Patent Application
20190393522
The following is directed to electrochemical assemblies, particularly, to electrochemical assemblies including an electrochemical device and heat exchanger.
Solid oxide fuel cells (SOFC) are electrochemical devices that operate at high temperatures (e.g., 600° C. to 1000° C.). A hot box enclosing an SOFC stack can include insulation to maintain the fuel cells at the desired operating temperatures. The heat generated by the fuel cells is used to maintain the temperature within the hot box. However, maintaining a uniform distribution of the temperature throughout the hot zone can be challenging both because the heat may be generated non-uniformly and the incoming flows provide a cooling effect. Thus, in a well-insulated hot box, gas outlet faces can be significantly hotter than gas inlet faces, which can cause undesired thermal gradients in the fuel cell stack leading to non-uniform current distribution, local thermal stresses, and performance degradation. This issue can be magnified with state-of-the-art SOFC stacks formed with only ceramics (referred to as “all-ceramic stack” hereinafter), because components of an all-ceramic stack have relatively low thermal conductivity, e.g., at least 10 times lower, compared to those containing bulk metal components commonly used in fuel cells. Larger thermal gradients can be generated within an all-ceramic stack, which can accelerate performance degradation of the stack.
All-ceramic stacks also have advantages over metal-supported SOFC stacks and stacks having metal interconnects. For instance, all-ceramic stacks can be formed by co-sintering a plurality or an entire stack of fuel cells, which can simplify the manufacturing process and reduce associated cost. Additionally, it is possible to obtain a tight match of thermal expansion coefficients (CTEs) between components by carefully selecting suitable materials, which helps to reduce the risk of formation of cracks during firing processes or operations, induced by thermal stress due to mismatched CTEs. Metals often have much higher CTEs compared to ceramic materials used in fuel cell stacks, rendering it difficult to match the CTEs of an adjacent ceramic component to the metal component. Furthermore, at solid oxide fuel cell operation temperatures, metal surfaces tend to oxidize, which can increase the contact resistance between the metal and adjacent ceramic component, resulting in degradation of electrochemical performance of fuel cells. Using surface coatings may help to reduce oxidation of metal surfaces, but it significantly increases the manufacturing cost.
The industry continues to demand fuel cells with improved performance, stability, and efficiency.
The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings.
Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures can be exaggerated relative to other elements to help improve understanding of embodiments of the invention. The use of the same reference symbols in different drawings indicates similar or identical items.
The following description in combination with the figures is provided to assist in understanding the teachings disclosed herein. The following discussion will focus on specific implementations and embodiments of the teachings. This focus is provided to assist in describing the teachings and should not be interpreted as a limitation on the scope or applicability of the teachings.
As used herein, the terms “comprises,” “comprising,” “includes”, “including”, “has”, “having,” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but can include other features not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).
The use of “a” or “an” is employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural, or vice versa, unless it is clear that it is meant otherwise.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, methods, and examples are illustrative only and not intended to be limiting.
Embodiments relate to an electrochemical assembly including an electrochemical device disposed within a housing and a heat exchanger disposed adjacent to a gas outlet surface of the electrochemical device. The electrochemical device can operate at a relatively high temperature, such as between 500 to 1000° C. The heat exchanger can help to maintain a relative uniform heat distribution within the housing. For instance, the heat exchanger can be configured to transfer radiated heat energy generated by outlet gas of the electrochemical device to an inlet gas such that the temperature of the gas outlet surface can be reduced, and the temperature of the gas inlet surface can be increased by the pre-heated inlet gas, which helps to reduces the temperature difference and thermal stress within the electrochemical assembly. In an embodiment, the heat exchanger can be placed within a gas outlet chamber that is in fluid communication with the gas outlet surface of the electrochemical device. In another instance, the heat exchanger can be at least partially embedded in a wall of the gas outlet chamber. The electrochemical assembly including the heat exchanger is expected to have improved performance over time and service life.
In an embodiment, the electrochemical device can include a fuel cell, such as a solid oxide fuel cell, an electrolyzer, a hydrogen pump, an oxygen pump, a battery, or the like. In a further embodiment, the electrochemical device can include a stack of solid oxide fuel cells, where adjacent solid oxide fuel cells can be separated by an interconnect layer. In another embodiment, a solid oxide fuel cell can include an anode, a cathode, and an electrolyte disposed between the anode and cathode, where each of the anode and cathode can include a porous layer.
Each cathode 103 can include oxygen-containing gas channels having openings 110 and extending between a surface 120 and the opposite surface (not illustrated). A skilled artisan would understand that the other opening of each oxygen-containing gas channel is formed on the opposite surface. Each anode 105 can include fuel gas channels having openings 112 and extending between the opposite surface (not illustrated) and the surface 122. As illustrated, the stack 100 has a cross flow configuration, where fuel gas and oxygen-containing gas channels extend in respective electrode layers in the cross directions.
