inlet 720 of the fuel oxidizer, the tail gas generated by the stack 600 can enter the fuel oxidizer, and the fuel oxidizer oxidizes the residual fuel in the tail gas to avoid explosion hazard in the subsequent discharge process. The tail gas generated after the fuel oxidation will be divided into a first branch 110 and a second branch 120 through the diverter 100, wherein the fuel oxidation tail gas of the first branch 110 will enter the water evaporator 200, and after heat exchange with the liquid water passed into the water evaporator 200, the cooled tail gas will be discharged through the outlet 220 of the first heat exchange side of the water evaporator 200, and the high-temperature water vapor formed after the liquid water absorbs heat will mix with the fuel, and the mixed fuel can be transported to the anode of the stack 600 to participate in the redox reaction. The fuel oxidation exhaust gas of the second branch 120 will be introduced into the air heat exchanger 500 for heat exchange, and the high-temperature air generated after the heat exchange can be transported to the cathode of the fuel cell stack 600 to participate in the redox reaction and output electrical energy.

[0049] It is understandable that by introducing compressed gas into the exhaust pipe 400, the fuel oxidation exhaust gas entering the water evaporator 200 can be reduced, and the fuel oxidation exhaust gas entering the air heat exchanger 500 can be increased, so that the flow rate of the fuel oxidation exhaust gas entering the water evaporator 200 can match the flow rate of liquid water entering the water evaporator 200, thereby slowing down the thermal reaction in the water evaporator 200 and suppressing the sudden temperature change of the water evaporator 200.

[0050] See also Figure 3In some embodiments, the fuel cell system further includes a fuel heat exchanger 810, the water vapor flowing out of the second heat exchange side outlet 240 of the water evaporator 200 is used to mix with the fuel and pass into the third heat exchange side of the fuel heat exchanger 810, the inlet 813 of the fourth heat exchange side of the fuel heat exchanger 810 is connected to the anode outlet 620 of the stack 600, the anode tail gas in the stack 600 is used to heat the third heat exchange side, the outlet 812 of the third heat exchange side is connected to the anode inlet 610 of the stack 600, and the outlet 814 of the fourth heat exchange side is connected to one of the inlets 710 of the fuel oxidizer. By providing the fuel heat exchanger 810, the fuel is preheated by using the tail gas heat generated by the stack 600 before the fuel is transported to the stack 600, which can not only improve the redox reaction efficiency of the stack 600, but also recycle the heat generated by the stack 600, improve the thermal efficiency of the fuel cell system, and reduce heat energy loss.

[0051] Optionally, a pre-reformer 820 may be provided between the inlet 811 of the third heat exchange side of the fuel heat exchanger 810 and the outlet 240 of the second heat exchange side of the water evaporator 200. After the fuel input into the fuel cell system is mixed with the high-temperature water vapor generated by the water evaporator 200, it will be first transported to the pre-reformer 820, and the fuel will be processed by the pre-reformer 820 before being introduced into the third heat exchange side of the fuel heat exchanger 810. The pre-reformer 820 can reform the fuel, optimize the fuel performance, and improve the output efficiency of the fuel cell system.

[0052] Optionally, an anode tail gas diverter 830 may be provided between the outlet 814 of the fourth heat exchange side of the fuel heat exchanger 810 and one of the inlets 710 of the fuel oxidizer. The anode tail gas diverter 830 may divert a portion of the anode tail gas to the fuel oxidizer 700 for reaction, and another portion of the anode tail gas may be recycled as fuel and remixed with the high-temperature water vapor generated by the water evaporator 200 to be transported to the fuel cell stack 600 to participate in the redox reaction.

[0053] See also Figure 4 In a third aspect, the present application provides a control method for a fuel cell tail gas recovery system, which adopts the fuel cell tail gas recovery system provided in the first aspect of the present application and includes:

[0054] S1000: introducing a first branch flow 110 of gas into a first heat exchange side of the water evaporator 200, and the first branch flow 110 of gas enters the exhaust pipe 400 from an outlet 220 of the first heat exchange side;

[0055] S2000: Supplying compressed gas to the exhaust pipe 400 using the regulating assembly 300;

[0056] S3000: Regulate the amount of compressed gas introduced to change the gas flow rate of the first branch stream 110; wherein, when the power output of the fuel cell system increases, the compressed gas input flow rate is reduced; and when the power output of the fuel cell system decreases, the compressed gas input flow rate is increased.

