JP2016533628A - Integrated power generation and chemical production using solid oxide fuel cells - Google Patents

Abstract

In various aspects, systems and methods are provided for operating a solid oxide fuel cell at conditions that can improve or optimize the combined electrical and chemical efficiency of the fuel cell. Instead of selecting conventional conditions for maximizing the fuel cell electrical efficiency, the operating conditions can allow for the output of excess synthesis gas and / or hydrogen in the anode discharge of the fuel cell. . Syngas and / or hydrogen can then be used in a variety of applications including chemical synthesis processes and recovery of hydrogen for use as a fuel.

Description

(Field of Invention)
In various aspects, the present invention relates to chemical generation and / or power generation processes integrated with power generation using solid oxide fuel cells.

(Background of the Invention)
Solid oxide fuel cells use hydrogen and / or other fuels to generate electricity. Hydrogen may be provided in a steam reformer upstream of the fuel cell or by reforming methane or other reformable fuel in the fuel cell. The reformable fuel can include a hydrocarbon material that can react with steam and / or oxygen at elevated temperatures and / or pressures to produce a gas product containing hydrogen. Alternatively or additionally, the fuel can be reformed in the anode cell of a solid oxide fuel cell that can be operated to produce the proper conditions for reforming the fuel at the anode. Alternatively or additionally, reforming can occur both outside and inside the fuel cell.

  Traditionally, solid oxide fuel cells are operated to maximize electricity generation per unit of fuel input, which can also be described as the electrical efficiency of the fuel cell. This maximization can be based on fuel cells alone or combined heat and power applications. To achieve increased electricity generation and manage heat generation, fuel utilization within the fuel cell is typically maintained between 70% and 85%.

  In US Pat. No. 6,057,056, a system and method for co-production of hydrogen and electrical energy is described. The co-production system includes a fuel cell and a separation unit configured to receive an anode exhaust stream and separate hydrogen. A portion of the anode discharge is recycled to the anode inlet. The operating range given in the publication US Pat. Solid oxide fuel cells are described as an alternative.

US Patent Application Publication No. 2005/0123810

(Summary of the Invention)
In one aspect, a method is provided for producing electricity and hydrogen or synthesis gas using a solid oxide fuel cell having an anode and a cathode. This method introduces a fuel stream containing reformable fuel into a solid oxide fuel cell anode, an internal reforming element associated with a solid oxide fuel cell anode, or a combination thereof. Introducing a cathode inlet stream comprising O ₂ into the cathode of the solid oxide fuel cell; generating electricity within the solid oxide fuel cell; and H ₂ from the anode exhaust. Recovering a gas stream comprising H ₂ , a gas stream comprising H ₂ and CO, or a combination thereof, wherein the electrical efficiency of the solid oxide fuel cell is from about 10% to about 50%, and the total solid oxide fuel cell The fuel cell productivity is at least about 150 mW / cm ² .

1 schematically illustrates an example of a configuration for a solid oxide fuel cell and associated reforming and separation stages. Figure 7 schematically illustrates another example of a configuration for a solid oxide fuel cell and associated reforming and separation steps. 1 schematically illustrates an example of the operation of a solid oxide fuel cell.

(Detailed description of embodiment)
SUMMARY In various aspects, systems and methods are provided that perform the generation of large amounts of hydrogen or syngas in addition to generating electricity from a solid oxide fuel cell (SOFC) at high total fuel cell efficiency. The Embodiments of the present invention can use any planar or tubular battery. Total fuel cell efficiency generally refers to the combined electrical and chemical efficiency of the fuel cell. A more complete definition of total fuel cell efficiency is provided below.

  A typical fuel cell system can be designed and operated for optimized electrical efficiency at the cost of any other parameter. The generated heat, whether in situ and / or as a result of burning off-gas and anode products, should be utilized to the extent required to maintain fuel cell operation at stable conditions. Can do. Like most power generation methods, primarily conventional fuel cell systems estimate electricity generation. Conventional fuel cell systems can be used in applications where the main purpose in distributed power generation or backup generation is efficient power generation.

  Aspects of the invention can establish fuel cell operating parameters such that total fuel cell efficiency exceeds conventional fuel cell efficiency. Additionally or alternatively, the present invention provides a method for increasing total fuel cell productivity while maintaining very high overall system efficiency. In one aspect, productivity is a useful product produced per unit time (eg, syngas, heat, electricity) for the indicated amount of fuel cell capacity, eg, measured in fuel cell cross-sectional area. Is the total amount. If, instead of selecting conventional conditions for maximizing the fuel cell's electrical efficiency, the electrical efficiency will be lower than the optimum electrical efficiency required in the above typical fuel cell system, the operating conditions are Because of the system, much higher overall fuel cell efficiency and / or productivity can be produced. As described in more detail below, total fuel cell efficiency is a measure of the amount of energy produced in a fuel cell compared to the amount of energy delivered to the fuel cell, while productivity is the size of the fuel cell ( For example, a measure of the amount of energy (total chemical, electrical and thermal energy) produced by a fuel cell compared to the anode area. Conditions that can achieve high overall fuel cell efficiency and / or productivity allow for the output of excess syngas and / or hydrogen in the fuel cell anode emissions, It can be achieved by completely or partially separating the input and output from the anode and cathode to allow the production of an excess of product. This excess may be due to, for example, reducing the electrical efficiency of the battery (eg, by operating at a lower voltage) and / or for efficient generation of chemical energy (eg, in the form of synthesis gas). This can be made possible by using heat generated in situ. As a result, fuel cells are much larger in quantity while maintaining a total output efficiency (sum of chemical, electrical and useful thermal energy) that is similar to or higher than that known in the art. All fuel input to the anode can be handled. The higher the productivity, the more efficient use of the fuel cell within the combined system is possible.

The electrochemical process occurring at the anode can result in an anode output stream of synthesis gas containing a combination of at least H ₂ , CO, and CO ₂ . Is then used to water gas shift reaction, the desired composition of the synthesis gas is generated, and as compared with / or other synthesis gas components can result in an increase or maximize and H ₂ generation. Syngas and / or hydrogen can then be used in a variety of applications including, but not limited to, chemical synthesis processes and / or recovery of hydrogen for use as a “clean” fuel.

  As used herein, the term “electrical efficiency” (“EE”) is a fuel cell divided by the rate of the lower heating value (“LHV”) of the fuel input to the fuel cell. Defined as the resulting electrochemical power. Fuel input to the fuel cell includes both the fuel delivered to the anode and any fuel used to maintain the temperature of the fuel cell, for example, the fuel delivered to the burner associated with the fuel cell. It is. In this description, the power generated by the fuel may be described in terms of LHV (el) fuel rate.

  As used herein, the term “electrochemical power” or LHV (el) is the power generated by the movement of oxygen ions through the fuel cell electrolyte and the circuit connecting the cathode to the anode in the fuel cell. is there. Electrochemical power eliminates power generated from the fuel cell or consumed in upstream or downstream equipment. For example, electricity resulting from heat in a fuel cell waste stream is not considered part of the electrochemical power. Similarly, the power generated in a gas turbine or other device upstream of the fuel cell is not part of the generated electrochemical power. “Electrochemical power” does not take into account the power consumed during the operation of the fuel cell or any losses caused by the conversion from direct current to alternating current. In other words, the power used to provide fuel cell operation or otherwise to operate the fuel cell is not subtracted from the DC power generated by the fuel cell. As used herein, power density is current density multiplied by voltage. As used herein, current density is current per unit area. As used herein, total fuel cell power is the power density multiplied by the fuel cell area.

  As used herein, the term “anode fuel input”, denoted as LHV (anode_in), is the amount of fuel in the anode inlet stream. The term “fuel input”, denoted as LHV (in), refers to fuel delivered to a fuel cell that includes both the amount of fuel in the anode inlet stream and the amount of fuel used to maintain the temperature of the fuel cell. Is the total amount of. Fuels may include reformable and non-reformable fuels based on the definition of reformable fuel provided herein. Fuel input is not the same as fuel use.

As used herein, the term “total fuel cell efficiency” (“TFCE”) refers to the electrochemical power generated by a fuel cell and the LHV of the syngas generated by the fuel cell. Defined as the sum of the rate divided by the rate of LHV of the fuel input to the anode. In other words, TFCE = (LHV (el) + LHV (sg net)) / LHV (anode_in), where LHV (anode_in) is the fuel component (eg, H ₂ , CH ₄ and / or CO) at the anode LHV as delivered and LHV (sg net) refers to the rate at which synthesis gas (H ₂ , CO) is produced at the anode, which is the synthesis gas input to the anode and the synthesis gas output from the anode Is the difference between LHV (el) describes the electrochemical power generation of the fuel cell. Total fuel cell efficiency eliminates the heat generated by the fuel cell, which is advantageously used outside the fuel cell. In operation, the heat generated by the fuel cell may be advantageously used in downstream equipment. For example, heat may be used to generate additional electricity or to heat water. These applications are not part of the overall fuel cell efficiency as the terminology used in this application if they occur away from the fuel cell. Total fuel cell efficiency relates only to fuel cell operation and does not include power generation or fuel cell consumption upstream or downstream.

As used herein, the term “chemical efficiency” refers to the lower heating value of H ₂ and CO in the fuel cell anode emissions divided by the fuel input or LHV (in), or LHV. Defined as (sg out).

As used herein, the term “total fuel cell productivity” (“TFCP”) is the product produced per unit of fuel cell cross-sectional area per unit time due to conversion of input fuel. Is defined as the total energy value of. The fuel may be converted in an oxidation reaction, a reforming reaction and / or a water gas shift reaction. The total energy of the product may be expressed in any convenient unit, such as mW per cm ² . Products produced in a fuel cell can include electrochemical power, synthesis gas and / or hydrogen, and heat. The generated heat may be determined by measuring the temperature difference between the anode inlet and the anode outlet. As an example, the productivity of a fuel cell can be expressed as mW per 1 cm ² cross-sectional area of the fuel cell anode. The fuel cell operating conditions can be arbitrarily selected to produce both high total fuel cell productivity and high total fuel cell efficiency.

  As used herein, the term “total reformable fuel productivity” (“TRFP”) refers to reformable fuel to the anode per unit of fuel cell cross-sectional area. The difference between the LHV of the input and the LHV of the reformable fuel received from the anode outlet. The difference between the reformable fuel at the anode inlet and outlet is that the amount of the reformable fuel converted to syngas and / or hydrogen from the newly generated syngas consumed in the oxidation reaction that ultimately produces electricity and It can be approximately equal to the amount of hydrogen minus the amount. Newly generated syngas and / or hydrogen arises at the anode or in the associated reforming stage heat integrated with the fuel cell. Syngas and / or hydrogen provided to the anode inlet is not newly generated. The fuel cell operating conditions can be arbitrarily selected to produce both high total reformable fuel productivity and high total fuel cell efficiency.

  In some embodiments, the operation of the fuel cell can be characterized on the basis of electrical efficiency. When operating a fuel cell to have a low electrical efficiency (EE), the solid oxide fuel cell may have an electrical efficiency of about 50% or less, for example, an EE of about 45% or less, an EE of about 40% or less, about 35% It can be operated to have the following EE, or about 30% or less EE, about 25% or less EE, about 20% or less EE, about 15% or less EE, or about 10% or less EE. Additionally or alternatively, the EE can be at least about 5%, or at least about 10%, or at least about 15%, at least about 20%, at least about 25%, or at least about 30%. Additionally or alternatively, fuel cell operation can be characterized on the basis of total fuel cell efficiency (TFCE), such as the combined electrical and chemical efficiency of the fuel cell. When the fuel cell is operated to have a high overall fuel cell efficiency, the solid oxide fuel cell is about 55% or more, such as about 60% or more, or about 65% or more, or about 70% or more, or about 75%. Or may be operated to have a TFCE (and / or combined electrical and chemical efficiency) of about 80% or more, or about 85% or more. It should be noted that with respect to overall fuel cell efficiency and / or combined electrical and chemical efficiency, any additional electricity generated from the use of excess heat generated by the fuel cell can be excluded from the efficiency calculation.

  In various aspects of the invention, fuel cell operation can be characterized on the basis of a desired electrical efficiency of about 50% or less and a desired overall fuel cell efficiency of 55% or more. When the fuel cell is operated to have the desired electrical efficiency and the desired overall fuel cell efficiency, the solid oxide fuel cell has an electrical efficiency of 50% or less, for example, about 60% or more with about 55% or more TFCE. About 40% or less EE with about TFCE, about 35% or less EE with about 65% or more TFCE, about 30% or less EE with about 70% or more TFCE, or about 20% or less with about 75% or more TFCE EE, or about 15% or less EE with about 80% or more TFCE, or about 10% or less EE with about 85% or more TFCE.

In various aspects of the invention, fuel cell operation may be characterized based on a desired total fuel cell productivity (“TFCP”) of about 150 mW / cm ² or greater and a desired total fuel cell efficiency of 55% or greater. it can. When the fuel cell is operated to have a desired TFCP greater than 150 mW / cm ² and the desired total fuel cell efficiency, the solid oxide fuel cell is greater than about 55%, eg, greater than about 60%, about 65% More than about 70%, or about 75%, or about 80%, or about 85% or more can be operated. When the fuel cell is operated to have a desired total fuel cell efficiency of 55% or higher, the solid oxide fuel cell is at least about 150 mW / cm ² , or at least about 200 mW / cm ² , or at least about 250 mW / cm. ² , or at least about 300 mW / cm ² , or at least about 350 mW / cm ² TFCP. In such embodiments, it TFCP is about 800 mW / cm ² or less, or about 700 mW / cm ² or less, or about 600 mW / cm ² or less, or about 500 mW / cm ² or less, or about 400 mW / cm ² or less Can do.

In various aspects of the invention, fuel cell operation can be characterized based on a desired total reformable fuel productivity of about 75 mW / cm ² or greater and a desired total fuel cell efficiency of 55% or greater. If the fuel cell is operated to have a desired reformable fuel productivity greater than about 75 mW / cm ² and a desired total fuel cell efficiency, the solid oxide fuel cell is greater than about 55%, eg, about 60 % Or more, about 65% or more, about 70% or more, or about 75% or more, or about 80% or more, or about 85%, or about 90% or more. When the fuel cell is operated to have a desired total fuel cell efficiency of 55% or greater, the solid oxide fuel cell is at least about 75 mW / cm ² , or at least about 100 mW / cm ² , or at least about 125 mW / cm. ^2, or may be operated to have at least about 150 mW / cm ^2, or at least about 175mW / cm ^2, or at least about 200 mW / cm ^2, or at least modifiable fuel productivity of about 300 mW / cm ^2,,, . In such embodiments, the reformable fuel productivity is about 600 mW / cm ² or less, or about 500 mW / cm ² or less, or about 400 mW / cm ² or less, or about 300 mW / cm ² or less, or about 200 mW / cm. It can be ² or less.

