System and method for recovering capacity of halogen-containing flow battery on line and application

Abstract

The invention relates to the technical field of flow batteries, in particular to a system and method for recovering the capacity of a halogen-containing flow battery on line and application. The system comprises a flow battery working subsystem, a flow battery rebalancing subsystem and a halogen recovery subsystem, and electrolyte in the flow battery working subsystem contains halogen; the flow battery rebalancing subsystem is used for recovering the capacity of the flow battery working subsystem on line; and the halogen recovery subsystem is used for recovering halogen gas generated in the process that the redox flow battery rebalance subsystem recovers the capacity of the redox flow battery working subsystem on line. The capacity recovery process system and strategy provided by the invention are generally suitable for halogen-containing flow batteries, especially iron-chromium flow batteries, and are suitable for flow battery energy storage systems and projects of various scales, so that stable operation with high electrolyte utilization rate, high storage capacity, high performance, high cycle index and long service life is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to a system, method and application for online recovery of the capacity of a halogen-containing liquid flow battery. Background Art

[0002] Liquid flow battery is a new type of large-scale electrochemical energy storage device. It stores electrical energy in electrolyte solution during charging and converts the stored energy into electrical energy during discharge. The output power of the battery depends on the size and number of battery stacks, and the storage capacity depends on the concentration and volume of the electrolyte. During the battery charging and discharging process, only the ion valence state in the positive and negative electrolytes changes. The electrolyte can be recycled and reused, and the operation is safe.

[0003] During the long-term operation of liquid flow batteries, the occurrence of side reactions such as hydrogen evolution will cause an imbalance in ion valence, resulting in a decrease in battery capacity, reduced performance, and shortened service life. Therefore, it is usually necessary to restore the ion valence and material regularly. For sulfuric acid-based systems represented by all-vanadium liquid flow batteries, recovery is often carried out by adding reducing agents or electrolysis. However, for hydrochloric acid-based systems represented by iron-chromium liquid flow batteries, as well as other liquid flow battery systems containing elements such as chlorine Cl, bromine Br, and iodine I, due to the relatively low reduction potential of halogens, the reduction reaction required by the battery cannot be carried out independently, and is inevitably accompanied by the generation of halogen monomers, and is affected by the battery temperature and escapes from the system in gaseous form, causing a variety of adverse effects. Therefore, designing unique methods and systems to restore the active ion concentrations of the positive and negative electrolytes to their initial states so that the capacity of the battery system can be restored is one of the key research and development technologies for iron-chromium liquid flow batteries. In the early research on NASA's iron-chromium liquid flow battery system, Fe 3+ -H2 rebalances the battery to achieve capacity recovery, but its hydrogen electrode requires the use of Pt or W catalysts, and Pt will penetrate into the negative electrode electrolyte through the ion membrane, thereby contaminating the negative electrode electrolyte. In addition, Pt is relatively expensive and not suitable for industrial applications; W catalysts have poor stability and will deactivate after a period of use. The Chinese patent (patent number CN 105702997 A) uses a method of reducing Fe by electrolytic reduction through a rebalanced battery. 3+ The positive electrode solution of the rebalanced battery is a positive electrode electrolyte containing active cations, and the negative electrode solution is a positive electrode storage tank of the main system flow battery. However, the cost of the rebalanced solution in this method is high, and each rebalancing requires draining the waste liquid, filling with new liquid, and treating the waste liquid. The labor cost and waste liquid treatment cost are also high.

[0004] Therefore, researching and designing a method for realizing capacity recovery in an efficient, convenient and easy-to-operate manner is currently one of the focuses of researchers in this field. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a system, method and application for online recovery of the capacity of a halogen-containing flow battery. The present invention provides the following technical solutions:

[0006] In a first aspect of the present invention, a system for online recovery of the capacity of a halogen-containing flow battery is provided, the system comprising a flow battery operating subsystem, a flow battery rebalancing subsystem and a halogen recovery subsystem, wherein:

[0007] The electrolyte in the working subsystem of the flow battery contains halogen;

[0008] The liquid flow battery rebalancing subsystem is used to restore the capacity of the liquid flow battery working subsystem online;

[0009] The halogen recovery subsystem is used to recover the halogen gas generated during the process of the liquid flow battery rebalancing subsystem online restoring the capacity of the liquid flow battery working subsystem.

[0010] Furthermore, the liquid flow battery working subsystem includes a working positive electrode storage tank, a liquid flow battery unit, a working negative electrode storage tank, a gas phase connecting pipe and a working exhaust pipe connected in sequence;

[0011] The working positive electrode storage tank is used to store an electrolyte containing a low-valent first ion, and the working negative electrode storage tank is used to store an electrolyte containing a high-valent second ion; the liquid flow battery unit is used to convert the low-valent first ions in the working positive electrode storage tank into high-valent first ions, and is also used to convert the high-valent second ions in the working negative electrode storage tank into low-valent second ions;

[0012] One end of the gas phase connecting pipe is connected to the top of the working positive electrode storage tank, and the other end extends into the top of the electrolyte interface of the working negative electrode storage tank; a working exhaust pipe is arranged above the working negative electrode storage tank.

[0013] Further, the flow battery rebalancing subsystem includes a rebalancing positive electrode storage tank, a rebalancing negative electrode storage tank, an electrolytic battery stack, a rebalancing positive electrode pump, a rebalancing negative electrode pump, and an electrolytic power supply;

[0014] The electrolysis power supply is arranged on the electrolysis stack, and the electrolysis power supply is used to supply power to the electrolysis stack;

[0015] The rebalanced positive electrode storage tank is used to store an electrolyte containing a reducing agent;

[0016] The rebalanced cathode storage tank is used to reduce the substance that can lose electrons in the electrolyte into a mixed gas containing halogen gas through the rebalanced cathode pump and the electrolytic stack;

[0017] The rebalancing negative electrode storage tank is the working positive electrode storage tank or the working negative electrode storage tank.

