Online regeneration system and method for positive electrode precipitate of flow battery

Abstract

The invention discloses an online regeneration system and method for positive electrode precipitates of a flow battery, and the regeneration system comprises a precipitate collection unit which is arranged at the bottom of a positive electrode liquid storage tank; the electrolytic regeneration unit is used for carrying out electrolytic reduction on the positive electrode precipitation electrolytic mixed liquid, and the electrolytic regeneration unit is connected with the positive electrode liquid storage tank through a conveying unit; the sampling and diluting unit is used for sampling according to a preset period in the reduction process and diluting a sample to a preset concentration; and the detection and analysis unit is used for carrying out absorbance detection on a sample obtained by sampling, and determining an electrolysis end point when the detected absorbance value reaches a preset light absorption threshold value, so as to control the electrolysis regeneration unit to stop and re-inject the reduced electrolyte into the positive electrode liquid storage tank through the conveying unit. According to the invention, the on-line regeneration of the precipitate is realized, and only the precipitate part is collected from the electrolytic regeneration unit, so that the normal work of the positive electrode liquid storage tank is not influenced, and the operation stability of the battery energy storage system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to an online regeneration system and method for positive electrode sediment of a liquid flow battery. Background Art

[0002] Energy storage technology is one of the important technologies in the energy field. Especially when a large amount of energy is generated but cannot be connected to the grid, long-term energy storage is the key means to solve this problem. Among the many energy storage methods, flow batteries are favored by the market due to their stable performance, high safety and suitability for long-term energy storage. Among them, the most advantageous is the all-vanadium flow battery.

[0003] All-vanadium liquid flow batteries usually include power units, energy units, and transport units. The energy unit determines the energy density of the energy storage system. Generally, the higher the concentration of active substances in the electrolyte, the greater the energy density. Under the same energy density conditions, the volume of the electrolyte can be reduced. In order to increase the energy density, the method adopted is to increase the concentration of active substances in the electrolyte as much as possible. For all-vanadium liquid flow batteries, the concentration of vanadium active substances is usually 1.5-1.9 mol / L, and the supporting electrolyte is 3-4 mol / L sulfuric acid. After charging, the positive electrode electrolyte is mainly pentavalent vanadium, but the stability of pentavalent vanadium is poor. At a temperature of about 50°C, pentavalent vanadium will form V 2 O 5 , irreversible deactivation occurs, and this process is usually uncontrollable, especially in the later stage of charging, when the thermal effect inside the battery stack is obvious. After long-term operation, the energy density of the positive electrode electrolyte will be significantly reduced, and at the same time, an imbalance of the positive and negative electrode electrolytes will be caused, increasing the probability of the negative electrode electrolyte migrating across the membrane to the positive electrode, and further causing the energy density of the electrolyte to decrease, forming a vicious circle.

[0004] Since the positive electrode generates V 2 O 5 It is an irreversible process, and V 2 O 5 It is usually in a precipitated state, which can easily lead to pipe blockage, break the stack diaphragm, and reduce the stability of the flow battery system. At present, after the electrolyte decays to a certain extent, a reducing agent is usually added to the electrolyte offline, and the pentavalent vanadium is regenerated after the reduction reaction, so that the electrolyte can be reused. When the electrolyte needs to be regenerated, its energy density continues to decrease, and the electrolyte utilization rate continues to decrease during the operation of the system. Therefore, the system needs to be shut down by adding a reducing agent offline, resulting in the system being unable to operate continuously and stably. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide an online regeneration system and method for positive electrode sediments in a liquid flow battery, which has the advantages of realizing online regeneration of positive electrode sediments and ensuring continuous and stable operation of the battery energy storage system.

