KR20160064187A - Cathode combustion for enhanced fuel cell syngas production - Google Patents

Abstract

A molten carbonate fuel cell is operated using a cathode inlet stream containing a certain amount of a combustible gas, which may be hydrocarbon, hydrogen, or other gas that combines with oxygen to form heat on the surface of the cathode catalyst. The combustible gas may react at a stage that is thermally integrated with the cathode and / or the cathode. Heat generated by the combustion reaction in the cathode may be used to cause additional endothermic reactions (e.g., reforming) to occur, for example, at the anode portion of the fuel cell, while still maintaining the desired temperature gradient across the fuel cell . Optionally, the cathode of the fuel cell can be altered to further improve or control combustion in the cathode, for example, by introducing an additional catalyst surface to the cathode.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a cathode combustion method for enhancing fuel cell synthesis gas production,

In various aspects, the present invention is directed to a method of operating a molten carbonate fuel cell.

Molten carbonate 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 that is either in front of the fuel cell or in the fuel cell. The reformable fuel may include a hydrocarbonaceous material capable of reacting with steam and / or oxygen at elevated temperature and / or pressure to produce a gaseous product comprising hydrogen. Alternatively or additionally, the fuel can be reformed in an anode cell of a molten carbonate fuel cell (which can be operated to form conditions suitable for reforming the fuel at the anode). Alternatively or additionally, reforming can be done both outside and inside the fuel cell.

Traditionally, molten carbonate fuel cells are operated to maximize the production of electricity per unit fuel input (which may be referred to as the fuel efficiency of the fuel cell). This maximization may be based only on the fuel cell or on a fuel cell with other power generation systems. To increase electrical production and manage heat generation, the fuel utilization rate in the fuel cell is typically maintained at 70% to 75%.

U.S. Patent Publication No. 2011/0111315 describes a fuel cell system having significant hydrogen content in the anode inlet stream and a method of operating the system. The technique of '315 relates to providing sufficient fuel to the anode inlet so that sufficient fuel remains for the oxidation reaction when the fuel is near the anode outlet. To make the fuel suitable, the '315 provides fuel with high H ₂ concentration. H ₂ not used for the oxidation reaction is recycled to the anode for use in the next pass. On a one pass basis, the H ₂ utilization may be between 10% and 30%. The '315 reference does not describe a significant modification in the anode, but instead mainly depends on the external modification.

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 (which is configured to receive the anode exhaust gas and separate the hydrogen). A portion of the anode exhaust gas is also recycled to the anode inlet. The operating range given in the '810 publication appears to be based on solid oxide fuel cells. A molten carbonate fuel cell is described as an alternative.

U.S. Patent Publication No. 2003/0008183 describes a system and method for simultaneous production of hydrogen and electric power. Fuel cells are mentioned in the general form of chemical conversion devices for the conversion of hydrocarbon-type fuels to hydrogen. The fuel cell system also includes an external reformer and a high temperature fuel cell. An embodiment of a fuel cell system is described which has an electrical efficiency of about 45% and a compound production rate of about 25%, which shows a system simultaneous production efficiency of about 70%. '183 does not appear to describe the electrical efficiency of the fuel cell isolated from the system.

U.S. Patent No. 5,084,362 describes a system that integrates a vaporization system and a fuel cell so that coal gas can be used as a fuel source for the fuel cell anode. Hydrogen generated by a fuel cell is used as an input to a vaporizer used to generate methane from coal gas (or other coal) inputs. Then, methane from the vaporizer is used as at least a part of the fuel injected into the fuel cell. Therefore, at least a portion of the hydrogen generated by the fuel cell is indirectly recirculated to the fuel cell anode inlet in the form of methane generated by the vaporizer.

A paper by Journal of Fuel Cell Science and Technology [G. Manzolini et al., J. Fuel Cell Sci. and Tech. , Vol. 9, February 2012] describes a power generation system that combines a combustion generator and a molten carbonate fuel cell. Various arrangements and operating parameters of fuel cells are described. The combustion output from the combustion generator is used, in part, as input to the cathode of the fuel cell. One objective of the simulation in the Manzolini paper is to separate the CO ₂ from the generator's exhaust using an MCFC. The simulation described in the Manzolini paper points to a maximum exit temperature of 660 ° C, and the inlet temperature should be sufficiently low due to the temperature increase across the fuel cell. In the base model, the electrical efficiency (ie, generated electricity / fuel input) of the MCFC fuel cell is 50%. The electrical efficiency for a test model optimized for CO ₂ sequestration is also 50%.

Desideri et al . [ Intl. J. of Hydrogen Energy , Vol. 37, 2012] describes a method for modeling the performance of a power generation system using a fuel cell to separate CO ₂ . The anode exhaust gas is recycled to the anode inlet and the cathode exhaust gas is recirculated to the cathode inlet to improve the performance of the fuel cell. The model parameter describes the MCFC electrical efficiency of 50.3%.

In one aspect, a method of producing electricity is provided. The method includes introducing an anode fuel stream comprising a reformable fuel into an anode of a molten carbonate fuel cell, an internal reforming element followed by an anode of the molten carbonate fuel cell, or a combination thereof; Introducing a cathode inlet stream comprising CO ₂ , O ₂ , and at least one fuel compound into a cathode of a molten carbonate fuel cell; Generate electricity in the molten carbonate fuel cell; Generating an anode exhaust gas comprising H ₂ , CO and CO ₂ ; About 1% by volume or more of O _2, and includes a cache Sikkim generating a cathode exhaust gas that contains one or more fuel compound of about 100vppm below, where the one or more fuel compound is H _2, one or more hydrocarbon-quality fuel compound, CO, Or combinations thereof, wherein the concentration of the at least one fuel compound in the cathode inlet stream is at least about 0.01% by volume, and wherein the concentration of the at least one fuel compound in the cathode inlet stream is greater than or equal to the operating condition in the cathode of the fuel cell Is less than the spontaneous ignition concentration in the exhaust gas.

In another aspect, a method of producing electricity is provided. The method includes introducing an anode fuel stream comprising a reformable fuel into an anode of a molten carbonate fuel cell, an internal reforming element followed by an anode of the molten carbonate fuel cell, or a combination thereof; Introducing a cathode inlet stream comprising CO ₂ , O ₂ , and at least one fuel compound into a cathode of a molten carbonate fuel cell; Generate electricity in the molten carbonate fuel cell; Generating an anode exhaust gas comprising H ₂ , CO and CO ₂ ; About 1% by volume or more of O ₂ and from about 0.01% by volume (methylene-equivalent volume%) a cache Sikkim generating a cathode exhaust gas that contains one or more fuel The following compounds, where the one or more fuel compound is one or more aromatic At least one carbon-containing fuel compound having at least 5 carbons, or combinations thereof, wherein the at least one fuel compound in the cathode inlet stream comprises at least about 0.02% by volume methylene-equivalent volume (defined below) Wherein the concentration of the at least one fuel compound in the cathode inlet stream is less than the spontaneous concentration in the operating conditions in the cathode of the fuel cell, and the cathode of the molten carbonate fuel cell has an electrode surface and an ancillary catalyst surface Wherein said secondary catalyst surface comprises at least one Group VIII metal, In the presence of the catalytic surface comprises Sikkim at least a portion of the oxidation one or more fuel compound.

In another aspect, a molten carbonate fuel cell system is provided. A molten carbonate fuel cell system includes a molten carbonate fuel cell having an anode and a cathode, wherein the cathode includes an ancillary catalyst surface comprising an electrode surface and one or more Group VIII metals, wherein the ancillary catalyst surface Wherein the concentration of the at least one Group VIII metal is lower in a first region of the catalyst surface that is incidental to the concentration of the at least one Group VIII metal in the second region of the ancillary catalyst surface and the first region of the ancillary catalyst surface is incidental Is closer to the cathode inlet of the cathode of the molten carbonate fuel cell than the second region of the cathode catalyst surface. Optionally, the at least one Group VIII metal is selected from the group consisting of Ni, Pt, Pd, Co, Rh, Ru, Re, Ir, Fe, or combinations thereof, preferably Ni, Co, Fe, Pt, Pd, Or more. Optionally, the area of the secondary catalyst surface comprises a continuously increasing concentration gradient of one or more Group VIII metals. In some embodiments, the first region of the ancillary catalyst surface comprises at least one Group VIII metal, and the second region of the ancillary catalyst surface is at least one of the at least one Group VIII metal of the first region of the ancillary catalyst surface Additional Group VIII metals. In another embodiment, the second region of the secondary catalyst surface comprises at least one Group VIII metal, and the first region of the secondary catalyst surface is at least one of a group III metal of the second region of the secondary catalyst surface Additional Group VIII metals.

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

summary

In various embodiments, a molten carbonate fuel cell uses a cathode inlet stream that contains a non-trivial portion of a combustible gas, which may be hydrocarbon, hydrogen, or other gas that combines with oxygen to form heat on the surface of the cathode catalyst . The combustible gas may react at a stage that is thermally integrated with the cathode and / or the cathode. Heat generated by the combustion reaction in the cathode may be used to cause additional endothermic reactions (e.g., reforming) to occur, for example, at the anode portion of the fuel cell, while still maintaining the desired temperature gradient across the fuel cell . Optionally, the cathode of the fuel cell can be altered to further improve or control combustion in the cathode, for example, by introducing an additional catalyst surface to the cathode.

One strategy to reduce or minimize the amount of carbon released from combustion sources, such as gas turbines, internal combustion engines, fired boilers or other combustion sources, is to integrate combustion sources with molten carbonate fuel cells (MCFC) . The molten carbonate fuel cell may receive the CO ₂ -containing exhaust gas from the combustion source as part of the cathode inlet flow to the fuel cell. As part of the cathode reaction, CO ₂ can be transported from the cathode to the anode across the fuel cell electrolyte. This allows the molten carbonate fuel cell to help concentrate the CO ₂ to the anode output from the fuel cell, and this concentration facilitates capturing the CO ₂ for other purposes, thereby releasing CO ₂ to the atmosphere .

In a typical molten carbonate fuel cell configuration, the primary concern may be to operate the molten carbonate fuel cell at high electrical efficiency while maintaining the temperature gradient across the fuel cell within the desired range. Some of the challenges during conventional operation may be to avoid excessively high temperature gradients across the fuel cell due to excessive heat or waste heat generated within the fuel cell. When operating a molten carbonate fuel cell for high efficiency, the cell is typically operated close to the maximum temperature rise allowed in the fuel cell because the net operation at high efficiency is exothermic.

