A multi-stage liquid equalizing and heat exchanging integrated device applied to a vanadium redox flow battery

Abstract

The application discloses a multistage liquid equalizing and heat exchanging integrated device applied to a full vanadium redox flow battery, which comprises a positive electrode storage tank and a negative electrode storage tank, a positive electrode liquid returning and liquid distributing pipe, a cooling water inlet and a cooling water outlet are connected to the positive electrode storage tank, the positive electrode liquid returning and liquid distributing pipe is directly connected with an electric pile, a negative electrode liquid returning and liquid sucking pipe is connected to the negative electrode storage tank, and the negative electrode liquid returning and liquid sucking pipe is also directly connected with the electric pile, a primary heat exchanging device is arranged on the positive electrode electrolyte liquid returning pipe through design, the largest heat transfer temperature difference characteristic of the out-pile electrolyte and the coolant is effectively utilized, the design of the primary heat exchanging device can effectively reduce the energy consumption of the rear-end heat exchanging system, the primary heat exchanging device is coupled with the liquid returning and liquid equalizing device, and the organic combination and mutual promotion of the two are realized, and the top of the storage tank is designed with the liquid returning four-stage liquid equalizing design and the bottom of the storage tank is designed with the conical liquid collecting and distributed liquid sucking pipe design, so that the uniform distribution and the uniform liquid sucking of the electrolyte are fully ensured.

Description

Technical Field

[0001] The present invention relates to the field of all-vanadium redox flow batteries, and in particular to a multi-stage liquid equalization and heat exchange integrated device applied to all-vanadium redox flow batteries. Background Art

[0002] At present, the design of the electrolyte circulation system of all-vanadium liquid flow batteries adopts the method of spraying the electrolyte out of the battery stack directly from the top of the storage tank, and the circulation pump draws the liquid from the liquid distribution pipe arranged horizontally at the bottom of the storage tank. This design method can effectively save equipment construction costs and equipment floor space, but the ion cross-talk between the electrolyte returning from the battery stack and the original electrolyte inside the storage tank will reduce the utilization rate of the electrolyte entering the battery stack, while reducing the battery conversion efficiency, it will also increase the ion cross-talk self-discharge loss and the energy consumption of auxiliary equipment.

[0003] At the same time, during charging and discharging, chemical reactions in all-vanadium flow batteries, accompanied by heat absorption and release, cause the temperature of the electrolyte solution, the energy storage medium of the battery system, to fluctuate. Heat generation and absorption primarily include reaction heat, polarization heat, Joule heat, self-discharge heat, and the conversion of mechanical energy into thermal energy. The vast majority of this heat enters the electrolyte directly, causing the electrolyte temperature to rise. As the electrolyte circulates, some of this heat is transferred to the external environment through conduction, convection, and radiation.

[0004] Currently, the DC-side charge and discharge efficiency of all-vanadium redox flow batteries reaches 75%-80%, with an energy loss rate of 20%-25%. Based on measurements and statistics of actual operating data from typical all-vanadium redox flow batteries, approximately 15% of the charging energy and 60%-75% of the total energy loss are converted into heat and stored in the battery system's electrolyte solution.

[0005] Both high and low electrolyte temperatures in vanadium flow batteries can cause vanadium ions to precipitate, leading to blockage in the battery stack and potentially posing a safety hazard. Therefore, a separate heat exchanger is required to heat the electrolyte and ensure safe and normal operation of the system.

[0006] Currently, heat exchangers used in all-vanadium flow battery systems are primarily located on the cathode electrolyte outlet pipeline. These include traditional air-cooled heat exchangers and plate-type heat exchangers with compressors. Air-cooled heat exchangers are significantly affected by ambient temperature and suffer from poor cooling performance, while plate-type heat exchangers with compressors suffer from high energy consumption. Furthermore, the temperature difference between the electrolyte and the refrigerant decreases after mixing in the storage tank, hindering heat exchange between the two. Summary of the Invention

[0007] The purpose of the present invention is to provide a multi-stage liquid equalization and heat exchange integrated device for all-vanadium liquid flow batteries. By designing a first-stage heat exchange device to be arranged on the positive electrolyte return line, the characteristic of the largest heat transfer temperature difference between the electrolyte leaving the stack and the coolant is effectively utilized. The design of the first-stage heat exchange device can effectively reduce the energy consumption of the back-end heat exchange system. The first-stage heat exchange device is coupled with the liquid return equalization device to achieve an organic combination and mutual promotion of the two. By designing a four-stage liquid return equalization design at the top of the storage tank and a conical liquid collection and distributed suction pipe design at the bottom of the storage tank, the uniform distribution of the electrolyte and uniform liquid absorption are fully guaranteed.