In an embodiment, the surface 120 of the stack 100 can be an oxygen-containing gas outlet surface, where the outlet gas (e.g., an exhaust gas and water vapor) can flow out of the openings 110 of cathode channels. The opposite surface can be the oxygen-containing gas inlet surface to receive the inlet gas. In another embodiment, the surface 122 can be the fuel gas outlet surface, and exhaust of the fuel gas can exit the openings 112. The surface opposite the surface 122 can be the fuel gas inlet surface to receive the inlet gas.
The solid oxide fuel cells 102 can be formed using suitable materials and methods known in the art. In an embodiment, each of the anode 103, electrolyte 104, cathode 105, and interconnect 108 can include a ceramic compound. In a particular embodiment, the anode 103 can include a cermet material. In another embodiment, the interconnect 108 can be essentially free of a metal material. In still another embodiment, the interconnect 108 can consist of a ceramic material. An exemplary interconnect material can include a lanthanum strontium titanate compound, a lanthanum chromite, platinum, cermets, a non-conducting ceramic material including conducting metal vias, or the like.
In an embodiment, the cathode 103 can be porous, and the surface 122 of the stack 100 can include a coating to help to prevent gas leakage from the cathode 103. In a further embodiment, the coating can include a glass material or a ceramic material. For instance, the coating can include BaO, Al2O3, SiO2, or any combination thereof. In another embodiment, the anode 105 can be porous, and the coating can be applied to the surface 120 to reduce gas leakage.
In an embodiment, the solid oxide fuel cell stack 100 can have a height 130, length 132, and width 134. In an embodiment, the height 130 can be at least 180 mm, such as at least 190 mm, at least 200 mm, or at least 220 mm. In another embodiment, the height 130 can be at most 600 mm or at most 570 mm, or at most 550 mm. Moreover, the height 130 can be within a range including any of the minimum and maximum values noted herein. In another embodiment, the width 134 can be at least 60 mm, at least 70 mm or at least 80 mm. In still another embodiment, the width 134 can be at most 300 mm or at most 280 mm or at most 250 mm. The width can be within a range including any of the minimum and maximum values noted herein. In another embodiment, the length 132 can be same with the width 134. In still another embodiment, the length 132 can be at least 60 mm or at least 70 mm or at least 80 mm. In a further embodiment, the length 132 can be at most 300 mm or at most 280 mm or at most 260 mm or at most 250 mm. It is to be appreciated that the length can be in a range including any of the minimum and maximum value noted herein.
In a further embodiment, the solid oxide fuel cell stack 100 can be configured to operate at a temperature in a range including at least 500° C. and at most 1000° C. In a particular embodiment, a suitable operation temperature can be at least 650° C. or at least 750° C. or at least 800° C.
In an embodiment, an electrochemical assembly can include a housing that encloses the electrochemical device.
As illustrated in
A tube 214 can be coupled to the chamber 222 such that the tube 214 can be in fluid communication with the chamber 222 and surface 246. In an embodiment, the surface 246 can be similar to the surface 120 of the stack 100. In another embodiment, the surface 246 can be a gas outlet surface for an exhaust to flow out of the stack 210, the chamber 222 can be a gas outlet chamber configured to contain the exhaust, and the tube 214 can be an outlet tube configured to transport the exhaust out of the housing 202. In a particular embodiment, the tube 214 can be the fuel gas outlet tube and configured to transport fuel exhaust, the chamber 222 can be the fuel gas outlet chamber, and the surface 246 can be the fuel gas outlet surface. In another embodiment, the tube 214, the wall 254, and chamber 222 can be part of an outlet manifold.
The stack 210 can include a surface 250 extending between the surfaces 244 and 246. In an embodiment, the surface 250 can be similar to the surface 122 of the stack 100.