During conventional operation of a molten carbonate fuel cell, the amount of combustible gas present when the cathode input stream enters the cathode may typically be less than 100 vppm, such as less than about 10 vppm. In addition, the combustible gas may typically correspond to a compound having a relatively low calorific value per molecule, such as H ₂ or CH ₄ . The amount of this combustion component produces very little heat when reacting with oxygen on the cathode as compared to the heat production in the entire fuel cell system. In the portion of the cathode input stream derived from the exhaust gas of the combustion source, the remaining combustible material may reflect the fact that the exhaust gas has already been exposed to combustion conditions optimized to achieve substantially complete combustion of the input fuel. In some conventional arrangements, a portion of the cathode input stream may also correspond to the recirculated portion of the anode output stream. In this conventional configuration, the recirculated portion of the anode output stream typically can pass through the burner before entering the cathode, which can also achieve substantial complete combustion of any fuel of the anode output stream portion.

Instead of operating the molten carbonate fuel cell in a conventional manner, a molten carbonate fuel cell may be operated using a cathode input stream comprising a combustible material such as one or more fuel compounds. The fuel compound may correspond to CO, H ₂ , CH ₄ , other hydrocarbon and / or hydrocarbonaceous compounds that may be combusted, or other compounds that can be burned (oxidized) to generate heat. In some embodiments, the cathode inlet streams may include a fuel compound corresponding to CO, H ₂ and / or CH _4. In another embodiment, the cathode inlet stream may contain H ₂ and / or carbon-containing fuel compounds having up to four carbon atoms. In another embodiment, the fuel compound portion in the cathode inlet stream may correspond to an aromatic compound, or a carbon-containing compound having five or more carbon atoms, or a combination thereof.

The amount of combustible material in the cathode inlet stream can be characterized in various ways. One option may be to use the volume percent of the total combustible material. Another option may be to weigh the volume percent of combustible material based on the number of carbons present in the combustible material and / or the number of heavy atoms. The latter option may be due to differences in calorific values between compounds such as hydrogen and distillate boiling range molecules. Both exist as gases occupying similar volumes at the temperature at the cathode inlet, but the calorific value of the distillate boiling range molecules is significantly greater.

For example, one option may be at least about 0.01 vol%, or at least about 0.02 vol%, or at least about 0.03 vol%, or at least about 0.05 vol%, or at least about 0.1 vol%, or at least about 0.25 vol% (As a lower limit) containing at least about 0.5 volume percent, or at least about 1.0 volume percent, or at least about 1.5 volume percent, or at least about 2.0 volume percent, or at least about 2.5 volume percent, or at least 3.0 volume percent, It may be to use a cathode inlet stream. Additionally or alternatively, the cathode inlet stream may contain no more than about 5.0 vol%, or no more than about 4.0 vol%, or no more than about 3.5 vol%, or no more than about 3.0 vol%, or at least about 2.5 vol% (As upper limit). The lower limit for the amount of one or more fuel compounds in the cathode inlet stream is clearly contemplated with each upper limit for the amount of one or more fuel compounds in the cathode inlet stream. The upper limit for the amount of combustible material may be varied, but below the concentration that allows spontaneous ignition of the cathode inlet stream under conditions at the cathode (on the order of several vol.%, Depending on the composition of the compound).

Additionally or alternatively, another option for characterizing the amount of combustible material in the cathode inlet stream may be to weigh the volume percentage of combustible material based on the number of carbons in the combustible material, or alternatively the number of heavy atoms . The calorific value of the hydrocarbons is approximately proportional to the number of carbon atoms present in the hydrocarbons. Except oxygen, any additional heteroatoms present in the hydrocarbonaceous material (i.e., non-hydrogen atoms or heavy atoms) also contribute in a substantially proportional manner. In order to account for the additional calorific value of the larger fuel component, it is possible to multiply the volume percent of the fuel component by the number of carbon atoms in the component, or alternatively, the number of non-oxygen heavy atoms in the component multiplied by the volume percentage modified. If the altered volume percent is based solely on carbon atoms in the fuel component, the modified volume percent is defined herein as the "methylene-equivalent" volume percent of the fuel component. If the altered volume percent is based on non-oxygen heavy atoms in the fuel component, the modified volume percent is defined herein as the "heavy atom-equivalent" In order to define the methylene-equivalent volume% and the heavy atom-equivalent volume%, the hydrogen molecule is defined as having a carbon atom or heavy atom value of 0.5. The CO molecule is similarly defined as having a carbon atom or heavy atom value of 0.5. This reflects the fact that these compounds have some calorific values but do not have as much calorific value as the hydrocarbonaceous compounds.

In various embodiments, the methylene-equivalent volume percent in the cathode inlet stream is at least about 0.01 vol%, or at least about 0.02 vol%, or at least about 0.03 vol%, or at least about 0.05 vol% Or about 0.5% by volume or more, or about 0.5% by volume or more, or about 1.0% by volume or more, or about 1.5% by volume or more, or about 2.0% by volume or more, or about 2.5% % ≪ / RTI > Additionally or alternatively, the cathode inlet stream may contain no more than about 5.0 vol%, or no more than about 4.0 vol%, or no more than about 3.5 vol%, or no more than about 3.0 vol%, or no more than about 2.5 vol% ≪ / RTI > The lower limit for the methylene-equivalent volume percent of one or more fuel compounds in the cathode inlet stream is explicitly contemplated with each upper limit for the methylene-equivalent volume percent of one or more fuel compounds in the cathode inlet stream. As an example of calculating the methylene-equivalent volume percent, the hypothetical cathode inlet feed may contain a fuel compound corresponding to 0.02% by volume of ethylene and 0.01% by volume of H ₂ . In this hypothetical example, the methylene-equivalent volume percent of the feed is 0.045% by volume. Ethylene contains two carbons per molecule, so that ethylene contributes 0.02 x 2 = 0.04% by volume to the total methylene-equivalent volume%. H ₂ is defined as being calculated as 0.5 carbon atoms per molecule, so H ₂ contributes 0.01 x 0.5 = 0.005% by volume to the total methylene-equivalent volume%.

Additionally or alternatively, another option to characterize the amount of combustible material in the cathode inlet stream is to determine the amount of fuel delivered to the cathode inlet, which is compared to the energy value of the fuel delivered to the corresponding anode inlet of the molten carbonate fuel cell And may be based on relative energy values. The amount of fuel in the cathode inlet stream can be about 12% or less, or about 10% or less, or about 8% or less of the energy value of the anode inlet stream. For example, if the ratio of fuel delivered to the anode inlet corresponds to a power of about 1 MW, the fuel input rate into the cathode of the cathode inlet stream may be about 120 kW or less, or about 100 kW or less, or about 80 kW or less . The cathode inlet stream also includes a cathode outlet stream having a residual oxygen content after combustion of any of the cathode inlet streams that is sufficient to enable the fuel cell reaction and still has an oxygen content of at least about 1 volume percent, Lt; RTI ID = 0.0 > of oxygen. ≪ / RTI >

In some embodiments, the cathode inlet stream containing one or more fuel compounds may have a reduced or minimized sulfur content. The sulfur content of the cathode inlet stream can be about 25 wppm or less, or about 15 wppm or less, or about 10 wppm or less. Optionally, some heteroatoms, different from C, H, and O, may be present in the oxidizable compound (i.e., fuel compound) contained in the cathode inlet stream. For example, the carbon-containing fuel compound in the cathode inlet stream may optionally contain nitrogen atoms. It is noted that N ₂ is not an oxidizable compound under the conditions present at the cathode inlet and therefore the presence of N _{2 in} the cathode inlet stream does not constitute a heteroatom present in the oxidizable compound. In another embodiment, the cathode inlet stream may contain less than about 100 wppm, or less than about 10 wppm heteroatoms different from C, H, and O in the fuel compound.

Additional fuel content in the cathode inlet stream can be combusted in the cathode based on the conditions at the cathode and the presence of the catalyst surface at the cathode. One suitable catalyst surface may be a nickel surface such as a nickel surface commonly used as an electrode adjacent to a molten carbonate electrolyte but may be any other convenient catalyst capable of catalytically oxidizing a fuel component such as a Group VIII metal, A combustion catalyst may be used. The cathode electrode surface may facilitate oxidation of the H ₂ and / or carbon-containing fuel (including CO) so that the fuel present in the cathode inlet stream can be converted to a typical combustion product such as H ₂ O and CO ₂ .

In the embodiment where the fuel is H ₂ , CO and / or CH ₄ in the cathode inlet stream, the electrode surface (typically Ni) may be sufficient to promote combustion of the fuel in the cathode inlet stream. The electrode surface may also be suitable for promoting the reaction of smaller amounts of other hydrocarbons. For example, the electrode surface can be at least a few tens of parts per million, such as from about 10 to about 10,000, or from about 10 to about 1000, or from about 10 to about 200, or from about 10 to about 100, From about 50 vppm to about 1000 vppm, or from about 50 vppm to about 200 vppm, or from about 100 vppm to about 10,000 vppm, or from about 100 vppm to about 1000 vppm. For aliphatic hydrocarbons or other non-aromatic hydrocarbon compounds, the electrode surface may be suitable for promoting up to about 1% by volume of the compound.

In some embodiments, the catalytic activity for oxidizing the fuel in the cathode can be improved by providing an additional catalyst surface. For example, one configuration of a conventional molten carbonate fuel cell may be one having a cathode portion of the fuel cell defined as a parallel plate. One parallel plate may correspond to the electrode surface adjacent to the molten carbonate electrolyte. Typically, the opposing surface (the surface not adjacent to the molten carbonate electrolyte) may be a steel surface or other surface corresponding to a suitable structural material. Instead of having a steel surface (or other less reactive surface) on the opposite side of the electrode, the opposite surface can be coated with a catalytic material to enhance the ability to promote combustion of the fuel in the cathode inlet stream. One option may be to provide a surface similar to an electrolyte surface, such as a Ni surface. Another option may be to use a surface with higher activity to promote the combustion of aromatic compounds and / or C2 + hydrocarbon compounds. Examples of suitable catalytic materials may include, but are not limited to, Group VIII metals such as Ni, Fe, Co, Pt and / or Pd. Any suitable metal or metal alloy can be used directly on the steel surface, or supported on a typical catalyst support. Catalyst formulations useful as combustion catalysts are well known in the art and may employ any catalyst suitable for the fuel cell operating temperature range (e.g., from about 400 ° C to about 800 ° C). Group VIII metals Several alloys and / or alloys of Group VIII metals, such as alloys of Group VIII metals and other transition metals, may also be suitable. The catalyst material can be coated directly on the plate surface of the cathode, or can support the catalyst material on, for example, an oxide support.

