CN114944502B - Control method for prolonging service life of solid oxide fuel cell system - Google Patents
Control method for prolonging service life of solid oxide fuel cell system Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
- H01M8/04746—Pressure; Flow
- H01M8/04753—Pressure; Flow of fuel cell reactants
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
- H01M8/04858—Electric variables
- H01M8/04865—Voltage
- H01M8/0488—Voltage of fuel cell stacks
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
- H01M8/04858—Electric variables
- H01M8/04895—Current
- H01M8/0491—Current of fuel cell stacks
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
- H01M2008/1293—Fuel cells with solid oxide electrolytes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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- Y02E60/50—Fuel cells
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Abstract
The invention discloses a control method for prolonging the service life of a solid oxide fuel cell system, wherein the output power of the system is the initial power when the system operates under the initial working condition, and the method comprises the following steps: when the output power of the system is reduced from the initial power to the first power, adopting a regulation and control mode for controlling the fuel flow; when the output power of the system is reduced from the initial power to the second power, adopting a regulation mode for controlling the fuel utilization rate; when the output power of the system is reduced from the initial power to the third power, adopting a regulation mode of cooperatively controlling the fuel utilization rate and the voltage; the initial power is greater than the first power, the first power is greater than the second power, and the second power is greater than the third power. When the system is subjected to performance attenuation after long-term operation and does not meet the design requirement, the corresponding regulation and control modes can be selected in different attenuation stages by using the method of the invention, so that the output power of the system can be recovered to the initial level, the service life of the system is prolonged, and the economical efficiency is improved.
Description
Technical Field
The invention belongs to the technical field of fuel cells, and particularly relates to a control method for prolonging the service life of a solid oxide fuel cell system.
Background
A Solid Oxide Fuel Cell (SOFC) belongs to a type of fuel cell, and can directly convert chemical energy contained in fuel into electric energy for output, so that the energy conversion efficiency is high. Meanwhile, compared with other fuel cells, the SOFC has the advantages of wide fuel applicability, low cost, less emission, environmental friendliness and the like, and has wide application prospects in the fields of distributed power generation, household cogeneration, mobile power stations and the like.
As shown in fig. 1, the SOFC power generation system generally includes core components such as an SOFC stack, an afterburner, a reformer, a heat exchanger, a fan, a fuel pump, and a power electronic control cabinet, and can provide stable power output to the outside. The SOFC cogeneration system additionally comprises a heating module which, while supplying electricity to the outside, additionally provides heat, typically in the form of hot water or steam.
After long-term operation, SOFC systems experience performance degradation, primarily manifested as a drop in system output voltage under comparable operating conditions. After performance attenuation occurs, the output power of the system can be correspondingly reduced, the output power after attenuation is lower than the initial design power, and the system can not meet the original design requirement. When the performance of the system is attenuated, the system can be repaired by replacing a new electric pile; however, the old pile still has better performance, and direct replacement can cause economic loss, thereby increasing the use cost of the SOFC system.
Disclosure of Invention
The present invention aims to improve at least to some extent at least one of the above technical problems.
In order to improve the above technical problems, the present invention provides a control method for prolonging the service life of a solid oxide fuel cell system, wherein the output power of the system when the system is operated under an initial working condition is the initial power, and the method comprises: when the output power of the system is reduced from the initial power to the first power, adopting a regulation mode for controlling the fuel flow; when the output power of the system is reduced from the initial power to the second power, adopting a regulation mode for controlling the fuel utilization rate; when the output power of the system is reduced from the initial power to the third power, adopting a regulation mode of cooperatively controlling the fuel utilization rate and the voltage; wherein the initial power is greater than the first power, the first power is greater than the second power, and the second power is greater than the third power. Therefore, when the performance of the system is attenuated after long-term operation and the original design requirement is not met, the method can select corresponding regulation and control modes in different attenuation stages, can compensate the power loss, and can recover the output power of the system to the initial level, thereby prolonging the service life of the system and improving the economical efficiency. In addition, the regulation and control mode can ensure that the system stably operates in a safe and efficient interval.
