Fuel cell system including anode exhaust diversion and method of operating the same

Abstract

To provide a method of operating a fuel cell system.SOLUTION: The method of operating a fuel cell system comprises: providing fuel and air to a stack (102) of fuel cells located in a hotbox (100); operating the stack to generate anode exhaust and cathode exhaust; in a startup mode, providing a first amount of the anode exhaust and the cathode exhaust to an anode tail gas oxidizer (130) located in the hotbox to oxidize the anode exhaust and to generate heat to be provided to the stack; and, in a steady-state mode, stopping providing the anode exhaust to the anode tail gas oxidizer (130) or providing the anode tail gas oxidizer (130) with a second amount of the anode exhaust which is less than the first amount, and providing the anode exhaust and the cathode exhaust to an outside of the hotbox (100).SELECTED DRAWING: Figure 1

Description

Technical field

[0001] Aspects of the present invention relate to fuel cell systems and methods, and more particularly to fuel cell systems that include an anode exhaust diverting element. [Background technology]

[0002] A fuel cell, such as a solid oxide fuel cell, is an electrochemical device capable of converting energy stored in a fuel into electrical energy with high efficiency. High temperature fuel cells include solid oxide fuel cells and molten carbonate fuel cells. These fuel cells can operate using hydrogen and / or hydrocarbon fuels. There is a class of fuel cells, such as solid oxide regenerative fuel cells, which can re-reduce oxidized fuel to non-oxidized fuel using electrical energy as input. As such, the reverse operation is also possible. [Outline of the invention]

[0003] According to various embodiments, a fuel cell system includes a stack of fuel cells, an anode tail gas oxidizer (ATO) configured to oxidize anode exhaust output from the stack, and an exhaust conduit configured to output the anode exhaust; a bypass conduit configured to divert anode exhaust output from the stack to the exhaust conduit; and controlling anode exhaust flow through the bypass conduit. and an ATO conduit configured to supply anode exhaust to said anode tailgas oxidizer.

[0004] According to various embodiments, a method of operating a fuel cell system includes supplying fuel and air to a stack of fuel cells located within a hotbox; operating and, in a start-up mode, placing a first quantity of the anode exhaust and the cathode exhaust in the hot box to oxidize the anode exhaust and generate heat that is supplied to the stack; supplying an anode tail gas oxidizer (ATO); and in a steady state mode, stopping supplying the anode exhaust to the anode tail gas oxidizer, or supplying the anode tail gas oxidizer to the first and supplying a second amount of the anode exhaust that is less than the amount of the hot box and supplying the anode exhaust and the cathode exhaust outside the hot box.

[0005] According to various embodiments, a method of operating a fuel cell system includes supplying fuel and air to a stack of fuel cells located within a hotbox; Operating and in a low current draw steady-state mode in which insufficient current is drawn from the stack to maintain a predetermined steady-state stack operating temperature, the anode exhaust is oxidized to reduce the heat supplied to the stack. supplying a first amount of the anode exhaust and the cathode exhaust to an anode tailgas oxidizer (ATO) located within the hotbox to generate and maintain the predetermined steady state stack operating temperature; In a normal steady-state mode in which sufficient current is drawn from the stack to allow the anode exhaust to cease supplying the anode tailgas oxidizer, or a second amount less than the first amount supplying a quantity of the anode exhaust to the anode tailgas oxidizer and supplying the anode exhaust and the cathode exhaust to the exterior of the hot box.

[0006] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention, taken in conjunction with the general description given above and the detailed description given below. [Brief description of the drawing]

[0007]

Figure 1

Figure 2

[0008] Various embodiments are 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 to particular examples and embodiments are made for purposes of illustration and are not intended to limit the scope of the invention or the claims.

[0009] In solid oxide fuel cell (SOFC) systems, the fuel inlet stream can be humidified to promote fuel reforming reactions such as steam reforming and water gas shift reactions. Additionally, water can be added to the fuel inlet stream to prevent coking of system components such as catalysts during system startup, shutdown, and power grid interruption events. Conventionally, such humidification is accomplished by evaporating water in steam generators containing corrugated lines. The water flows through the corrugated conduit and is heated by the cathode recuperator exhaust stream flowing around the outside of the conduit. However, utilizing the relatively cold cathode recuperator exhaust stream typically requires a significant length of corrugated line to absorb sufficient heat to evaporate the water. Additionally, steam generators are relatively large and bulky, which also increases the size, complexity, and manufacturing cost of the system.

[0010] In contrast, embodiments of the present disclosure inject water directly into the anode exhaust recirculation stream to provide heat to evaporate the water to water vapor and / or aerosolize the water to To provide a water injector configured to make droplets small enough to entrain in a stream. The anode exhaust recirculation stream is recirculated into the fuel inlet stream supplied into the stack of fuel cells such that humidified fuel is supplied to the fuel cells of the stack of fuel cells. Thus, prior art steam generators can be omitted to reduce system size, complexity, and cost. Additionally, the system of embodiments can operate using relatively short, non-corrugated water conduits, which can improve system response time and reduce system size and cost.

