KR20160064188A - Integrated power generation and chemical production using solid oxide fuel cells - Google Patents

Abstract

In various aspects, a system and method are provided for operating a solid oxide fuel cell under conditions that can improve or maximize the integrated electrical efficiency and chemical efficiency of the fuel cell. Instead of selecting conventional conditions to maximize the electrical efficiency of the fuel cell, the operating conditions may enable the production of excess syngas and / or hydrogen in the anode exhaust of the fuel cell. The syngas and / or hydrogen can then be used for a variety of applications including the chemical synthesis process and the collection of hydrogen for use as fuel.

Description

TECHNICAL FIELD [0001] The present invention relates to an integrated power generation and chemical production method using a solid oxide fuel cell,

In various aspects, the present invention is directed to a chemical production and / or generation method integrated with power generation using a solid oxide fuel cell.

Solid oxide fuel cells generate electricity using hydrogen and / or other fuels. Hydrogen can be provided by reforming methane or other reformable fuel in a steam reformer located in front of the fuel cell or located in the fuel cell. The reformable fuel may comprise a hydrocarbonaceous material capable of reacting with steam and / or oxygen at elevated temperature and / or pressure to produce a gaseous product comprising hydrogen. Additionally or alternatively, the fuel can be reformed in an anode cell of a solid oxide fuel cell that can be operated to form conditions suitable for reforming the fuel at the anode. Additionally or alternatively, the reforming can take place inside and outside the fuel cell.

Traditionally, solid oxide fuel cells are operated to maximize electrical production per unit of fuel input (which may be referred to as the fuel efficiency of the fuel cell). This maximization can be based only on fuel cells or on integrated heat and power applications. In order to increase electricity generation and manage heat generation, the fuel utilization rate in the fuel cell is maintained at 70% to 85%.

U.S. Patent Publication No. 2005/0123810 describes a system and method for simultaneously generating hydrogen and electrical energy. The co-production system includes a fuel cell and a separation unit device configured to receive the anode exhaust gas stream and separate the hydrogen. A portion of the anode exhaust gas is also recirculated to the anode inlet. The operating range described in the '810 publication appears to be based on molten carbonate fuel cells. Solid oxide fuel cells are described as alternatives.

In one aspect, a method of generating electricity and hydrogen or syngas using a solid oxide fuel cell having an anode and a cathode is provided. The method includes introducing a fuel stream comprising a reformable fuel into an anode of a solid oxide fuel cell, an internal reforming element associated with an anode of the solid oxide fuel cell, or a combination thereof; Introducing a cathode inlet stream comprising O ₂ into a cathode of a solid oxide fuel cell; Generate electricity within the solid oxide fuel cell; Recovering a gas stream comprising H ₂ from the anode exhaust gas, 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 fuel cell productivity of the solid oxide fuel cell is about 150 mW / cm ² or more.

Figure 1 schematically illustrates an example of the configuration of a solid oxide fuel cell and its associated reforming and separation stages.
Fig. 2 schematically shows another example of the configuration of a solid oxide fuel cell and its accompanying reforming and separation stages.
Figure 3 schematically shows an example of the operation of a solid oxide fuel cell.

summary

In various aspects, systems and methods are provided for producing a large amount of hydrogen or syngas in addition to producing electricity from a solid oxide fuel cell (SOFC) with high total fuel cell efficiency. Aspects of the present invention may employ planar cells or tubular cells. Total fuel cell efficiency typically refers to the integrated electrical efficiency and chemical efficiency of a fuel cell. A more detailed definition of the total fuel cell efficiency is then provided.

A typical fuel cell system can be designed and operated to optimize electrical efficiency at the expense of any other parameter (s). The heat generated as a result of combustion of the waste gas and the anode product in the in situ and / or to the extent necessary to maintain fuel cell operation at constant conditions can be used. As in most power generation methods, conventional fuel cell systems consume electrical products first. The fuel cell system can be used for applications in which the primary purpose is the production of efficient power, for example in the production of distributed or backup production.

Aspects of the present invention can establish fuel cell operating parameters that allow total fuel cell efficiency to exceed conventional fuel cell efficiencies. Additionally or alternatively, the present invention provides a method for increasing total fuel cell productivity while maintaining high overall system efficiency. In one embodiment, productivity is the total amount of useful product (e.g., syngas, heat, electricity) produced per unit time for a specified amount of fuel cell capacity, as measured, for example, by the cross-sectional area of the fuel cell. Instead of choosing conventional conditions to maximize the electrical efficiency of the fuel cell, if the electrical efficiency can fall below the optimum electrical efficiency pursued in the typical fuel cell system described above, then the operating conditions are much higher for the total system, Efficiency and / or productivity. As described in more detail below, total fuel cell efficiency is a measure of the amount of energy generated by the fuel cell relative to the amount of energy delivered to the fuel cell, while productivity is a function of the amount of energy delivered to the fuel cell It is a measure of the amount of energy (total chemical, electrical, and thermal energy) Conditions that can achieve high total fuel cell efficiency and / or productivity can result in excess syngas and / or hydrogen being produced in the anode exhaust gas of the fuel cell, and can be reduced to an anode and a cathode By completely or partially separating the inputs and outputs from the < / RTI > Such excess can be achieved, for example, by heat generated within the in-situ reaction system for efficient production of the battery (e. G., By operating at lower voltages) and / or by chemical energy ≪ / RTI > As a result, the fuel cell can handle a greater amount of the total fuel input to the anode while maintaining a total output efficiency (sum of chemical energy, electrical energy and useful thermal energy) similar to or higher than those known in the art . Higher productivity allows fuel cells to be used more efficiently in integrated systems.

The electrochemical process taking place at the anode can cause an anode-output flow of the synthesis gas containing at least a combination of H ₂ , CO and CO ₂ . Then, the purpose of the composition of the syngas using a water gas shift reaction products and / or to increase the H ₂ production, or maximizing than other synthesis gas components. Syngas and / or hydrogen may then be used for a variety of applications including, but not limited to, chemical synthesis processes and / or collection of hydrogen for use as a "clean" fuel.

As used herein, the term " electrical efficiency "(" EE ") is defined as the electrochemical power produced by the fuel cell divided by the low calorific value (" LHV ") ratio of fuel input to the fuel cell. The fuel input to the fuel cell includes both the fuel delivered to the anode, as well as any fuel used to maintain the temperature of the fuel cell (e.g., fuel delivered to the fuel cell). In this description, the power generated by the fuel can be described in terms of the LHV (el) fuel rate.

As used herein, the term " electrochemical power "or LHV (el) is the power generated by a circuit in a fuel cell connecting a cathode to an anode and transporting carbonate ions across the electrolyte of the fuel cell. The electrochemical power excludes the power generated or consumed by equipment located in front of or behind the fuel cell. For example, the current generated from heat in the fuel cell exhaust stream is not considered part of the electrochemical power. Similarly, the power generated by a gas turbine or other device located in front of the fuel cell is not part of the generated electrochemical power. "Electrochemical power" does not take into account the power consumed during operation of the fuel cell, or take into account any losses caused by the conversion of the direct current to alternating current. In other words, the power supplied to the fuel cell operation or otherwise used to operate the fuel cell is not subtracted from the DC power generated by the fuel cell. The power density used herein is the current density multiplied by the voltage. The current density used herein is the current per unit area. As used herein, the term total fuel cell power is the power density multiplied by the fuel cell area.

The term "anode fuel input, " as used herein, referred to as LHV (anode_in), is the amount of fuel in the anode inlet stream. The term "fuel input " referred to as LHV (in) is the total amount of fuel delivered to the fuel cell, including both the amount of fuel in the anode inlet strip and the amount of fuel used to maintain the temperature of the fuel cell. The fuel may include both a reformable fuel and a non-reformable fuel based on the definition of the reformable fuel provided herein. Fuel inputs are not the same as fuel utilization.

As used herein, the term " total fuel cell efficiency "(" TFCE ") means the ratio of the LHV of the syngas produced by the fuel cell to the electrochemical power generated by the fuel cell divided by the ratio of the LHV of the fuel input to the anode Lt; / RTI > 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) and LHV (sg net) indicates the rate at which the synthesis gas (H ₂ , CO) is produced at the anode, which is the difference between the synthesis gas input to the anode and the synthesis gas output from the anode. LHV (el) describes the electrochemical evolution of fuel cells. Total fuel cell efficiency excludes heat generated by the fuel cell, which is advantageously used outside the fuel cell. In operation, the heat generated by the fuel cell can be advantageously used by devices located behind the process. For example, heat can be used to generate additional electricity or to heat water. When used separately from the fuel cell, these applications are not part of the total fuel cell efficiency when this term is used herein. Total fuel cell efficiency applies only to fuel cell operation and does not include power generation, or consumption in front of or behind the fuel cell.

As used herein, the term "chemical efficiency" is defined as the low calorific value or LHV (sg out) of H ₂ and CO in the anode exhaust of a fuel cell divided by the fuel input or LHV (in).

As used herein, the term "total fuel cell productivity"("TFCP") is defined as the total energy value of a product produced per unit fuel cell unit area per unit time due to deformation of the input fuel. Fuel can be modified in oxidation, reforming and / or water gas-phonetic reactions. The total energy of the product can be expressed in any convenient unit, for example in mW per cm < ² >. The product produced by the fuel cell may comprise electrochemical power, syngas and / or hydrogen, and heat. By measuring the temperature difference between the anode inlet and the anode outlet, the generated heat can be determined. By way of example, the productivity of a fuel cell can be expressed as mW per 1 cm ² of fuel cell anode cross-section. The fuel cell operating conditions may optionally be selected to produce high total fuel cell productivity and high total fuel cell efficiency.

Between herein the term "total reforming possible fuel productivity" as used in ( "TRFP") is a fuel cell cross-section one unit of fuel Accepted is modified possible received from modified LHV and the anode outlet of the available fuel inputs to the ^second party, the anode LHV Difference. The difference between the reformatable fuel at the anode inlet and the outlet is that the amount of reformatted fuel converted to syngas and / or hydrogen ultimately leads to the production of freshly produced syngas and / or hydrogen Can be approximately equal to the subtracted amount. The freshly produced syngas and / or hydrogen are produced in the subsequent reforming stage which is thermally integrated with the anode or fuel cell. Syngas and / or hydrogen provided to the anode inlet are not freshly produced. The fuel cell operating conditions may be selected to produce both high total modifiable fuel productivity and high total fuel cell efficiency.

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

In various aspects of the invention, the operation of the fuel cell may be characterized based on a desired electrical efficiency of about 50% or less and a desired total fuel cell efficiency of 55% or more. When the fuel cell is operated to have the desired electrical efficiency and the desired total fuel cell efficiency, the solid oxide fuel cell has a TFCE of about 55% or more and an electrical efficiency of 50% or less, such as about 60% or more TFCE and about 40% Less than about 65% TFCE and less than about 35% EE, less than about 70% TFCE and less than about 30% EE, less than about 75% TFCE and less than about 20% EE, or greater than about 80% TFCE About 15% or less EE, or about 85% or more TFCE and about 10% or less EE.

In various aspects of the present invention, the operation of the fuel cell can be characterized based on the desired total fuel cell productivity ("TFCP") above about 150 mW / cm ² and the desired total fuel cell efficiency above 55%. When the fuel cell is operated to have a desired TFCP of about 150 mW / cm < ² > and the desired total fuel cell efficiency, the solid oxide fuel cell has about 55% or more, such as about 60% Or more, or about 75% or more, or about 80% or more, or about 85% or more TFCE. When the operation so as to have a total of the fuel cell efficiency that the fuel cell is at least 55% purpose, solid oxide fuel cells is about 150mW / cm ² or more, or from about 200mW / cm ² or more, or from about 250mW / cm ² or more, or from about 300mW / cm < ² >, or greater than about 350 mW / cm < ² > In this embodiment, TFCP may be up to about 800mW / cm ² or less, or from about 700mW / cm ² or less, or from about 600mW / cm ² or less, or from about 500mW / cm ² or less, or from about 400mW / cm ^2.

In various embodiments of the present invention, the operation of the fuel cell can be characterized based on a desired total reformable fuel productivity of at least about 75 mW / cm ² and a desired total fuel cell efficiency of at least 55%. When the fuel cell is operated to have a desired modifiable fuel productivity of greater than about 75 mW / cm < ² > and the desired total fuel cell efficiency, the solid oxide fuel cell has a fuel cell efficiency of at least about 55%, such as at least about 60% , About 70% or more, or about 75% or more, or about 80% or more, or about 85% or more, or about 90% or more of the TFCE. When the operation so as to have a total of the fuel cell efficiency that the fuel cell is at least 55% purpose, solid oxide fuel cells is about 75mW / cm ² or more, or from about 100mW / cm ² or more, or from about 125mW / cm ² or more, or from about 150mW / cm ² or more, or from about 175mW / cm ² or more, or from about 200mW / cm ² to have the, or at least about 300mW / cm ² or more modified possible fuel productivity can be operated. In this embodiment, the reforming possible fuel productivity can be up to about 600mW / cm ² or less, or from about 500mW / cm ² or less, or from about 400mW / cm ² or less, or from about 300mW / cm ² or less, or from about 200mW / cm ^2.

In a variety of ways, the solid oxide fuel cell can be operated to have the desired electrical efficiency, chemical efficiency, and / or total fuel cell efficiency. In some embodiments, by increasing the amount of modification carried out in the fuel cell (and / or in the reforming stage followed by the fuel cell assembly) relative to the amount of oxidation of hydrogen in the anode to generate electricity, Chemical efficiency can be increased. Conventionally, solid oxide fuel cells have been operated to maximize power generation efficiency relative to the amount of fuel consumed while maintaining a thermal balance that is adequate to maintain the overall system temperature. In this type of operating condition, the fuel utilization rate at the anode of about 70% to about 85% is desirable to maximize the electrical efficiency at a desirable (i.e., high) voltage for electricity delivery and to maintain thermal balance within the fuel cell . At high fuel utilization values, only a modest amount of hydrogen (or syngas) remains in the anode exhaust for synthesis gas formation. For example, at a fuel utilization rate of about 75%, about 25% of the fuel entering the anode may exit as a combination of syngas and / or unreacted fuel. A suitable amount of hydrogen or syngas can typically be sufficient to maintain enough hydrogen concentration at the anode to facilitate the anode oxidation reaction and sufficient fuel to heat the reactant and / or inlet stream to the proper fuel cell operating temperature have.

