System and method for exhausting combustion gases from gas turbine engines

A system includes a gas turbine engine that includes a combustor section having one or more combustors configured to generate combustion products and a turbine section having one or more turbine stages between an upstream end and a downstream end. The one or more turbine stages are driven by the combustion products. The gas turbine engine also includes an exhaust section disposed downstream from the downstream end of the turbine section. The exhaust section has an exhaust passage configured to receive the combustion products as an exhaust gas. The gas turbine engine also includes a mixing device disposed in the exhaust section. The mixing device is configured to divide the exhaust gas into a first exhaust gas and a second exhaust gas, and to combine the first and second exhaust gases in a mixing region to produce a mixed exhaust gas.

BACKGROUND

The subject matter disclosed herein relates to gas turbine engines, and more specifically, to systems and methods for exhausting combustion gases from gas turbine engines.

Gas turbine engines are used in a wide variety of applications, such as power generation, aircraft, and various machinery. Gas turbine engines generally combust a fuel with an oxidant (e.g., air) in a combustor section to generate hot combustion products, which then drive one or more turbine stages of a turbine section. In turn, the turbine section drives one or more compressor stages of a compressor section. Again, the fuel and oxidant mix in the combustor section, and then combust to produce the hot combustion products. The thermal energy of the hot combustion products from the turbine section may be used to produce steam. However, the hot combustion products may be treated before being used to produce the steam. For example, a catalyst may be used to treat the hot combustion products to reduce the amounts of certain compounds. Unfortunately, inadequate mixing and/or distribution of the hot combustion products before contacting the catalyst may degrade catalyst performance and/or shorten the life of the catalyst. Furthermore, gas turbine engines typically consume a vast amount of air as the oxidant, and output a considerable amount of exhaust gas into the atmosphere. In other words, the exhaust gas is typically wasted as a byproduct of the gas turbine operation.

BRIEF DESCRIPTION

In one embodiment, a system includes a gas turbine engine that includes a combustor section having one or more combustors configured to generate combustion products and a turbine section having one or more turbine stages between an upstream end and a downstream end. The one or more turbine stages are driven by the combustion products. The gas turbine engine also includes an exhaust section disposed downstream from the downstream end of the turbine section. The exhaust section has an exhaust passage configured to receive the combustion products as an exhaust gas. The gas turbine engine also includes a mixing device disposed in the exhaust section. The mixing device is configured to divide the exhaust gas into a first exhaust gas and a second exhaust gas, and to combine the first and second exhaust gases in a mixing region to produce a mixed exhaust gas.

In a second embodiment, a system includes a turbine exhaust section configured to mount downstream from a turbine section of a gas turbine engine. The turbine exhaust section includes an exhaust passage configured to receive exhaust gas from the turbine section. The system also includes a mixing device disposed in the turbine exhaust section. The mixing device is configured to divide the exhaust gas into a first exhaust gas and a second exhaust gas, and to combine the first and second exhaust gases to produce a mixed exhaust gas.

In a third embodiment, a system includes a turbine mixing device configured to mount in a turbine exhaust section of a gas turbine engine. The mixing device includes a first section configured to convey an inner portion of an exhaust gas from the turbine exhaust section to a mixing region, and a second section configured to convey an outer portion of the exhaust gas to the mixing region. The second section circumferentially surrounds the first section, and the mixing region is configured to mix the inner and outer portions of the exhaust gas to produce a mixed exhaust gas.

In a fourth embodiment, a method includes combusting a fuel with an oxidant and an exhaust gas in a combustion portion of a turbine combustor to generate combustion products, driving a turbine with the combustion products from the turbine combustor, expanding the combustion products from the turbine through an exhaust passage in an exhaust section, dividing the combustion products from the exhaust section into a first exhaust gas and a second exhaust gas using a mixing device, and combining the first and second exhaust gases to produce a mixed exhaust gas using the mixing device such that a downstream radial uniformity of the mixed exhaust gas is greater than an upstream radial uniformity of the combustion products.

DETAILED DESCRIPTION

One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in an engineering or design project, numerous implementation-specific decisions are made to achieve the specific goals, such as compliance with system-related and/or business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

Accordingly, while example embodiments are capable of various modifications and alternative forms, embodiments thereof are illustrated by way of example in the figures and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed, but to the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of the present invention.

Certain terminology may be used herein for the convenience of the reader only and is not to be taken as a limitation on the scope of the invention. For example, words such as “upper”, “lower”, “left”, “right”, “front”, “rear”, “top”, “bottom”, “horizontal”, “vertical”, “upstream”, “downstream”, “fore”, “aft”, and the like; merely describe the configuration shown in the FIGS. Indeed, the element or elements of an embodiment of the present invention may be oriented in any direction and the terminology, therefore, should be understood as encompassing such variations unless specified otherwise.

As discussed in detail below, the disclosed embodiments relate generally to gas turbine systems with exhaust gas recirculation (EGR), and particularly stoichiometric operation of the gas turbine systems using EGR. For example, the gas turbine systems may be configured to recirculate the exhaust gas along an exhaust recirculation path, stoichiometrically combust fuel and oxidant along with at least some of the recirculated exhaust gas, and capture the exhaust gas for use in various target systems. The recirculation of the exhaust gas along with stoichiometric combustion may help to increase the concentration level of carbon dioxide (CO2) in the exhaust gas, which can then be post treated to separate and purify the CO2and nitrogen (N2) for use in various target systems. The gas turbine systems also may employ various exhaust gas processing (e.g., heat recovery, catalyst reactions, etc.) along the exhaust recirculation path, thereby increasing the concentration level of CO2, reducing concentration levels of other emissions (e.g., carbon monoxide, nitrogen oxides, and unburnt hydrocarbons), and increasing energy recovery (e.g., with heat recovery units). Furthermore, the gas turbine engines may be configured to combust the fuel and oxidant with one or more diffusion flames (e.g., using diffusion fuel nozzles), premix flames (e.g., using premix fuel nozzles), or any combination thereof. In certain embodiments, the diffusion flames may help to maintain stability and operation within certain limits for stoichiometric combustion, which in turn helps to increase production of CO2. For example, a gas turbine system operating with diffusion flames may enable a greater quantity of EGR, as compared to a gas turbine system operating with premix flames. In turn, the increased quantity of EGR helps to increase CO2production. Possible target systems include pipelines, storage tanks, carbon sequestration systems, and hydrocarbon production systems, such as enhanced oil recovery (EOR) systems.

The disclosed embodiments provide systems and methods having a mixing device coupled to an exhaust section of a gas turbine engine with EGR. The gas turbine engine may include a combustor section having one or more combustors configured to generate combustion products. The gas turbine engine may also include a turbine section having one or more turbine stages between an upstream end and a downstream end. The one or more turbine stages may be driven by the combustion products. The gas turbine engine may also include an exhaust section disposed downstream from the downstream end of the turbine section. The exhaust section may include an exhaust passage configured to receive the combustion products as an exhaust gas. Further, the gas turbine engine may include the mixing device coupled to the exhaust section. The mixing device may divide the exhaust gas into a first exhaust gas and a second exhaust gas. In addition, the mixing device may combine the first and second exhaust gases in a mixing region to produce a mixed exhaust gas. In certain embodiments, the exhaust gas entering the mixing device may have a nonuniform distribution, such as a nonuniform radial distribution and/or a nonuniform circumferential distribution. For example, an inner portion of the exhaust gas may have different characteristics than an outer portion of the exhaust gas. Specifically, a pressure, temperature, flow rate, and/or composition of the inner portion of the exhaust gas may be different from the outer portion of the exhaust gas.

The different characteristics between the inner and outer portions of the exhaust gas may affect the operation of equipment and/or processes downstream from the exhaust section. For example, a catalyst may be disposed downstream from the exhaust section to reduce amounts of certain components from the exhaust gas. The catalyst performance may be negatively affected by the difference in compositions between the inner and outer portions of the exhaust gas. For example, certain portions of the catalyst may be used up or fouled at a faster rate than other portions of the catalyst. As described in detail below, embodiments of the mixing device may improve the radial and/or circumferential uniformity of the exhaust gas. Specifically, the mixing device may divide the exhaust gas into the first and second exhaust gases, which may correspond to the inner and outer portions of the exhaust gas described above. The mixing device may combine the first and second exhaust gases in the mixing region to produce the mixed exhaust gas, which may have properties reflective of both the first and second exhaust gases. Thus, instead of the catalyst receiving first and second exhaust gases with different properties, the mixing device provides the mixed exhaust gas characterized by a uniform property to the catalyst. By using the mixing device to provide the mixed exhaust gas to the catalyst, catalyst performance may be improved. In addition, in certain embodiments, the mixing device may be characterized by a low pressure drop, which may improve the pressure recovery of the exhaust section of the gas turbine engine. Therefore, embodiments of the mixing device may improve the overall efficiency and cost-effectiveness of the gas turbine engine.

FIG. 1is a diagram of an embodiment of a system10having an hydrocarbon production system12associated with a turbine-based service system14. As discussed in further detail below, various embodiments of the turbine-based service system14are configured to provide various services, such as electrical power, mechanical power, and fluids (e.g., exhaust gas), to the hydrocarbon production system12to facilitate the production or retrieval of oil and/or gas. In the illustrated embodiment, the hydrocarbon production system12includes an oil/gas extraction system16and an enhanced oil recovery (EOR) system18, which are coupled to a subterranean reservoir20(e.g., an oil, gas, or hydrocarbon reservoir). The oil/gas extraction system16includes a variety of surface equipment22, such as a Christmas tree or production tree24, coupled to an oil/gas well26. Furthermore, the well26may include one or more tubulars28extending through a drilled bore30in the earth32to the subterranean reservoir20. The tree24includes one or more valves, chokes, isolation sleeves, blowout preventers, and various flow control devices, which regulate pressures and control flows to and from the subterranean reservoir20. While the tree24is generally used to control the flow of the production fluid (e.g., oil or gas) out of the subterranean reservoir20, the EOR system18may increase the production of oil or gas by injecting one or more fluids into the subterranean reservoir20.

Accordingly, the EOR system18may include a fluid injection system34, which has one or more tubulars36extending through a bore38in the earth32to the subterranean reservoir20. For example, the EOR system18may route one or more fluids40, such as gas, steam, water, chemicals, or any combination thereof, into the fluid injection system34. For example, as discussed in further detail below, the EOR system18may be coupled to the turbine-based service system14, such that the system14routes an exhaust gas42(e.g., substantially or entirely free of oxygen) to the EOR system18for use as the injection fluid40. The fluid injection system34routes the fluid40(e.g., the exhaust gas42) through the one or more tubulars36into the subterranean reservoir20, as indicated by arrows44. The injection fluid40enters the subterranean reservoir20through the tubular36at an offset distance46away from the tubular28of the oil/gas well26. Accordingly, the injection fluid40displaces the oil/gas48disposed in the subterranean reservoir20, and drives the oil/gas48up through the one or more tubulars28of the hydrocarbon production system12, as indicated by arrows50. As discussed in further detail below, the injection fluid40may include the exhaust gas42originating from the turbine-based service system14, which is able to generate the exhaust gas42on-site as needed by the hydrocarbon production system12. In other words, the turbine-based system14may simultaneously generate one or more services (e.g., electrical power, mechanical power, steam, water (e.g., desalinated water), and exhaust gas (e.g., substantially free of oxygen)) for use by the hydrocarbon production system12, thereby reducing or eliminating the reliance on external sources of such services.

In the illustrated embodiment, the turbine-based service system14includes a stoichiometric exhaust gas recirculation (SEGR) gas turbine system52and an exhaust gas (EG) processing system54. The gas turbine system52may be configured to operate in a stoichiometric combustion mode of operation (e.g., a stoichiometric control mode) and a non-stoichiometric combustion mode of operation (e.g., a non-stoichiometric control mode), such as a fuel-lean control mode or a fuel-rich control mode. In the stoichiometric control mode, the combustion generally occurs in a substantially stoichiometric ratio of a fuel and oxidant, thereby resulting in substantially stoichiometric combustion. In particular, stoichiometric combustion generally involves consuming substantially all of the fuel and oxidant in the combustion reaction, such that the products of combustion are substantially or entirely free of unburnt fuel and oxidant. One measure of stoichiometric combustion is the equivalence ratio, or phi (Φ), which is the ratio of the actual fuel/oxidant ratio relative to the stoichiometric fuel/oxidant ratio. An equivalence ratio of greater than 1.0 results in a fuel-rich combustion of the fuel and oxidant, whereas an equivalence ratio of less than 1.0 results in a fuel-lean combustion of the fuel and oxidant. In contrast, an equivalence ratio of 1.0 results in combustion that is neither fuel-rich nor fuel-lean, thereby substantially consuming all of the fuel and oxidant in the combustion reaction. In context of the disclosed embodiments, the term stoichiometric or substantially stoichiometric may refer to an equivalence ratio of approximately 0.95 to approximately 1.05. However, the disclosed embodiments may also include an equivalence ratio of 1.0 plus or minus 0.01, 0.02, 0.03, 0.04, 0.05, or more. Again, the stoichiometric combustion of fuel and oxidant in the turbine-based service system14may result in products of combustion or exhaust gas (e.g.,42) with substantially no unburnt fuel or oxidant remaining. For example, the exhaust gas42may have less than 1, 2, 3, 4, or 5 percent by volume of oxidant (e.g., oxygen), unburnt fuel or hydrocarbons (e.g., HCs), nitrogen oxides (e.g., NOX), carbon monoxide (CO), sulfur oxides (e.g., SOX), hydrogen, and other products of incomplete combustion. By further example, the exhaust gas42may have less than approximately 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 1000, 2000, 3000, 4000, or 5000 parts per million by volume (ppmv) of oxidant (e.g., oxygen), unburnt fuel or hydrocarbons (e.g., HCs), nitrogen oxides (e.g., NOX), carbon monoxide (CO), sulfur oxides (e.g., SOX), hydrogen, and other products of incomplete combustion. However, the disclosed embodiments also may produce other ranges of residual fuel, oxidant, and other emissions levels in the exhaust gas42. As used herein, the terms emissions, emissions levels, and emissions targets may refer to concentration levels of certain products of combustion (e.g., NOX, CO, SOX, O2, N2, H2, HCs, etc.), which may be present in recirculated gas streams, vented gas streams (e.g., exhausted into the atmosphere), and gas streams used in various target systems (e.g., the hydrocarbon production system12).