[0011] FIG. 1 is a schematic diagram of a SOFC system 10 according to the first embodiment of the present disclosure. Referring to FIG. 1, system 10 comprises a hotbox 100 and various components located within or adjacent to it. The hotbox 100 may include at least one fuel cell stack 102, such as a solid oxide fuel cell stack containing alternating fuel cells and interconnects. A solid oxide fuel cell in one of the stacks has 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. , nickel-YSZ, nickel-SSZ, or nickel-doped ceria cermet, and a cathode electrode such as lanthanum strontium manganite (LSM). The interconnects can be metal alloy interconnects, such as chromium-iron alloy interconnects. Stacks 102 can be arranged on top of each other in multiple columns.

[0012] The hotbox 100 includes an anode recuperator 110, a cathode recuperator 120, an anode tail gas oxidizer (ATO) 130, an anode exhaust cooling heat exchanger 140, an optional splitter 170, and water injectors. 160 can also be included. The system 10 comprises a catalytic partial oxidation (CPOx) reactor 200, a mixer 210, a CPOx blower 204 (eg, air blower), a system blower 208 (eg, air blower), and an anode recycle blower 212. Also, they can be located outside the hotbox 100 . However, this disclosure does not limit each of the components to specific locations with respect to hotbox 100 .

[0013] CPOx reactor 200 receives fuel inlet flow from fuel inlet 300 through fuel conduit 300A. Fuel inlet 300 can be a fuel tank or utility natural gas line with a valve to control the amount of fuel supplied to CPOx reactor 200 . A CPOx blower 204 can supply air to the CPOx reactor 200 at system startup. Fuel and / or air may be supplied to mixer 210 by fuel conduit 300B. Fuel flows from mixer 210 to anode recuperator 110 through fuel conduit 300C. The fuel is heated by the fuel exhaust in anode recuperator 110, after which the fuel flows from anode recuperator 110 to stack 102 through fuel conduit 300D.

[0014] System blower 208 may be configured to provide airflow (eg, air inlet flow) to anode exhaust cooler 140 through air conduit 302A. Air flows from anode exhaust cooler 140 to cathode recuperator 120 through air conduit 302B. Air is heated by the ATO exhaust in the cathode recuperator 120 . Air flows from cathode recuperator 120 to stack 102 through air conduit 302C.

[0015] Anode exhaust (eg, fuel exhaust stream) generated within stack 102 is supplied to anode recuperator 110 through anode exhaust conduit 308 . The anode exhaust may contain unreacted fuel and is sometimes referred to herein as fuel exhaust. Anode exhaust may be supplied from anode recuperator 110 to mixer 210 by recycle conduit 310, which may include a first recycle conduit 310A and a second recycle conduit 310B. In particular, a first recirculation conduit 310 A can fluidly connect the outlet of the anode recuperator 110 to the inlet of the anode exhaust cooler 140 . A second recirculation conduit 310B may fluidly connect the outlet of anode exhaust cooler 140 to the inlet of mixer 210 .

[0016] Water flows from a water source 206 , such as a water tank or water pipe, through a water conduit 306 to the water injector 160 . Water injector 160 may be configured to inject water into the anode exhaust flowing through first recirculation conduit 310A. Heat from the anode exhaust (also referred to as a recirculated anode exhaust stream) evaporates water to produce water vapor, thereby humidifying the anode exhaust. Humidified anode exhaust is provided to anode exhaust cooler 140 . Heat from the anode exhaust supplied to the anode exhaust cooler 140 can be transferred from the system blower 208 to the air inlet stream supplied to the cathode recuperator 120 . The cooled, humidified anode exhaust can then be supplied to mixer 210 from anode exhaust cooler 140 via second recirculation conduit 310B. Anode recirculation blower 212 may be configured to move anode exhaust through second recirculation conduit 310B.

[0017] Mixer 210 is configured to mix humidified anode exhaust with fresh fuel (ie, fuel inlet stream). This humidified fuel mixture can then be heated in the anode recuperator 110 by the anode exhaust before being supplied to the stack 102 . System 10 may also include one or more fuel reforming catalysts 112 , 114 , and 116 positioned within and / or downstream of anode recuperator 110 . The reforming catalyst(s) reform the humidified fuel mixture before it is fed to stack 102 .

[0018] Splitter 170 may be operatively connected to first recirculation conduit 310A and may be configured to divert a portion of the anode exhaust to ATO 130 via ATO conduit 312A. ATO conduit 312 A can be fluidly connected to cathode exhaust conduit 304 A or ATO 130 .

[0019] Cathode exhaust generated in stack 102 is supplied to ATO 130 by cathode exhaust conduit 304A. The cathode exhaust can be mixed with the anode exhaust before or after it is supplied to ATO 130 . A mixture of anode and cathode exhaust can be oxidized in ATO 130 to generate ATO exhaust. ATO exhaust flows from ATO 130 to cathode recuperator 120 through cathode exhaust conduit 304B. Exhaust flows from cathode recuperator 120 out of hot box 100 through cathode exhaust conduit 304C.

