Patent Publication Number: US-2018038277-A1

Title: Closed-loop gas turbine generator

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to power production, and particularly to a closed-loop gas turbine generator utilizing an oxygen transport reactor. 
     2. Description of the Related Art 
     A typical gas turbine generator makes use of a combustion chamber in communication with a gas turbine. A hydrocarbon fuel (such as propane or the like) is fed into the combustion chamber, along with a stream of air as an oxygen source, where the fuel is combusted, resulting in carbon dioxide, water, nitrogen, excess oxygen and heat. The heated exhaust gases are fed to the gas turbine, for the driving thereof, and the gas turbine may then be connected to an external load for providing power thereto. 
     The carbon dioxide produced by such combustion reactions is a major component of the greenhouse gases that are presently causing global climate change. Although it would be impossible to combust hydrocarbons without the production of carbon dioxide, it would obviously be desirable to be able to minimize the amount of carbon dioxide emitted into the atmosphere during hydrocarbon-based power production. Further, since the air-to-fuel ratio in gas turbines is typically very high, it would be further desirable to be able to make use of the excess oxygen to increase the efficiency of the system, thus further decreasing the carbon dioxide emissions. 
     Thus, a closed-loop gas turbine generator addressing the aforementioned problems is desired. 
     SUMMARY OF THE INVENTION 
     The closed-loop gas turbine generator is a combustion-based gas reactor for producing usable power to drive external loads. The closed-loop gas turbine generator includes a combustion chamber for combusting pre-heated air and fuel input thereto. A first gas turbine is in communication with the combustion chamber and is driven by combustion products produced thereby. The first gas turbine may be connected to an external load for delivering power thereto, either through direct mechanical interconnection for driving a mechanical load, or by driving an electrical generator for producing electrical power. A compressor is also driven by the first gas turbine to compress environmental air into a stream of compressed air. 
     An oxygen transport reactor receives a first gas turbine exhaust output from the first gas turbine. The oxygen transport reactor has a feed side and a permeate side, which are separated from one another by an ion transport membrane. The ion transport membrane is selective to oxygen, only allowing oxygen to pass therethrough. The first gas turbine exhaust output from the first gas turbine is fed into the feed side of the oxygen transport reactor, and the ion transport membrane selectively transports oxygen therefrom to the permeate side. This leaves a syngas in the feed side, which is then extracted and externally transported to the permeate side to react with the oxygen therein. The reaction of the syngas with the oxygen produces carbon dioxide and water. 
     A second gas turbine is in communication with the oxygen transport reactor and is driven by the carbon dioxide and the water produced in the permeate side thereof. The second gas turbine may also be connected to an external load for delivering power thereto. As with the first gas turbine, the second gas turbine may either have a direct mechanical interconnection for driving a mechanical load, or may drive an electrical generator for producing electrical power. 
     A heat exchanger receives the stream of compressed air produced by the compressor, as well as the second gas turbine exhaust output from the second gas turbine. Thermal transfer between the stream of compressed air and the second gas turbine exhaust produces the pre-heated air fed to the combustion chamber. 
     These and other features of the present, invention will become readily apparent upon further review of the following specification and drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The sole drawing FIGURE is a schematic diagram of a closed-loop gas turbine generator according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The closed-loop gas turbine generator  10  is a combustion-based gas reactor for producing usable power to drive external loads. As shown in the sole drawing FIGURE, the closed-loop gas turbine generator  10  includes a combustion chamber (CC)  12  for combusting pre-heated air and fuel input thereto. It should be understood that the combustion chamber  12  may be any suitable type of combustion chamber for combusting a hydrocarbon fuel, as is conventionally known. The products produced by the combustion chamber  12  include a mixture of nitrogen (N 2 ), carbon dioxide (CO 2 ), water (H 2 O) and oxygen (O 2 ) gases. A first gas turbine  14  (labeled T 1  in the sole FIGURE) is in communication with the combustion chamber  12  and is driven by the combustion products produced thereby. The first gas turbine  14  may be connected to an external load for delivering power thereto, either through direct mechanical interconnection for driving a mechanical load (i.e., mechanical work W), or by driving an electrical generator for producing electrical power. A compressor (C)  34  is also driven by the first gas turbine  14  to compress environmental air into a stream of compressed air (CA). 