[0018] Furthermore, when the working positive electrode storage tank also serves as the rebalancing negative electrode storage tank of the flow battery rebalancing subsystem,

[0019] The working cathode storage tank is connected to the electrolytic stack via a rebalancing cathode pump, and is used to oxidize the high-valent first ions in the working cathode storage tank into low-valent first ions.

[0020] Furthermore, the working negative electrode storage tank also serves as a rebalancing negative electrode storage tank of the liquid flow battery rebalancing subsystem; wherein, the working negative electrode storage tank is connected to the electrolytic cell stack via a rebalancing negative electrode pump, and is used to oxidize the high-valent second ions in the working negative electrode storage tank into low-valent second ions.

[0021] Furthermore, the components of the electrolyte containing the reducing agent include the reducing agent and other auxiliary components, wherein:

[0022] The reducing agent includes one or more compounds containing hydrogen, carbon, nitrogen and / or oxygen elements;

[0023] The other auxiliary components include one or more of water, sulfuric acid, hydrochloric acid, the first ion and / or the second ion.

[0024] Furthermore, the halogen recovery subsystem includes a rebalance exhaust pipe and a bubbler, wherein:

[0025] One end of the rebalancing exhaust pipe is connected to the rebalancing positive electrode storage tank, and the other end is connected to a bubbler, and the bubbler is immersed in the electrolyte of the rebalancing negative electrode storage tank.

[0026] Furthermore, the halogen recovery subsystem also includes a gas-liquid mixer, wherein:

[0027] One end of the gas-liquid mixer is connected to the rebalanced negative electrode storage tank through a rebalanced negative electrode pump, and is used to receive the electrolyte in the rebalanced negative electrode storage tank;

[0028] The gas-liquid mixer is also used to receive the halogen-containing gas generated by the rebalanced positive electrode storage tank, and pass the gas obtained by mixing the halogen-containing gas with the electrolyte of the rebalanced negative electrode storage tank into the rebalanced positive electrode storage tank.

[0029] Furthermore, the halogen recovery subsystem also includes a sprayer, wherein the sprayer is arranged above the electrolyte inside the rebalanced negative electrode storage tank.

[0030] Furthermore, the halogen recovery subsystem further comprises a spray tower, wherein a sprayer is arranged above the inside of the spray tower, a packing layer is arranged in the middle of the spray tower, and the bottom of the spray tower is connected to the rebalanced negative electrode storage tank;

[0031] The sprayer is used to transport the electrolyte inside the rebalanced negative electrode storage tank to the spray tower;

[0032] The lower part of the packing layer of the spray tower is connected to the rebalancing exhaust pipe.

[0033] Furthermore, an alkali absorption tank is provided at the outlet end of the working exhaust pipe.

[0034] In a second aspect of the present invention, a method for online recovery of the capacity of a halogen-containing flow battery is provided, characterized in that the method adopts the above-mentioned system for online recovery of the capacity of a halogen-containing flow battery, and comprises the following steps:

[0035] When the liquid flow battery working subsystem is in operation, excess high-valence first ions are continuously accumulated in the working positive electrode storage tank;

[0036] The operation of the liquid flow battery working subsystem is stopped, the electrolysis power supply charges the electrolysis stack, and the reducing agent in the rebalancing positive electrode storage tank loses electrons and is oxidized into a mixed gas containing halogen gas;

[0037] The high-valent first ions in the rebalanced negative electrode storage tank obtain electrons and are reduced to low-valent first ions; or the high-valent second ions in the rebalanced negative electrode storage tank obtain electrons and are reduced to low-valent second ions;

[0038] After the mixed gas containing halogen gas enters the halogen recovery subsystem for processing, the halogen gas in the mixed gas containing halogen gas reacts with the electrolyte in the rebalanced negative electrode storage tank and is converted into a halogen ion form, which is absorbed by the electrolyte in the rebalanced negative electrode storage tank.

[0039] Furthermore, after the mixed gas containing halogen gas enters the halogen recovery subsystem for treatment, other gases in the mixed gas containing halogen gas are discharged along the exhaust pipe;

[0040] The other gases are gases that do not react with the electrolyte in the rebalanced negative electrode storage tank, including N2 and / or CO2.

[0041] Furthermore, the method also includes: regularly replenishing the system with reducing agent according to the cumulative amount of reducing agent consumed.

[0042] Furthermore, the calculation steps of the cumulative amount of reducing agent consumed are as follows:

[0043] Measuring the initial low-valent state of the first ion or the second ion concentration C1 in the electrolyte in the rebalanced negative electrode storage tank and the volume of the electrolyte in the rebalanced negative electrode storage tank as V;

[0044] After the electrolysis is finished, the charge amount x0 is recorded, and the concentration C2 of the first ion or the second ion in the low-valent state after electrolysis in the electrolyte in the rebalanced negative electrode storage tank is measured;

[0045] Based on the concentration difference of the low-valent first ion or the second ion in the rebalanced negative electrode storage tank before and after electrolysis, the volume and charge amount of the electrolyte in the rebalanced negative electrode storage tank, the electrolysis efficiency of the flow battery rebalance subsystem is obtained;

[0046] The amount of electricity that needs to be restored is calculated using the capacity deviation method;

[0047] Based on the electrolysis efficiency of the flow battery rebalancing subsystem and the amount of electricity that needs to be recovered, the cumulative amount of reduced power consumed is obtained.

