CN113013450A - Method for determining self-heating balance of hydrocarbon fuel solid oxide fuel cell stack and application - Google Patents

Method for determining self-heating balance of hydrocarbon fuel solid oxide fuel cell stack and application Download PDF

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CN113013450A
CN113013450A CN202110221247.6A CN202110221247A CN113013450A CN 113013450 A CN113013450 A CN 113013450A CN 202110221247 A CN202110221247 A CN 202110221247A CN 113013450 A CN113013450 A CN 113013450A
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solid oxide
fuel cell
cell stack
current density
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CN113013450B (en
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吕泽伟
韩敏芳
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Tsinghua University
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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
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H01M8/04574—Current
    • H01M8/04589—Current of fuel cell stacks
    • 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
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H01M8/04544—Voltage
    • H01M8/04559—Voltage of fuel cell stacks
    • 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
    • H01M8/04895—Current
    • H01M8/0491—Current of fuel cell stacks
    • 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
    • H01M8/04992—Processes for controlling fuel cells or fuel cell systems characterised by the implementation of mathematical or computational algorithms, e.g. feedback control loops, fuzzy logic, neural networks or artificial intelligence
    • 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
    • H01M8/124—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte
    • H01M8/1246—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte the electrolyte consisting of oxides
    • 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
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • 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
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Abstract

The invention discloses a method for determining self-heating balance of a solid oxide fuel cell stack of hydrocarbon fuel and application thereof, which comprises the steps of measuring a current density-voltage curve of the solid oxide fuel cell stack under a selected hydrocarbon fuel component, and calculating the power generation power of the solid oxide fuel cell stack under different current densities; obtaining components of anode tail gas under different current densities, and calculating enthalpy change of the selected hydrocarbon fuel from an inlet to an outlet under different current densities; calculating heat release Q under different current densities based on the generated power under different current densities and the enthalpy change from the inlet to the outlet; the current density at which the exotherm Q is 0 is taken as the autothermal equilibrium current density of the solid oxide fuel cell stack at the selected hydrocarbon fuel composition. The self-heating balance working point determined by the method can provide guidance for selecting the operation parameters of the solid oxide fuel cell stack, and contributes to system heat management and efficiency improvement.

Description

Method for determining self-heating balance of hydrocarbon fuel solid oxide fuel cell stack and application
Technical Field
The invention relates to the technical field of solid oxide cells, in particular to a hydrocarbon fuel solid oxide fuel cell self-heating balance determination method and application.
Background
A solid oxide fuel cell (solid oxide fuel cell) directly converts chemical energy of fuel into electric energy through electrochemical reaction, has higher energy conversion efficiency compared with the conventional thermal power generation, and is a fourth generation power generation technology following hydroelectric power generation, thermal power generation and atomic power generation. At present, the solid oxide fuel cell power generation technology is successfully applied to the fields of household distributed combined heat and power systems, medium and small distributed power stations, power sources for vehicles and the like, and shows good development prospects.
Compared with other types of fuel cells, one of the most prominent advantages of the solid oxide fuel cell is its wide fuel adaptability, i.e., clean and efficient conversion of various fuels such as hydrogen, alkane, alkene, alcohol, etc. can be realized. When hydrocarbon fuels such as alkane, alkene, alcohol and the like are used, the fuel can be supplied to the anode only through reforming, and reforming modes comprise external reforming, direct internal reforming, indirect internal reforming and the like. In an integrated power generation system, where the endothermic reforming reaction and the exothermic electrochemical reaction are performed simultaneously, under suitable operating conditions, the solid oxide fuel cell (including the reforming component) is capable of achieving autothermal equilibrium, i.e., no net heat is released or absorbed from the outside. Operating near this operating point helps to increase the energy efficiency of the fuel cell system and is of great benefit to the thermal management of the system.
At present, the selection of the operating parameters (such as current density) of the solid oxide fuel cell/electric stack is mainly based on the operation stability of the cell/electric stack, and is rarely optimized from the aspect of thermoelectric management and control, so that the energy conversion efficiency of the whole system is low.
