Electrochemical cell system containing column compression springs located in air flow zone of a hotbox

Abstract

An electrochemical cell system includes a hotbox and one or more electrochemical cell columns located in the hotbox. Each electrochemical cell column includes at least one electrochemical cell stack and a compression assembly located above the at least one electrochemical cell stack. The compression assembly includes a metal compression spring located in an air flow zone of the hotbox.

Description

ELECTROCHEMICAL CELL SYSTEM CONTAINING COLUMN COMPRESSIONSPRINGS LOCATED IN AIR FLOW ZONE OF A HOTBOXFIELD

[0001] Aspects of the present invention relate to electrochemical cell systems and methods, and more particularly, to fuel cell or electrolyzer cell systems including column compression springs located in relatively cool air flow zone of a hotbox.BACKGROUND

[0002] Fuel cells, such as solid oxide fuel cells, are electrochemical devices which can convert energy stored in fuels to electrical energy with high efficiencies. High temperature fuel cells include solid oxide and molten carbonate fuel cells. These fuel cells may operate using hydrogen and / or hydrocarbon fuels. There are classes of fuel cells, such as the solid oxide regenerative fuel cells, that also allow reversed operation, such that oxidized fuel can be reduced back to unoxidized fuel using electrical energy as an input.SUMMARY

[0003] According to various embodiments, an electrochemical cell system includes a hotbox and one or more electrochemical cell columns located in the hotbox. Each electrochemical cell column includes at least one electrochemical cell stack, and a compression assembly located above the at least one electrochemical cell stack. The compression assembly includes a metal compression spring located in an air flow zone of the hotbox.

[0004] According to various embodiments, a method of operating an electrochemical cell system includes providing a reactant stream to one or more electrochemical cell columns located in the hotbox, and providing an air inlet stream to each electrochemical cell column. Each electrochemical cell column comprises at least one electrochemical cell stack, and a compression assembly located above the at least one electrochemical cell stack. The air inlet stream flows around at least a part of a metal compression spring of the compression assembly.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate example embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain the features of the invention.

[0006] FIG. 1 A is a perspective view of an electrochemical cell column, FIG. IB is a perspective view of one counter-flow solid oxide electrochemical cell (e.g., solid oxide fuel cell (SOFC) or solid oxide electrolyzer cell (SOEC)) stack included in the column of FIG. 1A, and FIG. 1C is a side cross-sectional view of a portion of the stack of FIG. IB. FIG. ID is a schematic of a fuel cell system, according to various embodiments of the present disclosure.

[0007] FIG. 2A is a sectional view showing components of the hot box of the system of FIG. ID, FIG. 2B shows an enlarged portion of the system of FIG. 2A, FIG. 2C is a three dimensional cut-away view of a central column of the system of FIG. 2A, and FIG. 2D is a perspective view of an anode hub structure disposed below the central column of the system of FIG. 2A, according to various embodiments of the present disclosure.

[0008] FIGS. 3 A-3C are sectional views showing fuel and air flow through the central column of the system of FIG. 2A, according to various embodiments of the present disclosure.

[0009] FIG. 4A is a partial perspective view of a water injector disposed in the central column of the system of FIG. 2A, FIG. 4B is a top view of components of the water injector of FIG. 4A, and FIG. 4C is a perspective view of the water injector, according to various embodiments of the present disclosure.

[0010] FIG. 5 is a side cross-sectional view showing an alternative embodiment of the components of the hot box of the system of FIG. ID.

[0011] FIG. 6A is a vertical cross sectional view of an upper portion of an electrochemical cell column, according to various embodiments of the present disclosure. FIG. 6B is a perspective view of the upper portion of the electrochemical cell column of FIG. 6A. FIG. 6C is vertical cross sectional view of the electrochemical cell column, according to variousembodiments of the present disclosure. The area “A” corresponds to the upper portion of the electrochemical cell column of FIG. 6A. FIG. 6D is a perspective view of the electrochemical cell column of FIG. 6C. The area “B” corresponds to the upper portion of the electrochemical cell column of FIG. 6B.

[0012] FIG. 7A is a cut-away perspective view of an upper portion of a hotbox, according to various embodiments of the present disclosure. FIG. 7B is a cut-away perspective view of the hotbox of FIG. 7 A. The area “A” corresponds to the upper portion of the hotbox of FIG. 7A. FIG. 7C is a perspective view of the hotbox of FIG. 7B.

[0013] FIG. 8 is a cut-away perspective view of the upper portion of the electrochemical cell column of FIGS. 6A - 6D located in the hotbox of FIGS. 7A-7C, according to various embodiments of the present disclosure.

[0014] FIG. 9A is a vertical cross sectional view of a compression assembly, according to an alternative embodiment of the present disclosure. FIG. 9B is a vertical cross sectional view of an electrochemical cell column including the compression assembly of FIG. 9 A, according to the alternative embodiment of the present disclosure.

[0015] FIG. 10A is perspective cut-away view of hotbox lid components, according to various embodiments of the present disclosure. FIG. 10B is a perspective cut-away view of the upper portions of electrochemical cell columns in the hotbox containing the hotbox lid components of FIG. 10A, according to various embodiments of the present disclosure.

[0016] FIG. 11 is a perspective cut-away view of an upper portion of the electrochemical cell column in the hotbox of FIG. 10B.

[0017] FIG. 12A is a perspective cut-away view of an upper portion of an electrochemical cell column in a hotbox, according to another alternative embodiment of the present disclosure. FIGS. 12B and 12C are perspective views of steps of fabricating the electrochemical cell column of FIG. 12 A.

[0018] FIG. 13 A is a perspective cut-away view of an upper portion of an electrochemical cell column in a hotbox, according to another alternative embodiment of the present disclosure. FIGS. 13B and 13C are perspective views of steps of fabricating the electrochemical cell column of FIG. 13 A.DETAILED DESCRIPTION

[0019] The various embodiments will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. References made to particular examples and implementations are for illustrative purposes and are not intended to limit the scope of the invention or the claims.