[0020] System 10 may further comprise a system controller 225 configured to control various elements of system 10 . Controller 225 may comprise a central processing unit configured to execute stored instructions. For example, controller 225 may be configured to control fuel and / or airflow through system 10 according to fuel composition data.

[0021] The inventors have determined that the desired steady-state operating temperature of the SOFC stack 102 (e.g., greater than 700°C, e.g. °C) may not require an exotherm of ATO. However, in conventional systems, ATO can still operate during steady state mode to oxidize carbon monoxide present in the anode exhaust supplied to ATO. However, this oxidation may result in the release of significant amounts of heat that may not be required for steady state operation.

[0022] Conventionally, the rate of system air flow (ie, air inlet flow) supplied by system blower 208 can be increased to compensate for such ATO heat dissipation. However, as the air flow rate increases, the temperature range of the fuel cells within the stack may also increase. For example, higher air flow rates may result in certain fuel cells operating at less than optimum temperatures, thus reducing total power production. In addition, higher airflow can also create more pressure drop along the airflow path. Both higher airflow and higher pressure drop can result in a higher total system balance-of-plant power consumption and lower overall system efficiency.

[0023] In view of the above and / or other problems of conventional systems, in some embodiments of the present disclosure, at least during steady state operation of the system, the anode exhaust exits the hotbox 100 instead of being fed to the ATO. It can be mixed with the cathode exhaust, or alternately fresh airflow. In some embodiments, a catalyst is utilized to help oxidize carbon monoxide, hydrocarbon fuel, and / or hydrogen remaining in the anode exhaust. In alternative embodiment systems using only hydrogen fuel, the anode exhaust can be vented directly from the hotbox 100 if desired. For combined heat and power (CHP) configurations, the anode exhaust may be vented into the cathode exhaust conduit upstream of the CHP heat exchanger, providing heat that is recovered in the CHP heat exchanger.

[0024] Referring again to FIG. 1, the SOFC system 10 can include a bypass conduit 316, a bypass valve 320, and an exhaust oxidizer 330. As shown in FIG. A bypass conduit 316 fluidly connects the second recirculation conduit 310B to the cathode exhaust conduit 304C. In some embodiments, bypass conduit 316 is downstream of anode recirculation blower 212 with respect to the anode exhaust flow direction through second recirculation conduit 310B to provide additional exhaust flow pressure to cathode exhaust conduit 304C. , can be connected to the second recirculation conduit 310B. However, in other embodiments, the bypass conduit 316 may be fluidly connected to the second recirculation conduit 310B upstream of the anode recirculation blower 212.

[0025] Exhaust oxidizer 330 may be configured to oxidize the ATO exhaust output from ATO 130 and / or the anode exhaust output from bypass conduit 316 . For example, the exhaust oxidizer 330 may include tubes or conduits containing catalysts that promote oxidation of carbon monoxide and / or hydrogen to carbon dioxide and / or water, respectively. In one embodiment, the exhaust oxidizer 330 is located outside the hotbox 100 . Therefore, heat generated by exhaust oxidizer 330 is not used to heat SOFC stack 102 .

[0026] ATO conduit 312 A supplies anode exhaust (eg, ATO fuel stream) output from splitter 170 to ATO 130 . The anode exhaust flow from splitter 170 through ATO conduit 312 A can be controlled by controlling the speed of anode recirculation blower 212 . For example, a faster anode recirculation blower 212 may result in less anode exhaust flow to the ATO 130 and a slower anode recirculation blower 212 may result in a greater anode exhaust flow to the ATO 130 . In some embodiments, the speed of anode recirculation blower 212 may be limited to prevent backflow of cathode exhaust entering splitter 170 through ATO conduit 312A.

[0027] The bypass valve 320 may be located outside the hotbox 100 to prevent damage to the bypass valve 320 from exposure to the high temperatures inside the hotbox 100 . Bypass valve 320 may be configured to control anode exhaust flow from anode exhaust conduit 310 through bypass conduit 316 . In particular, during start-up of system 10, bypass valve 320 can be closed to prevent anode exhaust from being supplied to exhaust oxidizer 330 and cathode exhaust conduit 304C, and anode recirculation blower 212 prevents ATO fuel flow from being supplied to ATO 130. As shown, it can be operated at speeds that do not draw all of the anode exhaust out of the hotbox 100 . Thus, ATO 130 operates during the startup mode of system 10 to use the cathode exhaust to oxidize the anode exhaust to generate heat. ATO heat is used to raise the temperature of the stack 102 during start-up mode before the stack 102 reaches its steady state operating temperature (eg, above 700° C., eg, 750° C.-900° C.). .

[0028] In contrast, during steady-state operation after stack 102 reaches its steady-state operating temperature (eg, above 700° C., eg, 750° C.-900° C.), at least a portion of the anode exhaust flows through bypass conduit 316. Bypass valve 320 can be opened to provide anode exhaust to ATO 130 via conduit 312A while preventing backflow of cathode exhaust. The speed / flow rate of the anode recirculation blower 212 can be increased to minimize the volume.

