CN109659587B - Flow battery capacity attenuation control system and method - Google Patents
Flow battery capacity attenuation control system and method Download PDFInfo
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Abstract
A redox flow battery capacity attenuation control system and method belong to the field of redox flow batteries and solve the problem of high maintenance cost of all-vanadium redox flow batteries, and the technical key points are as follows: gas chromatography, measuring and calculating the concentration of hydrogen in the cathode electrolyte storage tank; a total hydrogen evolution amount calculation device for periodically calculating a total hydrogen evolution amount from the concentration of the hydrogen gas; the monitoring equipment is used for monitoring the charging and discharging states of the flow battery; and the capacity recovery device is used for replenishing the positive electrolyte storage tank with a corresponding amount of capacity recovery agent in the discharging end state of the flow battery so as to control the capacity attenuation of the flow battery. The effect is as follows: the maintenance frequency is reduced, the labor cost is also reduced, and meanwhile, the abnormal phenomenon of the hydrogen evolution speed of the system can be found in real time, and measures can be taken in real time.
Description
Technical Field
The invention belongs to the field of flow batteries, and relates to a flow battery control system and a flow battery control method.
Background
After the flow battery is charged and discharged for a long time, the discharge capacity of the system is gradually attenuated, and the comprehensive valence state of the electrolyte deviates from 3.5 (the initial equilibrium valence state of the electrolyte) and gradually rises. How to find the attenuation reason of the battery system from different technical angles, implement monitoring and take control measures at the same time is a powerful means for inhibiting the attenuation of the system discharge capacity, reducing the system maintenance frequency and ensuring the long-time stable operation of the system.
The existing method adopts a capacity recovery means when the attenuation degree of the discharge capacity displayed according to the system appearance reaches the lower limit accepted by a client, and judges the attenuation degree of the actual theory of the system by carrying out comprehensive valence state measurement on the positive and negative electrolytes of the battery system.
The all-vanadium redox flow battery becomes a preferred scheme for large-scale energy storage due to the advantages of high safety, long service life, independent power capacity and convenience for large-scale production.
However, the negative electrode electrolyte of the all-vanadium flow battery has a hydrogen evolution side reaction:
2H++2V2+＝2V3++H2↑
since the reaction belongs to the self-discharge reaction of the negative electrode, the long-term accumulation of the hydrogen evolution side reaction can cause the continuous attenuation of the system discharge capacity, and is one of the main reasons of the capacity attenuation of the all-vanadium redox flow battery.
However, the monitoring and control of the capacity attenuation of the all-vanadium redox flow battery are only reported, and a special instrument and an operator are required to be configured to test the total valence state deviation of the battery system, so that the maintenance cost is increased.
At present, when the discharge capacity of a system is attenuated to a required lower limit, the system capacity can be recovered by leveling the total valence state of the system, but no matter a method of adding a reducing agent or using online electrolysis is adopted, no report on monitoring the capacity attenuation is provided all the time, the attenuation can be monitored and preliminarily controlled in a more convenient and low-cost adjusting mode in the prior period, the existing detection method can bring the investment and loss of manpower, material resources, equipment and system outage, the maintenance cost is high, and taking a 1MW/2MWh system as an example, the system valence state is deviated from 30%, and the annual maintenance cost is close to 3 ten thousand yuan.
Chinese patent application publication No. CN103733409A discloses a system and method for sensing and reducing hydrogen evolution in a flow cell system, which uses current generated by reaction with reactants to detect hydrogen in order to detect hydrogen content in real time, but the real-time detection of hydrogen concentration has a large error due to the fluctuation of hydrogen content.
Disclosure of Invention
In order to solve the problem of high capacity attenuation and maintenance cost of the all-vanadium redox flow battery, the invention provides the following technical scheme:
a flow battery capacity fade control system, comprising:
gas chromatography, measuring and calculating the concentration of hydrogen in the cathode electrolyte storage tank;
a total hydrogen evolution amount calculation device for periodically calculating a total hydrogen evolution amount from the concentration of the hydrogen gas;
the monitoring equipment is used for monitoring the charging and discharging states of the flow battery;
and the capacity recovery device is used for adding a capacity recovery agent to the positive electrolyte storage tank in the discharge termination state of the flow battery so as to control the capacity fading of the flow battery.