[0048] Further, the calculation formula of the amount of the consumed reducing agent is as follows:

[0049]

[0050]

[0051]

[0052] Wherein, c1 represents the initial concentration of the low-valent first ion or the second ion in the electrolyte in the rebalanced negative electrode storage tank; c2 represents the concentration of the low-valent first ion or the second ion in the electrolyte in the rebalanced negative electrode storage tank after electrolysis; V represents the volume of the electrolyte in the rebalanced negative electrode storage tank; x0 represents the charge amount; q1 represents the amount of electricity to be restored; M represents the molar mass of the reducing agent; z represents the number of electrons transferred in the reduction reaction; y1 represents the electrolysis efficiency of the flow battery rebalancing subsystem; y2 represents the amount of reducing agent consumed.

[0053] In a third aspect of the present invention, the system for online recovery of the capacity of a halogen-containing flow battery as described above is used to recover the capacity of an iron-chromium flow battery or a hydrochloric acid all-vanadium flow battery or other halogen-containing flow batteries.

[0054] Technical effects and advantages of the present invention:

[0055] The rebalancing process system of the present invention adjusts the charge of the positive and negative electrodes in the battery by adding hydrogen ions and electrons to the main system battery, so that the battery is restored to the optimal working state. This rebalancing process technology is based on monitoring the state of charge and storage capacity during the charging process. When the storage capacity is lost to a certain value, the excess high-valent positive / negative active reaction substances in the electrolyte are efficiently electrolytically reduced to balance the charge state and storage capacity of the positive and negative electrolytes, restore the system electrolyte to the initial state, and thus restore the performance and capacity of the liquid flow battery to the initial state. This system is simple to operate, can be quantitatively controlled, and does not produce "three wastes". It is suitable for halogen-containing liquid flow battery energy storage systems and projects of various sizes, and can achieve high-performance, long-life stable operation.

[0056] 1. The capacity recovery process system and strategy provided by the present invention are generally applicable to halogen-containing liquid flow batteries (especially iron-chromium liquid flow batteries), and are applicable to liquid flow battery energy storage systems and projects of various sizes, so as to achieve high electrolyte utilization, high storage capacity, high performance (voltage efficiency, stack efficiency, system efficiency, etc.), high number of cycles, and long service life. Stable operation;

[0057] 2. The present invention effectively solves the problem that most reducing agents cannot react directly, and the electrolysis method will produce halogen elements;

[0058] 3. The present invention innovatively proposes that the high-valent ions in any storage tank of the main system can be electrolytically reduced to restore the capacity of the main system;

[0059] 4. In the present invention, the halogen gas generated during the capacity recovery process is absorbed by the liquid in the system, and a variety of engineering examples for enhanced absorption are proposed, thereby achieving internal recycling and ensuring the stability of the solution composition;

[0060] 5. The present invention realizes a method for automatically operating a liquid flow battery online to recover its capacity.

[0061] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a system diagram for online recovery of the capacity of a halogen-containing flow battery provided in the first embodiment of the present application;

[0063] Figure 2 is a system diagram for online recovery of the capacity of a halogen-containing flow battery provided in the second embodiment of the present application;

[0064] Figure 3 is a system diagram for online recovery of the capacity of a halogen-containing flow battery provided in the third embodiment of the present application;

[0065] Figure 4 A system diagram for online recovery of the capacity of a halogen-containing flow battery provided in the fourth embodiment of the present application;

[0066] Figure 5 This is a diagram showing the operating effect of the battery system provided in the fifth embodiment of the present application.

[0067] In the figure: 1. working positive electrode storage tank; 2. working negative electrode storage tank; 3. liquid flow battery unit; 4. rebalancing positive electrode storage tank; 5. electrolytic stack; 6. rebalancing positive electrode pump; 7. rebalancing negative electrode pump; 8. electrolytic power supply; 9. rebalancing exhaust pipe; 10. bubbler; 11. gas phase connecting pipe; 12. working exhaust pipe; 13. working positive electrode pump; 14. working negative electrode pump; 15. gas-liquid mixer; 16. sprayer; 17. alkali absorption tank; 18. spray tower; 19. packing layer; 20. spray liquid circulation pipeline. DETAILED DESCRIPTION

[0068] 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.

[0069] To solve the deficiencies of the prior art, the present invention discloses a system for online recovery of the capacity of a halogen-containing flow battery, such as Figure 1-4 As shown, the system includes a liquid flow battery working subsystem, a liquid flow battery rebalancing subsystem and a halogen recovery subsystem, wherein the electrolyte in the liquid flow battery working subsystem contains halogen; the liquid flow battery working subsystem includes a working positive electrode storage tank, a liquid flow battery unit, a working negative electrode storage tank, a gas phase interconnecting pipe and a working exhaust pipe connected in sequence; the working positive electrode storage tank is used to store an electrolyte containing a low-valent first ion, and the working negative electrode storage tank is used to store an electrolyte containing a high-valent second ion; the liquid flow battery unit is used to convert the low-valent first ions in the working positive electrode storage tank into high-valent first ions, and is also used to convert the high-valent second ions in the working negative electrode storage tank into low-valent second ions; one end of the gas phase interconnecting pipe is connected to the top of the working positive electrode storage tank, and the other end extends into the electrolyte in the working negative electrode storage tank; a working exhaust pipe is arranged above the working negative electrode storage tank.

[0070] The liquid flow battery rebalancing subsystem is used to restore the capacity of the liquid flow battery working subsystem online; the liquid flow battery rebalancing subsystem includes a rebalancing positive electrode storage tank, a rebalancing negative electrode storage tank, an electrolytic cell stack, a rebalancing positive electrode pump, a rebalancing negative electrode pump, and an electrolytic power supply; the electrolytic power supply is arranged on the electrolytic cell stack, and the electrolytic power supply is used to energize the electrolytic cell stack; the rebalancing positive electrode storage tank is used to store an electrolyte containing a reducing agent; the rebalancing positive electrode storage tank is connected to the electrolytic cell stack through the rebalancing positive electrode pump, so that the reducing agent in the electrolyte loses electrons and is reduced to a mixed gas containing halogen gas; the rebalancing negative electrode storage tank is the working positive electrode storage tank or the working negative electrode storage tank.