In an embodiment, the inlet manifolds and/or outlet manifolds can include a material that is heat-resistant, oxidation-resistant, and/or corrosion-resistant. In a particular embodiment, any or all the manifolds can include a ceramic material including an oxide, such as aluminum oxide, zirconium oxide, silicon oxide, or a combination thereof, a carbide, such as silicon carbide, a nitride, such as silicon nitride, boron nitride, or a combination thereof, mullite, or the like, or any combination thereof. In another particular embodiment, any or all the manifolds can include substantially a ceramic-based insulation material. The insulation material can include, for example, ceramic fiber (e.g., alumina fiber), refractory ceramic fiber, silica, silicate (e.g., calcium silicate), or any combination thereof. A more particular example can include ZIRCAR® SALI, ZIRCAR® Uniform C2, Calcast® CC500, Silca Silicapan, Silca Silcapor, the like, or any combination thereof. In another particular embodiment, the manifold can include a glass-ceramic material, such as MACOR®. In another embodiment, the manifold can include a metal, such as alumina scale-forming material, an interconnect material, a superalloy, or any combination thereof. An exemplary alumina scale-forming material can include a ferritic alloy, such as an iron chromium-aluminum alloy (e.g., Kanthal APM™ and APMT™, Nisshin Steel NCA-1™), a nickel-chromium-aluminum-iron alloy (e.g., Haynes® 214®), or a high-carbon nickel-chromium-iron alloy (e.g., Nicrofer® 6025 HT-Alloy 602 CA). An exemplary interconnect material can include a metallic interconnect material, such as an iron-chromium alloy (e.g., Hitachi® ZMG232G10®, Crofer 22® APU), or a high temperature stainless steel (e.g., Crofer®22H, Sanergy HT 441, E-Brite®). An exemplary superalloy can include a nickel-chromium based superalloy (e.g., Inconel® 600, 601, or 625), a nickel-based steel alloy (e.g., Hastalloy®), a nickel-based superalloy (e.g., Waspaloy®, Rene® 41, or Incoloy®), or any combination thereof.
As illustrated in
The electrochemical assembly 200 can include a heat exchanger 230 disposed within the housing 202. As illustrated in
In an embodiment, the heat exchanger 230 can be coupled or connected to a gas inlet tube 216 such that the inlet gas can flow along a continuous gas passageway and be transported to the inlet surface 248. In an embodiment, the heat exchanger 230 can be configured to transfer heat energy from the outlet gas or the stack 210 to the inlet gas, before the inlet gas is delivered to the gas inlet surface. In a further embodiment, the heat exchanger 230 can be configured to transfer radiated heat energy, particularly from the oxygen-containing gas outlet surface 250, to the inlet gas. The pre-heated inlet gas can be delivered to the inlet surface 248 by the inlet tube 216. The heat exchanger at the gas outlet chamber 226 can help to reduce the temperature differences between the outlet and inlet surfaces 250 and 248.
In an embodiment, the fuel gas can include hydrogen (e.g. pure or humidified), a mixture of 50% of hydrogen and 50% of nitrogen or a humidified mixture thereof, a reformate of a mixture of CH4, CO2, CO, H2, H2O, or a hydrocarbon. An exemplary composition for a reformate can include 36±10% of H2, 8±5% of CH4, 22±5% of CO2, 5±3% of CO, and 29±10% of H2O. Another example of the reformate composition can include 54±10% of H2, 8±5% of CH4, 5±3% of CO2, 11±5% of CO, and 22±10% of H2O. CH4 and H2O can react in the stack by internal steam reforming (CH4+H2O→CO+3H2) and absorb part of the heat generated by the stack under electrical power generation.
In a further embodiment, an inlet gas provided to the heat exchanger 230 can have a temperature at least 50° C. less than the temperature of the surface 250 or at least 100° C. or at least 150° C. or at least 200° C. or at least 250° C. or at least 300° C. or at least 350° C. less than the temperature of the surface 250. The pre-heated inlet gas can be transported to the chamber 224 and enter gas channels openings (not illustrated) at the surface 248. Outlet gas generated by electrochemical reactions can exit the gas outlet surface 250 into the chamber 226, where heat from the outlet gas and generated by the stack 210 can be utilized by the heat exchanger 230 to continue to heat inlet gas.
In a well-insulated hot box, without the heat exchanger, heat generated by a solid oxide fuel cell stack can be primarily removed by internal reforming and/or air cooling to maintain stable operation. Heat is primarily transferred by convection in the absence of the heat exchanger, which can be determined by the formula Q′=δT×m×Cp, where Q′ represents heat transferred by convection, δT is the temperature difference between the air inlet surface and air outlet surface of the stack, m represents the mass of the fluid (air), and Cp represents the fluid specific heat capacity. In order to maximize stack performance and durability, it is important to maintain uniform temperature distribution in the stack. This means δT has to be kept as small as possible. To reduce δT, the flowrate of air needs to be increased, which in turn reduces the air utilization of the stack. In the absence of the heat exchanger, the air utilization of the stack is typically kept below 20% in order to keep a low thermal gradient and thermal stress in the stack. The use of the heat exchanger 230 can help to reduce δT and allow higher air utilization to be obtained, because the heat exchanger can remove heat from the stack through radiative heat transfer from the stack air-outlet surface. In the presence of the heat exchanger, heat is mainly transferred by radiation and convection, which can be determined by the formula Q″=Qrad+(δT×m×Cp), where Q″ represents heat transferred by radiation and convection, and Qrad represents heat transferred by radiation to the heat exchanger. With the addition of Qrad, heat transferred by convection, δT×m×Cp, can be significantly reduced, and air flowrate (m) can be reduced to allow improved air utilization, while a lower δT is maintained. With a lower air flowrate, the blower power consumption can be reduced, which improves the systems overall efficiency. Internal reforming of the fuel can further help to cool the stack in cases where methane and vapor is contained in the fuel flow. In an embodiment, Qrad can be at least 20%, such as at least 30%, at least 40%, at least 50% or at least 60% of the total heat generated by the SOFC stack. Greater Qrad can allow the heat generated by the stack to be effectively recycled to preheat the hot box inlet air, and thus help to reduce heat loss and improve overall hot box thermal efficiency.
