Gas turbine system and method with supersonic carbon dioxide separator

Abstract

The gas turbine system comprises a gas turbine engine and a flue gas exhaust line fluidly coupled to the exhaust side of the gas turbine engine and adapted to deliver flue gas to a flue gas compressor. The delivery side of the flue gas compressor is fluidly coupled to an expansion device, where the compressed flue gas is expanded, changing the carbon dioxide phase from gaseous to liquid and / or solid. Liquid or solid carbon dioxide particles are removed from the flue gas before it is discharged into the atmosphere. In this way, at least partial carbon dioxide capture is achieved. To improve the efficiency of the system, a recirculation line is further provided, connecting the flue gas exhaust line to the intake side and adapted to recirculate a portion of the exhausted flue gas to the intake side of the gas turbine engine.

Description

【Technical Field】 【0001】 The present disclosure relates to improvements in gas turbine engine systems equipped with carbon dioxide capture devices and related methods. 【Background Art】 【0002】 Power generation still largely depends on fossil fuels such as natural gas and oil. A mixture of air and fuel in liquid or gaseous form is ignited in the combustor of a gas turbine engine, and the resulting hot and pressurized combustion gas containing carbon dioxide is expanded in the turbine to generate mechanical power. The mechanical power is partly used to drive the air compressor of the gas turbine engine and partly made available at the output shaft of the turbine to drive loads such as compressors (so-called "mechanical drive applications") or made available by a generator to convert the mechanical power into electrical power (so-called "power generation applications"). 【0003】 Carbon dioxide is a greenhouse gas that has an adverse impact on the environment and is a cause of climate change. Efforts have been made to remove carbon dioxide from the expanded combustion gas, i.e., the flue gas, or at least reduce its content before discharging the flue gas into the environment. Several combined carbon capture systems are currently under research. 【0004】 A simple method for capturing carbon dioxide from exhaust flue gases produced by the combustion of fossil fuels is to expand the flue gas in a supersonic expansion nozzle. The rapid temperature drop in the supersonic expansion nozzle liquefies or solidifies the carbon dioxide. Solid or liquid carbon dioxide particles can then be separated from the gaseous flue gas flow and released into the environment (Morten Hammer et al: "CO2 capture from off-shore gas turbines using supersonic gas separation", in Energy Procedia 63(2014)243-252; doi:10.1016 / j.egypro.2014.11.026, available online at www.sciencedirect.com). 【0005】 Currently known supersonic separation systems for carbon capture are not entirely satisfactory and are energy-consuming. The power required to operate carbon capture systems reduces the overall energy efficiency of the system and, therefore, diminishes the benefits of carbon capture. 【0006】 Therefore, improvements to gas turbine engines and systems using supersonic separation for carbon capture would be welcome in the field of technology. [Overview of the Initiative] 【0007】 This specification discloses a gas turbine system comprising a gas turbine engine and a flue gas exhaust line fluidly coupled to the exhaust side of the gas turbine engine and adapted to deliver flue gas to a flue gas compressor. The delivery side of the flue gas compressor is fluidly coupled to an expansion unit, where the compressed flue gas is expanded, changing the carbon dioxide phase from gaseous to liquid and / or solid. Liquid or solid carbon dioxide particles separated from the expanding flue gas flow are removed from the flue gas before the flue gas is discharged into the atmosphere. In this way, at least partial carbon dioxide capture is achieved. To improve the efficiency of the system, a recirculation line is further provided and adapted to connect the flue gas exhaust line to the intake side and to recirculate a portion of the exhausted flue gas to the intake side of the gas turbine engine. 