Further, the system also comprises a gas sampling device, wherein the gas sampling device is positioned in the negative electrolyte storage tank and used for collecting gas in the negative electrolyte storage tank, the gas sampling device is connected with the gas chromatography, and the gas in the negative electrolyte storage tank is periodically sent into the gas detection device of the gas chromatography.
Further, the system also comprises a control cabinet, wherein the control cabinet is connected with a deflation valve of the cathode electrolyte storage tank and is also connected with the total hydrogen evolution amount calculation device.
Furthermore, the system also comprises a control cabinet which is connected with the communicating valves of the positive and negative electrolyte storage tanks.
Further, the hydrogen evolution amount calculation device stores a plurality of instructions, and the instructions are suitable for the processor to load and execute: calculating the hydrogen evolution amount in the electrolyte storage tank according to the concentration of the hydrogen;
the hydrogen evolution quantity calculation formula is as follows:
M＝C*Vsign board
M is the total mass of hydrogen in the storage tank;
c: mass volume concentration of hydrogen on the upper layer of the tank body;
Vsign board: the gas volume of the upper space of the tank body;
Vsign board＝P1V1T1/PSign boardTSign board；
V1: the gas volume of the upper space of the tank body;
P1: the air pressure value in the tank body;
Psign board: 1 standard atmospheric pressure;
T1: the temperature in the storage tank;
Tsign board＝273K。
Further, the gas volume of the upper space of the tank body is obtained by automatically acquiring data by an electrolyte storage tank liquid level meter, and the gas temperature of the upper space of the tank body is obtained by automatically acquiring data by an electrolyte storage tank temperature sensor; and transmitting the acquired data to a hydrogen evolution amount calculation device, wherein the addition amount of the capacity recovery agent is determined by the relation between the hydrogen evolution amount and electrolyte imbalance and is obtained by the gain-loss electron ratio of vanadium ions and the capacity recovery agent.
The invention also relates to a flow battery capacity attenuation control method, which comprises the steps of setting a hydrogen generation speed value under continuous charge-discharge operation according to the system parameters of the flow battery, detecting the actual hydrogen generation speed to determine the fluctuation range of the hydrogen evolution speed in the front-back ratio interval of two continuous charge-discharge cycles, and taking corresponding measures to adjust if the fluctuation range exceeds the limit.
Further, periodically calculating the total hydrogen evolution amount according to the concentration of the hydrogen, converting the total hydrogen evolution amount into the total electrolyte valence offset to obtain the discharge capacity of the flow battery system, and recovering the discharge capacity when the discharge capacity value of the flow battery system is reduced to the required lower limit.
Further, the hydrogen generation speed fluctuation range overrun and adjustment method comprises the following steps: when the fluctuation range of the ratio of the hydrogen evolution speed of the next cycle period to the hydrogen evolution speed of the previous cycle period exceeds the limit value, if the hydrogen evolution speed of the next cycle period is higher, part of the positive electrolyte is led into a negative electrolyte storage tank to reduce the SOC of the negative electrolyte, and meanwhile, the solution is adjusted to reduce the temperature through a heat exchanger of the battery system; if the hydrogen evolution speed of the next cycle period is low, and the SOC of the negative electrode is determined to be too low, the state of the electrolyte of the positive electrode and the negative electrode is adjusted, and the negative electrode solution is introduced into a part of the positive electrode, so that the SOC of the next charge-discharge cycle is increased. Further, the fluctuation range overrun and adjustment method comprises the following steps: when the hydrogen evolution speed of the next cycle period is 1.3 times higher than that of the current cycle period, namely A is more than or equal to 1.3, part of the positive electrolyte is led into the negative electrolyte storage tank to reduce the State of Charge (SOC) of the negative electrolyte until the SOC of the negative electrolyte is lower than 70%, and meanwhile, the electrolysis is carried out through a heat exchanger of the battery systemAdjusting the temperature of the liquid to below 35 ℃; and when A is less than or equal to 0.7 and the SOC of the negative electrode is lower than 50%, regulating the state of the electrolyte of the positive electrode and the negative electrode.
