Method for producing a nitrogen-enriched current from an electrochemical system

Abstract

A method for producing a nitrogen-enriched current from an electrochemical system. The method includes operating the electrochemical system in a running state, operating the electrochemical system in a shut-off state to produce a nitrogen-enriched current on a cathode side of the electrochemical system, and venting the nitrogen-enriched current from the cathode side of the electrochemical system through a vent valve to remove the nitrogen-enriched current from the electrochemical system. The generated nitrogen gas can be used for purging, covering, cooling, and / or diagnosing the state of health (SoH) of an electrochemical system, such as a PEMFC system.

Description

Technical field

[0001] The present disclosure relates to a method for producing a nitrogen-enriched current from an electrochemical system. The nitrogen-enriched current can be discharged from the electrochemical system and used for rinsing, covering, cooling, and / or diagnosing the state of health (SoH) of the electrochemical system. background

[0002] With a volume of 78% in air, nitrogen is abundant on Earth. Nitrogen is widely used in the chemical industry. Nitrogen gas is commonly used to provide an inert atmosphere for chemical reactions, storage, and transport of materials. It can be used to purge chemical processing equipment and pipelines by displacing air and creating an oxygen-free environment. Nitrogen gas can also be used as a reactant in chemical production (e.g., as a feed gas for ammonia synthesis).

[0003] There are several well-known large-scale nitrogen production processes in commercial settings. Some of the most commonly used methods include cryogenic separation and pressure swing adsorption.

[0004] Cryogenic separation involves cooling air to extremely low temperatures, causing the various components of the air to liquefy and separate based on their boiling points. Cryogenic separation is frequently used in large air separation plants to obtain nitrogen with exceptional purity levels (e.g., 99.9999%). However, due to the significant space requirements, substantial costs, and energy consumption associated with constructing cryogenic plants, there is a growing interest in alternatives to cryogenic separation processes.

[0005] Pressure swing adsorption (PSA) utilizes the selective adsorption properties of various porous materials (e.g., zeolites or activated carbon) to separate nitrogen from other components in air. PSA can produce nitrogen gas with varying degrees of purity (e.g., 95% to 99.999%) depending on the operating parameters and the specific adsorption materials used. PSA processes can be relatively expensive due to adsorbent degradation and replacement, as well as relatively high energy consumption. Summary

[0006] According to one embodiment, a method for producing a nitrogen-enriched current from an electrochemical system is disclosed. The method comprises operating the electrochemical system in an operating state. The electrochemical system comprises an anode side and a cathode side. The anode side comprises an anode and an anode inlet that supplies an anode reactant to the anode. The anode side comprises an anode outlet that discharges an excess of the anode reactant from the anode. The cathode side comprises a cathode and a cathode inlet that supplies a cathode reactant to the cathode. The cathode side comprises a cathode outlet that discharges an excess of the cathode reactant and / or a cathode reactant from the cathode. The anode inlet, the anode outlet, the cathode inlet, and the cathode outlet are in open positions in the operating state.The process further includes operating the electrochemical system to generate a nitrogen-enriched current on the cathode side of the electrochemical system. The process also includes draining the nitrogen-enriched current from the cathode side of the electrochemical system through a drain valve to remove the nitrogen-enriched current from the electrochemical system.

[0007] According to a second embodiment, a method for producing a nitrogen-enriched current from an electrochemical system is disclosed. The method comprises flowing an anode reactant through an anode side of the electrochemical system and a cathode reactant through a cathode side of the electrochemical system. The method further comprises reducing the flow of the cathode reactant through the cathode side of the electrochemical system while the flow of the anode reactant through the anode side of the electrochemical system continues, in order to produce a nitrogen-enriched current on the cathode side of the electrochemical system. The method also includes draining the nitrogen-enriched current from the cathode side of the electrochemical system through a drain valve to produce the nitrogen-enriched current from the electrochemical system.

