TWI464955B - Systems and processes of operating fuel cell systems - Google Patents

Description

Fuel cell system and method of operating same

The present invention relates to fuel cell systems and methods of operating fuel cells. In particular, the present invention relates to systems and methods for operating a molten carbonate fuel cell system.

Molten carbonate fuel cells convert chemical energy into electrical energy. Molten carbonate fuel cells are useful because they deliver high quality, reliable electrical power, clean and relatively compact generators. These features make the use of molten carbonate fuel cells as a power source in urban areas, ships or remote areas where access to power sources is limited.

A molten carbonate fuel cell is formed by an anode, a cathode, and an electrolytic layer sandwiched between the anode and the cathode. The electrolyte comprises an alkali metal carbonate, an alkaline earth metal carbonate, a molten alkali metal carbonate, or a mixture thereof, which is suspended in a porous, insulating, and chemically inert matrix. An oxidizable fuel gas or a gas recombinable in the fuel cell to an oxidizable fuel gas is fed to the anode. The oxidizable fuel gas fed to the anode is typically a mixture of syngas-oxidizable components, molecular hydrogen, carbon dioxide, and carbon monoxide. An oxidant-containing gas, typically air and carbon dioxide, can be fed to the cathode to provide a chemical reactant that produces a carbonate anion. The carbonate anions are constantly being updated during operation of the fuel cell.

The molten carbonate fuel cell is operated at a high temperature (typically from 550 ° C to 700 ° C) to react oxygen in the oxidant-containing gas with carbon dioxide to produce a carbonate anion. The carbonate anions cross the electrolyte to react with hydrogen and/or carbon monoxide from the fuel gas at the anode. Electrical power is generated by the conversion of oxygen and carbon dioxide at the cathode to carbonate ions and the chemical reaction of carbonate ions with hydrogen and/or carbon monoxide at the anode. The following reaction illustrates the electrochemical reaction in a battery in the absence of carbon monoxide:

Cathodic charge transfer: CO ₂ +0.5 O ₂ +2e ^- →CO ₃ ⁼

Anode charge transfer: CO ₃ ⁼ +H ₂ →H ₂ O+CO ₂ +2e ^- and

Total reaction: H ₂ +0.5 O ₂ →H ₂ O

If carbon monoxide is present in the fuel gas, the following chemical reaction illustrates the electrochemical reaction in the cell.

Cathodic charge transfer: CO ₂ +O ₂ +4e ^- →2 CO ₃ ⁼

Anode charge transfer: CO ₃ ⁼ +H ₂ →H ₂ O+CO ₂ +2e ^- and

CO ₃ ⁼ +CO→2 CO ₂ +2e ^-

Total reaction: H ₂ +CO+O ₂ →H ₂ O+CO ₂

An electrical load or storage device can be coupled between the anode and the cathode to allow current to flow between the anode and the cathode. This current supplies power to the electrical load or provides electrical power to the storage device.

The fuel gas is typically supplied to the anode by a steam reformer that recombines a low molecular weight hydrocarbon and steam into hydrogen and carbon oxides. For example, methane in natural gas is used to produce one of the preferred low molecular weight hydrocarbons for the fuel cell. Alternatively, the fuel cell anode can be designed to internally react recombination of one of the low molecular weight hydrocarbons (e.g., methane) supplied to the anode of the fuel cell with steam.

Methane steam recombination provides a fuel gas containing hydrogen and carbon monoxide according to the following reaction: CH ₄ +H ₂ O CO+3H ₂ . Typically, the steam reforming reaction is carried out at a temperature effective to convert a significant amount of methane to steam to hydrogen and carbon monoxide. The conversion reaction of steam and carbon monoxide by a water gas in a steam reformer: H ₂ O+CO CO ₂ +H _{2 is} converted to hydrogen and carbon dioxide to achieve further hydrogen production.

However, in a conventional operating steam reformer for supplying fuel gas to a molten carbonate fuel cell, a small amount of hydrogen is produced by the water gas shift reaction because the steam reformer is energetically beneficial to borrow The steam recombination reaction produces a temperature of one of carbon monoxide and hydrogen. Operating at this temperature is not conducive to the production of carbon dioxide and hydrogen by the water gas shift reaction.

Since carbon monoxide can be oxidized in the fuel cell to provide electrical energy and carbon dioxide is not available, the recombination reaction is generally carried out at a temperature that facilitates the recombination of hydrocarbons and steam to hydrogen and carbon monoxide, generally to provide fuel for the fuel cell. A preferred method. Since the fuel gas is usually supplied to the anode by external or internal steam recombination, it contains hydrogen, carbon monoxide and a small amount of carbon dioxide, unreacted methane, and water as steam.

However, a fuel gas containing a non-hydrogen compound such as carbon monoxide is inefficient for producing a relatively pure hydrogen fuel gas stream in a molten carbonate fuel cell. At a given temperature, the electrical power that can be produced in a molten carbonate fuel cell increases as the hydrogen concentration increases. This is due to the electrochemical oxidation potential of molecular hydrogen relative to other compounds. For example, Watanabe et al., in "Applicability of molten carbonate fuel cells to various fuels" (Journal of Power Sources, 2006, pp. 868-871), states that at a pressure of 90% fuel and a pressure of 0.49 MPa, 1500 One of the A/m ² current density operations of a 10 kW molten carbonate fuel cell stack with a 50% molecular hydrogen and 50% water feed produces an electrical power density of 0.12 W/cm ^{2 at} 0.792 volts, while operating under the same operating conditions The next 50% carbon monoxide and 50% water feed produced only one electrical power density of 0.11 W/cm ^{2 at} 0.763 volts. Therefore, a fuel gas stream containing a large amount of non-hydrogen compounds is less effective in generating electric power in a molten carbonate fuel cell than most fuel gases containing hydrogen.

However, molten carbonate fuel cells are typically commercially operated in a "hydrogen lean" mode in which the fuel gas is selected, for example, by steam recombination to limit the amount of hydrogen exiting the fuel cell in the fuel gas. This is done to balance the electrical potential of the hydrogen in the fuel gas with the potential energy (electrochemistry + heat) lost by the hydrogen exiting the cell without being converted to electrical energy.

However, certain measures have been taken to recapture the energy of hydrogen exiting the fuel cell, the energy efficiency of such hydrogen being significantly lower than the situation in which hydrogen reacts electrochemically in the fuel cell. For example, the anode exhaust gas generated by electrochemical reaction of the fuel gas in the fuel cell has been combusted to drive a turboexpander to generate electricity. However, doing so is significantly less efficient than capturing the electrochemical potential of hydrogen in the fuel cell due to many thermal energy losses in thermal energy rather than conversion to electrical energy by the expander. The fuel gas exiting the fuel cell has been combusted to provide thermal energy for various heat exchange applications. However, after combustion, almost 50% of the thermal energy is lost in such heat exchange applications. Hydrogen is used to ignite an extremely expensive gas used in one of the burners used in inefficient energy recovery systems, and thus conventionally adjusts the amount of hydrogen used in a molten carbonate fuel cell to utilize hydrogen supplied to the fuel cell Most of this produces electrical power and minimizes the amount of hydrogen that exits the fuel cell in the fuel cell exhaust.

Other measures have been taken to recycle more hydrogen from the fuel gas present in the anode exhaust and/or to recycle the hydrogen in the anode gas by providing the fuel gas to a post-recombiner and/or gas separation unit. To recover hydrogen and/or carbon dioxide, the fuel gas present in the anode is recombined in a post-recombiner to concentrate the hydrogen in the anode gas stream and/or undergo a water gas shift reaction to form hydrogen and carbon dioxide. Heat can be supplied by the anode gas stream.

The heat used to induce the methane vapor recombination reaction in a steam reformer and/or to convert the liquid fuel to the feed for the steam reformer has also been provided by the burner. A burner that combusts an oxygen-containing gas with a fuel, typically a hydrocarbon fuel such as natural gas, can be used to provide the required heat to the steam reformer. Flameless combustion has been utilized to provide heat for driving a steam recombination reaction, wherein flameless combustion is also driven by providing a hydrocarbon fuel and oxidant to a flameless combustion chamber by avoiding the relative amount of induced flaming combustion. The energy efficiency of such methods for providing the heat necessary to drive the steam recombination reaction and/or the water gas shift reaction is relatively low because the large amount of thermal energy provided by combustion is not captured and lost.

The hydrogen and carbon dioxide in the reformed gas stream can be separated from the anode gas, for example by using a pressure swing adsorption unit and/or a membrane separation unit. The temperature of the anode exhaust gas is typically higher than the temperature required for commercial hydrogen and/or carbon dioxide separation units. For example, the flow can be cooled by a heat exchanger, although thermal energy can be lost during the cooling process.

The separated hydrogen is fed to the anode portion of the fuel cell. Recirculating hydrogen to the anode allows the fuel gas entering the molten carbonate fuel cell to be enriched in hydrogen. The separated carbon dioxide is fed to the cathode portion of the fuel cell. Recirculating carbon dioxide to the cathode allows the air entering the molten carbonate fuel cell to be enriched with carbon dioxide.

The battery potential (V) of a molten carbonate fuel cell is given by the difference between the open circuit voltage (E) and the loss. For high temperature fuel cells, the startup losses are minimal and the battery potential can be obtained over the actual current density range by considering only ohmic losses. Therefore, the battery potential V = E - iR, where V and E have units of volts or millivolts, i is the current density (mA / cm ² ) and R is the total ohmic resistance of the electrolyte, cathode and anode combined (Ωcm ² ). The open circuit voltage is the main item in the battery potential. A molten carbonate fuel can be expressed using the Nernst equation E=E ^o +(RT/2F)ln(P _H2 P _O2 ^.5 /P _H2O )+(RT/2F)ln(P _CO2 ^c /P _CO2 ^a ) The total voltage of the battery (electromotive force), where E is the standard battery potential, the R system general gas constant is 8.314472 JK ^-1 mol ^-1 , the T system is absolute temperature, and the F system Faraday constant is 9.64853399 × 104 C mol ^-1 . As shown, the cell voltage of a molten carbonate fuel cell can be varied by varying the concentration of carbon dioxide, hydrogen, and oxygen.

Certain measures have been taken to adjust the concentration of hydrogen, oxygen, and carbon dioxide provided to the fuel cell to maximize battery voltage. U.S. Patent No. 7,097,925 (the '925 patent) maximizes the following denominator by enriching the flow of the anode fed to a molten carbonate fuel cell with hydrogen enriched with oxygen and carbon dioxide at the feed to the cathode:

A stream rich in hydrogen and rich in oxygen and carbon dioxide is supplied from the pressure swing adsorption unit.

While the prior art is effective in providing hydrogen, oxygen, and carbon dioxide to fuel cells at different concentrations, the process is relatively inefficient in producing hydrogen, carbon dioxide, and oxygen streams. This method is also relatively inefficient in the generation of gases and in the thermal process because the anode gas is cooled to remove water prior to entering the pressure swing adsorption unit. In addition, the reformer does not convert a liquid hydrocarbon feedstock to a lower molecular weight feed for one of the steam reformers and may provide insufficient heat from the fuel cell to do so.

Further improvements in operating the molten carbonate fuel cell system for generating electricity and enhancing the power density of the molten carbonate fuel cell can be desired.

The present invention relates to a method for operating a molten carbonate fuel cell, comprising: providing a hydrogen-containing stream comprising molecular hydrogen to an anode portion of a molten carbonate fuel cell; controlling the hydrogen-containing stream to the anode One flow rate such that the molecular hydrogen utilization rate in the anode is less than 50%; mixing an anode exhaust gas comprising molecular hydrogen from the molten carbonate fuel cell with a hydrocarbon stream comprising a hydrocarbon, wherein the hydrocarbon stream is mixed with the hydrocarbon stream The anode exhaust gas has a temperature from one of 500 ° C to 700 ° C; contacting at least a portion of the mixture of the anode exhaust gas and the hydrocarbon stream with a catalyst to produce a gas comprising one or more gaseous hydrocarbons, molecular hydrogen, and at least one carbon oxide a steam recombination feed; separating at least a portion of the molecular hydrogen from the steam reforming feed; and providing at least a portion of the separated molecular hydrogen to the molten carbonate fuel as at least a portion of the hydrogen-containing hydrogen stream comprising the molecular hydrogen Battery anode.

In another aspect, the present invention is directed to a molten carbonate fuel cell system comprising: a molten carbonate fuel cell configured to receive a hydrogen-containing stream comprising molecular hydrogen at a first rate to cause the melting The hydrogen utilization rate in one of the carbonate fuel cells is less than 50%; one or more recombiners operatively coupled to the molten carbonate fuel cell, at least one recombinator configured to receive from the molten carbonate An anode exhaust of a fuel cell and a hydrocarbon, and configured to allow the anode exhaust to be thoroughly mixed with hydrocarbons to at least partially recombine certain hydrocarbons of the hydrocarbons to produce a recombined product stream, wherein the reconstituted product stream Including molecular hydrogen and at least one carbon oxide; and a high temperature hydrogen separation unit that is part of or coupled to at least one of the recombiners and is operatively coupled to the melting a carbonate fuel cell, wherein the high temperature hydrogen separation device comprises one or more high temperature hydrogen separation membranes and is configured to receive a recombination product stream and to include at least one of the molecular hydrogen Ilk portion provided to the molten carbonate fuel cell.

The invention set forth herein provides an efficient method for operating a molten carbonate fuel cell to produce electricity at a high electrical power density and a system for performing such a method. First, the methods set forth herein maximize the electrical power density of the fuel cell system by minimizing, rather than maximizing, fuel utilization per fuel path in the molten carbonate fuel cell. The fuel utilization per pass is minimized to reduce the concentration of carbon dioxide and oxidation products (specifically water) throughout the length of the anode path of the fuel cell such that a high hydrogen concentration is maintained throughout one of the lengths of the anode path. The fuel cell provides a high electrical power density due to the presence of excess hydrogen at the anode electrode along the entire anode path length of the fuel cell. In one method for achieving a high fuel utilization per pass (eg, greater than 60% fuel utilization), the concentration of oxidation products and carbon dioxide may include greater than fuel before the fuel has traveled through even half of the fuel cell. 40% of the flow. In fuel cell exhaust, the concentration of oxidation products and carbon dioxide can be a multiple of the hydrogen concentration such that the electrical power provided along the anode path can be significantly reduced as the fuel provided to the fuel cell advances through the anode.

In the method set forth herein, the anode is flooded with hydrogen over the entire path length of the anode of a molten carbonate fuel cell such that the concentration of hydrogen at the anode electrode available for electrochemical reaction is maintained throughout the length of the anode path. At a high level. Therefore, the electric power density of the fuel cell is maximized.

The use of primary hydrogen or preferably almost all hydrogen-rich fuel in the process maximizes the electrical power density of the fuel cell system due to the hydrogen ratio typically used in other carbonated fuel cell systems. (for example, carbon monoxide) has a significantly larger electrochemical potential.

Compared to the system disclosed in the prior art, the method described herein utilizes a hydrogen-rich fuel and minimizes, rather than maximizes, fuel efficiency per fuel cell in a molten carbonate fuel cell system. Produces a higher electrical power density. The minimization is achieved by separating and recycling hydrogen trapped from the fuel exhaust of the fuel cell (eg, anode exhaust) and feeding the hydrogen from a feed and recycle stream at a selected rate to a minimum. The fuel utilization rate of each pass.