The electrochemical assembly disclosed in embodiments can have improved air utilization compared to a similar electrochemical assembly without a heat exchanger. For instance, the air utilization can be at least 25%, such as at least 30%, at least 35%, at least 40%, at least 45%, or at least 50%. The air utilization can be calculated using the formula, Uo=(Aoc/Ap)×100%, wherein Uo is the utilization, Aoc is the amount of oxygen consumed by electrochemical reactions within the electrochemical device, and Ap is the amount of oxygen supplied to the electrochemical device. The electrochemical assembly can operate at a relatively high air utilization, which can also help to reduce power consumption caused by an air blower and improve overall efficiency of the assembly. In a further embodiment, the electrochemical device can have a reduced temperature difference between air outlet surface and air inlet surface. For instance, the temperature difference can be at most 50° C., at most 30° C., or at most 20° C.
In another embodiment, the heat exchanger can include a fuel reformer or a vaporizer that is capable of performing an endothermic reaction to facilitate improved utilization of the fuel gas. For example, a reformer can convert a portion of methane (CH4) fuel and water (H2O) vapor to hydrogen (H2) and carbon-monooxide (CO) with a methane steam reforming reaction CH4+H2O→CO+3H2. CO and H2 are more readily usable as a fuel in SOFCs compared to methane. Heavier hydrocarbon fuels, such as C2H6, C3H8, and the like, can be converted to H2 and CO in the reformer in a similarly manner. In another embodiment, the heat exchanger can include a catalyst for an endothermic reaction. In a further embodiment, the heat exchanger 430 can be embedded into the wall 452 at a predetermined depth 460. In a further embodiment, the depth 460 can be selected to optimize a fuel gas composition through an endothermic reaction. In a further embodiment, the depth 460 can be selected such that a predetermined temperature of the heat exchanger can be achieved. For instance, in applications where the heat exchanger includes a fuel reformer or a vaporizer, the embedded depth can be selected such that the heat exchanger can have a temperature that facilitates improved performance of the fuel reformer or vaporizer. In applications where a fuel reformer is included in the heat exchanger, the embedded depth can be selected such that the reformer temperature can reach a target temperature, such as the desired equilibrium temperature for achieving the target fuel gas composition (i.e., methane or hydrocarbon conversion). Typically, the target temperature of the reformer can be 400° C. to 700° C. It is ideal to keep a small amount of methane in the fuel stream after the reformer (methane conversion rate is 30% to 70% in the reformer) so that the stack can be cooled with an adequate amount of endothermic internal reforming. For applications using a vaporizer, the embedded depth can be selected such that the vaporizer temperature can be 20° C. to 100° C. higher than the water boiling point under the stack operation pressure, so that the vaporization process can be well controlled without large pressure fluctuations.
In another embodiment, a plurality of heat exchangers can be embedded in the same wall in a spaced-apart manner to allow the heat exchangers to have differently optimized temperatures. For instance, as illustrated in
After reading this disclosure, a skilled artisan would understand that various numbers and different placement of the heat exchangers can be used to facilitate improved heat transfer from the electrochemical device to the inlet gas and performance of the electrochemical devices. For instance,
In
In
In an embodiment, the inlet tube 716 is configured to transport the fuel gas, and the outlet chamber 726 is configured to contain the oxygen-containing outlet gas. In another embodiment, the inlet tube is configured to transport the oxygen-containing gas, and the outlet chamber 726 is configured to contain the fuel outlet gas. In an embodiment, the heat exchanger 730 can be a steam-reformer with endothermic reaction that can utilize the heat collected from the oxygen-containing outlet stream and radiation from the oxygen-containing gas outlet surface of the stack.