Although the SEGR gas turbine system52and the EG processing system54may include a variety of components in different embodiments, the illustrated EG processing system54includes a heat recovery steam generator (HRSG)56and an exhaust gas recirculation (EGR) system58, which receive and process an exhaust gas60originating from the SEGR gas turbine system52. The HRSG56may include one or more heat exchangers, condensers, and various heat recovery equipment, which collectively function to transfer heat from the exhaust gas60to a stream of water, thereby generating steam62. The steam62may be used in one or more steam turbines, the EOR system18, or any other portion of the hydrocarbon production system12. For example, the HRSG56may generate low pressure, medium pressure, and/or high pressure steam62, which may be selectively applied to low, medium, and high pressure steam turbine stages, or different applications of the EOR system18. In addition to the steam62, a treated water64, such as a desalinated water, may be generated by the HRSG56, the EGR system58, and/or another portion of the EG processing system54or the SEGR gas turbine system52. The treated water64(e.g., desalinated water) may be particularly useful in areas with water shortages, such as inland or desert regions. The treated water64may be generated, at least in part, due to the large volume of air driving combustion of fuel within the SEGR gas turbine system52. While the on-site generation of steam62and water64may be beneficial in many applications (including the hydrocarbon production system12), the on-site generation of exhaust gas42,60may be particularly beneficial for the EOR system18, due to its low oxygen content, high pressure, and heat derived from the SEGR gas turbine system52. Accordingly, the HRSG56, the EGR system58, and/or another portion of the EG processing system54may output or recirculate an exhaust gas66into the SEGR gas turbine system52, while also routing the exhaust gas42to the EOR system18for use with the hydrocarbon production system12. Likewise, the exhaust gas42may be extracted directly from the SEGR gas turbine system52(i.e., without passing through the EG processing system54) for use in the EOR system18of the hydrocarbon production system12.

The exhaust gas recirculation is handled by the EGR system58of the EG processing system54. For example, the EGR system58includes one or more conduits, valves, blowers, exhaust gas treatment systems (e.g., filters, particulate removal units, gas separation units, gas purification units, heat exchangers, heat recovery units, moisture removal units, catalyst units, chemical injection units, or any combination thereof), and controls to recirculate the exhaust gas along an exhaust gas circulation path from an output (e.g., discharged exhaust gas60) to an input (e.g., intake exhaust gas66) of the SEGR gas turbine system52. In the illustrated embodiment, the SEGR gas turbine system52intakes the exhaust gas66into a compressor section having one or more compressors, thereby compressing the exhaust gas66for use in a combustor section along with an intake of an oxidant68and one or more fuels70. The oxidant68may include ambient air, pure oxygen, oxygen-enriched air, oxygen-reduced air, oxygen-nitrogen mixtures, or any suitable oxidant that facilitates combustion of the fuel70. The fuel70may include one or more gas fuels, liquid fuels, or any combination thereof. For example, the fuel70may include natural gas, liquefied natural gas (LNG), syngas, methane, ethane, propane, butane, naphtha, kerosene, diesel fuel, ethanol, methanol, biofuel, or any combination thereof.

The SEGR gas turbine system52mixes and combusts the exhaust gas66, the oxidant68, and the fuel70in the combustor section, thereby generating hot combustion gases or exhaust gas60to drive one or more turbine stages in a turbine section. In certain embodiments, each combustor in the combustor section includes one or more premix fuel nozzles, one or more diffusion fuel nozzles, or any combination thereof. For example, each premix fuel nozzle may be configured to mix the oxidant68and the fuel70internally within the fuel nozzle and/or partially upstream of the fuel nozzle, thereby injecting an oxidant-fuel mixture from the fuel nozzle into the combustion zone for a premixed combustion (e.g., a premixed flame). By further example, each diffusion fuel nozzle may be configured to isolate the flows of oxidant68and fuel70within the fuel nozzle, thereby separately injecting the oxidant68and the fuel70from the fuel nozzle into the combustion zone for diffusion combustion (e.g., a diffusion flame). In particular, the diffusion combustion provided by the diffusion fuel nozzles delays mixing of the oxidant68and the fuel70until the point of initial combustion, i.e., the flame region. In embodiments employing the diffusion fuel nozzles, the diffusion flame may provide increased flame stability, because the diffusion flame generally forms at the point of stoichiometry between the separate streams of oxidant68and fuel70(i.e., as the oxidant68and fuel70are mixing). In certain embodiments, one or more diluents (e.g., the exhaust gas60, steam, nitrogen, or another inert gas) may be pre-mixed with the oxidant68, the fuel70, or both, in either the diffusion fuel nozzle or the premix fuel nozzle. In addition, one or more diluents (e.g., the exhaust gas60, steam, nitrogen, or another inert gas) may be injected into the combustor at or downstream from the point of combustion within each combustor. The use of these diluents may help temper the flame (e.g., premix flame or diffusion flame), thereby helping to reduce NOXemissions, such as nitrogen monoxide (NO) and nitrogen dioxide (NO2). Regardless of the type of flame, the combustion produces hot combustion gases or exhaust gas60to drive one or more turbine stages. As each turbine stage is driven by the exhaust gas60, the SEGR gas turbine system52generates a mechanical power72and/or an electrical power74(e.g., via an electrical generator). The system52also outputs the exhaust gas60, and may further output water64. Again, the water64may be a treated water, such as a desalinated water, which may be useful in a variety of applications on-site or off-site.

Exhaust extraction is also provided by the SEGR gas turbine system52using one or more extraction points76. For example, the illustrated embodiment includes an exhaust gas (EG) supply system78having an exhaust gas (EG) extraction system80and an exhaust gas (EG) treatment system82, which receive exhaust gas42from the extraction points76, treat the exhaust gas42, and then supply or distribute the exhaust gas42to various target systems. The target systems may include the EOR system18and/or other systems, such as a pipeline86, a storage tank88, or a carbon sequestration system90. The EG extraction system80may include one or more conduits, valves, controls, and flow separations, which facilitate isolation of the exhaust gas42from the oxidant68, the fuel70, and other contaminants, while also controlling the temperature, pressure, and flow rate of the extracted exhaust gas42. The EG treatment system82may include one or more heat exchangers (e.g., heat recovery units such as heat recovery steam generators, condensers, coolers, or heaters), catalyst systems (e.g., oxidation catalyst systems), particulate and/or water removal systems (e.g., gas dehydration units, inertial separators, coalescing filters, water impermeable filters, and other filters), chemical injection systems, solvent based treatment systems (e.g., absorbers, flash tanks, etc.), carbon capture systems, gas separation systems, gas purification systems, and/or a solvent based treatment system, exhaust gas compressors, any combination thereof. These subsystems of the EG treatment system82enable control of the temperature, pressure, flow rate, moisture content (e.g., amount of water removal), particulate content (e.g., amount of particulate removal), and gas composition (e.g., percentage of CO2, N2, etc.).

The extracted exhaust gas42is treated by one or more subsystems of the EG treatment system82, depending on the target system. For example, the EG treatment system82may direct all or part of the exhaust gas42through a carbon capture system, a gas separation system, a gas purification system, and/or a solvent based treatment system, which is controlled to separate and purify a carbonaceous gas (e.g., carbon dioxide)92and/or nitrogen (N2)94for use in the various target systems. For example, embodiments of the EG treatment system82may perform gas separation and purification to produce a plurality of different streams95of exhaust gas42, such as a first stream96, a second stream97, and a third stream98. The first stream96may have a first composition that is rich in carbon dioxide and/or lean in nitrogen (e.g., a CO2rich, N2lean stream). The second stream97may have a second composition that has intermediate concentration levels of carbon dioxide and/or nitrogen (e.g., intermediate concentration CO2, N2stream). The third stream98may have a third composition that is lean in carbon dioxide and/or rich in nitrogen (e.g., a CO2lean, N2rich stream). Each stream95(e.g.,96,97, and98) may include a gas dehydration unit, a filter, a gas compressor, or any combination thereof, to facilitate delivery of the stream95to a target system. In certain embodiments, the CO2rich, N2lean stream96may have a CO2purity or concentration level of greater than approximately 70, 75, 80, 85, 90, 95, 96, 97, 98, or 99 percent by volume, and a N2purity or concentration level of less than approximately 1, 2, 3, 4, 5, 10, 15, 20, 25, or 30 percent by volume. In contrast, the CO2lean, N2rich stream98may have a CO2purity or concentration level of less than approximately 1, 2, 3, 4, 5, 10, 15, 20, 25, or 30 percent by volume, and a N2purity or concentration level of greater than approximately 70, 75, 80, 85, 90, 95, 96, 97, 98, or 99 percent by volume. The intermediate concentration CO2, N2stream97may have a CO2purity or concentration level and/or a N2purity or concentration level of between approximately 30 to 70, 35 to 65, 40 to 60, or 45 to 55 percent by volume. Although the foregoing ranges are merely non-limiting examples, the CO2rich, N2lean stream96and the CO2lean, N2rich stream98may be particularly well suited for use with the EOR system18and the other systems84. However, any of these rich, lean, or intermediate concentration CO2streams95may be used, alone or in various combinations, with the EOR system18and the other systems84. For example, the EOR system18and the other systems84(e.g., the pipeline86, storage tank88, and the carbon sequestration system90) each may receive one or more CO2rich, N2lean streams96, one or more CO2lean, N2rich streams98, one or more intermediate concentration CO2, N2streams97, and one or more untreated exhaust gas42streams (i.e., bypassing the EG treatment system82).

The EG extraction system80extracts the exhaust gas42at one or more extraction points76along the compressor section, the combustor section, and/or the turbine section, such that the exhaust gas42may be used in the EOR system18and other systems84at suitable temperatures and pressures. The EG extraction system80and/or the EG treatment system82also may circulate fluid flows (e.g., exhaust gas42) to and from the EG processing system54. For example, a portion of the exhaust gas42passing through the EG processing system54may be extracted by the EG extraction system80for use in the EOR system18and the other systems84. In certain embodiments, the EG supply system78and the EG processing system54may be independent or integral with one another, and thus may use independent or common subsystems. For example, the EG treatment system82may be used by both the EG supply system78and the EG processing system54. Exhaust gas42extracted from the EG processing system54may undergo multiple stages of gas treatment, such as one or more stages of gas treatment in the EG processing system54followed by one or more additional stages of gas treatment in the EG treatment system82.

At each extraction point76, the extracted exhaust gas42may be substantially free of oxidant68and fuel70(e.g., unburnt fuel or hydrocarbons) due to substantially stoichiometric combustion and/or gas treatment in the EG processing system54. Furthermore, depending on the target system, the extracted exhaust gas42may undergo further treatment in the EG treatment system82of the EG supply system78, thereby further reducing any residual oxidant68, fuel70, or other undesirable products of combustion. For example, either before or after treatment in the EG treatment system82, the extracted exhaust gas42may have less than 1, 2, 3, 4, or 5 percent by volume of oxidant (e.g., oxygen), unburnt fuel or hydrocarbons (e.g., HCs), nitrogen oxides (e.g., NOX), carbon monoxide (CO), sulfur oxides (e.g., SOX), hydrogen, and other products of incomplete combustion. By further example, either before or after treatment in the EG treatment system82, the extracted exhaust gas42may have less than approximately 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 1000, 2000, 3000, 4000, or 5000 parts per million by volume (ppmv) of oxidant (e.g., oxygen), unburnt fuel or hydrocarbons (e.g., HCs), nitrogen oxides (e.g., NOX), carbon monoxide (CO), sulfur oxides (e.g., SOX), hydrogen, and other products of incomplete combustion. Thus, the exhaust gas42is particularly well suited for use with the EOR system18.

The EGR operation of the turbine system52specifically enables the exhaust extraction at a multitude of locations76. For example, the compressor section of the system52may be used to compress the exhaust gas66without any oxidant68(i.e., only compression of the exhaust gas66), such that a substantially oxygen-free exhaust gas42may be extracted from the compressor section and/or the combustor section prior to entry of the oxidant68and the fuel70. The extraction points76may be located at interstage ports between adjacent compressor stages, at ports along the compressor discharge casing, at ports along each combustor in the combustor section, or any combination thereof. In certain embodiments, the exhaust gas66may not mix with the oxidant68and fuel70until it reaches the head end portion and/or fuel nozzles of each combustor in the combustor section. Furthermore, one or more flow separators (e.g., walls, dividers, baffles, or the like) may be used to isolate the oxidant68and the fuel70from the extraction points76. With these flow separators, the extraction points76may be disposed directly along a wall of each combustor in the combustor section.

