Oxygen-fueled combined cycle power plant

Abstract

The Company provides an oxy-fuel combined cycle power plant. An oxy-combustion combined cycle power plant includes a gas turbine engine configured to combust natural gas and pure oxygen to generate electricity and configured to exhaust therefrom an exhaust gas consisting essentially of carbon dioxide and water. A heat recovery system for the power plant includes a fluid path, the fluid path being a closed loop, having a working fluid flowing therethrough, the working fluid being carbon dioxide. A first heat exchanger is coupled along the fluid path, and a turbine is coupled along the fluid path downstream from the first heat exchanger. The first heat exchanger is configured to transfer heat from the exhaust gas to the working fluid, and the turbine is configured to generate electricity using the heated working fluid received from the first heat exchanger.

Description

[Technical Field]

[0001] The present disclosure relates generally to oxy-combustion combined cycle power plants, and more particularly to oxy-combustion combined cycle power plants having integrated closed loop carbon dioxide cycles with oxy-combustion to produce zero or near-zero emissions. [Background technology]

[0002] For example, gas turbine combustion engines can generate electricity by burning fuels such as gasoline, natural gas, biogas, vegetable oil, and diesel fuel. The burned fuel drives a turbine cycle, which is connected to a generator to utilize the electricity generated by the turbine cycle. However, burning fuel produces exhaust gases that are released into the atmosphere, and controlling these emissions is a costly and difficult process. Such combustion operations generate waste heat, which can be used to generate additional power, such as in the bottoming steam Rankine cycle. A Rankine cycle typically includes a turbogenerator, an evaporator / boiler, a condenser, and a liquid pump. However, water-based steam Rankine cycles require bulky and complex equipment and may only be effective under certain conditions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Patent Application Publication No. WO2019 / 002956 Summary of the Invention

[0004] One embodiment is an oxy-fuel combined cycle power plant. The oxy-fuel combined cycle power plant includes a gas turbine engine configured to combust natural gas and pure oxygen to generate electricity and configured to emit exhaust gases therefrom consisting essentially of carbon dioxide and water. A heat recovery system for the power plant includes a closed-loop fluid path having a working fluid flow therethrough, the working fluid being carbon dioxide. A first heat exchanger is coupled along the fluid path, and a turbine is coupled along the fluid path downstream from the first heat exchanger. The first heat exchanger is configured to transfer heat from the exhaust gases to the working fluid, and the turbine is configured to generate electricity using the heated working fluid received from the first heat exchanger.

[0005] Another aspect is an oxy-fuel-fired combined cycle power plant. The oxy-fuel-fired combined cycle power plant includes a gas turbine engine configured to generate electricity by combusting fuel and oxygen and configured to emit exhaust gases containing carbon dioxide therefrom. A heat recovery system of the power plant includes a closed-loop fluid path through which a working fluid, the working fluid being carbon dioxide, flows. A first heat exchanger is coupled along the fluid path, and a turbine is coupled along the fluid path downstream from the first heat exchanger. The first heat exchanger is configured to transfer heat from the exhaust gas to the working fluid, and the turbine is configured to generate electricity using the heated working fluid received from the first heat exchanger.

[0006] Yet another aspect is a zero-emission oxy-fuel combined cycle power plant. The oxy-fuel combined cycle power plant includes a gas turbine engine configured to generate electricity by combusting natural gas and pure oxygen and configured to emit exhaust gas consisting essentially of carbon dioxide and water therefrom. A heat recovery system of the power plant includes a closed-loop fluid path through which a working fluid, the working fluid being carbon dioxide, flows. A first heat exchanger is coupled along the fluid path, and a turbine is coupled downstream from the first heat exchanger along the fluid path. The first heat exchanger is configured to transfer heat from the exhaust gas to the working fluid, and the turbine is configured to generate power using the heated working fluid received from the first heat exchanger. A recycle path extends between an outlet and an inlet of the gas turbine engine, and the recycle path channels at least a first portion of the exhaust gas from the outlet toward the inlet. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of an exemplary oxy-combustion combined cycle power plant. [Figure 2] 1 is a schematic diagram of an alternative oxy-combustion combined cycle power plant. DETAILED DESCRIPTION OF THE INVENTION

