Patent Publication Number: US-2012023954-A1

Title: Power plant and method of operation

Description:
BACKGROUND OF THE INVENTION 
     The subject matter of the present disclosure relates generally to the field of electric power plants, and more particularly to methods of operating stoichiometric exhaust gas recirculation turbine systems. Various types of gas turbine systems are known and in use for electricity generation in power plants. Typically, the gas turbine systems include a turbine compressor for compressing an air flow and a turbine combustor that combines the compressed air with a fuel and ignites the mixture to generate an exhaust gas. The exhaust gas may then be expanded through a turbine, thereby causing the turbine to rotate, which in turn may be connected to a turbine generator via a turbine shaft, for power generation. Gas turbines have traditionally used excess air within the combustion process to control turbine temperatures and manage undesirable emissions. This often results in an exhaust stream with large amounts of excess oxygen. 
     Accordingly, there exists a need for a power plant arrangement that uses a gas turbine system that may operate without an exhaust stream with large amounts of excess oxygen. Furthermore, it would be desirable for the power plant arrangement to provide for the option to further reduce emissions through treatment of exhaust gases and/or to recover streams of carbon dioxide, nitrogen, and water. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, a power plant arrangement is provided. The power plant arrangement includes at least one main air compressor for compressing ambient air into a compressed ambient gas and at least one gas turbine assembly. The gas turbine assembly comprises a turbine combustor, fluidly connected to the at least one main air compressor, for mixing the compressed ambient gas with at least a first portion of a recirculated low oxygen content gas flow and a fuel stream to form a combustible mixture and for burning the combustible mixture and forming the recirculated low oxygen content flow. The gas turbine assembly further comprises a turbine connected to the turbine combustor and to a turbine shaft. The turbine is arranged to be driven by the recirculated low oxygen content gas flow from the turbine combustor. The assembly further comprises a turbine compressor, fluidly connected to the turbine combustor, and connected to the turbine shaft and being arranged to be driven thereby. The assembly also comprises a recirculation loop for recirculating the recirculated low oxygen content gas flow from the turbine to the turbine compressor. Finally, the assembly comprises an integrated inlet bleed heat conduit that fluidly connects the at least one gas turbine assembly to an input of the at least one main air compressor for delivering at least a second portion of the recirculating low oxygen content gas flow from the at least one gas turbine assembly to the input of the at least one main air compressor. 
     In another aspect, a method for operating a power plant is provided. The method includes compressing ambient air with at least one main air compressor to form a compressed ambient gas flow, delivering the compressed ambient gas flow to a turbine combustor of at least one gas turbine assembly, and mixing the compressed ambient gas flow with at least a first portion of a recirculated low oxygen content gas flow and a fuel stream to form a combustible mixture and burning the mixture in the turbine combustor to produce the recirculated low oxygen content gas flow. The method further comprises driving a turbine using the recirculated low oxygen content gas flow, wherein the turbine is connected to a turbine shaft. A turbine compressor, that is fluidly connected to the turbine combustor, is driven by rotation of the turbine shaft. The method also comprises recirculating the recirculated low oxygen content gas flow from the turbine to the turbine compressor using a recirculation loop. Additionally, the method comprises bleeding at least a second portion of the recirculated low oxygen content gas flow from the at least one gas turbine assembly to an input of the at least one main air compressor, using an integrated inlet bleed heat conduit that fluidly connects the at least one gas turbine assembly to the input of the at least one main air compressor. 
     Additional aspects will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the aspects described below. The advantages described below will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, where the components are not necessarily to scale, and in which corresponding reference numerals designate corresponding parts throughout the drawings, wherein: 
         FIG. 1  is a diagrammatical illustration of an exemplary power plant arrangement  10  in accordance with an embodiment of the present invention. 
         FIG. 2  is a diagrammatical illustration of another exemplary power plant arrangement  100  in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, numerous specific details are given to provide a thorough understanding of embodiments. The embodiments can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the embodiments. 
     Reference throughout this specification to “one embodiment,” “an embodiment,” or “embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     Recent requirements in the power generation industry have necessitated the development of a gas turbine arrangement that may be configured to consume substantially all of the oxygen in the air working fluid to produce an essentially oxygen-free exhaust stream. Such an exhaust stream may be more easily suited to emissions reductions using NO x  catalysts. Additionally, such an exhaust stream may be better suited to post combustion carbon capture solutions due to the low oxygen concentrations. Furthermore, a largely oxygen-free exhaust stream may be more easily suited to enhanced oil recovery applications. 
     A substantially oxygen-free exhaust from a gas turbine may be accomplished by stoichiometric burning in the combustion system. That is, the oxygen-containing fresh air supply may be matched to the fuel flow such that the combustion process operates at near combustion stoichiometry. 