[0029] Thus, if sufficient current is drawn from the stack 102 (i.e., if the stack outputs power above a threshold inherent to the stack 102), the stack 102 will maintain the desired steady state operating temperature during steady state mode. The stack 102 does not require the heat of the ATO. In some embodiments, anode exhaust is supplied to ATO 130 during start-up mode and / or during a low current draw steady-state mode in which insufficient current is drawn from stack 102 to maintain the desired steady-state operating temperature. be done.

[0030] For example, the system controller 225 determines that the current drawn from the stack 102 is at a desired steady-state operating temperature (i.e., a stack operating temperature value above a temperature threshold (e.g., a temperature above 700°C, e.g., 750°C-900°C)). A portion of the anode exhaust is supplied to the ATO 130 to generate heat within the ATO 130 when it detects that it is below a predetermined current threshold required to maintain . ATO heat is supplied to the stack 102 to keep the stack above the temperature threshold. The current threshold depends on the size of the stack, the configuration of the fuel cell, the composition of the fuel supplied to the stack, the cumulative level of degradation of the stack, and the like. In one embodiment, the current threshold can include 10 amps to 30 amps, such as 20 amps to 25 amps. The anode exhaust may or may not be supplied to the exhaust oxidizer 330 during the low current draw steady state mode.

[0031] When system controller 225 detects that sufficient current is being drawn in stack 102 equal to or exceeding the current threshold required to keep the stack above the temperature threshold, system 10 enters a low current draw steady state state. Exit mode and enter normal steady state mode. In normal steady state mode, the flow of anode exhaust through anode recirculation blower 212 is increased to provide a minimal amount of anode exhaust to ATO 130 . For example, during normal steady state mode, the anode recirculation blower 212 can operate at a relatively high speed such that most of the anode exhaust is drawn from the hotbox 100 and supplied to the exhaust oxidizer 330. Together, no or very little (eg, less than 20 weight percent, eg, 1 to 10 weight percent) anode exhaust is supplied to the ATO 130 .

[0032] In one embodiment, bypass valve 320 may be a proportional valve configured to control anode exhaust flow through bypass conduit 316 . In some embodiments, the system controller 225 gradually opens the bypass valve 320 and gradually increases the speed of the anode recirculation blower 212 during the transition from startup to steady state operation and / or during steady state operation. can be configured as Additionally, system controller 225 may be configured to gradually reduce the speed of system blower 208 to compensate for the reduction in ATO 130 heat output.

[0033] The exhaust oxidizer 330 can be located outside the hotbox 100 so that the heat generated by the oxidation reaction does not unnecessarily heat the system components. As a result, the overall system airflow can be reduced. In particular, the system air blower 208 can operate at a lower speed during steady state operation compared to when the anode exhaust is supplied to the ATO 130 . In other words, the steady state power consumption of system blower 208 can be significantly reduced. In addition, cell-to-cell temperature variations can be reduced, thereby increasing cell voltage and efficiency.

[0034] In some embodiments, system 10 can optionally include a cabinet air blower 209 configured to supply cabinet air to cathode exhaust conduit 304C or system exhaust conduit 332. In particular, system 10 can be placed within a cabinet, and cabinet air blower 209 provides cabinet air to cool exhaust air output from system 10 in embodiments where cooler system exhaust air is required. can be configured to provide

[0035] In various other embodiments, the system 10 includes a system exhaust conduit 332 configured to supply the exhaust output from the exhaust oxidizer 330 to a combined heat and power (CHP) system 400, as described below with respect to FIG. be prepared. In one embodiment shown in FIG. 1, additional air can be supplied to cathode exhaust conduit 304C by cabinet air blower 209 to reduce the exhaust temperature.

[0036] In some embodiments, a portion of the anode exhaust can be supplied to the ATO 130 during startup and steady state operating modes. In other embodiments shown in FIGS. 2 and 3, splitter 170 and ATO conduit 312A may be omitted. In these embodiments, anode exhaust is not supplied directly to ATO 130 from within hotbox 100 during any mode of operation.

[0037] FIG. 2 is a schematic diagram of a SOFC system 12 according to a second embodiment of the present disclosure. SOFC system 12 is similar to SOFC system 10 of FIG. Therefore, only the differences from SOFC system 10 will be described in detail.

[0038] Referring to FIG. 2, SOFC system 12 may include bypass conduit 316A, ATO conduit 312B, and ATO valve 324. As shown in FIG. A bypass conduit 316A may fluidly connect the second recirculation conduit 310B upstream of the anode recirculation blower 212 to the cathode exhaust conduit 304C. However, in other embodiments, the bypass conduit 316A can be connected downstream of the anode recirculation blower 212 to the second recirculation conduit 310B if more anode exhaust flow is required. ATO conduit 312 B may fluidly connect bypass conduit 316 to ATO 130 .