【0008】 More specifically, in one embodiment, this specification discloses a gas turbine system comprising a gas turbine engine and a flue gas discharge line that fluidly connects the gas turbine engine to an expansion unit. The expansion unit is adapted to expand the flue gas and thereby separate carbon dioxide from the flue gas flowing through the expansion unit. The system further comprises a flue gas compressor along the flue gas discharge line upstream of the expansion unit to increase the pressure of the flue gas discharged by the gas turbine engine to a pressure adapted for subsequently expanding the flue gas in the expansion unit and separating carbon dioxide from it. The carbon dioxide is separated from the flue gas in the expansion unit after a phase change from gaseous carbon dioxide to liquid or solid carbon dioxide. 【0009】 A carbon dioxide collection line fluidically coupled to the expansion unit is adapted to collect carbon dioxide separated from the flue gas in the expansion unit. Therefore, the flue gas discharged into the atmosphere after carbon dioxide separation is either carbon dioxide-free or a CO2-dilute flue gas with reduced carbon dioxide content. 【0010】 The recirculation line is adapted to connect the flue gas exhaust line to the intake side of the gas turbine engine and recirculate a portion of the exhausted flue gas to the intake side of the gas turbine engine. By recirculating a portion of the flue gas, the percentage of carbon dioxide in the flue gas that is processed through the flue gas compressor and expansion unit increases. This results in more efficient carbon dioxide removal. Compared with current systems in which the flue gas is not recirculated, the configuration disclosed herein has the advantage of (among other things) reducing the size of the flue gas compressor and achieving effective carbon dioxide capture and removal with less energy required to drive the compressor. Furthermore, the higher partial pressure of carbon dioxide in the flue gas expanded in the expansion unit is beneficial and can lead to more efficient solidification or liquefaction of carbon dioxide in the expansion unit. 【0011】 The expansion device may include an expander such that power can be generated by the expansion of flue gas, while carbon dioxide is separated from the flue gas flow through the expansion. The expansion device is combined with a heating device adapted to heat the expansion device to at least partially prevent solidified carbon dioxide from adhering to the inner surface of the supersonic expansion device. 【0012】 In a preferred embodiment, the expansion device comprises a supersonic expansion nozzle rather than an expander. Although no power is recovered from the expansion of the flue gas, the supersonic expansion nozzle is less susceptible to wear caused by solidified carbon dioxide particles. 【0013】 Further features and embodiments of the gas turbine system described herein are described below with reference to the accompanying drawings and are set forth in the accompanying claims. 【0014】 In a further embodiment, a method for generating power from a hydrocarbon-containing fuel and capturing carbon dioxide from flue gas is disclosed herein. A process for generating mechanical power in a gas turbine engine having an intake side and an exhaust side. A process of discharging flue gas from a gas turbine engine in a flue gas discharge line that is fluidly coupled to the exhaust side of a gas turbine engine. A process of recirculating the first portion of flue gas discharged from the flue gas discharge line toward the intake side of the gas turbine engine. A process of compressing a second portion of the discharged flue gas in a flue gas compressor. A process of expanding a compressed portion of flue gas in an expansion device along the flue gas discharge line, and separating carbon dioxide from the flue gas flowing through the expansion device. The process includes heating the expansion device to prevent solidified carbon dioxide from adhering to the inner surface of the expansion device. 【0015】 According to some embodiments, the inflation device comprises an inflator, or preferably a supersonic inflation nozzle. 【0016】 Further features and embodiments of the method described herein are described below with reference to the accompanying drawings and are set forth in the accompanying claims. [Brief explanation of the drawing] 【0017】 Here, we will briefly refer to the attached diagram. [Figure 1] A schematic diagram of the gas turbine system of this disclosure in one embodiment is shown. [Figure 2] A schematic diagram of the gas turbine system of the present disclosure in a further embodiment is shown. [Figure 3] A schematic diagram of the gas turbine system of the present disclosure in a further embodiment is shown. [Figure 4] A schematic diagram of the gas turbine system of this disclosure in a further embodiment is shown. [Figure 5] A schematic diagram of the gas turbine system of this disclosure, in