Method for producing nitrogen-rich stream from electrochemical system

Abstract

The invention relates to a method for producing a nitrogen-rich stream from an electrochemical system. A method of generating a nitrogen-rich stream from an electrochemical system. The method includes operating the electrochemical system in an operating state, operating the electrochemical system in a bleed state to produce a nitrogen-rich stream at a cathode side of the electrochemical system, and exhausting the nitrogen-rich stream from the cathode side of the electrochemical system through an exhaust valve to produce the nitrogen-rich stream from the electrochemical system. The generated nitrogen gas may be used to purge, cover, cool, and / or diagnose the state of health (SoH) of an electrochemical system, such as a PEMFC system.

Description

Technical Field

[0001] This invention relates to a method for generating a nitrogen-rich gas stream from an electrochemical system. The nitrogen-rich gas stream can be discharged from the electrochemical system and used for purging, covering, cooling, and / or diagnosing the health status (SoH) of the electrochemical system. Background Technology

[0002] Nitrogen makes up 78% of the volume of air and is abundant on Earth. It has wide applications in the chemical industry, providing an inert atmosphere for chemical reactions, material storage, and transportation. Nitrogen gas can be used to purge chemical processing equipment and pipelines, helping to displace air and create an oxygen-free environment. It can also be used as a reactant in chemical production (e.g., as a feedstock for ammonia synthesis).

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

[0004] Cryogenic separation involves cooling air to extremely low temperatures and liquefying and separating the different components of the air based on their boiling points. Cryogenic separation is commonly used in large air separation plants to produce nitrogen with extremely high purity levels (e.g., 99.9999%). However, due to the significant space requirements, high costs, and energy consumption associated with constructing cryogenic facilities, there is growing interest in alternatives to cryogenic separation processes.

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

[0006] According to one embodiment, a method for generating a nitrogen-rich gas flow from an electrochemical system is disclosed. The method includes operating the electrochemical system in an operating state. The electrochemical system includes an anode side and a cathode side. The anode side includes an anode and an anode inlet for allowing anolyte reactants to flow into the anode. The anode side includes an anode outlet for discharging excess anolyte reactants from the anode. The cathode side includes a cathode and a cathode inlet for allowing cathode reactants to flow into the cathode. The cathode side includes a cathode outlet for discharging excess cathode reactants and / or cathode reactants from the cathode. The anode inlet, anode outlet, cathode inlet, and cathode outlet are in an open position in the operating state. The method further includes operating the electrochemical system to generate a nitrogen-rich gas flow on the cathode side of the electrochemical system. The method also includes discharging the nitrogen-rich gas flow from the cathode side of the electrochemical system through an exhaust valve to generate a nitrogen-rich gas flow from the electrochemical system.

[0007] According to a second embodiment, a method for generating a nitrogen-rich gas flow from an electrochemical system is disclosed. The method includes passing an anolyte reactant through the anode side of the electrochemical system and a cathode reactant through the cathode side of the electrochemical system. The method further includes reducing the cathode reactant passing through the cathode side of the electrochemical system while continuing to pass the anolyte reactant through the anode side of the electrochemical system to generate a nitrogen-rich gas flow on the cathode side of the electrochemical system. The method also includes discharging the nitrogen-rich gas flow from the cathode side of the electrochemical system through an exhaust valve to generate a nitrogen-rich gas flow from the electrochemical system.

[0008] According to another embodiment, a method for generating a nitrogen-rich gas flow from an electrochemical system is disclosed. The method includes providing a first electrochemical stack and a second electrochemical stack to the electrochemical system. The method further includes passing an anode reactant through the anode side of the first electrochemical stack and passing a cathode reactant through the cathode side of the first electrochemical stack. The method also includes reducing the cathode reactant passing through the cathode side of the first electrochemical stack while continuing to pass the anode reactant through the anode side of the first electrochemical stack to generate a nitrogen-rich gas flow on the cathode side of the first electrochemical stack. The method further includes discharging the nitrogen-rich gas flow from the cathode side of the first electrochemical stack through an exhaust valve to generate the nitrogen-rich gas flow from the first electrochemical stack. The method also includes applying nitrogen from the nitrogen-rich gas flow to the second electrochemical stack for operational diagnostic testing of the second electrochemical stack. Attached Figure Description

[0009] Figure 1 A schematic side view depicts some components of a single polymer electrolyte membrane fuel cell (PEMFC) in operation according to one embodiment.