[0039] Bypass valve 320 may be configured to control anode exhaust flow through bypass conduit 316A, and ATO valve 324 controls flow of anode exhaust (eg, ATO fuel flow) to ATO 130 through ATO conduit 312B. can be configured to In some embodiments, valves 320 and 324 may be proportional valves configured to provide varying flow rates through respective conduits 316A and 312B. In particular, at system startup, bypass valve 320 can be closed and ATO valve 324 can be opened by system controller 225, thereby supplying anode exhaust to ATO 130, while cathode exhaust conduit 304C and Avoid supplying anode exhaust to the exhaust oxidizer 330 .

[0040] During steady state operation, system controller 225 allows bypass valve 320 to be opened and ATO valve 324 to be closed so that a portion of the anode exhaust in second recirculation conduit 310B is diverted to the cathode exhaust. It is diverted into conduit 304C and supplied to exhaust oxidizer 330, but prevents anode exhaust from being supplied to ATO 130 via ATO conduit 312B.

[0041] In some embodiments, the system controller 225 is configured to gradually open the bypass valve 320 and gradually close the ATO valve 324 during the transition from startup to steady state operation and / or during steady state operation. can do. Additionally, system controller 225 may gradually reduce the speed of system blower 208 as ATO fuel flow decreases and / or after ATO fuel flow has stopped to compensate for the reduction in ATO 130 heat output. Can be configured.

[0042] FIG. 3 is a schematic diagram of a SOFC system 14 according to a third embodiment of the disclosure. SOFC system 14 is similar to SOFC system 12 of FIG. Therefore, only the differences from SOFC system 12 will be described in detail.

[0043] Referring to FIG. 3, the SOFC system 14 can include a bypass conduit 316B fluidly connecting the first recirculation conduit 310A to the cathode exhaust conduit 304C. In other words, bypass conduit 316B may be configured to divert anode exhaust flowing from anode recuperator 110 to anode exhaust cooler 140 to cathode exhaust conduit 304C, thereby diverting a portion of the anode exhaust to Upstream of anode exhaust cooler 140 it may be diverted to exhaust oxidizer 330 . Optional ATO conduit 312 B fluidly connects bypass conduit 316 B to ATO 130 .

[0044] Bypass valve 320 may be configured to control anode exhaust flow through bypass conduit 316B, and ATO valve 324 may be configured to control anode exhaust flow to ATO 130 through ATO conduit 312B. can. In particular, at system startup, bypass valve 320 can be closed and ATO valve 324 can be opened by system controller 225, thereby supplying anode exhaust to ATO 130, while cathode exhaust conduit 304C and Avoid supplying anode exhaust to the exhaust oxidizer 330 . During steady state operation, system controller 225 allows bypass valve 320 to be opened and ATO valve 324 to be closed, thereby supplying anode exhaust to exhaust oxidizer 330 and ATO 130 to the anode exhaust. prevent it from being supplied.

[0045] In some embodiments, the system controller 225 is configured to gradually open the bypass valve 320 and gradually close the ATO valve 324 during the transition from startup to steady state operation and / or during steady state operation. can do. Additionally, system controller 225 may gradually reduce the speed of system blower 208 as ATO fuel flow decreases and / or after ATO fuel flow has stopped to compensate for the reduction in ATO 130 heat output. Can be configured.

[0046] FIG. 4 is a cross-sectional view of a portion of central column 101 that may be included within SOFC systems 10, 12, and / or 14. FIG. 1-4, the central column 101 can comprise an anode recuperator 110, an ATO 130, and an anode exhaust cooler 140. As shown in FIG. Anode recuperator 110 is located within the core of central column 101 . ATO 130 may include a toroidal manifold containing ATO catalyst surrounding anode recuperator 110 . Anode exhaust cooler 140 may be located above anode recuperator 110 and ATO 130 . A fuel cell stack 102 may surround the ATO 130 and a cathode recuperator 120 may surround the fuel cell stack 102 .

[0047] ATO conduit 312, which can be any of ATO conduits 312A, 312B, 312C described above, includes two or more column conduits (e.g., two of the manifolds) extending from the top of central column 101 to ATO injector 172. 6 tubes) 314 can be divided. ATO injector 172 may comprise an annular space having a radially inner wall 174 connected to the outlet of column conduit 314 and an outer wall 176 projecting into the top of ATO 130 . In one embodiment, the outer wall 176 can have a curved vertical profile with a central section projecting radially outwardly from tapered top and bottom sections. Outer wall 176 includes one or more openings 178, such as slits, located in the central section. Aperture 178 fluidly connects the interior space of ATO injector 172 to the interior space of ATO 130 . In particular, column conduit 314 can be configured to provide multiple anode exhaust streams from ATO conduit 312 to ATO 130 through openings 178 in ATO injector 172, as indicated by dashed arrows in FIG. Radially separating the anode exhaust stream into multiple anode exhaust streams within the ATO injector improves mixing of the radial flow within the ATO 130 and the anode exhaust.