How to determine the self-heating balance point of the practical solid oxide fuel cell/electric stack and realize the operation near the self-heating balance point is a technical problem to be solved urgently in the field.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a hydrocarbon fuel solid oxide fuel cell stack self-heating balance determination method and application, wherein the self-heating balance current density and the fuel utilization rate of the solid oxide fuel cell stack are obtained by combining the output performance of the solid oxide fuel cell stack and a thermodynamic method, and a fuel cell module near the working point can realize internal heat balance, namely no net heat is released or absorbed externally, and the enthalpy change Delta H of fuel reaction is completely converted into electric energy. The method can be applied to a power generation system consisting of multi-stage fuel cell stacks, so that each stage of the fuel cell stacks can work at an autothermal equilibrium working point, and the highest power generation efficiency is realized. The invention can provide guidance for the selection of the operation parameters of the solid oxide fuel cell stack, and is beneficial to the heat management and the efficiency improvement of the whole system.
In order to achieve the above object, in one aspect, a method for determining an autothermal balance of a hydrocarbon fuel solid oxide fuel cell stack is provided, including:
measuring a current density-voltage curve of the solid oxide fuel cell stack under the selected hydrocarbon fuel component, and calculating the power generation power of the solid oxide fuel cell stack under different current densities;
obtaining components of anode tail gas under different current densities, and calculating enthalpy change of the selected hydrocarbon fuel under different current densities;
calculating heat release Q under different current densities based on the generated power under different current densities and the enthalpy change of the hydrocarbon fuel;
the current density at which the exotherm Q is 0 is taken as the autothermal equilibrium current density of the solid oxide fuel cell stack at the selected hydrocarbon fuel composition.
Further, calculating the generated power of the solid oxide fuel cell stack at different current densities comprises: fitting to obtain a relation between current density and voltage according to a current density-voltage curve; calculating the generated power W of the solid oxide fuel cell stack under different current densities according to the relation between the current density and the voltagee：
We＝j×V×Scell
Where j is the current density, V is the fitted voltage, ScellIs the solid oxide fuel cell active area.
Further, polynomial fitting is carried out by adopting a least square method, and a judgment coefficient R is satisfied2Greater than 0.99.
Further, obtaining the components of the anode tail gas at different current densities comprises: and calculating thermodynamic equilibrium state components of the anode tail gas under different current densities based on a Gibbs free energy minimization principle, or testing actual components of the anode tail gas under different current densities.
Further, calculating the heat release Q at different current densities comprises:
Q＝-ΔH-We
ΔH＝Houtlet-Hinlet
wherein HoutletIs the enthalpy value of the anode tail gas, HinletIs the enthalpy value of the hydrocarbon fuel at the inlet, Δ H is the enthalpy change of the hydrocarbon fuel, WeIs the generated power.
The second aspect provides a method for realizing self-heating balance of a single-stage hydrocarbon fuel solid oxide fuel cell stack, which comprises the following steps:
for each type of hydrocarbon fuel components adopted by the solid oxide fuel cell stack, respectively calculating the self-heating balance current density by the self-heating balance determination method of the hydrocarbon fuel solid oxide fuel cell stack;
based on the currently used hydrocarbon fuel composition, the corresponding auto-thermal equilibrium current density is employed as the SOFC stack operating current density.
The third aspect provides a single-stage hydrocarbon fuel solid oxide fuel cell stack, which comprises a storage unit and a control unit;
for each type of hydrocarbon fuel components adopted by the solid oxide fuel cell stack, respectively adopting the hydrocarbon fuel solid oxide fuel cell stack self-heating balance determination method to calculate self-heating balance current density, and storing the corresponding relation between the hydrocarbon fuel components and the self-heating balance current density in the storage unit;
and the control unit acquires the self-heating balance current density from the corresponding relation of the hydrocarbon fuel component and the self-heating balance current density based on the currently used hydrocarbon fuel component, and takes the self-heating balance current density as the operating current density of the solid oxide fuel cell stack.
A fourth aspect provides a method for realizing self-heating balance of a multi-stage hydrocarbon fuel solid oxide fuel cell stack, comprising:
for each type of hydrocarbon fuel components adopted by each stage of solid oxide fuel cell stack, respectively adopting the hydrocarbon fuel solid oxide fuel cell stack self-heating balance determination method to calculate self-heating balance current density;
and adopting the corresponding self-heating balance current density as the operation current density of each stage based on the hydrocarbon fuel component used by each solid oxide fuel cell stack at present.