  Operating a solid oxide fuel cell having the desired electrical efficiency, chemical efficiency and / or total fuel cell efficiency can be accomplished in various ways. In some embodiments, the chemical efficiency of the solid oxide fuel cell is within the fuel cell (and / or the associated reforming stage of the fuel cell assembly) as compared to the amount of oxidation of hydrogen in the anode to generate electricity. Can be increased by increasing the amount of reforming performed. Traditionally, solid oxide fuel cells have been operated to maximize the efficiency of power generation compared to the amount of fuel consumed, while maintaining an appropriate heat balance to maintain the overall system temperature. It was. In this type of operating condition, about 70% to about 85% fuel at the anode to maximize electrical efficiency at the desired (ie high) voltage for electrical output and maintain thermal balance within the fuel cell. Use is desirable. At high fuel utilization values, only a small amount of hydrogen (or synthesis gas) remains in the anode exhaust due to the formation of synthesis gas. For example, with about 75% fuel utilization, about 25% of the fuel entering the anode can exit as a combination of synthesis gas and / or unreacted fuel. A small amount of hydrogen or synthesis gas typically provides sufficient fuel to promote the anodic oxidation reaction and to heat the reactant and / or inlet stream to the appropriate fuel cell operating temperature. , Sufficient to maintain a sufficient hydrogen concentration at the anode.

In contrast to this conventional operation, solid oxide fuel cells are operated at low fuel utilization and higher fuel flow rates with little or no fuel recycling from the anode exhaust to the anode inlet. Can be. By operating with low fuel utilization while reducing or minimizing fuel recycling to the anode inlet, higher amounts of H ₂ and / or CO are available in the anode emissions. This excess of H ₂ and CO can be recovered as a synthesis gas product and / or a hydrogen product. In various aspects, fuel utilization in a fuel cell can be at least about 5%, such as at least about 10%, or at least about 15%, or at least about 20%. Additionally or alternatively, in low fuel utilization embodiments, fuel utilization can be about 60% or less, or about 50% or less, or about 40% or less.

  One option for increasing the chemical efficiency of a fuel cell can be to increase the reformable hydrogen content of the fuel delivered to the fuel cell. For example, the reformable hydrogen content of the reformable fuel in the input stream delivered to the anode and / or the reforming stage associated with the anode is at least about 50% greater than the net amount of hydrogen reacted at the anode, For example, it can be at least about 75% more, or at least about 100% more. Additionally or alternatively, the reformable hydrogen content of the fuel in the input stream delivered to the anode and / or the reforming stage associated with the anode is at least about 50 greater than the net amount of hydrogen reacted at the anode. %, For example, at least about 75% more, or at least about 100% more. In various embodiments, the ratio of the reformable hydrogen content of the reformable fuel in the fuel stream to the amount of hydrogen reacted at the anode is at least about 1.5: 1, or at least about 2.0: 1, or It can be at least about 2.5: 1, or at least about 3.0: 1. Additionally or alternatively, the ratio of the reformable hydrogen content of the reformable fuel in the fuel stream to the amount of hydrogen reacted at the anode is about 20: 1 or less, such as about 15: 1 or less, or It can be about 10: 1 or less. In one aspect, it is believed that less than 100% of the reformable hydrogen content of the anode inlet stream can be converted to hydrogen. For example, at least about 80%, eg, at least about 85%, or at least about 90% of the reformable hydrogen content of the anode inlet stream can be converted to hydrogen at the anode and / or associated reforming stages.

  Either hydrogen or synthesis gas can be recovered from the anode exhaust as a chemical energy output. Hydrogen can be used as a clean fuel that does not produce greenhouse gases during combustion. Additionally, hydrogen can be a valuable input for various purifier processes and / or other synthetic processes. Syngas can also be a valuable input for various processes. In addition to having a fuel value, synthesis gas is used to produce other higher value products, for example, by using synthesis gas as an input for Fischer-Tropsch synthesis and / or methanol synthesis processes. Can be used as a raw material.

In various embodiments, the anode emissions are from about 1.5: 1 to about 10: 1, such as at least about 3.0: 1, or at least about 4.0: 1, or at least about 5.0: 1. And / or have a ratio of H ₂ : CO of about 8.0: 1 or less, or about 6.0: 1 or less. A synthesis gas stream can be recovered from the anode exhaust. In various embodiments, the synthesis gas stream recovered from the anode exhaust is at least about 0.9: 1, such as at least about 1.0: 1, or at least about 1.2: 1, or at least about 1.5. : 1 or at least about 1.7: 1 or at least about 1.8: 1 or at least about 1.9: can have a molar ratio of 1 of _{H 2} molar pairs CO. Additionally or alternatively, the H ₂ : CO molar ratio of the synthesis gas recovered from the anode exhaust is about 3.0: 1 or less, such as about 2.7: 1 or less, or about 2.5 1 or less, or about 2.3: 1 or less, or about 2.2: 1 or less, or about 2.1: 1 or less. However, many types of synthesis gas applications benefit from synthesis gas having a H ₂ : CO molar ratio of at least about 1.5: 1 to about 2.5: 1 or less, for example, about 1.7 It may be desirable for some applications to form a synthesis gas having a molar ratio of: 1 to about 2.3: 1 H ₂ : CO content.

Syngas can be recovered from the anode exhaust by any convenient method. In some embodiments, synthesis gas is recovered from the anode exhaust by performing a separation in the anode exhaust to remove at least a portion of the components in the anode exhaust that are different from H ₂ and CO. Can do. For example, the anode exhaust can be initially passed through an optional water gas shift stage to adjust the relative amounts of H ₂ and CO. One or more separation stages can then be used to remove H ₂ O and / or CO ₂ from the anode exhaust. The remaining portion of the anode discharge can then correspond to a synthesis gas stream, which can then be recovered for use in any convenient manner. Additionally or alternatively, the recovered synthesis gas stream can be passed through one or more water gas shift stages and / or can be passed through one or more separation stages.

An additional or other method for modifying the H ₂ : CO molar ratio in the recovered synthesis gas is to separate the H ₂ stream from the anode exhaust and / or synthesis gas, for example, by performing membrane separation. It should be noted that it is possible to be. Such separation to form a separate H ₂ output stream may involve components in the anode exhaust before and / or after passing the anode exhaust through the water gas shift reaction stage and different from H ₂ and CO. It can be performed at any convenient location, such as before and / or after passing the anode effluent through one or more separation stages for removal. Optionally, a water gas shift stage can be used before and after separation of the H ₂ stream from the anode effluent. In additional or other embodiments, H ₂ can optionally be separated from the recovered synthesis gas stream. In some embodiments, the separated H ₂ stream is at least about 90% by volume H ₂ , such as an H ₂ stream containing at least about 95% by volume H ₂ , or at least about 99% by volume H ₂ , etc. High purity H ₂ stream.

  As an addition, supplement, and / or alternative to the fuel cell operating strategy described herein, solid oxide fuel cells (eg, fuel cell assemblies) are in excess compared to the amount of hydrogen that reacts at the fuel cell anode. It can be operated with an amount of reformable fuel. Instead of selecting fuel cell operating conditions to improve or maximize fuel cell electrical efficiency, an excess amount of reformable fuel is fed to the fuel cell anode to increase the fuel cell chemical energy output. Can be passed. Optionally but preferably, this can lead to an increase in the overall efficiency of the fuel cell based on the combined electrical and chemical efficiency of the fuel cell.

  In some embodiments, the reformable hydrogen content of the reformable fuel in the input stream delivered to the anode and / or the reforming stage associated with the anode is at least about 50% greater than the amount of hydrogen oxidized at the anode. Many, for example, can be at least about 75% more, or at least about 100% more. In various embodiments, the ratio of the reformable hydrogen content of the reformable fuel in the fuel stream to the amount of hydrogen reacted at the anode is at least about 1.5: 1, or at least about 2.0: 1, or It can be at least about 2.5: 1, or at least about 3.0: 1. Additionally or alternatively, the ratio of the reformable hydrogen content of the reformable fuel in the fuel stream to the amount of hydrogen reacted at the anode is about 20: 1 or less, such as about 15: 1 or less, or It can be about 10: 1 or less. In one aspect, it is believed that less than 100% of the reformable hydrogen content of the anode inlet stream can be converted to hydrogen. For example, at least about 80%, eg, at least about 85%, or at least about 90% of the reformable hydrogen content of the anode inlet stream can be converted to hydrogen at the anode and / or associated reforming stages.

  Additionally or alternatively, the amount of reformable fuel delivered to the anode is characterized based on the lower calorific value (LHV) of the reformable fuel compared to the LHV of hydrogen oxidized at the anode. be able to. This can be referred to as a reformable fuel surplus ratio. In such embodiments, the reformable fuel excess ratio can be at least about 2.0, such as at least about 2.5, or at least about 3.0, or at least about 4.0. Additionally or alternatively, the reformable fuel excess ratio can be about 25.0 or less, such as about 20.0 or less, or about 15.0 or less, or about 10.0 or less.

In various aspects of the invention, fuel cell operation can be characterized based on a desired total fuel cell productivity (“TFCP”) of at least about 150 mW / cm ² and a desired reformable fuel excess ratio. For example, the solid oxide fuel cell has a TFCP of at least about 150 mW / cm ² and a reformable fuel excess of at least about 2.0, such as at least about 2.5, or at least about 3.0, or at least about 4.0. It can be operated to have a ratio. Additionally or alternatively, the TFCP can be greater than about 150 mW / cm ² and the reformable fuel excess ratio is about 25.0 or less, such as about 20.0 or less, or about 15. It can be 0 or less, or about 10.0 or less. When the fuel cell is operated to have a reformable fuel excess ratio of at least about 2.0, the solid oxide fuel cell is at least about 150 mW / cm ² , or at least about 200 mW / cm ² , or at least about 250 mW. Can be actuated to have a TFCP of / cm ² , or at least about 300 mW / cm ² , or at least about 350 mW / cm ² . In such embodiments, it TFCP is about 800 mW / cm ² or less, or about 700 mW / cm ² or less, or about 600 mW / cm ² or less, or about 500 mW / cm ² or less, or about 400 mW / cm ² or less Can do.

In various aspects of the invention, fuel cell operation can be characterized based on a desired total reformable fuel productivity and a desired reformable fuel excess ratio of about 75 mW / cm ² or greater. In some embodiments, the fuel cell has a desired reformable fuel productivity greater than about 75 mW / cm ² and at least about 2.0, such as at least about 2.5, or at least about 3.0, or at least It can be operated to have a reformable fuel excess ratio of about 4.0. Additionally or alternatively, the total reformable fuel productivity can be greater than about 75 mW / cm ² and the reformable fuel excess ratio is about 25.0 or less, such as about 20.0. Or about 15.0 or less, or about 10.0 or less. When the fuel cell is operated to have a reformable fuel excess ratio of at least about 2.0, the solid oxide fuel cell is at least about 75 mW / cm ² , or at least about 100 mW / cm ² , or at least about 125 mW. / cm ^2, or at least about 150 mW / cm ^2, or at least about 175MW / cm ^2, or at least about 200 mW / cm ² or actuated by it to have at least about 300 mW / cm ² of reformable fuel productivity,,,, Can do. In such embodiments, the reformable fuel productivity is about 600 mW / cm ² or less, or about 500 mW / cm ² or less, or about 400 mW / cm ² or less, or about 300 mW / cm ² or less, or about 200 mW / cm. It can be ² or less.

As an addition, supplement, and / or alternative to the fuel cell operating strategy described herein, the amount of reforming is selected relative to the amount of oxidation to achieve the desired heat ratio for the fuel cell. The solid oxide fuel cell can be operated so that it can. As used herein, “heat ratio” is defined as the heat generated by an exothermic reaction in the fuel cell assembly divided by the endothermic heat demand of the reforming reaction occurring in the fuel cell assembly. Mathematically expressed, the heat ratio (TH) = Q _EX / Q _EN , Q _EX is the total heat generated by the exothermic reaction, and Q _EN is consumed by the endothermic reaction occurring in the fuel cell. Is the sum of heat done. The heat generated by the exothermic reaction corresponds to any heat generated by the reforming reaction, the water gas shift reaction, and the electrochemical reaction in the battery. The heat generated by the electrochemical reaction can be calculated based on the ideal electrochemical potential of the fuel cell reaction across the electrolyte, minus the actual output voltage of the fuel cell. For example, the ideal electrochemical potential of the SOFC reaction is considered to be about 1.04 V, based on the net reaction that occurs in the battery. During operation of the SOFC, the battery typically has an output voltage of less than 1.1V due to various losses. For example, the common output / operating voltage can be about 0.65V, or about 0.7V, or about 0.75V, or about 0.8V. The heat generated is equal to the electrochemical potential of the battery (eg, about 1.04V) minus the operating voltage. For example, the heat generated by the electrochemical reaction in the battery is about 0.34V for an output voltage of about 0.7V. Thus, in this scenario, the electrochemical reaction produces about 0.7V electricity and about 0.34V thermal energy. In such an embodiment, the electrical energy of about 0.7V are _not included as part of _{Q EX.} In other words, thermal energy is not electrical energy.

  In various embodiments, the SOFC operating parameter is at least less than 0.7V, such as at least less than 0.65V, or such as at least less than 0.6V, or such as at least less than 0.5V, or such as at least less than 0.4V, or such as, for example. It can be set to achieve an operating voltage of at least less than 0.3V.

  In various embodiments, the heat ratio may be measured as a fuel cell stack, individual fuel cells within the fuel cell stack, a fuel cell stack with an integrated reforming stage, an integrated endothermic reaction stage ( It can be determined for any convenient fuel cell structure, such as a fuel cell stack with an integrated endothermic reaction stage), or a combination thereof. The heat ratio may be calculated for different units within a fuel cell stack, such as a fuel cell or an assembly of fuel cell stacks. For example, the heat ratio may be an integrated reforming stage that is sufficiently close to a single anode in a single fuel cell, an anode portion in a fuel cell stack, or an anode portion that is integrated in terms of thermal integration and It may also be calculated for the anode part in the fuel cell stack with integrated endothermic reaction stage elements. As used herein, an “anode portion” includes an anode within a fuel cell stack that shares a common inlet or outlet manifold.