Once the exhaust gas66, oxidant68, and fuel70flow through the head end portion (e.g., through fuel nozzles) into the combustion portion (e.g., combustion chamber) of each combustor, the SEGR gas turbine system52is controlled to provide a substantially stoichiometric combustion of the exhaust gas66, oxidant68, and fuel70. For example, the system52may maintain an equivalence ratio of approximately 0.95 to approximately 1.05. As a result, the products of combustion of the mixture of exhaust gas66, oxidant68, and fuel70in each combustor is substantially free of oxygen and unburnt fuel. Thus, the products of combustion (or exhaust gas) may be extracted from the turbine section of the SEGR gas turbine system52for use as the exhaust gas42routed to the EOR system18. Along the turbine section, the extraction points76may be located at any turbine stage, such as interstage ports between adjacent turbine stages. Thus, using any of the foregoing extraction points76, the turbine-based service system14may generate, extract, and deliver the exhaust gas42to the hydrocarbon production system12(e.g., the EOR system18) for use in the production of oil/gas48from the subterranean reservoir20.

FIG. 2is a diagram of an embodiment of the system10ofFIG. 1, illustrating a control system100coupled to the turbine-based service system14and the hydrocarbon production system12. In the illustrated embodiment, the turbine-based service system14includes a combined cycle system102, which includes the SEGR gas turbine system52as a topping cycle, a steam turbine104as a bottoming cycle, and the HRSG56to recover heat from the exhaust gas60to generate the steam62for driving the steam turbine104. Again, the SEGR gas turbine system52receives, mixes, and stoichiometrically combusts the exhaust gas66, the oxidant68, and the fuel70(e.g., premix and/or diffusion flames), thereby producing the exhaust gas60, the mechanical power72, the electrical power74, and/or the water64. For example, the SEGR gas turbine system52may drive one or more loads or machinery106, such as an electrical generator, an oxidant compressor (e.g., a main air compressor), a gear box, a pump, equipment of the hydrocarbon production system12, or any combination thereof. In some embodiments, the machinery106may include other drives, such as electrical motors or steam turbines (e.g., the steam turbine104), in tandem with the SEGR gas turbine system52. Accordingly, an output of the machinery106driven by the SEGR gas turbines system52(and any additional drives) may include the mechanical power72and the electrical power74. The mechanical power72and/or the electrical power74may be used on-site for powering the hydrocarbon production system12, the electrical power74may be distributed to the power grid, or any combination thereof. The output of the machinery106also may include a compressed fluid, such as a compressed oxidant68(e.g., air or oxygen), for intake into the combustion section of the SEGR gas turbine system52. Each of these outputs (e.g., the exhaust gas60, the mechanical power72, the electrical power74, and/or the water64) may be considered a service of the turbine-based service system14.

The SEGR gas turbine system52produces the exhaust gas42,60, which may be substantially free of oxygen, and routes this exhaust gas42,60to the EG processing system54and/or the EG supply system78. The EG supply system78may treat and delivery the exhaust gas42(e.g., streams95) to the hydrocarbon production system12and/or the other systems84. As discussed above, the EG processing system54may include the HRSG56and the EGR system58. The HRSG56may include one or more heat exchangers, condensers, and various heat recovery equipment, which may be used to recover or transfer heat from the exhaust gas60to water108to generate the steam62for driving the steam turbine104. Similar to the SEGR gas turbine system52, the steam turbine104may drive one or more loads or machinery106, thereby generating the mechanical power72and the electrical power74. In the illustrated embodiment, the SEGR gas turbine system52and the steam turbine104are arranged in tandem to drive the same machinery106. However, in other embodiments, the SEGR gas turbine system52and the steam turbine104may separately drive different machinery106to independently generate mechanical power72and/or electrical power74. As the steam turbine104is driven by the steam62from the HRSG56, the steam62gradually decreases in temperature and pressure. Accordingly, the steam turbine104recirculates the used steam62and/or water108back into the HRSG56for additional steam generation via heat recovery from the exhaust gas60. In addition to steam generation, the HRSG56, the EGR system58, and/or another portion of the EG processing system54may produce the water64, the exhaust gas42for use with the hydrocarbon production system12, and the exhaust gas66for use as an input into the SEGR gas turbine system52. For example, the water64may be a treated water64, such as a desalinated water for use in other applications. The desalinated water may be particularly useful in regions of low water availability. Regarding the exhaust gas60, embodiments of the EG processing system54may be configured to recirculate the exhaust gas60through the EGR system58with or without passing the exhaust gas60through the HRSG56.

In the illustrated embodiment, the SEGR gas turbine system52has an exhaust recirculation path110, which extends from an exhaust outlet to an exhaust inlet of the system52. Along the path110, the exhaust gas60passes through the EG processing system54, which includes the HRSG56and the EGR system58in the illustrated embodiment. The EGR system58may include one or more conduits, valves, blowers, gas treatment systems (e.g., filters, particulate removal units, gas separation units, gas purification units, heat exchangers, heat recovery units such as heat recovery steam generators, moisture removal units, catalyst units, chemical injection units, or any combination thereof) in series and/or parallel arrangements along the path110. In other words, the EGR system58may include any flow control components, pressure control components, temperature control components, moisture control components, and gas composition control components along the exhaust recirculation path110between the exhaust outlet and the exhaust inlet of the system52. Accordingly, in embodiments with the HRSG56along the path110, the HRSG56may be considered a component of the EGR system58. However, in certain embodiments, the HRSG56may be disposed along an exhaust path independent from the exhaust recirculation path110. Regardless of whether the HRSG56is along a separate path or a common path with the EGR system58, the HRSG56and the EGR system58intake the exhaust gas60and output either the recirculated exhaust gas66, the exhaust gas42for use with the EG supply system78(e.g., for the hydrocarbon production system12and/or other systems84), or another output of exhaust gas. Again, the SEGR gas turbine system52intakes, mixes, and stoichiometrically combusts the exhaust gas66, the oxidant68, and the fuel70(e.g., premixed and/or diffusion flames) to produce a substantially oxygen-free and fuel-free exhaust gas60for distribution to the EG processing system54, the hydrocarbon production system12, or other systems84.

As noted above with reference toFIG. 1, the hydrocarbon production system12may include a variety of equipment to facilitate the recovery or production of oil/gas48from a subterranean reservoir20through an oil/gas well26. For example, the hydrocarbon production system12may include the EOR system18having the fluid injection system34. In the illustrated embodiment, the fluid injection system34includes an exhaust gas injection EOR system112and a steam injection EOR system114. Although the fluid injection system34may receive fluids from a variety of sources, the illustrated embodiment may receive the exhaust gas42and the steam62from the turbine-based service system14. The exhaust gas42and/or the steam62produced by the turbine-based service system14also may be routed to the hydrocarbon production system12for use in other oil/gas systems116.

The quantity, quality, and flow of the exhaust gas42and/or the steam62may be controlled by the control system100. The control system100may be dedicated entirely to the turbine-based service system14, or the control system100may optionally also provide control (or at least some data to facilitate control) for the hydrocarbon production system12and/or other systems84. In the illustrated embodiment, the control system100includes a controller118having a processor120, a memory122, a steam turbine control124, a SEGR gas turbine system control126, and a machinery control128. The processor120may include a single processor or two or more redundant processors, such as triple redundant processors for control of the turbine-based service system14. The memory122may include volatile and/or non-volatile memory. For example, the memory122may include one or more hard drives, flash memory, read-only memory, random access memory, or any combination thereof. The controls124,126, and128may include software and/or hardware controls. For example, the controls124,126, and128may include various instructions or code stored on the memory122and executable by the processor120. The control124is configured to control operation of the steam turbine104, the SEGR gas turbine system control126is configured to control the system52, and the machinery control128is configured to control the machinery106. Thus, the controller118(e.g., controls124,126, and128) may be configured to coordinate various sub-systems of the turbine-based service system14to provide a suitable stream of the exhaust gas42to the hydrocarbon production system12.

In certain embodiments of the control system100, each element (e.g., system, subsystem, and component) illustrated in the drawings or described herein includes (e.g., directly within, upstream, or downstream of such element) one or more industrial control features, such as sensors and control devices, which are communicatively coupled with one another over an industrial control network along with the controller118. For example, the control devices associated with each element may include a dedicated device controller (e.g., including a processor, memory, and control instructions), one or more actuators, valves, switches, and industrial control equipment, which enable control based on sensor feedback130, control signals from the controller118, control signals from a user, or any combination thereof. Thus, any of the control functionality described herein may be implemented with control instructions stored and/or executable by the controller118, dedicated device controllers associated with each element, or a combination thereof.

In order to facilitate such control functionality, the control system100includes one or more sensors distributed throughout the system10to obtain the sensor feedback130for use in execution of the various controls, e.g., the controls124,126, and128. For example, the sensor feedback130may be obtained from sensors distributed throughout the SEGR gas turbine system52, the machinery106, the EG processing system54, the steam turbine104, the hydrocarbon production system12, or any other components throughout the turbine-based service system14or the hydrocarbon production system12. For example, the sensor feedback130may include temperature feedback, pressure feedback, flow rate feedback, flame temperature feedback, combustion dynamics feedback, intake oxidant composition feedback, intake fuel composition feedback, exhaust composition feedback, the output level of mechanical power72, the output level of electrical power74, the output quantity of the exhaust gas42,60, the output quantity or quality of the water64, or any combination thereof. For example, the sensor feedback130may include a composition of the exhaust gas42,60to facilitate stoichiometric combustion in the SEGR gas turbine system52. For example, the sensor feedback130may include feedback from one or more intake oxidant sensors along an oxidant supply path of the oxidant68, one or more intake fuel sensors along a fuel supply path of the fuel70, and one or more exhaust emissions sensors disposed along the exhaust recirculation path110and/or within the SEGR gas turbine system52. The intake oxidant sensors, intake fuel sensors, and exhaust emissions sensors may include temperature sensors, pressure sensors, flow rate sensors, and composition sensors. The emissions sensors may includes sensors for nitrogen oxides (e.g., NOXsensors), carbon oxides (e.g., CO sensors and CO2sensors), sulfur oxides (e.g., SOXsensors), hydrogen (e.g., H2sensors), oxygen (e.g., O2sensors), unburnt hydrocarbons (e.g., HC sensors), or other products of incomplete combustion, or any combination thereof.

Using this feedback130, the control system100may adjust (e.g., increase, decrease, or maintain) the intake flow of exhaust gas66, oxidant68, and/or fuel70into the SEGR gas turbine system52(among other operational parameters) to maintain the equivalence ratio within a suitable range, e.g., between approximately 0.95 to approximately 1.05, between approximately 0.95 to approximately 1.0, between approximately 1.0 to approximately 1.05, or substantially at 1.0. For example, the control system100may analyze the feedback130to monitor the exhaust emissions (e.g., concentration levels of nitrogen oxides, carbon oxides such as CO and CO2, sulfur oxides, hydrogen, oxygen, unburnt hydrocarbons, and other products of incomplete combustion) and/or determine the equivalence ratio, and then control one or more components to adjust the exhaust emissions (e.g., concentration levels in the exhaust gas42) and/or the equivalence ratio. The controlled components may include any of the components illustrated and described with reference to the drawings, including but not limited to, valves along the supply paths for the oxidant68, the fuel70, and the exhaust gas66; an oxidant compressor, a fuel pump, or any components in the EG processing system54; any components of the SEGR gas turbine system52, or any combination thereof. The controlled components may adjust (e.g., increase, decrease, or maintain) the flow rates, temperatures, pressures, or percentages (e.g., equivalence ratio) of the oxidant68, the fuel70, and the exhaust gas66that combust within the SEGR gas turbine system52. The controlled components also may include one or more gas treatment systems, such as catalyst units (e.g., oxidation catalyst units), supplies for the catalyst units (e.g., oxidation fuel, heat, electricity, etc.), gas purification and/or separation units (e.g., solvent based separators, absorbers, flash tanks, etc.), and filtration units. The gas treatment systems may help reduce various exhaust emissions along the exhaust recirculation path110, a vent path (e.g., exhausted into the atmosphere), or an extraction path to the EG supply system78.

In certain embodiments, the control system100may analyze the feedback130and control one or more components to maintain or reduce emissions levels (e.g., concentration levels in the exhaust gas42,60,95) to a target range, such as less than approximately 10, 20, 30, 40, 50, 100, 200, 300, 400, 500, 1000, 2000, 3000, 4000, 5000, or 10000 parts per million by volume (ppmv). These target ranges may be the same or different for each of the exhaust emissions, e.g., concentration levels of nitrogen oxides, carbon monoxide, sulfur oxides, hydrogen, oxygen, unburnt hydrocarbons, and other products of incomplete combustion. For example, depending on the equivalence ratio, the control system100may selectively control exhaust emissions (e.g., concentration levels) of oxidant (e.g., oxygen) within a target range of less than approximately 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 250, 500, 750, or 1000 ppmv; carbon monoxide (CO) within a target range of less than approximately 20, 50, 100, 200, 500, 1000, 2500, or 5000 ppmv; and nitrogen oxides (NOX) within a target range of less than approximately 50, 100, 200, 300, 400, or 500 ppmv. In certain embodiments operating with a substantially stoichiometric equivalence ratio, the control system100may selectively control exhaust emissions (e.g., concentration levels) of oxidant (e.g., oxygen) within a target range of less than approximately 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 ppmv; and carbon monoxide (CO) within a target range of less than approximately 500, 1000, 2000, 3000, 4000, or 5000 ppmv. In certain embodiments operating with a fuel-lean equivalence ratio (e.g., between approximately 0.95 to 1.0), the control system100may selectively control exhaust emissions (e.g., concentration levels) of oxidant (e.g., oxygen) within a target range of less than approximately 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, or 1500 ppmv; carbon monoxide (CO) within a target range of less than approximately 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, or 200 ppmv; and nitrogen oxides (e.g., NOX) within a target range of less than approximately 50, 100, 150, 200, 250, 300, 350, or 400 ppmv. The foregoing target ranges are merely examples, and are not intended to limit the scope of the disclosed embodiments.