Further, when every two adjacent cycles of the gas chromatography are discharged, the computer program controls the gas in the cathode electrolyte storage tank to be sampled, the gas pressure in the storage tank is detected, and when the pressure in the storage tank is negative, argon or nitrogen is used for supplementing pressure to be equal to the external atmospheric pressure.
Further, a calculation formula of the hydrogen evolution amount in the electrolyte storage tank is as follows:
M＝C*Vsign board
M is the total mass of hydrogen in the storage tank;
c: mass volume concentration of hydrogen on the upper layer of the tank body;
Vsign board: the gas volume of the upper space of the tank body;
Vsign board＝P1V1T1/(PSign boardTSign board)；
V1: the gas volume of the upper space of the tank body;
P1: the air pressure value in the tank body;
Psign board: 1 standard atmospheric pressure;
T1: the temperature in the storage tank;
Tsign board：＝273K。
The discharge capacity is recovered to be added with the capacity recovery agent, the addition amount of the capacity recovery agent is determined by the relation between the hydrogen evolution amount and the electrolyte imbalance, and is obtained by the electron gain and loss ratio of the vanadium electrolyte and the capacity recovery agent. The capacity restorer is a reducing micromolecular organic matter such as commercially available glycerol, oxalic acid, EDTA, tartaric acid and the like.
Has the advantages that: the invention monitors the hydrogen evolution in real time to maintain the hydrogen evolution at a fixed reaction level, and adopts regulation and control measures according to attenuation requirements to maintain the hydrogen evolution once (once in 2-3 years) within a fixed period, thereby reducing the maintenance frequency, reducing the labor cost, and simultaneously discovering the abnormal phenomenon of the hydrogen evolution speed of the system in real time and taking measures in real time.
For the cited patent applications in the background art: firstly, since the vanadium redox flow battery is an aqueous battery, the problem and principle of hydrogen evolution of the negative electrode electrolyte are common knowledge, and the following is to compare the technical scheme of the present application with the technical scheme of the cited patent application:
1. test equipment and method comparison of two schemes
The cited patent application adopts an electrode to detect hydrogen, and utilizes the current generated by the reaction of the electrode and a reactant to detect the hydrogen, so that the equipment precision is unknown for detecting the hydrogen content in real time, but because of the fluctuation of the hydrogen content, the error of detecting the hydrogen concentration in real time is very large, and experimental data shows that more than 2 hours are needed for thoroughly and uniformly mixing two gases; and the hydrogen gas precipitation speed is not in a strict linear relation in the process that the SOC of the electrolyte is from low to high, and the error of taking measures in real time is large.
The invention applies the portable gas chromatography to directly and accurately measure the hydrogen content at the end of each charge-discharge cycle. So as to judge the hydrogen evolution condition of the previous cycle process and adjust the next cycle in time.
Meanwhile, because the hydrogen evolution reaction is a main factor causing the valence state unbalance of the electrolyte of the battery system, the equipment in the patent recovers the discharge capacity of the attenuated battery system by adding and calculating the total hydrogen evolution amount of the system and adding a capacity recovery agent after a certain number of cycles.
2. Comparison of hydrogen evolution inhibition means
The operation of the cited patent application is to reduce the current density by reducing the charging power by the power converter during charging when the system SOC is too high, i.e. there is a risk of overcharging, it is known that the hydrogen evolution rate is directly related to the electrolyte SOC level and temperature, and that reducing the current density does not reduce hydrogen evolution, charging at low current density, and the cathode electrolyte hydrogen evolution rate will increase as long as the SOC still rises.
The subject matter concerned by the patent is the potential problem affecting the SOC of the electrolyte, namely volume migration or valence state unbalance of the positive and negative electrodes electrolyte, and the prevention of the unbalance of the total vanadium valence states of the positive and negative electrodes needs to inhibit the generation of high SOC of the electrolyte from the root.
3. Features of the invention
Hydrogen evolution in battery systems is an inevitable process that can only be controlled or suppressed by taking measures, experiments have shown that hydrogen evolution is only exacerbated when the electrolyte is at a high SOC (i.e. SOC > 70%). The method of reducing the current density in the cited patent application is not theoretically applicable. The technical scheme for reducing the electrolyte SOC can effectively reduce the hydrogen evolution speed in a practical large MW-level battery system, thereby reducing the discharge capacity of the battery system, inhibiting the decay rate and reducing the maintenance cost.