  In various aspects of the invention, the operation of the fuel cell can be characterized on the basis of the heat ratio. When the fuel cell is operated to have a desired heat ratio, the solid oxide fuel cell is about 1.5 or less, such as about 1.3 or less, or about 1.15 or less, or about 1.0 or less, or It can be operated to have a heat ratio of about 0.95 or less, or about 0.90 or less, or about 0.85 or less, or about 0.80 or less, or about 0.75 or less. Additionally or alternatively, the heat ratio can be at least about 0.25, or at least about 0.35, or at least about 0.45, or at least about 0.50.

In various aspects of the invention, fuel cell operation can be characterized based on a desired total reformable fuel productivity and a desired heat ratio of about 75 mW / cm ² or greater. In some embodiments, the fuel cell has a desired reformable fuel productivity greater than about 75 mW / cm ² and about 1.5 or less, such as about 1.3 or less, or about 1.15 or less, or about Operated to have a heat ratio of 1.0 or less, or about 0.95 or less, or about 0.90 or less, or about 0.85 or less, or about 0.80 or less, or about 0.75 or less Can do. Additionally or alternatively, the total reformable fuel productivity can be greater than about 75 mW / cm ² and the heat ratio is at least about 0.25, or at least about 0.35, or at least about It can be 0.45, or at least about 0.50. When the fuel cell is operated to have a heat ratio of about 0.25 to about 1.3, the solid oxide fuel cell is at least about 75 mW / cm ² , or at least about 100 mW / cm ² , or at least about 125 mW / cm ^2, or at least about 150 mW / cm ^2, or at least about 175mW / cm ^2, or at least about 200 mW / cm ^2, or at least about 300 mW / cm ² of be actuated to have a reformable fuel productivity, Is possible. In such embodiments, the reformable fuel productivity is about 600 mW / cm ² or less, or about 500 mW / cm ² or less, or about 400 mW / cm ² or less, or about 300 mW / cm ² or less, or about 200 mW / cm. It can be ² or less.

In various aspects of the invention, fuel cell operation can be characterized based on a desired total fuel cell productivity and a desired heat ratio of about 150 mW / cm ² or greater. In one aspect, the fuel cell has a desired total fuel cell productivity greater than about 150 mW / cm ² and about 1.5 or less, such as about 1.3 or less, or about 1.15 or less, or about 1.0. Or less than about 0.95, or about 0.90 or less, or about 0.85 or less, or about 0.80 or less, or about 0.75 or less. Additionally or alternatively, the total fuel cell productivity can be greater than about 150 mW / cm ² and the heat ratio is at least about 0.25, or at least about 0.35, or at least about 0.00. 45, or at least about 0.50. When the fuel cell is operated to have a heat ratio of about 0.25 to about 1.3, the solid oxide fuel cell is at least about 150 mW / cm ² , or at least about 200 mW / cm ² , or at least about 250 mW / It can be operated to have a TFCP of cm ² , or at least about 300 mW / cm ² , or at least about 350 mW / cm ² . In such embodiments, it TFCP is about 800 mW / cm ² or less, or about 700 mW / cm ² or less, or about 600 mW / cm ² or less, or about 500 mW / cm ² or less, or about 400 mW / cm ² or less Can do.

  Additionally or alternatively, in some embodiments, the fuel cell has a temperature increase between the anode input and anode output of about 40 ° C. or less, such as about 20 ° C. or less, or about 10 ° C. or less. It can be activated. Additionally or alternatively, the fuel cell can be operated to have an anode outlet temperature that is from about 10 ° C. to about 10 ° C. higher than the temperature of the anode inlet. Still further or alternatively, the fuel cell has an anode inlet that is above the anode outlet temperature, eg, at least about 5 ° C., or at least about 10 ° C., or at least about 20 ° C., or at least about 25 ° C. higher. It can be actuated to have a temperature. Still further, or alternatively, the fuel cell is about 100 ° C. or less from the anode outlet temperature, such as about 80 ° C. or less, or about 60 ° C. or less, or about 50 ° C. or less, or about 40 ° C. or less, or about It can be operated to have a high anode inlet temperature at a temperature of 30 ° C. or lower, or about 20 ° C. or lower, or about 10 ° C. or lower. Minimizing the difference between the anode inlet temperature and the outlet temperature can be beneficial in maintaining the mechanical integrity of the ceramic components in the solid oxide fuel cell.

As an addition, supplement, and / or alternative to the fuel cell operating strategy described herein, the solid oxide fuel cell (eg, fuel cell assembly) is operated at conditions that can provide an increase in power density. Can do. The power density of the fuel cell corresponds to a value obtained by multiplying the actual operating voltage _VA by the current density I. Respect Solid oxide fuel cell operated at a voltage _{V A,} a fuel cell, the difference between _{V A} and the ideal voltage _{V 0} to a fuel cell to provide a current density I as a base _{(V 0} -V ^A) * I The waste heat defined as can also tend to generate. A portion of this waste heat can be consumed by reforming the reformable fuel within the anode of the fuel cell. The rest of this waste heat can be absorbed by the surrounding fuel cell structure and gas flow, resulting in a temperature difference across the fuel cell. Under conventional operating conditions, the power density of a fuel cell can be limited based on the amount of waste heat that the fuel cell can withstand without degrading the integrity of the fuel cell.

In various aspects, the amount of waste heat that a fuel cell can withstand can be increased by performing an effective amount of endothermic reaction within the fuel cell. An example of an endothermic reaction includes steam reforming of a reformable fuel within the fuel cell anode and / or associated reforming stages, such as an integrated reforming stage in a fuel cell stack. Additional reforming so that additional waste heat can be consumed by providing additional reformable fuel to the anode (or integrated / associated reforming stage) of the fuel cell Can be executed. As a result, the amount of temperature difference in the entire fuel cell can be reduced, and therefore the fuel cell can be operated under operating conditions in which the amount of waste heat is increased. Loss of electrical efficiency is capable of being canceled by the generation of additional product streams, such as syngas, and / or H _2, which comprises an additional power generating to Zaisa further extend the power range of the system Can be used for various purposes.

In various embodiments, the amount of waste heat generated by the fuel cell, as defined above (V ₀ -V _A ) ^* I, is at least about 30 mW / cm ² , eg, at least about 40 mW / cm ² , or at least about 50 mW / cm ^2, or at least about 60 mW / cm ^2, or at least about 70 mW / cm ^2, or at least about 80 mW / cm ^2, or at least about 100 mW / cm ^2, or at least about 120 mW / cm ^2, or at least about 140 mW, / cm ^2, or at least about 160 mW / cm ^2, or at least about 180 mW / cm ^2, or at least about 200 mW / cm ^2, or at least about 220 mW / cm ^2, or at least about 250 mW / cm ^2, or at least about 300mW / cm,,,, It can be. Additionally or alternatively, the amount of waste heat generated by the fuel cell is less than about 400 mW / cm ^2, for example, less than about 300 mW / cm ^2, less than about 200 mW / cm ^2, or less than about 175mW / cm ^2, Or less than about 150 mW / cm ² .

Although the amount of waste heat generated can be relatively high, such waste heat may not necessarily represent operating the fuel cell with low efficiency. Instead, waste heat can be generated by operating the fuel cell with increased power density. Part of improving the power density of the fuel cell can include operating the fuel cell at a sufficiently high current density. In various embodiments, the current density generated by the fuel cell is at least about 150 mA / cm ^2, for example, at least about 160 mA / cm ^2, or at least about 170 mA / cm ^2, or at least about 180 mA / cm ^2,, or at least about 190 mA, / cm ^2, or can be at least about 200 mA / cm ^2, or at least about 300 mA / cm ^2, or at least about 400mA / cm ^2,,, or at least about 800 mA / cm ^2. Additionally or alternatively, the current density generated by the fuel cell is about 800 mA / cm ² or less, for example 450 mA / cm ² or less, or 300 mA / cm ² or less, or 250 mA / cm ² or less, or 200 mA / cm ² Can be:

  In various aspects, performing an effective amount of an endothermic reaction (eg, a reforming reaction) to increase power generation, increase the generation of waste heat, and allow the fuel cell to operate. Can do. Alternatively, other endothermic reactions unrelated to anode operation may be used to dissipate waste heat by interspersing “plates” or stages in fuel cell arrays that are in thermal communication rather than fluid communication with either the anode or cathode. Can be used. An effective amount of endothermic reaction can be performed in the associated reforming stage, integrated reforming stage, integrated stacking element, or combinations thereof for performing the endothermic reaction. An effective amount of endothermic reaction is that the temperature rise from the fuel cell inlet to the fuel cell outlet is less than about 100 ° C., such as less than about 90 ° C., or less than about 80 ° C. Or less than about 50 ° C., or about 40 ° C. or less, or an amount sufficient to reduce to about 30 ° C. or less. Additionally or alternatively, an effective amount of endothermic reaction is about 100 ° C. or lower, such as about 90 ° C. or lower, or about 80 ° C. or lower, or about 70 ° C. or lower, or about 60 ° C. or lower, or about 50 Or less than about 40 ° C, or less than about 30 ° C, or less than about 20 ° C, or equivalent to an amount sufficient to cause a temperature decrease from the fuel cell inlet to the fuel cell outlet below about 10 ° C. it can. A temperature decrease from the fuel cell inlet to the fuel cell outlet can occur when the effective amount of endothermic reaction is greater than the generated waste heat. Additionally or alternatively, this may be an endothermic reaction (eg, a combination of reforming and another endothermic reaction) that consumes at least about 40% of the waste heat generated by the fuel cell, eg, waste It may correspond to consuming at least about 50% of heat, or at least about 60% of waste heat, or at least about 75% of waste heat. Additionally or alternatively, the endothermic reaction can consume less than about 95% waste heat, such as less than about 90% waste heat, or less than about 85% waste heat.

Additional Definitions Syngas: In the present description, synthesis gas is defined as a mixture of H ₂ and CO in any ratio. Optionally, H ₂ O and / or CO ₂ may be present in the synthesis gas. Optionally, inert compounds (eg, nitrogen) and residual reformable fuel compounds may be present in the syngas. When components other than H ₂ and CO are present in the synthesis gas, the combined volume percent of H ₂ and CO in the synthesis gas is at least 25% by volume, eg, at least 40% compared to the total volume of the synthesis gas. It can be vol%, or at least 50 vol%, or at least 60 vol%. Additionally or alternatively, the combined volume percent of H ₂ and CO in the syngas can be 100% or less, such as 95% or less, or 90% or less.

Reformable fuel (reformable fuel): reformable fuel is reformable carbon in order to generate the H ₂ - is defined as a fuel containing hydrogen bonds. Like other hydrocarbon compounds such as alcohol, hydrocarbons are examples of reformable fuels. CO and H ₂ O can participate in the water gas shift reaction to form hydrogen, but CO is not considered a reformable fuel in this definition.

Reformable hydrogen content (reformable hydrogen content): reformable hydrogen content of fuel, the fuel reforming, followed by completing the water gas shift reaction to maximize of H ₂ generation, fuel Defined as the number of H ₂ molecules that can be derived from In the present specification, H ₂ itself is not defined as a reformable fuel, but H ₂ by definition has a reformable hydrogen content of 1. Similarly, CO has a reformable hydrogen content of 1. CO is not possible reforming strictly, but by completing the water gas shift reaction, exchange of CO is brought against H _2. As an example of the reformable hydrogen content for a reformable fuel, the reformable hydrogen content of methane is 4H ₂ molecules and the reformable hydrogen content of ethane is 7H ₂ molecules. More generally, when the fuel has the composition CxHyOz, the reformable hydrogen content of the fuel at 100% reforming and water gas shift is n (H ₂ maximum reforming) = 2x + y / 2−z. Based on this definition, the fuel utilization in the cell can then be expressed as n (H ₂ ox) / n (H ₂ maximum reforming). Of course, the reformable hydrogen content of a mixture of components can be determined based on the reformable hydrogen content of the individual components. The reformable hydrogen content of compounds containing other heteroatoms such as oxygen, sulfur or nitrogen can be calculated in a similar manner.

Oxidation reaction: In this discussion, the oxidation reaction in the anode of the fuel cell is defined as the reaction corresponding to the oxidation of H ₂ that forms H ₂ O by reaction with O ²⁻ . It should be noted that the reforming reaction in the anode where the compound containing carbon-hydrogen bonds is converted to H ₂ and CO or CO ₂ is excluded from this definition of oxidation reaction at the anode. The water gas shift reaction is similar except for this definition of oxidation reaction. Still further, reference to a combustion reaction is that H ₂ or a compound containing a carbon-hydrogen bond reacts with O _{2 in} a non-electrochemical burner such as a combustion region of a combustion generator to produce H ₂ O and carbon oxide. Is defined as a reference to the reaction that forms

  Embodiments of the invention can adjust anode fuel parameters to achieve a desired operating range for a fuel cell. The anode fuel parameters can be characterized directly and / or with respect to other fuel cell processes in the form of one or more ratios. For example, the anode fuel parameter achieves one or more ratios including fuel utilization, fuel cell heating value, fuel excess ratio, reformable fuel excess ratio, reformable hydrogen content fuel ratio, and combinations thereof. In order to be able to control.

Fuel utilization: Fuel utilization is based on the amount of fuel oxidized compared to the reformable hydrogen content of the input stream that can be used to define fuel utilization for the fuel cell. An option to characterize the operation of the anode. In this discussion, “fuel utilization” refers to the amount of hydrogen oxidized at the anode for electricity generation (as described above) and the reformable hydrogen content of the anode input (any associated reforming stage also Defined as a ratio. The reformable hydrogen content is the amount of H ₂ molecules that can be derived from the fuel, as described above, by reforming the fuel and then completing the water gas shift reaction to maximize H ₂ production. Defined as a number. For example, each methane introduced into the anode and exposed to steam reforming conditions results in the generation of 4H ₂ molecular equivalents at maximum production (depending on reforming and / or anode conditions, Instead, it can correspond to a non-aqueous gas shift product in which one or more of the H ₂ molecules are present in the form of CO molecules). Thus, methane is defined as having a reforming possible hydrogen content 4H ₂ molecule. As another example, in this definition, ethane has a reforming possible hydrogen content 7H ₂ molecule.

