A direct methanol fuel cell system suitable for inferior fuel and a method for purifying feed

Abstract

The present invention provides a direct methanol fuel cell system suitable for inferior fuel, comprising: a buffer tank, a first liquid pump, a fuel purification module, a stack, an air compressor, a three-way solenoid valve, a fuel tank and a second liquid pump, wherein the fuel purification module is provided with a finished product layer, a raw material layer and a tail gas layer, the buffer tank, the first liquid pump, the finished product layer and the stack are connected in sequence, the inlet of the buffer tank is connected to the anode side outlet of the stack, the cathode inlet of the stack is connected to the air compressor, the cathode outlet of the stack is connected to the inlet of the three-way solenoid valve, the second outlet of the three-way solenoid valve is connected to the inlet of the tail gas layer, the raw material layer inlet is connected to the outlet of the second liquid pump, and the inlet of the second liquid pump is connected to the outlet of the fuel tank. The technical solution of the present invention solves the problem in the prior art that there is a lack of a direct methanol fuel cell system that can adapt to inferior methanol fuel without changing the stack state and operation strategy.

Description

Technical Field

[0001] The present invention relates to the technical field of direct methanol fuel cell systems, and in particular to a direct methanol fuel cell system suitable for inferior fuels and a method for purifying feed. Background Art

[0002] Direct methanol fuel cell (DMFC) is a power generation device that directly converts chemical energy into electrical energy. It has the advantages of low pollution, continuous power generation and high power generation efficiency. It has potential application prospects in many fields such as automotive power supply, aviation power supply, and marine power supply. In the application process, due to the diversity of the source and impurity composition of the raw material methanol, the performance and life of DMFC are quite different when used in different scenarios, which seriously hinders the development and promotion of DMFC. Therefore, the construction of DMFC suitable for inferior fuels containing many impurities has become one of the key technical issues for the commercial application of methanol fuel cells.

[0003] For dealing with impurities in inferior fuels, the traditional method is to improve the tolerance and endurance of the fuel cell stack to impurities in methanol by optimizing the fuel cell stack operation strategy or improving the fuel cell stack catalyst components, or to reduce the impurities adsorbed on the catalyst and regularly discharge the impurities in the fuel cell stack. The above methods can improve the adaptability of the fuel cell stack to inferior fuels, but all change the main state of the fuel cell stack and affect the performance and stability of the fuel cell stack. At present, there is still a lack of direct methanol fuel cell systems that can adapt to inferior fuels without changing the fuel cell stack state and operation strategy. Summary of the invention

[0004] According to the above-mentioned technical problem of lacking a direct methanol fuel cell system that can adapt to inferior methanol fuel without changing the state of the stack and the operating strategy, a direct methanol fuel cell system suitable for inferior fuel and a method for purifying feed are provided. The present invention uses a fuel purification module to purify methanol in inferior fuel without changing the state of the stack and the operating strategy, and uses it for stack operation, thereby improving the performance and stability of the direct methanol fuel cell system using inferior fuel, as well as the tolerance to inferior fuel, and reducing the requirements for fuel quality and the stack operation cost.

[0005] The technical means adopted by the present invention are as follows:

[0006] A direct methanol fuel cell system suitable for inferior fuels, comprising: a buffer tank, a first liquid pump, a fuel purification module, a fuel stack, an air compressor, a three-way solenoid valve, a fuel tank and a second liquid pump;

[0007] The fuel purification module is provided with a finished product layer, a raw material layer and an exhaust gas layer from top to bottom;

[0008] The finished product layer is provided with a finished product layer inlet and a finished product layer outlet;

[0009] The raw material layer is provided with a raw material layer inlet and a raw material layer outlet;

[0010] The tail gas layer is provided with a tail gas layer inlet and a tail gas layer outlet;