[0071] The components of the electrolyte containing the reducing agent include the reducing agent and other auxiliary components, wherein the reducing agent includes one or more compounds containing hydrogen and / or carbon and / or nitrogen and / or oxygen elements; the other auxiliary components include one or more of water, sulfuric acid, hydrochloric acid, first ions and / or second ions. For solid / gas reducing agents, the concentration range is 0 mol / L to the maximum solubility concentration; for liquid reducing agents, the concentration range is 0 mol / L to pure reducing agent solution.

[0072] The halogen recovery subsystem is used to recover the halogen gas generated by the liquid flow battery rebalancing subsystem in the process of online recovery of the capacity of the liquid flow battery working subsystem. The halogen recovery subsystem includes a rebalancing exhaust pipe and a bubbler, wherein one end of the rebalancing exhaust pipe is connected to the rebalancing positive electrode storage tank, and the other end is connected to the bubbler, and the bubbler is immersed in the electrolyte of the rebalancing negative electrode storage tank.

[0073] The present invention also provides a method for online recovery of the capacity of a halogen-containing flow battery, comprising the following steps:

[0074] When the liquid flow battery working subsystem is in operation, excess high-valence first ions are continuously accumulated in the working positive electrode storage tank;

[0075] The operation of the liquid flow battery working subsystem is stopped, and the electrolysis power supply charges the electrolysis stack. The reducing agent in the rebalancing positive electrode storage tank loses electrons and is oxidized to a mixed gas containing halogen gas; the high-valent first ions in the rebalancing negative electrode storage tank obtain electrons and are reduced to low-valent first ions; or the high-valent second ions in the rebalancing negative electrode storage tank obtain electrons and are reduced to low-valent second ions;

[0076] After the mixed gas containing halogen gas enters the halogen recovery subsystem for processing, the halogen gas in the mixed gas containing halogen gas reacts with the electrolyte in the rebalanced negative electrode storage tank and is converted into a halogen ion form, which is absorbed by the electrolyte in the rebalanced negative electrode storage tank.

[0077] After the mixed gas containing halogen gas enters the halogen recovery subsystem for processing, other gases in the mixed gas containing halogen gas are discharged along the exhaust pipe; the other gases are gases that do not react with the electrolyte in the rebalanced negative electrode storage tank, including N2 and / or CO2.

[0078] Regularly replenish the system with reducing agent based on the cumulative amount of reducing agent consumed.

[0079] The calculation steps for the cumulative amount of reducing agent consumed are as follows:

[0080] The concentration C1 of the initial low-valent first ion or second ion in the electrolyte in the rebalanced negative electrode storage tank and the volume of the electrolyte in the rebalanced negative electrode storage tank are measured; after the electrolysis is completed, the charge amount x0 is recorded, and the concentration C2 of the low-valent first ion or second ion after electrolysis in the electrolyte in the rebalanced negative electrode storage tank is measured; based on the concentration difference of the low-valent first ion or second ion in the rebalanced negative electrode storage tank before and after electrolysis, the volume of the electrolyte in the rebalanced negative electrode storage tank and the charge amount, the electrolysis efficiency of the liquid flow battery rebalancing subsystem is obtained, wherein the calculation formula of the electrolysis efficiency is:

[0081]

[0082] Wherein, c1 represents the initial concentration of the low-valent first ion or the second ion in the electrolyte in the rebalanced negative electrode storage tank; c2 represents the concentration of the low-valent first ion or the second ion in the electrolyte in the rebalanced negative electrode storage tank after electrolysis; V represents the volume of the electrolyte in the rebalanced negative electrode storage tank; x0 represents the charge amount; y1 represents the electrolysis efficiency of the liquid flow battery rebalancing subsystem.

[0083] It should be noted that when the rebalanced negative electrode storage tank is the working positive electrode storage tank, the concentration c1 of the initial low-valent first ion in the electrolyte in the rebalanced negative electrode storage tank is measured;

[0084] When the rebalanced negative electrode tank is the working negative electrode tank, the concentration c1 of the initial low-valent second ion in the electrolyte in the rebalanced negative electrode tank is measured.

[0085] The main system (working subsystem) gives the amount of electricity q1 (Ah) that needs to be restored based on the capacity deviation or other measurement methods. The electrolysis system operates continuously or intermittently and stops when the cumulative charge amount X reaches q1 / y1. The main system can be restored once after a period of time according to the operation requirements, or it can be restored in small amounts and multiple times.

[0086] Where, the molar mass of the reducing agent is M (g / mol), the number of electrons transferred in the reduction reaction is z, and the amount of reducing agent consumed is y2 (g):

[0087] The amount of electricity that needs to be restored is calculated according to the capacity deviation method; and the cumulative amount of reducing agent consumed is obtained based on the electrolysis efficiency of the liquid flow battery working subsystem and the amount of electricity that needs to be restored.

[0088] The calculation formula of the amount of the consumed reducing agent is as follows:

[0089]

[0090]

[0091] In the formula, q1 represents the amount of electricity that needs to be restored; M represents the molar mass of the reducing agent; z represents the number of electrons transferred by the reduction reaction; and y2 represents the amount of reducing agent consumed.

[0092] According to the cumulative amount of reducing agent consumed, the system is regularly replenished with reducing agent to maintain a stable solution state.