The system set forth herein allows a hydrogen rich stream to be provided to the molten carbonate fuel cell while minimizing the amount of hydrocarbons provided to the fuel cell, as compared to conventional systems. The system produces a hydrogen rich stream that can be introduced directly into the anode portion of the molten carbonate fuel cell.

The system does not require direct coupling to the anode of the molten carbonate fuel cell and/or a recombiner positioned in the anode to ensure sufficient hydrogen production as a fuel for the anode of the fuel cell. Removal or elimination of a recombiner or recombination zone in the molten carbonate fuel cell allows the molten carbonate fuel cell to be flooded with hydrogen while supplying a substantial portion of the heat from the anode exhaust to a first recombiner. Fuel cells that have been equipped with internal recombination zones can be used in combination with the systems set forth herein. Such fuel cells can operate more economically and efficiently than systems disclosed in the art.

In the method set forth herein, the cathode is flooded with carbon dioxide over the entire path length of the cathode of a molten carbonate fuel cell such that the concentration of carbon dioxide at the cathode electrode available for electrochemical reaction is maintained throughout the length of the cathode path. At a high level. Therefore, the electrical power density and/or battery voltage of the fuel cell is maximized.

The method set forth herein utilizes a stream containing a carbon dioxide rich oxidant gas, thereby allowing operation of the fuel cell such that a portion of the cathode portion of the molten carbonate fuel cell has a higher partial pressure of carbon dioxide than the molten carbonate fuel The partial pressure of carbon dioxide in most of the anode portion of the battery. Operating the fuel cell in this manner produces a higher electrical power density than the systems disclosed in the prior art.

The carbon dioxide oxidant gas is used to raise the voltage of the molten carbonate fuel cell and to suppress carbon dioxide deficiency of the molten carbonate fuel cell. "Insufficient carbon dioxide" means that the partial pressure of carbon dioxide (P _CO2 ^c ) exiting the cathode is less than the partial pressure of carbon dioxide (P _CO2 ^a ) exiting the anode. Providing excess carbon dioxide to the molten carbonate fuel cell at a minimum hydrogen utilization allows for higher voltages and/or current densities to be obtained from the molten carbonate fuel cell.

The system described herein allows a carbon dioxide rich stream to be supplied to the fuel cell from hydrocarbons provided to the molten carbonate fuel cell as compared to conventional systems. The carbon dioxide produced from the system can be introduced directly into the cathode portion of the molten carbonate fuel cell. The system does not require an external source of carbon dioxide to ensure sufficient carbon dioxide as a feed to the cathode of the fuel cell.

The methods described herein are also highly efficient because hydrogen and carbon dioxide that are not utilized in the fuel cell to produce electricity are continuously recycled through the fuel cell system. This achieves a high electrical power density relative to one of the lowest heating values of the fuel by solving the problem associated with the loss of hydrogen and/or carbon dioxide energy from the battery that is not converted to electrical energy.

The system allows an appropriate amount of air or molecular oxygen to be simultaneously fed to the cathode of the fuel cell such that the carbon dioxide to molecular oxygen molar ratio in the feed to the cathode minimizes concentration polarization at the electrode of the fuel cell . The system does not require oxygen-enriched air. The process of the present invention allows flooding of the anode with hydrogen while flooding the cathode with carbon dioxide while controlling the amount of molecular oxygen such that the carbon dioxide to molecular oxygen molar ratio in the feed to the cathode is at least 2 or at least 2.5.

The use of the fuel cell system set forth in the present invention allows the molten carbonate fuel cell to be operated at a high power density at 0.1 MPa (1 atm). Typically, molten carbonate fuel cells operate at pressures from atmospheric to about 1 MPa (10 atm). Operating at pressures above atmospheric pressure can affect the life of the seal in various portions of the molten carbonate fuel cell. Operating the molten carbonate fuel cell at or near atmospheric pressure extends the life of the seal in the molten carbonate fuel cell while generating electricity at a high current density for a given cell voltage and/or power density.

In the methods set forth herein, the per unit of electricity produced by the process produces relatively little carbon dioxide. The heat buildup of a first recombiner, a second recombiner, and a high temperature hydrogen separation unit with the fuel cell is reduced and preferably eliminates the additional energy required to drive the endothermic recombination reaction in one or both of the recombiners, wherein Directly transferring heat generated in the fuel cell to the first recombiner by providing a hot anode exhaust stream from the fuel cell to the first recombiner, and then directly directing the product of the first recombinator Feeding into the second reformer, and then providing the product of the second reformer directly to the high temperature hydrogen separation unit. This thermal product reduces (eg, by burning) the need to provide additional energy. Therefore, the amount of carbon dioxide produced when the energy is supplied to drive the recombination reaction is reduced.

By separating carbon dioxide from the reformed gas product and subsequently feeding a carbon dioxide containing gas stream to the fuel cell, recirculating the anode exhaust stream through the system and providing a carbon dioxide gas stream to the fuel cell reduces carbon dioxide required to be produced by combustion the amount. This recycling increases the electrical efficiency of the process and thereby reduces any carbon dioxide emissions.

Additionally, by separating the hydrogen-containing stream from the reformed gas product and subsequently feeding the hydrogen-containing stream to the fuel cell, the anode exhaust stream is recirculated through the system and one of the molecular hydrogen-rich hydrogen-containing streams is provided. To the fuel cell, the amount of hydrogen required by the second recombiner is reduced. This recycling of the anode exhaust increases the electrical efficiency of the process. In addition, the power density of the molten carbonate fuel cell is improved, so that to generate the same amount of power, a fuel cell having a smaller size than a conventional fuel cell can be used to generate power.

The methods described herein are more thermally and energy efficient than the methods disclosed in the art. Thermal energy from a fuel cell exhaust is delivered directly to a first recombiner. In some embodiments, a portion of the transferred thermal energy is subsequently transferred from the first recombiner to a second recombiner. The transfer of thermal energy directly from the anode of the fuel cell to the first recombiner is efficient because the transfer is performed directly from the hot anode exhaust stream from the fuel cell in the first recombiner This is achieved by a molecular mixing of a hydrocarbon stream comprising hydrocarbons and steam. A hot feed is produced from the first reformer and subsequently fed to the second reformer. The transfer of thermal energy from the first recombiner to the second recombiner is also efficient because the thermal energy is included in the feed from the first recombiner to the second recombiner.

The methods described herein are more thermally efficient than the methods disclosed in the prior art because the heat from the anode exhaust is used to produce hydrogen at temperatures below the typical steam recombination process. In the process of the present invention, hydrogen can be separated from the reformed product gas using a high temperature hydrogen separation unit, wherein the high temperature hydrogen separation unit is a membrane separation unit. The high temperature hydrogen separation unit can be operatively coupled to the second reformer such that hydrogen can be separated from the reformed gas as the recombination reaction occurs in the second reformer. The separation of hydrogen drives equilibrium against the production of hydrogen and reduces the temperature required to produce hydrogen. In addition, more hydrogen can be produced at lower recombination temperatures due to water gas shift reaction (H ₂ O+CO) The balance of CO ₂ + H ₂ ) facilitates the production of hydrogen at lower recombination temperatures, which is detrimental at conventional recombination reaction temperatures. A large or all of the molecular hydrogen and carbon dioxide produced from the second reformer is supplied to the molten carbonate fuel cell.

The methods described herein allow for the use of liquid fuels. The use of liquid fuel allows one fuel to be used by more than one power source. For example, diesel fuel can be used on a ship to power a molten carbonate fuel cell and engine. Hydrogen is added to the first recombiner through mixing of the anode exhaust with the liquid feed. The recycle of hydrogen eliminates the need for one of the individual hydrogen sources for thermal cracking of the liquid feed. Although some hydrogen is consumed, hydrogen is produced after the recombination of the cracked hydrocarbons. The integration of the recombiner with the high temperature hydrogen separation unit allows the system to produce substantially all of the hydrogen required by the methods.

The recombination and/or hydrocracking of liquid fuel produces more carbon dioxide per mole of hydrogen produced by the fuel having a carbon number greater than 6 (eg, diesel and naphtha) having a hydrogen to carbon ratio less than less than The hydrogen to carbon ratio of a 6 carbon number fuel (eg, methane). The hydrogen produced by each mole produces more carbon dioxide to allow substantially all or all of the carbon dioxide required to produce the molten carbonate fuel cell from the liquid fuel. Producing carbon dioxide in this manner eliminates or reduces the need to use a portion of the anode gas and/or feed gas as a fuel for a thermally inefficient combustion combustor to produce carbon dioxide. In the process set forth herein, excess hydrogen and carbon dioxide are produced which allows hydrogen and carbon dioxide to be recycled through the system.

The method of the present invention allows a molten carbonate fuel cell to operate at a pressure of 0.1 MPa (1 atm) or less than 0.1 MPa (1 atm) and provides a power density of at least 0.12 W/cm ² and/or a battery of at least 800 mV Voltage. In certain embodiments, the method of the present invention allows a molten carbonate fuel cell to operate at a pressure of 0.1 MPa (1 atm) or less than 0.1 MPa (1 atm) and provides a power density of at least 0.12 W/cm ² and/or Or at least 800 mV of battery voltage.

As used herein, unless otherwise indicated, the term "hydrogen" refers to molecular hydrogen.

As used herein, the term "hydrogen source" refers to a compound from which one of the free hydrogens can be produced. For example, the source of hydrogen can be, for example, a hydrocarbon of methane or a mixture of such compounds or a hydrocarbon-containing mixture such as natural gas.

As used herein, when two or more elements are described as "connected operatively" or "operably coupled", the elements are defined as being directly or indirectly connected to allow the Direct or indirect fluid flow. As used herein, the term "fluid flow" refers to the flow of a gas or a fluid. The term "indirect fluid flow" as used in the definition of "operatively connected" or "coupled operationally" means that a fluid or a medium between two defined elements can be directed through one or more additional elements. The flow of gas changes one or more aspects of the fluid or gas as it flows between the two defined elements. A state in which a fluid or a gas can change in an indirect fluid flow includes physical properties (such as the temperature or pressure of a gas or a fluid) and or the composition of the gas or fluid (eg, by isolating the gas or fluid) One part or condensed water by a gas stream containing one of the steam. As defined herein, "indirect fluid flow" does not include the chemical reaction (eg, oxidation) or reduction of one or more elements of the fluid or gas to alter the gas or fluid between the two defined elements. composition.

As used herein, the term "selectively permeable to hydrogen" is defined as being permeable to molecular hydrogen or elemental hydrogen and impermeable to other elements or compounds such that up to 10%, or up to 5, of the non-hydrogen element or compound % or up to 1% can penetrate substances that are permeable to molecular hydrogen or elemental hydrogen.

As used herein, the term "high temperature hydrogen separation unit" is defined as the separation of hydrogen in a molecular or elemental form from a gas stream at a temperature of at least 250 ° C (eg, at a temperature from 300 ° C to 650 ° C). A device or device that is valid.

As used herein, the "per-pass hydrogen utilization rate" of the utilization of hydrogen in a fuel in a molten carbonate fuel cell is defined as being relative to a single pass through to the molten carbonate fuel cell. The total amount of hydrogen in one of the fuel cells in the fuel cell is the amount of hydrogen used in the fuel to produce electricity in the pass. The hydrogen utilization rate per pass can be calculated by measuring the amount of hydrogen fed to one of the anodes of a fuel cell; measuring the amount of hydrogen in the anode exhaust of the fuel cell; The amount of hydrogen fed to the fuel of the fuel cell minus the amount of hydrogen in the anode exhaust of the fuel cell to determine the amount of hydrogen used in the fuel cell; and the calculated The amount of hydrogen used in the fuel cell is divided by the amount of hydrogen fed to the fuel of the fuel cell as measured. The hydrogen utilization per pass can be expressed as a percentage by multiplying the calculated hydrogen utilization per pass by 100.

As used herein. "Excess carbon dioxide" means one of the partial pressure differences (ΔP _CO2 ) of the carbon dioxide between the anode and the cathode of the molten carbonate fuel cell. "Excess carbon dioxide" (ΔP _CO2 ) is calculated by measuring the partial pressure of carbon dioxide in the anode and cathode exhaust gases at the anode and cathode outlets, respectively; and the carbon dioxide partial pressure value of the cathode from the measured The carbon dioxide partial pressure value of the measured anode is subtracted (for example, ΔP _CO2 = (P _CO2 ^c ) - (P _CO2 ^a )). For convection of one of the feeds to the anode and cathode, "excess carbon dioxide" is calculated by measuring the partial pressure of carbon dioxide in the anode and cathode exhausts at the anode outlet and the cathode inlet; The measured carbon dioxide partial pressure value of the cathode is subtracted from the measured carbon dioxide partial pressure value of the anode (for example, ΔP _CO2 = (P _CO2 ^cinlet ) - (P _CO2 ^aoutlet )).

The average excess carbon dioxide is calculated by the following equation.

ΔP _CO2 (avg)=[{P _CO2 ^cinlet +P _CO2 ^coutlet }-{P _CO2 ^ainlet +P _CO2 ^aoutlet }]/2

"Local excess carbon dioxide" refers to one of the partial pressure differences ([Delta] _PCO2(local) ) of the carbon dioxide of the molten carbonate fuel cell per percent hydrogen utilization at a normalized distance in the y-direction (width). The local excess carbon dioxide is calculated by ΔP _CO2 (x) = (P _CO2 ^c )(x) - (P _CO2 ^a )(x), where x is normalized along one of the lengths of the anode compartment.

1 through 3 illustrate schematic diagrams of embodiments of the system of the present invention for performing a method for operating a molten carbonate fuel cell to produce electricity in accordance with the present invention. The fuel cell system 10 includes a molten carbon carbonate fuel cell 12 , a first recombiner 14 , a second recombiner 16 , a high temperature hydrogen separation device 18, and an oxidation unit 20 . In a preferred embodiment, the second recombiner 16 , the high temperature hydrogen separation unit 18, and the oxidation unit 20 are one unit. In a preferred embodiment, oxidizing unit 20 is a catalytic partial oxidation recombiner. In one embodiment, the high temperature hydrogen separation unit 18 is a molecular hydrogen membrane separation unit. In one embodiment, the second recombiner 16 includes a recombination zone, a high temperature hydrogen separation unit 18 , a catalytic partial oxidation recombiner 20, and a heat exchanger 22 . The heat accumulator system provides sufficient hydrogen and carbon dioxide to produce electricity for continued operation of the molten carbonate fuel cell.

The molten carbonate fuel cell 12 includes an anode 24 , a cathode 26, and an electrolyte 28 . Electrolyte 28 is interposed between anode 24 and cathode 26 and contacts the anode and cathode. The molten carbonate fuel cell 12 can be a conventional molten carbonate fuel cell and preferably can have a tubular or planar configuration. The molten carbonate fuel cell 12 can include a plurality of individual fuel cells stacked together. The individual fuel cells can be electrically coupled by interconnecting and operatively connected such that one or more gas streams can flow through the anode of the stacked fuel cell and an oxidant-containing gas can flow through the cathode of the stacked fuel cell . As used herein, the term "molten carbonate fuel cell" is defined as a single molten carbonate fuel cell or a plurality of fused carbonate fuel cells that are operatively connected or stacked. The anode 24 of the molten carbonate fuel cell 12 can be formed of a porous sintered nickel compound, a nickel-chromium alloy, nickel and/or nickel-copper alloy having lithium chromium oxide, or any material suitable for use as an anode of a molten carbonate fuel cell. The cathode 26 of the molten carbonate fuel cell 12 can be formed from a porous sintered material (e.g., nickel oxide, lithium-nickel-iron oxide) or any material suitable for use as one of the cathodes of a molten carbonate fuel cell.

