CPOX reactor control system and method

Abstract

To provide an SOFC system that uses external temperature sensors.SOLUTION: Provided is a fuel reformer module for initiating catalytic partial oxidation (CPOX) to reform hydrocarbon fuel oxidant mixtures (2025, 3025) to output a syngas reformate (2027) to a solid oxide fuel cell stack. A solid non-porous ceramic catalyzing body (3030) includes a plurality of catalyst coated fuel passages. Thermally conductive elements (9005, 10005, 11005, 13005), with a coefficient of thermal conductivity of 50 W / m° K or greater are thermally conductively coupled with the catalyzing body. A first thermal sensor (8030) is thermally conductively coupled with the thermally conductive elements. A second thermal sensor (8040) is thermally conductively coupled with a surface of the fuel cell stack. A control method independently modulates an oxidant input flow rate, based on first thermal sensor signal values, a hydrocarbon fuel input flow rate, based on second thermal sensor signal values.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] Exemplary technology described herein relates to solid oxide fuel cell (SOFC) systems, and in particular to structural features and methods of forming an enclosure that forms enclosure walls from thermally conductive materials and provides thermal conduction paths designed to dissipate thermal energy by thermal conduction in a desired manner. More particularly, the present disclosure relates to thermal energy management within SOFC systems by providing thermal conduction paths configured to improve operational performance, safety, and reliability. [Background technology]

[0002] Related Technology Conventional solid oxide fuel cell (SOFC) systems used to generate electrical energy through an electrochemical process that typically utilizes a gas-to-gas heat exchanger to transfer thermal energy from the exhaust gas to the incoming air. Exemplary embodiments are disclosed in U.S. Patent No. 8,557,451, entitled "Fuel Processor for Fuel Cell System," and U.S. Patent No. 8,197,976, entitled "Solid Oxide Fuel Cell System with Hot Zones and Two-Stage Tail Gas Combustors," issued on October 15, 2013. While the gas-to-gas heat exchanger transfers waste heat from the exhaust gas to the incoming cathode air, the overall system operates with hot spots in the tail gas combustion chamber and other locations where fuel is being combusted.

[0003] In conventional SOFC systems, the temperatures surrounding the hot spots tend to exceed the safe operating temperatures for many highly thermally conductive metals, such as copper and aluminum. In addition, highly thermally conductive metals, such as copper and aluminum, are often damaged by oxidation when exposed to the oxygen-rich cathode gas used in conventional SOFC systems. This has led the art to shy away from using high thermal conductivity metals with conventional SOFC systems, instead constructing them with temperature resistant metals surrounding the hot spots to avoid burn-through and other failures, including shortened product life caused by metal oxidation. Temperature resistant metals tend to include temperature resident superalloys, typically including nickel and cobalt, such as Hastelloy, Monel, Inconel, and others, that are less susceptible to damage by prolonged temperature and oxygen exposure. One problem with using temperature resistant superalloys is that they have low thermal conductivity coefficients, such as less than about 40 W / m°K, more commonly less than 20 W / m°K. Compared to more thermally conductive metals (e.g., aluminum and copper alloys) that have thermal conductivity coefficients above 200 W / m°K, the high-temperature tolerant superalloys are less suitable heat conductors. As a result, heat transfer by conduction in conventional SOFC enclosures is slow, and the slow rate of heat transfer tends to create persistent hot spots or temperature gradients in the overall structure of the SOFC system.

[0004] More recently, SOFC systems have been constructed to promote thermal energy transfer by thermal conduction to reduce temperature gradients. One such system is U.S. Patent Application No. 14 / 399,795, entitled "SOFC-Conduction," published as US20160099476A1 on April 7, 2016. Disclosed herein is a SOFC system formed with inner and outer metal enclosures formed as thermal conduction paths made from more thermally conductive metals, such as aluminum and copper alloys, to improve thermal conductivity from hot spots of the structure to cooling zones. By providing thermal conduction paths with higher thermal conductivity coefficients and providing walls with greater thermal mass than others, each distinct enclosure wall system allows for more rapid heat transfer through aluminum and copper enclosure walls, in some cases including copper cores, which tend to normalize more quickly to a uniform temperature, thereby reducing temperature gradients.

[0005] Conventional SOFC systems utilize internal temperature sensors to measure instantaneous temperatures at hot spot locations located within the hot zone of the SOFC system. An electronic controller monitors the instantaneous temperatures reported by each internal temperature sensor. If an over-temperature condition is detected, the electronic controller is operable to shut down operation of the SOFC system by closing the inlet fuel valve. However, one problem with the use of internal sensors in elevated temperature environments is that the thermal sensors may not provide an instantaneous internal temperature at all, or may provide an inaccurate instantaneous temperature. Damage to or inaccuracy from the internal thermal sensor may result in an over-temperature condition going undetected, causing catastrophic events such as melt-through of one of the enclosure walls. Other consequences include damage to the insulation around the hot zone and damage to the coating layers applied to the inner and outer enclosure walls. Even if damage from an over-temperature condition is minimal, if an internal temperature sensor fails, it will require replacement. Replacing a damaged internal temperature sensor requires disassembly of the SOFC system, which is costly.

[0006] In view of the foregoing considerations, there is a need in the art to provide a SOFC system that uses an external temperature sensor to detect over-temperature operating conduction that may lead to system damage or failure, without relying on an internal sensor. There is a further need in the art to provide a passive back-up to the thermal sensor that detects an over-temperature condition. If the temperature sensor fails or otherwise reports an inaccurate temperature, a passive back-up is provided to shut down the SOFC system. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 8,557,451 [Patent Document 2] U.S. Patent No. 8,197,976 Summary of the Invention

[0008] The present disclosure solves problems related to the control of solid oxide fuel cell systems and catalytic partial oxidation (CPOX) fuel reformers that operate to reform a mixture of a hydrocarbon fuel and an oxidant, such as air. The syngas reformate is delivered to the anode side of a plurality of solid oxide fuel cells (SOFCs) that operate to generate electrical power. The CPOX reformer of the present disclosure includes a control system and method for monitoring the change in temperature of each CPOX reaction and the change in temperature or SOFC reaction, as well as control elements for independently varying the input flow rate of the hydrocarbon fuel and independently varying the input flow rate of the oxidant.

[0009] The fuel reformer module of the present disclosure initiates a CPOX reaction to reform a hydrocarbon fuel oxidant mixture into a syngas reformate. The fuel reformer module includes a catalyst body having an input end for receiving a hydrocarbon fuel oxidant mixture therein and an output end for delivering a syngas reformate therefrom. The catalyst body is formed from a solid non-porous ceramic substrate having a plurality of independent catalyst fuel passages extending between the input end and an output end of each fuel passage. An inner surface of each catalyst fuel passage is coated with a catalyst layer including a material selected to initiate a CPOX reaction. A heat conducting element including a material having a thermal conductivity coefficient of 50 W / m°K or greater, preferably 100 W / m°K or greater, is thermally conductively coupled to the catalyst body over a contact surface area. The contact surface area can be an exterior or interior surface of the catalyst body, and preferably extends along a longitudinal axis of the catalyst body. A first thermal sensor is thermally conductively coupled to the heat conducting element. The first thermal sensor generates a first temperature signal corresponding to a surface temperature of the heat conducting element proximate any surface of the heat conducting element to which the first thermal sensor is coupled.

[0010] The SOFC system of the present disclosure includes the fuel reformer module described above and a fuel oxidizer control module configured to mix the hydrocarbon fuel oxidizer mixture in various proportions. The fuel oxidizer control module is disposed between a hydrocarbon fuel source, an oxidizer source, and an input end of the catalyst body. A hydrocarbon fuel flow modulator is disposed between the hydrocarbon fuel source and the input end. An oxidizer flow modulator is disposed between the oxidizer source and the input end. An electronic controller is operative to send independent command and control signals to each of the hydrocarbon fuel flow modulator and the oxidizer flow modulator.

[0011] The SOFC system comprises a solid oxide fuel cell (SOFC) stack including a plurality of individual SOFC fuel cells each including a solid oxide anode electrode layer. A syngas reformate output from the fuel reformer module is directed to flow over the solid oxide anode electrode layer to initiate and sustain the SOFC reaction. The hot zone enclosure comprises a plurality of hot zone enclosure walls joined together to enclose a hot zone cavity surrounding the SOFC stack. The hot zone enclosure walls are formed from a material having a thermal conductivity coefficient of 100 W / m°K or greater and joined together to form a first continuous thermal conduction path including all of the hot zone enclosure walls. A second thermal sensor is thermally conductively coupled to a surface of the first thermal conduction path and generates a second temperature signal corresponding to a temperature of a surface of the first thermal conduction path to which the second thermal sensor is coupled.

[0012] A range of first setpoint temperature values ​​is stored by the electronic controller. The range of first setpoint values ​​corresponds to a calibrated operating temperature range known to produce a syngas reformate having a desired syngas composition. In one example, the first setpoint temperature value corresponds to a syngas composition having a low percentage of unreacted hydrocarbon fuel molecules. A range of second setpoint temperature values ​​is stored by the electronic controller. The range of second setpoint values ​​corresponds to a known calibrated operating temperature range to produce a desired performance characteristic of the SOFC stack. In one example, the second setpoint temperature value corresponds to a fuel-to-power efficiency rating.

[0013] The electronic controller operates a first control loop based on the sampling of the first thermal sensor signal value. The first control loop commands the oxidant flow modulator to increase or decrease the oxidant flow rate to maintain the sampled first temperature signal value within a first setpoint value. The electronic controller operates a second control loop based on the sampling of the second thermal sensor signal value. The second control loop commands the hydrocarbon fuel flow modulator to increase or decrease the hydrocarbon fuel flow rate to maintain the sampled second temperature signal value within a second setpoint value.

[0014] A method for controlling a SOFC system included delivering a mixture of a hydrocarbon fuel and an oxidant to an input end of a catalyst body. A hydrocarbon fuel flow modulator is disposed between a hydrocarbon fuel source and the input end of the catalyst body. An oxidant flow modulator is disposed between the oxidant source and the input end of the catalyst body. An electronic controller delivers a first command and control signal to the oxidant flow modulator to regulate the flow rate of the oxidant. The electronic controller delivers a second command and control signal to the hydrocarbon fuel flow modulator to regulate the flow rate of the hydrocarbon fuel. An input manifold disposed between an output end of the catalyst body and the SOFC stack delivers a syngas reformate output from the catalyst body to a solid oxide anode electrode of the solid oxide fuel cell (SOFC) stack to initiate a SOFC reaction at a SOFC reaction temperature. The electronic controller samples a first temperature control signal generated by a first temperature sensor and also samples a second temperature control signal generated by a second temperature sensor. The electronic controller stores a range of first setpoint temperature values ​​corresponding to a desired composition of the syngas reformate output from the fuel reformer module and stores a range of second setpoint temperature values ​​corresponding to a desired performance characteristic of the SOFC stack. The electronic controller operates a first control loop based on sampling the first temperature sensor signal value and commanding the oxidant flow modulator to increase or decrease the flow rate of the oxidant to maintain the sampled first temperature signal value within the range of the first setpoint value. The electronic controller operates a second control loop based on sampling the second temperature signal value and commanding the hydrocarbon fuel flow modulator to increase or decrease the flow rate of the hydrocarbon fuel to maintain the second thermal sensor signal value within the range of the second setpoint value. [Brief description of the drawings]

[0015] The features of the present disclosure will be best understood from a detailed description of the subject technology and illustrative embodiments thereof, selected for purposes of illustration and illustrated in the accompanying drawings. [Figure 1] 1 shows a schematic diagram of an exemplary, non-limiting SOFC system according to the present disclosure. [Diagram 2] FIG. 1 shows a schematic cross-sectional side view of an exemplary, non-limiting solid oxide fuel cell stack assembly according to the present disclosure. [Diagram 3] 1 shows a schematic side cross-sectional view of an exemplary, non-limiting fuel reformer module according to the present disclosure; [Figure 4] 1 shows a schematic cross-sectional side view of a non-limiting exemplary catalyst body embodiment of a SOFC system according to the present disclosure. [Figure 4A] 2 is a schematic diagram illustrating the surface area of ​​a reactor base wall available to absorb thermal energy radiating from a catalytic fuel passage according to the present disclosure; FIG. [Diagram 5] 1 shows a schematic top cross-sectional view of an exemplary, non-limiting cathode chamber according to the present disclosure. [Figure 6] 1 shows a bottom schematic cross-sectional view of an exemplary, non-limiting fuel reformer module according to the present disclosure. [Figure 7] FIG. 1 shows a schematic cross-sectional side view of an exemplary, non-limiting solid oxide fuel cell stack assembly according to the present disclosure. [Figure 8] 1 shows a schematic representation of a further non-limiting exemplary embodiment of a solid oxide fuel cell (SOFC) system including a fuel and air input system according to the present disclosure. [Figure 9] 1 illustrates a first exemplary non-limiting heat conducting element embodiment in heat conducting contact with a catalytic body according to the present disclosure. [Figure 10] 1 illustrates a second exemplary non-limiting heat conducting element embodiment in heat conducting contact with a catalytic body according to the present disclosure. [Figure 11] 1 illustrates a third exemplary non-limiting heat conducting element embodiment in heat conducting contact with a catalytic body according to the present disclosure. [Figure 12] 1 illustrates a fourth exemplary non-limiting embodiment of a heat conducting element in heat conducting contact with a catalytic body according to the present disclosure. [Figure 13A] FIG. 13 illustrates an isometric top view of a fifth exemplary, non-limiting embodiment showing a cylindrical catalyst body formed with a central longitudinal passage adapted to receive a heat conducting element therein, in accordance with the present disclosure. [Figure 13B]FIG. 2 is a cross-sectional view through the longitudinal axis of a cylindrical catalyst body formed with a central longitudinal passage and showing a solid cylindrical heat conducting element therein according to the present disclosure. [Figure 14] FIG. 14 illustrates an isometric top view of a sixth exemplary non-limiting heat conducting element embodiment in heat conducting contact with a catalyst body formed as a solid non-porous ceramic foam material formed with interconnected open cells distributed throughout the solid ceramic foam structure according to the present disclosure. [Figure 15A] Graphical representations of O:C ratio versus T_CPOX, %CH4 and %C2HX values ​​are shown. [Figure 15B] FIG. 15A shows a data table listing the O:C ratios versus T_CPOX, %CH4 and %C2Hx values ​​plotted.

[0016] 4.Definition Unless otherwise indicated, the following definitions are used throughout: [Table 1]

[0017] 5. Item Number List Unless otherwise indicated, the following section numbers are used throughout: [Table 2-1] [Table 2-2] [Table 2-3] [Table 2-4] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Solid Oxide Fuel Cell System Referring to Figure 1, a schematic diagram of a first exemplary, non-limiting embodiment of the present disclosure illustrates a solid oxide fuel cell (SOFC) system (100). The system (100) includes a hot zone (105) enclosed within a hot zone enclosure wall (115), which in this embodiment encloses a cylindrical hot zone cavity (120). The hot zone enclosure wall (115) is further enclosed by an insulating layer (130), which is further enclosed by an outer enclosure wall (132). The hot zone enclosure wall (115) and the outer enclosure wall (132) each include separate cylindrical sidewalls with each sidewall mechanically interacting with a different pair of opposing disk-shaped end walls, which are further described below.

[0019] The hot zone enclosure wall (115) encloses a fuel cell stack (135). The fuel cell stack (135) includes at least one SOFC fuel cell, but preferably includes multiple SOFC fuel cells, each electrically interconnected in series or parallel with a DC power output module (140). The DC power output module receives the power generated by the fuel cell stack and delivers the output power to an external power load (not shown). Each fuel cell includes a solid oxide cathode electrode (155) that is oriented for exposure to a cathode gas present within the hot zone cavity (120). The hot zone cavity (120) is filled with a cathode gas including at least oxygen, e.g., air (126), during operation, and the cathode gas within the hot zone cavity (120) chemically reacts with the surface of the solid oxide cathode electrode (155). Each fuel cell further comprises a solid oxide anode electrode (150) oriented so that it is not exposed to the hot zone cavity (120) or the cathode gas contained therein, but instead to the anode gas (reformate) (125) over which the anode gas passes during operation to chemically react with the solid oxide anode electrode (150). The SOFC fuel cell further comprises a solid electrolyte layer (145) disposed to separate the solid oxide cathode electrode (155) from the solid oxide anode electrode (150). The solid electrolyte layer (145) is an oxygen ion conducting layer that serves as an ion exchange medium for ion exchange between the solid oxide anode electrode (150) and the solid oxide cathode electrode (155).

[0020] The fuel cell stack (135) is maintained at an elevated operating temperature (e.g., in the range of 350-1200°C) depending on the composition of the solid material layers of the fuel cell stack and the properties of the anode and cathode gases. A preferred operating temperature is selected to support efficient electrochemical energy generation. Electrical energy is produced by the fuel cell stack (135) when the anode gas (125) containing hydrogen reacts with the solid oxide anode electrode (150) and the cathode gas (126) containing oxygen reacts with the solid oxide cathode electrode (155).

[0021] The hot zone (105) further encloses a combustor module (180) or tail gas combustor that includes a combustion chamber configured to receive the spent anode gas (125a) and the spent cathode gas (126a) after they react with the corresponding solid oxide anode electrode (150) and solid oxide cathode electrode (155), respectively. Upon mixing within the combustor module (180), the spent anode gas (125a) and the spent cathode gas (126a) are combusted. Thermal energy generated by the combustion occurring within the combustion module (180) is used to heat the hot zone enclosure wall (115) as well as the hot zone cavity (120).

[0022] The hot zone cavity (120) further encloses a recuperator module (175). The recuperator module (175) is in fluid communication with the combustor module (180) and receives the combustion exhaust gas (127) exiting therefrom. The combustion exhaust gas (127) passes through the recuperator module (175) and transfers thermal energy therefrom to the incoming air (170) as the combustion exhaust gas (127) and the incoming air (170) pass through separate gas conduits of a gas counterflow heat exchanger (not shown). The spent combustion exhaust gas (127a) then exits the recuperator module (175) and is delivered from the hot zone via an exhaust port (185). The incoming air (170) after exiting the recuperator module (175) includes the cathode gas (126) that is delivered to the hot zone cavity (120).

[0023] The cold zone (110) of the system includes a fuel input module (197). Various hydrocarbon fuels, such as propane, methane, or kerosene, as well as other suitable fuels, are received into the fuel input module (197) from various fuel sources (not shown). The fuel input module (197) is operable to condition the incoming fuel (160) delivered from the fuel source and deliver a desired volume or volumetric flow rate of the incoming fuel (160) to the fuel reformer module (165). The fuel reformer (165) is operable to reform the incoming fuel in a manner suitable for a desired chemical reaction with the solid oxide anode electrode (150).

[0024] The incoming fuel (160) includes liquid or gaseous hydrocarbon compounds from which hydrogen can be extracted. The incoming fuel (160) may be mixed with air, atomized, or otherwise vaporized. The fuel reformer module (165) of the present disclosure comprises a catalytic partial oxidation (CPOX) reactor providing a catalyst support structure (167) having some of its surfaces coated with a catalyst layer, as described below. As the incoming fuel passes over the catalyst layer, the fuel is combusted or partially combusted within the catalyst support structure (167). Heat generated by the combustion reforms the incoming fuel (160) into hydrogen gas (H.sub.2) and carbon monoxide gas (CO). The reformed fuel exits the fuel reformer module (165) as anode gas (125) that reacts with the solid oxide anode electrodes (150) of each fuel cell in the SOFC fuel cell stack (135).

[0025] The cold zone (110) of the system includes an air input module (198) for inlet air (170) or another oxygen-rich source gas to the recuperator module (175). Air or any other oxygen-rich source gas is received into the air input module (198) from various air sources (not shown) or the air includes room air that is pumped to the recuperator module (175) by a fan. The air input module (198) is operable to regulate the flow of air to the recuperator module (175). The recuperator module (175) heats the inlet air (170) with the combustion exhaust gas (127) by passing the combustion exhaust gas through a gas counterflow heat exchanger (not shown). The heated air exits the recuperator as cathode gas (126).

[0026] The cold zone (110) of the system includes an electronic controller (190) in electrical communication with a fuel input module (197) and an air input module (198). The electronic controller (190) includes a digital data processor and associated digital data memory having various operating programs and / or digital logic control elements operating thereon to manage the operation of the SOFC system (100). The electronic controller (190) is in electrical communication with a DC power output module (140) to monitor and regulate the DC power output to the load. The electronic controller is also in electronic communication with a fuel input module (197) to monitor and regulate the incoming fuel (160), and further in electronic communication with an air input module (198) to monitor and regulate the incoming air (170), and further in electronic communication with at least one temperature sensor (157) to monitor the temperature of one or more of the hot zone enclosure wall (115), the outer enclosure wall (132), the fuel reformer module (165), and other surfaces as may be required to monitor the temperature of various surfaces of the SOFC system (100).

[0027] The fuel input module (197) and the air input module (198) may each include one or more gas pressure regulators, gas flow actuator valves, mass or volumetric gas flow controllers, and / or volumetric flow sensors, gas pressure sensors, temperature sensors, and the like, each operable with or in electrical communication with the electronic controller (190) to regulate the incoming fuel (160) to the fuel reformer module (165) or the incoming air (170) to the recuperator module (175). More specifically, the fuel input module (197) in cooperation with the electronic controller (190) is operable to regulate the input fuel pressure, dynamically adjust the incoming fuel mass or volumetric flow, and, if necessary, stop the incoming fuel (160) from entering the SOFC system (100). Similarly, the air input module (198), in cooperation with the electronic controller (190), may also be operable to adjust the input air pressure, dynamically adjust the incoming air volume or flow rate, and, if necessary, stop the incoming air (170) from entering the SOFC system (100). In some operating environments, the air input module (198) may comprise a simple fan operating at a constant angular velocity without any additional air input control sensors or elements.

[0028] In accordance with the present disclosure, the fuel reformer module (165) is configured to effect an exothermic reaction between an incoming fuel (160) and a catalyst layer disposed on a surface of a ceramic catalyst support structure (167) to reform the fuel into hydrogen gas (H.sub.2) and carbon monoxide (CO). Further in accordance with the present disclosure, the improved fuel reformer module (165) comprises a ceramic catalyst support structure (167) including a plurality of longitudinal fuel flow passages, as described below, each longitudinal fuel flow passage being coated on its inner surface with a catalyst layer. Additionally, the fuel reformer module (165) is configured to prevent auto-ignition of untreated fuel entering the ceramic catalyst support structure (167), in part, by providing the longitudinal fuel flow passages as a means for transferring thermal energy generated by exothermic reactions occurring within the ceramic catalyst support structure (167) from the ceramic catalyst support structure (167) along a longitudinal path toward the incoming fuel. 1 , the fuel reformer module (165) is disposed partially between and partially outside the outer enclosure walls (132), and is further configured to provide a heat transfer path through the outer enclosure walls (132). In addition, the SOFC system (100) optionally includes one or more cooling devices (e.g., air fans, water pumps, etc.) for cooling the portion of the fuel reformer module (165) disposed outside the outer enclosure walls (132).

[0029] The SOFC system (100) may optionally include a cold start module (195). The cold start module (195) is configured to receive and combust a portion of the incoming fuel (160) redirected to the cold start module (195). Operation of the cold start module (195) is initiated by the electronic controller (190) when the temperature of the incoming fuel (160) or the temperature of the hot zone enclosure wall (115) or the temperature of the fuel cell stack (135) falls below a desired operating or reaction temperature. During operation, a portion of the incoming fuel (160) is diverted to a combustion chamber associated with the cold start module (195). A controllable fuel igniter is provided within the combustion chamber of the cold start module (195), and fuel within the combustion chamber is ignited and combusted to heat the incoming fuel (160), the fuel reformer module (165), and the hot zone enclosure wall (115) during a cold start. Once the SOFC system (100) has reached the desired operating temperature, operation of the cold start module (195) is terminated.