[0093] The present invention also provides an application of a system for online recovery of the capacity of a halogen-containing flow battery in recovering the capacity of an iron-chromium flow battery or recovering the capacity of a hydrochloric acid all-vanadium flow battery or recovering the capacity of other energy storage systems such as halogen-containing flow batteries.

[0094] The present invention adjusts the charge of the positive and negative electrodes in the battery by adding hydrogen ions and electrons to the main system battery, so that the battery is restored to the optimal working state. This rebalancing process technology is based on monitoring the state of charge and storage capacity during the charging process. When the storage capacity is lost to a certain value, the excess high-valent positive / negative active reaction substances in the electrolyte are efficiently electrolytically reduced to balance the charge state and storage capacity of the positive and negative electrolytes, restore the system electrolyte to its initial state, and thus restore the performance and capacity of the liquid flow battery to its initial state. This system is simple to operate, can be quantitatively controlled, and does not produce "three wastes". It is suitable for halogen-containing liquid flow battery energy storage systems and projects of various sizes, and can achieve high-performance, long-life stable operation.

[0095] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0096] In a first specific embodiment of the present invention, Figure 1 Taking the iron-chromium liquid flow battery as an example, the liquid flow battery working subsystem includes a working positive electrode storage tank 1, a liquid flow battery unit 3, a working negative electrode storage tank 2, a gas phase connecting pipe 11 and a working exhaust pipe 12 connected in sequence;

[0097] The working positive electrode storage tank 1 is used to store an electrolyte containing iron ions, and the working negative electrode storage tank 2 is used to store an electrolyte containing chromium ions; the liquid flow battery unit 3 is used for the mutual conversion of divalent iron ions and trivalent iron ions in the working positive electrode storage tank 1, and is also used for the mutual conversion of trivalent chromium ions and divalent chromium ions in the working negative electrode storage tank 2; one end of the gas phase connecting pipe 11 is connected to the top of the working positive electrode storage tank 1, and the other end extends into the electrolyte of the working negative electrode storage tank 2; a working exhaust pipe 12 is arranged above the working negative electrode storage tank 2.

[0098] The liquid flow battery rebalancing subsystem also includes a rebalancing positive electrode storage tank 4, an electrolytic battery stack 5, a rebalancing positive electrode pump 6, a rebalancing negative electrode pump 7, and an electrolytic power supply 8, wherein:

[0099] The electrolytic power supply 8 is arranged on the rebalancing battery 5, and the DC power supply 8 is used to supply power to the electrolytic stack;

[0100] The working positive electrode storage tank 1 also serves as a rebalancing negative electrode storage tank of the liquid flow battery rebalancing subsystem. The working positive electrode storage tank is connected to the electrolytic cell stack 5 via a rebalancing negative electrode pump 7, and is used to oxidize the trivalent iron ions in the working positive electrode storage tank into divalent iron ions.

[0101] The rebalanced positive electrode storage tank 4 is used to store an electrolyte containing a reducing agent, which is a compound containing hydrogen and / or carbon and / or nitrogen and / or oxygen elements that can be reduced (i.e., the valence state of the element can be increased) (chemical formula: H a C b O c N d , wherein a-d is 0-4), the compound may be solid, liquid or gas. The reducing agent may also be a mixture of the above substances. Other components of the electrolyte include water, sulfuric acid, hydrochloric acid, etc., and may also include active ions of the main system reaction, such as Fe ions and / or Cr ions, and other auxiliary components that do not participate in the reaction.

[0102] The rebalanced cathode storage tank 4 is used to make the reducing agent in the electrolyte lose electrons and be reduced to a mixed gas containing halogens through the rebalanced cathode pump 6 and the electrolytic stack 5; the mixed gas includes halogen gas (for example, chlorine, bromine vapor, iodine vapor), N2 and / or CO2.

[0103] The halogen recovery subsystem includes a rebalancing exhaust pipe 9 and a bubbler 10, wherein one end of the rebalancing exhaust pipe 9 is connected to the rebalancing positive electrode storage tank 4, and the other end is connected to the bubbler 10, and the bubbler is immersed in the electrolyte of the working positive electrode storage tank 1.

[0104] When the liquid flow battery unit 3 in the working subsystem is in operation, excess high-valent first ions (Fe 3+ The electrolytic power supply 8 charges the electrolytic stack 5, so that the high-valent first ions (Fe 3+ ) gains electrons and turns back to the low-valent first ion (Fe 2+ ). At the same time, the reductant in the rebalanced positive electrode storage tank 4 loses electrons and is reduced to N2 and / or CO2.

[0105] In the embodiment of the present invention, the positive electrode liquid of the electrolytic stack 5 comes from the rebalancing positive electrode storage tank 4, and the negative electrode liquid comes from the working positive electrode storage tank 1 of the working subsystem, and circulates through the rebalancing positive electrode pump 5 and the rebalancing negative electrode pump 6 respectively.

[0106] Since the electrolytes in the working positive electrode storage tank and the working negative electrode storage tank in the liquid flow battery working subsystem contain halogens, during the electrolysis process, the positive electrode of the electrolytic stack 5 will also produce halogen gas, such as chlorine, bromine vapor, and iodine vapor, which will return to the rebalancing positive electrode storage tank 4 with the electrolyte and then enter the halogen recovery subsystem.

[0107] The mixed gas containing halogen enters the positive electrode storage tank 1 through the rebalance exhaust pipe 9 and is discharged through the bubbler 10. During the discharge process, the Fe 2+ It reacts and turns back into the halogen ion form, which is absorbed.

[0108] While the halogen gas is being absorbed, since N2 and CO2 are inert components and do not participate in the reaction, they escape from the solution to the top of the storage tank and enter the working cathode storage tank 2 along the positive gas phase connecting pipe 11. The working cathode storage tank 2 contains hydrogen, a byproduct generated by the charging and discharging of the liquid flow battery unit 3, which is replaced by an inert gas (a gas that does not participate in the reaction) and discharged along the working exhaust pipe 12 to ensure system safety.