[0010] Figure 2 The description depicts a bleed-down state according to one implementation scheme. Figure 1A schematic side view of a single PEMFC.

[0011] Figure 3 A flowchart depicting the use of nitrogen emitted from an electrochemical cell is provided. Detailed Implementation

[0012] Embodiments of this disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples and other embodiments may take various and alternative forms. The drawings are not necessarily to scale; some features may be enlarged or minimized to show details of particular components. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but rather as a representative basis for teaching those skilled in the art to utilize the embodiments in various ways. As will be understood by those skilled in the art, the various features illustrated and described with reference to any of the drawings can be combined with features illustrated in one or more other drawings to derive embodiments that are not explicitly illustrated or described. Combinations of illustrated features provide representative embodiments for typical applications. However, specific applications or implementations may require various combinations and modifications of features consistent with the teachings of this disclosure.

[0013] Unless otherwise expressly stated in the examples or herein, all numerical quantities indicating the amount of material or reaction and / or conditions of use in this specification should be understood to be modified by the word “about” to describe the widest scope of the invention. It is generally preferred to practice within the stated numerical limits. Furthermore, unless otherwise expressly stated: percentages, “parts”, and ratio values ​​are all by weight; the term “polymer” includes “oligomer,” “copolymer,” “terpolymer,” etc.; describing a group or class of materials as suitable or preferred for a given purpose related to the invention means that a mixture of any two or more members of that group or class is equally suitable or preferred; the molecular weights provided for any polymer are exponential molecular weights; descriptions of components in chemical terms refer to components added to any combination specified in the specification and do not necessarily exclude chemical interactions between components of the mixture; the initial definition of acronyms or other abbreviations applies to all subsequent uses of the same abbreviations herein and, with necessary modifications, applies to normal grammatical variations of the originally defined abbreviations; and, unless otherwise expressly stated, measurements of properties are determined by the same technique referenced previously or subsequently for the same property.

[0014] This invention is not limited to the specific embodiments and methods described below, as specific components and / or conditions can certainly vary. Furthermore, the terminology used herein is for describing embodiments of the invention only and is not intended to be limiting in any way.

[0015] As used in the specification and appended claims, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” include plural references. For example, references to components in the singular form are intended to include multiple components.

[0016] The term "substantially" is used herein to describe the disclosed or claimed embodiments. The term "substantially" may modify values ​​or relative characteristics disclosed or claimed in this disclosure. In this case, "substantially" may mean that the value or relative characteristic it modifies is within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or 10% of the value or relative characteristic.

[0017] Known commercial-scale nitrogen production processes (such as cryogenic separation) may have one or more drawbacks (such as high cost and space requirements to achieve high purity levels), making these processes unsuitable in some situations. Polymer membrane separation technology can be used as a means to meet the needs of medium-sized air separation plants that do not require ultra-high purity levels.

[0018] Polymer membrane separation can be based on the concentration or partial pressure gradient of nitrogen and oxygen across the membrane. Separation can be achieved via 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 challenging to achieve high selective permeability with polymer membranes. Selective permeability refers to the degree to which a polymer membrane allows certain ions and / or molecules to pass through while blocking others. Furthermore, these membranes are limited by their poor chemical and thermal stability when used for gas separation.

[0019] Many possible methods for generating nitrogen raise issues related to nitrogen transport logistics. Nitrogen transport complicates the utilization of nitrogen (N2) in various applications. Nitrogen is typically transported as a compressed gas in high-pressure cylinders or as a liquid in dedicated tank trucks. Currently, mobile generation and on-demand utilization of nitrogen are not common, and achieving this could create applications such as covering and purging gases to protect valuable products from contaminants. With the anticipated widespread adoption of hydrogen as a fuel, nitrogen could be used to protect electronic control units, provide inert cooling systems, and serve as a control gas for local system diagnostics, including fuel cell health measurements.