In a further embodiment, the electrochemical assembly can include an additional heat exchanger disposed in another gas outlet chamber such that both inlet gases can be pre-heated before being transported to the respective surfaces of the electrochemical device.
Notably, the heat exchangers described in embodiments herein can have any shape that can facilitate improved heat energy transfer to the inlet gas. For instance, turning to
Referring to
In another embodiment, the heat exchanger can include a gas inlet portion close to the inlet opening, and a gas outlet portion close to the outlet opening, such as the outlet portions 1010, 1110, and 1130, and the inlet portions 1020 and 1120 of the heat exchangers 1000 and 1100. In a further embodiment, the gas inlet portion of the heat exchanger can be aligned with and exposed to gas outlet openings (e.g., 110 and 112) at the gas outlet surface of the electrochemical device. In a more particular embodiment, the inlet portion can be aligned with and exposed to oxygen-containing gas outlet openings such that the outlet gas can directly impinge on the inlet portion of the heat exchanger.
In an embodiment, a gas outlet surface of the electrochemical device can include surface portions having different temperatures. The heat exchanger can be disposed such that a colder portion (i.e., the gas inlet portion) of the heat exchanger is aligned with a hotter surface portion of the gas outlet surface. In particular implementations, the gas inlet portion of the heat exchanger can be aligned with the hottest surface portion, such as the surface portion that has the maximum temperature of the gas outlet surface. In more particular instances, the gas inlet portion of the heat exchanger can be aligned with a surface portion that can be the hottest portion of the entire electrochemical device.
For example, the oxygen-containing gas outlet surface can have a temperature gradient in the lateral direction. In some implementations, the heat exchanger can be disposed such that the gas inlet portion of the heat exchanger is aligned with a hotter surface portion of the oxygen-containing gas outlet surface. In a particular instance, when the SOFC stack (e.g., 100) uses only hydrogen as the fuel gas, the highest temperature of the stack is adjacent to the corner formed by the air outlet surface and the hydrogen inlet surface. In order to reduce the maximum stack temperature, the heat exchanger can be disposed in the air outlet chamber and the inlet portion can be aligned with the area of the air outlet surface that is adjacent the edge of the hydrogen inlet surface. In another particular instance, when using a fuel gas with a greater content of methane, the corner formed by the air outlet surface and fuel gas outlet surface can have the highest temperature, and the heat exchanger can be disposed in the air outlet chamber or the fuel outlet chamber, where the inlet portion of the heat exchanger can be aligned with the surface area adjacent the edge of the fuel gas outlet surface. In another embodiment, the outlet portion of the heat exchanger can be aligned with the hotter surface portion of a gas outlet surface, which can facilitate increased heat transfer from the stack to the heat exchanger. After reading this disclosure, a skilled artisan would understand that the hottest portion of an electrochemical device can be dependent on the fuel, the geometry of the device, the hot box geometry, and operation conditions and be able to determine the hottest portion of a gas outlet surface and alignment of the heat exchanger.
In a further embodiment, the heat exchanger can have a shape of a plate or a box, as illustrated in
In a further embodiment, the heat exchanger can include a fin, a baffle, or a combination thereof to improve the heat exchange.
In an embodiment, the heat exchanger can be disposed in a gas outlet chamber and parallel to the gas outlet surface of an electrochemical device. The heat exchanger can directly face the gas outlet surface and have a surface area that is directly exposed to the gas outlet surface. In an embodiment, the surface area can be at least 25%, at least 40%, at least 60%, or at least 75% of a total area of the gas outlet surface to facilitate improved heat transfer efficiency.
In another embodiment, the heat exchanger may not extend the full height (e.g., 130, referred to as “H” hereinafter) of an electrochemical device.
The heat exchanger 1704 can have a height 1718 that is substantially the same as the height z of the middle portion 1710. In an embodiment, the height 1718 may be smaller than the height z of the middle portion 1710. In another embodiment, the height 1718 can be greater than z of the middle portion. In another embodiment, at least 60%, at least 80%, or at least 90%, or 100% of the height z is aligned with at least a portion of the height 1718, the majority of the height 1718, or the entire height 1718 of the heat exchanger 1704.
In an embodiment, the heat exchanger can have a length 1719 extending in parallel with the length 1720 of the gas outlet surface 1716. In another embodiment, the length 1719 of the heat exchanger and the length 1720 of the gas outlet surface can be offset, such as forming an acute angle. For example, the offset angle may be not greater than 10°, such as not greater than 8° or not greater than 5°. As illustrated, the length 1720 of the heat exchanger is smaller than the length 1720 of the device 1704. In another embodiment, the length 1719 can be the same as or greater than the length 1720. In a further embodiment, the surface area SAHX, wherein SAHX=1719×1718, can be at least 80%, such as at least 90% or at least 95% or 100% of the surface area SAMP, wherein SAMP=1710×1720.