Drawings
Fig. 1 is a block diagram schematically showing the structure of the control system described in embodiment 2.
Detailed Description
Example 1:
a flow battery capacity fade control system includes
Gas chromatography, measuring and calculating the concentration of hydrogen in the cathode electrolyte storage tank;
a total hydrogen evolution amount calculation device for periodically calculating a total hydrogen evolution amount from the concentration of the hydrogen gas; the electrolyte valence offset is measured according to the total hydrogen evolution amount, of course, the total hydrogen evolution amount calculation device can be an embedded system of a gas chromatograph, or concentration data measured and calculated by the gas chromatograph can be transmitted to an upper computer in a wired or wireless mode and is positioned in the upper computer to calculate the total hydrogen evolution amount.
The monitoring equipment is used for monitoring the charging and discharging states of the flow battery;
and the capacity recovery device is used for adding a corresponding amount of capacity recovery agent to the positive electrolyte storage tank in the discharge termination state of the flow battery so as to control the capacity fading of the flow battery. The discharge termination state is a discharge completion state, and if the discharge termination state is in a discharge state, the addition of the restoring agent affects the discharge amount, so that the discharge state needs to be monitored, and the restoring agent is added in the discharge completion state to avoid affecting discharge. In one embodiment, the flow battery capacity fading control system further comprises a gas sampling device, wherein the gas sampling device can be a sub-device belonging to the total hydrogen evolution amount calculation device, or an independently arranged device, is positioned in the negative electrolyte storage tank and is used for collecting gas in the negative electrolyte storage tank, is connected with the gas chromatograph, and periodically sends the gas in the negative electrolyte storage tank to the gas detection device of the gas chromatograph.
In one embodiment, the flow battery capacity fading control system further comprises a control cabinet, which may be a sub-device belonging to the capacity recovery device, or an independently arranged device, connected to the purge valve of the negative electrolyte storage tank, and further connected to the total hydrogen evolution amount calculation device, wherein the total hydrogen evolution amount calculation device outputs data of the total amount (total volume) of the negative hydrogen to the control cabinet, and when the data of the total amount of the negative hydrogen obtained by the control cabinet is close to the explosion limit compared with the total space of the workshop, the control cabinet outputs a control signal to the purge valve to open the purge valve to lead the hydrogen out of the workshop, and thus, the purge valve is preferably an electromagnetic valve, wherein the connection mode is signal connection.
In one embodiment, the flow battery capacity fading control system further comprises a control cabinet, which is connected with the positive electrolyte storage tank and the negative electrolyte storage tank through the communication valve, and adjusts the SOC level of the electrolyte in the negative electrolyte storage tank by opening and closing the communication valve, that is, by opening the communication valve, a part of the positive electrolyte is introduced into the negative electrolyte storage tank to reduce the SOC of the negative electrolyte, so as to complete SOC adjustment.
In one embodiment, the hydrogen evolution amount calculation device stores a plurality of instructions adapted to be loaded and executed by a processor to: calculating the hydrogen evolution amount in the electrolyte storage tank according to the concentration of the hydrogen;
the hydrogen evolution quantity calculation formula is as follows:
M＝C*Vsign board
M total mass of hydrogen in the storage tank
C: the mass volume concentration of the hydrogen on the upper layer of the tank body is unit mg/L.
VSign board: gas volume of upper space of tank
VSign board＝P1V1T1/(PSign boardTSign board)
V1: gas volume of upper space of tank
P1: value of air pressure in tank
PSign board: 1 standard atmospheric pressure
T1: temperature in the storage tank
TSign board：273K
The gas volume of the upper space of the tank body is obtained by automatically acquiring data by a liquid level meter arranged on the electrolyte storage tank, and the gas temperature of the upper space of the tank body is obtained by automatically acquiring data by a temperature sensor of the electrolyte storage tank; and transmits the collected data to a hydrogen evolution amount calculation device.