[0008] Embodiments described herein relate to an oxy-fuel combined cycle power plant with integrated closed-loop carbon dioxide cycles for generating zero or near-zero emissions. The closed-loop cycles include a closed oxy-fuel combustion gas turbine cycle and a supercritical carbon dioxide (SCO2) cycle. The closed oxy-fuel combustion gas turbine cycle burns natural gas or a mixture of natural gas and hydrogen using pure oxygen instead of air as the oxidant. The only combustion products are carbon dioxide and water. Most of the water is condensed in an exhaust gas condenser (FGC), leaving the carbon dioxide-rich exhaust gas. Most of the carbon dioxide-rich exhaust gas is recirculated to the compressor of the combustion gas turbine cycle. Meanwhile, the SCO2 cycle receives waste heat from the exhaust gas to heat the working fluid within the SCO2 cycle. In some embodiments, a recuperator can be used to utilize the heat remaining in the exhaust gas before the water condenses in the FGC. The power plant therefore achieves zero emissions while maintaining high gas turbine performance. Moreover, the power plant has a compact design compared to other gas turbine cycles with carbon capture and water heat recovery.

[0009] Unless otherwise indicated, approximation terms such as "generally," "substantially," and "about" used herein indicate that the modified term may apply only to an approximate degree, as recognized by one of ordinary skill in the art, rather than to an absolute or complete degree. Thus, values ​​modified by terms such as "about," "approximately," and "substantially" are not limited to the exact value specified. In at least some instances, approximation may correspond to the precision of an instrument for measuring the value. Furthermore, unless otherwise indicated, terms such as "first," "second," and the like are used herein merely as labels and are not intended to impose any hierarchical, positional, or other requirements on the items referred to by these terms. Furthermore, a reference to, for example, a "second" item does not require or exclude the presence of, for example, a "first" or lower-numbered item, or a "third" or higher-numbered item.

[0010] 1 is a schematic diagram of an exemplary oxy-fuel combined cycle power plant 100. The oxy-fuel combined cycle power plant 100 includes an air separation unit 102 and an oxygen compressor 104. The air separation unit 102 receives air 106, separates oxygen from the air 106, and provides pure oxygen 108 to the oxygen compressor 104. The oxygen compressor 104 compresses the pure oxygen 108 and provides compressed oxygen 110 as an oxidant to a gas turbine engine 112. By-products of the air separation, such as nitrogen, can be used for storage and / or other uses. As used herein, "pure oxygen" refers to a product stream having an oxygen content of at least 90%, at least 95%, or at least 99% by weight of the product stream.

[0011] The gas turbine engine 112 includes a compressor section 114, a combustor section 116, and a turbine section 118. The combustor section 116 receives fuel 120 and compressed oxygen 110 for combustion purposes. The fuel 120 may be any hydrocarbon fuel that enables the gas turbine engine 112 to function as described herein. Non-limiting examples of fuels include heavy hydrocarbons, natural gas, methane, and ethanol. In one embodiment, the fuel 120 is natural gas (i.e., primarily methane (CH4)), and the reaction products of the fuel 120 and oxygen 110 (O2) are carbon dioxide, water, and trace amounts of carbon monoxide and oxygen in the form of exhaust gas 122 exhausted from an outlet 124 of the turbine section 118. Thus, the exhaust gas 122 is substantially free of nitrogen oxides and / or other potentially harmful gases resulting from the combustion of the fuel and air.

[0012] In some embodiments, an inert gas injection unit 126 is coupled in flow communication with the combustor section 116. The inert gas injection unit 126 selectively supplies an inert gas 128 to the combustor section 116 for use in combustion with the fuel 120 and oxygen 110. For example, helium, neon, argon, xenon, or any other suitable inert gas may be added to the air-fuel mixture in the combustor section 116 as desired and / or needed to adjust operating parameters (e.g., sound speed) of the combustion operation.

[0013] As described above, the turbine section 118 combusts the fuel 120 and oxygen 110 to produce exhaust gases 122. Combustion of the fuel 120 and oxygen 110 drives the turbine section 118, which is coupled to a generator 130 for storing the power generated by the gas turbine engine 112. The exhaust gases 122 exit at a high temperature, and the waste heat can be used to generate additional power, as described in more detail below.