The top portion 1706 and the bottom portion 1708 can be colder than the middle portion 1710 which can be caused by heat losses by conductive transfer through current collectors or thermal insulation. The placement of the heat exchanger relative to the stack, as illustrated in
In an embodiment, the heat exchanger can include a material that can facilitate improved heat transfer efficiency of the heat exchanger. For example, the heat exchanger can include a material having an emissivity of at least 0.90 or at least 0.95 to help improve absorption of radiated heat energy. In another particular embodiment, the heat exchanger can have a black outer surface. In another embodiment, the heat exchanger may be formed with a material having a relatively lower emissivity and coated with another material having the desired emissivity. In another embodiment, the heat exchanger can include a heat-resistant, oxidation-resistant, or a corrosion-resistant material. In a particular embodiment, the heat exchanger can include an alumina scale-forming material, an interconnect material, or any combination thereof. An exemplary alumina scale-forming material can include a ferritic alloy, such as an iron-chromium-aluminum alloy (e.g., Kanthal APM™ and APMT™, Nisshin Steel NCA-1™), a nickel-chromium-aluminum-iron alloy (e.g., Haynes® 214®), or a high-carbon nickel-chromium-iron alloy (e.g., Nicrofer® 6025 HT-Alloy 602 CA). An exemplary interconnect material can include a metallic interconnect material, such as an iron-chromium alloy (e.g., Hitachi® ZMG232G10®, Crofer 22® APU), or a high temperature stainless steel (e.g., Crofer® 22H, Sanergy HT 441, E-Brite®). In a particular embodiment, a coating material can be applied to the surface of the heat exchanger including a metallic interconnect material. The coating can include a glass material, an oxide, such as alumina and manganese cobalt oxide or the like, or any combination thereof. Another example of an interconnect material can include a ceramic material known in the art. In another embodiment, the heat exchanger can include an oxide, such as beryllium oxide, a carbide (e.g., SiC), a nitride, such as aluminum nitride. In yet another embodiment, the heat exchanger can include a superalloy, such as a nickel-chromium based superalloy (e.g., Inconel® 600, 601, or 625), a nickel-based steel alloy (e.g., Hastalloy®), a nickel-based superalloy (e.g., Waspaloy®, Rene® 41, or Incoloy®), or any combination thereof. Emissivity can be measured in accordance with ASTM E408-13.
In an embodiment, the heat exchanger can face a gas outlet surface of the electrochemical device, such that the outlet the gas can directly impinge on at least a portion of the heat exchanger. In a further embodiment, an area of the gas outlet surface corresponding to the heat exchanger can be at least 25%, at least 40%, at least 60%, or at least 75% of a total area of the gas outlet surface. The higher the corresponding area, the higher likelihood more heat can be received by the heat exchanger. In a particular embodiment, the area of the gas outlet surface corresponding to the heat exchanger can be at least 50% of the total surface area of the gas outlet surface. In another embodiment, the corresponding area may be limited by the size or shape of the heat exchanger or the volume of the gas outlet chamber. For instance, the corresponding area may be at most 90% or at most 80% of the total area of the gas outlet surface. Moreover, the corresponding area of the gas outlet surface facing the heat exchanger can be within a range including any of the minimum and maximum percentages noted herein.
In an embodiment, the fuel gas inlet tube and the oxygen-containing gas inlet tube can include any material disclosed with respect to the heat exchanger. In another embodiment, the fuel gas outlet tube oxygen-containing gas outlet tube can include any material disclosed with respect to the heat exchanger.
An electrochemical assembly, comprising:
An electrochemical assembly, comprising:
The electrochemical assembly of embodiment 1 or 2, wherein the electrochemical device comprises a stack of solid oxide fuel cells, a battery, or a solid oxide electrolyzer cell.
The electrochemical assembly of embodiment 3, wherein the electrochemical device comprises a stack of solid oxide fuel cells and the stack of solid oxide fuel cells has a cross-flow configuration.
The electrochemical assembly of any one of embodiments 1 to 4, wherein the electrochemical device comprises a first gas channel extending between a second surface and the first surface of the electrochemical device, the second surface being opposite the first surface, wherein the first gas channel comprises a gas outflow end at the first surface, the gas outflow end facing the heat exchanger.
The electrochemical device of any one of embodiments 1 to 5, wherein the heat exchanger is positioned such that a major surface of the heat exchanger faces the first surface.
The electrochemical assembly of any one of embodiments 1 to 6, wherein the heat exchanger includes a surface area that is directly exposed to the first surface, wherein the surface area is at least 25%, at least 40%, at least 60%, or at least 75% of a total area of the first surface.