     A stoichiometric combustion reaction of methane and oxygen is illustrated below: 
       CH 4 +2O 2 →CO 2 +2H 2 O
 
     Stoichiometric combustion results in gas temperatures that may be too high for the materials and cooling technology employed in gas turbine engines. In order to reduce those high temperatures, a portion of the gas turbine exhaust products may be recirculated back to the combustion system to dilute the combustion temperatures. Ideally, this diluent gas should also be significantly oxygen free so as to not introduce additional oxygen into the system and thereby reduce the advantages of stoichiometric combustion. The gas turbine application using stoichiometric combustion and recirculated exhaust gas is referred to as Stoichiometric Exhaust Gas Recirculation (SEGR). 
     As discussed in detail below, embodiments of the present invention may function to minimize emissions in gas turbine power plant systems by using an SEGR cycle that may enable substantially stoichiometric combustion reactions for power production. The SEGR gas turbine may be configured so as to provide a low oxygen content exhaust. This low oxygen content exhaust may be used with an NO x  reduction catalyst to provide an exhaust stream that may also be free of NO x  contaminants. 
     In some embodiments, an integrated inlet bleed heat may be used to, without being bound to any theory, protect the compressors during start-up and heat the compressor inlets so that a smaller air volume is pulled into the compressors during operation. In some of the specific embodiments, the present technique includes using the SEGR cycle to provide low oxygen content streams of carbon dioxide, nitrogen, and water. 
     Power Plant Arrangements 
     Turning now to the drawings and referring first to  FIG. 1  a power plant arrangement  10  is illustrated. The power plant arrangement  10  includes a main air compressor  12  for compressing ambient air into at least a first portion of a compressed ambient gas flow  26 . The at least a first portion of the compressed ambient gas flow  26  may be vented to the atmosphere via a variable bleed valve  14 . Further, the power plant arrangement  10  includes a turbine combustor  32  that is fluidly connected to the main air compressor  12 . The turbine combustor  32  is configured to receive the at least a first portion of the compressed ambient gas flow  26  from the main air compressor  12 , at least a first portion of a recirculated low oxygen content gas flow  50  from a turbine compressor  30 , and a fuel stream  28 , to form a combustible mixture and to burn the combustible mixture to generate the recirculated low oxygen content gas flow  50 . The flow of the at least a first portion of the compressed ambient gas flow  26  may be regulated by an air flow valve  25 . The flow of the fuel stream  28  may be regulated by a fuel stream valve  27 . 
     In addition, the power plant arrangement  10  includes a turbine  34  located downstream of the turbine combustor  32 . The turbine  34  is configured to expand the recirculated low oxygen content gas flow  50  and may drive an external load such as a turbine generator  20  via a turbine shaft  22  to generate electricity. In the illustrated embodiment  10 , the main air compressor  12  and the turbine compressor  30  are driven by the power generated by the turbine  34  via the turbine shaft  22 . 
     As illustrated in  FIG. 1 , in some embodiments, the turbine shaft  22  may be a “cold-end drive” configuration, meaning the turbine shaft  22  may connect to the turbine generator  20  at the compressor end of the turbine assembly. In other embodiments, the turbine shaft  22  may be a “hot-end drive” configuration, meaning the turbine shaft  22  may connect to the turbine generator  20  at the turbine end of the turbine assembly. 
     As used herein, the term “recirculated low oxygen content gas flow” refers to the gas flow generated by the burning of the combustible mixture in the turbine combustor  32  and flowing through a recirculation loop  52 . In some embodiments, the term “low oxygen content” refers to an oxygen content of below about 5 vol %, below about 2 vol %, or below about 1 vol %. 
     As used herein, the term “gas turbine assembly” refers to all listed components of the power plant arrangements except for the main air compressor  12 . In embodiments comprising multiple main air compressors, the term “gas turbine assembly” refers to all listed components of the power plant arrangements except for the multiple main air compressors. 
     In some embodiments, the recirculated low oxygen content gas flow  50  may be directed from the turbine  34  through the recirculation loop  52  to a heat recovery steam generator  36  for the generation of steam. A steam turbine may be configured to generate additional electricity using the steam from the heat recovery steam generator  36 , and the steam turbine may be connected to a steam generator. In some embodiments, the steam turbine may be arranged to be connected to the turbine shaft  22 . The recirculated low oxygen content gas flow  50  may then be directed back into the recirculation loop  52  to a recirculated gas flow cooler  40 . In still other embodiments, the recirculation loop  52  may not contain a heat recovery steam generator  36  and the recirculated low oxygen content gas flow  50  may instead be introduced directly into the recirculated gas flow cooler  40  upon exit from the turbine  34 . In other embodiments, the recirculation loop  52  may not comprise the recirculated gas flow cooler  40 . 
     The recirculated gas flow cooler  40  may be incorporated into the recirculation loop  52  anywhere downstream from the turbine  34 . The recirculated gas flow cooler  40  may be configured to lower the temperature of the recirculated low oxygen content gas flow  50  to a suitable temperature for downstream delivery into the turbine compressor  30  via the recirculation loop  52 . In some embodiments, a suitable temperature may be below about 66° C., below about 49° C., or below about 45° C. 