And when the attenuation is too large, the control method of the invention fails, the system does not meet the original design requirement, and the galvanic pile needs to be replaced in time or the external load is reduced, so the method provides a basis for judging whether the SOFC system is damaged.
In addition, the method can maintain the thermal balance state of the electric pile, thereby ensuring the working temperature of the electric pile to be stable and realizing quick response.
According to an embodiment of the present invention, the regulation manner for controlling the fuel flow includes: and controlling the fuel flow of the system to be unchanged, and increasing the working current of the system to ensure that the output power of the system is equal to the initial power.
According to an embodiment of the present invention, the regulation and control manner for controlling the fuel utilization rate includes: and maintaining the fuel utilization rate of the system unchanged, and proportionally increasing the fuel flow and the working current of the system to ensure that the output power of the system is equal to the initial power.
According to an embodiment of the present invention, the control manner of cooperatively controlling the fuel utilization rate and the voltage includes: firstly, adopting a regulation and control mode for controlling the fuel utilization rate, keeping the fuel utilization rate of the system unchanged, and proportionally increasing the fuel flow and the working current of the system until the voltage of the system is reduced to a safe working voltage critical value, wherein the output power of the system is lower than the initial power; and then, adopting a control mode of control voltage to maintain the voltage of the system as a safe working voltage critical value unchanged, and improving the fuel flow and working current of the system to ensure that the final output power of the system is the same as the initial power.
According to the embodiment of the invention, the first power is reduced by a first reduction compared with the initial power, and the first reduction is less than or equal to 5%; the amplitude reduction of the second power compared with the initial power is a second amplitude reduction, the second amplitude reduction is more than 5 percent, and is less than or equal to 12.5 percent; the third power is reduced by a third reduced amplitude compared with the initial power, and the third reduced amplitude is more than 12.5% and less than or equal to 15%.
According to an embodiment of the present invention, the control method is disabled when the output power of the system is reduced from the initial power to a fourth power; wherein the fourth power is less than the third power.
According to an embodiment of the present invention, the fourth power is reduced by a fourth reduction in amplitude compared to the initial power, and the fourth reduction in amplitude is greater than 15%.
According to an embodiment of the invention, the solid oxide fuel cell system comprises a fuel pump, a fuel preheater, a reformer, an SOFC stack, a controller, a blower, an air preheater, an afterburner and a heating module; the fuel pump is connected with the fuel preheater through a first pipeline, and a fuel valve is arranged on the first pipeline; the fuel preheater is connected with the reformer, and the reformer is connected with the SOFC stack; the fan is connected with the air preheater through a second pipeline, and the air preheater is connected with the SOFC stack; the SOFC stack is connected with the controller; the SOFC stack is connected with the afterburner, the afterburner is connected with the air preheater, the air preheater is connected with the fuel preheater, and the fuel preheater is connected with the heat supply module.
According to an embodiment of the invention, adjusting the fuel flow is achieved by adjusting the fuel valve; the fuel utilization rate, the working voltage and the working current are all adjusted by adjusting the controller.
According to an embodiment of the invention, an air valve is provided on the second conduit.
After the output power of the system is recovered by adopting different regulation and control modes, the heat load of the electric pile is rebalanced by regulating the air flow, so that the temperature of the electric pile is stable and unchanged. In particular, the air flow rate may be regulated by an air valve.
The heat load of the electric pile is calculated based on the energy conservation criterion in the electric pile, and the heat load of the electric pile is equal to the chemical energy of the fuel participating in the electrochemical reaction minus the electric energy output by the electric pile and the heat energy taken away by the gas flowing through the electric pile.
