System and method for in-situ VRFB electrolyte purification

Abstract

A VRFB commissioning subsystem and method for in-situ purification of a VRFB electrolyte is provided. In embodiments, a conventional VRFB system is combined with a novel portable commissioning system for preparing and providing a purified electrolyte solution for the VRFB. This in-situ purification has a particular synergistic effect with the transport of the electrolyte in the form of a gel, since the electrolyte can be produced in a dense form and is only diluted with water until the in-situ.

Description

Technical Field

[0001] The present disclosure relates to redox flow batteries, electrolyte solutions, and electrochemical-based purification of electrolyte solutions therefor, and more particularly, to a system and method for on-site vanadium redox flow battery (VRFB) electrolyte purification. Background Art

[0002] Electrolytes used in batteries and other applications are generally required to be free of impurities that are harmful to those applications. For example, in the case of redox flow batteries, each electrolyte used needs to be free of impurities that contaminate the battery components. In a specific example, a vanadium redox flow battery (VRFB) is a system that converts electrical energy into chemical energy and then releases the chemical energy as electricity when there is demand. This type of battery is often paired with solar and / or wind farms to help eliminate the intermittency in electricity production associated with these renewable energy sources.

[0003] Patent US10333164B2, entitled "Electrochemical-based purification ofelectrolyte solutions, and related systems and methods", issued on June 25, 2019, discloses methods and related systems for preparing VRFB electrolyte solutions for use in VRFBs, for example, for commissioning such VFRBs, the entire contents of which are incorporated herein by reference. In short, and in an embodiment of the method, an electrolyte solution having an initial average valence is provided, which has at least one impurity (i.e., a non-vanadium impurity), and when the valence of the solution is equal to or lower than the precipitation valence (e.g., lower than 3.0), the impurity precipitates from the solution. The valence of the solution is reduced from the initial average valence to a valence lower than 3.0 so that at least one impurity precipitates as a solid precipitate. When the valence is lower than 3.0, the solid precipitate is mechanically separated using a flow-through porous filter or a hydrocyclone to purify the electrolyte solution. This method is performed using a dedicated electrolyte purification system. The purified solution is delivered, for example, to the installation site of the VRFB, and the battery is conditioned with the purified solution.

[0004] It is desirable to improve electrolyte purification for VFRBs and related methods and systems for providing purified electrolyte solutions to VFRBs. Summary of the invention

[0005] A VRFB commissioning subsystem and method for on-site purification of VRFB electrolyte is provided. In an embodiment, a conventional VRFB system is combined with a novel portable commissioning system for preparing and providing purified electrolyte solution to a VRFB. This on-site purification is particularly synergistic with the transportation of electrolyte in gel form, as the electrolyte can be produced in a dense form and not diluted with water until on-site. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic diagram of a battery and a commissioning system according to an embodiment, wherein the commissioning subsystem includes an impurity separator (eg, a filter) to remove impurities from the negative electrolyte.

[0007] Figure 2 is a flowchart of operations according to an embodiment, for example, for operating Figure 1 of batteries and debugging system.

[0008] Figure 3 is a schematic diagram of a battery and a commissioning system according to an embodiment, wherein the commissioning subsystem includes an additional impurity separator (e.g., a filter) to remove impurities from a negative electrolyte flowing through a balancing line for providing the negative electrolyte from a negative electrolyte tank to a positive electrolyte tank.

[0009] Figure 4A and Figure 4B Schematic diagrams of batteries and debugging systems according to corresponding embodiments.

[0010] Figure 5A and Figure 5B is a flow chart of operations according to an embodiment, for example, Figure 4A or Figure 4B of the battery and debug system operation.

[0011] Figure 6 According to the embodiment Figure 1 A schematic diagram of a battery and commissioning system, which also has a large resistor for discharging the battery stack.

[0012] Figure 7 is a flow chart of the operation according to an embodiment, such as for debugging Figure 6 system.

[0013] Figure 8 is a schematic diagram of a portion of a battery and a commissioning system according to an embodiment, showing a commissioning subsystem according to an embodiment and selected anode-side components of a VRFB system suitable for use with the commissioning subsystem.

[0014] Fig. 9 is a schematic diagram of a filter flushing subsystem of a commissioning subsystem according to an embodiment. DETAILED DESCRIPTION

[0015] Figure 1 1 is a schematic diagram of a battery and commissioning system 100 according to an embodiment. A commissioning subsystem (CSS) 102 is shown, which includes a pump 104 and a contaminant separator, which includes a filter 106 coupled to a VRFB system 108 (e.g., which is configured as a conventional VRFB system). Although a filter 106 is shown, a hydrocyclone is another example of a contaminant separator. In an embodiment, the filter 106 includes a fine media filter. Preferably, the media in the filter is rated for particle size less than 2 microns, and further preferably less than or equal to 0.5 microns.

[0016] The VRFB system 108 is simplified and generally includes additional components shown external to the commissioning subsystem 102, etc. The VRFB system 108 includes corresponding tanks 110 and 112 and a battery stack 114 therebetween. The tanks 110 and 112 include a negative electrolyte tank (V2 / V3) 110 and a positive electrolyte tank (V4 / V5) 112 for storing corresponding solutions (i.e., a negative electrolyte 116 and a positive electrolyte 118). It should be understood that the nomenclature "Vn" refers to vanadium and its corresponding oxidation state. The oxidation state shown is the oxidation state that exists during normal operation (i.e., after the "electrolyte forms a charge" described below). Although a single corresponding tank 110 and 112 are shown, multiple tanks can be connected.

