Fuel cell system with low attenuation rate and control method

Abstract

The invention relates to a fuel cell system with a low attenuation rate and a control method. The fuel cell system comprises an electric pile, a fuel gas side and an air side, in the fuel gas side, fuel enters the electric pile after being mixed and preheated, and a fuel outlet of the electric pile is connected with the combustor; one path of air in the air side is preheated and mixed with the other path of air passing through the chromium absorber to enter the electric pile together, an air outlet of the electric pile is connected with the combustor, and the chromium absorber is connected with the heater; the chromium absorber is additionally arranged at an air inlet of the galvanic pile, and the voltage output by the galvanic pile is controlled by changing the airspeed ratio and the working temperature of the chromium absorber, so that the attenuation of the galvanic pile is relieved. The cold air bypass is added to prevent overtemperature of an electric pile inlet, and when the temperature of the electric pile inlet exceeds a required value, the cold bypass butterfly valve, the rotating speed of the fan and the power of the electric heating furnace are sequentially changed, the actual temperature of the electric pile inlet is reduced, and overtemperature of the electric pile is prevented.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fuel cell technology, in particular to a fuel cell system with low decay rate and a control method. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] The fuel cell uses components containing chromium alloy inside, under high temperature conditions, these components have a protective chromium oxide shell on the surface. As the stack operates, chromium (Cr) accumulates on the air side (cathode), and the accumulation of chromium causes the performance of the stack to decay, i.e. chromium poisoning.

[0004] The prior art sets a chromium absorption material on the outer surface of the cathode electrode of the stack, so that the chromium in the cathode gas is deposited on the chromium absorption material, thereby capturing the chromium and alleviating the problem of stack performance decay.

[0005] The chromium absorption material needs to be at a certain temperature to achieve ideal performance, and the chromium absorption material is integrated inside the stack, which limits the working temperature of the stack and makes it difficult to control the temperature of the chromium absorption material to achieve ideal performance. SUMMARY

[0006] To solve the technical problems in the background art, the present application provides a fuel cell system with low decay rate and a control method, which increases a chromium absorber at the air inlet of the stack, controls the voltage of the stack by changing the air speed ratio and working temperature of the chromium absorber, thereby reducing the decay rate of the stack; at the same time, by increasing the bypass of cold air to prevent the temperature of the stack inlet from overheating, and by sequentially changing the air bypass valve, fan speed and working temperature of the chromium absorber when the temperature of the stack inlet exceeds the required value, the temperature of the stack inlet is reduced to prevent the stack from overheating.

[0007] To achieve the above purpose, the present application adopts the following technical solutions: The first aspect of the present application provides a fuel cell system with low decay rate, comprising a stack, a gas side and an air side; The gas side, specifically: the fuel is mixed and preheated before entering the stack, and the fuel outlet of the stack is connected to the burner; The air side, specifically: one way of air is preheated and mixed with another way of air passing through the chromium absorber before entering the stack together, the air outlet of the stack is connected to the burner, and the chromium absorber is connected to the heater; by changing the air speed ratio and working temperature of the chromium absorber, the voltage output by the stack is controlled to alleviate the decay of the stack.

[0008] Further, the fuel is mixed and preheated before entering the stack, specifically, the external fuel enters the mixer B, and is sequentially passed through the mixer B, the fuel heat exchanger and the stack under the driving of the circulating pump.

[0009] Further, the fuel outlet of the stack is connected to the combustor, specifically, the fuel at the outlet of the stack is used as a heat source to preheat the fuel entering the stack by the fuel heat exchanger, and the fuel after heat release is divided into two paths, one of which enters the combustor to participate in combustion, and the other returns to the circulating pump to continue circulation.

[0010] Further, one path of air is preheated and mixed with another path of air passing through the chromium absorber before entering the stack, specifically, the external cold air is pressurized by the fan, and is passed through at least two air circuits, one of which enters the mixer A through the main path control valve and the air preheater, and the other enters the mixer A through the bypass control valve, and the two paths of air are mixed in the mixer A before entering the stack.

[0011] Further, the combustor has an external fuel inlet for igniting combustion by introducing external fuel during startup, and also has a tail gas outlet connected to the air preheater, which uses the tail gas of the combustor as a heat source to preheat the main path air.

[0012] Further, by changing the air speed ratio and working temperature of the chromium absorber, the voltage output by the stack is controlled to alleviate the decay of the stack, specifically: When the voltage output by the stack is less than the required value, the working temperature of the chromium absorber is maintained within a set range by controlling the power of the heater, and the air flow rate through the chromium absorber is controlled to increase the air speed ratio, so as to improve the efficiency of the chromium absorber and alleviate the decay of the stack; Or, When the voltage output by the stack is less than the required value, the air speed ratio is maintained within a set range by controlling the air flow rate through the chromium absorber, and the working temperature of the chromium absorber is gradually increased by controlling the power of the heater, so as to improve the efficiency of the chromium absorber and alleviate the decay of the stack.