[0006] The purpose of the present invention is achieved by the following technical solutions: According to a first aspect of an embodiment of the present disclosure, there is provided an online regeneration system for positive electrode precipitates of a flow battery, comprising: A precipitation collection unit is disposed at the bottom of the positive electrode liquid storage tank and is used to collect high-valent vanadium oxide precipitation; An electrolytic regeneration unit is connected to the precipitation collection unit through a pipe valve module, the pipe valve module is used to deliver a predetermined volume of positive electrode precipitation electrolytic mixed solution to the electrolytic regeneration unit when the electrolyte utilization rate decreases below a preset utilization rate, the electrolytic regeneration unit is used to electrolytically reduce the positive electrode precipitation electrolytic mixed solution, and the electrolytic regeneration unit is connected to the positive electrode liquid storage tank through a delivery unit; A sampling and dilution unit, used for sampling according to a preset period during the electrolytic reduction process of the electrolytic regeneration unit and diluting the sample to a predetermined concentration; The detection and analysis unit is used to detect the absorbance of the sample obtained by sampling, and determine the electrolysis endpoint when the detected absorbance value reaches a preset absorbance threshold value, so as to control the shutdown of the electrolysis regeneration unit and re-inject the reduced electrolyte into the positive electrode storage tank through the conveying unit.

[0007] To implement the above technical solution, when the liquid flow battery energy storage system is working, a high-valent vanadium oxide precipitate will be generated at the bottom of the positive electrode storage tank and collected by the precipitate collection unit, and the electrolyte utilization rate will gradually decrease. When the electrolyte utilization rate decreases to below the preset utilization rate, the high-valent vanadium oxide precipitate needs to be reduced and regenerated. At this time, the positive electrode precipitation electrolytic mixed solution composed of the high-valent vanadium oxide precipitate and the positive electrode electrolyte is input into the electrolytic regeneration unit with a predetermined volume through the pipe valve module. When the electrolytic regeneration unit is started, the high-valent vanadium oxide precipitate is electrolytically reduced. During the electrolytic reduction process, samples are periodically taken from the electrolytic regeneration unit through the sampling dilution unit, and the sample is diluted to a predetermined volume after each sampling. Concentration, absorbance detection is performed through the detection and analysis unit, and the measured absorbance value is compared with the preset absorbance threshold value. Since there is a fixed relationship between the absorbance value and the vanadium ion concentration, when the absorbance value is consistent with the preset absorbance threshold value, it means that the high-valent vanadium oxide precipitation has completed the reduction and regeneration process. At this time, sampling can be stopped and the electrolysis endpoint can be determined. The electrolysis regeneration unit is shut down and the electrolyte in the electrolysis regeneration unit is re-transported to the positive electrode storage tank through the transport unit, thereby realizing online regeneration of the precipitate without the need for shutdown operation. Since only the precipitated part is collected in the electrolysis regeneration unit, it will not affect the normal operation of the positive electrode storage tank, thereby improving the stability of the battery energy storage system.

[0008] In some exemplary embodiments, the precipitation collection unit is a conical cylinder bottom formed at the bottom of the positive electrode liquid storage tank.

[0009] To implement the above technical solution, the conical bottom structure makes it easier for the high-valent vanadium oxide precipitate to accumulate and makes it easier for the precipitate to be transported to the electrolytic regeneration unit.

[0010] In some exemplary embodiments, the electrolytic regeneration unit comprises: An electrolytic cell, wherein the electrolytic cell is divided into a cathode electrolytic cell and an anode electrolytic cell by a proton membrane, wherein the cathode electrolytic cell is used to contain a positive electrode precipitation electrolytic mixed solution, and the anode electrolytic cell is used to contain an equal volume of electrolyte; A cathode electrode disposed in the cathode electrolytic cell; and An anode electrode is arranged in the anode electrolytic cell.

[0011] To implement the above technical solution, after the positive electrode precipitation electrolyte mixture is transported to the cathode electrolytic cell, an equal volume of electrolyte is added to the anode electrolytic cell, and then the cathode electrode and the anode electrode are energized to perform electrolytic reduction treatment.

[0012] In some exemplary embodiments, the cathode electrode is a reducing electrode, and the anode electrode is an oxidation-resistant electrode.

[0013] In some exemplary embodiments, the sampling dilution unit comprises: A sampler connected to the cathode electrolytic cell; The dilution container is used for storing a diluent and supplying the diluent to the sampler to dilute the sample supplied to the sampler to a predetermined concentration.

[0014] To implement the above technical solution, samples are taken from the cathode electrolytic cell at regular intervals through a sampler, and after sampling, a dilution container supplies a quantitative diluent into the sampler to dilute the sample to a predetermined concentration, and then a detection and analysis unit performs absorbance detection on the diluted sample.