A gas stream is fed to the anode and cathode to provide the reactants necessary to produce electricity in the fuel cell 12 . The hydrogen containing stream enters the anode 24 and contains an oxidant gas stream into the cathode 26 . Electrolyte section 28 is positioned in the fuel cell to prevent the flow of hydrogen containing gas from entering the cathode and to prevent the flow of oxidant containing oxygen (the flow of oxygen and carbon dioxide) from entering the anode. The oxidant-containing gas stream comprises one or more streams containing oxygen and/or carbon dioxide.

Electrolyte section 28 directs carbonate ions from the cathode to the anode to effect an electrochemical reaction with an oxidizable compound (eg, hydrogen and, optionally, carbon monoxide) in the anode gas stream at one or more anode electrodes. The electrolyte section 28 can be formed from a molten salt of an alkali metal carbonate, an alkaline earth metal carbonate, or a combination thereof. Examples of the electrolyte material include a porous material formed of sodium lithium carbonate, lithium carbonate, sodium carbonate, sodium lithium carbonate, sodium lithium carbonate, and lithium potassium carbonate.

Fuel cell 12 is configured to allow a hydrogen containing stream to flow from anode inlet 30 through anode 24 and out of anode exhaust outlet 32 . The hydrogen containing stream contacts one or more anode electrodes over the length of the anode path from anode inlet 30 to anode exhaust outlet 32 .

In one embodiment, a gas stream containing molecular hydrogen (hereinafter referred to as "a hydrogen-containing stream") or a hydrogen source is fed through line 34 to the anode inlet 30 . A throttle valve 36 can be used to select and control the flow rate of the hydrogen-containing stream to the anode inlet 30 . In a preferred embodiment, hydrogen is fed from the high temperature hydrogen separation unit 18 to the anode 24 of the fuel cell 12 , wherein the high temperature hydrogen separation unit is a thin film unit, as described in detail below. In an embodiment, the hydrogen-containing stream may contain at least 0.6, or at least 0.7, or at least 0.8, or at least 0.9, or at least 0.95, or at least 0.98 mole fraction of hydrogen.

One of the gases fed to the cathode contains an oxidant. As referred to herein, "oxidant" refers to a compound that can be reduced by reaction with molecular hydrogen. In certain embodiments, the oxidant-containing gas fed to the cathode comprises oxygen, carbon dioxide, an inert gas, or a mixture thereof. In one embodiment, the oxidant-containing gas system comprises an oxygen-containing gas stream combined with one of the carbon dioxide-containing gas streams or an oxygen-containing/carbon dioxide stream. In a preferred embodiment, the oxygen-containing system fed to the cathode has been mixed with sufficient carbon dioxide or oxygen-enriched air such that the molar ratio of carbon dioxide to oxygen is at least 2 or at least 2.5.

An oxidant-containing gas can flow from the cathode inlet 38 through the cathode 26 and then out through the cathode exhaust outlet 40 . The oxidant-containing gas contacts one or more cathode electrodes over the length of the cathode path from the cathode inlet 38 to the cathode exhaust outlet 40 . In one embodiment, an oxidant-containing gas can convect relative to the flow of hydrogen-containing gas flowing to one of the anodes 24 of the fuel cell 12 .

In one embodiment, the oxidant-containing gas stream is fed through line 44 from oxidant-containing gas source 42 to cathode inlet 38 . A throttle valve 46 can be used to select and control the rate at which the gas stream is fed to the cathode 26 . In certain embodiments, the oxidant-containing gas is provided by an air compressor. The oxidant-containing gas stream can be air. In one embodiment, the oxidant-containing gas can be pure oxygen. In one embodiment, the oxidant-containing gas stream can be an oxygen- and/or carbon dioxide-rich air containing at least 13% by weight oxygen and/or at least 26% by weight carbon dioxide. In a preferred embodiment, the flow of air and/or carbon dioxide is controlled such that the molar ratio of carbon dioxide to molecular oxygen in the air is at least 2 or at least 2.5.

In one embodiment, the oxidant-containing gas stream is provided by a carbon dioxide-containing gas stream and an oxygen-containing gas stream. The carbon dioxide stream and the oxygen containing stream can come from two separate sources. In a preferred embodiment, most or substantially all of the carbon dioxide used to melt the carbonate fuel cell 12 is derived from a hydrocarbon stream comprising hydrocarbons provided to the first reformer 14 . The carbon dioxide containing gas stream is fed through line 44 from the carbon dioxide source to the cathode inlet 38 . The carbon dioxide containing gas stream provided to fuel cell 12 can be fed to the same cathode inlet 38 with an oxygen containing stream, or can be mixed with an oxygen containing stream prior to feeding to cathode inlet 38 . Alternatively, the carbon dioxide containing gas stream can be supplied to the cathode 26 through a separate cathode inlet.

In a preferred embodiment, the carbon dioxide stream is supplied from high temperature hydrogen separation unit 18 to cathode 26 of fuel cell 12 via lines 48 and 44 , as set forth herein. Oxygen may be provided to cathode 26 of fuel cell 12 via line 44 .

The gas (whether one or more streams) fed to the cathode and/or anode may be heated in a heat exchanger 22 or other heat exchanger prior to feeding to the cathode 26 and/or the anode 24 , preferably by Heat is exchanged by the oxygen depleted cathode exhaust stream exiting the cathode exhaust port 40 and connected to the heat exchanger 22 through the line 50 .

In the process of the present invention, a hydrogen containing stream is mixed with an oxidant at one or more of the anode electrodes of the molten carbonate fuel cell 12 to produce electricity. The oxidant is preferably derived from the reaction of carbon dioxide and oxygen flowing through the cathode 26 and directed through the carbonate ions of the electrolyte of the fuel cell. The hydrogen-containing gas stream is mixed with the oxidant at one or more anode electrodes of the fuel cell by feeding a hydrogen-containing gas stream and/or an oxidant-containing gas stream to the fuel cell 12 at a selected independent rate, as discussed in further detail below . Preferably, the hydrogen-containing stream and the oxidant are mixed at one or more anode electrodes of the fuel cell to be at least 0.1 W/cm ² , or at least 0.15 W/cm ² , or at least 0.2 W/cm ² at 1 bar. An electric power density of at least 0.3 W/cm ² or at least 0.6 W/cm ² produces electricity. Higher power densities can be obtained at higher pressures and/or by using an oxidant-rich gas stream (eg, oxidant-rich air).

The molten carbonate fuel cell 12 is operated at a temperature that enables carbonate ions to be effective from the cathode 26 across the electrolyte portion 28 to the anode 24 . The molten carbonate fuel cell 12 can be operated at a temperature from 550 ° C to 700 ° C or from one of 600 ° C to 650 ° C. The hydrogen and carbonate ions are exothermicly reacted at one or more of the anode cells. The heat of the reaction produces the heat required to operate the molten carbonate fuel cell 12 . The temperature at which the molten carbonate fuel cell is operated can be controlled by a number of factors including, but not limited to, adjusting the feed temperature and feed flow of the hydrogen-containing gas and the oxygen-containing gas. Since hydrogen utilization is minimized, excess hydrogen is fed to the system and unreacted hydrogen can partially cool the molten carbonate fuel cell by carrying excess heat to the first reformer. Adjusting the flow of carbon dioxide and/or the flow of the oxidant-containing stream to maintain the molar ratio of carbon dioxide to molecular oxygen at about 2 requires sufficient oxidant-containing gas to achieve an amount that is about to react with the portion of the hydrogen utilized in the anode. An excess of one to three times the molecular oxygen of 1.3 to 2.0. Thus, an excess of oxygen depleted air or oxidant containing gas exiting the cathode exhaust may carry a significant amount of heat from the molten carbonate fuel cell. The supply of hydrogen to the molten carbonic acid may be reduced by heat recovery (e.g., through heat exchanger 22 ) prior to providing a hydrogen-containing stream from the high temperature hydrogen separation unit 18 to the anode 24 of the molten carbonate fuel cell 12 , as described below. The temperature of the hydrogen-containing stream of the anode of the salt fuel cell. The supply to the molten carbonic acid may be reduced by heat recovery (e.g., through heat exchanger 22 ) prior to providing a high pressure carbon dioxide stream as described below from high temperature hydrogen separation unit 18 to cathode 26 of molten carbonate fuel cell 12 . The temperature of the high pressure carbon dioxide stream of the cathode of the salt fuel cell. The temperature of the effluent stream can be reduced by heat recovery (e.g., through heat exchanger 22 ) prior to providing an effluent stream from catalytic partial oxidation recombiner 20 to the molten carbonate fuel cell cathode. Waste heat from the fuel cell can be used to heat one or more of the streams utilized in the system. If necessary, any supplemental system known in the art for cooling molten carbonate fuel can be used to control the temperature of the molten carbonate fuel cell.

In one embodiment, the oxidant-containing gas stream fed to the cathode can be heated to a temperature of at least 150 ° C or from one of 150 ° C to 350 ° C prior to feeding to the cathode 26 . In one embodiment, when an oxygen-containing gas is used, the temperature of an oxygen-containing gas stream is controlled to a temperature from one of 150 ° C to 350 ° C.

To initiate operation of the fuel cell 12 , the fuel cell is heated to its operating temperature - a temperature sufficient to melt the electrolyte salt to allow carbonate ions to flow. As shown in FIG. 1, the hydrogen-containing stream can be initiated by feeding a hydrogen-containing stream in the catalytic partial oxidation reformer 20 and feeding the hydrogen-containing stream through the lines 52 and 34 to the anode 24 of the molten carbonate fuel cell 12 . Operation of molten carbonate fuel cells.

In the presence of a conventional partial oxidation catalyst, one of the hydrocarbon streams described below, including a hydrocarbon stream, or a different hydrocarbon stream (eg, one of the natural gas enriched) is combusted in the catalytic partial oxidation reformer 20 . a fuel stream) and an oxidant-containing gas to produce a hydrogen-containing stream in the catalytic partial oxidation reformer 20 , wherein the amount of oxygen fed to the oxidant-containing gas of the catalytic partial oxidation reformer 20 is relative to the hydrocarbon stream Substoichiometric amount of one of the hydrocarbons. The flow of the hydrogen containing stream can be controlled by valve 60 .

As shown in FIG. 2, the fuel cell is heated to the anode of the molten carbonate fuel cell by generating a hydrogen-containing stream in the oxidation unit 20 and feeding the hydrogen-containing stream through the lines 96 , 104, and 34 to the anode 24 of the molten carbonate fuel cell. Operating temperature. The rate at which the hydrogen containing stream is fed from the oxidation unit 20 to the anode 24 via lines 96 , 104 is controlled by a three-way valve 102 . A portion of the heat from the hydrogen-containing stream can pass through heat exchanger 98 via line 96 to provide heat to first recombiner 14 and/or to a hydrocarbon stream comprising hydrocarbons entering the first recombiner.

Referring to Figures 1 and 2, the fuel fed to the catalytic partial oxidation reformer 20 can be a liquid or gaseous hydrocarbon or hydrocarbon mixture, and is preferably the same hydrocarbon stream comprising hydrocarbons provided to the first reformer 14 . Fuel may be fed via line 62 to catalytic partial oxidation reformer 20 . In one embodiment, the natural gas and/or hydrogen-rich feed from hydrogen source 64 is fed to the fuel that catalyzes partial oxidation of reformer 20 .

The oxidant fed to the catalytic partial oxidation reformer 20 may be pure oxygen, air or oxygen-enriched air (hereinafter referred to as "oxidant-containing gas"). Preferably, the oxidant-containing system air. The oxidant should be provided to the catalytic partial oxidation reformer 20 such that one of the amounts of oxygen in the oxidant is in a substoichiometric amount relative to the hydrocarbon fed to the catalytically partially oxidatively recombined. In a preferred embodiment, the oxidant-containing gas is fed from oxidant source 42 to catalytic partial oxidation reformer 20 via line 56 . Valve 58 controls the rate at which oxidant-containing gas (air) is fed to catalytic partial oxidation oxidizer 20 and/or cathode 26 of fuel cell 12 . In one embodiment, the oxidant-containing gas entering the catalytic partial oxidation recombiner 20 can be heated by exchanging heat with the oxygen-depleted cathode exhaust stream exiting the cathode exhaust port 40 .

In the catalytic partial oxidation reformer 20 , a hydrogen-containing stream is formed by burning a hydrocarbon and an oxidant in the presence of a conventional partial oxidation catalyst, wherein the oxidant is in a substoichiometric amount relative to the hydrocarbon. The hydrogen-containing stream formed by the contact of the hydrocarbon with the oxidant in the catalytic partial oxidation reformer 20 can be oxidized in the fuel cell anode 24 by contact with carbonate ions at one or more of the anode electrodes. Compound. The hydrogen-containing stream from the catalytic partial oxidation reformer 20 preferably does not contain a compound that oxidizes one or more of the anodes 24 of the fuel cell 12 .

The hydrogen-containing gas stream formed in the catalytic partial oxidation reformer 20 is hot and may have a temperature of at least 700 ° C, or from 700 ° C to 1100 ° C or from 800 ° C to 1000 ° C. In the process of the present invention, it is preferred to use the hot hydrogen stream from the catalytic partial oxidation reformer 20 to initiate the firing of the molten carbonate fuel cell 12 because it allows the temperature of the fuel cell to rise almost instantaneously to The operating temperature of the fuel cell. In one embodiment, when starting the operation of the fuel cell, from the heat in the catalytic partial oxidation reformer in heat exchanger 2220 in thermal hydrogen-containing gas fed to the cathode 26 between one of the oxidizing gas containing exchange.

Referring to Figure 1, valve 60 can be used to regulate the flow of hot hydrogen containing stream from catalytic partial oxidation recombiner 20 into fuel cell 12 while the hydrogen containing stream is fed to anode 24 by opening valve 36 . The valve 60 can be closed after initial flow from a hydrogen containing stream of the high temperature hydrogen separation unit 18 while reducing or stopping the flow of the hydrocarbon feed permeate line 62 and the oxidant feed permeate line 56 to the catalytic partial oxidation recombiner 20 .

Referring to Figure 2, a three-way throttle valve 102 can be used to regulate the flow of hot hydrogen containing gas from the catalytic partial oxidation recombiner 20 to the fuel cell 12 via line 96 while simultaneously feeding the hydrogen containing stream by opening valve 36 . To the anode 24 . The valve 102 can be closed after generating a hydrogen-containing stream from the high temperature hydrogen separation unit 18 while reducing or stopping the flow of the hydrocarbon feed permeate line 62 and the oxidant feed permeate line 56 to the catalytic partial oxidation recombiner 20 . The continued operation of the fuel cell can then be carried out in accordance with the method of the present invention.

The three-way throttle valve 102 controls the flow of the effluent from the catalytic partial oxidation recombiner 20 to the anode 24 or cathode 26 . The effluent from the catalytic partial oxidation reformer 20 is enriched with hydrogen during startup, so the effluent is directed to the anode 24 via line 104 after passing through the heat exchanger 98 via line 96 . After initial startup and if catalytic partial oxidation recombiner 20 is used to generate carbon dioxide for cathode 26 , throttle valve 102 controls the flow of effluent from catalytic partial oxidation oxidizer recombiner 20 to cathode 26 via line 96 .