[0008] According to yet another embodiment, a method for producing a nitrogen-enriched current from an electrochemical system is disclosed. The method comprises providing the electrochemical system with a first electrochemical stack and a second electrochemical stack. The method further comprises passing an anode reactant through an anode side of the first electrochemical stack and a cathode reactant through a cathode side of the first electrochemical stack. The method also comprises reducing the flow of the cathode reactant through the cathode side of the first electrochemical stack while the flow of the anode reactant through the anode side of the first electrochemical stack continues, in order to produce a nitrogen-enriched current on the cathode side of the first electrochemical stack.The procedure also includes draining the nitrogen-enriched current from the cathode side of the first electrochemical stack through a drain valve to produce the nitrogen-enriched current from the first electrochemical stack. The procedure also includes applying nitrogen from the nitrogen-enriched current to a second electrochemical stack to perform a diagnostic test on the second electrochemical stack. Brief description of the drawings Fig. Figure 1 shows a schematic side view of certain components of an individual polymer electrolyte membrane fuel cell (PEMFC) in an operating state according to an embodiment. Fig. 2 shows a schematic side view of the individual PEMFC of the Fig. 1 in a locked state according to one embodiment. Fig. Figure 3 shows a flowchart of uses for nitrogen drained from an electrochemical cell. Detailed description

[0009] Herein are described embodiments of the present disclosure. It is understood, however, that the disclosed embodiments are merely examples and that other embodiments may take different and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or reduced in size to show details of certain components. The specific structural and functional details disclosed herein are therefore not to be considered limiting, but merely a representative basis for teaching persons skilled in the art to use the embodiments in various ways. Persons skilled in the art will recognize that various features illustrated and described with reference to any one of the figures can be combined with features illustrated in at least one other figure to produce embodiments that are not explicitly illustrated or described.The combinations of illustrated features provide representative embodiments for typical applications. However, different combinations and modifications of the features consistent with the teachings of this disclosure may be desirable for particular applications or implementations.

[0010] Except in the examples or where expressly stated otherwise, all numerical quantities in this description indicating amounts of material or reaction conditions and / or a use are to be understood as modified by the word "approximately" when describing the broadest scope of protection of the invention. Practice within the specified numerical limits is generally preferred. Furthermore, unless expressly stated otherwise: values ​​in percent, "proportions of," and ratios are based on mass; the term "polymer" includes "oligomer," "copolymer," "terpolymer," and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more elements of the group or class are equally suitable or preferred.Molecular masses provided for any polymers refer to a number-averaged molecular mass; a description of constituents in chemical terms refers to the constituents at the time of their addition to a combination specified in the description and does not necessarily exclude chemical interactions among the constituents of a mixture once it is mixed; the first definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation herein and applies mutatis mutandis to normal grammatical variations of the abbreviation initially defined; and, unless expressly specified otherwise, a measurement of a property is determined by the same procedure as previously or subsequently specified for the same property.

[0011] This invention is not limited to the specific embodiments and methods described below, as specific components and / or conditions may naturally vary. Furthermore, the terminology used herein is employed solely for the purpose of describing embodiments of the present invention and is not intended to be limiting in any way.

[0012] As used in the description and the attached claims, the singular forms "ein", "eine" and "der, die, das" include plural representations unless the context clearly indicates otherwise. For example, a singular reference to a single component is intended to encompass multiple components.

[0013] The term "essentially" can be used here to describe disclosed or claimed embodiments. The term "essentially" can modify a value or relative feature disclosed or claimed in the present disclosure. In such cases, "essentially" can mean that the value or relative feature it modifies is within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or 10% of the value or relative feature.

[0014] Known large-scale processes for nitrogen production (e.g., cryogenic separation) can have at least one disadvantage (e.g., high costs and space requirements to achieve high purity levels) that renders the processes unusable under certain circumstances. Polymer membrane separation technology can be used as a means to meet the requirements of small to medium-sized air separation plants that do not require ultra-high purity levels.

[0015] Polymer membrane separation can separate nitrogen and oxygen based on their concentration or partial pressure gradient across the membrane. Separation can be achieved through a solution diffusion mechanism, which can be controlled by the permeability and selectivity of the polymer membrane. However, the kinetic diameters of oxygen and nitrogen are very similar, making it difficult to achieve high permselectivity with polymer membranes. Permselectivity refers to the degree to which the polymer membrane allows the passage of certain ions and / or molecules while blocking the passage of others. Furthermore, these membranes are limited in their use for gas separation by their poor chemical and thermal stability.

[0016] Many potential nitrogen production approaches raise questions related to the logistics of nitrogen transportation. Nitrogen transport adds another layer of complexity to the use of nitrogen (N2) in various applications. Nitrogen is typically transported as a compressed gas in high-pressure cylinders or in liquid form in specialized tank trucks. Mobile production and on-demand deployment of nitrogen are not currently common, and if this is achieved, applications could emerge, such as using it as a covering and purging gas to protect valuable products from contamination. With the anticipated widespread adoption of hydrogen as a fuel, nitrogen could be used to protect electronic control units, provide inert cooling systems, and act as a pilot gas for local system diagnostics to monitor the health of fuel cells.