Based on the presence of an electrode (Ni) surface and / or an additional catalyst surface, H ₂ , CO and hydrocarbon / hydrocarbon compounds in the cathode inlet stream can be combusted in the cathode. This generates additional heat in the cathode. In normal operation, this additional heat imposes a difficulty because the optimized operation for electrical efficiency typically operates at an acceptable temperature rise limit. However, in various embodiments additional heat generated in the cathode may be used to provide additional heat for an endothermic reaction. The endothermic reaction may correspond to a modification in the anode, or to another endothermic reaction taking place in the reaction stage that is thermally integrated with the cathode. For example, if the anode portion of the molten carbonate fuel cell is operated to have a low one pass fuel utilization rate for hydrogen and / or synthesis gas production, the additional heat generated in the cathode may be used to control the temperature The gradient can be maintained in the desired range.

It may be desirable to distribute the combustion of the fuel across the cathode inlet stream across a larger portion of the length of the cathode, although the additional heat generated in the cathode may be advantageous. One way to distribute the combustion of fuel across a larger portion of the cathode into the cathode inlet stream may be to use an additional catalyst surface with a gradient of catalyst material. For example, the concentration of catalytic material on the additional catalyst surface may be lower near the inlet to the cathode (where the concentration of combustible material and oxygen is highest) and may increase subsequently over the length of the cathode. Any convenient strategy can be used to increase the concentration, such as a continuous gradient, a series of stepwise increments, or any other way to have a higher catalyst material concentration at a location further from the cathode inlet. The initial concentration of catalytic material on the additional surface at the cathode inlet may be any convenient value, including the option of causing the catalytic material on the additional surface to begin at the position after the cathode inlet. The pattern or gradient of the catalyst, and subsequent heat release, can be optimized to spread the total heat production across the cathode area and prevent the high temperature zone, which can damage the overall fuel cell operation.

As an example of a method of operating a molten carbonate fuel cell to utilize the additional heat generated in the cathode, the molten carbonate fuel cell can be operated while increasing the production of syngas and / or hydrogen. This can be achieved by increasing the amount of modification carried out in the fuel cell (and / or the internal reforming stage, e.g. a reforming stage of the fuel cell assembly) relative to the amount of hydrogen oxidized in the anode and generating electricity. As defined above, a fuel cell stack (or other fuel cell assembly) may be formed by a) the heat generated in the anode by an electrochemical reaction and b) the sum of the heat generated in the cathode by the combustion of the fuel c) This can be achieved by operating the fuel cell with the fuel cell temperature ratio related to the heat consumed in the fuel cell. For example, the reforming reaction in the anode and / or the internal reforming stage may typically be an endothermic reaction. Therefore, the exothermic reforming reaction can be balanced by the pyrogenic electrochemical reaction for the generation of electricity together with the pyrogenic cathode combustion reaction. Rather than seek to transport heat generated by the exothermic fuel cell reaction (s) away from the fuel cell, this excess heat can be used in situ as a heat source for reforming and / or other endothermic reactions. This can achieve a more efficient use of heat energy and / or a reduction in the need for additional external or internal heat exchange. Essentially, the production and use of such efficient heat energy within the in-situ reaction system can reduce the complexity and components of the system while maintaining advantageous operating conditions. In some embodiments, the amount of reforming or other endothermic reaction is significantly less than the heat demand typically described in the prior art, rather than the amount of heat generated by the exothermic reaction (s) or has a greater endothermic heat requirement Can be selected.

Additionally or alternatively, the fuel cell may be operated such that the temperature difference between the anode inlet and the anode outlet may be negative rather than positive. Therefore, instead of having a temperature increase between the anode inlet and the anode outlet, a sufficient amount of reforming and / or other endothermic reaction may be performed to cause the output stream from the anode outlet to be cooler than the anode inlet temperature. Additionally or alternatively, additional fuel may be supplied to the heater for the fuel cell and / or internal reforming stage (or other internal endothermic reaction stage) such that the temperature difference between the anode inlet and the anode outlet is greater than the temperature of the endothermic reaction May be less than the expected difference based on the combined pyrogenic heat generation of the relative consumption and cathode combustion reaction and the anode reaction to generate power. Operating the fuel cell to modify the excess fuel, in embodiments where reforming can be utilized as an endothermic reaction, can reduce the complexity of the system for heat exchange and reforming, Can be increased. Additional syngas and / or additional hydrogen may be used in a variety of applications, including tailoring hydrogen to collection / use for chemical synthesis processes and / or for use as "clean" fuels.

The amount of heat generated per mole of hydrogen oxidized by the exothermic reaction at the anode may be substantially greater than the amount of heat consumed per mole of hydrogen generated by the reforming reaction. In a molten carbonate fuel cell, the net reaction of hydrogen (H ₂ + ½O ₂ ⇒ H ₂ O) can have a reaction enthalpy of about -285 kJ per mole of hydrogen molecule. At least a part of the energy can be converted into electrical energy in the fuel cell. However, the difference between the enthalpy of the reaction and the electrical energy produced by the fuel cell (roughly) can be heat in the fuel cell. This amount of energy can be otherwise expressed as the difference between the theoretical maximum voltage and the actual voltage of the fuel cell and the current density (current per unit area) of the multiplied battery, or < current density > * (V _max -V _actual ). The amount of this energy is defined as the "waste heat" of the fuel cell. As an example of the modification, the enthalpy of the reforming of methane (CH ₄ + 2H ₂ O ⇒ 4H ₂ + CO ₂ ) may be about 250 kJ per mole of methane, or about 62 kJ per mole of hydrogen molecule. From the viewpoint of thermal equilibrium, each hydrogen molecule that is electrochemically oxidized can generate sufficient heat to generate more than one hydrogen molecule by modification. In a conventional configuration, this excessive amount of heat can cause a significant temperature difference from the anode inlet to the anode outlet. Instead of having this excess heat used to increase the temperature of the fuel cell, it can consume excessive heat by performing a corresponding amount of reforming reaction. Excess heat generated in the anode can be supplemented with excess heat generated by the combustion reaction in the fuel cell. More generally, excessive heat can be consumed by performing an endothermic reaction at the endothermic reaction stage thermally integrated with the fuel cell anode and / or the fuel cell.

Depending on the embodiment, the amount of reforming and / or other endothermic reaction can be selected relative to the amount of hydrogen reacted at the anode to achieve the desired temperature ratio of the fuel cell. As used herein, the "temperature ratio" refers to the heat generated by the exothermic reaction in the fuel cell assembly (including the exothermic reaction in both the anode and the cathode), 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. The heat generated by the exothermic reaction can correspond to any heat in the cell, such as a reforming reaction, a water gas-phone reaction, a combustion reaction in the cathode (e.g., oxidation of the fuel component) and / or an electrochemical reaction Pay attention. 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, it is believed that the ideal electrochemical potential of the reaction in the MCFC is about 1.04V based on the net reaction in the cell. During operation of the MCFC, the cell can typically have an output voltage of less than 1.04 V due to various losses. For example, a typical output / operating voltage may be about 0.7V. The generated heat may be equal to [the electrochemical potential of the cell (i.e., about 1.04 V) - the operating voltage]. For example, heat generated by an electrochemical reaction in a cell may be about 0.34 V when an output voltage of about 0.7 V is obtained in the fuel cell. 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.

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. The temperature ratio 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 (or a plurality of fuel cells) in a fuel cell stack together with an integrated reforming stage and / or an integrated endothermic reaction stage element that are close enough to the fuel cell (s) Temperature ratio can be calculated.

In terms of thermal integration, the characteristic width of the fuel cell stack may be the height of the individual fuel cell elements. Note that the individual reforming stages and / or separate endothermic reaction stages may have different heights in the stack than the fuel cell. In such a scenario, the height of the fuel cell element can be used as the characteristic height. In this discussion, the integrated endothermic reaction stage can be defined as a stage thermally integrated with one or more fuel cells so that the integrated endothermic reaction stage can use heat from the fuel cell as a heat source for modification. This integrated endothermic reaction stage can be defined as being located less than 10 times the height of the stack element from the fuel cell providing heat to the integrated stage. For example, the integrated endothermic reaction stage (e. G., A reforming stage) may be less than ten times the height of the stack element from any thermally integrated fuel cell, or less than eight times the height of the stack element, Of the stack element, or less than three times the height of the stack element. In this discussion, an integrated reforming stage and / or an integrated endothermic reaction stage that provides a stack element adjacent a fuel cell element is defined as being one or less stack element heights away from adjacent fuel cell elements.

A temperature ratio of 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 0.90 or less, or about 0.85 or less, or about 0.80 or less, or about 0.75 or less, May be lower than the temperature ratio sought. In embodiments of the present invention, the temperature ratio can be reduced to increase and / or optimize synthesis gas production, hydrogen generation, generation of other products through endothermic reactions, or combinations thereof.

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 molten carbonate fuel cell may have a temperature 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 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. 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 can be about 100 캜 or lower, such as about 80 캜 or lower, or about 60 캜 or lower, or about 50 캜 or lower, or about 40 캜 or lower, or about 30 캜 or lower, Lt; RTI ID = 0.0 &gt; anode &lt; / RTI &gt;

Several operating parameters can be manipulated to produce the desired temperature ratio. Some parameters are similar to those currently recommended for fuel cell operation. The parameters operated in a manner different from conventional operation are the amount of fuel provided to the anode; The composition of the fuel provided to the anode; The amount of fuel compound contained in the cathode inlet stream; And / or separation and capture of syngas in the anode output without substantial recycle to the anode input (e.g., without syngas from the anode output to the anode input or recycle of hydrogen).

Modification of hydrocarbons to form hydrogen and carbon dioxide is an example of an endothermic reaction. Modification is also an example of a reaction that can be performed in the anode and / or in an integrated reaction stage. In some aspects of the present invention, the amount of fuel input to the anode may comprise more reformable fuel than the amount of reformable fuel used during conventional fuel cell operation. In such an embodiment, the object may be to produce an excess of syngas at the anode and / or through the reforming in the reforming stage that accompanies the fuel cell assembly containing the anode. In one embodiment, the amount of reformable fuel introduced into the anode (or a subsequent modified stage, or combination thereof) is based on the amount by which the fuel cell can be reformed, taking into account the physical limitations of the particular fuel cell and other selected operating parameters Can be selected. For example, the anode catalyst can contribute to the reforming process. The amount of surface area of the anode catalyst may be a limitation on the amount of modification that can occur. Similarly, the amount of modification can be limited by the amount of heat available in the anode and the temperature changes that occur across the anode.