[0013] The second aspect of the present application provides a control method of a fuel cell system with low decay rate, comprising the following steps: The fan and the circulating pump are started to introduce external fuel into the combustor, the combustor is ignited and burned by the pre-set air-fuel ratio, and the fuel switching, the stack power generation and the chromium absorber starting are sequentially performed according to the temperature of the stack; After the chromium absorber is started, the voltage output by the stack is controlled by changing the air speed ratio and / or the working temperature of the chromium absorber; When the air inlet temperature of the stack exceeds the set upper limit value, the opening degree of the bypass control valve, the rotating speed of the fan and the working temperature of the chromium absorber are adjusted in sequence to reduce the air inlet temperature of the stack below the upper limit value, so as to maintain the stable operation state of the fuel cell system.

[0014] Further, according to the temperature of the electric pile, the fuel switching, the electric pile power generation and the chromium absorber starting are sequentially performed, including the following steps: The electric pile is heated to a set temperature T1, the burner outlet temperature is maintained within a set range, the amount of external fuel entering the burner is gradually reduced, and the amount of fuel entering the mixer B is gradually increased; The electric pile continues to be heated to a set temperature T2, fuel and air enter the electric pile for power generation; The electric pile continues to be heated to a set temperature T3, the heater is started, the chromium absorber is heated to a set working temperature, and the chromium absorber is started.

[0015] Further, by changing the air speed ratio and working temperature of the chromium absorber, the voltage output by the electric pile is controlled, and the electric pile attenuation is alleviated, specifically: When the electric pile output voltage is less than the required value, the working temperature of the chromium absorber is maintained within a set range by controlling the power of the heater, and the air flow through the chromium absorber is controlled to increase the air speed ratio, so as to improve the efficiency of the chromium absorber and alleviate the electric pile attenuation; Or, When the electric pile output voltage is less than the required value, the air flow through the chromium absorber is controlled to maintain the air speed ratio within a set range, and the power of the heater is controlled to gradually increase the working temperature of the chromium absorber, so as to improve the efficiency of the chromium absorber and alleviate the electric pile attenuation.

[0016] Further, the opening of the bypass control valve, the speed of the fan and the working temperature of the chromium absorber are sequentially adjusted to reduce the electric pile air inlet temperature to below the upper limit value, including the following steps: When the electric pile air inlet temperature exceeds the upper limit value, the fan maintains the current speed, the chromium absorber maintains the current working temperature, and the opening of the bypass control valve is gradually increased until the electric pile air inlet temperature is reduced to below the upper limit value; If the opening of the bypass control valve reaches the maximum and the electric pile air inlet temperature still exceeds the upper limit value, the current opening of the bypass control valve is maintained, the speed of the fan is gradually increased until the electric pile air inlet temperature is reduced to below the upper limit value; If the speed of the fan reaches the maximum and the electric pile air inlet temperature still exceeds the upper limit value, the opening of the bypass control valve and the speed of the fan are maintained, and the power of the heater is gradually reduced until the electric pile air inlet temperature is reduced to below the upper limit value.

[0017] Compared with the prior art, the above one or more technical solutions have the following beneficial effects: 1. Existing technologies integrate chromium absorbers within the fuel cell stack, resulting in their operating temperature being limited by the stack temperature. This makes it difficult to control the temperature of the chromium absorber to achieve its ideal performance. Considering the conflict between the global thermal management of the fuel cell stack and the local temperature requirements of the chromium absorber, and the fact that the performance of the chromium absorber is highly temperature-dependent, while the stack temperature is the result of compromises among multiple factors, making optimization for a single function difficult, embedding the chromium absorber within the stack simplifies the structure but sacrifices the flexibility of temperature control. Therefore, this solution adds a chromium absorber before the fuel cell stack, using a separate heater to control its operating temperature, maintaining it within a set temperature range. This allows for the continuous absorption of chromium from the air entering the fuel cell stack, ensuring reliable absorption efficiency and achieving its ideal performance.

[0018] 2. During system operation, the output voltage of the fuel cell stack is adjusted by changing the space velocity ratio and operating temperature of the chromium absorber, thereby reducing fuel cell stack degradation. Specifically, the temperature of the chromium absorber is first controlled within a set range, and then the space velocity ratio is increased; or the space velocity ratio is first controlled within a set range, and then the temperature is increased, ensuring that the efficiency of the chromium absorber gradually increases to the ideal state, thereby reducing fuel cell stack degradation.