[0017] In at least one embodiment, a method for generating a nitrogen-enriched current from an electrochemical system is disclosed. At least one of the disclosed methods can be used in mobile units, including vehicles, trucks, buses, vans, emergency power generators, boats, drones, and / or computing devices. In at least one embodiment, the electrochemical system can be a fuel cell system. The fuel cell system can be a polymer electrolyte membrane fuel cell (PEMFC) system. The nitrogen-enriched current can be used for purging, covering, cooling, and / or diagnosing the state of health (SoH) of an electrochemical system, such as a PEMFC system.In at least one embodiment, a nitrogen-enriched stream refers to a gas having a nitrogen volume greater than the nitrogen volume in air (78%). In at least one embodiment, the nitrogen volume in the nitrogen-enriched stream can be any of the following volumes or a range of any two of the following volumes: 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0018] Fig. Figure 1 shows a schematic side view of certain components of an individual PEMFC 10 in an operating state according to one embodiment. A number of individual PEMFCs 10 can be combined to form a fuel cell stack. As shown in Fig. As shown in Figure 1, the PEMFC 10 comprises an anode 12, a cathode 14, and a polymer electrolyte membrane (PEM) 16 extending between the anode 12 and the cathode 14. A catalyst material, such as platinum, is used in the anode 12 and the cathode 14. The PEMFC also includes a first and a second gas diffusion layer (GDL) 18 and 20. The anode 12, the cathode 14, the PEM 16, and the first and second GDLs 18 and 20 are contained within the membrane electrode assembly 22. In operation, the PEMFC consumes hydrogen to generate electricity as air flows through the cathode.

[0019] The anode inlet 24 and the anode outlet 26 are in fluid communication with the flow channels and the first GDL 18, which is in fluid communication with the anode 12. In the operating state of the PEMFC 10, the anode inlet 24 and the anode outlet 26 are in open positions. As indicated by arrow 28, the anode inlet 24 is configured to allow fuel (e.g., hydrogen (H₂) fuel) to flow through the flow channels and the first GDL 18 into the PEMFC 10 and into the anode 12 (as indicated by arrow 30). The anode fuel is electrochemically oxidized in the presence of a catalyst to convert the H₂ into protons (H₂). + ) and electrons (e - ) to split (as indicated by arrow 32). Excess anode fuel leaves the PEMFC 10 through the anode outlet 34, as shown by arrow 34. As shown by arrow 36, the protons (H + ) through PEM 16 to cathode 14, while the electrons (e -) flow through an external circuit 38 to the cathode 14 (as shown by arrow 40). The electron flow (e - ) through the external circuit 38 generates an electric current to power the electrical device 42 or to charge a battery.

[0020] The cathode inlet 44 and the cathode outlet 46 are in fluid communication with the flow channels and the second GDL 20, which is in fluid communication with the cathode 14. In the operating state of the PEMFC 10, the cathode inlet 44 and the cathode outlet 46 are in open positions. As shown by arrow 48, the cathode inlet 44 is configured to allow air to flow through flow channels and the second GDL 20 into the PEMFC 10 and into the cathode 14 (as indicated by arrow 50). The oxygen (O2) supplied to the cathode 14 reacts with the protons (H₂). + ), which have migrated through PEM 16. The electrons (e -The fluids flowing through the external circuit 38, as shown by arrow 52, ​​form a water byproduct, as shown by arrows 54. The water byproduct and the excess air leave the cathode 14 and the PEMFC 10 through the cathode outlet 46, as shown by arrow 56.

[0021] Fig. 2 shows a schematic side view of the individual PEMFC 10 of the Fig. Figure 1 represents a closed-off state according to one embodiment. In the closed-off state, as indicated by the crossed-out arrows 58 and 60, the cathode inlet 44 and the cathode outlet 46 are in a closed position for a specified closure period, while hydrogen continues to flow through the anode 12. The closure period can last for any one of the following time intervals or within a range of any two of the following time intervals: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 seconds. In other embodiments, the lockdown duration can last for any one of the following periods or within a range of any two of the following periods: 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 and 5.0 minutes.In the shut-off state, the electrochemical reaction consumes the oxygen at the cathode 14 until the system voltage drops to a negligible level, as indicated by cross 62, while nitrogen 64 remains on the cathode side of the PEMFC 10. The remaining nitrogen 64 can be used for purging, covering, cooling, and / or diagnosing the state of health (SoH) of a PEMFC system. The remaining nitrogen 64 can be discharged through the nitrogen outlet 66 (e.g., a nitrogen-enriched stream) to perform at least one of the functions described herein in at least one embodiment. The nitrogen outlet 66 can include at least one pneumatic component (e.g., valves) configured to discharge the nitrogen-enriched stream.