When the fuel cell is operated at a temperature ratio of less than 1, a temperature drop across the fuel cell may occur. In some embodiments, the temperature drop from the anode inlet to the anode outlet is less than or equal to about 100 ° C, such as less than or equal to about 80 ° C, or less than or equal to about 60 ° C, or less than or equal to about 50 ° C, or less than or equal to about 40 ° C, The amount of reforming and / or other endothermic reaction may be limited to be below about 20 ° C. Limiting the temperature drop from the anode inlet to the anode outlet may be advantageous, for example, to maintain a temperature sufficient to allow a complete or substantially complete conversion (due to modification) of the fuel at the anode. In another embodiment, the anode inlet temperature is below about 100 캜, such as below about 80 캜, or about 60 캜 or below, or about 50 캜 or below, due to the balance of the heat consumed by the endothermic reaction and the additional external heat supplied to the fuel cell Additional heat may be supplied to the fuel cell (e.g., by heat exchange or combustion of additional fuel) such that the temperature is higher than the anode outlet temperature by about 40 ° C or less, or about 30 ° C or less, or about 20 ° C or less.

The amount of the reforming and / or other endothermic reaction may additionally or alternatively be limited by the operating temperature of the fuel cell. For example, in general, reforming of the fuel may occur more rapidly at higher temperatures. Further, when more heat is available for the reforming process, more reforming can be achieved. As noted, embodiments of the present invention can be operated within a typical fuel cell temperature range. The temperature range may be selected for various reasons apart from the considerations related to aspects of the present invention. For example, the cathode or anode inlet stream may already be heated to a high temperature by the source of the stream. These cathode inlet streams can further generate heat based on the combustion of the fuel in the cathode inlet stream in the cathode. Additionally or alternatively, the fuel cell electrolyte temperature may be maintained at a temperature sufficient to maintain the carbonate electrolyte in the molten state. Whichever temperature is selected, it can affect the amount of reforming that can occur at the anode, and it may be necessary to adjust the amount of reformable fuel input to the anode accordingly.

The amount of modification may additionally or alternatively depend on the utilization of the fuel that can be reformed. For example, in the case where the fuel contains only H ₂ , since H ₂ has already been reformed and can not be reformed, the reforming does not occur. The amount of "syngas produced" by the fuel cell can be defined as the difference in the LVH value of the synthesis gas in the anode input versus the LVH value of the synthesis gas in the anode output. The resulting syngas LHV (sg net) = (LHV (sg out) -LHV (sg in)) where LHV (sg in) and LHV (sg out) are the syngas at the anode inlet and the anode outlet stream Or LHV of the flowing gas. A fuel cell provided with a fuel containing a substantial amount of H ₂ can be limited in terms of possible syngas production because the fuel contains a considerable amount of already modified H ₂ as opposed to containing an additional reformable fuel .

One example of a method of operating a fuel cell having the above-described reduced temperature ratio is to balance and / or match the generation and consumption of heat in the fuel cell or to perform an excessive reforming of the fuel to consume more heat than produced Lt; / RTI &gt; Modifying the reformable fuel to form H ₂ and / or CO may be an endothermic process, while the anode electrochemical oxidation reaction and the cathode combustion reaction (s) may be exothermic. During conventional fuel cell operation, the amount of modification needed to feed the feed components for fuel cell operation may typically consume less heat than the amount of heat generated by the anode oxidation reaction. For example, conventional operation at a fuel utilization rate of about 70% or about 75% produces a temperature ratio that is substantially greater than 1, for example, a temperature ratio of about 1.4 or more, or 1.5 or more. As a result, the output stream of the fuel cell may be hotter than the input stream. Instead of this type of conventional operation, the amount of fuel that is reformed in the reforming stage that accompanies the anode can be increased. For example, additional fuel can be reformed so that the heat generated by the exothermic fuel cell reaction is (approximately) balanced with / consumed by the heat consumed in the reforming and / or can consume more heat than is generated. This can produce a significant excess of hydrogen relative to the amount oxidized at the anode for power production and is less than or equal to about 1.0, such as less than or equal to about 0.95, or less than or equal to about 0.90, or less than or equal to about 0.85, or less than or equal to about 0.80, Lt; / RTI &gt; temperature ratio.

In an aspect of the invention, the temperature ratio can be selected based on the desired temperature reduction across the fuel cell. Some fuel cells may have physical aspects that can be damaged if there is a temperature difference between the inlet and the outlet that is greater than the threshold. The temperature reduction can be calculated by measuring the heat transfer by the bulk stream (e. G., Anode charge, anode charge, cathode charge and cathode charge). The temperature reduction may be a function of total heat consumed in the endothermic reaction, heat released in the exothermic reaction, heat loss through the fuel cell hardware, and any heat added directly to the fuel cell separately from the bulk stream. The heat loss through the fuel cell hardware may be an estimate.

For example up to about 1.0, or up to about 0.95, or up to about 0.90, or up to about 0.85, or up to about 0.80, or up to about 0.75, in contrast to the operating conditions described above for maximum electrical production By operating the fuel cell at a temperature ratio, additional syngas can be generated. This means that an arbitrarily increased amount of chemical energy product can be recovered from the fuel cell product. Excess hydrogen generated by operating at a temperature ratio of about 1.3 or less can be used, for example, as a fuel that is separated from the anode output flow and does not emit greenhouse gases. Alternatively, a water gas-phonetic reaction can be used to balance the amount of hydrogen and CO present in the anode product for use as a synthesis gas having the desired synthesis gas composition, e.g., the desired H ₂ to CO ratio.

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. Instead, in the case of hydrogen generated by the modification of hydrocarbons (or hydrocarbonaceous compounds), CO ₂ is already "trapped" in the anode loop. In addition, hydrogen can be an important input to various refining processes and / or other synthetic processes. Syngas can also be an important input to various processes. In addition to having calorific values, synthesis gas can be used as feedstock to produce other higher value products, for example, by using syngas as input for the Fischer-Tropsch synthesis and / or methanol synthesis process.

Additional fuel cell operating strategies

In addition to, and / or as an alternative to, the fuel cell operating strategy described herein, a molten carbonate fuel cell (e.g., a fuel cell assembly) may have a CO ₂ utilization value of, for example, greater than about 60% Such as the fuel consumption rate of the engine. In this type of construction, the molten carbonate fuel cell can be effective for carbon capture, because the CO ₂ utilization can advantageously be high enough. Rather than attempting to maximize electrical efficiency, this type of configuration can improve or increase the total efficiency of the fuel cell based on the combined electrical and chemical efficiencies. The chemical efficiency may be based on the recovery of the hydrogen and / or syngas stream from the anode exhaust as an output for use in other processes. The electrical efficiency may be reduced compared to some conventional configurations, but it may be possible to use the chemical energy output in the anode exhaust gas to achieve the desired total efficiency of the fuel cell.

In various embodiments, the fuel utilization rate in the fuel cell anode may be about 50% or less, such as about 40% or less, or about 30% or less, or about 25% or less, or about 20% or less. In various embodiments, the fuel utilization rate in 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%, or at least about 25% Or about 30% or more. Additionally or alternatively, the CO ₂ utilization may be at least about 60%, such as at least about 65%, or at least about 70%, or at least about 75%.

In some embodiments, the reformable fuel 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 reacting at the anode , Or greater than about 100%. Additionally or alternatively, the reformable hydrogen content of the fuel in the feed stream delivered to the reforming stages followed by the anode and / or anode may be at least about 50%, such as at least about 75%, or more than the net amount of reacting hydrogen at the anode, or Can be about 100% larger. 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 (s) have. 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 various embodiments, 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 addition to, and / or as an alternative to, the fuel cell operating strategy described herein, molten carbonate fuel cells (e.g., fuel cell assemblies) can also be used to improve or optimize the combined electrical and chemical efficiencies of fuel cells Lt; / RTI &gt; 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. Syngas and / or hydrogen may be used for a variety of applications including chemical synthesis and collection of hydrogen for use as "clean" fuel. In an embodiment of the present invention, it is possible to achieve a high overall efficiency by reducing the electrical efficiency, which is the chemical efficiency based on the chemical energy value of the syngas and / or hydrogen produced for the energy value of the fuel input of the fuel cell .

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 molten carbonate fuel cell may be less than about 40%, such as less than about 35% EE, less than about 30% EE, less than about 25% , About 15% EE or less, or about 10% EE or less. Additionally or alternatively, the EE may be at least about 5%, or at least about 10%, or at least about 15%, or at least about 20%. Additionally or alternatively, the operation of the fuel cell may be characterized based on total fuel cell efficiency (TFCE) such as the combined electrical and chemical efficiencies of the fuel cell (s). When the fuel cell is operated to have a high total fuel cell efficiency, the molten carbonate fuel cell may be operated at a temperature 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 efficiency). For total fuel cell efficiency and / or combined electrical efficiency and chemical efficiency, any additional electricity generated from the use of excess heat generated by the fuel cell may be excluded from the efficiency calculation.

In various embodiments of the invention, the operation of the fuel cell may be characterized based on a desired electrical efficiency of about 40% or less and a desired total fuel cell efficiency of about 55% or more. When the fuel cell is operated to have the desired electrical efficiency and the desired total fuel cell efficiency, the molten carbonate fuel cell has an electrical efficiency of about 40% or less and a TFCE of about 55% or greater, for example, about 35% About 60% or more TFCE, about 30% or less EE and about 65% or more TFCE, about 25% or less EE and about 70% or more TFCE, about 20% or less EE, about 75% or more TFCE, And about 80% or more TFCE, or about 10% or less EE and about 85% or more TFCE.

Justice

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 anode of the fuel cell is defined as a reaction to oxidize the H ₂ by the reaction of the CO ₃ ^2- Sikkim corresponding to generate H ₂ O and CO _2. 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).

Lower calorific value: The lower calorific value is defined as the enthalpy of combustion of the fuel component into the fully oxidized product of the gas phase (ie, the 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 "CO ₂ utilization" and / or "oxidant" utilization. CO ₂ availability and / or oxidant utilization rate values may also be defined in a similar manner.

