A method for controlling low-pressure operation of a high-temperature fuel cell

Abstract

This invention relates to a low-pressure operation control method for a high-temperature fuel cell, comprising: obtaining the gas pressure at the outlet of the cathode gas supply pipeline of the fuel cell stack through a cathode gas pressure acquisition element, and controlling the speed of the gas pump according to the gas pressure value; obtaining the gas pressure at the outlet of the anode gas supply pipeline of the fuel cell stack through an anode gas pressure acquisition element, and controlling the pulse frequency of the gas injection valve according to the gas pressure value; changing the air demand on the cathode side of the fuel cell stack by adjusting the speed of the gas pump when the gas pressure conditions change; and adjusting the pulse frequency of the gas injection valve when the air flow on the cathode side changes rapidly, so that the instantaneous flow rate of gas in the anode supply pipeline responds quickly to the change of the gas pump speed, thereby maintaining the gas pressure ratio at the inlet of the cathode and anode sides of the fuel cell stack at the measured parameter ratio under normal gas pressure conditions, ensuring the stable output and safe operation of the high-temperature methanol fuel cell system stack.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature fuel cells, and in particular to a low-pressure operation control method for a high-temperature fuel cell. Background Art

[0002] The high-temperature methanol fuel cell system discharges electricity through an electrochemical reaction between the hydrogen-rich methanol reforming reaction gas at the anode and the oxygen in the cathode air. The working conditions of the fuel cell system include pressure, temperature, and flow rate. The control goal of flow regulation is to ensure that sufficient reactants are provided for consumption by the fuel cell system. When the fuel cell system is operated in a high-altitude, low-pressure area, the ambient air density is less than the density under normal pressure conditions due to the low pressure, and the oxygen content per unit volume of air also decreases. To supply the high-temperature methanol fuel cell system with the same flow of cathode air (oxygen) as under normal pressure conditions, the cathode air pump speed needs to be increased compared to normal pressure conditions.

[0003] However, as the air pump speed increases, the air pump operating point shifts, which causes the pressure and air flow at the cathode inlet of the fuel cell system stack to change simultaneously with the air pump speed. In order to increase the output power of the fuel cell system per unit amount of methanol consumed, it is of great significance to control the flow rate of methanol reforming reaction gas entering the anode side of the fuel cell system stack to quickly and safely respond to the changes in the gas pressure and flow rate on the cathode side. Summary of the invention

[0004] The present invention provides a control method for a high-temperature methanol fuel cell system operating under low pressure conditions, which can be achieved in the following manner.

[0005] A method for controlling low-pressure operation of a high-temperature fuel cell, comprising:

[0006] The gas pressure at the outlet of the cathode gas supply pipeline of the stack is obtained by placing a cathode gas pressure obtaining element on the cathode gas supply pipeline, and the speed of the gas pump is controlled according to the obtained gas pressure value; the gas pressure at the outlet of the anode gas supply pipeline of the stack is obtained by placing an anode gas pressure obtaining element on the anode gas supply pipeline, and the pulse frequency of the gas injection valve on the anode gas supply pipeline is controlled according to the obtained gas pressure value;

[0007] When the air pressure condition changes, the air demand on the cathode side of the stack is changed by adjusting the speed of the air pump; when the air flow on the cathode side changes rapidly, the pulse frequency of the gas injection valve and the speed of the air pump are adjusted;

[0008] The anode side exhaust pipeline and the cathode side exhaust pipeline are respectively connected to the anode side and the cathode side of the fuel cell stack.

[0009] The method is implemented based on a high-temperature methanol fuel cell system, which includes: a fuel cell stack, a reformer reactor, a stack anode gas supply pipeline, a stack cathode gas supply pipeline, an air pump, a controller, an anode side exhaust pipeline, and a cathode side exhaust pipeline;

[0010] A fuel cell stack generates electricity through electrochemical reactions between anode gas and cathode gas;

[0011] The reformer reactor is used for reforming methanol to provide hydrogen-rich fuel gas and is placed at the front end of the anode gas supply pipeline;

[0012] A fuel cell stack anode gas supply pipeline, the anode supply pipeline is provided with an anode gas pressure acquisition element and a gas injection valve, and transports the methanol reforming reaction gas into the fuel cell stack anode;

[0013] A cathode gas supply pipeline for the fuel cell stack, which is provided with a cathode gas pressure acquisition element for conveying air into the cathode of the fuel cell stack;