The control system100also may be coupled to a local interface132and a remote interface134. For example, the local interface132may include a computer workstation disposed on-site at the turbine-based service system14and/or the hydrocarbon production system12. In contrast, the remote interface134may include a computer workstation disposed off-site from the turbine-based service system14and the hydrocarbon production system12, such as through an internet connection. These interfaces132and134facilitate monitoring and control of the turbine-based service system14, such as through one or more graphical displays of sensor feedback130, operational parameters, and so forth.

Again, as noted above, the controller118includes a variety of controls124,126, and128to facilitate control of the turbine-based service system14. The steam turbine control124may receive the sensor feedback130and output control commands to facilitate operation of the steam turbine104. For example, the steam turbine control124may receive the sensor feedback130from the HRSG56, the machinery106, temperature and pressure sensors along a path of the steam62, temperature and pressure sensors along a path of the water108, and various sensors indicative of the mechanical power72and the electrical power74. Likewise, the SEGR gas turbine system control126may receive sensor feedback130from one or more sensors disposed along the SEGR gas turbine system52, the machinery106, the EG processing system54, or any combination thereof. For example, the sensor feedback130may be obtained from temperature sensors, pressure sensors, clearance sensors, vibration sensors, flame sensors, fuel composition sensors, exhaust gas composition sensors, or any combination thereof, disposed within or external to the SEGR gas turbine system52. Finally, the machinery control128may receive sensor feedback130from various sensors associated with the mechanical power72and the electrical power74, as well as sensors disposed within the machinery106. Each of these controls124,126, and128uses the sensor feedback130to improve operation of the turbine-based service system14.

In the illustrated embodiment, the SEGR gas turbine system control126may execute instructions to control the quantity and quality of the exhaust gas42,60,95in the EG processing system54, the EG supply system78, the hydrocarbon production system12, and/or the other systems84. For example, the SEGR gas turbine system control126may maintain a level of oxidant (e.g., oxygen) and/or unburnt fuel in the exhaust gas60below a threshold suitable for use with the exhaust gas injection EOR system112. In certain embodiments, the threshold levels may be less than 1, 2, 3, 4, or 5 percent of oxidant (e.g., oxygen) and/or unburnt fuel by volume of the exhaust gas42,60; or the threshold levels of oxidant (e.g., oxygen) and/or unburnt fuel (and other exhaust emissions) may be less than approximately 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 1000, 2000, 3000, 4000, or 5000 parts per million by volume (ppmv) in the exhaust gas42,60. By further example, in order to achieve these low levels of oxidant (e.g., oxygen) and/or unburnt fuel, the SEGR gas turbine system control126may maintain an equivalence ratio for combustion in the SEGR gas turbine system52between approximately 0.95 and approximately 1.05. The SEGR gas turbine system control126also may control the EG extraction system80and the EG treatment system82to maintain the temperature, pressure, flow rate, and gas composition of the exhaust gas42,60,95within suitable ranges for the exhaust gas injection EOR system112, the pipeline86, the storage tank88, and the carbon sequestration system90. As discussed above, the EG treatment system82may be controlled to purify and/or separate the exhaust gas42into one or more gas streams95, such as the CO2rich, N2lean stream96, the intermediate concentration CO2, N2stream97, and the CO2lean, N2rich stream98. In addition to controls for the exhaust gas42,60, and95, the controls124,126, and128may execute one or more instructions to maintain the mechanical power72within a suitable power range, or maintain the electrical power74within a suitable frequency and power range.

FIG. 3is a diagram of embodiment of the system10, further illustrating details of the SEGR gas turbine system52for use with the hydrocarbon production system12and/or other systems84. In the illustrated embodiment, the SEGR gas turbine system52includes a gas turbine engine150coupled to the EG processing system54. The illustrated gas turbine engine150includes a compressor section152, a combustor section154, and an expander section or turbine section156. The compressor section152includes one or more exhaust gas compressors or compressor stages158, such as 1 to 20 stages of rotary compressor blades disposed in a series arrangement. Likewise, the combustor section154includes one or more combustors160, such as 1 to 20 combustors160distributed circumferentially about a rotational axis162of the SEGR gas turbine system52. Furthermore, each combustor160may include one or more fuel nozzles164configured to inject the exhaust gas66, the oxidant68, and/or the fuel70. For example, a head end portion166of each combustor160may house 1, 2, 3, 4, 5, 6, or more fuel nozzles164, which may inject streams or mixtures of the exhaust gas66, the oxidant68, and/or the fuel70into a combustion portion168(e.g., combustion chamber) of the combustor160.

The fuel nozzles164may include any combination of premix fuel nozzles164(e.g., configured to premix the oxidant68and fuel70for generation of an oxidant/fuel premix flame) and/or diffusion fuel nozzles164(e.g., configured to inject separate flows of the oxidant68and fuel70for generation of an oxidant/fuel diffusion flame). Embodiments of the premix fuel nozzles164may include swirl vanes, mixing chambers, or other features to internally mix the oxidant68and fuel70within the nozzles164, prior to injection and combustion in the combustion chamber168. The premix fuel nozzles164also may receive at least some partially mixed oxidant68and fuel70. In certain embodiments, each diffusion fuel nozzle164may isolate flows of the oxidant68and the fuel70until the point of injection, while also isolating flows of one or more diluents (e.g., the exhaust gas66, steam, nitrogen, or another inert gas) until the point of injection. In other embodiments, each diffusion fuel nozzle164may isolate flows of the oxidant68and the fuel70until the point of injection, while partially mixing one or more diluents (e.g., the exhaust gas66, steam, nitrogen, or another inert gas) with the oxidant68and/or the fuel70prior to the point of injection. In addition, one or more diluents (e.g., the exhaust gas66, steam, nitrogen, or another inert gas) may be injected into the combustor (e.g., into the hot products of combustion) either at or downstream from the combustion zone, thereby helping to reduce the temperature of the hot products of combustion and reduce emissions of NOX(e.g., NO and NO2). Regardless of the type of fuel nozzle164, the SEGR gas turbine system52may be controlled to provide substantially stoichiometric combustion of the oxidant68and fuel70.

In diffusion combustion embodiments using the diffusion fuel nozzles164, the fuel70and oxidant68generally do not mix upstream from the diffusion flame, but rather the fuel70and oxidant68mix and react directly at the flame surface and/or the flame surface exists at the location of mixing between the fuel70and oxidant68. In particular, the fuel70and oxidant68separately approach the flame surface (or diffusion boundary/interface), and then diffuse (e.g., via molecular and viscous diffusion) along the flame surface (or diffusion boundary/interface) to generate the diffusion flame. It is noteworthy that the fuel70and oxidant68may be at a substantially stoichiometric ratio along this flame surface (or diffusion boundary/interface), which may result in a greater flame temperature (e.g., a peak flame temperature) along this flame surface. The stoichiometric fuel/oxidant ratio generally results in a greater flame temperature (e.g., a peak flame temperature), as compared with a fuel-lean or fuel-rich fuel/oxidant ratio. As a result, the diffusion flame may be substantially more stable than a premix flame, because the diffusion of fuel70and oxidant68helps to maintain a stoichiometric ratio (and greater temperature) along the flame surface. Although greater flame temperatures can also lead to greater exhaust emissions, such as NOXemissions, the disclosed embodiments use one or more diluents to help control the temperature and emissions while still avoiding any premixing of the fuel70and oxidant68. For example, the disclosed embodiments may introduce one or more diluents separate from the fuel70and oxidant68(e.g., after the point of combustion and/or downstream from the diffusion flame), thereby helping to reduce the temperature and reduce the emissions (e.g., NOXemissions) produced by the diffusion flame.

In operation, as illustrated, the compressor section152receives and compresses the exhaust gas66from the EG processing system54, and outputs a compressed exhaust gas170to each of the combustors160in the combustor section154. Upon combustion of the fuel60, oxidant68, and exhaust gas170within each combustor160, additional exhaust gas or products of combustion172(i.e., combustion gas) is routed into the turbine section156. Similar to the compressor section152, the turbine section156includes one or more turbines or turbine stages174, which may include a series of rotary turbine blades. These turbine blades are then driven by the products of combustion172generated in the combustor section154, thereby driving rotation of a shaft176coupled to the machinery106. Again, the machinery106may include a variety of equipment coupled to either end of the SEGR gas turbine system52, such as machinery106,178coupled to the turbine section156and/or machinery106,180coupled to the compressor section152. In certain embodiments, the machinery106,178,180may include one or more electrical generators, oxidant compressors for the oxidant68, fuel pumps for the fuel70, gear boxes, or additional drives (e.g. steam turbine104, electrical motor, etc.) coupled to the SEGR gas turbine system52. Non-limiting examples are discussed in further detail below with reference to TABLE 1. As illustrated, the turbine section156outputs the exhaust gas60to recirculate along the exhaust recirculation path110from an exhaust outlet182of the turbine section156to an exhaust inlet184into the compressor section152. Along the exhaust recirculation path110, the exhaust gas60passes through the EG processing system54(e.g., the HRSG56and/or the EGR system58) as discussed in detail above.

Again, each combustor160in the combustor section154receives, mixes, and stoichiometrically combusts the compressed exhaust gas170, the oxidant68, and the fuel70to produce the additional exhaust gas or products of combustion172to drive the turbine section156. In certain embodiments, the oxidant68is compressed by an oxidant compression system186, such as a main oxidant compression (MOC) system (e.g., a main air compression (MAC) system) having one or more oxidant compressors (MOCs). The oxidant compression system186includes an oxidant compressor188coupled to a drive190. For example, the drive190may include an electric motor, a combustion engine, or any combination thereof. In certain embodiments, the drive190may be a turbine engine, such as the gas turbine engine150. Accordingly, the oxidant compression system186may be an integral part of the machinery106. In other words, the compressor188may be directly or indirectly driven by the mechanical power72supplied by the shaft176of the gas turbine engine150. In such an embodiment, the drive190may be excluded, because the compressor188relies on the power output from the turbine engine150. However, in certain embodiments employing more than one oxidant compressor is employed, a first oxidant compressor (e.g., a low pressure (LP) oxidant compressor) may be driven by the drive190while the shaft176drives a second oxidant compressor (e.g., a high pressure (HP) oxidant compressor), or vice versa. For example, in another embodiment, the HP MOC is driven by the drive190and the LP oxidant compressor is driven by the shaft176. In the illustrated embodiment, the oxidant compression system186is separate from the machinery106. In each of these embodiments, the compression system186compresses and supplies the oxidant68to the fuel nozzles164and the combustors160. Accordingly, some or all of the machinery106,178,180may be configured to increase the operational efficiency of the compression system186(e.g., the compressor188and/or additional compressors).

The variety of components of the machinery106, indicated by element numbers106A,106B,106C,106D,106E, and106F, may be disposed along the line of the shaft176and/or parallel to the line of the shaft176in one or more series arrangements, parallel arrangements, or any combination of series and parallel arrangements. For example, the machinery106,178,180(e.g.,106A through106F) may include any series and/or parallel arrangement, in any order, of: one or more gearboxes (e.g., parallel shaft, epicyclic gearboxes), one or more compressors (e.g., oxidant compressors, booster compressors such as EG booster compressors), one or more power generation units (e.g., electrical generators), one or more drives (e.g., steam turbine engines, electrical motors), heat exchange units (e.g., direct or indirect heat exchangers), clutches, or any combination thereof. The compressors may include axial compressors, radial or centrifugal compressors, or any combination thereof, each having one or more compression stages. Regarding the heat exchangers, direct heat exchangers may include spray coolers (e.g., spray intercoolers), which inject a liquid spray into a gas flow (e.g., oxidant flow) for direct cooling of the gas flow. Indirect heat exchangers may include at least one wall (e.g., a shell and tube heat exchanger) separating first and second flows, such as a fluid flow (e.g., oxidant flow) separated from a coolant flow (e.g., water, air, refrigerant, or any other liquid or gas coolant), wherein the coolant flow transfers heat from the fluid flow without any direct contact. Examples of indirect heat exchangers include intercooler heat exchangers and heat recovery units, such as heat recovery steam generators. The heat exchangers also may include heaters. As discussed in further detail below, each of these machinery components may be used in various combinations as indicated by the non-limiting examples set forth in TABLE 1.

Generally, the machinery106,178,180may be configured to increase the efficiency of the compression system186by, for example, adjusting operational speeds of one or more oxidant compressors in the system186, facilitating compression of the oxidant68through cooling, and/or extraction of surplus power. The disclosed embodiments are intended to include any and all permutations of the foregoing components in the machinery106,178,180in series and parallel arrangements, wherein one, more than one, all, or none of the components derive power from the shaft176. As illustrated below, TABLE 1 depicts some non-limiting examples of arrangements of the machinery106,178,180disposed proximate and/or coupled to the compressor and turbine sections152,156.