[0030] During operation, the electronic controller (190) is in communication with electronic elements, such as one or more cooling fans, one or more electrically operable gas flow actuator valves, gas flow detectors, and / or gas modulators, associated with a fuel input module (197), an air input module (198), and a power output detector, and other elements that may be required to control various operating parameters of the SOFC (100). The electronic controller (190) further operates to monitor the DC current / power output as well as temperatures, such as measured by one or more thermocouples, and to vary the volumetric flow rates of the incoming fuel and optionally the incoming air as a means of increasing or decreasing the DC current / power output.

[0031] 8.2 Solid oxide fuel cell stack side section 2, a second non-limiting exemplary embodiment of an improved SOFC fuel cell stack assembly (2000) according to the present disclosure is shown in a side cross-sectional view. The SOFC fuel cell stack assembly (2000) includes a SOFC fuel cell stack (2005) including a plurality of tubular fuel cells (2080) each extending longitudinally along a substantially cylindrical hot zone cavity or cathode chamber (2010).

[0032] 2, a second non-limiting exemplary embodiment of an improved SOFC fuel cell stack assembly (2000) according to the present disclosure is shown in a side cross-sectional view. The SOFC fuel cell stack assembly (2000) includes a SOFC fuel cell stack (2005) including a plurality of tubular fuel cells (2080) each extending longitudinally along a substantially cylindrical hot zone cavity or cathode chamber (2010).

[0033] In this exemplary embodiment, the disk-shaped bottom end wall (2016) also forms the bottom wall of the recuperator chamber (2210). As described above, the recuperator chamber (2210) is provided to heat the incoming air (2200) that enters the fuel cell stack assembly via the cathode supply tube (2145). The incoming air (2200), i.e., cathode gas, enters the recuperator chamber (2210) via the recuperator input port (2230) and exits the recuperator chamber (2010) via the recuperator output port (2235) back to the cathode supply tube (2145). One or more of the recuperator input port (2230) and the recuperator output port (2235) may be disposed around the cathode supply tube (2145). The flow barrier (2212) directs the air flow to the peripheral wall of the recuperator chamber (2210), thereby increasing the exchange of heat energy between the air passing through the recuperator chamber and its peripheral wall. The recuperator chamber (2210) is surrounded on its upper side by a disk-shaped isolation wall (2214) disposed between the combustion chamber (2135) and the recuperator chamber (2210). The disk-shaped isolation wall (2214) is configured to absorb heat energy as spent anode and spent cathode gas is combusted in the combustion chamber (2135) such that the absorbed heat energy is re-released inside the recuperator chamber (2210).

[0034] The intermediate cylindrical enclosure surrounds the hot zone enclosure wall. The intermediate cylindrical enclosure is surrounded by an open ended longitudinal intermediate cylindrical side wall (2510) that mechanically interacts with a disk-shaped intermediate bottom end wall (2511) and an opposing disk-shaped intermediate top end wall (2513). The intermediate cylindrical enclosure is sized to form a gap (2155) that substantially surrounds the longitudinal cylindrical side wall (2015) and the disk-shaped top end wall (2017). The gap (2155) provides a fluid flow passage adjacent a portion of the hot zone enclosure wall, and the fluid passage is in fluid communication with a system outlet port (2165). The air gap (2155) is further in fluid communication with the combustion chamber (2135) through one or more combustor exit ports (2150) and with one or more cold start combustion chambers (2300) through one or more cold start exit ports (2302). Thus, exhaust gases exiting each of the combustion chambers (2135) and the cold start combustion chamber (2300) flow over the outer surface of the hot zone enclosure wall before exiting the fuel cell stack assembly (2000) through the system exit port (2165). In one non-limiting exemplary embodiment, the dimension of the air gap (2155) from the outer surface of the wall (2015) to the inner surface of the wall (2510) ranges from 1 to 4 mm. The intermediate cylindrical enclosure also encloses the cold start combustion chamber (2300), which is further described below.

[0035] Each of the intermediate enclosure walls (2510, 2511, and 2513) comprises Hastelloy, a cobalt-nickel-chromium-tungsten alloy that combines excellent high temperature strength up to 2000°F (1095°C) with very good resistance to oxidizing environments. Other metal alloys are also suitable, including Monel, a family of alloys containing about 30% copper with up to 67% metallic nickel and small amounts of iron, manganese, carbon, and silicon. In any case, the intermediate enclosure walls (2510, 2511, and 2513) are preferably formed from a metal alloy having a thermal conductivity coefficient of less than about 25.0 W / m°K at the operating temperature of the hot zone. This much lower thermal conductivity coefficient of the intermediate enclosure wall compared to the thermal conductivity of the hot zone enclosure wall results in a much slower conductive heat flow from one area of ​​the intermediate enclosure wall to another compared to the much higher heat flow of a hot zone enclosure wall formed from a metal alloy having a thermal conductivity coefficient of at least four times that of the hot zone enclosure wall. Thus, in accordance with one aspect of the disclosure, the intermediate enclosure walls (2510, 2511, and 2513) are formed as a second heat conduction path having a slower rate of heat transfer. In one other embodiment, the intermediate enclosure walls (2510, 2511, and 2513) may include steel or other metal alloys that may have a thermal conductivity coefficient of less than about 50.0 W / m°K without departing from the disclosure.

[0036] The outer cylindrical enclosure surrounds the intermediate cylindrical enclosure. The outer enclosure is surrounded by an open ended outer cylindrical side wall (2514) that mechanically interacts with a disk-shaped outer bottom wall (2518) and an opposing disk-shaped outer top end wall (2516). Each of the walls (2514, 2518, and 2516) preferably comprises aluminum or an aluminum alloy having a thermal conductivity coefficient of greater than 140 W / m°K to support rapid thermal energy conduction in order to provide a substantially uniform temperature of the outer cylindrical enclosure during operation. A thermal insulation layer (2512) is disposed between the outer surface of the intermediate enclosure wall and the inner surface of the outer enclosure wall, and the thermal insulation layer (2512) inhibits thermal energy radiated across the gap (2155) or carried through the gap by exhaust gases exiting the SOFC system from reaching the surfaces of the outer cylindrical side wall (2514) and the disk-shaped outer bottom wall (2518). Preferably, the insulating layer (2512) is configured to ensure that the surfaces of the outer cylindrical sidewall (2514) and the disk-shaped outer bottom wall (2518) remain within operating parameters, for example, the insulating layer (2512) is configured such that the temperature of the outer cylindrical sidewall (2514) and the disk-shaped outer bottom wall (2518) does not reach above about 110° C. Thus, according to one embodiment of the present disclosure, the outer enclosure walls (2514, 2518, and 2516) are formed as a third thermally conductive path.

[0037] A plurality of tubular fuel cells (2080), also known as fuel rods or rods, are supported longitudinally inside the cathode chamber (2010) between a disk-shaped tube top support wall (2082) and an opposing disk-shaped tube bottom support wall (2084). Each tubular fuel cell (2080) includes a solid oxide anode electrode support structure that forms the inner diameter of the tube. A solid ceramic electrolyte layer is formed on the outer diameter of the solid oxide anode electrode support layer, and a solid oxide cathode electrode layer is formed on the outer diameter of the solid electrolyte layer. Each tubular fuel cell (2080) is open at both ends and provides a cylindrical fluid conduit through which anode gas, also referred to herein as reformed fuel or syngas, flows. A plurality of tube retention flanges (2086) are optionally provided to support the tube ends against the tube top support wall (2082) and bottom tubular support wall (2084). Each tube retention flange (2086) also includes a conductive terminal that electrically interfaces with a DC power output module (140).

[0038] The solid anode electrode used to form the support layer of each tubular fuel cell (2080) may include a cermet material such as nickel and doped zirconia, nickel and doped ceria, or copper and ceria. Alternatively, the solid anode electrode may include a perovskite such as Sr2Mg1-xMnxMoO6-δ or La0.75Sr0.25Cr0.5Mn0.5O3-δ. In either case, the inner surface of each of the tubular fuel cells (2080) includes a solid oxide anode electrode, and the anode gas stream (2115) passes through each disk-shaped tube upper support wall (2082) so that only the anode gas stream (2115) enters each of the tubular fuel cells (2080) through the fuel inlet manifold (2055) and reacts with the solid anode electrode.

[0039] The solid oxide cathode electrode may include any one of lanthanum strontium cobalt oxide (LSC), lanthanum strontium cobalt iron oxide (LSCF), or lanthanum strontium manganite (LSM). The solid oxide cathode electrode forms the outer surface of each tubular fuel cell (2080). When the cathode chamber (2010) is filled with incoming air (2200) (i.e., cathode gas), the cathode gas reacts with the solid oxide cathode electrode formed on the outer surface of each tubular fuel cell (2080).

[0040] The electrolyte layer is disposed between the anode layer and the cathode layer. A preferred electrolyte layer includes an ion-conducting ceramic medium, preferably an oxygen ion conductor such as yttrium-doped zirconia or gadolinium-doped ceria. Alternatively, the electrolyte layer is a proton-conducting ceramic such as barium cerate or barium zirconate. Ideally, the electrolyte layer is formed with a sufficient thickness to provide a near-hermetic barrier between the anode and cathode electrodes to prevent anode and cathode gases from passing through the electrolyte layer.

[0041] The improved SOFC fuel cell stack assembly (2000) optionally includes a cold start combustion chamber (2300). The cold start combustion chamber (2300) is contained within the intermediate chamber wall and is surrounded by an intermediate longitudinal cylindrical side wall (2510), an intermediate top end wall (2513), and a disk-shaped top end wall (2017) of the cathode chamber. The cold start combustion chamber (2300) forms an annular chamber volume that partially surrounds the fuel reformer module (2020). When starting up the SOFC system from a cold start, a portion of the incoming fuel air mixture (2025) is diverted into the cold start chamber (2300) via the fuel inlet (2304) and ignited by the igniter (2306). Thus, during cold start, a portion of the incoming fuel air mixture (2025) is combusted in the cold start combustion chamber (2300). Thermal energy generated by the combustion in the cold start combustion chamber (2300) is radiated to its surrounding walls, including a disk-shaped top wall (2017) specially constructed with a copper core that is adapted to rapidly absorb the thermal energy. The disk-shaped top wall (2017) is further part of the hot zone enclosure wall surrounding the cathode chamber (2010) forming the first thermal conduction path. Once absorbed by the disk-shaped top wall (2017), the thermal energy is rapidly conducted through the hot zone enclosure walls, all of which are comprised of highly thermally conductive materials. Exhaust from the combustion occurring inside the cold start chamber (2300) exits the chamber through the exhaust port (2302) and passes through the air gap (2155) to the system exit port (2165). While passing through the gap (2155), the combustion exhaust transfers thermal energy to the hot zone enclosure walls (2015) and (2016) by radiation and convection to further assist in heating the hot zone enclosure walls to the desired steady state operating temperature.

[0042] The incoming fuel air mixture (2025) enters the improved SOFC fuel cell stack assembly (2000) via a fuel reformer module (2020). In the preferred embodiment, the fuel reformer is a catalytic partial oxidation (CPOX) reactor. The fuel reformer module (2020) receives the incoming fuel air mixture (2025) through a fuel input conduit (2045) and reforms the incoming fuel air mixture (2025) to provide a reformed fuel or syngas (2027) that is used as an anode gas to react with the solid oxide anode electrodes formed on the inner walls of each of the tubular fuel cells (2080). The reformed fuel or syngas (2027) exits the fuel reformer module (2020) and enters a fuel inlet manifold (2055). The fuel inlet manifold (2055) is configured to distribute the anode gas to the top or input end of each of the multiple tubular fuel cells (2080). At the lower or output end of each tubular fuel cell (2080), the spent fuel (2028), including hydrogen-depleted anode gas, exits the tubular fuel cell into a combustion chamber (2135) where it is mixed with spent cathode gas (2026) or oxygen-depleted air and burned.

[0043] Inlet air (2200), or cathode gas, shown as a dotted line, enters the improved SOFC fuel cell stack assembly (2000) via the cathode supply tube (2145), passes through the recuperator chamber (2210) where it is heated by its surface, and then re-enters the cathode supply tube via the recuperator output port (2235). The heated air then passes through the combustion chamber (2135) as it flows through the cathode supply tube (2145), where the air is further heated by the thermal energy generated by combustion and transferred to the wall of the cathode supply tube (2145) before entering the cathode chamber (2010). A number of air outlet ports (2240) pass through the cathode supply tube (2145) and into the interior of the cathode chamber (2010), where the heated air enters the cathode chamber (2010) through the air outlet port (2240). Once inside the cathode chamber, the heated air or cathode gas reacts with the solid oxide cathode electrodes formed on the outer surface of each tubular fuel cell (2080). The spent cathode gas (2026) exits the cathode chamber through the cathode chamber exit port (2245) into the combustion chamber (2135) where it is mixed with the spent anode gas (2028) and combusted. The exhaust gas exits the combustion chamber (2135) through the combustor exit port (2150) into the air gap (2155), heating the walls of the recuperator chamber (2210) as it flows towards the system exit port (2165).

[0044] Cross-section of top of solid oxide fuel cell stack The schematic diagram of Figure 2 shows a schematic side cross-sectional view of an improved SOFC fuel cell stack assembly (2000) showing only two tubular fuel cells (2080) for ease of illustration. However, a preferred stack includes more than two tubular fuel cells (2080) with the fuel cells arranged within the cathode chamber (2005) in a manner that provides efficient use of space, promotes efficient gas flow patterns, and provides the desired power output at the desired voltage.

[0045] Referring now to Figure 5, the figure shows a non-limiting schematic top cross-sectional view of a non-limiting exemplary cathode chamber of an improved SOFC stack (5000) of one example of the present disclosure. The cathode chamber (5002) is surrounded by an open-ended longitudinal cylindrical sidewall, such as the longitudinal cylindrical sidewall (2015) shown in Figure 2, that defines a circumferential edge (5010). The inner shaded region (5015) represents the longitudinal middle cylindrical sidewall (2510) and the void (2155) shown in Figure 2. The outer shaded region (5020) represents the insulation layer (2512) and the outer cylindrical sidewall (2514) shown in Figure 2.

[0046] The cathode supply tube (5025) is positioned at the center of the cathode chamber (5002) and distributes cathode gas within the cathode chamber through a plurality of radially disposed air outlet ports, such as (2240) shown in Figure 2. A central longitudinal axis (5030) centers the cathode supply tube (5025) and the circumferential edge (5010).

[0047] The improved SOFC stack (5000) includes a plurality of substantially coincident tubular fuel cells (5040), each including a solid oxide anode electrode having a solid oxide cathode electrode formed on the outer diameter of each tubular fuel cell (5040) structurally forming an inner diameter of each tubular fuel cell (5040). The first plurality of tubular fuel cells are arranged in an inner circular pattern (5035), with the centers of each of the first plurality of tubular fuel cells being at the same radial distance from the longitudinal central axis (5030) as indicated by the inner circular pattern (5035). The inner circular pattern (5035) may be a symmetrical circular pattern with the inner tubular fuel cells equally spaced around the inner circular pattern (5035), or the first plurality of tubular fuel cells may be positioned around the inner circular pattern (5035) with a non-uniform angular distribution or separation.

[0048] The second plurality of tubular fuel cells are arranged in an outer circular pattern (5045) with the center of each of the second plurality of tubular fuel cells being the same radial distance from the central longitudinal axis (5030) as indicated by the outer circular pattern (5045). The outer circular pattern (5045) may be a symmetrical circular pattern with the second plurality of fuel cells equally spaced about the outer circular pattern (5045) or the second plurality of fuel cells may be positioned about the outer circular pattern (5045) with a non-equilibrium angular distribution of angular separation. In this exemplary embodiment, the total number of fuel cells is twenty-two (22). Other patterns of fuel cell distribution with other total numbers of fuel cells may be used without departing from this disclosure.

[0049] Improved CPOX fuel reformer 2-4, a fuel reformer system (3000) according to the present disclosure is shown in schematic side cross-sectional view in FIG. 3 and in partially exploded side cross-sectional views in FIGS. 4 and 4A. The fuel reformer system (3000) includes a fuel reformer module (3020) mounted on a fuel inlet manifold (3055). The fuel reformer module (3020) includes a fuel furnace body (3040) configured to receive an incoming fuel air mixture (3025), i.e., unformed fuel, in a cylindrical fuel chamber (3005) surrounded by an annular perimeter wall (3010), by a reactor shield base wall (3015), and by a fuel chamber cap (3017). In a preferred embodiment, the fuel chamber cap (3017) is welded to the annular side wall (3010). The fuel reformer system (3000) further includes a cylindrical catalyst body (3030). Each of the fuel furnace body (3040) and the cylindrical catalyst body (3030) is installed in a cylindrical catalyst cavity (3035) where the cylindrical catalyst body (3030) is located immediately above the fuel inlet manifold (3055) and the fuel furnace body (3040) is located immediately above the cylindrical catalyst body (3030). Each of the fuel furnace body (3040) and the cylindrical catalyst body (3030) is configured to provide fluid communication between the cylindrical fuel chamber (3005) and the fuel inlet manifold (3055).

[0050] Preferred reactor body materials have a thermal conductivity coefficient greater than 100 W / m°K and sufficient thermal mass or material volume to rapidly conduct thermal energy away from the interface between the fuel reactor body (3040) and the catalyst body (3030). Preferred catalyst body materials include ceramic substrates configured to provide reliable operation in the elevated temperature and chemically harsh environment of the CPOX reaction. Typically, ceramic materials have a thermal conductivity coefficient less than about 40 W / m°K, but often less than about 10 W / m°K, reducing the rate of thermal conduction from one region of the catalyst body to another.

[0051] In this non-limiting exemplary embodiment, the cylindrical catalyst cavity (3035) has a sidewall formed by the inner diameter of the annular enclosure wall (3060) formed with a central longitudinal axis coaxial with the central longitudinal axis (2060) as shown in Figure 2. The cylindrical catalyst cavity (3035) includes two open ends, each forming one circular opening through the disk-shaped outer top end wall (2516) of the outer enclosure and the other circular opening through the disk-shaped top end wall (2017) of the hot zone enclosure.

[0052] In a preferred embodiment, the annular enclosure wall (3060) is formed to have a lower thermal conductivity than the fuel furnace body (3040) to inhibit heat transfer between the annular enclosure wall (3060) and the fuel furnace body (3040). In a preferred embodiment, the annular enclosure wall (3060) comprises Hastelloy or Monel, each having a high nickel content to resist oxidation damage, each having a suitable service temperature rating, for example, greater than 400°C, and each having a thermal conductivity coefficient of less than about 25.0 W / m°K. Additionally, the annular enclosure wall (3060) is a thin wall, for example, 0.02 to 0.1 inches thick, to further facilitate heat transfer therethrough.

[0053] The annular enclosure wall (3060) is thermally conductively connected to the disk-shaped top wall (2017) at its lower open end, which is part of the hot zone enclosure wall defined above as the first thermal conduction path. The annular enclosure wall is thermally conductively connected to the disk-shaped outer top wall (2516) at its upper open end, which is part of the outer enclosure wall defined above as the third thermal conduction path. The annular enclosure wall (3060) is thermally conductively connected to the intermediate top wall (2513) between its upper end and the open end of its lower end, which is part of the intermediate enclosure wall described above as the second thermal conduction path. Thus, according to one aspect of the present disclosure, the annular enclosure wall (3060) is formed as a fourth thermal conduction path that is thermally conductively connected to each of the first thermal conduction path, the second thermal conduction path, and the third thermal conduction path.

[0054] The catalyst body support flange (3065) extends from or is formed by the disk-shaped top end wall (2017). The catalyst body support flange (3065) is sized to define a diameter of the circular opening (3070) that is small enough to prevent the cylindrical catalyst body (3030) from passing through the circular opening (3070). The first annular washer (3075) is disposed between the catalyst body support flange (3065) and a bottom surface of the cylindrical catalyst body (3030). The first annular washer (3075) provides a gas seal with the cylindrical catalyst cavity (3035) when a longitudinal downward pressure is applied to the cylindrical catalyst body (3030). In addition, the first annular washer (3075) is configured as an insulator that thermally isolates the catalyst body support flange (3065) from the disk-shaped top end wall (2017). Preferably, the first annular washer (3075) comprises alumina formed with a sufficient thickness and appropriate outer peripheral diameter dimensions to provide the desired gas seal and thermal insulation properties. More generally, the first annular washer (3075) preferably comprises a non-porous material with very low thermal conductivity, for example having a thermal conductivity coefficient of less than 40 W / m°K, including most ceramic materials.

[0055] The diameter of the cylindrical catalyst cavity (3035) is sized to receive an annular insulating element (3080) within the cylindrical catalyst cavity (3035) surrounding the cylindrical catalyst body (3030). The annular insulating element (3080) is provided to thermally isolate the cylindrical catalyst body (3030) from the annular enclosure wall (3060). In addition, the annular insulating element (3080) is configured to precisely center the cylindrical catalyst body (3030) with respect to the central longitudinal axis of the cylindrical catalyst cavity (3035) and may be further configured to angularly orient the cylindrical catalyst body (3030) for precise angular alignment with one or more features of the fuel furnace body (3040). Both the first annular washer (3075) and the annular insulating element (3080) are provided to prevent heat conduction from the enclosure walls, e.g., the annular enclosure wall (3060) and the top end wall (2017), to the catalyst body (3030), which preferably operates at a higher temperature than the cylindrical catalyst body.

[0056] The cylindrical catalyst body (3030) comprises a solid non-porous ceramic substrate formed to include a plurality of longitudinally disposed catalytic fuel passages (3085) each completely passing through the cylindrical catalyst body (3030). Each catalytic fuel passage (3085) provides an individual fuel conduit extending longitudinally through the cylindrical catalyst body (3030). As such, each catalytic fuel passage provides fluid communication between the cylindrical catalyst cavity (3035) and the fuel inlet manifold (3055). Additionally, the inner surface of each of the catalytic fuel passages (3085) is formed with a catalytic layer (3090) coated thereon. The catalytic layer (3090) includes a catalytic material usable to reform an incoming fuel-air mixture (3025) by catalytic partial oxidation, an exothermic reaction that causes partial combustion of the fuel-air mixture (3025). In this non-limiting exemplary embodiment, the preferred catalytic layer (3090) includes a metallic or oxidized phase of rhodium (Rh). Other suitable catalysts that can be used for the catalyst layer (3090) include Pt, Pd, Cu, Ni, Ru, and Ce. The solid non-porous ceramic substrate used to form the cylindrical catalyst body (3030) preferably comprises alumina or any other non-porous material that has a relatively low thermal conductivity coefficient compared to the thermal conductivity coefficient of the fuel furnace body (3040). In this non-limiting embodiment where a ceramic substrate is used, the thermal conductivity coefficient of the catalyst body is less than 40 W / m°K.

[0057] As explained further below, the incoming fuel-air mixture (3025) enters the cylindrical fuel chamber (3005), passes through the reactor shield base wall (3015), and enters each of the catalytic fuel passages (3085) where it reacts with the catalytic layer (3090) and then enters the fuel inlet manifold (3055) that is distributed to each of the tubular fuel cells (2080).

[0058] Fuel furnace body 2, 3, 4, and 4A, the fuel furnace body (3040) is partially disposed within the cylindrical catalyst cavity (3035) and extends partially into the cold zone through the disk-shaped outer top end wall (2516), such that at least a portion of the fuel furnace body (3040) is exposed to the outside air. The annular perimeter wall (3010) provides a cylindrical sidewall of the cylindrical fuel chamber (3005). The fuel input conduit (2025) passes through the annular perimeter wall (3010) to deliver the incoming air-fuel mixture (2025 / 3025) to the cylindrical fuel chamber (3005). As will be appreciated, other geometric shapes can be used to form the annular perimeter wall (3010) and the fuel chamber (3005), which can have a rectangular, oblong or other cross section in their transverse cross section.