In contrast to this conventional operation, the solid oxide fuel cell can be operated with little or no recirculation of fuel from the anode exhaust to the anode inlet at low fuel utilization and higher fuel flow rates. By operating at a low fuel utilization rate while reducing or minimizing fuel recirculation to the anode inlet, a greater amount of H ₂ and / or CO can be obtained in the anode exhaust gas. This excess of H ₂ and CO can be recovered as syngas product and / or hydrogen product. In various embodiments, the fuel utilization of the fuel cell may 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 a low fuel utilization aspect, the fuel utilization rate may be less than or equal to about 60%, or less than or equal to about 50%, or less than or equal to about 40%.

One option to increase the chemical efficiency of the fuel cell may be to increase the reformable hydrogen content of the fuel delivered to the fuel cell. For example, the modifiable hydrogen content of the reformable fuel in the feed stream delivered to the reforming stage that accompanies the anode and / or anode is at least about 50%, such as at least about 75% greater than the net amount of hydrogen reacted at the anode, or It can be more than about 100% more. Additionally or alternatively, the reformable hydrogen content of the fuel in the feed stream delivered to the reforming stage followed by the anode and / or anode may be at least about 50%, such as at least about 75% greater than the net amount of hydrogen reacting at the anode , Or about 100% or more. In various embodiments, the ratio of the modifiable hydrogen content of the reformable fuel to the amount of hydrogen reacting at the anode is at least about 1.5: 1, or at least about 2.0: 1, or at least about 2.5: 1, : It can be more than 1. Additionally or alternatively, the ratio of the modifiable hydrogen content of the reformable fuel to the amount of hydrogen reacting at the anode may be about 20: 1 or less, such as about 15: 1 or less, or about 10: 1 or less. In one embodiment, it is believed that less than 100% of the reformable hydrogen content in the anode inlet stream can be converted to hydrogen. For example, at least about 80%, such as at least about 85%, or at least about 90%, of the reformable hydrogen content in the anode inlet stream can be converted to hydrogen in the anode and / or the modified stage (s) involved.

Hydrogen or syngas can be recovered from the anode exhaust as a chemical energy output. Hydrogen can be used as a clean fuel without generating greenhouse gases when burned. In addition, hydrogen can be an important input to a variety of refining processes and / or other synthetic processes. Syngas can also be an important input to various processes. In addition to having calorific values, syngas can be used as feedstock to produce other higher value products by using syngas as an input, for example, for Fischer-Tropsch synthesis and / or methanol synthesis processes.

In various embodiments, the anode exhaust gas may be from about 1.5: 1 to about 10: 1, such as about 3.0: 1 or more, or about 4.0: 1 or more, or about 5.0: 1 or more, and / or about 8.0: : Can have an H ₂ to CO ratio of 1 or less. The syngas stream can be recovered from the anode exhaust gas. In various embodiments, the syngas stream recovered from the anode exhaust gas may be 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: or about 1.8: can have a molar ratio of moles of CO for one or more H _2: 1, or at least about 1.9. Additionally or alternatively, the molar ratio of H ₂ to CO in the syngas recovered from the anode exhaust may be 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: About 2.2: 1 or less, or about 2.1: 1 or less. However, many types of syngas applications advantageously utilize syngas having a molar ratio of H ₂ to CO of from about 1.5: 1 to about 2.5: 1, and thus, for example, from about 1.7: 1 to about 2.3: 1 H ₂ It may be desirable for some applications to form a syngas stream having a molar ratio of CO content.

The synthesis gas can be recovered from the anode exhaust gas by any convenient method. In some embodiments, the syngas can be recovered from the anode exhaust gas by performing separation on the anode exhaust gas to remove at least some of the components in the anode exhaust gas other than H ₂ and CO. For example, the anode exhaust gas may first be passed through an optional water gas telephone stage to adjust the relative amounts of H ₂ and CO. One or more separation stages may then be used to remove H ₂ O and / or CO ₂ from the anode exhaust gas. The remaining portion of the anode exhaust gas then corresponds to a syngas stream, which can be recovered for use in any convenient manner. Additionally or alternatively, the recovered syngas stream may be passed through one or more water gas telephone stages and / or passed through one or more separation stages.

Note that additional or other ways of changing the molar ratio of H ₂ to CO in the syngas recovered may be to separate the H ₂ stream from the anode exhaust gas and / or the synthesis gas, for example, by performing a membrane separation. Of this separation to form an additional H ₂ output streams, e.g., the anode exhaust gas the water gas to pass through the reaction stages before and / or after, and the anode exhaust gas to anode exhaust gas non-H ₂ and CO Such as before and / or after passing the one or more separation stages for removing the components of the substrate. Optionally, a water gas telephone stage may be used before and after the H ₂ stream is separated from the anode exhaust gas. In additional or alternative embodiments, H ₂ may be optionally separated from the recovered syngas stream. In some embodiments, separating the H ₂ stream is about 90% by volume or more of H _2, for example about 95% by volume or more of H _2, or about 99 can correspond to high purity H ₂ stream, such as H ₂ stream containing vol% or more H ₂ have.

In addition to, and / or as an alternative to, the fuel cell operating strategy described herein, a solid oxide fuel cell (e.g., a fuel cell assembly) uses an excess amount of reformable fuel relative to the amount of hydrogen that reacts at the anode of the fuel cell . Instead of selecting operating conditions of the fuel cell to improve or maximize the electrical efficiency of the fuel cell, an excess of the reformable fuel may be passed into the anode of the fuel cell to increase the chemical energy output of the fuel cell. Optionally, but preferably, it can increase the total efficiency of the fuel cell based on the sum of the electrical efficiency and the chemical efficiency of the fuel cell.

In some embodiments, the modifiable hydrogen content of the reformable fuel in the feed stream delivered to the reforming stage followed by the anode and / or anode is at least about 50%, such as at least about 75% greater than the net amount of hydrogen oxidized at the anode , Or about 100% or more. In various embodiments, the ratio of the modifiable hydrogen content of the reformable fuel to the amount of hydrogen reacting at the anode is at least about 1.5: 1, or at least about 2.0: 1, or at least about 2.5: 1, : It can be more than 1. Alternatively or in addition, the ratio of the reformable fuel's hydrogen content in the fuel stream to the amount of hydrogen reacting at the anode may be up to about 20: 1, for example up to about 15: 1 or up to about 10: 1 . In one embodiment, it is believed that less than 100% of the reformable hydrogen content in the anode inlet stream can be converted to hydrogen. For example, at least about 80%, such as at least about 85%, or at least about 90%, of the reformable hydrogen content in the anode inlet stream can be converted to hydrogen in the anode and / or its associated reforming stage.

Additionally or alternatively, the amount of reformable fuel delivered to the anode can be characterized based on the LHV of the reformable fuel relative to the lower calorific value (LHV) of the hydrogen oxidized at the anode. This can be referred to as a fuelable excess fuel ratio. In this alternative, the fuelable excess fuel ratio may be greater than or equal to about 2.0, such as greater than or equal to about 2.5, or greater than or equal to about 3.0, or greater than or equal to about 4.0. Additionally or alternatively, the fuelable excess fuel 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 embodiments of the present invention, the operation of the fuel cell may be characterized based on the desired total fuel cell productivity ("TFCP") of greater than about 150 mW / cm ² and the desired modifiable fuel excess ratio. For example, a solid oxide fuel cell can be operated to have a TFCP of about 150 mW / cm ² or more and a reformable fuel overage ratio of about 2.0 or more, such as about 2.5 or more, or about 3.0 or more, or about 4.0 or more. Additionally or alternatively, the TFCP may be greater than or equal to about 150 mW / cm ² , and the reformable fuel excess ratio may be less than or equal to about 25.0, such as less than or equal to about 20.0, or less than or equal to about 15.0, or less than or equal to about 10.0. When the fuel cell is operated so as to have a modified possible fuel rich ratio of at least about 2.0, a solid oxide fuel cell is from about 150mW / cm ² or more, or from about 200mW / cm ² or more, or from about 250mW / cm ² or more, or from about 300mW / cm ² , or greater than about 350 mW / cm < ² >. In this embodiment, TFCP may be up to about 800mW / cm ² or less, or from about 700mW / cm ² or less, or from about 600mW / cm ² or less, or from about 500mW / cm ² or less, or from about 400mW / cm ^2.

In various embodiments of the present invention, the operation of the fuel cell may be characterized based on the desired total reformable fuel productivity and the desired modifiable fuel excess ratio above about 75 mW / cm ² . In some embodiments, the fuel cell can be operated to have a desired reformable fuel productivity of at least about 75 mW / cm ^{2 and a} reformable fuel overage of about 2.0 or more, such as about 2.5 or more, or about 3.0 or more, have. Additionally or alternatively, the total reformable fuel productivity may be greater than about 75 mW / cm ² and the modifiable fuel excess ratio may be less than or equal to about 25.0, such as less than or equal to about 20.0, or less than or equal to about 15.0, or less than or equal to about 10.0 . When the fuel cell is operated so as to have a modified possible fuel rich ratio of at least about 2.0, a solid oxide fuel cell is approximately 75mW / cm ² or more, or from about 100mW / cm ² or more, or from about 125mW / cm ² or more, or from about 150mW / cm at least ^2, or from about 175mW / cm ² or more, or from about 200mW / cm ² to have the, or at least about 300mW / cm ^2, the fuel reforming possible productivity than may be enabled. In this embodiment, the reforming possible fuel productivity can be up to about 600mW / cm ² or less, or from about 500mW / cm ² or less, or from about 400mW / cm ² or less, or from about 300mW / cm ² or less, or from about 200mW / cm ^2.

In addition to, and / or as an alternative to, the fuel cell operating strategy described herein, the solid oxide fuel cell can be operated to select an amount of oxidation to obtain the desired temperature ratio in the fuel cell . As used herein, the "temperature ratio" is defined as the heat generated by the exothermic reaction in the fuel cell assembly, divided by the endothermic heat demand of the reforming reaction occurring in the fuel cell assembly. Mathematically speaking, the temperature ratio (TH) = Q _EX / Q _EN . Where Q _EX is the sum of the heat generated by the exothermic reaction and Q _EN is the sum of the heat consumed by the endothermic reaction in the fuel cell. Note that the heat generated by the exothermic reaction corresponds to any heat in the cell due to the reforming reaction, the water gas-phone reaction, and the electrochemical reaction. 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 reaction in an SOFC is assumed to be about 1.04V based on the net reaction in the cell. During operation of the SOFC, the cell typically has an output voltage of less than 1.1 V due to various losses. For example, the typical output / operating voltage may be about 0.65V, or about 0.7V, or about 0.75V, or about 0.8V. The generated heat is equal to [the electrochemical potential of the battery (e.g., about 1.04 V) - the operating voltage]. For example, the heat generated by an electrochemical reaction in a cell is about 0.34 V when the output voltage is about 0.7V. Therefore, in this scenario, the electrochemical reaction produces a current of about 0.7V and a thermal energy of about 0.34V. In this example, an electrical energy of about 0.7 V is not included as part of Q _EX . In other words, thermal energy is not electrical energy.

In various embodiments, the operating parameters of the SOFC are selected to achieve an operating voltage of less than at least 0.7 V, such as at least 0.65 V, or at least less than 0.6 V, or at least less than 0.5 V, or at least less than 0.4 V, Can be set.

For various convenient fuel cell structures, such as fuel cell stacks, individual fuel cells in a fuel cell stack, fuel cell stacks with integrated reforming stages, fuel cell stacks with integrated endothermic reaction stages, or combinations thereof, The ratio can be determined. In addition, temperature ratios can be calculated for different unit devices in a fuel cell stack, such as, for example, an assembly of fuel cells or a fuel cell stack. For example, a fuel cell stack with an integrated reforming stage and / or an integrated endothermic reaction stage element that is close enough to a single anode in a single fuel cell, an anode zone within the fuel cell stack, or an anode zone integrated in terms of heat integration, Lt; / RTI > can be calculated for the anode zone in the < / RTI > The term "anode zone" as used herein includes an anode in 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 based on a temperature ratio. When the fuel cell is operated to have the desired temperature ratio, the solid oxide fuel cell may have a temperature of about 1.5 or less, for example about 1.3 or less, or about 1.15 or less, or about 1.0 or less, or about 0.95 or less, Or about 0.85 or less, or about 0.80 or less, or about 0.75 or less. Additionally or alternatively, the temperature ratio can be about 0.25 or more, or about 0.35 or more, or about 0.45 or more, or about 0.50 or more.

In various embodiments of the present invention, the operation of the fuel cell can be characterized based on the desired total modifiable fuel productivity and the desired temperature ratio of at least about 75 mW / cm ² . In some embodiments, the fuel cell has a desired total modifiable fuel productivity of at least about 75 mW / cm ^{2, and} a total modifiable fuel productivity of 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 about 0.95 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 reformable fuel productivity may be greater than about 75 mW / cm ² , and the temperature ratio may be about 0.25 or more, or about 0.35 or more, or about 0.45 or more, or about 0.50 or more. When the fuel cell is operated so as to have a temperature ratio of about 0.25 to about 1.3, a solid oxide fuel cell is approximately 75mW / cm ² or more, or from about 100mW / cm ² or more, or from about 125mW / cm ² or more, or from about 150mW / cm at least ^2, or from about 175mW / cm ² or more, or from about 200mW / cm ² to have the, or at least about 300mW / cm ^2, the fuel reforming possible productivity than may be enabled. In this embodiment, the reforming possible fuel productivity can be up to about 600mW / cm ² or less, or from about 500mW / cm ² or less, or from about 400mW / cm ² or less, or from about 300mW / cm ² or less, or from about 200mW / cm ^2.