[0014] In the illustrated embodiment, a condenser 132 is positioned downstream of the turbine section 118 and receives the exhaust gas 122. The condenser 132 receives a cooling liquid 134 circulated therein for interaction with the exhaust gas 122. An exemplary cooling liquid includes, but is not limited to, water. The cooling liquid circulated within the condenser 132 cools the exhaust gas 122 to a temperature below its saturation temperature with respect to water vapor, thus causing condensation of at least a portion of the water vapor content. Thus, condensed water 136 and purified carbon dioxide 138 are separated from the exhaust gas 122, after which each component may exit the condenser 132 in its own stream.

[0015] The carbon dioxide 138 discharged from the condenser 132 is channeled along a recycle path 140 extending from the condenser 132 to the gas turbine section 118. More specifically, the carbon dioxide 138 is channeled from the condenser 132 to an inlet 142 of the compressor section 114 for use as a working fluid in the gas turbine engine 112. The carbon dioxide 138 facilitates temperature regulation of the combustor section 116 and, when combined with an inert gas, provides a mixed fluid that simulates the properties of air in a conventional air-fuel combustion gas turbine. In some embodiments, a portion 144 of the carbon dioxide 138 is withdrawn from the recycle path 140 to be compressed and / or stored for further use. A capture system may be located downstream of and in flow communication with the portion 144 of the carbon dioxide 138. The capture system may be used to capture the inert gas contained therein and recycle it to the gas turbine engine 112.

[0016] The oxy-fuel-fired combined cycle power plant 100 also includes a waste heat recovery system 146 thermally coupled to the gas turbine engine 112. For example, the waste heat recovery system 146 includes a heat exchanger 148, a turbine expander 150, a heater 152, and a pump 154 ​​all coupled along a closed-loop fluid path 156 that channels a working fluid 158 therethrough. In one example, the working fluid 158 is carbon dioxide, and the waste heat recovery system 146 is operable to heat the carbon dioxide to a supercritical level before entering the turbine expander 150.

[0017] For example, a heat exchanger 148 is thermally coupled along both the recycle path 140 and the fluid path 156 to facilitate heat transfer between the exhaust gas 122 and the working fluid 158. The working fluid 158 exits the heat exchanger 148 in a supercritical state and is then channeled toward the turbine expander 150. The working fluid 158 drives the turbine expander 150 and is coupled to a generator 160 for storing electrical power generated by the turbine expander 150. The electrical power from the generator 160 can be used to provide electrical power to operate exemplary parasitic loads of the oxygen-fueled gas turbine cycle, such as electrical power from the air separation unit 102, the oxygen compressor 104, and / or the compressor section 114.

[0018] The working fluid 158 discharged from the turbine expander 150 is passed through a heater 152 and a pump 154 ​​before being recirculated through the heat exchanger 148. As described above, the fluid path 156 is a closed loop such that the working fluid 158 is continuously recirculated therein without being discharged to the ambient environment. Similarly, the recirculation path 140 is generally a closed loop such that no components of the exhaust gas 122 are discharged to the ambient environment, but rather are adapted for use in other applications or stored. Thus, the oxy-fuel combined cycle power plant 100 is capable of generating electricity without discharging potentially harmful emissions, such as nitrogen oxides, into the ambient environment.

[0019] 2 is a schematic diagram of an alternative oxy-fuel-fired combined cycle power plant 162. In the illustrated embodiment, the oxy-fuel-fired combined cycle power plant 162 includes a heat exchanger 164 coupled along the recycle path 140 and a bleed path 166 extending from the compressor section 114 to the combustor section 116 of the gas turbine engine 112. As shown, the heat exchanger 164 is disposed along the recycle path 140 between the heat exchanger 148 and the condenser 132. As such, the heat exchanger 164 receives the exhaust gas 122 that has been cooled by heat transfer occurring between the exhaust gas 122 and the working fluid 158 in the heat exchanger 148. The heat exchanger 164 facilitates heat transfer between the exhaust gas 122 and a compressor bleed fluid 168 extracted from the compressor section 114 and channeled into the bleed path 166. Therefore, the remaining waste heat to be recovered from the exhaust gas 122 may be transferred to the compressor bleed fluid 168, which is then flowed towards the combustor section 116. In this way, the thermal efficiency of the oxy-fuel-fired combined cycle power plant 100 is improved.