[0020] Electrochemical cell systems include fuel cell and electrolyzer cell systems. In a high temperature fuel cell system, such as a solid oxide fuel cell (SOFC) system, an oxidizing flow is directed to the cathode side of the fuel cell while a fuel (i.e., reactant) flow is directed to the anode side of the fuel cell. The oxidizing flow is typically air, while the fuel flow can be hydrogen (H2) or a hydrocarbon fuel, such as methane, natural gas, ethanol, or methanol, or a hydrogen containing fuel such as ammonia. The fuel cell, operating at a typical temperature between 750°C and 950°C, enables the transport of negatively charged oxygen ions from the cathode flow stream to the anode flow stream, where the ions combine with either free hydrogen or hydrogen in a hydrocarbon molecule to form water vapor and / or with carbon monoxide to form carbon dioxide. The excess electrons from the negatively charged ions are routed back to the cathode side of the fuel cell through an electrical circuit completed between anode and cathode, resulting in an electrical current flow through the circuit.

[0021] In an electrolyzer system, such as a solid oxide electrolyzer system (SOEC), a reactant flow comprising water (e.g., steam) is separated into hydrogen and oxygen by applying a voltage across the electrolyzer cells. In the SOEC stack, the anode is the air electrode and the cathode is the reactant electrode. Thus, the electrode to which the reactant (e.g., hydrogen, ammonia or hydrocarbon fuel in a SOFC, and steam in a SOEC) is supplied may be referred to as the reactant electrode and the opposing electrode may be referred to as the air electrode in both SOFC and SOEC cells.

[0022] FIG. 1 A is a perspective view of an electrochemical cell column 30, FIG. IB is a perspective view of one counter-flow solid oxide electrochemical cell (e.g., SOFC or SOEC) stack 102 included in the column 30 of FIG. 1 A, and FIG. 1C is a side cross-sectional view of a portion of the stack 102 of FIG. IB.

[0023] Referring to FIGS. 1 A and IB, the column 30 may include one or more electrochemical cell stacks 102, a reactant inlet conduit 32, a reactant exhaust conduit 34, andreactant feed / retum assemblies 36 (e.g., reactant splitter plates (RSPs) 36). The reactant inlet conduit 32 is fluidly connected to RSPs 36 and is configured to provide the reactant feed to each RSP 36, and reactant exhaust conduit 34 is fluidly connected to RSPs 36 and is configured to receive reactant exhaust from each RSP 36.

[0024] The RSPs 36 are disposed between the stacks 102 and are configured to provide a reactant (e.g., fuel or steam) feed to the stacks 102 and to receive reactant exhaust from the stacks 102. A RSP 36 may also be positioned adjacent a single stack depending upon the number of stacks in the column 30. RSPs 36 may be fluidly connected to internal reactant holes 22 formed in the stacks 102.

[0025] The column 30 may also include a compression assembly 40, and a ceramic frame comprising side baffles 41, a top plate 42, a bottom plate 43, top connectors 44 and bottom connectors 45. The top connectors 44 and the bottom connectors 45 connect the side baffles 41 to the top plate 42 and the bottom plate 43, respectively.

[0026] Referring to FIG. 1C, the stack 102 includes multiple electrochemical cells 1 that are separated by interconnects 2, which may also be referred to as gas flow separator plates or bipolar plates. Each electrochemical cell 1 includes an air electrode 3, a solid oxide electrolyte 5, and a reactant electrode 7.

[0027] Each interconnect 2 electrically connects adjacent electrochemical cells 1 in the stack 102. In particular, an interconnect 2 may electrically connect the reactant electrode 7 of one electrochemical cell 1 to the air electrode 3 of an adjacent electrochemical cell 1. FIG. 1C shows that the lower electrochemical cell 1 is located between two interconnects 2.

[0028] Each interconnect 2 includes reactant ribs 12A that at least partially define reactant channels 8A and air ribs 12B that at least partially define the air channels 8B. The interconnect 2 may operate as a gas-reactant separator that separates a reactant flowing to the reactant electrode of one cell in the stack from oxidant, such as air, flowing to the air electrode 3 of an adjacent cell in the stack. At either end of the stack 102, there may be an air end plate or reactant end plate (not shown) for providing air or reactant, respectively, to the end electrode in the stack. The end plate may comprise an interconnect 2 where the channels on one side of the interconnect are not utilized for air or reactant flow as the case may be.

[0029] FIG. ID is a schematic representation of a SOFC system 10, according to various embodiments of the present disclosure. While FIG. ID illustrates a SOFC system 10, in other embodiments, the electrochemical cell system of the embodiments of the present disclosure may comprise a SOEC system.

[0030] Referring to FIG. ID, the system 10 includes a hotbox 100 and various components disposed therein or adjacent thereto. The hot box 100 may contain fuel cell stacks 102, such as SOFC stacks containing alternating fuel cells and interconnects. One SOFC of the stack contains a ceramic electrolyte, such as yttria stabilized zirconia (YSZ), scandia stabilized zirconia (SSZ), scandia and ceria stabilized zirconia or scandia, yttria and ceria stabilized zirconia, an anode electrode, such as a nickel-YSZ, a nickel-SSZ or nickel-doped ceria cermet, and a cathode electrode, such as lanthanum strontium manganite (LSM). The interconnects may be metal alloy interconnects, such as chromium-iron alloy, ferritic or martensitic stainless steels, or cast iron interconnects. The stacks 102 may be arranged over each other in a plurality of columns.

[0031] The hot box 100 may also contain an anode recuperator heat exchanger 110, a cathode recuperator heat exchanger 120, an anode tail gas oxidizer (ATO) 130, an anode exhaust cooler heat exchanger 140, a splitter 510, a vortex generator 550, and a water injector 160. The system 10 may also include a catalytic partial oxidation (CPOx) reactor 200, a mixer 210, a CPOx blower 204 (e.g., air blower), a system blower 208 (e.g., air blower), and an anode recycle blower 212, which may be disposed outside of the hotbox 100. However, the present disclosure is not limited to any particular location for each of the components with respect to the hotbox 100.

