Power plants – Combustion products used as motive fluid
Reexamination Certificate
2000-11-14
2002-05-28
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
C060S039120, C060S039465
Reexamination Certificate
active
06393821
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the use of low-level fuel gas emissions from natural and man-made sources and more particularly to an apparatus and method for the capture and use of low-level fuel gas emissions to produce electricity or other useful work.
2. Description of Field and Related Art
The following references are relevant to the present application:
Acheson, et al. U.S. Pat. No. 4,202,169, describes a gas turbine system for the recovery of power from fuel gases having a low heating value, i.e., below about 80 Btu/scf, and usually in the range of 35 to 70 Btu/scf, has an external catalytic combustor. The catalytic combustor is divided into a primary and a secondary catalytic combustion chamber with a heat exchanger between the two combustion chambers. In the preheater the low heating value gas mixed with combustion air is passed in indirect heat exchange with products of combustion from the first combustion chamber before the low heating value gas is delivered to the first combustion chamber. The turbine system is particularly advantageous in recovering power from low heating value gas in which the combustibles are hydrocarbons, primarily methane.
Ricks, U.S. Pat. No. 4,209,303, describes a method and apparatus is disclosed for recovery of combustible gas formed from combustible refuse or vegetable matter in an enclosed space from which the combustible gas is collected. Water can be injected into the apparatus and the decay process initiated and promoted by activating a heating element projecting upwardly from the base of the apparatus into the material undergoing decomposition. The combustible gas contains a substantial proportion of methane.
Zison, U.S. Pat. No. 4,442,901, describes a method of collecting landfill gas from a landfill comprising providing a porous collector in the landfill having a relatively broad collection zone in the path of migrating landfill gas, controlling the pressure in the collector to induce the landfill gas near the collector to flow into the collector, removing the landfill gas from the collector, and substantially excluding air from the atmosphere from entering the collector when the collector is collecting landfill gas.
Zison , et al. U.S. Pat. No. 4,469,176, describes landfill gas recovery system, the breakthrough danger is minimized, and the system efficiency is improved, by providing pressure-equalizing low-impedance gas paths such as aggregate-filled. symmetry trenches positioned within the landfill and surrounding, at least partially, the primary collection zone. The symmetry trenches may be connected to the system's low-pressure source to serve as secondary collectors. A sensing trench positioned within the landfill along the periphery of the collector's zone of influence can be used to monitor the collector pressure and to automatically maintain it at a safe level. The sensing trench can also serve as a secondary equalizing path in heterogeneous landfills. Hot spots may advantageously be tapped by auxiliary collectors whose pressure level bears a predetermined proportional relationship to the primary collector pressure.
Moilliet, U.S. Pat. No. 4,493,770, describes a method which heat can be recovered by biological generation of heat upon aeration of refuse, such as garbage or sludge, in an aeration vessel by introducing oxygen-containing gas, such as air, in a closed cycle to thereby enrich gas withdrawn from the vessel with the oxygen, typically by reintroduction of gas withdrawn from an upper gas portion of the vessel, after introduction of additional oxygen, for example controlled by a valve into a lower portion of the contents of the aeration chamber. Control can be effected automatically, by a control unit through a valve or manually; automatic control can be effected, for example, by sensing oxygen or carbon dioxide concentration by suitable sensors within the vessel. To permit recovery of methane of high quality in a subsequent decomposition and methane recovery container, material withdrawn from the aeration vessel is degassed in degassing chambers for example by storage for about ½ hour, and venting of emanating gases. Control of valves regulating flow from, and to, the aerating vessel and the degassing chambers permits preheating of freshly introduced refuse by the material withdrawn from the degassing chambers in a counter flow heat exchanger, while preventing possible escape of non-aerated substances from the vessel by isolating the aeration vessel during introduction of new refuse, and emptying only a chamber of said degassing chamber system.
O'Brien et al., U.S. Pat. No. 4,681,612, describes a recycle process for the separation of landfill gas containing a wide variety of impurities into a carbon dioxide product stream and a fuel-grade-pressurized methane product stream, the process providing for the removal of both the impurities and the carbon dioxide in a cryogenic column as a bottom stream, the separation of the methane from the overhead product stream by a membrane process, and, optionally, the removal of impurities from the carbon dioxide bottom stream in a separate purification column, to recover a high-quality, liquid, carbon dioxide stream.
Nobilet et al., U.S. Pat. No. 4,769,149, describes a process for recovery of energy from waste and residues is disclosed. The residues, after sieving, are subjected to bacterial digestion in a methanization reactor and the solid phase of the digestate is then subjected to incineration in a furnace supplying a heat recuperator, the furnace being supplied with complementary combustible by the methane coming from the digester, while the circuit of the fumes downstream of the recuperator is used for heating by at least one secondary circuit, the magma in the course of treatment in the digester and/or the sludge separated from the digestate before recycling thereof towards the digester.
Watson et al., U.S. Pat. No. 5,059,405, describes a process and apparatus for removing the impurities from a gas stream produced from a landfill such that essentially pure carbon dioxide and methane is recovered. After the landfill gas is mechanically dewatered, the gas is filtered of particulate solids and aerosols and purified by removing sulfur compounds using zinc oxide columns, removing halogens using activated alumina columns, removing hydrocarbons using activated charcoal columns, and oxidizing remaining impurities using potassium permanganate impregnated activated alumina columns. Lastly the gas is incinerated in a boiler/incinerator combustion furnace to produce an exit stream containing essentially pure carbon dioxide and air, which is further treated in a conventional carbon dioxide treatment process.
Siwajek, U.S. Pat. No. 5,842,357, describes a process for concentrating and recovering methane and carbon dioxide from landfill gas includes absorption of commonly occurring pollutants using a reduced amount of carbon dioxide absorbent which itself may be an in situ derived and recoverable constituent. Separated methane may be concentrated into a high heating value fuel, and a highly pure food-grade carbon dioxide product may also be recovered. Process streams may be used to provide fuel for compression and refrigeration and/or to regenerate carbon dioxide absorbent.
In addition to the above prior art references we know that methane emissions, from many sources, such as cattle, landfills, marshes, swamps and from coal, natural gas and petroleum exploration and production seeps into the atmosphere in very low concentrations. The U.S. EPA estimates the aggregate amount of human-related sources of such methane emissions are 70 percent of the total and are over 30 million tons of methane emitted annually in the U.S., causing global warming and other environmental problems. About 19% of the methane emitted due to human activities comes directly from farm animals, 20 percent from oil and natural gas operations, 36% from landfills, 10 percent from coal mines, 9 percent from animal manure and the rest from other
Gartenberg Ehud
Gene Scott-Patent Law & Venture Group
Thorpe Timothy S.
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