     In some embodiments, the power plant arrangement  10  may include an integrated inlet bleed heat conduit  44  that fluidly connects the gas turbine assembly to an input of the main air compressor  12 . The integrated inlet bleed heat conduit  44  may be configured to deliver at least a second portion of the recirculated low oxygen content gas flow  50  from the gas turbine assembly to the input of the main air compressor  12 . The flow of the at least a second portion of the recirculated low oxygen content gas flow  50  through the integrated inlet bleed heat conduit  44  may be regulated by an adjustable integrated inlet bleed heat valve  43 . 
     As depicted in  FIG. 1 , the integrated inlet bleed heat conduit  44  may fluidly connect an output of the turbine compressor  30  to the input of the main air compressor  12 . Turning now to  FIG. 2 , in another embodiment the integrated inlet bleed heat conduit  44  may fluidly connect at least one point in the recirculation loop  52  to the input of the main air compressor  12 . In some embodiments, the integrated inlet bleed heat conduit  44  may be connected to the recirculation loop  52  at a point that is upstream of the recirculated gas flow cooler  40 . In other embodiments, the integrated inlet bleed heat conduit  44  may be connected to the recirculation loop  52  at a point that is upstream of the heat recovery steam generator  36 . 
     In some embodiments, the gas turbine assembly may further comprise a secondary flow path  31  that delivers at least a third portion of the recirculated low oxygen content gas flow  50  from the turbine compressor  30  to the turbine  34  as a secondary flow. The secondary flow may be used to cool and to seal the turbine  34 , including individual components of the turbine  34  such as the turbine shroud, the turbine nozzle, the turbine blade tip, the turbine bearing support housing, and the like. After cooling and sealing the turbine  34  and any individual turbine components, the secondary flow may be directed into the recirculation loop  52  near the output of the turbine  34 . 
     In some embodiments, the power plant arrangement  10  may further comprise a turbine bypass conduit  49  that fluidly connects the output of the turbine compressor  30  with the recirculation loop  52 . The turbine bypass conduit  49  may be configured to bypass the turbine combustor  32  with at least a fourth portion of the recirculated low oxygen content gas flow  50  and to deliver a bypass flow of the at least a fourth portion of the recirculated low oxygen content gas flow  50  to the recirculation loop  52  downstream of the turbine  34 . In some embodiments, the bypass flow may be regulated by a turbine bypass valve  47 . 
     In some embodiments, the power plant arrangement  10  may further comprise a recirculated gas flow extraction valve  45  located downstream of the turbine compressor  30  and in fluid connection with the at least a fifth portion of the recirculated low oxygen content gas flow  50  via a turbine compressor output flow  41 . In some embodiments, the recirculated gas flow extraction valve  45  may be fluidly connected to the turbine bypass conduit  49 . In other embodiments, the recirculated gas flow extraction valve  45  may be fluidly connected to the turbine bypass conduit  49  at a point that is either upstream of or downstream from the turbine bypass valve  47 . In some embodiments, the recirculated gas flow extraction valve  45  may be fluidly connected to a gas separation system such as a carbon capture sequestration (CCS) system via an exhaust gas extraction point  48 . In still other embodiments, the gas separation system may produce a stream of concentrated carbon dioxide and concentrated nitrogen, both with a low oxygen content. 
     In some embodiments, a booster compressor  24  may be incorporated downstream of and in fluid connection with the main air compressor  12  and upstream of and in fluid connection with the turbine combustor  32 . The booster compressor  24  may further compress the compressed ambient gas flow  26  before delivery into the turbine combustor  32 . 
     In still other embodiments, a blower  42  may be fluidly connected to the recirculation loop  52  upstream of or downstream from the recirculated gas flow cooler  40 . The blower  42  may be configured to increase the pressure of the recirculated low oxygen content gas flow  50  prior to delivery into the turbine compressor  30  via the recirculation loop  52 . 
     In some embodiments, the main air compressor  12  may further comprise adjustable inlet guide vanes to control the flow of air into the main air compressor  12 . Additionally, the turbine compressor  30  may further comprise adjustable inlet guide vanes to control the flow of air into the turbine compressor  30 . 
     In some embodiments, the power plant arrangement  10  may include a damper door  38  connected to the recirculation loop  52 . The damper door  38  may be opened to vent a portion of the recirculated low oxygen gas content flow  50  to the atmosphere. 
     As used herein, the term “slave” is synonymous with the terms secondary, auxiliary, or additional. In the following embodiments, the term “slave” refers to the second of two gas turbine assemblies, but can also mean any additional gas turbine assemblies operated with a main gas turbine assembly such as is the second gas turbine assembly in the following embodiments. 