[0020] In one or more embodiments, a method for generating a nitrogen-rich gas flow from an electrochemical system is disclosed. The disclosed method or methods can be used in mobile units, including vehicles, trucks, buses, vans, emergency backup power units, ships, drones, and / or computing devices. In one or more embodiments, 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-rich gas flow can be used to purge, cover, cool, and / or diagnose the state of health (SoH) of the electrochemical system (such as a PEMFC system). In one or more embodiments, a nitrogen-rich gas flow refers to a gas with a nitrogen volume higher than the nitrogen volume in air (78%). In one or more embodiments, the nitrogen volume in the nitrogen-rich gas flow can be any one of the following volumes or within the 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%.

[0021] Figure 1 A schematic side view of some components of a single PEMFC 10 in operation according to one embodiment is depicted. Multiple individual PEMFC 10s can be combined to form a fuel cell stack. Figure 1 As shown, the PEMFC 10 includes 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 for the anode 12 and the cathode 14. The PEMFC also includes first and second gas diffusion layers (GDLs) 18 and 20. The anode 12, cathode 14, PEM 16, and the first GDL 18 and the second GDL 20 constitute a membrane electrode assembly 22. In operation, the PEMFC consumes hydrogen fuel to generate electricity when air flows through the cathode.

[0022] Anode inlet 24 and anode outlet 26 are in fluid communication with the flow channel and the first GDL 18, which in turn is in fluid communication with the anode 12. During the operation of the PEMFC 10, anode inlet 24 and anode outlet 26 are in the open position. As indicated by arrow 28, anode inlet 24 is configured to allow fuel (e.g., hydrogen (H2) fuel) to flow into the PEMFC 10 through the flow channel and the first GDL 18, and into the anode 12 (as indicated by arrow 30). The anode fuel undergoes electrochemical oxidation in the presence of a catalyst to decompose H2 into protons (H2O). + ) and electrons (e - (As shown by arrow 32). Excess anode fuel is discharged from PEMFC 10 through anode outlet 34, as shown by arrow 34. As shown by arrow 36, protons (H +Electrons are transferred to cathode 14 via PEM 16, while electrons (e) - The electron flow (e) flows through external circuit 38 to cathode 14 (as shown by arrow 40). - The current flows through the external circuit 38 to generate current, which powers the electrical equipment 42 or charges the battery pack.

[0023] Cathode inlet 44 and cathode outlet 46 are in fluid communication with a flow channel and a second GDL 20 that is in fluid communication with cathode 14. During the operation of PEMFC 10, cathode inlet 44 and cathode outlet 46 are in the open position. As shown by arrow 48, cathode inlet 44 is configured to allow air to flow into PEMFC 10 through the flow channel and second GDL 20, and into cathode 14 (as shown by arrow 50). Oxygen (O2) fed into cathode 14 reacts with protons (H2) passing through PEM 16. + The reaction. As shown by arrow 52, ​​electrons (e) flow from the water byproduct as shown by arrow 54 through external circuit 38. - Water byproducts and excess air exit cathode 14 and PEMFC 10 through cathode outlet 46, as indicated by arrow 56.

[0024] Figure 2 Depicting according to an implementation scheme Figure 1 A schematic side view of a single PEMFC 10 in the venting state. In the venting state, as indicated by the crossed arrows 58 and 60, the cathode inlet 44 and cathode outlet 46 are closed during the venting period, while hydrogen continues to flow through the anode 12. The venting period can last for any one of the following periods or within any two of the following periods: 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 venting period can last for any one of the following periods or within 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 venting state, the electrochemical reaction consumes oxygen at cathode 14 until the system voltage drops to a negligible level, as shown by cross 62, while nitrogen 64 remains on the cathode side of PEMFC 10. The remaining nitrogen 64 can be used for purging, covering, cooling, and / or diagnosing the health status (SoH) of the PEMFC system. In one or more embodiments, the remaining nitrogen 64 can be vented via a nitrogen venting device 66 (e.g., a nitrogen-enriched gas flow) to achieve one or more of the tasks described herein. The nitrogen venting device 66 may include one or more pneumatic components (e.g., valves) configured to vent a nitrogen-enriched gas flow.