[0109] In a second embodiment of the present invention, Figure 2 As shown by the solid line, different from the first embodiment, the working positive electrode storage tank 1 in the working subsystem is connected to the liquid flow battery unit 3 through the working positive electrode pump 13; the working negative electrode storage tank 2 is connected to the liquid flow battery unit 3 through the working negative electrode pump 14;

[0110] In this embodiment, the rebalancing cathode pump 7 can be replaced by a working cathode pump 13, thereby saving one device.

[0111] like Figure 2 As shown by the middle dotted line, the electrolytic stack 5 can also take liquid from the working negative electrode storage tank 2, that is, the working negative electrode storage tank 2 also serves as the rebalancing negative electrode storage tank of the liquid flow battery rebalancing subsystem; wherein, the working negative electrode storage tank 2 is connected to the electrolytic stack 5 through the rebalancing negative electrode pump 7, which is used to oxidize the high-valent second ions in the negative working positive electrode storage tank 2 into low-valent second ions, and the generated halogen-containing mixed gas enters the halogen recovery subsystem;

[0112] The structure of the halogen recovery subsystem is the same as that of the first embodiment, and the halogen recovery subsystem includes a rebalancing exhaust pipe 9 and a bubbler 10, wherein one end of the rebalancing exhaust pipe 9 is connected to the rebalancing positive electrode storage tank 4, and the other end is connected to the bubbler 10, and the bubbler 10 is immersed in the electrolyte of the working positive electrode storage tank 1.

[0113] In the halogen recovery subsystem, the mixed gas containing halogen directly enters the working cathode storage tank 1 for absorption and is discharged through the bubbler 10. During the discharge process, the mixed gas is mixed with the Fe 2+ It reacts and turns back into the halogen ion form, which is absorbed.

[0114] Alternatively, the structure of the halogen recovery subsystem is different from that of the first embodiment, and the halogen recovery subsystem includes a rebalancing exhaust pipe 9 and a bubbler 10, wherein one end of the rebalancing exhaust pipe 9 is connected to the rebalancing positive electrode storage tank 4, and the other end is connected to the bubbler 10, and the bubbler is immersed in the electrolyte of the working negative electrode storage tank 2.

[0115] In the halogen recovery subsystem, the mixed gas containing halogen directly enters the working cathode storage tank 2 for absorption and is discharged through the bubbler 10. During the discharge process, the Cr 2+ The reaction takes place and turns back to the halogen ion form, that is, it is absorbed. The negative electrode storage tank 2 contains hydrogen gas, a byproduct of the main system charging and discharging, which is replaced by inert gas and discharged along the exhaust pipe 12 to ensure system safety.

[0116] In the third specific embodiment of the present invention, different from the first embodiment, this embodiment is an improvement in the halogen recovery subsystem, wherein the halogen recovery subsystem is additionally provided with a gas-liquid mixer 15, a sprayer 16 and an alkali absorption tank 17; wherein,

[0117] One end of the gas-liquid mixer 15 is connected to the rebalancing negative electrode storage tank through the rebalancing negative electrode pump 7. In this embodiment, the working positive electrode storage tank 1 is the rebalancing negative electrode storage tank, and the working negative electrode storage tank 2 can also be the rebalancing negative electrode storage tank (not shown in the figure), which is used to receive the electrolyte of the rebalancing negative electrode storage tank;

[0118] The gas-liquid mixer is also used to receive the halogen-containing gas generated by the positive electrode of the electrolytic stack 5, and pass the gas obtained by mixing the halogen-containing gas with the electrolyte in the rebalanced negative electrode storage tank into the rebalanced positive electrode storage tank 4.

[0119] The gas mixer 15 mixes the halogen gas with the liquid from the rebalanced cathode storage tank to complete the first absorption, thereby reducing the gas concentration in the rebalanced cathode storage tank 4 and improving safety. A sprayer 16 may also be added to the rebalanced cathode storage tank (in this embodiment, the working cathode storage tank 1 is the rebalanced cathode storage tank, and the working cathode storage tank 2 may also be the rebalanced cathode storage tank (not shown in the figure)), and the rebalanced cathode pump 7 is used for circulating spraying. After the gas discharged from the bubbler 10 is absorbed twice, it is sprayed again to complete the third absorption. After the gas is discharged from the working cathode storage tank 2, an alkali absorption tank 17 may be added to further absorb the extremely small amount of halogen gas or volatile acid gas discharged from the system.

[0120] In the fourth specific embodiment of the present invention, different from the first embodiment, the bubbler 10 is not provided in this embodiment, and a spray tower 18 is provided alone to absorb the halogen gas.

[0121] like Figure 4As shown, a sprayer 16 is arranged above the inside of the spray tower 18, a packing layer 19 is arranged in the middle of the spray tower 18, and the bottom of the spray tower 18 is connected to the rebalanced negative electrode storage tank (in this embodiment, the working positive electrode storage tank 1 is the rebalanced negative electrode storage tank, and the working negative electrode storage tank 2 can also be the rebalanced negative electrode storage tank (not shown in the figure)), and the sprayer 16 is used to transport the electrolyte inside the rebalanced negative electrode storage tank to the spray tower 18; the packing layer 19 of the spray tower 18 is connected to the rebalanced exhaust pipe 9 below.