[0020] The embodiments described herein relate to the integration of two closed-loop carbon dioxide cycles: a closed direct oxy-fuel combustion gas turbine cycle and a supercritical carbon dioxide waste heat recovery cycle. The integration of these two cycles provides high-performance power generation while substantially eliminating harmful gas emissions typically associated with other types of combustion operations. Additional benefits include the production of useful by-products such as nitrogen, water, and carbon dioxide, and a more compact design than other gas turbine cycles with carbon capture or waste heat recovery. Thus, the power plant achieves zero emissions while maintaining high gas turbine performance.

[0021] The foregoing description is intended to be illustrative only, and those skilled in the art will recognize that modifications can be made to the described embodiments without departing from the scope of the invention disclosed. Modifications that fall within the scope of the invention will be apparent to those skilled in the art in light of a review of this disclosure, and such modifications are intended to fall within the scope of the appended claims.

[0022] Exemplary embodiments of oxy-combustion combined cycle power plants using carbon dioxide as the working fluid are described above in detail. The systems and methods described herein are not limited to the specific embodiments described herein; rather, the steps of the methods may be utilized independently and separately from other steps described herein. For example, the methods described herein are not limited to implementation with the industrial gas turbine engines described herein. Rather, the exemplary embodiments may be implemented and utilized in connection with any application where zero-emission power generation is desired.

[0023] Further aspects of the present disclosure are provided by the subject matter of the following clauses. [Embodiment 1] 1. An oxy-fuel combined cycle power plant, comprising: a gas turbine engine configured to combust natural gas and pure oxygen to generate power and configured to emit exhaust gases consisting essentially of carbon dioxide and water; A heat recovery system; Including, The heat recovery system comprises: a closed-loop fluid path through which a working fluid, which is carbon dioxide, flows; a first heat exchanger coupled along the fluid path; a turbine coupled along the fluid path downstream from the first heat exchanger; Including, the first heat exchanger is configured to transfer heat from the exhaust gas to the working fluid; The oxy-fuel combined cycle power plant, wherein the turbine is configured to generate electrical power using the heated working fluid received from the first heat exchanger. [Embodiment 2] 2. The oxy-fuel combined cycle power plant of embodiment 1, further comprising an air separation unit configured to receive air, separate oxygen from the air to produce pure oxygen, and channel the pure oxygen to the gas turbine engine for combustion with natural gas. [Embodiment 3] 2. The oxy-fuel-combustion combined cycle power plant of embodiment 1, further comprising a recycle path extending between an outlet and an inlet of the gas turbine engine, the recycle path channeling at least a portion of the exhaust gas from the outlet toward the inlet. [Embodiment 4] 4. The oxy-fuel-combustion combined cycle power plant of embodiment 3, further comprising a second heat exchanger coupled along the recycle path and a bleed path through which compressor bleed air flows, the first heat exchanger coupled upstream from the second heat exchanger and transferring heat from the compressor bleed air to the exhaust gas. [Embodiment 5] 2. The oxy-fuel combined cycle power plant of embodiment 1, further comprising a condenser coupled downstream of the turbine to receive the exhaust gas, the condenser configured to separate water from the exhaust gas. [Embodiment 6] 2. The oxy-fuel combined cycle power plant of embodiment 1, wherein the first heat exchanger is adapted to heat carbon dioxide in the fluid path to a supercritical level. [Embodiment 7] 2. The oxy-fuel combined cycle power plant of embodiment 1, further comprising an inert gas injection unit configured to supply an inert gas to a gas turbine engine for use in combustion of the natural gas with pure oxygen. [Embodiment 8] 1. An oxy-fuel combined cycle power plant, comprising: a gas turbine engine configured to combust fuel and oxygen to generate power and emit