The electrochemical assembly of any one of embodiments 1 to 7, wherein the heat exchanger is in fluid communication with a first gas inlet chamber, and wherein the first gas inlet chamber is in fluid communication with the second surface of the electrochemical device.
The electrochemical assembly of any one of embodiments 1 to 8, wherein the first gas outlet chamber is an oxygen-containing gas outlet chamber.
The electrochemical assembly of any one of embodiments 1 to 9, further comprising a second gas outlet chamber in fluid communication with a third surface of the electrochemical device, and a second gas inlet chamber in fluid communication with a fourth surface of the electrochemical device.
The electrochemical assembly of embodiment 10, further comprising a second heat exchanger, wherein the second heat exchanger is disposed within the second gas outlet chamber or at least partially embedded in a wall of the second gas outlet chamber.
The electrochemical assembly of embodiment 11, wherein the second heat exchanger is in fluid communication with the first heat exchanger and the first gas inlet chamber.
The electrochemical assembly of embodiment 11, wherein the second heat exchanger is in fluid communication with the second gas inlet chamber.
The electrochemical assembly of any one of embodiments 1 to 13, wherein the first heat exchanger, the second exchanger, or both has a serpentine pattern.
The electrochemical assembly of any one of embodiments 1 to 13, wherein the first heat exchanger, the second heat exchanger, or both has a shape of a plate.
The electrochemical assembly of any one of embodiments 1 to 15, wherein the first heat exchanger, the second heat exchanger, or both includes a fin.
The electrochemical assembly of any one of embodiments 1 to 16, wherein the first heat exchanger, the second heat exchanger or both includes a baffle.
The electrochemical assembly of any one of embodiments 1 to 17, wherein the first heat exchanger, the second heat exchanger, or both includes a single gas passageway.
The electrochemical assembly of any one of embodiments 1 to 17, wherein the first heat exchanger, the second heat exchanger, or both includes a first and second gas passageway that extend away from each other.
The electrochemical assembly of any one of embodiments 3 to 19, wherein each layer of the solid oxide fuel cell stack comprises a ceramic compound.
The electrochemical assembly of any one of embodiments 1 to 20, wherein the heat exchanger comprises a material having an emissivity of at least 0.90 or at least 0.95.
The electrochemical assembly of any one of embodiments 1 to 21, wherein the heat exchanger includes a ceramic, a metal, or any combination thereof.
The electrochemical assembly of any one of embodiments 1 to 22, wherein the heat exchanger includes an alumina scale-forming material, a metal, or any combination thereof.
The electrochemical assembly of any one of embodiments 1 to 23, wherein the first heat exchanger, the second heat exchanger, or both includes an oxide, a carbide, a nitride, an iron-containing alloy, a superalloy, or any combination thereof.
The electrochemical assembly of any one of embodiments 1 to 24, wherein the first heat exchanger, the second heat exchanger, or both includes a stainless steel or a ceramic material.
The electrochemical assembly of any one of embodiments 1 to 9, wherein at least one of the first heat exchanger and the second heat exchanger comprises a fuel reformer or a vaporizer.
The electrochemical assembly of any one of embodiments 1 to 9 and 26, wherein the heat exchanger comprises a material including a catalyst for an endothermic reaction.
The electrochemical device of any one of embodiments 1 to 27, wherein an inlet portion of the heat exchanger is aligned with a surface area adjacent an edge of the first surface.
The electrochemical device of any one of embodiments 1 to 27, wherein the first surface includes a first surface portion and a second surface portion, wherein the first surface portion is hotter than the second surface portion, and wherein an inlet portion of the heat exchanger is aligned with the first surface portion.
The electrochemical assembly of any one of embodiments 3 to 29, wherein the solid oxide fuel cell stack has an air utilization efficiency at least 20% or at least 25% or at least 30% or at least 35% or at least 40% or at least 45% or at least 50%.
The electrochemical assembly of any one of embodiments 1 to 30, wherein the first surface of the electrochemical device comprises a coating including a glass or ceramic material.
The electrochemical assembly of any one of embodiments 3 to 31, wherein the stack of solid oxide fuel cell comprises an interconnect layer between solid oxide fuel cells, wherein the interconnect layer comprises a ceramic material or consists essentially of the ceramic material.
The electrochemical device of any one of embodiments 1 to 32, wherein the first gas outlet chamber is a part of a first gas outlet manifold.
The electrochemical device of any one of embodiments 8 to 33, wherein the first gas inlet chamber is a part of a first inlet gas manifold.