In another embodiment, prior to introduction to the fuel cell 12, the hydrogen containing gas stream via line 66, can be launched through a heater (not shown) with the fuel cell to its operating temperature of the hydrogen from the source 64 Hydrogen initiated gas flow initiates operation of the fuel cell, as shown in FIG. The hydrogen source 64 can be one of the storage tanks that can receive hydrogen from the high temperature hydrogen separation unit 18 . The hydrogen source can be operatively coupled to the fuel cell to permit introduction of a hydrogen-producing gas stream into the anode of the molten carbonate fuel cell. The generator heater indirectly heats the hydrogen-producing gas stream to a temperature from 750 ° C to 1000 ° C. Alternatively, the launch heater can provide hydrogen by incomplete combustion of hydrogen supplied from the hydrogen source 64 to the heater. The engine can be an electric heater or can be a combustion heater. After the operating temperature of the fuel cell is reached, the flow of hydrogen to the fuel cell can be shut off by a valve, and the hydrogen-containing stream can be introduced by opening a valve from the hydrogen generator to the anode of the fuel cell. The fuel cell is used to start the operation of the fuel cell.

In one embodiment, the first recombiner 14 includes a catalytic partial oxidation recombiner for providing hydrogen to the molten carbonate fuel cell upon actuation. The first recombiner 14 can include one or more catalyst beds that allow the first recombiner to be used for autothermal recombination and then for steam recombination once the molten carbonate fuel cell has reached operating temperature.

Once the fuel cell 12 has begun to operate, the cathode 26 and the anode 24 emit exhaust gas. The exhaust from the cathode 26 and the anode 24 is hot and the heat from the exhaust can be thermally integrated with other units to produce a thermal integrated system that produces all of the fuel necessary for operation of the fuel cell. (hydrogen) and oxidant (carbonate ion).

As shown in Figures 1 and 2, the method set forth herein utilizes a system comprising a thermal integrated hydrogen separation and separation device 18 , a molten carbonate fuel cell 12 , a first recombiner 14, and a second recombiner 16. And (in certain embodiments) catalyzing the partial oxidation recombiner 20 . The high temperature hydrogen separation unit 18 includes one or more high temperature hydrogen separation membranes 68 and is operatively coupled to the molten carbonate fuel cell 12 . The high temperature hydrogen-separation device 18 comprising primarily hydrogen-containing gas stream to provide one of the hydrogen molecules to the anode 12 of the fuel cell 24, and the anode exhaust gas line from the molten carbonate fuel cell 12 is supplied to a first reformer 14. The first recombiner 14 and the second recombiner 16 can be a unit or two units that are operatively coupled. The first recombiner 14 and the second recombiner 16 may comprise one or more recombination zones. In one embodiment, the first recombiner 14 and the second recombiner 16 comprise a unit of a first recombination zone and a second recombination zone.

A hydrocarbon stream comprising hydrocarbons is provided via line 62 to the first reformer 14 and the anode exhaust is mixed with the hydrocarbons. The method is a thermal assembly wherein the anode exhaust gas from the exothermic molten carbonate fuel cell 12 is directly driven within the first recombiner and/or with hydrocarbons provided to the first recombiner hydrocarbon stream. The heat of the endothermic recombination reaction in recombiner 14 . In one embodiment, a portion of the heat from the anode exhaust is mixed with a hydrocarbon in a heat exchanger located in the first reformer or operatively coupled to the first reformer. As shown in FIG. 2, additional heat to the first reformer 14 may be provided from a hot effluent stream from the catalytic partial oxidation reformer 20 . In the first reformer 14 , at least a portion of the hydrocarbons from the hydrocarbon stream are cracked and/or recombined to produce a feed stream provided to one of the second reformers 16 via line 70 .

The second recombiner 16 is operatively coupled to the high temperature hydrogen separation unit 18 and the high temperature hydrogen separation unit produces at least a portion, a majority, at least 75% by volume, or at least 90% by volume or substantially all of the anode 24 entering the molten carbonate fuel cell 12 . Hydrogen-containing gas. The high temperature hydrogen separation unit can be positioned after the second reformer 16 and before the molten carbonate fuel cell 12 . In a preferred embodiment, the high temperature hydrogen separation unit 18 is a membrane separation unit that is part of the second reformer 16 . The high temperature hydrogen separation unit 18 separates hydrogen from the recombined product. The separated hydrogen is supplied to the anode 24 of the molten carbonate fuel cell 12 .

In one embodiment of the method, the hydrocarbon stream contains one or more of any evaporable hydrocarbons which are liquid at 20 ° C at atmospheric pressure (as appropriate for oxygenation) and up to 400 ° C at atmospheric pressure. Evaporates at temperature. Such hydrocarbons may include, but are not limited to, petroleum fractions having a boiling range of from 50 ° C to 360 ° C, such as naphtha, diesel, jet fuel, gasoline, and kerosene. In one embodiment, the hydrocarbon stream is decane. In a preferred embodiment, the hydrocarbon stream is a diesel fuel. In one embodiment, the hydrocarbon stream contains hydrocarbons having a carbon number ranging from five to twenty-five. In a preferred embodiment, the hydrocarbon stream contains at least 0.5, or at least 0.6, or at least 0.7 or at least 0.8 mole percent of a hydrocarbon containing at least five, or at least six or at least seven carbon atoms.

The hydrocarbon stream may optionally contain certain hydrocarbons which are gaseous at 25 ° C, such as methane, ethane, propane or other compounds containing from one to four carbon atoms which are gaseous at 25 ° C. The hydrocarbon stream can be treated prior to feeding to the first reformer 14 and/or heated in heat exchanger 72 for removal to convert higher molecular weight hydrocarbons to lower molecular weights in the first reformer. Any material that has a detrimental effect on any of the hydrocarbons. For example, the hydrocarbon stream may have undergone a series of treatments to remove metal, sulfur, and/or nitrogen compounds.

In one embodiment of the method, the hydrocarbon stream is mixed with natural gas containing at least 20% by volume, or at least 50% by volume or at least 80% by volume of carbon dioxide. If necessary, the natural gas has been treated to remove hydrogen sulfide. In one embodiment, a hydrocarbon stream having at least 20% by volume carbon dioxide, at least 50% by volume carbon dioxide, or at least 70% by volume carbon dioxide can be used as a fuel source.

In one embodiment, the hydrocarbon stream can be supplied to the first reformer 14 at a temperature of at least 150 ° C, preferably from 200 ° C to 400 ° C, wherein the hydrocarbon stream can be heated to a desired temperature in the heat exchanger Temperature, as explained below. The temperature at which the hydrocarbon stream is fed to the first reformer 14 can be selected to be as high as possible to evaporate the hydrocarbons without producing coke. The temperature of the hydrocarbon stream can range from 150 °C to 400 °C. Another option is (but less preferred), provided that the sulfur content of the hydrocarbon stream is low, the hydrocarbon stream can be fed directly to the first reformer 14 at a temperature below one of, for example, 150 ° C without heating the Hydrocarbon stream.

As shown in Figure 1, the hydrocarbon stream can be passed through one or more heat exchangers 72 to heat the feed. The hydrocarbon stream can be heated by exchanging heat with a cathode exhaust stream that is separated from the cathode 26 of the molten carbonate fuel cell 12 and fed to the heat exchanger 72 via line 74 . The rate at which the cathode exhaust stream is fed to the heat exchangers 72 and 22 can be controlled by adjusting the throttle valves 76 and 78 .

In a preferred embodiment, a separate anode exhaust stream is fed via line 80 to one or more recombination zones of the first reformer 14 . The rate at which the anode exhaust stream is fed to the first recombiner 14 can be controlled by adjusting the throttle valve 82 . The temperature of the anode exhaust gas may range from about 500 ° C to about 700 ° C, and preferably about 650 ° C.

The anode exhaust stream contains hydrogen, steam, and reaction products from oxidation of fuel fed to the anode 24 of the fuel cell 12 , as well as unreacted fuel. In an embodiment, the anode exhaust stream contains at least 0.5, or at least 0.6 or at least 0.7 mole fraction of hydrogen. Hydrogen fed to the first recombiner 14 or the anode exhaust stream of one of the recombination zones of the first recombiner can help prevent the formation of coke in the first recombiner. In one embodiment, the anode exhaust stream contains water (as steam) from 0.0001 to about 0.3, or from 0.001 to about 0.25 or from 0.01 to about 0.2 moles. In addition to hydrogen, steam present in the anode exhaust stream fed to the first reformer 14 or a recombination zone of one of the first reformers can also help prevent the formation of coke in the first reformer. The anode exhaust stream may contain sufficient hydrogen to inhibit coking and contain sufficient steam to recombine a majority of the hydrocarbons in the hydrocarbon stream to methane, hydrogen, and carbon monoxide. Thus, less steam may be required in the first reformer and/or the second reformer to recombine the hydrocarbons.

Optionally, steam may be fed via line 84 to the first recombiner 14 or a recombination zone of the first recombiner to mix with the hydrocarbon stream in the recombination zone of the first recombiner or the first recombiner. Steam may be fed to the first recombiner 14 or a recombination zone of the first recombinator to inhibit or prevent coke formation in the first recombiner and optionally for recombination achieved in the first recombiner In the reaction. In one embodiment, steam is fed to the first recombiner 14 or the recombination zone of the first recombiner at a rate, wherein a molar ratio of total steam added to the first recombiner is added to the first At least two or at least three times the amount of carbon in the hydrocarbon stream of the reformer. The total steam added to the first reformer can include steam from the anode exhaust, steam from an external source (e.g., through line 84 ), or a mixture thereof. Providing at least 2:1, or at least 2.5:1, or at least 3:1 or at least 3.5:1 in a recombination zone of the first recombiner 14 or the first recombinator, a steam to carbon molar ratio can be used to inhibit The formation of coke in the first recombiner. The throttle valve 86 can be used to control the rate at which the vapor is fed through the line 84 to the first recombiner 14 or a recombination zone of the first recombiner. Since the anode exhaust contains a large amount of hydrogen, less coking tends to occur during recombination. Thus, the amount of optional steam fed to the first reformer 14 can be significantly less than the amount of steam used in conventional recombination units.

Steam may be at least 125 deg.] C, preferably at from one to 150 ℃ 300 ℃ temperature of the feed to the first reformer 14, and may have from one to 0.1 MPa 0.5 MPa pressure, preferably equal to or below the feed One of the pressures to the anode exhaust stream of the first reformer, as set forth herein. Steam can be produced by heating high pressure water having a pressure of at least 1.0 MPa, preferably 1.5 Mpa to 2.0 MPa (by passing the high pressure water through line 88 through heat exchanger 90 ). The high pressure water is heated to exchange high pressure steam by exchanging heat with the cathode exhaust gas fed after the cathode exhaust feed has been passed through the heat exchanger 72 through line 74 . Alternatively, the cathode exhaust can be fed directly to a heat exchanger 90 (not shown) or one or more heat exchangers. If more than one heat exchanger is utilized, the high pressure steam can then be fed to line 84 via line 92 after exiting heat exchanger 90 or the final heat exchanger. The high pressure steam can be depressurized to a desired pressure by expanding the high pressure steam through an expander and then fed to the first reformer. Alternatively, steam for use in the first reformer can be produced by feeding low pressure water through one or more heat exchangers 90 and passing the resulting vapor to the first reformer 14 .

Optionally, high pressure steam not utilized in the first recombiner 14 or the second recombiner 16 may pass through other power devices (eg, a turbine (not shown)) along with any unused high pressure carbon dioxide stream or, as appropriate, The high pressure carbon dioxide stream expands together. The power source can be used to generate electricity and/or electricity in addition to the electricity generated by the fuel cell 12 . The power generated by the power source and/or fuel cell can be used to power compressor 94 and/or any other compressor used in the method of the present invention.

The hydrocarbon stream, the optional steam, and the anode exhaust stream are recombined in the first recombiner 14 or one of the first recombiners at a temperature that is effective to evaporate any hydrocarbons that are not in vapor form and cleave the hydrocarbons to form a feed. The zone is mixed with and contacted with a recombination catalyst.

The recombination catalyst can be a conventional recombination catalyst and can be any of the catalysts known in the art. Typical recombination catalysts that can be used include, but are not limited to, Group VIII transition metals, particularly nickel and one of the carriers or substrates that are inert under high temperature reaction conditions. Suitable inert compounds for use as a carrier for the high temperature recombination/hydrocracking catalyst include, but are not limited to, alpha-alumina and zirconia.

In a preferred embodiment, the hydrocarbon stream, the anode exhaust, and the optional vapor are mixed and contacted with a catalyst at a temperature of from about 500 ° C to about 650 ° C or from about 550 ° C to 600 ° C, wherein the recombination reaction All the heat necessary is supplied by the anode exhaust. In one embodiment, the hydrocarbon stream, the optional steam, and the anode exhaust stream are mixed with a catalyst at a temperature of at least 400 ° C, or from 450 ° C to 650 ° C or from one of 500 ° C to 600 ° C and contact.

The heat supplied from the anode exhaust stream fed from the exothermic molten carbonate fuel cell 12 to the first reformer 14 or the recombination zone of one of the first reformers drives the endothermic cracking and recombination reaction in the first reformer. The anode exhaust stream fed from the molten carbonate fuel cell 12 to the first recombiner 14 and/or the recombination zone of the first recombiner is extremely hot, having a temperature of at least 500 ° C, typically from 550 ° C to 700 ° C or a temperature from 600 ° C to 650 ° C. The transfer of thermal energy from the molten carbonate fuel cell 12 to the first recombiner 14 or the recombination zone of one of the first recombiners is quite effective because the thermal energy from the fuel cell is contained in the anode exhaust stream and is borrowed The mixture of hydrocarbon stream, optional vapor and anode exhaust stream is passed to the first recombiner 14 or a recombination zone of one of the first reformers by directly mixing the anode exhaust stream with the hydrocarbon stream and steam.

In a preferred embodiment of the method set forth herein, the anode exhaust stream provides a mixture of hydrocarbon stream, optional steam, and anode exhaust to produce at least 99% or substantially all of the heat required to feed. In a particularly preferred embodiment, no other heat source other than the anode exhaust stream is provided to the first reformer 14 to convert the hydrocarbon stream to feed.

In one embodiment, the anode exhaust stream, hydrocarbon stream, and optional vapor may be in contact with the recombination catalyst in the first reformer 14 at a pressure ranging from 0.07 MPa to 3.0 MPa. If high pressure steam is not fed to the first reformer 14 , the anode exhaust stream, hydrocarbon stream, and optional low pressure steam may be at a pressure at the lower end of the range (typically from 0.07 MPa to 0.5 MPa or from 0.1 MPa) Contacted with the recombination catalyst in the first recombiner to 0.3 MPa). If high pressure steam is fed to the first reformer 14 , the anode exhaust stream, hydrocarbon stream and steam may be at the higher end of the pressure range (typically from 1.0 MPa to 3.0 MPa or from 1.5 MPa to 2.0 MPa) with the recombination Catalyst contact.