which the expansion device includes an expander, is shown. [Modes for carrying out the invention] 【0018】 In summary, a gas turbine engine system according to the present disclosure includes a flue gas discharge line that collects flue gas exhausted from a power turbine. The flue gas is compressed in a flue gas compressor and expanded in an expansion device such as a supersonic expansion nozzle or a flue gas expander to separate at least a portion of the carbon dioxide contained in the flue gas. An efficiency improvement is achieved by adding a recirculation line through which a portion of the flue gas is recirculated toward the intake side of the gas turbine engine before recompression in the flue gas compressor. The percentage of the amount of carbon dioxide in the combustion gas increases, and thus, the separation of carbon dioxide in the supersonic expansion nozzle is improved. 【0019】 Some improvements to the basic system outlined above, along with the related advantages thereby achieved, are described in more detail below. 【0020】 FIG. 1 shows a first schematic view of a gas turbine engine system 1 according to the present disclosure. The gas turbine engine system 1 includes a gas turbine engine 3 shown only schematically in FIG. 1. 【0021】 In the view of FIG. 1, the gas turbine engine 3 includes an air compressor section 3.1, a combustor 3.2, and a turbine section 3.3. The turbine section 3.3 is drivably coupled to a turbine output shaft 3.4, and useful power generated by the gas turbine engine 3 is available. The output shaft 3.4 can be drivably coupled to a generator or any other load, such as, for example, a gas compressor. In FIG. 1, the output shaft 3.4 is drivably coupled to a generator 5. The latter is electrically coupled, for example, to a power distribution network 7. A shaft 3.5 drivably couples the turbine section 3.3 to the air compressor section 3.1. Reference numeral 3.6 indicates the intake side of the gas turbine engine 3, and reference numeral 3.7 indicates the delivery side of the gas turbine engine 3. 【0022】 In FIG. 1, the gas turbine engine is schematically represented as a single-shaft gas turbine engine, but in other embodiments, the gas turbine engine 3 may include any type of gas turbine, such as an aircraft-derivative gas turbine or a high durability gas turbine having a combination of a variable number of shafts, a pneumatic compressor, and a turbine wheel. 【0023】 Compressed air, or more specifically, a mixture of compressed air and recirculated flue gas, as will be described in more detail below, is delivered from the air compressor 3.1 to the combustor 3.2, fuel is added (fuel line 3.8), and mixed into the compressed air stream. The mixture is ignited, and the hot pressurized combustion gas is delivered from the combustor 3.2 to the turbine section 3.3, where the combustion gas expands and cools. The gas enthalpy drop is converted into mechanical power that is used in part to drive the air compressor section 3.1 via the shaft 3.5 and in part is made available at the output shaft 3.4. 【0024】 The exhaust side 3.7 of the gas turbine engine 3 is fluidly coupled to the flue gas exhaust line 9, and along the flue gas exhaust line, a water removal unit 11 for removing water from the flue gas may be provided. The water removal unit 11 may include one or more devices such as a liquid / gas separator, a molecular sieve, etc. 【0025】 In some embodiments, an exhaust duct 12 may be provided along the exhaust line 9, for example, upstream of the water separator 11, to directly discharge a portion of the flue gas into the atmosphere if necessary. 【0026】 Downstream of the water removal unit 11, a flue gas compressor 13 is disposed, and the dehydrated flue gas is compressed for subsequent expansion in an expansion device. In this embodiment, the expansion device includes a supersonic expansion nozzle (such as a Laval nozzle) schematically shown at 15. The flue gas compressor 13 may be driven by a drive device such as an electric motor 14 that may be electrically coupled to the power distribution network 7. 【0027】 The supersonic expansion nozzle 15 features a supersonic gas separator in which the flue gas is expanded and rapidly cooled so that the carbon dioxide contained within it is liquefied and / or solidified. 