[0057] It is understandable that, since the control method of the fuel cell exhaust gas recovery system adopts the fuel cell exhaust gas recovery system described in the first aspect above, the control method of the fuel cell exhaust gas recovery system has the beneficial effect of avoiding the water evaporator 200 from being subjected to rapid temperature changes as described in the first aspect above, thereby maintaining the working stability of the water evaporator 200 and extending the service life of the water evaporator 200, and ensuring the long-term normal operation of the fuel cell system, which will not be repeated here. Specifically, when the power output of the fuel cell system is increased, the system needs to generate more high-temperature water vapor to mix with the fuel to participate in the redox reaction of the stack 600 to output more power. Therefore, compared with before the power output is increased, the input flow rate of the compressed gas needs to be reduced. At this time, the pressure loss of the first heat exchange side in the water evaporator 200 is reduced, causing the pressure loss of the first branch 110 to be reduced, and more fuel oxidation exhaust gas will enter the water evaporator 200 to undergo heat exchange reaction with liquid water, thereby generating more high-temperature water vapor. On the contrary, when the power output of the fuel cell system is reduced, too much high-temperature water vapor is not needed to participate in the reaction. Compared with before the power output is reduced, the input flow rate of the compressed gas needs to be increased. By increasing the pressure loss on the first heat exchange side of the water evaporator 200, the pressure loss of the first branch 110 is increased, which can prevent too much fuel oxidation tail gas from entering the water evaporator 200, thereby causing the water evaporator 200 to accumulate heat exceeding its normal operating requirements and causing its own temperature to rise sharply. By adjusting the compressed gas flow rate, the pressure loss on the first heat exchange side of the water evaporator 200 can be adjusted, thereby controlling the pressure loss of the first branch 110, and realizing the control of the fuel oxidation tail gas flow ratio of the first branch 110 and other branches. Therefore, when the flow rate of liquid water entering the water evaporator 200 changes according to the actual power consumption demand, the flow rate of fuel oxidation exhaust gas entering the first branch can be matched with the flow rate of liquid water by adjusting the flow rate of compressed gas, so that after the high-temperature exhaust gas in the water evaporator 200 undergoes a heat exchange reaction with liquid water, high-temperature water vapor that meets the use requirements of the fuel cell system can be formed, while the water evaporator 200 can also be prevented from suddenly changing its own temperature due to excessive heat accumulation or excessive heat loss.

[0058] In some embodiments, the above step S2000 of supplying compressed gas to the exhaust pipe 400 using the regulating assembly 300 includes:

[0059] S2100 : The adjustment component 300 adjusts the intake angle of the compressed gas in the exhaust duct 400 .

[0060] See also Figure 5 , by adjusting the intake angle α of the compressed gas in the exhaust pipe 400, the influence of the compressed gas on the pressure loss of the first heat exchange side can be adjusted, so that the pressure loss of the first heat exchange side can be fine-tuned without changing the flow rate of the compressed gas, thereby achieving fine-tuning of the flow rate of the fuel oxidation tail gas entering the water evaporator 200. It can be understood that, when the flow rate of the compressed gas remains unchanged, the smaller the value of α, the greater the pressure loss caused to the first heat exchange side. When the value of α is zero, that is, when the compressed gas enters the outlet 220 of the first heat exchange side at an angle parallel to the exhaust pipe 400, the pressure loss caused is the largest.

[0061] Optionally, the amount of compressed gas input and the intake angle of the compressed gas in the exhaust duct 400 may be adjusted simultaneously according to the actual fuel oxidation exhaust gas usage of the water evaporator 200 .