[0048] Referring again to FIGS. 1-3 according to the first through third embodiments, the exhaust oxidizer 330 is used in the SOFC system 10, 12, 14 when the system operates using hydrogen as a fuel source. can be omitted from In one embodiment shown in FIG. 1, if exhaust oxidizer 330 is omitted, additional air can be supplied to cathode exhaust conduit 304C by cabinet air blower 209 to reduce the exhaust temperature.

[0049] In various embodiments, exhaust oxidizer 330 can include an oxidation catalyst such as that described in U.S. Provisional Patent Application No. 63 / 220,659, filed July 12, 2021, which is incorporated herein by reference. The application is incorporated herein by reference in its entirety. For example, the oxidation catalyst may be a D block metal such as gold (Au) and / or platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), osmium (Os), ruthenium (Ru), etc. or combinations thereof. In some embodiments, Au, Pt, Pd, and Rh can exhibit the highest catalytic activity. In some embodiments, the oxidation catalyst is Au and / or another metal such as manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and / or copper (Cu). A stabilized platinum group metal may be included.

[0050] In various embodiments, the anode exhaust is diverted from the anode exhaust stream flowing from the anode recuperator 110 to the anode exhaust cooler 140 or the anode exhaust stream output from the anode exhaust cooler 140 and exiting the hot box 100. It can be fed to an exhaust oxidizer 330 located. Anode exhaust flow to ATO 130 may be reduced and / or shut off during steady state operation to reduce heat generation of ATO 130, and system airflow may be correspondingly reduced. Therefore, the temperature uniformity and performance of the entire system can be increased.

[0051] In some embodiments, the SOFC systems 10, 12, 14 can operate (eg, in a steady state mode) under low current load conditions or in response to transients in current load conditions, thereby , may require additional heat to maintain stack operating temperature. Under such conditions, anode exhaust can be periodically supplied to ATO 130 to periodically increase the temperature within hotbox 100 . For example, anode exhaust may vary from 5 seconds to 20 seconds per minute, 30 seconds to 3 minutes every 10 minutes, 5 minutes to 15 minutes per hour, etc. depending on the amount of additional heating required to maintain the stack operating temperature. can be supplied to the ATO on a schedule based on In these embodiments, valve 320 may be periodically closed and / or valve 324 (if present) may provide a portion of the anode exhaust to ATO 130 during steady state mode. It can be opened periodically. After anode exhaust is supplied to the ATO via conduit 312A or 312B, valve 320 can be opened and / or valve 324 (if present) can be closed. These steps of opening and closing valve(s) 320 and / or 324 may be repeated periodically. Alternatively or additionally, the speed / flow rate of anode recirculation blower 212 may be varied periodically to control the amount of anode exhaust supplied to ATO 130 . For example, the velocity can be decreased over a first time period to supply or increase the amount of anode exhaust supplied to ATO 130 . The velocity can then be increased for a second time period to stop or reduce the amount of anode exhaust flowing to the ATO 130 . The above steps may be repeated periodically in response to low output current or current transients. Low output current or transient current can be detected by measuring the current output by the stack and / or by measuring the temperature of the stack using a thermocouple or another suitable temperature sensor. .

[0052] FIG. 5 is a schematic diagram of a CHP system 400 according to various embodiments of the present disclosure. Referring to FIG. 5, CHP system 400 may comprise heat exchanger 410 , boiler 420 , steam turbine 422 and generator 424 . Boiler 420 provides steam to operate turbine 422, which rotates generator 424 to generate electricity.

[0053] Heat exchanger 410 receives water from water inlet conduit 412 and the hot exhaust stream output from exhaust oxidizer 330 via conduit 332 of SOFC system 10, 12, or 14, as described above. Can be configured. In particular, heat exchanger 410 may be configured to extract heat from the exhaust stream to heat water supplied from water inlet conduit 412 and provide steam and / or hot water. Heated water (or a mixture of heated water and steam) can be supplied to boiler 420 . Alternatively, a fully vaporized (and possibly superheated) steam stream may be supplied to turbine 422 . The hot exhaust stream is cooled in heat exchanger 410 and exhausted from heat exchanger 410 through outlet conduit 414 . Thus, heat exchanger 410 can reduce fuel consumption of boiler 420 for a given amount of power output from generator 424 by utilizing the heat output from the SOFC system.

[0054] Additional water and fuel may be supplied to boiler 420 to boil water therein and steam may be supplied from boiler 420 to steam turbine 422 . Steam and / or hot water may be supplied from steam turbine 422 to cooling or heating system 430 of structure 432 (eg, a building or facility such as a factory). The electricity generated by generator 424 is supplied to structure 432 and / or power grid 434 . In some embodiments, steam superheater 421 may be fluidly connected between boiler 420 and steam turbine 422 . Steam superheater 421 may be configured to superheat steam output from boiler 420 by extracting heat from the flue gas generated by combustion of boiler fuel.

[0055] FIG. 6 is a flow chart illustrating steps of a method of operating a fuel cell system according to various embodiments of the present disclosure. The method will be described with respect to a generic SOFC system that can include components as described with respect to any of the fuel cell systems 10, 12, 14 disclosed herein.