[0032] The CPOx reactor 200 receives a fuel inlet stream from a fuel inlet 300, through fuel conduit 300 A. The fuel inlet 300 may be a fuel tank or a utility natural gas line including a valve to control an amount of fuel provided to the CPOx reactor 200. The CPOx blower 204 may provide air to the CPOx reactor 202 during system start-up. The fuel and / or air may be provided to the mixer 210 by fuel conduit 300B. Fuel flows from the mixer 210 to the anode recuperator 110 through fuel conduit 300C. The fuel is heated in the anode recuperator 110 by a portion of the fuel exhaust and the fuel then flows from the anode recuperator 110 to the stack 102 through fuel conduit 300D.

[0033] The main air blower 208 may be configured to provide an air stream (e.g., air inlet stream) to the anode exhaust cooler 140 through air conduit 302 A. Air flows from the anode exhaust cooler 140 to the cathode recuperator 120 through air inlet conduit 302B. The air is heated by the ATO exhaust in the cathode recuperator 120. The air flows from the cathode recuperator 120 to the stack 102 through air conduit 302C.

[0034] An anode exhaust stream (e.g., the fuel exhaust stream described below with respect to FIGS. 3A-3C) generated in the stack 102 is provided to the anode recuperator 110 through anode exhaust conduit 308A. The anode exhaust may contain unreacted fuel and may also be referred to herein as fuel exhaust. The anode exhaust may be provided from the anode recuperator 110 to the splitter 510 by anode exhaust conduit 308B. A first portion of the anode exhaust may be provided from the splitter 510 to the anode exhaust cooler 140 through the water injector 160 and the anode exhaust conduit 308C. A second portion of the anode exhaust is provided from the splitter 510 to the ATO 130 through the anode exhaust conduit 308D. The first portion of the anode exhaust heats the air inlet stream in the anode exhaust cooler 140 and may then be provided from the anode exhaust cooler 140 to the mixer 210 through the anode exhaust conduit 308E. The anode recycle blower 212 may be configured to move anode exhaust though anode exhaust conduit 308E, as discussed below.

[0035] Cathode exhaust generated in the stack 102 flows to the ATO 130 through exhaust conduit 304A. The vortex generator 550 may be disposed in exhaust conduit 304A and may be configured to swirl the cathode exhaust. The anode exhaust conduit 308D may be fluidly connected to the vortex generator 550 or to the cathode exhaust conduit 304A or the ATO 130 downstream of the vortex generator 550. The swirled cathode exhaust may mix with the second portion of the anode exhaust provided by the splitter 510 before being provided to the ATO 130. The mixture may be oxidized in the ATO 130 to generate an ATO exhaust. The ATO exhaust flows from the ATO 130 to the cathode recuperator 120 through exhaust conduit 304B. Exhaust flows from the cathode recuperator and out of the hotbox 100 through exhaust conduit 304C.

[0036] Water flows from a water source 206, such as a water tank or a water pipe, to the water injector 160 through water conduit 306. The water injector 160 injects water directly into the first portion of the anode exhaust provided in conduit 308C. Heat from the first portion of the anode exhaust (also referred to as a recycled anode exhaust stream) provided in exhaust conduit 308C vaporizes the water to generate steam. The steam mixes with theanode exhaust, and the resultant mixture is provided to the anode exhaust cooler 140. The mixture is then provided from the anode exhaust cooler 140 to the mixer 210 through the anode exhaust conduit 308E. The mixer 210 is configured to mix the steam and first portion of the anode exhaust with fresh fuel (i.e., fuel inlet stream). This humidified fuel mixture may then be heated in the anode recuperator 110 by the anode exhaust, before being provided to the stack 102. The system 10 may also include one or more fuel reforming catalysts 112, 114, and 116 located inside and / or downstream of the anode recuperator 100. The reforming catalyst(s) reform the humidified fuel mixture before it is provided to the stack 102.

[0037] The system 10 may further a system controller 225 configured to control various elements of the system 10. The controller 225 may include a central processing unit configured to execute stored instructions. For example, the controller 225 may be configured to control fuel and / or air flow through the system 10, according to fuel composition data.

[0038] FIG. 2A is a sectional view showing components of the hot box 100 of the system 10 of FIG. ID, and FIG. 2B shows an enlarged portion of FIG. 2A. FIG. 2C is a three dimensional cut-away view of a central column 400 of the system 10, according to various embodiments of the present disclosure, and FIG. 2D is a perspective view of an anode hub structure 600 disposed in a hot box base 101 on which the column 400 may be disposed.

[0039] Referring to FIGS. 2A-2D, the fuel cell stacks 102 may be disposed around the central column 400 in the hot box 100. For example, the stacks 102 may be disposed in a ring configuration around the central column 400 and may be positioned on the hot box base 101. The column 400 may include the anode recuperator 110, the ATO 130, and the anode exhaust cooler 140. In particular, the anode recuperator 110 is disposed radially inward of the ATO 130, and the anode exhaust cooler 140 is mounted over the anode recuperator 110 and the ATO 130. In one embodiment, an oxidation catalyst 112 and / or the hydrogenation catalyst 114 may be located in the anode recuperator 110. A reforming catalyst 116 may also be located at the bottom of the anode recuperator 110 as a steam methane reformation (SMR) insert.

[0040] The ATO 130 comprises an outer cylinder 130A that is positioned around inner ATO insulation 130B / outer wall of the anode recuperator 110. Optionally, the insulation 130B may be enclosed by an inner ATO cylinder 130C. Thus, the insulation 130B may be located between the anode recuperator 110 and the ATO 130. An ATO oxidation catalyst may belocated in the space between the outer cylinder 130A and the ATO insulation 130B. A fuel inlet path bellows 854 may be located between the anode exhaust cooler 140 and the inner ATO cylinder 130C. An ATO thermocouple feed through 1601 extends through the anode exhaust cooler 140, to the top of the ATO 130. The temperature of the ATO 130 may thereby be monitored by inserting one or more thermocouples (not shown) through this feed through 1601.

[0041] The anode hub structure 600 may be positioned under the anode recuperator 110 and ATO 130 and over the hot box base 101. The anode hub structure 600 is covered by an ATO skirt 1603. The vortex generator (e.g., ATO mixer) 550 and fuel exhaust splitter 510 are located over the anode recuperator 110 and ATO 130 and below the anode exhaust cooler 140. An ATO glow plug 1602, which initiates the oxidation of the stack fuel exhaust in the ATO during startup, may be located near the bottom of the ATO 130.