     In this embodiment, and as depicted in  FIG. 1 , the above-described gas turbine assembly may be connected to a slave gas turbine assembly via an inter-train conduit  19  that is regulated by an inter-train valve  16 . The main air compressor  12  may compress ambient air into at least a second portion of a compressed ambient gas flow  66  that may be delivered to a slave turbine combustor  72 . The at least a second portion of the compressed ambient gas flow  66  may be vented to the atmosphere via a slave variable bleed valve  18 . 
     The slave turbine combustor  72  may be configured to receive the at least a second portion of the compressed ambient gas flow  66  from the main air compressor  12 , at least a first portion of a slave recirculated low oxygen content gas flow  90  from a slave turbine compressor  70 , and a slave fuel stream  68 , to form a slave combustible mixture and to burn the slave combustible mixture to generate the slave recirculated low oxygen content gas flow  90 . The flow of the at least a second portion of the compressed ambient gas flow  66  may be regulated by a slave air flow valve  65 . The flow of the slave fuel stream  68  may be regulated by a slave fuel stream valve  67 . 
     In addition, a slave turbine  74  may be located downstream of the slave turbine combustor  72 . The slave turbine  74  is configured to expand the slave recirculated low oxygen content gas flow  90  and may drive an external load such as a slave turbine generator  60  via a slave turbine shaft  62  to generate electricity. 
     As illustrated in  FIG. 1 , in some embodiments, the slave turbine shaft  62  may be a “cold-end drive” configuration, meaning the slave turbine shaft  62  may connect to the slave turbine generator  60  at the compressor end of the turbine assembly. In other embodiments, the slave turbine shaft  62  may be a “hot-end drive” configuration, meaning the slave turbine shaft  62  may connect to the slave turbine generator  60  at the turbine end of the turbine assembly. 
     As used herein, the term “slave recirculated low oxygen content gas flow” refers to the gas flow generated by the burning of the slave combustible mixture in the slave turbine combustor  72  and flowing through a slave recirculation loop  92 . In some embodiments, the term “low oxygen content” refers to an oxygen content of below about 5 vol %, below about 2 vol %, or below about 1 vol %. 
     In embodiments, the slave recirculated low oxygen content gas flow  90  may be directed from the slave turbine  74  through the slave recirculation loop  92  to a slave heat recovery steam generator  76  for the generation of steam. A slave steam turbine may be further configured to generate additional electricity using the steam from the slave heat recovery steam generator  76 , and the slave steam turbine may be connected to a slave steam generator. In some embodiments, the slave steam turbine may be arranged to be connected to the slave turbine shaft  62 . The slave recirculated low oxygen content gas flow  90  may then be directed back into the slave recirculation loop  92  to a slave recirculated gas flow cooler  80 . In still other embodiments, the slave recirculation loop  92  may not contain a slave heat recovery steam generator  76  and the slave recirculated low oxygen content gas flow  90  may instead be introduced directly into the slave recirculated gas flow cooler  80  upon exit from the slave turbine  74 . In other embodiments, the slave recirculation loop  92  may not comprise the slave recirculated gas flow cooler  80 . 
     The slave recirculated gas flow cooler  80  may be incorporated into the slave recirculation loop  92  anywhere downstream from the slave turbine  74 . The slave recirculated gas flow cooler  80  may be configured to lower the temperature of the slave recirculated low oxygen content gas flow  90  to a suitable temperature for downstream delivery into the slave turbine compressor  70  via the slave recirculation loop  92 . In some embodiments, a suitable temperature may be below about 66° C., below about 49° C., or below about 45° C. 
     In some embodiments, a slave integrated inlet bleed heat conduit that fluidly connects the slave gas turbine assembly to an input of the main air compressor  12  may be used. The slave integrated inlet bleed heat conduit may be configured to deliver at least a second portion of the slave recirculated low oxygen content gas flow  90  from the gas turbine assembly to the input of the main air compressor  12 . The flow of the at least a second portion of the slave recirculated low oxygen content gas flow  90  through the slave integrated inlet bleed heat conduit may be regulated by a slave adjustable integrated inlet bleed heat valve. 
     The slave integrated inlet bleed heat conduit may fluidly connect an output of the slave turbine compressor  70  to the input of the main air compressor  12 . The slave integrated inlet bleed heat conduit may fluidly connect at least one point in the slave recirculation loop  92  to the input of the main air compressor  12 . In some embodiments, the slave integrated inlet bleed heat conduit may be connected to the slave recirculation loop  92  at a point that is upstream of the slave recirculated gas flow cooler  80 . In other embodiments, the slave integrated inlet bleed heat conduit may be connected to the slave recirculation loop  92  at a point that is upstream of the slave heat recovery steam generator  76 . 
     In some embodiments, the gas turbine assembly further comprises a slave secondary flow path  71  that delivers at least a third portion of the slave recirculated low oxygen content gas flow  90  from the slave turbine compressor  70  to the slave turbine  74  as a slave secondary flow. The slave secondary flow may be used to cool and to seal the slave turbine  74 , including individual components of the slave turbine  74  such as the turbine shroud, the turbine nozzle, the turbine blade tip, the turbine bearing support housing, and the like. After cooling and sealing the slave turbine  74  and any individual turbine components, the slave secondary flow may be directed into the slave recirculation loop  92  near the output of the slave turbine  74 . 