[0017] Conventionally, the cell stack 114 includes a negative electrode side 114A and a positive electrode side 114B with a membrane 120 therebetween. Further conventionally, the respective electrolyte solutions 116 and 118 are circulated from the respective tanks 110, 112 to the respective sides 114A, 114B of the cell stack via respective supply lines (e.g., including conduits 122A and 124A) and respective return lines (e.g., including conduits 122B and 124B). The supply conduits 122A and 124A are coupled to respective pumps (e.g., 126, 128) to assist in the circulation. However, unconventionally, and as shown in the present embodiment, the commissioning subsystem 102 is coupled to the negative electrolyte supply line (e.g., coupled to conduit 122A). Within CSS 102, pump 104 and filter 106 are coupled via an electrolyte line (generally 107), and electrolyte line 107 is configured to couple to the negative electrolyte supply line of conduit 122A via a coupler (not shown). Pump 104 assists fluid flow, for example, to account for the additional pressure drop across filter 106.

[0018] A single tank balancing line 129 or tank exchange line is shown having a conduit 130 with a small electrolyte transfer pump 134 for rebalancing the electrolyte by transferring electrolyte between the two electrolyte tanks. A second (eg, opposite direction) balancing line is typically present but is not shown for simplicity.

[0019] As described above, the VRFB system 108 is simplified. For example, a state of charge (SOC) detector is not shown, for example, for measuring the SOC of the electrolyte solution, preferably each of the negative electrolyte solution 116 and the positive electrolyte solution 118. For simplicity, a thermal management system (TMS) is also not shown, which is used to manage the heat generated by the VRFB system 108, the electrical load / power source, and the battery management system (BMS) for controlling the battery.

[0020] The debug subsystem 102 may be coupled to, for example, Figure 1 , for performing debug operations as further described herein. The debug subsystem 102 can be decoupled from the VRFB system 108 being debugged, e.g., for normal use of the VRFB system 108. Thus, the debug subsystem 102 can be used with different instances of a VRFB system (not shown), e.g., one at a time, to perform debugging of each of the different instances.

[0021] Although not shown, in an embodiment, the commissioning subsystem 102 includes a housing, such as a metal and / or plastic body, to house the pump 104 and the filter 106. The negative electrode line can protrude through the housing (e.g., via a port), and a conduit interface / connector, such as for coupling to the supply conduit 122A, can be accessible on the outer surface of the housing. One or more holes, access ports, and / or doors are provided to access the interior of the housing, such as access to one or both of the pump 104 and the filter 106. Also included (not shown) are wiring, such as for power and / or signals. The subsystem can be coupled to an external power source, such as via a suitable electrical plug and wiring extending to the housing externally, or the housing can have a port to receive wires passing therethrough, thereby coupling to a bus or other receiver therein. The housing can provide an external interface, such as for a switch, to operate the CSS 102. The housing should also be designed to serve as a secondary container for any electrolyte that may leak from the CSS 102 or the coupler. The CSS can also have a leak sensor that is designed to shut down the entire system if a large leak is detected. In an embodiment, although not shown, the CSS 102 is mounted on a truck or other conveyance, and is preferably operable while on the truck. In an embodiment, a coupling interface for coupling the CSS 102 and the VRFB 108 is provided on one side thereof, for example, to facilitate easier coupling. In an embodiment, the top thereof is configured to be open so that any escaping gas can be vented. In an embodiment, a partition or other configuration is employed to allow an individual to work in and around the filter housing, for example to monitor the pressure in the filter and replace the filter.

[0022] In an embodiment, the CSS 102 includes a TMS (not shown) to handle heat generated by the commissioning and purification process. In an embodiment, the TMS includes a heat exchanger on the electrolyte line 107 to remove additional heat that may be generated by the electrolyte purification process. In an example, the heat exchanger includes a liquid-liquid heat exchanger, and the heat exchanger is configured to use a coolant, such as ethylene glycol, that is circulated to an air-cooled radiator. In an embodiment, the TMS includes an active cooling subsystem, such as an air conditioner or a heat pump. The TMS can use active and passive techniques, such as actively cooling the liquid (e.g., ethylene glycol) used in the liquid-liquid heat exchanger. The TMS can help cool the electrolyte and promote greater precipitation. In an embodiment, the TMS is located / used upstream of the filter 106. In an embodiment, the TMS is not provided, is not used if provided, or is operated in a manner that promotes precipitation (e.g., at a higher temperature) if provided, for example, to promote more favorable dynamics.

[0023] Although only a single filter is shown, more than one filter may be used in a specific line of filtration. The use of a parallel configuration may facilitate removal / replacement of filter media during continuous charging operations, such as when fluid is temporarily confined to one of the parallel routes. Using, for example, a first coarser rated filter (<2 microns) followed by a second finer rated filter (e.g., 0.5 microns) in a series configuration may facilitate more efficient filtration. The CSS filter 106 may include porous carbon (e.g., carbon paper or cloth) as the filter media. Other materials that are compatible with the electrolyte (e.g., polypropylene filters) or other materials (e.g., polymers) may be used. In an embodiment, the filter is a 99.00% efficiency filter.

[0024] As further described, CSS 102 may include one or more additional devices to determine when the electrolyte purification process is complete and / or provide a means for sampling the electrolyte for purity measurement. Such samples may be measured remotely outside the CSS, for example, by mass spectrometry equipment, etc., as further described herein.