[0025] In such Figure 1The PEMFC shown generates electricity during operation by using hydrogen as fuel to react with oxygen in the air flowing at the cathode side. Figure 2 As shown, in the venting state of the PEMFC, the PEMFC cathode valve is closed to generate a nitrogen-rich gas flow on the cathode side, while hydrogen flows at the anode. The venting state results in the consumption of residual oxygen in the confined cathode environment, thereby reducing the power output of the PEMFC. Ultimately, moist nitrogen remains in the cathode environment. The relative humidity of the residual nitrogen can be any one or a range of any two of the following values: 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%. The humidity of the nitrogen-rich gas flow can be reduced by a dehumidifier configured to reduce moisture and / or vapor in the nitrogen-rich gas flow. The nitrogen-rich gas flow can be filtered using a filter gas other than gas to further improve the purity of nitrogen in the nitrogen-rich gas flow. In one or more embodiments, the nitrogen-rich gas flow can be filtered after the humidity of the nitrogen-rich gas flow has been reduced.

[0026] In another embodiment, the electrochemical system can operate in a substoichiometric mode, where the cathode inlet and outlet are open, but the oxygen stoichiometry at a given current is less than 1, and in some embodiments less than 0.9. In this embodiment, a continuous flow of oxygen-deficient (i.e., nitrogen-rich) gas exits the cathode outlet.

[0027] Figure 3 A flowchart 100 depicts the use of a nitrogen-rich gas flow from an electrochemical cell. Operation 102 involves discharging the nitrogen-rich gas flow from the PEMFC. Operations 102, 104, and 106 are operations that can be performed using a nitrogen-rich gas flow. One or more of these operations can be performed using a nitrogen-rich gas flow.

[0028] Operation 104 includes performing diagnostics on a second PEMFC stack in a multi-stack PEMFC arrangement using a nitrogen-rich gas flow from a first PEMFC stack. The nitrogen-rich gas flow can be fed to the cathode of a subsequent PEMFC stack to perform diagnostics in an H2 / N2 environment (e.g., using conditions similar to laboratory conditions). Diagnostics can be performed by voltage / current step cycling and analyzing the cell response or by performing cyclic voltammetry testing to estimate the electrochemically active surface area (ECSA). While Operation 104 discloses the diagnostic use of a nitrogen-rich gas flow emitted from one stack for another stack, more than one stack can be emitted, and the emitted nitrogen-rich gas flow can be used for multiple other stacks. Nitrogen depletion diagnostic testing can be performed using voltage / current step cycling or cyclic voltammetry.

[0029] Operation 106 involves using a nitrogen-enriched gas stream to purge trace amounts of hydrogen accumulated in PEMFC system components. The nitrogen-enriched gas stream can be used to purge hydrogen from system components in a PEMFC, such as control components. Hydrogen accumulation can have a gradually destructive effect on the mechanical properties of temperature sensors, semiconductor devices, and metal components. Removing hydrogen from electronic components reduces the likelihood of sparking and / or electronic discharge. Non-limiting examples of system components include one or more diagnostic components, monitoring components, humidification controls, gas supply controls, hydrogen supply controls, thermal management components, power management units, and fuel cell controllers.

[0030] Operation 108 includes performing cooling or covering functions using a nitrogen-enriched gas flow. Nitrogen can be used for fire suppression or cooling system components. Non-limiting examples of system components include one or more diagnostic components, monitoring components, humidification controls, air supply controls, hydrogen supply controls, thermal management components, power management units, and fuel cell controllers.

[0031] Although exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms covered by the claims. The language used in this specification is descriptive rather than restrictive, and it should be understood that various changes may be made without departing from the spirit and scope of this disclosure. As previously stated, features of various embodiments may be combined to form other embodiments of the invention that may not be explicitly described or illustrated. While various embodiments may be described as providing an advantage or preference over other embodiments or prior art implementations with respect to one or more desired characteristics, those skilled in the art will recognize that one or more features or characteristics may be sacrificed to achieve desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, cost, strength, durability, life cycle cost, merchantability, appearance, packaging, size, suitability, weight, manufacturability, ease of assembly, etc. Therefore, any embodiment described as less desirable with respect to one or more characteristics than other embodiments or prior art implementations is not outside the scope of this disclosure and may be ideal for a particular application.