[0059] The reactor shield base wall (3015) comprises a circular bottom wall of a cylindrical fuel chamber (3005) that is preferably integrally formed with the annular perimeter wall (3010). However, the reactor shield base wall (3015) and the annular perimeter wall can be formed as separate pieces and joined together, for example, by welding, soldering, mechanical fasteners, and other suitable joining techniques. A plurality of base wall fuel passages (3095) each pass completely through the reactor shield base wall (3015) along a longitudinal axis, for example, with each base wall fuel passage parallel to the central longitudinal axis (2060). Each base wall fuel passage (3095) provides a fuel conduit that extends longitudinally through the reactor shield base wall (3015). Additionally, each base wall fuel passage (3095) is longitudinally aligned with, and in fluid communication with, a corresponding one of the plurality of catalyst fuel passages (3085) passing through the cylindrical catalyst body (3030).

[0060] As shown in Figures 4 and 4A, the interface (3032) is defined by the bottom outer surface of the reactor shield base wall (3015) and the top or input surface of the cylindrical catalyst body (3030). In a non-limiting exemplary embodiment, one or the other or both of the two surfaces forming the interface (3032) include a raised feature (3033). The raised feature may include a circular ring or multiple, preferably three, discreet raised protrusions formed at one or more locations extending from the bottom surface of the reactor shield base wall (3015) in a position that brings the raised feature into contact with the opposing surfaces at the interface (3032) to provide a small gap between the two opposing surfaces. More generally, the interface (3032) is formed with a gap between the bottom surface of the reactor shield base wall (3115) and the top surface of the cylindrical catalyst body (3030). All of the gaps are provided to allow radiative thermal energy emanating from each of the catalytic fuel passages to impinge on the bottom surface of the reactor shield base wall (3015) and to allow substantially all of the bottom surface of the reactor shield base wall (3015) to be available to absorb the thermal radiation impinging thereon.

[0061] At the interface (3032), each base-wall fuel passage (3095) is aligned with its corresponding catalyzed fuel passage (3085) along a substantially coaxial longitudinal axis. In this configuration, the fuel-air mixture (2025) delivered to the cylindrical fuel chamber (3005) passes from the cylindrical fuel chamber (3005) through each of the base-wall fuel passages (3095), flows across a gap provided between the surfaces at the interface (3032), and enters each of the corresponding catalyzed fuel passages (3085). Once inside the catalyzed fuel passages (3085), the fuel-air mixture begins to react with the catalyst-coated sidewall surface (3090), and the fuel-air mixture initiates a catalyzed partial oxidation reaction used to convert the fuel-air mixture to reformed fuel or syngas. According to one aspect of the present disclosure, thermal energy generated by the CPOX reaction occurring within the catalytic fuel passages (3085) is radiated onto a bottom surface of the reactor shield base wall (3115) for partial absorption thereby. Additionally, thermal energy generated by the CPOX reaction occurring within the catalytic fuel passages (3085) is radiated onto an inner surface of the base wall fuel passages (3095) for partial absorption thereby.

[0062] The fuel furnace body (3040) is formed from a material that has a relatively high thermal conductivity compared to that of the ceramic material used to form the cylindrical catalyst body (3030). A preferred reactor body material has a thermal conductivity coefficient of greater than 100 W / m°K. Thus, in one non-limiting exemplary embodiment, the entire fuel furnace body (3040) is formed from a unitary piece of copper or a copper alloy, from a unitary piece of beryllium or a beryllium alloy, from a unitary piece of aluminum or an aluminum alloy, from a unitary piece of brass or a brass alloy, from a unitary piece of tungsten or a tungsten alloy, where the alloy may include molybdenum, nickel, chromium, brass, tungsten, etc. In this example, unitary means that the entire fuel furnace body (3040) is formed from a single piece of metal, for example, cast or machined. In an alternative embodiment, the fuel furnace body (3040) can be formed from multiple cast or machined elements assembled together, for example, welded, brazed, or mechanically fastened in a manner that provides a continuous thermal conduction path. In either case, the desired material has a thermal conductivity coefficient of at least 100 W / m°K, with materials having a thermal conductivity coefficient of greater than 300 W / m°K being used. In addition, the wall thickness and / or thermal mass of the fuel reactor body (3040) is sufficient to promote rapid heat transfer from hot regions of the reactor body (3040) proximate the interface (3032) to cooler regions of the reactor body (3040), e.g., regions disposed outside the hot zone, to minimize temperature gradients between the interface (3032) and elements of the reactor body disposed outside the hot zone. A further feature of the reactor body material is that it preferably has a service temperature of at least greater than 200°C, and preferably up to 1000°C.

[0063] In this non-limiting exemplary embodiment, the fuel furnace body (3040) is formed from aluminum, preferably aluminum 6061 alloy, which has a thermal conductivity coefficient of about 167 W / m°K. Aluminum and aluminum alloys are preferred because they spontaneously form a stable oxide layer that protects the bulk structure from corrosive oxidation damage and can be used without additional applied protective coatings. In addition, aluminum and aluminum alloys can be anodized to prevent or reduce surface oxidation. In a preferred embodiment, the entire fuel furnace body (3040) includes a solid element including one piece of aluminum 6061 alloy, however, the fuel furnace body (3040) may include an assembly formed by assembling multiple individual subassembly elements using mechanical fasteners, welding or brazing, or using interlocking mechanical features, etc., without departing from this disclosure.

[0064] More specifically, in accordance with an important aspect of the present disclosure, the relative thermal conductivities of each of the cylindrical catalyst body (3030), the annular enclosure wall (3060), and the fuel furnace body (3040) are selected to facilitate heat transfer from the interface (3032) to the heat sink flange (3100) disposed outside the hot zone, and to facilitate absorption of thermal radiation impinging on the surface of the reactor shield base wall (2015). This is accomplished by configuring the fuel furnace body (3040) as the most thermally conductive element locally at the interface (3032) and configuring the fuel furnace body (3040) to extend outside the hot zone, for example, by exposing the surface of the fuel furnace body (3040) to the outside air, for example, by either moving air passing over the surface of the fuel furnace body or by passively cooling it. Thus, the configuration of the fuel furnace body (3040) establishes and maintains a temperature gradient between the interface (3032) and the ambient air outside the hot zone by providing a thermal conduction path between the interface (3032) and the ambient air, and a cooler portion of the fuel furnace body provided by exposing a portion of the fuel furnace body to the ambient air. The resulting temperature gradient between the portion of the fuel furnace body exposed to the ambient air and the portion of the reactor body proximate the interface (3032) tends to promote substantially continuous thermal energy conduction through the fuel furnace body (3040) from the interface (3032) to the portion of the fuel furnace body exposed to the ambient air.

[0065] The fuel furnace body (3040) includes a heat dissipating flange (3100), e.g., a disk-shaped flange, extending radially from the annular peripheral wall (3010). The heat dissipating flange (3100) is supported outside the outer enclosure on the disk-shaped outer top wall (2516) and exposed to the atmosphere. Preferably, the heat dissipating flange (3100) is integrally formed with the annular peripheral wall (3010), although the heat dissipating flange (3100) may include a separate element attached to the annular peripheral wall (3010) by welding, soldering, mechanical fasteners, or other attachment means.

[0066] The annular seal plate (3105) is disposed between the disk-shaped outer top wall (2516) and the heat dissipation flange (3100) and provides a mechanical interface between the top surface of the disk-shaped outer top wall (2516) and the bottom surface of the heat dissipation flange (3100). The annular seal plate (3105) includes a central through hole sized to receive the annular peripheral wall (3010) therethrough. An O-ring seal element (3110) or the like is disposed between the annular seal plate (3105) and the heat dissipation flange (3100), for example in an O-ring groove, and serves to gas seal the upper portion of the cylindrical catalyst cavity (3035). A second O-ring seal element (3115) may be provided between the top surface of the disk-shaped outer top wall (2516) and the bottom surface of the annular seal plate (3105).

[0067] Both the annular seal plate (3105) and the heat dissipation flange (3100) are attached to the disk-shaped outer top end wall (2516) by fasteners or the like in a manner that applies a downward force against the fuel reactor body (3040) to secure the bottom surface of the reactor shield base wall (3015) against the upper surface of the cylindrical catalyst body (3030) at interface (3032), or a raised surface (3033) formed thereon, and further to compress the O-ring seal element (3110).

[0068] 6, a schematic top cross-sectional view of the fuel furnace body (3040) shows a heat release flange (3100) extending radially from the annular perimeter wall (3010). Fasteners (3120) extend through the heat release flange (3100) and the annular seal plate (3105) to attach the heat release flange (3100) and the annular seal plate (3105) to the disk-shaped outer top end wall (2516). The annular perimeter wall (3010) extends radially outward from the annular enclosure wall (3060) such that the seal plate (3105) seals the cylindrical catalyst cavity (3035). An array (3125) of base wall fuel passages (3095) are shown passing through the reactor shield base wall (3015).

[0069] Referring now to FIG. 3, the fuel reformer system (3000) may include external cooling and temperature sensing elements readable by the electronic controller (190). In one non-limiting exemplary embodiment, an air moving element (3130), such as a rotating fan blade attached to a rotating motor operable by the electronic controller (190), is arranged to induce airflow over the heat dissipation flange (3100), thereby increasing convective thermal energy transfer from the flange (3100) to the surrounding outside air. In addition, a temperature sensing element (3135) in contact with a surface of the heat dissipation flange (3100), or one or more other surfaces of the fuel furnace body (3040), can be used to deliver a temperature signal to the electronic controller (190) via a communication path (3140). The operation of the air moving element (3130) may be constant or variably triggered by changes in the temperature signal emitted by the temperature sensing element (3135). In one non-limiting operating mode, the air movement element (3130) is activated when the temperature sensing element (3135) reports a temperature above a desired high temperature limit, e.g., above 50°C, and the air movement element (3130) is not activated when the temperature sensing element (3135) reports a temperature below the desired high temperature limit, e.g., below 45°C.

[0070] In addition, the temperature signal emitted by the temperature sensing element (3135) can be used to control the operation of the cold start combustion chamber (2300) to stop the flow of fuel to the cold start combustion chamber (2300) when the temperature of the heat dissipation flange (3100) reaches a desired steady state temperature range.

[0071] In one example mode of operation, the electronic controller (190) receives a temperature signal from the temperature sensing element (3135) via the communication path (3140) and determines an instantaneous flange temperature based thereon. The electronic controller (190) then determines whether the flange temperature is within one or more desired temperature ranges, and if not, executes various commands such as operating the air moving element (3130) by commanding the fuel delivery module (197) to close a gas flow actuator valve or the like, or starting or stopping the flow of fuel to the cold start combustion chamber (2300), or stopping fuel delivery to the fuel reformer system (3000) when the instantaneous temperature indicated by the temperature sensing element (3135) exceeds a safe operating limit. In one non-limiting mode of operation, the electronic controller (190) is configured to operate the air moving element (3130) when the temperature of the heat dissipating flange (3100) exceeds 50° C. In other exemplary embodiments, the air moving element (3130) may have multiple operating modes that can be used to move more or less air as needed based on different temperature thresholds.

[0072] Interface configuration 4, an exploded side cross-sectional view of the interface (3032) between a corresponding pair of base wall fuel passages (3095) and catalytic fuel passages (3085) shows that each of the corresponding pairs of reactor shield base wall fuel passages (3095) and catalytic fuel passages (3085) are aligned along a common longitudinal axis. Thus, each corresponding pair of base wall fuel passages and catalytic fuel passages provides a vertical flow path for the fuel-air mixture to pass from the cylindrical fuel chamber (3005) to the fuel inlet manifold (3055). As mentioned above, a gap may be provided between the mating surfaces of the interface (3032) to expose a surface of the reactor shield base wall (3015) to thermal radiation emitted by the CPOX reaction, although the gap is not shown in FIG. 4 to simplify the present disclosure. As indicated by reference numeral (3090), a catalyst layer is formed on the sidewall of each catalytic fuel passage (3090). As further shown in FIG. 4, the arrow pointing to FIG. 4A indicates that FIG. 4A is a schematic diagram of the interface (3032) as viewed from the interior of the catalytic fuel passage (3085) toward its fuel input end. In this non-limiting exemplary embodiment, the diameter (D) of each of the circular base wall fuel passages (3095) is 1.3 mm, and the thickness of the reactor shield base wall is 13 mm, so that each fuel passage (3095) is 13 mm long. In a preferred embodiment, the ratio of the longitudinal length of a fuel passage to its diameter is at least 5, preferably 10, and up to 20. The sidewall dimension of each of the rectangular catalytic fuel passages (3085) is 1.3 mm, and the thickness of the cylindrical catalytic body (3030) is approximately 25.4 mm, so that each catalytic fuel passage (3085) is 25.4 mm long. In a preferred embodiment, the ratio of the longitudinal length of a catalyst passage to its rectangular side dimension is at least 10, preferably 15-25, and up to 40.

[0073] The cylindrical catalyst body (3030) has a circular cross-section and an array of catalytic fuel passages (3085) are formed within the circular cross-section over a circular area of ​​25.4 mm (1.0 inch) diameter. Each of the catalytic fuel passages of the array has a rectangular cross-section and extends completely through the cylindrical catalyst body (3030). In this non-limiting exemplary embodiment, each rectangular catalytic fuel passage has a side dimension of 1.3 mm and a length of 25.4 mm. Alternatively, the catalyst body (3030) and array of fuel passages may have other non-circular cross-sections without departing from this disclosure.

[0074] The reactor shield base wall (3015) is formed with an array of circular base wall fuel passages (3095) formed in a circular array area of ​​25.4 mm (1.0 inch) diameter opposite the circular array area of ​​the cylindrical catalyst body (3030). In this non-limiting exemplary embodiment, each circular base wall fuel passage (3095) has a diameter of 1.3 mm and a length of 13.0 mm. Alternatively, the reactor shield base wall (3015) and the array area formed thereon can have other non-circular cross sections without departing from this disclosure. As described above, each circular base wall fuel passage (3095) in the array of base wall fuel passages is coaxial with one of the rectangular catalyst fuel passages (3088) in the array of catalyst fuel passages, such that the central longitudinal axis of each base wall fuel passage (3095) is coaxial with the central longitudinal axis of the corresponding catalyst fuel passage (3085).

[0075] The solid material of the reactor shield base wall (3015) surrounds each circular base wall fuel passage, and the solid material of the cylindrical catalyst body (3030) surrounds each rectangular catalyst fuel passage. In a non-limiting exemplary array pattern, all passages are arranged in multiple parallel linear arrays. Each linear array is offset from an adjacent linear array by the same pitch dimension of 1.2 times the diameter of the circular passage. In this example, the pitch dimension is 1.56 mm. Based on this non-limiting exemplary array disposed on a circle with a diameter of 25.4 mm, the total number or circular passages (3095) within the circular array area is approximately 208.

[0076] The combined area of ​​the 208 passages, each with a diameter of 1.3 mm, is 276 mm 2 The total area of ​​the array with a diameter of 25.4 mm is 507 mm 2 Therefore, the bottom surface of the reactor shield base wall (3015) has approximately 231 mm of space facing the interface (3032) available to absorb radiant heat energy impinging thereon. 2 The area of ​​solid material within the circular array area is approximately 231 mm 2 In this exemplary embodiment, the ratio of solid surface area to hole diameter area is 0.84. As a percentage of the total area of ​​the circular array, approximately 54% of the total area is circular passage area and approximately 46% of the total area is solid material area. As will be appreciated by those skilled in the art, the ratio of surface area to hole diameter area can be increased by decreasing the diameter of the circular base wall fuel passages. Since the surface area at the interface (3032) is impinged by the radiant heat energy released by the CPOX reaction, increasing the solid surface area without a change in temperature increases the thermal energy absorption into the reactor shield base wall (3015). In a preferred embodiment, the ratio of solid surface area to hole diameter area is in the range of 0.75 to 0.9.

[0077] As discussed above, the radiant heat energy released by the CPOX reaction also enters the circular base wall fuel passages (3095) and impinges on their inner surfaces with at least a portion of the radiant heat energy. The angle of incidence of the radiant heat energy impinging on the inner surfaces of the circular base wall fuel passages (3095) is approximately the grazing angle, but is long compared to the diameter of the passage and the reflected energy, even if reflected at incidence near the grazing angle, will eventually impinge on and be reflected from the inner surface over many reflection cycles as it traverses the fuel passage (3095). The total surface area of ​​the inner surfaces of all 208 circular passages is approximately 11043 mm 2 It is.

[0078] Referring now to FIG. 4A, the diagram illustrates the interface (3032) of a single circular fuel passage (3095) and a single rectangular catalytic fuel passage (3085) as viewed from the fuel inlet manifold (3055). As further illustrated, in accordance with the present disclosure, each base wall passage (3095) has a circular cross-section having a diameter (D) along its entire longitudinal length, and each catalytic fuel passage (3085) has a rectangular cross-section having a lateral dimension (S) along its entire longitudinal length. In the non-limiting exemplary embodiment of FIG. 4A, the diameter (D) and lateral dimension (S) are equal, and the area filled by the vertical lines (B) is the exposed surface area of ​​the bottom surface of the reactor shield base wall (3015). The surface area (B) is located at the interface (3032) proximate the input end of each catalytic fuel passage (3085) and is specifically configured to absorb thermal radiation emanating from the catalytic surface (3090). In addition, when a gap is provided between the opposing surfaces of the interface (3032), thermal radiation enters the gap in part by reflection from the surface area (B).

[0079] Equation (1) below provides the area of ​​the surface area (B). A s -A c =S 2 -π(D / 2) 2 Equivalent: 1

[0080] However, A s is the area of ​​a rectangle (3085) with side length (S).

[0081] A C is the area of ​​the circle (3095) with diameter (D).

[0082] When S=D, the surface area AB of surface area (B) is: (A B )=S 2 (1-π / 4)=0.2146S 2 Equivalent: 2

[0083] In other words, the area of ​​surface (B) is approximately 21% of the area of ​​rectangle (3085). As will be appreciated, by increasing area AB, for example by increasing the side dimension from (S) to (S1), or decreasing the diameter (D) of circular passage (3095), the exposure of surface (B) to thermal radiation generated within the catalyst fuel passage may be increased. As the side dimension of the catalyst fuel passage increases from (S) to (S1), area SB may increase to 50% of the area of ​​the rectangle of dimension (S1) when the ratio S1 / D is equal to approximately 1.253.

[0084] The surface area (B) is directly exposed to the CPOX reaction occurring inside the rectangular catalytic fuel passage (3085) and is in an optimal position to absorb the thermal energy radiated from the catalytic fuel passage. Even if there is no gap at the interface (3032), in a non-limiting exemplary embodiment of the present disclosure, the surface (B) as well as the inner surface of the base wall fuel passage (3095) provide sufficient surface area of ​​the cooler reactor shield base wall (3015) to absorb enough radiant heat energy released by the CPOX reaction to prevent burn-through of the catalyst layer. However, as will be appreciated by those skilled in the art, when gaps are provided, additional radiant heat energy may enter the gap and be reflected back to impinge on the cooler solid material surface area of ​​the reactor shield base wall (3015) over many cycles to absorb the additional thermal energy released by the CPOX reaction.

[0085] Thermal Energy Transfer Without wishing to be bound by theory, applicants believe that as the fuel-air mixture (2025, 3025) heats to a suitable reaction temperature, an exothermic catalyzed partial oxidation reaction is initiated as soon as it contacts the catalyst layer (3090) proximate the interface (3032). Applicants further believe that the exothermic catalyzed partial oxidation reaction reaches a maximum temperature proximate the interface (3032), the maximum temperature being approximately 900-1000°C. In response to the rapid heating proximate the interface (3032), the temperature of the fuel-air mixture entering the catalyst fuel passages (3085) and the catalyst layer (3090) increases rapidly as thermal energy is absorbed by the fuel-air mixture, as well as by the catalyst layer (3090). In response to the increase in temperature, the fuel-air mixture rapidly expands in volume to fill the catalyst fuel passages (3085) and exits the catalyst fuel passages to fill the cylindrical catalyst cavity (3035) and the fuel inlet manifold (3055). During the expansion of the gases, more of the fuel / air mixture contacts the catalyst layer (3090) distal from the interface (3032) and contributes to the exothermic catalyzed partial oxidation reaction, thereby further heating and expanding the fuel / air mixture. Thus, most of the thermal energy generated by the catalyzed partial oxidation reaction is absorbed by the fuel / air mixture and transported through the catalytic fuel passages to the fuel inlet manifold (2055). In one example mode of operation, the volume of fuel / air mixture delivered to the CPOX reactor is expected to generate approximately 300 watts during the CPOX reaction.

[0086] A portion of the thermal energy generated by the catalyzed partial oxidation reaction is absorbed by the catalyst layer (3090). In this embodiment, the catalyst layer is a metal (e.g., Rh) with a thermal conductivity of about 150 W / m°K. Thus, the thermal energy absorbed by the catalyst layer (3090) is thermally conducted through the thickness of the catalyst layer to the ceramic catalyst body (3030) and further along the longitudinal length of the catalyst layer (3090). However, since the catalyst body (3030) is a ceramic material with a thermal conductivity of about 45 W / m°K, the thermal flux density (W / m 2) is low, so that thermal energy absorbed by the catalyst layer is re-released to the catalyst fuel passages instead of being thermally conducted into the ceramic material. However, this result is desirable because the low thermal flux density along the radial axis of the ceramic catalyst body prevents thermal energy from being conducted radially out of the catalyst fuel passages to the extent that the thermal energy is a) transferred to the fuel air mixture inside the fuel passages, or b) radiated from the ends of the fuel passages to either the fuel inlet manifold or surface area (B) described above, or c) radiated onto other exposed solid material surfaces of the reactor shield base wall, for example by entering gaps provided at the interfaces, or d) radiated into the circular base wall fuel passages and transferred by convection heat transfer to the incoming gas air mixture, or e) radiated onto the inner surface of the base wall fuel passages (3095) where it is absorbed thereby.

[0087] Therefore, the thermal energy absorbed by the catalyst layer is not easily dissipated into the ceramic catalyst body (3030). Instead, the thermal energy is re-emitted into the catalyst fuel passages, further heating the fuel-air mixture. In addition, the thermal energy emitted or reflected by the catalyst layer impinges on other surfaces of the catalyst layer, thereby being partially absorbed and partially reflected. However, without at least one outlet for the thermal radiation to exit the catalyst fuel passages, the energy absorption rate of the catalyst layer (3090) may exceed the energy re-emission rate, thereby causing the temperature of the catalyst layer to continue to increase until it burns out causing permanent damage to the catalyst body fuel passages.

[0088] As noted above, Applicants believe the total power generated by the CPOX reaction is 300 W. Using the Stefan-Boltzmann equation, listed below as Equation 3, the total power that can be absorbed by the collective surface area (B) shown in Figure 4A, i.e., based on 208 base wall passages (3095), can be estimated taking into account the surface area and temperature.

[0089] P=eσAS f (Tc 4 -Tb 4 )equivalent 3

[0090] Where P = net absorbed power (watts), e = surface emissivity, σ = 5.6703 x 10 -8 (W / m 2 K 4 ) Stefan-Boltzmann constant, A = area over which radiation is emitted (m 2 ), Sf - the view factor related to the angle of incidence at which radiation strikes a surface area A, T c = temperature of the radiation source (°K), and T b = temperature of surface area A (°K).

[0091] Of particular importance is when Tc and Tb are equal. Equation 3 indicates that the net radiated power absorbed by the reactor shield base wall (3015) is zero. Therefore, without the cooled surface area provided by the reactor shield base wall (3015), the surface temperatures inside the catalyst fuel passages could continue to increase until the catalyst layer overheated and burned out.

[0092] In a non-limiting exemplary embodiment, each rectangular catalyst fuel passage (3085) has a lateral dimension (S) equal to 1.3 mm (0.0013 m) and each circular base wall passage (3095) has a diameter of 1.3 mm. In a non-limiting exemplary embodiment, the collective area of ​​all surface areas (B) shown for an array of 208 passages is 7.38×10 m 2 Using the simplified case of a CPOX reaction temperature of 1000°C (1273°K), a temperature of each surface area AB of 100°C (373°K), and an emission coefficient e = 1.0, Equation 3 predicts that the combined surface area ABt can absorb about 11 W or about 3.6% of the power generated by the CPOX reaction.