[0015] In some exemplary embodiments, the detection and analysis unit comprises: A spectrometer is used to detect the absorbance value of the diluted sample; The processor is used to compare the detected absorbance value with a preset absorbance threshold value, and determine the electrolysis endpoint when the absorbance value is consistent with the preset threshold value.

[0016] According to a second aspect of an embodiment of the present disclosure, a method for online regeneration of positive electrode precipitates in a flow battery is provided. The method is implemented based on the system according to the first aspect, and comprises: When it is detected that the utilization rate of the electrolyte drops below a preset utilization rate, a predetermined volume of the positive electrode precipitation electrolyte mixture is delivered to the cathode electrolytic cell through the pipe valve module; adding an electrolyte of equal volume and concentration to the anode electrolytic cell to perform electrolytic reduction; During the electrolytic reduction process, sampling is performed from the cathode electrolytic cell according to a preset period and the sample is diluted to a predetermined concentration; Performing spectral analysis on the diluted sample to obtain the absorbance value of its characteristic peak, and comparing the absorbance value with a preset absorbance threshold value; If the absorbance value is inconsistent with the preset absorbance threshold, the sampling action is repeated; If the absorbance value is consistent with the preset absorbance threshold, the electrolysis endpoint is determined, the electrolysis regeneration unit is controlled to shut down, and the reduced electrolyte is re-injected into the positive electrode storage tank through the delivery unit, and the sampling action is stopped.

[0017] In some exemplary embodiments, the preset utilization rate is 75%-85%, and the predetermined volume is set to account for 6%-8% of the electrolyte in the positive electrode storage tank.

[0018] In some exemplary embodiments, during electrolytic reduction, the current density is controlled to be 5-200 mA / cm 2 .

[0019] In some exemplary embodiments, diluting the sample to a predetermined concentration specifically comprises: The absorbance value of the characteristic peak is set to 0.2-1, and the sample taken for the first time is initially diluted. If the absorbance value of the diluted sample is detected to be less than 0.2-1, resample and adjust the dilution factor until the absorbance value of the diluted sample is detected to be 0.2-1, and the dilution factor is determined.

[0020] In summary, compared with the prior art, the present invention has the following beneficial effects: The embodiment of the present invention provides a liquid flow battery positive electrode precipitate online regeneration system and method. When the liquid flow battery energy storage system is working, a high-valent vanadium oxide precipitate is generated at the bottom of the positive electrode storage tank and is collected by a precipitate collection unit, and the electrolyte utilization rate gradually decreases. When the electrolyte utilization rate decreases to a preset utilization rate, the high-valent vanadium oxide precipitate needs to be reduced and regenerated. At this time, a positive electrode precipitation electrolytic mixed solution composed of a high-valent vanadium oxide precipitate and a positive electrode electrolyte is input into an electrolytic regeneration unit in a predetermined volume through a pipe valve module. When the electrolytic regeneration unit is started, the high-valent vanadium oxide precipitate is electrolytically reduced. During the electrolytic reduction process, a sampling dilution unit is used to periodically sample from the electrolytic regeneration unit. Each sampling After sampling, the sample is diluted to a predetermined concentration, and then the absorbance is detected by the detection and analysis unit, and the measured absorbance value is compared with the preset absorbance threshold value. Since there is a fixed relationship between the absorbance value and the vanadium ion concentration, when the absorbance value is consistent with the preset absorbance threshold value, it means that the high-valent vanadium oxide precipitation has completed the reduction and regeneration process. At this time, the sampling can be stopped and the electrolysis endpoint can be determined. The electrolysis regeneration unit is shut down and the electrolyte in the electrolysis regeneration unit is re-transported to the positive electrode storage tank through the transport unit, thereby realizing online regeneration of the precipitate without the need for shutdown operation. Since only the precipitated part is collected from the electrolysis regeneration unit, it will not affect the normal operation of the positive electrode storage tank, thereby improving the stability of the battery energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the online regeneration system for positive electrode sediment of a flow battery in an embodiment of the present invention.

[0022] Figure 2 Flow chart of the online regeneration method of positive electrode sediment of a liquid flow battery in an embodiment of the present invention.