The use of fuel at the anode is associated with the lower calorific value of the hydrogen oxidized at the anode by the fuel cell anode reaction compared to the lower calorific value of all fuel delivered to the anode and / or the reforming stage associated with the anode. It can also be characterized by defining the heating value utilization based on the ratio. As used herein, “fuel cell heating value utilization” can be calculated using the flow rate and lower heating value (LHV) of the fuel components entering and leaving the fuel cell anode. As such, the fuel cell heating value utilization can be calculated as (LHV (anode_in) −LHV (anode_out)) / LHV (anode_in). Where LHV (anode_in) and LHV (anode_out) refer to the LHV of the fuel components (eg, H ₂ , CH ₄ and / or CO) in the anode inlet and outlet streams or flows, respectively. In this definition, the flow or flow LHV may be calculated as the sum of the values of each fuel component of the input and / or output flow. The contribution of each fuel component to the sum can correspond to the fuel component flow rate (eg, mol / hour) multiplied by the fuel component's LHV (eg, joule / mol).

Lower heating value: Lower heating value is defined as the enthalpy of combustion of fuel components into gas phase fully oxidized products (eg, gas phase CO ₂ and H ₂ O products). The For example, any CO ₂ present in the anode input stream does not contribute to the fuel content of the anode input because CO ₂ is already fully oxidized. With respect to this definition, the amount of oxidation that occurs at the anode by the anode fuel cell reaction is defined as the oxidation of H ₂ at the anode as part of the electrochemical reaction of the anode, as defined above.

Note that for the case only the fuel at the anode input flow is a special and H _2, the only reaction that fuel component can occur at the anode are involved, represents the conversion of H ₂ to H _{2 O.} In such cases special, fuel utilization, _{(H 2} - Rate - In (rate-in) -H ₂ - Rate - out _{(rate-out)) / H} 2 - Rate - is simplified as in. In such a case, H ₂ is the only fuel component, and the H ₂ LHV is offset from the equation. In the more general case, the anode feed may contain, for example, CH ₄ , H ₂ and CO in various amounts. Since these species can typically be present in different amounts in the anode outlet, a summary is necessary to determine fuel utilization, as described above.

  In addition to or in addition to fuel utilization, the utilization of other reactants in the fuel cell can be characterized. For example, fuel cell operation can additionally or alternatively be characterized with respect to “oxidant” utilization. Values for oxidant utilization can be specified in a similar manner.

Fuel surplus ratio: Yet another way to characterize the reaction in a solid oxide fuel cell is to compare the anode and / or anode with the lower heating value of hydrogen oxidized at the anode by the fuel cell anode reaction. By defining utilization based on the ratio of the lower heating value of all fuels delivered to the relevant reforming stage. This amount is called the fuel excess ratio. As such, the fuel excess ratio can be calculated as (LHV (anode_in) / (LHV (anode_in) −LHV (anode_out)), where LHV (anode_in) and LHV (anode_out) are respectively , Refers to the LHV of the fuel component (eg, H ₂ , CH ₄ and / or CO) in the anode inlet and outlet streams or flows In various embodiments of the invention, the solid oxide fuel cell is at least about 1.0, eg It can be operated to have a fuel excess ratio of at least about 1.5, or at least about 2.0, or at least about 2.5, or at least about 3.0, or at least about 4.0. Or alternatively, the fuel excess ratio is about 25 Can be 0 is less than or equal to the.

  Note that not all of the reformable fuel in the input stream for the anode can be reformed. Preferably, at least about 90%, such as at least about 95%, or at least about 98% of the reformable fuel in the input stream to the anode (and / or associated reforming stage) can be reformed before leaving the anode. It is. In some other embodiments, the amount of reformable fuel that is reformed can be from about 75% to about 90%, such as at least about 80%.

  The above definition for the excess fuel ratio indicates that the reforming that occurs within the reforming stage associated with the anode and / or the fuel cell as compared to the amount of fuel consumed at the fuel cell anode for power generation. Provides a way to characterize quantities.

Optionally, the fuel excess ratio can be varied to account for the condition where fuel is recycled from the anode output to the anode input. When fuel (eg, H ₂ , CO and / or unreformed or partially reformed hydrocarbons) is recycled from the anode output to the anode input, such recycled fuel components It does not represent an excess of reformable or reformed fuel that can be used for the purpose. Instead, such recycled fuel components merely indicate a desire to reduce fuel utilization in the fuel cell.

Reformable fuel surplus ratio: Calculating the reformable fuel surplus ratio means that such recycled fuel components contain only the LHV of reformable fuel in the input stream to the anode. This is one option that indicates limiting the definition of excess fuel. As used herein, “reformable fuel excess ratio” refers to the anode and / or anode associated with the anode as compared to the lower heating value of hydrogen oxidized at the anode by the fuel cell anode reaction. Defined as the lower heating value of the reformable fuel delivered to the reforming stage. In the definition for reformable fuel excess ratio, any H ₂ or CO LHV at the anode input is excluded. Such LHV for reformable fuels can still be measured by characterizing the actual composition entering the fuel cell anode, and a distinction between recycled and new components is necessary. Not. Although some unreformed or partially reformed fuels may also be recycled, in most embodiments, the majority of the fuel recycled to the anode is the reformed product (eg, H ₂ or CO). Expressed mathematically, the reformable fuel excess ratio (R _RFS ) = LHV _RF / LHV _OH , where LHV _RF is the lower calorific value (LHV) of the reformable fuel, and LHV _OH is The lower heating value (LHV) of hydrogen oxidized at the anode. The LHV of hydrogen oxidized at the anode may be calculated by subtracting the LHV of the anode outlet stream from the LHV of the anode inlet stream (eg, LHV (anode_in) −LHV (anode_out)). In various aspects of the invention, the solid oxide fuel cell is at least about 0.25, such as at least about 0.5, or at least about 1.0, or at least about 1.5, or at least about 2.0, or It can be operated to have a reformable fuel excess ratio of at least about 2.5, or at least about 3.0, or at least about 4.0. Additionally or alternatively, the reformable fuel excess ratio can be about 25.0 or less. Note that this narrower definition based on the amount of reformable fuel delivered to the anode compared to the amount of oxidation at the anode distinguishes two types of fuel cell operating methods with low fuel utilization. can do. Some fuel cells achieve low fuel utilization by recycling a substantial portion from the anode output to the anode input. This recycling allows any hydrogen at the anode input to be used again as input to the anode. This can reduce the amount of reforming and at least a portion of the unused fuel is recycled in subsequent passes even if the fuel utilization is low for a single pass of the fuel cell. Thus, fuel cells with a wide variety of fuel utilization values may have the same ratio of reformable fuel delivered to the anode reforming stage to hydrogen oxidized in the anode reaction. In order to change the ratio of reformable fuel delivered to the anode reforming stage with respect to the amount of oxidation at the anode, an anode feed with the original content of non-reformable fuel needs to be identified or the anode Unused fuel at the output needs to be recovered for other uses, or both.

Reformable hydrogen surplus ratio: Yet another option for characterizing the operation of a fuel cell is based on the “reformable hydrogen surplus ratio”. The reformable fuel excess ratio defined above is defined based on the lower heating value of the reformable fuel component. Reformable hydrogen excess ratio is defined as the reformable hydrogen content of the reformable fuel delivered to the anode and / or the reforming stage associated with the anode as compared to the hydrogen reacted at the anode by the fuel cell anode reaction. Is done. As such, the “reformable hydrogen excess ratio” can be calculated as (RFC (reformable_anode_in) / (RFC (reformable_anode_in) −RFC (anode_out)), where (RFC (reformable_anode_in) is: Refers to the reformable hydrogen content of the reformable fuel in the anode inlet stream or flow, and RFC (anode_out) is the fuel component of the anode inlet and outlet stream or flow (eg, H ₂ , CH ₄ and / or CO) Reformable hydrogen content refers to RFC, which can be expressed in moles / second, moles / hour, etc. Fuel with a large ratio of reformable fuel to anode oxidation delivered to the anode reforming stage How to activate the battery Examples are to balance the generation and consumption of heat in the fuel cell, to reform the reformable fuel to form a can .H ₂ and CO that is excessive way modification is performed Is an endothermic process, which can be countered by the generation of current in the fuel cell, which is the energy that exits the fuel cell in the form of heat and flow generated by the anodic oxidation and cathodic reactions. The excess heat per mole of hydrogen involved in the anodic oxidation / cathode reaction can be generated by the reforming to generate a mole of hydrogen. As a result, fuel cells operated under conventional conditions show an increase in temperature from the inlet to the outlet. As an alternative to this type of conventional operation, the amount of fuel reformed in the reforming stage associated with the anode can be increased, for example, the heat generated by the exothermic fuel cell reaction is modified. The heat consumed by the quality can be (approximately) balanced, or the heat consumed by reforming can be greater than the excess heat generated by fuel oxidation, resulting in a temperature drop across the fuel cell. The additional fuel can be reformed to provide a substantial excess of hydrogen compared to the amount required for power generation, as an example. The feed to the fuel cell anode inlet or associated reforming stage may consist essentially of a reformable fuel, such as a substantially pure methane feed. Kill. During conventional operation for power generation using such fuels, solid oxide fuel cells can operate at about 75% fuel utilization. This then uses about 75% (or 3/4) of the fuel content delivered to the anode to form hydrogen that reacts with oxygen ions to form H ₂ O at the anode. Means that. In conventional operation, the remaining approximately 25% of the fuel content can be reformed to H ₂ in the fuel cell (or passing through an unreacted fuel cell for any CO or H _{2 in} the fuel). Can then be combusted outside the fuel cell to form H ₂ O and provide heat to the fuel cell for the cathode inlet. The reformable hydrogen excess ratio in this state can be 4 / (4-1) = 4/3.

  Electrical efficiency: As used herein, the term “electric efficiency” (EE) is the fuel divided by the rate of the lower heating value (“LHV”) of the fuel input to the fuel cell. Defined as the electrochemical power generated in the battery. Fuel input to the fuel cell includes both the fuel delivered to the anode and any fuel used to maintain the temperature of the fuel cell, for example, the fuel delivered to the burner associated with the fuel cell. It is. In this description, the power generated by the fuel may be described in terms of LHV (el) fuel rate.

  Electrochemical power: As used herein, the term “electrochemical power” or LHV (el) passes through the circuit that connects the cathode to the anode in the fuel cell and the electrolyte of the fuel cell. This is the power generated by the movement of oxygen ions. Electrochemical power eliminates power generated from the fuel cell or consumed in upstream or downstream equipment. For example, electricity resulting from heat in a fuel cell waste stream is not considered part of the electrochemical power. Similarly, the power generated in a gas turbine or other device upstream of the fuel cell is not part of the generated electrochemical power. “Electrochemical power” does not take into account the power consumed during the operation of the fuel cell or any losses caused by the conversion from direct current to alternating current. In other words, the power used to provide fuel cell operation or otherwise to operate the fuel cell is not subtracted from the DC power generated by the fuel cell. As used herein, power density is current density multiplied by voltage. As used herein, total fuel cell power is the power density multiplied by the fuel cell area.

  Fuel input: As used herein, the term “anode fuel input”, denoted as LHV (anode_in), is the amount of fuel in the anode inlet stream. The term “fuel input”, denoted as LHV (in), refers to fuel delivered to a fuel cell that includes both the amount of fuel in the anode inlet stream and the amount of fuel used to maintain the temperature of the fuel cell. Is the total amount of. Fuels may include reformable and non-reformable fuels based on the definition of reformable fuel provided herein. Fuel input is not the same as fuel use.

Total fuel cell efficiency: As used herein, the term “total fuel cell efficiency” (“TFCE”) is generated by a fuel cell to the electrochemical power generated by the fuel cell. It is defined as the sum of the LHV rate of synthesis gas divided by the LHV rate of the fuel input to the anode. In other words, TFCE = (LHV (el) + LHV (sg net)) / LHV (anode_in), where LHV (anode_in) is the fuel component (eg, H ₂ , CH ₄ and / or CO) at the anode LHV as delivered and LHV (sg net) refers to the rate at which synthesis gas (H ₂ , CO) is produced at the anode, which is the synthesis gas input to the anode and the synthesis gas output from the anode Is the difference between LHV (el) describes the electrochemical power generation of the fuel cell. Total fuel cell efficiency eliminates the heat generated by the fuel cell, which is advantageously used outside the fuel cell. In operation, the heat generated by the fuel cell may be advantageously used in downstream equipment. For example, heat may be used to generate additional electricity or to heat water. These applications are not part of the overall fuel cell efficiency as the terminology used in this application if they occur away from the fuel cell. Total fuel cell efficiency relates only to fuel cell operation and does not include power generation or fuel cell consumption upstream or downstream.

Chemical efficiency: As used herein, the term “chemical efficiency” refers to the lower heating value of H ₂ and CO in the fuel cell anode emissions divided by the fuel input or LHV (in). Or LHV (sg out).

Neither electrical efficiency nor overall system efficiency takes into account the efficiency of upstream or downstream processes. For example, it may be advantageous to use turbine emissions as a source of O ₂ for the fuel cell cathode. In this arrangement, turbine efficiency is not considered as part of the calculation of electrical efficiency or total fuel cell efficiency. Similarly, the output from the fuel cell may be recycled as input to the fuel cell. When calculating electrical efficiency or total fuel cell efficiency in single pass mode, the recycle loop is not considered.

  Syngas produced: As used herein, the term “produced syngas” is the difference between the syngas input to the anode and the syngas output from the anode. Syngas may be used, at least in part, as an input or fuel for the anode. For example, the system may include an anode recycle loop that is supplemented with natural gas or other suitable fuel to return synthesis gas from the anode exhaust to the anode inlet. The generated synthesis gas LHV (sg net) = (LHV (sg out) −LHV (sg in)), where LHV (sg in) and LHV (sg out) are the syngas LHV and anode outlet flow of the anode inlet. Or, it refers to the LHV of the synthesis gas in the flow. It should be noted that at least a portion of the synthesis gas produced by the reforming reaction within the anode can typically be utilized at the anode to generate electricity. The hydrogen used to generate electricity does not exit the anode and is therefore not included in the definition of “generated synthesis gas”. As used herein, the term “synthesis gas ratio” refers to the LHV of the generated net synthesis gas divided by the LHV of the fuel input to the anode, or LHV (sg net) / LHV (anode in). ). Syngas and fuel molar flow rates can be used to represent mole-based syngas ratios and mole-based produced syngas instead of LHV.

Steam to carbon ratio (S / C): As used herein, the steam to carbon ratio (S / C) is the steam to carbon reformable carbon mole ratio in the flow. It is. Carbon in the form of CO and CO ₂ is not included as modifiable carbon in this definition. The steam to carbon ratio can be measured and / or controlled at different points in the system. For example, the composition of the anode inlet stream can be modified to achieve the appropriate S / C for modification at the anode. S / C can be given as the molar flow rate of H ₂ O divided by the product of the molar flow rate of the fuel, eg, the fuel multiplied by the number of carbon atoms in the methane. Thus, S / C = f _H2O / (f _CH4 x # C) where f _H2O is the molar flow rate of water and f _CH4 is the molar flow rate of methane (or other fuel). And #C is the number of carbons in the fuel. In various embodiments, the S / C can be about 2, or about 1: 3, or about 0.5: 5. Because excess steam dilutes the anode reactant and sacrifices the resulting energy, it may be desirable to provide only enough steam to meet the stoichiometry of the reforming reaction and prevent fouling.