[0093] If the interface (3032) is gapped such that the entire solid surface area of ​​the bottom of the reactor shield base wall (3015), denoted AS, is potentially available to absorb thermal energy, then the available solid material surface area AS is 2.31 x 10- 4 m 2and Equation 3 predicts that the area AS can absorb about 34 W or about 11.3% of the power generated by the CPOX reaction.

[0094] In addition, if the surface area of ​​the inside surfaces of all 208 circular fuel passages (3095) were potentially available to absorb thermal energy, the available surface area of ​​all circular fuel passages, denoted AP, would be 1.1043 x 10 2 m 2 , and Equation 3 predicts that the surface area AP can absorb about 1632 W or about 211% of the power generated by the CPOX reaction.

[0095] As a practical matter, the thermal energy absorption values ​​listed above are calculated using a view factor Sf=1 when thermal radiation impinges on the surface at normal incidence. For surface areas AS and AP, as well as for surface area ABt, a value of Sf=1 is not realistic. Furthermore, as a practical matter, the surface emissivity (e) of a severely oxidized aluminum surface is not 1.0, but instead is about 0.25 or less. Therefore, the energy absorption values ​​can be more realistically expressed using Equation 3 with a surface emissivity e=0.25 for all three surface areas ABt, AS, and AP, and a view factor Sf=1 for surface area ABt, and Sf=0.1 for surface areas AS and AP. In this case, Equation 3 predicts that surface area ABt potentially absorbs about 2.75 W, surface area AS potentially absorbs about 0.85 W, and surface area AP potentially absorbs about 44.6 W. Therefore, when maintained at approximately 100° C., the reactor shield base wall (3015) potentially absorbs approximately 16% of the total power released by the CPOX reaction.

[0096] Those skilled in the art will recognize that additional thermal energy may be absorbed by increasing the available surface area or by lowering the temperature of the reactor shield base wall (3015). As described above in accordance with this disclosure, the surface temperature of the heat sink flange (3100) is preferably maintained in the range of 50-100°C. This provides a temperature gradient between the reactor base wall (3015) and the heat sink flange (3100) while likely maintaining the temperature throughout the reactor shield body (3040) at approximately the same temperature due to the high thermal conductivity of the fuel furnace body (3040). As described above, this allows for the absorption of thermal energy from the CPOX reaction and prevents the unprocessed fuel passing through the fuel furnace body (3040) from reaching its auto-ignition temperature of 295-580°C depending on which fuel is being used.

[0097] Thus, maintaining the reactor shield base wall (3015) at a temperature of 100° C. during operation and providing a small gap at the interface (3032), e.g., about 1 mm, has the potential to absorb about 43 W of thermal energy, or about 14% of the total energy radiated by the CPOX reaction at a temperature of 1000° C. However, one skilled in the art will recognize that additional thermal energy can be removed from each of the catalyst fuel passages (3085) by increasing the view factor, increasing the surface area, and reducing the temperature of the fuel reactor body (3040).

[0098] Operational Mode Cold Start 1-3, the fuel input module (197) is operated by the electronic controller (190) from a cold start to deliver a fuel-air mixture to the cold start combustion chamber (2300) via a fuel input inlet (2304) and ignite the fuel-air mixture inside the cold start combustion chamber (2300) using an electrical igniter (2306) operable by the electronic controller (190). Simultaneously or immediately thereafter, the fuel input module (197) is also operated to deliver the fuel / air mixture to the fuel reformer module (3020) via a fuel input conduit (2045), through which the fuel-air mixture passes to the fuel input manifold (2055). Preferably, the initial flow rate of the fuel-air mixture delivered through the fuel reformer module is very low and is only intended to fill the SOFC system with an approximately fixed volume of the fuel-air mixture.

[0099] The ignition fuel inside the cold start combustion chamber (2300) heats the walls of the cold start combustion chamber (2300), but the top wall (2017) is configured to absorb more thermal energy than the other walls of the cold start combustion chamber. As the temperature of the top wall (2017) increases, thermal energy is thermally transferred from the top wall (2017) to other areas of the hot zone enclosure wall (115). In addition, the top wall (2017) and other walls of the hot zone enclosure (115) begin to emit thermal radiation to the fuel inlet module (2055) that is absorbed by the fuel-air mixture contained therein, increasing its temperature. Exhaust gases generated by burning the fuel-air mixture inside the cold start combustion chamber (2300) exit the cold start combustion chamber (2300) through the cold start outlet port (2302) and flow through the air gap (2155) to the system outlet port (2165). As the hot exhaust gas flows through the gap (2010), it radiates thermal energy to the outer surface of the longitudinal cylindrical side wall (2015) where the temperature increases.

[0100] The top end wall (2017) is attached to a longitudinal cylindrical side wall (2015) which is further attached to a disk-shaped tube bottom support wall (2084) and a disk-shaped isolation wall (2214). Collectively, each of the top end wall (2017), longitudinal cylindrical side wall (2015), disk-shaped tube bottom support wall (2084), and disk-shaped isolation wall (2114) form a hot zone enclosure wall (115). As discussed above, each of the hot zone enclosure walls is fabricated from one or more of copper, molybdenum, aluminum copper, copper nickel alloy, or combinations thereof, such that the entire hot zone enclosure wall structure (115) forms a continuous heat conduction path having a thermal conductivity coefficient of about 100-300 W / m°K, preferably greater than 200 W / m°K. Additionally, if any surface of the hot zone enclosure wall is exposed to an oxygen rich environment, preferably the wall surface is coated with nickel to prevent oxidation.

[0101] In the case of the three disk-shaped walls (2017, 2084, and 2214), each of these walls is configured to provide a thermal mass that can absorb heat energy and redistribute the absorbed heat energy to other regions of the hot zone enclosure wall by thermal conduction and by re-ejecting it to cooling areas around each disk-shaped wall, such as within the fuel inlet manifold (2055), cathode chamber (2010), combustion chamber (2135), recuperator chamber (2210), etc. Thus, when the top wall (2017) is heated by combustion inside the cold start combustion chamber (2300), the heat energy is absorbed by the top wall and rapidly conducted to all regions of the hot zone enclosure walls (2017), 2015, 2084, and 2214) until the entire hot zone enclosure wall assembly reaches an equilibrium temperature. Furthermore, as thermal energy is absorbed or released by the hot zone enclosure wall, its equilibrium temperature changes substantially uniformly across all areas of the hot zone enclosure wall due to its high thermal conductivity.

[0102] Thus, during startup, at least a portion of the thermal energy generated by the combustion of fuel in the cold start combustion chamber (2300) is absorbed by the top wall (2017). A further portion is absorbed by the longitudinal cylindrical side wall (2015) as the hot exhaust gases flow through the gap (2155) to the system exit port (2165). As the temperature of the top wall (2017) increases, it begins to re-emit thermal energy into the cooler fuel inlet manifold (2055), serving to increase the temperature of whatever fuel-air mixture is contained and / or flowing through it.

[0103] Eventually, the temperature of the fuel air mixture within the fuel inlet manifold (2055) reaches a suitable reaction temperature to initiate the CPOX reaction. The initial CPOX reaction occurs when the fuel air mixture, heated to the reaction temperature, contacts the catalyst layer (3090) adjacent the catalyst body input or top surface of the catalyst body located at the rear end or bottom surface and interface (3032) of the fuel reformer module (3020). Once the CPOX reaction is initiated at the output ends of some or all of the catalytic fuel passages (3085), the temperature within each catalytic fuel passage (3085) increases rapidly along its longitudinal length spreading the CPOX reaction to the interface (3032) and the CPOX reaction becomes self-sustaining.

[0104] Once a self-sustaining CPOX reaction is achieved, the fuel input module (197) is operated to discontinue the flow of the fuel-air mixture to the cold start combustion chamber (2300) and adjust the input rate of the fuel-air mixture delivered through the fuel reformer module (3020) as necessary to maintain the self-sustaining CPOX reaction and generate electrical power. However, combustion within the cold start combustion chamber (2300) may continue until the full power DC power output is also self-sustaining. The electronic controller (190) can recognize the self-sustaining CPOX reaction by various sensors including temperature sensors on the walls of the hot zone enclosure, by a temperature sensor (3135) on the heat dissipation flange (3100), by a temperature sensor located proximate the system exhaust port (2165), by detecting the DC power signal at the DC power output module (140), and by various other sensing means.

[0105] To heat the cathode gas, the electronic controller (190) operates the air input module (198) to deliver a flow of air / cathode gas to the air input port (2205). This step can occur simultaneously with ignition of the cold start chamber, or before ignition of the cold start chamber, but can also be delayed until a self-sustaining CPOX reaction is achieved. Preferably, the initial flow rate of the incoming air delivered through the recuperator chamber (2210) is very low, intended to fill the SOFC system with an approximately fixed volume of air.

[0106] The incoming air stream exits the cathode supply tube (2145) via the recuperator input port (2235), passes through the recuperator chamber (2210) to the recuperator output port (2235), and exits the cathode supply tube (2145) to the cathode chamber (2010) via a number of air outlet ports (2240). After reacting with the solid oxide cathode electrodes formed on the outer surface of each tubular fuel cell (2080), the air / cathode gas exits the combustion chamber (2135) and passes through the cathode chamber exit port (2245) to the combustion chamber (2135) where it mixes with the spent fuel-air mixture and is combusted. The combustion by-products then exit the combustion chamber via the combustor exit port (2150) to the void (2155) and exit the system via the system exit port (2165).

[0107] The primary air heating element is the disk-shaped isolation wall (2214) located inside the recuperator chamber (2210). As mentioned above, the disk-shaped isolation wall (2214) is part of the hot zone enclosure and therefore begins to increase in temperature during the start-up phase at approximately the same time as the increase in temperature of the disk-shaped top wall (2017) forming the base wall of the cold start combustion chamber (2300). In addition, the disk-shaped isolation wall (2214) is thermally coupled to the disk-shaped tube bottom support wall (2084), both walls being heated by burning the mixture of spent fuel and spent air inside the combustion chamber (2135). Thus, at approximately the same time that the disk-shaped top wall (2017) begins to radiate sufficient heat energy into the fuel input manifold (2055) to increase the fuel temperature, the disk-shaped isolation wall (2214) begins to radiate sufficient heat energy into the recuperator chamber (2210) to increase the incoming air temperature. At the same time, the hot zone enclosure walls are heating the air contained therein and radiating thermal energy to the cathode chamber (2010) which serves to heat the walls of the tubular fuel cells of the fuel cell stack (2005). Once the CPOX reaction becomes self-sustained, the flow rates of both the incoming air and the fuel-air mixture can be adjusted as needed to maintain the self-sustaining CPOX reaction and generate power at the desired power output amplitude.

[0108] 8.8.2 Initiation of SOFC reaction As described above, the fuel-air mixture and the incoming air / cathode gas are heated by the hot zone enclosure walls, which are heated by the combustion occurring inside the cold start combustion chamber (2300). Eventually, a self-sustaining CPOX reaction is initiated inside the catalytic fuel passages (3085), which heats the fuel-air mixture to a higher temperature and reforms the fuel into a syngas that can react with the solid oxide anode electrodes formed on the inner surface of each of the tubular fuel cells (2080). The higher temperature syngas also radiates thermal energy to the anode electrodes as it passes through the tubular fuel cells (2080). As the temperature of the anode electrodes increases, the cathode electrodes are heated by the thermal energy radiated to the cathode chamber (2010) by the longitudinal cylindrical side walls (2015) and by the heated air / cathode gas entering the cathode chamber (2010) from the recuperator chamber (2210).

[0109] Eventually, the anode and cathode electrodes, syngas, and air / cathode gas inside the cathode chamber reach reaction temperature and DC power begins to be generated and output to the DC power terminals. Eventually, the gas temperature inside the combustion chamber (2135) reaches the combustion temperature and the thermal energy generated by the combustion occurring inside the combustion chamber increases the incoming air temperature to a steady state operating temperature. In one non-limiting example operating mode, the syngas, incoming air, and tubular fuel cell (2080) have a steady state operating temperature of 350-1200°C, with a preferred operating temperature range of 800-1000°C. Meanwhile, the hot zone enclosure wall (115) constantly redistributes the thermal energy by thermal conduction such that the hot zone enclosure wall temperature rises and falls substantially uniformly over its entire area until the steady state operating temperature is reached and then maintained.

[0110] Fuel Reformer Operation Mode 3-4A, as discussed above, the fuel reformer module (3020) is at least partially thermally isolated from the cold start combustion chamber (2300) and the hot zone enclosure walls to prevent the fuel-air mixture inside the fuel chamber (3005) from reaching its auto-ignition temperature before entering the cylindrical catalyst body (3030). More specifically, depending on the fuel used, the fuel auto-ignition temperature range is approximately 295-580°C. In comparison, the operating temperature range of a SOFC system is 350-1200°C, depending on the fuel and electrode layer materials. In addition, as discussed above, the CPOX reaction temperature range is estimated to be 900-1000°C.

[0111] During cold start, the fuel air mixture (3020) enters the cylindrical fuel chamber (3005), passes through the reactor shield base wall (3015), then through the cylindrical catalyst body (3032) to the fuel input manifold (3055). The fuel air mixture then passes through the tubular fuel cells and finally exits the system. As mentioned above, the present disclosure manages the thermal energy generated by combustion inside the cold start combustion chamber (2300) in a manner that facilitates the transfer of the thermal energy to the disk-shaped top wall (2017) of the hot zone enclosure, rather than to the other cold start combustion chamber walls (2510 and 2511) and (2513). This is managed by constructing the disk-shaped top wall (2017) with a greater thermal mass than the combined thermal mass of the other walls (2510 and 2513).

[0112] More specifically, the thermal energy transfer (Q) is determined by the following equation 4: Q=Q=C th ΔTQ equivalent 4

[0113] Where Q = heat energy transfer (J), C th = thermal mass of the wall (J / °C), and ΔT = temperature difference between the hot gas and the wall.

[0114] In this example, ΔT is almost the same for each wall, but the thermal mass of each wall is different. this defined as the product of the component material mass (m) in g and the specific heat capacity (μ) in J / g°C, where the mass (m) is in cm 3 ) and the volume V of the component material in units (g / cm 3 ) multiplied by the material density (ρ). C th =ρVμ equivalent 5

[0115] In the formula, ρ=material density (g / cm 3 ), V = material volume (cm 3 ), and μ = material specific heat capacity of the material (J / g °C).

[0116] In a non-limiting exemplary embodiment, the disk-shaped top wall (2017) of the hot zone enclosure comprises mostly copper and includes other walls (2510), (2511), and (2513) of an intermediate enclosure surrounding the cold start combustion chamber (2300), each further surrounding a hot zone enclosure comprising mostly Hastelloy. For copper, the specific heat capacity (μ) is 0.385 J / g°C. For Hastelloy, a cobalt-nickel-chromium-tungsten alloy that combines excellent high temperature strength up to 2000°F (1095°C) with very good resistance to oxidizing environments, the specific heat capacity (μ) is 0.450 J / g°C. For copper, the density (ρ) is 8.96 g / cm 3 and for Hastelloy, the density (ρ) is 8.22 g / cm 3 The reason why the end wall (2017) absorbs more heat energy than the other walls adjacent to the cold start chamber (2300) is that the disk-shaped upper end wall (2017) (Q t ) of all the other walls connected (Q o ), which, when written in terms of Equation 4 when the term ΔT is the same for each wall, simplifies to: C th t>C th o or (ρ c Vtμ c )>(ρ h Voμ h )

[0117] In the formula, C th t = thermal mass of the top wall, C th o = combined thermal mass of other walls, Vt = volume of top wall, Vo = combined volume of other walls, ρ c = density of copper, ρ h = density of Hastelloy, and μ c = specific heat of copper, μ h = Specific heat Hastelloy.

[0118] As a result of this embodiment, Vt>1.07Vo.

[0119] In other words, the thermal mass of the upper disk-shaped top wall (2017) exceeds the thermal mass of the other cold start combustion chamber walls (2510 and 2513) when the volume (Vt) of the disk-shaped top wall (2017) exceeds 1.07 times the combined volume (Vo) of the other walls (2510 and 2513). Thus, according to the present disclosure, the thermal mass of the upper disk-shaped top wall (2017) exceeds the thermal mass of the intermediate enclosure walls (2510 and 2513), preferably by more than 100%. To calculate (Vo) above, only the walls that actually surround the cold start chamber (2300) are considered. In the above example, (Vo) includes the entire volume of the wall (2513) and only the portion of the wall (2510) that actually surrounds the cold start chamber (2300). Using this model, when the volume of the disk-shaped top wall (2017) (Vt) is 2.14 times (Vo), the thermal mass of the wall (2513) and the portion of wall (2510) surrounding the cold start chamber is exceeded by 100%.

[0120] As a result, more heat energy is absorbed by the top wall (2017) than is absorbed by all other cold start combustion chamber walls. The primary advantage of this embodiment is that it absorbs a majority of the heat energy generated by the fuel air mixture combusted inside the cold start combustion chamber (2300) in the top wall (2017). Because the top wall and other hot zone enclosure walls are more thermally conductive than the walls (2510 and 2513), the heat energy absorbed by the top wall is rapidly conducted by the thermal conduction path formed by the hot zone enclosure walls. This is further facilitated by forming the intermediate enclosure walls (2510, 2511, and 2513) and the annular enclosure wall (7060) from Hastelloy or another high nickel-containing metal having a thermal conductivity coefficient of less than about 25.0 W / m°K, which causes a much slower conductive heat flow away from the hot zone enclosure walls than through them.

[0121] During the cold start process, the combustion energy from the cold start chamber is primarily absorbed by the top end wall (2017) and re-emitted to the fuel inlet manifold (2055) to heat the fuel air mixture contained therein sufficiently to a high enough temperature to initiate the CPOX reaction at the output end (3034) of the catalytic fuel passage (3085). A secondary advantage of this embodiment is that the majority of the heat energy generated by the fuel air mixture combusted inside the cold start combustion chamber (2300) is instead diverted away from the fuel reformer module (3020) by providing a higher conductive heat flow from the disk-shaped top end wall (2017) to the other hot zone enclosure walls (2015 and 2511), as well as the disk-shaped isolation wall (2214) and the disk-shaped tube bottom support wall (2084).

[0122] Once the CPOX reaction is initiated and self-sustaining, the fuel reactor body (3040) provides a thermal conduction path and sufficient thermal mass to rapidly transfer thermal energy from the reactor shield base wall (3015) to the heat sink flange (3100). In particular, because the interface (3032) is in close proximity to the CPOX reaction, which has a temperature of 900-1000°C, thermal energy reaches the reactor shield base wall (3015) in varying amounts by radiation, thermal conduction, and convection, and is absorbed by the exposed surface (b) and the remaining solid material on the bottom surface of the reactor shield base wall (3015), as well as the inner surface of the circular base wall fuel passage (3095) shown in Figures 4 and 4A. As a result, the incipient CPOX reaction in close proximity to the interface (3032) is effectively quenched, preventing auto-ignition of the incoming fuel-air mixture. The combined surface area (B), represented by ABt, potentially absorbs approximately 1% of the total thermal radiation emitted from all catalyst fuel passages (3085), the solid surface area of ​​the reactor shield base wall at the interface, represented by AS above, potentially absorbs approximately 0.2% of the total thermal radiation emitted from all catalyst fuel passages (3085), and the inner surface of the base wall fuel passages (3095) potentially absorbs approximately 13.6% of the total, approximately 15%.

[0123] According to the present disclosure, the thermal mass, i.e., the material volume thereof (see Equation 5 above), of the reactor shield base wall (3015) is made large enough to provide sufficient energy transfer from the catalytic fuel passages (3085) to prevent excessive heating therein when the reactor shield base wall can be maintained at or below 100° C. Additionally, according to the present disclosure, the thermal mass, i.e., the material volume thereof, of the fuel reactor body (3040) is made large enough to provide sufficient energy transfer by thermal conduction from the reactor shield base wall (3015) to the heat sink flange (3100) so that the entire fuel reactor body (3040) can be maintained at a substantially uniform temperature with a small temperature gradient maintained between the higher temperature reactor shield base wall and the heat sink flange (3100). Further, in accordance with the present disclosure, the surface area of ​​the heat dissipation flange (3100) is large enough to dissipate heat energy therefrom at a rate equal to the rate of heat energy absorbed by the reactor shield base wall (3015), which is approximately 44 W as discussed above. Further, in accordance with the present disclosure, the fuel furnace body (3040) is configured to dissipate sufficient heat therefrom such that the fuel-air mixture passing through the cylindrical fuel chamber (3005) does not exceed its auto-ignition temperature. More specifically, the heat dissipation flange (3100) is configured to dissipate sufficient heat energy to the ambient air to maintain the temperature of the fuel furnace body (3040) below approximately 295° C., equal to the lowest anticipated auto-ignition temperature of the fuel-air mixture, and preferably to maintain the temperature of the entire fuel furnace body (3040) between approximately 100-250° C. during all modes of operation. It is also contemplated that the temperature of the heat dissipation flange (3100) is monitored during all stages of operation, and if the temperature of the heat dissipation flange exceeds a desired high temperature limit, in the range of 100-250°C, the incoming fuel-air mixture may be stopped by an operable element in the fuel input module (197) to prevent fuel from entering the reformer (167) until further operation, or the air moving element (3130) may reduce the temperature of the heat dissipation flange (3100) to a safe operating temperature.

[0124] Alternative Fuel Reformer and Outer Enclosure Embodiments 2-4 and 7, exemplary, non-limiting, alternative embodiments of a SOFC system (7000) include alternative embodiments of a fuel reformer module (7020) and associated elements. The SOFC system (7000) has substantially the same construction and similar modes of operation as compared to the systems (2000 and 3000) shown in FIGS. 2-4, except for additional features and different modes of operation of the system (7000) as outlined below. To clarify the similarities and differences between the systems, the following SOFC system embodiments (2000, 3000, and 7000) use like reference numbers where referenced items have substantially the same structure in each of the systems (2000, 3000, and 7000).

[0125] 7, the alternative fuel reformer module (7020) includes a fuel furnace body (7040) including an annular perimeter wall (7010) attached to or integrally formed with a reactor shield base wall (7015). The fuel furnace body (7040) is formed to provide a cylindrical fuel chamber (7005) bounded by the annular perimeter wall (7010), the reactor shield base wall (7015), and a disk-shaped outer enclosure top flange (7102). A fuel inlet conduit (7045) is disposed to pass through the disk-shaped outer enclosure top flange (7102) into the fuel chamber (7005).

[0126] The fuel reformer module (7020) further includes the cylindrical catalyst body (3030) described above. Each of the fuel furnace body (7040) and the cylindrical catalyst body (3030) is installed in a cylindrical catalyst cavity (7035) where the cylindrical catalyst body (3030) is located immediately above the fuel inlet manifold (3055) and the fuel furnace body (7040) is located immediately above the cylindrical catalyst body (3030). Each of the fuel furnace body (7040) and the cylindrical catalyst body (3030) is configured to provide fluid communication between the cylindrical fuel chamber (7005) and the fuel inlet manifold (3055), as shown in Figures 4 and 4A and described above. The fuel reactor body (7040) is formed using a material having a thermal conductivity coefficient greater than 100 W / m°K and sufficient thermal mass to rapidly conduct thermal energy away from the interface between the reactor shield base wall (7015) and the catalyst body (3030).

[0127] In this alternative non-limiting embodiment of the SOFC system (7000), the cylindrical catalyst cavity (7035) has a sidewall formed by the inner diameter of the annular enclosure wall (7060). The inner diameter of the annular enclosure wall (7060) is formed with a central longitudinal axis disposed coaxially with the central longitudinal axis (2060). The cylindrical catalyst cavity (7035) includes two open ends, each forming a circular opening with a top circular opening facing the disk-shaped outer enclosure top flange (7102) and a bottom circular opening facing the fuel inlet manifold (3055). The annular enclosure wall (7060) includes an annular seal plate (7105) surrounding an upper circular opening that mechanically interacts with a disk-shaped outer enclosure top flange (7102), to which the annular seal plate (7105) is attached by mechanical fasteners or the like, not shown. An O-ring seal element (7110) or the like is disposed between the annular seal plate (7105) and the disk-shaped outer enclosure top flange (7102), e.g., in an O-ring groove, and serves to gas seal an upper portion of the cylindrical catalyst cavity (7035).