Referring to Figure 2, the first recombiner 14 can be heated to above 630 ° C, or from 650 ° C to 900 ° C or from 700 ° C to 800 ° C by exchanging heat with the effluent from the catalytic partial oxidation recombiner 20 via line 96 . temperature. Line 96 is operatively coupled to heat exchanger 98 . Heat exchanger 98 can be part of line 96 . The heat exchanger 98 can be located in the first reformer 14 or connected to the first reformer such that heat can be exchanged with the hydrocarbon stream entering the first reformer. The rate at which the effluent is fed from the catalytic partial oxidation recombiner 20 to the first reformer 14 can be controlled by adjusting the throttle valve 100 and the three-way throttle valve 102 .

Contacting hydrocarbon stream, steam, catalyst, and anode exhaust in first recombiner 14 at a temperature of at least 500 ° C, or from 550 ° C to 950 ° C, or from 600 ° C to 800 ° C or from 650 ° C to 750 ° C The stream can crack and/or recombine at least a portion of the hydrocarbons and form a feed. The hydrocarbons in the cracked and/or recombined hydrocarbon stream reduce the number of carbon atoms in the hydrocarbon compound in the hydrocarbon stream, thereby producing a hydrocarbon compound having a reduced molecular weight. In one embodiment, the hydrocarbon stream may comprise a hydrocarbon containing at least 5, or at least 6 or at least 7 carbon atoms, which are converted to a maximum of 4, which may be used as a feed to the second reformer 16 , Or hydrocarbons of up to 3 or up to 2 carbon atoms. In one embodiment, the hydrocarbons in the hydrocarbon stream may be reacted in the first recombiner 14 or a recombination zone of the first recombiner such that the feed produced from the first recombiner may be no more than 0.1, or A hydrocarbon composition having four carbon atoms or more of carbon atoms of not more than 0.05 or not more than 0.01 mole fraction. In one embodiment, the hydrocarbons in the hydrocarbon stream may be cracked and/or recombined such that at least 0.7, or at least 0.8, or at least 0.9 or at least 0.95 moles of the feed from the hydrocarbons in the hydrocarbon stream are produced. The resulting hydrocarbon is methane. In one embodiment, the hydrocarbons in the cracked and/or reformed hydrocarbon stream produce hydrocarbons having a feed having at most 1.3, at most 1.2, or at most 1.1 one of the average carbon numbers.

As noted above, the hydrogen and vapor from the anode exhaust stream and the additional steam added to the first reformer 14 inhibit the formation of coke in the first recombiner upon cracking the hydrocarbon to form a feed. In a preferred embodiment, the relative rates of anode exhaust stream, hydrocarbon stream, and steam feed to first reformer 14 are selected such that hydrogen and vapor in the anode exhaust stream are added to the first recombination via line 84. The steam of the device prevents the formation of coke in the first reformer.

In one embodiment, the hydrocarbon stream, vapor, and anode exhaust are contacted with the recombination catalyst in the first reformer 14 at a temperature of at least 500 ° C, or from 550 ° C to 700 ° C or from one of 600 ° C to 650 ° C. It is also possible to effect at least some of the recombination of hydrocarbons in the hydrocarbon stream with the feed produced in the first reformer 14 to produce hydrogen and carbon oxides (specifically, carbon monoxide). The amount of recombination can be substantial, wherein the feed resulting from both cleavage and recombination in the recombination zone of the first recombiner 14 or the first recombiner can contain at least 0.05, or at least 0.1 or at least 0.15 mole fraction of carbon monoxide. .

The temperature and pressure conditions in the recombination zone of the first recombiner 14 or the first recombiner may be selected such that the feed produced in the first recombiner comprises a gaseous state at 20 ° C, typically containing 1 to 4 Light hydrocarbons of carbon atoms. In a preferred embodiment, the hydrocarbons produced by the first reformer (hereinafter referred to as "steam recombination feed") have a hydrocarbon content of at least 0.6, or at least 0.7, or at least 0.8, or at least 0.9 moles. Methane composition. The steam recombination feed also includes hydrogen from the anode exhaust stream and, if further recombination is achieved in the first recombiner, includes hydrogen from the recombined hydrocarbon. The steam recombination feed also includes steam from the anode exhaust stream and optionally from the reformer steam feed. If a large amount of recombination is achieved in the recombination zone of the first recombiner 14 or the first recombiner, the feed supplied to the second recombiner 16 from the first recombiner may include carbon monoxide other than carbon dioxide.

In the method of the present invention, the steam reforming feed line from the first 14 to 70 provides recombinant operatively connected to the second reformer of the reformer 16 through a first line. The steam recombination feed exiting the first reformer 14 can have a temperature from 500 ° C to 650 ° C or from 550 ° C to 600 ° C. In the first exit reformer 14 steam reforming of the second feed prior to the feed to the reformer 16, to be fed by the reducing heat exchange in one or more heat exchangers 90 before the second reformer 16 The temperature of the steam recombination feed exiting the first reformer. Optionally, the steam recombination feed is not cooled prior to entering the second reformer. 14 by the first recombinant other sources (e.g., shown in Figure 2, steam and / or heat from the catalytic partial oxidation of reformer 20) of a heating embodiment, the feed to the first exit of the reformer may have From one of 650 ° C to 950 ° C, or from 700 ° C to 900 ° C or from 750 ° C to 800 ° C.

The steam recombination feed can be cooled by exchanging heat with water fed to the system, cooling the feed, and producing steam that can be fed to the first reformer 14 , as set forth above. If more than one heat exchanger 90 is utilized, the steam recombination feed and water/steam may be fed sequentially to each of the heat exchangers, preferably in a two-way flow to cool the feed and heat the water/ steam. The steam recombination feed can be cooled to a temperature from 150 ° C to 650 ° C, or from 150 ° C to 300 ° C, or from 400 ° C to 650 ° C or from 450 ° C to 550 ° C.

The cooled steam recombination feed may be fed from heat exchanger 90 to compressor 94 or, in another embodiment, directly to second reformer 16 . Alternatively (but less preferred), the steam recombination feed exiting the first recombiner 14 or a recombination zone of the first recombiner can be fed to the compressor 94 or the second recombiner 16 without cooling. The compressor 94 is capable of operating a compressor at a high temperature, and is preferably a commercially available StarRotor compressor. The steam reforming feed can have a pressure of at least one of 0.5 MPa and a temperature of from 400 ° C to 800 ° C, preferably from 400 ° C to 650 ° C. The steam recombination feed may be compressed by compressor 94 to a pressure of at least 0.5 MPa, or at least 1.0 MPa, or at least 1.5 MPa, or at least 2 MPa, or at least 2.5 MPa or at least 3 MPa to maintain recombination of second recombiner 16 . Sufficient pressure in zone 108 . In one embodiment, the steam recombination feed is compressed to a pressure from 0.5 MPa to 6.0 MPa prior to providing the feed stream to the second reformer.

Optionally, the hydrogen recombination feed comprising hydrogen, light hydrocarbons, steam, and (as appropriate) carbon monoxide, optionally cooled, is fed to a second reformer 16 . The steam recombination feed can have a pressure of at least one of 0.5 MPa and a temperature of from 400 ° C to 800 ° C, preferably from 400 ° C to 650 ° C. In one embodiment, if necessary, the vapor recombination feed from the first recombiner 14 may be increased after exiting the compressor 94 by cycling a portion of the feed through the heat exchangers 90 and/or 72 . The temperature of the steam recombination feed produced by the first reformer.

Optionally, additional steam may be added to the recombination zone 108 of the second recombiner 16 for mixing with the steam recombination feed produced by the first recombiner, if necessary to recombine the feed. In a preferred embodiment, additional steam may be added by injecting high pressure water from water inlet line 88 into compressor 94 via line 110 for mixing with the feed as it is compressed in the compressor. . In an embodiment (not shown), the high pressure water can be injected into the feed by mixing high pressure water with the feed in heat exchanger 90 . In another embodiment (not shown), high pressure water may be injected into line 110 before or after the feed is passed to heat exchanger 90 or before or after the feed is delivered to compressor 94. In the material. In an embodiment, high pressure water may be injected into line 70 or injected into compressor 94 or injected into heat exchanger 90 , wherein the compressor or the heat exchanger is not included in the system.

The high pressure water is heated to form steam by mixing with a steam reforming feed, and the steam recombination feed is cooled by mixing with the water. The cooling provided to the heat exchanger 90 by the water supplied to the steam reforming feed can eliminate or reduce the need for the heat exchanger 90 , preferably limiting the number of heat exchangers used to cool the steam recombination feed to at most one.

Alternatively (but less preferred), high pressure steam may be injected into the recombination zone 108 of the second recombiner 16 or injected into the line 70 of the second recombiner for mixing with the steam recombination feed. The high pressure steam may be steam produced by heating the high pressure water injected into the system through the water inlet line 88 in heat exchanger 90 (by exchanging heat with the feed exiting the first reformer 14 ). High pressure steam can be fed through line 112 to second reformer 16 . A throttle valve 114 can be used to control the flow of steam to the second reformer. The high pressure steam can have a pressure similar to the pressure of the feed being fed to the second reformer. Alternatively, the high pressure steam can be fed to line 70 to mix with the feed prior to feeding the feed to compressor 94 so that the mixture of steam and feed can be compressed together to a selected pressure. The high pressure steam may have a temperature from 200 ° C to 500 ° C.

The rate at which the high pressure water or high pressure steam is fed to the system can be selected and controlled to provide a quantity of steam effective to produce a hydrogen containing stream to the first reformer 14 and/or Two recombiners 16 . By adjusting the throttle valves 116 and 118 (which control the rate at which water is fed to the system) or by adjusting the throttle valves 86 , 120 and 114 (which control the steam feed to the first recombiner 14 , The rate of the second reformer 16 ) controls the rate at which steam other than the vapor in the anode exhaust stream is supplied to the first reformer 14 . Steam can be supplied to additional components in the system (eg, a turbine).

If high pressure water is injected into the second recombiner 16 , the throttle valves 114 and 120 can be adjusted to control the rate at which water is injected through the line 112 into the second recombiner. If high pressure steam is injected into the second reformer 16 or injected into line 70 , the throttle valves 114 , 116, and 118 can be adjusted to control the rate at which steam is injected into the second reformer 16 or injected into the line 70 . The flow of steam can be adjusted to provide at least 2:1, or at least 2.5:1, or at least 3:1 or at least 3.5:1 molar ratio of steam to carbon.

The steam recombination feed produced by the first reformer and, as the case may be, additional steam is fed to the recombination zone 108 of the second reformer 16 . The recombination zone can, and preferably does, contain a recombination catalyst therein. The recombination catalyst can be a conventional vapor recombination catalyst and can be known in the art. Typical vapor recombination catalysts that may be used include, but are not limited to, Group VIII transition metals, particularly nickel. It is generally desirable to support the recombination catalysts on a refractory substrate (or carrier). The carrier, if used, is preferably an inert compound. Suitable inert compounds for use as a carrier contain elements of Groups III and IV of the Periodic Table, such as oxides or carbides of Al, Si, Ti, Mg, Ce and Zr.

The steam recombination feed and, optionally, additional steam are mixed and contacted with the recombination catalyst in recombination zone 108 at a temperature effective to form one of the hydrogen and carbon dioxide recombination product gases. The recombined product gas can be formed by steam reforming the hydrocarbons in the feed. The reformed product gas may also be formed by subjecting steam to a water gas shift reaction with one of the carbon oxides in the feed and/or by steam recombining the feed. In one embodiment, if a large amount of recombination is achieved in the recombination zone of the first recombiner 14 or the first recombiner and the steam recombination feed contains a large amount of carbon monoxide, the second recombiner 16 may serve as a water gas shift reaction. Device. The recombined product gas comprises hydrogen and at least one carbon oxide. In one embodiment, the recombined product gas comprises a gaseous hydrocarbon, hydrogen, and at least one carbon oxide. The carbon oxides that may be present in the reformed product gas comprise carbon monoxide and carbon dioxide.

In one embodiment, the heat from the effluent from the catalytic partial oxidation reformer 20 can be heat exchanged with the steam recombination feed stream being provided to and/or in the recombination zone 108 . The temperature of one of the effluents from the catalytic partial oxidation reformer 20 can range from 750 ° C to 1050 ° C, or from 800 ° C to 1000 ° C or from 850 ° C to 900 ° C. The heat from the effluent can heat the recombination zone 108 of the second reformer 16 to a temperature from about 500 ° C to about 850 ° C or from about 550 ° C to 700 ° C. One of the temperatures in the recombination zone 108 of the second recombiner 16 may be sufficient to recombine substantially all or all of the feed from the first recombiner 14 to produce a recombined product gas comprising hydrogen and at least one carbon oxide.

The recombined product gas can enter a high temperature hydrogen separation unit 18 operatively coupled to the second reformer 16 . As shown in Figures 1 and 2, the high temperature hydrogen separation unit 18 is part of the second reformer 16 . As shown in FIG. 3, the high temperature hydrogen separation unit 18 is separated from the second recombiner 16 and operatively coupled to the second recombiner via line 122 .

The high temperature hydrogen separation unit 18 may comprise one or more high temperature tubular hydrogen separation membranes 68 . The membrane 68 can be located in the recombination zone 108 of the second recombiner 16 and positioned such that the feed and recombined product gas can contact the membrane 68 . Hydrogen may pass through the membrane wall film 68 (not shown) to a hydrogen conduit 124 located within the film 68. The film walls of each individual membrane separate hydrogen conduit 124 from gas communication with the recombined product gas, feed, and non-hydrogen compounds in the recombination zone 108 of the second reformer 16 . The walls of the membrane are selectively permeable to hydrogen (elements and/or molecules) such that hydrogen in the recombination zone 108 can pass through the membrane wall of the membrane 68 to the hydrogen conduit 124 , while other gases in the recombination zone are passed through the membrane wall. It is prevented from being delivered to the hydrogen conduit. The hydrogen flux across the high temperature hydrogen separation unit 18 can be increased or decreased by adjusting the pressure in the second reformer 16 . The pressure in the second reformer 16 can be controlled by the rate at which the anode exhaust stream is fed to the first reformer 14 .

Referring to Figure 3, the feed from the second reformer 16 is fed via line 122 to a high temperature hydrogen separation unit 18 . The high temperature hydrogen separation unit 18 can include a member that is selectively permeable to hydrogen (in molecular or elemental form). In a preferred embodiment, the high temperature hydrogen separation unit comprises a membrane that is selectively permeable to hydrogen. In one embodiment, the high temperature hydrogen separation unit comprises a tubular film coated with a palladium or palladium alloy that is selectively permeable to hydrogen.

The gas stream entering the high temperature hydrogen separation unit 18 via line 122 may comprise hydrogen, carbon oxides, and hydrocarbons. The gas stream can contact the tubular hydrogen separation membrane 68 and hydrogen can pass through a membrane wall to a hydrogen conduit 124 located within the membrane 68 . The membrane wall separates the hydrogen conduit 124 from gas communication with the non-hydrogen compound and is selectively permeable to hydrogen (elements and/or molecules) such that hydrogen in the incoming gas can pass through the membrane wall to the hydrogen conduit 124 , Other gases are prevented from being transferred to the hydrogen conduit by the walls of the membrane.