The addition amount of the capacity recovery agent is determined by the relation between the hydrogen evolution amount and the electrolyte imbalance, and is obtained by the electron gain and loss ratio of the vanadium electrolyte and the capacity recovery agent.
In one embodiment, the method comprises the steps of setting a hydrogen generation speed value under continuous charge and discharge operation, detecting the actual hydrogen generation speed to determine the fluctuation range of the hydrogen evolution quantity of two continuous charge and discharge cycles in a front-rear ratio interval, and if the fluctuation range exceeds the limit, taking corresponding measures to adjust, periodically counting the total hydrogen evolution quantity in the cycle, converting the total hydrogen evolution quantity into electrolyte valence state offset, and recovering the discharge capacity when the numerical value reaches the lower limit.
The fluctuation range overrun and adjustment method comprises the following steps: when A is larger than or equal to 1.3, introducing part of the positive electrolyte into a negative electrolyte storage tank to reduce the SOC of the negative electrolyte, and regulating the temperature of the electrolyte to reduce through a heat exchanger of the battery system; and when A is less than or equal to 0.7 and the SOC of the negative electrolyte is determined to be too low, adjusting the state of the positive electrolyte and the negative electrolyte.
In the method, a gas chromatograph is controlled by a computer program to sample gas in a negative electrolyte storage tank according to fixed time, detect the gas pressure in the storage tank, and when the pressure in the storage tank is negative, argon or nitrogen is used for supplementing the pressure to be equal to the external atmospheric pressure.
The calculation formula of the hydrogen evolution amount in the electrolyte storage tank is as follows:
M＝C*Vsign board
M is the total mass of hydrogen in the storage tank;
c: the mass volume concentration of the hydrogen on the upper layer of the tank body is unit mg/L.
VSign board: the gas volume of the upper space of the tank body;
Vsign board＝P1V1T1/(PSign boardTSign board)；
V1: the gas volume of the upper space of the tank body;
P1: the air pressure value in the tank body;
Psign board: 1 standard atmospheric pressure;
T1: the temperature in the storage tank;
Tsign board＝273K。
The discharge capacity recovery method is characterized in that a capacity recovery agent is added, the addition amount of the capacity recovery agent is determined by the relation between the hydrogen evolution amount and the electrolyte imbalance, and is obtained by the electron gain-loss ratio of vanadium ions and the capacity recovery agent.
Example 2:
the technical solution in this embodiment may be used as an independent solution, or as a supplement to the solution in embodiment 1: a flow battery capacity attenuation control system is applied to the negative electrode side of a flow battery system and used for detecting the self-discharge problem caused by oxygen entering an electrolyte storage tank due to side reaction hydrogen evolution or storage tank sealing problem of the negative electrode system. The application mode is through UNICOM's negative pole electrolyte storage tank upper strata gas and gas chromatography detect to grasp the capacity decay condition of system in real time, the system includes: the all-vanadium redox flow battery system comprises a positive electrode electrolyte storage tank, a negative electrode electrolyte storage tank and a connecting pipeline for connecting the battery and the electrolyte. A capacity recovery device: and calculating the total hydrogen evolution amount according to a hydrogen calculation program arranged in the hydrogen calculation control equipment so as to obtain the required recovery dosage, and adding a certain amount of capacity recovery agent into the positive electrolyte by recovery agent adding equipment. Wherein the control device comprises: monitoring device for monitoring the charge and discharge state of a system, and control cabinet deviceThe system is provided with a signal of the completion of discharge, a recovery agent is added in a discharge state, and the control cabinet equipment is used for controlling the opening of a negative pole air release valve and the opening of a communicating valve and a liquid pouring pump of the positive and negative pole electrolyte storage tanks so as to adjust the danger brought by the hydrogen accumulation of the negative pole storage tank and adjust the SOC of the negative pole electrolyte. The detection system comprises a gas chromatograph, a gas sampling device and a gas protection device, wherein the gas sampling device is arranged in the cathode electrolyte storage tank and used for collecting gas in the cathode electrolyte storage tank, the gas sampling device is connected with the gas chromatograph through a PE (polyethylene) hose with the diameter of 3mm, and the gas in the storage barrel is pumped into the gas detection unit by a built-in air pump of the gas chromatograph at fixed intervals. Gas chromatography for detecting and calculating H in cathode electrolyte storage tank by total hydrogen2Ppm concentration of (d); one end of the gas protection device is connected with a safety valve of the cathode electrolyte storage tank, when the total amount of cathode hydrogen is close to an explosion limit compared with the total space of a workshop, the system judges that the safety valve is opened to guide the hydrogen out of the workshop, the protection device is connected to a PLC control cabinet to start a switching valve of the cathode gas, and one end of the control cabinet is connected with a computer control program of the gas chromatograph to calculate the total gas amount.