[0025] Figure 2 2 is a flow chart of operation 200 according to an embodiment. For example, operation 200 will be performed using system 100. At 202, the operation couples debug subsystem 102 and VRFB system 108, such as Figure 1 At 204, the operation fills the corresponding tanks 110 and 112 with a V3 / V4 electrolyte solution for commissioning the system 100. Each of the negative tank 110 and the positive tank 112 receives a similar V3 / V4 electrolyte solution for initiating the system 100. A V3 / V4 electrolyte (typically 50% each) is commonly used to commission VRFB systems because the electrolyte is stable and a single electrolyte can be used instead of two different electrolyte compositions.

[0026] At 206, operations use a conventional electrolyte forming charging process for the VRFB system 108 to form a V2 / V3 electrolyte (116) in the negative electrode tank 110 and a V4 / V5 electrolyte (118) in the positive electrode tank 112. In accordance with the use of the CSS 102 as described herein, at 208, operations use the filter 106 of the CSS 102 to filter out solids (e.g., metal ion impurities reduced to insoluble metals) generated in the negative electrolyte 116. In an embodiment, operations 206 and 208 overlap in time, for example, to protect stack components from impurities.

[0027] At 210, the operation slowly mixes the negative electrolyte solution 116 and the positive electrolyte solution 118, for example using a balancing line (e.g., conduit 130 and pump 134), while charging to maintain a high SOC electrolyte in the negative tank 110. In the context and example, "slowly" means that the flow rate through the balancing line is at least 5 times lower than the flow rate of the electrolyte through one side of the stack. In the context and example, "slowly" means that the flow rate is the flow rate adopted by the remixing operation within the normal battery, consistent with the main design of those pumps. In an embodiment, the mixing rate is determined by the rate at which heat can be removed from the system. Heat is generated when high-price and low-price electrolytes are mixed together (i.e., during the mixing provided by these pumps). In an embodiment, mixing should be started, for example, after V2 / V3 is formed in the negative tank 110. As a non-limiting example, it should be understood that the balancing flow is bidirectional. Assuming a 10 hour system is used to charge at the rated system power output (i.e., the tanks are sized to discharge at rated power for 10 hours / cycle), such a system should be able to mix at an equivalent rate to maintain a fairly constant SOC. The long mixing time ensures that most of the electrolyte has spent some time in the two tanks, e.g., >20 hours (e.g., >2 times the discharge time).

[0028] At 212, operations continue filtering the negative electrolyte until it is determined that the electrolyte has been sufficiently purified. In an embodiment, the control system is configured to control the purge operation and stop and / or send a signal for stopping the purge operation. For example, the purge is further described below. At 214, operations disconnect the CSS 102 and the VRFB system 108, coupling the tank 110 to circulate via the pump 126 without passing the electrolyte through the commissioning subsystem 102. At 216, a conventional electrolyte forming charging process is performed until the negative tank consists of V2 / V3 and the positive tank consists of V4 / V5.

[0029] Figure 3 is a schematic diagram of a battery and debugging system 300 according to an embodiment. System 300 is configured similarly to system 100. It should be noted that in system 300, there is a debugging subsystem 302 in place of debugging subsystem 102, and debugging subsystem 302 is similar to subsystem 102. However, in debugging subsystem 302, there are two impurity separators, namely filters 106A and 106B.

[0030] Filter 106A is similarly coupled via supply conduit 122A for circulating electrolyte to stack 114. Filter 106B is coupled to filter impurities in the negative electrolyte, which is delivered between tanks 110 and 112 via balance line 329. While not being bound by any theory of operation, it is believed, for example by observation, that precipitates form in the negative tank, particularly when the electrolyte therein is at a high SOC. Figure 3A conduit 330 is shown coupled to an electrolyte delivery pump 332, similar to the conduit 330 coupled to an electrolyte delivery pump 332. Figure 1 The electrolyte delivery pump 134 is connected to the conduit 130, but in Figure 3 In the embodiment of the present invention, the electrolyte flows in the opposite direction. A balance line 129 operating in the other direction may be provided, but is not shown for simplicity.

[0031] The conduits 329 / 330 are coupled to the inlet conduit 136A and the outlet conduit 136B via a pair of valves 134A, 134B to feed the filter 106B in the balance line 329. The valves 134A, 134B are configured to allow fluid to flow through the conduit 329 (e.g., in a first position) or to divert the fluid through the filter 106B (e.g., in a second position). The valves herein may occupy discrete positions between the full range of operation. Other arrangements may be envisioned. For example, the valves 134A, 134B and the conduits 136A, 136B may be components of the commissioning subsystem 302.

[0032] In an embodiment, the operation of system 300 and its subsystem 302 is similar to operation 200. For example, operation 210 may be adapted to flow fluid to filter 106B, such as when mixing negative and positive electrolytes via line 329.

[0033] Figure 4A and 4B 4 are schematic diagrams of batteries and debugging systems 400A and 440B according to corresponding embodiments. Systems 400A and 400B are configured similarly to system 100. It should be noted that there is a debugging subsystem 402 in system 400, replacing the debugging subsystem 102, and the debugging subsystem 402 is similar to the subsystem 102. However, in the debugging subsystem 402, there are two impurity separators, namely filters 106A and 106B, additional conduits 440A, 440B and valves 442, 444A, 444B, as further described. In addition, there is a small high SOC V2 / V3 tank 446 (e.g., small tank 446) coupled between the pump 102 and the filter 106A.