  Fuel cell and fuel cell components: In this discussion, a fuel cell can correspond to a cell having an anode and a cathode separated by an electrolyte. Solid oxide fuel cells can be either planar or tubular. As used herein, a fuel cell can refer to one or both forms. The anode and cathode can receive an input gas flow to facilitate their respective anode and cathode reactions to transport charge across the electrolyte and generate electricity. A fuel cell stack can represent multiple cells in an integrated unit. A fuel cell stack can include multiple fuel cells, which can typically be connected in parallel, and so that they collectively represent a single fuel cell of larger diameter (approximately) Can function. When the input flow is delivered to the anode or cathode of the fuel cell stack, the fuel stack is a flow channel for splitting the input flow between each cell in the stack and the flow for combining the output flows from the individual cells. Channels can be included. In this discussion, the fuel cell array is a plurality of fuel cells (eg, a plurality of fuel cell stacks) arranged in series, parallel, or any other convenient manner (eg, in a combination of series and parallel). Can be used to refer to. The fuel cell array includes one or more stages of fuel cells and / or fuel cell stacks, where the anode / cathode output from the first stage can serve as the anode / cathode input for the second stage. Can do. Note that the anodes of the fuel cell array need not be connected in the same manner as the cathodes of the array. For convenience, the input to the first anode stage of the fuel cell array may be referred to as the anode input for the array, and the input to the first cathode stage of the fuel cell array is the input to the array. It may be called the cathode input. Similarly, the output from the final anode / cathode stage may be referred to as the anode / cathode output from the array.

  References herein to the use of fuel cells typically indicate a “fuel cell stack” comprised of individual fuel cells and, more generally, one or more fuel cells in fluid communication. It should be understood that it refers to the use of lamination. Individual fuel cell elements (plates or cylinders) can typically be “stacked” together in a rectangular array called a “fuel cell stack”. This fuel cell stack typically can provide a flow between all individual fuel cells and can distribute reactants, and then collect products from each of these elements. be able to. When viewed as a unit, an active fuel cell stack can be considered as a unity, even if it is composed of many (often ten or hundreds) individual fuel cell elements. These individual fuel cell elements can typically have similar voltages (similar reactant and product concentrations), and the total power output is when the elements are electrically connected in series, It can result from the sum of all currents of the battery element. The stacks can also be arranged in series to produce a high voltage. A parallel arrangement can increase the current. If a sufficiently large volume fuel cell stack is available to handle a given stream, the stems and methods described herein can be used in a single solid oxide fuel cell stack. In other aspects of the invention, multiple fuel cell stacks may be desirable or required for various reasons.

  For the purposes of the present invention, unless otherwise specified, the term “fuel cell” refers to one or more individual, where there is a single input and output as the manner in which the fuel cell is typically utilized in practice. Should be understood as referring to and / or including reference to it. Similarly, the term fuel cell (s) should also be understood to refer to and / or include a plurality of individual fuel cell stacks unless specifically stated otherwise. In other words, all references within the scope of this specification are interchangeably applicable to the operation of a fuel cell stack as a “fuel cell” unless specifically indicated. For example, the volume of emissions generated in commercial scale combustion generators can be large for processing with conventional diameter fuel cells (eg, single stack). Multiple fuel cells (ie, two or more individual fuel cells or fuels) so that each fuel cell can (almost) treat an equivalent portion of the combustion emissions in order to fully process the emissions. Battery stacks) can be arranged in parallel. Although multiple fuel cells can be used, the fuel cells typically can be operated on a given (approximately) equivalent portion of the combustion emissions in a generally similar manner.

  “Internal reforming” and “external reforming”: A fuel cell or fuel cell stack may include one or more internal reforming portions. As used herein, the term “internal reforming” refers to fuel reforming that occurs within the body of the fuel cell (fuel cell stack) or otherwise within the fuel cell assembly. External reforming is often used with fuel cells, but occurs in each of the devices located outside the fuel cell stack. In other words, the body of the external reformer is not in direct physical contact with the body of the fuel cell or fuel cell stack. In a typical configuration, the output from the external reformer can be fed to the anode inlet of the fuel cell. Unless specifically stated otherwise, the modification described in this application is an internal modification.

  Internal reforming may occur within the fuel cell anode. Internal reforming can occur additionally or alternatively within an internal reforming element that is integrated within the fuel cell assembly. Integrated reforming elements may be located between fuel cell elements in the fuel cell stack. In other words, one of the stacked trays can be a reforming part instead of a fuel cell element. In one aspect, the flow arrangement within the fuel cell stack directs fuel to the internal reforming element and then to the anode portion of the fuel cell. Thus, from a flow point of view, the internal reforming element and the fuel cell element can be arranged in series within the fuel cell stack. As used herein, “anode reforming” is fuel reforming that occurs within the anode. As used herein, the term “internal reforming” is the reforming that occurs within an integrated reforming element, not the anode portion.

  In some embodiments, the reforming stage that is internal to the fuel cell assembly can be considered as associated with the anode of the fuel cell assembly. In some alternative embodiments, for a reforming stage of a fuel cell stack that can be associated with an anode (eg, associated with multiple anodes), the output flow from the reforming stage is passed to at least one anode. As such, a flow path can be available. This can correspond to having an initial portion of the fuel cell plate that is not in contact with the electrolyte and instead serves as a reforming catalyst. Another option for the associated reforming stage is as one of the elements of the fuel cell stack, which separates the output from the integrated reforming stage back to one or more input sides of the fuel cell stack fuel cell. Having an integrated reforming stage.

  From the viewpoint of thermal integration, the characteristic height of the fuel cell stack can be the height of the individual fuel cell stack elements. It should be noted that separate reforming stages or separate endothermic reaction stages could have a different stack height than the fuel cell. In such a scenario, the height of the fuel cell element can be used as a characteristic height. In some embodiments, the integrated endothermic reaction stage includes one or more such that the integrated endothermic reaction stage can use heat from the fuel cell as a heat source for reforming. It can be defined as a stage that is thermally integrated with the fuel cell. Such an integrated endothermic reaction stage is defined as being placed at a height that is less than 5 times the height of the laminated element from any fuel cell that provides heat to the integrated stage. be able to. For example, an integrated endothermic reaction stage (eg, reforming stage) is less than 5 times the height of the stack element from any thermally integrated fuel cell, eg, less than 3 times the height of the stack element. Can be arranged in height. In the present discussion, an integrated reforming stage or integrated endothermic reaction stage representing a stack element adjacent to a fuel cell element is no more than about one stack element height from the adjacent fuel cell element. Can be defined as

  In some embodiments, the separate reforming stage that is heat integrated with the fuel cell element can also correspond to the reforming stage associated with the fuel cell element. In such embodiments, the integrated fuel cell element can provide at least a portion of the heat to the associated reforming stage, and the associated reforming stage fuels at least a portion of the reforming stage output. The fuel cell can be provided as a stream. In other embodiments, the separate reforming stages can be integrated with the fuel cell for heat transfer without being associated with the fuel cell. In this type of situation, a separate reforming stage can receive heat from the fuel cell, but the output of the reforming stage is not used as an input to the fuel cell. Instead, the output of such reforming stages is used for other purposes, such as adding the output directly to the anode exhaust stream, or to form a separate output stream from the fuel cell assembly. be able to.

  More generally, separate stack elements of the fuel cell stack are used to perform any convenient type of endothermic reaction that can take advantage of the waste heat provided by the integrated fuel cell stack elements. can do. Instead of a suitable plate for carrying out the reforming reaction in the hydrocarbon stream, a separate lamination element can have a suitable plate to catalyze another type of endothermic reaction. Other arrangements of inlet conduits in the manifold or fuel cell stack can be used to provide appropriate input flow to the respective stack elements. Other arrangements of similar manifolds or outlet conduits can be used to recover the output flow from the respective stack elements. Optionally, the output flow from the endothermic reaction stage of the stack can be recovered from the fuel cell stack without passing the output flow through the fuel cell anode. In any such embodiment, the product of the exothermic reaction thus exits the fuel cell stack without passing through the fuel cell anode. Examples of other types of endothermic reactions that can be performed in the stack elements of a fuel cell stack include ethylene and ethanol dehydration to form an ethane crack.

Recycling: As defined herein, recycling of a portion of a fuel cell output to a fuel cell inlet (eg, an anode exhaust or a stream that is separated or recovered from an anode exhaust) is It can correspond to a direct or indirect recycling stream. Direct recycling of the flow to the fuel cell inlet is defined as recycling of the flow without passing through the intermediate process, and for indirect recycling, the recycling after passing the flow through one or more intermediate processes Is involved. For example, if the anode effluent passes through a CO ₂ separation stage prior to recycling, this is considered an indirect recycling of the anode effluent. If a portion of the anode exhaust recovered from the anode exhaust, for example a H ₂ stream, passes through a gasifier to convert coal into a suitable fuel for introduction into the fuel cell, this is also It is considered indirect recycling.

Anode Input and Output In various embodiments of the present invention, the SOFC array includes, for example, hydrogen and hydrocarbons, such as methane (or alternatively, hydrocarbons or hydrocarbons that may contain heteroatoms different from C and H or Fuel received at the anode inlet can be provided, including hydrocarbon-like compounds). Most methane (or other hydrocarbons or hydrocarbon-like compounds) fed to the anode can typically be fresh methane. In this description, new fuel, such as new methane, refers to fuel that is not recycled from another fuel cell process. For example, methane recycled from the anode outlet stream to the anode inlet is not considered “fresh” methane and can instead be described as recovered methane. The fuel source used can be shared with other components such as a turbine. The fuel source input can include water in an appropriate proportion to the fuel to reform the hydrocarbon (or hydrocarbon-like) compound in the reforming section that generates hydrogen. For example, when methane is the fuel inputs for reforming to generate the H _2, the molar ratio of water to fuel is about 1: to be 1: 1 to about 10: 1, such as at least about 2 it can. A ratio of 4: 1 or higher is typical for external reforming, but lower values can be typical for internal reforming. To the extent that H ₂ is part of the fuel source, in some optional embodiments, oxidation of H _{2 at} the anode tends to yield H ₂ O that can be used to reform the fuel. Is possible, no additional water may be required for the fuel. The fuel source may optionally contain components that are not important to the fuel source (eg, a natural gas supply may contain some content of CO ₂ as an additional component). For example, the natural gas supply can contain CO ₂ , N ₂ and / or other inert (inert) gases as additional components. Optionally, in some embodiments, the fuel source may contain CO, such as CO from the recycled portion of the anode exhaust. An additional or alternative potential source for CO in the fuel to the fuel cell assembly may be CO generated by steam reforming of hydrocarbon fuel performed on the fuel prior to entering the fuel cell assembly. it can.

  More generally, various types of fuel streams may be suitable for use as an input stream for the anode of a solid oxide fuel cell. Some fuel streams may correspond to streams containing hydrocarbons and / or hydrocarbon-like compounds that may contain heteroatoms different from C and H. In this discussion, unless otherwise stated, references to fuel streams containing hydrocarbons for SOFC anodes are defined to include fuel streams containing such hydrocarbon-like compounds. Examples of hydrocarbon (including hydrocarbon-like) fuel streams include natural gas, streams containing C1-C4 carbon compounds (eg, methane or ethane), and heavier C5 + hydrocarbons (hydrocarbon-like compounds). Stream), as well as combinations thereof. Still other additional or alternative examples of potential fuel streams used for anode input may include biogas type streams, such as methane resulting from natural (biological) decomposition of organic materials.

In some embodiments, solid oxide fuel cells can be used to process input streams such as natural gas and / or hydrocarbon streams with low energy content due to the presence of diluent compounds. For example, some sources of methane and / or natural gas are sources that can include substantial amounts of O ₂ or other inert molecules such as nitrogen, argon or helium. Due to the presence of increased amounts of CO ₂ and / or inerts, the energy content of the source-based fuel stream can be reduced. The use of low energy content fuels in combustion reactions (such as for powering combustion power turbines) can present problems. However, solid oxide fuel cells can generate power based on low energy content fuel sources with little or no impact on fuel cell efficiency. The presence of an additional gas volume may require additional heat to raise the fuel temperature to the temperature for reforming and / or anodic reaction. Additionally, due to the equilibrium nature of the water gas shift reaction within the fuel cell anode, the presence of additional CO ₂ can have an effect on the relative amounts of H ₂ and CO present in the anode output. However, inert compounds can have only minimal direct impact on reforming and anodic reactions in other cases. The amount of CO ₂ and / or inert compounds in the fuel stream for a solid oxide fuel cell, if present, is at least about 1% by volume, such as at least about 2% by volume, or at least about 5% by volume, or at least about 10 vol%, or at least about 15 vol%, or at least about 20 vol%, or at least about 25 vol%, or at least about 30 vol%, or at least about 35 vol%, or at least about 40 vol%, or at least about 45 It can be vol%, or at least about 50 vol%, or at least about 75 vol%. Additionally or alternatively, the amount of CO ₂ and / or inert compounds in the fuel stream for the solid oxide fuel cell is about 90% or less, such as about 75% or less, or about 60% or less, Or about 50% or less, or about 40% or less, or about 35% or less.

Yet another example of a potential source for the anode input stream may correspond to a refiner and / or other industrial process output stream. For example, coking is a common process in many refiners to convert heavier compounds to a lower boiling range. Coking typically produces off-gas containing various compounds that are gases at room temperature, including CO and various C1-C4 hydrocarbons. This off-gas can be used as at least part of the anode input stream. Other refiner off-gas streams can be additionally or alternatively suitable for inclusion in the anode input stream, e.g., light fractions generated during cracking or other refiner processes ( C1-C4). Still other suitable refiner streams can additionally or alternatively include a refiner stream containing CO or CO ₂ that also contains H ₂ and / or reformable fuel compounds.

Still other potential sources for anode input can additionally or alternatively include streams having increased water content. For example, an ethanol output stream from an ethanol plant (or another type of fermentation process) contains a substantial portion of H ₂ O prior to final distillation. Such H ₂ O can typically have only minimal impact on the operation of the fuel cell. Thus, a fermentation mixture of alcohol (or other fermentation product) and water can be used as at least a portion of the anode input stream.