     In this embodiment, the power plant arrangement  10  may include a slave turbine bypass conduit  89  that fluidly connects the output of the slave turbine compressor  70  with the slave recirculation loop  92 . The slave turbine bypass conduit  89  may be configured to bypass the slave turbine combustor  72  with at least a fourth portion of the slave recirculated low oxygen content gas flow  90  and to deliver a slave bypass flow of the at least a fourth portion of the slave recirculated low oxygen content gas flow  90  to the slave recirculation loop  92  downstream of the slave turbine  74 . In some embodiments, the slave bypass flow may be regulated by a slave turbine bypass valve  87 . 
     In embodiments, the power plant arrangement  10  may include a slave recirculated gas flow extraction valve  85  located downstream of the slave turbine compressor  70  and in fluid connection with the at least a fifth portion of the slave recirculated low oxygen content gas flow  90  via a slave turbine compressor output flow  81 . In some embodiments, the slave recirculated gas flow extraction valve  85  may be fluidly connected to the slave turbine bypass conduit  89 . In other embodiments, the slave recirculated gas flow extraction valve  85  may be fluidly connected to the slave turbine bypass conduit  89  at a point that is either upstream of or downstream from the slave turbine bypass valve  87 . In some embodiments, the slave recirculated gas flow extraction valve  85  may be fluidly connected to a slave gas separation system such as a slave carbon capture sequestration (CCS) system via a slave exhaust gas extraction point  88 . In still other embodiments, the slave gas separation system may produce a stream of concentrated carbon dioxide and concentrated nitrogen, both with a low oxygen content. 
     In some embodiments, a slave booster compressor  64  may be incorporated downstream of and in fluid connection with the main air compressor  12  and upstream of and in fluid connection with the slave turbine combustor  72 . The slave booster compressor  64  may further compress the at least a second portion of the compressed ambient gas flow  66  before delivery into the slave turbine combustor  72 . 
     In still other embodiments, a slave blower  82  may be fluidly connected to the slave recirculation loop  92  upstream of or downstream from the slave recirculated gas flow cooler  80 . The slave blower  82  may be configured to increase the pressure of the slave recirculated low oxygen content gas flow  90  prior to delivery into the slave turbine compressor  70  via the slave recirculation loop  92 . 
     In some embodiments, the slave turbine compressor  70  may further comprise adjustable inlet guide vanes to control the flow of air into the slave turbine compressor  70 . 
     In some embodiments, the power plant arrangement  10  may include a slave damper door  78  connected to the slave recirculation loop  92 . The slave damper door  78  may be opened to vent a portion of the slave recirculated low oxygen gas content flow  90  to the atmosphere. 
     In some embodiments, the power plant arrangement comprises one gas turbine assembly. In other embodiments, the power plant arrangement comprises two or more gas turbine assemblies that are fluidly connected by the inter-train conduit  19 . As used herein, the term “inter-train conduit” may refer to any fluid connection between two or more gas turbine assemblies and one or more main air compressors. In still other embodiments, the power plant arrangement comprises three or more gas turbine assemblies and one or more additional main air compressors, wherein the additional main air compressors are in fluid connection with each other and with the gas turbine assemblies. In yet other embodiments, the power plant arrangement is configured for substantially stoichiometric combustion. In still other embodiments, the power plant arrangement is configured for substantially zero emissions power production. 
     In some embodiments, the fuel stream  28  and/or the slave fuel stream  68  comprises an organic gas, including but not limited to methane, propane, and/or butane. In still other embodiments, the fuel stream  28  and/or the slave fuel stream  68  comprises an organic liquid, including but not limited to methanol and/or ethanol. In yet other embodiments, the fuel stream  28  and/or the slave fuel stream  68  comprises a fuel source obtained from a solid carbonaceous material such as coal. 
     Method of Operation 
     In one embodiment, a method for operating a power plant arrangement  10  is provided, wherein ambient air is compressed using a main air compressor  12  to form a compressed ambient gas flow  26 . At least a first portion of the compressed ambient gas flow  26  may be delivered to a gas turbine assembly. The at least a first portion of the compressed ambient gas flow  26  may be delivered directly to a turbine combustor  32 . The at least a first portion of the compressed ambient gas flow  26  may then be mixed with at least a first portion of a recirculated low oxygen content gas flow  50  and a fuel stream  28  to form a combustible mixture. The combustible mixture may be burned in the turbine combustor  32  to produce the recirculated low oxygen content gas flow  50 . 
     In this embodiment, a turbine  34  may be driven using the recirculated low oxygen content gas flow  50 , thereby causing the turbine  34  to rotate. As used herein, the term “driven using the recirculated low oxygen content gas flow” means the recirculated low oxygen content gas flow  50  expands upon exit from the turbine combustor  32  and upon entrance into the turbine  34 , thereby causing the turbine  34  to rotate. 