[0014] An air pump, which obtains cathode gas from the external environment and delivers external air to the fuel cell stack, is placed at the front end of the cathode gas supply pipeline;

[0015] A controller, electrically connected to the gas injection valve, the anode gas pressure acquisition element, the cathode gas pressure acquisition element, and the air pump, for collecting the gas pressure on the anode gas supply pipeline and the cathode gas supply pipeline of the stack, and adjusting the opening of the gas injection valve and the speed of the air pump;

[0016] The anode side exhaust pipeline and the cathode side exhaust pipeline are respectively connected to the anode side and the cathode side of the fuel cell stack.

[0017] The gas injection valve adopts a pulse electromagnetic valve, which is placed on the anode supply pipeline. The instantaneous flow rate of the gas in the anode supply pipeline is changed by setting the pulse frequency of the gas injection valve.

[0018] The anode gas pressure acquisition element is a pressure gauge, which is placed on the anode gas supply pipeline close to the anode inlet of the stack to monitor the gas pressure at the outlet of the anode gas supply pipeline.

[0019] The cathode gas pressure acquisition element is a pressure gauge, which is placed on the cathode gas supply pipeline close to the cathode inlet of the fuel cell stack and is used to monitor the gas pressure at the outlet of the cathode gas supply pipeline.

[0020] The measured value under normal air pressure conditions is 1 to 1.5, preferably 1.2; when the gas pressure ratio on the cathode side of the fuel cell system stack is controlled to be equal to the threshold value, the stable operation of the battery system can be ensured.

[0021] When the air pressure condition changes, the air demand on the cathode side of the stack is changed by adjusting the speed of the air pump: due to the normal air pressure conditions, the relationship between the change in the delivery gas flow rate and the change in the air pump head when the air pump speed is changed is that the head change is proportional to the square of the change in the delivery gas flow rate, the air flow rate on the cathode side of the fuel cell system stack can be changed according to different demands for the output power of the high-temperature methanol fuel cell.

[0022] When the air flow rate on the cathode side changes rapidly, the flow rate in the anode supply pipeline responds quickly by controlling the gas injection valve pulse frequency.

[0023] The ratio Pb / Pa of the gas pressure obtained by the anode supply pipeline and the gas pressure obtained by the cathode supply pipeline is always maintained equal to the gas pressure ratio threshold value of the cathode side and the anode side of the fuel cell system stack measured in the high-temperature methanol fuel cell operation experiment under normal gas pressure conditions, which is used to ensure that the internal structure of the fuel cell system stack is not damaged due to excessive pressure on either side, thereby ensuring the safe operation of the high-temperature methanol fuel cell system stack.

[0024] The present invention has the following beneficial effects and effects:

[0025] 1. In the control method of the present invention, the control parameters of the control part are based on the measured values ​​under normal air pressure conditions. A high-temperature methanol fuel cell operation experiment was carried out under normal air pressure conditions. The fuel cell system involved in the experiment was the above-mentioned fuel cell system. The gas pressure ratio on the cathode side of the fuel cell system stack was controlled to be equal to the threshold value (the measured value is (1 to 1.5), preferably 1.2), which can ensure the stable operation of the battery system. Under normal air pressure conditions, when the air pump speed is changed, the relationship between the change in the delivery gas flow rate and the air pump head is that the change in the head is proportional to the square of the change in the delivery gas flow rate. In the experiment, the air flow rate on the cathode side of the fuel cell system stack was changed according to different requirements for the output power of the high-temperature methanol fuel cell.

[0026] 2. In the control method of the present invention, the control part of the anode supply pipeline is based on the rapid response of the flow in the anode supply pipeline by controlling the pulse frequency of the gas injection valve when the air flow on the cathode side changes rapidly. When the methanol consumption remains unchanged within a certain interval, the flow of the methanol reforming reaction gas flowing through the gas injection valve during this interval will not change. When the gas flow required on the cathode side decreases, the total flow of the methanol reforming reaction gas is mainly changed by reducing the methanol flow entering the reforming reactor. The transient response of changing the cathode side air flow by changing the air pump speed is faster than controlling the anode side methanol reforming reaction gas by changing the methanol feed. Therefore, the gas injection valve frequency conversion control is used on the anode supply pipeline, and as a result, a transient response of rapid flow changes on the anode side can be achieved.