exhaust gases comprising carbon dioxide; A heat recovery system; Including, The heat recovery system comprises: a closed-loop fluid path through which a working fluid, which is carbon dioxide, flows; a first heat exchanger coupled along the fluid path; a turbine coupled downstream from the first heat exchanger along the fluid path; the first heat exchanger is configured to transfer heat from the exhaust gas to the working fluid; The oxy-fuel combined cycle power plant, wherein the turbine is configured to generate electrical power using the heated working fluid received from the first heat exchanger. [Embodiment 9] 9. The oxy-fuel combined cycle power plant of embodiment 8, wherein the gas turbine engine is configured to combust fuel and oxygen to produce exhaust gases that are substantially free of nitrogen oxides. [Embodiment 10] 9. The oxy-fuel combined cycle power plant of embodiment 8, further comprising an air separation unit configured to receive air, separate oxygen from the air to produce pure oxygen, and channel the pure oxygen to a gas turbine engine for combustion with natural gas. [Embodiment 11] 9. The oxy-fuel combined cycle power plant of embodiment 8, further comprising a recycle path extending between an outlet and an inlet of the gas turbine engine, the recycle path channeling at least a portion of the exhaust gas from the outlet toward the inlet. [Embodiment 12] 12. The oxy-fuel-combustion combined cycle power plant of embodiment 11, further comprising a second heat exchanger coupled along the recycle path and a bleed path through which compressor bleed air flows, wherein a first heat exchanger is coupled upstream from the second heat exchanger and configured to transfer heat from the compressor bleed air to the exhaust gas. [Embodiment 13] 9. The oxy-fuel combined cycle power plant of embodiment 8, further comprising a condenser coupled downstream of the turbine to receive the exhaust gas, the condenser configured to separate water from the exhaust gas. [Embodiment 14] 9. The oxy-fuel combined cycle power plant of embodiment 8, wherein the first heat exchanger is adapted to heat carbon dioxide in the fluid path to a supercritical level. [Embodiment 15] 9. The oxy-fuel combined cycle power plant of embodiment 8, further comprising an inert gas injection unit configured to supply an inert gas to a gas turbine engine for use in combustion with the natural gas and pure oxygen. [Embodiment 16] 1. A zero-emission oxy-fuel combined cycle power plant, comprising: a gas turbine engine configured to combust natural gas and pure oxygen to generate power and emit exhaust gases consisting essentially of carbon dioxide and water; A heat recovery system; Including, The heat recovery system comprises: a closed-loop fluid path through which a working fluid, which is carbon dioxide, flows; a first heat exchanger coupled along a fluid path; a turbine coupled along a fluid path downstream from a first heat exchanger, the first heat exchanger configured to transfer heat from the exhaust gases to a working fluid, the turbine configured to generate power using the heated working fluid received from the first heat exchanger; a recycle path extending between an outlet and an inlet of the turbine gas turbine engine, the recycle path flowing at least a first portion of the exhaust gas from the outlet toward the inlet. [Embodiment 17] 17. A zero-emission oxy-combustion combined cycle power plant as recited in embodiment 16, further comprising a storage device configured to receive a second portion of the exhaust gas discharged from the gas turbine engine. [Embodiment 18] 17. A zero-emission oxy-combustion combined cycle power plant as described in embodiment 16, further comprising a recycle path extending between an outlet and an inlet of the gas turbine engine, the recycle path channeling at least a portion of the exhaust gas from the outlet toward the inlet. [Embodiment 19] 20. The zero-emission oxy-combustion combined cycle power plant of claim 18, further comprising a second heat exchanger coupled along the recycle path and a bleed path through which compressor bleed air flows, the first heat exchanger being coupled upstream from the second heat exchanger and configured to transfer heat from the compressor bleed air to the exhaust gas. [Embodiment 20] 17. A zero-emission oxy-combustion combined cycle power plant as described in embodiment 16, wherein the first heat exchanger is adapted to heat carbon dioxide in the fluid path to a supercritical level.