     In this embodiment, rotation of the turbine  34  may cause the turbine shaft  22  and also the turbine compressor  30  to rotate. The turbine shaft  22  may rotate in the turbine generator  20 , such that rotation of the turbine shaft  22  may cause the turbine generator  20  to generate electricity. In this embodiment, the turbine compressor  30  may be fluidly connected to the turbine combustor  32  such that the turbine compressor  30  may compress and deliver the recirculated low oxygen content gas flow  50  to the turbine combustor  32 . 
     As illustrated in  FIG. 1 , in some embodiments, the turbine shaft  22  may be a “cold-end drive” configuration, meaning the turbine shaft  22  may connect to the turbine generator  20  at the compressor end of the turbine assembly. In other embodiments, the turbine shaft  22  may be a “hot-end drive” configuration, meaning the turbine shaft  22  may connect to the turbine generator  20  at the turbine end of the turbine assembly. 
     In this embodiment, the recirculated low oxygen content gas flow  50  may be directed from the turbine  34  through the recirculation loop  52  to a heat recovery steam generator  36  for the generation of steam. A steam turbine may be configured to generate additional electricity using the steam from the heat recovery steam generator  36 , and the steam turbine may be connected to a steam generator. In some embodiments, the steam turbine may be arranged to be connected to the turbine shaft  22 . The recirculated low oxygen content gas flow  50  may then be directed back into the recirculation loop  52  to a recirculated gas flow cooler  40 . In still other embodiments, the recirculation loop  52  may not contain a heat recovery steam generator  36  and the recirculated low oxygen content gas flow  50  may instead be introduced directly into the recirculated gas flow cooler  40  upon exit from the turbine  34 . In other embodiments, the recirculation loop  52  may not comprise the recirculated gas flow cooler  40 . 
     The recirculated gas flow cooler  40  may be incorporated into the recirculation loop  52  anywhere downstream from the turbine  34 . The recirculated gas flow cooler  40  may be configured to lower the temperature of the recirculated low oxygen content gas flow  50  to a suitable temperature for downstream delivery into the turbine compressor  30  via the recirculation loop  52 . In some embodiments, a suitable temperature may be below about 66° C., below about 49° C., or below about 45° C. 
     In this embodiment, at least a second portion of the recirculated low oxygen content gas flow  50  may bleed from the gas turbine assembly to the input of the main air compressor  12 . The bleed flow may be delivered to the main air compressor  12  via an integrated inlet bleed heat conduit  44  that fluidly connects the gas turbine assembly to the input of the main air compressor  12 . The flow of the at least a second portion of the recirculated low oxygen content gas flow  50  through the integrated inlet bleed heat conduit  44  may be regulated by an adjustable integrated inlet bleed heat valve  43 . 
     As depicted in  FIG. 1 , the integrated inlet bleed heat conduit  44  may fluidly connect an output of the turbine compressor  30  to the input of the main air compressor  12 . Turning now to  FIG. 2 , in another embodiment the integrated inlet bleed heat conduit  44  may fluidly connect at least one point in the recirculation loop  52  to the input of the main air compressor  12 . In some embodiments, the integrated inlet bleed heat conduit  44  may be connected to the recirculation loop  52  at a point that is upstream of the recirculated gas flow cooler  40 . In some embodiments, the integrated inlet bleed heat conduit  44  may be connected to the recirculation loop  52  at a point that is upstream of the heat recovery steam generator  36 . 
     In some embodiments, the gas turbine assembly further comprises a secondary flow path  31  that delivers at least a third portion of the recirculated low oxygen content gas flow  50  from the turbine compressor  30  to the turbine  34  as a secondary flow. The secondary flow may be used to cool and seal the turbine  34 , including individual components of the turbine  34  such as the turbine shroud, the turbine nozzle, the turbine blade tip, the turbine bearing support housing, and the like. After cooling and sealing the turbine  34  and any individual turbine components, the secondary flow may be directed into the recirculation loop  52  near the output of the turbine  34 . 
     In some embodiments, the at least a fourth portion of the recirculated low oxygen content gas flow  50  may bypass the turbine combustor  32  using the turbine bypass conduit  49 . The turbine bypass conduit  49  may deliver the bypass flow of the at least a fourth portion of the recirculated low oxygen content gas flow  50  to the recirculation loop  52 . 
     In embodiments, at least a fifth portion of the recirculated low oxygen content gas flow  50  may be extracted from that gas turbine assembly using the recirculated gas flow extraction valve  45  located downstream of the turbine compressor  30  via a turbine compressor output flow  41 . In some embodiments, the recirculated gas flow extraction valve  45  may be fluidly connected to the turbine bypass conduit  49 . In other embodiments, the recirculated gas flow extraction valve may be fluidly connected to the turbine bypass conduit  49  at a point that is either upstream or downstream from the turbine bypass valve  47 . In some embodiments, the recirculated gas flow extraction valve  45  may be fluidly connected to a gas separation system such as a carbon capture sequestration (CCS) system via an exhaust gas extraction point  48 . In still other embodiments, the gas separation system may produce a stream of concentrated carbon dioxide and concentrated nitrogen, both with a low oxygen content. 