[0022] During the operating state of the PEMFC, as in Fig. As shown in Figure 1, electricity is generated by using hydrogen as fuel when it reacts with the oxygen in the air flowing over the cathode side. In the shut-off state of the PEMFC, as shown in Figure 1, the PEMFC is powered by hydrogen. Fig. As shown in Figure 2, the PEMFC cathode valves are closed to create a nitrogen-enriched stream on the cathode side, while hydrogen flows at the anode. The closed state results in the consumption of residual oxygen in a closed cathode environment, thus reducing the PEMFC's current output. Eventually, moist nitrogen remains in the cathode environment. The relative humidity of the remaining nitrogen can be any of the following values ​​or within any two of the following: 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%. The humidity of the nitrogen-enriched stream can be reduced by a dehumidification device designed to remove water vapor and / or steam from the nitrogen-enriched stream.The nitrogen-enriched stream can be filtered using a filter gas other than nitrogen to further increase the purity of the nitrogen in the nitrogen-enriched vapor. In at least one embodiment, the nitrogen-enriched stream can be filtered after reducing its moisture content.

[0023] In another embodiment, the electrochemical system can be operated in a substoichiometric mode in which the cathode inlet and outlet are open, but the oxygen stoichiometry at a given current is lower than 1 and, in some embodiments, lower than 0.9. In this embodiment, a continuous stream of oxygen-depleted (i.e., nitrogen-enriched) gas exits the cathode outlet.

[0024] Fig.Figure 3 presents a flowchart 100 that includes uses for a nitrogen-enriched current from an electrochemical cell. Operation 102 involves venting the nitrogen-enriched current from a PEMFC. Operations 102, 104, and 106 are operations that can be performed using the nitrogen-enriched current. At least one of these operations can be performed using the nitrogen-enriched current.

[0025] Operation 104 involves performing a diagnosis on a second PEMFC stack using the nitrogen-enriched current from a first PEMFC stack in a multi-stack PEMFC array. The nitrogen-enriched current can be supplied to a subsequent PEMFC stack cathode to perform a diagnosis in a H₂ / N₂ environment (e.g., using conditions similar to laboratory conditions). A diagnosis can be obtained by voltage / current step cycles and analyzing the cell response or by performing a cyclic voltammetry test to estimate an electrochemically active surface area (ECSA). While Operation 104 discloses that one stack drains a nitrogen-enriched current for diagnostic use on another stack, draining can occur from more than one stack, and the drained nitrogen-enriched current can be used on multiple other stacks.Diagnostic tests with released nitrogen can be performed using voltage / current steps or cyclic voltammetry.

[0026] Operation 106 involves purging trace amounts of accumulated hydrogen from system components of a PEMFC using the nitrogen-enriched stream. The nitrogen-enriched stream can be used to purge hydrogen from system components such as control components within the PEMFC. The buildup of hydrogen can have gradual detrimental effects on temperature sensors, semiconductor devices, and the mechanical properties of metallic components. Purging hydrogen from electronic components can reduce the likelihood of sparking and / or electronic discharge. Non-restrictive examples of system components include at least one diagnostic component, monitoring component, humidification control, air supply control, hydrogen supply control, thermal management component, power management unit, and fuel cell control.

[0027] Operation 108 involves performing a cooling or covering function using the nitrogen-enriched stream. The nitrogen can be used for fire covering or cooling system components. Non-limiting examples of system components include at least one diagnostic component, monitoring component, humidification control, air supply control, hydrogen supply control, thermal management component, power management unit, and fuel cell control.

[0028] Although exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms included in the claims. The words used in the description are descriptive rather than limiting, and it is understood that various modifications can be made without departing from the spirit and scope of the disclosure. As previously described, the features of the various embodiments can be combined to form further embodiments of the invention that cannot be explicitly described or illustrated.While various embodiments could have been described as offering advantages or being preferred over other embodiments or implementations according to the prior art with respect to at least one desirable feature, those skilled in the art recognize that at least one property or feature may be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, but are not limited to, cost, strength, durability, lifetime cost, marketability, appearance, packaging, size, maintainability, mass, manufacturability, ease of assembly, etc.Insofar as embodiments are described as less desirable than other embodiments or implementations according to the prior art with respect to at least one property, these embodiments as such are not outside the scope of protection of the disclosure and may be desirable for certain applications.