Fuel excess ratio: Another method of characterizing the reaction in a molten carbonate fuel cell is to determine the amount of hydrogen that is to be oxidized in the anode due to the fuel cell anode reaction, the amount of all the fuel that is delivered 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 molten carbonate fuel cell has an 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 &lt; / RTI &gt; 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 molten carbonate fuel cell has a melting point of at least about 0.25, such as at least about 0.5, or at least about 1.0, or at least about 1.5, or at least about 2.0, or at least about 2.5, or at least about 3.0, 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 though the fuel utilization rate is low once passed through the fuel cell. 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 &quot;. 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 can resist the endothermic reaction, which generates a correspondingly large amount of heat (approximately) to the difference between the amount of heat generated by the anode oxidation reaction and the carbonate formation 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 / carbonate production reaction may be larger than the heat absorbed by the reforming to generate 1 mole of hydrogen. As a result, the fuel cell 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 (Almost) the heat consumed by the reforming, or even the heat consumed by the reforming In excess of the excess heat generated by the charges oxide to be a temperature drop across the fuel cell occurs, it is possible to modify the 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. During operation in a conventional manner for power generation using such fuel, the molten carbonate fuel cell can be operated at a fuel utilization rate of about 75%. This means that about 75% (or ¾) of the fuel delivered to the anode is used to form hydrogen, which reacts with the carbonate ion at the anode to form H ₂ O and CO ₂ . In conventional operation, the remaining about 25% of the fuel content is reformed into H ₂ in the fuel cell (or may pass through the fuel cell without reacting in the case of any CO or H ₂ in the fuel) It is possible to provide heat to the cathode inlet to the fuel cell by burning outside the cell to form H ₂ O and CO ₂ . 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 fuel delivered to the anode, fuel delivered to the cathode, and any fuel used to maintain the temperature of the fuel cell (e.g., fuel delivered to the burner associated with 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) refers to the amount of fuel in the anode inlet stream, the amount of fuel in the cathode inlet stream, and the amount of fuel used to maintain the temperature of the fuel cell Which is the total amount of fuel delivered to 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 &lt; / RTI &gt; 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.

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.

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 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 &gt; 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) 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 &gt; The stacks may also be arranged in a tandem arrangement to produce a high voltage. The parallel arrangement can boost the current. The system and method described herein can be used with a single molten carbonate fuel cell stack when treating a given exhaust gas flow with a sufficiently large volume of the 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 may instead serve 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 .

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 and / 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 the endothermic reaction. This integrated endothermic reaction stage can be defined as being located less than 10 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 less than 10 times the height of the stack element from any heat-integrated fuel cell, or less than 8 times the height of the stack element, 5 times, or less than three times the height of the stack element. In this discussion, the integrated reforming stage and / or the integrated endothermic reaction stage representing the stack elements adjacent to the fuel cell element can be defined as being less than or equal to about one stack element height away from adjacent fuel cell elements.

In some embodiments, a separate reforming stage that is thermally integrated with the fuel cell element may 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 receive heat from the fuel cell, but can be determined not to use the product of the reforming stage as an input to the fuel cell. Instead, one can decide to use the output of this modification stage for other purposes, such as adding the product directly to the anode exhaust stream and / 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. A similar manifold or other arrangement of outlet conduits may be used additionally or otherwise 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 can exit 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 the fuel cell stack may include, but are not limited to, 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 is not passed through 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, MCFC arrays include, but are not limited to, 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 turbines, that provide a CO ₂ -containing stream to the cathode input 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 molten carbonate 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, a reference to a hydrocarbon-containing fuel stream for an MCFC 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 molten carbonate 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, molten carbonate 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 molten carbonate 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 molten carbonate fuel cell may be less than or equal to about 90 vol%, such as less than or equal to about 75 vol%, alternatively less than or equal to about 60 vol%, alternatively less than or equal 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 &lt; RTI ID = 0.0 &gt; C1-C4 &lt; / RTI &gt; 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 MCFC 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.

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 molten carbonate 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 &gt; is not provided. After reforming, the reformed fuel stream 115 may be passed into the anode 127 of the fuel cell 120. The CO ₂ and O ₂ -containing stream 119 may also be passed into the cathode 129. The flow of carbonate ions 122 CO ₃ ^2- from the cathode portion 129 of the fuel cell can provide the remainder of the reactants needed for the anode fuel cell reaction. Based on the reaction at the anode 127, the generated anode exhaust gas 125 is at least one of H ₂ O, CO ₂ , one or more components corresponding to the incompletely reacted fuel (H ₂ , CO, CH ₄ , other equivalent components to the fuel), and optionally may include one or more additional non-reactive component such as N _2, part, and / or other contaminants in 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 &gt; CO ₂ &lt; / RTI &gt; separation stage. Optionally, the anode exhaust gas may first be passed through a water gas-catalyzed reactor 130 to remove any CO (with some H ₂ O) present in the anode exhaust gas, optionally in an aqueous 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 after the CO ₂ separation stage 140, it may optionally be located before the CO ₂ separation stage 140. 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 can 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 CO 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 achieve 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 an input to the desired chemical synthesis process . 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 molten carbonate 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 CO ₂ provided to the cathode, and the internal resistance of the fuel cell. In part, it is possible to typically provide CO ₂ to the cathode by using the anode exhaust gas as at least a portion of the cathode feed stream. In contrast, the present invention may use separate / different sources for anode inputs and cathode inputs. By eliminating any direct connection between the anode charge flow and the composition of the cathode charge flow, it is possible to reduce the total efficiency (electrical + chemical power) of the fuel cell, in particular by generating and / or increasing the amount of syngas, An additional option is available to operate the fuel cell to improve the fuel cell.

In a molten carbonate fuel cell, the transport of carbonate ions across the electrolyte of the fuel cell may provide a way to transport CO ₂ from the first flow path to the second flow path, enabling further transport to the high concentration (anode) from the cathode), which thus can facilitate the capture of CO _2. Some of the selectivity of the fuel cell for CO ₂ separation may be based on an electrochemical reaction that causes the cell to generate power. In the case of a non-reactive material (e.g., N ₂ ) that does not participate effectively in the electrochemical reaction in the fuel cell, the reaction and the transport from the cathode to the anode may be present in negligible amounts. In contrast, the potential (voltage) difference between the cathode and the anode can provide a strong driving force for the transport of carbonate ions across the fuel cell. As a result, the transport of carbonate ions in the molten carbonate fuel cell can cause CO ₂ to be transported from the cathode (lower CO ₂ concentration) to the anode (higher CO ₂ concentration) with relatively high selectivity. However, a difficulty in using a molten carbonate fuel cell for carbon dioxide removal may be that the fuel cell has limited ability to remove carbon dioxide from a relatively dilute cathode feed. The voltage and / or power generated by the carbonate fuel cell may begin to plunge as the CO ₂ concentration falls below about 1.0 mol%. As the CO ₂ concentration decreases at some point, for example, to less than about 0.3% by volume, the voltage across the fuel cell becomes sufficiently low that little or no additional transport of the carbonate occurs and the fuel cell stops operating . Therefore, at least some of the CO ₂ will be present in the exhaust gas from the cathode stage of the fuel cell under commercially viable operating conditions.

The amount of carbon dioxide delivered to the fuel cell cathode (s) may be determined based on the CO ₂ content of the source of the cathode inlet and / or the amount of carbon-containing fuel in the cathode inlet stream. In the case of a cathode inlet stream containing a carbon-containing fuel, an amount of CO ₂ proportional to the volume percent of the fuel in the cathode inlet stream multiplied by the average number of carbons in the fuel compound can be generated in the in- have. For example, H ₂ has no carbon, CO and CH ₄ have one carbon, ethane has two carbons, and so on. As a result, it is possible to reach about 0.25% by volume to about 10% by volume from the amount of CO ₂ N cache of CO ₂ supplied to the cathode (a cathode of the fuel when both the H ₂₎ by the combustion of the fuel. The upper limit of the range of CO ₂ resulting from the burned fuel represents a situation in which a significant amount of the fuel corresponds to an aromatic compound and / or to another fuel having a plurality of carbons. The CO ₂ content of the cathode inlet stream resulting from the combustion of the fuel may also be any CO ₂ present in the cathode inlet stream when the stream enters the cathode.

An example of a CO ₂ -containing stream suitable for use as a cathode feed stream may be an output from an combustion source or an exhaust gas stream. Examples of combustion sources include, but are not limited to, sources based on combustion of natural gas, combustion of coal, and / or combustion of other hydrocarbon-type fuels (including fuel derived from an organism). Additional or other sources may include other types of devices that burn carbon-containing fuels to heat other types of boilers, flammable heaters, furnaces, and / or other components (e.g., water or air). Approximately, the CO ₂ content of the output flow from the combustion source can be small in the flow. Even in the case of a higher CO ₂ content of exhaust gas flow, such as a coal-flamed combustion source, the CO ₂ content from most commercial coal-fired power plants can be less than about 15% by volume. More generally, the CO ₂ content in the output or exhaust gas flow from the combustion source is greater than or equal to about 1.5%, or greater than or equal to 1.6%, or greater than or equal to 1.7%, or greater than or equal to 1.8%, or greater than or equal to 1.9% , Or at least 2 vol%, or at least about 4 vol%, or at least about 5 vol%, or at least about 6 vol%, or at least about 8 vol%. Additionally or alternatively, the CO ₂ content of the product or exhaust gas flow from the combustion source can be up to about 20 vol%, for example up to about 15 vol%, or up to about 12 vol%, or up to about 10 vol% About 9 vol% or less, or about 8 vol% or less, or about 7 vol% or less, or about 6.5 vol% or less, or about 6 vol% or less, or about 5.5 vol% May be less than or equal to 4.5 vol%. The given concentration is a drying criterion. Note that there may be lower CO ₂ content values in some natural gas or exhaust gases from a methane combustion source, such as generators that are part of a power generation system that may or may not be included in the exhaust gas recycle loop.

Other possible sources of cathode input streams may additionally or alternatively comprise a source of biologically generated CO ₂ . This example, as CO ₂ is generated during the ethanol production organisms may include a CO ₂ generated during the processing of the derived compound. Additional or other examples may include CO ₂ generated by the combustion of bio-generated fuel, such as combustion of lignocellulosic. Another additional or other possible CO ₂ source CO ₂ generated by the plant for the production of steel, cement and / or paper-may correspond to the output or the exhaust gas streams from various industrial processes on the same bearing stream.

Another additional or other possible sources of CO ₂ is CO ₂ from the fuel cell may be a containing stream. The CO ₂ -containing stream from the fuel cell may be a cathode output stream from a different fuel cell, an anode output stream from a different fuel cell, a recycle stream from the cathode product of the fuel cell to the cathode input, and / May correspond to a recycle stream from the anode output to the cathode input. For example, an MCFC operating in a stand-alone manner under conventional conditions can produce a cathode exhaust gas having a CO ₂ concentration of at least about 5 vol%. Such CO ₂ -containing cathode exhaust gases may be used as cathode inputs to MCFCs operated in accordance with embodiments of the present invention. More generally, other types of fuel cells that produce CO ₂ output from cathode exhaust gases, as well as CO ₂ -containing streams that are not generated by a "combustion" reaction and / Other types may be used additionally or otherwise. Optionally, but preferably, the CO ₂ -containing stream from another fuel cell can be from another molten carbonate fuel cell. For example, in the case of a molten carbonate fuel cell connected in series with a cathode, the output from the cathode of the first molten carbonate fuel cell can be used as an input to the cathode of the second molten carbonate fuel cell.