[0128] The disk-shaped outer enclosure top flange (7102) is attached to the outer cylindrical side wall (2514), with the joint between the two elements providing a continuous thermal conduction path. Like the fuel reactor body (7040) and the other outer enclosure walls (2514) and (2518), the outer enclosure top flange (7102) is formed from a material having a thermal conductivity coefficient greater than 100 W / m°K and sufficient thermal mass to rapidly conduct thermal energy from the interface between the reactor shield base wall (7015) and the catalyst body (3030). As described above, thermal energy absorbed by the outer enclosure top flange (7102) is rapidly conducted to the outer cylindrical wall (2514) to minimize temperature gradients from one region of the outer enclosure to another. The disk-shaped outer enclosure top flange (7102) is attached to the outer cylindrical wall (2514) by mechanical fasteners (not shown), such as by welding, soldering, or the like. In any event, the joint formed between the top flange (7102) and the outer cylindrical wall (2514) is gas sealed and provides a substantially continuous thermal conduction path.

[0129] As described above, the reactor shield base wall (7015) is configured to absorb the thermal energy generated within the cylindrical catalyst body (3030). The entire fuel furnace body (7040) is configured to provide a continuous thermal conduction path to the disk-shaped outer enclosure top flange (7102) for rapid conduction of the thermal energy generated within the cylindrical catalyst body (3030) to the disk-shaped outer enclosure top flange (7102) and then to the cylindrical side wall (2514) and the outer bottom wall (2518). Thus, any instantaneous temperature change in the reactor shield base wall (7015) is followed by a corresponding rapid change in temperature throughout the outer enclosure.

[0130] 8.10 Thermal Energy Transfer from Hot Zone Enclosure to Outer Enclosure As detailed above, each wall of the outer enclosure (2514), (2518), (7102) comprises a material having a high thermal conductivity, for example between 100-300 W / m°K, preferably greater than 140 W / m°K. Thus, the outer cylindrical side wall (2514), the disk-shaped outer bottom wall (2518), and the disk-shaped outer enclosure top flange (7102) are fabricated from one or more of copper, molybdenum, aluminum copper, copper nickel alloy, or combinations thereof. Each of the walls (2514), (2518), and (7102) preferably comprises aluminum or an aluminum alloy having a thermal conductivity coefficient greater than 140 W / m°K, and each having sufficient thermal mass, i.e. thickness, to rapidly conduct thermal energy throughout its volume and from one adjacent wall to another. In this non-limiting exemplary embodiment, the outer cylindrical wall (2514) and the disk-shaped outer bottom wall (2518) have a material thickness in the range of 0.5-6.5 mm (0.20-0.25 inches) and the outer enclosure top flange (7102) has a material thickness in the range of 4.0-10.0 mm (0.16-0.39 inches), although other thickness ranges can be used without departing from this disclosure.

[0131] Specifically, each of the outer enclosure walls (2514, 2518, 7102) is configured to provide a substantially continuous thermal conduction path for rapidly transferring thermal energy by thermal conduction from one region of the outer enclosure to another in order to more rapidly reduce temperature gradients between regions of the outer enclosure so that the entire outer enclosure wall structure remains at substantially the same uniform temperature throughout.

[0132] As further described above, the hot zone enclosure walls (2015, 2016, and 2017) and (2214 and 2080) form a continuous thermal conduction path suitable for rapid heat transfer from one region of the hot zone enclosure wall to another to more rapidly reduce the temperature gradient between the hot zone enclosure walls and maintain the entire hot zone enclosure wall structure at substantially the same temperature. The intermediate enclosure walls (2510, 2511, and 2513) are thermally conductively coupled to the hot zone enclosure walls by the disk-shaped end walls (2017). As detailed above, each of the intermediate enclosure walls includes a material having a thermal conductivity of less than about 25.0 W / m°K, compared to the thermal conductivity coefficient of the hot zone enclosure walls of 100 W / m°K or more. Additionally, the disk-shaped walls (2017, 2084, and 2214) provide a greater thermal mass compared to the lesser thermal mass provided by the intermediate enclosure walls. As a result, the hot zone enclosure wall absorbs and conducts heat energy at a faster rate than the intermediate enclosure wall. The hot zone enclosure wall is thermally conductively connected to the intermediate enclosure wall by a disk-shaped wall (2017), but the thermal mass of the connection is intentionally small to slow the conductive heat flow across the thermal conduction path formed by the wall (2017). This provides a temperature gradient between the hot zone enclosure wall and the intermediate enclosure wall. The advantage of the temperature gradient provided between the hot zone enclosure wall and the intermediate enclosure wall is that the increased thermal radiation emitted from the hot zone enclosure wall more rapidly heats the incoming cathode air into the recuperator chamber (2210) and the air present in the cathode chamber (2010).

[0133] As described in further detail above, each wall of the outer enclosure (2514, 2518, and 7102) comprises a material having a high coefficient of thermal conductivity, for example, 100 to 300 W / m°K, preferably greater than 140 W / m°K. Thus, the outer cylindrical side wall (2514), the disk-shaped outer bottom wall (2518), and the disk-shaped outer enclosure top flange (7102) are fabricated from one or more of copper, molybdenum, aluminum, nickel, or alloys thereof. In one non-limiting embodiment, the walls (2514, 2518, 2516, and 7102) comprise aluminum or an aluminum alloy, preferably having a coefficient of thermal conductivity greater than 140 W / m°K. Additionally, each of the walls (2514, 2518, 2516, and 7102) is formed with sufficient thermal mass, i.e., thickness or total volume, to rapidly conduct thermal energy throughout its volume, e.g., from one adjacent outer enclosure wall to another. In the present non-limiting exemplary embodiment shown in Figures 3 and 7, the outer enclosure walls (2514 and 2518) have a material thickness in the range of 0.5-6.5 mm (0.02-0.25 inches) and the wall (7102) has a material thickness in the range of 4.0-10.0 mm (0.16-0.39 inches), although other thickness ranges can be used without departing from the present disclosure. In the present non-limiting exemplary embodiment shown in Figures 2 and 7, the hot zone walls (2015) and (2016) have a material thickness in the range of 0.5-13 mm (0.02-0.5 inches), although other thickness ranges can be used without departing from the present disclosure.

[0134] A layer of insulation (2512) The insulation layer (2512) is disposed between the outer surface of the intermediate enclosure wall and the inner surface of the outer enclosure wall. Preferably, the insulation layer (2512) is constructed to ensure that the surfaces of the outer cylindrical side wall (2514), the disk-shaped outer bottom wall (2518), and the disk-shaped outer enclosure top flange (7102) remain within a desired operating temperature range, for example, 95-110°C.

[0135] The annular enclosure wall (7060) comprises a high temperature resistant material such as Hastelloy or Monel, each having a high nickel content to resist oxidation damage, and each having a suitable service temperature rating, for example, above 400° C. However, the thermal conductivity coefficients of both Hastelloy and Monel are less than about 25.0 W / m° K. In addition, the annular enclosure wall (7060) may be formed with a wall thickness ranging from 0.02 to 0.1 inches, but in any event, the thickness of the annular enclosure wall (7060) is selected to provide a lower thermal mass than the thermally conductive wall of the hot zone enclosure wall when compared to the thermal mass of the hot zone enclosure wall and the intermediate enclosure wall, in order to reduce the relative thermal mass of the annular enclosure wall (7060). Thus, due to its low thermal conductivity and reduced thermal mass, the annular enclosure wall (7060) resists conductive thermal energy transfer between the hot zone enclosure wall and the outer enclosure wall to maintain a temperature gradient between the hot zone enclosure wall and the outer enclosure wall. However, this resistance to conductive thermal energy transfer by the annular enclosure wall (7060) only reduces the rate of thermal conductivity or heat flow from the hot hot zone enclosure wall to the cooler outer enclosure wall. More specifically, the configuration of the annular enclosure wall (7060) provides a temperature gradient between the hot zone enclosure wall and the hot zone enclosure wall.

[0136] Over-temperature protection system Excessive heat generation at various locations within the SOFC system (7000) can result in potentially dangerous and harmful over-temperature conditions. During operation, over-temperature conditions can occur within the cell stack (2005), within the cylindrical catalyst body (7030), and other locations such as within or adjacent to the combustion chamber (2135), within or adjacent to the cold start combustion chamber (2300), and / or within the air gap (2155).

[0137] An over-temperature condition can escalate quickly and lead to catastrophic failure of the SOFC fuel cell, such as an explosion or fire. An over-temperature condition often leads to burn-through, where the metal walls are partially melted or otherwise damaged, destroying or permanently rendering the insulating layer (2512) less effective. Catastrophic failure can include fuel combustion within the cylindrical fuel chamber (3005), where fuel combustion is not intended. Thus, if an over-temperature condition occurs anywhere in the SOFC system, it is desirable to stop fuel from entering the SOFC system (7000) as soon as possible, before the over-temperature condition leads to catastrophic failure or damages the SOFC system.

[0138] Conventional SOFC systems use internal temperature sensors to monitor the internal temperature. The temperature sensors are located within the SOFC system in close proximity to critical areas where overheating or underheating conditions may adversely affect the performance of the SOFC system. Each internal temperature sensor communicates with an electronic controller via a wired communication interface. The electronic controller interprets the temperature signals received from the internal temperature sensors and executes software or other logical process steps to monitor and record the temperature sensor input. Typically, the electronic controller (190) stores temperature limit ranges in a memory module, each temperature limit range relating to a different operating mode and / or different internal sensor location. One problem with internal temperature sensors is that they cannot be easily replaced if they fail. Additionally, internal temperature sensors in SOFC systems are in high temperature and often polluted environments that may shorten the useful life of the sensor. There is a need in the art to use external temperature sensors to determine SOFC temperature levels, preferably a single external temperature sensor to determine a single instantaneous SOFC surface temperature that can be used to trigger various SOFC system process controls.

[0139] According to the present disclosure, process control may be triggered by changes in temperature monitored by a single external temperature sensor. In one exemplary embodiment described above, operation of the air moving device (3130) shown in Figure 3 is responsive to changes in temperature of the exterior surface of the SOFC system (3000). In particular, the electronic controller (190) using the temperature sensor signal from the external temperature sensor (3135) switches the air moving device (3130) on or off depending on the instantaneous temperature change indicated by the external temperature sensor (3135).

[0140] Referring to FIG. 7, the SOFC system (7000) includes an external temperature sensor (7135) mounted in contact with an outer surface of the disk-shaped outer enclosure top flange (7102). Alternatively, the external temperature sensor (7135) may be mounted in contact with any outer surface of the outer enclosure wall. The external temperature sensing element (7135) communicates with the electronic controller (190) and delivers a temperature signal to the electronic controller (190) via a communication path (7140). In various embodiments, the SOFC system (7000) may also include an air moving element (3130), shown in FIG. 3 and described above, operable by the electronic controller (190) to move air over the disk-shaped outer enclosure top flange (7102) to reduce its temperature.

[0141] In an exemplary mode of operation, the electronic controller (190) receives temperature signals from the external temperature sensing element (7135) via communication path (7140) and determines the instantaneous temperature of the exterior surface to which the external temperature sensing element is attached. If the instantaneous temperature is not within an expected temperature range, the electronic controller is programmed, using software and other logical operators, to perform various operational procedures in response to the out-of-range instantaneous temperature value.

[0142] In a first example, the SOFC system is operating in a normal operating mode generating DC output power, and is operating with a steady, uniform flow of incoming fuel-air mixture entering the fuel chamber (7005) from the fuel input module (197), as shown in FIG.

[0143] The fuel input module (197) includes an operable fuel supply valve (7610). The operable fuel supply valve is disposed along a fuel input conduit (7045) between a fuel source and the fuel reformer (7020). The operable fuel supply valve communicates with the electronic controller (190) via a communication channel (7666) and with an electrical power source via a power conduit (7830), not shown. The operable fuel supply valve (7610) has a default state in which the valve is closed, e.g., held closed, such as by a spring force. The valve is operated by the electronic controller (190) to open by overcoming the spring force when a power signal is applied to an actuator within or incorporated within or associated with the valve.

[0144] In one non-limiting embodiment, the electronic controller (190) applies a power signal to the valve actuator to overcome a spring force and open the fuel supply valve (7610). Depending on the amplitude of the power signal, the valve may be opened slightly, e.g., at a threshold power signal amplitude, or the valve may be fully opened, e.g., at a maximum power signal amplitude. In operation, the electronic controller (190) is operable to vary the power signal amplitude in a manner that moves the valve actuator to various open positions ranging from slightly or partially open to fully open, in response to changes in the amplitude of the power signal delivered to the valve actuator. The electronic controller (190) operates to regulate the mass or volumetric flow rate of the fuel-air mixture (3025) passing through the input conduit (7045) to the cylindrical fuel chamber (7005) by varying the amplitude of the power signal on the power conduit (7830).

[0145] In the operating modes of the present disclosure, the electronic controller (190) monitors the external temperature sensing element (7102) to determine the instantaneous temperature of the disk-shaped top flange (7102). A software program or other logical operator running on the electronic controller (190) compares the measured instantaneous temperature of the top flange to a temperature range associated with the current operating mode of the SOFC system. The temperature ranges for the different operating modes are stored in a memory associated with the electronic controller (190). Non-limiting example operating modes include a start-up operating mode when the cold start combustion chamber (2300) is in use, a steady state operating mode in which the cold start combustion chamber is not in use, and others in which the flow rate of incoming fuel is adjusted to provide more or less DC power output from the fuel stack.

[0146] In either case, if the instantaneous temperature sensed by the external temperature sensing element (7102) is within the expected temperature range, the electronic controller (190) will not operate. However, if the instantaneous temperature sensed by the external temperature sensing element (7102), i.e., the temperature of the top flange (7102), is not within the expected temperature range, the electronic controller (190) will operate.

[0147] As a safety feature, the expected temperature range for any of the operating modes has an upper limit called the "controller failsafe temperature." In this non-limiting example operating mode, the controller failsafe temperature is 140° C. In particular, if the instantaneous temperature measured by the external sensor (7135) is equal to or greater than 140° C., the electronic controller will initiate a safety shutdown procedure that includes de-energizing the operable fuel supply valve (7610) actuators to at least prevent further fuel flow into the SOFC system.

[0148] When the controller failsafe temperature is detected, the electronic controller initiates a software or logic controlled shutdown process, including commanding the fuel supply module (197) to close the fuel supply valve (7610) by disconnecting power to the fuel supply module (197). In addition, the controlled shutdown process may include stopping fuel delivery to the cold start combustion chamber (2300), stopping air input by the air input module (198), and activating the air movement device (3210) if the SOFC system is so equipped and if the air movement device is not already operational.

[0149] More generally, due to the thermal conduction paths and the relatively high thermal conductivity provided by the improved outer enclosure of the present disclosure, a single external temperature sensing element (7135) positioned on any surface of the outer enclosure eccentrically senses the instantaneous temperature of the entire outer enclosure wall (132).

[0150] In a further aspect of the disclosure, a thermal fuse (7860) including a meltable link is disposed in contact with an outer surface of the disk-shaped outer enclosure top flange (7102) or in contact with any outer surface of the outer enclosure. The thermal fuse (7860) is disposed along the fuel supply power conduit (7830) between the source power supply and the operable fuel supply valve (7610). The thermal fuse (7860) is a passive device and is independent of the electronic controller (190). The thermal fuse is configured to interrupt power transmitted from the supply valve power supply (7610) to the operable fuel supply valve (7610) when the meltable link melts, creating a short circuit inside the thermal fuse (7860), not shown. The meltable link has a particular melting temperature equal to the fail-safe temperature of the system. In this non-limiting exemplary embodiment, the fail-safe temperature of the system is equal to a temperature higher than the fail-safe temperature of the controller. In one non-limiting exemplary mode of operation, the system fail-safe temperature is 180° C. In particular, when the temperature of the meltable link reaches the system fail-safe temperature of 180° C., the meltable link melts, thereby creating a short circuit across the thermal fuse (7860). The short circuit causes the power amplitude at the operable valve (7610) to close to zero, thus preventing fuel flow to the fuel chamber (7005). In an exemplary non-limiting embodiment, the thermal fuse (7860) comprises any one of commercially available thermal fuses, such as the Tamura LE series, NEC SeFuse SF series, MicroTemp G4A series, and Hosho Elmwood D series, where the fuse selected is configured with a meltable link that melts at the desired system fail-safe temperature.

[0151] As described above, the system (7000) includes an electronic controller (190) operable to execute a software or logic shutdown procedure when the single external temperature sensor (7135) reports an instantaneous temperature equal to the controller's failsafe temperature. The software or logic shutdown procedure includes at least closing the operable fuel supply valve (7610) using logic commands. On the other hand, if the meltable link of the thermal fuse (7860) reaches the system's failsafe temperature, the thermal fuse will prevent power from reaching the operable fuel supply valve (7610), thereby stopping the flow of fuel to the fuel chamber if the flow of fuel was not previously stopped by the software or logic shutdown procedure.

[0152] Since each of the outer enclosure walls (2514, 2518, and 7102) is configured to provide a thermal conduction path with a high thermal conductivity coefficient, the entire outer enclosure wall structure rapidly reaches thermal equilibrium at substantially the same instantaneous temperature, as described above. Thus, the temperature sensing element (7135) and the thermal fuse (7860) can be located on any outer surface of the outer enclosure, including on different outer surfaces of the outer enclosure. Furthermore, as described above, the instantaneous temperature of the outer enclosure increases and decreases in response to increases and decreases in the temperature of the hot zone enclosure wall that is thermally connected on the annular enclosure wall (7060). Thus, any prolonged increase in instantaneous temperature at any location within the SOFC system (7000) will cause an increase in the temperature of the outer enclosure wall, as monitored by the electronic controller (190), and ultimately, detected by the external temperature sensing element (7135).

[0153] Fuel / Oxidizer Input Control Module Referring now to Figure 8, a schematic representation of a further non-limiting, exemplary embodiment of a solid oxide fuel cell (SOFC) system (8000) according to the present disclosure is shown. The SOFC system (8000) includes a fuel / oxidant input control module (8005), also shown in Figure 1 as fuel input module (197). The fuel / oxidant input control module (8005) includes or is fluidly coupled to each of an oxidant source (8010) and a hydrocarbon fuel source (8020). The oxidant source (8010) is in fluid communication with a mixing chamber (8015), e.g., a spiral mixing chamber, by a connecting oxidant input conduit (8017). The fuel source (8020) is in fluid communication with the mixing chamber (8015) by a connecting fuel input conduit (8022). An oxidant flow modulator (8025) is disposed along the oxidant input conduit (8017) between the oxidant source (8010) and the mixing chamber (8015). A hydrocarbon fuel flow modulator (8035) is disposed along the fuel input conduit (8022) between the hydrocarbon fuel source (8020) and the mixing chamber (8015). Each flow modulator (8025, 8035) includes at least one electromechanical actuator, not shown, controlled by an electronic controller (190). The electronic controller (190) is configured to independently regulate the input oxidant flow rate and the input hydrocarbon fuel flow rate to the mixing chamber (8015). Each of the input oxidant flow rate and the input hydrocarbon fuel flow rate may be regulated between substantially zero input flow rate and a maximum input flow rate. In an alternative embodiment, the mixing chamber (8015) is eliminated and the oxidizer input conduit (8017) and the fuel input conduit (8022) are each connected between a corresponding source formed inside the fuel reactor system (3000) shown in Figures 3, 4, 4A and 7 and the fuel chamber (3005).

[0154] Compressed gas cylinders In one non-limiting, exemplary embodiment, one or both of the oxidant source (8010) and the hydrocarbon fuel source (8020) are compressed gas containers, such as pressurized oxygen or air containers, or pressurized hydrocarbon fuel containers. In either case, the pressurized container includes a passive pressure regulator, not shown. The passive pressure regulator is disposed between the compressed gas container and the mixing chamber (8015) and operates to pressure regulate or adjust the flow of high pressure gas exiting the compressed gas container. The flow of low pressure gas is released by the pressure regulator into the corresponding input conduit (8017, 8022), where the low pressure gas is released at a much lower gas pressure compared to the high pressure gas stored inside the compressed gas container. The passive pressure regulator also functions as a passive gas flow modulator. This occurs when the gas pressure inside the corresponding conduit is reduced by the low pressure gas exiting the mixing chamber (8015) from the corresponding input conduit (8017, 8022). In response to the drop in gas pressure, a passive pressure regulator within the corresponding conduit releases gas from a pressurized gas container into the corresponding conduit until the gas pressure in the corresponding conduit is restored to the set pressure of the passive gas regulator. Thus, the gas flow rate exiting any one of the input conduits (8017, 8022), for example to the mixing chamber (8015), is replaced by the corresponding gas flow rate released by the corresponding passive pressure regulator. Thus, each gas regulator operates to maintain a constant gas pressure within the corresponding input conduit (8017, 8022).

[0155] Air pump / fan In another non-limiting, exemplary embodiment, the oxidant source (8010) is an air pump or fan, etc., that draws air from the ambient environment or an air inlet into the oxidant input conduit (8017). In one non-limiting, exemplary embodiment, the air pump or fan also operates as an oxidant flow modulator (8025) when the air pump or fan includes a controllable electromechanical actuator in communication with the electronic controller (190). The controllable electromechanical actuator, not shown, operates to rotate a controllable air moving device, e.g., pump vanes, fan blades, etc., or otherwise associated with the air pump or fan. Movement of the air moving device induces or draws oxidant into the oxidant input conduit (8017), and the oxidant fuel flow rate is changed by changing the speed of the air moving device, e.g., by changing the angular velocity of the rotating pump vanes or fan blades. The change in speed of the air moving device is driven by control and command signals received from the electronic controller (190). The command and control signals received by the air moving device adjust the speed of the air moving device which corresponds to regulating the flow rate of air through the oxidant input conduit (8017) to the mixing chamber (8015). When operating as an oxidant flow modulator (8025), the air pump or fan is controlled by the electronic controller (190) and operates to regulate the fluid flow rate of air through the oxidant input conduit (8017) to the mixing chamber (8015) between substantially zero oxidant flow rate and a maximum oxidant flow rate.

[0156] In a further non-limiting embodiment, the oxidant source (8010) is an air pump or fan that draws air from the ambient environment or from an air inlet or the like into the oxidant input conduit (8017) at a substantially constant air flow rate, with air flow modulation being accomplished by a gas control valve described below.

[0157] liquid fuel supply In another non-limiting, exemplary embodiment, the hydrocarbon fuel source (8020) includes a liquid hydrocarbon fuel, such as kerosene, gasoline, or the like. In this embodiment, the hydrocarbon fuel source (8020) includes a liquid fuel container, which may be pressurized, and a vaporizer or atomizer module disposed between the liquid fuel container and the mixing chamber (8105). The liquid fuel is delivered to the vaporizer or atomizer configured to convert the liquid fuel into a hydrocarbon gas vapor or a mist including liquid fuel droplets. The hydrocarbon gas vapor or mist is delivered to a hydrocarbon fuel input conduit (8022) for delivery to the mixing chamber (8015). In this embodiment, the vaporizer or atomizer may be operated as a hydrocarbon fuel flow modulator (8035) when the vaporizer or atomizer includes an electromechanical actuator or the like that is controllable in communication with the electronic controller (190). The controllable electromechanical actuator operates to move or otherwise manipulate elements associated with vaporizing or atomizing the liquid fuel supply to regulate the flow rate of the hydrocarbon fuel to the mixing chamber (8015).