【0028】 The supersonic expansion nozzle 15 can be configured as described by Hammer et al. in the paper referenced in the introduction to this disclosure. Swirling vanes may be provided within or upstream of the supersonic expansion nozzle 15 to impart a tangential velocity component to the flue gas, thereby facilitating the separation of carbon dioxide for condensation or solidification. Solid or liquid carbon dioxide particles may accumulate around the intermediate section of the supersonic expansion nozzle 15 and be collected in the carbon dioxide collection line 17. Typically, not all of the carbon dioxide contained in the flue gas is separated from the flue gas, but only a portion is separated, while some of the carbon dioxide may remain in the flue gas released into the environment by the supersonic expansion nozzle 15. Thus, CO2-rich flow is collected in the carbon dioxide collection line 17, while CO2-dilute flue gas is discharged into the atmosphere from the supersonic expansion nozzle 15 21. In this disclosure, the term “CO2-rich flue gas” refers to flue gas containing a higher percentage of carbon dioxide than “CO2-dilute flue gas”. Specifically, CO2-rich flue gas is the flue gas that enters the CO2 supersonic expansion nozzle, i.e., the flue gas before CO2 removal, while CO2-dilute flue gas is the flue gas that exits the supersonic expansion nozzle after at least a portion of the CO2 has been removed from the flue gas. 【0029】 As a non-limiting example, CO2-rich flue gas may contain 5% to 15% by weight of CO2, preferably 8% to 13% by weight of CO2, while CO2-dilute flue gas may contain 0% to 2.5% by weight of CO2. 【0030】 In the embodiment shown in Figure 1, a portion of the flue gas discharged from the gas turbine engine 3 is returned to the intake side 3.6 of the gas turbine engine 3 via the flue gas discharge line 9 and recirculated. The recirculated flue gas is then mixed with fresh air entering the air compressor 3.1 in 3.10. The recirculation line 23 branches off from the flue gas discharge line 9 and returns a portion of the recirculated flue gas to the intake side 3.6 of the gas turbine engine 3. 【0031】 By recirculating a portion of the flue gas before it is compressed in the flue gas compressor 13, the flow rate of the flue gas to be compressed is reduced, increasing the percentage of carbon dioxide contained in the flue gas. The flue gas is then compressed in the flue gas compressor 13 and expanded in the supersonic expansion nozzle 15. Consequently, the efficiency of carbon dioxide separation by supersonic expansion is improved, and the power required for carbon dioxide separation, i.e., the power required to operate the flue gas compressor 13, is reduced. 【0032】 The flue gas discharged from the exhaust side 3.7 of the gas turbine engine 3 contains waste heat at a relatively high temperature, for example, in the range of 700°C. To further improve the separation and capture of carbon dioxide, the flue gas expanded in the supersonic expansion nozzle 15 is at a lower temperature. 【0033】 In some embodiments, as shown in the schematic diagram of Figure 1, at least a portion of the waste heat contained in the flue gas discharged by the gas turbine engine 3 may be removed and used to power a lower thermodynamic circulation schematically shown in 25. The lower thermodynamic circulation 25 may include a steam Rankine circulation, an organic Rankine circulation using an organic working fluid such as cyclopentane or carbon dioxide, or any other thermodynamic circulation using a working fluid suitably selected based on the operating conditions of the system, e.g., the temperature at which heat is discharged from the flue gas and absorbed in the lower thermodynamic circulation. 【0034】 As a mere example, and relating to the diagram in Figure 1, we refer to the steam Rankine circulation 25. The circuit of the lower thermodynamic circulation 25 schematically includes a heat exchanger 27 having a high-temperature side, through which flue gas flows, exchanging heat with the working fluid flowing through the low-temperature side of the heat exchanger 27. The heat transferred from the flue gas to the working fluid of the lower thermodynamic circulation heats and vaporizes the working fluid. The high-temperature vaporized working fluid, e.g., steam, expands in a turbine schematically shown in 29, e.g., a steam turbine, condenses in a condenser 31, and is pumped towards the heat exchanger 27 by a pump 33. 【0035】 The turbine shaft 35 of the steam turbine 29 can be drivably coupled to a load, for example, a generator 37. The latter can be electrically coupled to a power distribution network 7. 【0036】 As described above, the lower thermodynamic circulation 25 may be a steam Rankine cycle, but this is not the only possible option. In some embodiments, an organic Rankine cycle (ORC) is used, and the working fluid may undergo a circulating thermodynamic transformation with or without phase change. For example, the lower thermodynamic circulation may be a supercritical CO2 organic Rankine cycle using supercritical carbon dioxide. 