In various embodiments of the present invention, the operation of the fuel cell may be characterized based on the desired total fuel cell productivity and the desired temperature ratio of greater than or equal to about 150 mW / cm ² . In one embodiment, the fuel cell has a desired total fuel cell productivity of at least about 150 mW / cm ² and a total fuel cell productivity of 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 about 0.93 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 may be greater than about 150 mW / cm ² , and the temperature ratio may be about 0.25 or more, or about 0.35 or more, or about 0.45 or more, or about 0.50 or more. When the fuel cell is operated so as to have a temperature ratio of about 0.25 to about 1.3, a solid oxide fuel cell is from about 150mW / cm ² or more, or from about 200mW / cm ² or more, or from about 250mW / cm ² or more, or from about 300mW / cm ² , or greater than about 350 mW / cm < ² >. In this embodiment, TFCP may be up to about 800mW / cm ² or less, or from about 700mW / cm ² or less, or from about 600mW / cm ² or less, or from about 500mW / cm ² or less, or from about 400mW / cm ^2.

Additionally or alternatively, in some embodiments, the fuel cell may be operated to have a temperature rise between the anode input and the anode output of about 40 캜 or less, such as about 20 캜 or less, or about 10 캜 or less. Additionally or alternatively, the fuel cell may be operated to have an anode outlet temperature from about 10 [deg.] C lower than the anode inlet temperature to about 10 [deg.] C higher. Additionally or alternatively, an anode can be provided that is higher than the anode outlet temperature, such as greater than about 5 degrees Celsius, or greater than about 10 degrees Celsius, or greater than about 20 degrees Celsius, The fuel cell can be operated to have an inlet temperature. Additionally or alternatively, the anode outlet temperature may be about 100 DEG C or less, such as about 80 DEG C or less, or about 60 DEG C or less, or about 50 DEG C or less, or about 40 DEG C or less, Lt; RTI ID = 0.0 > and / or < / RTI > Minimizing the difference between the anode inlet temperature and the outlet temperature can help maintain the mechanical integrity of the ceramic components in the solid oxide fuel cell.

In addition to, and / or as an alternative to the fuel cell operating strategy described herein, a solid oxide fuel cell (e. G., A fuel cell assembly) can be operated under conditions that can increase the power density. The power density of the fuel cell corresponds to the actual operating voltage V _A multiplied by the current density I. In the case of a solid oxide fuel cell operated at voltage V _A , the fuel cell may also tend to generate waste heat, and the waste heat is based on the difference between V _A of the fuel cell providing the current density I and the ideal voltage V ₀ Is defined as (V ₀ -V _A ) * I. A part of the waste heat can be consumed by reforming the reformable fuel in the anode of the fuel cell. The remaining portion of the waste heat is absorbed by the surrounding fuel cell structure and the gas flow, so that a temperature difference across the fuel cell can be generated. Under conventional operating conditions, the power density of the fuel cell can be limited based on the amount of waste heat that the fuel cell can tolerate without sacrificing the integrity of the fuel cell.

In various embodiments, the amount of waste heat that a fuel cell can tolerate can be increased by performing an endothermic reaction in an effective amount in the fuel cell. One example of an endothermic reaction involves the steam reforming of the reformable fuel in the fuel cell anode and / or its subsequent reforming stage, such as an integrated reforming stage of the fuel cell stack. By providing additional reformable fuel to the anode (or integrated / subsequent reforming stage) of the fuel cell, further reforming can be performed such that additional waste heat can be consumed. This can reduce the amount of temperature difference across the fuel cell, allowing the fuel cell to operate under operating conditions with larger amounts of waste heat. Loss of electrical efficiency can be offset by the formation of additional product streams such as syngas and / or H ₂ that can be used for a variety of purposes, including further development, further extending the power range of the system.

In various embodiments, the amount of waste heat (V ₀ -V _A ) * I generated by the fuel cell as defined above is greater than or equal to about 30 mW / cm ² , such as greater than or equal to about 40 mW / cm ² , ^2, or at least about 60mW / cm ² or more, or from about 70mW / cm ² or more, or from about 80mW / cm ² or more, or from about 100mW / cm ² or more, or from about 120mW / cm ² or more, or from about 140mW / cm ² or more , or from about 160mW / cm ² or more, or from about 180mW / cm ² or more, or from about 200mW / cm ² or more, or from about 220mW / cm ² or more, or from about 250mW / cm ² or more, or from about 300mW / cm ² may be at least . Or alternatively to add is less than the amount of waste heat ² from about 400mW / cm generated by the fuel cell, for example, from about 300mW / cm ² or less, or from about 200mW / cm ² or less, or from about 175mW / cm ² or less, or about 150mW / cm < ² >.

Although the amount of waste heat generated may be relatively high, such waste heat may not necessarily indicate that the fuel cell operates with poor efficiency. Instead, waste heat can be generated by operating the fuel cell at a high power density. Some of the improvements in the power density of the fuel cell may include operating the fuel cell at a sufficiently high current density. In various embodiments, the current density generated by the fuel cell is about 150mA / cm ² or more, for example, about 160mA / cm ^2, or at least about 170mA / cm ^2, or at least about 180mA / cm ^2, or at least about 190mA / cm ² or more, or about 200 mA / cm ² or more, or about 300 mA / cm ² or more, or about 400 mA / cm ² or more, or about 800 mW / cm ^{2 or} more. In addition or alternatively, the current density generated by the fuel cell is about 800mA / cm ² or less, for example, 450mA / cm ² or less, or 300mA / cm ² or less, or 250mA / cm ² or less, or 200mA / cm ² or less .

In various embodiments, an effective amount of an endothermic reaction (e. G., A reforming reaction) may be performed to operate the fuel cell while increasing power generation and increasing waste heat generation. Alternatively, another endothermic reaction not related to anode operation can be utilized to utilize the waste heat by placing a "plate" or stage into the fuel cell array in thermal communication (but not in fluid communication) with the anode or cathode. An effective amount of an endothermic reaction can be performed in a subsequent reforming stage, an integrated reforming stage, an integrated stacking element for performing an endothermic reaction, or a combination thereof. An effective amount of the endothermic reaction may be achieved by increasing the temperature increase from the fuel cell inlet to the fuel cell outlet to about 100 캜 or less, such as about 90 캜 or less, or about 80 캜 or less, or about 70 캜 or less, About 50 DEG C or less, or about 40 DEG C or less, or about 30 DEG C or less. Additionally or alternatively, an effective amount of endothermic reaction may be conducted at a temperature of about 100 占 폚 or lower, such as about 90 占 폚 or lower, or about 80 占 폚 or lower, or about 70 占 폚 or lower, or about 60 占 폚 or lower, 40 DEG C or less, or about 30 DEG C or less, or about 20 DEG C or less, or about 10 DEG C or less, to the fuel cell outlet. When the effective amount of the endothermic reaction exceeds the waste heat generated, a temperature decrease may occur from the fuel cell inlet to the fuel cell outlet. Additionally or alternatively, it consumes at least about 40% of the waste heat generated by the fuel cell, for example at least about 50% of the waste heat, or at least about 60% of the waste heat, or at least about 75% (S) (e. G., A combination of reforming and other endothermic reactions). ≪ / RTI > Additionally or alternatively, the endothermic reaction (s) may consume less than about 95% of the waste heat, such as less than about 90% of the waste heat, or less than about 85% of the waste heat.

Additional definitions

Syngas. In this definition, synthesis gas is defined as a mixture of any ratio of the H ₂ and CO. Optionally, H ₂ O and / or CO ₂ may be present in the syngas. Optionally, an inert compound (e.g., nitrogen) and the remaining reformable fuel compound may be present in the synthesis gas. When the components other than H ₂ and CO are present in the syngas, the combined volume percentages of H ₂ and CO in the syngas are at least 25 vol%, such as at least 40 vol%, or at least 50 vol% Or 60% by volume or more. Alternatively, or alternatively, the combined volume percentage of H ₂ and CO in the syngas may be up to 100 vol%, for example up to 95 vol%, or up to 90 vol%.

Modifiable fuel: A fuel that can be reformed is defined as a fuel containing carbon-hydrogen bonds that can be reformed to generate H ₂ . As is the case with other hydrocarbonaceous compounds (such as alcohols), hydrocarbons are an example of a fuel that can be reformed. CO and H ₂ O may participate in water gas-phos- phonation reactions to form hydrogen, but CO is not considered a reformable fuel under this definition.

Modifiable hydrogen content: The reformable hydrogen content of the fuel is defined as the number of H ₂ molecules that can be derived from the fuel by maximizing H ₂ production by allowing the water gas conversion to be completed after reforming the fuel. Note that H ₂ by this definition has a reformable hydrogen content of 1, but H ₂ itself is not defined herein as a reformable fuel. Similarly, CO has a reformable hydrogen content of 1. CO is not strictly modifiable, but exchanges CO with H ₂ by allowing the water gas-phonetic reaction to be completed. As an example of the reformable hydrogen content of the reformable fuel, the reformable hydrogen content of methane is four H ₂ molecules while the reformable hydrogen content of ethane is seven H ₂ molecules. More generally, if the fuel has a composition of C _x H _y O _z , then the reformable hydrogen content of the fuel at 100% reforming and water gas switching is n (maximal reforming H ₂ ) = 2x + y / 2-z. Based on this definition, the fuel utilization rate in the cell can be expressed as n (H ₂ O ₂ ) / n (maximum reforming H ₂ ). Of course, the reformable hydrogen content of the mixture of components can be determined based on the reformable hydrogen content of the individual components. Modifiable hydrogen content of compounds containing other heteroatoms such as oxygen, sulfur or nitrogen can also be calculated in a similar manner.

Oxidation reaction: In this discussion, the oxidation reaction in the fuel cell anode is oxidized to H ₂ O by the reaction of ^2- is defined as the response corresponding to Sikkim generate H ₂ O. Note that the reforming reaction in the anode in which a compound containing carbon-hydrogen bonds is converted to H ₂ and CO or CO ₂ is excluded from this definition of the oxidation reaction at the anode. The water gas-phonetic reaction is similarly excluded from this definition of the oxidation reaction. Citation of the combustion reaction refers to the reaction in which a compound containing H ₂ or carbon-hydrogen bond (s) reacts with O ₂ in a non-electrochemical burner, such as the combustion zone of a generator that draws power from combustion, to form H ₂ O and carbon dioxide It is also noted that it is defined as a quotation of.

Aspects of the present invention can adjust the anode fuel parameters to achieve the desired operating range of the fuel cell. The anode fuel parameters may be characterized directly with respect to other fuel cell processes in the form of and / or one or more ratios. For example, the anode fuel parameters can be controlled to obtain one or more ratios including fuel utilization, fuel cell heat utilization, fuel surplus ratio, reformable fuel surplus ratio, reformable hydrogen content fuel ratio, and combinations thereof.

Fuel Utilization: The fuel utilization rate is an option that characterizes the operation of the anode based on the amount of oxidized fuel relative to the reformable hydrogen content of the feed stream that can be used to define the fuel utilization of the fuel cell. In this discussion, the "fuel utilization rate" is defined as the ratio of the amount of hydrogen oxidized at the anode to the reformable hydrogen content of the anode input (including any subsequent reforming stage) for power generation (as described above). The reformable hydrogen content is defined above as the number of H ₂ molecules that can be derived from the fuel by maximizing H ₂ production by allowing the water gas conversion to be completed after reforming the fuel. For example, each methane that is introduced into the anode and exposed to the steam reforming process produces four H ₂ molecules at maximum production. (Depending on the modification and / or the anode conditions, modified products may correspond to a water gas non-phone product, this time is one or more H ₂ molecule is present instead in the form of CO molecules.) Thus, the methane is four H ₂ Is defined as having a reformable hydrogen content of the molecule. As another example, under this definition ethane has a seven-modified available hydrogen content H ₂ molecules.

The rate of utilization of the fuel at the anode is determined by the ratio of the lower calorific value of hydrogen oxidized at the anode due to the fuel cell anode reaction to the lower heating value of all the fuel delivered to the reforming stage accompanied by the anode and / By defining the heating value utilization rate based on the heating value. As used herein, the "fuel cell calorific value utilization rate" can be calculated using the flow rate and the low calorific value (LHV) of the fuel component entering and leaving the fuel cell anode. Thus, the fuel cell calorific utilization rate can be calculated as (LHV (anode_in) -LHV (anode_out)) / LHV (anode_in), where LHV (anode_in) and LHV (anode_out) are the anode inlet and outlet streams, Refers to the LHV of a component (e.g., H ₂ , CH _4, and / or CO). In this definition, the LHV of the stream or stream can be calculated as the sum of the values of each fuel component in the input and / or output stream. The contribution of each fuel component to the sum may correspond to the flow rate (e.g., mol / hour) of the fuel component multiplied by the LHV of the fuel component (e.g., J / mol).

Low calorific value: The low calorific value is defined as the enthalpy in which the fuel component is burned into the completely oxidized products of the gas phase (ie, gaseous CO ₂ and H ₂ O products). For example, any CO ₂ present in the anode input stream does not contribute to the fuel content of the anode charge, since CO ₂ is already fully oxidized. In this definition, the amount of oxidation generated at the anode due to the anode fuel cell reaction is defined as the H ₂ oxidation at the anode as part of the electrochemical reaction at the anode, as defined above.

The only fuel for anode input flow in a special case of H _2, only the reaction containing the fuel component that may occur in the anode is noticed indicating the transition to H ₂ O of H _2. In this special case, the fuel utilization is simplified as feed rate of the / H ₂ (-H ₂ feed rate calculated rate of the H _2). In this case, H ₂ is the only fuel component, and so H ₂ LHV falls out of the equation. If a more general, the anode feed may for example contain a CH _4, H ₂ and CO in various amounts. Since these materials are typically present in different amounts at the anode outlet, the sum described above may be necessary to determine the fuel utilization rate.