As illustrated above in TABLE 1, a cooling unit is represented as CLR, a clutch is represented as CLU, a drive is represented by DRV, a gearbox is represented as GBX, a generator is represented by GEN, a heating unit is represented by HTR, a main oxidant compressor unit is represented by MOC, with low pressure and high pressure variants being represented as LP MOC and HP MOC, respectively, and a steam generator unit is represented as STGN. Although TABLE 1 illustrates the machinery106,178,180in sequence toward the compressor section152or the turbine section156, TABLE 1 is also intended to cover the reverse sequence of the machinery106,178,180. In TABLE 1, any cell including two or more components is intended to cover a parallel arrangement of the components. TABLE 1 is not intended to exclude any non-illustrated permutations of the machinery106,178,180. These components of the machinery106,178,180may enable feedback control of temperature, pressure, and flow rate of the oxidant68sent to the gas turbine engine150. As discussed in further detail below, the oxidant68and the fuel70may be supplied to the gas turbine engine150at locations specifically selected to facilitate isolation and extraction of the compressed exhaust gas170without any oxidant68or fuel70degrading the quality of the exhaust gas170.

The EG supply system78, as illustrated inFIG. 3, is disposed between the gas turbine engine150and the target systems (e.g., the hydrocarbon production system12and the other systems84). In particular, the EG supply system78, e.g., the EG extraction system (EGES)80), may be coupled to the gas turbine engine150at one or more extraction points76along the compressor section152, the combustor section154, and/or the turbine section156. For example, the extraction points76may be located between adjacent compressor stages, such as 2, 3, 4, 5, 6, 7, 8, 9, or 10 interstage extraction points76between compressor stages. Each of these interstage extraction points76provides a different temperature and pressure of the extracted exhaust gas42. Similarly, the extraction points76may be located between adjacent turbine stages, such as 2, 3, 4, 5, 6, 7, 8, 9, or 10 interstage extraction points76between turbine stages. Each of these interstage extraction points76provides a different temperature and pressure of the extracted exhaust gas42. By further example, the extraction points76may be located at a multitude of locations throughout the combustor section154, which may provide different temperatures, pressures, flow rates, and gas compositions. Each of these extraction points76may include an EG extraction conduit, one or more valves, sensors, and controls, which may be used to selectively control the flow of the extracted exhaust gas42to the EG supply system78.

The extracted exhaust gas42, which is distributed by the EG supply system78, has a controlled composition suitable for the target systems (e.g., the hydrocarbon production system12and the other systems84). For example, at each of these extraction points76, the exhaust gas170may be substantially isolated from injection points (or flows) of the oxidant68and the fuel70. In other words, the EG supply system78may be specifically designed to extract the exhaust gas170from the gas turbine engine150without any added oxidant68or fuel70. Furthermore, in view of the stoichiometric combustion in each of the combustors160, the extracted exhaust gas42may be substantially free of oxygen and fuel. The EG supply system78may route the extracted exhaust gas42directly or indirectly to the hydrocarbon production system12and/or other systems84for use in various processes, such as enhanced oil recovery, carbon sequestration, storage, or transport to an offsite location. However, in certain embodiments, the EG supply system78includes the EG treatment system (EGTS)82for further treatment of the exhaust gas42, prior to use with the target systems. For example, the EG treatment system82may purify and/or separate the exhaust gas42into one or more streams95, such as the CO2rich, N2lean stream96, the intermediate concentration CO2, N2stream97, and the CO2lean, N2rich stream98. These treated exhaust gas streams95may be used individually, or in any combination, with the hydrocarbon production system12and the other systems84(e.g., the pipeline86, the storage tank88, and the carbon sequestration system90).

Similar to the exhaust gas treatments performed in the EG supply system78, the EG processing system54may include a plurality of exhaust gas (EG) treatment components192, such as indicated by element numbers194,196,198,200,202,204,206,208, and210. These EG treatment components192(e.g.,194through210) may be disposed along the exhaust recirculation path110in one or more series arrangements, parallel arrangements, or any combination of series and parallel arrangements. For example, the EG treatment components192(e.g.,194through210) may include any series and/or parallel arrangement, in any order, of: one or more heat exchangers (e.g., heat recovery units such as heat recovery steam generators, condensers, coolers, or heaters), catalyst systems (e.g., oxidation catalyst systems), particulate and/or water removal systems (e.g., inertial separators, coalescing filters, water impermeable filters, and other filters), chemical injection systems, solvent based treatment systems (e.g., absorbers, flash tanks, etc.), carbon capture systems, gas separation systems, gas purification systems, and/or a solvent based treatment system, or any combination thereof. In certain embodiments, the catalyst systems may include an oxidation catalyst, a carbon monoxide reduction catalyst, a nitrogen oxides reduction catalyst, an aluminum oxide, a zirconium oxide, a silicone oxide, a titanium oxide, a platinum oxide, a palladium oxide, a cobalt oxide, or a mixed metal oxide, or a combination thereof. The disclosed embodiments are intended to include any and all permutations of the foregoing components192in series and parallel arrangements. As illustrated below, TABLE 2 depicts some non-limiting examples of arrangements of the components192along the exhaust recirculation path110.

As illustrated above in TABLE 2, a catalyst unit is represented by CU, an oxidation catalyst unit is represented by OCU, a booster blower is represented by BB, a heat exchanger is represented by HX, a heat recovery unit is represented by HRU, a heat recovery steam generator is represented by HRSG, a condenser is represented by COND, a steam turbine is represented by ST, a particulate removal unit is represented by PRU, a moisture removal unit is represented by MRU, a filter is represented by FIL, a coalescing filter is represented by CFIL, a water impermeable filter is represented by WFIL, an inertial separator is represented by INER, and a diluent supply system (e.g., steam, nitrogen, or other inert gas) is represented by DIL. Although TABLE 2 illustrates the components192in sequence from the exhaust outlet182of the turbine section156toward the exhaust inlet184of the compressor section152, TABLE 2 is also intended to cover the reverse sequence of the illustrated components192. In TABLE 2, any cell including two or more components is intended to cover an integrated unit with the components, a parallel arrangement of the components, or any combination thereof. Furthermore, in context of TABLE 2, the HRU, the HRSG, and the COND are examples of the HE; the HRSG is an example of the HRU; the COND, WFIL, and CFIL are examples of the WRU; the INER, FIL, WFIL, and CFIL are examples of the PRU; and the WFIL and CFIL are examples of the FIL. Again, TABLE 2 is not intended to exclude any non-illustrated permutations of the components192. In certain embodiments, the illustrated components192(e.g.,194through210) may be partially or completed integrated within the HRSG56, the EGR system58, or any combination thereof. These EG treatment components192may enable feedback control of temperature, pressure, flow rate, and gas composition, while also removing moisture and particulates from the exhaust gas60. Furthermore, the treated exhaust gas60may be extracted at one or more extraction points76for use in the EG supply system78and/or recirculated to the exhaust inlet184of the compressor section152.

As the treated, recirculated exhaust gas66passes through the compressor section152, the SEGR gas turbine system52may bleed off a portion of the compressed exhaust gas along one or more lines212(e.g., bleed conduits or bypass conduits). Each line212may route the exhaust gas into one or more heat exchangers214(e.g., cooling units), thereby cooling the exhaust gas for recirculation back into the SEGR gas turbine system52. For example, after passing through the heat exchanger214, a portion of the cooled exhaust gas may be routed to the turbine section156along line212for cooling and/or sealing of the turbine casing, turbine shrouds, bearings, and other components. In such an embodiment, the SEGR gas turbine system52does not route any oxidant68(or other potential contaminants) through the turbine section156for cooling and/or sealing purposes, and thus any leakage of the cooled exhaust gas will not contaminate the hot products of combustion (e.g., working exhaust gas) flowing through and driving the turbine stages of the turbine section156. By further example, after passing through the heat exchanger214, a portion of the cooled exhaust gas may be routed along line216(e.g., return conduit) to an upstream compressor stage of the compressor section152, thereby improving the efficiency of compression by the compressor section152. In such an embodiment, the heat exchanger214may be configured as an interstage cooling unit for the compressor section152. In this manner, the cooled exhaust gas helps to increase the operational efficiency of the SEGR gas turbine system52, while simultaneously helping to maintain the purity of the exhaust gas (e.g., substantially free of oxidant and fuel).

FIG. 4is a flow chart of an embodiment of an operational process220of the system10illustrated inFIGS. 1-3. In certain embodiments, the process220may be a computer implemented process, which accesses one or more instructions stored on the memory122and executes the instructions on the processor120of the controller118shown inFIG. 2. For example, each step in the process220may include instructions executable by the controller118of the control system100described with reference toFIG. 2.

The process220may begin by initiating a startup mode of the SEGR gas turbine system52ofFIGS. 1-3, as indicated by block222. For example, the startup mode may involve a gradual ramp up of the SEGR gas turbine system52to maintain thermal gradients, vibration, and clearance (e.g., between rotating and stationary parts) within acceptable thresholds. For example, during the startup mode222, the process220may begin to supply a compressed oxidant68to the combustors160and the fuel nozzles164of the combustor section154, as indicated by block224. In certain embodiments, the compressed oxidant may include a compressed air, oxygen, oxygen-enriched air, oxygen-reduced air, oxygen-nitrogen mixtures, or any combination thereof. For example, the oxidant68may be compressed by the oxidant compression system186illustrated inFIG. 3. The process220also may begin to supply fuel to the combustors160and the fuel nozzles164during the startup mode222, as indicated by block226. During the startup mode222, the process220also may begin to supply exhaust gas (as available) to the combustors160and the fuel nozzles164, as indicated by block228. For example, the fuel nozzles164may produce one or more diffusion flames, premix flames, or a combination of diffusion and premix flames. During the startup mode222, the exhaust gas60being generated by the gas turbine engine156may be insufficient or unstable in quantity and/or quality. Accordingly, during the startup mode, the process220may supply the exhaust gas66from one or more storage units (e.g., storage tank88), the pipeline86, other SEGR gas turbine systems52, or other exhaust gas sources.

The process220may then combust a mixture of the compressed oxidant, fuel, and exhaust gas in the combustors160to produce hot combustion gas172, as indicated by block230. In particular, the process220may be controlled by the control system100ofFIG. 2to facilitate stoichiometric combustion (e.g., stoichiometric diffusion combustion, premix combustion, or both) of the mixture in the combustors160of the combustor section154. However, during the startup mode222, it may be particularly difficult to maintain stoichiometric combustion of the mixture (and thus low levels of oxidant and unburnt fuel may be present in the hot combustion gas172). As a result, in the startup mode222, the hot combustion gas172may have greater amounts of residual oxidant68and/or fuel70than during a steady state mode as discussed in further detail below. For this reason, the process220may execute one or more control instructions to reduce or eliminate the residual oxidant68and/or fuel70in the hot combustion gas172during the startup mode.

The process220then drives the turbine section156with the hot combustion gas172, as indicated by block232. For example, the hot combustion gas172may drive one or more turbine stages174disposed within the turbine section156. Downstream of the turbine section156, the process220may treat the exhaust gas60from the final turbine stage174, as indicated by block234. For example, the exhaust gas treatment234may include filtration, catalytic reaction of any residual oxidant68and/or fuel70, chemical treatment, heat recovery with the HRSG56, and so forth. The process220may also recirculate at least some of the exhaust gas60back to the compressor section152of the SEGR gas turbine system52, as indicated by block236. For example, the exhaust gas recirculation236may involve passage through the exhaust recirculation path110having the EG processing system54as illustrated inFIGS. 1-3.

In turn, the recirculated exhaust gas66may be compressed in the compressor section152, as indicated by block238. For example, the SEGR gas turbine system52may sequentially compress the recirculated exhaust gas66in one or more compressor stages158of the compressor section152. Subsequently, the compressed exhaust gas170may be supplied to the combustors160and fuel nozzles164, as indicated by block228. Steps230,232,234,236, and238may then repeat, until the process220eventually transitions to a steady state mode, as indicated by block240. Upon the transition240, the process220may continue to perform the steps224through238, but may also begin to extract the exhaust gas42via the EG supply system78, as indicated by block242. For example, the exhaust gas42may be extracted from one or more extraction points76along the compressor section152, the combustor section154, and the turbine section156as indicated inFIG. 3. In turn, the process220may supply the extracted exhaust gas42from the EG supply system78to the hydrocarbon production system12, as indicated by block244. The hydrocarbon production system12may then inject the exhaust gas42into the earth32for enhanced oil recovery, as indicated by block246. For example, the extracted exhaust gas42may be used by the exhaust gas injection EOR system112of the EOR system18illustrated inFIGS. 1-3.

FIG. 5is a diagram of a portion of the gas turbine engine150coupled to the HRSG56. Elements inFIG. 5in common with those shown in previous figures are labeled with the same reference numerals. The axial direction of the gas turbine engine150is indicated by arrow260, the radial direction is indicated by arrow262, and the circumferential direction is indicated by arrow264. These directions are all with respect to the rotational axis162. In the illustrated embodiment, the turbine section156includes an upstream end266and a downstream end268. Specifically, the products of combustion172enter the upstream end266and exit the downstream end268as the exhaust gas60. An exhaust section270(e.g., diffuser) is disposed downstream from the downstream end268of the turbine section156. The exhaust section270may be used to expand and/or cool the exhaust gas60before directing the exhaust gas60to the exhaust recirculation path110(e.g., HRSG56). Specifically, a cross-sectional area of the exhaust section270may increase in the direction of the exhaust gas60flow, thereby increasing the static pressure of the exhaust gas60by decreasing the kinetic energy of the exhaust gas60. As shown inFIG. 5, the exhaust section270may include an exhaust passage272to receive the products of combustion172and/or exhaust gas60. In addition, the exhaust section270may include a center body271, which may surround a portion of the rotor of the turbine section156. The center body271may be defined by an inner wall (e.g., inner barrel)273.