The chemical energy of the fuel participating in the electrochemical reaction is calculated according to the output current of the system to obtain the fuel quantity participating in the electrochemical reaction, and then the chemical energy of the fuel participating in the electrochemical reaction is determined according to the fuel type and the fuel quantity.
The heat energy carried away by the gas flowing through the pile comprises two parts of heat carried away by the fuel gas and heat carried away by the air.
The heat quantity carried away by the fuel gas is calculated by multiplying the temperature difference of the inlet and the outlet of the anode of the electric pile by the heat capacity of the fuel gas, wherein the heat quantity carried away by the fuel gas is equal to the flow rate of the fuel gas flowing through the anode of the electric pile.
The heat quantity taken away by the air is calculated by multiplying the air flow rate passing through the cathode of the electric pile by the temperature difference of the inlet and the outlet of the cathode of the electric pile and by the heat capacity of the air.
The balancing of the heat load of the electric pile means that the heat load of the electric pile is the same as the heat dissipated from the outer surface of the electric pile, the electric pile is in a heat balance state, and the temperature is stable and unchanged.
Drawings
Fig. 1 is a schematic diagram of a solid oxide fuel cell system in accordance with an embodiment of the present invention.
Detailed Description
Embodiments of the present application are described in detail below. The embodiments described below are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents used were not manufacturer-identified and were all commercially available conventional products.
The invention provides a control method for prolonging the service life of a solid oxide fuel cell system, wherein the output power of the system when the system operates under an initial working condition is the initial power, and the method comprises the following steps: when the output power of the system is reduced from the initial power to the first power, adopting a regulation mode for controlling the fuel flow; when the output power of the system is reduced from the initial power to the second power, adopting a regulation mode for controlling the fuel utilization rate; when the output power of the system is reduced from the initial power to the third power, adopting a regulation mode of cooperatively controlling the fuel utilization rate and the voltage; wherein the initial power is greater than the first power, the first power is greater than the second power, and the second power is greater than the third power. Therefore, when the performance of the SOFC system is attenuated after long-term operation, the method can be adopted to compensate the performance loss of the system caused by attenuation, thereby prolonging the actual service life of the system. Specifically, the invention can select corresponding regulation and control modes according to different attenuation degrees to change the running condition of the system after performance attenuation, improve the output power of the attenuation system, and return the output power to the level of the initial design power again, thereby prolonging the actual service life of the system and achieving the purpose of prolonging the service life.
In the initial stage of attenuation, the system performance only slightly decreases, and the output voltage and output power only slightly decrease, so that the power can be recovered to the initial level only by small-amplitude adjustment, and a fuel flow regulation method with the least influence on the system is adopted.
According to an embodiment of the present invention, the regulation manner for controlling the fuel flow includes: and controlling the fuel flow of the system to be unchanged, and increasing the working current of the system to ensure that the output power of the system is equal to the initial power. Thus, by increasing the system output current, the output power is correspondingly increased, thereby compensating for the power loss caused by attenuation. After the regulation mode is adopted, the fuel actually consumed by the system is not increased, the electrical efficiency of the system is restored to the initial level, the performance of the system lost due to attenuation is compensated, and the performance of the system is improved.
After the attenuation system adopts a regulation mode for controlling the fuel flow, the output voltage of the system can be further reduced. For long-term, steady-state operation of the system, the output voltage should not be below a certain limit (e.g., the chip average voltage is not below 0.65V), otherwise the system performance will decay rapidly. Therefore, the regulation mode has limited application range, and becomes not applicable after the system is obviously attenuated.
In the middle period of attenuation, when the system performance is obviously reduced, the regulation and control mode for controlling the fuel flow is not applicable any more, and the regulation and control mode for controlling the fuel utilization rate is needed to be adopted, so that the output power can be recovered to the initial level while the system voltage is ensured to be in the safe interval.