[0011] The outlet of the buffer tank is connected to the inlet of the first liquid pump, the outlet of the first liquid pump is connected to the inlet of the finished product layer, the outlet of the finished product layer is connected to the inlet of the anode side of the fuel cell stack, and the outlet of the anode side of the fuel cell stack is connected to the inlet of the buffer tank;

[0012] The cathode inlet of the fuel cell stack is connected to the air compressor, the cathode outlet of the fuel cell stack is connected to the inlet of the three-way solenoid valve, the first outlet of the three-way solenoid valve is connected to the atmosphere, the second outlet of the three-way solenoid valve is connected to the inlet of the tail gas layer, the outlet of the tail gas layer is connected to the atmosphere, the inlet of the raw material layer is connected to the outlet of the second liquid pump, the inlet of the second liquid pump is connected to the outlet of the fuel tank, and the outlet of the raw material layer is connected to the atmosphere.

[0013] Furthermore, a channel for the tail gas to flow is provided inside the tail gas layer, and two ends of the channel are respectively connected to the tail gas layer inlet and the tail gas layer outlet;

[0014] An area for storing low-quality fuel is provided inside the raw material layer, and two ends of the area are respectively connected to the raw material layer inlet and the raw material layer outlet;

[0015] An area for storing buffer solution is arranged inside the finished product layer, and two ends of the area are respectively connected with the finished product layer inlet and the finished product layer outlet.

[0016] Furthermore, the fuel purification module is also provided with: an electric heating plate, a molecular sieve membrane and a hydrophobic layer;

[0017] The electric heating plate is a flat plate structure and is provided with a positive electrode tab and a negative electrode tab;

[0018] The hydrophobic layer is composed of a hydrophobic filter membrane;

[0019] One side of the electric heating plate contacts the outer wall surface of the exhaust gas channel, and the other side contacts one side of the inferior fuel storage area of ​​the raw material layer, one side of the molecular sieve membrane contacts the other side of the inferior fuel storage area of ​​the raw material layer, the other side of the molecular sieve membrane contacts one side of the hydrophobic layer, and the other side of the hydrophobic layer contacts the buffer solution in the finished product layer.

[0020] Furthermore, the molecular sieve membrane is a NaA type molecular sieve membrane with a pore size of 0.4 nm.

[0021] Furthermore, the wall surface of the tail gas channel in the tail gas layer is made of metal or graphite.

[0022] Furthermore, the electric heating plate is a composite structural material with a resistance wire wrapped inside a ceramic plate, graphite, silicon carbide or a composite material.

[0023] Furthermore, the hydrophobic filter membrane is a polytetrafluoroethylene filter membrane or a polyvinylidene fluoride membrane.

[0024] Furthermore, the system also includes an auxiliary heating power supply, and the auxiliary heating power supply is connected to the positive electrode tab and the negative electrode tab respectively.

[0025] A method for purifying feed suitable for low-quality fuel, the method comprising the following steps:

[0026] S1. After the stack is running, set the initialization parameters: set the lower limit of methanol concentration C to maintain stable operation of the stack LOW , methanol concentration upper limit C HIGH and methanol concentration reference value C REF , the relationship C must be satisfied LOW ≤C REF ≤C HIGH , and set the methanol boiling point temperature T B 64.7℃;

[0027] S2, start the second liquid pump to introduce the inferior fuel into the raw material layer;

[0028] S3, open the first outlet of the three-way solenoid valve, close the second outlet of the three-way solenoid valve, and discharge the tail gas of the fuel cell stack directly into the atmosphere;

[0029] S4. Monitor the temperature T of the stack exhaust gas W and the methanol concentration in the buffer solution C NOW ;

[0030] S5, perform steps S6 and S7 simultaneously;

[0031] S6, when C NOW <C LOW When the auxiliary heating power is turned on, NOW >C HIGH When the auxiliary heating power is turned off, the cycle returns to step S5 and continues;

[0032] S7, when T W <T B When T W >T B And C NOW <CREF When C NOW >C REF When the first outlet of the three-way solenoid valve is opened, the second outlet of the three-way solenoid valve is closed, so that the tail gas of the fuel cell stack is directly discharged into the atmosphere, and then return to step 5 to continue the cycle.