[0034] Balancing lines 129 and 329 are shown, wherein line 329 is coupled to commissioning subsystem 402 after filter 106B, as further described. Valves 444A and 444B can be coupled to battery stack 114 from return conduit 122B. In system 400A, conduit 122B can allow negative electrolyte to pass through subsystem 402 to tank 110 (e.g., when valves 444A and 444B are in a first position). This configuration may be optional. As shown in system 400B, conduit 112B does not extend through valve 444A to negative electrolyte tank 110. Tank 110 only receives electrolyte from line 130 in system 400B. In each system 400A and 400B, valve 444A is coupled to conduit 440B to divert fluid to supply filter 106B (e.g., when valve 444A is in the second position in system 400A), which in turn can be coupled to conduit 330 of balance line 329 to deliver negative electrolyte to tank 112 when in a balanced configuration. Although not shown, in alternative embodiments of system 400B, for example, only one of valves 444A or 444B is present. In an embodiment, one or more valves are continuously controlled valves (i.e., can be opened from 0 to 100%), such that a portion of the fluid is directed in one direction (e.g., 10%) and a complementary portion (90%) is directed in another direction. In an embodiment, the conduit (e.g., 440B) and / or valve is associated with a corresponding (additional) pump (not shown). For example, conduit 440B can be coupled to a pump (not shown), for example, before filter 106B. Valve 444B is also coupled to conduit 440A to divert fluid (e.g., when valve 444B is in a second position) to small tank 446, such as when in a (first) charging configuration. Valve 442, which can be coupled to supply conduit 122A, can be in an open or closed position to provide fluid from tank 110 to pump 102 for supplying small tank 446, or to prevent the provision of fluid. In an embodiment, for example, using a continuous control valve that allows a portion of the fluid to be directed in one direction and a complementary portion in another direction, during steady-state operation, approximately 10% of the flow leaving stack 114A in conduit 122B is directed through filter 106B, while the other 90% is returned to the small tank via conduit 440A.

[0035] Figure 5A is a flow diagram of operation 500A, such as for operation of system 400A or 400B, according to an embodiment. Operation 500A is similar to operation 200.

[0036] V3 / V4 electrolyte can be provided to small tank 446, for example, from tank 110 through valve 442 (e.g., in an open position) and pump 102. During initial charging, valves 442, 444A, 444B are positioned so that only the electrolyte in small tank 446 circulates to the battery stack 114 (negative side 114A). Once small tank 446 reaches a high SOC, valves 442, 444A, 444B are positioned so that some electrolyte (via small tank 446) moves from the large negative tank 110 to the negative electrode (114A) of the battery stack 114. Some electrolyte from the negative battery outlet (e.g., via the return conduit 122B between the battery stack 114 and the subsystem 402) can also be returned to small tank 406 (to help maintain a high SOC in the small tank), and some electrolyte can be sent to tank 112 via filter 106B. Some electrolyte can be sent from tank 112 to tank 110 to balance the liquid flow.

[0037] At 502, the operation connects the CSS 402 to the VRFB system 108. The operation here is different from the operation 202 of coupling the balance line 329 to the CSS 402, for example.

[0038] At 504, the operation fills the VRFB system tanks 110 and 112 with V3 / V4 electrolyte, similar to operation 204. Valve 442 may be in a closed position. At 506, the operation fills the small tank 446 in the CSS 402 with V3 / V4 electrolyte. This may include a separate filling operation, or may be filled via tank 110 with open valve 442. In an embodiment, the small tank 446 is pre-filled with electrolyte, such as pre-purified electrolyte, which may include an amount obtained from a previous purification process, which may be V2 / V3 or V3 / V4, it being understood that V2 will oxidize with exposure to air, leaving only V3.

[0039] At 508 , with valves 442 , 444A, and 444B properly positioned, operation circulates electrolyte through small tank 446 , otherwise forming a high SOC V2 / V3 electrolyte in small tank 446 using a conventional VRFB charging process.

[0040] At 510, operation reconfigures the CSS (e.g., valves 442, 444A, and 444B (e.g., depending on system 400A or 400B)) to circulate some of the negative electrolyte between the large negative electrolyte tank 110 while continuing the charging process and maintaining a high SOC V2 / V3 electrolyte in the small tank 446.

[0041] At 512 , operations are performed such that after all V4 in the large negative electrolyte tank has been converted to V3 or V2 , operations begin mixing the positive and negative electrolytes while continuing to charge and maintain the high SOC V2 / V3 electrolyte in the small tank 466 .

[0042] At 514, the operation uses the filters 106A, 106B in the CSS to filter out solids (e.g., metal ion impurities reduced to insoluble metals) produced in the negative electrolyte. The valve is configured to allow the negative electrolyte and the positive electrolyte to mix simultaneously (via lines 129 and 329) while the charging process continues to charge and maintain the high SOC V2 / V3 electrolyte in the small tank 446.

[0043] At 516 , similar to the operation at 212 , operations continue to filter the negative electrolyte until it is determined that the electrolyte has been sufficiently purified, as further described herein.

[0044] At 518 , the operation disconnects the CSS 402 from the VRFB system 108 .

[0045] At 520, a charge formation process may need to be completed similar to operation 216. Therefore, a conventional electrolyte formation charging process is performed until the negative electrode tank 110 consists of V2 / V3 and the positive electrode tank 112 consists of V4 / V5.