According to an embodiment of the present invention, the regulation and control manner for controlling the fuel utilization rate includes: and maintaining the fuel utilization rate of the system unchanged, and proportionally increasing the fuel flow and the working current of the system to ensure that the output power of the system is equal to the initial power. Therefore, the output power of the system can be improved by increasing the fuel flow and the working current of the system in equal proportion, so that the system is restored to the original design level, and the power loss of the system is compensated.
After the regulation mode for controlling the fuel utilization rate is adopted, the output power of the system is restored to the initial level, but the fuel quantity actually consumed by the system is increased, so that the system electrical efficiency at the moment is lower than the initial level. The system fuel utilization rate is kept unchanged, and the regulated output voltage is slightly lower than the output voltage before regulation, so that the system electrical efficiency is almost the same as the system electrical efficiency after attenuation, which means that the method does not lose the system electrical efficiency.
The system electrical efficiency will maintain the attenuated level by means of regulation to control fuel utilization. That is, the system electrical efficiency after adopting the regulation and control mode for controlling the fuel utilization rate in the middle period of the attenuation is not much different from the system electrical efficiency after adopting the regulation and control mode for controlling the fuel utilization rate in the middle period of the attenuation.
And in the late stage of attenuation, when the system performance is seriously reduced, controlling the fuel utilization rate to fail in a regulation mode, namely, controlling the regulated voltage to be lower than a safe working voltage critical value, and adopting a regulation mode of cooperatively controlling the fuel utilization rate and the voltage.
According to an embodiment of the present invention, the control manner of cooperatively controlling the fuel utilization rate and the voltage includes: firstly, adopting a regulation and control mode for controlling the fuel utilization rate, keeping the fuel utilization rate of the system unchanged, and proportionally increasing the fuel flow and the working current of the system until the voltage of the system is reduced to a safe working voltage critical value, wherein the output power of the system is lower than the initial power; and then, adopting a control mode of control voltage to maintain the voltage of the system as a safe working voltage critical value unchanged, and improving the fuel flow and working current of the system to ensure that the final output power of the system is the same as the initial power.
The voltage of the system (e.g., the chip average voltage) should be varied between an upper and a lower voltage limit, i.e., the voltage of the system should be within a safe operating voltage range during regulation. Too low a voltage can directly reduce the system performance and also reduce the service life of the system; too high a voltage can reduce the system power density, rendering the system impractical.
The safe operating voltage threshold value refers to a lower limit value of the safe operating voltage range. The control mode of cooperatively controlling the fuel utilization rate and the voltage can ensure that the actual working voltage of the system is not lower than the critical value of the safe working voltage, namely the actual working voltage is not lower than the lower limit value of the range of the safe working voltage, and can avoid the occurrence of bad problems such as damaged system performance or unsafe operation.
In the control voltage unchanged control stage in the control mode of cooperatively controlling the fuel utilization rate and the voltage, the fuel utilization rate of the system is obviously reduced, and the electrical efficiency of the system is rapidly reduced. This stage therefore compensates for the lack of system power at the expense of system performance. In the long term, the regulation mode ensures that the system operates at a relatively low performance level, but prolongs the actual service life of the system, and has certain economic value.
After the mode of cooperative regulation and control of the fuel utilization rate and the voltage is adopted, the system electrical efficiency is lower than the level after attenuation, but the service life is prolonged. Namely, the system electrical efficiency after adopting a mode of controlling the fuel utilization rate and the voltage cooperatively in the late period of attenuation is lower than that when not adopting the mode of controlling the fuel utilization rate and the voltage cooperatively in the late period of attenuation. But the service life of the system can be prolonged by adopting a control mode of cooperatively controlling the fuel utilization rate and the voltage.