In the illustrated embodiment, a mixing device274(e.g., mixer) is disposed in the exhaust section270. Thus, the mixing device274receives the exhaust gas60conveyed by the exhaust passage272. As discussed in detail below, the mixing device274may divide the exhaust gas60into first and second exhaust gases and combine the first and second exhaust gases to produce a mixed exhaust gas276. In addition, the mixing device274may be a static mixing device with no moving parts. As shown inFIG. 5, the mixing device274may be disposed in the exhaust section270upstream of the HRSG56. Specifically, the mixed exhaust gas276may enter an inlet section278of the HRSG56from the mixing device274. The mixed exhaust gas276may expand as the mixed exhaust gas276flows through the inlet section278before reaching a catalyst section280. The catalyst section280may include one or more of any of the catalyst units discussed in detail above, such as, but not limited to, the catalyst unit, the oxidation catalyst unit, or any combination thereof. As discussed below, the mixing device274may be disposed anywhere in the exhaust section270. For example, the mixing device274may be disposed downstream of the center body271or may be coupled to the center body271.

As discussed in detail below, the radial and/or circumferential uniformity of the mixed exhaust gas276may be greater than the radial and/or circumferential uniformity of the exhaust gas60entering the mixing device274. For example, the degree of mixing of the mixed exhaust gas276may be quantified by a mathematical expression in which the concentration of hydrogen is added to the concentration of carbon monoxide and the sum is divided by the concentration of oxygen. Values of mass or volumetric flow rates may also be used in the expression instead of concentrations. In certain embodiments, a value greater than approximately 2 for the expression may indicate sufficient mixing of the components of the mixed exhaust gas276. Thus, values of greater than approximately 2 distributed radially and/or circumferentially throughout the cross-section of the inlet section278may indicate improved radial and/or circumferential uniformity of the mixed exhaust gas276. This improved radial and/or circumferential uniformity of the mixed exhaust gas276may increase the catalyst performance of the catalyst system280. For example, the catalyst section280may be more uniformly affected by the mixed exhaust gas276and thus, the overall life of the catalyst section280may be increased. In contrast, the life of certain portions of the catalyst section280may be decreased when treating the nonuniform products of combustion172and/or exhaust gas60, thereby causing the entire catalyst section280to be replaced even if some portions of the catalyst section280still have additional life. Treated exhaust gas282from the catalyst section280may pass through a first heat exchanger284of the HRSG56. In certain embodiments, the first heat exchanger284(e.g., first HRSG unit) may include a plurality of heat exchanger tubes and may be used to generate steam62. In further embodiments, the HRSG56may include additional heat exchangers (e.g., two, three, four, or more heat exchangers) that use the treated exhaust gas282to produce additional steam62(e.g., second, third, fourth, or more HRSG units). The exhaust gas66exiting from the HRSG56may be recirculated, as described in detail above.

As shown inFIG. 5, the control system100may be used to control one or more aspects of the operation of the gas turbine engine150and/or the HRSG56. Specifically, the control system100may receive one or more input signals286from various sensors disposed throughout the gas turbine engine150and/or the HRSG56. For example, an upstream sensor288may be disposed upstream of the mixing device274and a downstream sensor290may be disposed downstream of the mixing device274. In other embodiments, a plurality of sensors (e.g., a grid) may be located at one axial260location in the inlet section278and distributed radially262and/or circumferentially264throughout the inlet section278to provide an indication of the radial and/or circumferential uniformity of the mixed exhaust gas276. In further embodiments, the plurality of sensors maybe distributed at different axial260, radial262, and/or circumferential264positions upstream and/or downstream of the mixing device274. In the illustrated embodiment, the upstream sensor288may provide information to the control system100indicative of the properties of the exhaust gas60entering the mixing device274and the downstream sensor290may send information indicative of the properties of the mixed exhaust gas276. For example, the upstream and downstream sensors288and290may provide information indicative of the temperature, pressure, flow rate, and/or composition (e.g., oxygen, fuel, carbon monoxide, etc.) of the exhaust gas60and the mixed exhaust gas276, respectively. Thus, the information provided by the upstream and downstream sensors288and290may be used by the control system100to determine the effectiveness of the mixing device274. The control system100may then send an output signal292to one or more control elements294based on the performance of the mixing device274. The control elements294may represent various elements of the gas turbine engine150and/or the HRSG56, such as, but limited to, control valves, motors, actuators, or any combination thereof.

FIG. 6is a schematic diagram of an embodiment of the mixing device274, which may be mounted in any location within the exhaust section270. In other words, the mixing device274may be located in the exhaust section270anywhere between the turbine156and the HRSG56. For example, the mixing device274may be placed on the center body271and coupled to the inner barrel273of the exhaust section270. As shown inFIG. 6, the exhaust gas60enters an upstream side310of the mixing device274and the mixed exhaust gas276exits a downstream side312. In addition, the mixing device274includes a first section314and a second section316that circumferentially264surrounds the first section314. Thus, the mixing device274divides the exhaust gas60into a first exhaust gas318and a second exhaust gas320. In other words, the first section314conveys the first exhaust gas318in a central region (e.g., a central exhaust gas flow) and the second section316conveys the second exhaust gas320in a peripheral region (e.g., a peripheral exhaust gas flow). As shown inFIG. 6, the first section314conveys the first exhaust gas318to a mixing region322, and the second section316conveys the second exhaust gas320to the mixing region322. Thus, the first and second exhaust gases318and320mix in the mixing region322to generate the mixed exhaust gas276. In certain embodiments, the first section314may have a constant width, an increasing width, a decreasing width, or a combination thereof in the downstream direction. In other words, the first section314may have a constant cross-section, a diverging cross-section, or a converging cross-section.

In certain embodiments of the mixing device274, the second section316may have an annular shape surrounding the first section314. In other embodiments, the second section316may have a rectangular, square, oval, triangular, polygonal or other shape. In further embodiments, the first and second sections314and316may be mounted independently from one another in the exhaust section270. For example, the first section314may be upstream of the second section316or vice versa. In further embodiments, the mixing device274may include only the first section314or only the second section316. For example, the first section314may divide the exhaust gas60into the first exhaust gas318and the portion of the exhaust gas60not passing through the first section314may be the second exhaust gas320. Similarly, the second section316may divide the exhaust gas60into the second exhaust gas320and the portion of the exhaust gas60not passing through the second section316may be the first exhaust gas318. In either embodiment, the first and second exhaust gases318and320are mixed together in the mixing region322to generate the mixed exhaust gas276. In addition, the mixing device274may have various configurations to generate the mixed exhaust gas276, as described in detail below.

FIG. 7is an axial cross-sectional view of an embodiment of the mixing device274. As shown inFIG. 7and described in detail below, the mixing device274is a static mixing device with no moving parts. In the illustrated embodiment, the first section314is a lobe mixer with an inlet340and an outlet342. Lobe mixers generally have an annular, lobe-shaped (e.g., sinusoidal) surface that divides a gas stream into inner and outer portions. In addition, lobe mixers may have a lower pressure drop than other mixing devices. Further, the shape and/or number of lobes of the lobe mixer may be adjusted to achieve a desired separation of the gas stream. As shown in FIG.7, the first exhaust gas318enters and flows through the first section314(e.g., lobe mixer), which divides the first exhaust gas318into a first portion344directed away from the axial axis260and a second portion346directed toward the axial axis260. As shown inFIG. 7, a longitudinal axis348of the mixing device274may be generally parallel with the axial axis260. Thus, the first section314surrounds the longitudinal axis348. By dividing the first exhaust gas318into the first and second portions344and346, the first section314may improve the mixing of the first exhaust gas318with the second exhaust gas320. Specifically, the first portion344may be directed toward the second exhaust gas320to mix thoroughly with the second exhaust gas320. The second portion346may also mix with the first portion344and/or the second exhaust gas320. In the illustrated embodiment, the first section314has a diverging or expanding wall with an upstream diameter350that is less than a downstream diameter352. Thus, the first exhaust gas318may generally expand as the first exhaust gas318flows through the first section314. In other embodiments, the first section314has a converging or contracting wall with the upstream diameter350less than the downstream diameter352. In some embodiments, the upstream and downstream diameters350and352may be approximately the same. In further embodiments, other types of mixers and/or flow separators may be used as the first section314instead of the lobe mixer shown inFIG. 7. In some embodiments, one or more fixtures (e.g., radial supports) may be coupled to the first section314and/or the second section316to help support the sections within the exhaust section270. In certain embodiments, the first section314and/or the second section316may be coupled to the inner barrel273of the center body271for support, as indicated by the dashed lines inFIG. 7. In further embodiments, the first section314may be conical, curved, annular, convex, or concave. For example, a wall of the first section314may be tapered or curved in the downstream direction with an annular, rectangular, or other cross-section.

As shown inFIG. 7, the second section316includes an inner annular wall354, an outer annular wall356surrounding the inner annular wall354, and an annular passage358disposed between the inner and outer annular walls354and356. The annular passage358may convey the second exhaust gas320to the mixing region322. The inner annular wall354may be generally straight and may include a plurality of openings360to convey the second exhaust gas320from the annular passage358to the mixing region322. As shown inFIG. 7, the plurality of openings360may be configured to generally direct the second exhaust gas320toward the longitudinal axis348to help increase mixing of the first and second exhaust gases318and320. Thus, the second exhaust gas320may mix with the first and second portions344and346of the first exhaust gas318in the mixing region322to generate the mixed exhaust gas276exiting the downstream side312of the mixing device274. As shown inFIG. 7, an upstream diameter362of the inner annular wall354is less than a downstream diameter364. Thus, the inner annular wall354may have a generally conical shape that diverges toward the downstream side312. In other embodiments, the upstream diameter362may be greater than the downstream diameter364(i.e., the conical shape converges toward the downstream side312) or the upstream and downstream diameters362and364may be approximately the same. For example, the inner annular wall354may have a generally conical shape in an opposite direction than that shown inFIG. 7or may have a generally cylindrical shape. The degree of the conical shape of the inner annular wall354may be characterized by an inner annular wall angle366with respect to the longitudinal axis348.

In addition, the outer annular wall356of the second section316may be characterized by an upstream diameter368and a downstream diameter370. As shown inFIG. 7, the upstream diameter368is less than the downstream diameter370. Thus, the outer annular wall356has a generally conical shape. In other embodiments, the outer wall356may have an oval, square, rectangular, triangular, polygonal, or other cross-sectional shape. Thus, the mixing device274may generally follow the expanding shape of the exhaust section270to which the mixing device274is coupled thereto. As a result of the conical shapes of the inner and outer annular walls354and356, a cross-sectional area of the annular passage358may generally decrease from the upstream side310toward the downstream side312. In other embodiments, the upstream diameter368may be greater than the downstream diameter370or the upstream and downstream diameters368and370may be approximately the same. In certain embodiments, a portion372of the second exhaust gas320may exit the second section316through openings374between the inner and outer annular walls354and356to help provide cooling and/or help reduce hot spots adjacent the outer annular wall356downstream of the mixing device274. In further embodiments, the second section316may have a rectangular, square, triangular, polygonal, oval, or other cross-sectional shape and the second section316may have walls that diverge, converge or are approximately the same distance from one another.

FIG. 8is a radial perspective view of an embodiment of the mixing device274. The axial cross-sectional view of the mixing device274shown inFIG. 7is taken along the line7-7ofFIG. 8. As shown inFIG. 8, the second section316circumferentially264surrounds the first section314. In addition, the plurality of openings360are distributed uniformly circumferentially about the inner annular wall354of the second section316. For example, the plurality of openings360may be arranged in a pattern of radial spokes (e.g., aligned in the radial direction262) and circumferential rings (e.g., concentric rings of openings360). Thus, the second section316provides a generally uniform distribution of the second exhaust gas320. In other embodiments, the pattern of the plurality of openings360may be different than that shown inFIG. 8or may be an irregular pattern. For example, more of the plurality of openings360may be distributed toward the longitudinal axis348than toward the outer annular wall356or vice versa. In the illustrated embodiment, each of the plurality of openings360may be of approximately the same size. In other embodiments, sizes of the plurality of openings360may be adjusted to achieve a desired mixing of the first and second exhaust gases318and320. For example, increasing the sizes of the plurality of openings360may reduce the pressure drop associated with the second section316. Thus, by combining the low pressure drop of the first section314(e.g., lobe mixer) with the low pressure drop of the second section316may produce a mixing device274with an overall low pressure drop. In various embodiments, the mixing device274may have a pressure loss between approximately 125 pascals to approximately 500 pascals, approximately 200 pascals to approximately 425 pascals, approximately 250 pascals to approximately 375 pascals, or approximately 300 pascals to approximately 325 pascals. For example, in one embodiment, the mixing device274may have a pressure loss less than approximately 500 pascals. By using embodiments of the mixing device274with such low pressure drops, there may be little to no change to the efficiency of the gas turbine engine150and/or the pressure recovery of the exhaust section270. In other words, the mixing device274may have only a small effect on the efficiency and/or pressure recovery. In other embodiments, the plurality of openings360may have different shapes, such as, but not limited to, circles, ovals, squares, rectangles, triangles, polygons, slots, and so forth.