In addition to the fuel utilization rate, or in addition to the fuel utilization rate, the utilization rate of other reactants of the fuel cell can be characterized. For example, the operation of the fuel cell may be further or alternatively characterized in terms of the "oxidant" utilization. The oxidizer utilization value can also be defined in a similar manner.

Fuel excess ratio: Another way to characterize the reaction in a solid oxide fuel cell is to measure the low calorific value of the hydrogen oxidized at the anode due to the fuel cell anode reaction, all of which is transferred to the anode and / The utilization rate is limited based on the ratio of the low calorific value of the fuel. This amount is referred to as fuel surplus. Thereby, 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 the anode inlet and outlet streams, Refers to the LHV of a component (e.g., H ₂ , CH _4, and / or CO). In various embodiments of the present invention, the solid oxide fuel cell has a LHV of at least about 1.0, such as at least about 1.5, About 2.5 or more, or about 3.0 or more, or about 4.0 or more. In addition, or alternatively, the fuel excess ratio can be about 25.0 or less.

It is noted that not all of the reformable fuel in the input stream of 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 feed stream to the anode (and / or the subsequent reforming stage) can be reformed before leaving the anode. In some other embodiments, the amount of reformable fuel that is modified may be from about 75% to about 90%, such as about 80% or more.

The above definition of an excess fuel ratio provides a method for characterizing the amount of reforming done in the reforming stage (s) followed by the anode and / or the fuel cell, relative to the amount of fuel consumed in the fuel cell anode for power generation .

Optionally, the excess fuel ratio may be changed due to the situation where the fuel is recycled from the anode output to the anode input. When fuel (e. G., H ₂ , CO and / or unmodified or partially reformed hydrocarbons) is recycled from the anode output to the anode input, such recycled fuel components can be converted to reformable or reformable fuels Of the < / RTI > Instead, these recycled fuel components only represent a demand to reduce the fuel utilization in the fuel cell.

Modifiable fuel surplus ratio: Calculating the reformable fuel surplus ratio is one option to account for this recycled fuel composition and narrows the definition of excess fuel so that only the LHV of the reformable fuel is included in the input stream to the anode . As used herein, "reformable fuel excess ratio" is defined as the lower calorific value of the reformable fuel delivered to the reforming stage followed by the anode and / or anode, relative to the lower calorific value of hydrogen oxidized at the anode due to the fuel cell anode reaction. do. Under the definition of a reformable fuel excess ratio, any H ₂ or CO LHV in the anode charge is excluded. The LHV of such a reformable fuel can be measured by characterizing the actual composition entering the fuel cell anode, so there is no need to distinguish between recycled and new components. Although some unmodified or partially reformed fuel can also be recycled, in most embodiments, the majority of the fuel recycled to the anode may correspond to a modified product such as H ₂ or CO. Mathematically speaking, 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 calorific value LHV). The LHV of the oxidized hydrogen at the anode can be calculated (e.g., LHV (anode_in) -LHV (anode_out)] by subtracting the LHV of the anode exit stream from the LHV of the anode inlet stream. In various embodiments of the present invention, the solid oxide fuel cell has a power of about 0.25 or more, such as about 0.5 or more, or about 1.0 or more, or about 1.5 or more, or about 2.0 or more, or about 2.5 or more, or about 3.0 or more, Can be operated to have a reformable fuel excess ratio. Additionally or alternatively, the fuelable excess fuel ratio can be about 25.0 or less. Note that this narrower definition based on the amount of reformable fuel delivered to the anode relative to the amount of oxidation at the anode can distinguish between two types of fuel cell operating methods with lower fuel utilization. Some fuel cells achieve a low fuel utilization rate by recirculating a significant amount of anode output back to the anode input. This recycle may allow any of the anode inputs to be used again as an input to the anode. This can reduce the amount of reforming because at least a portion of the unused fuel is recycled for use in subsequent passes even if the fuel utilization rate is low when the fuel cell is passed through once. Therefore, a fuel cell having various fuel utilization values may have the same ratio of hydrogen oxidized in the reformable fuel to anode reaction delivered to the anode reforming stage (s). In order to change the ratio of the amount of oxidation at the anode to the amount of reformable fuel delivered to the anode reforming stage, it is necessary to identify the anode feed having a natural content of the fuel that can not be reformed, There is a need to reclaim for, or both.

Modifiable hydrogen excess ratio: Another option to characterize the operation of a fuel cell is based on a "reformable hydrogen excess ratio ". The above-defined modifiable fuel excess ratio is defined based on the calorific value of the reformable fuel component. The modifiable hydrogen excess ratio is defined as the modifiable hydrogen content of the reformable fuel that is delivered to the reforming stage followed by the anode and / or anode for the hydrogen reacting at the anode due to the fuel cell anode reaction. As such, the "reformable hydrogen excess ratio" can be calculated as (RFC (reformable_anode_in) / (RFC (reformable_anode_in) -RFC (anode_out)) where the reformable_anode_in is the reforming of the anode inlet stream, Refers to the possible hydrogen content, while RFC (anode_out) refers to the reformable hydrogen content of the anode inlet and outlet streams or the hydrotreating fuel components (e.g., H ₂ , CH ₄ and / or CO) Mol / hour, etc. An example of a method of operating a fuel cell with a large ratio of reformable fuel to anode amount of oxidation delivered to the anode reforming stage (s) is a balance of heat generation and consumption in the fuel cell The reforming of the reformable fuel to form H ₂ and CO is an endothermic reaction. The solution may counter the endothermic reaction, which generates an excess of heat (approximately) corresponding to the difference between the amount of heat generated by the anode oxidation reaction and the cathode reaction and the energy exiting the fuel cell in the form of current Excess heat per mole of hydrogen contained in the anode oxidation reaction / cathode reaction may be greater than the heat absorbed by the reforming to produce 1 mole of hydrogen. As a result, the fuel cell, which operates under conventional conditions, Instead of this type of conventional operation, it is possible to increase the amount of fuel to be reformed in the reforming stage that accompanies the anode. For example, it may be caused by an exothermic fuel cell reaction So that the heat being consumed by the reforming can be (almost) balanced with the heat consumed in the reforming, or even the heat consumed by the reforming, So that the temperature drop across more than the excess amount of heat across the fuel cell can be generated which can be modified for additional fuel, which may produce a considerable excess of hydrogen compared to the amount necessary for power generation. As an example, the anode inlet of the fuel cell or the feed to the subsequent reforming stage may be substantially composed of a reformable fuel, such as a substantially pure methane feed. While operating in a conventional manner to generate electricity using these fuels, the solid oxide fuel cell can be operated at a fuel utilization rate of about 75%. This means that about 75% (or ¾) of the fuel content delivered to the anode is used to form hydrogen, which reacts with oxygen ions at the anode to form H ₂ O. In conventional operation, the remaining approximately 25% of the fuel content is reformed into H ₂ in the fuel cell (or may pass through the fuel cell unreacted in the case of any CO or H ₂ in the fuel) And can be externally burned to form H ₂ O to provide heat to the cathode inlet to the fuel cell. In this situation, the reformable hydrogen excess ratio may be 4 / (4-1) = 4/3.

Electrical Efficiency: As used herein, the term "electrical efficiency"("EE") is defined as the electrochemical power produced by a fuel cell divided by the low calorific value ("LHV") ratio of the fuel input to the fuel cell. The fuel input to the fuel cell includes both the fuel delivered to the anode, as well as any fuel used to maintain the temperature of the fuel cell (e.g., fuel delivered to the fuel cell). In this description, the power generated by the fuel can be described in terms of the LHV (el) fuel rate.

Electrochemical Power: As used herein, the term "electrochemical power" or LHV (el) is the power generated by a circuit in a fuel cell that connects a cathode to an anode and transports carbonate ions across the electrolyte of the fuel cell. The electrochemical power excludes the power generated or consumed by equipment located in front of or behind the fuel cell. For example, the current generated from heat in the fuel cell exhaust stream is not considered part of the electrochemical power. Similarly, the power generated by a gas turbine or other device located in front of the fuel cell is not part of the generated electrochemical power. "Electrochemical power" does not take into account the power consumed during operation of the fuel cell, or take into account any losses caused by the conversion of the direct current to alternating current. In other words, the power supplied to the fuel cell operation or otherwise used to operate the fuel cell is not subtracted from the DC voltage generated by the fuel cell. The power density used herein is the current density multiplied by the voltage. As used herein, the term total fuel cell power is the power density multiplied by the fuel cell area.

Fuel Input : The term "anode fuel input", as used herein, referred to as LHV (anode_in), is the amount of fuel in the anode inlet stream. The term "fuel input " referred to as LHV (in) is the total amount of fuel delivered to the fuel cell, including both the amount of fuel in the anode inlet stream and the amount of fuel used to maintain the temperature of the fuel cell. The fuel may include both a reformable fuel and a non-reformable fuel based on the definition of the reformable fuel provided herein. Fuel inputs are not the same as fuel utilization.

Total Fuel Cell Efficiency: The term "total fuel cell efficiency"("TFCE") as used herein refers to the ratio of the electrochemical power generated by the fuel cell to the LHV of the syngas produced by the fuel cell to the fuel input LHV < / RTI > 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) and LHV (sg net) indicates the rate at which the synthesis gas (H ₂ , CO) is produced at the anode, which is the difference between the synthesis gas input to the anode and the synthesis gas output from the anode. LHV (el) describes the electrochemical evolution of fuel cells. Total fuel cell efficiency excludes heat generated by the fuel cell, which is advantageously used outside the fuel cell. In operation, the heat generated by the fuel cell can be advantageously used by devices located behind the process. For example, heat can be used to generate additional electricity or to heat water. When used separately from the fuel cell, these applications are not part of the total fuel cell efficiency when this term is used herein. Total fuel cell efficiency only applies to fuel cell operation and does not include power generation, or consumption before or after the fuel cell.

Chemical Efficiency: As used herein, the term "chemical efficiency" is defined as the LHV (sg out) of H ₂ and CO in the anode exhaust of a fuel cell divided by the fuel input or LHV (in).

Electricity efficiency and total system efficiency also do not take into account the efficiency of processes located either before or after the process. For example, it may be advantageous to use the turbine exhaust gas as the source of CO ₂ of the fuel cell cathode. In this arrangement, the efficiency of the turbine is not considered to be part of the calculation of electric efficiency or total fuel cell efficiency. Similarly, the output of the fuel cell can be recycled as an input to the fuel cell. Recirculation loops are not considered when calculating the electrical efficiency or the total fuel cell efficiency in a one-pass mode.

Synthetic gas produced: The term "produced syngas" as used herein is the difference between a syngas input to the anode and a synthesis gas output from the anode. The syngas can be used, at least in part, as an anode charge or fuel. For example, the system may include an anode recycle loop that returns syngas from the anode exhaust gas to the anode inlet (where syngas is supplemented with natural gas or other suitable fuel). Wherein the LHV (sg in) and LHV (sg out) are the LHV of the synthesis gas at the anode inlet and the LHV of the anode at the anode inlet, respectively, Gt; LHV < / RTI > of the syngas in the outlet stream or flow. It is noted that at least some of the syngas produced by the reforming reaction in the anode can typically be used in the anode to generate electricity. Hydrogen used to generate electricity is not included in the definition of "produced syngas" since it does not exit the anode. As used herein, the term "syngas ratio" is the LHV, or LHV (sg net) / LHV (anode in), of the produced pure syngas divided by the LHV of the fuel input to the anode. The molar flow rate of the syngas and fuel can be used instead of LHV to express the resulting syngas based on the molar-based syngas ratio and on the molar basis.

Water vapor to carbon ratio (S / C): The steam to carbon ratio (S / C) used herein is the molar ratio of water vapor in flow to reformable carbon in flow. Carbon in the form of CO and CO ₂ is not included in the reformable carbon in this definition. The water vapor to carbon ratio can be measured and / or controlled at different points in the system. For example, the composition of the anode inlet water vapor can be manipulated to obtain S / C suitable for reforming at the anode. S / C can be given as the molar flow rate of H ₂ O divided by the product of the molar flux of fuel and the number of carbon atoms in the fuel (for example, one for methane). Therefore, in the _{S / C = f H20 / (} f CH4 × # C) and, here, f _H2O is the molar flow rate of water, f _CH4 is the mole flow rate of methane (or other fuel), #C is the carbon in the fuel Number. In various embodiments, the S / C can be about 2, or about 1 to about 3, or about 0.5 to about 5. It is desirable to provide enough steam to meet the stoichiometry of the reforming reaction and to prevent contamination because excessive water vapor energizes to dilute and generate the anode reactants.

Fuel Cell and Fuel Cell Components: In this discussion, a fuel cell may correspond to a single cell having an anode and a cathode separated by an electrolyte. The solid oxide fuel cell may take a planar or tubular form. The fuel cell as used herein may refer to either one or both forms. The anode and cathode can accept an incoming gas flow to facilitate individual anode and cathode reactions for charge transport and generation across the electrolyte. The fuel cell stack may represent a plurality of cells in an integrated unit. Although the fuel cell stack can include a plurality of fuel cells, the fuel cells can typically be connected in parallel and (almost) the whole can act as a single size fuel cell. When the input flow is transferred to the anode or cathode of the fuel cell stack, the fuel cell stack may include a flow channel for dividing the incoming flow between each cell of the stack and a flow channel for combining the output flow from the individual cells . In this discussion, a plurality of fuel cells (e.g., a plurality of fuel cell stacks) arranged in series, in parallel, or in any other convenient manner (e.g., in series and parallel combination) Lt; / RTI > The fuel cell array may include one or more stages of a fuel cell and / or a fuel cell stack, wherein the anode / cathode output from the first stage may serve as an anode / cathode input of the second stage . Note that the anode of the fuel cell array need not be connected in the same manner as the cathode of the array. Conveniently, the input of the fuel cell array to the first anode stage may be referred to as the anode input of the array, and the input to the first cathode stage of the fuel cell array may be referred to as the cathode input of the array. Similarly, the output from the final anode / cathode stage may be referred to as the anode / cathode output from the array.