[0042] The anode hub structure 600 is used to distribute fuel evenly from the central column to fuel cell stacks 102 disposed around the central column 400. The anode flow hub structure 600 includes a grooved cast base 602 and a “spider” hub of fuel inlet conduits 300D and outlet conduits 308A. Each pair of conduits 300D, 308A connects to a fuel cell stack 102. Anode side cylinders (e.g., anode recuperator 110 inner and outer cylinders and ATO outer cylinder 130A) are then welded or brazed into the grooves in the base 602, creating a uniform volume cross section for flow distribution as discussed below.

[0043] A lift base 1604 is located under the hot box base 101, as illustrated in FIG. 2C. In an embodiment, the lift base 1604 includes two hollow arms with which the forks of a forklift can be inserted to lift and move the system, such as to remove the system from a cabinet (not shown) for repair or servicing.

[0044] As shown by the arrows in FIGS. 2 A and 2B, air enters the top of the hot box 100 and then flows into the cathode recuperator 120 where it is heated by ATO exhaust (not shown) from the ATO 130. The heated air then flows inside the cathode recuperator 120 through a first vent or opening 121. The air then flows through the stacks 102 and reacts with fuel (i.e., fuel inlet stream) provided from the anode hub structure 600. Air exhaust flows from the stacks 102, through a second vent or opening 123. The air exhaust then passes through vanes of the vortex generator 550 and is swirled before entering the ATO 130.

[0045] The splitter 510 may direct the second portion of the fuel exhaust exiting the top of the anode recuperator 100 through openings (e.g., slits) in the splitter into the swirled air exhaust (e.g., in the vortex generator 550 or downstream of the vortex generator in conduit 304A or in the ATO 130). The fuel and air exhaust may be mixed before entering the ATO 130.

[0046] FIGS. 3A and 3B are side cross-sectional views showing flow distribution through the central column 400, and 3C is top cross-sectional view taken through the anode recuperator 110. Referring to FIGS. 2 A, 2B, 3A, and 3C, the anode recuperator 110 includes an inner cylinder 110A, a corrugated plate HOB, and an outer cylinder 110C that may be coated with the ATO insulation 130B. Fuel from fuel conduit 300C enters the top of the central column 400. The fuel then bypasses the anode exhaust cooler 140 by flowing through its hollow core and then flows through the anode recuperator 110, between the outer cylinder 110C and the and the corrugated plate HOB. The fuel then flows through the hub base 602 and conduits 300D of the anode hub structure 600 shown in FIG. 3B, to the stacks 102.

[0047] Referring to FIGS. 2A, 2B, 2C, 3A, and 3B, the fuel exhaust flows from the stacks 102 through conduits 308 A into the hub base 602, and from the hub base 602 through the anode recuperator 110, between in inner cylinder 110A and the corrugated plate 110B, and through conduit 308B into the splitter 510. The first portion of the fuel exhaust flows from the splitter 510 to the anode exhaust cooler 140 through conduit 308C, while the second portion flows from the splitter 510 to the ATO 130 through conduit 308D, as shown in FIG. ID. Anode exhaust cooler inner core insulation 140A may be located between the fuel conduit 300C and bellows 852 / supporting cylinder 852A located between the anode exhaust cooler 140 and the vortex generator 550, as shown in FIG. 3A. This insulation minimizes heat transfer and loss from the first portion of the anode exhaust stream in conduit 308C on the way to the anode exhaust cooler 140. Insulation 140A may also be located between conduit 300C and the anode exhaust cooler 140 to avoid heat transfer between the fuel inlet stream in conduit 300C and the streams in the anode exhaust cooler 140. In other embodiments, insulation 140 A may be omitted from inside the cylindrical anode exhaust cooler 140.

[0048] FIG. 3B also shows air flowing from the air conduit 302A to the anode exhaust cooler 140 (where it is heated by the first portion of the anode exhaust) and then from the anode exhaust cooler 140 through conduit 302B to the cathode recuperator 120. The first portionof the anode exhaust is cooled in the anode exhaust cooler 140 by the air flowing through the anode exhaust cooler 140. The cooled first portion of the anode exhaust is then provided from the anode exhaust cooler 140 to the anode recycle blower 212 shown in FIG. ID.

[0049] As will be described in more detail below and as shown in FIGS. 2A and 3B, the anode exhaust exits the anode recuperator 110 and is provided into splitter 510 through conduit 308B. The splitter 510 splits the anode exhaust into first and second anode exhaust portions (i.e., streams). The first stream is provided into the anode exhaust cooler 140 through conduit 308C. The second stream is provided to the ATO 130 through conduit 308D.

[0050] The relative amounts of anode exhaust provided to the ATO 130 and the anode exhaust cooler 140 is controlled by the anode recycle blower 212. The higher the blower 212 speed, the larger portion of the anode exhaust is provided into conduit 308C and a smaller portion of the anode exhaust is provided to the ATO 130 via conduit 308D, and vice-versa.

[0051] The anode exhaust provided to the ATO 130 is not cooled in the anode exhaust cooler 140. This allows higher temperature anode exhaust to be provided into the ATO 130 than if the anode exhaust were provided after flowing through the anode exhaust cooler 140. For example, the anode exhaust provided into the ATO 130 from the splitter 510 may have a temperature of above 350 °C, such as from about 350 to about 500 °C, for example, from about 375 to about 425 °C, or from about 390 to about 410 °C. Furthermore, since a smaller amount of anode exhaust is provided into the anode exhaust cooler 140 (e.g., not 100% of the anode exhaust is provided into the anode exhaust cooler due to the splitting of the anode exhaust in splitter 510), the heat exchange area of the anode exhaust cooler 140 may be reduced. The anode exhaust provided to the ATO 130 may be oxidized by the stack cathode (i.e., air) exhaust and provided to the cathode recuperator 120 through conduit 304B.