[0019] 3. Considering the chromium absorber's proximity to the fuel cell stack's air inlet, which could potentially interfere with the stack temperature, a bypass of unpreheated cold air is added to the air circuit. When the stack inlet temperature exceeds the limit, the opening of the cold air bypass valve, the fan speed, and the heater power are controlled in stages to reduce the actual stack inlet temperature and prevent overheating. During this process, the bypass air volume is adjusted first, followed by increasing the total air volume, and finally, the chromium absorber's operating temperature is reduced. This staged control method achieves an optimal trade-off between safety, efficiency, and component lifespan in the fuel cell system. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0021] Figure 1 This is a schematic diagram of the fuel cell system architecture provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the control process of the chromium absorber during fuel cell control provided in one or more embodiments of the present invention; Figure 3 This is a schematic diagram illustrating the control of the fuel cell stack output voltage based on the air velocity ratio or temperature of the chromium absorber during fuel cell control, provided by one or more embodiments of the present invention. Figure 4is a schematic diagram of the fuel cell control during the control of the stack operation according to the limit value of the stack inlet temperature provided by one or more embodiments of the present application; Figure 5 is a schematic diagram of the fuel cell system architecture provided by embodiment two of the present application.

[0022] In the figure: 1 (first stage) stack, 2 second stage stack, 101 mixer B, 102 fuel heat exchanger, 103 burner, 104 circulating pump, 201 fan, 202 butterfly valve A, 203 butterfly valve B, 2031 butterfly valve C, 204 chromium absorber (A), 2041 chromium absorber B, 205 mixer A, 2051 mixer C, 301 air preheater. DETAILED DESCRIPTION

[0023] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0024] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0025] It should be noted that the terms used herein are merely for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form, and in addition, it should be understood that when the terms "comprise" and / or "include" are used in the present specification, they indicate the presence of the features, steps, operations, devices, components and / or combinations thereof.

[0026] Term explanation: Chromium poisoning: The bipolar plate (BPP) of a fuel cell is usually made of stainless steel, which contains chromium. In the operating environment of acid, high temperature and potential fluctuation, stainless steel will corrode and release Cr³⁺ / Cr 6 ⁺ ions. The dissolved chromium ions migrate to the cathode and combine with the platinum (Pt) catalyst, covering the active sites or changing the electronic structure of the catalyst, resulting in a decrease in oxygen reduction reaction (ORR) activity and a decrease in battery performance.

[0027] Chromium absorption material, used to capture and neutralize chromium pollutants generated during battery operation, common metal oxides (such as titanium dioxide TiO2, cerium oxide CeO2, manganese oxide MnO2, etc.), through surface adsorption or chemical reaction to fix chromium ions. Ion exchange resin (such as sulfonated polymer), capture Cr³⁺ by ion exchange. Carbon-based materials (such as activated carbon, graphene), use high specific surface area to physically adsorb chromium. Composite coating (such as TiO2-CeO2 mixed coating).

[0028] The prior art chromium absorption material needs to be under certain temperature conditions to exert ideal performance, and for the problem of chromium poisoning, the prior art integrates the chromium absorption material in the stack, which limits the working temperature of the stack and makes it difficult to control the temperature of the chromium absorption material to exert ideal performance.

[0029] The reason for this problem is that there is a conflict between the global thermal management of the stack and the local temperature requirement of the chromium absorption material, the performance of the chromium absorption material is highly dependent on the temperature, and the stack temperature is the result of multiple factors compromising, which is difficult to optimize for a single function. Embedding the chromium absorption material in the stack inside simplifies the structure, but sacrifices the flexibility of temperature control.

[0030] Therefore, the following embodiments give a fuel cell system with low attenuation rate and a control method, for the problem of chromium poisoning, a chromium absorber is added at the air inlet of the stack, by changing the air speed ratio and working temperature of the chromium absorber, the stack voltage is controlled, thereby reducing the stack attenuation rate; At the same time, by increasing the cold air bypass to prevent the stack inlet temperature from overheating, and when the stack inlet temperature exceeds the required value, the air bypass valve, fan speed and chromium absorber working temperature are changed in turn to reduce the stack inlet temperature and prevent the stack from overheating.

[0031] Embodiment one: The fuel cell system in this embodiment includes a stack, a fuel gas side and an air side.

[0032] The fuel gas side adopts a medium temperature cycle mode, and the main working process is: the fuel enters the fuel heat exchanger for preheating and then enters the stack for power generation, the high-temperature fuel at the stack outlet enters the fuel heat exchanger and is divided into two parts, one part enters the circulating pump, and the circulating fuel mixed with the inlet fuel enters the heat exchanger, the other part enters the TGB combustion, and the combustion high-temperature tail gas enters the air preheater to provide heat source for preheating cold air. The tail gas at the outlet of the hot side of the air preheater is directly discharged from the system.