[0008] A multi-stage liquid equalization and heat exchange integrated device for an all-vanadium redox flow battery includes a positive electrode storage tank and a negative electrode storage tank. The positive electrode storage tank is connected to a positive electrode liquid return distribution pipe, a cooling water inlet, and a cooling water outlet. The positive electrode liquid return distribution pipe is directly connected to the battery stack. The negative electrode storage tank is connected to a negative electrode liquid return distribution pipe, which is also directly connected to the battery stack.

[0009] The bottom of the positive electrode storage tank and the negative electrode storage tank are both provided with distributed suction pipes. The distributed suction pipe at the bottom of the positive electrode storage tank is connected to the positive electrode liquid outlet heat exchanger through an embedded suction pipe. The positive electrode liquid outlet heat exchanger is connected to the battery stack. The distributed suction pipe at the bottom of the negative electrode storage tank is directly connected to the battery stack through another embedded suction pipe.

[0010] Preferably, a positive electrode return liquid cooling device and a positive electrode uniformly distributed liquid mixing tank are provided on the top of the positive electrode storage tank, the positive electrode return liquid distribution pipe, the cooling water inlet and the cooling water outlet are all connected to the top of the positive electrode return liquid cooling device, the positive electrode uniformly distributed liquid mixing tank is connected to the bottom of the positive electrode return liquid cooling device, and a liquid equalizer is provided at the bottom of the positive electrode uniformly distributed liquid mixing tank.

[0011] Preferably, a negative electrode uniform distribution mixing tank is provided on the top of the negative electrode storage tank, the negative electrode liquid return pipette is directly connected to the top of the negative electrode uniform distribution mixing tank, and a liquid equalizer is also provided at the bottom of the negative electrode uniform distribution mixing tank.

[0012] Preferably, the embedded liquid suction tube connected to the positive electrode storage tank is connected to a positive electrode liquid suction pump, and the embedded liquid suction tube connected to the negative electrode storage tank is connected to a negative electrode liquid suction pump.

[0013] Preferably, the positive electrode liquid outlet heat exchanger is further connected to a cooling fan via a three-way reversing valve, the cooling fan is further connected to a compressor, and the cooling fan is further connected to a coolant storage tank.

[0014] Preferably, the coolant storage tank is also connected to the positive electrode liquid outlet heat exchanger, and a refrigerant circulation pump is also connected between the coolant storage tank and the positive electrode liquid outlet heat exchanger.

[0015] The advantages of the present invention are:

[0016] 1. The heat exchange device of this design adopts a three-stage heat exchange design: first, a first-stage heat exchange design is adopted in the electrolyte return pipeline, which effectively utilizes the characteristic of the largest heat transfer temperature difference between the electrolyte leaving the stack and the coolant, and uses cheap and easily available underground cooling water to perform primary heat exchange on the electrolyte, which can effectively reduce the energy loss of subsequent heat exchange equipment; secondly, a second-stage and third-stage heat exchange design of an air-cooled fluorine system and a compressor fluorine system is adopted in the electrolyte outlet pipeline. When the ambient temperature is lower than the setting threshold of the third-stage heat exchange temperature, the second-stage air-cooled heat exchange with lower energy consumption is adopted. When the ambient temperature reaches the setting threshold of the third-stage heat exchange temperature, the third-stage compressor plate heat exchange is started to ensure that the electrolyte temperature is within the safe operating temperature range.