[0056] 1-6, at step 502, the SOFC system operates in startup mode. In particular, fuel may be supplied to the stack 102 from fuel inlet 300 and air may be supplied to the stack by system air blower 208 . Additionally, the anode and cathode exhausts generated by the stack 102 can be supplied to the ATO 130 for oxidation, thereby providing heat and increasing the temperature of the stack 102 .

[0057] For example, the speed of anode recirculation blower 212 can be decreased and / or ATO valve 324 can be opened to supply anode exhaust to ATO 130 via respective ATO conduit 312A or 312B. Additionally, bypass valve 320 may be closed so that anode exhaust does not flow through bypass conduit 316 . In some embodiments, the CPOx reactor 200 can operate to partially reform fuel during start-up mode.

[0058] Once the stack 102 reaches the set steady state operating temperature, the SOFC system can transition to steady state mode. Specifically, in step 504, the anode exhaust flow to ATO 130 may be stopped or reduced. For example, the speed of anode recirculation blower 212 can be increased and / or ATO valve 324 can be closed to stop anode exhaust flow to ATO 130 through respective ATO conduit 312A or 312B. .

[0059] At step 506, a portion of the anode exhaust generated by stack 102 may be diverted to exhaust oxidizer 330, where the mixture of anode and cathode exhaust is reacted to oxidize carbon monoxide and / or hydrogen. be able to. For example, bypass valve 320 can be opened to divert a portion of the anode exhaust to exhaust oxidizer 330 . For example, the anode exhaust can be diverted from either conduit 310A or 310B upstream or downstream of anode exhaust cooler 140. FIG.

[0060] The anode exhaust can be diverted by closing ATO valve 324 and a portion of the anode exhaust generated by stack 102 can be diverted to exhaust oxidizer 330 for oxidizing the cathode exhaust. For example, bypass valve 320 can be opened such that a portion of the anode exhaust is diverted from conduit 310A or 310B to exhaust oxidizer 330 via bypass conduit 316, 316A, or 316B. In various embodiments, the anode exhaust flow rate to the exhaust oxidizer 330 during steady state operation may be less than the anode exhaust flow rate to the ATO 130 during start-up operation.

[0061] At step 508, the system airflow may optionally be adjusted based on changes in the temperature of the SOFC system. For example, the speed of system air blower 208 can be adjusted based on the temperature of stack 102 . In particular, if the temperature of stack 102 decreases due to the reduced heat output of ATO 130, the air flow rate of system air blower 208 may correspondingly decrease.

[0062] In some embodiments, at step 510 , the method may optionally include providing exhaust output from the exhaust oxidizer 330 to the combined heat and power (CHP) system 400 . For example, exhaust air can be supplied to heat exchanger 410 to provide steam and / or hot water.

[0063] In some embodiments, the method can operate the SOFC system in a low current draw steady state mode. For example, if the current load applied to the stack is insufficient to maintain a predetermined steady state stack operating temperature, step 504 may maintain the temperature of stack 102 within the selected operating temperature range. As such, it may include periodically supplying anode exhaust to the ATO 130 to generate heat that is supplied to the stack 102 . For example, the anode exhaust can be periodically fed to the ATO where it can be mixed with the cathode exhaust and fed continuously to the ATO 130 . For example, anode exhaust can be supplied according to a schedule that can be based on the amount of heating required to maintain stack 102 at a particular operating temperature or temperature range. For example, anode exhaust can be supplied for X minutes during Y period. Here, X can range from about 10 seconds to about 5 minutes, for example, about 30 seconds to about 3 minutes, and Y can range from about 5 minutes to about 1 hour, for example, about 10 minutes to about 30 minutes. can be in the range of minutes.

[0064] Thus, in start-up mode and / or in low current draw steady-state modes in which insufficient current is drawn from the stack to maintain a predetermined steady-state stack operating temperature, the first amount (e.g., the first volume or flow rate) of the anode and cathode exhausts are supplied to the ATO 130 located within the hot box 100 to oxidize the anode exhaust and generate heat that is supplied to the stack 102 . In contrast, in the normal steady-state mode in which sufficient current is drawn from the stack to maintain a given steady-state stack operating temperature, the anode exhaust flow to the ATO is turned off or A smaller second amount (eg, a second volume or flow rate) of anode exhaust is supplied to ATO 130 while another portion (ie, amount) of the anode and cathode exhaust is located outside hot box 100. It is supplied to an exhaust oxidizer 330 that

[0065] The previous 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. Also, the general principles defined herein may be applied to other aspects without departing from the scope of the invention. Accordingly, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein. do.