[0033] Furthermore, C LOW , C REF and C HIGH is an empirical parameter set according to the membrane electrode type. When the membrane electrode of the stack is Nafion117 membrane, C LOW 0.5mol / L, C HIGH 1.3 mol / L, C REF is 0.8 mol / L. When the membrane electrode of the stack is Nafion212 membrane, C LOW 0.3 mol / L, C HIGH 0.7 mol / L, C REF It is 0.5mol / L.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] 1. The present invention provides a direct methanol fuel cell system and a method for purifying feed that is suitable for inferior fuels. By adding a fuel purification module, methanol in inferior fuels can be purified and used for stack operation without changing the stack state and operation strategy. This improves the tolerance of direct methanol fuel cells to inferior fuels and reduces the requirements for fuel quality and stack operation costs.

[0036] 2. The present invention provides a direct methanol fuel cell system suitable for inferior fuels and a method for purifying feed, which can significantly improve the performance and stability of direct methanol fuel cells when using inferior fuels with more impurities.

[0037] In summary, by applying the technical solution of the present invention to add a fuel purification module, methanol in low-quality fuel can be purified and used for stack operation without changing the stack state and operation strategy, thereby improving the tolerance of direct methanol fuel cells to low-quality fuels and reducing the requirements for fuel quality and stack operation costs. Therefore, the technical solution of the present invention solves the problem in the prior art that there is a lack of direct methanol fuel cell systems that can adapt to low-quality methanol fuel without changing the stack state and operation strategy.

[0038] Based on the above reasons, the present invention can be widely promoted in the fields of direct methanol fuel cell systems and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0040] Figure 1 This is a schematic diagram of the direct methanol fuel cell system of the present invention.

[0041] Figure 2 It is a schematic diagram of the structure of the fuel purification module described in the present invention.

[0042] Figure 3 This is a control flow chart of the purification feed method applicable to inferior fuels according to the present invention.

[0043] Figure 4 This is a comparison chart of the fuel cell stack performance before and after purification of the inferior fuel in Example 1.

[0044] In the figure: 1. buffer tank; 2. first liquid pump; 3. fuel purification module; 4. fuel cell stack; 5. air compressor; 6. three-way solenoid valve; 7. fuel tank; 8. second liquid pump; 9. auxiliary heating power supply; 10. finished product layer; 11. hydrophobic layer; 12. molecular sieve membrane; 13. raw material layer; 14. electric heating plate; 15. tail gas layer; 16. finished product layer inlet; 17. finished product layer outlet; 18. raw material layer inlet; 19. raw material layer outlet; 20. positive electrode ear of electric heating plate; 21. negative electrode ear of electric heating plate; 22. tail gas layer outlet; 23. tail gas layer inlet. DETAILED DESCRIPTION

[0045] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0048] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0049] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0050] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0051] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] like Figures 1-2 As shown, the present invention provides a direct methanol fuel cell system suitable for inferior fuel, comprising: a buffer tank 1, a first liquid pump 2, a fuel purification module 3, a fuel stack 4, an air compressor 5, a three-way solenoid valve 6, a fuel tank 7, a second liquid pump 8 and an auxiliary heating power supply 9;

[0054] The fuel cell purification module 3 is provided with a six-layer structure, which includes, from bottom to top, a tail gas layer 15, an electric heating plate 14, a raw material layer 13, a molecular sieve membrane 12, a hydrophobic layer 11 and a finished product layer 10;

[0055] The tail gas layer 15 is provided with a channel for the tail gas to flow, and the two ends of the channel are connected to the tail gas layer inlet 23 and the tail gas layer outlet 22 respectively;

[0056] The electric heating plate 14 is a flat plate structure with good thermal conductivity and certain resistance;