[0017] 2. This design uses an integrated heat exchange and liquid equalization device on the top of the storage tank. The positive electrode return liquid first passes through the positive electrode return liquid distribution pipe for a uniform liquid distribution, then flows through the open cooling device to exchange heat with the cooling water while being disturbed by the heat exchange tube for a second uniform liquid distribution. The electrolyte flowing out of the heat exchanger is distributed three times by the stepped spreading plate and then thrown out after passing through the liquid equalizer, realizing a four-fold uniform liquid distribution of the return liquid. The design of the four-fold uniform liquid distribution fully ensures the uniform distribution of the electrolyte returned to the storage tank.

[0018] 3. This design uses a conical liquid collection trough at the bottom of both the positive and negative electrode storage tanks. The conical liquid collection trough and the storage tank are cast as one piece, and an embedded liquid suction pipe is arranged above the conical liquid collection trough. Each embedded liquid suction pipe is evenly distributed with liquid suction holes. The electrolyte sucked in by the embedded liquid suction pipe is collected in the main pipe at the bottom of the conical trough and then sucked out. While ensuring that there is no dead zone in the liquid suction at the bottom of the storage tank, the electrolyte is evenly absorbed, which can effectively improve the vanadium ion uniformity of the electrolyte and the electrolyte utilization rate, reduce the number of times the electrolyte is added to the stack, thereby reducing the energy consumption of the auxiliary system and improving the system conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the system principle of the device of the present invention;

[0020] Figure 2 Schematic diagram of the top structure of the positive electrode storage tank in the device of the present invention;

[0021] Figure 3 It is a side view of the top of the positive electrode storage tank in the device of the present invention;

[0022] Figure 4 for Figure 2 Enlarged view of part A;

[0023] Among them, 1. positive electrode return liquid distribution pipe, 2. positive electrode return liquid cooling device, 3. uniformly distributed mixing tank, 4. cooling water inlet, 5. cooling water outlet, 6. liquid equalizer, 7. conical liquid collection tank, 8. distributed suction pipe, 9. embedded suction pipe, 10. positive electrode suction pump, 11. positive electrode liquid outlet heat exchanger, 12. three-way reversing valve, 13. cooling fan, 14. fuel cell stack, 15. compressor, 16. coolant storage tank, 17. refrigerant circulation pump, 18. negative electrode suction pump, 19. negative electrode collection tank, 20. negative electrode return liquid distribution suction pipe, 21. uniformly distributed mixing tank. DETAILED DESCRIPTION

[0024] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0025] like Figures 1 to 4 As shown, the present invention includes a positive electrode storage tank and a negative electrode storage tank. The positive electrode storage tank is connected to a positive electrode liquid return distribution pipe 1, a cooling water inlet 4 and a cooling water outlet 5. The positive electrode liquid return distribution pipe 1 is directly connected to the battery stack 14. The negative electrode storage tank is connected to a negative electrode liquid return distribution pipe 20. The negative electrode liquid return distribution pipe 20 is also directly connected to the battery stack 14.

[0026] A distributed suction pipe 8 is provided at the bottom of the positive electrode storage tank and the negative electrode storage tank. The distributed suction pipe 8 at the bottom of the positive electrode storage tank is connected to the positive electrode liquid outlet heat exchanger 11 through an embedded liquid suction pipe 9. The positive electrode liquid outlet heat exchanger 11 is connected to the battery stack 14. The distributed suction pipe 8 at the bottom of the negative electrode storage tank is directly connected to the battery stack 14 through another embedded liquid suction pipe 9.

[0027] A positive electrode return liquid cooling device 2 and a positive electrode uniformly distributed liquid mixing tank 3 are provided on the top of the positive electrode storage tank. The positive electrode return liquid distribution pipe 1, the cooling water inlet 4 and the cooling water outlet 5 are all connected to the top of the positive electrode return liquid cooling device 2. The positive electrode uniformly distributed liquid mixing tank 3 is connected to the bottom of the positive electrode return liquid cooling device 2. A liquid equalizer 6 is provided at the bottom of the positive electrode uniformly distributed liquid mixing tank 3.

