Expander for oxy-fuel combustion cycles and similar

Description

1 / 22 EXPANDER FOR OXY-FUEL AND SIMILAR COMBUSTION CYCLES DESCRIPTION TECHNICAL FIELD

[0001] The present disclosure relates to gas expanders particularly adapted for use in oxy-fuel combustion cycles operating with process gas at high pressures, for example, CO2 cycles (SCO2 cycles), such as Aliam cycles, also called NET Power Cycle. FUNDAMENTALS OF THE TECHNIQUE

[0002] Fossil fuels are an important source of chemical energy used for the generation of mechanical power. Fossil fuels are mixed with air and burned to generate a high-pressure, high-temperature combustion gas, which expands in an expander. The expander converts the enthalpy of the combustion gas into mechanical power available at the turbine output shaft and used to drive a load, such as a compressor or compressor train, or to turn an electric generator and convert mechanical power into electrical energy.

[0003] One of the main concerns regarding the combustion of fossil fuels relates to the production of carbon dioxide, a greenhouse gas considered one of the main contributors to global warming and climate change.

[0004] To reduce the environmental impact of energy generation through the combustion of fossil fuels, the option of post-combustion carbon dioxide capture has been investigated. Carbon dioxide capture facilities have been developed to process exhaust combustion gases from gas turbines and remove carbon dioxide from them before discharging the combustion gases into the environment. The costs of a carbon dioxide capture facility are high, both in terms of CAPEX and in terms of the energy required to operate the facility, which reduces the overall thermodynamic efficiency of the system. The percentage of carbon dioxide Petition 870250086194, dated 09 / 24 / 2025, page 16 / 197 The carbon content in flue gas is low at 2 / 22. This requires large volumes of flue gas to be processed through the carbon dioxide capture facility and makes the capture process particularly inefficient.

[0005] In recent years, oxy-combustion cycles, also known as oxy-fuel cycles or oxy-fuel combustion cycles, have been developed, wherein the fuel, such as natural gas or other fossil fuel, is mixed in a mixture of an oxidant consisting mainly of oxygen (O2) and carbon dioxide (CO2) at high pressure. The fuel, oxidant and carbon dioxide mixture burns in a combustor of an expander which produces a pressurized combustion gas consisting exclusively or almost exclusively of carbon dioxide and water.

[0006] The combustion gas is expanded in the expander to generate mechanical energy. The exhaust combustion gas discharged on the discharge side of the expander is cooled in a regenerative heat exchanger and further cooled to condense water which can thus be removed from the cooled combustion gas. The low-temperature combustion gas, consisting mainly or exclusively of carbon dioxide, is pressurized and recycled through the regenerative heat exchanger towards the expander combustor.

[0007] The oxygen supplied to the expander combustor can be obtained by separating it from ambient air, removing nitrogen from it, so that the working fluid supplied to the combustor consists mainly of oxygen and carbon dioxide and does not include nitrogen. The resulting combustion gas consists mainly of water and carbon dioxide. The water is removed from the combustion gas by condensation, and the water-free portion of the combustion gas, which is not recycled to the combustor, can be efficiently processed in a carbon dioxide capture unit.

[0008] The oxy-fuel cycle summarized above is a semi-closed cycle, in which only a fraction of the combustion gas exits the cycle after the water has been removed from it. Petition 870250086194, dated 09 / 24 / 2025, page 17 / 197 3 / 22

[0009] Oxy-fuel combustion cycles, such as those described above, are particularly interesting in terms of efficiency, reduction of harmful emissions and CO2 sequestration. However, they operate under supercritical CO2 conditions at the expander inlet and are characterized by high pressure values ​​within the expander jacket. These operating conditions represent difficult constraints in jacket design.