The high temperature tubular hydrogen separation membrane 68 of Figures 1 and 2 can comprise a support coated with a thin layer of one of the metals or alloys selectively permeable to hydrogen. The carrier may be formed from a ceramic or a metallic material that permeates hydrogen. Porous stainless steel or porous alumina is a preferred material for the carrier of film 68 . The hydrogen-selective metal or alloy coated on the support may be selected from the following Group VIII metals, including but not limited to Pd, Pt, Ni, Ag, Ta, V, Y, Nb, Ce, In, Ho, La, Au. And Ru (specifically in the form of an alloy). Palladium and palladium alloys are preferred. A particularly preferred film 68 used in the method has a very thin palladium alloy film having a high surface area coated with a porous stainless steel support. A film of this type can be prepared using the method disclosed in U.S. Patent No. 6,152,987. A film of platinum or platinum alloy having a high surface area will also be suitable as a hydrogen selection material.

The pressure in the recombination zone 108 of the second recombiner 16 is maintained at a level substantially higher than the pressure within the hydrogen conduit 124 of the tubular membrane 68 such that forced hydrogen is forced through the recombination zone 108 of the second recombiner 16 . The film wall is in the hydrogen conduit 124 . In one embodiment, the hydrogen conduit 124 is maintained at or near atmospheric pressure and the recombination zone 108 is maintained at a pressure of at least 0.5 MPa, or at least 1.0 MPa, or at least 2 MPa or at least 3 MPa. As described above, the recombination zone 108 can be maintained at such elevated pressures by compressing the feed from the first reformer 14 with the compressor 94 and injecting the feed mixture at high pressure into the recombination zone 108 . Alternatively, as set forth above may be by high pressure steam with the feed mixture and the mixture was injected into a high pressure second recombination region 16 of the reformer 108 to the recombination zone 108 is maintained at such a high pressure. Alternatively, the first recombiner can be mixed with the hydrocarbon stream by recombination zone in the first recombiner 14 or one of the first recombiners and directly or through one or more heat exchangers 90 . One of the high pressure feeds produced in the second reformer 16 is injected to maintain the recombination zone 108 at such high pressures. The recombination zone 108 of the second recombiner 16 can be maintained at a pressure of at least 0.5 MPa, or at least 1.0 MPa, or at least 2.0 MPa or at least 3.0 MPa.

The steam recombination feed and, as the case may be, additional steam are mixed and contacted with the recombination catalyst in the recombination zone 108 of the second reformer 16 at a temperature of at least 400 ° C, and preferably from 400 ° C to 650 ° C. The range is preferably in the range from 450 ° C to 550 ° C. A typical steam recombiner operates at a temperature of 750 ° C or higher to achieve a sufficiently high equilibrium conversion. In the present method, the hydrogen is continuously removed from the recombination zone 108 into the hydrogen conduit 124 of the membrane 68 (and thus removed from the second recombiner 16 ) in a recombiner operating temperature range of 400 ° C to 650 ° C. The recombination reaction is driven toward the production of hydrogen. In this way, the process achieves near-to-complete conversion of the reactants to hydrogen without equilibrium limitations. An operating temperature of 400 ° C to 650 ° C is also advantageous for shifting the reaction to convert carbon monoxide and steam to more hydrogen and then removing the hydrogen from the reforming zone 108 into the hydrogen conduit 124 through the membrane wall of the membrane. Nearly complete conversion of hydrocarbons and carbon monoxide to hydrogen and carbon dioxide by recombination and water gas shift reactions can be achieved in the second reformer 16 because equilibrium is never achieved due to the continuous removal of hydrogen from the second reformer.

In one embodiment, the steam recombination feed supplied to the second recombiner 16 from the first recombiner 14 and/or one of the first recombiner recombination zones supplies heat to drive the reaction in the second recombiner. The steam recombination feed to the second recombiner 16 from the first recombiner 14 and/or the recombination zone of one of the first recombiners may contain sufficient thermal energy to drive the reaction in the second recombiner and may have From one of 400 ° C to 950 ° C temperature. The thermal energy of the steam recombination feed produced from the first recombiner 14 and/or the recombination zone of one of the first recombiners may exceed the thermal energy required to drive the reaction in the second recombiner 16 , and as set forth above, The feed may be cooled to a temperature from 400 ° C to less than 600 ° C in heat exchanger 90 and/or by injecting water into the feed prior to feeding to second reformer 16 . It may be preferred to have one of the temperatures required at or near the second recombiner 16 such that 1) the temperature within the second recombiner 16 can be adjusted to facilitate hydrogen production in the water gas shift reaction; 2) Extending the life of the film 68 ; and 3) improving the performance of the compressor 94 . The transfer of thermal energy from the first recombiner 14 to the second recombiner 16 is quite efficient because the thermal energy from the first recombiner is included in the feed, the feed being closely related to the second recombiner reaction.

The hydrogen-containing stream is formed from the reformed product gas in a high temperature hydrogen separation unit 18 by selectively passing hydrogen through the membrane wall of the hydrogen separation membrane 68 into the hydrogen conduit 124 to separate the hydrogen-containing stream from the reformed product gas. The hydrogen-containing stream may contain a very high hydrogen concentration and may contain at least 0.9, or at least 0.95 or at least 0.98 moles of hydrogen.

Due to the high flux of hydrogen through the hydrogen separation membrane 68 , the hydrogen containing stream can be separated from the recombined product gas at a relatively high rate. In one embodiment, the hydrogen separation membrane 68 is separated from the recombination product gas by a temperature of at least 300 ° C, or from about 350 ° C to about 600 ° C or from 400 ° C to 500 ° C. Since hydrogen is present in the second reformer 16 at a high partial pressure, hydrogen passes through the hydrogen separation membrane 68 at a high flux rate. The high partial pressure of hydrogen in the second reformer 16 is due to 1) a large amount of hydrogen fed to the first reformer 14 and passed to the anode reformer in the second reformer in the feed; 2) at the first Hydrogen produced in the reformer and fed to the second recombiner; and 3) hydrogen produced by the recombination and shift reaction in the second recombiner. Due to the high rate of hydrogen separation from the recombined product, no sweep gas is required to assist in the removal of hydrogen from the hydrogen conduit 124 and removal of the high temperature hydrogen separation unit 18 .

As shown in FIGS. 1-2, the hydrogen-containing stream exits the high temperature hydrogen separation unit 18 and passes through the hydrogen conduit 124 through lines 126 and 34 to the anode inlet 30 to enter the anode 24 of the molten carbonate fuel cell 12 . Alternatively, the hydrogen containing system is fed directly to the anode inlet 30 via line 126 . The hydrogen stream provides hydrogen to the anode 24 to achieve an electrochemical reaction with the oxidant at one or more anode electrodes along the length of the anode path in the fuel cell 12 . The partial pressure of one of the molecular hydrogen entering the second reformer 16 is higher than the partial pressure of the molecular hydrogen in the hydrogen-containing stream exiting the high temperature hydrogen separation unit 18 . The partial pressure difference between the second reformer 16 and the partial pressure of molecular hydrogen in the hydrogen-containing stream exiting the high temperature hydrogen separation unit 18 drives the recombination reaction and/or the water gas shift reaction to produce more hydrogen. In some embodiments, a sweep gas (eg, steam) can be injected into the hydrogen conduit to sweep hydrogen from the interior portion of the membrane wall member into the hydrogen conduit, thereby increasing the separation of the membrane by hydrogen. The rate at which the recombination zone separates hydrogen.

The hydrogen containing stream or a portion thereof may be fed to heat exchanger 72 via line 128 to heat the hydrocarbon stream and cool the hydrogen stream prior to feeding the hydrogen containing stream to anode 24 . After exiting the high temperature hydrogen separation unit 18 , the hydrogen containing stream may have a temperature from 400 ° C to 650 ° C (typically from one of 450 ° C to 550 ° C). The pressure of the hydrogen-containing gas exiting the high temperature hydrogen separation unit 18 may have a pressure of about 0.1 MPa, or from 0.01 MPa to 0.5 MPa, or from 0.02 MPa to 0.4 MPa or from 0.3 to 0.1 MPa. In a preferred embodiment, one of the hydrogen-containing streams exiting the high temperature hydrogen separation unit 18 has a temperature of about 450 ° C and a pressure of about 0.1 MPa. The pressure and temperature of the hydrogen-containing stream exiting the high temperature hydrogen separation unit 18 can be adapted to directly feed the hydrogen-containing stream directly to the anode inlet 30 of the molten carbonate fuel cell 12 .

The hydrocarbon stream can optionally be heated by exchanging heat with the hydrogen stream in heat exchanger 72 and optionally by exchanging heat with the carbon dioxide gas stream, as set forth below. And selected and controlled fed to a molten carbonate fuel cell cathode 12 of the 26 temperature of the composition containing the oxidant stream may be fed to a molten carbonate fuel cell anode 12 of hydrogen stream 24 is cooled up to 400 ℃, or at most 300 °C, or at most 200 ° C, or at most one temperature of 150 ° C, or from 20 ° C to 400 ° C or from 25 ° C to 250 ° C to control the operating temperature of the molten carbonate fuel cell from 600 ° C to 700 ° C Within a range. The hydrogen containing stream or a portion thereof can typically be cooled to a temperature from 200 ° C to 400 ° C by exchanging heat with the hydrocarbon stream in heat exchanger 72 . Optionally, the hydrogen stream or a portion thereof may be passed from heat exchanger 72 to one or more additional heat exchangers (not shown) for further in each of the one or more additional heat exchangers. The hydrocarbon stream is either exchanged with a stream of water to further cool the stream of hydrogen or a portion thereof. If additional heat exchangers are employed in the system, the hydrogen stream or a portion thereof may be cooled to a temperature from 20 ° C to 200 ° C, preferably from 25 ° C to 100 ° C. In one embodiment, a portion of the hydrogen stream may be cooled in heat exchanger 72 and, where appropriate, one or more additional heat exchangers, and a portion of the hydrogen stream may be cooled without being cooled in a heat exchanger. Feeding to the anode 24 of the molten carbonate fuel cell 12 , wherein the combined portion of the hydrogen stream can be at a temperature of up to 400 ° C, or at most 300 ° C, or at most 200 ° C, or at most 150 ° C, or from 20 ° C to 400 It is fed to the anode of the fuel cell at a temperature of from °C to 100 °C.

The flow rate of the hydrogen stream or a portion thereof to the heat exchangers 72 , 22 and (as appropriate) to one or more additional heat exchangers can be selected and controlled to control the hydrogen fed to the anode 24 of the molten carbonate fuel cell 12 . The temperature of the flow. The flow rate of the hydrogen stream or a portion thereof to the heat exchanger 22 and optional additional heat exchangers can be selected and controlled by adjusting the throttle valves 36 , 130, and 132 . The throttle valves 36 and 130 can be adjusted to control the flow of the hydrogen stream or a portion thereof through the line 126 to the anode 24 of the molten carbonate fuel cell 12 without cooling the hydrogen stream or a portion thereof. The throttle valve 130 can also control the flow of the hydrogen stream or a portion thereof to the heat exchanger 22 . The throttle valve 132 can be adjusted to control the flow of the hydrogen stream or a portion thereof through the line 128 to the heat exchanger 72 and any optional additional heat exchanger. The throttle valves 130 and 132 can be coordinated to provide the desired degree of cooling to the hydrogen stream prior to feeding the hydrogen stream to the anode 24 of the molten carbonate fuel cell 12 . In one embodiment, throttles 130 and 132 may be automatically coordinated in response to feedback measurements of the temperature of the anode exhaust stream and/or cathode exhaust stream exiting fuel cell 12 . The hydrogen stream provides hydrogen to the anode 24 to achieve an electrochemical reaction with the oxidant at one or more anode electrodes along the length of the anode path in the fuel cell 12 . May be selected by the feed rate of the feed to the reformer 16 of the second selected rate of the hydrogen gas stream fed to the anode of a molten carbonate fuel cell 12 of the 24, and fed to the feed rate of the second reformer 16 but also to the hydrocarbon stream fed by a first recombination rate of 14 to select, and the hydrocarbon stream fed to the first turn of the reformer 14 by adjusting the rate of the hydrocarbon stream inlet valve 106 is controlled.

Any portion of the hydrogen-containing stream fed to heat exchanger 72 and, where appropriate, the additional heat exchanger, may be fed from the heat exchanger or through a last additional heat exchanger for cooling the hydrogen-containing stream, wherein Any portion of the hydrogen stream is routed around the heat exchangers to the anode of the molten carbonate fuel cell. In one embodiment, the combined portion of the hydrogen-containing stream or the hydrogen-containing stream exiting the high temperature hydrogen separation unit 18 may be compressed in a compressor (not shown) to increase the pressure of the hydrogen stream, and then the hydrogen stream may be subsequently flowed. Feed to the anode. In one embodiment, the hydrogen stream can be compressed to a pressure from 0.15 MPa to 0.5 MPa, or from 0.2 MPa to 0.3 MPa, or up to 0.7 MPa or up to 1 MPa. All of the energy or portion of the energy required to drive the compressor can be provided by expanding one of the high pressure carbon dioxide streams and/or through the high pressure steam of one or more turbines as set forth below.

Alternatively, the rate at which the hydrogen stream is fed to the anode 24 of the molten carbonate fuel cell 12 can be selected by controlling the throttle valves 36 and 134 in a coordinated manner. The throttle valve 36 can be adjusted to increase or decrease the flow of hydrogen into the anode 24 . The throttle valve 134 can be adjusted to increase or decrease the flow of hydrogen to the hydrogen source 64 . The throttle valves 36 and 134 can be controlled in a coordinated manner such that a selected rate of hydrogen flow can be fed through line 34 to the anode 24 of the molten carbonate fuel cell 12 beyond the amount of hydrogen flow required to provide the selected rate. A portion of the hydrogen stream can be fed to hydrogen source 64 via line 136 .

A hydrogen depleted recombined product gas stream can be removed from high temperature hydrogen separation unit 18 via line 48 , wherein the hydrogen depleted recombined product gas stream can comprise unreacted feed and gaseous non-hydrogen recombination in the reformed product gas. product. The non-hydrogen recombined products and unreacted feed may comprise carbon dioxide, water (as steam), and small amounts of carbon monoxide and unreacted hydrocarbons. The hydrogen depleted reconstituted product stream may also contain a small amount of hydrogen.

In one embodiment, the hydrogen depleted recombined product gas stream exiting the high temperature hydrogen separation unit 18 can be a carbon dioxide gas stream having a carbon dioxide content of at least 0.8, or at least 0.9, or at least 0.95, or at least 0.98 mole percent carbon dioxide on a dry basis. The carbon dioxide gas stream is a high pressure gas stream having a pressure of at least 0.5 MPa, or at least 1 MPa, or at least 2 MPa or at least 2.5 MPa. In the following, the hydrogen depleted recombined product gas will be referred to as a high pressure carbon dioxide gas stream. The temperature of the high pressure carbon dioxide gas stream exiting the hydrogen separation unit 18 is at least 400 ° C or typically between 425 ° C and 600 ° C or between 450 ° C and 550 ° C.

The high pressure carbon dioxide gas stream can exit the high temperature hydrogen separation unit 18 and be fed to the cathode 26 of the fuel cell 12 via lines 48 and 44 . As shown, the high pressure carbon dioxide gas stream passes through heat exchanger 22 and can be used to heat the oxidant gas stream. In one embodiment, a portion of the carbon dioxide stream is directly mixed with the oxidant stream entering the cathode 26 via line 44 .