[0158] In a further non-limiting embodiment, the vaporizer or atomizer delivers liquid hydrocarbon fuel mist or vapor from a liquid fuel source to the liquid hydrocarbon fuel input conduit (8022) at a substantially constant flow rate of hydrocarbon fuel, with regulation of the flow rate of the hydrocarbon fuel being performed by a gas flow control valve described below.

[0159] Gas Flow Control Valve In a further non-limiting, exemplary embodiment, one or both of the oxidant flow modulator (8025) and the hydrocarbon fuel flow modulator (8035) include a gas flow control valve disposed along a corresponding input conduit (8017, 8022) between the corresponding oxidant source (8010) or hydrocarbon fuel source (8020) and the mixing chamber (8015). Each gas flow valve includes an electromechanical actuator in communication with the electronic controller (190). The electromechanical actuator operates to rotate or otherwise move a movable gate or the like, which is disposed inside the gas flow control valve or inside the corresponding input conduit (8017, 8022). The movable gate is moved in response to control and command signals received from the electronic controller (190) to independently regulate the flow rate of each of the oxidant and hydrocarbon fuel through the gas control valve and into the mixing chamber (8015). Thus, each of the gas flow valves operating as either an oxidizer flow modulator (8025) or a fuel flow modulator (8035) is operated by an electronic controller (190) configured to regulate the fluid flow rate through the movable gate such that the fluid flow rate ranges between substantially zero oxidizer or hydrocarbon fuel flow rate and a maximum oxidizer or hydrocarbon fuel flow rate. Preferably, the gas flow valves are operable to provide a plurality of discreet incremental volumetric flow levels over a flow rate range, each incremental volumetric flow level changing the flow rate by approximately 0.1 to 1.0 standard cubic centimeters per minute (SCCM).

[0160] Cathode Air Pump The fuel cell stack includes a cathode air input port (2205) leading to the cathode chamber (2010), as shown in FIG. 2. A cathode air or other oxidant source (8045) is disposed to deliver a cathode air flow or other oxidant flow to a cathode air input conduit (8055) that leads to the air input port (2205). A cathode air flow modulator (8050) is disposed along the cathode air input conduit (8055) between the cathode air source (8045) and the cathode air input port (2205). The cathode air flow modulator (8050) includes at least one controllable electromechanical actuator (not shown) that is controlled by the electronic controller (190). In one exemplary embodiment, the cathode air source (8045) is an air pump or fan that also operates as the cathode flow modulator (8050). In this example, the air pump or fan includes a controllable electromechanical actuator in communication with the electronic controller (190). The controllable electromechanical actuator operates to rotate or otherwise move a controllable air moving device, e.g., pump vanes, fan blades, etc., associated with the air pump or fan, at different speeds. The movement of the air moving device induces or draws cathode air into the cathode air input conduit (8055), and the volumetric flow rate of the cathode air is varied by varying the speed of the air moving device, e.g., by varying the angular velocity of the pump vanes or fan blades. The change in speed of the air moving device is driven by control and command signals received from the electronic controller (190). The command and control signals vary the speed of the air moving device to regulate the volumetric flow rate of cathode air through the cathode air input conduit (8055) to the cathode air input port (2205). Thus, the air pump or fan operating as the cathode flow modulator (8050) is operated by the electronic controller (190), which is configured to regulate the volumetric fluid flow rate of cathode air passing through the cathode air input conduit (8055) to the cathode air input port (2205) between a substantially zero cathode air flow rate and a maximum cathode air flow rate.Preferably, the air moving device used to adjust the volumetric flow rate of the cathode air provides a plurality of discreet incremental volumetric flow levels over a volumetric flow range, with each incremental volumetric flow level changing the flow rate by approximately 0.5 to 2.0 standard cubic centimeters per minute (SCCM).

[0161] As described above with respect to the oxidant source (8010), the cathode air source (8045) may include a compressed gas container, e.g., a pressurized oxygen or air tank, including a passive pressure regulator. Alternatively, the cathode source (8045) may include an air pump or fan or the like that draws air from the surrounding environment or from a ventilation conduit or the like into the cathode air input conduit (8055). However, the air pump or fan does not operate as the cathode air flow modulator (8050). Instead, the flow rate of cathode air delivered by the air pump or fan to the cathode air conduit (8055) is substantially constant when the air pump or fan speed is not regulated by the electronic controller. In this embodiment, regulation of the fuel flow is performed by a gas flow control valve disposed along the fuel input conduit (8022), as described above.

[0162] Fuel Air Mixture The mixing chamber (8015) is preferably a spiral chamber used to mix the hydrocarbon fuel stream and the oxidizer stream to produce a fuel-air mixture (2025, 3025). The fuel-air mixture preferably has an oxygen to carbon (O:C) ratio in the range of 1.0 to 2.2, where the O:C ratio corresponds to a molar ratio, e.g., the oxygen atom to carbon atom ratio.

[0163] The fuel air mixture (2025, 3025) exits the mixing chamber (8015) into a gas flow conduit (2045, 7045) which extends from the fuel / oxidizer input control module (8005) to the fuel chamber (3005) and is formed within the fuel chamber system (3000) shown in Figures 3, 4, 4A and 7 and described above. The preferred hydrocarbon fuel of the present disclosure is methane (CH4), although other suitable fuels include ethane (C2H6), propane (C3H8), butane (C4H4), and ethane (C2H5).10 Other longer hydrocarbon chains can be used, including CH. 12 ~C 18 H 32 Liquid hydrocarbon fuels having hydrocarbon chains in the range of may be reformed by the systems and methods of the present disclosure.

[0164] CPOX reaction The fuel furnace system (3000) is configured to reform the fuel-air mixture (2025, 3025) by catalytic partial oxidation (CPOX). The CPOX reaction is an exothermic reaction (flameless combustion) that converts the fuel-air mixture into syngas (2027). The syngas (2027) is a reformate containing anode gas that is used to react with the solid oxide anode electrode surface formed on the inner surface of each tubular fuel cell (2080) of the SOFC stack (135, 2005). The anode gas reactants are H2 and CO, since both reactants can combine with oxygen atoms available on the solid oxide anode electrode surface. Combination of oxygen atoms or ions available on the anode electrode surface with the H2 reactant to form H2O and with the CO reactant to form CO2 generates a direct current that is output from each of the tubular fuel cells (2080) to the DC power module (140) shown in FIG. 1. In an alternative embodiment, the CPOX reactor and fuel reforming methods of the present disclosure can be used to deliver syngas to a planar solid oxide anode electrode surface without departing from the present disclosure.

[0165] The oxygen atoms or ions available on the solid oxide anode electrode surface are received from oxygen gas O2 available from the cathode air pumped into the cathode chamber (2010). The input volumetric flow rate of the cathode air is adjusted to keep up with the demand for oxygen atoms or ions on the solid anode electrode surface. The oxygen gas from the cathode air reacts with the solid oxide cathode electrode surface (155) and is formed on the outer surface of each tubular fuel cell (2080) or on the flat solid oxide cathode electrode surface. The oxygen gas O2 is separated into individual oxygen atoms or ions passing through the solid oxide cathode electrode, passing through an electrolyte layer disposed between the cathode electrode and the anode electrode, and passing through the solid oxide anode electrode exposed to the anode gas.

[0166] Equation 6, shown below, details the CPOX chemical reaction associated with converting a fuel-air mixture to synthesis gas (2027). The CPOX chemical reaction in Equation 6 is initiated when the fuel-air mixture contacts a catalyst layer (3090) coated on the inner surface of the catalytic fuel passages. The catalyst layer (3090) initiates the CPOX chemical reaction at a CPOX reaction temperature of 600-900°C. Without the catalyst layer (3090), the CPOX reaction temperature would be 1000-1200°C.

[0167] C n H m +(n / 2)O2→nCO+m / 2H2 equivalent 6

[0168] Based on Equation 6, when the hydrocarbon fuel is methane (CH4), the fuel-air mixture has an O:C ratio equal to 1.0 and a CO:H2 output ratio of 0.5. When the hydrocarbon fuel is ethane (C2H6), the fuel-air mixture has an O:C ratio equal to 1.0 and a CO:H2 output ratio of 0.66. When the hydrocarbon fuel is propane (C3H8), the fuel-air mixture has an O:C ratio equal to 1.0 and a CO:H2 output ratio of 0.75.

[0169] However, Equation 6 does not describe the use of air as the oxidant instead of pure oxygen or the use of a mixture of hydrocarbon molecules of different chain lengths and / or a heterogeneous hydrocarbon fuel source containing other contaminants. Furthermore, Equation 6 assumes a precise molar ratio of reactants, which is difficult to achieve in practice. Without the precise molar ratio of the fuel-air mixture, the syngas reaction may be incomplete. In one example, when the fuel-air mixture has a low O:C ratio, e.g., less than 1.0, i.e., there are more hydrocarbon fuel molecules than available oxygen molecules to react with, the syngas may contain unreacted hydrocarbon fuel molecules CnHm. When this occurs, the unreacted hydrocarbon fuel is flushed from the fuel cell without generating any power. In the other case, when the fuel-air mixture has a high O:C ratio, greater than 1.0, i.e., there are more oxygen molecules than hydrocarbon fuel molecules, the syngas contains excess oxygen gas (O2) that can combine with the H2 and CO components of the syngas, thereby reducing the available anode gas reactants to contribute to the generated power. Thus, an important aspect of the present disclosure is to balance the components of the fuel-air mixture of Equation 6 to provide an O:C ratio that eliminates unreacted hydrocarbon fuel, e.g., free carbon atoms and excess oxygen gas, from the syngas that can react to form methane (CH4). As described below, the present disclosure uses removed methane from the syngas formed by the CPOX reaction as a control indicator to establish the desired O:C ratio.

[0170] Other known problems associated with the CPOX chemical reaction include coke formation and undesirable reactions due to fuel contamination. Coke formation occurs when carbon molecules bond with the surface of the catalyst layer (3090) during the CPOX reaction. Carbon molecules contained in the syngas output can also contaminate the surface of the solid oxide anode electrode layer (150), reducing the efficiency of the anode electrode layer. In both cases, coke formation tends to reduce the overall efficiency of the SOFC system. Also, as mentioned above, a low O:C ratio can further contribute to unreacted hydrocarbon atoms and / or free carbon atoms that can contribute to coke formation.

[0171] Coke formation is temperature dependent and tends to be more thermodynamically favorable at CPOX reaction temperatures below about 800°C. Therefore, in order to avoid coke formation, it is important to maintain the minimum CPOX reaction temperature above about 800°C, and preferably above about 850-950°C. As discussed above, the maximum CPOX reaction temperature occurs proximate the interface (3032) where the incoming fuel-air mixture makes initial contact with the catalyst layer. However, a portion of the fuel-air mixture will likely make initial contact with the catalyst layer more distal from the interface layer (3032) and react at a lower CPOX reaction temperature than the CPOX reaction temperature at the interface. Thus, maintaining a minimum CPOX reaction temperature of about 800°C proximate the interface (3032) does not necessarily eliminate coke formation distal to the interface (3032) where the reaction temperature may be below 800°C. Coke formation is also stimulated by a low O:C ratio, e.g., less than 1.0, but because the actual O:C ratio of the fuel / air mixture exiting the mixing chamber when the oxidant is air is somewhat uncertain, it may be desirable to provide another indicator, e.g., a lack or minimization of methane in the syngas, as an indication that the desired O:C ratio is being provided.

[0172] The CPOX reaction control method is discussed and addressed in U.S. Patent No. 8,337,757 by Roychoubhury et al. entitled Reactor Control Method. Roychoubhury et al. disclose a CPOX reactor control method that includes periodically measuring the CPOX reaction temperature at three separate locations in the CPOX reactor. The reactor control method includes selecting a steady state operating temperature and a maximum safe operating temperature. Based on the CPOX reaction temperature measured at each of the three separate locations, the reactor control method determines a maximum temperature, a minimum temperature, and a difference between the maximum and minimum temperatures. The reactor control method then modifies three control parameters to alter the O:C ratio of the incoming fuel-air mixture in a manner that prevents the maximum temperature from exceeding the maximum safe operating temperature while minimizing the difference between the maximum and minimum temperatures. The three control parameters that are modified to effectively change the O:C ratio include modifying only the fuel input flow rate, modifying only the air input flow rate, and alternating between modifying the fuel input flow rate and modifying the air input flow rate.

[0173] Roychoubhury et al. disclose a CPOX reactor control method that addresses the need to vary the O:C ratio to minimize the difference between the maximum and minimum temperatures at three separate locations in the CPOX reactor, however, one problem with the control method disclosed by Roychoubhury et al. is that it requires the placement of three different thermal sensors, one at each of the three separate locations in the reactor. Another problem with the CPOX reactor control method disclosed by Roychoubhury et al. is that it does not take into account that the change in O:C ratio used to vary the CPOX reaction temperature may adversely affect the SOFC reaction temperature to such an extent that the overall power conversion efficiency of the SOFC system may be compromised. Specifically, using the CPOX reaction temperature alone as an indication of the desired O:C ratio may compromise system power conversion. Tar (C 10Fuel contaminants such as sulfur dioxide (H8), and other long chain hydrocarbon molecules can contribute to coke formation. Sulfur is a fuel contaminant that forms sulfides either in the fuel / air mixture or in the syngas. Sulfides, including carbon disulfide (CS2), hydrogen sulfide (HS), sulfur dioxide (SO2), and others, can poison the catalyst layer in a CPOX reactor and compete for oxygen sites in the solid oxide anode electrode layer (150) in a SOFC stack. Therefore, it is desirable for the hydrocarbon fuel source to have a low sulfur content, e.g., less than about 50 parts per million (PPM). Another issue that reduces CPOX conversion efficiency is burn-through of the catalyst layer, which occurs when a part or catalyst layer is permanently damaged by prolonged exposure to excessive reaction temperatures. For this reason, it is important that the CPOX reaction temperature does not exceed the burn-through temperature.

[0174] Despite the complexity of syngas generation, when air is used as the oxidant, syngas primarily contains varying percentages of the major fractions N2, H2, and CO, along with a small percentage of CO2. However, the weight percentages of each of the syngas components, including the weight percentages of the reactants H2 and CO, vary with changes in the O:C ratio, the CPOX reaction temperature, the type of hydrocarbon fuel, and the homogeneity and contaminant content of the hydrocarbon fuel. Thus, syngas may contain small percentages of other components, such as unreacted hydrocarbons, oxygen gas, sulfides, water, and the weight percentages of each major fraction of syngas components will vary with changes in the O:C ratio of the fuel-air mixture, as well as changes in the CPOX reaction temperature.

[0175] Thus, an objective of one embodiment of the present disclosure is to maximize the conversion efficiency of the CPOX reaction by maximizing the weight percentage of the anode gas reactants H and CO, while also minimizing the weight percentage of unreacted hydrocarbons (e.g., methane (CH) and oxygen gas (O)) in the syngas produced by the CPOX reaction.

[0176] 8.12.8 First Thermal Sensor and Thermally Conductive Coupling 9-12, 13A, 13B and 14, there are shown a number of different non-limiting exemplary embodiments of a first thermal sensor (8030) attached to a heat conducting element (9005, 10005, 11005, 12005, 13005). In each of the non-limiting exemplary embodiments, the corresponding heat conducting element is supported in mating contact with a longitudinal surface of a cylindrical catalyst body (3030) and is formed from a material having a thermal conductivity coefficient of 50 W / m°K or greater, preferably 100 W / m°K or greater. This compares to a thermal conductivity of a ceramic catalyst body of about 2-7 W / m°K. Additionally, each of the heat conducting elements is formed with a contact area between the heat conducting element and the catalyst body sufficient to facilitate a high conductive thermal energy transfer rate from the catalyst body (3030) to the heat conducting element across the contact area. When the temperature difference between the catalyst body and the heat conducting element is large, for example, at initial start-up, the thermal conductivity across the contact area is large. However, as the temperature difference approaches zero, the largest influences on the thermal conductivity between the catalyst body and the heat conducting element are the thermal conductivity of the heat conducting element, the contact area between the heat conducting element and the catalyst body, and the thermal mass of the heat conducting element (see Equation 5 above). However, for materials with high thermal conductivity coefficients, such as copper, aluminum, which are primarily metals, the difference in thermal mass is more simply expressed as the difference in material volume. Thus, except for selecting a material with a high thermal conductivity coefficient, the heat conducting element of the present disclosure is formed with a sufficient contact area between the catalyst body and the heat conducting element, and with a material volume to rapidly conduct thermal energy from the catalyst body (3030) to the heat conducting element. Preferably, the contact surface area is sized to promote a sufficiently high thermal conductivity between the catalyst body and the heat conducting element to substantially match the temperature of the contact area surface with the temperature of the heat conducting element.

[0177] Each heat transfer element is supported in mating contact with either the exterior or interior longitudinal surface of the cylindrical catalyst body (3030). The contact area between the catalyst body and the heat transfer element is defined as the product of the circumferential contact area and the longitudinal contact area, where the longitudinal contact area extends along the longitudinal axis of the catalyst body and the circumferential contact area extends along the circumferential surface of the catalyst body perpendicular to the longitudinal axis. Other contact area shapes and orientations can be used without departing from this disclosure.

[0178] When formed with sufficient thermal mass and contact area, the heat transfer element is configured to rapidly transfer thermal energy across the contact area until the temperature of the heat transfer element is substantially equal to the average or bulk surface temperature of the catalytic body across the contact surface area. Furthermore, based on the high thermal conductivity provided across the contact surface area, a change in the bulk or average temperature of the contact surface area of ​​the catalytic body is rapidly followed by a similar change in temperature of the heat transfer element. Thus, the temperature sensed by the first thermal sensor (8030) provides a reliable and repeatable indication of the average or bulk surface temperature of the catalytic body across the contact area.

[0179] The first thermal sensor (8030) generates a first temperature signal (8031) that is sampled by the electronic controller at a sampling frequency that produces a continuous stream of first temperature signal values ​​each corresponding to the instantaneous temperature as the surface of the heat conducting element to which the first thermal sensor is attached. Because the temperature sensed by the first thermal sensor (8030) provides a reliable and repeatable indication of the average or bulk surface temperature of the catalyst body across the contact area, changes in the first temperature signal (8031) correspond to proportional changes in the CPOX reaction temperature, for example, as the O:C ratio of the inflowing fuel changes. Viewed another way, changes in the first temperature signal (8031) indicate the heat flux density (W / m 2 ) is proportional to the change in

[0180] As mentioned above, the temperature of the CPOX reaction is likely to vary along the longitudinal length of the cylindrical catalyst body. According to a conventional reactor control method disclosed by Roychoubhury et al., three temperature sensors are disposed at three separate longitudinal locations to sense three different temperatures along the longitudinal length of the catalyst body. An algorithm determines the maximum and minimum temperatures corresponding to the temperatures output by the three sensors, and based on the temperature distribution, the O:C ratio of the incoming fuel-air mixture is changed in a manner that minimizes the difference between the maximum and minimum temperatures sensed by the three temperature sensors. However, the present disclosure uses only one temperature sensor coupled with a heat conducting element that is supported in contact with the catalyst body over a contact area that extends along a portion of the longitudinal dimension of the catalyst body. The present disclosure reduces the number of sensors by sensing only the first temperature signal (8031) and reduces complexity and improves reliability by eliminating the algorithm for calculating the temperature diffusion. 9-12 and 13A and 13B are formed from any one of copper, aluminum, nickel, brass, beryllium, iridium, magnesium, molybdenum, tungsten, and zinc and / or alloys thereof. Additionally, for materials susceptible to oxidation damage at operating temperatures above about 400° C., the outer surface of the heat conducting element is coated with a material that is resistant to oxidation, such as, for example, nickel plating.

[0181] Referring to FIG. 9 in a first exemplary non-limiting embodiment, the first heat transfer element includes a prismatic rod (9005) disposed in mating contact with the outer surface (9010) of the catalyst body (3030). The longitudinal axis (9015) of the prismatic rod (9005) is oriented substantially parallel to the longitudinal axis (9020) of the catalyst body (3030). The catalyst body (3030) is a cylindrical element including a ceramic substrate with a diameter of 25.4 mm and a longitudinal length of 25.4 mm. When installed in the cylindrical catalyst cavity (3035), the catalyst body (3030) has an input end at the interface (3032) and an output end (3034) that delivers the syngas (2027) to the fuel inlet manifold (3055), as shown in FIG. 7.

[0182] The prismatic rod (9005) of the first heat conducting element has a diameter of 3.2 mm, which is approximately one-eighth (1 / 8) of the diameter of the catalytic body (3030). The prismatic rod (9005) has a longitudinal length of 6.3-12.7 mm, which is approximately one-quarter (1 / 4) to one-half (1 / 2) of the longitudinal length of the catalytic body (3030). The prismatic rod (9005) may be positioned longitudinally to contact the outer surface (9010) of the catalytic body (3030) at any longitudinal position between the input or interface end (3032) and the output end (3034). The optimal longitudinal contact position of the prismatic rod (9005) may be determined by experiment, for example during system calibration, or by a support structure provided to support the prismatic rod (9005) in mating contact with the contact surface, or the like. Other prism rods (9005) having different longitudinal and outer diameter dimensions may be used without departing from this disclosure.

[0183] The first thermal sensor (8030) is attached to or supported by the prismatic rod (9005) to provide a thermally conductive coupling between at least one surface of the prismatic rod (9005) and the first thermal sensor (8030). In the exemplary embodiment of FIG. 9, the prismatic rod (9005) includes a through hole or a blind hole (9025) extending along the longitudinal axis (9015) of the prismatic rod. The first thermal sensor (8030) is installed in the through or blind hole (9025) and held in place. Alternatively, the first thermal sensor (8030) is thermally conductively coupled to any external or internal surface of the prismatic rod (9005) by one or more mechanical fasteners or clamps, by brazing with a thermally conductive adhesive, or the like.

[0184] The prismatic rod (9005) is attached to or supported in mating contact with the outer surface (9010) of the catalyst body (3030) by radially inward pressure exerted by an insulating element (3080) disposed inside the catalyst cavity (3035). As best shown in FIG. 3, the insulating element (3080) is formed as an annular ring disposed inside the catalyst cavity (3035) between the annular enclosure wall (3060) and the cylindrical catalyst body (3030). By mounting the prismatic rod (9005) and the first thermal sensor (8030) in the catalyst cavity (3035) between the insulating element (3080) and the outer surface of the catalyst body (3030), the insulating element (3080) provides a radially directed compressive force sufficient to support the prismatic rod (9005) in mating contact with the cylindrical catalyst body (3030). The compressive force is sufficient to thermally conductively couple the prismatic rod to the cylindrical catalytic body (3030) across the contact area. Alternatively, the prismatic rod (9005) is coupled to the outer surface of the catalytic body (3030) by brazing, a thermally conductive adhesive, one or more fasteners or clamps, or the like. Preferably, the configuration of the prismatic rod (9005), the configuration of the first thermal sensor (8030), the longitudinal position between the interface (3032) and the output end (3034), and the contact method used to secure the prismatic rod (9005) relative to the outer surface of the catalytic body provide a first temperature signal output from the first thermal sensor (8030) that is repeatable and sufficiently responsive to temperature changes in the bulk, or average temperature, of the contact area primarily associated with changes in the flow rate of oxidant delivered to the mixing chamber (8015).

[0185] 10, the second heat transfer element embodiment (10010) includes a cylindrical segment (10005). The cylindrical segment (10005) includes a contact surface area (10008) formed with a radius of curvature that matches the radius of curvature of the outer circumferential surface of the cylindrical catalyst body (3030). The cylindrical segment (10005) includes a longitudinal axis (10015) that is oriented parallel to the longitudinal axis (10020) of the cylindrical catalyst body (3030). The cylindrical segment (10005) is formed from a prismatic rod having a diameter of about 6.4 mm, which is about one-quarter (¼) the diameter of the cylindrical catalyst body (3030). The cylindrical segment (10005) has a longitudinal length of 6.3 to 12.7 mm, which is approximately one-quarter (¼) to one-half (½) of the longitudinal length dimension of the catalyst body (3030). The cylindrical segment (10005) may be longitudinally positioned to contact the outer surface (10010) of the catalyst body (3030) at any longitudinal location between the input or interface end (3032) and the output end (3034). Other cylindrical segments (10005) having other rod diameters and longitudinal length dimensions may be used without departing from this disclosure.