Claims

[1] Method for producing a nitrogen-enriched current from an electrochemical system, the method comprising the following: Operating the electrochemical system in an operating state, wherein the electrochemical system comprises an anode side and a cathode side, the anode side comprising an anode and an anode inlet that supplies an anode reactant to the anode, the anode side comprising an anode outlet that discharges an excess of the anode reactant from the anode, the cathode side comprising a cathode and a cathode inlet that supplies a cathode reactant to the cathode, the cathode side includes a cathode outlet that diverts an excess amount of the cathode reactant and / or a cathode reactant from the cathode, and the anode inlet, anode outlet, cathode inlet and cathode outlet are in open positions in the operating state; and Operating the electrochemical system to produce a nitrogen-enriched current on the cathode side of the electrochemical system; and Draining the nitrogen-enriched current from the cathode side of the electrochemical system through a drain valve to produce the nitrogen-enriched current from the electrochemical system. [2] Method according to claim 1, wherein the operating step comprises operating the electrochemical system in a shut-off state to produce the nitrogen-enriched current on the cathode side of the electrochemical system, the anode inlet and the anode outlet being in open positions in the shut-off state and the cathode inlet and the cathode outlet being in closed positions in the shut-off state. [3] Method according to claim 1, wherein the first operating step takes place before the second operating step. [4] Method according to claim 2, wherein the second operating step is carried out for a period of time. [5] Method according to claim 4, wherein the time duration is 1 to 20 seconds. [6] The method of claim 1, further comprising applying nitrogen from the nitrogen-enriched current to the electrochemical system to perform a diagnostic test on the electrochemical system. [7] Method according to claim 6, wherein the diagnostic test comprises a voltage / current step cycle and an analysis of the response of the electrochemical system. [8] Method according to claim 6, wherein the diagnostic test comprises performing a cyclic voltammetry test to estimate an electrochemical active surface area (ECSA). [9] The method of claim 1, further comprising purging hydrogen from at least one system component with nitrogen from the nitrogen-enriched stream. [10] Method according to claim 9, wherein the at least one system component comprises at least one diagnostic component, monitoring component, humidification control, air supply control, hydrogen supply control, thermal management component, power management unit and fuel cell control. [11] Method according to claim 1, further comprising cooling the electrochemical system using nitrogen from the nitrogen-enriched current. [12] Method according to claim 1, further comprising covering the electrochemical system using nitrogen from the nitrogen-enriched current. [13] Method according to claim 1, wherein the electrochemical system is a polymer electrolyte membrane fuel cell system (PEMFC system). [14] Method for producing a nitrogen-enriched current from an electrochemical system, the method comprising the following: Flow of an anode reactant through an anode side of the electrochemical system and of a cathode reactant through a cathode side of the electrochemical system; Reducing the cathode reactant through the cathode side of the electrochemical system, while the anode reactant current continues through the anode side of the electrochemical system, in order to produce a nitrogen-enriched current on the cathode side of the electrochemical system; and Draining the nitrogen-enriched current from the cathode side of the electrochemical system through a drain valve to produce the nitrogen-enriched current from the electrochemical system. [15] Method according to claim 14, wherein the step of reducing comprises reducing an oxygen stoichiometry to less than 1. [16] Method according to claim 14, wherein the reduction step is an interruption step that is carried out for a period of time. [17] Method according to claim 16, wherein the time duration is 1 to 20 seconds. [18] Method according to claim 14, wherein the electrochemical system is a polymer electrolyte membrane fuel cell system (PEMFC system). [19] Method for producing a nitrogen-enriched current from an electrochemical system, the method comprising the following: Providing the electrochemical system with a first electrochemical stack and a second electrochemical stack; Flow of an anode reactant through an anode side of the first electrochemical stack and of a cathode reactant through a cathode side of the first electrochemical stack; Reducing the cathode reactant through the cathode side of the first electrochemical stack, while the current of the anode reactant continues through the anode side of the first electrochemical stack to produce a nitrogen-enriched current on the cathode side of the first electrochemical stack; Draining the nitrogen-enriched current from the cathode side of the first electrochemical stack through a drain valve to produce the nitrogen-enriched current from the first electrochemical stack; and Applying nitrogen from the nitrogen-enriched current to a second electrochemical stack to perform a diagnostic test on the second electrochemical stack. [20] Method according to claim 19, wherein the electrochemical system is a polymer electrolyte membrane fuel cell system (PEMFC system).

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