In a preferred embodiment, a high pressure carbon dioxide gas stream is fed via line 48 to the catalytic partial oxidation reformer 20 . In the catalytic partial oxidation reformer 20 , the remaining hydrocarbons (e.g., methane, ethane, and propane) in the carbon dioxide stream are combusted in the presence of oxygen or air fed from the oxidant source 42 via line 56 to form via line 138. A hot effluent combustion stream is passed through heat exchanger 22 and via line 44 to one of cathodes 26 . In one embodiment, the combustion stream is fed directly to the cathode 26 via lines 138 and 44 . The amount of molecular oxygen fed to the oxidant-containing stream of the catalytic partial oxidation reformer 20 is at least 0.9 times but not more than 1.1 times the stoichiometric amount required for complete combustion of the hydrocarbons in the carbon dioxide stream.

The hot combustion stream can contain a significant amount of carbon dioxide, but can also include nitrogen and water. The hot combustion stream exiting the catalytic partial oxidation reformer 20 can have a temperature in a range from at least 750 ° C to 1050 ° C, or from 800 ° C to 1000 ° C or from 850 ° C to 900 ° C. The heat from the hot combustion gases can be exchanged with the hydrogen containing stream in heat exchanger 22 and/or with the oxidant containing gas stream in the heat exchanger. As shown in FIG. 2, at least a portion of the heat from the combustion stream exiting the catalytic partial oxidation recombination 20 can be exchanged with the first reformer 14 in heat exchanger 98 via line 96 .

In an embodiment, the hot combustion gases may be fed directly to the cathode exhaust inlet 38 . The temperature of one of the oxidant-containing gases can be adjusted such that the temperature of one of the cathode exhaust streams exiting the fuel cell ranges from 550 ° C to 700 ° C. The temperature of the oxidant-containing gas can be adjusted to a temperature from one of 150 ° C to 450 ° C by cooling and/or heating in the heat exchanger 22 . The flow of the oxidant-containing gas stream from the high temperature hydrogen separation unit 18 to the heat exchanger 22 and/or the catalytic partial oxidation reformer 20 can be controlled by adjusting the throttle valves 46 , 58 and 140 .

When the hot combustion gas stream exits the catalytic partial oxidation recombination 20 , it may contain a large amount of water as steam. In one embodiment, the hot combustion gas stream can be cooled and condensed from the steam by heat exchanger 22 and/or in heat exchanger 72 and, if desired, one or more additional heat exchangers (not shown). Steam is removed from the hot combustion gas stream.

The hydrocarbon stream is heated by a high pressure carbon dioxide gas stream from high temperature hydrogen separation unit 18 by passing a carbon dioxide containing gas stream through line 142 to heat exchanger 72 while passing hydrocarbon stream through heat exchanger stream 62 to heat exchanger 72 . The flow of the high pressure thermal oxidizing carbon stream from the high temperature hydrogen separation unit 18 to the heat exchanger 72 can be controlled by adjusting the throttle valve 144 . The throttle valve 144 can be adjusted to control the flow of carbon dioxide to the heat exchanger 72 to heat the hydrocarbon stream to a selected temperature. The hydrocarbon stream can be heated to a temperature such that the hydrocarbon stream has a temperature of at least 150 ° C or from 200 ° C to 500 ° C when the hydrocarbon stream is fed to the first reformer 14 .

The throttle valves 46 , 58 and 140 can be automatically adjusted by a feedback mechanism that measures the temperature of the cathode exhaust stream exiting the fuel cell 12 and/or the temperature of the hydrocarbon stream entering the first reformer 14 and The throttle valves 46 , 58 and 140 are adjusted to maintain the temperature of the cathode exhaust stream and/or the hydrocarbon stream entering the first reformer 14 within a set limit while separating the second recombiner 16 and/or high temperature hydrogen The internal pressure within the device 18 is maintained at a desired level.

The hydrogen stream and the oxidant (carbonate ion) produced by the reaction of oxygen with carbon dioxide at the cathode are preferably mixed at one or more anode electrodes of the fuel cell 12 (as set forth above) to at least 0.1 W/cm ^{2 .} More preferably, at least 0.15 W/cm ² , or at least 0.2 W/cm ² or at least 0.3 W/cm ² of one electrical power density produces electricity. Electricity can be generated at such electrical power densities by selecting and controlling the rate at which the hydrogen stream is fed to the anode 24 of the fuel cell 12 and the rate at which the oxidant-containing gas stream is fed to the cathode 26 of the fuel cell 12 . The flow rate of the oxidant-containing gas stream to the cathode 26 of the fuel cell 12 can be selected and controlled by adjusting the oxidant gas inlet valve 46 .

As explained above, the flow rate of the hydrogen stream to the anode 24 of the fuel cell 12 can be selected and controlled by selecting and controlling the rate at which the feed is fed to the second reformer 16 , and the feed is fed to the second. the turn rate of the reformer 16 by the hydrocarbon stream fed to the reformer 14 of the first rate be selected and controlled, and the hydrocarbon stream fed to the first turn of the reformer 14 by adjusting the rate of the hydrocarbon stream inlet valve 106 to choose and control. Alternatively, as explained above, the rate at which the hydrogen stream is fed to the anode 24 of the fuel cell 12 can be selected and controlled by controlling the throttle valves 36 , 130 , 132, and 134 in a coordinated manner. In an embodiment, the throttle valves 36 , 130 , 132, and 134 may be automatically adjusted by a feedback mechanism to maintain a flow of hydrogen to a selected flow rate of the anode 24 , wherein the feedback mechanism may be based on the anode exhaust stream. The hydrogen content, or the water content of the anode exhaust stream, or the ratio of the water formed in the fuel cell to the hydrogen in the anode exhaust stream is measured.

In the method of the present invention, the hydrogen stream is mixed with the oxidant at one or more anode electrodes to produce water by oxidation of the oxidant by a portion of the hydrogen present in the hydrogen stream fed to the fuel cell 12 (as steam). Water produced by the oxidation of hydrogen and oxidant is swept through the unreacted portion of the hydrogen stream through the anode 24 of the fuel cell 12 to exit the anode 24 as part of the anode exhaust stream.

In one embodiment of the method of the present invention, the flow rate of the hydrogen stream feed to the anode 24 can be selected and controlled, such that the amount of water formed in the fuel cell 12 per unit time is the hydrogen in the anode exhaust per unit time. The ratio of amounts is at most 1.0, or at most 0.75, or at most 0.67, or at most 0.43, or at most 0.25 or at most 0.11. In one embodiment, the amount of water formed in the fuel cell 12 and the amount of hydrogen in the anode exhaust gas can be measured in a molar manner such that the amount of water formed in the fuel cell per unit time is per unit time. The ratio of the amount of hydrogen in the anode exhaust gas is at most 1.0, or at most 0.75, or at most 0.67, or at most 0.43, or at most 0.25 or at most 0.11 in moles per unit time. In one embodiment, the flow rate of the hydrogen stream feed to the anode 24 can be selected and controlled such that the hydrogen utilization rate per pass in the fuel cell 12 is less than 50%, or up to 45%, or up to 40%, or up to 30 %, or up to 20% or up to 10%.

In another embodiment of the method of the present invention, the flow rate of the hydrogen stream feed to the anode 24 can be selected and controlled such that the anode exhaust stream contains at least 0.6, or at least 0.7, or at least 0.8, or at least 0.9 mole fraction. hydrogen. In a further embodiment, the flow rate of the hydrogen stream fed to the anode 24 can be selected and controlled such that the anode exhaust stream contains greater than 50%, or at least 60, of the hydrogen in the hydrogen stream fed to the anode 24 . %, or at least 70%, or at least 80%, or at least 90%.

In certain embodiments, the flow rate of the carbon dioxide stream feed to the cathode 26 can be selected and controlled such that the partial pressure of carbon dioxide in the majority of the cathode portion of the molten carbonate fuel cell is higher than that of the molten carbonate fuel cell. One of the carbon dioxide in one of the majority of the anode portion is divided. In one embodiment, the flow rate of the carbon dioxide stream feed to the cathode 26 can be selected and controlled such that the partial pressure of carbon dioxide in the cathode exhaust stream exiting the fuel cell is greater than the carbon dioxide in the anode exhaust stream exiting the fuel cell. The partial pressure. Selecting and controlling the flow rate of carbon dioxide such that at least 75%, or at least 95% or substantially all of the carbon dioxide partial pressure of the molten carbonate fuel cell is greater than at least 75%, 95% of the molten carbonate fuel cell or A partial pressure of one of the carbon dioxide of substantially all of the anode portion.

Operating the molten carbonate fuel cell to control ΔP _CO2 at a pressure above 0 at any air concentration and/or any hydrogen utilization rate, inhibiting carbon dioxide deficiency of the molten carbonate fuel cell and enhancing the molten carbonate The battery potential of the fuel cell. The flow rate of the carbon dioxide stream feed to the cathode 26 of the molten carbonate fuel cell 12 can be selected and controlled such that the hydrogen utilization rate is at most 60%, at most 50% or at most 40%, at most 30%, at most 20%, or at most 10 When % is determined by the equation (ΔP _CO2 ) = (P _CO2 ^c ) - (P _CO2 ^a ), the partial pressure of carbon dioxide is about 0 bar or higher than 0 bar, from 0.01 to 0.2 bar or from 0.05 to 0.15 bar. And/or controlling the empty flow such that the molar ratio of carbon dioxide to molecular oxygen is about 2.

Instance

Non-binding examples are set forth below.

One of the combinations with the calculation of the battery potential UniSim A simulation program (Honeywell) was used to construct a detailed process simulation of one of the molten carbonate fuel cell systems of the present invention. The UniSim program is used to obtain material balance and energy balance data. The detailed process simulation is repeated for different hydrogen utilization values and other related system parameters. The detailed process simulation output contains detailed information on all process flows into and out of the molten carbonate fuel cell.

For high temperature fuel cells, the startup losses are small and the battery potential can be obtained over the actual current density range by considering only ohms and electrode losses. Thus, the battery potential (V) of a molten carbonate fuel cell is the difference between the open circuit voltage (E) and the loss (iR) as shown in equation (1).

V=E-iR (1)

Where V and E have units of volts and millivolts, i is the current density (mA/cm ² ) and R (Ωcm ² ) is the ohmic (R _ohm ), cathode (η _c ) that combines the electrolyte, the cathode and the anode. The combination with the anode (η _a ) resistance is as shown in equation (2).

R=R _ohm +η _c +η _a (2)

The E system is obtained from the Nernst equation:

E=E ^o +(RT/2F)ln(P _H2 P _O2 ^0.5 /P _H2O )+(RT/2F) ln(P _CO2 ^c /P _CO2 ^a ) (3)

Example 1 uses the detailed process simulations set forth above to simulate cell voltage versus current density and power density formation for the molten carbonate fuel cell system set forth herein, wherein the first recombiner is heated by the anode exhaust without additional heating . For example, the system illustrated in FIG. The heat for the second recombiner is heated by exchange with a hot effluent from the catalytic partial oxidation recombiner. The output temperature of the effluent from the catalytic partial oxidation recombiner is increased by using a cathode exhaust to preheat the catalytic oxidation recombiner air feed.

Example 2 uses the simulations set forth above to simulate cell voltage versus current density and power density formation for the molten carbonate fuel cell system set forth herein, with anode venting and heat from a catalytic partial oxidation recombiner. Heat the first recombinator. For example, the system depicted in Figure 2.

For Examples 1 and 2, the molten carbonate fuel cell was operated at a pressure of 1 bar (about 0.1 MPa or about 1 atm) and at a temperature of 650 °C. The flow to the feed to the cathode of the molten carbonate fuel cell is convected with the flow to the feed to the anode. Use air as the source of oxygen. The value of air is used to produce a molar ratio of carbon dioxide to molecular oxygen of 2 at various hydrogen utilization rates. The percent hydrogen utilization of the molten carbonate fuel cell simulated in Examples 1 and 2, the operating conditions of the first and second reformers, the steam to carbon ratio, and the percent conversion of benzene to hydrogen are set forth in Table 1. R in Equation 2 is obtained from J. Power Sources 2002, 112, pp. 509-518 and is assumed to be equal to 0.75 Ωcm ² .

The battery voltages and currents from the molten carbonate fuel cells of the state of the art as set forth in Examples 1 and 2 and the current state of the art set forth by Larmine et al., "Fuel Cell Systems Explained" (2003, Wiley & Sons, p. 199). The literature values of density and power density were compared.

Figure 4 is a graph showing the battery voltage (mV) versus current density (mA/cm ² ) for a molten carbonate fuel cell system simulated in Examples 1 and 2 and a molten carbonate fuel cell having one of the reconstituted oils as a feed. Document value. The molten carbonate fuel cells were operated at a hydrogen utilization rate of 20% and 30%. Data line 160 shows the cell voltage (mV) versus current density (mA/cm ² ) at 20% hydrogen utilization for one of the molten carbonate fuel cell systems of Examples 1 and 2. Data line 162 is shown for Examples 1 and 2 for battery voltage (mV) versus current density (mA/cm ² ) at 30% hydrogen utilization. Data line 164 depicts battery voltage (mV) vs. current for a state of the art molten carbonate fuel cell system as described by Larmine et al., "Fuel Cell Systems Explained" (2003, Wiley & Sons, page 199). Density (mA/cm ² ). As shown in Figure 4, for a given current density, the battery voltage of the molten carbonate fuel cell system set forth herein is higher than that of a molten carbonate fuel cell having the state of the art as a feedstock of reconstituted oil gas. battery voltage.

Figure 5 is a graph showing the power density (W/cm ² ) versus current density (mA/cm ² ) for the molten carbonate fuel cell system simulated in Examples 1 and 2 operating at 20% and 30% hydrogen utilization. A literature value for a molten carbonate fuel cell having one of the reconstituted oil gases as one of the feeds. Data line 166 is shown for Examples 1 and 2 for power density (W/cm ² ) versus current density (mA/cm ² ) at 20% hydrogen utilization. Data line 168 is shown for Examples 1 and 2 for power density (W/cm ² ) versus current density (mA/cm ² ) at 30% hydrogen utilization. Data line 170 illustrates power density (W/cm ^{2 for} a molten carbonate fuel cell system as taught by Larmine et al., "Fuel Cell Systems Explained" (2003, Wiley & Sons, page 199). ) Current density (mA/cm ² ). As shown in Figure 5, for a given current density, the power density of the molten carbonate fuel cell system set forth herein is higher than the power density of a molten carbonate fuel cell having a reconstituted oil gas as a feed.

Figure 6 shows, for Example 1, excess carbon dioxide (ΔP _CO2 (bar)) and total fuel cell potential (mV) versus hydrogen utilization. Data line 172 represents the excess carbon dioxide value (at a given hydrogen utilization rate and one current density of 200 mA/cm ² ). Data 174 represents the average excess carbon dioxide value at a given hydrogen utilization rate. Data line 176 represents the total battery potential (mV) of the fuel cell as determined by the Nernst equation at a given hydrogen utilization rate. As shown in FIG. 6, as the hydrogen utilization rate increases, ΔP _CO2 decreases and the cell potential increases, so operating the molten carbonate fuel system under less than 50% hydrogen utilization and carbon dioxide flooding results in the molten carbonic acid. Enhanced battery potential for salt fuel cells.

Figure 7 is a graph showing the carbon dioxide portion of the fuel cell potential (mV) of Figure 6. The data line 178 represents the carbon dioxide portion of the battery potential (mV) of the fuel cell (for example, the (RT/2F)ln(P _CO2 ^c /P _CO2 ^a ) portion of the Nernst equation). As shown in FIG. 7, when the cathode portion of the fuel cell is flooded with carbon dioxide, the cell voltage of one of the fuel cells rises. For example, the fuel cell is operated at a 20% hydrogen utilization rate and at an excess carbon dioxide value of about 0.105, and the total fuel cell potential of 30 mV is caused by the excess carbon dioxide.