[0186] The first thermal sensor (8030) is attached to or supported by the cylindrical segment (10005) and provides a first temperature signal (8031) corresponding to the temperature of the cylindrical segment (10005) proximate to a surface in contact therewith. In the exemplary embodiment of FIG. 10, the cylindrical segment (10005) includes a through hole or blind hole (10025) extending along its longitudinal axis (10015), and the first thermal sensor (8030) is installed in the through hole or blind hole (10025). Alternatively, the first thermal sensor (8030) is thermally coupled to any exterior or interior surface of the cylindrical segment (10005) by brazing with a thermally conductive adhesive, with one or more fasteners of a clamp, or the like.

[0187] The cylindrical segment (10005) is attached to or supported in mating contact with the outer surface (10010) of the catalyst body (3030) by an internal radial pressure exerted by an insulating element (3080) disposed inside the catalyst cavity (3035). As best shown in FIG. 3, the insulating element (3080) is formed as an annular ring disposed inside the catalyst cavity (3035) between the annular enclosure wall (3060) and the cylindrical catalyst body (3030). By mounting the cylindrical segment (10005) and the first thermal sensor (8030) in the catalyst cavity (3035), the insulating element (3080) provides sufficient radial compressive force between the insulating element (3080) and the outer surface of the catalyst body (3030) to support the cylindrical segment (10005) in mating contact with the cylindrical catalyst body (3030). The compressive force is sufficient to thermally conductively couple the cylindrical segment (10005) to the cylindrical catalyst body (3030) over the entire surface contact area (10008). Alternatively, the cylindrical segment (10005) is coupled to the outer surface of the catalyst body (3030) by brazing, a thermally conductive adhesive, one or more fasteners or clamps, or the like. Preferably, the configuration of the cylindrical segment (10005), the configuration of the first thermal sensor (8030), the longitudinal position between the interface (3032) and the output end (3034), and the contact method used to secure the cylindrical segment (10005) to the outer surface of the catalyst body provide a first temperature signal output from the first thermal sensor (8030) that is repeatable and sufficiently responsive to temperature changes in the bulk, or average temperature, of the contact area primarily associated with changes in the flow rate of oxidant delivered to the mixing chamber (8015).

[0188] 11, in a third exemplary, non-limiting embodiment, the third heat transfer element includes a hollow cylinder (11005) having an inner diameter sized to provide mating contact with the outer diameter of the catalyst body (3030) and an outer diameter sized to provide a desired thickness or material volume of the annular wall formed by the hollow cylinder (11005). The hollow cylinder (11005) has a longitudinal axis (11015) oriented substantially coaxially with the longitudinal axis (11020) of the catalyst body (3030). The contact area between the hollow cylinder (11005) and the catalyst body (3030) extends over a surface of the inner diameter of the hollow cylinder (11005).

[0189] The hollow cylinder (11005) is formed with an annular wall thickness of about 1.6 mm and a longitudinal length of 6.3-12.7 mm, which is about one-quarter (¼) to one-half (½) of the longitudinal length of the catalyst body (3030). The hollow cylinder (11005) may be longitudinally positioned to contact the outer surface (10010) of the catalyst body (3030) at any longitudinal location between the input and output ends (3034) of the interface end (3032). The hollow cylinder (11005) is held in mating contact with the outer surface (11010) of the catalyst body (3030) by soldering, by a thermally conductive adhesive, by crimping, by fasteners or clamps, by an interference fit, etc. Other hollow cylinders (11005) having different longitudinal lengths or material thicknesses may be used without departing from this disclosure.

[0190] The first thermal sensor (8030) is attached to or supported in mating contact with an outer surface of the hollow cylinder (11005) to provide a thermally conductive coupling between the outer surface of the hollow cylinder (11005) and the first thermal sensor (8030). In the exemplary embodiment of Figure 11, the first thermal sensor (8030) is thermally conductively coupled to or supported in mating contact with the outer surface of the hollow cylinder (11005) by one of: by inward radial pressure applied by an insulating element (3080) disposed inside the catalyst cavity (3035), by brazing, by a thermally conductive adhesive, by one or more fasteners or clamps, etc., as shown in Figure 3 above and described above.

[0191] 12, a fourth exemplary, non-limiting embodiment of a conductive element includes a spiral portion (12005) of a hollow cylinder. The spiral portion (12005) has an inner radius sized to provide mating contact with the outer surface (12010) of the catalyst body (3030) and an outer radius sized to provide a desired thickness of the spiral portion of (12005). The spiral portion has a longitudinal axis (12015) that is oriented substantially coaxially with the longitudinal axis (12020) of the catalyst body (3030).

[0192] The helical portion (12005) is formed with an annular wall thickness of about 1.6 mm and a longitudinal length of 12.7-25.4 mm, i.e., about one-half (1 / 2) of the total longitudinal length of the catalyst body (3030). The helical portion (12005) may be longitudinally positioned to contact the outer surface (11010) of the catalyst body (3030) at any longitudinal location between the interface end (3032) and the output end (3034). Other helical portions (12005) having different longitudinal length and thickness dimensions may be used without departing from this disclosure.

[0193] The first thermal sensor (8030) is attached to or supported in mating contact with an outer surface of the helical portion (12005) to provide a thermally conductive coupling between the outer surface of the helical portion and the first thermal sensor (8030). In the exemplary embodiment of Figure 12, the first thermal sensor (8030) is thermally conductively coupled to or supported in mating contact with the outer surface of the helical portion (12005) by one of: by inward radial pressure applied by an insulating element (3080) disposed inside the catalyst cavity (3035), by brazing, by a thermally conductive adhesive, by one or more fasteners or clamps, etc., as shown in Figure 3 above and described above.

[0194] 13A and 13B, the cylindrical catalyst body (13030) includes a plurality of catalyst fuel passages (3085), each of which provides an individual conduit extending longitudinally through the cylindrical catalyst body (13030). The central cavity (13007) is formed by a through hole or blind hole that extends completely or partially through the cylindrical catalyst body (13030) along its longitudinal axis (13020). As shown in the cross-sectional view of FIG. 13B, a fifth exemplary non-limiting conductive element embodiment includes a solid cylinder (13005) disposed inside the central cavity (13007). The solid cylinder (13005) is supported within and in mating contact with the inner diameter of the central cavity (13007). The solid cylinder (13005) has a longitudinal axis that extends substantially coaxially with the longitudinal axis (13020) of the catalyst body (13030).

[0195] The solid cylinder (13005) is formed with an outer diameter sized equal to, slightly larger than, or slightly smaller than the inner diameter of the central cavity (13007). Non-limiting exemplary diameters of the solid cylinder (13005) are 1.5-6.4 mm in diameter with a longitudinal length of 6.3-12.7 mm, which is approximately one-quarter (¼) to one-half (½) of the longitudinal length of the catalyst body (13030). The solid cylinder (13005) may be longitudinally positioned to contact the central cavity (13007) at any longitudinal position between the input or interface end (3032) and the output end (3034). Other solid cylinder (13005) embodiments having different longitudinal lengths and external cylinder diameter dimensions may be used without departing from this disclosure.

[0196] The first thermal sensor (8030) is attached to the solid cylinder (13005) or provides a thermally conductive coupling between at least one surface of the solid cylinder (13005) and the first thermal sensor (8030). In the exemplary embodiment of FIG. 13B, the solid cylinder (13005) includes a through hole or blind hole (13025) that extends along or parallel to the longitudinal axis (13020) of the solid cylinder (13005). The first thermal sensor (8030) is installed in the through hole or blind hole (13025) and held in place. Alternatively, the first thermal sensor (8030) is thermally conductively coupled to any external or internal surface of the solid cylinder (13005) by brazing with a thermally conductive adhesive, with one or more mechanical fasteners or clamps, or the like.

[0197] Referring to FIG. 14 in a sixth exemplary, non-limiting embodiment, the catalyst body (14030) is formed as an open-cell solid foam structure, including a solid, non-porous, ceramic foam material formed with a plurality of interconnected open cells distributed throughout the solid ceramic foam structure. The open cells extend between an input or interface end (3032) and an output end (3034). However, some open cells may extend from the input or interface end (3032) to a sidewall of the cylindrical catalyst body (14030). Each of the plurality of open cells (14031) includes an inner surface thereof coated with a catalyst layer (3090). The open-cell solid foam structure is formed as a cylindrical catalyst body (14030) having a circumferential diameter of 25.4 mm and a longitudinal length of 25.4 mm. When installed in the cylindrical catalyst cavity (3035), the input end (14032) of the cylindrical catalyst body (14030) is inserted to contact the reactor shield base wall (3015) at the interface (3032), and the fuel-air mixture (2025, 3025) exiting the reactor shield base wall (3015) enters the input end of the solid foam structure through its open cells (14031) and passes through the open cells to the output end (14034) or through the open cell openings passing through the open cells to the circumferential outer surface (14010). While passing through the open cells, the fuel-air mixture (2025, 3025) contacts the catalyst layer (3090) to initiate the CPOX reaction. After exiting the open cells, the reformed fuel or syngas (2027) passes from the catalyst cavity to the fuel inlet manifold (3055).

[0198] The prismatic rod (9005) can be used as a heat conducting element. As described above, the prismatic rod (9005) has a diameter of 3.2 mm, which is about one-eighth (1 / 8) of the diameter of the cylindrical catalyst body (14030), and a longitudinal length of 6.3 to 12.7 mm, which is about one-quarter (1 / 4) to one-half (1 / 2) of the longitudinal length of the cylindrical catalyst body (14030). The prismatic rod (9005) can be positioned longitudinally to contact the circumferential outer surface (14010) at any longitudinal position between the interface end (13032) and the output end (13034). Similarly, any of the heat conducting elements (10005, 11005, 12005, 13005) described above can be used in combination with the open cell solid foam structure of the catalyst body (14030).

[0199] The first thermal sensor (8030) is attached to or supported by the prismatic rod (9005) to provide a thermally conductive coupling between at least one surface of the prismatic rod (9005) and the first thermal sensor (8030). In the exemplary embodiment of FIG. 14, the prismatic rod (9005) includes a through hole or blind hole (9025) extending along its longitudinal axis (9015), and the first thermal sensor (8030) is installed in the through hole or blind hole (9025). Alternatively, the first thermal sensor (8030) is thermally conductively coupled to any exterior or interior surface of the prismatic rod (9005) by brazing, by a thermally conductive adhesive, by one or more clamp fasteners, or the like.

[0200] The prism rod (9005) is attached or supported by mating contact with the circumferential outer surface (14010) of the cylindrical catalyst body (14030) by radial pressure applied by an insulating element (3080) disposed inside the catalyst cavity (3035), or by brazing, by a thermally conductive adhesive, by one or more fasteners or clamps, etc., as shown in FIG. 3 and described above.

[0201]

[0202] Second Thermal Sensor 8, the second thermal sensor (8040) is thermally conductively coupled to an exterior surface of one of the hot zone enclosure walls (115), for example, the outer surface of the longitudinal cylindrical side wall (2015) shown in FIG. 2. Alternatively, the second thermal sensor (8040) can be positioned on an interior or exterior surface of any one of the hot zone enclosure walls forming the first thermal conduction path. The second thermal sensor (8040) generates a second temperature signal at a sampling frequency that is sampled by the electronic controller to generate a continuous stream of second temperature signal values ​​each corresponding to an instantaneous temperature of the surface of one of the hot zone enclosure walls (115). However, the hot zone enclosure wall (115) is thermally conductively coupled to the disk-shaped support walls (2082, 2084) that support the opposing ends of each tubular fuel cell (2080) of the SOFC stack such that the change in temperature represented by the change in the second temperature signal corresponds to or is proportional to the change in the SOFC reaction temperature, for example, when the O:C ratio of the incoming fuel changes. Alternatively, in other non-limiting embodiments, the second thermal sensor (8040) is thermally conductively coupled to any surface of the intermediate enclosure (2510) that forms the second thermal conduction path, or to any one of the outer enclosure walls (2514, 2516, 2518) that form the third thermal conduction path without departing from this disclosure, so long as the change in temperature represented by the change in the second temperature signal corresponds to or is proportional to the change in the SOFC reaction temperature, for example, when the O:C ratio of the incoming fuel changes.

[0203] Third thermal sensor: 3, the third thermal sensor (3135) is thermally coupled to a surface of the heat dissipation flange 3100 shown in FIG. 3. Alternatively, the third thermal sensor (3135) can be positioned on any surface of the fuel furnace body (3040) that extends outside the outer enclosure walls (2514, 2516, 2518) that form the third thermal conduction path. The third thermal sensor (3135) generates a third temperature signal that is sampled by the electronic controller at a sampling frequency that generates a continuous stream of third temperature signal values ​​each corresponding to an instantaneous temperature corresponding to a surface of the third thermal conduction path associated with a surface of the fuel furnace body (3040). However, because the third thermal conduction path also extends to elements that do not extend outside the outer enclosure wall, such as the annular perimeter wall (3010) and the reactor shield base wall (3015), changes in the third temperature signal will ideally correspond to or be proportional to changes in temperature of the fuel furnace body as the temperature inside the fuel chamber approaches a fuel auto-ignition temperature in the range of 295-580°C, depending on the type of hydrocarbon fuel, for example. Alternate Operating Modes CPOX reaction temperature

[0204] 8, in a non-limiting exemplary mode of operation, a first temperature signal (8031) is received by the electronic controller (190) from a first thermal sensor (8030). The first temperature signal (8030) may include an analog or digital signal corresponding to a voltage or current amplitude, a normalized voltage or current amplitude, or the like, with each different voltage or current amplitude value of the first temperature signal (8031) corresponding to an actual instantaneous temperature or a relative instantaneous temperature sensed by the first thermal sensor (8030). The electronic controller (190) stores a plurality of first temperature setpoint values. The plurality of first temperature setpoint values ​​may include different first temperature setpoint values ​​for each type of hydrocarbon fuel used by the SOFC system, such as a first temperature setpoint value for propane (C3H8) and a different first temperature setpoint value for natural gas or methane (CH4). The plurality of first temperature setpoint values ​​may include a different first temperature setpoint value for each operating mode of the SOFC system, e.g., a first temperature setpoint value associated with a start-up mode when the fuel is propane and a different first temperature setpoint value associated with a steady state operating mode when the fuel is propane, etc. The plurality of first temperature setpoint values ​​may also include a first temperature setpoint value associated with a maximum safe operating temperature, e.g., when the fuel is methane, etc. Additionally, each first temperature setpoint value may include a range of values, e.g., defined by a maximum and minimum first temperature setpoint value, defined by a median value with a plus or minus range, etc.

[0205] Based on the calibration process described below, each first temperature setpoint value or range of first setpoint values ​​corresponds to a desired syngas composition, for example, where the syngas composition is free or substantially free of unreacted hydrocarbon fuel and / or hydrogen and carbon-based by-products of the CPOX reaction. As an example, where the hydrocarbon fuel used is methane, the desired first temperature setpoint value may be a value that is free of methane (CH4) and other by-products of the CPOX reaction, such as CH X Tar (C 10 H8), and It produces a syngas composition that is free or substantially free of other long chain hydrocarbon molecules, particularly those that can contribute to coke formation, sulfides such as carbon disulfide (CS2), hydrogen sulfide (HS), sulfur dioxide (SO2), etc., that can compete for oxygen sites on and / or damage the solid oxide anode electrode layer (150) in the SOFC stack. In another example, when the hydrocarbon fuel used is propane (C3H8), the desired first temperature set point value produces a syngas composition that is substantially free of propane, methane, and other by-products of the CPOX reaction described above.

[0206] FIG. 15A is a graphical representation (1500) of the calibration data listed in the table (1505) of FIG. 15b. The data includes the O:C or oxygen to carbon ratio of the incoming hydrocarbon fuel air mixture (2025, 3025), T_CPOX, or the first temperature in degrees Celsius based on weight percent, %CH4 and %CH2H x With reference to FIG. 15A, the O:C ratio is shown along the horizontal axis over a range of 1.2 to 1.5, and the O:C ratio is plotted versus T_CPOX(c) or first temperature, shown on the left vertical axis of FIG. 15A over a range of 608 to 630 degrees Celsius. The data includes methane (CH4) and (C2H x ), or the right vertical axis of FIG. 15A. Thus, the right axis further includes the weight percent of various undesirable by-products of the CPOX reaction, such as CH x Tar (C 10 H8), and other long chain hydrocarbon molecules, particularly those that can contribute to coke formation, sulfides, such as carbon disulfide (CS2), hydrogen sulfide (HS), sulfur oxide (SO2), etc., that can compete for oxygen sites in and / or damage the solid oxide anode electrode layer (150) in the SOFC stack.

[0207] As best seen in FIG. 15A, the plot (1510) of O:C ratio versus T_CPOX (°C) is linear. The plot (1510) shows that the temperature T_CPOX (°C), which corresponds to the instantaneous temperature sensed by the first thermal sensor (8030), increases linearly with increasing O:C ratio. In other words, as air is added to the hydrocarbon fuel-air mixture (2025, 3025), the temperature T_CPOX (°C) increases.

[0208] Also in FIG. 15A, the plot (1515) of O:C ratio vs. %CH4 is non-linear. Plot (1515) shows that the percentage of methane remaining in the syngas composition decreases non-linearly with increasing O:C ratio. Thus, when the percentage of unreacted methane is substantially zero, increasing O:C ratios decrease the percentage of unreacted methane as T_CPOX increases until an O:C ratio of 1.4 or greater is reached. As further shown in FIG. 15A, an O:C ratio of 1.4 corresponds to a T_CPOX temperature of 628° C. Also in FIG. 15A, the plot (1515) of O:C ratio vs. %CH2H4 shows that the percentage of unreacted methane remaining in the syngas composition decreases non-linearly with increasing O:C ratio. X The plot (1520) of is not clearly nonlinear. The plot (1520) shows the % CH remaining in the syngas composition. X This indicates that a proportion of the

[0209] Thus, FIG. 15A illustrates that by detecting a temperature T_CPOX corresponding to a first temperature signal (8031), the O:C ratio and syngas composition can be determined based solely on the T_CPOX value, such that at least the T_CPOX temperature setpoint value or range of setpoint values ​​(1530) is greater than or equal to methane (CH4), (CH2H4), or (CH4H2O). X15A ) and other long chain hydrocarbon molecules from the synthesis gas produced. More specifically, a CPOX reaction supported while the T_CPOX temperature is maintained at a set point value within the range of set point values ​​(1530) shown in FIG. 15A is free of undesired hydrocarbon components. Furthermore, the T_CPOX temperature can be controlled simply by varying the oxidant flow rate. Thus, based on the plot shown in FIG. 15A and the data listed in FIG. 15B, the first temperature set point range (1530) corresponds to a set point temperature T_CPOX(C) of about 618-623° C., which corresponds to an O:C ratio range of about 1.38-1.42. During steady state operation, the electronic controller (190) samples the first temperature signal (8031) at a sampling frequency to generate a continuous stream of first temperature signal values ​​(8031), each corresponding to an instantaneous temperature of a heat transfer element supported in mating contact with a catalyst body as shown in any one of Figures 9-14 above. The electronic controller compares each first temperature signal value (8031) to an appropriate setpoint temperature value, or to a range of appropriate setpoint values. The setpoint values ​​are stored by the electronic controller, and different setpoint values ​​or setpoint value ranges may correspond to different hydrocarbon fuel types, different SOFC system configurations, different heat transfer element types, and other operating parameters such as operating mode, oxidant type, fuel-air mixture temperature, DC power output of the SOFC system, etc. The electronic controller does not operate when the sampled first temperature signal value (8031) is equal to or within a range of appropriate first temperature setpoint values. When the sampled first temperature signal value is not equal to or within the range of the appropriate first temperature setpoint value, the electronic controller draws a logical conclusion to either increase or decrease the oxidant delivered to the mixing chamber (8015) and then sends one or more command and control signals to the oxidant flow modulator (8025), the command and control signals corresponding to either an increase or decrease in the oxidant flow rate called for by that logical conclusion.

[0210] In one non-limiting exemplary mode of operation, when the sampled first temperature signal value (8031) is less than a minimum allowed first signal value, the electronic controller (190) commands the oxidant flow modulator (8025) to increase the mass or volumetric flow rate of oxidant entering the mixing chamber (8015), thereby increasing the O:C ratio, resulting in an increase in the CPOX reaction temperature and a corresponding increase in the temperature T_CPOX(°C) and the corresponding first temperature signal value (8031). Alternatively, when the sampled first temperature signal is greater than the maximum allowed first temperature signal value (8031), the electronic controller (190) commands the oxidant flow modulator (8025) to decrease the mass or volumetric flow rate of oxidant entering the mixing chamber (8015), thereby decreasing the CPOX reaction temperature. In each case, an increase or decrease in the CPOX reaction temperature causes a corresponding proportional increase or decrease in the temperature of a heat conductive element thermally coupled between the catalyst body (9005, 10005, 11005, 12005, 13005) and the first thermal sensor (8030). In non-limiting exemplary embodiments, the sampling rate of the first signal ranges from about 5 Hz to 100 KHz. In non-limiting exemplary embodiments, the minimum incremental change in the volumetric flow rate of the oxidant ranges from 0.1 to 2.0 standard cubic centimeters per minute (SCCM).

[0211] 8.12.11.2 SOFC reaction temperature In an exemplary mode of operation, a second temperature signal (8041) is received by the electronic controller (190) from the second thermal sensor (8040). The second temperature signal (8041) may include an analog or digital signal corresponding to a voltage or current amplitude, a normalized voltage or current amplitude, or the like, with each different voltage or current amplitude value of the second temperature signal (8041) corresponding to a different temperature sensed by the second thermal sensor (8040). The electronic controller (190) stores one or more second temperature set point values. Each second temperature set point value corresponds to a second temperature signal value or range of values ​​that corresponds to a SOFC reaction temperature that produces a desired result.

[0212] The desired outcome may include any one of a threshold DC power or current output value corresponding to a median, maximum, or other DC power or current amplitude output of DC power or current production by the SOFC fuel cell stack. Other desired outcome criteria are, for example, the composition of exhaust gas exiting the system exhaust port (2165), or the exhaust gas exiting the SOFC tubes into the combustion chamber (2135), where the exhaust gas composition is substantially free of unreacted anode gas components, H2 and CO, and / or by-products that may indicate incomplete conversion of the anode gas to power. Still other desired outcome criteria are various measurable characteristics of the efficiency of the fuel cell, such as electrical energy output per unit volume of hydrocarbon fuel input.

[0213] As discussed above with respect to the first setpoint temperature value, since each fuel type and each operating mode of the SOFC system may have a different second temperature setpoint value corresponding to only one hydrocarbon fuel type or only one operating mode, the electronic controller (190) preferably stores a different second temperature setpoint value for each of a plurality of different hydrocarbon fuel types, for each operating mode, and so on. Thus, the electronic controller (190) may also sense the hydrocarbon fuel type being used by the SOFC system, or a user may input the hydrocarbon fuel type and other parameters of the SOFC system. In either case, the electronic controller selects the appropriate second temperature setpoint value corresponding to the fuel type and operating mode.

[0214] The second temperature setpoint values ​​stored by the electronic controller (190) may include one second temperature signal value or a range of second temperature signal values ​​corresponding to the second temperature setpoint. The correlation between the desired DC power and the second temperature setpoint value or range of second temperature signal values ​​is determined by system calibration, described below. In addition to storing multiple second setpoint values ​​or ranges corresponding to different hydrocarbon fuel types, the electronic controller may further store other temperature signal values ​​corresponding to other desired operating conditions, such as a safe maximum operating temperature, a minimum or threshold temperature for DC power, etc.