[0028] A negative electrode uniformly distributed liquid mixing tank 21 is provided on the top of the negative electrode storage tank. The negative electrode liquid return pipe 20 is directly connected to the top of the negative electrode uniformly distributed liquid mixing tank 21. A liquid equalizer 6 is also provided at the bottom of the negative electrode uniformly distributed liquid mixing tank 21.

[0029] The embedded liquid suction pipe 9 connected to the positive electrode storage tank is connected to a positive electrode liquid suction pump 10, and the embedded liquid suction pipe 9 connected to the negative electrode storage tank is connected to a negative electrode liquid suction pump 18.

[0030] The positive electrode liquid outlet heat exchanger 11 is further connected to a cooling fan 13 via a three-way reversing valve 12 . The cooling fan 13 is further connected to a compressor 15 , and the cooling fan 13 is further connected to a coolant storage tank 16 .

[0031] The coolant storage tank 16 is also connected to the cathode liquid outlet heat exchanger 11 , and a refrigerant circulation pump 17 is also connected between the coolant storage tank 16 and the cathode liquid outlet heat exchanger 11 .

[0032] Specific implementation and principle:

[0033] The positive electrode storage tank is provided with an integrated liquid equalizing cooling device and a conical liquid collecting tank. During the operation of the system, the positive electrode pump 10 is connected to the distributed liquid equalizing pipe 8 at the bottom of the barrel through the embedded liquid equalizing pipe 9 to absorb liquid, ensuring that the valence of the vanadium ions in the inhaled liquid is balanced. At the same time, a heat exchanger 11 is set at the liquid outlet of the pump 10 for cooling (the cooling method here adopts two methods: air-cooled fluorine system and compressor fluorine system, which can be switched to cope with system operation in different environments) to ensure that the temperature of the liquid entering the fuel cell stack is within the design range. After the reaction of the fuel cell stack 14, the electrolyte enters the integrated liquid equalizing cooling device through the return liquid pipe, first fully distributes the liquid in the return liquid distribution pipe 1, enters the open cooling device 2 for cooling, and then enters the uniform liquid mixing tank 3 for equalization to ensure that the valence of the vanadium ions in the return liquid is balanced. Finally, it is evenly distributed again through the liquid equalizer 6. Through this multiple distribution and mixing method, the valence of the vanadium ions in the liquid is kept balanced, thereby improving the utilization efficiency of the electrolyte.

[0034] Negative electrode storage tank: The negative electrode storage tank is equipped with a liquid equalizing device and a conical liquid collecting tank. The operation of this system is similar to that of the positive electrode system, except that the cooling system is reduced in the liquid inlet and liquid return systems, and the multiple distribution and mixing method is retained to ensure that the valence state of vanadium ions in the liquid remains balanced and improve the utilization efficiency of the electrolyte.

[0035] The existing mainstream all-vanadium flow battery design mainly uses air cooling heat exchange or compressor plate refrigeration heat exchange in the positive electrode electrolyte outlet pipeline. However, the heat transfer temperature difference between the electrolyte and the refrigerant is reduced after the electrolyte storage tank is mixed, and the heat exchange effect is not ideal.

[0036] The first-stage heat exchanger of this design is set on the positive electrode electrolyte return pipeline, which effectively utilizes the characteristic of the largest heat transfer temperature difference between the electrolyte leaving the stack and the coolant. The design of the first-stage heat exchanger can effectively reduce the energy consumption of the back-end heat exchange system.

[0037] In the previous design process of the all-vanadium liquid flow battery system, the heat exchange device and the liquid equalization device were designed separately, and the two failed to be organically combined to achieve mutual promotion.

[0038] The first-stage heat exchange device of this design is coupled with the liquid return and equalization device, realizing the organic combination and mutual promotion of the two.

[0039] The traditional design adopts the method of spraying the electrolyte return directly into the storage tank from the top, resulting in uneven return liquid distribution. In addition, there is a liquid dead zone when the electrolyte is absorbed through the liquid distribution pipe at the bottom of the storage tank, which is not conducive to improving the utilization rate of the electrolyte.