[0023] The numbers and letters in the figure represent the corresponding component names: 10. Precipitation collection unit; 20. Electrolysis regeneration unit; 21. Electrolytic cell; 211. Cathode electrolytic cell; 212. Anode electrolytic cell; 22. Cathode electrode; 23. Anode electrode; 30. Pipe valve module; 40. Transport unit; 50. Sampling dilution unit; 51. Sampler; 52. Dilution container; 60. Detection and analysis unit; 61. Spectrometer; 62. Processor; 70. Positive electrode storage tank. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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. 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.

[0025] like Figure 1 As shown, the first aspect of the embodiment of the present invention provides an online regeneration system for positive electrode sediment of a flow battery, comprising: a sediment collection unit 10, which is arranged at the bottom of a positive electrode storage tank 70 and is used to collect high-valent vanadium oxide sediment; an electrolytic regeneration unit 20, which is connected to the sediment collection unit 10 through a pipe valve module 30, and the pipe valve module 30 is used to transport a predetermined volume of positive electrode sedimentation electrolytic mixed solution to the electrolytic regeneration unit 20 when the electrolyte utilization rate decreases below a preset utilization rate, and the electrolytic regeneration unit 20 is used to electrolytically reduce the positive electrode sedimentation electrolytic mixed solution. The electrolytic regeneration unit 20 is connected to the positive electrode storage tank 70 through the conveying unit 40; the sampling and dilution unit 50 is used to take samples according to a preset period during the electrolytic reduction process of the electrolytic regeneration unit 20, and dilute the samples to a predetermined concentration; and the detection and analysis unit 60 is used to detect the absorbance of the sampled sample, and determine the electrolysis endpoint when the detected absorbance value reaches a preset absorbance threshold value, so as to control the electrolytic regeneration unit 20 to shut down and re-inject the reduced electrolyte into the positive electrode storage tank 70 through the conveying unit 40.

[0026] Specifically, the precipitate collection unit 10 is a conical bottom formed at the bottom of the positive electrode liquid storage tank 70. It can be understood that the precipitate collection unit 10 can be formed by setting the bottom of the positive electrode liquid storage tank 70 to be conical. Obviously, the precipitate collection unit 10 needs to be made of corrosion-resistant material; the conical bottom structure makes it easier for high-valent vanadium oxide precipitates to accumulate, and makes it easier for the precipitates to be transported to the electrolytic regeneration unit 20.

[0027] The electrolytic regeneration unit 20 includes: an electrolytic cell 21, which is divided into a cathode electrolytic cell 211 and an anode electrolytic cell 212 by a proton membrane, the cathode electrolytic cell 211 is used to accommodate the positive electrode precipitation electrolytic mixed solution, and the anode electrolytic cell 212 is used to accommodate an equal volume of electrolyte; a cathode electrode 22 arranged in the cathode electrolytic cell 211; and, an anode electrode 23 arranged in the anode electrolytic cell 212.

[0028] Among them, the cathode electrode 22 is a reducing electrode, for example, a graphite electrode, a carbon felt electrode, a carbon paper electrode, a carbon cloth electrode, a titanium mesh electrode or a lead mesh electrode can be used, and a carbon felt electrode is preferably used; the anode electrode 23 is an oxidation-resistant electrode, for example, a ruthenium-iridium electrode, an iridium-tantalum electrode, a graphite electrode or a BDD electrode can be used, and an iridium-tantalum electrode is preferably used.

[0029] The electrolyte added to the anode electrolytic cell 212 usually contains a supporting electrolyte, which can be, for example, sulfuric acid or hydrochloric acid. The preferred supporting electrolyte is 3-4 mol / L sulfuric acid. After the positive electrode precipitation electrolyte mixture is transported to the cathode electrolytic cell 211, an equal volume of electrolyte is added to the anode electrolytic cell 212, and then the cathode electrode 22 and the anode electrode 23 are energized to perform electrolytic reduction treatment.

[0030] The pipe-valve module 30 is connected between the bottom of the precipitation collection unit 10 and the cathode electrolytic cell 211, and specifically includes a liquid inlet pipeline and an electrically controlled valve. When the utilization rate of the electrolyte drops below a preset utilization rate, for example, when the utilization rate of the electrolyte drops to the initial 75%-85%, the electrically controlled valve opens, and under the action of the internal pressure of the positive electrode storage tank 70, the positive electrode precipitation electrolyte mixture in the precipitation collection unit 10 is transported to the cathode electrolytic cell 211 by static pressure. When the preset volume is reached, the electrically controlled valve is closed. The preset volume is generally 6%-8%, preferably 7%, of the volume of the electrolyte in the positive electrode storage tank 70. Of course, in some embodiments, a delivery pump may also be configured in the pipe-valve module 30 to pump liquid.