Biogas or digester gas is another additional or alternative potential source for the anode input. Biogas may contain mainly methane and CO ₂ and is typically generated by decomposition or digestion of organic substances. Anaerobic bacteria may be used to digest organic material and produce biogas. Prior to use as an anode input, impurities (eg, sulfur-containing compounds) may be removed from the biogas.

The output stream from the SOFC anode can include H ₂ O, CO ₂ , CO, and H ₂ . Optionally, the anode output stream could have unreacted fuel (eg, H ₂ or CH ₄ ) or inert compounds in the feed as an additional output component. Instead of using this output stream as a fuel source to provide heat for the reforming reaction or as a combustion fuel to heat the cell, it has a potential value as an input to another process One or more separations can be performed in the anode output stream to separate CO ₂ from the components (eg, H ₂ or CO). H ₂ and / or CO can be used as a synthesis gas for chemical synthesis, as a source of hydrogen for chemical reactions, and / or as a fuel with reduced greenhouse gas emissions.

In various embodiments, the composition of the output stream from the anode can be influenced by several factors. Factors that can affect the anode output composition can include the composition of the input stream to the anode, the amount of current generated in the fuel cell, and / or the temperature at the outlet of the anode. The temperature at the anode outlet can be related due to the equilibrium nature of the water gas shift reaction. In a typical anode, at least one of the plates forming the anode wall can be suitable for catalyzing the water gas shift reaction. As a result, a) the composition of the anode input stream is known, b) the reformable range of reformable fuel in the anode input stream is known, and c) from the cathode (corresponding to the amount of current generated). If the amount of oxygen ions transported to the anode is known, the composition of the anode output can be determined based on the equilibrium constant for the water gas shift reaction.
K _eq = [CO ₂ ] [H ₂ ] / [CO] [H ₂ O]

In the above equation, K _eq is the equilibrium constant for the reaction at a given temperature and pressure, and [X] is the partial pressure of component X. Based on the water gas shift reaction, an increase in CO ₂ concentration at the anode input can tend to result in additional CO formation (at the expense of H ₂ ), and an increase in H ₂ O concentration is an additional There may be a tendency to result in high H ₂ formation (at the expense of CO).

To determine the composition at the anode output, the composition of the anode input can be used as a starting point. This composition can then be modified to reflect the extent of any reformable fuel reforming that can occur in the anode. Such reforming can reduce the hydrocarbon content of the anode input in exchange for increased hydrogen and CO ₂ . Next, based on the amount of current generated, the amount of H _{2 at} the anode input can be reduced in exchange for additional H ₂ O and CO ₂ . This composition can then be adjusted based on the equilibrium constant for the water gas shift reaction to determine the outlet concentrations of H ₂ , CO, CO ₂ and H ₂ O.

In various aspects, the operating temperature of the SOFC can be selected to achieve a desired ratio of H ₂ , CO and CO ₂ in the syngas output. The operating temperature may be selected to produce a suitable ratio of syngas output for use in the intended process. In one aspect, the operating temperature can range from about 700 ° C. to 1200 ° C., for example, the operating temperature can be about 800 ° C., about 900 ° C., about 1000 ° C. or about 1100 ° C. .

Optionally, one or more water gas shift reaction stages can be included after the anode output, if desired, to convert CO and H ₂ O to CO ₂ and H ₂ at the anode output. . The amount of H ₂ present in the anode output is obtained by converting H ₂ O and CO present in the anode output to H ₂ and CO ₂ , for example, by using a water gas shift reactor at a lower temperature. Can be increased. Since SOFCs can be operated at about 700 ° C. to 1200 ° C., it may be particularly desirable to promote the water gas shift reaction when the anode output is cooled for use in subsequent processes. Alternatively, the temperature can be increased to reverse the water gas shift reaction and produce more CO and H ₂ O from H ₂ and CO ₂ . Water is expected to be the output of the reaction that occurs at the anode, and the anode output typically has an excess of H ₂ O compared to the amount of CO present in the anode output. it can. Alternatively, H ₂ O can be added to the stream after the anode outlet but before the water gas shift reaction. CO may be due to incomplete carbon conversion during reforming and / or between H ₂ O, CO, H ₂ and CO ₂ under any conditions present during reforming conditions or anodic reactions. Can be present at the anode output for equilibrium balancing the reaction at (ie, water gas shift equilibrium). The water gas shift reactor can be operated under conditions that further promote equilibrium in the direction of forming CO ₂ and H ₂ at the expense of CO and H ₂ O. Higher temperatures can tend to result in the formation of CO and H ₂ O. Thus, one option for operating the water gas shift reactor is to anode output to a suitable catalyst, such as iron oxide, zinc oxide, copper on zinc oxide, at a suitable temperature, eg, about 190 ° C. to about 210 ° C. Can be exposed to the stream. Optionally, the water gas shift reactor can include two stages to reduce the CO concentration in the anode output stream, with the first high temperature stage operating at a temperature of at least about 300 ° C to about 375 ° C. And the second low temperature stage is operated at a temperature of about 225 ° C. or less, eg, about 180 ° C. to about 210 ° C. In addition to increasing the amount of H ₂ present at the anode output, the water gas shift reaction can increase the amount of CO ₂ additionally or alternatively at the expense of CO. This allows carbon monoxide (CO), which is difficult to remove, to be more easily removed by condensation (eg, low temperature removal), chemical reaction (eg, amine removal) and / or other CO ₂ removal methods. Can be exchanged for carbon. Additionally or alternatively, it may be desirable to increase the CO content present in the anode exhaust to achieve the desired ratio of H ₂ : CO.

After passing through any water gas shift reaction stage, the anode output can pass through one or more separation stages for removal of water and / or CO ₂ from the anode output stream. For example, one or more CO ₂ output streams can be formed by performing CO ₂ separation at the anode output using one or more methods, individually or in combination. Such a method may be used to generate a CO ₂ output stream having a CO ₂ content of 90% or more by volume, eg, at least 95% by volume CO ₂ , or at least 98% by volume CO _2. it can. Such methods are at least about 70% of the CO ₂ content of the anode outputs, for example, can be at least about 80% of the CO ₂ content of the anode outputs, or at least about 90% recovered. Alternatively, in some embodiments, be desirable to recover only a portion of the CO ₂ in the anode output stream obtained, recovered part of the CO ₂ is about 33% of the anode output of CO ₂ ~ about 90% For example, at least about 40%, or at least about 50%. For example, it may be desirable to maintain some CO ₂ in the anode output flow so that the desired composition can be achieved in a subsequent water gas shift stage. Suitable separation methods include physical solvents (eg Selexol ™ or Rectisol ™), amines or other bases (eg MEA or MDEA), refrigeration (eg cryogenic separation), pressure swing adsorption, vacuum swing It may also include the use of adsorption, and combinations thereof. A low temperature CO ₂ separator can be an example of a suitable separator. As the anode output is cooled, most of the water in the anode output can be separated as a condensed (liquid) phase. Since the remaining remaining components of the anode output flow (eg, H ₂ , N ₂ , CH ₄ ) do not tend to form easily condensed phases, then further cooling of the water depleted anode output flow and High purity CO ₂ can be separated by pressure loading. The low temperature CO ₂ separator can recover from about 33% to about 90% of the CO ₂ present in the flow, depending on the operating conditions.

Removal of water from the anode effluent forming one or more water output streams before, during or after the CO ₂ separation run can be advantageous. The amount of water in the anode output can vary depending on the operating conditions selected. For example, the steam to carbon ratio established at the anode inlet can affect the water content of the anode exhaust, with a high steam to carbon ratio typically resulting in a large amount of water, which is unreacted. It can pass through the anode as is and / or reacting only by water gas shift equilibrium at the anode. Depending on the embodiment, the water content of the anode discharge can correspond to up to about 30% or more of the volume of the anode discharge. Additionally or alternatively, the moisture content can be about 80% or less of the volume of the anode discharge. Such water can be removed by compression and / or cooling and condensation can be obtained, but such removal of water can result in additional compressor power and / or heat exchange surface area and excessive cooling. Can need water. One advantageous method of removing a portion of this excess water can be based on the use of an adsorbent bed that can be dehumidified from the wet anode effluent, and then additional water is added to the anode. The dry anode feed gas can be used to “regenerate” to provide for supply. HVAC style (heating, ventilation and air conditioning) adsorption wheel design allows anode emissions and inlets to be similar in pressure, and a mild leak from one stream to the other for the overall process It can be applicable because it can have minimal impact. In embodiments where CO ₂ removal is performed using a low temperature process, water removal, including removal with a triethylene glycol (TEG) system and / or desiccant, during or prior to CO ₂ removal may be desirable. In contrast, if the amine wash for removing CO ₂ is used, water can be removed from the anode effluent downstream of the CO ₂ removal stage.

As an alternative to or in addition to the CO ₂ output stream and / or water output stream, the anode output is used to form one or more product streams containing the desired chemical or fuel product. Can do. Such a product stream can correspond to a synthesis gas stream, a hydrogen stream or both a synthesis gas product and a hydrogen product stream. For example, a hydrogen product stream can be formed that contains at least about 70 volume% H ₂ , such as at least about 90 volume% H ₂ , or at least about 95 volume% H ₂ . Additionally or alternatively, a synthesis gas stream can be formed that contains at least about 70% by volume of the combined H ₂ and CO, such as at least about 90% by volume of H ₂ and CO. One or more product streams is at least about 75% of H ₂ and CO gas volume which is combined at the anode output, for example, corresponds to at least about 85% of the combined H ₂ and CO gas volume or at least about 90% Can have a gas volume. It should be noted that the relative amounts of H ₂ and CO in the product stream may be different from the H ₂ : CO ratio in the anode output based on the use of a water gas shift reaction stage that converts between products.

In some embodiments, it may be desirable to remove or separate a portion of H ₂ present at the anode output. For example, in some embodiments, the anode exhaust H ₂ : CO ratio can be at least about 3.0: 1. In contrast, processes utilizing synthesis gas, such as Fischer-Tropsch synthesis, may consume H ₂ and CO at different ratios (eg, a ratio closer to 2: 1). One alternative can be to use a water gas shift reaction to modify the anode output content to have H ₂ at a CO ratio closer to the desired synthesis gas composition. Another alternative is to use membrane separation to remove a portion of H ₂ present in the anode output, or still as an alternative, to achieve the desired ratio of H ₂ and CO. It can be to use a combination of water gas shift reactions. One advantage of using membrane separation to remove only a portion of the anode output H ₂ can be that the desired separation can be performed at relatively mild conditions. One goal can be to produce a residue that still has substantial H ₂ content, so that high purity hydrogen permeation occurs by membrane separation without requiring harsh conditions. be able to. For example, the permeate side still has sufficient driving force to perform membrane separation compared to the surrounding, rather than having a pressure of about 100 kPaa or less (eg, ambient pressure) on the permeate side of the membrane. Can be high pressure. Additionally or alternatively, a scavenging gas such as methane can be used to provide driving force to the membrane separation. This can reduce the purity of the H ₂ permeate, but can be advantageous depending on the desired use of the permeate.

In various aspects of the invention, at least a portion of the anode exhaust stream (preferably after the separation of CO ₂ and / or H ₂ O) is provided as a feed for processes external to the fuel cell and associated reforming stage. Can be used. In various embodiments, the anode emissions are from about 1.5: 1 to about 10: 1, such as at least about 3.0: 1, or at least about 4.0: 1, or at least about 5.0: 1. It can have a ratio of H ₂ : CO. A syngas stream can be generated from the anode exhaust or can be recovered. The anode effluent gas, optionally after CO ₂ and / or H _{2 O} separation, and optionally, to remove excess hydrogen, after performing the water gas shift reaction and / or membrane separation, H ₂ And / or can correspond to a stream containing a substantial portion of CO. For streams with a relatively low content of CO, for example, in streams where the ratio of H ₂ : CO is at least about 3: 1, the anode exhaust can be suitable for use as an H ₂ feed. . Examples of processes that can benefit from the H ₂ supply, without limitation, may include purification unit processes, ammonia synthesis plant or (different) turbine power generation system, or combinations thereof. Depending on the application, still lower CO ₂ content can be desirable. For streams having a ratio of H ₂ : CO of less than about 2.2 to 1 and greater than about 1.9: 1, the stream can be suitable for use as a syngas feed. Examples of processes that can benefit from a syngas supply include, but are not limited to, a gas-to-liquid plant (eg, a plant using a Fischer-Tropsch process with a non-shifting catalyst) and / or Or a methanol synthesis plant can be included. The amount of anode effluent used as a feed for the external process can be any convenient amount. Optionally, if a portion of the anode exhaust is used as a feed for an external process, the second portion of the anode exhaust can be recycled to the anode input and / or for a combustion power generator Can be recycled to the combustion area.

Input streams useful for different types of Fischer-Tropsch synthesis processes can provide examples of different types of product streams that may be desirable to generate from the anode output. For a Fischer-Tropsch synthesis reaction using a shifting catalyst such as an iron-based catalyst, the desired input stream to the reaction system can include CO ₂ in addition to H ₂ and CO. If there is not enough CO _{2 in} the input stream, a Fischer-Tropsch catalyst with water gas shift activity can consume CO to generate additional CO ₂ , resulting in CO-free syngas. . Due to the integration of such Fischer-Tropsch processes with SOFC fuel cells, the separation stage for the anode output will retain the desired amount of CO ₂ (and optionally H ₂ O) in the syngas product. Can be operated. In contrast, for a Fischer-Tropsch catalyst based on a non-shifting catalyst, any CO ₂ present in the product stream can serve as an inert component in the Fischer-Tropsch reaction system.

In embodiments where the membrane is scavenged by a scavenging gas, such as methane scavenging gas, the methane scavenging gas may be used as an anode fuel or in a different low pressure process, such as a boiler, furnace, gas turbine, or other fuel consuming device. Can correspond to the methane stream used in In such embodiments, low concentrations of CO ₂ permeation through the membrane can have minimal consequences. Such CO ₂ that can permeate the membrane can have a minimal impact on the reaction in the anode, and such CO ₂ can remain contained in the anode product. Thus, the CO ₂ lost through the membrane by permeation (if present) does not need to be transferred again through the SOFC electrolyte. This can significantly reduce the separation selectivity requirement of the hydrogen permeable membrane. This allows, for example, the use of higher permeability membranes with lower selectivity, and this allows the use of lower pressure and / or reduced membrane surface area. In such embodiments of the present invention, the volume of scavenging gas can be many times greater than the volume of hydrogen in the anode exhaust, thereby maintaining an effective hydrogen concentration on the permeate side near zero. It becomes possible. The hydrogen so separated can be incorporated into the turbine feed methane, thereby improving the turbine combustion characteristics as described above.