[0033] The main working process of the air side is: the air is divided into two ways, the main air enters the air preheater for temperature rise, and the heated air enters the chromium absorber for Cr element absorption, wherein the chromium absorber is externally heated by an electric furnace for temperature control, and the gas at the outlet of the chromium absorber enters the mixer A to mix with the bypass air to reach the specified temperature and then enters the stack first. The hot air at the outlet of the stack directly enters the burner to provide oxygen for the combustion reaction.

[0034] TGB combustion refers to Tail Gas Burner (tail gas burner) or Thermal Gas Burner (thermal gas burner).

[0035] In this embodiment, the fuel gas side structure of the fuel cell system is as shown in Figure 1As shown, the fuel enters the mixer B101, and under the drive of the circulating pump 104, sequentially passes through the mixer B101, the fuel heat exchanger 102 and the stack 1, the unreacted fuel with residual heat, and after passing through the fuel heat exchanger 102 again, is divided into two paths, one of which enters the combustor 103 to participate in combustion, and the other returns to the circulating pump 104 to continue circulation.

[0036] In this embodiment, the part of the fuel entering the combustor 103 to participate in combustion needs to supplement part of the fresh fuel when necessary.

[0037] In this embodiment, the fuel heat exchanger 102 uses the high-temperature fuel at the outlet of the stack 1 as a heat source to heat the fuel entering the stack 1, and the high-temperature fuel after releasing heat enters the combustor 103 to participate in combustion and returns to the circulating pump 104 to continue circulation.

[0038] In this embodiment, the air side structure of the fuel cell system is as shown in the figure. Figure 1 As shown, the ambient air is divided into two paths under the action of the fan 201, one of which sequentially passes through the butterfly valve A202, the air preheater 301 and the chromium absorber 204 to enter the mixer A205, and the other air enters the mixer A205 through the butterfly valve B203, the two parts of air enter the stack 1 through the mixer A205, and the exhaust air enters the combustor 103.

[0039] In this embodiment, the air preheater 301 uses the exhaust gas of the combustor 103 as a heat source to heat the air entering the stack 1, and two sets of butterfly valves are used to control the two paths of air entering the stack 1, so that the air enters the stack 1 after being preheated and Cr absorbed, or directly enters the stack 1, for adjusting the inlet temperature of the stack 1.

[0040] In this embodiment, the chromium absorber 204 is provided with a heater, for example, an electric heating furnace, for controlling the working temperature of the chromium absorber 204 to ensure the reliable performance of Cr absorption.

[0041] In this embodiment, the chromium absorber 204 is similar to the Cr absorption material in the prior art, both of which intercept the chromium ions before they reach the catalyst inside the stack through chemical or physical adsorption, and the present scheme is arranged as a separate device before the inlet of the stack, which is conducive to subsequent separate temperature control.

[0042] The present scheme arranges the chromium absorber in front of the inlet of the stack on the air side. The cold air flows through the air preheater to be heated, and the Cr element-containing substances volatilized from the surface of the stainless steel and the metal containing Cr element under high-temperature conditions are mixed into the high-temperature air. After the high-temperature air passes through the chromium absorber, the Cr element-containing substances in the air will be absorbed by the chromium absorber, which can prevent the stack from decaying.

[0043] Wherein, the electric heating furnace is placed outside the chromium absorber to control the temperature of the absorber, maintain the chromium absorber in the range of 300-900℃, continuously absorb the Cr substance in the air entering the fuel cell stack, and control the stack voltage (required to be greater than the safety threshold Vmin) by adjusting the temperature of the chromium absorber or the air speed ratio, the specific control method is as shown in Figures 2-4

[0044] As shown in Figure 2 The fan and the circulating pump receive the enable signal, and the air in the fuel cell system is circulated by setting the rotating speed of the fan and the circulating pump. The burner is supplied with fuel, and the burner is ignited by the pre-set air-fuel ratio to provide energy for the entire fuel cell system. The fuel cell system is heated to the set temperature T1, fuel switching is performed, the fuel amount supplied to the burner is reduced under the condition that the actual value of the outlet temperature of the burner is consistent with the required value, and the fuel amount supplied to the mixer B is gradually increased. The fuel cell system is heated to the set temperature T2, and the fuel and air enter the stack to generate electricity. The fuel cell system is heated to the set temperature T3, the electric heating furnace is started to heat the chromium absorber to T3, and the chromium absorber starts to work to monitor the actual value of the outlet voltage of the stack.

[0045] At this time, the fuel cell system and the chromium absorber have completed the start and entered the normal running state, and the stack voltage is controlled by adjusting the temperature of the chromium absorber or the air speed ratio, as shown in Figure 3

[0046] As shown in Figure 3 The stack voltage is controlled by adjusting the temperature of the chromium absorber, including the following steps: When the output voltage of the stack is less than the required value, the temperature before the electric heating furnace is monitored, the working temperature of the chromium absorber is maintained in the set range by controlling the power of the electric heating furnace, and during this period, the Cr element absorption rate is improved by gradually increasing the air speed ratio of the chromium absorber, and the output voltage of the stack is indirectly improved. When the output voltage of the stack is not less than the required value, the temperature at the outlet and the inlet of the mixer A is monitored to determine the actual value of the air temperature entering the stack, and it is ensured that the air entering the stack does not exceed the set range.