The control method of the control system comprises the following steps: 1) setting the hydrogen generation speed at 6L/100L under continuous charge-discharge operation according to the operation mode of the systemNegtive SolutionCycle, the speed is the gas volume under the standard condition after the conversion, the calculation method and the detection program for determining the hydrogen evolution speed determine whether the hydrogen evolution speed ratio A of two continuous charge-discharge cycles of the battery system meets 0.7<A<1.3；
2) If A is less than or equal to 0.7 or A is more than or equal to 1.3, the fluctuation range of the hydrogen evolution speed of the next cycle is more than +/-30 percent than that of the hydrogen evolution speed of the previous cycle, the hydrogen evolution quantity of the system exceeds the standard or the utilization rate of the electrolyte of the system is insufficient, and a control program of the system gives an alarm and takes measures.
The testing period of the hydrogen evolution speed is the interval time between every two times of testing, and the testing period of the patent is the system laying-aside stage after each cycle of discharging. I.e. once after each complete charge-discharge cycle.
The system alarms and takes measures as follows:
when A is more than or equal to 1.3, introducing a part of the positive electrolyte into a negative electrolyte storage tank to reduce the SOC of the negative electrolyte to lower the SOC of the negative electrolyte to below 70%, and simultaneously regulating the temperature of the electrolyte to below 35 ℃ through a heat exchanger of a battery system;
when A is less than or equal to 0.7, checking whether the SOC of the cathode electrolyte is too low, namely checking whether the SOC of the cathode electrolyte is lower than 50%, and if the SOC is confirmed to be lower than 50%, adjusting the state of the cathode electrolyte: namely, a part of the negative electrolyte is led into a positive electrolyte storage tank, so that the SOC of the negative electrolyte in the next circulation is more than 60 percent under the same operation mode.
SOC definition:
and (3) positive electrode: the concentration of the 5-valent ions accounts for the proportion of the total vanadium concentration of the positive electrolyte;
negative electrode: the concentration of the 2-valent ions accounts for the proportion of the total vanadium concentration of the positive electrolyte;
3) and periodically counting the total hydrogen evolution quantity of the system, converting the total hydrogen quantity into the valence state offset of the electrolyte of the system, and when the numerical value reaches the lower limit required by the system, alarming by the system to prompt the recovery of the discharge capacity. The period can be determined according to the type and mode of the flow battery system or mainly according to the use frequency of the flow battery system, and can be set to 1 month if the flow battery system is frequently used, or can be set to 3 months if the flow battery system is frequently used, or of course, other time intervals can be used.
From the above, the scheme in this embodiment may relate to the amount of hydrogen evolution, the rate of hydrogen evolution and the total amount of hydrogen evolution.
Wherein the hydrogen evolution speed is obtained by the ratio of the difference of the hydrogen evolution quantity and the time, and the unit is L/cycle, which can reflect the fixation
The amount of hydrogen evolved over time. The hydrogen evolution volume is the volume of hydrogen evolved in a fixed time and is given in units of L. Total hydrogen evolution means a period of time
The sum of the amounts of evolved hydrogen in the interval, which can be defined artificially, for example, 2 months or 3 months.
Systematic recovery dose addition:
according to the reaction equation: 2V2++2H+＝2V3++H2×) yielding hydrogen gasThe relationship between the output and the system electrolyte imbalance is obtained by the proportion of gain and loss electrons of the 5-valent vanadium electrolyte and the recovery agent:
for example: the calculation shows that the valence state unbalance caused by 249L hydrogen evolution can be compensated by each kg of oxalic acid, and the system automatically calculates the weight of the restoring agent to be added according to the total amount of the hydrogen.