[0010] A new expander design adapted to achieve higher power rates in an oxy-fuel combustion cycle would be welcome in the art. SUMMARY

[0011] To meet the aforementioned needs, a high-pressure expander comprising an outer casing, a rotor housed in the outer casing for rotation around an axis of rotation, and at least one combustor is disclosed in this document. The outer casing comprises a high-pressure casing and a low-pressure exhaust casing coupled to each other with a flange connection along a plane orthogonal to the axis of rotation of the rotor. The low-pressure exhaust casing comprises a discharge-filled space, adapted to collect expanded combustion gas through a gas expansion flow path, and at least one exhaust port.

[0012] Specifically, the expander may be a supercritical expander. As understood in this document, a supercritical expander is an expander adapted to receive a working fluid in a supercritical condition in the first stage of expansion. The embodiments described herein are particularly adapted as supercritical CO2 expanders, i.e., expanders adapted to expand carbon dioxide from a supercritical condition.

[0013] The combustor can be mounted on or around the expander casing. In some embodiments, the combustor is at least partially housed within the casing. Petition 870250086194, dated 09 / 24 / 2025, page 18 / 197 4 / 22

[0014] Other features and embodiments of the expander are described below with reference to the accompanying drawings and outlined in the appended claims.

[0015] According to a further aspect, an oxy-fuel combustion system is disclosed in this document, comprising an expander as described above and a compression system adapted to provide a flow of compressed process gas to the expander. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Now, brief reference is made to the attached drawings, in which:

[0017] Figure 1 is a schematic of an oxy-fuel power circuit;

[0018] Figure 2 is a cross-sectional view of an expander in one embodiment;

[0019] Figures 3, 4, 5 and 6 illustrate axonometric views of a low-pressure exhaust casing with multiple discharge openings, in various embodiments;

[0020] Figures 7, 8 and 9 illustrate cutaway views of low-pressure exhaust jacket discharge openings with adapted measures to prevent thermal damage and reduce the thermal load on the low-pressure exhaust jacket, in various embodiments;

[0021] Figures 10 to 21 illustrate details of the coupling between the high-pressure jacket and the low-pressure exhaust jacket in various embodiments;

[0022] Figure 22 illustrates a schematic cross-sectional view of an expander designed for front insertion of the rotor;

[0023] Figure 23 is a cross-sectional view of two adjacent combustion chambers; and

[0024] Figures 24, 25, 26 and 27 are schematic representations of alternative arrangements of the exhaust ports provided in the low-pressure exhaust jacket. Petition 870250086194, dated 09 / 24 / 2025, page 19 / 197 5 / 22 DETAILED DESCRIPTION

[0025] The diagram in Figure 1 illustrates a simplified oxy-fuel cycle operating with supercritical carbon dioxide at the expander inlet (briefly SCO2 cycle), such as an Aliam cycle or NET Power oxy-fuel cycle.

[0026] The energy system 1 shown in Figure 1 comprises an expander 3 which includes an expansion section 5 and a combustor 7. The combustor 7 may be an annular combustor, a can-type combustor, a can-type annular combustor or the like, for example. In currently preferred embodiments, the combustor is a can-type combustor comprising a plurality of combustor chambers arranged around the axis of rotation of the expander 3, as shown in more detail in Figure 2. The combustor chambers are housed in an outer casing of the expander, as will be described in more detail below.

[0027] Reference number 7.1 in Figure 2 designates the combustion chamber of the combustor of an annular combustor or each combustion chamber of a can-type or annular can combustor. In some embodiments, each combustion chamber 7.1 is housed in a respective seat 41.4 formed in the high-pressure jacket 41.1. The combustion chambers 7.1 are arranged circumferentially around the axis of rotation of the expander 3.

[0028] Combustor 7 is supplied with an oxidizing stream distributed by an oxidizing source. The oxidizer may be oxygen (O2) or a mixture of oxygen and carbon dioxide (CO2). The oxidizing stream may be produced by an air separation unit 9, which has an oxidizing source. The air separation unit 9 may remove nitrogen or nitrogen and carbon dioxide from ambient air to produce the required oxidizing stream which is supplied through an oxidizing line 11 to combustor 7 from expander 3.