[0047] As shown in Figure 3 The stack voltage is controlled by adjusting the air speed ratio of the chromium absorber, including the following steps: When the output voltage of the stack is less than the required value, the air speed ratio of the chromium absorber is maintained in the set range, and during this period, the air temperature before the electric heating furnace is obtained, the working temperature of the chromium absorber is improved by gradually increasing the power of the electric heating furnace, the Cr element absorption rate is indirectly improved, and the output voltage of the stack is improved.​​ When the stack output voltage is not less than the required value, the actual value of the air temperature entering the stack is determined by monitoring the temperature at the outlet and the inlet of the mixer A, to ensure that the air entering the stack does not exceed the set range.

[0048] In this embodiment, the space velocity ratio (SV) is a parameter for measuring the ability of the catalyst to treat the gas, and represents the volume flow rate of the gas per unit time through a unit volume of catalyst, which can be adjusted by adjusting the gas flow rate through the chromium absorber, i.e., adjusting the air supply amount of the fan 201 or the opening degree of the butterfly valve A 202. During operation, the air flow rate output by the fan 201 is the upper limit of the air flow rate of the entire fuel cell system, so the opening degree of the butterfly valve A 202 is adjusted to change the space velocity ratio.

[0049] During actual application, any one set of control logic can be selected according to the actual situation. The temperature of the chromium absorber can be controlled within the set range first, and then the space velocity ratio can be increased to improve the efficiency of the chromium absorber; or the space velocity ratio can be controlled within the set range first, and then the temperature of the chromium absorber can be increased. Regardless of the method adopted, the efficiency of the chromium absorber gradually increases to the ideal state, and the actual value of the air temperature entering the stack is continuously monitored to ensure that the air entering the stack does not exceed the set range.

[0050] The air temperature entering the stack is continuously monitored to ensure that the air entering the stack does not exceed the set range, as shown in FIG. 6, including the following steps: Figure 4 When the stack air inlet temperature exceeds the upper limit value, the opening degree of the butterfly valve B 203 is increased under the condition that the total amount of air entering is unchanged (the speed of the fan 201 is unchanged), and the air entering the mixer A 205 through the butterfly valve B 203 is not preheated, so that the cold air flow rate entering the mixer A 205 can be increased and the temperature of the stack air inlet can be reduced. If the stack air inlet temperature is reduced to below the upper limit value at this time, the fuel cell system enters a stable operating state. When the opening degree of the butterfly valve B 203 reaches the maximum, if the stack air inlet temperature still exceeds the upper limit value at this time, the opening degree of the butterfly valve B 203 is maintained at the maximum, and the speed of the fan 201 is increased, so that the cold air flow rate entering the mixer A 205 is increased and the temperature of the stack air inlet is further reduced by increasing the total air flow rate of the system. If the stack air inlet temperature is reduced to below the upper limit value at this time, the fuel cell system enters a stable operating state. ​When the rotation speed of the blower 201 reaches the maximum, if the air inlet temperature of the stack is still higher than the upper limit value, the opening of the butterfly valve B203 and the rotation speed of the blower 201 are maintained, the power of the electric heater is reduced, the temperature of the chromium absorber 204 is reduced, and the temperature of the air inlet of the stack is further reduced. If the air inlet temperature of the stack is reduced to below the upper limit value, the fuel cell system enters a stable operation state.

[0051] In this embodiment, the fuel cell system is maintained in a stable operation state by step-by-step control. When the chromium absorber is maintained at a high-efficiency operating point, the temperature required by the chromium absorber 204 may exceed the temperature limit of the stack 1. At this time, the bypass air amount of the mixer A 205 is first increased, and part of the cold air is introduced into the stack 1 to attempt to reduce the temperature. If the temperature cannot be reduced, the total air amount provided by the blower 201 is increased while the heating device remains unchanged. If the temperature still cannot be reduced, the temperature of the chromium absorber is reduced.

[0052] The bypass air amount is adjusted first. Since the bypass air is cold air that has not been heated, it can directly enter the stack to quickly and locally reduce the temperature, and has the least disturbance to the overall system conditions (such as pressure and humidity). The cold air directly targets the hot spot for temperature reduction, without the need to change the operating state of other components, avoiding the immediate increase in total air amount (which may affect the efficiency of the stack reaction or the humidity balance).