[0027] 3. In the control method of the present invention, the ratio Pb / Pa of the gas pressure obtained by the anode supply pipeline and the gas pressure obtained by the cathode supply pipeline is always maintained equal to the gas pressure ratio threshold value of the cathode side and the anode side of the fuel cell system stack measured in the high-temperature methanol fuel cell operation experiment under normal air pressure conditions. At the same time, both sides of the fuel cell system stack are guaranteed to avoid damage to the internal structure of the stack due to excessive pressure on either side, thereby ensuring the safe operation of the high-temperature methanol fuel cell system stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of the fuel cell system configuration;

[0029] Figure 2 Flow chart of cathode side control part 11;

[0030] Figure 3 Anode side control part 12 flow chart; DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation method of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the invention, so the present invention is not limited by the specific implementation disclosed below.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0033] The control method in the present invention relates to a high-temperature methanol fuel cell system, including: a fuel cell stack, which generates electricity through electrochemical reaction between anode gas and cathode gas; an anode gas supply pipeline of the stack, which is provided with a gas pressure acquisition element and a gas injection valve, which transports methanol reforming reaction gas into the anode of the fuel cell stack; a gas injection valve (pulse solenoid valve), which is placed on the anode supply pipeline and changes the instantaneous flow of gas in the anode supply pipeline by setting the pulse frequency of the gas injection valve; a cathode gas supply pipeline of the stack, which is provided with a gas pressure acquisition element and transports air into the cathode of the fuel cell stack; a reformer reactor, which provides hydrogen-rich fuel gas for methanol reforming reaction and is placed at the front end of the anode gas supply pipeline; an anode gas pressure acquisition element (pressure gauge), which is placed on the anode gas supply pipeline close to the anode inlet of the stack and is used to monitor the gas pressure of the anode gas supply pipeline; and a cathode gas supply pipeline. A pressure acquisition element (pressure gauge) is placed on the cathode gas supply pipeline near the anode inlet of the fuel cell stack to monitor the gas pressure of the cathode gas supply pipeline; an air pump obtains cathode gas from the external environment and delivers external air to the fuel cell stack, and is placed at the front end of the cathode gas supply pipeline; a control part on the cathode supply pipeline is configured to obtain the gas pressure at the cathode outlet of the fuel cell stack through the pressure acquisition element placed on the cathode pipeline. In order to ensure that there is sufficient air on the cathode side of the fuel cell stack and avoid the occurrence of oxygen starvation under low-pressure environmental conditions, the speed of the air pump is controlled and increased according to the obtained gas pressure value; the control part on the anode supply pipeline is configured to compare the gas pressures at the inlets on the cathode and anode sides. When the pressure ratio is not equal to the threshold value, the pulse frequency of the gas injection valve is controlled so that the instantaneous flow of the gas in the anode supply pipeline responds quickly to the change of the air pump speed; anode side exhaust pipeline; cathode side exhaust pipeline.

[0034] In the above control method, the control parameters of the control part are based on the measured values ​​under normal air pressure conditions. A high-temperature methanol fuel cell operation experiment is carried out under normal air pressure conditions. The fuel cell system involved in the experiment is the above-mentioned fuel cell system. The gas pressure ratio on the cathode side of the fuel cell system stack is controlled to be equal to the gas pressure on the anode side of the threshold value (the measured value is (1 to 1.5), preferably 1.2), which can ensure the stable operation of the battery system. Under normal air pressure conditions, when the air pump speed is changed, the relationship between the change in the delivery gas flow rate and the air pump head is that the change in the head is proportional to the square of the change in the delivery gas flow rate. In the experiment, the air flow rate on the cathode side of the fuel cell system stack is changed according to the different requirements for the output power of the high-temperature methanol fuel cell.

[0035] In the above control method, the control part of the anode supply pipeline is based on the rapid response of the flow in the anode supply pipeline by controlling the pulse frequency of the gas injection valve when the air flow on the cathode side changes rapidly. When the methanol consumption remains unchanged within a certain interval, the flow of the methanol reforming reaction gas flowing through the gas injection valve during this interval will not change. When the gas flow required on the cathode side decreases, the total flow of the methanol reforming reaction gas is mainly changed by reducing the methanol flow entering the reforming reactor. The transient response of changing the cathode side air flow by changing the air pump speed is faster than controlling the anode side methanol reforming reaction gas by changing the methanol feed. Therefore, the gas injection valve frequency conversion control is used on the anode supply pipeline, and as a result, a rapid transient response of the anode side flow change can be achieved.