[0122] The positive electrode electrolyte in part of the working positive electrode storage tank 1 can be transported to the spray tower 18 by means of the rebalancing negative electrode pump 7 to form a spray, and then returned to the positive electrode pump 7 or the working positive electrode storage tank 1 of the main system through the spray liquid circulation pipeline 20; the gas in the rebalancing positive electrode storage tank 4 enters the spray tower 18 along the rebalancing exhaust pipe 9; the mixed gas containing the halogen gas and the spray liquid contact and react in the packing layer 19, the halogen components are absorbed, and the remaining inert components can be directly discharged or discharged through alkali absorption, or discharged after passing through the working positive electrode storage tank 1 and / or the working negative electrode storage tank 2 of the working subsystem.

[0123] In the fifth specific embodiment of the present invention, the iron-chromium liquid flow battery capacity system suitable for engineering applications provided by the present invention can be automatically restored online. After the system is started, it is only necessary to add the reducing agent to the dosing box at a fixed period. The operation process is simple and can achieve long-term operation of the battery and efficient use of the electrolyte.

[0124] The reducing agent is oxalic acid (C2H2O4), i.e. H a C b O c N d Where a=2, b=2, c=4, d=0. The system flow chart is as above Figure 1 As shown, the overall reaction is:

[0125] V2H2O4+2Fe 3+ =2Fe 2+ +2CO2+2H +

[0126] After the main system ran 50 charge and discharge cycles, Fe 2+ The concentration is 1.03 mol / L, i.e. c1 = 1.03; the electrolysis system is started at this time, charging 2.1 Ah, i.e. X = 2.1; after the electrolysis is completed, Fe 2+ The concentration is 1.12 mol / L, that is, c2 = 1.12; the electrolyte volume V = 0.5 L, then the electrolysis efficiency is:

[0127]

[0128] The amount of C2H2O4 consumed is:

[0129]

[0130] The molecular weight of oxalic acid is M=90.03 g / mol, and the number of transferred electrons is z=2.

[0131] The battery system operates as follows Figure 5 As shown in Table 1:

[0132] Table 1

[0133] Capacity retention rate Before rebalancing 100％ Rebalance - 50 cycles 98.30％ Rebalance - 50 cycles 98.84％ Rebalance - Continuous 100％

[0134] According to Table 1 and Figure 5 It can be seen that after being processed by the method of the present invention, the capacity retention rate of the liquid flow battery during automatic online continuous operation can reach about 100%.

[0135] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for online recovery of the capacity of a halogen-containing flow battery, characterized in that: The system includes a liquid flow battery working subsystem, a liquid flow battery rebalancing subsystem and a halogen recovery subsystem, wherein: The electrolyte in the working subsystem of the flow battery contains halogen; The liquid flow battery rebalancing subsystem is used to restore the capacity of the liquid flow battery working subsystem online; The halogen recovery subsystem is used to recover the halogen gas generated during the process of the liquid flow battery rebalancing subsystem online restoring the capacity of the liquid flow battery working subsystem.

2. The system for online recovery of the capacity of a halogen-containing flow battery according to claim 1, characterized in that: The liquid flow battery working subsystem comprises a working positive electrode storage tank, a liquid flow battery unit, a working negative electrode storage tank, a gas phase connecting pipe and a working exhaust pipe connected in sequence; The working positive electrode storage tank is used to store an electrolyte containing a low-valent first ion, and the working negative electrode storage tank is used to store an electrolyte containing a high-valent second ion; the liquid flow battery unit is used to convert the low-valent first ions in the working positive electrode storage tank into high-valent first ions, and is also used to convert the high-valent second ions in the working negative electrode storage tank into low-valent second ions; One end of the gas phase connecting pipe is connected to the top of the working positive electrode storage tank, and the other end extends into the top of the electrolyte interface of the working negative electrode storage tank; a working exhaust pipe is arranged above the working negative electrode storage tank.

3. The system for online recovery of the capacity of a halogen-containing flow battery according to claim 2, characterized in that: The liquid flow battery rebalancing subsystem includes a rebalancing positive electrode storage tank, a rebalancing negative electrode storage tank, an electrolytic stack, a rebalancing positive electrode pump, a rebalancing negative electrode pump and an electrolytic power supply, wherein: The electrolysis power supply is arranged on the electrolysis stack, and the electrolysis power supply is used to supply power to the electrolysis stack; The rebalanced positive electrode storage tank is used to store an electrolyte containing a reducing agent; The rebalanced cathode storage tank is used to reduce the substance that can lose electrons in the electrolyte into a mixed gas containing halogen gas through the rebalanced cathode pump and the electrolytic stack; The rebalancing negative electrode storage tank is the working positive electrode storage tank or the working negative electrode storage tank.

4. The system for online recovery of the capacity of a halogen-containing flow battery according to claim 3, characterized in that: When the working positive electrode storage tank also serves as the rebalancing negative electrode storage tank of the flow battery rebalancing subsystem, The working cathode storage tank is connected to the electrolytic stack via a rebalancing cathode pump, and is used to oxidize the high-valent first ions in the working cathode storage tank into low-valent first ions.

5. The system for online recovery of the capacity of a halogen-containing flow battery according to claim 3, characterized in that: The working negative electrode storage tank also serves as a rebalancing negative electrode storage tank of the liquid flow battery rebalancing subsystem; wherein, the working negative electrode storage tank is connected to the electrolytic cell stack via a rebalancing negative electrode pump, and is used to oxidize the high-valent second ions in the working negative electrode storage tank into low-valent second ions.

6. The system for online recovery of the capacity of a halogen-containing flow battery according to claim 3, characterized in that: The components of the electrolyte containing a reducing agent include a reducing agent and other auxiliary components, wherein: The reducing agent includes one or more compounds containing hydrogen, carbon, nitrogen and / or oxygen elements; The other auxiliary components include one or more of water, sulfuric acid, hydrochloric acid, the first ion and / or the second ion.