The electrochemical assembly of any one of embodiments 10 to 34, wherein the second gas outlet chamber and the second gas inlet chamber is part of a second gas outlet manifold and a second gas inlet manifold, respectively.
The electrochemical assembly of any one of embodiments 2 to 35, wherein the heat exchanger is at least partially embedded into the wall of the gas outlet chamber at a predetermined depth.
The electrochemical assembly of any one of embodiments 1 to 36, wherein the heat exchanger is configured to remove at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70% of heat produced by the electrochemical device.
A method of using the electrochemical assembly of any one of embodiments 1 to 37, comprising:
The method of embodiment 38, wherein the heat exchanger faces the first surface and the outlet gas passing through the first surface passes across or impinges upon the heat exchanger.
A representative electrochemical device S1, as illustrated in
The electrochemical devices S1 and C1 were tested under the conditions noted in Tables 2 to 3. Simulated reformate (33% H2, 9% CH4, 30% CO2, and 28% H2O) and air was used as the fuel gas and the oxygen-containing gas, respectively. Inlet air was preheated for both device S1 and C1. Electrical currents were applied to both SOFC stacks, as soon as they were heated to reach the operating temperature of 750° C. Several air flow rates were used to test effect of air utilization on the stack temperature profile. The temperature difference (ST) between the air-in and air-out surfaces was measured by thermocouples that was installed in the devices and is included in Tables 1 and 2.
16 A
Comparing to C1, S1 was able to operate with improved air utilization (lower air flowrate) and significantly lower temperature difference between the air-in and air-out surfaces. At similar electric currents and air utilizations, the heat exchanger helped to decrease the δT from 115° C. (C1 at 10 A and 24% air utilization) to 3.3° C. (S1 at 9.6 A and 25% air utilization), which is more than 30-fold reduction. Moreover, in the presence of the heat exchanger, the δT of device S1 was controlled to be within the range from 3° C. to 24° C. compared to 59° C. to 115° C. of C1, indicating that the stack temperature profile of S1 is nearly symmetrical with a minimum thermal gradient in the direction of the air flow. Note that at higher current load (12.8 A and 16 A) for S1, the hot box air inlet temperature was able to be lowered significantly as the air receives further heat in the heat exchanger placed in the air outlet chamber.
A representative electrochemical device S2 was designed as illustrated in
A representative electrochemical device S3 was designed as illustrated in
Thermofluidic-electrochemical simulations were performed using different current loads and fuel compositions. For simulation 1 and 2, the fuel composition was 48.5% H2/48.5% N2/3% H2O, and fuel utilization was 75%. For simulation 3, the fuel composition was 28% H2/33% H2O/5% CO/25% CO2/9% CH4 and fuel utilization was 65%. Heat generated in the stack and heat collected at the heat exchanger is included in Table 4.
In simulation 3, part of the heat generated at the stack was absorbed by the endothermic reforming reaction (CH4+H2O->CO+3H2) in the stack. In all simulated tests, the heat exchanger was capable of absorbing 50-80% of the heat generated by the stack, which can be expected to reduce temperature differences in the stack and improve overall thermal efficiency of the hot box by recycling the heat inernally within the hot box.
Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required, and that one or more further activities may be performed in addition to those described. Still further, the order in which activities are listed is not necessarily the order in which they are performed.
Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims. Reference herein to a material including one or more components may be interpreted to include at least one embodiment wherein the material consists essentially of the one or more components identified. The term “consisting essentially” will be interpreted to include a composition including those materials identified and excluding all other materials except in minority contents (e.g., impurity contents), which do not significantly alter the properties of the material. Additionally, or in the alternative, in certain non-limiting embodiments, any of the compositions identified herein may be essentially free of materials that are not expressly disclosed. The embodiments herein include range of contents for certain components within a material, and it will be appreciated that the contents of the components within a given material total 100%.
The specification and illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The specification and illustrations are not intended to serve as an exhaustive and comprehensive description of all of the elements and features of apparatus and systems that use the structures or methods described herein. Separate embodiments may also be provided in combination in a single embodiment, and conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. Further, reference to values stated in ranges includes each and every value within that range. Many other embodiments may be apparent to skilled artisans only after reading this specification. Other embodiments may be used and derived from the disclosure, such that a structural substitution, logical substitution, or another change may be made without departing from the scope of the disclosure. Accordingly, the disclosure is to be regarded as illustrative rather than restrictive.
This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 62/689,335, filed Jun. 25, 2018, entitled “ELECTROCHEMICAL ASSEMBLY INCLUDING HEAT EXCHANGER,” by Brian P. FELDMAN et al., which is assigned to the current assignee hereof and incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62689335 | Jun 2018 | US |