[0036] In the above control method, the ratio Pb / Pa of the gas pressure obtained by the anode supply pipeline and the gas pressure obtained by the cathode supply pipeline is always maintained equal to the gas pressure ratio threshold value of the cathode side and the anode side of the fuel cell system stack measured in the high-temperature methanol fuel cell operation experiment under normal gas pressure conditions. At the same time, both sides of the fuel cell system stack are guaranteed to avoid damage to the internal structure of the stack due to excessive pressure on either side, thereby ensuring the safe operation of the high-temperature methanol fuel cell system stack.

[0037] Figure 1 An example of a high-temperature methanol fuel cell system to which an embodiment of the present invention is applied is shown.

[0038] As shown in the figure, the hydrogen-rich methanol reformed gas produced by the methanol reforming reactor 3 (methanol-steam reforming reaction) enters the anode side of the stack 1 through the anode gas supply pipeline 4. The anode gas supply pipeline is equipped with an anode gas pressure acquisition element 8 (a pressure gauge is used here) and a gas injection valve 10 (a pulse solenoid valve is used here). The remaining gas is discharged from the fuel cell system stack through the exhaust pipeline 5 on the anode side of the stack.

[0039] Air flows through the cathode supply pipeline 6 via the air pump 2 and enters the cathode side of the stack 1, and the remaining air is discharged from the fuel cell system stack via the cathode side exhaust pipeline 7. The cathode supply pipeline is provided with a cathode gas pressure acquisition element 9 (a pressure gauge is used in this case).

[0040] The above fuel cell system operates under normal atmospheric pressure and discharges at a constant power of 500W. The methanol reforming reaction gas and air requirements under discharge requirements are obtained through experimental testing, which is used as a reference for the operation of the fuel cell system under low pressure conditions. Under low pressure conditions, the air flow is controlled by the control part 11 on the cathode supply pipeline, such as Figure 2 When the external air pressure is lower than the normal pressure (P02), increase the air pump speed (P03) to increase the air flow. The relationship between flow and speed is as follows: The relationship between the pressure head and the speed provided by the air pump 9 conforms to: When the pressure gauge 9 obtains that the pressure at point b is equal to the required value of P01 (P04), the speed is maintained constant (P05). When the pressure at point b is not equal to the required value of P01 and is greater than the required value of P01 (P06), the air pump speed is reduced (P07), otherwise the pump speed continues to be increased. The control purpose of the cathode side control part 11 is to ensure that there is sufficient air on the cathode side of the fuel cell stack to avoid oxygen starvation under low pressure environmental conditions.

[0041] As described above, when the fuel cell system is operated under low pressure conditions, the hydrogen-rich methanol reforming reaction gas on the anode side is controlled by the control part 12 on the cathode supply pipeline, such as Figure 3 The discharge requirement (P01) is the same as that on the cathode side. Figure 1 When the pressure at a and b is Pb / Pa = threshold (the value used here is 1.2) (P11), the fuel cell system operates stably and the pulse frequency of the pulse solenoid valve is constant. Under low pressure conditions, the pressure at b changes with the air pump 2. When Pb / Pa is greater than 1.2 (P13), the gas injection valve pulse injection time is reduced or the pulse interval time is increased (P14), and the instantaneous pressure at a on the anode side is increased. Similarly, when Pb / Pa is less than 1.2, the gas injection valve pulse injection time is increased or the pulse interval time is reduced (P15), and the instantaneous pressure at a on the anode side is reduced.

[0042] Through the above implementation, the high temperature methanol fuel cell system can meet the 500W constant power discharge under the low pressure environment of the plateau. The gas injection valve on the anode supply pipeline is controlled by frequency conversion to achieve a fast transient response to the flow change on the anode side, which makes up for the control lag of responding only by controlling the methanol flow entering the reforming reactor. At the same time, it ensures that the pressure ratio between the anode side and the cathode side is within the safety threshold, avoiding safety problems caused by damage to the internal structure of the fuel cell stack.

[0043] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should be regarded as within the scope of protection of the present invention.