[0031] The delivery unit 40 is usually a tube pump combination. It is understandable that the delivery unit 40 is used to deliver the regenerated electrolyte after electrolytic reduction back to the positive electrode storage tank 70. For example, it may include a liquid supply pipeline and a liquid supply pump.

[0032] The sampling and dilution unit 50 includes: a sampler 51 connected to the cathode electrolytic cell 211; a dilution container 52, which is used to store a diluent and supply the diluent to the sampler 51 to dilute the sample supplied to the sampler 51 to a predetermined concentration. The diluent is 3-4 mol / L sulfuric acid, and the dilution container 52 and the sampler 51 can also be connected through a tube pump combination so that a certain amount of diluent can be added to the sampler 51 after the sampling is completed. The sampler 51 takes samples from the cathode electrolytic cell 211 at a fixed time. After sampling, the dilution container 52 supplies a certain amount of diluent to the sampler 51 to dilute the sample to a predetermined concentration, and then the detection and analysis unit 60 performs absorbance detection on the diluted sample.

[0033] The detection and analysis unit 60 includes: a spectrometer 61 for detecting the absorbance value of the diluted sample; a processor 62 for comparing the detected absorbance value with a preset absorbance threshold value, and determining the electrolysis end point when the absorbance value is consistent with the preset threshold value. In this embodiment, the spectrometer 61 adopts an ultraviolet visible spectrophotometer, and the absorbance detection can be performed after the diluted sample enters the sample cell of the ultraviolet visible spectrophotometer. The processor 62 pre-stores a standard absorption spectrum corresponding to the standard electrolyte. By setting a preset absorbance threshold value at a certain dilution concentration and comparing it with the currently detected absorbance value, it is determined whether the electrolytic reduction unit has completed the electrolytic reduction regeneration work, and the real-time monitoring of the electrolytic reduction process is realized.

[0034] When the liquid flow battery positive electrode precipitate online regeneration system of the present invention is working in the liquid flow battery energy storage system, a high-valent vanadium oxide precipitate will be generated at the bottom of the positive electrode storage tank 70 and collected by the precipitate collection unit 10, and the electrolyte utilization rate will gradually decrease. When the electrolyte utilization rate is reduced to below the preset utilization rate, the high-valent vanadium oxide precipitate needs to be reduced and regenerated. At this time, the positive electrode precipitation electrolytic mixed solution composed of the high-valent vanadium oxide precipitate and the positive electrode electrolyte is input into the electrolytic regeneration unit 20 in a predetermined volume through the pipe valve module 30. When the electrolytic regeneration unit 20 is started, the high-valent vanadium oxide precipitate is electrolytically reduced. During the electrolytic reduction process, samples are periodically taken from the electrolytic regeneration unit 20 through the sampling dilution unit 50. After each sampling, the sample is diluted. After dilution to a predetermined concentration, the absorbance is detected by the detection and analysis unit 60, and the measured absorbance value is compared with the preset absorbance threshold value. Since there is a fixed relationship between the absorbance value and the vanadium ion concentration, when the absorbance value is consistent with the preset absorbance threshold value, it means that the high-valent vanadium oxide precipitation has completed the reduction and regeneration process. At this time, sampling can be stopped and the electrolysis endpoint can be determined. The electrolytic regeneration unit 20 is shut down and the electrolyte in the electrolytic regeneration unit 20 is re-transported to the positive electrode storage tank 70 by the transport unit 40, thereby realizing online regeneration of the precipitate without the need for shutdown operation. Since only the precipitated part is collected from the electrolytic regeneration unit 20, the normal operation of the positive electrode storage tank 70 is not affected, thereby improving the stability of the battery energy storage system.