[0053] The total air amount is increased second. If the bypass air amount has reached the upper limit and the temperature still cannot be reduced, it indicates that the overall heat generation of the stack is too high, and global heat dissipation is required. Increasing the total air amount can improve the convective heat dissipation capacity, but the oxygen supply needs to be balanced (to avoid excessive dilution of the reaction gas), and the high-efficiency operation of the chromium absorber is crucial to the performance of the system (such as pollutant treatment). Therefore, preferential adjustment of the air amount can reduce interference with the chromium absorber.

[0054] Finally, the temperature of the chromium absorber is reduced. Reducing the temperature may sacrifice its efficiency or emission treatment capacity, but at this time, after two rounds of control, the stack inlet temperature still cannot be reduced, and the safety of the stack needs to be prioritized to avoid overheating and damaging the stack (the service life and safety of the stack are higher than the efficiency of the chromium absorber).

[0055] This scheme adds a chromium absorber in front of the stack of the fuel cell, which can absorb the Cr-containing substances volatilized from the surface of stainless steel and metals containing Cr elements under high temperature conditions, prevent the decay of the stack, and protect the performance of the stack. A heater, such as an electric heater, is provided outside the chromium absorber. By controlling the temperature of the heater, the chromium absorber is maintained within the range of 300-900°C, continuously absorbs Cr substances in the air entering the fuel cell stack, and ensures the reliability of the absorption efficiency of the chromium absorber.

[0056] By adjusting the space velocity ratio and operating temperature of the chromium absorber, the voltage output by the stack is adjusted, and the decay of the stack is reduced.

[0057] Considering that the chromium absorber's proximity to the fuel cell stack's air inlet could affect the stack temperature, a bypass of unpreheated cold air was added to the air circuit. When the stack inlet temperature exceeds the required value, the opening of the cold air bypass valve, the fan speed, and the heater power are controlled in stages to reduce the actual stack inlet temperature, preventing overheating and achieving an optimal trade-off between safety, efficiency, and component lifespan in the fuel cell system.

[0058] Example 2: This embodiment presents another fuel cell system architecture, which is consistent with... Figure 1 The main difference is that it adopts a two-stage stack arrangement, with the gas side connected in parallel and the air side connected in series.

[0059] like Figure 5 As shown, the system includes a primary fuel cell stack 1 and a secondary fuel cell stack 2. Fuel enters the mixer B101 and is preheated by the circulation pump 104, passing through the mixer B101 and the fuel heat exchanger 102 in sequence. The preheated fuel then enters the primary fuel cell stack 1 and the secondary fuel cell stack 2 respectively. The unreacted fuel with residual heat at the outlets of the two stacks passes through the fuel heat exchanger 102 again and is divided into two paths. One path enters the burner 103 to participate in combustion, while the other path returns to the circulation pump 104 to continue circulating.

[0060] Outside air is divided into three streams by the fan 201. One stream passes through butterfly valve A202, air preheater 301 and chromium absorber A204 in sequence and enters mixer A205. Another stream of air enters mixer A205 through butterfly valve B203. The third stream of air enters mixer C2041 through butterfly valve C2051. Mixer A205 mixes two streams of air and enters the first-stage fuel cell stack 1. The exhaust air enters chromium absorber B2041 and mixes with the third stream of air before entering the second-stage fuel cell stack 2. The exhaust air from the second-stage fuel cell stack 2 enters burner 103.

[0061] The main working process on the air side is as follows: cold air is divided into three paths. The main path air enters the air preheater for heating. After heating, the hot air enters the chromium absorber A204 for chromium absorption. The chromium absorber A204 is externally heated by an electric furnace 1, which controls the temperature of the chromium absorber A204. The gas exiting the chromium absorber A204 enters the mixer A and mixes with one bypass air path. After reaching the specified temperature, the gas first enters the primary fuel cell stack. The hot air exiting the primary fuel cell stack enters the chromium absorber B for chromium absorption. Similarly, the chromium absorber B2041 is externally heated by an electric furnace, which controls its temperature. The gas exiting the chromium absorber B enters the mixer C and mixes with another bypass air path. After reaching the specified temperature, the gas first enters the secondary fuel cell stack. The air exiting the secondary fuel cell stack directly enters the burner to provide oxygen for the combustion reaction.

[0062] The main working process of the gas side is as follows: the fuel is preheated by the fuel heat exchanger and then divided into two parts, which are respectively introduced into the first-stage and second-stage electric piles. The high-temperature fuel gas after the electric pile generation is mixed and then introduced into the fuel heat exchanger, one part of which is introduced into the circulating pump, and the fuel circulating back is mixed with the inlet fuel and then introduced into the heat exchanger, and the other part is introduced into the TGB for combustion. The high-temperature exhaust gas of the combustion is introduced into the air preheater to provide a heat source for preheating the cold air. The exhaust gas at the outlet of the hot side of the air preheater is directly discharged from the system.