It should be appreciated that references to the use of fuel cells herein typically refer to the "fuel cell stack" consisting of individual fuel cells, and more generally to the use of one or more fuel cell stacks in fluid communication. Individual fuel cell elements (plates or cylinders) can be "laminated" together in a rectangular array, typically referred to as a "fuel cell stack ". The fuel cell stack may typically have a feed stream, distribute the reactants among all the individual fuel cell elements, and collect the product from each of these elements. When viewed as a unit, the fuel cell stack to be operated can be taken as a whole despite being composed of a plurality of (often dozens or hundreds) individual fuel cell elements. These individual fuel cell elements can typically have similar voltages (because reactants and product concentrations are similar), and the total power output is calculated from the sum of all currents at all battery elements when the elements are electrically connected in series Lt; / RTI > The stacks may also be arranged in a tandem arrangement to produce a high voltage. The parallel arrangement can boost the current. When treating a given flow with a sufficiently large volume of the fuel cell stack, the systems and methods described herein can be used with a single solid oxide fuel cell stack. In another aspect of the invention, a plurality of fuel cell stacks may be desirable or necessary for various reasons.

In the present invention, unless otherwise specified, the term "fuel cell" refers to a reference to a fuel cell stack consisting of a set of one or more individual fuel cell elements in which a single input and output are present, (Since this is how the fuel cell is typically used in practice). Similarly, it should be appreciated that the term fuel cell (s) is defined to refer to / indicate or include a plurality of separate fuel cell stacks, unless otherwise specified. In other words, all citations within this disclosure may interchangeably refer to the operation of the fuel cell stack as a "fuel cell" unless otherwise specifically indicated. For example, the volume of exhaust gas generated by a commercial scale combustion generator may be too large to be processed by a conventional sized fuel cell (e.g., a single stack). To treat the entire exhaust gas, a plurality of fuel cells (i.e., two or more separate fuel cells or fuel cell stacks) may be arranged in parallel to allow each fuel cell to treat (approximately) the same amount of combustion exhaust gas have. Although multiple fuel cells can be used, each fuel cell can typically be operated in a substantially similar manner given (approximately) the same amount of combustion exhaust gas.

"Internal reforming" and "external reforming": The fuel cell or fuel cell stack may include one or more internal reforming zones. As used herein, the term "internal reforming" refers to fuel reforming occurring in a fuel cell body, a fuel cell stack, or alternatively, a fuel cell assembly. External reforming, often used with fuel cells, is performed in a separate device located outside the fuel cell stack. In other words, the external reformer body is not in direct physical contact with the fuel cell or the body of the fuel cell stack. In a typical setup, an output from an external reformer can be supplied to the anode inlet of the fuel cell. Unless specifically stated otherwise, the modifications described herein are internal modifications.

Internal reforming may occur within the fuel cell anode. The internal reforming may additionally or alternatively be carried out in an internal reforming element incorporated in the fuel cell assembly. The integrated reforming element may be located between the fuel cell elements within the fuel cell stack. In other words, one of the trays of the stack may be a reforming zone instead of the fuel cell element. In one embodiment, the flow arrangement within the fuel cell stack directs fuel into the internal reforming element and then into the anode portion of the fuel cell. Therefore, from the viewpoint of flow, the internal reforming element and the fuel cell element can be arranged in series in the fuel cell stack. The term "anode reforming" as used herein is a fuel reforming done in the anode. As used herein, the term "internal reforming" is a modification that takes place in the integrated reforming element, not in the anode region.

In some aspects, a reforming stage that is internal to the fuel cell assembly can be thought of as being carried on the anode (s) in the fuel cell assembly. In some other embodiments, in the case of a reforming stage of a fuel cell stack that can be accompanied by an anode (e.g., to be associated with a plurality of anodes), a flow path may be used so that the output flow from the reforming stage passes into one or more anodes. This may correspond to having an initial zone of the fuel cell plate that is not in contact with the electrolyte and instead serves as a reforming catalyst. Another option of the subsequent reforming stage may be to have a separate integrated reforming stage as one of the elements of the fuel cell stack wherein the product from the integrated reforming stage is returned to the input side of one or more fuel cells of the fuel cell stack do.

From the heat integration point of view, the characteristic height of the fuel cell stack can be the height of the individual fuel cell stack elements. Note that a separate reforming stage or a separate endothermic reaction stage may have a different height than the fuel cell in the stack. In such a scenario, the height of the fuel cell element can be used as the characteristic height. In some embodiments, an integrated endothermic reaction stage can be defined as a stage that is thermally integrated with one or more fuel cells, such that the integrated endothermic reaction stage can use heat from the fuel cell as a heat source for reforming. This integrated endothermic reaction stage can be defined as being located less than five times the height of the stack element from any fuel cell that provides heat to the integrated stage. For example, an integrated endothermic reaction stage (e.g., a reforming stage) may be located less than five times the height of the stack element from any heat-integrated fuel cell, for example, less than three times the height of the stack element . In this discussion, an integrated reforming stage or an integrated endothermic reaction stage that represents a stack element adjacent to the fuel cell element can be defined as less than or equal to about one stack element height away from an adjacent fuel cell element.

In some embodiments, a separate reforming stage that is thermally integrated with the fuel cell element may also correspond to a reforming stage followed by the fuel cell element. In such an embodiment, the integrated fuel cell element may provide at least a portion of the heat to the subsequent reforming stage, and the subsequent reforming stage may provide at least a portion of the reforming stage output to the integrated fuel cell as a fuel stream. In another aspect, a separate reforming stage can be integrated with the fuel cell for heat exchange without involving the fuel cell. In this type of situation, a separate reforming stage can accept heat from the fuel cell, but does not use the product of the reforming stage as an input to the fuel cell. Instead, the output of such a reforming stage can be used for other purposes such as adding the product directly to the anode exhaust gas stream or forming a separate output stream from the fuel cell assembly.

More generally, a separate stack element of the fuel cell stack can be used to perform any convenient type of endothermic reaction that can take advantage of the waste heat provided by the integrated fuel cell stack element. Instead of a plate suitable for carrying out the reforming reaction on the hydrocarbon fuel stream, a separate stack element may have a plate suitable for promoting another type of endothermic reaction. Different arrangements of manifolds or inlet conduits of the fuel cell stack can be used to provide a suitable input flow to each stack element. Other manifolds of similar manifolds or outlet conduits may also be used to recover the output flow from each stack element. 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 this optional embodiment, therefore, the product of the exothermic reaction leaves the fuel cell stack without passing through the fuel cell anode. Examples of other types of endothermic reactions that may be performed in the stack elements of a fuel cell stack include ethanol dehydration and ethane classification to form ethylene.

Recirculation: Recirculating a portion of the fuel cell output (eg, a stream separated or recovered from the anode exhaust gas or the anode exhaust gas) defined herein to the fuel cell inlet may correspond to a direct or indirect recycle stream. Direct recirculation of the stream to the fuel cell inlet is defined as recirculation of the stream that does not pass the intermediate process, while indirect recirculation includes recirculation after passing the stream through one or more intermediate processes. For example, if the anode exhaust gas passes through a CO ₂ separation stage before it is recirculated, it is thought to be indirect recirculation of the anode exhaust gas. If a portion of the anode exhaust gas, such as the H ₂ stream recovered from the anode exhaust gas, is passed into the vaporizer to convert the coal to fuel suitable for introduction into the fuel cell, this is also considered indirect recirculation.

Anode inputs and outputs

In various embodiments of the present invention, the SOFC arrays include, for example, hydrocarbons, such as hydrocarbons such as hydrocarbons or hydrocarbons, which may contain hydrogen and methane (or alternatively may contain heteroatoms other than C and H) Acceptable fuel can be supplied. The majority of methane (or other hydrocarbon or hydrocarbon compounds) fed to the anode may typically be fresh methane. In this document, new fuels, such as fresh methane, refer to fuels that are not recycled from other fuel cell processes. For example, methane recycled back to the anode inlet from the anode outlet stream can not be thought of as "fresh" methane, but instead can be described as regenerated methane. The fuel source used may be shared with other components, such as a turbine, using a portion of the fuel source. The fuel source input may include water in proportion to the fuel suitable to reform the hydrocarbon (or hydrocarbon) compound in the reforming zone that generates hydrogen. For example, if the fuel input for reforming to generate H ₂ is methane, the molar ratio of water to fuel may be from about 1: 1 to about 10: 1, such as greater than about 2: 1. A ratio of at least 4: 1 is typical for external reforming, but a lower value for internal reforming may be typical. To the extent that H ₂ is part of the fuel source, in some optional embodiments, no additional water may be required for the fuel, because the oxidation of H _{2 in} the anode tends to produce H ₂ O that can be used to modify the fuel This can happen. The fuel source may also optionally contain additional components to the fuel source (e.g., the natural gas feed may contain some CO ₂ content as an additional component). For example, the natural gas feed may contain CO ₂ , N ₂ , and / or another inert gas (noble gas) as an additional component. Optionally, in some embodiments, the fuel source may also contain CO, such as CO from the recycled portion of the anode exhaust gas. An additional or other possible source of CO in the fuel into the fuel cell assembly may be CO generated by steam reforming of the hydrocarbon fuel performed on the fuel prior to entering the fuel cell assembly.

More generally, various types of fuel streams may be suitable for use as an input stream of an anode of a solid oxide fuel cell. Some fuel streams may correspond to a stream containing hydrocarbons and / or compounds such as hydrocarbons which may also contain heteroatoms different from C and H. [ In this discussion, unless stated otherwise, the reference to a hydrocarbon-containing fuel stream for an SOFC anode is defined to include a fuel stream containing such a hydrocarbon-like compound. Examples of hydrocarbons (including compounds such as hydrocarbons) fuel streams include not only streams containing natural gas, C1-C4 carbon compounds (e.g., methane or ethane), and heavier C5 + hydrocarbons (including compounds such as hydrocarbons) And combinations thereof. Yet another or additional example of a fuel stream for use in the anode input may comprise a biogas-type stream such as methane produced from natural (biological) degradation of organic material.

In some embodiments, a solid oxide fuel cell can be used to treat a feed fuel stream, such as a natural gas and / or hydrocarbon stream, having a low energy content due to the presence of a diluent compound. For example, some sources of methane and / or natural gas are sources that can contain significant amounts of CO ₂ or other inert molecules (e.g., nitrogen, argon or helium). Due to the presence of increasing amounts of CO ₂ and / or inert compounds, the energy content of the fuel stream based on the source can be reduced. There may be difficulties in using a fuel with a low energy content in the combustion reaction (e.g., to provide power to a turbine that is powered by combustion). However, solid oxide fuel cells can generate power based on a fuel source with a low energy content, with little or no effect on the efficiency of the fuel cell. The presence of an additional gas volume may require additional heat to raise the temperature of the fuel to the temperature of the reforming and / or anode reaction. In addition, due to the equilibrium state characteristic of the aqueous gas-phonetic reaction in the fuel cell anode, the presence of additional CO ₂ can affect the relative amounts of H ₂ and CO present in the anode product. However, inert compounds can only have a direct effect on the reforming and the anode reaction. When present, the amount of CO ₂ and / or inert compound in the fuel stream of the solid oxide fuel cell may be greater than about 1 volume%, such as greater than about 2 volume%, or greater than about 5 volume%, or greater than about 10 volume% Or about 15% by volume, or about 20% by volume or more, or about 25% by volume or more, or about 30% by volume or more, or about 35% by volume or more, or about 40% by volume or more, or about 45% About 50% by volume or more, or about 75% by volume or more. Additionally or alternatively, the amount of CO ₂ and / or inert compound in the fuel stream of the solid oxide fuel cell may be up to about 90 vol%, such as up to about 75 vol%, or up to about 60 vol%, or up to about 50 vol% Or about 40% by volume, or about 35% by volume or less.

Another example of a possible source for the anode input stream may correspond to refining and / or other industrial process output streams. For example, coking is a common process in many refinements to convert heavy compounds into a low-cost range. Coking typically produces an off-gas containing various compounds that are gases at room temperature, including CO and various < RTI ID = 0.0 > C1-C4 < / RTI > hydrocarbons. This off-gas can be used as at least a portion of the anode input stream. Other scouring off-gas streams, such as hard-terminated (C1-C4), generated during sorting or other scouring processes may additionally or alternatively be suitable for inclusion in the anode input stream. Another suitable refining stream may additionally or alternatively comprise a CO or CO ₂ -containing refining stream containing H ₂ and / or a reformable fuel compound.

Other possible sources of anode input may additionally or alternatively comprise a stream of high water content. For example, an ethanol output stream from an ethanol plant (or other type of fermentation process) may contain significant amounts of H ₂ O prior to final distillation. Such H ₂ O can typically only have a minimal impact on the operation of the fuel cell. Therefore, a fermentation mixture of alcohol (or other fermentation product) and water may be used as at least a portion of the anode input stream.

The biogas, or digester gas, is an additional or other possible source of anode input. Biogas can include mainly methane and CO ₂ , and is typically produced by destruction or digestion of organic materials. Anaerobic bacteria can be used to digest organic materials and produce biogas. Impurities such as sulfur-containing compounds may be removed from the biogas prior to use as the anode input.