     An oxygen transport reactor  18  receives a first gas turbine exhaust output from the first gas turbine  14 . Preferably, as shown, a nitrogen separator (NS)  16  removes nitrogen gas from the first gas turbine exhaust output prior to injection thereof into the oxygen transport reactor  18 . Thus, the oxygen transport reactor  18  receives a mixture of carbon dioxide, water and oxygen gases. The removal of nitrogen from the first gas turbine exhaust output assists in the operation of the oxygen transport reactor  18 . As will be described in greater detail below, the oxygen transport reactor  18  includes an ion transport membrane  24  for the permeation of oxygen therethrough. The permeation of oxygen across the membrane  24  depends on the partial pressure difference across the membrane. Removal of the nitrogen from the first gas turbine exhaust aids in producing higher oxygen partial pressure on the feed side of the membrane  24 . 
     The oxygen transport reactor  18  has a feed side  20  and a permeate side  22 , which are separated from one another by the ion transport membrane  24 . The ion transport membrane  24  is selectively permeable to oxygen, only allowing oxygen (O 2 ) to pass therethrough. The first gas turbine exhaust output from the first gas turbine  14  is fed into the feed side  20  of the oxygen transport reactor  18 , and the ion transport membrane  24  selectively transports oxygen (O 2 ) therefrom to the permeate side  22 . The water vapor in the first gas turbine exhaust is split (by the oxygen permeation across the membrane  24 ), resulting in hydrogen gas. Similarly, the carbon dioxide is also split, resulting in carbon monoxide gas. The mixture of carbon monoxide (CO) and hydrogen (H 2 ) gases is a syngas produced in the feed side  20 . 
     The syngas is extracted from the feed side  20  and externally transported to the permeate side  22  to react with the oxygen therein (i.e., the O 2  transported across the ion transport membrane  24 ). The reaction of the syngas with the oxygen produces carbon dioxide (CO 2 ) and water (H 2 O). As shown in the sole FIGURE, a first diffuser  30  is preferably mounted in the feed side  20 , and a second diffuser  32  is preferably mounted in the permeate side  22 . The first diffuser  30  receives the first gas turbine exhaust and outputs the first gas turbine exhaust uniformly within the feed side  20 , thus providing a high degree of oxygen concentration. Similarly, the second diffuser  32  receives the syngas and outputs the syngas uniformly within the permeate side  22  for providing greater stability for the membrane  24 . The reaction of the syngas with the oxygen in the permeate side  22  reduces the partial pressure of oxygen in the permeate side  22 , further enhancing the permeation rate of oxygen across the membrane  24 . Permeation of oxygen across the membrane  24  is also aided by the relatively high temperature of the first turbine exhaust gases, which are fed into the oxygen transport reactor  18 . 
     A second gas turbine  26  (labeled as T 2  in the sole FIGURE) is in communication with the oxygen transport reactor  18  and is driven by carbon dioxide (CO 2 ) and water (H 2 O) produced in the permeate side  22 . The second gas turbine  26  may also be connected to an external load for delivering power thereto. As with the first gas turbine, the second gas turbine  26  may either have a direct mechanical interconnection for driving a mechanical load (i.e., mechanical work W), or may drive an electrical generator for producing electrical power. 
     A heat exchanger (HE)  28  receives the stream of compressed air CA produced by the compressor  34  as well as the second gas turbine exhaust (CO 2  and H 2 O) output from the second gas turbine  26 . Thermal transfer between the stream of compressed air CA and the second gas turbine exhaust produces pre-heated air fed to the combustion chamber  12 , forming the closed loop cycle. The pre-heating of the compressed air CA improves energy conservation by reducing the fuel flow rate into the combustion chamber  12 , thus improving overall system efficiency. The heat exchange results in condensation of the water, which can then be easily separated out, leaving behind only carbon dioxide gas. The remaining carbon dioxide (which may still contain traces of water) may either then be collected for storage or may be re-introduced into the oxygen transport reactor  18  (with the first gas turbine exhaust) for a continued cyclic process. 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.