[0215] The electronic controller (190) periodically samples the second temperature signal (8041) received thereby and compares the sampled second temperature signal value to an appropriate second temperature setpoint or range of second temperature setpoint values. If the sampled second temperature signal is equal to the second temperature setpoint or is within the second setpoint range, the electronic controller does not operate. If the sampled second temperature signal is not equal to the second temperature setpoint value or is not within the second setpoint value range, the electronic controller logically concludes by increasing or decreasing the flow rate of hydrocarbon fuel delivered to the mixing chamber (8015) and then sending one or more control and command signals to the hydrocarbon fuel flow rate modulator (8035), where the control signal corresponds to either increasing or decreasing the flow rate of hydrocarbon fuel to the mixing chamber (8015).

[0216] In one non-limiting exemplary mode of operation, when the second temperature signal value is less than a minimum allowed second temperature signal value, the electronic controller (190) commands the hydrocarbon fuel flow modulator (8035) to increase the mass or volumetric flow rate of the hydrocarbon fuel entering the mixing chamber (8015). Alternatively, when the sampled second temperature signal is greater than a maximum allowed second temperature signal value, the electronic controller (190) commands the hydrocarbon fuel flow modulator (8035) to decrease the mass or volumetric flow rate of the hydrocarbon fuel entering the mixing chamber (8015). In a first example, an increase in the flow rate of the hydrocarbon fuel entering the mixing chamber (8015) increases the volume of the hydrocarbon fuel converted to syngas, ultimately increasing the temperature of the syngas and the tubular SOFC rods, which ultimately increases the temperature of the outer enclosure wall sensed by the second thermal sensor (8040). In a second example, a reduction in the flow rate of hydrocarbon fuel entering the mixing chamber (8015) reduces the volume of hydrocarbon fuel converted to syngas, ultimately reducing the temperature of the syngas and the tubular SOFC rods, which ultimately reduces the temperature of the outer enclosure wall sensed by the second thermal sensor (8040).

[0217] Thus, the electronic controller (190) periodically samples the second signal (8041) produced by the second thermal sensor (8040) at a second signal sampling rate and makes appropriate adjustments to increase or decrease the temperature sensed by the second thermal sensor (8040) by increasing or decreasing the mass or volumetric flow rate of the hydrocarbon fuel entering the mixing chamber (8015). The second signal sampling rate is in the range of approximately 5 Hz to 100 KHz. The minimum incremental change in the volumetric flow rate of the hydrocarbon fuel is in the range of 0.1 to 2.0 standard cubic centimeters per minute (SCCM).

[0218] As will be appreciated by those skilled in the art, changing the oxidizer flow rate into the mixing chamber (8015) without also changing the flow rate of the hydrocarbon fuel will result in a change in the O:C ratio. Similarly, when the flow rate of the hydrocarbon fuel into the mixing chamber (8015) is changed without also changing the flow rate of the oxidizer, the O:C ratio will also change. As demonstrated by the plot in FIG. 15A, a change in the O:C ratio, whether due to only changing the oxidizer flow rate or only changing the flow rate of the hydrocarbon fuel, will result in a change in the temperature sensed by the first thermal sensor (8030). Similarly, a change in the O:C ratio, whether due to only changing the oxidizer flow rate or only changing the flow rate of the hydrocarbon fuel, will result in a change in the composition of the syngas, with an increase in methane content occurring as the O:C ratio becomes less than about 1.35.

[0219] According to one non-limiting exemplary method of operation of the present disclosure, a first control loop is operated by the electronic controller (190). In the first control loop, a first thermal sensor (8030) is sampled at a first sampling rate, for example, 50 Hz, with each sample providing a first temperature signal value corresponding to the first thermal sensor (8030). In addition, an oxidant flow rate modulator (8025) is controlled to adjust the oxidant flow rate to increase or decrease the oxidant flow rate as necessary to maintain the first temperature signal value at a set point value or within a range of a set point value corresponding to the first temperature signal stored by the electronic controller. The oxidant flow rate modulator (8025) can be adjusted at the same rate as the first sampling rate of 50 Hz, although the first sampling rate of the first temperature signal value and the adjustment rate of the oxidant flow rate modulator (8025) may be different. Preferably, the first control loop operates independently of a second control loop described below.

[0220] A non-limiting exemplary method of operation further includes operating a second control loop by the electronic controller (190). In the second control loop, the second thermal sensor (8040) is sampled at a second sampling rate, e.g., 50 Hz, with each sample providing a second temperature signal value corresponding to the second thermal sensor (8040). In addition, the hydrocarbon fuel flow rate modulator (8035) is controlled to adjust the flow rate of the hydrocarbon fuel to increase or decrease the flow rate of the hydrocarbon fuel as necessary to maintain the second temperature signal value at a set point value or within a range of a set point value corresponding to the second temperature signal stored by the electronic controller. The hydrocarbon fuel flow rate modulator (8035) may be adjusted at the same rate as the second sampling rate of 50 Hz, although the sampling rate of the second temperature signal value and the adjustment rate of the hydrocarbon fuel flow rate modulator (8035) may be different. Preferably, the second control loop operates independently from the first control loop described above.

[0221] A non-limiting exemplary method of operation further includes operating a third control loop by the electronic controller (190). In the third control loop, each second temperature signal value corresponding to the second thermal sensor (8040) is compared to a control fail-safe temperature corresponding to the location of the second thermal sensor stored by the electronic controller (190). The control fail-safe temperature corresponding to the location of the second thermal sensor is a maximum safe operating temperature for the location of the second thermal sensor (8040), which in this exemplary embodiment is a surface of the hot zone enclosure wall or any other surface of the first heat transfer path. When the control fail-safe temperature corresponding to the location of the second thermal sensor is detected by the electronic controller, the electronic controller is configured to close the hydrocarbon fuel flow modulator (8035) to stop further fuel flow to the mixing chamber (8015). While the hydrocarbon fuel flow modulator is closed, the electronic controller is configured to fully open the oxidant and cathode gas flow modulators (8025, 8050) to pump oxidant through the SOFC system for cooling.

[0222] A non-limiting example method of operation further includes operating a fourth control loop by the electronic controller (190). In the fourth control loop, the SOFC system is intentionally operated at a high O:C ratio, e.g., corresponding to a first warm-up thermal sensor value T_CPOX, as shown in plot (1510) of FIG. 15A. The warm-up sensor value T_CPOX selected for the fourth control loop is greater than the set value T_CPOX or the range of sensor values ​​T_CPOX (1530) used during normal operation. The fourth control loop may be used during a start-up mode, e.g., to more rapidly heat the SOFC system to a SOFC reaction temperature, e.g., as sensed by the second thermal sensor (8040). The fourth control loop may also be used to intentionally overheat the SOFC system, e.g., to burn off tar deposits, as a means to clean the catalyst layer (3090) and the solid oxide anode electrode layer (150).

[0223] The fourth control loop is initiated to operate the SOFC system at an O:C ratio corresponding to the first warming up thermal sensor signal T_CPOX. In the example calibration chart of FIG. 15A, the first warming up thermal sensor signal T_CPOX corresponds to an O:C ratio of at least about 1.4. In one non-limiting embodiment, the fourth control loop is configured to run the SOFC system at an O:C ratio of 1.5 or greater for a predetermined period of time or until the first warming up thermal sensor signal T_CPOX reaches an upper set point corresponding to a maximum first thermal sensor signal T_CPOX.

[0224] The fourth control loop includes an elevated value or range of values ​​associated with the first elevated temperature thermal sensor signal T_CPOX. The T_CPOX elevated value provides a corresponding elevated temperature O:C ratio that is greater than an O:C ratio corresponding to a setpoint temperature or setpoint temperature range (1530) used for normal operation. Preferably, the elevated temperature O:C ratio is in the range of 2.0 to 2.2. Alternatively, the elevated temperature T_CPOX is a range of temperature values ​​corresponding to the first temperature signal (8031) that provides an O:C ratio between about 2.0 to 2.2.

[0225] One non-limiting exemplary implementation of the fourth control loop is to change the setpoint value or range of values ​​(1530) corresponding to the first thermal sensor signal used for normal operation to an elevated T_CPOX setpoint value or range of values ​​corresponding to the desired elevated temperature O:C ratio, and then the fourth control loop adjusts the oxidant flow rate as necessary to raise the first temperature signal value to within the elevated T_CPOX setpoint value or range of values, without changing the hydrocarbon fuel flow rate. After a desired period of time at elevated temperature or O:C ratio, the fourth control loop terminates its operation and returns the elevated T_CPOX elevated temperature setpoint value or range of values ​​to the setpoint value or range of values ​​(1530) corresponding to the first thermal sensor signal used for normal operation, and returns control to the first and second control loops. Other parameters that can be used to terminate operation of the fourth control loop include monitoring the second temperature signal (8041) and monitoring the DC power or current amplitude generated by the SOFC stack as a means of determining when the SOFC stack has reached an acceptable operating temperature.

[0226] Calibration Procedure According to the present disclosure, it is desirable to maximize the weight percent of the anode gas components H and CO in the syngas while preserving unreacted hydrocarbons (e.g., CH, CH X and ethane (C2H6), propane (C3H8), butane (C4H 10 An optimization process is performed to minimize the weight percent of other long hydrocarbon molecular chains, including oxygen gas, water, nitrogen gas, carbon monoxide, carbon dioxide, tar (C), etc. In some calibration procedures, the optimization process also includes the optimization of the weight percent of other long hydrocarbon molecular chains, including carbon monoxide, carbon dioxide, tar (C), etc. 10The optimization process includes characterizing the weight percentage of methane (H8), and other components of the syngas (2027), such as carbon disulfide (CS2), hydrogen sulfide (HS), and sulfur dioxide (SO2). More generally, the optimization process is performed to identify a primary setpoint value or range of setpoint values ​​that corresponds to the first temperature signal (8031). The primary setpoint value or range of setpoint values ​​corresponds to a value produced by the first thermal sensor (8030) and corresponds to a repeatable desired outcome that is related to the characteristics of the CPOX reaction. As discussed above, the desired outcome is a desired syngas composition, although a different, more simple desired outcome could be a weight percentage of methane of less than 0.01%.

[0227] The optimization process is performed to qualify a system design based on a particular hydrocarbon fuel type. The system design includes the configuration and location of the heat transfer elements, (9005, 10005, 11005, 12005, 13005), the configuration and location of the first thermal sensor (8031) relative to the heat transfer elements, the configuration and physical dimensions of the catalyst body (3030), the configuration and location of the second thermal sensor (8040), and a repeatable desired outcome selected to characterize the CPOX reaction.

[0228] In a first calibration step, the SOFC system is placed into a calibration tool or instrument that includes elements provided to measure various operating parameters of the SOFC system, such as, for example, DC output power, and / or current generated in, for example, conduits (8017) and (8022) by the flow rates of the SOFC system oxidant and hydrocarbon fuel, for example, cathode gas flow rate in, for example, conduit (8055), syngas composition in, for example, input manifold (3055), and exhaust gas composition at the outlet of the SOFC stack, for example, combustion chamber (2135).

[0229] The calibration tool or fixture includes at least one gas chromatograph probe positioned in a sample syngas exiting the catalyst body (3030) and a gas chromatograph configured to perform a desired syngas composition analysis. Optionally, a second gas chromatograph probe is positioned to sample the exhaust gas exiting the SOFC stack, for example, disposed inside the combustion chamber (2135), and the second gas chromatograph configured to perform a desired exhaust gas composition analysis. The calibration tool or fixture also provides masses of volumetric flow meters associated with each of the oxidant flow modulator (8025) and the hydrocarbon fuel modulator (8035), and optionally, the cathode flow modulator (8050) for measuring the appropriate gas flow rates. The calibration tool or equipment includes a calibration controller configured to operate the SOFC system, for example, to sample sample thermal sensor signals (8031) and (8040), DC power values ​​(e.g., current and / or power amplitude), adjust oxidant, hydrocarbon fuel, and cathode air flow rates, sample flow meters, store set point values, analyze and store gas composition data, determine and select set point values ​​or value ranges for each of the thermal sensor signals (8031) and (8040), etc. The calibration controller is configured to perform logical operations associated with performing a calibration process by collecting gas chromatograph sample data, flow meter data, and first and second thermal sensor data, and analyzing the data associated with achieving one or more repeatable desired results related to characteristics of the CPOX reaction and / or associated with achieving repeatable desired results related to characteristics of the SOFC reaction.

[0230] In a second calibration step, the SOFC system is brought into a steady state operating mode where the SOFC reaction is initiated and the SOFC system is generating DC power. The operating parameters of the SOFC system are then altered by the calibration controller as necessary to achieve a repeatable desired result related to a characteristic of the SOFC reaction. As described above, the desired result related to a characteristic of the SOFC reaction may be related to a characteristic of the DC power or current output. In one example, the second signal value output by the second thermal sensor (8040) is monitored over a range of flow rates of the hydrocarbon fuel while the flow rate of the oxidant is constant, plotting the DC power output over a range of O:C ratios. In one non-limiting exemplary embodiment, the calibration system may select a second temperature signal set point value or a range of second temperature signal set point values ​​corresponding to a DC power output characteristic, such as a set point corresponding to the start of the DC power output, a set point corresponding to a maximum obtainable DC power output, and a set point corresponding to a median DC power output.

[0231] In another non-limiting exemplary embodiment, the calibration system may select a second temperature signal setpoint value, or a range of second temperature signal setpoint values, corresponding to a composition of exhaust gas exiting the SOFC stack that demonstrates that the exhaust gas is substantially free of anode gas components. In yet another non-limiting exemplary embodiment, the calibration system may select a second temperature signal setpoint value, or a range of second temperature signal setpoint values, or a ratio of the flow rate of the hydrocarbon fuel to the DC current output, or the like. Regardless of which desired output of the SOFC system is being evaluated to determine the second signal value output by the second thermal sensor (8040), the second signal value output by the second thermal sensor (8040) is monitored over any range of flow rates of the hydrocarbon fuel while the oxidant flow rate is constant, and the desired output of the SOFC system versus the O:C ratio is plotted. Additionally, these plots may be repeated for one or more different oxidant flow rates to find an optimal O:C ratio and a corresponding optimal second signal value or range of values ​​corresponding to the desired output of the SOFC system.

[0232] In a third calibration step, the weight percentage of each syngas component or selected syngas components is determined by analyzing a sample of the syngas by the gas chromatograph across a number of different O:C ratios. The O:C ratio is varied by modifying only the oxidant flow rate, a process performed by the calibration controller. During the third calibration step, the flow rate of the hydrocarbon fuel is not changed. The calibration controller also samples the first temperature signal (8031) and the oxidant flow meter data across a number of different O:C ratios and stores the first signal values ​​and the oxidant flow rate values. The calibration controller is configured to analyze the syngas component weight percentages for each O:C ratio and associate the first temperature signal values ​​and the oxidant flow rate values ​​with each O:C ratio. Additionally, during the third calibration step, the calibration controller is configured to monitor and record data associated with a desired output of the SOFC system. Data related to the desired output of the SOFC system includes at least a second temperature signal (8041) at each O:C ratio, and one or more of the following: hydrocarbon fuel and cathode air flow rates, DC output power characteristics of the SOFC stack, and exhaust gas composition from the SOFC stack determined from gas chromatograph data.

[0233] In a fourth calibration step, the weight percentage of each syngas component corresponding to each of the multiple different O:C ratios produced by the third calibration step is analyzed to determine which O:C ratio consistently produces the desired syngas composition, e.g., the weight percentage of methane is less than 0.01%. The fourth calibration step further includes determining, by the calibration controller, a first temperature signal value or a range of first temperature signal values ​​modified by the first thermal sensor (8030) associated with providing the desired syngas composition. As shown by the plot (1510) in FIG. 15A, the first setpoint value or range of values ​​(1530) corresponds to the lowest temperature of the first temperature signal value T_CPOX that satisfies the desired syngas composition. However, other higher temperature values ​​may be selected without departing from this disclosure. Once a first setpoint value or range of setpoint values ​​(1530) is selected, the fourth calibration process can be re-run using other fixed hydrocarbon fuel flow rates to refine the SOFC system operation by making small changes to each of the first and second setpoint values ​​using a fixed hydrocarbon fuel flow rate corresponding to a second setpoint value or range of values ​​corresponding to the second thermal sensor (8040).

[0234] If a calibration fixture is used, the calibration procedure needs to be performed only once for a given SOFC system configuration using a given hydrocarbon fuel type to determine the CPOX reaction temperature set point associated with the first thermal sensor (8030) and the SOFC stack temperature set point associated with the second thermal sensor (8040).

[0235] The calibration fixture optionally also includes a plurality of different hydrocarbon fuel sources, each corresponding to a different hydrocarbon fuel type, for calibrating the SOFC system for each of the plurality of different hydrocarbon fuel types. Thus, the fifth calibration step includes repeating the calibration step two to four times for each of the plurality of different hydrocarbon fuel types, thereby allowing for the selection of a different CPOX reaction temperature set point and a different SOFC stack temperature set point for each of the different hydrocarbon fuel types.

[0236] Although the present invention has been described above with respect to preferred embodiments, those skilled in the art will understand that it is not limited thereto. The various features and aspects of the invention described above can be used individually or together. Moreover, while the present invention has been described in the context of particular environments and particular applications (e.g., solid oxide fuel systems including fuel reformer modules performing exothermic reactions), those skilled in the art will recognize that its usefulness is not so limited and that the present invention may be beneficially utilized in any number of environments and embodiments in which it is desirable to manage thermal energy in high temperature corrosive environments that process combustible materials. Accordingly, the claims set forth below should be construed in light of the full scope and spirit of the invention as disclosed herein.

Claims

1. 1. A solid oxide fuel cell (SOFC) system, comprising: a catalyst body having an input end and an output end, the catalyst body including a solid substrate formed to include a plurality of fuel passages, and a catalyst layer including a material selected to initiate a hydrocarbon fuel reforming reaction formed on an inner surface of one or more of the plurality of fuel passages; a first thermal sensor thermally conductively coupled to a heat conducting element having a thermal conductivity coefficient of 50 W / mK or greater, the heat conducting element being thermally coupled to the catalytic body; at least one SOFC disposed within a hot zone cavity formed within a hot zone enclosure, the hot zone enclosure comprising a structure formed from at least one material having a thermal conductivity coefficient of at least 100 W / mK at an operating temperature of the at least one SOFC; a second thermal sensor positioned to sense the temperature of a surface that changes in temperature proportional to changes in temperature of the hot zone enclosure; a hydrocarbon fuel flow modulator disposed between a hydrocarbon fuel source and the input end; an oxidant flow modulator disposed between a source of oxidant and the input end; an electronic controller operative to send independent command and control signals to each of said hydrocarbon fuel flow modulators and to said oxidant flow modulator; The electronic controller further comprises: receiving a first temperature signal from the first thermal sensor and comparing the first temperature signal to at least a first threshold temperature value or range of first threshold temperature values; operative to receive a second temperature signal from the second thermal sensor and compare the second temperature signal to at least one second threshold temperature value or range of second threshold temperature values; The electronic controller operates a third control loop, and when the value of the second temperature signal is equal to or greater than a control failsafe temperature value, the electronic controller controls the hydrocarbon fuel flow modulator to stop the flow of hydrocarbon fuel to the catalyst body.

2. 2. The SOFC system of claim 1, wherein operating the third control loop further comprises the electronic controller controlling the oxidant flow modulator to provide an oxidant flow to the SOFC system for cooling.

3. The SOFC system further includes a cathode gas flow modulator that provides a flow of cathode gas to the hot zone enclosure; The SOFC system of claim 2 , wherein operating the third control loop includes the electronic controller controlling the oxidant flow modulator to provide an oxidant flow to the SOFC system for cooling.

4. The SOFC system of claim 1 , wherein the second thermal sensor is thermally conductively coupled to and attached to the hot zone enclosure.

5. The SOFC system of claim 1 , wherein the electronic controller operates a first control loop to control operation of the oxidant flow modulator based on a first temperature signal received from the first thermal sensor.

6. The SOFC system of claim 1 , wherein the electronic controller operates a second control loop to control operation of the hydrocarbon fuel flow modulator based on a second temperature signal received from the second thermal sensor.

7. 13. The SOFC system of claim 1, wherein the electronic controller operates a fourth control loop to control the flow of one or more oxidants and a hydrocarbon fuel to operate the one or more catalyst bodies and at least one SOFC at a temperature sufficient to combust carbon-based deposits.

8. 2. The SOFC system of claim 1, wherein the heat conducting element is thermally coupled to the catalytic body, and a contact area between the heat conducting element and the catalytic body is greater than a contact area between the first thermal sensor and the heat conducting element.

9. the input end and the output end are separated by a first longitudinal dimension extending along a longitudinal axis of the catalyst body, and the heat conducting element includes a longitudinal length having a second longitudinal dimension extending along the longitudinal axis; The SOFC system of claim 1 , wherein the second longitudinal dimension is at least one-quarter of the first longitudinal dimension.

10. 2. The SOFC system of claim 1, wherein the SOFC system includes an intermediate enclosure surrounding the hot zone enclosure, an outer enclosure surrounding the intermediate enclosure, and an insulating layer disposed between the intermediate enclosure and the outer enclosure, the outer enclosure being formed from a material having a thermal conductivity coefficient of 100 W / mK or greater.

11. The SOFC system of claim 10 , wherein the second thermal sensor is thermally conductively coupled to the intermediate enclosure.

12. The SOFC system of claim 10 , wherein the second thermal sensor is thermally conductively coupled to the outer enclosure.

13. The SOFC system further includes a thermal conduction path extending from an input of the catalyst body to an outer enclosure of the SOFC system; The thermal conduction path is formed from a material having a thermal conductivity coefficient of 100 W / mK or more at 350 degrees; The SOFC system of claim 1 , wherein the outer enclosure includes an outer enclosure wall formed of at least one material having a thermal conductivity coefficient of at least 100 W / mK.

14. The SOFC system of claim 13 , wherein a third thermal sensor is disposed in thermally conductive contact with an exterior surface of the outer enclosure and configured to provide a third temperature signal to the electronic controller.

15. 15. The SOFC system of claim 14, wherein the electronic controller operates to control a fuel supply valve to enable a software controlled shutdown based on at least the third temperature signal, the electronic controller controlling the fuel supply valve to stop the flow of fuel to the catalyst body.

16. 15. The SOFC system of claim 14, wherein the SOFC system includes a thermal fuse thermally coupled to the outer enclosure, the thermal fuse configured to cut off power to a fuel flow modulator to stop fuel flow to the catalyst body when the thermal fuse reaches a temperature equal to or greater than a preconfigured fusible link melting temperature.

17. 15. The SOFC system of claim 14, further comprising a cold start chamber, and wherein the electronic controller operates to control a flow of a fuel and air mixture to the cold start chamber based on at least one temperature signal received by the electronic controller from at least one temperature sensor, thereby enabling shutoff of fuel and air to the cold start chamber when the catalyst body reaches a CPOX reaction temperature or when one or more hot zone enclosures and at least one SOFC reach an SOFC operating temperature.

18. 15. The SOFC system of claim 14, further comprising an air moving device arranged to provide an air flow for convective cooling of the outer enclosure, the electronic controller operative to control operation of the air moving device based on at least one temperature signal received by the electronic controller from at least one temperature sensor coupled to the air moving device.

19. The heat conduction path is a fuel furnace body enclosing a fuel chamber surrounded by a peripheral wall disposed along a longitudinal axis of the chamber; a reactor shield base wall attached to the outer perimeter wall and disposed to surround a bottom end of the fuel chamber; the reactor shield base wall includes a base wall top surface facing the fuel chamber, a substantially parallel and opposing base wall bottom surface facing the fuel chamber, and a plurality of base wall fuel passages, each extending through the reactor shield base wall from the base wall top surface to the base wall bottom surface; The bottom surface of the base wall is thermally coupled to the catalyst body; The SOFC system of claim 14 , wherein the fuel reactor body is formed as a substantially continuous thermally conductive pathway extending from a bottom surface of the reactor shield base wall to the outer enclosure.

20. 20. The SOFC system of claim 19, wherein the bottom surface of the base wall is thermally coupled to the catalyst body by thermal radiation.

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