According to the redox equation, complete oxidation of oxalic acid per mol provides two electrons for the reduction of two vanadium ions.
The lower limit of the system requirement is as follows: the customer can generally accept a 30% reduction in discharge capacity, H2The relationship between total and valence excursions is given by: 2V2++2H+＝2V3++H2And ℃,. i.e. when 1mol of hydrogen is released, the concentration of 2-valent vanadium in the negative electrode electrolyte is reduced by 2 mol. By analogy, the raising amount of the comprehensive valence state of the electrolyte can be obtained according to the total hydrogen evolution amount.
4) The system sets a program, and counts the total hydrogen concentration in the anode and cathode electrolyte storage tanks in the system at intervals of one week to determine whether the total hydrogen concentration reaches a danger limit value, and evacuation treatment is carried out on the system in time.
Hazard limit value: and when the total volume of the hydrogen in the storage tank and the total volume of the workshop space reach explosion limits, defining the total volume as a danger limit value of the hydrogen. The explosion limit of hydrogen refers to the volume content of hydrogen of 4-72 percent.
The hydrogen detection is a full-automatic system, gas in the negative pole storage tank is sampled according to fixed time through a program control gas chromatograph, the air pressure in the storage tank is automatically detected, and when the negative pressure in the tank is negative, argon or nitrogen is automatically started to supplement the pressure until the pressure is equal to the external atmospheric pressure.
5) Substituting the hydrogen amount in the electrolyte storage tank into a formula to calculate the total hydrogen amount of the system according to the hydrogen concentration measured by the gas chromatography, wherein the total hydrogen amount is as follows:
M＝C*Vsign board
M is the total mass of hydrogen in the storage tank;
c: the mass volume concentration of the hydrogen on the upper layer of the tank body is unit mg/L. (gas chromatography estimation of hydrogen concentration in the negative electrolyte tank can be directly converted into the mass volume concentration of hydrogen in the upper layer of the tank).
VSign board: the gas volume of the upper space of the tank body;
Vsign board＝P1V1T1/(PSign boardTSign board)；
V1: the gas volume of the upper space of the tank body;
P1: the air pressure value in the tank body;
Psign board: 1 standard atmospheric pressure;
T1: the temperature in the storage tank;
Tsign board＝273K。
The above description is only for the purpose of creating a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the technical scope of the present invention.
Claims (10)
1. A flow battery capacity fade control system is characterized by comprising
Gas chromatography, measuring and calculating the concentration of hydrogen in the cathode electrolyte storage tank;
a total hydrogen evolution amount calculation device for periodically calculating a total hydrogen evolution amount from the concentration of the hydrogen gas;
the monitoring equipment is used for monitoring the charging and discharging states of the flow battery;
the capacity recovery device is used for adding a capacity recovery agent to the positive electrolyte storage tank to control the capacity attenuation of the flow battery in the discharge termination state of the flow battery;
the total hydrogen evolution amount calculation device stores a plurality of instructions, and the instructions are suitable for a processor to load and execute: calculating the total hydrogen evolution amount in the electrolyte storage tank according to the concentration of the hydrogen;
the total hydrogen evolution quantity calculation formula is as follows:
M=C*Vsign board
M is the total mass of hydrogen in the storage tank;
c: mass volume concentration of hydrogen on the upper layer of the tank body;
Vsign board: the current temperature in the storage tank is TSign boardWhen the pressure value in the tank body is PSign boardThe gas volume of the upper space of the tank body;
Vsign board= P1V1T1/PSign boardTSign board；
V1: the current temperature in the storage tank is T1When the pressure value in the tank body is P1The gas volume of the upper space of the tank body;
P1: the air pressure value in the tank body;
Psign board: 1 standard atmospheric pressure;
T1: the temperature in the storage tank;
Tsign board=273K。
2. The flow battery capacity fade control system of claim 1, further comprising a gas sampling device located in the negative electrolyte reservoir for collecting gas in the negative electrolyte reservoir, connected to the gas chromatograph, for periodically sending gas from the negative electrolyte reservoir to the gas detection device of the gas chromatograph.