For various types of CO ₂ -containing streams from sources other than combustion sources, the CO ₂ content of the stream can vary widely. CO ₂ content in the input stream of the cathode draw may contain from about 2 vol.% Or more, such as about 4% by volume or more, preferably about 5% by volume or more, or about 6% by volume, or at least about 8% by volume or more of CO ₂ . Additionally or alternatively, the CO ₂ content in the feed stream to the cathode may be up to about 30% by volume, such as up to about 25% by volume, or up to about 20% by volume, or up to about 15% by volume, Or about 8% by volume, or about 6% by volume or less, or about 4% by volume or less. For some higher CO ₂ content streams, the CO ₂ content may be greater than about 30% by volume, such as a stream substantially consisting of CO ₂ and other compounds in balance. As an example, a gas-fired turbine without exhaust gas recirculation can produce an exhaust gas stream having a CO ₂ content of about 4.2 vol.%. Using exhaust gas recirculation, a gas-fired turbine can produce an exhaust gas stream having a CO ₂ content of about 6 to 8% by volume. The stoichiometric combustion of methane can produce an exhaust stream having a CO ₂ content of about 11% by volume. Combustion of coal can produce an exhaust stream having a CO ₂ content of about 15 to 20% by volume. A flammable heater using refining off-gas can produce an exhaust stream having a CO ₂ content of about 12 to 15 vol.%. A gas turbine operating on low BTU gas without any exhaust gas recirculation can produce an exhaust gas stream having a CO ₂ content of about 12% by volume.

In addition to CO ₂ , the cathode feed stream must contain O ₂ to provide the components needed for the cathode reaction. Some cathode input streams may be based on having air as a constituent. For example, combustion exhaust gas streams can be formed by burning hydrocarbon fuel in the presence of air. Other types of cathode feed streams having an oxygen content based on the inclusion of such combustion exhaust gas streams or air may have an oxygen content of up to about 20 vol%, such as up to about 15 vol%, or up to about 10 vol%. Additionally or alternatively, the oxygen feed rate of the cathode feed stream can be at least about 4 vol.%, Such as at least about 6 vol.%, Or at least about 8 vol.%. More generally, the cathode input stream may have an oxygen content suitable for performing the cathode reaction. In some embodiments, it may correspond to an oxygen content of from about 5% by volume to about 15% by volume, for example from about 7% by volume to about 9% by volume. For many types of cathode feed streams, the combined amount of CO ₂ and O ₂ may correspond to less than about 21% by volume of the feed stream, such as less than about 15% by volume of the stream, or less than about 10% by volume of the stream. The oxygen-containing air stream can be combined with a CO ₂ source having a low oxygen content. For example, the exhaust gas stream generated by burning coal may include a low oxygen content that can mix with air to form a cathode inlet stream.

In addition to CO ₂ and O ₂ , the cathode feed stream may also be composed of inert / non-reactive materials such as N ₂ , H ₂ O, and other typical oxidant (air) components. For example, in the case of cathode inputs derived from the exhaust gas from the combustion reaction, if air is used as part of the oxidant source of the combustion reaction, the exhaust gas can include N ₂ , H ₂ O, and trace amounts of other Lt; RTI ID = 0.0 &gt; air. &Lt; / RTI &gt; Depending on the nature of the fuel source of the combustion reaction, additional substances present after combustion based on the fuel source may be present in the fuel such as H ₂ O, oxides of nitrogen (NO _x ) and / or oxides of sulfur (SO _x ) Or other compounds that are part or completely combustion products of the compounds present in the fuel. These materials may be present in an amount that can reduce overall cathode activity but not contaminate the cathode catalyst surface. This reduction in performance can be tolerated, or the material interacting with the cathode catalyst can be reduced to a level acceptable by known contaminant removal techniques.

The amount of O ₂ present in the cathode feed stream (e.g., the cathode feed stream based on the combustion exhaust gas) may advantageously be sufficient to provide the oxygen required for the cathode reaction of the fuel cell. Therefore, the volume percentage of O ₂ can advantageously be at least 0.5 times the amount of CO ₂ in the exhaust gas. Optionally, additional air can be added to the cathode feed, if necessary, to provide sufficient oxidant for the cathode reaction. When some type of air is used as the oxidant, 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 least about 95 vol%. In some embodiments, the cathode feed stream may additionally or alternatively contain a compound that is typically seen as a contaminant (e.g., H ₂ S or NH ₃ ). In another embodiment, the cathode input stream can be cleaned to reduce or minimize the content of such contaminants.

In addition to the reaction to form carbonate ions for transport across the electrolyte, the conditions of the cathode may also be suitable for the conversion of nitrogen oxides to nitrates and / or nitrate ions. Hereinafter, for convenience, only nitrate ions are referred to. The resulting nitrate ions may also be transported across the electrolyte for reaction at the anode. The NO _x concentration in the cathode feed stream can typically be in the order of ppm and thus this nitrate transport reaction can have a minimal impact on the amount of carbonate transported across the electrolyte. However, this NO _x removal method may be advantageous for a cathode input stream based on combustion exhaust gas from a gas turbine because it can provide a mechanism for reducing NO _x emissions. The conditions of the cathode may additionally or alternatively be suitable for the conversion of unburned hydrocarbons (with O _{2 in the} cathode feed stream) to typical combustion products (e.g., CO ₂ and H ₂ O).

Suitable temperatures for operation of the MCFC may be from about 450 캜 to about 750 캜, such as about 500 캜 or higher, the inlet temperature is about 550 캜, and the outlet temperature is about 625 캜. Before entering the cathode, heat may be applied to the combustion exhaust gas, if necessary, or heat may be removed from the combustion exhaust gas to provide heat for other processes such as, for example, reforming the fuel input of the anode. For example, when the source of the cathode input stream is a combustion exhaust stream, the combustion exhaust stream may have a temperature higher than the desired temperature of the cathode inlet. In this embodiment, heat may be removed from the combustion exhaust gas prior to use as a cathode feed stream. Alternatively, the combustion exhaust gas may be at a very low temperature, for example after a wet gas scrubber on a coal-fired boiler, in which case the combustion exhaust gas may be below about 100 ° C. Alternatively, the combustion exhaust gas may be an exhaust gas of a gas turbine operating in a combined cycle mode, and in a combined cycle mode, the gas may be cooled by rising steam to operate the steam turbine for further power generation. In this case, the gas may be less than about 50 캜. Heat can be applied to the combustion exhaust gas, which is colder than required.

Molten carbonate fuel cell operation

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 into the anode inlet using the modified product. Optionally, the CO ₂ from the anode outlet can be recycled to the cathode inlet during operation of the MCFC in a one-pass mode. More generally, in some other embodiments, recirculation from the anode outlet to the cathode inlet can be made when operating the MCFC in a one-pass manner. 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 the MCFC for generating power. In Figure 3, the anode portion of the fuel cell can receive fuel and water vapor (H ₂ O) as inputs, and can contain water, CO ₂ , and optionally H ₂ , CH ₄ (or other hydrocarbons) and / CO. The cathode portion of the fuel cell the output corresponding to CO ₂ and some of the oxidant (e.g., air / O ₂₎ of the received, there might be, O ₂ is reduced in the depleted oxidant (air), the amount CO ₂ as inputs . The cathode portion may also be the combustion heat, it is possible to accept at least one compound as part of the fuel inlet stream which can generate CO ₂ and H ₂ O. In the fuel cell, CO ₃ ^2- ions formed at the cathode side can be transported across the electrolyte to provide the carbonate ions necessary for the reaction at the anode.

Several reactions can be made in a molten carbonate 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 + CO ₃ ^2- => H ₂ O + CO ₂ + 2e ^-

(5) <Cathode> ½O ₂ + CO ₂ + 2e ^- => CO ₃ ^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) with carbonate ions either present in the feed or optionally in reaction (2) to form H ₂ O, CO ₂ and electrons to the circuit . Reaction (5) combines the electrons from O ₂ , CO ₂ , and the circuit to produce carbonate ions. Carbonate ions produced by the reaction (5) can be transported across the electrolyte of the fuel cell to provide the carbonate ions needed for the reaction (4). With the transport of carbonate 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.

Integrated example: for integration with combustion turbines

In some aspects of the invention, a combustion source for generating power or for exhausting CO ₂ -containing exhaust gas may be integrated with the operation of the molten carbonate fuel cell. An example of a suitable combustion source is a gas turbine. Preferably, the gas turbine is capable of combusting natural gas, methane gas, or other hydrocarbon gas in a combined cycle mode integrated with steam recovery and heat recovery for additional efficiency. Currently, natural gas combined cycle efficiency is the largest and is about 60% of the latest design. It can be produced containing the exhaust stream - MCFC CO ₂ generated by the operation and compatible elevated temperature, for example 700 to 300 ℃ ℃, preferably from 500 ℃ to 650 ℃. Prior to introduction into the turbine, sulfur-like contaminants that can contaminate the MCFC may be optionally but preferably cleaned from the gas source. Alternatively, the gas source may be a coal-fired generator, which in this case typically flushes the exhaust after combustion, due to the higher level of pollutants in the exhaust. In this alternative, some heat exchange from / to the gas may be needed to allow cleaning at low temperatures. In additional or alternative embodiments, the source of CO ₂ -containing exhaust gas may be a boiler, combustor, or other heat source that burns carbon-rich fuel. In other additional or alternative embodiments, the source of the CO ₂ -containing exhaust gas may be bio-generated CO ₂ combined with other sources.

In some embodiments, the operation of the combustion source may be altered to utilize the ability of the cathode to burn fuel in the cathode inlet stream. In the case of a conventional combustion reaction, a typical objective may be to substantially burn all the fuel delivered to the combustion reaction zone. This can simplify the treatment of the exhaust gas, since the fuel remains in the combustion exhaust gas with little or no residue. However, implementing a combustion reaction zone to achieve substantially complete combustion does not necessarily correspond to the most efficient manner of operating the combustion zone. Instead, in order to improve the overall efficiency of the combustion reaction, it may be desirable to operate the combustion zone to have a residual fuel content after combustion. Typically, such residual fuel is liable to be discarded due to the low concentration of fuel in the combustion exhaust gas. In addition, the discarded fuel may be a source of pollution, or may require a pollution control device to remove it. However, in the case of treating such exhaust gas using a molten carbonate fuel cell, it is also possible to use the residual fuel to generate additional CO _2, to generate additional heat for the fuel cell, A combination of these can be achieved. At least in part, the amount of fuel remaining in the combustion exhaust gas used as part of the cathode inlet stream of the fuel cell is greater than or equal to about 0.5% by volume, or greater than or equal to about 1.0% by volume, as previously described for the fuel content of the cathode inlet stream, and About 5.0 vol% or less.