[0029] Reference number 13 indicates a fuel supply line, for example, adapted to supply natural gas, such as methane, to combustor 7, specifically to each combustor chamber 7.1. The oxidizer and fuel are supplied on the inlet side of expander 3 to Petition 870250086194, dated 09 / 24 / 2025, page 20 / 197 6 / 22 Combustor 7 at high pressure, for example, at 50 barA or higher, preferably equal to or higher than 100 barA, more preferably equal to or higher than 150 barA, and more preferably equal to or higher than 200 barA. In some embodiments, the upper cycle pressure may be equal to or higher than 250 barA, or higher, for example, equal to or higher than 300 barA. The oxidizer-fuel mixture is burned in combustor 7. The resulting pressurized hot combustion gas expands in the expansion section 5 of expander 3.

[0030] In some embodiments, the temperature at the inlet of the gas expansion flow path, i.e., at the rotor inlet, may be equal to or greater than 800°C and preferably equal to or less than 1500°C.

[0031] The expelled exhaust combustion gas is discharged on a discharge side of the expander 3 into a discharge line 15. The combustion gas in the discharge line 15 may be around 600°C, for example, and at a pressure that may vary between 10 barA and 100 barA, for example, between 20 barA and 60 barA.

[0032] The power rating of expander 3 may be greater than 50 MW, for example, equal to or greater than 100 MW, for example, 150 MW or greater, for example, 200 MW or greater. In some embodiments, the rated power is equal to or greater than 300 MW. In some embodiments, the rated power is equal to or less than 2,000 MW, for example, equal to or less than 1,500 MW, or equal to or less than 1,000 MW. For example, the rated power may be between 200 MW and 650 MW. Intermediate values ​​of the upper and lower limits of each range mentioned above are also expressly disclosed herein.

[0033] The circuit further comprises a regenerative heat exchanger 17, wherein the hot combustion gas flowing through a hot side 17.1 of the regenerative heat exchanger 17 is cooled by heat exchange with a stream of chilled combustion gas flowing in a cold side 17.2 of the regenerative heat exchanger 17. The combustion gas discharged from the hot side 17.1 of the regenerative heat exchanger 17 is further cooled in a cooling heat exchanger 19 to a temperature that causes condensation of water vapor contained in the exhaust combustion gas. Petition 870250086194, dated 09 / 24 / 2025, page 21 / 197 7 / 22 expelled. Condensation water is removed from the exhausted flue gas in a water / gas separator 21.

[0034] The expelled and cooled dehydrated exhaust combustion gas, consisting mainly or exclusively of carbon dioxide, is compressed in a combustion gas compressor 23 to the pressure on the inlet side of the expander 3. While in the diagram of Figure 1 the combustion gas compressor 23 is pictorially represented as a single compressor, in some embodiments a multiple compressor may be used. For example, the combustion gas compressor 23 may be a multi-stage compressor or a set of compressors and may include one or more intercoolers.

[0035] The compressed combustion gas supplied by the combustion gas compressor 23 is partially removed from the cycle via a discharge line 25. Most of the compressed combustion gas is distributed through the cold side 17.2 of the regenerative heat exchanger 17 and is heated by heat exchange with the hot combustion gas flowing through the hot side 17.1 of the regenerative heat exchanger 17 and recycled to the expander 3 via a recycling line 25. The combustion gas recycled via the recycling line 25 is mixed with the combustion gas generated in the combustor 7 or with the oxidizing stream of the oxidizing line 11.

[0036] A side stream of cooled combustion gas is distributed through a cooling line 27, which bypasses the regenerative heat exchanger 17, towards the expander components 3 that require cooling. An additional side stream of chilled and dehydrated combustion gas can be distributed through a line 28 to the air separator 9 and / or to the oxidizer line 11 to add carbon dioxide to the oxygen distributed to the combustor 7.