[0046] Figure 5B 5 is a flow chart of operation 500B according to an embodiment, such as for operation of system 400B. Some operations 500A (e.g., 502 to 508 and 516 to 520) can also be found in operation 500B. In operation 500B, after establishing a high SOC in small tank 446, at 540, the operation reconfigures CSS 402 to circulate some negative electrolyte from small high SOC V2 / V3 tank 446 to positive electrolyte tank 112, and circulate some positive electrolyte 118 from positive electrolyte tank 112 to large negative electrolyte tank 110, while continuing the electrolyte formation charging process and maintaining the high SOC V2 / V3 electrolyte in small tank 446. At 542, the operation continues to operate the system in this manner until it is determined that the electrolyte has been sufficiently purified. At 544, the operation filters out the precipitate using the filter (106A, 106B) located downstream of the small high SOC V2 / V3 tank 446, and then directs the filtered electrolyte to the positive tank 112, while simultaneously transferring the electrolyte from the positive tank 112 to the negative tank 110 (e.g., via line 129). It should be understood that some operations overlap in time (e.g., operations 542 and 544).

[0047] Figure 6is a schematic diagram of a battery and debugging system 600 according to an embodiment. System 600 is configured similarly to system 100, but the system may be illustrated as being similar to system 300. It should be noted that in system 600, CSS 602 is present in place of CSS 102, and CSS 602 is similar to CSS 102. In an embodiment, CSS 602 is similar to CSS 302. However, unlike each of CSS 102 and CSS 302, CSS 602 includes a large resistor 650 that is coupled to the negative side 114A and the positive side 114B of the battery stack 114. The large resistor 650 may be used, for example, to discharge the battery stack 114 prior to performing an operation to reverse the polarity of the charge of the battery stack 114, as further described as part of the debugging operation 700 ( Figure 7 ). The change in polarity may be performed manually as such change is performed only once in operation 700. Operation 700 may begin with the cell stack 114 of the VRFB system 108 being in reverse polarity relative to normal use operation of the VRFB system 108 and therefore in a normal configuration after such polarity reversal. The commissioning operation may also be performed without transporting electrolyte between tanks 110 and 112. In an embodiment, the CSS is first coupled to the positive tank and operated to filter impurities, and then the CSS is coupled to the negative tank and operated to filter impurities, so that when precipitation removal is completed, the negative electrolyte is in the negative tank.

[0048] Figure 7 6 is a flow chart of operations according to an embodiment of the debugging system 600, for example. Operation 700 is similar to operation 200. Operation 702 of connecting the CSS 602 and the VRFB system 108 is similar to operation 202, but includes connecting a large resistor (e.g., to the battery stack) to enable a later discharge operation. Operations 704, 706, 708, and 710 are substantially the same as operations 204-210. At 712, operation 700 differs from operation 200 in that the VRFB system 108 is fully discharged. Resistor 650 may be used. Other approaches may be employed, and the CSS need not include such a resistor.

[0049] At 714, the operation reconfigures the VRFB system 108 so that the negative electrode becomes the positive electrode and vice versa (polarity reversal). The CSS 602 moves to the opposite electrolyte loop ( Figure 6 104 and filter 106 are coupled to another electrolyte tank, for example. At 716, operations 708-710 are repeated in the new configuration of the VRFB system 108. At 718, operations disconnect the CSS 602, for example, including disconnecting a resistor. Similar to 216, operations at 720 begin normal VRFB operation.

[0050] As noted herein with respect to operation, filtering related steps are performed until sufficient purification is determined. Various approaches may be employed, such as based on the total time of charging and filtering at a predetermined SOC (or range thereof). Preferably, real-time measurements indicating sufficient purification are included. One or more of the following properties may be monitored / measured and determinations may be made: i) hydrogen generation as a byproduct of reduction; ii) coulombic efficiency (CE) of a VRFB system; iii) rate of increase of pressure drop across the filter in a CSS; or iv) direct measurement of impurities, such as using mass spectrometry. Examples are described below.

[0051] In an embodiment, sufficient purge is determined by monitoring hydrogen generation during the electrolyte purge process. Figure 8 is a schematic diagram of a portion of a battery and commissioning system 800 showing a commissioning subsystem 802 and a portion of a VRFB system 808 (eg, anode-side components) suitable for use with the commissioning subsystem 802 . Figure 8 Components for monitoring hydrogen are shown according to an embodiment. The commissioning subsystem 802 is similar to other commissioning subsystem embodiments described herein. However, the commissioning subsystem 802 includes a small RFB cell 860, i.e., a symmetrical cell having corresponding negative and positive sides and on the order of 5 to 50 square centimeters, which is coupled after the filter 106 and before the small high SOC tank 840. The tank 840 can be coupled to the pump 126, for example, via the conduit 122A, to feed electrolyte to the negative side 114A of the battery stack 114. The small RFB cell 860 is fed with the same electrolyte on both sides, starting as a V3 / V4 electrolyte, and transforming to V2 / V3 due to the charging process. A small DC power supply (not shown) can be used to drive the small RFB cell 860 to a desired current (or cell potential) that is sufficient to significantly change the SOC of the electrolyte fed to the cell (e.g., >5%). At the negative electrode of any VRFB cell, some H2 is generated, especially at abnormally high SOC (e.g., >90% SOC) and high current density. The amount of H2 generated can be used to determine whether sufficient purge levels have been achieved, as some impurities can act as catalysts for the H2 generation reaction. The H2 gas enters the tank 840 with the liquid electrolyte and eventually enters the headspace 842 of the small tank. This H2 detection only needs to be activated after the purge process has been performed, as the purpose is to determine when the electrolyte purge level is sufficient.