To integrate with a combustion source, several other configurations for treating the fuel cell anode may be desirable. For example, another configuration may be to recycle at least a portion of the exhaust gas from the fuel cell anode to the input of the fuel cell anode. The output stream from the MCFC anode may contain H ₂ O, CO ₂ , optionally CO, and optionally but typically unreacted fuel (eg, H ₂ or CH ₄ ) as the main output component. Instead of using this output stream as an external fuel stream and / or an input stream for integration with other processes, it is also possible to separate the CO ₂ from components having a potential calorific value (e.g., H ₂ or CO) One or more separations may be performed on the output stream. The component having the calorific value can then be recycled to the anode input.

This type of configuration can provide one or more advantages. First, it is possible to separate CO ₂ from the anode product, for example, by using a cryogenic CO ₂ separator. Some of the components of the anode output (H ₂ , CO, CH ₄ ) are components that can not be easily condensed, whereas CO ₂ and H ₂ O can be separated separately as condensed phases. 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. Alternatively, in some embodiments, less CO ₂ is removed from the anode product so that from about 50% to about 90%, such as less than about 80%, or less than about 70%, by volume of CO ₂ in the anode product can be isolated can do. After separation, the remainder of the anode output may correspond to a component having primarily a calorific value, and a reduced amount of CO ₂ and / or H ₂ O. This portion of the anode output after separation may be recycled for use as part of the anode charge with additional fuel. In this type of configuration, the fuel utilization of the first pass through the MCFC (s) may be low, but the unused fuel may be advantageously recirculated for another pass through the anode. As a result, the one-pass fuel utilization rate may be at a reduced level while avoiding the loss (discharge) of unburned fuel to the environment.

In addition to or in lieu of recycling some of the anode exhaust gas to the anode input, another configuration option may be used as an input for the combustion reaction of a turbine or other combustion device (e.g., a boiler, furnace and / It may be using part of the gas. The relative amount of anode exhaust gas recycled to the anode input and / or as input to the combustion apparatus may be any convenient or desirable amount. When the anode exhaust gas is recycled only to one of the anode input and the combustion device, the amount of recycle may be adjusted to any convenient amount, for example up to 100% of the remaining anode exhaust gas fraction after removal of CO ₂ and / or H ₂ O by separation Lt; / RTI &gt; When a portion of the anode exhaust gas is recycled to both the anode input and the combustion apparatus, the total amount recycled by definition may be less than 100% of the remainder of the anode exhaust gas. Alternatively, any convenient split of the anode exhaust gas may be used. In various embodiments of the present invention, the amount of recycle into the anode input may be at least about 10%, such as at least about 25%, at least about 40%, at least about 50%, at least about 60% About 75% or more, or about 90% or more. In addition to or in addition to these embodiments, the amount of recycle into the anode input may be less than about 90%, such as less than about 75%, less than about 60%, less than about 50% of the remaining anode exhaust gas , About 40% or less, about 25% or less, or about 10% or less. Additionally or alternatively, in various embodiments of the present invention, the amount of recycle to the combustion apparatus can be at least about 10%, such as at least about 25%, at least about 40%, at least about 50% About 60% or more, about 75% or more, or about 90% or more. In addition to or in addition to these embodiments, the amount of recycle to the combustion apparatus may be less than about 90%, such as less than about 75%, less than about 60%, less than about 50% About 40% or less, about 25% or less, or about 10% or less.

In another embodiment of the present invention, the fuel for the combustion apparatus may additionally or alternatively be inert and / or a fuel having an increased amount of the component acting as a diluent in the fuel. CO ₂ and N ₂ are examples of components of a natural gas feed that can be relatively inert during the combustion reaction. Once the amount of inert components in the fuel feed reaches a sufficient level, the performance of the turbine or other combustion sources may be affected. The effect may be due in part to the ability of the inert component to absorb heat (which may tend to quench the combustion reaction). An example of a fuel feed with sufficient levels of inert components is a fuel feed containing about 20 vol% or more CO ₂ , or a fuel feed containing about 40 vol% or more N ₂ , It may comprise a fuel feed containing a combination of CO ₂ and N ₂ having a heat capacity inert. (Note that CO ₂ has a greater heat capacity than N ₂ , so lower CO ₂ concentrations can have an effect similar to higher N ₂ concentrations. CO ₂ also participates in the combustion reaction more easily than N ₂ number, and may do so to remove the H ₂ from the combustion while. consumption of such a H ₂ can reduce the flame speed and by narrowing the flammable range of the air-fuel mixture have a great influence on the combustion of fuel.) more Generally, for a fuel feed containing an inert component that affects the flammability of the fuel feed, the inert component in the fuel feed is at least about 20 vol%, such as at least about 40 vol%, or at least about 50 vol% Can be at least 60 vol.%. Preferably, the amount of inert component in the fuel feed may be less than about 80% by volume.

If a sufficient amount of inert component is present in the fuel feed, the resulting fuel feed may be outside the flammable window of the fuel component of the feed. In this type of situation, H ₂ from the recycled portion of the anode exhaust gas can be added to the combustion zone of the generator to expand the flammability window of the combination of fuel feed and H ₂ , for example, about 20 vol% Or more of CO ₂ or about 40% by volume or more of N ₂ (or another combination of CO ₂ and N ₂ ) can be successfully burned.

For the total volume of fuel feed and H ₂ delivered to the combustion zone, the amount of H ₂ to expand the flammable window is at least about 5% by volume, such as at least about 10% by volume of the total volume of fuel feed and H ₂ , / Or about 25% by volume or less. Another option to characterize the amount of H ₂ added to expand the flammable window may be based on the amount of fuel component present in the fuel feed prior to the addition of H ₂ . The fuel component may correspond to methane, natural gas, other hydrocarbons, and / or other components commonly seen as a fuel for turbines or other generators powered by combustion. The amount of H ₂ added to the fuel feed is about one-third (1: 3 ratio of H ₂ : fuel component) of the volume of the fuel component in the fuel feed, eg, about 1/2 of the volume of the fuel component 1: 2 ratio). Additionally or alternatively, the amount of H ₂ added to the fuel feed may be approximately equal to or less than the volume of the fuel component in the fuel feed (ratio of 1: 1). For example, in the case of a feed containing about 30 vol.% CH ₄ , about 10% N _2, and about 60% CO ₂ , an amount sufficient to attain a H ₂ to CH ₄ ratio of about 1: 2 Of the anode exhaust gas may be added to the fuel feed. H ₂ only in the case of the idealized anode exhaust gas containing, 1: Addition of H ₂ for obtaining a ratio of 2 is about 26% by volume of CH _4, 13% by volume of H _2, 9% by volume of N ₂ and 52 Yielding a feed containing vol.% CO ₂ .

Additional embodiments

The invention further includes, or alternatively comprises one or more of the following embodiments listed below.

Embodiment 1. A fuel cell system comprising: an anode fuel stream comprising a reformable fuel; an internal reforming element associated with an anode of a molten carbonate fuel cell; an internal reforming element associated with the anode of the molten carbonate fuel cell;

Introducing a cathode inlet stream comprising CO ₂ , O ₂ , and at least one fuel compound into a cathode of a molten carbonate fuel cell;

Generate electricity in the molten carbonate fuel cell;

Generating an anode exhaust gas comprising H ₂ , CO and CO ₂ ;

A method for generating electricity comprising a cache Sikkim generating a cathode exhaust gas containing about 1 vol% or more O ₂ and at least one compound of the fuel 100vppm about or less, at this time,

Wherein the at least one fuel compound comprises H ₂ , at least one carbon-containing fuel compound, or a combination thereof, wherein the concentration of the at least one fuel compound in the cathode inlet stream is at least about 0.01% Wherein the concentration of the at least one fuel compound is less than the spontaneous concentration in the operating conditions in the cathode of the fuel cell.

Embodiment 2. The method of Embodiment 1, wherein the methylene-equivalent volume percent of the at least one fuel compound is at least about 0.02% by volume.

Embodiment 3. The method of embodiment 3 wherein the molten carbonate fuel cell comprises an electrode surface and an ancillary catalyst surface, wherein the ancillary catalyst surface comprises at least one Group VIII metal and the generation of the cathode exhaust gas comprises the presence &Lt; / RTI &gt; The method of embodiment 1 or embodiment 2 comprising oxidizing at least a portion of one or more fuel compounds.

Embodiment 4. A fuel cell system, comprising: introducing an anode fuel stream comprising a reformable fuel into an anode of a molten carbonate fuel cell, an internal reforming element followed by an anode of the molten carbonate fuel cell, or a combination thereof;

Introducing a cathode inlet stream comprising CO ₂ , O ₂ , and at least one fuel compound into a cathode of a molten carbonate fuel cell;

Generate electricity in the molten carbonate fuel cell;

Generating an anode exhaust gas comprising H ₂ , CO and CO ₂ ;

To generate a cathode exhaust gas containing about 1% by volume or more of O ₂

A method of generating electricity, comprising:

Wherein the at least one fuel compound comprises at least one aromatic compound, at least one carbon-containing fuel compound having at least 5 carbons, or a combination thereof, wherein the at least one fuel compound in the cathode inlet stream comprises at least about 0.02% - equivalent volume percent, wherein the concentration of the at least one fuel compound in the cathode inlet stream is less than the spontaneous concentration in the operating conditions at the cathode of the fuel cell, and the methylene equivalent volume percent of the at least one fuel compound is less than Wherein the cathode of the molten carbonate fuel cell is at least about 50% lower than the methylene-equivalent volume percent of the cathode inlet stream and the methylene-equivalent volume percentage of the cathode exhaust gas is optionally no more than about 0.01% And an ancillary catalyst surface, said ancillary catalyst surface comprising one or more Group VIII metals , Wherein the cache comprises the generation of the cathode exhaust gas oxidising at least a portion of one or more of the fuel compound in the presence of additional catalyst surface.

Embodiment 5. The method of claim 1, wherein the at least one Group VIII metal comprises Ni, Pt, Pd, Co, Rh, Ru, Re, Ir, Fe, The method of Embodiment 3 or Embodiment 4, comprising a combination of these.