[0062] In some embodiments, the step S3000 of adjusting the amount of compressed gas introduced to change the gas flow rate of the first branch stream 110 includes:

[0063] S3110: Adjust the compressed gas flow rate so that the fluid temperature at the outlet 220 of the first heat exchange side of the water evaporator 200 is maintained within a preset temperature range when the fuel cell system is in a full-load power generation state and when the fuel cell system is in a heat preservation state.

[0064] When the fuel cell system is in a full-load power generation state, the output electric energy is the highest. When the fuel cell system is in a heat preservation state, the output electric energy of the fuel cell system is the lowest. By controlling the flow rate of compressed gas, the fluid temperature at the outlet 220 of the first heat exchange side can be maintained within a preset range when the fuel cell system is in two boundary states, so that the fluid temperature at the outlet 220 of the first heat exchange side will not differ too much, thereby maintaining the thermal balance of the water evaporator 200 and preventing the water evaporator 200 from being damaged faster due to excessive temperature gradient when the fuel cell system is quickly adjusted from the heat preservation state to the full-load power generation state, or from the full-load power generation state to the heat preservation state.

[0065] Optionally, the fluid temperature at the outlet 220 of the first heat exchange side when the fuel cell system is in a full-load power generation state is set to T1, and the fluid temperature at the outlet 220 of the first heat exchange side when the fuel cell system is in a heat preservation state is set to T2, and T1 and T2 satisfy |T2-T1| / T1≤0.5.

[0066] Optionally, the temperature range of T1 is 100°C≤T1≤250°C, the temperature range of T1 is 100°C≤T2≤250°C, and optionally, T2≈T1±50°C.

[0067] In some embodiments, the step S3000 of adjusting the amount of compressed gas introduced to change the gas flow rate of the first branch stream 110 includes:

[0068] S3120: Adjust the flow rate of compressed gas so that the temperature change rate of the fluid at the outlet 220 of the first heat exchange side of the water evaporator 200 does not exceed a preset value.

[0069] The temperature change rate of the fluid at the outlet 220 of the first heat exchange side of the water evaporator 200 refers to the temperature change value of the fluid at the outlet 220 of the first heat exchange side per unit time. By controlling the temperature change rate of the fluid at the outlet 220 of the first heat exchange side of the water evaporator 200 not to exceed a preset value, the water evaporator 200 can be prevented from being subjected to temperature change values ​​that exceed the tolerable value of its own material, thereby maintaining the normal operating performance of the water evaporator 200.

[0070] It is understandable that a failure test can be performed on the water evaporator 200 according to the manufacturing material of the water evaporator 200, so as to obtain a preset value of the temperature change rate for a specific water evaporator 200. For example, the preset value of the temperature change rate can be set to 600°C / h.

[0071] In some embodiments, the step S3000 of adjusting the amount of compressed gas introduced to change the gas flow rate of the first branch stream 110 includes:

[0072] S3130: When the power output of the fuel cell system increases and the temperature change rate of the fluid at the outlet 220 of the first heat exchange side exceeds a preset value, if the fluid temperature at the outlet 220 of the first heat exchange side rises, the change rate of the compressed gas flow rate is slowed down; if the fluid temperature at the outlet 220 of the first heat exchange side drops, the change rate of the compressed gas flow rate is accelerated.