[0052] FIG. 4A is a sectional perspective view showing the water injector 160 in the central column of FIG. 2 A, FIG. 4B is a top view showing an injector ring 162 and a baffle 168 of FIG. 4A, and FIG. 4C is a perspective view of the water injector 160, according to various embodiments of the present disclosure. In the embodiment of FIG. 4A, the splitter 510 may comprise tubes that extend through the outer wall of the anode exhaust conduit 308B rather than horizontal slits shown in FIG. 3 A. It should be understood that either the tube or slit type of splitter 510 may be used with the water injector 160 of the present embodiment.Referring to FIGS. 1, 4 A, 4B and 4C, the water injector 160 may include the injector ring 162, restraint tabs 164, a shroud 166, and the baffle 168.

[0053] The injector ring 162 may be disposed inside the anode exhaust conduit 308C between the anode exhaust cooler 140 and the anode recuperator 110 and may be fluidly connected to the water conduit 306. The injector ring 162 is a tube that extends around the fuel conduit 300C. The injector ring 162 may include injection apertures (i.e., openings) 162 A configured to inject water directly into the first portion of the anode exhaust flowing in the conduit 308C from the splitter 510 and anode recuperator 110. The water may be vaporized by the hot first portion of the anode exhaust. The injection apertures 162 A may be configured to generate streams or droplets of water, which may be vaporized instantaneously or within seconds of emerging from the injector ring 162. The injection apertures 162A may be located on any one or more surfaces of the injector ring 162, such as the upper surface of the injector ring 162 (as shown in FIG. 4 A), the inner surface of the injector ring 162 (as shown in FIG. 4C), the lower surface of the injector ring 162 and / or the outer surface of the injector ring 162. For example, as shown in the embodiment of FIG. 4A, the injection apertures 162A may be evenly distributed on an upper surface of the injector ring 162 to provide uniform water upward into the anode exhaust to decrease the amount of water dripping down toward the splitter 510. The injector ring 162 may also be sized to provide substantially uniform circumferential flow of water therein and to minimize a pressure drop in the anode exhaust flowing thereby.

[0054] The restraint tabs 164 may be attached to the fuel conduit 300C and / or the shroud 166 and may be configured to support the injector ring 162. In particular, the restraint tabs 164 may be configured to align and control the orientation of the injector ring 162 and prevent uneven water distribution or buildup thereon. For example, the restraint tabs 164 may be configured to horizontally align the injector ring 162. The restraint tabs 164 may also prevent water from accumulating on the injector ring 162 in any particular location. As such, the restraint tabs 164 may be configured to prevent water from accumulating on the outer surface of the injector ring 162 and dripping in only one location, which may be especially important if the injector ring 162 is not perfectly level.

[0055] The shroud 166 may be a cylinder which surrounds the injector ring 162. The shroud 166 may be configured to segregate the water from the second portion of the anode exhaust flowing into the ATO 130 through the splitter 510. In particular, the second portion of theanode exhaust flowing outside of the shroud 166 may be directed by the splitter 510 radially outward toward the anode exhaust conduit 308D and the ATO 130, while the first portion of the anode exhaust flowing inside of the shroud 166 is directed upward by the splitter 510 toward the injector ring 162 in the anode exhaust conduit 308C. Accordingly, the shroud 166 may be configured to prevent or reduce the amount of water and / or the first portion of the anode exhaust that has been humidified by the injected water from being injected into the ATO 130 by the splitter 510. In other words, the shroud 166 is configured such that substantially all of the water and the humidified first portion of the anode exhaust are directed towards the anode exhaust cooler 140.

[0056] The baffle 168 may be disposed inside the anode exhaust conduit 308C below the injector ring 162 and around the fuel conduit 300C. The baffle 168 may include a baffle ring 168 A and baffle tabs 168B that extend therefrom. The baffle tabs 168B may contact the fuel conduit 300C and the shroud 166 and may operate to keep both the shroud 166 and the baffle ring 168A aligned around the fuel conduit 300C within the central column 400. In particular, the baffle ring 168 A may be aligned to vertically overlap with (e.g., be concentric with) the injector ring 162, as shown in FIG. 4B.

[0057] Therefore, the baffle 168 may operate as a surface to catch and vaporize water droplets that do not instantaneously transform into steam and drip from the injector ring 162. Accordingly, the baffle 168 also protects brazed joints of the anode recuperator 110 that are located below the injector ring 162 from contact with water droplets and corresponding thermal shock caused by such contact.

[0058] In various embodiments, the water injector 160 may optionally include a mesh 169 or porous material disposed below the baffle 168. The mesh 169 may be configured to capture any droplets that drip from the injector ring 162 and bypass the baffle 168, such that the captured droplets are vaporized before reaching the anode recuperator 110 and / or the splitter 510.

[0059] FIG. 5 illustrates an alternative configuration of hot box 100 components of the fuel cell system 10. As illustrated in FIG. 5, the central column 400 includes the slit type splitter 510 described above with respect to FIG. 3 A instead of the tube type splitter 510 described above with respect to FIG. 4 A. Furthermore, the water injector 160 of FIG. 5 A includes injection apertures 162 A on the inner surface of the injector ring 162. Finally, the catalysts112, 114 and 116 of FIG. 5 are located inside the inner plenum, which is surrounded by the anode recuperator 110, similar to the configuration described in U.S. Patent Number 9,287,572 B2, issued March 15, 2016 and incorporated herein by reference in its entirety. Other components shown in FIG. 5 are the same as or similar to those shown in FIG. 4A. Any one or more components from the central column shown in FIG. 5 may be used in the central column shown in FIG. 4A.

[0060] Furthermore, while the water injectors 160 shown in FIGS. 4 A to 4C and 5 include an injector ring 162 with injection apertures 162 A, other water injector configurations may be used instead. For example, the water may be injected into the first portion of the anode exhaust directly from the water conduit 306 without using the injector ring 162.Alternatively, water may be injected from plural tubes arranged in any suitable configuration in the exhaust conduit 308C. The tubes may be fluidly connected to the water conduit 306. Furthermore, one or more of the shroud 166, the baffle 168 and / or mesh 169 may be omitted.