[0052] CSS 802 also includes a hydrogen measurement device 862, which is in fluid communication with the small tank 840 to receive gas from the small tank, for example, from the head space 842 therein. The gas includes hydrogen as a byproduct of the reaction in the small RFB cell 860. The hydrogen measurement device 862 can be a gas analyzer or a small fuel cell. The hydrogen measurement device 862 is also in fluid communication with the tank 110 (preferably its head space 866), for example, via a conduit 864, to receive gas therefrom. The gas from the tank 110 includes hydrogen as a byproduct of the reaction in the battery stack 114. Therefore, monitoring can be accomplished by: i) measuring H2 generated from a small and dedicated cell in the CSS, for example, using gas from the head space of the small tank 840; or ii) measuring H2 in the gas space 866, preferably above the V2 / V3 tank 110; or iii) measuring the product from the small cell and the tank 110 (e.g., the gas space 866). In an embodiment, the hydrogen measurement device 862 comprises a fuel cell with a current measurement sensor. The H2 can simply be vented to the atmosphere, consumed in the fuel cell (if used), or fed to the headspace of one of the electrolyte tanks.

[0053] Inert gas purging of headspace 866 and / or 842 may be used to ensure gas flow to the hydrogen measurement equipment.

[0054] When the amount of H2 generated has dropped below a desired set point (e.g., a threshold amount), indicating that the H2 catalyst has been sufficiently removed from the electrolyte in the respective tank 110, 840, the electrolyte purge process may be considered complete. In an embodiment, manual electrolyte maintenance is performed to overcome electrolyte changes that occur due to H2 generation (e.g., as taught in U.S. Patent Application 20160056487, entitled "Method of maintaining health of a flow battery," published on February 25, 2016, which is incorporated herein by reference in its entirety). Completion may be responsive to the frequency with which electrolyte maintenance is desired.

[0055] In an embodiment, adequate purification is determined by a measurement similar to the proxy for monitoring hydrogen generation during the electrolyte purification process. For example, in an embodiment, monitoring of the coulombic efficiency (CE) of the VRFB system 800 is used as an indirect way to determine that undesirable side reactions (e.g., H2 generation) indicate that adequate purification is not being accomplished. For such an embodiment, the CSS 802 need not be completely as Figure 8 In an embodiment, a sufficient measurement is performed after the charge is formed (e.g., after the expected completion time). The CE can be compared to a normal CE value (e.g., a value compiled from normal operation using a purified electrolyte).

[0056] In an embodiment, sufficient purification is determined by measuring the rate of increase of the pressure drop across the filter in the CSS. A pressure sensor may be included in an embodiment of the CSS (not shown) to receive pressure information from the filter. When the pressure drop across the filter has stopped increasing (or the rate of increase is below a set point), the electrolyte purification process may be considered complete as this indicates that the filter is no longer capturing impurities. For such an embodiment, the CSS does not need to be as Figure 8 Configure as shown.

[0057] In an embodiment, sufficient purification is determined by directly measuring the level of impurities in the electrolyte. Highly sensitive measurement methods can be used, for example, by using mass spectrometry techniques (e.g., inductively coupled plasma mass spectrometry (ICP-MS)). For such embodiments, the CSS does not need to be as Figure 8 Configure as shown.

[0058] Operations 200, 500, and 700 as described above, and any modifications, include the step of determining when the electrolyte has been sufficiently purged. The following describes operations that may be involved in, for example, servicing a CSS after a purging operation.

[0059] In an embodiment, after all electrolyte (e.g., for both cells 110 and 112) has been purged (i.e., after step 212 in operation 200, after step 516 in operation 500, or after step 716 in operation 700, or after any similar step in a similar such operation to complete the purge), one or more steps are performed to ensure that impurities in the negative electrode are removed. For example, in an embodiment, the operation steps pump a small amount of positive electrolyte through the negative electrode, and the steps discard the electrolyte (this can be achieved using a modified CSS). In an embodiment, the CSS is decoupled from the negative electrolyte loop and coupled to receive positive electrolyte, for example, from a balancing line or a positive loop line. A small pump within the CSS can be operated to direct the positive electrolyte into the negative electrode 114A.

[0060] In embodiments with a small CSS tank (e.g., 840), the tank can be drained and used as a reservoir for flushing electrolyte. Care should be taken because such a tank (e.g., the electrolyte remaining therein after draining) may become contaminated.

[0061] In an embodiment, the operating step flushes the filter in the CSS with V4 / V5 (or V3 / V4) electrolyte. Flushing is further described below.

[0062] In an embodiment, even if sufficient purge is achieved, the operation extends the purge time by continuously mixing some of the positive and negative electrolytes while charging the VRFB system. For example, this modification can be applied to operations 200 and 500. For operation 200, this modification extends step 210, for example, beyond the extent required to completely pass all of the electrolyte through the negative electrode. In an alternative, this modification can be an additional step after step 210 or after step 518 of operation 500.

[0063] In an embodiment, operation 500 is modified at step 506 to start from a high SOC V2 / V3 in the small slot.

[0064] In embodiments where a small tank is used, the electrolyte in the small tank is discarded after the purification process because the electrolyte may contain a large amount of impurities, or in embodiments, the electrolyte is treated (e.g., filtered) and then recycled, such as by using an external process.

[0065] In an embodiment, an operation may be utilized by starting with a concentrated electrolyte in a tank and adding appropriate deionized water until a desired VRFB electrolyte composition is achieved. For example, any of steps 204, 504, 506, and 704 may be modified.

[0066] Filter media in a CSS that has been exposed to impurities can be flushed to extend service life. In an embodiment, the electrolyte filter is flushed with a VRFB electrolyte having an average oxidation state (AOS) ≥ 3.5 after the electrolyte filter has been exposed to the anolyte for a sufficient time to collect impurities. Flushing can reduce field labor and the need to replace filters.