【0037】 The heat exchange directed toward the lower thermodynamic circulation reduces the temperature of the flue gas before compression in the flue gas compressor, and a portion of the waste heat removed from the flue gas is converted into useful mechanical power or electricity, thereby improving the overall energy efficiency of System 1. 【0038】 The flue gas exiting the heat exchanger 27 may still contain waste heat that can be removed to improve carbon capture in the supersonic expansion nozzle 15. 【0039】 In the embodiment shown in Figure 1, a further heat exchanger 41 is included, which is fluidically coupled to the carbon dioxide collection line 17. The carbon dioxide flowing through the carbon dioxide collection line 17 is at a low temperature and can be in liquid phase, solid phase, or a mixture of liquid and solid phases. In the heat exchanger 41, heat can be removed from the flue gas by heat exchange with the carbon dioxide in the carbon dioxide collection line 17. References A and B schematically represent the thermal coupling between the heat exchanger 41 and the carbon dioxide collection line 17. The thermal coupling can be achieved by flowing the flue gas through the high-temperature side of the heat exchanger 41 and the carbon dioxide through the low-temperature side of the heat exchanger 41 directly. In other embodiments, as schematically shown in Figure 1, heat can be indirectly transferred from the heat exchanger 41 to the carbon dioxide flowing through the heat exchanger 42 using an intermediate heat transfer fluid. References A and B represent the heat transfer fluid connection between the heat exchangers 41 and 42. 【0040】 The heat exchanger 41 may be located upstream of the inlet end of the recirculation line 23, as shown in the schematic diagram of Figure 1. In this way, the entire flue gas flow is cooled in the heat exchangers 27 and 41 and then divided into a first flue gas flow that is delivered to the flue gas compressor 13 and the supersonic expansion nozzle 15, and a second flue gas flow that is recirculated through the recirculation line 23. In some embodiments, the heat exchanger 41 may be located downstream of the point where the recirculation line 23 branches off from the flue gas discharge line 9. In this case, an additional heat exchanger is located along the recirculation line 23. 【0041】 In the embodiment shown in Figure 1, the heat exchanger 41 is located upstream of the inlet end of the recirculation line 23, and nevertheless, a further heat exchanger 45 is provided along the recirculation line 23. Thus, in this configuration, a portion of the flue gas recirculated toward the intake side of the gas turbine engine 3 can be cooled in heat exchanger 27, heat exchanger 41, and further cooled in heat exchanger 45. Providing separate heat exchangers 41 and 45 can improve the operating conditions of System 1 by providing additional adjustment possibilities that allow for balanced removal of waste heat from the entire flue gas flow (in heat exchanger 41) and from a partial recirculated flue gas flow (in heat exchanger 45). 【0042】 Similar to heat exchanger 41, heat exchanger 45 may also be thermally coupled to the carbon dioxide collection line 17, for example, via an intermediate heat transfer loop, where C and D are connection points to heat exchanger 42 (or additional heat exchangers along the carbon dioxide collection line 17) and heat exchanger 45. 【0043】 In other embodiments, a heat exchanger 45 may be provided that includes a high-temperature side through which recirculated flue gas flows, and a low-temperature side through which collected carbon dioxide (or a portion thereof) flows after heat exchange with the recirculated flue gas. 【0044】 The carbon dioxide (or more generally, the CO2-rich flow) collected in the carbon dioxide collection line 17 can be stored by any known method or used in industrial processes. 