[0024] Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. Moreover, references to "one embodiment" in the above description are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. In accordance with the principles of the invention, any feature of a drawing may be referenced and / or claimed in combination with any feature of any other drawing.

[0025] While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims. [Explanation of symbols]

[0026] 100: Oxygen-fired combined cycle power plant 102: Air separation unit 104: Oxygen compressor 106: Air 108: Pure oxygen 110: Compressed oxygen 112: Gas turbine engine 114: Compressor section 116: Combustor section 118: Turbine section 120: Fuel 122: Exhaust gas 124: Outlet 126: Inert gas injection section 128: Inert gas 130: Generator 132: Condenser 134: Coolant 136: Condensate 138: Carbon dioxide 140: Recycle path 142: Inlet 144: Carbon dioxide fraction 146: Waste heat recovery system 148: Heat exchanger 150: Turbine expander 152: Heater 154: Pump 156: Closed-loop fluid path 158: Working fluid 160: Generator 162: Alternative oxyfuel-fired combined cycle power plant 164: Heat exchanger 166: Bleed path 168: Compressor bleed fluid

Claims

1. 1. An oxy-fuel combined cycle power plant, comprising: a gas turbine engine configured to combust natural gas and pure oxygen to generate power and configured to emit exhaust gases consisting essentially of carbon dioxide and water; A heat recovery system; Including, The heat recovery system comprises: a closed-loop fluid path through which a working fluid, which is carbon dioxide, flows; a first heat exchanger coupled along the fluid path; a turbine coupled along the fluid path downstream from the first heat exchanger; a heater (152) coupled downstream from the turbine along the fluid path; a pump (154) coupled along the fluid path downstream from the heater (152) to supply the working fluid to the first heat exchanger; Including, the first heat exchanger is configured to transfer heat from exhaust gas to the working fluid; The oxy-fuel combined cycle power plant, wherein the turbine is configured to generate electrical power using the heated working fluid received from the first heat exchanger.

2. 10. The oxy-fuel combined cycle power plant of claim 1, further comprising an air separation unit configured to receive air, separate oxygen from the air to produce pure oxygen, and channel the pure oxygen to the gas turbine engine for combustion with natural gas.

3. 2. The oxy-fuel-combustion combined cycle power plant of claim 1, further comprising a recycle path extending between an outlet and an inlet of the gas turbine engine, the recycle path channeling at least a portion of the exhaust gas from the outlet toward the inlet.

4. 4. The oxy-fuel-combustion combined cycle power plant of claim 3, further comprising a second heat exchanger coupled along the recycle path and a bleed path through which compressor bleed air flows, the first heat exchanger coupled upstream from the second heat exchanger to transfer heat from the compressor bleed air to the exhaust gases.

5. 10. The oxy-fuel-combustion combined cycle power plant of claim 1, further comprising a condenser coupled downstream of the turbine to receive the exhaust gas, the condenser configured to separate water from the exhaust gas.

6. The oxy-fuel combined cycle power plant of claim 1 , wherein the first heat exchanger is adapted to heat carbon dioxide in the fluid path to a supercritical level.

7. 2. The oxy-fuel combined cycle power plant of claim 1, further comprising an inert gas injection unit configured to supply inert gas to a gas turbine engine for use in combustion of the natural gas with pure oxygen.

8. 1. An oxy-fuel combined cycle power plant, comprising: a gas turbine engine configured to combust fuel and oxygen to generate power and emit exhaust gases comprising carbon dioxide; A heat recovery system; Including, The heat recovery system comprises: a closed-loop fluid path through which a working fluid, which is carbon dioxide, flows; a first heat exchanger coupled along the fluid path; a turbine coupled along the fluid path downstream from the first heat exchanger; a heater (152) coupled downstream from the turbine along the fluid path; a pump (154) coupled along the fluid path downstream from the heater (152) to supply the working fluid to the first heat exchanger; the first heat exchanger is configured to transfer heat from exhaust gas to the working fluid; The oxy-fuel combined cycle power plant, wherein the turbine is configured to generate electrical power using the heated working fluid received from the first heat exchanger.

9. The oxy-fuel combined cycle power plant of claim 8 , wherein the gas turbine engine is configured to combust fuel and oxygen to produce exhaust gases that are substantially free of nitrogen oxides.

10. 10. The oxy-fuel combined cycle power plant of claim 8, further comprising an air separation unit configured to receive air, separate oxygen from the air to produce pure oxygen, and channel the pure oxygen to the gas turbine engine for combustion with natural gas.

11. 9. The oxy-fuel-combustion combined cycle power plant of claim 8, further comprising a recycle path extending between an outlet and an inlet of the gas turbine engine, the recycle path channeling at least a portion of the exhaust gas from the outlet toward the inlet.

12. 12. The oxy-fuel-fired combined cycle power plant of claim 11, further comprising a second heat exchanger coupled along the recycle path and a bleed path through which compressor bleed air flows, wherein a first heat exchanger is coupled upstream from the second heat exchanger and configured to transfer heat from the compressor bleed air to the exhaust gas.

13. 10. The oxy-fuel-combustion combined cycle power plant of claim 8, further comprising a condenser coupled downstream of the turbine to receive the exhaust gas, the condenser configured to separate water from the exhaust gas.

14. The oxy-fuel combined cycle power plant of claim 8 , wherein the first heat exchanger is adapted to heat carbon dioxide in the fluid path to a supercritical level.

15. 11. The oxy-fuel combined cycle power plant of claim 10, further comprising an inert gas injection unit configured to supply an inert gas to a gas turbine engine for use in combustion with the natural gas and pure oxygen.

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