[0073] It is understandable that when the power output of the fuel cell system increases, the system needs more high-temperature water vapor to participate in the redox reaction of the stack 600 to output more power. Therefore, compared with the increase in power output, the amount of compressed gas introduced needs to be reduced. However, if the rate of decrease of the compressed gas flow is too fast, the pressure loss of the first branch 110 connected to the water evaporator 200 will decrease rapidly, and a large amount of high-temperature fuel oxidation tail gas will flow into the water evaporator 200 per unit time and produce a violent heat exchange reaction with liquid water, thereby causing the water evaporator 200 to cause a sharp rise in temperature due to excessive heat supply per unit time, and causing the temperature of the fluid discharged at the outlet 220 of the first heat exchange side to rise and exceed the preset temperature change rate value. Therefore, at this time, it is necessary to reduce the rate of decrease of the compressed gas flow so that the pressure loss of the first branch 110 connected to the water evaporator 200 decreases slowly, so that the flow of fuel oxidation tail gas entering the water evaporator 200 gradually increases, so that a stable heat exchange reaction can be carried out inside the water vapor. Similarly, if the decrease rate of the compressed gas flow is too slow, the pressure loss of the first branch 110 connected to the water evaporator 200 will not decrease significantly, resulting in insufficient high-temperature fuel oxidation exhaust gas entering the water evaporator 200 to participate in heat exchange per unit time. Since the heat provided by the fuel oxidation exhaust gas is insufficient to meet the heat exchange requirements of the water evaporator 200 under normal operating conditions, the temperature of the exhaust fluid at the outlet 220 of the first heat exchange side drops sharply and exceeds the preset temperature change rate value. Therefore, it is necessary to accelerate the decrease rate of the compressed gas flow so that more fuel oxidation exhaust gas can enter the water evaporator 200 to provide sufficient heat.

[0074] In some embodiments, the above step S3000 adjusts the amount of compressed gas introduced to change the gas flow rate of the first branch stream 110, and further includes:

[0075] S3140: When the power output of the fuel cell system decreases and the temperature change rate of the fluid at the outlet 220 of the first heat exchange side exceeds a preset value, if the fluid temperature at the outlet 220 of the first heat exchange side rises, the change rate of the compressed gas flow rate is accelerated; if the fluid temperature at the outlet 220 of the first heat exchange side decreases, the change rate of the compressed gas flow rate is slowed down.

[0076] It is understandable that when the power output of the fuel cell system is reduced, too much high-temperature water vapor is not required to participate in the reaction, and the input flow rate of the compressed gas needs to be increased compared to before the power output is reduced. However, if the increase rate of the compressed gas flow is too slow, the increase rate of the pressure loss of the first branch 110 connected to the water evaporator 200 is too slow, resulting in a large amount of high-temperature fuel oxidation tail gas entering the water evaporator 200 per unit time. The water evaporator 200 has a sharp rise in temperature due to excessive heat supply per unit time, so that the temperature change rate of the fluid discharged at the outlet 220 of the first heat exchange side exceeds the preset value. Therefore, at this time, it is necessary to accelerate the increase rate of the compressed gas flow, so that the pressure loss of the first heat exchange side connected to the water evaporator 200 increases, thereby reducing the fuel oxidation tail gas entering the water evaporator 200 and avoiding a sudden increase in the temperature of the water evaporator 200. Similarly, if the increase rate of the compressed gas flow rate is too fast, the increase rate of the pressure loss of the first branch 110 connected to the water evaporator 200 is too fast, resulting in insufficient amount of high-temperature fuel oxidation exhaust gas entering the water evaporator 200 for heat exchange per unit time. Since the heat provided by the fuel oxidation exhaust gas is insufficient to meet the heat exchange requirements of the water evaporator 200 under normal operating conditions, the temperature of the discharged fluid at the outlet 220 of the first heat exchange side drops sharply and exceeds the preset temperature change rate value. At this time, it is necessary to reduce the increase rate of the compressed gas flow rate so as to slow down the increase rate of the pressure loss of the first branch 110 connected to the water evaporator 200, thereby maintaining a sufficient amount of high-temperature fuel oxidation exhaust gas to enter the water evaporator 200 for heat exchange and maintain the thermal balance of the water evaporator 200.

[0077] The above is a detailed description of the implementation methods of the present application in conjunction with the accompanying drawings, but the present application is not limited to the above implementation methods. Various changes can be made within the knowledge of ordinary technicians in the technical field without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A fuel cell tail gas recovery system, characterized in that: include A flow divider, the flow divider is used to receive the tail gas and divide the tail gas into at least a first branch flow and a second branch flow; A water evaporator, the water evaporator comprising a first heat exchange side and a second heat exchange side, the first branch is connected to the inlet of the first heat exchange side, and the second heat exchange side is used for introducing liquid water; an exhaust pipe, one end of which is connected to the outlet of the first heat exchange side; A regulating component is connected to the exhaust pipe, and the regulating component is used to introduce compressed gas into the exhaust pipe.