[0063] In the fuel cell system of the embodiment, the fuel preheated by the fuel heat exchanger 102 is respectively introduced into the first-stage and second-stage electric piles. The air side part is additionally provided with an air loop which does not pass through the air preheater 301 after the fan and is introduced into the mixer C2051. The preheating mode is achieved by directly mixing the outlet air of the first-stage electric pile 1 with the cold air from the fan in the mixer C2051 after passing through the chromium absorber B2041. In the specific control process, the electric pile voltage is adjusted by adjusting the temperature or air speed ratio of the chromium absorber, and the two electric piles of the embodiment correspond to the respective chromium absorbers. Therefore, the electric pile voltage is adjusted by adjusting the temperature or air speed ratio of the chromium absorber.

[0064] During the electric pile operation, the inlet temperature of the first-stage and second-stage electric piles is respectively taken as a target value, and the opening degree of the butterfly valve on the corresponding air loop is preferentially adjusted. The butterfly valve B203 adjusts the inlet temperature of the first-stage electric pile, and the butterfly valve C2031 adjusts the outlet temperature of the second-stage electric pile. If the opening degree reaches the limit and still cannot reduce the temperature at the inlet of the respective electric pile, the speed of the fan 201 is increased under the condition that the opening degrees of the butterfly valve B203 and the butterfly valve C2031 are unchanged. If the inlet temperature of the electric pile is still overheated, the power of the external electric heater of the corresponding chromium absorber is reduced.

[0065] Embodiment three The control method of the fuel cell system with a low decay rate comprises the following steps: The fan and the circulating pump are started, the external fuel is introduced into the combustor, the combustor is ignited and burned by the pre-set air-fuel ratio, the fuel switching, electric pile generation and chromium absorber starting are sequentially performed according to the temperature of the electric pile; After the chromium absorber is started, the voltage output by the electric pile is controlled by changing the air speed ratio and / or working temperature of the chromium absorber; When the inlet temperature of the electric pile air exceeds the set upper limit value, the opening degree of the bypass control valve, the speed of the fan and the working temperature of the chromium absorber are sequentially adjusted to reduce the inlet temperature of the electric pile air to below the upper limit value, so as to maintain the stable operation state of the fuel cell system.

[0066] As a further embodiment, the fuel switching, electric pile generation and chromium absorber starting are sequentially performed according to the temperature of the electric pile, which comprises the following steps: The stack is heated to a set temperature T1, the burner outlet temperature is maintained within a set range, the amount of external fuel supplied to the burner is gradually reduced, and the amount of fuel supplied to the mixer B is gradually increased; The stack continues to be heated to a set temperature T2, fuel and air enter the stack to generate electricity; The stack continues to be heated to a set temperature T3, the heater is started to heat the chromium absorber to a set operating temperature, and the chromium absorber is started.

[0067] As a further embodiment, by changing the air speed ratio and operating temperature of the chromium absorber, the voltage output of the stack is controlled, and the stack attenuation is alleviated, specifically: When the stack output voltage is less than the required value, the operating temperature of the chromium absorber is maintained within a set range by controlling the power of the heater, and the air speed ratio is increased by controlling the air flow through the chromium absorber to improve the efficiency of the chromium absorber and alleviate the stack attenuation; Or, when the stack output voltage is less than the required value, the air speed ratio is maintained within a set range by controlling the air flow through the chromium absorber, and the operating temperature of the chromium absorber is gradually increased by controlling the power of the heater to improve the efficiency of the chromium absorber and alleviate the stack attenuation.

[0068] As a further embodiment, the opening of the bypass control valve, the speed of the fan, and the operating temperature of the chromium absorber are adjusted in sequence to reduce the stack air inlet temperature below the upper limit value, including the following steps: When the stack air inlet temperature exceeds the upper limit value, the fan maintains the current speed, the chromium absorber maintains the current operating temperature, and the opening of the bypass control valve is gradually increased until the stack air inlet temperature is reduced below the upper limit value; If the opening of the bypass control valve reaches the maximum and the stack air inlet temperature still exceeds the upper limit value, the current opening of the bypass control valve is maintained, the speed of the fan is gradually increased until the stack air inlet temperature is reduced below the upper limit value; If the speed of the fan reaches the maximum and the stack air inlet temperature still exceeds the upper limit value, the opening of the bypass control valve and the speed of the fan are maintained, and the power of the heater is gradually reduced until the stack air inlet temperature is reduced below the upper limit value.

[0069] The prior art integrates the chromium absorption material inside the stack, which limits the working temperature of the chromium absorption material to the temperature of the stack, and it is difficult to control the temperature of the chromium absorption material to make it work ideally. Considering that there is a conflict between the global thermal management of the stack and the local temperature requirement of the chromium absorption material, the performance of the chromium absorption material is highly dependent on the temperature, and the temperature of the stack is the result of multiple factors compromise, and it is difficult to optimize for a single function, embedding the chromium absorption material inside the stack simplifies the structure, but sacrifices the flexibility of temperature control. Therefore, the present scheme adds a chromium absorber in front of the fuel cell stack, controls the working temperature of the chromium absorber through a separate heater, keeps it within a certain temperature range, continuously absorbs Cr substances in the air entering the fuel cell stack, ensures the reliability of the absorption efficiency of the chromium absorber, and thus plays its ideal performance.