As illustrated inFIG. 8, each of the plurality of openings360has an axis oriented at an offset from the longitudinal axis348, such that the plurality of openings360imparts a swirling motion to the second exhaust gas320, as represented by the direction of the arrows representing the second exhaust gas320. In other words, the second exhaust gas320has a generally clockwise circumferential swirling motion, as shown inFIG. 8. In other embodiments, the plurality of openings360may impart a generally counterclockwise circumferential swirling motion to the second exhaust gas320. In further embodiments, the plurality of openings360may impart both clockwise and counterclockwise swirling motion to the second exhaust gas320. For example, a first circumferential ring of openings360may impart a clockwise swirling motion and a second circumferential ring of openings360disposed inside or outside the first circumferential ring may impart a counterclockwise swirling motion to help increase mixing of the second exhaust gas320with the first exhaust gas318. In such embodiments, the plurality of openings360may be disposed in a pattern including 2, 3, 4, 5, or more circumferential rings.

As shown inFIG. 8, the first section314is a lobe mixer with an annular sinusoidal shape. As illustrated, the annular sinusoidal shape of the first section314includes alternating first open-ended passages390and second open-ended passages392. The first open-ended passages390direct the first portion344of the first exhaust gas318away from the longitudinal axis348and the second open-ended passages392direct the second portion346of the first exhaust gas318toward the longitudinal axis348. Thus, the first and second portions344and346may diverge from one another. The first section314(e.g., lobe mixer) may also be characterized by peaks394and valleys396. The peaks394may correspond to the first open-ended passages390and the valleys396may correspond to the second open-ended passages392. Although shown with a particular shape and arrangement of first and second open-ended passages390and392inFIG. 8, in other embodiments, the first section314(e.g., lobe mixer) may have other configurations to achieve a desired mixing of the first and second exhaust gases318and320to generate the mixed exhaust gas276. For example, the shape of the first section314(e.g., lobe mixer) may be adjusted and/or the number of peaks394and valleys396may be varied. In certain embodiments, the first section314(e.g., lobe mixer) may be configured to impart a swirling motion to the first exhaust gas318. In other words, each of the first and second open-ended passages390and392may have an axis oriented at an offset from the longitudinal axis348such that the passages390and392impart a swirling motion to the first exhaust gas318, as represented by the direction of the arrows representing the first and second portions344and346. As shown inFIG. 8, the first and second portions344and346may have a generally counterclockwise swirling motion. Thus, the first and second section314and316may impart opposite swirling motions to the first and second exhaust gases318and320to improve mixing of the mixed exhaust gas276, thereby improving the radial and/or circumferential uniformity of the mixed exhaust gas276. In other words, the mixing device274homogenizes the spatial (or radial and/or circumferential) variation of the exhaust gas60to produce the mixed exhaust gas276. In other embodiments, the first and second sections314and316may impart swirling motions to the first and second exhaust gases318and320in the same direction.

FIG. 9is a partial perspective view of the first section314. As shown inFIG. 9, the first section314is a lobe mixer. As illustrated, the first exhaust gas318is divided into the first and second portions344and346by the first and second open-ended passages390and392. Although only a portion of the first section314is shown inFIG. 9, it is understood that the alternating sinusoidal pattern (e.g., wavy, zig-zagy, alternating inward and outward curving, etc.) of the first section314(e.g., lobe mixer) may continue circumferentially264about the longitudinal axis348. As illustrated, the first open-ended passages390(e.g., peaks394) may be characterized by a first width398and the second open-ended passages392(e.g., valleys396) may be characterized by a second width400. As shown inFIG. 9, the width398of the first open-ended passages390may be greater than the width400of the second open-ended passages392to direct more of the first exhaust gas318into the first portion344than the second portion346. In other embodiments, the second width400may be greater than the first width398or the first and second widths398and400may be approximately the same.

FIG. 10is a partial perspective view of the first section314of the mixing device274with scalloped lobes410. In other words, the scalloped lobes410have portions removed (e.g., radial openings or cuts) compared to the first section314(e.g., lobe mixer) shown inFIG. 9. The scalloped lobes410may affect the distribution of the first and second portions344and346. In addition, the scalloped lobes410may improve the amount of mixing of the first and second exhaust gases318and320, thereby improving radial and/or circumferential uniformity of the mixed exhaust gas276.

FIG. 11is a partial perspective view of the first section314of the mixing device274with multiple lobes. Specifically, each of the peak areas394may include a first peak420, a second peak422, and a valley424, which may change the distribution of the first and second portions344and346. In addition, the configuration of the peak area394may direct more of the first exhaust gas318toward the second exhaust gas320, thereby improving radial and/or circumferential uniformity of the mixed exhaust gas276. In certain embodiments, one or more of the lobes of the first section314may include turbulators to increase the amount of mixing of the mixed exhaust gas276.

FIG. 12is a perspective view of the first section314of the mixing device274with angled lobes. Specifically, each of the lobes may be aligned with a lobe axis440that is offset from a radial axis442by an angle444, which may impart a swirling motion to the first and second portions344and346of the first exhaust gas318. Thus, the first section314shown inFIG. 12may help improve circumferential mixing of the first and second exhaust gases318and320, thereby improving radial and/or circumferential uniformity of the mixed exhaust gas276. In addition, the first section314may cause more of the second exhaust gas320to move toward the first exhaust318, also improving the radial and/or circumferential uniformity of the mixed exhaust gas276.

FIG. 13is a perspective view of the first section314of the mixing device274with ribbed lobes460, which may increase mixing of the first and second exhaust gases318and320, thereby improving the radial and/or circumferential uniformity of the mixed exhaust gas276. In certain embodiments, the ribbed lobes460may be uniform or non-uniform, may increase or decrease in frequency or amplitude of waves that define the ribs in either the radial inward or outward direction. The amount of ribbing may vary from one lobe to another or be the same.

FIG. 14is a perspective view of the first section314of the mixing device274with serrated lobes470(i.e., edges of the lobes are serrated), which may increase mixing of the first and second exhaust gases318and320, thereby improving the radial and/or circumferential uniformity of the mixed exhaust gas276. In certain embodiments, the serrated lobes460may be uniform or non-uniform, may increase or decrease in frequency or amplitude of waves. The amount of serrating may vary from one lobe to another or be the same.

FIG. 15is an axial cross-sectional view of an embodiment of the mixing device274. In the illustrated embodiment, the inner annular wall354of the second section316gradually expands (e.g., diverges) and then contracts (e.g., converges) in a downstream direction, thereby defined a curved shape of the wall in the downstream direction. Specifically, the inner annular wall354has a concave shape in the downstream direction along the longitudinal axis348. Thus, the second exhaust gas320may be directed toward the first exhaust gas318in a different manner than that of the mixing device274shown inFIG. 7. Accordingly, the mixed exhaust gas276may have a different radial and/or circumferential uniformity than that shown inFIG. 7. In addition, the upstream diameter362of the inner annular wall354is greater than the downstream diameter364. Thus, the cross-sectional area of the annular passage358generally decreases and then increases from the upstream side310to the downstream side312. In other embodiments, the upstream diameter362may be less than the downstream diameter364or the upstream and downstream diameters362and364may be approximately the same. In certain embodiments, more of the second exhaust gas320may exit the second section316through the openings374. In other respects, the embodiment of the mixing device274shown inFIG. 10is similar to other embodiments described in detail above.

FIG. 16is an axial cross-sectional view of an embodiment of the mixing device274. In the illustrated embodiment, the inner annular wall354gradually contracts (e.g., converges) and then expands (e.g., diverges) in a downstream direction, thereby defining a curved shape of the wall in the downstream direction. Specifically, the inner annular wall354has a convex shape in the downstream direction along the longitudinal axis348. Thus, the second exhaust gas320may be directed toward the first exhaust gas318in a different manner than that of the mixing devices274shown inFIGS. 7 and 15. Accordingly, the mixed exhaust gas276may have a different radial and/or circumferential uniformity than that shown inFIGS. 7 and 15. In addition, the upstream diameter362of the inner annular wall354is less than the downstream diameter364. Thus, the cross-sectional area of the annular passage358generally increases and then decreases from the upstream side310to the downstream side312. In other embodiments, the upstream diameter362may be greater than the downstream diameter364or the upstream and downstream diameters362and364may be approximately the same. In other respects, the embodiment of the mixing device274shown inFIG. 15is similar to other embodiments described in detail above.

FIG. 17is a partial perspective view of the second section316of an embodiment of the mixing device274with vortex generators480, which may be shaped and/or configured in a variety of ways. For example, the vortex generators480may have a generally triangular cross-sectional shape that increases in the downstream direction. As shown inFIG. 17, the vortex generators480may be coupled to an inner surface of the outer annular wall356. Such vortex generators480may impart turbulence and/or a vortex to the second exhaust gas320downstream of the vortex generators480, thereby increasing the radial and/or circumferential uniformity of the mixed exhaust gas276. In addition, the vortex generators480may provide additional mixing near the outer annular wall356.

FIG. 18is a partial perspective view of the second section316of an embodiment of the mixing device274with semi-spherical protrusions490, which may impart turbulence and/or a vortex to the second exhaust gas320downstream of the vortex generators480, thereby increasing the radial and/or circumferential uniformity of the mixed exhaust gas276. As shown inFIG. 17, the semi-spherical protrusions480may be coupled to an inner surface of the outer annular wall356. In addition, the semi-spherical protrusions490may provide additional mixing near the outer annular wall356. In other embodiments, the semi-spherical protrusions490may have other shapes, such as cylindrical rods, squares, triangles, and so forth.

FIG. 19is a partial perspective view of the second section316of an embodiment of the mixing device274with guide vanes (e.g., impellers)500coupled to the inner surface of the outer annular wall356. The guide vanes500may be shaped and/or configured in a variety of ways to impart a swirl to the second exhaust gas320. For example, as shown inFIG. 19, the guide vanes500may be shaped to redirect the flow of the second exhaust gas320from generally parallel to the axial direction260to being offset at an angle502from the longitudinal axis348as indicated by arrows501, thereby imparting swirl to the second exhaust gas320. In various embodiments, the swirl imparted to the second exhaust gas320may be in a clockwise direction or a counterclockwise direction. Thus, the guide vanes500of the second section316shown inFIG. 19may help improve circumferential mixing of the first and second exhaust gases318and320, thereby improving radial and/or circumferential uniformity of the mixed exhaust gas276.

FIG. 20is a partial perspective view of the second section316of an embodiment of the mixing device274with open lobes (i.e., flow enters both above and below each lobe). Specifically, the second exhaust gas320may enter the upstream side310of the second section316(e.g., lobe mixer) and exit as a first outer stream520and a second outer stream522, which both may then mix with the first exhaust gas318to produce the mixed exhaust gas276. As with the first section314, the shape and/or number of lobes of the lobe mixer of the second section316may be adjusted to achieve a desired separation of the gas second exhaust gas320into the first and second outer streams520and522.

FIG. 21is a partial perspective view of the second section316of an embodiment of the mixing device274with closed lobes (i.e., flow enters only below each lobe). Specifically, a portion of the second exhaust gas320may enter the upstream side310of the second section316(e.g., lobe mixer) and exit as a first outer stream520and the rest of the second exhaust gas320may bypass the second section316. As with the first section314, the shape and/or number of lobes of the lobe mixer of the second section316may be adjusted to achieve a desired separation of the gas second exhaust gas320into the first and second outer streams520and522.

FIG. 22is a diagram of a portion of the gas turbine engine150coupled to the HRSG56. Elements inFIG. 22in common with those shown in previous figures are labeled with the same reference numerals. In the illustrated embodiment, the mixing device274(e.g., mixer) divides the exhaust gas60into first and second exhaust gases and combines the first and second exhaust gases to produce the mixed exhaust gas276. As shown inFIG. 22, the gas turbine engine150includes an exhaust injection system540that injects a pressurized exhaust gas (e.g., the exhaust gas42, exhaust gas60, or exhaust gas66, or any combination thereof) into the mixing device274. In various embodiments, the pressurized exhaust gas may be any low-oxygen containing gas present or generated in the turbine-based service system14that is at a pressure greater than the pressure of the exhaust section270. For example, the pressurized exhaust gas may be exhaust gas42extracted from the combustors160or from one or more stages of the compressor section152. As described in detail below, the injection of the pressurized exhaust gas may further improve mixing of the first and second exhaust gases to produce the mixed exhaust gas276. For example, the injection of the pressurized exhaust gas may further homogenize any spatial variation in the mixed exhaust gas276, which may increase the catalyst performance of the catalyst system280, as described in detail above. In certain embodiments, the exhaust injection system540may be disposed upstream of the mixing device274.

In shown inFIG. 22, the flow of the pressurized exhaust gas (e.g., the exhaust gas42, exhaust gas60, or exhaust gas66, or any combination thereof) to the exhaust gas injection system540may be adjusted using the control element294(e.g., a control valve). In addition, a catalyst system sensor542may be disposed in the catalyst system280and used to provide an indication of the condition of the catalyst system280. In certain embodiments, a plurality of catalyst system sensors542(e.g., a grid) may be located within the catalyst system280. The catalyst system sensor542may provide an indication of a pressure, temperature, flow rate, and/or composition within the catalyst system280. The control system100may receive the input signal286from at least one of the catalyst system sensor542, the upstream sensor288, or the downstream sensor290, or any combination thereof to determine whether to adjust the flow rate of the pressurized exhaust gas to the exhaust gas injection system540using the control element294(e.g., control valve). For example, the plurality of catalyst system sensors542may indicate that some portions of the catalyst system280are at a higher temperature than other portions, which may indicate a nonuniform distribution of the mixed exhaust gas276. In response, the control system100may increase the flow of the pressurized exhaust gas to the exhaust gas injection system540to help increase the uniformity of the mixed exhaust gas276.