【0045】 In the embodiment shown in Figure 1, carbon dioxide flowing through the carbon dioxide collection line 17 can be further expanded to generate additional useful mechanical power and / or electricity. For this purpose, a carbon dioxide expander 47 is provided, having an inlet side fluidically coupled to the carbon dioxide collection line 17 and adapted to expand carbon dioxide to generate mechanical power, which is made available on the output shaft 49 of the carbon dioxide expander 47. The carbon dioxide expander includes a bladed rotor drivably connected to the output shaft. The expanded carbon dioxide is discharged along the discharge line 50. A generator 51 is drivably coupled to the output shaft 49 of the carbon dioxide expander 47 to convert the mechanical power into electricity, which is delivered to a power distribution network 7 to which the generator 51 is electrically connected. In other embodiments, the output shaft 49 may be drivably coupled to different loads, such as a pump or compressor, or any other rotary-driven machinery. 【0046】 In some embodiments, measures may be taken to prevent solidified carbon dioxide from adhering to the inner surface of the supersonic expansion nozzle 15. For example, components of the supersonic expansion nozzle 15 can be heated for this purpose. 【0047】 In the embodiment shown in Figure 1, waste heat from the flue gas is used to heat the supersonic expansion nozzle 15. To achieve this, a heating device is provided, schematically shown in Figure 1 as a heating coil surrounding the supersonic expansion nozzle 15. The heating device is thermally coupled to a heat exchanger 53 located along the flue gas discharge line 9, which removes heat from the flue gas and transfers it to the supersonic expansion nozzle 15 via the heating device, which includes the heating coil. Heat can be transferred from the heat exchanger 53 to the heating coil in heat exchange with the supersonic expansion nozzle via a circulation loop 55 through which a heat transfer fluid circulates. The heat exchanger 53 can be located at any suitable position along the flue gas discharge line, for example, between a heat exchanger 41 and a water removal unit 11, as shown in Figure 1. In some embodiments, different heat sources, such as electrical resistors, may be provided to heat the supersonic expansion nozzle 15. In some embodiments, if the waste heat available from the flue gas is insufficient, an auxiliary heat source can be used in combination with the circulation loop 55 and the heat exchanger 53 to provide supersonic expansion nozzle heating during the transient phase. 【0048】 Further embodiments of the gas turbine engine system 1 according to this disclosure are shown in Figure 2, with continued reference to Figure 1. The same reference numerals indicate the same components and parts as in Figure 1 and above. These parts will not be described again. 【0049】 The main difference between the embodiment in Figure 1 and the embodiment in Figure 2 concerns how the carbon dioxide collected by the supersonic expansion nozzle 15 is processed. 【0050】 More specifically, in the embodiment shown in Figure 2, a carbon dioxide collection container 61 is provided, which is adapted to collect liquefied or solidified carbon dioxide exiting the supersonic expansion nozzle 15. 【0051】 In the embodiment shown in Figure 2, a separator, such as a cyclone separator 63, is added to the carbon dioxide exhaust end of the supersonic expansion nozzle 15 to separate solid or liquid carbon dioxide particles from the gaseous components, i.e., mainly flue gas, that are moved through the supersonic expansion nozzle. A similar separator can also be provided in the embodiment shown in Figure 1. 【0052】 The carbon dioxide exiting the separator 63 is collected in the container 61, where it can be partially evaporated until it reaches the settle-out pressure (SOP). The thus pressurized carbon dioxide can be further processed, e.g., transported or stored, or fully or partially expanded in a carbon dioxide expander, as shown in Figure 1. 【0053】 Further embodiments of the gas turbine engine system 1 according to this disclosure are shown in Figure 3, with continued reference to Figures 1 and 2. The same reference numerals indicate the same components and parts as in Figures 1 and 2 and described above. These parts will not be described again. 【0054】 The main difference between the embodiments in Figures 1 and 2 and the embodiment in Figure 3 is that an additional heat exchanger 71 is located along the flue gas discharge line 9 between the delivery side of the flue gas compressor 13 and the supersonic expansion nozzle 15. In Figure 3, the additional heat exchanger 71 is shown in the system according to Figure 2, but the same additional heat exchanger 71 can be added to the system according to Figure 1. The additional heat exchanger 71 is intended to remove heat from the compressed flue gas before expansion, thereby achieving a lower temperature through the supersonic expansion nozzle and enabling more efficient carbon dioxide separation. The heat exchanger 71 can be thermally coupled to the carbon dioxide collection line 17 (see connections E, F), thereby cooling the compressed flue gas before expansion by direct or indirect heat exchange with the carbon dioxide separated from the flue gas in the supersonic expansion nozzle 15. 