[0035] A second aspect of an embodiment of the present invention provides an online regeneration method for positive electrode sediments of a flow battery, the method being implemented based on the system of the first aspect, comprising: S100, when it is detected that the electrolyte utilization rate drops below a preset utilization rate, a predetermined volume of positive electrode precipitation electrolyte mixture is delivered to the cathode electrolytic cell 211 through the pipe valve module 30.

[0036] Specifically, the preset utilization rate is 75%-85%, preferably set to 80%. The electrolyte utilization rate can be specifically determined by the ratio of the actual energy storage value to the theoretical energy storage value. The predetermined volume is set to 6%-8% of the electrolyte in the positive electrode storage tank 70, preferably 7%. The volume of the precipitation collection unit 10 is usually set to be greater than or equal to 7% of the volume of the positive electrode storage tank 70, so as to ensure that the positive electrode precipitation electrolyte mixture transported each time is the substance in the precipitation collection unit 10. It can be understood that the positive electrode precipitation electrolyte mixture is a mixture of high-valent vanadium oxide precipitate and positive electrode electrolyte, the high-valent vanadium oxide.

[0037] When it is detected that the electrolyte utilization rate drops to between 75% and 85%, the electrically controlled valve in the tube valve module 30 opens automatically, and under the action of the internal pressure of the positive electrode storage tank 70, the positive electrode precipitation electrolyte mixture in the precipitation collection unit 10 is transported to the cathode electrolytic cell 211 through static pressure.

[0038] S200, adding an electrolyte of equal volume and concentration to the anode electrolytic cell 212 for electrolytic reduction. Specifically, after the pipe-valve module 30 has transported the positive electrode precipitation electrolyte mixture to the cathode electrolytic cell 211, an equal volume of electrolyte is added according to the volume pumped in by the pipe-valve assembly. The electrolyte contains a supporting electrolyte, and the supporting electrolyte is 3-4 mol / L sulfuric acid. Preferably, an equal volume of 4 mol / L sulfuric acid aqueous solution is added to the anode electrolytic cell 212.

[0039] S300, during the electrolytic reduction process, sampling is performed from the cathode electrolytic cell 211 according to a preset cycle, and the sample is diluted to a predetermined concentration. Specifically, the electrolytic reduction process is started by energizing the cathode electrode 22 and the anode electrode 23. During the electrolytic reduction process, the current density is controlled to be 5-200mA / cm2, preferably 20-70mA / cm2, and the duration of the electrolysis is determined based on the results of subsequent detection and analysis feedback.

[0040] Wherein, diluting the sample to a predetermined concentration specifically includes: The absorbance value of the characteristic peak is set to 0.2-1, and the sample taken for the first time is initially diluted. If the absorbance value of the diluted sample is detected to be less than 0.2-1, resample and adjust the dilution factor until the absorbance value of the diluted sample is detected to be 0.2-1, and the dilution factor is determined.

[0041] It is understandable that it may be difficult to determine the dilution factor during the initial dilution. In this case, it is necessary to repeatedly sample and adjust according to the results of the absorbance test. When the absorbance of the diluted sample is detected to be greater than 1, it means that the dilution factor is too low. At this time, it is necessary to resample and dilute. According to the previous dilution factor and the absorbance value of the characteristic peak, the dilution factor is increased in proportion. After dilution, the absorbance test is performed again until the absorbance value of the characteristic peak is less than 1, indicating that the dilution factor is reasonable. On this basis, the subsequent dilution factor can be determined; and correspondingly, if the absorbance of the diluted sample is detected to be less than 0.2, it means that the dilution factor is too high. At this time, it is necessary to resample and dilute. According to the previous dilution factor and the absorbance value of the characteristic peak, the dilution factor is reduced in proportion. After dilution, the absorbance test is performed again until the absorbance value of the characteristic peak is greater than 0.2, indicating that the dilution factor is reasonable.

[0042] Based on the above relationship, for a specific sample system, the dilution multiple at a specific time interval can be accurately obtained, and the relationship between the absorbance value and the vanadium ion concentration can be accurately obtained.

[0043] In a specific example, the absorbance value of the characteristic peak is set to 0.7. When the absorbance value of the diluted sample deviates from 0.7 by 40%, it is necessary to re-sample and dilute the sample to achieve S400, performing spectral analysis on the diluted sample to obtain the absorbance value of its characteristic peak, and comparing the absorbance value with a preset absorbance threshold value.