It should be noted that the excess amount of H ₂ generated at the anode can represent fuel from which greenhouse gases have already been separated. Any CO _{2 at} the anode output can be easily separated from the anode output, such as by an amine wash, a low temperature CO ₂ separator, and / or a pressure or vacuum swing absorption process. Some of the components of the anode output (H ₂ , CO, CH ₄ ) are not easily removed, but CO ₂ and H ₂ O can usually be easily removed. Depending on the embodiment, at least about 90% by volume of the CO ₂ of the anode output can be separated to form a relatively pure CO ₂ output stream. Therefore, any CO ₂ generated at the anode can be efficiently separated and a high purity CO ₂ output stream is formed. After separation, the remaining portion of the anode output can correspond primarily to components having chemical and / or fuel values with a reduced amount of CO ₂ and / or H ₂ O. Since a substantial portion of the CO ₂ generated by the initial fuel (before reforming) can be separated, the amount of CO ₂ generated by subsequent combustion of the remaining portion of the anode output can be reduced. . In particular, the fuel of the remainder of the anode output is to the extent it is H _2, additional greenhouse gases, the combustion of the fuel, can not be typically formed.

  Anode emissions can be subject to various gas treatment options, including water gas shift and separation of components from each other. Two general anodization schemes are shown in FIGS.

FIG. 1 schematically illustrates an example of a reaction system for operating a fuel cell array of solid oxide fuel cells in connection with a chemical synthesis process. In FIG. 1, a fuel stream 105 is provided to a reforming stage 110 associated with a fuel cell 120, eg, a fuel cell anode 127 that is part of a fuel cell stack of a fuel cell array. The reforming stage 110 associated with the fuel cell 120 can be internal to the fuel cell assembly. In some optional embodiments, an external reforming stage (not shown) may also be used to reform a portion of the reformable fuel in the input stream before passing the input stream through the fuel cell assembly. it can. The fuel stream 105 can preferably include a reformable fuel, such as methane, other hydrocarbons, and / or other hydrocarbon-like compounds, such as organic compounds containing carbon-hydrogen bonds. The fuel stream 105 may optionally contain H ₂ and / or CO, eg, H ₂ and / or H ₂ provided by the optional anode recycle stream 185. Note that the anode recycle stream 185 is optional, and in many embodiments, the recycle stream is directly from the anode exhaust 125 through the anode stream 125 or in combination with the fuel stream 105 or the modified fuel stream 115. 127 is not provided. After reforming, the reformed fuel stream 115 can be passed through the anode 127 of the fuel cell 120. An O ₂ containing stream 119 can also be passed through the cathode 129. The flow of oxygen ions 122, O ₂ ²⁻ from the cathode portion 129 of the fuel cell provides the remaining reactants required for the anode fuel cell reaction. Based on the reaction at the anode 127, the resulting anode exhaust 125 is equivalent to H ₂ O, one or more incompletely reacted fuel components (H ₂ , CO, CH ₄ , or reformable fuel). As well as optionally one or more additional non-reactive components, such as CO ₂ , N ₂ , and / or other contaminants that are part of the fuel stream 105. The anode exhaust 125 can then be passed through one or more separation stages. For example, CO ₂ removal stage 140, the low-temperature CO ₂ removal system, the acidic amine washing step for the removal of gas or CO ₂ output stream 143 for separating from the anode effluent CO ₂ separation stage, such as CO ₂ Can correspond to another appropriate kind of. Optionally, anode discharge is first passed through water gas shift reactor 130 so that any CO present in the anode discharge (in addition to any H ₂ O) is optionally water gas shifted anode discharge 13. Can be converted to CO ₂ and H ₂ . Depending on the nature of the CO ₂ removal stage, the water condensation or removal stage 150 may be desirable to remove the water output stream 153 from the anode effluent. Although shown in FIG. 1 after the CO ₂ separation stage 140, it may instead be optionally located before the CO ₂ separation stage 140. Additionally, in order to generate the high purity permeate stream 163 of H _2, can use any membrane separation stage 160 for H ₂ separation. The resulting retained stream 166 can then be used as an input to the chemical synthesis process. Stream 166 can be additionally or alternatively shifted in the second water gas shift reactor 131 to adjust the H ₂ , CO and CO ₂ content to different ratios, in a chemical synthesis process This produces an output stream 168 for further use. In FIG. 1, the anode recycle stream 185 is shown as being recovered from the retentate stream 166, but the anode recycle stream 185 is additionally or alternatively from various separation stages or other advantageous locations therebetween. Can be recovered. The separation stages and shift reactors can be configured additionally or alternatively in different orders and / or in a parallel configuration. Eventually, a stream with a reduced content of O ₂ 139 can be generated as output from the cathode 129. For simplicity, the various stages of compression and heat addition / removal and steam addition or removal that may be useful in the process are not shown.

As described above, the various types of separations performed in the anode discharge can be performed in any convenient order. FIG. 2 shows another sequence of examples for performing separation in the anode discharge. In FIG. 2, the anode effluent 125 can first pass through a separation stage 260 to remove a portion 263 of the hydrogen content from the anode effluent 125. This can allow for a reduction in the H ₂ content of the anode effluent, for example, to provide retentate 266 at a H ₂ : CO ratio closer to 2: 1. The H ₂ : CO ratio can then be adjusted to achieve the desired value in the water gas shift stage 230. The water gas shifted output 235 can then be passed through a CO ₂ separation stage 240 and a water removal stage 250 to produce a stream 275 suitable for use as an input to the desired chemical synthesis process. Optionally, the output stream 275 can be exposed to an additional water gas shift stage (not shown). A portion of the output stream 275 can optionally be recycled to the anode input (not shown). Of course, still other combinations and arrangements of separation steps can be used to generate a stream based on the anode output having the desired composition. For simplicity, the various stages of compression and heat addition / removal, and steam addition or removal that may be useful in the process are not shown.

Cathode Inlet and Output Conventionally, solid oxide fuel cells can be operated on the basis of drawing a desired load while consuming some portion of the fuel in the fuel stream delivered to the anode. The fuel cell voltage can then be determined by the load, the fuel input to the anode, the air and O ₂ provided to the cathode, and the internal resistance of the fuel cell. By removing any direct association between the anode input flow and cathode input flow compositions, additional options become available to operate the fuel cell, for example, generating excess amounts of synthesis gas. And / or particularly improve the overall efficiency (electrical and chemical power) of the fuel cell.

The amount of O ₂ present in the cathode input stream can advantageously be sufficient to provide the oxygen required for the cathode reaction in the fuel cell. Thus, the volume percentage of O ₂ can advantageously be at least 0.5 times the amount of O _{2 in} the cathode exhaust. Optionally, if necessary, additional air can be added to the cathode input to provide sufficient oxidant for the cathode reaction. If some form of air is used as the oxidant, the amount of N ₂ in the cathode exhaust should be at least about 78% by volume, such as at least about 88% by volume, and / or not more than about 95% by volume. Can do. In some embodiments, the cathode input stream can additionally or alternatively contain compounds commonly found as contaminants, such as H ₂ S or NH ₃ . In other embodiments, the cathode input stream can be cleaned to reduce or minimize the content of such contaminants.

Conditions at the cathode are additionally or alternatively for the conversion of unburned hydrocarbons (in combination with cathode input stream O ₂ ) to typical combustion products such as CO ₂ and H ₂ O. Can be appropriate.

Fuel cell arrangement
In various aspects, the fuel cell array is used to improve or maximize the energy output of the fuel cell, eg, total energy output, electrical energy output, syngas chemical energy output, or combinations thereof. Can be operated. For example, solid oxide fuel cells use an excessive amount of reformable fuel in various states, for example, for the generation of synthesis gas streams used in chemical synthesis plants and / or for the generation of high purity hydrogen streams. Can be activated. The syngas stream and / or the hydrogen stream can be used as a syngas source, a hydrogen source, a clean fuel source, and / or for any other convenient application. In such embodiments, the amount of O ₂ in the cathode effluent, the amount of O ₂ in the cathode input flow, and fuel cell energy output improves or O ₂ at the desired operating conditions for maximizing, Can be related to usage.

Operation of Solid Oxide Fuel Cells In one aspect, the operating temperature of the SOFC can range from about 700 ° C. to 1200 ° C., for example, the operating temperature is about 800 ° C., about 900 ° C., about 1000 ° C. or It can be about 1100 ° C. In one aspect, the operating temperature may be selected to promote the WGS reaction in the anode to a desired ratio.

  In some embodiments, the fuel cell may be operated in a single pass or once-through mode. In single pass mode, the modified product of the anode exhaust is not returned to the anode inlet. Thus, recycling syngas, hydrogen or some other product directly from the anode output to the anode inlet is not done in a single pass operation. More generally, in single-pass operation, the modified product of the anode exhaust is, for example, by using the modified product to treat the fuel stream subsequently introduced into the anode inlet. Is not returned indirectly. Heat from the anode exhaust or output may be recycled additionally or alternatively in a single pass mode. For example, the anode output flow may pass through a heat exchanger where the anode output is cooled and the input stream for another stream, such as the anode and / or cathode, is warmed. Recycling heat from the anode to the fuel cell is consistent with use in single pass or once-through mode operation. Optionally, but not preferred, the components of the anode output may be combusted to provide heat to the fuel cell during the single pass mode.

FIG. 3 shows a schematic embodiment of the operation of the SOFC for power generation. In FIG. 3, the anode portion of the fuel cell can receive fuel and steam (H ₂ O) as inputs, water, and optionally excess H ₂ , CH ₄ (or other hydrocarbons) and / or CO is the output. The cathode portion of the fuel cell can receive O ₂ (eg, air) as an input, and the output corresponds to an O ₂ deficient oxidant (air). Within the fuel cell, the O ₂ ²⁻ ions formed on the cathode side can be transported through the electrolyte and provide the oxygen ions required for the reaction occurring at the anode.

Several reactions can occur within a solid oxide fuel cell, such as the example fuel cell shown in FIG. Reforming reaction can be any, if sufficient H ₂ is provided directly to the anode, it is possible to reduce or, or eliminated. The following reactions are based on CH ₄ , but similar reactions can occur when other fuels are used in the fuel cell.
(1) <Anode reforming> CH ₄ + H ₂ O => 3H ₂ + CO
(2) <Water gas shift> CO + H ₂ O => H ₂ + CO ₂
(3) <Combined reforming and water gas shift> CH ₄ + 2H ₂ O => 4H ₂ + CO ₂
(4) <Anode H ₂ oxidation> H ₂ + O ₂ ²⁻ => H ₂ O + 2e ⁻
(5) <Cathode> 1 / 2O ₂ + 2e ⁻ => O ₂ ²⁻

Reaction (1) represents a basic hydrocarbon reforming reaction to generate H ₂ for use in a fuel cell anode. The CO formed in reaction (1) can be converted to H ₂ by the water gas shift reaction (2). The combination of reactions (1) and (2) is shown as reaction (3). Reactions (1) and (2) can occur outside the fuel cell and / or reforming can be carried out inside the anode.

Reactions (4) and (5) represent reactions that can cause power generation in the fuel cell at the anode and cathode, respectively. Reaction (4) is either present in the feed, or oxygen ions combined with H ₂ generated arbitrarily by the reaction (1) and / or (2), forming an electron to H 2 _O and circuits. Reaction (5) combines O ₂ and electrons from the circuit to form oxygen ions. The oxygen ions generated by reaction (5) can be transported through the fuel cell electrolyte to provide the oxygen ions required for reaction (4). In combination with the transport of oxygen ions through the electrolyte, a closed current loop can then be formed by providing an electrical connection between the anode and the cathode.

In various embodiments, the goal of operating the fuel cell can be to improve the overall efficiency of the fuel cell and / or the overall efficiency of the fuel cell and the integrated chemical synthesis process. This is typical of conventional fuel cell operation, where the goal can be to operate a fuel cell with high electrical efficiency for using the fuel provided to the cell for power generation. In contrast. As defined above, overall fuel cell efficiency may be determined by dividing the fuel cell electrical output and the lower heating value of the fuel cell output by the lower heating value of the input component for the fuel cell. . In other words, TFCE = (LHV (el) + LHV (sg out)) / LHV (in), where LHV (in) and LHV (sg out) are the fuel components delivered to the fuel cell (eg, H ₂ , CH ₄ and / or CO) and the LHV of the synthesis gas (H ₂ , CO and / or CO ₂ ) in the anode outlet stream or flow. This can provide a measure of the electrical and chemical energy generated by the fuel cell and / or the integrated chemical process. It should be noted that under this definition of total efficiency, the thermal energy used in the fuel cell and / or used in the integrated fuel cell / chemical synthesis system can be donated to the total efficiency. However, any excess heat that is exchanged or otherwise recovered from the fuel cell or integrated fuel cell / chemical synthesis system is excluded from this definition. Thus, if an excessive amount of heat from the fuel cell is used, for example, to generate steam for power generation by a steam turbine, such excessive amount of heat is excluded from the definition of total efficiency.

  Some operating parameters may be modified to operate the fuel cell with an excess amount of reformable fuel. Some parameters can be similar to those currently recommended for fuel cell operation. In some embodiments, the cathode conditions and temperature input to the fuel cell can be similar to those recommended in the literature. For example, the desired electrical efficiency and the desired total fuel cell efficiency can be achieved in the range of fuel cell operating temperatures typical for solid oxide fuel cells. In typical operation, the temperature can be increased through the fuel cell.

In other embodiments, the operating parameters of the fuel cell are typical so that the fuel cell is operated to allow temperature reduction from the anode inlet to the anode outlet and / or from the cathode inlet to the cathode outlet. You can deviate from the conditions. For example, the reforming reaction that converts hydrocarbons to H ₂ and CO is an endothermic reaction. The net heat balance in the fuel cell can be endothermic if a sufficient amount of reforming is performed at the fuel cell anode as compared to the amount of hydrogen oxidation that generates current. This can cause a temperature drop between the inlet and outlet of the fuel cell. During endothermic operation, the temperature drop of the fuel cell can be controlled so that the electrolyte remains in the molten state in the fuel cell.

  Parameters that can be modified in ways that differ from those currently recommended include the amount of fuel provided to the anode, the composition of the fuel provided to the anode, and / or the anode input or Separation and capture of the syngas at the anode output without significant recycling of the syngas to any of the cathode inputs can be included. In some embodiments, the recycle of synthesis gas or hydrogen from the anode exhaust to either the anode input or the cathode input may not occur directly or indirectly. In additional or alternative embodiments, a limited amount of recycling can occur. In such embodiments, the amount of recycling from the anode exhaust to the anode input and / or cathode input is less than about 10% by volume of the anode exhaust, such as less than about 5% by volume, or less than about 1% by volume. be able to.