[0040] Operational process after the change: This design fully ensures the uniform distribution and uniform absorption of electrolyte by designing a four-level liquid equalization design for liquid return at the top of the tank and a conical liquid collection and distributed liquid suction pipe design at the bottom of the tank.

[0041] Based on the above, the present invention effectively utilizes the maximum temperature difference between the heat transfer of the electrolyte leaving the stack and the coolant by designing a first-stage heat exchange device to be arranged on the positive electrode electrolyte return line. The design of the first-stage heat exchange device can effectively reduce the energy consumption of the back-end heat exchange system. The first-stage heat exchange device is coupled with the return liquid equalization device to achieve an organic combination and mutual promotion of the two. By designing a four-stage return liquid equalization design at the top of the storage tank and a conical liquid collection and distributed suction pipe design at the bottom of the storage tank, the uniform distribution of the electrolyte and uniform liquid absorption are fully guaranteed.

[0042] It is understood from common technical knowledge that the present invention may be implemented by other embodiments that do not depart from its spirit or essential features. Therefore, the embodiments disclosed above are, in all respects, merely illustrative and not exclusive. All modifications within the scope of the present invention or equivalent to the scope of the present invention are intended to be encompassed by the present invention.

Claims

1. A multi-stage liquid equalization and heat exchange integrated device for all-vanadium redox flow batteries, comprising a positive electrode storage tank and a negative electrode storage tank, characterized in that: The positive electrode storage tank is connected to a positive electrode liquid return distribution pipe (1), a cooling water inlet (4) and a cooling water outlet (5), the positive electrode liquid return distribution pipe (1) is directly connected to the battery stack (14), and the negative electrode storage tank is connected to a negative electrode liquid return distribution pipe (20), the negative electrode liquid return distribution pipe (20) is also directly connected to the battery stack (14); The bottoms of the positive electrode storage tank and the negative electrode storage tank are both provided with distributed suction pipes (8), the distributed suction pipes (8) at the bottom of the positive electrode storage tank are connected to the positive electrode liquid outlet heat exchanger (11) via an embedded liquid suction pipe (9), the positive electrode liquid outlet heat exchanger (11) is connected to the battery stack (14), and the distributed suction pipes (8) at the bottom of the negative electrode storage tank are directly connected to the battery stack (14) via another embedded liquid suction pipe (9); The top of the positive electrode storage tank is provided with a positive electrode liquid return cooling device (2) and a positive electrode uniformly distributed liquid mixing tank (3); the positive electrode liquid return distribution pipe (1), the cooling water inlet (4) and the cooling water outlet (5) are all connected above the positive electrode liquid return cooling device (2); the positive electrode uniformly distributed liquid mixing tank (3) is connected below the positive electrode liquid return cooling device (2); and a liquid equalizer (6) is provided at the bottom of the positive electrode uniformly distributed liquid mixing tank (3); The positive electrode liquid outlet heat exchanger (11) is also connected to a cooling fan (13) through a three-way reversing valve (12); the cooling fan (13) is also connected to a compressor (15), and the cooling fan (13) is also connected to a coolant storage tank (16); the coolant storage tank (16) is also connected to the positive electrode liquid outlet heat exchanger (11), and a refrigerant circulation pump (17) is also connected between the coolant storage tank (16) and the positive electrode liquid outlet heat exchanger (11).

2. The multi-stage liquid equalization and heat exchange integrated device for all-vanadium redox flow batteries according to claim 1, characterized in that: A negative electrode uniformly distributed liquid mixing tank (21) is provided on the top of the negative electrode storage tank, the negative electrode liquid return pipe (20) is directly connected to the top of the negative electrode uniformly distributed liquid mixing tank (21), and a liquid equalizer (6) is also provided at the bottom of the negative electrode uniformly distributed liquid mixing tank (21).

3. The multi-stage liquid equalization and heat exchange integrated device for all-vanadium redox flow batteries according to claim 1, characterized in that: The embedded liquid suction pipe (9) connected to the positive electrode storage tank is connected to a positive electrode liquid suction pump (10), and the embedded liquid suction pipe (9) connected to the negative electrode storage tank is connected to a negative electrode liquid suction pump (18).

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