Claims

1. A method for generating a nitrogen-rich gas stream from an electrochemical system, the method comprising: The electrochemical system is operated in operation. The electrochemical system includes an anode side and a cathode side. The anode side includes an anode and an anode inlet for introducing anolyte reactants into the anode. The anode side also includes an anode outlet for discharging excess anolyte reactants from the anode. The cathode side includes a cathode and a cathode inlet for introducing cathode reactants into the cathode. The cathode side also includes a cathode outlet for discharging excess cathode reactants and / or cathode reactants from the cathode. The anode inlet, the anode outlet, the cathode inlet, and the cathode outlet are in the open position in operation. and The electrochemical system is operated to generate a nitrogen-rich gas flow on the cathode side of the electrochemical system. and A nitrogen-rich gas stream is discharged from the cathode side of the electrochemical system through an exhaust valve to generate a nitrogen-rich gas stream from the electrochemical system.

2. The method of claim 1, wherein the operating step comprises operating the electrochemical system in a venting state to generate a nitrogen-rich gas flow on the cathode side of the electrochemical system, wherein the anode inlet and the anode outlet are in an open position in the venting state, and the cathode inlet and the cathode outlet are in a closed position in the venting state.

3. The method according to claim 1, wherein the first operation step occurs before the second operation step.

4. The method according to claim 2, wherein the second operation step is performed for a period of time.

5. The method of claim 4, wherein the time period is 1 to 20 seconds.

6. The method of claim 1, further comprising applying nitrogen gas from a nitrogen-rich gas stream to the electrochemical system for performing operational diagnostic tests on the electrochemical system.

7. The method of claim 6, wherein the diagnostic test comprises voltage / current step cycling and analysis of the response of the electrochemical system.

8. The method of claim 6, wherein the diagnostic test comprises performing a cyclic voltammetry test to assess the electrochemically active surface area (ECSA).

9. The method of claim 1, further comprising purging hydrogen from one or more system components with nitrogen from a nitrogen-rich gas stream.

10. The method of claim 9, wherein the one or more system components include one or more diagnostic components, monitoring components, humidification control, air supply control, hydrogen supply control, thermal management components, power management unit, and fuel cell controller.

11. The method of claim 1, further comprising cooling the electrochemical system with nitrogen from the nitrogen-rich gas stream.

12. The method of claim 1, further comprising covering the electrochemical system with nitrogen from the nitrogen-rich gas stream.

13. The method of claim 1, wherein the electrochemical system is a polymer electrolyte membrane fuel cell (PEMFC) system.

14. A method for generating a nitrogen-rich gas stream from an electrochemical system, the method comprising: The anodic reactant flows through the anode side of the electrochemical system, and the cathode reactant flows through the cathode side of the electrochemical system. The cathode reactants passing through the cathode side of the electrochemical system are reduced, while the anode reactants continue to flow through the anode side of the electrochemical system to generate a nitrogen-rich gas flow on the cathode side of the electrochemical system. and A nitrogen-rich gas stream is discharged from the cathode side of the electrochemical system through an exhaust valve to generate a nitrogen-rich gas stream from the electrochemical system.

15. The method of claim 14, wherein the reducing step comprises reducing the oxygen stoichiometry to less than 1.

16. The method of claim 14, wherein the reduction step is an interruption step performed over a period of time.

17. The method of claim 16, wherein the time period is 1 to 20 seconds.

18. The method of claim 14, wherein the electrochemical system is a polymer electrolyte membrane fuel cell (PEMFC) system.

19. A method for generating a nitrogen-rich gas stream from an electrochemical system, the method comprising: The electrochemical system is provided with a first electrochemical stack and a second electrochemical stack; The anodic reactant flows through the anode side of the first electrochemical stack, and the cathode reactant flows through the cathode side of the first electrochemical stack. Reduce the cathode reactants passing through the cathode side of the first electrochemical stack, while continuing to allow the anode reactants to flow through the anode side of the first electrochemical stack, so as to generate a nitrogen-rich gas flow on the cathode side of the first electrochemical stack. A nitrogen-rich gas flow is discharged from the cathode side of the first electrochemical stack through an exhaust valve to generate a nitrogen-rich gas flow from the first electrochemical stack. and Nitrogen gas from a nitrogen-rich gas stream is applied to the second electrochemical stack for operational diagnostic testing of the second electrochemical stack.

20. The method of claim 19, wherein the electrochemical system is a polymer electrolyte membrane fuel cell (PEMFC) system.

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