According to the embodiment of the invention, the first power is reduced by a first reduction compared with the initial power, and the first reduction is less than or equal to 5%; the amplitude reduction of the second power compared with the initial power is a second amplitude reduction, the second amplitude reduction is more than 5 percent, and is less than or equal to 12.5 percent; the third power is reduced by a third reduced amplitude compared with the initial power, and the third reduced amplitude is more than 12.5% and less than or equal to 15%. In general, the invention can change the operation parameters of the system by adopting corresponding regulation and control modes according to different attenuation degrees, so that the output power of the system returns to the design power again, and the system can meet the external requirements again, thereby prolonging the service life of the system and improving the economical efficiency. It should be noted that the first drop is less than or equal to 5%, the second drop is greater than or equal to 5%, and at the same time is less than or equal to 12.5%, and the third drop is greater than 12.5%, and at the same time is less than or equal to 15%, which is a specific embodiment of the control method, that is, the conditions satisfied by different regulation modes of the control method for prolonging the service life of the system when the operating parameters in the solid oxide fuel cell system are fixed, are only for illustrative purposes, but not for limiting the invention. That is, when some operating parameters of the solid oxide fuel cell system are changed, even if the first drop is not within the range of 5% or less, the fuel flow control manner may be adopted, for example, in other embodiments, when the first drop is 11% or less, specifically, when the first drop is 10%, the fuel flow control manner is adopted, and the method is still within the protection scope of the present invention.
That is, the specific conditions satisfied by the different regulation modes of the control method for extending the life of the system are not fixed, and the conditions can be adjusted according to the operating parameters of the solid oxide fuel cell system, but the general trend of adopting the different regulation modes is unchanged. The output power of the system when running under the initial working condition is initial power, when the initial power is larger than first power, the first power is larger than second power, and the second power is larger than third power, the method can be adopted, and particularly, when the output power of the system is reduced from the initial power to the first power, a regulation mode for controlling the fuel flow is adopted; when the output power of the system is reduced from the initial power to the second power, adopting a regulation mode for controlling the fuel utilization rate; and when the output power of the system is reduced from the initial power to the third power, adopting a regulation mode of cooperatively controlling the fuel utilization rate and the voltage.
When the system performance is seriously attenuated and the system electrical efficiency is too low after adopting a control mode of cooperatively controlling the fuel utilization rate and the voltage, the SOFC system can be considered to be damaged and a new electric pile needs to be replaced.
According to an embodiment of the present invention, the control method is disabled when the output power of the system is reduced from the initial power to a fourth power; wherein the fourth power is less than the third power. When the method fails, the SOFC stack in the system can be considered to be damaged, and a new stack needs to be replaced in time or the external load of the system is reduced. The method can be used as a basis for judging whether the galvanic pile is damaged.
According to an embodiment of the present invention, the fourth power is reduced by a fourth reduction in amplitude compared to the initial power, and the fourth reduction in amplitude is greater than 15%. It should be noted that, the fourth drop is greater than 15%, which is a specific embodiment of the control method, that is, the condition satisfied by different regulation modes of the control method for prolonging the service life of the system when the operating parameters in the solid oxide fuel cell system are fixed, is only for illustration, but not for limiting the present invention. For example, when some of the operating parameters of the solid oxide fuel cell system are changed, the control method may be disabled even if the fourth reduced amplitude range is not within a range of more than 15%. That is, in other embodiments, the fourth drop is greater than 12%, specifically, the control fails when the fourth drop is 13%. While remaining within the scope of the present invention.
According to an embodiment of the present invention, referring to fig. 1, the solid oxide fuel cell system includes a fuel pump, a fuel preheater, a reformer, an SOFC stack, a controller (not shown), a blower, an air preheater, an afterburner and a heating module;
the fuel pump is connected with the fuel preheater through a first pipeline, and a fuel valve is arranged on the first pipeline; the fuel preheater is connected with the reformer, and the reformer is connected with the SOFC stack;
the fan is connected with the air preheater through a second pipeline, and the air preheater is connected with the SOFC stack;
the SOFC stack is connected with the controller;
the SOFC stack is connected with the afterburner, the afterburner is connected with the air preheater, the air preheater is connected with the fuel preheater, and the fuel preheater is connected with the heat supply module.