[0057] The raw material layer 13 is provided with an area for storing low-quality fuel, and the two ends of the area are connected to the raw material layer inlet 18 and the raw material layer outlet 19 respectively;

[0058] The molecular sieve membrane 12 is a NaA type molecular sieve membrane with a pore size of 0.4 nm;

[0059] The hydrophobic layer 11 is composed of a hydrophobic filter membrane;

[0060] The finished product layer 10 is provided with an area for storing a buffer solution, wherein the buffer solution is a methanol aqueous solution, and both ends of the area are connected to a finished product layer inlet 16 and a finished product layer outlet 17 respectively;

[0061] One side of the electric heating plate 14 contacts the outer wall surface of the exhaust gas channel, and the other side contacts one side of the inferior fuel storage area of ​​the raw material layer 13, the other side of the inferior fuel storage area of ​​the raw material layer 13 contacts one side of the molecular sieve membrane 12, one side of the hydrophobic layer 11 contacts the other side of the molecular sieve membrane 12, and the other side of the hydrophobic layer 11 contacts the buffer solution in the finished product layer 10.

[0062] The tail gas layer 5 is used to transfer the heat in the tail gas discharged from the fuel cell stack 4 to the electric heating plate 14, so as to utilize the waste heat of the discharged tail gas.

[0063] The electric heating plate 14 is used to heat the inferior fuel in the raw material layer 13 to vaporize the methanol in the inferior fuel. When the exhaust gas temperature is high, the electric heating plate 14 collects the heat of the exhaust gas and transfers it to the inferior fuel. When the temperature is low, the electric heating plate 14 starts to generate heat and heat the inferior fuel.

[0064] The raw material layer 13 is used to separate methanol from other high-boiling-point impurities (such as formic acid) in the inferior fuel.

[0065] The molecular sieve membrane 12 is used to screen the mixed gas after the inferior fuel in the raw material layer 13 is vaporized. The screening is performed by utilizing the difference in molecular size. The diameter of methanol molecules is about 0.36nm, the diameter of ethanol molecules is about 0.44nm, the diameter of acetone molecules is about 0.61nm, and the molecular diameters of other impurities are generally greater than 0.4nm. Therefore, a molecular sieve membrane with a pore size of 0.4nm can be used to purify methanol vapor.

[0066] The hydrophobic layer 11 is used to prevent the buffer solution from penetrating into the molecular sieve membrane 12, so that the methanol vapor passes through the hydrophobic filter membrane, while the buffer solution cannot pass through the hydrophobic filter membrane. The hydrophobic filter membrane can use all hydrophobic membranes, not limited to polytetrafluoroethylene membranes or polyvinylidene fluoride membranes.

[0067] The finished product layer 10 is used to dissolve the purified methanol vapor in the buffer solution, increase the methanol concentration in the buffer solution, replenish part of the methanol consumed by the fuel cell stack 4, and maintain the stability of the methanol concentration in the buffer solution.

[0068] The outlet of the buffer tank 1 is connected to the inlet of the first liquid pump 2 , the outlet of the first liquid pump 2 is connected to the finished product layer inlet 16 , the finished product layer outlet 17 is connected to the anode side inlet of the fuel cell stack 4 , and the anode side outlet of the fuel cell stack 4 is connected to the inlet of the buffer tank 1 .

[0069] The cathode inlet of the fuel cell stack 4 is connected to the air compressor 5, the cathode outlet of the fuel cell stack 4 is connected to the inlet of the three-way solenoid valve 6, the first outlet of the three-way solenoid valve 6 is connected to the atmosphere, the second outlet of the three-way solenoid valve 6 is connected to the tail gas layer inlet 23, the tail gas layer outlet 22 is connected to the atmosphere, the raw material layer inlet 18 is connected to the outlet of the second liquid pump 8, the inlet of the second liquid pump 8 is connected to the outlet of the fuel tank 7, and the raw material layer outlet 19 is connected to the atmosphere.