3. The flow battery capacity fade control system of claim 1, further comprising a control cabinet connected to a purge valve of the negative electrolyte storage tank and further connected to the total hydrogen evolution volume calculation device.
4. The flow battery capacity fade control system of claim 1 or 3, further comprising a control cabinet connected to the positive and negative electrolyte tank communication valves.
5. The flow battery capacity fade control system of claim 1, wherein the gas volume in the tank headspace is obtained from automatically collected data from an electrolyte tank level gauge, and the gas temperature in the tank headspace is obtained from automatically collected data from an electrolyte tank temperature sensor; and transmitting the acquired data to a hydrogen evolution amount calculation device, wherein the addition amount of the capacity recovery agent is determined by the relation between the hydrogen evolution amount and the solution unbalance, and is obtained by the gain-loss electron ratio of the vanadium ions and the capacity recovery agent.
6. A method for controlling the capacity attenuation of a flow battery is characterized by comprising the following steps: setting a hydrogen generation speed value under continuous charge-discharge operation according to parameters of a flow battery system, detecting the actual hydrogen generation speed to determine the fluctuation range of the hydrogen evolution speed of two continuous charge-discharge cycles in a front-rear ratio interval, and taking corresponding measures to adjust if the fluctuation range exceeds the limit.
7. The method for controlling the capacity fading of the flow battery as claimed in claim 6, wherein the total hydrogen evolution amount is periodically calculated according to the concentration of the hydrogen, the total hydrogen evolution amount is converted into the total electrolyte valence offset to obtain the discharge capacity of the flow battery system, and the discharge capacity is recovered when the discharge capacity value of the flow battery system is reduced to the required lower limit.
8. The flow battery capacity fade control method of claim 6 or 7, wherein the hydrogen generation rate fluctuation range overrun and regulation method is: when the fluctuation range of the ratio of the hydrogen evolution speed of the next cycle period to the hydrogen evolution speed of the previous cycle period exceeds the limit value, if the hydrogen evolution speed of the next cycle period is higher, part of the positive electrolyte is led into a negative electrolyte storage tank to reduce the SOC of the negative electrolyte, and meanwhile, the solution is adjusted to reduce the temperature through a heat exchanger of the battery system; if the hydrogen evolution speed of the next cycle period is low, and the SOC of the negative electrode is determined to be too low, the state of the electrolyte of the positive electrode and the negative electrode is adjusted, and the negative electrode solution is introduced into a part of the positive electrode, so that the SOC of the next charge-discharge cycle is increased.
9. The flow battery capacity fading control method as claimed in claim 8, wherein the specific method for judging and adjusting the fluctuation range overrun is as follows: when A is more than or equal to 1.3, introducing part of the positive electrolyte into a negative electrolyte storage tank to reduce the charge state of the negative electrolyte until the SOC of the negative electrolyte is lower than 70%, and simultaneously adjusting the temperature of the electrolyte to be lower than 35 ℃ through a heat exchanger of a battery system; when A is less than or equal to 0.7 and the SOC of the negative electrode is confirmed to be lower than 50%, adjusting the state of the electrolyte of the positive electrode and the negative electrode, and introducing the negative electrode solution into a part of the positive electrode to increase the SOC of the next charge-discharge cycle, wherein: a = hydrogen evolution rate of the latter cycle/hydrogen evolution rate of the former cycle.
10. The method for controlling the capacity fade of a flow battery as claimed in claim 6 or 7, wherein the gas chromatography is controlled by a computer program to sample the gas in the negative electrolyte tank at a fixed time, detect the pressure in the tank, and when the pressure in the tank is negative, supplement the pressure to be equal to the external atmospheric pressure by using argon or nitrogen.
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| CN103733409A (en) * | 2011-06-20 | 2014-04-16 | 联合工艺公司 | System and method for sensing and mitigating hydrogen evolution within a flow battery system |
| CN107195932A (en) * | 2016-03-14 | 2017-09-22 | 大连融科储能技术发展有限公司 | The stable regulation and control method of flow battery capacity, system and flow battery |
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| CN103733409A (en) * | 2011-06-20 | 2014-04-16 | 联合工艺公司 | System and method for sensing and mitigating hydrogen evolution within a flow battery system |
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