     In some embodiments, the at least a first portion of the compressed ambient gas flow  26  may be further compressed by a booster compressor  24 . The booster compressor  24  may be incorporated downstream from and in fluid connection with the main air compressor  12  and upstream of an in fluid connection with the turbine combustor  32 . 
     In another embodiment, a method for operating a power plant arrangement  10  is provided, wherein the slave gas turbine assembly is also operated. At least a second portion of the compressed ambient gas flow  66  may be delivered to a slave gas turbine assembly. The at least a second portion of the compressed ambient gas flow  66  may be delivered directly to a slave turbine combustor  72 . The at least a second portion of the compressed ambient gas flow  66  may then be mixed with at least a first portion of a slave recirculated low oxygen content gas flow  90  and a slave fuel stream  68  to form a slave combustible mixture. The slave combustible mixture may be burned in the slave turbine combustor  72  to produce the slave recirculated low oxygen content gas flow  90 . 
     In this embodiment, a slave turbine  74  may be driven using the slave recirculated low oxygen content gas flow  90 , thereby causing the slave turbine  74  to rotate. As used herein, the term “driven using the slave recirculated low oxygen content gas flow” means the slave recirculated low oxygen content gas flow  90  expands upon exit from the slave turbine combustor  72  and upon entrance into the slave turbine  74 , thereby causing the slave turbine  74  to rotate. 
     In this embodiment, rotation of the slave turbine  74  may cause the slave turbine shaft  62  and also the slave turbine compressor  70  to rotate. The slave turbine shaft  62  may rotate in the slave turbine generator  60 , such that rotation of the slave turbine shaft  62  may cause the slave turbine generator  60  to generate electricity. In this embodiment, the slave turbine compressor  70  may be fluidly connected to the slave turbine combustor  72  such that the slave turbine compressor  70  may compress and deliver the slave recirculated low oxygen content gas flow  90  to the slave turbine combustor  72 . 
     As illustrated in  FIG. 1 , in some embodiments, the slave turbine shaft  62  may be a “cold-end drive” configuration, meaning the slave turbine shaft  62  may connect to the slave turbine generator  60  at the compressor end of the turbine assembly. In other embodiments, the slave turbine shaft  62  may be a “hot-end drive” configuration, meaning the slave turbine shaft  62  may connect to the slave turbine generator  60  at the turbine end of the turbine assembly. 
     In some embodiments, the slave recirculated low oxygen content gas flow  90  may be directed from the slave turbine  74  through the slave recirculation loop  92  to a slave heat recovery steam generator  76  for the generation of steam. A slave steam turbine may be configured to generate additional electricity using the steam from the slave heat recovery steam generator  76 , and the slave steam turbine may be connected to a slave steam generator. In some embodiments, the slave steam turbine may be arranged to be connected to the slave turbine shaft  62 . The slave recirculated low oxygen content gas flow  90  may then be directed back into the slave recirculation loop  92  to a slave recirculated gas flow cooler  80 . In still other embodiments, the slave recirculation loop  92  may not contain a slave heat recovery steam generator  76  and the slave recirculated low oxygen content gas flow  90  may instead be introduced directly into the slave recirculated gas flow cooler  80  upon exit from the slave turbine  74 . In other embodiments, the slave recirculation loop  92  may not comprise the slave recirculated gas flow cooler  80 . 
     The slave recirculated gas flow cooler  80  may be incorporated into the slave recirculation loop  92  anywhere downstream from the slave turbine  74 . The slave recirculated gas flow cooler  80  may be configured to lower the temperature of the slave recirculated low oxygen content gas flow  90  to a suitable temperature for downstream delivery into the slave turbine compressor  70  via the slave recirculation loop  92 . In some embodiments, a suitable temperature may be below about 66° C., below about 49° C., or below about 45° C. 
     In this embodiment, at least a second portion of the slave recirculated low oxygen content gas flow  90  may bleed from the slave gas turbine assembly to the input of the main air compressor  12 . The slave bleed flow may be delivered to the main air compressor  12  via a slave integrated inlet bleed heat conduit that fluidly connects the slave gas turbine assembly to the input of the main air compressor  12 . The flow of the at least a second portion of the slave recirculated low oxygen content gas flow  90  through the slave integrated inlet bleed heat conduit may be regulated by a slave adjustable integrated inlet bleed heat valve. 