The fifth aspect provides a multi-stage hydrocarbon fuel solid oxide fuel cell stack, which comprises a storage unit and a control unit;
for each type of hydrocarbon fuel components adopted by each stage of solid oxide fuel cell stack, calculating the self-heating balance current density by respectively adopting the hydrocarbon fuel solid oxide fuel cell stack self-heating balance determination method, and storing the corresponding relation between the hydrocarbon fuel components and the self-heating balance current density in the storage unit;
and the control unit acquires corresponding self-heating balance current density according to the corresponding relation between the hydrocarbon fuel component and the self-heating balance current density based on the currently used hydrocarbon fuel component of each stage of the solid oxide fuel cell stack, and takes the self-heating balance current density as the operating current density of the stage.
A sixth aspect provides a method of selecting operating parameters of a multi-stage solid oxide fuel cell stack, comprising:
for each type of hydrocarbon fuel components adopted by each stage of solid oxide fuel cell stack, respectively adopting the hydrocarbon fuel solid oxide fuel cell stack self-heating balance determination method to calculate self-heating balance current density;
calculating the fuel utilization rate of various hydrocarbon fuel components adopted by each stage of solid oxide fuel cell stack based on the self-heating balance current density;
and selecting the hydrocarbon fuel component with the maximum fuel utilization rate for each stage of the solid oxide fuel cell stack, and adopting the self-heating balance current density as the current density of the stage of the running current.
Further, calculating the fuel utilization includes:
Figure BDA0002954992210000041
wherein n isO2,maxThe molar flow rate of oxygen required for complete oxidation of the selected hydrocarbon fuel, F being the Faraday constant, ScellIs the effective area of the solid oxide fuel cell, UTAs fuel utilization factor, jTIs the self-heating equilibrium current density.
The technical scheme of the invention has the following beneficial technical effects:
(1) the invention provides a method for determining the self-heating balance of a hydrocarbon fuel solid oxide fuel cell stack, which is characterized in that the enthalpy change delta H of fuel reaction is completely converted into electric energy under the self-heating balance working point, namely no net heat is released or absorbed outwards; for the multi-stage solid oxide fuel cell stack, each stage is controlled to work in an autothermal equilibrium state, the energy conversion efficiency is highest, and the fuel is saved most.
(2) The self-heating balance realization method provided by the invention can be applied to a power generation system consisting of multiple stages of fuel cell stacks, wherein each stage of fuel cell stack respectively obtains a self-heating balance working point, and each stage of fuel cell stack is controlled to work at the self-heating balance working point, so that the whole system can realize the highest power generation efficiency and is beneficial to thermoelectric control of the system.
(3) The hydrocarbon fuel comprises fuel containing alkane, olefin, alcohol, etc. as main components and added reforming medium (such as H)2O、CO2) The mixed fuel of the latter component; reforming modes of the hydrocarbon fuel in the solid oxide fuel cell comprise direct internal reforming, indirect internal reforming and external reforming, and if the reforming mode is external reforming, the fuel cell module comprises an external reformer; the self-heating balance working points are respectively confirmed for different hydrocarbon fuels, so that the fuel applicability of the method is wide.
(4) The self-heating balance working point obtained by the method can provide guidance for the selection of the operation parameters of the solid oxide fuel cell stack, and is beneficial to the heat management and the efficiency improvement.
Drawings
FIG. 1 is a flow chart of a method for implementing self-heating balance of a hydrocarbon fuel solid oxide fuel cell stack.
Fig. 2 is a schematic diagram of a power generation system composed of a multi-stage fuel cell stack.
Fig. 3 shows current density-voltage curves and polynomial fitting results for solid oxide fuel cell stacks at different water to carbon ratios (S/C).
Fig. 4 shows the thermodynamic equilibrium state components of the anode tail gas at different current densities when S/C is 1.
FIG. 5 shows the self-heating equilibrium current density and the corresponding fuel utilization for different S/C.
FIG. 6 shows different COs2/CH4And (3) carrying out current density-voltage curve and polynomial fitting result of the solid oxide fuel cell stack under the partial pressure ratio.
FIG. 7 shows CO2/CH4And (3) the components of the thermodynamic equilibrium state of the anode tail gas under different current densities when the partial pressure ratio is 1.