According to an embodiment of the invention, adjusting the fuel flow is achieved by adjusting the fuel valve;
the fuel utilization rate, the working voltage and the working current are all adjusted by adjusting the controller.
According to an embodiment of the invention, an air valve is provided on the second conduit.
In the process of prolonging the service life of the system by using the method, the heat balance of the electric pile needs to be maintained, and the working temperature of the electric pile is stabilized.
The heat balance of the electric pile means that the heat of the electric pile by-product is equal to the heat dissipated by the electric pile in the discharging process.
The secondary heat generation of the electric pile is related to the output power and the working voltage of the system. When the system performance is attenuated, the secondary heat generation of the electric pile is increased under the same working condition.
The heat dissipated by the cell stack comprises two parts, namely the heat dissipated by the outer surface of the cell stack and the heat taken away from the interior of the cell stack by the gas flowing through the cell stack.
The heat dissipated from the outer surface of the electric pile is related to parameters such as the size of the electric pile, a heat insulation structure, the working temperature and the like, and once the electric pile stably operates at a certain working temperature, the heat dissipation capacity can be considered to be stable and unchanged.
The heat taken away from the inside of the pile by the gas flowing through the pile is related to parameters such as gas flow, temperature difference between the gas flowing in and out of the pile, gas type and the like. In some embodiments, the air flow may be used to regulate the amount of heat dissipated in the portion.
When the system performance is attenuated and the system output power is recovered by adopting the method, the heat generation quantity of the electric pile is changed, and the air flow is required to be regulated to enable the electric pile to reach new heat balance, so that the temperature stability of the electric pile is maintained, and the operation life of the system is prolonged.
The specific method comprises the following steps: according to the related parameters such as flow, temperature, working current, working voltage and the like, the size of the heat load of the electric pile under the current situation is calculated, and the final air flow is reversely pushed through the heat balance relation. The more severe the decay, the greater the corresponding air equivalence ratio of the thermal equilibrium; when a regulation mode for controlling the fuel flow is adopted, the air equivalence ratio is rapidly increased; when the regulation and control mode for controlling the fuel utilization rate is adopted, the air equivalence ratio is increased compared with the initial working condition, but if the regulation and control mode for controlling the fuel flow rate is adopted under the attenuation condition, the increase rate of the air equivalence ratio can be reduced by adopting the regulation and control mode for controlling the fuel utilization rate, namely the air equivalence ratio can be slowly increased by adopting the regulation and control mode for controlling the fuel utilization rate; when the mode of controlling the fuel utilization rate and the voltage cooperatively is adopted, the air equivalence ratio is increased compared with the initial working condition, but if the mode of controlling the fuel utilization rate is adopted under the attenuation condition, the air equivalence ratio can be properly reduced by adopting the mode of controlling the fuel utilization rate and the voltage cooperatively.
It should be emphasized that the temperature of the galvanic pile is stable and unchanged, which means that the temperature parameter with great thermal inertia is stable and unchanged; the method only relates to the regulation and control of the flow parameter and the current parameter, so that the system can realize quick response.
In summary, the control method of the solid oxide fuel cell system provided by the invention is not only suitable for the whole life cycle of the system, but also has the following gain effects: after performance attenuation, the system can still output initial design power, and the service life of the system is prolonged; ensuring that the electric pile is in a thermal balance state, ensuring that the working temperature is stable and unchanged, and avoiding thermal shock; the quick response is realized, and the long-term safe, efficient and stable operation of the system is ensured; can be used as a basis for judging the damage of the system so as to replace a new electric pile in time.
The invention will now be described with reference to specific examples, which are intended to be illustrative only and not limiting in any way.
FIG. 1 is a diagram of a 1kW methanol SOFC cogeneration system in accordance with an embodiment of the invention, and initial design parameters and performance of the 1kW methanol SOFC cogeneration system are shown in Table 1 below.