[0070] The buffer tank 1 is filled with a certain amount of the buffer solution, and the buffer solution can circulate between the buffer tank 1, the first liquid pump 2, the finished product layer 10 and the battery stack 4 when the battery stack 4 is working.

[0071] The air compressor 5 is used to provide the oxidant (air) required for the operation of the fuel cell stack 4. The function of the three-way solenoid valve 6 is to transport the exhaust gas, and the exhaust gas of the fuel cell stack 4 is transported to the exhaust gas layer 15 for waste heat utilization. The raw material layer outlet 19 is used to discharge impurities and pollutants in the inferior fuel.

[0072] Furthermore, the wall surface of the tail gas channel in the tail gas layer 15 is made of materials such as metal and graphite with high thermal conductivity.

[0073] Furthermore, the electric heating plate 14 may be made of graphite, silicon carbide or other composite materials, or a composite structure material in which a resistance wire is wrapped inside a ceramic plate.

[0074] Furthermore, the hydrophobic filter membrane is a polytetrafluoroethylene filter membrane.

[0075] Furthermore, the electric heating plate 14 is provided with a positive electrode tab and a negative electrode tab, and the auxiliary heating power supply 9 is respectively connected to the positive electrode tab and the negative electrode tab. The auxiliary heating power supply 9 is used to drive the electric heating plate 14 to generate Joule heat to heat the inferior fuel when the temperature of the exhaust gas is low.

[0076] The working process of the direct methanol fuel cell system suitable for low-quality fuel is as follows:

[0077] When the fuel cell stack 4 starts to work, the second liquid pump 8 is started to inject the inferior fuel in the fuel tank 7 into the raw material layer 13, and the inferior fuel in the raw material layer 13 is heated by the electric heating plate 14 to vaporize substances with lower boiling points (such as methanol, ethanol, acetone, etc.) to form a mixed gas, and impurities with high boiling points remain in liquid state and are discharged through the raw material layer outlet 19. The methanol in the mixed gas passes through the molecular sieve membrane 12 and reaches the hydrophobic layer 11 to form methanol vapor. The remaining impurity mixed gas is directly discharged into the atmosphere through the raw material layer outlet 19 or dissolved in liquid impurities and discharged. The methanol vapor passes through the hydrophobic filter membrane to reach the finished product layer 10, and the first liquid pump 2 is turned on. The buffer solution stored in the buffer tank 1 is injected into the finished product layer 10, and the methanol vapor dissolves in the buffer solution, thereby increasing the methanol concentration in the buffer solution so that the methanol concentration in the buffer solution reaches the range required for the stable operation of the fuel cell 4. The buffer solution that meets the methanol concentration range flows into the fuel cell 4 from the finished product layer outlet 17 to participate in the reaction. The buffer solution after the reaction flows out of the fuel cell 4 and enters the buffer tank 1 to continue circulating. The exhaust gas generated by the fuel cell 4 in the reaction enters the exhaust layer 15 through the cathode outlet of the fuel cell 4 and the three-way solenoid valve 6, indirectly providing heat for the inferior fuel in the raw material layer 13, and is finally discharged into the atmosphere through the exhaust layer outlet 22.

[0078] The function of the fuel purification module 3 is to maintain the methanol concentration in the buffer solution entering the fuel cell stack 4 within a specified range. When the methanol concentration in the buffer solution is low, the purification rate of methanol in the inferior fuel is accelerated, so that more methanol vapor is dissolved in the buffer solution and the methanol concentration is increased. When the methanol concentration in the buffer solution is high, the purification rate of methanol in the inferior fuel is reduced, the amount of methanol purification is reduced, and the methanol concentration in the buffer solution is reduced, so that the methanol concentration is reduced to within the specified range.