[0061] During operation of the fuel cell system 10, such as during system startup, water is generally not required until the stack 102 reaches a temperature of about 300 °C or more, such as a temperature ranging from about 300 °C to about 325 °C. Once the stack 102 approaches about 300 °C, water is provided from the water source 206 to water conduit 306 at the top of the central column 400. The water conduit 306 passes through the insulation 140A that that is located between and separates the fuel conduit 300C from the anode exhaust cooler 140. The insulation reduces the amount of heat exchange between the water in the water conduit 306 and the anode exhaust cooler 140. Accordingly, while passing through water conduit 306, the water may be slightly heated above ambient temperature by anode exhaust in the surrounding toroidal anode cooler 140. However, it is believed that at least the majority of the water remains in a liquid state while in the water conduit 306.

[0062] The water is then provided by the water conduit 306 to the water injector 160. For example, the water is provided by the water conduit into the injector ring 162. The water flows circumferentially in the injector ring 162 and is circumferentially dispersed before being ejected into the first portion of the anode exhaust through the injection apertures 162 A. In one embodiment, at least a portion of the water is injected in the liquid state into the first portion of the anode exhaust stream. The water is then vaporized in the first portion of the anode exhaust to form a humidified anode exhaust. The humidified anode exhaust is then provided through conduit 308E to the mixer 210 for mixing with fresh fuel (i.e., fuel inletstream) before being provided to the anode recuperator 110 and the stack 102 as discussed above.

[0063] FIGS. 6 A - 6D illustrate an electrochemical cell column 30 according to an embodiment of the present disclosure. The column 30 includes a compression assembly 40 which includes a metal compression spring 61 located in a relatively cool air flow zone of the hotbox 100. The metal compression spring 61 may be made of a metal or a conductive metal alloy. For example, the metal compression spring may be made of an Inconel alloy, such as Inconel X-750 or Inconel 718. Inconel X-750 alloy includes at least 70 weight percent nickel and at least 10 weight percent of chromium, such as nickel (Ni): 70% minimum, chromium (Cr): 14-17%, titanium (Ti): 2.25-2.75%, niobium (Nb) + tantalum (Ta): 0.70-1.20%, aluminum (Al): 0.40-1.00%, manganese (Mn): 1.00% maximum, silicon (Si): 0.50% maximum, and copper (Cu): 0.50% maximum. Inconel 718 alloy includes at least 50 weight percent nickel and at least 15 weight percent each of iron and chromium, such as Ni: 52.5%, Fe: 18.5%, Cr: 19%, Cb, Ta and / or Nb: 5.13%, Mo: 3.05%, Ti: 0.9%, Al: .5%, and Co: 1% maximum. Other high temperature stable metals or metal alloys may be used. The metal compression spring 61 may comprise a coil spring.

[0064] The column 30 may shrink due to cycling of the electrical load on the stacks 102 (e.g., power output of fuel cell stacks or applied current for electrolyzer cell stacks). In contrast to a prior art ceramic matrix composite (CMC) leaf compression springs, a metal coil compression spring 61 has a less steep load versus deflection curve. Therefore, in case of column 30 shrinkage, the mechanical load applied by the metal coil compression spring 61 to the stacks 102 of the column 30 drops less rapidly than the mechanical load applied by the CMC leaf compression spring. Furthermore, a metal coil compression spring 61 is typically less expensive than a CMC leaf compression spring.

[0065] However, the metal coil compression spring 61 may suffer from creep related failure over time due to a high column 30 operating temperature. In one embodiment, the present inventors realized that the metal coil compression spring 61 may be located higher above the stacks 102 of the column 30 in a relatively cooler air flow zone of the hotbox 100, rather than directly on top of the high temperature stacks 102. The air flow zone comprises an area of the hotbox 100 in which the air inlet stream and / or the air exhaust (e.g., system exhaust) stream flow above the stacks 102 of the columns 30.

[0066] The compression assembly 40 includes the metal coil compression spring 61 located in a spring housing (e.g., load housing). In the embodiment of FIGS. 6A - 6D, the spring housing comprises a ceramic housing 62, such as a hollow cylindrical ceramic housing. An optional ceramic top block or plate 63 is located on top of the spring housing. The spring is located 61 in the hollow interior space of the spring housing 62. Optionally, one or more ceramic shims 64, such as “C” shaped ceramic shim plates may be located between the top of the spring 61 and the bottom of ceramic top block or plate 63 of the spring housing 62. The ceramic top block or plate 63 and the one or more ceramic shims 64 include a central recess (i.e., a pass through opening) 65 which is configured to receive a load rod. The spring housing 62 may include at least one slot 66 in its sidewall for loading of the one or more ceramic shims 64. A ceramic load ram 50 and load plate 51 are located below the bottom surface of the spring. The load ram 50 comprises a ceramic rod or column located in the spring housing, and the load plate 51 comprises a ceramic plate at the bottom of the load ram. The load ram 50 and load plate 51 may comprise a single integral component or separate components. The load plate 51 may compress the stacks 102 and the RSPs 36 of the column 30 due to the compression applied by the compression spring 61 onto the load ram 50. An optional compression block 67 may be located between the compression spring 61 and the ceramic shims 64. The compression block 67 may comprise a protrusion in its bottom end which fits inside the compression spring 61 and holds the spring 61 in place in the spring housing 62. The compression block 67 may comprise a ceramic block. The load rod is configured to protrude through the central recess 65 and press down on the compression block 67 to compress the compression spring 61 downward.

[0067] The space between the load ram 50 and the side baffles 41 may be filled with air blocking insulation and / or a ceramic paper fill 68. The ceramic paper may comprise an intumescent paper which expands at an elevated temperature. For example, the ceramic paper may be formed from Kaowool ceramic fibers, organic binders and other additives.

[0068] An optional ceramic termination plate 46 and an electrical contact plate 47 may be located between the load plate and the stacks 102 and the RSPs 36 of the column 30. A jumper (i.e., a conductive wire or cable) may electrically connect in series the electrical contact plates 47 of adjacent columns 30.

[0069] FIGS. 7A - 7C illustrate the hotbox 100 and the location of the air heat exchanger(e.g., cathode recuperator) 120, the air inlet conduit 302B and the air exhaust conduit 304C inthe hotbox 100. FIG. 8 illustrates the column 30 including the compression assembly 40 of FIGS. 6A - 6D located in the hotbox 100 of FIGS. 7A - 7C.