     In some embodiments, the slave integrated inlet bleed heat conduit may fluidly connect an output of the slave turbine compressor  70  to the input of the main air compressor  12 . In another embodiment, the slave integrated inlet bleed heat conduit may fluidly connect at least one point in the slave recirculation loop  92  to the input of the main air compressor  12 . In some embodiments, the slave integrated inlet bleed heat conduit may be connected to the slave recirculation loop  92  at a point that is upstream of the slave recirculated gas flow cooler  80 . In some embodiments, the slave integrated inlet bleed heat conduit may be connected to the slave recirculation loop  92  at a point that is upstream of the slave heat recovery steam generator  76 . 
     In some embodiments, the gas turbine assembly further comprises a slave secondary flow path  71  that delivers at least a third portion of the slave recirculated low oxygen content gas flow  90  from the slave turbine compressor  70  to the slave turbine  74  as a slave secondary flow. The slave secondary flow may be used to cool and seal the slave turbine  74 , including individual components of the slave turbine  74  such as the turbine shroud, the turbine nozzle, the turbine blade tip, the turbine bearing support housing, and the like. After cooling and sealing the slave turbine  74  and any individual turbine components, the slave secondary flow may be directed into the slave recirculation loop  92  near the output of the slave turbine  74 . 
     In some embodiments, at least a fourth portion of the slave recirculated low oxygen content gas flow  90  may bypass the slave turbine combustor  72  using the slave turbine bypass conduit  89 . The slave turbine bypass conduit  89  may deliver the slave bypass flow of the at least a fourth portion of the slave recirculated low oxygen content gas flow  90  to the slave recirculation loop  92 . 
     In some embodiments, at least a fifth portion of the slave recirculated low oxygen content gas flow  90  may be extracted from the slave gas turbine assembly using the slave recirculated gas flow extraction valve  85  located downstream of the slave turbine compressor  70  via a slave turbine compressor output flow  81 . In some embodiments, the slave recirculated gas flow extraction valve  85  may be fluidly connected to the slave turbine bypass conduit  89 . In other embodiments, the slave recirculated gas flow extraction valve may be fluidly connected to the slave turbine bypass conduit  89  at a point that is either upstream of or downstream of the slave turbine bypass valve  87 . In some embodiments, the slave recirculated gas flow extraction valve  85  may be fluidly connected to a slave gas separation system such as a slave carbon capture sequestration (CC S) system via a slave exhaust gas extraction point  88 . In still other embodiments, the slave gas separation system may produce a stream of concentrated carbon dioxide and concentrated nitrogen, both with a low oxygen content. 
     In some embodiments, the at least a second portion of the compressed ambient gas flow  66  may be further compressed by a slave booster compressor  64 . The slave booster compressor  64  may be incorporated downstream of and in fluid connection with the main air compressor  12  and upstream of an in fluid connection with the slave turbine combustor  72 . 
     In some embodiments, the method comprises operating a power plant arrangement that comprises one gas turbine assembly. In other embodiments, the method comprises operating a power plant arrangement that comprises two or more gas turbine assemblies that are fluidly connected by the inter-train conduit  19 . In still other embodiments, the method comprises operating a power plant arrangement that comprises three or more gas turbine assemblies and one or more additional main air compressors, wherein the additional main air compressors are in fluid connection with each other and with the gas turbine assemblies. In yet other embodiments, the method comprises operating a power plant arrangement that is configured for substantially stoichiometric combustion. In still other embodiments, the method comprises operating a power plant arrangement that is configured for substantially zero emissions power production. 
     Other configurations and methods of operation are provided by U.S. Patent Applications including “Power Plant and Method of Operation” to Daniel Snook, Lisa Wichmann, Sam Draper, Noemie Dion Ouellet, and Scott Rittenhouse (filed Aug. 25, 2011), “Power Plant and Method of Operation” to Daniel Snook, Lisa Wichmann, Sam Draper, Noemie Dion Ouellet, and Scott Rittenhouse (filed Aug. 25, 2011), “Power Plant Start-Up Method” to Daniel Snook, Lisa Wichmann, Sam Draper, Noemie Dion Ouellet, and Scott Rittenhouse (filed Aug. 25, 2011), “Power Plant and Control Method” to Daniel Snook, Lisa Wichmann, Sam Draper, and Noemie Dion Ouellet (filed Aug. 25, 2011), “Power Plant and Method of Operation” to Predrag Popovic (filed Aug. 25, 2011), “Power Plant and Method of Operation” to Sam Draper and Kenneth Kohl (filed Aug. 25, 2011), “Power Plant and Method of Operation” to Sam Draper (filed Aug. 25, 2011), “Power Plant and Method of Operation” to Sam Draper (filed Aug. 25, 2011), “Power Plant and Method of Use” to Daniel Snook, Lisa Wichmann, Sam Draper, and Noemie Dion Ouellet (filed Aug. 25, 2011), and “Power Plant and Control Method” to Karl Dean Minto (filed Aug. 25, 2011), the disclosures of which are incorporated by reference herein. 
     It should be apparent that the foregoing relates only to the preferred embodiments of the present invention and that numerous changes and modifications may be made herein without departing from the spirit and the scope of the invention as defined by the following claims and equivalents thereof.