[0079] like Figure 3 As shown, according to the direct methanol fuel cell system suitable for inferior fuel, the present invention also provides a controlled purification feed method suitable for inferior fuel, the method comprising the following steps:

[0080] S1. After the stack is running, set the initialization parameters: set the lower limit of methanol concentration C to maintain stable operation of the stack LOW , methanol concentration upper limit C HIGH and methanol concentration reference value C REF , which needs to satisfy the relationship C LOW ≤C REF ≤C HIGH , and set the methanol boiling point temperature T B 64.7℃;

[0081] S2, start the second liquid pump to introduce the inferior fuel into the raw material layer;

[0082] S3, open the first outlet of the three-way solenoid valve, close the second outlet of the three-way solenoid valve, and discharge the tail gas of the fuel cell stack directly into the atmosphere;

[0083] S4. Monitor the temperature T of the stack exhaust gas W , monitor the methanol concentration C in the buffer solution NOW ;

[0084] S5, perform steps S6 and S7 simultaneously;

[0085] S6, when C NOW <C LOW When the auxiliary heating power is turned on, NOW >C HIGH When the auxiliary heating power is turned off, the cycle returns to step S5 and continues;

[0086] S7, when T W <T B When T W >T B And C NOW <C REF When C NOW >C REF When the first outlet of the three-way solenoid valve is opened, the second outlet of the three-way solenoid valve is closed, so that the tail gas of the fuel cell stack is directly discharged into the atmosphere, and then return to step 5 to continue the cycle.

[0087] Furthermore, C LOW , C REF and C HIGH is an empirical parameter set according to the membrane electrode type. When the membrane electrode of the stack is Nafion117 membrane, C LOW 0.5mol / L, C HIGH 1.3 mol / L, C REF is 0.8 mol / L. When the membrane electrode of the stack is Nafion212 membrane, C LOW 0.3 mol / L, C HIGH 0.7 mol / L, C REF It is 0.5mol / L.

[0088] Using the direct fuel cell system and the controlled purification feeding method of inferior fuel, a 25W direct methanol fuel cell was tested using purified fuel and inferior fuel respectively. The results of the two tests were compared. Figure 4 As shown, from the analysis data in the diagram, it can be seen that within the 4h running test, the average voltage of the fuel cell stack using inferior fuel is 13.18V, and the voltage drop rate is 22.73mV / h. The average voltage of the fuel cell stack using purified fuel is 13.61V, and the voltage drop rate is 2.94mV / h, indicating that the performance of the fuel cell stack after purification is better than that of the inferior fuel cell stack, proving that the present invention can improve both the performance and stability of the fuel cell stack.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A direct methanol fuel cell system suitable for low-quality fuel, characterized in that: include: Buffer tank, first liquid pump, fuel purification module, fuel stack, air compressor, three-way solenoid valve, fuel tank and second liquid pump; The fuel purification module is provided with a finished product layer, a raw material layer and an exhaust gas layer from top to bottom; The finished product layer is provided with a finished product layer inlet and a finished product layer outlet; The raw material layer is provided with a raw material layer inlet and a raw material layer outlet; The tail gas layer is provided with a tail gas layer inlet and a tail gas layer outlet; The outlet of the buffer tank is connected to the inlet of the first liquid pump, the outlet of the first liquid pump is connected to the inlet of the finished product layer, the outlet of the finished product layer is connected to the inlet of the anode side of the fuel cell stack, and the outlet of the anode side of the fuel cell stack is connected to the inlet of the buffer tank; The cathode inlet of the fuel cell stack is communicated with the air compressor, the cathode outlet of the fuel cell stack is communicated with the inlet of the three-way solenoid valve, the first outlet of the three-way solenoid valve is communicated with the atmosphere, the second outlet of the three-way solenoid valve is communicated with the inlet of the tail gas layer, the outlet of the tail gas layer is communicated with the atmosphere, the inlet of the raw material layer is communicated with the outlet of the second liquid pump, the inlet of the second liquid pump is communicated with the outlet of the fuel tank, and the outlet of the raw material layer is communicated with the atmosphere; The tail gas layer is provided with a channel for tail gas flow, and two ends of the channel are respectively connected to the tail gas layer inlet and the tail gas layer outlet; An area for storing low-quality fuel is provided inside the raw material layer, and two ends of the area are respectively connected to the raw material layer inlet and the raw material layer outlet; An area for storing buffer solution is provided inside the finished product layer, and two ends of the area are respectively connected to the finished product layer inlet and the finished product layer outlet; The fuel purification module is also provided with: an electric heating plate, a molecular sieve membrane and a hydrophobic layer; The electric heating plate is a flat plate structure and is provided with a positive electrode tab and a negative electrode tab; The hydrophobic layer is composed of a hydrophobic filter membrane; One side of the electric heating plate contacts the outer wall surface of the channel of the tail gas layer, and the other side contacts one side of the inferior fuel storage area of ​​the raw material layer, the other side of the inferior fuel storage area of ​​the raw material layer contacts one side of the molecular sieve membrane, the other side of the molecular sieve membrane contacts one side of the hydrophobic layer, and the other side of the hydrophobic layer contacts the buffer solution in the finished product layer; The molecular sieve membrane is a NaA type molecular sieve membrane with a pore size of 0.4 nm.