[0070] The inlet air stream may flow from the anode exhaust cooler heat exchanger 140 to the air heat exchanger (e.g., the cathode recuperator heat exchanger) 120 through the air inlet conduit 302B at a temperature between 100 and 150 degrees Celsius, such as between 120 and 140 degrees Celsius. The spring housing (e.g., load housing) 62 is at least partially located in the air inlet conduit 302B. For example, the spring housing 62 may protrude through or into the air inlet conduit 302B, as shown in FIG. 8. The air inlet conduit 302B surrounds a part of the spring housing 62.

[0071] The spring housing 62 may also be partially located in the air exhaust conduit 304C which is located above the air inlet conduit 302B. For example, the spring housing may protrude through or into the air exhaust conduit 304C, as shown in FIG. 8. The air exhaust conduit 304C surrounds another part of the spring housing. The air exhaust (e.g., ATO exhaust) may flow through the air exhaust conduit 304C at a temperature between 350 and 380 degrees Celsius.

[0072] Therefore, the spring housing 62 is located in a relatively cool air flow zone of the hotbox 100 (i.e., in conduits 302B and / or 304C) which are maintained at a temperature below 400 degrees Celsius, such as between 130 and 380 degrees Celsius. In other words, the metal compression spring 61 is cooled to a temperature of 650 degrees Celsius or less, such as less than 400 degrees Celsius by at least the air inlet stream during operation of the column 30. Temperatures of 650 degrees Celsius or less are sufficiently cool to avoid significant creep induced damage to the metal coil compression spring located in the spring housing.Specifically, it is estimated that the stiffness loss of Inconel X-750 springs operated at 650 degrees Celsius over 5 years is only about 18%. Thus, by operating the spring 61 at 650 degrees Celsius or less, such as 130 to 400 degrees Celsius for 5 years, the spring stiffness loss is estimated to be below 20%, such as 18% or less. In contrast, operating the Inconel X- 750 springs at 760 degrees Celsius for only 1000 hours is estimated to lead to a much greater than 20% loss of spring stiffness.

[0073] In the embodiment of FIG. 8, the spring housing 62 is located in a compression assembly housing 72. The compression assembly housing 72 may comprise a hollow cylinder (e.g., metal cylinder) which is welded to the conduits 302B and / or 304C to form aweld seal 73. The air inlet stream in the air inlet conduit 302B and the air exhaust stream (e.g., ATO exhaust stream) in the air exhaust conduit 304C flow around the sides of the compression assembly housing 72.

[0074] Free flow insulation 74 may surround the top block or plate 63 of the spring housing 62. The free flow insulation 74 is a fluid that can be poured into the hotbox 100 and solidifies into a high temperature resistant material when cured. Ceramic paper insulation 75 and super wool insulation 76 may be located above the top block or plate 63 of the compression assembly housing 72. Pass through insulation 77 and additional ceramic paper 78 may partially surround the compression assembly housing 72.

[0075] FIGS. 9 A and 9B illustrate an alternative configuration of the spring housing 62 according to an alternative embodiment. In this embodiment, the spring housing 62 comprises a metal housing, such as a hollow metal or metal alloy cylinder. A ceramic load ram (e.g., pusher rod) 50 and at least one load plate 51 A, 5 IB may be located below the metal coil compression spring 61. The ceramic load ram 50 and at least one load plate 51 A, 5 IB may be similar to the load ram 50 and load plate 51 described above with respect to FIGS. 6A - 6D, except that the load plate may comprise plural vertically stacked ceramic plates 51 A and 5 IB, and an additional ceramic plate 52 is located in the spring housing 52 on top of the ceramic load ram 50 in the embodiment of FIGS. 9A and 9B. The upper ceramic load plate 51 A may function as a thermal barrier which reduces heat transfer between the at least one electrochemical stack and the spring. The lower ceramic load plate 5 IB may comprise a load transfer plate which transfers the spring load to the at least one electrochemical stack. The upper ceramic load plate 51 A may have a lower density and / or higher compliance than the lower ceramic load plate 5 IB in order to function as a thermal barrier. For example, the upper ceramic load plate 51 A may comprise super wool or another porous ceramic material (e.g., a flexible thermal blanket material), while the lower ceramic load plate 5 IB may comprise a dense, non-porous ceramic material, such a rigid alumina plate. The ceramic top block or plate 42 of the column 30 surrounds the metal spring housing. Optional ceramic spring shims 64A may surround the spring housing 62 below the top block or plate 42.

[0076] As shown in FIGS. 7A - 7C and 10A - 10B, the hotbox 100 includes a cylindrical uni-shell 701 and dual uni-shell lids 702, 703 located on the uni-shell 703. The lids include nested upward protrusions (i.e., air inlet and outlet caps) 704 configured to accommodate the spring housing 62 of the compression assembly 40 of the embodiments of the presentdisclosure. The air inlet conduit 302B is located between the upper lid 702 and the lower lid 703. The air exhaust conduit 304C is located above the upper lid 703 and below a cover plate 705. The hotbox 100 also includes system exhaust outlets 706 (e.g., outlet tubes) protruding above the cover plate 705 which outlet the hotbox air exhaust (i.e., ATO 130 exhaust) stream flowing through the air exhaust conduit 304C from the hotbox 100. Referring to FIGS. 10A and 10B, the protrusions 704 include an air outlet cap 704A (e.g., a protrusion in the upper lid 702) and an air inlet cap 704B (e.g., a protrusion in the lower lid 703).

[0077] Referring to FIG. 11, the air inlet stream flows through the air inlet conduit 302B between the uni-shell lids 702 and 703 and around the air inlet cap 704B. The air exhaust stream flows through the air exhaust conduit 304C above the upper lid 702 and below the cover plate 705 and around the air outlet cap 704A. Thus, the air inlet stream flows through the portion of the air inlet conduit 302B located between the air inlet cap 704B and the air outlet cap 704A, while the air exhaust stream flows through the portion of the air exhaust conduit 304C located between the air outlet cap 704A and the cover plate 705. The heat transfer (shown by symbols 320) between the spring housing 62 (and thus the metal coil compression spring 61) and the air inlet cap 704B and the air outlet cap 704A is enhanced due to the metal surfaces. Thus, the air flows cool the metal coil compression spring 61 due to indirect heat transfer to reduce or eliminate creep induced failure of the spring 61. A gap 707 is located between the spring housing 62 and the air inlet cap 704B to allow of radial expansion of the column 30 of cell stacks 102.