TABLE 1kW methanol SOFC cogeneration System design parameters
| Design parameters | Numerical value | Design parameters | Numerical value |
| Type of fuel | Methanol | Fuel utilization rate | 73.3％ |
| Air flow rate | 82L/min | Air preheating temperature | 525℃ |
| Fuel flow rate | 7.8g/min | Preheating temperature of fuel | 450℃ |
| Air equivalent ratio | 2 | Reforming temperature | 700℃ |
| Reforming water to carbon ratio | 1 | SOFC operating temperature | 750℃ |
| Sheet average voltage | 0.8V | Exhaust outlet temperature | 50℃ |
| Electric power | 1000W | Electric efficiency | 38.1％ |
| Thermal power | 1180W | Thermal efficiency | 45.1％ |
| Pile heat load | 100W | Overall efficiency | 83.2％ |
After long-time operation, the system performance gradually decays, the average voltage of the chip is continuously reduced from the initial 0.8V, but the reduction amplitude is not large, at the moment, the real-time regulation and control are carried out by adopting a regulation and control mode for controlling the fuel flow, and the system output power is ensured to be stable as the design power. The specific implementation method of the regulation mode is described by taking the case that the attenuation rate is 5% as a case. At this time, the sheet was lowered to 0.76V, the actual power was lowered to 950W, and the system parameters after regulation are shown in Table 2.
Along with further attenuation of the system performance, the regulation and control mode for controlling the fuel flow is not applicable any more, and the regulation and control mode for controlling the fuel utilization rate is switched to be used for regulating and controlling the system in real time. The specific implementation method of the regulation mode is described by taking the case that the attenuation rate is 10% as a case. At this time, the sheet average voltage was further reduced to 0.72V, the actual power was reduced to 900W, and the regulated operating parameters are shown in table 2.
When the attenuation of the system is further deepened and the regulation and control mode for controlling the fuel utilization rate is not applicable any more, the regulation and control mode for cooperatively controlling the fuel utilization rate and the voltage is switched to recover the output power of the system. The specific implementation method of the regulation mode is described by taking the case that the attenuation rate is 15% as a case. At this time, the average voltage and the output power were reduced to 0.68V and 850W, and the relevant parameters after the regulation are shown in Table 2.
TABLE 2 operating parameters and Performance of SOFC systems under different attenuation levels regulated by the control method of the present invention
As can be seen from Table 2, the control method provided by the present invention can restore the output power of the system to the original design level at different attenuation stages, and at the same time, maintain the operating temperature of the galvanic pile stable. In the initial stage of attenuation, the control method can compensate partial performance loss; in mid-decay, the control method may slightly impair system performance; later in decay, the control method trades longer use time at the expense of efficiency.
For this embodiment, the final control method is shown in table 3 below.
TABLE 3 control method used for different attenuation stages
As can be seen from table 3, in the present embodiment, the system power attenuation of less than 5% is regarded as the initial attenuation period, and a regulation manner of controlling the fuel flow is preferably adopted; the power attenuation is an intermediate attenuation period between 5% and 12.5%, and a regulation and control mode for controlling the fuel utilization rate is suitable for use; the attenuation amplitude is between 12.5 and 15 percent, namely the later period of attenuation, and a regulation mode of cooperatively controlling the fuel utilization rate and the voltage is adopted; if the attenuation exceeds 15%, the system is considered to be damaged, and a new SOFC stack should be replaced in time, or the external load is reduced, so that the SOFC stack can continue to operate under the low power condition.
Although the present invention has been described with reference to the drawings and the simulation examples, it is not limited to the specific application scenario, and various modifications or variations can be made by those skilled in the art without the need of inventive effort on the basis of the technical solution of the present invention.
It should be noted that, in the present specification, the terms "first," "second," "third," "fourth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
Although embodiments of the present application have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the application, and that variations, modifications, alternatives, and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the application.