The output stream from the SOFC anode may contain H ₂ O, CO ₂ , CO and H ₂ . Optionally, the anode output stream may also have unreacted fuel (e.g., H ₂ or CH ₄ ), or an inert compound in the feed as an additional output component. Instead of using this output stream as the fuel source providing heat for the reforming reaction or as the combustion fuel for heating the cell, one or more separations can be carried out on the anode output stream to provide an effluent stream as an input to another process such as H ₂ or CO CO ₂ can be separated from the expected value component. H ₂ and / or CO may be used as synthesis gas for chemical synthesis, as a hydrogen source, and / or the greenhouse gas emissions are reduced fuel for reaction.

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 may include the composition of the input stream to the anode, the amount of current generated by the fuel cell, and / or the temperature at the outlet of the anode. The temperature at the anode outlet may be related due to the equilibrium state characteristic of the water gas telephone reaction. In a typical anode, one or more of the plates forming the walls of the anode may be suitable for promoting the water gas-phonetic reaction. B) knowing the degree of modification of the reformable fuel in the anode input stream; c) determining the amount of oxygen ions transported from the cathode to the anode (corresponding to the amount of generated current) , The composition of the anode output can be determined based on the equilibrium constant of the water gas conversion reaction:

K _eq = [CO ₂ ] [H ₂ ] / [CO] [H ₂ O]

In the above equation, K _eq is the equilibrium constant of the reaction at a predetermined temperature and pressure, and [X] is the partial pressure of the component X. On the basis of the water gas-phosphating reaction, increased CO ₂ concentration in the anode charge may tend to cause additional CO formation (consuming H ₂ ), while increased H ₂ O concentration causes additional H ₂ formation (CO Of the total amount of money spent).

To determine the composition in the anode output, the composition of the anode input may be used as a starting point. This composition can then be varied to reflect the degree of modification of any reformable fuel that may occur in the anode. Such a modification can reduce the hydrocarbon content of the anode charge instead of increasing the hydrogen and CO ₂ . Then, based on the amount of current generated, the amount of H _{2 in} the anode charge can be reduced instead of the additional H ₂ O and CO ₂ . The outlet concentration of H ₂ , CO, CO _2, and H ₂ O can then be determined by adjusting this composition based on the equilibrium constant of the water gas conversion reaction.

In various embodiments, the operating temperature of the SOFC may be selected to obtain the desired ratio of H ₂ , CO, and CO ₂ in the syngas product. The operating temperature may be selected to produce a syngas having a ratio suitable for use in the intended process. In one embodiment, the operating temperature may be between about 700 ° C and 1200 ° C, for example the operating temperature may be about 800 ° C, about 900 ° C, about 1000 ° C, or about 1100 ° C.

Optionally, if desired, one or more aqueous gas-phased reaction stages may be provided after conversion of CO and H ₂ O in the anode product to CO ₂ and H ₂ . For example, the amount of H ₂ present in the anode product can be increased by converting H ₂ O and CO present in the anode product to H ₂ and CO ₂ using a water gas-catalyzed reactor at a lower temperature. Since the SOFC can be operated at about 700 ° C to 1200 ° C, it may be particularly desirable to assist the water gas-phonetic reaction when cooling the anode product for use in subsequent processes. Alternatively, more CO and H ₂ O can be generated from H ₂ and CO ₂ by increasing the temperature and reserving the water gas-phonetic reaction. Water is an expected output of the reaction occurring in the anode, and thus the anode output typically can have an excess of H ₂ O relative to the amount of CO present in the anode product. Alternatively, H ₂ O can be added to the stream after exiting the anode, but before the water gas-phonetic reaction. CO is due to an equilibrium state equilibrium reaction between H ₂ O, CO, H ₂ and CO ₂ (ie, water gas equilibrium state) due to incomplete carbon conversion during the reforming and / or under the conditions present during the reforming conditions or the anode reaction May be present in the anode product. The water gas telephone reactor can be operated under conditions that lead to equilibrium in the direction of forming CO ₂ and H ₂ at the expense of CO and H ₂ O. Higher temperatures may have a favorable tendency to form CO and H ₂ O. Thus, one option for operating the water gas telephone reactor is to add an anode output stream at a suitable temperature, for example, from about 190 ° C to about 210 ° C, to a catalyst including a suitable catalyst, such as iron oxide, zinc oxide, It can be exposed. Optionally, the water gas-telephone reactor is equipped with two stages for reducing the CO concentration in the anode output stream, namely a first high temperature stage operating at about 300 ° C to about 375 ° C, and a second high temperature stage at about 225 ° C or lower, Lt; 0 > C to about 210 < 0 > C. In addition to increasing the amount of H ₂ present in the anode effluent, the water gas-phonetic reaction can additionally or alternatively increase the amount of CO _{2 at} the expense of CO ₂ . This can be exchanged with carbon dioxide, the hard carbon monoxide (CO) to remove carbon dioxide can be more readily removed by condensation (e.g., cryogenic removal), chemical reaction (e.g., amine removed) and / or other CO ₂ removal have. Add or otherwise include, and to increase the amount of CO present in the anode exhaust gas may be desirable in order to obtain the desired ratio of H ₂ to CO dae.

After passing through an optional aqueous gas-phased reaction stage, the anode product can be passed to one or more separation stages for removing 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 on the anode output using one or more methods, either separately or together. Using this method, it is possible to produce a 90% by volume or more, for instance 95 vol% or 98 vol% or more of CO ₂ output stream having a CO ₂ content (s). This method can save more than 70% of the CO ₂ content of the anode outputs, for example, about 80% of the CO ₂ content of the anode outputs, or at least about 90% or more. Alternatively, in some embodiments, it may be desirable to recover at least a portion of the CO ₂ in the anode output stream, wherein the recovered CO ₂ portion is from about 33% to about 90% of the CO _{2 in} the anode product, 40% or more, or about 50% or more. For example, it may be desirable to have some CO ₂ in the anode output stream so that the desired composition can be achieved in a subsequent aqueous gas telephone stage. Suitable separation methods include, but are not limited to, physical solvents (e.g., Selexol ™ or Rectisol ™); Amine or other base (e.g., MEA or MDEA); Freezing (e. G., Cryogenic separation); Pressure swing adsorption; Vacuum swing adsorption; And combinations of these. A cryogenic CO ₂ separator may be an example of a suitable separator. As the anode product cools, most of the water in the anode product can be separated as a condensed (liquid) phase. Additional cooling and / or pressurization of the water-depleted anode output stream can separate high purity CO ₂ , since other residual components of the anode output flow (eg, H ₂ , N ₂ , CH ₄ ) It tends not to be easily formed. The cryogenic CO ₂ separator can recover from about 33% to about 90% of the CO ₂ present in the flow depending on operating conditions.

Before CO ₂ separation, during or after performing a separate CO ₂ CO ₂ separation, to removing water from the anode exhaust gas to form one or more output streams of water may also be advantageous. The amount of water in the anode effluent may vary depending on the operating conditions selected. For example, the water vapor-to-carbon ratio established at the anode inlet can affect the water content in the anode exhaust, since high water vapor-to-carbon ratios are typically unreacted and / or due to water gas equilibrium at the anode Thereby generating a large amount of water that can pass through the anode while being reacted. According to an embodiment, the water content in the anode exhaust gas may correspond to at least about 30% of the volume of the anode exhaust gas. Alternatively or in addition, the water content can be about 80% or less of the volume of the anode exhaust gas. Such water can be removed by cooling due to condensation that is compressed and / or produced, but removal of such water may require additional compressor power and / or heat exchange surface area and excess cooling water. One advantageous way of removing a portion of this excess water is to capture moisture from the humid anode effluent and to be " regenerated " using dry anode feed gas to provide additional water to the anode feed Lt; RTI ID = 0.0 > adsorbent. ≪ / RTI > HVAC-style (heating, venting and air conditioning) adsorption wheel designs can be applied because the anode exhaust gas and inlet can be similar in pressure and the minute leaks from one stream to the other stream Because it can have a minimal impact on. In embodiments where CO ₂ removal is performed using a cryogenic process, removal of water prior to or during CO ₂ removal, including removal by a triethylene glycol (TEG) system and / or a desiccant, may be desirable. In contrast, in the case of using an amine wash to remove CO _2, the process can be later than the CO ₂ removal stage to remove the water from the anode exhaust gas.

Unlike or in addition to the CO ₂ output stream and / or the water output stream, the anode output can be used to form one or more product streams containing the desired compound or fuel product. These product streams or streams may correspond to a syngas stream, a hydrogen stream, or both a syngas product and a hydrogen product stream. For example, a hydrogen product stream may be formed that contains at least about 70 vol% H ₂ , such as at least about 90 vol% H ₂ or at least about 95 vol% H ₂ . Additionally or alternatively, a syngas stream containing a total of about 70% by volume of H ₂ and CO, for example about 90% by volume of H ₂ and CO, can be formed. The at least one product stream may have a gas volume corresponding to at least about 75% by volume of the combined H ₂ and CO gas volumes in the anode product, such as at least about 85% or about 90% of the combined H ₂ and CO gas volumes have. It is noted that the relative amounts of H ₂ and CO in the product stream may differ from the H ₂ to CO ratio in the anode product based on the use of a water gas conversion stage to convert between products.

In some embodiments, it may be desirable to remove or separate a portion of the H ₂ present in the anode product. For example, in some embodiments, the H ₂ to CO ratio in the anode exhaust gas may be greater than about 3.0: 1. In contrast, processes using syngas such as Fischer-Tropsch synthesis can consume H ₂ and CO at different ratios, such as a ratio close to 2: 1. One alternative could be to use a water gas-to-gas conversion to change the content of the anode output to have a H ₂ to CO ratio that is closer to the desired syngas composition. Another alternative could be to use membrane separation to remove a portion of the H ₂ present in the anode product to obtain the desired H ₂ to CO ratio, or alternatively to utilize a combination of membrane separation and water gas-phonetic reaction. One advantage of using membrane separation to remove only a portion of the H _{2 in} the anode output may be that it is capable of performing the desired separation under relatively mild conditions. Pure hydrogen permeate can be produced by membrane separation without the need for extreme conditions, since one objective may still be to produce a retentate with a substantial H ₂ content. For example, rather than having a pressure of about 100 kPa or less (e.g., ambient pressure) on the permeate side of the membrane, the permeate side may be at pressurization rather than ambient pressure while still having sufficient driving force to perform membrane separation. Additionally or alternatively, a sweep gas such as methane may be used to provide a driving force for membrane separation. This may reduce the purity of the H ₂ permeate stream, but may be advantageous depending on the intended use of the permeate stream.

In various embodiments of the present invention, at least a portion of the anode exhaust gas stream (preferably after separation of CO ₂ and / or H ₂ O) may be used as a process external to the fuel cell and as a feed to the subsequent reforming stage. In various embodiments, the anode exhaust gas may have a ratio of H ₂ to CO of at least 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: . A syngas stream can be generated or recovered from the anode exhaust gas. Optionally, after separation of CO ₂ and / or H ₂ O and optionally also water gas-phonetic reaction and / or membrane separation to remove excess hydrogen, the anode exhaust gas contains a significant amount of H ₂ and / or CO ≪ / RTI > In the case of a stream having a relatively low CO content, such as a stream having a H ₂ to CO ratio of about 3: 1 or greater, the anode exhaust gas may be suitable for use as an H ₂ feed. Examples of processes that can take advantage of H ₂ feeds include, but are not limited to, a refining process, an ammonia synthesis plant, a turbine in a (different) power generation system, or a combination thereof. Depending on the application, lower CO ₂ content may be desirable. In the case of a stream having a H ₂ to CO ratio of less than about 2.2: 1 and greater than about 1.9: 1, the stream may be suitable for use as a syngas feed. Examples of processes that can take advantage of syngas feeds include gas liquefied fuel plants (e.g., plants that use a Fischer-Tropsch process with a non-conversion catalyst) and / or methanol synthesis plants, But are not limited thereto. The amount of anode exhaust gas used as a feed for the external process may be any convenient amount. Optionally, if some of the anode exhaust is used as a feed for an external process, it may be recycled to the combustion zone of a generator that recycles the second portion of the anode exhaust gas to the anode charge and / have.

A feed stream useful in different types of Fischer-Tropsch synthesis processes can provide an example of a different type of product stream that may be desired to be produced from the anode product. In a Fischer-Tropsch synthesis reaction system using a morphology catalyst such as an iron-based catalyst, the desired feed stream to the reaction system may include CO ₂ in addition to H ₂ and CO. If a sufficient amount of CO ₂ is not present in the feed stream, the Fischer-Tropsch catalyst with water gas-phos- phoretic activity can produce a syngas that may be lacking in CO by consuming CO to produce additional CO ₂ . In order to integrate this Fischer-Tropsch process with the SOFC fuel cell, the separation stage of the anode product can be operated to maintain the desired amount of CO ₂ (and optionally H ₂ O) in the syngas product. In contrast, in the case of a Fischer-Tropsch catalyst based on a non-transformed 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 swept with a sweep gas such as a methane sweep gas, the methane sweep gas may correspond to the methane stream used as an anode fuel or in a different low pressure process such as a boiler, furnace, gas turbine or other fuel-consuming device. In this embodiment, low CO ₂ permeation levels across the membrane can have minimal results. Such CO _2, which may be permeated across the membrane, may have minimal effect on the reaction in the anode, and such CO ₂ may remain retained in the anode product. Therefore, CO ₂ (if present) lost across the membrane due to permeation need not be passed back across the SOFC electrolyte. This can greatly reduce the separation selectivity condition in the hydrogen permeable membrane. This makes it possible, for example, to use a higher permeability membrane with lower selectivity, which makes it possible to utilize lower pressure and / or reduced membrane surface area. In this aspect of the invention, the volume of the sweep gas can be several times the volume of hydrogen in the anode exhaust gas, which can keep the effective hydrogen concentration on the permeate side close to zero. The thus separated hydrogen can be incorporated into the turbine-fed membrane, which can improve the turbine combustion characteristics as described above.

