Chemistry: electrical current producing apparatus – product – and – Having magnetic field feature
Reexamination Certificate
2000-12-15
2003-01-14
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Having magnetic field feature
C429S006000, C429S006000
Reexamination Certificate
active
06506510
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a novel apparatus and process for providing integrated heat and electricity needs for a building or residence using a fuel cell. Hydrogen production for consumption in the fuel cell (i.e. fuel processing) is based on the catalytic cracking of hydrocarbons (e.g. methane), followed by the regeneration of the resulting coked cracking catalyst using either oxygen or steam. The high temperature effluent gas from this regeneration step is useful in residential heating and even cooling applications if sorption cooling is incorporated.
BACKGROUND OF THE INVENTION
Fuel cells are chemical power sources in which electrical power is generated in a chemical reaction. The most common fuel cell is based on the chemical reaction between a reducing agent (e.g. hydrogen) and an oxidizing agent (e.g. oxygen). The consumption of these agents is proportional to the power load demanded from the fuel cell.
A specific, common fuel cell operation therefore comprises passing a hydrogen-rich feed stream, usually generated locally by a fuel processor, to the anode side of the fuel cell while simultaneously passing an oxygen-containing stream (e.g. air) to the cathode side of the fuel cell. The gases that contact both the anode and cathode sides of fuel cell are directed through porous metal plates separated by an electrolyte bath or a solid polymer electrolyte serving as a medium for the passage of ions. The plates have a single electrical connection to each other outside of the electrolyte. The anode plate converts molecular hydrogen to hydrogen ions, which migrate through the electrolyte bath or solid polymer, and electrons, which flow along a wire connected to the cathode plate. On the cathode side, molecular oxygen is cleaved into oxygen atoms that combine with the hydrogen ions and anode electrons to create water and heat. In this process, which is essentially the reverse of electrolysis, electricity can be utilized from the flow of electrons along the anode/cathode circuit, while water and heat are expelled from the electrolyte material as steam. This steam can be utilized either for heating applications and/or for humidifying the gas streams flowing to the fuel cell.
The hydrogen for use in fuel cells is typically produced at a point near the fuel cell, because hydrogen has a low volumetric energy density compared to fuels such as gasoline, making hydrogen costly to transport. A summary of fuel cell technical developments and associated methods of producing hydrogen is provided in “Will Developing Countries Spur Fuel Cell Surge?” by Rajindar Singh (
Chemical Engineering Progress,
March 1999, p. 59-66).
In fuel cells relying on the overall conversion of hydrogen and oxygen to water for electricity generation, polymers with high protonic conductivities (i.e. solid polymer electrolytes) are useful as proton exchange membranes (PEMs). Among the earliest proton exchange membranes were sulfonated, crosslinked polystyrenes. More recently sulfonated fluorocarbon polymers have been considered. Such proton exchange membranes are described in an article entitled, “New Hydrocarbon Proton Exchange Membranes Based on Sulfonated Styrene-Ethylene/Butylene-Styrene Triblock Copolymers”, by G. E. Wnek, J. N. Rider, J. M. Serpico, A. Einset, S. G. Ehrenberg, and L. Raboin presented in the Electrochemical Society Proceedings (1995), Volume 95-23, pages 247 to 251. PEM fuel cells are characterized as operating at relatively low temperatures (e.g. 100° C.), having a high power density, varying output quickly in response to shifts in demand, and being suitable for applications where quick startup is needed.
Because fuel cell operation does not involve the emission of hydrocarbons, sulfur oxides and nitrogen oxides into the environment, the applicability of fuel cells for electric powered vehicles is an attractive area of ongoing development. More immediate commercial uses of fuel cells involve stationary applications such as local electricity generation for business or residential consumption. Currently, most homes receive their electric power from a distribution grid operated by a commercial electric power generating company. This electric potential is created in large scale, capital intensive power plants through, for example, the combustion of coal, oil, or natural gas. Nuclear power is also generated in a centralized facility. While the generating efficiencies of these methods vary, all involve significant efficiency losses associated with power distribution to individual consumers.
Since fuel cells generate electrical power locally, they represent an alternative to current centralized power production and distribution systems. As mentioned, a fuel cell relies on the production of hydrogen from a fuel processor as its fuel source. This production results from the catalytic conversion of a hydrocarbon or alcohol feedstock into a hydrogen-rich product. In terms of this hydrogen generation, the prior art is generally directed to the reforming of hydrocarbons in the presence of steam (i.e. steam reforming). This process is an endothermic chemical reaction that requires a significant amount of heat input to drive the reforming reaction toward the production of hydrogen. Alternatively, the partial oxidation of hydrocarbons is a viable and commonly used means of hydrogen production. Partial oxidation refers to an exothermic reaction requiring the removal of heat for the equilibrium reaction to favor the production of the desired hydrogen-rich fuel. Often, in order to more efficiently balance the heat input requirement for the reforming reaction with the heat removal necessary for the partial oxidation, the two reactions are carried out simultaneously, typically in a catalytic autothermal reforming operation.
In addition to hydrogen generation techniques, the prior art also addresses the use of fuel cells for the integrated production of both electricity and heat. Because of the nature of the hydrogen generation chemistry and the fuel cell operation itself, such co-generation schemes can result in more efficient energy utilization than electricity production alone. Heat that is present in the hydrogen-rich reformate gas (i.e. reformer effluent) after being exposed to typical hydrocarbon reforming temperatures of 300° C. to 650° C. can be advantageously transferred to, for example, a heat distribution medium flowing through a home radiator. After such heat exchange, the cooled reformate is suitable for electricity generation in the fuel cell. Heat produced from the operation of the fuel cell itself, namely the heat of formation of water, may likewise be recovered for heating purposes.
Specific integrated electricity/heat generation flow schemes incorporating fuel cells are provided in prior art disclosures. For example, U.S. Pat. No. 5,335,628 includes a water recirculation loop that provides cooling to a fuel cell as well as heat for a boiler system. The boiler heat may be used, in turn, to provide energy for the reforming reaction that provides hydrogen to the fuel cell. In. addition, U.S. Pat. No. 5,401,589 discloses that heat produced in a fuel cell stack may be used for a reformer or for space heating. Additionally, the exhaust from a burner of a fuel processor can either 1) drive a turbine or generator for increased electrical power output, or 2) provide process or additional space heating. U.S. Pat. No. 5,432,710 discloses a system that includes a fuel cell, a reformer for supplying hydrogen to the fuel cell, a boiler, and a control system for optimizing energy utilization and costs. Finally, U.S. Pat. No. 5,985,474 describes a system of an integrated fuel processor, fuel cell, and furnace for providing heat and electrical power to a building. The flow of fuel to the fuel processor and/or the flow of reformate directly to the furnace may be varied or regulated using a controller, according to the heat and electricity demands of the building.
While these prior art integrated electricity/heat generating fuel cell systems rely on the reforming of hydrocarbons
Dunne Stephen R.
Galperin Leonid B.
Kulprathipanja Santi
Modica Frank S.
Oroskar Anil R.
Chaney Carol
Gooding Arthur E.
Molinaro Frank S.
Scaltrito Donald
Tolomei John G.
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