[0044] Specifically, since the diluted sample has been diluted to a certain dilution factor in the previous steps, the absorbance value of its characteristic absorption peak is different due to different dilution factors. Under the condition of a certain dilution factor, a preset absorbance threshold is set and marked as the standard absorption spectrum of the electrolyte. After each sampling and spectral analysis, the absorbance value of the characteristic peak of the diluted sample can be obtained. At this time, the absorbance value is compared with the preset absorbance threshold to determine whether the electrolytic reduction process is completed.

[0045] S500: If the absorbance value is inconsistent with the preset absorbance threshold, the sampling action is repeated, that is, steps S300 and S400 are repeated.

[0046] S600, if the absorbance value is consistent with the preset absorbance threshold, the electrolysis endpoint is determined, the electrolysis regeneration unit 20 is controlled to shut down, and the reduced electrolyte is re-injected into the positive electrode storage tank 70 through the delivery unit 40, and the sampling action is stopped.

[0047] Specifically, in actual operation, a vanadium electrolyte with an average valence of 3.5 is used as a standard electrolyte, and an absorption spectrum test is performed, wherein the characteristic absorption peak of trivalent vanadium is at 400nm, and the characteristic absorption peak of tetravalent vanadium is near 750nm. A coordinate system is established with the ratio of the absorbance value at 750nm to the absorbance value at 400nm as the ordinate and the abscissa as percentage. The ordinate value at 50% is the characteristic value of the vanadium electrolyte with an initial average valence of 3.5. The position of the characteristic absorption peak and the comparison of the characteristic absorption peak ratio with the standard spectrum are used as the basis for judging the end point of electrolysis.

[0048] After the electrolysis endpoint is determined, the electrolytic reduction process is completed. At this time, the electrolytic regeneration device is shut down, and the electrolyte in the cathode electrolytic cell 211 is the electrolyte after reduction and regeneration. The electrolyte after reduction is re-transported to the positive electrode storage tank 70 through the delivery unit 40, so as to replenish the part pumped out of the positive electrode storage tank 70. The working time of the delivery unit 40 can be determined according to the pumped volume until the electrolyte in the cathode electrolytic cell 211 is pumped out. At the same time, since the electrolytic reduction process has been completed, there is no need to perform sampling; After the electrolyte utilization rate drops to 75%-85% again, steps S100~S600 are executed again to achieve continuous online regeneration of the positive electrode precipitate without stopping the machine. Since only the precipitate part is collected by the electrolytic regeneration unit 20, the normal operation of the positive electrode storage tank 70 is not affected, thereby improving the stability of the battery energy storage system operation.

[0049] In a specific example, the electrolysis endpoint detection process is to dilute 1.7 mol / L vanadium with an average valence of 3.5 and 3 mol / L sulfuric acid electrolyte to a certain multiple, and control the maximum absorbance value of the detection characteristic peak to 0.7. Based on this, intermittent sampling and analysis are performed during the electrolytic reduction process. When the absorbance value of the characteristic peak of the diluted sample is detected to be consistent with the preset absorbance threshold, it is the electrolysis endpoint. When the electrolysis endpoint is not reached, the sampling test is repeated. The preset sampling period can preferably be set to 30 minutes. After reaching the electrolysis endpoint, the power is stopped, the electrolytic reduction process ends, and the electrolyte in the cathode electrolytic cell 211 is transported to the positive electrode storage tank 70 through the transport unit 40, completing the process of electroreduction, dissolution and regeneration of the high-valent vanadium oxide generated by the positive electrode electrolyte.

[0050] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which are equivalent modifications and improvements made to the above embodiments based on the essential technology of the present invention, and all of them belong to the protection scope of the present invention.