Excess H ₂ generated at the anode is noted that the number represent a greenhouse gas that is already separated fuel. Any CO ₂ from the anode output, for example by using an amine wash, the cryogenic CO ₂ separator and / or a pressure or vacuum swing adsorption processes can be easily separated from the anode product. Some of the components (H ₂ , CO, CH ₄ ) of the anode product are not easily removed, whereas CO ₂ and H ₂ O can usually be easily removed. According to an embodiment, at least about 90% by volume of CO _{2 in} the anode effluent can be separated to form a relatively high purity CO ₂ output stream. Therefore, any CO ₂ generated in the anode can be efficiently separated to form a high purity CO ₂ -containing stream. After separation, the remainder of the anode product may correspond to a reduced amount of CO ₂ and / or H ₂ O, as well as components having predominantly chemical and / or calorific value values. Since a significant amount of CO ₂ produced by the original fuel (before reforming) may have been isolated, the amount of CO ₂ generated by subsequent combustion of the remainder of the anode output may be reduced. In particular, additional greenhouse gases may not typically be generated by the combustion of this fuel, up to the limit that the fuel of the remainder of the anode output is H ₂ .

The anode exhaust gas can be applied to a variety of gas processing options including water gas phones and separation of components from each other. Two general anode processing methods are shown in Figures 1 and 2.

Figure 1 schematically illustrates an example of a reaction system for operating a fuel cell array of a solid oxide fuel cell with a chemical synthesis process. 1 supplies a fuel stream 105 to a reforming stage (or stages) 110 that is followed by an anode 127 of a fuel cell 120 such as a fuel cell that is part of the fuel cell stack in a fuel cell array. The reforming stage 110 that accompanies the fuel cell 120 may be inside the fuel cell assembly. In some optional embodiments, an external reforming stage (not shown) may also be used to reform some of the reformable fuel in the input stream before the input stream passes into the fuel cell assembly. The fuel stream 105 may preferably comprise a reformable fuel such as methane, other hydrocarbons and / or other compounds such as hydrocarbons (e.g., organic compounds containing carbon-hydrogen bonds). The fuel stream 105 may also contain H ₂ and / or CO, such as H ₂ and / or CO, optionally provided by an optional anode recycle stream 185. The anode recycle stream 185 is optional and may in some embodiments be indirectly recirculated from the anode exhaust gas 125 directly to the anode 127 or through a combination of the fuel stream 105 or the reformed fuel stream 115 Lt; / RTI > is not provided. After reforming, the reformed fuel stream 115 may be passed into the anode 127 of the fuel cell 120. The O ₂ -containing stream 119 may also be passed into the cathode 129. Oxygen ions from the cathode portion 129 of the fuel cell 122, the flow of O ₂ ^2- may provide the remaining reactant required for the fuel cell anode reaction. Based on the reaction at the anode 127, the generated anode exhaust gas 125 is converted to H ₂ O, one or more components corresponding to the incompletely reacted fuel (H ₂ , CO, CH ₄ , , And optionally one or more additional non-reactive components such as N ₂ and / or other contaminants that are part of the fuel stream 105. The anode exhaust gas 125 may then be passed into one or more separation stages. For example, the CO ₂ removal stage 140 may include a cryogenic CO ₂ removal system, an amine cleaning stage to remove acid gas, such as CO ₂ , or another suitable type for separating the CO ₂ output stream 143 from the anode exhaust gas Lt; RTI ID = 0.0 > CO ₂ < / RTI > separation stage. Optionally, the anode exhaust gas may first be passed through a water gas-catalyzed reactor 130 to provide any CO (with some H ₂ O) present in the anode exhaust gas, optionally an aqueous exhaust gas 135 ) To CO ₂ and H ₂ . Depending on the nature of the CO ₂ removal stage, a water condensation or removal stage 150 may be preferred to remove the water output stream 153 from the anode exhaust gas. Although shown in FIG. 1 behind the CO ₂ separation stage 140 in a processable manner, it may optionally be located in front of the CO ₂ separation stage 140 in front of the process. In addition, it is possible to use the optional membrane separation stage 160 for separating the H ₂ produced a high purity permeate stream 163 of H _2. The resulting retentate stream 166 may then be used as an input to the chemical synthesis process. Stream 166 is additionally or alternatively dialyzed in a second water gas telephony reactor 131 to adjust the H ₂ , CO and CO ₂ content to different ratios to produce an output stream 168 for further use in the chemical synthesis process Can be generated. Although anode recycle stream 185 is shown as being withdrawn from retentate stream 166 in Figure 1, anode recycle stream 185 may also or alternatively be withdrawn from various convenient stages, Can be recovered. The separation stage and the telephone reactor (s) may also or alternatively be arranged in different orders and / or in a parallel configuration. Finally, a stream 139 having a reduced O ₂ content can be generated as an output from the cathode 129. For simplicity, not only the various stages of compression and heat addition / removal useful in the process but also the addition or removal of water vapor are not shown.

As indicated above, various types of separations performed on the anode exhaust gas may be performed in any convenient order. Figure 2 shows an example of another sequence of performing separation on the anode exhaust gas. In FIG. 2, the anode exhaust gas 125 may first be passed into the separation stage 260 for removing a portion 263 of hydrogen content from the anode exhaust gas 125. This can, for example, reduce the H ₂ content of the anode exhaust gas to provide a retentate 266 with a ratio of H ₂ to CO close to 2: 1. The ratio of H ₂ to CO in the water gas telephone stage 230 can then be further adjusted to obtain the desired value. The water gas product 235 is then passed through a CO ₂ separation stage 240 and a water removal stage 250 to produce an output stream 275 suitable for use as the input to the desired chemical synthesis process. have. Optionally, the output stream 275 may be exposed to an additional water gas telephone stage (not shown). A portion of the output stream 275 may optionally be recycled to the anode input (not shown). Of course, another separation stage combination and sequence can be used to generate a stream based on the anode product with the desired composition. For simplicity, not only the various stages of compression and heat addition / removal useful in the process but also steam addition or removal are not shown.

Cathode inputs and outputs

Typically, the solid oxide fuel cell can be operated based on the desired load while consuming a portion of the fuel in the fuel stream delivered to the anode. The voltage of the fuel cell can be determined by the load, the fuel input to the anode, the air and O ₂ supplied to the cathode, and the internal resistance of the fuel cell. By removing any direct connection between the anode charge flow and the composition of the cathode charge flow, the fuel cell can be operated, in particular, to generate and / or to increase the excess syngas or to improve the total efficiency (electricity + chemical power) Additional options become available.

The amount of O ₂ present in the cathode feed stream may advantageously be sufficient to provide the oxygen required for the cathode reaction of the fuel cell. Therefore, the volume percentage of O ₂ may advantageously be at least 0.5 times the amount of O _{2 in} the cathode exhaust gas. Optionally, additional air can be added to the cathode feed, if desired, to provide sufficient oxidant for the cathode reaction. When a portion of the air is used as the oxidizing agent, the amount of N _{2 in} the cathode exhaust gas may be at least about 78 vol%, such as at least about 88 vol%, and / or at most about 95 vol%. In some embodiments, the cathode input stream may additionally or alternatively contain a compound (e.g., H ₂ S or NH ₃ ), which is commonly regarded as a contaminant. In another embodiment, the cathode feed stream can be cleaned to reduce or minimize the content of such contaminants.

The conditions of the cathode may additionally or alternatively be adapted to convert the unburned hydrocarbons to typical combustion products such as CO ₂ and H ₂ O (with O _{2 in the} cathode feed stream).

Fuel cell arrangement

In various embodiments, the fuel cell array can be operated to improve or maximize the energy output of the fuel cell, such as total energy output, electrical energy output, syngas chemical energy output, or combinations thereof. For example, it is possible to operate a solid oxide fuel cell in a variety of situations, for example for the production of a syngas stream for use in a compound synthesis plant and / or for the production of a high purity hydrogen stream, have. The syngas stream and / or the hydrogen stream may be used as a syngas source, as a hydrogen source, as a clean fuel source, and / or in any other convenient application. In this embodiment, the amount of O _{2 in} the cathode exhaust gas may be related to the amount of O _{2 in} the cathode feed stream and the O ₂ utilization in the operating conditions required to improve or maximize the fuel cell energy output.

Solid oxide fuel cell operation

In one embodiment, the operating temperature of the SOFC may be between about 700 ° C and 1200 ° C, for example, the operating temperature may be about 800 ° C, about 900 ° C, about 1000 ° C, or about 1100 ° C. In one embodiment, the operating temperature may be selected to advance the WGS reaction in the anode to a desired ratio.

In some embodiments, the fuel cell may be operated in a single pass or perfusion mode. In the one pass system, the reformed product in the anode exhaust gas is not returned to the anode inlet. Therefore, in a single pass operation, some other products from syngas, hydrogen, or an anode product are not recycled directly to the anode inlet. More generally, in one pass operation, the reformed product in the anode exhaust gas is not indirectly returned to the anode inlet, for example, by treating the fuel stream subsequently introduced to the anode inlet using the modified product. In the one-pass mode, the heat from the anode exhaust gas or the product can be recycled, additionally or otherwise. For example, the anode output flow can be passed through a heat exchanger that cools the anode output and warms up an input stream of another stream, such as an anode and / or a cathode. The recirculation of heat from the anode to the fuel cell is consistent in one pass or perfusion operation. Optionally, but undesirably, the components of the anode product may be fired to provide heat to the fuel cell during the single pass mode.

Figure 3 shows a schematic example of the operation of an SOFC for generating power. In Figure 3, the anode portion of the fuel cell as the inputs can receive fuel and water vapor (H ₂ O), water, and optionally an excess of H _2, CH ₄ (or other hydrocarbon) and / or the output of the CO Respectively. The cathode portion of the fuel cell can accept O ₂ (e.g., air) as an input and has an output corresponding to an oxidant (air) depleted in O ₂ . In the fuel cell, O ₂ ^2- ions formed at the cathode side can be transported across the electrolyte to provide oxygen ions necessary for the reaction at the anode.

Several reactions can be made in a solid oxide fuel cell, such as the exemplary fuel cell shown in FIG. The reforming reaction may be arbitrary and the reforming reaction may be reduced or eliminated if sufficient H ₂ is provided directly to the anode. To the reaction but is based on CH _4, a similar reaction can take place when the other fuel is used in a fuel cell.

(1) <Anode modification> CH ₄ + H ₂ O => 3H ₂ + CO

(2) <water gas phone> CO + H ₂ O => H ₂ + CO ₂

(3) <Complex Modification and Water Gas Telephone> 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> ½O ₂ + 2e ^- => O ₂ ^2-

Reaction (1) represents a basic hydrocarbon reforming reaction that generates H ₂ for use in an anode of a fuel cell. The CO produced in reaction (1) can be converted to H ₂ by water gas-catalyzed reaction (2). The combination of reactions (1) and (2) is shown as reaction (3). Reactions (1) and (2) may occur outside the fuel cell and / or the reforming may be performed within the anode.

Reactions (4) and (5) in the anodes and cathodes, respectively, indicate reactions that can generate power in the fuel cell. Reaction (4) combines H ₂ generated by reactions (1) and / or (2) in the feed or optionally with oxygen ions to form H ₂ O and electrons to the circuit. Reaction (5) combines the electrons from O ₂ and the circuit to produce oxygen ions. The oxygen ions produced by the reaction (5) can be transported across the electrolyte of the fuel cell to provide the oxygen ions necessary for the reaction (4). With the transport of oxygen ions across the electrolyte, a closed current loop can be formed by providing an electrical connection between the anode and the cathode.

In various embodiments, the purpose of fuel cell operation may be to improve the total efficiency of the fuel cell and / or the total efficiency of the chemical synthesis process integrated with the fuel cell. This is in contrast to the conventional operation of a fuel cell, which may typically be aimed at operating the fuel cell with high electrical efficiency to use the fuel provided to the cell for power generation. As defined above, the total fuel cell efficiency can be determined by dividing the sum of the electricity generation of the fuel cell and the low calorific value of the fuel cell output by the low calorific value of the input component of the fuel cell. In other words, LHV (in) and LHV (sg out) are the fuel components transferred to the fuel cell (for example, H ₂ (in) , CH ₄ and / or CO) and the anode means the LHV of the outlet stream flow or synthesis gas (H _2, CO and / or CO ₂₎ of the. This can provide a measure of the sum of electrical and chemical energy generated by the fuel cell and / or the integrated chemical process. It is noted that under this definition of total efficiency, the thermal energy used in fuel cell / chemical synthesis systems used and / or integrated in fuel cells can contribute to total efficiency. However, any excess heat exchanged or otherwise recovered from a fuel cell or an integrated fuel cell / chemical synthesis system is excluded from this definition. Therefore, when excess heat is used from a fuel cell to generate water vapor, for example, for power generation by a steam turbine, this excess heat is excluded from the definition of total efficiency.

Several operating parameters can be manipulated to operate the fuel cell with an excess of modifiable fuel. Some parameters may be similar to the parameters currently recommended for fuel cell operation. In some embodiments, the cathode conditions and the temperature input to the fuel cell may 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 a solid oxide fuel cell over a typical fuel cell operating temperature range. In typical operation, the temperature can be increased across the fuel cell.

In another aspect, the operating parameters of the fuel cell may be deviated from typical conditions to operate the fuel cell such that the temperature is reduced from the anode inlet to the anode outlet and / or from the cathode inlet to the cathode outlet. For example, a reforming reaction that converts hydrocarbons to H ₂ and CO is an endothermic reaction. The net thermal equilibrium in the fuel cell may be endothermic if a sufficient amount of modification relative to the oxidation amount of hydrogen generating the current is performed in the fuel cell anode. This may result in a temperature drop between the inlet and outlet of the fuel cell. During the endothermic operation, the temperature drop in the fuel cell can be controlled to keep the electrolyte in the fuel cell in a molten state.