Claims (6)
1. A control method for extending the life of a solid oxide fuel cell system, wherein the output power of the system when operating at an initial condition is the initial power, the method comprising:
when the output power of the system is reduced from the initial power to the first power, adopting a regulation mode for controlling the fuel flow;
when the output power of the system is reduced from the initial power to the second power, adopting a regulation mode for controlling the fuel utilization rate;
when the output power of the system is reduced from the initial power to the third power, adopting a regulation mode of cooperatively controlling the fuel utilization rate and the voltage;
wherein the initial power is greater than the first power, the first power is greater than the second power, and the second power is greater than the third power;
the regulation and control mode for controlling the fuel flow comprises the following steps: controlling the fuel flow of the system to be unchanged, and increasing the working current of the system to ensure that the output power of the system is equal to the initial power;
the regulation and control mode for controlling the fuel utilization rate comprises the following steps: maintaining the fuel utilization rate of the system unchanged, and increasing the fuel flow and the working current of the system in equal proportion to ensure that the output power of the system is equal to the initial power;
the regulation and control modes for cooperatively controlling the fuel utilization rate and the voltage comprise: firstly, adopting a regulation and control mode for controlling the fuel utilization rate, keeping the fuel utilization rate of the system unchanged, and proportionally increasing the fuel flow and the working current of the system until the voltage of the system is reduced to a safe working voltage critical value, wherein the output power of the system is lower than the initial power; then, a control mode of control voltage is adopted, the voltage of the system is maintained to be the critical value of safe working voltage, the fuel flow and the working current of the system are improved, and the final output power of the system is the same as the initial power;
when the output power of the system is reduced from the initial power to the fourth power, the control method fails, and a new electric pile is replaced or an external load is reduced;
wherein the fourth power is less than the third power.
2. The control method according to claim 1, characterized in that the first power is reduced by a first reduction in amplitude compared to the initial power, the first reduction in amplitude being 5% or less;
the second power is reduced by a second reduction compared with the initial power, wherein the second reduction is more than 5% and less than or equal to 12.5%;
the third power is reduced by a third reduced amplitude compared with the initial power, and the third reduced amplitude is more than 12.5% and less than or equal to 15%.
3. The control method of claim 1, wherein the fourth power is reduced by a fourth reduction in amplitude compared to the initial power, the fourth reduction in amplitude being greater than 15%.
4. The control method of claim 1, wherein the solid oxide fuel cell system comprises a fuel pump, a fuel preheater, a reformer, an SOFC stack, a controller, a fan, an air preheater, an afterburner, and a heating module;
the fuel pump is connected with the fuel preheater through a first pipeline, and a fuel valve is arranged on the first pipeline; the fuel preheater is connected with the reformer, and the reformer is connected with the SOFC stack;
the fan is connected with the air preheater through a second pipeline, and the air preheater is connected with the SOFC stack;
the SOFC stack is connected with the controller;
the SOFC stack is connected with the afterburner, the afterburner is connected with the air preheater, the air preheater is connected with the fuel preheater, and the fuel preheater is connected with the heat supply module.
5. The control method according to claim 4, characterized in that adjusting the fuel flow is achieved by adjusting the fuel valve;
the fuel utilization rate, the working voltage and the working current are all adjusted by adjusting the controller.
6. The control method according to claim 4, wherein an air valve is provided on the second pipe.
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| CN112736268A (en) * | 2020-12-17 | 2021-04-30 | 华中科技大学 | Control optimization method and system for prolonging service life of SOFC (solid oxide fuel cell) system |
| CN113488681A (en) * | 2021-07-02 | 2021-10-08 | 电子科技大学 | Control method and system for long-life vehicle fuel cell engine |
| CN113839066A (en) * | 2021-09-22 | 2021-12-24 | 电子科技大学 | Multi-pile integrated long-life fuel cell system |
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