FIG. 8 shows different COs2/CH4The self-heating balance current density under the partial pressure ratio and the corresponding fuel utilization rate.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
In one aspect, a method for determining self-heating balance of a hydrocarbon fuel solid oxide fuel cell stack is provided, which includes the following steps in conjunction with fig. 1:
(1) and measuring a current density-voltage curve of the solid oxide fuel cell stack under the selected hydrocarbon fuel component, and calculating the power generation power of the solid oxide fuel cell stack under different current densities.
1.1 testing results in a current density-voltage curve (j-V curve) for a solid oxide fuel cell stack under a selected hydrocarbon fuel.
1.2 the j-V curve obtained in step 1.1 is subjected to a least squares procedureFitting the polynomial to obtain each pending coefficient and decision coefficient R in the polynomial2To ensure the fitting accuracy, R2Should be greater than 0.99.
1.3 calculating the generated power W of the solid oxide fuel cell stack under different current densities based on the j-V curve fitting obtained in the step 1.2eThe calculation formula is as follows:
We＝j×V×Scell
where j is the current density, V is the fitting voltage, ScellIs the effective area of the cell.
(2) And acquiring components of the anode tail gas under different current densities, and calculating the enthalpy change of the selected hydrocarbon fuel from the inlet to the outlet under different current densities.
2.1 calculating the thermodynamic equilibrium state components of the tail gas at the anode outlet of the solid oxide fuel cell stack under different current densities based on the Gibbs free energy minimization principle, or testing by adopting equipment such as gas chromatography and the like to obtain the actual components of the tail gas at the anode outlet.
2.2 calculating the enthalpy change deltaH of the selected hydrocarbon fuel from the inlet to the outlet under different current densities based on the anode outlet tail gas component obtained in the step 2.1, wherein the calculation formula is as follows:
ΔH＝Houtlet-Hinlet
wherein HoutletIs the enthalpy value of the anode tail gas, HinletIs the enthalpy of the hydrocarbon fuel at the inlet. The enthalpy of the anode tail gas and the enthalpy of the hydrocarbon fuel at the inlet are calculated based on the components, and the enthalpy of each component can be consulted in a thermodynamic data manual.
(3) The heat release Q at different current densities is calculated based on the generated power at different current densities and the inlet-to-outlet enthalpy change.
Calculating the heat release Q under different current densities based on the generated power of the solid oxide fuel cell stack obtained in the step (1) and the reaction enthalpy change of the hydrocarbon fuel, wherein the calculation formula is as follows:
Q＝-ΔH-We
(4) the current density at the time of the heat release Q of 0 is selected as the solid oxide fuel cell stackHydrocarbon fuel composition of (a) self-heating equilibrium current density jT。
Selecting a current density j with Q equal to 0TNamely the self-heating balance working point, and the corresponding fuel utilization rate UTCan be calculated by the following formula:
Figure BDA0002954992210000071
wherein n isO2,maxThe molar flow rate of oxygen required for complete oxidation of the selected hydrocarbon fuel, F, is the Faraday constant of 96485C/mol.
The self-heating balance determining method of the hydrocarbon fuel solid oxide fuel cell stack can be applied to a single-stage or multi-stage solid oxide fuel cell stack, determine the self-heating balance working point, and respectively control each stage to work at the self-heating balance point.
The self-heating balance realization of the single-stage hydrocarbon fuel solid oxide fuel cell stack comprises the following steps: for each type of hydrocarbon fuel component adopted by the solid oxide fuel cell stack, the self-heating balance current density is calculated by respectively adopting the above-mentioned hydrocarbon fuel solid oxide fuel cell stack self-heating balance determination method, and the corresponding relation between the hydrocarbon fuel component and the self-heating balance current density is obtained. And based on the currently used hydrocarbon fuel component, searching for a corresponding self-heating balance current density, and adopting the corresponding self-heating balance current density as the solid oxide fuel cell stack operation current density.
The single-stage hydrocarbon fuel solid oxide fuel cell stack for realizing self-heating balance comprises a storage unit and a control unit besides normal power generation components. The storage unit stores the corresponding relation between the components of the hydrocarbon fuel and the self-heating balance current density; and the control unit acquires the self-heating balance current density from the corresponding relation of the hydrocarbon fuel component and the self-heating balance current density based on the currently used hydrocarbon fuel component, and takes the self-heating balance current density as the operating current density of the solid oxide fuel cell stack. The control unit may be implemented by a controller of the hydrocarbon fuel solid oxide fuel cell stack.