[0067] The auxiliary electrolyte collected after flushing will contain high concentrations of impurities. In an embodiment, the electrolyte can be sent for ICP analysis to verify the impurities removed from the system.

[0068] Since copper and other possible HER (hydrogen evolution reaction) catalysts are flushed out when they accumulate in the filter to a certain amount (at which point purification can continue), the hydrogen produced during the purification process can be reduced. In an embodiment, this collected auxiliary electrolyte can then be introduced into the electrolyte in another VRFB system having an impurity concentration in the metastable region, for example, to increase the critical concentration of the other VRFB system as required for precipitation to occur. Once the impurities in the electrolyte in the other VRFB system reach a critical concentration, the electrolyte in the other VRFB system can be purified using CSS.

[0069] Fig. 9A flushing subsystem 900 for a CSS (such as, but not limited to, CSS 102) according to an embodiment is shown. Subsystem 900 couples a flushing loop 902 into electrolyte line 107. Valves 904 and 906 isolate the filter from loop 902, while valves 908 and 910 can isolate loop 902 from line 107 / filter 106.

[0070] The loop 902 includes an auxiliary electrolyte reservoir 912 and couples the reservoir 912 to the filter 106 for flushing the filter medium (not shown). An auxiliary pump 914 helps circulate the auxiliary electrolyte. The electrolyte is preferably an electrolyte with AOS≥3.5. Although not shown, the reservoir 912 includes a drain or other hole to remove, for example, an auxiliary electrolyte for use and description. Although not shown, the reservoir 912 may include an air inlet to add a clean auxiliary electrolyte used as a flushing electrolyte. An air intake line 916 provides air to the loop 902, for example, between the reservoir 912 and the pump 914. The air intake line can be isolated or not isolated via valves 918 and 920. In an embodiment (not shown), a three-way valve is used at valve pairs 904 / 908, 906 / 910, and 918 / 920.

[0071] In operation, for example, to filter impurities, electrolyte line valves 904 and 906 are opened, while loop valves 908 and 910 are closed. Electrolyte (e.g., anolyte) is circulated to filter 106 with the assistance of pump 104. Once impurities are collected, the filter 106 is flushed. Line valves 904 and 906 are closed to isolate the filter from loop line 902, while valves 908, 910, and 920 are opened and valve 918 is closed. Auxiliary electrolyte is obtained from reservoir 912 and returned to the reservoir. Once flushed, the loop is cleaned. Air is obtained via intake line 916 and valve 918. In an embodiment, the auxiliary electrolyte reservoir has a purge hole for releasing air. Once flushed, the loop line can be closed and the electrolyte line opened to restore the purge / purge configuration.

[0072] It will be apparent to those skilled in the art that certain benefits can be achieved through the commissioning subsystems and methods for on-site purification described herein. In an embodiment, the electrolyte is prepared on-site, for example, by mixing V oxide, concentrated aqueous sulfuric acid, and water using a portable electrolyte mixing system. Local mixing can result in substantial cost savings.

[0073] Actual implementations may include any or all of the features described herein. These and other aspects, features, and various combinations may be expressed as methods, devices, systems, means for performing functions, program products, and in other ways combine the features described herein. A number of embodiments have been described. However, it should be understood that various modifications may be made without departing from the spirit and scope of the methods and techniques described herein. In addition, other steps may be provided or steps may be eliminated from the described process, and other components may be added to or removed from the described system. Therefore, other embodiments are within the scope of the appended claims.

[0074] Throughout the description and claims of this specification, the words "comprises" and "comprising" and variations thereof mean "including but not limited to", and are not intended to (and do not) exclude other components, integers or steps. Throughout the specification, the singular encompasses the plural, unless the context otherwise requires. In particular, where the indefinite article is used, the specification should be understood to contemplate the plural as well as the singular, unless the context otherwise requires.

[0075] Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example unless incompatible therewith. All features disclosed herein (including any accompanying claims, abstracts and drawings) and / or all steps of any method or process so disclosed may be combined in any combination, except that at least some of such features and / or steps are mutually exclusive combinations. The invention is not limited to the details of any foregoing examples or embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification (including any accompanying claims, abstracts and drawings), or to any novel feature or any novel combination of steps of any method or process disclosed.

Claims

1. A vanadium redox flow battery (VRFB) commissioning system for purifying VRFB electrolyte, comprising: Pumps; an impurity separator configured to separate impurities from the VRFB electrolyte; as well as An electrolyte pipeline is provided, which couples the pump and the impurity separator, and wherein the electrolyte pipeline is configured to be coupled to an electrolyte circulation loop of a conventional VRFB system.

2. The VRFB debugging system according to claim 1 further comprises a housing for accommodating a pump, a filter and an electrolyte pipeline.

3. The VRFB debugging system according to claim 2, comprises a coupler, wherein the coupler is used to couple the electrolyte pipeline to the electrolyte circulation loop through the shell.

4. The VRFB debugging system according to any one of claims 1 to 3, wherein: The impurity separator comprises a fine media filter, preferably wherein the filter media is rated less than 2 microns, more preferably less than or equal to 0.5 microns.

5. The VRFB commissioning system according to any one of claims 1 to 5, comprising a high state of charge (SOC) tank configured to provide a reservoir for a high SOC negative electrode electrolyte to facilitate precipitation of impurities separated by the impurity separator.

6. The VRFB debugging system according to claim 6, wherein: The high SOC tank is coupled in the electrolyte line between the pump and the impurity separator.