2. The fuel cell tail gas recovery system according to claim 1, characterized in that: The intake angle of the compressed gas into the exhaust pipe is adjustable.

3. The fuel cell tail gas recovery system according to claim 1, characterized in that: The exhaust pipe is provided with a preset pressure loss portion, and the preset pressure loss portion can be used to provide a preset pressure loss to the first heat exchange side.

4. The fuel cell tail gas recovery system according to claim 1, characterized in that: The fuel cell tail gas recovery system further includes a second heat exchanger, and the second branch flow is connected to one heat exchange side of the second heat exchanger.

5. A fuel cell system, characterized in that: It includes a fuel cell stack, a fuel oxidizer and the fuel cell exhaust gas recovery system as described in claim 4; the anode outlet and the cathode outlet of the fuel cell stack are both connected to the inlet of the fuel oxidizer, the outlet of the fuel oxidizer is connected to the diverter, and the second heat exchanger is an air heat exchanger, and the other heat exchange side of the air heat exchanger is connected to the cathode inlet of the fuel cell stack.

6. The fuel cell system according to claim 5, characterized in that: The fuel cell system also includes a fuel heat exchanger, and the water vapor flowing out from the second heat exchange side outlet of the water evaporator is used to mix with the fuel and pass into the third heat exchange side of the fuel heat exchanger, and the inlet of the fourth heat exchange side of the fuel heat exchanger is connected to the anode outlet of the fuel cell stack, and the anode tail gas in the fuel cell stack is used to heat the third heat exchange side, and the outlet of the third heat exchange side is connected to the anode inlet of the fuel cell stack, and the outlet of the fourth heat exchange side is connected to the inlet of the fuel oxidizer.

7. A control method for a fuel cell tail gas recovery system, characterized in that: A first branch gas is introduced into a first heat exchange side of the water evaporator, and the first branch gas enters an exhaust pipe from an outlet of the first heat exchange side; supplying compressed gas to the exhaust pipe using a regulating assembly; The amount of compressed gas introduced is adjusted to change the gas flow rate of the first branch; wherein, when the power output of the fuel cell system increases, the compressed gas input flow rate is reduced; and when the power output of the fuel cell system decreases, the compressed gas input flow rate is increased.

8. The control method of the fuel cell tail gas recovery system according to claim 7, characterized in that: The use of a regulating assembly to supply compressed gas to the exhaust pipe includes: The regulating assembly regulates an intake angle of compressed gas in the exhaust duct.

9. The control method of the fuel cell tail gas recovery system according to claim 7, characterized in that: The step of adjusting the amount of compressed gas introduced to change the gas flow rate of the first branch flow comprises: The compressed gas inlet flow rate is adjusted so that the heat exchange side of the water evaporator satisfies at least one of the following conditions: When the fuel cell system is in a full-load power generation state and when the fuel cell system is in a heat preservation state, the temperature of the fluid at the outlet of the first heat exchange side of the water evaporator is maintained within a preset temperature range; or The temperature change rate of the fluid at the outlet of the first heat exchange side of the water evaporator does not exceed a preset value.

10. The control method of the fuel cell tail gas recovery system according to claim 7, characterized in that: The step of adjusting the amount of compressed gas introduced to change the gas flow rate of the first branch flow comprises: When the power output of the fuel cell system increases and the temperature change rate of the fluid at the outlet of the first heat exchange side exceeds a preset value, if the temperature of the fluid at the outlet of the first heat exchange side rises, the change rate of the compressed gas flow rate is slowed down; if the temperature of the fluid at the outlet of the first heat exchange side drops, the change rate of the compressed gas flow rate is accelerated; When the power output of the fuel cell system decreases and the temperature change rate of the fluid at the outlet of the first heat exchange side exceeds a preset value, if the fluid temperature at the outlet of the first heat exchange side rises, the change rate of the compressed gas flow rate is accelerated; if the fluid temperature at the outlet of the first heat exchange side decreases, the change rate of the compressed gas flow rate is slowed down.

Images