[0078] In an alternative embodiment shown in FIG. 12A, the air inlet cap 704B is omitted. In this embodiment, the air inlet stream in the air inlet conduit 302B flows around and in contact with the outer surface of the spring housing 62. Thus, the air inlet stream actively (i.e., directly) cools the spring housing 62, which cools the spring 61 by indirect heat transfer.

[0079] FIGS. 12B and 12C illustrate steps in forming the column 30 shown in FIG. 12A. A cylindrical insulation insert 801 and a flanged cylindrical metal spacer 802 are located over the top block or plate 42 of the column 30. The spring housing 62 protrudes through the top block or plate 42, through the opening in the flanged cylindrical metal spacer 802 and through the cylindrical insulation insert 801. The flanged cylindrical metal spacer 802 includes a horizontal flange 802F that extends away from the bottom of the metal cylinder 802C to prevent air bypass between the spring housing 62 and the top block or plate 42. The cylindrical insulation insert 801 may comprise a ceramic paper insert which prevents airbypass into the column 30. The ceramic paper is compliant to permit radial expansion of the column 30 components.

[0080] In another alternative embodiment shown in FIG. 13 A, the metal coil compression spring 61 is actively (i.e., directly) cooled by the air inlet stream. In this embodiment, the spring housing 62 includes at least one opening into the air inlet conduit 302B. The at least one opening may include the slot 66 described above with respect to FIGS. 6A - 6D and / or may include one or more additional or different openings in the spring housing 62. For example, at least one air inlet opening 66A and at least one air outlet opening 66B are provided in the spring housing 62. At least a part of the air inlet stream flowing through the air inlet conduit 302B flows inside the spring housing 62 through the air inlet opening 66 A and makes contact with the metal coil compression spring 61 located inside the spring housing 62. The air inlet stream then flows out of the spring housing 62 through the air outlet opening 66B back into the air inlet conduit 302B. In this embodiment, a bellows 810 may be provided around the rod or column part of the load ram 50 in the spring housing 62 to seal the bottom of the spring housing 62 and to prevent direct air inlet stream flow from the spring housing 62 into the stacks 102 of the column 30. Thus, the bellows 810 provides an air seal and permits direct active cooling of the spring 61 by the air inlet stream.

[0081] FIGS. 13B and 13C illustrate steps in forming the column 30 shown in FIG. 13A. These steps are the same as those described above with respect to FIGS. 12A and 12B.

[0082] The preceding description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

CLAIMS1. An electrochemical cell system, comprising: a hotbox; and an electrochemical cell column located in the hotbox, wherein: the electrochemical cell column comprises at least one electrochemical cell stack, and a compression assembly located above the at least one electrochemical cell stack; and the compression assembly comprises a metal compression spring at least partially located in an air flow zone of the hotbox.

2. The electrochemical cell system of claim 1, wherein the metal compression spring comprises a metal coil compression spring, and the electrochemical cell column comprises a solid oxide fuel cell column or a solid oxide electrolyzer cell column.

3. The electrochemical cell system of claim 1, wherein the metal compression spring is located in a spring housing, and the spring housing is at least partially located in an air inlet conduit of the hotbox.

4. The electrochemical cell system of claim 3, wherein the air inlet conduit is fluidly connected through an air heat exchanger to an air inlet of the electrochemical cell column.

5. The electrochemical cell system of claim 4, wherein the air inlet conduit surrounds at least a first part of the spring housing.

6. The electrochemical cell system of claim 5, wherein an air exhaust conduit surrounds at least a second part of the spring housing.

7. The electrochemical cell system of claim 3, wherein the compression assembly further comprises a ceramic load ram located in the spring housing between the metal compression spring and the at least one electrochemical cell stack.

8. The electrochemical cell system of claim 3, wherein the spring housing comprises a cylindrical ceramic housing.

9. The electrochemical cell system of claim 3, wherein the spring housing comprises a cylindrical metal housing.

10. The electrochemical cell system of claim 3, wherein the hotbox comprises a cylindrical uni-shell and at least one uni-shell lid.

11. The electrochemical cell system of claim 10, wherein the at least one uni-shell lid comprises an upwardly protruding cap, and the spring housing extends at least partially into the upwardly protruding cap.

12. The electrochemical cell system of claim 3, wherein the spring housing comprises at least one opening into the air inlet conduit that permits an air inlet stream to flow from the air inlet conduit into the spring housing and to contact the metal compression spring.

13. A method of operating an electrochemical cell system, comprising: providing a reactant stream to an electrochemical cell column located in the hotbox; and providing an air inlet stream to the electrochemical cell column, wherein: the electrochemical cell column comprises at least one electrochemical cell stack, and a compression assembly located above the at least one electrochemical cell stack; and the air inlet stream flows around at least a part of a metal compression spring of the compression assembly.

14. The method of claim 13, wherein the electrochemical cell column comprises a solid oxide fuel cell column or a solid oxide electrolyzer column, and the metal compression spring is cooled to a temperature of 650 degrees Celsius or less by at least the air inlet stream during operation of the electrochemical cell column.

15. The method of claim 13, wherein the metal compression spring is located in a spring housing and the air inlet stream flows around at least a part of the spring housing.

16. The method of claim 15, wherein the air inlet stream flows from the spring housing to an air inlet of the electrochemical cell column through an air heat exchanger.

17. The method of claim 15, wherein an air exhaust stream from the electrochemical cell column flows around an additional part of the spring housing.

18. The method of claim 15, wherein the air inlet stream further flows into the spring housing and contacts the metal compression spring.

19. The method of claim 15, wherein the spring housing comprises a cylindrical ceramic or metal housing.

20. The method of claim 13, wherein the compression assembly further comprises a ceramic load ram located in the spring housing between the metal compression spring and the at least one electrochemical cell stack.

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