The parameters that can be manipulated in such a manner as to differ from those currently recommended are the amount of fuel provided to the anode, the composition of the fuel provided to the anode, and / or the anode charge or cathode charge of the syngas from the anode exhaust The separation and capture of syngas in the anode effluent without significant recycle of the synthesis gas. In some embodiments, the syngas or hydrogen from the anode exhaust may not be directly or indirectly recycled to the anode input or the cathode input. In additional or other embodiments, a limited amount of recirculation may be achieved. In this embodiment, the amount recycled from the anode exhaust gas to the anode input and / or the cathode input may be less than about 10%, such as less than about 5% or less than about 1% by volume of the anode exhaust gas.

In some embodiments, the fuel cell of the fuel cell array may be arranged such that only a single stage of the fuel cell (e.g., fuel cell stack) may be present. In this type of embodiment, the single-stage anode fuel utilization rate may represent the anode fuel utilization of the array. Another option may be that the fuel cell array may contain a plurality of anode stages and a plurality of cathode stages, wherein each anode stage has the same range of fuel utilization, for example, And has a fuel utilization rate within 10% of the value, for example, within 5% of the specified value. Another option may be that each anode stage has the same fuel utilization rate or a fuel utilization rate that is less than a specified value less than a specified amount, e.g., each anode stage is less than 10%, such as less than 5% It has a lower value than the specified value. As an illustrative example, a fuel cell array having a plurality of anode stages may have a respective anode stage within about 10% of the 50% fuel utilization, since each anode stage has a fuel utilization rate of about 40% to about 60% . As another example, a fuel cell array having a plurality of stages may have each anode stage with a maximum deviation of less than about 5% and less than or equal to 60% anode fuel utilization, with each anode stage having about 55% to about Equivalent to having a fuel utilization rate of 60%. In yet another example, at least one stage of the fuel cell in the fuel cell array may be operated at a fuel utilization rate of from about 30% to about 50%, for example, a plurality of fuel cell stages of the array may be operated at about 30% to about 50% Fuel ratio. More generally, any range of this type may be concurrent with any anode fuel utilization rate value defined herein.

Another additional or alternative option may be to define the overall average of fuel utilization across all fuel cells of the fuel cell array. In various embodiments, the overall average of the fuel utilization of the fuel cell array may be less than or equal to about 65%, such as less than or equal to about 60%, less than or equal to about 55%, less than or equal to about 50%, or less than or equal to about 45% , The overall average of the fuel utilization of the fuel cell array may be at least about 25%, such as at least about 30%, at least about 35%, or at least about 40%. This average fuel utilization rate does not necessarily have to limit the fuel utilization rate for any single stage, as long as the array of fuel cells satisfies the desired fuel utilization rate.

Uses of Synthetic Gases 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 may be to use the simple anode output as described above as a source of hydrogen. For SOFCs that are integrated or co-located with the refinery, hydrogen can be used as a hydrogen source for a variety of refining processes such as hydro-processing. Such hydrogen can be used as fuel for a boiler, furnace and / or flame heater in a refinery or other industrial facility, and / or hydrogen can be used as a feed for a generator such as a turbine. Hydrogen from an SOFC fuel cell may be additionally or otherwise used as an input stream for other types of fuel cells requiring hydrogen as input, possibly including vehicles that obtain power by the fuel cell. Another option may be to additionally or otherwise use the syngas generated as an output from the SOFC fuel cell as a fermentation input.

Another option may be to use additional or different syngas generated as the anode output. Of course, syngas based on fuel may still cause some CO ₂ production when burned as fuel, but syngas can be used as fuel. In another embodiment, a syngas output stream may be used as the input for the chemical synthesis process. One option may be to use a Fischer-Tropsch type process, and / or to add or otherwise use syngas to another process in which larger hydrocarbon molecules are formed from the synthesis gas feed. Another option may be to use additional or different syngas to form an intermediate product such as methanol. Methanol can be used as the final product, but in other embodiments, methanol produced from the synthesis gas can be used to produce larger compounds such as gasoline, olefins, aromatics and / or other products. Note that a small amount of CO ₂ may be allowed in the synthesis gas feed to the Fischer-Tropsch process using the methanol synthesis process and / or the morphology conversion catalyst. Hydroformylation is an additional or alternative example of another synthesis process in which synthesis gas feeds can be used.

One variation on the use of SOFCs to produce syngas is the use of SOFCs as part of a system for processing methane and / or natural gas recovered by coastal oil drilling platforms or other production systems with considerable distances from the ultimate market. It should be noted that fuel cells may be used. Instead of attempting to transport the meteorological output from the well, or attempting to store the meteorological product for a long time, the meteorological output from the well can be used as an input to the SOFC fuel cell array. This can lead to various advantages. First, the power generated from the fuel cell array can be used as a power source for the platform. Additionally, the syngas product from the fuel cell array can be used as feed for the Fischer-Tropsch process at the production site. This can lead to the formation of liquid hydrocarbon products that are more easily transported from the production site to, for example, a land plant or larger terminal by pipeline, ship or motor vehicle.

Another integration option may additionally or otherwise include the use of cathode artifacts as a source of higher purity heated nitrogen. Cathode inputs can often contain large amounts of air, which means that a significant amount of nitrogen can be included in the cathode input. The fuel cell transports O ₂ from the cathode to the anode across the electrolyte and the cathode product can have a higher concentration of N ₂ than that found in the lower concentration of O ₂ and hence in the air. With subsequent removal of residual O ₂ , this nitrogen product can be used as an input to produce ammonia, or other nitrogen-containing compounds (e.g., urea, ammonium nitrate, and / or nitric acid). It is noted that the urea synthesis can use CO ₂ separated from the anode product as an addition feed or additionally or otherwise.

Additional embodiments

Embodiment 1. A method of generating electricity and hydrogen or syngas using a solid oxide fuel cell having an anode and a cathode, comprising the steps of supplying a fuel stream comprising a reformable fuel to an anode of the solid oxide fuel cell, A reforming stage (including an internal reforming element) which is accompanied by an anode of the cell, or a combination thereof;

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;

A gas stream containing H ₂ from the anode exhaust gas, a gas stream containing H ₂ and CO, or a combination thereof

Wherein the electrical efficiency of the solid oxide fuel cell is about 10% to about 50%, and the total fuel cell productivity of the solid oxide fuel cell is about 150 mW / cm ² or more.

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

Embodiment 3. The method of Embodiment 1 or Embodiment 2, 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 one of embodiments 1 to 3, wherein the electrical efficiency of the solid oxide fuel cell is less than or equal to about 45%, or less than or equal to about 35%.

Embodiment 5. The method of any one of Embodiments 1 to 4, 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% Gt;

6. The exemplary embodiment has a total solid oxide fuel cell of the fuel cell productivity of about 150mW / cm ² or more, or from about 300mW / cm ² or more, or from about 350mW / cm ² or more, or from about 800mW / cm ² or less, aspects 1 to The method of any one of embodiment &lt; RTI ID = 0.0 &gt; 5.

Embodiment 7. The solid oxide fuel shot fuel reforming possible productivity of about 75mW / cm ² or more of the cells, or from about 100mW / cm ² or more, or from about 150mW / cm ² or more, or from about 200mW / cm ^2, or at least about 600mW / cm &lt; ² &gt;. The method of any one of embodiments 1 to 6,

Embodiment 8. A fuel cell system comprising: a reformable fuel reformable fuel which is introduced into an anode of a solid oxide fuel cell, a reforming stage (including internal reforming elements) followed by an anode of the solid oxide fuel cell, or a combination thereof, Is greater than about 75%, such as greater than about 100% greater than the amount of hydrogen that is reacted to generate hydrogen. &Lt; RTI ID = 0.0 &gt;

Embodiment 9. The method of any one of embodiments 1-8, wherein the fuel stream comprises at least about 10% by volume of an inert compound, at least about 10% by volume of CO ₂ , or a combination thereof.

Embodiment 10. The method of any one of embodiments 1 to 9, wherein the fuel cell is operated at a voltage (V _A ) of about 0.67 V or less, or about 0.5 V or less.

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

Embodiment 12. The anode exhaust gas is about 3.0: 1 or more exemplary H _2, with a ratio of CO embodiment 1 to embodiment 11, one method of one embodiment of the.

Embodiment 13. The method of any one of Embodiments 1 to 12, wherein said solid oxide fuel cell is a tubular solid oxide fuel cell.

Embodiment 14. The method of any one of embodiments 1 to 13, wherein the solid oxide fuel cell further comprises at least one integrated endothermic reaction stage.

15. The method of embodiment 15 wherein the at least one integrated endothermic reaction stage includes an integrated reforming stage wherein the fuel stream introduced into the anode of the solid oxide fuel cell passes through an integrated reforming stage before entering the anode of the solid oxide fuel cell &Lt; / RTI &gt;

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

Embodiment 17. The method of any one of embodiments 1 to 15 wherein the temperature at the anode inlet is different from the temperature at the anode outlet by about 20 占 폚 or less.

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

Embodiment 19. The method of any one of the preceding claims, wherein the temperature ratio is less than or equal to about 0.85, and wherein the method further comprises the step of supplying heat to the fuel cell to maintain the temperature at the anode outlet lower than the temperature at the anode inlet by about 5 & 15. The method of any one of embodiments &lt; RTI ID = 0.0 &gt; 1 &lt; / RTI &gt;

Embodiment 20. The method of any one of the preceding claims, further comprising modifying the reformable fuel, wherein the anode of the solid oxide fuel cell, the reforming stage (including internal reforming elements) followed by the anode of the solid oxide fuel cell, The method of any of embodiments 1-9, wherein at least about 90% of the reformable fuel introduced into the combination is reformed through the anode of the solid oxide fuel cell once.

While the invention has been described in terms of specific embodiments, it is not limited thereto. Variations / modifications suitable for operation under specific conditions will be apparent to those skilled in the art. Accordingly, the following claims should be construed as encompassing all such variations / modifications as fall within the true spirit / scope of the present disclosure.

Claims (19)

A method of generating electricity and hydrogen or syngas using a solid oxide fuel cell having an anode and a cathode,
Introducing a fuel stream comprising a reformable fuel into an anode of the solid oxide fuel cell, a reforming stage (comprising an internal reforming element) followed by an anode of the solid oxide 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 in the solid oxide fuel cell;
A gas stream containing H ₂ from the anode exhaust gas, a gas stream containing H ₂ and CO, or a combination thereof
Wherein the electrical efficiency of the solid oxide fuel cell is about 10% to about 50%, and the total fuel cell productivity of the solid oxide fuel cell is about 150 mW / cm ² or more. The method according to claim 1,
Wherein the solid oxide fuel cell is operated to generate electricity at a thermal ratio of about 0.25 to about 1.3, such as less than about 1.15, less than about 1.0, or less than about 0.75. 3. The method according to 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 according to any one of claims 1 to 3,
Wherein the electrical efficiency of the solid oxide fuel cell is less than or equal to about 45%, such as less than or equal to about 35%. 5. The method according to any one of claims 1 to 4,
Wherein 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%. 6. The method according to any one of claims 1 to 5,
The solid oxide fuel cell of the fuel cell total production of about 150mW / cm ² or more, for example from about 300mW / cm ^2, greater than or equal to about 350mW / cm ² or more, or from about 800mW / cm ² or less, the method. 7. The method according to any one of claims 1 to 6,
The solid oxide fuel has a total modified possible fuel productivity of the cell of about 75mW / cm ² or more, for example from about 100mW / cm ^2, greater than or equal to about 150mW / cm ^2, greater than or equal to about 200mW / cm ² or more, or from about 600mW / cm ² or less , Way. 8. The method according to any one of claims 1 to 7,
Wherein the reformable fuel content of the reformable fuel introduced into the anode of the solid oxide fuel cell, the reforming stage (including internal reforming elements) followed by the anode of the solid oxide fuel cell, or a combination thereof, Greater than or equal to about 75%, such as greater than about 100% greater than the amount of reacting hydrogen. 9. The method according to any one of claims 1 to 8,
Wherein the fuel stream comprises at least about 10% by volume of an inert compound, at least about 10% by volume of CO ₂ , or a combination thereof. 10. The method according to any one of claims 1 to 9,
Wherein the fuel cell is operated at a voltage (V _A ) of about 0.67 V or less, or about 0.5 V or less. 11. The method according to any one of claims 1 to 10,
The anode exhaust gas is about 1.5: 1 to about 10: 1, such as about 3.0: 1 or more of H _2, the method having the ratio of CO. 12. The method according to any one of claims 1 to 11,
Wherein the solid oxide fuel cell is a tubular solid oxide fuel cell. 13. The method according to any one of claims 1 to 12,
Wherein the solid oxide fuel cell further comprises at least one integrated endothermic reaction stage. 14. The method of claim 13,
Wherein the at least one integrated endothermic reaction stage includes an integrated reforming stage and wherein the fuel stream introduced into the anode of the solid oxide fuel cell passes through the integrated reforming stage before entering the anode of the solid oxide fuel cell . 15. The method according to any one of claims 1 to 14,
Wherein the temperature at the anode outlet is higher than the temperature at the anode inlet by no more than about 40 占 폚. 15. The method according to any one of claims 1 to 14,
Wherein the temperature at the anode inlet is different from the temperature at the anode outlet by about 20 DEG C or less. 15. The method according to any one of claims 1 to 14,
Wherein the temperature at the anode outlet is lower by about 10 캜 to about 80 캜 than the temperature at the anode inlet. 15. The method according to any one of claims 1 to 14,
Wherein the temperature ratio is about 0.85 or less,
Wherein the method further comprises supplying heat to the fuel cell to maintain a temperature at the anode outlet that is lower than the temperature at the anode inlet by about 5 占 폚 to about 50 占 폚. 19. The method according to any one of claims 1 to 18,
Wherein the method further comprises modifying the reformable fuel, wherein the reforming of the reformable fuel is carried out with the anode of the solid oxide fuel cell, the reforming stage followed by the anode of the solid oxide fuel cell (including internal reforming elements) Wherein at least about 90% of the reformable fuel introduced is reformed once through the anode of the solid oxide fuel cell.

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