As shown in Figures 6 and 7, when the amount of carbon dioxide supplied to the fuel cell is excessive (ΔP _CO2 > 0) and the percent hydrogen utilization is low (e.g., less than 35%, less than 30%, or less than 20%), The battery potential is maximized. Therefore, the molten carbonate fuel system is operated at a hydrogen utilization rate of less than 50% and excess carbon dioxide is supplied to a cathode portion of the molten carbonate fuel cell such that a majority of the cathode portion of the molten carbonate fuel cell is One of the partial pressures of carbon dioxide is higher than a partial pressure of carbon dioxide in a majority of the anode portion of the molten carbonate fuel cell, and thereby the battery voltage of the molten carbonate fuel cell is enhanced.

Example 3 is for a molten carbonic acid fuel cell system (eg, the system depicted in Figure 1) comprising a first recombiner heated by anode exhaust gas using a simulation as set forth above to determine at 7 bar (about 0.7 MPa) Or a current density, battery voltage, and power density of a molten carbonate fuel cell operating at about 7 atm). The molten carbonate fuel cell was operated at a pressure of one of 7 bar and a temperature of 650 ° C with a hydrogen utilization rate of 20% or 30%. The first recombiner has a steam to carbon ratio of 2.5. The temperature of the first recombiner is allowed to vary. The second recombiner in combination with the high temperature hydrogen separation unit has a temperature of one of 500 ° C and a pressure of one of 15 bar. Use air as the source of oxygen. The value of air is used to make the ratio of carbon dioxide to molecular oxygen in the cathode feed stoichiometric, thus minimizing cathode side concentration polarization. In all cases, the combined carbon conversion value of the system using benzene as the feed was between 93% and 95%. The heat of reaction for the second recombiner is supplied by the thermal product within the system. R is calculated by separately calculating the individual terms in Equation 2 above by the method set forth in CY Yuh and JR Selman, J. Electrochem. Soc. (Vol. 138, No. 12, December 1991). For Example 3, R was calculated to be 0.57 Ω.cm ² .

Figure 8 is a graph showing battery voltage (mV) versus current density (mA/cm ² ) for a molten carbonate fuel cell as depicted in Figure 1. Data line 180 depicts the cell voltage (mV) versus current density (mA/cm ² ) at 20% hydrogen utilization. Data line 182 depicts the cell voltage (mV) versus current density (mA/cm ² ) at 30% hydrogen utilization. Comparing Figure 4 with Figure 8, a molten carbonate fuel cell operating at a pressure of about 7 bar at a given current density compared to the cell voltage of a molten carbonate fuel cell system operating at 1 bar. The system observed a higher battery voltage.

Figure 9 illustrates power density (W/cm ² ) versus current density and one of the states of the molten carbonate fuel cell for a molten carbonate fuel cell system as illustrated in Figure 1. Data line 184 depicts the power density (W/cm ² ) versus current density (mA/cm ² ) at 20% hydrogen utilization. Data line 186 plots power density (W/cm ² ) versus current density (mA/cm ² ) at 30% hydrogen utilization. Data Point 188 shows power density (W/cm ² ) versus current density for a state of the art molten carbonate fuel cell system as described by JR Selman in Journal of Power Sources (2006, pages 852-857). (mA/cm ² ). Shown in FIG. 9, one at a current density of approximately ² 300 mA / cm, the power density of the molten carbonate fuel cell systems set forth herein, the power density above the current level of technology of the molten carbonate fuel cell.

Example 4 compares the use of methane as a fuel source for a molten carbonate fuel cell system with benzene using the simulations set forth above, where the first recombiner is heated by the anode exhaust without additional heating. For example, the system depicted in Figure 1. The heat of reaction for the second recombiner is supplied by the thermal product within the system. For these simulations, the molten carbonate fuel cell was operated at one of a pressure of 1 bar (about 0.1 MPa or about 1 atm) and a temperature of 650 °C. Use air as the source of oxygen. The value of air is used to produce a molar ratio of carbon dioxide to molecular oxygen of 2 at various hydrogen utilization rates. The amount of fuel feed to the first reformer was 100 kgmol/hr for the benzene system and 600 kgmol/hr for the methane system. The percent hydrogen utilization of the molten carbonate fuel cell, the operating conditions of the first and second reformers, and the steam to carbon ratio are listed for benzene in Table 2 and in Table 3 for methane.

As obtained from J. Power Sources 2002, 112, pages 509-518, it is assumed that R in Equation 2 is equal to 0.75 Ω.cm ² .

10 for the use of benzene or methane as a fuel source of a molten carbonate fuel cell system shows a battery voltage (mV) versus current density (mA / cm ^2). Data line 190 depicts the cell voltage (mV) versus current density (mA/cm ² ) at 20% hydrogen utilization using benzene as a feed source. Data line 192 depicts the cell voltage (mV) versus current density (mA/cm ² ) at 20% hydrogen utilization using methane as a feed source. As shown in Figure 10, a higher cell voltage was observed in the molten carbonate fuel cell system when benzene was used as a fuel source for the first recombiner.

FIG 11 at a current density for one ² 200 mA / cm benzene or methane as one of an average excess carbon dioxide a molten carbonate fuel cell fuel supply systems _{(ΔP CO2 (avg))} of hydrogen utilization percentage. Data line 194 represents the average excess carbon dioxide value for benzene at a given hydrogen utilization rate. Data line 196 represents the average excess carbon dioxide value for methane. As shown in Figure 11, benzene provides more excess carbon dioxide than methane at a given hydrogen utilization rate at less than 50% hydrogen utilization. Thus, when benzene is used as a fuel source, more moor carbon dioxide is produced per mole of hydrogen.

As shown in Examples 1 through 4, the molten carbonate fuel cell systems and methods set forth herein provide enhanced current density, current voltage, power density and inhibit carbon dioxide deficiency of the fuel cell by the following steps: a hydrogen-containing hydrogen stream is supplied to an anode portion of a molten carbonate fuel cell; a flow rate of the hydrogen-containing stream to the anode is controlled such that a molecular hydrogen utilization rate in the anode is less than 50%; and the fuel from the molten carbonate is included The anode exhaust of the molecular hydrogen of the battery is mixed with a hydrocarbon stream comprising a hydrocarbon, wherein the anode exhaust gas mixed with the hydrocarbon stream has a temperature from one of 500 ° C to 700 ° C; the mixture of the anode exhaust gas and the hydrocarbon stream At least a portion of the contact with a catalyst to produce a vapor recombination feed comprising one or more gaseous hydrocarbons, molecular hydrogen, and at least one carbon oxide; separating at least a portion of the molecular hydrogen from the vapor recombination feed; and separating At least a portion of the molecular hydrogen is provided to the molten carbonate fuel cell anode as at least a portion of the hydrogen-containing stream comprising molecular hydrogen.

10. . . Fuel cell system

12. . . Molten carbon carbonate fuel cell

14. . . First reorganizer

16. . . Second reorganizer

18. . . High temperature hydrogen separation unit

20. . . Oxidation unit

twenty two. . . Heat exchanger

twenty four. . . anode

26. . . cathode

28. . . Electrolyte

30. . . Anode inlet

32. . . Anode exhaust outlet

34. . . Pipeline

36. . . Throttle valve

38. . . Cathode inlet

40. . . Cathode exhaust outlet

42. . . Oxidizer source

44. . . Pipeline

46. . . Throttle valve

48. . . Pipeline

50. . . Pipeline

52. . . Pipeline

56. . . Pipeline

58. . . valve

60. . . valve

62. . . Pipeline

64. . . Hydrogen source

66. . . Pipeline

68. . . High temperature hydrogen separation film

70. . . Pipeline

72. . . Heat exchanger

74. . . Pipeline

76. . . Throttle valve

78. . . Throttle valve

80. . . Pipeline

82. . . Throttle valve

84. . . Pipeline

86. . . Throttle valve

88. . . Pipeline

90. . . Heat exchanger

92. . . Pipeline

94. . . compressor

96. . . Pipeline

98. . . Heat exchanger

100. . . Throttle valve

102. . . Three-way throttle

104. . . Pipeline

106. . . Hydrocarbon flow inlet valve

108. . . Recombination zone

110. . . Pipeline

112. . . Pipeline

114. . . Throttle valve

116. . . Throttle valve

118. . . Throttle valve

120. . . Throttle valve

122. . . Pipeline

124. . . Hydrogen conduit

126. . . Pipeline

128. . . Pipeline

130. . . Throttle valve

132. . . Throttle valve

134. . . Throttle valve

136. . . Pipeline

138. . . Pipeline

140. . . Throttle valve

142. . . Pipeline

144. . . Throttle valve

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic illustration of one embodiment of a system for a high temperature hydrogen separation unit comprising a first recombiner and a second recombiner in combination with one of the methods set forth herein.

2 is a schematic diagram of one of the embodiments of a system comprising one of a first recombiner having a heat exchanger and a high temperature hydrogen separation unit in combination with a second recombiner, for practicing one of the methods set forth herein. .

Figure 3 is a schematic illustration of one embodiment of a portion of a system in which a high temperature hydrogen separation unit is located external to the second reformer.

4 for the embodiment of FIG molten carbonate fuel cell systems operating at 1 bar it shows a battery voltage (mV) versus current density (mA / cm ^2).

Figure 5 illustrates power density (W/cm ² ) versus current density for an embodiment of a molten carbonate fuel cell system operating at 1 bar.

Figure 6 shows a battery voltage (mV) for various embodiments molten carbonate fuel cell systems operating at 7 bar of current density (mA / cm ^2).

Figure 7 illustrates power density (W/cm ² ) versus current density (mA/cm ² ) for an embodiment of a molten carbonate fuel cell system operating at 7 bar.

Figure 8 illustrates the percent hydrogen utilization versus ΔP _CO2 (bar) for an embodiment of operating a molten carbonate fuel cell using various amounts of excess air at a given hydrogen utilization rate.

Figure 9 illustrates the percent hydrogen utilization versus ΔP _CO2 (bar) for an embodiment of operating a molten carbonate fuel cell using methane or benzene as a feed source.

10 For embodiments using a variety of fuel sources molten carbonate fuel cell systems shows a battery voltage (mV) versus current density (mA / cm ^2).

Figure 11 illustrates the average excess carbon dioxide ([Delta] _PCO2(avg) ) versus percent hydrogen utilization for an embodiment of a molten carbonate fuel cell system using various fuel sources.

10. . . Fuel cell system

12. . . Molten carbon carbonate fuel cell

14. . . First reorganizer

16. . . Second reorganizer

18. . . High temperature hydrogen separation unit

20. . . Oxidation unit

twenty two. . . Heat exchanger

twenty four. . . anode

26. . . cathode

28. . . Electrolyte

30. . . Anode inlet

32. . . Anode exhaust outlet

34. . . Pipeline

36. . . Throttle valve

38. . . Cathode inlet

40. . . Cathode exhaust outlet

42. . . Oxidizer source

44. . . Pipeline

46. . . Throttle valve

48. . . Pipeline

50. . . Pipeline

52. . . Pipeline

56. . . Pipeline

58. . . valve

60. . . valve

62. . . Pipeline

64. . . Hydrogen source

66. . . Pipeline

68. . . High temperature hydrogen separation film

70. . . Pipeline

72. . . Heat exchanger

74. . . Pipeline

76. . . Throttle valve

78. . . Throttle valve

80. . . Pipeline

82. . . Throttle valve

84. . . Pipeline

86. . . Throttle valve

88. . . Pipeline

90. . . Heat exchanger

92. . . Pipeline

94. . . compressor

106. . . Hydrocarbon flow inlet valve

108. . . Recombination zone

110. . . Pipeline

112. . . Pipeline

114. . . Throttle valve

116. . . Throttle valve

118. . . Throttle valve

120. . . Throttle valve

124. . . Hydrogen conduit

126. . . Pipeline

128. . . Pipeline

130. . . Throttle valve

132. . . Throttle valve

134. . . Throttle valve

136. . . Pipeline

138. . . Pipeline

140. . . Throttle valve

142. . . Pipeline

144. . . Throttle valve

Claims (9)

A method of operating a molten carbonate fuel cell, comprising: providing a hydrogen-containing stream comprising molecular hydrogen to an anode portion of a molten carbonate fuel cell; controlling a flow rate of the hydrogen-containing stream to the anode to cause the The molecular hydrogen utilization rate in the anode is less than 50%; the anode exhaust gas including molecular hydrogen from the molten carbonate fuel cell is mixed with a hydrocarbon stream including hydrocarbons, wherein the anode exhaust gas mixed with the hydrocarbon stream has from 500 a temperature of from ° C to 700 ° C; contacting at least a portion of the mixture of anode exhaust gas and the hydrocarbon stream with a catalyst to produce a vapor recombination feed comprising one or more gaseous hydrocarbons, molecular hydrogen, and at least one carbon oxide And separating at least a portion of the molecular hydrogen from the steam reforming feed; and providing at least a portion of the separated molecular hydrogen to the molten carbonate fuel cell anode as at least a portion of the hydrogen-containing hydrogen stream comprising the molecular hydrogen. The method of claim 1, wherein the hydrogen-containing stream comprises at least 0.6 or at least about 0.95 mole fraction of molecular hydrogen. The method of claim 1 wherein at least some of the hydrocarbons of the hydrocarbon stream comprise one or two vaporizable hydrocarbons having a carbon number of at least four. The method of claim 1, further comprising feeding carbon dioxide to the cathode portion of the molten carbonate fuel cell in an amount such that a partial pressure of carbon dioxide in a majority of the cathode portion of the molten carbonate fuel cell is higher than the melting Dioxide in most of the anode portion of a carbonate fuel cell Carbon partial pressure. The method of claim 4, wherein a partial pressure of carbon dioxide at an inlet or an exhaust outlet of the cathode portion of the molten carbonate fuel cell and a partial pressure of carbon dioxide at the exhaust outlet of the anode portion of the molten carbonate fuel cell The difference between them is at least 0.05 bar, or at least 0.1 bar or at least 0.15 bar. The method of claim 4, wherein at least a portion of the carbon dioxide supplied to the cathode portion of the molten carbonate fuel cell is provided by a high temperature hydrogen separation unit. The method of claim 1, further comprising the step of separating at least a portion of the hydrogen depleted gas stream comprising at least one of the carbon oxides and at least one of the gaseous hydrocarbons from the steam recombination feed. Passing at least a portion of the separated hydrogen depleted stream with an oxidant to produce a heated stream, and providing at least a portion of the heat from the heated stream to the anode exhaust and/or to the hydrocarbon comprising hydrocarbon flow. The method of claim 1, further comprising: supplying air and carbon dioxide to one of the cathodes of the molten carbonate fuel cell, wherein the air comprises molecular oxygen; and controlling a flow rate of the air and/or carbon dioxide to cause carbon dioxide to the molecule One molar ratio of oxygen is at least 2. The method of claim 1, further comprising: mixing at least a portion of the molecular hydrogen supplied to the molten carbonate anode with the oxidant at one or more anode electrodes of one of the anodes of the molten carbonate fuel cell, and Electricity is generated from the molten carbonate fuel cell at an electrical power density of at least 0.1 W/cm ² .