FIG. 23is an axial cross-sectional view of an embodiment of the mixing device274. Elements inFIG. 23in common with those shown in previous figures are labeled with the same reference numerals. In the illustrated embodiment, the exhaust injection system540injects the pressurized exhaust gas (e.g., the exhaust gas42, exhaust gas60, or exhaust gas66, or any combination thereof) into the mixing device274. Specifically, the exhaust injection system540includes one or more injection structures550to convey the pressurized exhaust gas to portions of the mixing device274. In certain embodiments, each injection structure550may be a tube, pipe, conduit, or other structure configured to convey the pressurized exhaust gas. In particular embodiments, each injection structure550may be routed along one or more support structures disposed within the exhaust section270and/or mixing device274(e.g., support structures for the first section314). In addition, the one or more injection structures550may include a plurality of injection openings552to enable the pressurized exhaust gas to mix with the first exhaust gas318and/or the second exhaust gas320. For example, in various embodiments, the exhaust injection system540may be used to inject the pressurized exhaust gas into the first section314, the second section316, or both sections314and316depending on where additional homogenization of the mixed exhaust gas276is desired. In further embodiments, the exhaust injection system540may be configured to have a low pressure drop, thereby increasing the efficiency of the gas turbine engine150and/or improving the pressure recovery of the exhaust section270. For example, the injection structures550may have an aerodynamic cross-sectional shape. In other embodiments, it is envisioned that other configurations of the injection structure550and injection openings552may be used for the exhaust injection system540.

As described above, certain embodiments of the gas turbine engine150may include a combustor section154having one or more combustors160configured to generate combustion products. In addition, the gas turbine engine150may include the turbine section156having one or more turbine stages174between the upstream end266and the downstream end268, and the exhaust section270disposed downstream from the downstream end268. The mixing device274may be coupled to the exhaust section270. The mixing device274may divide the exhaust gas60into the first exhaust gas318and the second exhaust gas320, and combine the first and second exhaust gases318and320in the mixing region322to produce the mixed exhaust gas276. As a result of this process, the mixed exhaust gas276may have a more uniform radial and/or circumferential distribution of properties than the exhaust gas60. For example, one or more of the pressure, temperature, flow rate, and/or composition of the mixed exhaust gas276may be more radially and/or circumferentially uniform than the exhaust gas60. The improved radial and/or circumferential uniformity of the mixed exhaust gas276may have a positive impact on downstream equipment and processes. For example, the improved radial and/or circumferential uniformity of the composition of the mixed exhaust gas276may improve the performance of the catalyst section280. In addition, the configuration of the mixing device274may have a low pressure drop, thereby improving the overall pressure recovery of the exhaust section270. Thus, use of the mixing device274may improve the overall efficiency and cost-effectiveness of the SEGR gas turbine system52.

Additional Description

The present embodiments provide systems and methods for gas turbine engines. It should be noted that any one or a combination of the features described above may be utilized in any suitable combination. Indeed, all permutations of such combinations are presently contemplated. By way of example, the following clauses are offered as further description of the present disclosure:

A system, comprising: a combustor section having one or more combustors configured to generate combustion products; a turbine section having one or more turbine stages between an upstream end and a downstream end, wherein the one or more turbine stages are driven by the combustion products an exhaust section disposed downstream from the downstream end of the turbine section, wherein the exhaust section has an exhaust passage configured to receive the combustion products as an exhaust gas; and a mixing device disposed in the exhaust section, wherein the mixing device is configured to divide the exhaust gas into a first exhaust gas and a second exhaust gas, and to combine the first and second exhaust gases in a mixing region to produce a mixed exhaust gas.

The system of embodiment 1, wherein the mixing device comprises a first section configured to convey the first exhaust gas to the mixing region and a second section configured to convey the second exhaust gas to the mixing region, wherein the second section circumferentially surrounds the first section.

The system defined in any preceding embodiment, wherein the first section is disposed surrounding a longitudinal axis of the mixing device, and the second section comprises an annular shape surrounding the first section.

The system defined in any preceding embodiment, wherein the second section comprises a plurality of openings configured to convey the second exhaust gas to the mixing region.

The system defined in any preceding embodiment, wherein the plurality of openings are distributed uniformly circumferentially about the second section.

The system defined in any preceding embodiment, wherein each of the plurality of openings has an axis oriented at an offset from a longitudinal axis of the mixing device such that the plurality of openings are configured to impart a swirling motion to the second exhaust gas.

The system defined in any preceding embodiment, an inner annular wall; an outer annular wall surrounding the inner annular wall; and an annular passage disposed between the inner and outer annular walls, wherein the annular passage is configured to convey the second exhaust gas to the mixing region.

The system defined in any preceding embodiment, wherein the inner annular wall comprises a cylindrical shape or a tapered shape.

The system defined in any preceding embodiment, wherein the inner annular wall converges toward a downstream end of the mixing device, or diverges toward the downstream end.

The system defined in any preceding embodiment, wherein the inner annular wall is straight or curved.

The system defined in any preceding embodiment, wherein the first section comprises at least one of a lobe mixer, a scalloped lobe mixer, a multiple-lobe mixer, an angled lobe mixer, a ribbed lobe mixer, or a serrated lobe mixer, or any combination thereof.

The system defined in any preceding embodiment, wherein the first section comprises a lobe mixer having an annular sinusoidal shape with alternating first and second open-ended passages, the first open-ended passages are configured to direct a first portion of the first exhaust gas away from a longitudinal axis of the mixing device, and the second open-ended passages are configured to direct a second portion of the first exhaust gas toward the longitudinal axis.

The system defined in any preceding embodiment, wherein the first section comprises a lobe mixer configured to divide the first exhaust gas into an inner first exhaust gas and an outer first exhaust gas.

The system defined in any preceding embodiment, wherein the lobe mixer is configured such that the inner and outer first exhaust gases diverge from one another.

The system defined in any preceding embodiment, wherein the lobe mixer is configured to impart a swirling motion to the first exhaust gas.

The system defined in any preceding embodiment, wherein the first section is configured to impart swirling motion to the first exhaust gas in a first direction, the second section is configured to impart swirling motion to the second exhaust gas in a second direction, and the first and second directions are opposite from one another.

The system defined in any preceding embodiment, comprising a catalyst disposed downstream from the mixing device, wherein the catalyst is configured to treat the mixed exhaust gas from the mixing device to produce a treated exhaust gas.

The system defined in any preceding embodiment, comprising a heat recovery steam generator (HRSG) disposed downstream from the catalyst, wherein the HRSG is configured to generate steam by heating water with the treated exhaust gas.

The system defined in any preceding embodiment, wherein a pressure loss of the mixing device is less than approximately 500 pascals.

The system defined in any preceding embodiment, wherein the second section comprises at least one of a vortex generator, a semi-spherical protrusion, a lobe mixer, an open lobe mixer, or a closed lobe mixer, or any combination thereof.

The system defined in any preceding embodiment, comprising an exhaust gas extraction system coupled to the gas turbine engine, and a hydrocarbon production system coupled to the exhaust gas extraction system.

The system defined in any preceding embodiment, wherein the gas turbine engine is a stoichiometric exhaust gas recirculation (SEGR) gas turbine engine.

The system defined in any preceding embodiment, comprising an exhaust gas injection system configured to inject a pressurized exhaust gas at least into the mixing device, or upstream of the mixing device, or any combination thereof.

The system defined in any preceding embodiment, comprising a control element configured to adjust a flow of the pressurized exhaust gas to the exhaust gas injection system.

The system defined in any preceding embodiment, comprising a sensor disposed at least upstream of the mixing device, downstream of the mixing device, or within a catalyst disposed downstream from the mixing device, or any combination thereof, wherein the sensor is configured to provide a signal indicative of a temperature, pressure, flow rate, or composition, or any combination thereof.

The system defined in any preceding embodiment, wherein the exhaust gas injection system comprises an injection structure with a plurality of injection holes configured to inject the pressurized exhaust gas.

A system, comprising: a turbine exhaust section configured to mount downstream from a turbine section of a gas turbine engine, wherein the turbine exhaust section comprises an exhaust passage configured to receive exhaust gas from the turbine section; and a mixing device disposed in the turbine exhaust section, wherein the mixing device is configured to divide the exhaust gas into a first exhaust gas and a second exhaust gas, and to combine the first and second exhaust gases to produce a mixed exhaust gas.

The system defined in any preceding embodiment, comprising the gas turbine engine having the turbine exhaust section coupled to the turbine section.

The system defined in any preceding embodiment, wherein the gas turbine engine comprises: the turbine section having one or more turbine stages between an upstream end and a downstream end; a combustor section having a turbine combustor configured to generate combustion products to drive the one or more turbine stages in the turbine section; and a compressor section having an exhaust gas compressor driven by the turbine section, wherein the exhaust gas compressor is configured to compress and route the exhaust gas to the turbine combustor; wherein the turbine exhaust section is coupled to the gas turbine engine downstream from the downstream end of the turbine section.

The system defined in any preceding embodiment, wherein the gas turbine engine is a stoichiometric exhaust gas recirculation (SEGR) gas turbine engine.

The system defined in any preceding embodiment, wherein the mixing device comprises a first section configured to convey the first exhaust gas to a mixing region and a second section configured to convey the second exhaust gas to the mixing region, wherein the second section circumferentially surrounds the first section.

The system defined in any preceding embodiment, wherein the second section comprises: an inner annular wall; an outer annular wall surrounding the inner annular wall; and an annular passage disposed between the inner and outer annular walls, wherein the annular passage is configured to convey the second exhaust gas to the mixing region.

The system defined in any preceding embodiment, wherein the first section comprises a lobe mixer.

The system defined in any preceding embodiment, wherein the first section is configured to impart swirling motion to the first exhaust gas in a first direction, the second section is configured to impart swirling motion to the second exhaust gas in a second direction, and the first and second directions are opposite from one another.

The system defined in any preceding embodiment, wherein a pressure loss of the mixing device is less than approximately 500 pascals.

The system defined in any preceding embodiment, comprising an exhaust gas injection system configured to inject a pressurized exhaust gas at least into the mixing device, or upstream of the mixing device, or any combination thereof.

A system, comprising: a turbine mixing device configured to mount in a turbine exhaust section of a gas turbine engine, wherein the mixing device comprises a first section configured to convey an inner portion of an exhaust gas from the turbine exhaust section to a mixing region, and a second section configured to convey an outer portion of the exhaust gas to the mixing region, wherein the second section circumferentially surrounds the first section, and the mixing region is configured to mix the inner and outer portions of the exhaust gas to produce a mixed exhaust gas.

The system defined in any preceding embodiment, comprising the gas turbine engine having the turbine mixing device mounted in the turbine exhaust section.

The system defined in any preceding embodiment, wherein the first section is disposed surrounding a longitudinal axis of the mixing device, and the second section comprises an annular shape surrounding the first section.

The system defined in any preceding embodiment, wherein the first section comprises an annular sinusoidal shape comprising alternating first and second open-ended passages, the first open-ended passages are configured to direct a first portion of the inner portion of the exhaust gas away from a longitudinal axis of the mixing device, and the second open-ended passages are configured to direct a second portion of the inner portion of the exhaust gas toward the longitudinal axis.

The system defined in any preceding embodiment, comprising an exhaust gas injection system coupled to the turbine mixing device and configured to inject a pressurized exhaust gas into the turbine mixing device.

A method, comprising: combusting a fuel with an oxidant and an exhaust gas in a combustion portion of a turbine combustor to generate combustion products; driving a turbine with the combustion products from the turbine combustor; expanding the combustion products from the turbine through an exhaust passage in an exhaust section; dividing the combustion products from the exhaust section into a first exhaust gas and a second exhaust gas using a mixing device; and combining the first and second exhaust gases to produce a mixed exhaust gas using the mixing device such that a downstream radial uniformity of the mixed exhaust gas is greater than an upstream radial uniformity of the combustion products.

The method or system defined in any preceding embodiment, comprising conveying the first exhaust gas to a mixing region using a first section of the mixing device; and conveying the second exhaust gas to the mixing region using a second section of the mixing device disposed circumferentially surrounding the first section.

The method or system defined in any preceding embodiment, comprising conveying the second exhaust gas through a plurality of openings formed in the second section.

The method or system defined in any preceding embodiment, comprising imparting swirling motion to the first exhaust gas in a first direction using the first section; and imparting swirling motion to the second exhaust gas in a second direction using the second section, wherein the first and second directions are opposite from one another.

The method or system defined in any preceding embodiment, comprising dividing the first exhaust gas into an inner first exhaust gas and an outer first exhaust gas using a lobe mixer, wherein the inner and outer first exhaust gases diverge from one another.

The method or system defined in any preceding embodiment, wherein combusting comprises substantially stoichiometrically combusting the fuel with the oxidant and the exhaust gas.

The method or system defined in any preceding embodiment, comprising extracting a portion of the exhaust gas, and routing the portion of exhaust gas to a hydrocarbon production system.

The method or system defined in any preceding embodiment, comprising injecting a pressurized exhaust gas at least into the mixing device, or upstream of the mixing device, or any combination thereof using an exhaust gas injection system.