As shown in fig. 2, the obtained self-heating balance current density can be applied to a power generation system composed of multiple fuel cell stacks, wherein each fuel cell stack is operated at a self-heating balance operating point, and the overall system can achieve the highest power generation efficiency.
The self-heating balance realization of the multi-stage hydrocarbon fuel solid oxide fuel cell stack comprises the following steps: for each type of hydrocarbon fuel components adopted by each stage of solid oxide fuel cell stack, respectively adopting the above-mentioned hydrocarbon fuel solid oxide fuel cell stack self-heating balance determination method to calculate self-heating balance current density; and based on the hydrocarbon fuel composition currently used by each stage of the cell stack, adopting the corresponding self-heating balance current density as the current density for operating the stage of the cell stack.
The multi-stage hydrocarbon fuel solid oxide fuel cell stack for realizing self-heating balance comprises a storage unit and a control unit besides normal power generation components. And for each type of hydrocarbon fuel component adopted by each stage of solid oxide fuel cell stack, calculating the self-heating balance current density by respectively adopting the hydrocarbon fuel solid oxide fuel cell stack self-heating balance determination method, and storing the corresponding relation between the hydrocarbon fuel component of each stage of cell stack and the self-heating balance current density in the storage unit. And the control unit acquires corresponding self-heating balance current density from the corresponding relation of the hydrocarbon fuel component and the self-heating balance current density for each level of cell stack based on the currently used hydrocarbon fuel component, and takes the self-heating balance current density as the current density of the level of cell stack.
The self-heating balance power generation system is applied to a power generation system formed by multi-stage fuel cell stacks, and if each stage of the fuel cell stacks works at a self-heating balance working point, the whole system can achieve the highest power generation efficiency. The invention can also provide guidance for the selection of the operation parameters of the solid oxide fuel cell, and is beneficial to the heat management and the efficiency improvement of the whole system.
The operation parameters of the multi-stage solid oxide fuel cell can be selected by the following steps:
(1) respectively adopting the hydrocarbon fuel cell stack self-heating balance determination method to calculate the self-heating balance current density for various hydrocarbon fuel components adopted by each stage of cell stack of the solid oxide fuel cell;
(2) calculating the fuel utilization rate of various hydrocarbon fuel components adopted by each stage of the solid oxide fuel cell stack based on the self-heating balance current density:
Figure BDA0002954992210000091
wherein n isO2,maxThe molar flow rate of oxygen required for complete oxidation of the selected hydrocarbon fuel, F being the Faraday constant, ScellIs the effective area of the solid oxide fuel cell, UTAs fuel utilization factor, jTIs the self-heating equilibrium current density.
(3) And selecting the hydrocarbon fuel component with the maximum fuel utilization rate for each stage of cell stack, and adopting the self-heating balance current density as the current density for the operation of the stage of cell stack.
Example 1:
this example uses CH of different ratios4、H2The O mixed fuel is directly introduced into the anode of the solid oxide fuel cell stack, so that the heat absorption CH is generated at the anode side simultaneously4The steam reforming reaction is coupled with an exothermic electrochemical reaction, the example selecting an autothermal equilibrium operating point by the method illustrated in FIG. 1.
And testing current density-voltage curves (j-V curves) of the solid oxide fuel cell under different water-carbon ratios (S/C), and performing polynomial fitting on the obtained j-V curves by adopting a least square method. This example uses a cubic polynomial to fit, the fitting relationship is as follows:
V＝A0+A1j+A2j2+A3j3
the test results and the corresponding fitting curves are shown in fig. 3, and the undetermined coefficients and the determination coefficients obtained by fitting are shown in table 1. The judgment coefficients under different S/C are all larger than 0.99, so that the fitting accuracy is considered to be high enough to be used for calculating the generated power We。
TABLE 1 fitting results of j-V curves under different S/C
Figure BDA0002954992210000092
Figure BDA0002954992210000101
And calculating the thermodynamic equilibrium state components of the anode tail gas under different current densities and the enthalpy change delta H of the fuel from the inlet to the outlet according to the Gibbs free energy minimization principle. Fig. 4 shows the thermodynamic equilibrium state components of the anode tail gas at different current densities when S/C is 1.