2. The direct methanol fuel cell system suitable for low-quality fuel according to claim 1, characterized in that: The wall surface of the tail gas channel in the tail gas layer is made of metal or graphite.

3. The direct methanol fuel cell system suitable for low-quality fuel according to claim 1, characterized in that: The electric heating plate is a ceramic plate with a resistance wire composite structure material, graphite, silicon carbide or a composite material wrapped inside.

4. The direct methanol fuel cell system suitable for low-quality fuel according to claim 1, characterized in that: The hydrophobic filter membrane is a polytetrafluoroethylene filter membrane or a polyvinylidene fluoride membrane.

5. The direct methanol fuel cell system suitable for low-quality fuel according to claim 1, characterized in that: The system further comprises an auxiliary heating power source, and the auxiliary heating power source is connected to the positive electrode tab and the negative electrode tab respectively.

6. A method for purifying feed suitable for inferior fuel, characterized in that: The direct methanol fuel cell system suitable for low-quality fuel according to claim 1 is adopted, and the method comprises the following steps: S1. After the stack is running, set the initialization parameters: set the lower limit of methanol concentration C to maintain stable operation of the stack LOW , methanol concentration upper limit C HIGH and methanol concentration reference value C REF , which needs to satisfy the relationship C LOW ≤C REF ≤C HIGH , and set the methanol boiling point temperature T B 64.7℃; S2, start the second liquid pump to introduce the inferior fuel into the raw material layer; S3, open the first outlet of the three-way solenoid valve, close the second outlet of the three-way solenoid valve, and discharge the tail gas of the fuel cell stack directly into the atmosphere; S4. Monitor the temperature T of the stack exhaust gas W and the methanol concentration in the buffer solution C NOW ; S5, perform steps S6 and S7 simultaneously; S6, when C NOW <C LOW When the auxiliary heating power is turned on, NOW >C HIGH When the auxiliary heating power is turned off, the cycle returns to step S5 and continues; S7, when T W <T B When T W >T B And C NOW <C REF When C NOW >C REF When the first outlet of the three-way solenoid valve is opened, the second outlet of the three-way solenoid valve is closed, so that the tail gas of the fuel cell stack is directly discharged into the atmosphere, and then return to step 5 to continue the cycle.

7. The method for purifying feed suitable for inferior fuel according to claim 6, characterized in that: C LOW , C REF and C HIGH is an empirical parameter set according to the membrane electrode type. When the membrane electrode of the stack is Nafion117 membrane, C LOW 0.5mol / L, C HIGH 1.3 mol / L, C REF is 0.8 mol / L. When the membrane electrode of the stack is Nafion212 membrane, C LOW 0.3 mol / L, C HIGH 0.7 mol / L, C REF It is 0.5mol / L.

Images