Claims

1. A method for controlling low-pressure operation of a high-temperature fuel cell, characterized in that: include: The gas pressure at the outlet of the cathode gas supply pipeline (6) of the stack (1) is obtained by a cathode gas pressure obtaining element (9) placed on the cathode gas supply pipeline (6), and the rotation speed of the gas pump (2) is controlled according to the obtained gas pressure value; the gas pressure at the outlet of the anode gas supply pipeline (4) of the stack (1) is obtained by an anode gas pressure obtaining element (8) placed on the anode gas supply pipeline (4), and the pulse frequency of the gas injection valve (10) placed on the anode gas supply pipeline (4) is controlled according to the obtained gas pressure value; In the case of changing air pressure conditions, when the external air pressure is less than normal pressure, the air demand on the cathode side of the stack is changed by adjusting the rotation speed of the air pump (2); when the air flow on the cathode side changes rapidly, the pulse frequency of the gas injection valve (10) and the rotation speed of the air pump (2) are adjusted; The ratio Pb / Pa of the gas pressure Pa obtained by the anode gas supply pipeline (4) and the gas pressure Pb obtained by the cathode gas supply pipeline (6) is always maintained equal to the gas pressure ratio threshold of 1 to 1.5 on the cathode side and the anode side of the fuel cell system stack (1) measured in the high-temperature methanol fuel cell operation experiment under normal gas pressure conditions, so as to ensure that the internal structure of the fuel cell stack is not damaged due to excessive pressure on either side, thereby ensuring the safe operation of the high-temperature methanol fuel cell system stack; An anode-side exhaust pipeline (5) and a cathode-side exhaust pipeline (7) are respectively connected to the anode side and the cathode side of the fuel cell stack (1); The control method is implemented based on a high-temperature methanol fuel cell system, which comprises: a fuel cell stack (1), a reformer reactor (3), a stack anode gas supply pipeline (4), a stack cathode gas supply pipeline (6), an air pump (2), a controller, an anode side exhaust pipeline (5), and a cathode side exhaust pipeline (7); A fuel cell stack (1) generates electricity through an electrochemical reaction between an anode gas and a cathode gas; A reformer reactor (3), used for reforming methanol to provide hydrogen-rich fuel gas, is placed at the front end of the anode gas supply pipeline (4); A fuel cell stack anode gas supply pipeline (4), the anode gas supply pipeline (4) is provided with an anode gas pressure acquisition element (8) and a gas injection valve (10) for conveying methanol reforming reaction gas into the fuel cell stack anode; A cathode gas supply pipeline (6) for the fuel cell stack, wherein the cathode gas supply pipeline (6) is provided with a cathode gas pressure acquisition element (9) for conveying air into the cathode of the fuel cell stack; An air pump (2) is used to obtain cathode gas from the external environment and to supply external air to the fuel cell stack, and is placed at the front end of the cathode gas supply pipeline (6); A controller is electrically connected to the gas injection valve (10), the anode gas pressure acquisition element (8), the cathode gas pressure acquisition element (9), and the air pump (2), and is used to collect the gas pressure on the anode gas supply pipeline (4) and the cathode gas supply pipeline (6) of the stack, and to adjust the opening of the gas injection valve (10) and the rotation speed of the air pump (2); The anode side exhaust pipeline (5) and the cathode side exhaust pipeline (7) are respectively connected to the anode side and the cathode side of the fuel cell stack (1).

2. A method for controlling low-pressure operation of a high-temperature fuel cell according to claim 1, characterized in that: The gas injection valve adopts a pulse electromagnetic valve, which is placed on the anode gas supply pipeline (4). The instantaneous flow rate of the gas in the anode gas supply pipeline (4) is changed by setting the pulse frequency of the gas injection valve.

3. A method for controlling low-pressure operation of a high-temperature fuel cell according to claim 1, characterized in that: The anode gas pressure acquisition element (8) is a pressure gauge, which is placed on the anode gas supply pipeline (4) close to the anode inlet of the stack, and is used to monitor the gas pressure at the outlet of the anode gas supply pipeline (4).

4. A method for controlling low-pressure operation of a high-temperature fuel cell according to claim 1, characterized in that: The cathode gas pressure acquisition element (9) is a pressure gauge, which is placed on the cathode gas supply pipeline (6) close to the cathode inlet of the battery stack and is used to monitor the gas pressure at the outlet of the cathode gas supply pipeline (6).

5. A method for controlling low-pressure operation of a high-temperature fuel cell according to claim 1, characterized in that: The threshold is 1.2.

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