Power plants – Motive fluid energized by externally applied heat – Process of power production or system operation
Reexamination Certificate
2001-10-12
2002-12-24
Nguyen, Hoang (Department: 3748)
Power plants
Motive fluid energized by externally applied heat
Process of power production or system operation
C060S039010, C060S039182
Reexamination Certificate
active
06497098
ABSTRACT:
BACKGROUND
1. Field of the Invention
The invention relates to a method and to a device for generating hot combustion waste gases, in particular to a gas turbine system having an oxygen separation device that receives a portion of combustion waste gas and feeds oxygen from an oxygen-containing gas to the waste gas which is then fed with a fuel or fuel/steam mixture to a burner for catalytically initiated or stabilized combustion.
2. Background of the Invention
EP 0 882 486 A1 discloses a device of the above-mentioned type provided with a burner whose outlet side is connected to a waste gas line, from which a return line branches off. In this burner, a combustion that generates hot combustion waste gases takes place. These combustion waste gases exit the burner through the waste gas line, whereby one part of the combustion waste gases is branched off via the return line. The device is provided with an oxygen separation device, the first inlet of which is connected to the return line, and the second inlet of which is connected to a gas supply that provides oxygen-containing gas. The oxygen separation device therefore is supplied with branched-off or returned waste gas via its first inlet, and with oxygen-containing gas, for example concentrated ambient air, via its second inlet. The oxygen separation device contains oxygen separation means, for example an ion transport membrane. These oxygen separation means remove oxygen from the oxygen-containing gas and supply it with the branched off waste gas, so that the oxygen content of the oxygen-containing gas is reduced, and oxygen-enriched, branched-off waste gas is generated. The oxygen separation device is provided with a first outlet for the oxygen-enriched, branched-off waste gas as well as a second outlet for the gas that has been reduced with respect to its oxygen content. An inlet side of the burner is connected to the first outlet of the oxygen separation device as well as to a fuel supply that supplies fuel. In this manner, a combustion mixture that burns in the burner while forming the desired hot combustion waste gases is created no later than in the burner. The combustion gases generated in this manner can be used, in particular, in a gas turbine system in order to generate electrical energy.
By using such a device or method, it is possible to reduce noxious emissions during energy generation, in particular to significantly reduce CO
2
emissions during the combustion of fossil fuels.
The core concept of these methods and devices is that pure oxygen is used as an oxidant for the combustion, since this greatly simplifies the waste gas after treatment. The reason for this is that a combustion process with molecular oxygen provides a waste gas that essentially consists only of CO
2
and H
2
O. Since oxygen, which is produced in refrigerated plants, is very expensive, new technologies have been developed for oxygen production. Important factors hereby are oxygen separation devices that are provided with a membrane that is conductive for oxygen ions and electrons, a so-called MCM membrane (mixed conducting membrane). Such an MCM membrane has a retention side on which the oxygen-containing gas is located and a pass-through side on which the gas to be enriched is located. The MCM membrane transports oxygen ions from the retention side to the pass-through side and causes an electron transport from the pass-through side to the retention side. For this purpose, oxygen is removed from the gas on the retention side and is supplied to the gas on the pass-through side. In order to increase the conductivity of such a MCM membrane, it is advantageous to set a relatively high flow speed on the pass-through side in order to keep the oxygen concentration on the pass-through side as low as possible. A high flow speed on the pass-through side results only in a relatively small enrichment of the returned waste gases with oxygen, however, so that this oxygen/waste gas mixture shows only weak reactance and is not suitable for standard combustion methods.
U.S. Pat. No. 5,976,223 discloses a method and a device for producing carbon dioxide and oxygen. Into a first oxygen separation device working with a MCM membrane, compressed, heated, and oxygen-containing gas is introduced on the retention side. On the pass-through side, a gaseous fuel is supplied that reacts with the added oxygen and forms carbon dioxide. The oxygen-containing gas whose oxygen-content has been reduced is heated by the exothermic reaction taking place hereby. The oxygen-containing gas heated in this manner is then fed to a second oxygen separation device working with an MCM membrane on its retention side. The desired oxygen then collects on the pass-through side of this second oxygen separation device.
WO 98/55394 describes a method in which an oxygen separation device working with an MCM membrane is used as a burner in order to produce hot combustion waste gases for a gas turbine system. Hereby ambient air is compressed, heated, and fed to the retention side of this membrane reactor. A mixture of returned waste gas and fuel is fed to the retention side. Then oxygen is removed from the fed-in air in the membrane reactor and is fed into the mixture. On the pass-through side, the fuel then reacts with the oxygen on the membrane surface that is coated with an oxidation catalyzer. The resulting hot waste gases are then fed to a turbine.
WO 98/55208 discloses a further method for the production of hot combustion gases for the operation of a turbine, in which compressed fresh air is heated in a first burner and is fed to the retention side of a oxygen separation device working with an MCM membrane. Returned waste gas is fed together with fuel to a second burner that may be constructed as a catalyzer. The combustion gases generated there are then fed to the pass-through side of the oxygen separation device, where they are enriched with oxygen. The waste gases enriched with oxygen are then fed to a third burner and burned there with fuel in order to generate hot combustion gases that drive a turbine.
SUMMARY OF THE INVENTION
The invention at hand concerns the objective of disclosing for a method or device of the initially mentioned type an embodiment that has a higher efficiency.
According to the invention, this objective can be realized by a method for producing hot combustion waste gas, comprising the steps of producing a hot combustion waste gas by combustion in a burner that is catalytically initiated or stabilized, feeding a first portion of the combustion waste gas to a first inlet of a first oxygen separation device, feeding an oxygen-containing gas to a second inlet of the first oxygen separation device, removing oxygen from the oxygen-containing gas by an oxygen separation means of the first oxygen separation device and reducing an oxygen content of the oxygen-containing gas, feeding said oxygen to the first portion of the combustion waste gas and oxygen enriching an oxygen content of the first portion of the combustion waste gas, and feeding the oxygen-enriched, first portion of the combustion waste gas and a fuel or a fuel/steam mixture to the burner to form a combustion mixture that burns in the burner in the step of producing the hot combustion waste gas. This procedure allows the combustion mixture to react adequately even in the presence of relatively low oxygen concentrations in order to produce the desired hot combustion waste gases.
Since this means that a relatively low oxygen content in the combustion mixture will be sufficient, the flow speed of the returned waste gases can be increased on the pass-through side of an oxygen separation device working with an MCM membrane, increasing its efficiency and thus the efficiency of the entire process.
The objective underlying this invention is also realized with a device for producing a hot combustion waste gas, comprising a burner comprising an outlet side, an inlet side, and a catalyzer that initiates or stabilizes a combustion and a first oxygen separation device comprising a first inlet, a second inlet, a first oxygen s
Carroni Richard
Griffin Timothy A.
Winkler Dieter
Alstom (Switzerland Ltd
Burns Doane Swecker & Mathis L.L.P.
Nguyen Hoang
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