  In some embodiments, the fuel cells of the fuel cell array can be arranged such that only a single stage of fuel cells (eg, fuel cell stack) can exist. In this type of embodiment, the anode fuel utilization during a single stage can represent the anode fuel utilization of the array. Another option is that the fuel cell array can contain multiple stages of anodes and multiple stages of cathodes, each anode stage having fuel utilization within the same range, for example, each anode stage is Have a fuel utilization within 10% of the stated value, for example within 5% of the stated value. Yet another option is that each anode stage can have a fuel utilization that is equal to or less than the stated value, eg, each anode stage is 5% or less, eg, 10 % Or less, not greater than the specified value. As an illustrative example, a fuel cell array having a plurality of anode stages can have each anode stage in a range of about 10% of 50% fuel utilization, which is about 40% to about 60%. % Corresponding to each anode stage with fuel utilization. As another example, a fuel cell array having multiple stages can have each anode stage having a maximum deviation of less than about 5% and no higher than 60% anode fuel utilization, which is from about 55% to about Corresponds to each anode stage with 60% fuel utilization. In yet another embodiment, one or more stages of the fuel cells of the fuel cell array can be operated with about 30% to about 50% fuel utilization, such as about 30% to about 50% fuel. Utilization activates multiple fuel cell stages in the array. More generally, any of the above types of ranges can be combined with any of the anode fuel utilization values specified herein.

  Yet still another additional or alternative option may be to specify the overall average fuel usage in all fuel cells of the fuel cell array. In various aspects, the overall average fuel utilization for a fuel cell array can be about 65% or less, such as about 60% or less, about 55% or less, about 50% or less, or about 45% or less. (Additionally or alternatively, the total average fuel utilization for the fuel cell array can be at least about 25%, such as at least about 30%, at least about 35%, or at least about 40%). Such average fuel utilization need not necessarily limit fuel utilization in any single stage as long as the array of fuel cells meets the desired fuel utilization.

Use of Syngas Output After Capture The components from the anode output stream and / or the cathode output stream can be used for a variety of purposes. One option can be to use the anode output as a source of hydrogen as described above. With respect to SOFCs integrated with or co-located with the refiner, hydrogen can be used as a hydrogen source for various refiner processes such as hydrogenation. Such hydrogen can be used as fuel for boilers, furnaces, and / or burned heaters in refineries or other industrial equipment, and / or for generators such as turbines Hydrogen can be used as a feed. Hydrogen from SOFC fuel cells may additionally or alternatively be used as an input stream for other types of fuel cells that require hydrogen as an input, possibly including vehicles powered by fuel cells. Can be used. Yet another option may additionally or alternatively be to use synthesis gas generated as output from the SOFC fuel cell as fermentation input.

Another option may additionally or alternatively be to use synthesis gas generated from the anode output. Of course, the synthesis gas can still guide the generated CO ₂ some of the fuel based on when burned as fuel, synthesis gas can be used as fuel. In other embodiments, the syngas output stream can be used as an input for a chemical synthesis process. One option may additionally or alternatively be to use synthesis gas for a Fischer-Tropsch type process and / or another process in which larger hydrocarbon molecules are formed from the synthesis gas input. it can. Another option may additionally or alternatively be to use synthesis gas to form an intermediate product such as methanol. Although methanol can be used as the final product, in other embodiments, methanol generated from synthesis gas generates larger compounds, such as gasoline, olefins, aromatics and / or other products. Can be used for. Note that small amounts of CO ₂ can be acceptable in the synthesis gas supply to the methanol synthesis process and / or to the Fischer-Tropsch process utilizing a shifting catalyst. Hydroformylation is an additional or alternative example of yet another synthesis process that can utilize a syngas input.

  It should be noted that one variation regarding the use of SOFC to generate synthesis gas is for the treatment of methane and / or natural gas recovered by offshore oil mining equipment or other manufacturing systems that are a significant distance from the final market. It is possible to use SOFC fuel cells as part of the system. Instead of trying to transport the gas phase output from the well, or trying to store the gas phase product for a long time, use the gas phase output from the well as an input to the SOFC fuel cell array can do. This can lead to various advantages. First, the power generated by the fuel cell array can be used as a power source for the platform. Additionally, the syngas output from the fuel cell array can be used as an input for the Fischer-Tropsch process at the manufacturing site. This allows the formation of liquid hydrocarbon products that are more easily transported by pipeline, ship or rail vehicle from the production site to, for example, land equipment or larger terminals.

Still other integration options may additionally or alternatively include using the cathode output as a source of high purity heated nitrogen. The cathode input can often contain the majority of air, which means that a substantial portion of nitrogen can be included in the cathode input. The fuel cell can transport O ₂ through the electrolyte from the cathode to the anode, and the cathode outlet can have a lower concentration of O ₂ and therefore a higher concentration of N ₂ than is found in air. it can. By subsequent removal of residual O ₂ , this nitrogen output can be used as an input for the production of ammonia or other nitrogen-containing chemicals such as urea, ammonium nitrate and / or nitric acid. Incidentally, urea synthesis, additionally or alternatively, the anode output could be to use another CO ₂ as an input feed.

Additional Embodiments Embodiment 1
A method of producing electricity and hydrogen or synthesis gas using a solid oxide fuel cell having an anode and a cathode, wherein a fuel stream comprising a reformable fuel is passed through the anode, the solid oxide of the solid oxide fuel cell. Introducing into a reforming step (including internal reforming elements) associated with the anode of the fuel cell, or a combination thereof; introducing a cathode inlet stream comprising O ₂ into the cathode of the solid oxide fuel cell; Generating electricity within the solid oxide fuel cell; recovering a gas stream comprising H ₂ , a gas stream comprising H ₂ and CO, or a combination thereof from the anode exhaust; The solid oxide fuel cell has an electrical efficiency of about 10% to about 50%, and the total fuel cell life of the solid oxide fuel cell Sex is at least about 150 mW / cm ^2, method.

Embodiment 2
The solid oxide fuel cell is operated to generate electricity at a heat ratio of about 0.25 to about 1.3, alternatively about 1.15 or less, about 1.0 or less, or about 0.75 or less. The method of embodiment 1.

Embodiment 3
The method of any of the preceding embodiments, wherein the reformable fuel excess ratio of the fuel stream comprising the reformable fuel is at least about 2.0, or at least about 2.5.

Embodiment 4
The method of any of the preceding embodiments, wherein the electrical efficiency of the solid oxide fuel cell is about 45% or less, or about 35% or less.

Embodiment 5
The method of any of the preceding embodiments, wherein the solid oxide fuel cell has a total fuel cell efficiency of at least about 65%, or at least about 70%, or at least about 75%, or at least about 80%.

Embodiment 6
The solid the entire fuel cell productivity oxide fuel cell is at least about 150 mW / cm ^2, or at least about 300 mW / cm ^2, or at least about 350 mW / cm ^2, or about 800 mW / cm ² or less, the above embodiments Either way.

Embodiment 7
The total reformable fuel productivity of the solid oxide fuel cell is at least about 75 mW / cm ² , or at least about 100 mW / cm ² , or at least about 150 mW / cm ² , or at least about 200 mW / cm ² , or about 600 mW / The method of any of the preceding embodiments, wherein the method is cm ² or less.

Embodiment 8
Reformable hydrogen content of a reformable fuel introduced into the anode of the solid oxide fuel cell, a reforming stage (including internal reforming elements) associated with the anode of the solid oxide fuel cell, or a combination thereof The method of any of the preceding embodiments, wherein the amount is at least about 75% greater than the amount of hydrogen reacted to generate electricity, for example at least about 100% greater.

Embodiment 9
The method of any of the preceding embodiments, wherein the fuel stream comprises at least about 10% by volume inert compound, at least about 10% by volume CO ₂ , or combinations thereof.

Embodiment 10
The method of any of the preceding embodiments, wherein the fuel cell is operated at a voltage _VA of about 0.67 volts or less, or about 0.5 volts or less.

Embodiment 11
The method of any of the preceding embodiments, wherein the anode exhaust has a ratio of H ₂ : CO of about 1.5: 1 to about 10: 1.

Embodiment 12
The method of any of the preceding embodiments, wherein the anode exhaust has a ratio of H ₂ : CO of at least about 3.0: 1.

Embodiment 13
The method of any of the preceding embodiments, wherein the solid oxide fuel cell is a tubular solid oxide fuel cell.

Embodiment 14
The method of any of the preceding embodiments, wherein the solid oxide fuel cell further comprises one or more integrated endothermic reaction stages.

Embodiment 15
At least one integrated endothermic reaction stage includes an integrated reforming stage, and the fuel stream introduced into the anode of the solid oxide fuel cell enters the anode of the solid oxide fuel cell Embodiment 15. The method of embodiment 14 before passing through the integrated reforming stage.

Embodiment 16
The method of any of embodiments 1-15, wherein the temperature of the anode outlet is higher by about 40 ° C. or less than the temperature of the anode inlet.

Embodiment 17
The method of any of embodiments 1-15, wherein the temperature of the anode inlet differs from the temperature of the anode outlet by no more than about 20 ° C.

Embodiment 18
The method of any of embodiments 1-15, wherein the temperature of the anode outlet is lower by about 10 ° C. to about 80 ° C. than the temperature of the anode inlet.

Embodiment 19
The heat ratio is about 0.85 or less, and the method supplies heat to the fuel cell to maintain the anode outlet temperature at about 5 ° C. to about 50 ° C. lower than the anode inlet temperature. The method of any of embodiments 1-15, further comprising:

Embodiment 20.
Further comprising reforming the reformable fuel, the reforming step (including internal reforming elements) associated with the anode of the solid oxide fuel cell, the anode of the solid oxide fuel cell, or a combination thereof The method of any of the preceding embodiments, wherein at least about 90% of the reformable fuel introduced into the is reformed once through the anode of the solid oxide fuel cell.

  Although the present invention has been described in terms of particular embodiments, it is not so limited. Appropriate variations / modifications for operation under specific conditions will be apparent to those skilled in the art. Accordingly, it is intended that the following claims be interpreted as encompassing all such variations / modifications falling within the true spirit / range of the present invention.

Claims (19)

A method for producing electricity and hydrogen or synthesis gas using a solid oxide fuel cell having an anode and a cathode, comprising:
Introducing a fuel stream comprising a reformable fuel into the anode of the solid oxide fuel cell, a reforming stage (including internal reforming elements) associated with the anode of the solid oxide fuel cell, or a combination thereof; When;
Introducing a cathode inlet stream comprising O ₂ into the cathode of the solid oxide fuel cell;
Generating electricity in the solid oxide fuel cell;
Recovering a gas stream comprising H ₂ , a gas stream comprising H ₂ and CO, or a combination thereof from the anode exhaust;
The solid oxide fuel cell has an electrical efficiency of about 10% to about 50%, and the total fuel cell productivity of the solid oxide fuel cell is at least about 150 mW / cm ² ;
Method.   The solid oxide fuel cell is operated to generate electricity at a heat ratio of about 0.25 to about 1.3, such as about 1.15 or less, about 1.0 or less, or about 0.75 or less. The method of claim 1.   The method of claim 1 or 2, wherein the reformable fuel excess ratio of the fuel stream comprising the reformable fuel is at least about 2.0, such as at least about 2.5.   4. The method of any one of claims 1-3, wherein the electrical efficiency of the solid oxide fuel cell is about 45% or less, such as about 35% or less.   The total fuel cell efficiency of the solid oxide fuel cell is at least about 65%, such as at least about 70%, at least about 75%, or at least about 80%. Method. The total fuel cell productivity of the solid oxide fuel cell is at least about 150 mW / cm ^2, for example, at least about 300 mW / cm ^2, at least about 350 mW / cm ^2, or about 800 mW / cm ² or less, according to claim 1 The method of any one of -5. The total reformable fuel productivity of the solid oxide fuel cell is at least about 75 mW / cm ² , such as at least about 100 mW / cm ² , at least about 150 mW / cm ² , at least about 200 mW / cm ² , or about 600 mW / cm. The method according to claim 1, which is ² or less.   Reformable hydrogen content of a reformable fuel introduced into the anode of the solid oxide fuel cell, a reforming stage (including internal reforming elements) associated with the anode of the solid oxide fuel cell, or a combination thereof 8. The method of any one of claims 1-7, wherein the amount is at least about 75% greater than the amount of hydrogen reacted to generate electricity, for example at least about 100% greater. The fuel stream is at least about 10 volume percent inert compound comprises at least about 10% by volume of CO 2 or a combination _thereof, The method according to any one of claims 1-8. 10. _A method according to any one of the preceding claims, wherein the fuel cell is operated at a voltage _VA of about 0.67 volts or less, such as about 0.5 volts or less. The anode effluent is from about 1.5: 1 to about 10: 1, e.g., at least about 3.0: 1 _H 2: having a ratio of CO, according to any one of claims 1 to 10 Method.   The method according to claim 1, wherein the solid oxide fuel cell is a tubular solid oxide fuel cell.   13. A method according to any one of the preceding claims, wherein the solid oxide fuel cell further comprises one or more integrated endothermic reaction stages.   At least one integrated endothermic reaction stage includes an integrated reforming stage, and the fuel stream introduced into the anode of the solid oxide fuel cell enters the anode of the solid oxide fuel cell The method of claim 13, wherein the method passes through the integrated reforming stage before.   15. A method according to any one of the preceding claims, wherein the temperature of the anode outlet is higher than the temperature of the anode inlet by about 40C or less.   15. A method according to any one of the preceding claims, wherein the temperature of the anode inlet differs from the temperature of the anode outlet by no more than about 20C.   15. The method of any one of claims 1-14, wherein the anode outlet temperature is about 10C to about 80C lower than the anode inlet temperature.   The heat ratio is about 0.85 or less, and the method supplies heat to the fuel cell to maintain the anode outlet temperature at about 5 ° C. to about 50 ° C. lower than the anode inlet temperature. 15. The method according to any one of claims 1 to 14, further comprising:   Further comprising reforming the reformable fuel, the reforming step (including internal reforming elements) associated with the anode of the solid oxide fuel cell, the anode of the solid oxide fuel cell, or a combination thereof 19. The method of any one of claims 1-18, wherein at least about 90% of the reformable fuel introduced into the is reformed through a single pass through the anode of the solid oxide fuel cell.

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