Claims

1. An online regeneration system for positive electrode sediment of a flow battery, characterized in that: include: A precipitation collection unit is disposed at the bottom of the positive electrode storage tank and is used to collect high-valent vanadium oxide precipitation; An electrolytic regeneration unit is connected to the precipitation collection unit through a pipe valve module, the pipe valve module is used to deliver a predetermined volume of positive electrode precipitation electrolytic mixed solution to the electrolytic regeneration unit when the electrolyte utilization rate decreases below a preset utilization rate, the electrolytic regeneration unit is used to electrolytically reduce the positive electrode precipitation electrolytic mixed solution, and the electrolytic regeneration unit is connected to the positive electrode liquid storage tank through a delivery unit; A sampling and dilution unit, used for sampling according to a preset period during the electrolytic reduction process of the electrolytic regeneration unit and diluting the sample to a predetermined concentration; The detection and analysis unit is used to detect the absorbance of the sample obtained by sampling, and determine the electrolysis endpoint when the detected absorbance value reaches a preset absorbance threshold value, so as to control the shutdown of the electrolysis regeneration unit and re-inject the reduced electrolyte into the positive electrode storage tank through the conveying unit.

2. The online regeneration system for positive electrode sediment of a flow battery according to claim 1, characterized in that: The precipitation collection unit is a conical cylinder bottom formed at the bottom of the positive electrode liquid storage tank.

3. The online regeneration system for positive electrode sediment of a flow battery according to claim 1, characterized in that: The electrolytic regeneration unit comprises: An electrolytic cell, wherein the electrolytic cell is divided into a cathode electrolytic cell and an anode electrolytic cell by a proton membrane, wherein the cathode electrolytic cell is used to contain a positive electrode precipitation electrolytic mixed solution, and the anode electrolytic cell is used to contain an equal volume of electrolyte; A cathode electrode disposed in the cathode electrolytic cell; and An anode electrode is arranged in the anode electrolytic cell.

4. The online regeneration system for positive electrode sediment of a flow battery according to claim 3, characterized in that: The cathode electrode is a reducing electrode, and the anode electrode is an oxidation-resistant electrode.

5. The online regeneration system for positive electrode sediment of a flow battery according to claim 3, characterized in that: The sampling dilution unit comprises: A sampler connected to the cathode electrolytic cell; The dilution container is used for storing a diluent and supplying the diluent to the sampler to dilute the sample supplied to the sampler to a predetermined concentration.

6. The online regeneration system for positive electrode sediment of a flow battery according to claim 1, characterized in that: The detection and analysis unit comprises: A spectrometer is used to detect the absorbance value of the diluted sample; The processor is used to compare the detected absorbance value with a preset absorbance threshold value, and determine the electrolysis endpoint when the absorbance value is consistent with the preset threshold value.

7. A method for online regeneration of positive electrode sediment of a flow battery, characterized in that: The method is implemented based on the system according to any one of claims 1 to 6, and includes: When it is detected that the utilization rate of the electrolyte drops below a preset utilization rate, a predetermined volume of the positive electrode precipitation electrolyte mixture is delivered to the cathode electrolytic cell through the pipe valve module; adding an electrolyte of equal volume and concentration to the anode electrolytic cell to perform electrolytic reduction; During the electrolytic reduction process, sampling is performed from the cathode electrolytic cell according to a preset period and the sample is diluted to a predetermined concentration; Performing spectral analysis on the diluted sample to obtain the absorbance value of its characteristic peak, and comparing the absorbance value with a preset absorbance threshold value; If the absorbance value is inconsistent with the preset absorbance threshold, the sampling action is repeated; If the absorbance value is consistent with the preset absorbance threshold, the electrolysis endpoint is determined, the electrolysis regeneration unit is controlled to shut down, and the reduced electrolyte is re-injected into the positive electrode storage tank through the delivery unit, and the sampling action is stopped.

8. The method for online regeneration of positive electrode precipitates of a flow battery according to claim 7, characterized in that: The preset utilization rate is 75%-85%, and the predetermined volume is set to account for 6%-8% of the electrolyte in the positive electrode storage tank.

9. The method for online regeneration of positive electrode precipitates of a flow battery according to claim 7, characterized in that: When electrolytic reduction is performed, the current density is controlled to be 5-200 mA / cm 2 .

10. The method for online regeneration of positive electrode precipitates of a flow battery according to claim 7, characterized in that: The diluting the sample to a predetermined concentration specifically comprises: The absorbance value of the characteristic peak is set to 0.2-1, and the sample taken for the first time is initially diluted. If the absorbance value of the diluted sample is detected to be less than 0.2-1, resample and adjust the dilution factor until the absorbance value of the diluted sample is detected to be 0.2-1, and the dilution factor is determined.

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