7. The system for online recovery of the capacity of a halogen-containing flow battery according to claim 3, characterized in that: The halogen recovery subsystem includes a rebalance exhaust pipe and a bubbler, wherein: One end of the rebalancing exhaust pipe is connected to the rebalancing positive electrode storage tank, and the other end is connected to a bubbler, and the bubbler is immersed in the electrolyte of the rebalancing negative electrode storage tank.

8. The system for online recovery of the capacity of a halogen-containing flow battery according to claim 6, characterized in that: The halogen recovery subsystem also includes a gas-liquid mixer, wherein: One end of the gas-liquid mixer is connected to the rebalanced negative electrode storage tank through a rebalanced negative electrode pump, and is used to receive the electrolyte in the rebalanced negative electrode storage tank; The gas-liquid mixer is also used to receive the halogen-containing gas generated by the rebalanced positive electrode storage tank, and pass the halogen-containing gas mixed with the electrolyte of the rebalanced negative electrode storage tank into the rebalanced positive electrode storage tank.

9. The system for online recovery of the capacity of a halogen-containing flow battery according to any one of claims 3, 7 or 8, characterized in that: The halogen recovery subsystem further includes a sprayer, wherein the sprayer is disposed above the electrolyte inside the rebalanced negative electrode storage tank.

10. The system for online recovery of the capacity of a halogen-containing flow battery according to any one of claims 3, 7 or 8, characterized in that: The halogen recovery subsystem further comprises a spray tower, wherein a sprayer is arranged above the inside of the spray tower, a packing layer is arranged in the middle of the spray tower, and the bottom of the spray tower is connected to the rebalanced negative electrode storage tank; The sprayer is used to transport the electrolyte inside the rebalanced negative electrode storage tank to the spray tower; The lower part of the packing layer of the spray tower is connected to the rebalancing exhaust pipe.

11. The system for online recovery of the capacity of a halogen-containing flow battery according to claim 9, characterized in that: An alkali absorption tank is arranged at the outlet end of the working exhaust pipe.

12. A method for online recovery of the capacity of a halogen-containing flow battery, characterized in that: The method adopts the system for online recovery of the capacity of a halogen-containing flow battery according to any one of claims 1 to 11, comprising the following steps: When the liquid flow battery working subsystem is in operation, excess high-valence first ions are continuously accumulated in the working positive electrode storage tank; The operation of the liquid flow battery working subsystem is stopped, the electrolysis power supply charges the electrolysis stack, and the reducing agent in the rebalancing positive electrode storage tank loses electrons and is oxidized into a mixed gas containing halogen gas; The high-valent first ions in the rebalanced negative electrode storage tank obtain electrons and are reduced to low-valent first ions; or the high-valent second ions in the rebalanced negative electrode storage tank obtain electrons and are reduced to low-valent second ions; After the mixed gas containing halogen gas enters the halogen recovery subsystem for processing, the halogen gas in the mixed gas containing halogen gas reacts with the electrolyte in the rebalanced negative electrode storage tank and is converted into a halogen ion form, which is absorbed by the electrolyte in the rebalanced negative electrode storage tank.

13. The method for online recovery of the capacity of a halogen-containing flow battery according to claim 12, characterized in that: After the mixed gas containing halogen gas enters the halogen recovery subsystem for processing, other gases in the mixed gas containing halogen gas are discharged along the exhaust pipe; The other gases are gases that do not react with the electrolyte in the rebalanced negative electrode storage tank, including N2 and / or CO2.

14. The method for online recovery of the capacity of a halogen-containing flow battery according to claim 12, characterized in that: The method further includes: regularly replenishing the system with reducing agent according to the cumulative amount of reducing agent consumed.

15. The method for online recovery of the capacity of a halogen-containing flow battery according to claim 14, characterized in that: The calculation steps for the cumulative amount of reducing agent consumed are as follows: Measuring the initial low-valent state of the first ion or the second ion concentration C1 in the electrolyte in the rebalanced negative electrode storage tank and the volume of the electrolyte in the rebalanced negative electrode storage tank as V; After the electrolysis is finished, the charge amount x0 is recorded, and the concentration C2 of the first ion or the second ion in the low-valent state after electrolysis in the electrolyte in the rebalanced negative electrode storage tank is measured; Based on the concentration difference of the low-valent first ion or the second ion in the rebalanced negative electrode storage tank before and after electrolysis, the volume and charge amount of the electrolyte in the rebalanced negative electrode storage tank, the electrolysis efficiency of the flow battery rebalance subsystem is obtained; The amount of electricity that needs to be restored is calculated using the capacity deviation method; Based on the electrolysis efficiency of the flow battery rebalancing subsystem and the amount of electricity that needs to be recovered, the cumulative amount of reduced power consumed is obtained.

16. The method for online recovery of the capacity of a halogen-containing flow battery according to claim 15, characterized in that: The calculation formula of the amount of the consumed reducing agent is as follows: Wherein, c1 represents the initial concentration of the low-valent first ion or the second ion in the electrolyte in the rebalanced negative electrode storage tank; c2 represents the concentration of the low-valent first ion or the second ion in the electrolyte in the rebalanced negative electrode storage tank after electrolysis; V represents the volume of the electrolyte in the rebalanced negative electrode storage tank; x0 represents the charge amount; q1 represents the amount of electricity to be restored; M represents the molar mass of the reducing agent; z represents the number of electrons transferred in the reduction reaction; y1 represents the electrolysis efficiency of the flow battery rebalancing subsystem; y2 represents the amount of reducing agent consumed.

17. Use of the system for online recovery of the capacity of a halogen-containing flow battery as claimed in any one of claims 1 to 11 in recovering the capacity of an iron-chromium flow battery or recovering the capacity of a hydrochloric acid all-vanadium flow battery or other halogen-containing flow batteries.

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