The generated power W obtained according to the aboveeThe heat release Q under different current densities can be calculated according to the enthalpy change delta H of the hydrocarbon fuel, and the current density j with Q being 0 is selectedTNamely the self-heating balance working point. FIG. 5 shows different CHs4、H2Self-heating equilibrium current density j under O mixed fuelTAnd corresponding fuel utilization UT. It can be seen that this result can be regarded as different ratios of CH4、H2And selecting a self-heating balance working point under the O mixed fuel.
Example 2:
this example uses CH of different ratios4、CO2The mixed fuel is directly introduced into the anode of the solid oxide fuel cell, so that the endothermic CH is generated at the anode side simultaneously4The dry reforming reaction is coupled with an exothermic electrochemical reaction, the example selecting a self-heating equilibrium operating point by the method shown in FIG. 1.
Testing solid oxide fuel cell stacks at different CO2/CH4And (3) carrying out polynomial fitting on the obtained j-V curve by adopting a least square method. This example uses a cubic polynomial to fit, the fitting relationship is as follows:
V＝A0+A1j+A2j2+A3j3
the test results and corresponding fitted curves are shown in FIG. 6, each obtained by fittingThe term predetermined coefficient and the determination coefficient are shown in table 2. Different CO2/CH4The determination coefficients under the proportion are all larger than 0.99, so that the fitting accuracy is considered to be high enough to be used for calculating the generated power We。
TABLE 2 different CO2/CH4Fitting result of j-V curve under proportion
Figure BDA0002954992210000102
Figure BDA0002954992210000111
And calculating the thermodynamic equilibrium state components of the anode tail gas under different current densities and the enthalpy change delta H of the fuel from the inlet to the outlet according to the Gibbs free energy minimization principle. FIG. 7 shows CO2/CH4The thermodynamic equilibrium state component of the anode tail gas under different current densities is 1.
The generated power W obtained according to the aboveeAnd the enthalpy change deltaH, the heat release Q at different current densities can be calculated, and the current density j with Q equal to 0 is selectedTNamely the self-heating balance working point. FIG. 8 shows different CHs4、CO2Self-heating equilibrium current density j under mixed fuelTAnd corresponding fuel utilization UT. This result can be taken as different ratios of CH4、CO2And selecting a self-heating balance working point under the mixed fuel.
In summary, the invention discloses a method for determining the self-heating balance of a solid oxide fuel cell stack of hydrocarbon fuel and an application thereof, which comprises the steps of measuring a current density-voltage curve of the solid oxide fuel cell stack under a selected hydrocarbon fuel component, and calculating the power generation power of the solid oxide fuel cell stack under different current densities; obtaining components of anode tail gas under different current densities, and calculating enthalpy change of the selected hydrocarbon fuel from an inlet to an outlet under different current densities; calculating heat release Q under different current densities based on the generated power under different current densities and the enthalpy change from the inlet to the outlet; the current density at which the exotherm Q is 0 is taken as the autothermal equilibrium current density of the solid oxide fuel cell stack at the selected hydrocarbon fuel composition. The self-heating balance working point determined by the method can provide guidance for selecting the operation parameters of the solid oxide fuel cell stack, and contributes to system heat management and efficiency improvement.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.

Claims (10)

1. A method for determining a hydrocarbon fuel solid oxide fuel cell stack self-heating balance, comprising:
measuring a current density-voltage curve of the solid oxide fuel cell stack under the selected hydrocarbon fuel component, and calculating the power generation power of the solid oxide fuel cell stack under different current densities;
obtaining components of anode tail gas under different current densities, and calculating enthalpy change of the selected hydrocarbon fuel under different current densities;
calculating heat release Q under different current densities based on the generated power under different current densities and the enthalpy change of the hydrocarbon fuel;
the current density at which the exotherm Q is 0 is taken as the autothermal equilibrium current density of the solid oxide fuel cell stack at the selected hydrocarbon fuel composition.
2. The method of claim 1, wherein calculating the power generated by the SOFC stack at different current densities comprises: fitting to obtain a relation between current density and voltage from a current density-voltage curve(ii) a Calculating the generated power W of the solid oxide fuel cell stack under different current densities according to the relation between the current density and the voltagee：
We＝j×V×Scell
Where j is the current density, V is the fitted voltage, ScellIs the solid oxide fuel cell active area.
Further, polynomial fitting is carried out by adopting a least square method, and a judgment coefficient R is satisfied2Greater than 0.99.