Claims

1. 1. A fuel cell system, comprising: a stack of fuel cells configured to output an anode exhaust and a cathode exhaust; an anode tail gas oxidizer configured to oxidize the anode exhaust from the fuel cell stack; a cathode exhaust conduit configured to output the cathode exhaust and the anode exhaust from the fuel cell system; a bypass conduit configured to divert the anode exhaust from the stack of fuel cells to the cathode exhaust conduit; a bypass valve configured to control the flow of the anode exhaust through the bypass conduit; an ATO conduit configured to deliver the anode exhaust from the fuel cell stack to the anode tail gas oxidizer; an anode recuperator configured to use the anode exhaust from the fuel cell stack to heat fuel supplied to the fuel cell stack; an anode exhaust conduit configured to supply anode exhaust output from the fuel cell stack to the anode recuperator; an anode exhaust cooler configured to use the anode exhaust from the anode recuperator to heat air supplied to the fuel cell stack; Equipped with The fuel cell system, wherein the bypass conduit is configured to divert the anode exhaust from the stack of fuel cells after it has passed through the anode recuperator or after it has passed through both the anode recuperator and the anode exhaust cooler.

2. a hot box containing the stack, the anode tail gas oxidizer, the anode recuperator, and the anode exhaust cooler; an exhaust oxidizer configured to oxidize the anode exhaust received from the cathode exhaust conduit; Further provided with The fuel cell system of claim 1 , wherein the exhaust oxidizer is located outside the hot box.

3. an ATO injector comprising an annular space having a radially inner wall and an outer wall extending into the anode tail gas oxidizer, the ATO injector including one or more openings fluidly connecting the interior space of the ATO injector to the interior space of the anode tail gas oxidizer; at least one column conduit fluidly connecting the ATO conduit to the interior space of the ATO injector and extending through a central column of the fuel cell system to the ATO injector; a mixer configured to mix the anode exhaust with fresh fuel; a first recirculation conduit fluidly connecting an outlet of the anode recuperator to an inlet of the anode exhaust cooler; a second recirculation conduit fluidly connecting an outlet of the anode exhaust cooler to the mixer; an anode recirculation blower operatively connected to the second recirculation conduit; The fuel cell system of claim 1 further comprising:

4. the bypass conduit is fluidly connected to the second recirculation conduit upstream of the anode recirculation blower with respect to a flow direction of the anode exhaust through the second recirculation conduit; The fuel cell system of claim 3 , wherein the ATO conduit is fluidly connected to the bypass conduit.

5. the bypass conduit is fluidly connected to the second recirculation conduit downstream of the anode recirculation blower with respect to a flow direction of the anode exhaust through the second recirculation conduit; a splitter configured to split a portion of the anode exhaust flowing through the first recirculation conduit; The fuel cell system of claim 4 , wherein the ATO conduit fluidly connects the splitter to the ATO injector.

6. the bypass conduit is fluidly connected to the first recirculation conduit; The fuel cell system of claim 3 , wherein the ATO conduit fluidly connects the bypass conduit to the ATO injector.

7. a system air blower configured to supply air to the stack through the anode exhaust cooler; an ATO valve located outside the hot box and configured to control the flow of the anode exhaust through the ATO conduit; a system controller configured to control the bypass valve, the ATO valve, and the system air blower; Further provided with The system controller During a start-up mode of the fuel cell system, the ATO valve is opened and the bypass valve is closed; configured to close the ATO valve and open the bypass valve during a steady state mode of the fuel cell system after the fuel cell stack has reached a steady state operating temperature; 10. The fuel cell system of claim 1, wherein the system controller is configured to gradually reduce the operating speed of the system air blower during the steady state mode to maintain the fuel cell stack at the steady state operating temperature.

8. a system exhaust conduit fluidly connecting an outlet of the exhaust oxidizer to a combined heat and power system; The cogeneration system comprises: a heat exchanger configured to use heat extracted from the exhaust air provided by the system exhaust conduit to produce hot water or steam; Boiler and The turbine and A generator and The fuel cell system of claim 2 , comprising:

9. The fuel cell system of claim 1 , wherein the stack comprises a solid oxide fuel cell stack.

10. In a start-up mode, the fuel cell system is configured to supply a first amount of the anode exhaust and the cathode exhaust to the anode tail gas oxidizer located within a hot box to oxidize the anode exhaust and generate heat that is supplied to the stack; In a steady-state mode, the fuel cell system is configured to stop supplying the anode exhaust to the anode tail gas oxidizer, or to supply the anode exhaust to the anode tail gas oxidizer at a second amount less than the first amount, and to supply the anode exhaust and the cathode exhaust outside the hot box. The fuel cell system according to claim 1 .

11. in a low current draw steady state mode in which insufficient current is drawn from the stack to maintain a predetermined steady state stack operating temperature, the fuel cell system is configured to supply a first amount of the anode exhaust and the cathode exhaust to the anode tail gas oxidizer located within a hot box to oxidize the anode exhaust and generate heat that is supplied to the stack; and in a normal steady-state mode in which sufficient current is drawn from the stack to maintain the predetermined steady-state stack operating temperature, the fuel cell system is configured to either stop supplying the anode exhaust to the anode tail gas oxidizer or supply a second amount of the anode exhaust to the anode tail gas oxidizer, the second amount being less than the first amount, and supply the anode exhaust and the cathode exhaust outside the hot box. The fuel cell system according to claim 1 .

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