【0055】 Post-compression cooling of the same flue gas can be provided in the system shown in Figure 1. This configuration is shown in Figure 4, and the same parts already described in relation to Figures 1, 2, and 3 are labeled with the same reference numbers and will not be described again. 【0056】 In the embodiments described so far, the compressed flue gas flow from the flue gas compressor 13 is expanded in the supersonic expansion nozzle 15. However, in other embodiments, expansion may be carried out by an expansion device including a flue gas expander. The flue gas expander includes a bladed rotor that converts the pressure energy of the flue gas into mechanical energy, recovering at least a portion of the power required to compress the flue gas and converting that power into usable mechanical power on the shaft of the expander rotor. The flue gas expander may include one or more impellers that are rotationally driven by the expanding flue gas. The flow parameters in the flue gas expander are such that at least a portion of the carbon dioxide contained in the expanding flue gas can be converted from the gas phase to the liquid or solid phase and removed. An embodiment using a flue gas expander instead of a stationary supersonic expansion nozzle is shown in Figure 5. The embodiment in Figure 5 differs from the embodiment in Figure 4 only in terms of the type of expansion device used. The flue gas expander is labeled 16. The generator 18 is driven by the flue gas expander 16 and can convert the mechanical power generated by the expansion of the flue gas into electricity. The remaining components are the same as those shown in Figure 4 and are labeled with the same reference numbers. 【0057】 In other embodiments shown in Figures 1 to 3, a flue gas expander can be used instead of a supersonic expansion nozzle. 【0058】 Exemplary embodiments are disclosed above and shown in the accompanying drawings. Those skilled in the art will understand that various modifications, omissions, and additions may be made to those specifically disclosed herein without departing from the scope of the invention as defined in the following claims.

Claims

[Claim 1] It is a gas turbine system, A gas turbine engine having an intake side and an exhaust side, Fluidly coupled to the exhaust side of the gas turbine engine, An expansion device along the flue gas discharge line, wherein the expansion device is adapted to expand the flue gas and thereby separate carbon dioxide from the flue gas flowing through the expansion device. A flue gas compressor, located along the flue gas discharge line upstream of the expansion device, A carbon dioxide collection line, which is fluidly coupled to the expansion device and adapted to collect carbon dioxide separated from the flue gas in the expansion device, A recirculation line is provided, which connects the flue gas discharge line to the intake side and recirculates a portion of the exhausted flue gas to the intake side of the gas turbine engine, thereby increasing the overall percentage of carbon dioxide collected from the flue gas. A gas turbine system comprising a heating device adapted to heat the aforementioned expansion device. [Claim 2] The gas turbine system according to claim 1, wherein the expansion device comprises a supersonic expansion nozzle. [Claim 3] The gas turbine system according to claim 1 or 2, further comprising a first heat exchanger upstream of the flue gas compressor for removing heat from the flue gas. [Claim 4] The gas turbine system according to claim 3, wherein the first heat exchanger is thermally coupled to a lower thermodynamic circulation, and the thermodynamic circulation is adapted to convert the waste heat removed from the flue gas by the first heat exchanger into mechanical power. [Claim 5] The gas turbine system according to any one of claims 1 to 4, further comprising a second heat exchanger along the flue gas discharge line, which is adapted to cool the flue gas by heat exchange with carbon dioxide in the carbon dioxide collection line. [Claim 6] The gas turbine system according to claim 5, in which at least claim 4 applies, wherein the second heat exchanger is located downstream of the first heat exchanger with respect to the direction of the flow of the flue gas in the flue gas discharge line. [Claim 7] The gas turbine system according