3. The method for determining the autothermal balance of a hydrocarbon fuel solid oxide fuel cell stack as recited in claim 1 or claim 2, wherein obtaining the components of the anode tail gas at different current densities comprises: and calculating thermodynamic equilibrium state components of the anode tail gas under different current densities based on a Gibbs free energy minimization principle, or testing actual components of the anode tail gas under different current densities.
4. The hydrocarbon fuel solid oxide fuel cell stack autothermal balance determination method of claim 1 or claim 2, wherein calculating the heat release Q at different current densities comprises:
Q＝-ΔH-We
ΔH＝Houtlet-Hinlet
wherein HoutletIs the enthalpy value of the anode tail gas, HinletIs the enthalpy value of the hydrocarbon fuel at the inlet, Δ H is the enthalpy change of the hydrocarbon fuel, WeIs the generated power.
5. A method for realizing self-heating balance of a single-stage hydrocarbon fuel solid oxide fuel cell stack is characterized by comprising the following steps:
calculating the self-heating balance current density of each type of hydrocarbon fuel component adopted by the solid oxide fuel cell stack by respectively adopting the hydrocarbon fuel solid oxide fuel cell stack self-heating balance determination method of one of claims 1 to 4;
based on the currently used hydrocarbon fuel composition, the corresponding auto-thermal equilibrium current density is employed as the SOFC stack operating current density.
6. The single-stage hydrocarbon fuel solid oxide fuel cell stack is characterized by comprising a storage unit and a control unit;
calculating the self-heating balance current density of each type of hydrocarbon fuel component adopted by the solid oxide fuel cell stack by respectively adopting the hydrocarbon fuel solid oxide fuel cell stack self-heating balance determination method of one of claims 1 to 4, and storing the corresponding relation between the hydrocarbon fuel component and the self-heating balance current density in the storage unit;
and the control unit acquires the self-heating balance current density from the corresponding relation of the hydrocarbon fuel component and the self-heating balance current density based on the currently used hydrocarbon fuel component, and takes the self-heating balance current density as the operating current density of the solid oxide fuel cell stack.
7. A method for realizing self-heating balance of a multi-stage hydrocarbon fuel solid oxide fuel cell stack is characterized by comprising the following steps:
calculating the self-heating balance current density of each hydrocarbon fuel component adopted by each solid oxide fuel cell stack by respectively adopting the self-heating balance determination method of the hydrocarbon fuel solid oxide fuel cell stack in any one of claims 1 to 4;
and adopting the corresponding self-heating balance current density as the operation current density of each stage based on the hydrocarbon fuel component used by each solid oxide fuel cell stack at present.
8. The multi-stage hydrocarbon fuel solid oxide fuel cell stack is characterized by comprising a storage unit and a control unit;
calculating the self-heating balance current density of each hydrocarbon fuel component adopted by each solid oxide fuel cell stack by respectively adopting the hydrocarbon fuel solid oxide fuel cell stack self-heating balance determination method of one of claims 1 to 4, and storing the corresponding relation between the hydrocarbon fuel component and the self-heating balance current density in the storage unit;
and the control unit acquires corresponding self-heating balance current density according to the corresponding relation between the hydrocarbon fuel component and the self-heating balance current density based on the currently used hydrocarbon fuel component of each stage of the solid oxide fuel cell stack, and takes the self-heating balance current density as the operating current density of the stage.
9. A method of selecting operating parameters for a multi-stage solid oxide fuel cell stack, comprising:
calculating the self-heating balance current density of each hydrocarbon fuel component adopted by each solid oxide fuel cell stack by respectively adopting the self-heating balance determination method of the hydrocarbon fuel solid oxide fuel cell stack in any one of claims 1 to 4;
calculating the fuel utilization rate of various hydrocarbon fuel components adopted by each stage of solid oxide fuel cell stack based on the self-heating balance current density;
and selecting the hydrocarbon fuel component with the maximum fuel utilization rate for each stage of the solid oxide fuel cell stack, and adopting the self-heating balance current density as the current density of the stage of the running current.
10. The operating parameter selection method of claim 9, wherein calculating a fuel utilization comprises:
Figure FDA0002954992200000031
wherein n isO2,maxThe molar flow rate of oxygen required for complete oxidation of the selected hydrocarbon fuel, F being the Faraday constant, ScellIs the effective area of the solid oxide fuel cell, UTAs fuel utilization factor, jTIs the self-heating equilibrium current density.
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