7. The VRFB debugging system according to claim 6 or 7, wherein: The electrolyte pipeline comprises: (i) a supply portion for coupling into the loop to supply the VRFB electrolyte to the negative electrode side of the battery stack of the VRFB system; and (ii) a return portion for coupling into the loop to receive VRFB electrolyte from the negative side of the battery stack; and The VRFB commissioning system includes a plurality of valves and a loop line coupling a return portion to a high SOC tank to define a commissioning system loop configured to recirculate a volume of electrolyte within the VRFB commissioning system to a battery stack of the VRFB system.

8. The VRFB debugging system according to claim 6 or 7, wherein: The electrolyte pipeline comprises: (i) a supply portion for coupling into the loop to supply the VRFB electrolyte to the negative electrode side of the battery stack of the VRFB system; and (ii) a return portion for coupling into the loop to receive VRFB electrolyte from the negative side of the battery stack; and The VRFB commissioning system includes a negative electrode balancing line selectively coupled to the return portion, the negative electrode balancing line configured to be coupled to a VFRB balancing line to provide a negative electrolyte for tank balancing, the negative electrode balancing line having a balancing line impurity separator coupled therein for removing impurities.

9. The VRFB debugging system according to any one of claims 1 to 4, comprising a balancing pipeline impurity separator, which is configured to be coupled to a negative electrolyte balancing pipeline of the VRFB system, and the balancing pipeline impurity separator is configured to remove impurities in the negative electrolyte provided from the negative electrolyte tank of the VRFB system to balance the positive electrolyte tank of the VRFB system.

10. The VRFB commissioning system of any one of claims 1 to 9, comprising a thermal management system configured to reduce heat on the electrolyte line.

11. The VRFB debugging system according to claim 10, wherein: The thermal management system includes a heat exchanger located on the negative electrode electrolyte pipeline and an air-cooled radiator for reducing the heat generated by the electrolyte purification process. Preferably, the heat exchanger includes a liquid-liquid heat exchanger, and further preferably, it is configured to use a coolant circulated to the air-cooled radiator.

12. A VRFB commissioning system according to any one of claims 1 to 11, comprising a resistive load for discharging the VFRB system.

13. The VRFB commissioning system according to any one of claims 1 to 12, comprising a purification monitoring component, the purification monitoring component having a device for measuring the following characteristics: i) the VRFB commissioning system, ii) the VRFB system, or both i) and ii), the purification monitoring component being configured to determine sufficient purification of the electrolyte based on the characteristics.

14. The VRFB debugging system according to claim 13, wherein: The characteristics include: hydrogen generation measurement; pressure difference measurement across the impurity separator; Coulomb effect measurement.

15. The VRFB debugging system according to any one of claims 1 to 14, wherein: The VRFB system includes a positive electrolyte balancing line configured to balance the negative electrolyte tank volume with the positive electrolyte.

16. The VRFB commissioning system according to any one of claims 1 to 15, comprising a flushing circuit coupled to an auxiliary electrolyte reservoir, the auxiliary electrolyte reservoir being configured to circulate an auxiliary electrolyte to flush the impurity separator and collect the auxiliary electrolyte after flushing.

17. A method of charging and purifying an electrolyte in a vanadium redox flow battery (VRFB) system, the method comprising the steps of: performing a formation charging process to charge the raw electrolyte to a high state of charge (SOC) in the VRFB system; as well as operating a VRFB commissioning system coupled to the VRFB system to remove impurities from the charged electrolyte; The VRFB commissioning system includes a pump and an impurity separator coupled via an electrolyte pipeline, wherein the electrolyte pipeline has at least one coupler configured to receive and return electrolyte with the VRFB system.

18. The method of claim 17, comprising coupling the VRFB commissioning system to a negative electrolyte loop of the VRFB system.

19. The method according to claim 17 or 18, wherein: The charged electrolyte includes a negative electrode electrolyte and a positive electrode electrolyte.

20. The method of claim 19, comprising extending the time the electrolyte is at a high SOC by simultaneously charging and mixing the negative electrolyte and the positive electrolyte; and removing impurities from the charged electrolyte over the extended time using the VRFB commissioning system.

21. A method according to any one of claims 18 to 20, wherein claims 19 and 20 are dependent upon claim 18, wherein the VRFB commissioning system is coupled to the VRFB system to receive the negative electrolyte and return the negative electrolyte to the negative electrode of the battery stack of the VRFB.

22. The method of any one of claims 18 to 21, wherein claims 19 and 20 are dependent upon claim 18, wherein the impurity separator comprises one or more fine media filters, and the coupler positions the impurity separator between the negative electrolyte tank and the negative electrode of the VRFB to remove impurities.

23. The method according to claim 22, wherein: The size of the one or more fine media filters is selected to filter particles less than 2 microns and preferably less than or equal to 0.5 microns.

24. The method according to any one of claims 17 to 23, wherein: At least some of the impurities include metal ions that have been reduced by exposure to the highly charged negative electrode electrolyte.

25. The method according to any one of claims 19 to 23, wherein: The VRFB commissioning system includes a reservoir of highly charged anolyte through which anolyte received from the VRFB system is circulated to promote precipitation of impurities.

26. A method according to any one of claims 17 to 25, comprising determining a real time measure of cleanliness and ceasing to remove impurities in response to the real time measure of cleanliness.

27. The method according to claim 26, wherein: The real-time measurements include hydrogen generation rate.

28. The method according to claim 26, wherein: The real-time measurements include pressure drop measurements across the impurity separator.

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