to any one of claims 1 to 6, further comprising a third heat exchanger along the recirculation line, adapted to cool the flue gas recirculated by heat exchange with carbon dioxide in the carbon dioxide collection line. [Claim 8] The gas turbine system according to any one of claims 1 to 7, wherein the heating device is in a heat exchange relationship with the flue gas discharge line. [Claim 9] The gas turbine system according to claim 8, wherein the heating device includes a fourth heat exchanger adapted to remove heat from the flue gas discharge line. [Claim 10] The gas turbine system according to any one of claims 1 to 9, further comprising a fifth heat exchanger along the flue gas discharge line between the flue gas compressor and the expansion device, wherein the fifth heat exchanger is adapted to remove heat from the compressed flue gas delivered by the flue gas compressor. [Claim 11] The gas turbine system according to claim 10, wherein the fifth heat exchanger exchanges heat with the carbon dioxide collection line. [Claim 12] The gas turbine system according to any one of claims 1 to 11, further comprising a carbon dioxide expander for expanding carbon dioxide from the expansion device and generating mechanical power at the same time. [Claim 13] A gas turbine system according to any one of claims 1 to 12, comprising a carbon dioxide compression vessel, adapted to receive carbon dioxide from an expansion device, and to compress the carbon dioxide to a settling pressure (SOP) by evaporation in the compression vessel. [Claim 14] A method for generating power from hydrocarbon-containing fuel and capturing carbon dioxide from flue gas, A process for generating mechanical power in a gas turbine engine having an intake side and an exhaust side. A process of discharging flue gas from a gas turbine engine in a flue gas discharge line fluidly coupled to the discharge side of the gas turbine engine, A step of recirculating the first portion of the discharged flue gas from the flue gas discharge line toward the intake side of the gas turbine engine, A step in a flue gas compressor to compress the second portion of the discharged flue gas, A step of expanding the compressed portion of the flue gas in an expansion device along the flue gas discharge line, and separating carbon dioxide from the flue gas flowing through the expansion device. A method comprising the step of heating the expansion device. [Claim 15] The method according to claim 14, wherein the expansion device comprises a supersonic expansion nozzle. [Claim 16] The method according to claim 14 or 15, further comprising the step of removing heat from the flue gas upstream of the flue gas compressor. [Claim 17] The method according to claim 16, wherein the step of removing heat from the flue gas includes a step of delivering the waste heat from the flue gas to a lower thermodynamic circulation, and the lower thermodynamic circulation converts the waste heat into mechanical power. [Claim 18] The method according to claim 16 or 17, wherein the step of removing heat from the flue gas upstream of the flue gas compressor includes a step of cooling the flue gas by heat exchange with carbon dioxide separated from the flue gas in the expansion device. [Claim 19] The method according to any one of claims 14 to 18, further comprising the step of cooling a first portion of flue gas that has been recirculated upstream of the intake side of the gas turbine engine. [Claim 20] The method according to claim 19, wherein the step of cooling the first portion of the recirculated flue gas includes a step of removing heat from the recirculated flue gas by heat exchange with carbon dioxide separated from the flue gas in the expansion device. [Claim 21] The method according to any one of claims 14 to 20, wherein the step of heating the expansion device includes the step of removing waste heat from the flue gas and delivering the removed waste heat to the expansion device. [Claim 22] The method according to any one of claims 14 to 21, further comprising the step of cooling the compressed flue gas downstream of the flue gas compressor. [Claim 23] The method according to claim 22, wherein the step of cooling the compressed flue gas includes a step of cooling the compressed flue gas by heat exchange with carbon dioxide separated from the flue gas in the expansion device. [Claim 24] The method according to any one of claims 14 to 23, further comprising the step of expanding the carbon dioxide in a carbon dioxide expander to generate mechanical power.

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