[0070] During the operation of the system, the voltage output of the stack is adjusted by changing the space velocity ratio and working temperature of the chromium absorber, and the attenuation of the stack is reduced. That is, first control the temperature of the chromium absorber within a certain range, and then increase the space velocity ratio; or first control the space velocity ratio within a certain range, and then increase the temperature, ensure that the efficiency of the chromium absorber gradually rises to an ideal state, thereby reducing the attenuation of the stack.

[0071] Considering that the chromium absorber is too close to the air inlet of the stack, it may interact with the temperature of the stack. By adding cold air bypass that does not pass through preheating in the air circuit, when the inlet temperature of the stack exceeds the limit value, the opening degree of the cold air bypass valve, the speed of the fan and the power of the heater are controlled step by step to reduce the actual temperature of the stack inlet and prevent the stack from overheating. During this period, the bypass air amount is adjusted first, the total air amount is increased secondly, and finally the working temperature of the chromium absorber is reduced, forming a step-by-step control method to achieve the best trade-off between safety, efficiency and component life of the fuel cell system.

[0072] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A low decay rate fuel cell system, characterized by, The fuel cell system comprises a fuel cell, a fuel side and an air side. The fuel side comprises: the fuel is mixed and preheated before entering the fuel cell, and the fuel outlet of the fuel cell is connected to the combustor. The air side comprises: one air is preheated and mixed with another air passing through the chromium absorber before entering the fuel cell, and the air outlet of the fuel cell is connected to the combustor, and the chromium absorber is connected to the heater.

2. The low decay rate fuel cell system of claim 1, wherein, The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell.

3. The low decay rate fuel cell system of claim 1, wherein, The fuel outlet of the fuel cell is connected to the combustor, and the fuel outlet of the fuel cell is connected to the combustor.

4. The low decay rate fuel cell system of claim 1, wherein, The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell.

5. The low decay rate fuel cell system of claim 1, wherein, The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell.

6. The low decay rate fuel cell system of claim 1, wherein, The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell. The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell. The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell. The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell.

7. A control method for a low-deterioration-rate fuel cell system according to any one of claims 1 to 6, characterized by The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell. The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell. The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell. The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell.

8. The control method of a low-damping-rate fuel cell system according to claim 7, characterized by, The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell. The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell. The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell. The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell. The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell. The fuel is mixed and preheated before entering the fuel cell, and the fuel is mixed and preheated before entering the fuel cell. 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The stack continues to warm up to the set temperature T2, fuel and air enter the stack to generate electricity; The stack continues to warm up to the set temperature T3, the heater starts to warm up the chromium absorber to the set working temperature, and the chromium absorber starts to work.

9. The control method of a low-damping-rate fuel cell system according to claim 7, characterized by, By changing the air speed ratio and working temperature of the chromium absorber, the voltage of the stack output is controlled, and the stack attenuation is relieved, specifically: When the stack output voltage is less than the required value, the working temperature of the chromium absorber is maintained within the set range by controlling the power of the heater, and the air speed ratio is increased by controlling the air flow through the chromium absorber to improve the efficiency of the chromium absorber and relieve the stack attenuation. Or; When the stack output voltage is less than the required value, the air speed ratio is maintained within the set range by controlling the air flow through the chromium absorber, and the working temperature of the chromium absorber is gradually increased by controlling the power of the heater to improve the efficiency of the chromium absorber and relieve the stack attenuation.

10. The control method of a low-damping-rate fuel cell system according to claim 7, characterized by, The opening of the bypass control valve, the speed of the fan and the working temperature of the chromium absorber are adjusted in turn to reduce the stack air inlet temperature to below the upper limit value, including the following steps: When the stack air inlet temperature exceeds the upper limit value, the fan maintains the current speed, the chromium absorber maintains the current working temperature, and the opening of the bypass control valve is gradually increased until the stack air inlet temperature is reduced to below the upper limit value; If the opening of the bypass control valve reaches the maximum, and the stack air inlet temperature still exceeds the upper limit value, the current opening of the bypass control valve is maintained, the speed of the fan is gradually increased until the stack air inlet temperature is reduced to below the upper limit value; If the speed of the fan reaches the maximum, and the stack air inlet temperature still exceeds the upper limit value, the opening of the bypass control valve and the speed of the fan are maintained, and the power of the heater is gradually reduced until the stack air inlet temperature is reduced to below the upper limit value.

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