Embodiment 6. The method of any one of embodiments 1-5 wherein the cathode inlet stream has a sulfur content of less than or equal to about 25 wppm, such as less than or equal to about 15 wppm.

7. The method of claim 1 wherein the at least one fuel compound in the cathode inlet stream comprises a heteroatom different from C, H, and O, and wherein the concentration of heteroatoms different from C, H, and O is about The method of any one of embodiments &lt; RTI ID = 0.0 &gt; 1 to &lt; / RTI &gt;

Embodiment 8. The method of any of the preceding claims, wherein the cathode inlet stream comprises at least a portion of a combustion exhaust gas, and wherein at least a portion of the combustion exhaust gas optionally comprises at least about 0.02 vol.% Methylene- And wherein at least a portion of the combustion exhaust gas is optionally at least a portion of the exhaust gas from the gas turbine. &Lt; Desc / Clms Page number 13 &gt;

Embodiment 9. The method of any one of Embodiments 1 to 8, wherein the molten carbonate fuel cell is operated at a temperature ratio of from about 0.25 to about 1.3, for example, from about 0.25 to about 1.0, or from about 0.4 to about 1.0. Gt;

Embodiment 10. The method of any one of the preceding claims, wherein the amount of reformable fuel introduced into the anode of the molten carbonate fuel cell, the reforming stage (optionally an internal reforming element) followed by the anode of the molten carbonate fuel cell, The method of any one of the embodiments 1 to 9, wherein the molten carbonate fuel cell is at least about 75% more reactive than the amount of hydrogen that is reacted.

Embodiment 11. The method of any one of Embodiments 1 to 10, wherein the fuel utilization rate at the anode of the molten carbonate fuel cell is about 50% or less and the CO ₂ utilization rate at the cathode of the molten carbonate fuel cell is at least about 60% The method of one embodiment.

Embodiment 12. The method of any one of Embodiments 1 to 11, wherein the molten carbonate fuel cell has an electrical efficiency of about 10% to about 40% and a total fuel cell efficiency of the molten carbonate fuel cell is greater than or equal to about 55% Gt;

Embodiment 13. A molten carbonate fuel cell system comprising a molten carbonate fuel cell having an anode and a cathode, wherein the cathode comprises an ancillary catalyst surface comprising an electrode surface and at least one Group VIII metal, Wherein the concentration of the at least one Group VIII metal on the catalyst surface is lower in a first region of the catalyst surface relative to a concentration of the at least one Group VIII metal in the second region of the secondary catalyst surface, Lt; RTI ID = 0.0 &gt; 1 &lt; / RTI &gt; region is closer to the cathode inlet of the cathode of the molten carbonate fuel cell than the second region of the secondary catalyst surface.

Wherein the at least one Group VIII metal comprises Ni, Pt, Pd, Co, Rh, Ru, Re, Ir, Fe, or combinations thereof, , &Lt; / RTI &gt; or a combination thereof.

Embodiment 15. The system of embodiment 13 or embodiment 14 wherein the area of the ancillary catalyst surface comprises a steadily increasing concentration gradient of one or more Group VIII metals.

16. The catalyst according to any of the preceding claims, wherein the first region of the ancillary catalyst surface comprises at least one Group VIII metal and the second region of the ancillary catalyst surface is different from at least one Group VIII metal of the first region of the catalyst surface 15. The system of any one of embodiments 13 to 15, wherein the system comprises one or more additional Group VIII metals.

17. The catalyst according to any one of the preceding claims, wherein the second region of the secondary catalyst surface comprises at least one Group VIII metal and the first region of the secondary catalyst surface is different from at least one Group VIII metal of the secondary region of the catalyst surface 15. The system of any one of embodiments 13 to 15, wherein the system comprises one or more additional Group VIII metals.

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 (17)

Introducing an anode fuel stream comprising a reformable fuel into an anode of a molten carbonate fuel cell, an internal reforming element associated with an anode of the molten carbonate fuel cell, or a combination thereof;
Introducing a cathode inlet stream comprising CO ₂ , O ₂ , and at least one fuel compound into a cathode of the molten carbonate fuel cell;
Generating electricity in the molten carbonate fuel cell;
Generating an anode exhaust gas comprising H ₂ , CO and CO ₂ ;
Sikkim generating a cathode exhaust gas containing about 1 vol% or more O ₂ and at least one compound of the fuel below about 100vppm
A method of generating electricity, comprising:
Wherein the at least one fuel compound comprises H ₂ , at least one carbon-containing fuel compound, or a combination thereof, wherein the concentration of the at least one fuel compound in the cathode inlet stream is at least about 0.01 vol% Wherein the concentration of the one or more fuel compounds is less than the autoignition concentration in the operating conditions in the cathode of the fuel cell. The method according to claim 1,
Wherein the methylene-equivalent volume percent of the at least one fuel compound is at least about 0.02% by volume. 3. The method according to claim 1 or 2,
Said molten carbonate fuel cell comprising an electrode surface and an ancillary catalyst surface, said ancillary catalyst surface comprising at least one Group VIII metal, wherein the generation of said cathode exhaust gas is carried out in the presence of said ancillary catalyst surface, And oxidizing at least a portion of the at least one fuel compound. Introducing an anode fuel stream comprising a reformable fuel into an anode of a molten carbonate fuel cell, an internal reforming element followed by an anode of the molten carbonate fuel cell, or a combination thereof;
Introducing a cathode inlet stream comprising CO ₂ , O ₂ , and at least one fuel compound into a cathode of the molten carbonate fuel cell;
Generating electricity in the molten carbonate fuel cell;
Generating an anode exhaust gas comprising H ₂ , CO and CO ₂ ;
To generate a cathode exhaust gas containing about 1% by volume or more of O ₂
A method of generating electricity, comprising:
Wherein the at least one fuel compound comprises at least one aromatic compound, at least one carbon-containing fuel compound having at least 5 carbons, or a combination thereof,
Wherein the at least one fuel compound in the cathode inlet stream has a methylene-equivalent volume percentage of at least about 0.02% by volume, and wherein the concentration of the at least one fuel compound in the cathode inlet stream is greater than the concentration of the at least one fuel compound in the cathode operating conditions in the cathode of the fuel cell. Below the spontaneous ignition concentration,
Wherein the methylene-equivalent volume percent of the at least one fuel compound is at least about 50% lower than the methylene-equivalent volume percent of the cathode inlet stream and the methylene-equivalent volume percent of the cathode exhaust gas is at least about 0.01% ego,
Wherein the cathode of the molten carbonate fuel cell has an electrode surface and an ancillary catalyst surface, the ancillary catalyst surface comprises at least one Group VIII metal, and the generation of the cathode exhaust gas is carried out in the presence of the ancillary catalyst surface And oxidizing at least a portion of the at least one fuel compound. The method according to claim 3 or 4,
Wherein the at least one Group VIII metal comprises Ni, Pt, Pd, Co, Rh, Ru, Re, Ir, Fe, or a combination thereof and includes at least Ni, Co, Fe, Pt, Pd, / RTI &gt; 6. The method according to any one of claims 1 to 5,
Wherein the cathode inlet stream has a sulfur content of less than or equal to about 25 wppm, e.g., less than or equal to about 15 wppm. 7. The method according to any one of claims 1 to 6,
Wherein the at least one fuel compound in the cathode inlet stream comprises a heteroatom different from C, H, and O, and wherein the concentration of heteroatoms different from C, H, and O is about 100 wppm or less, Way. 8. The method according to any one of claims 1 to 7,
Wherein the cathode inlet stream comprises at least a portion of the combustion exhaust gas and wherein at least a portion of the combustion exhaust gas optionally comprises at least one carbon-containing fuel compound in an amount of at least about 0.02 vol% methylene-equivalent volume% Wherein at least a portion of the exhaust gas is optionally at least a portion of the exhaust gas from the gas turbine. 9. The method according to any one of claims 1 to 8,
Wherein the molten carbonate fuel cell is operated at a thermal ratio of from about 0.25 to about 1.3, such as from about 0.25 to about 1.0, or from about 0.4 to about 1.0. 10. The method according to any one of claims 1 to 9,
Wherein the amount of reformable fuel introduced into the anode of the molten carbonate fuel cell, the reforming stage (optionally an internal reforming element) followed by the anode of the molten carbonate fuel cell, or a combination thereof, The amount of hydrogen being reacted in the carbonate fuel cell is greater than about 75%. 11. The method according to any one of claims 1 to 10,
Wherein the fuel utilization rate at the anode of the molten carbonate fuel cell is less than or equal to about 50% and the CO ₂ in the cathode of the molten carbonate fuel cell Wherein the utilization rate is about 60% or more. 12. The method according to any one of claims 1 to 11,
Wherein the molten carbonate fuel cell has an electrical efficiency of about 10% to about 40%, and the molten carbonate fuel cell has a total fuel cell efficiency of about 55% or more. A molten carbonate fuel cell system comprising a molten carbonate fuel cell having an anode and a cathode,
Wherein the cathode comprises an ancillary catalyst surface comprising an electrode surface and at least one Group VIII metal,
Wherein the concentration of the at least one Group VIII metal on the ancillary catalyst surface is lower in a first region of the ancillary catalyst surface than the concentration of the at least one Group VIII metal in the second region of the ancillary catalyst surface,
Wherein the first region of the ancillary catalyst surface is closer to the cathode entrance of the cathode of the molten carbonate fuel cell than the second region of the ancillary catalyst surface. 14. The method of claim 13,
Wherein the at least one Group VIII metal comprises Ni, Pt, Pd, Co, Rh, Ru, Re, Ir, Fe, or a combination thereof and comprises at least Ni, Co, Fe, Pt, Pd, &Lt; / RTI &gt; The method according to claim 13 or 14,
Wherein the area of the ancillary catalyst surface comprises a steadily increasing concentration gradient of one or more Group VIII metals. 16. The method according to any one of claims 13 to 15,
Wherein a first region of the ancillary catalyst surface comprises at least one Group VIII metal and a second region of the ancillary catalyst surface is at least one additional region different from at least one Group VIII metal of the first region of the ancillary catalyst surface RTI ID = 0.0 &gt; VIII &lt; / RTI &gt; metal. 16. The method according to any one of claims 13 to 15,
Wherein the second region of the ancillary catalyst surface comprises at least one Group VIII metal and the first region of the ancillary catalyst surface is at least one additional region different from the at least one Group VIII metal of the second region of the ancillary catalyst surface RTI ID = 0.0 &gt; VIII &lt; / RTI &gt; metal.

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