[0037] The expander 3 may include an output shaft end 31 which may be integral with the central portion of the rotor, or may be mounted to the central portion of the rotor by bolting, welding, Hirth or groove connections, or the like, or a combination thereof. The energy Petition 870250086194, dated 09 / 24 / 2025, p. 22 / 197 The mechanical power generated by the expansion of the combustion gas in the expansion section 5 of the expander 3 is available at the end of the output shaft 31 for mechanical drive or power generation purposes. In the exemplary embodiment of Figure 1, the end of the output shaft 31 is coupled in a driveable manner to an electric generator 33 directly or through a gearbox, a joint, or combinations thereof. The electric generator 33 is in turn electrically coupled to an electrical power distribution network 35. In Figures 1 and 2, the end of the output shaft 31 is shown on the rear side of the expander 3. In other embodiments, not shown, the end of the output shaft 31 may be disposed on the front side of the expander. In still other embodiments, not shown, two output shaft ends may be provided, one on the front side and the other on the rear side of the expander.

[0038] As used in this document, front and rear refer to the direction of process gas flow through the expander 3. Therefore, front indicates a position on the side of the combustor 7 and rear indicates a position on the opposite side of the combustor 7, i.e., the discharge side of the expander 3.

[0039] Figure 2 illustrates a cross-sectional view of the expander 3 in one embodiment. The expander 3 may comprise an outer casing 41, which houses the combustor 7. In embodiments, the outer casing 41 includes a high-pressure casing 41.1 and a low-pressure exhaust casing 41.2. The high-pressure casing 41.1 may be in the form of a cylinder including a monolithic body, for example, manufactured by forging, casting or a combination thereof. The monolithic body extends around the longitudinal axis of the expander, i.e., around the axis of rotation.

[0040] Although in some embodiments the monolithic body is manufactured from a single block, as understood in this document, a monolithic body may also comprise a body assembled from several portions manufactured separately from one another and subsequently joined together by welding to obtain the final monolithic body. The various portions are irreversibly coupled to one another. To obtain strength Petition 870250086194, dated 09 / 24 / 2025, p. 23 / 197 9 / 22 higher mechanical, each part of the monolithic body preferably extends around the axis of rotation of the expander, that is, the parts of the monolithic body are coupled to each other along surfaces that extend transversely to the axis of rotation. Each part has an annular structure, that is, a continuous structure around the axis of rotation. As understood in this document, a continuous structure surrounding the axis of rotation of the expander is a structure, wherein closed lines surrounding the axis of rotation of the expander do not cross a welding or mechanical interface between parts that form the monolithic body.

[0041] A continuous structure around the axis of rotation has greater mechanical resistance to radial and tangential loads generated by internal pressure.

[0042] The single piece formed by the monolithic body (manufactured from a single piece or from individual components welded together and forming the final cylinder without reversible mechanical connections) provides adequate resistance against high pressure of the process fluid inside the expander 3 and specifically the most forward portion thereof.

[0043] The low-pressure exhaust jacket 41.2 can be positioned on the discharge side, i.e., on the rear side, of the expander 3, i.e., on the opposite side to the combustor 7. Furthermore, the low-pressure exhaust jacket 41.2 can be monolithic, i.e., it can consist of a single piece, as mentioned above, having a continuous structure that develops around the axis of rotation.

[0044] In other embodiments, the low-pressure exhaust casing 41.2 may be manufactured in two or more pieces connected to each other. For example, the low-pressure exhaust casing 41.2 may be manufactured as a two-piece body separated along a plane containing the rotor's axis of rotation. The two pieces may be welded together, i.e., they may be irreversibly connected to each other. In other embodiments, the parts from which the low-pressure exhaust casing 41.2 is made may be coupled to each other by tie rods, bolts, or other means. Petition 870250086194, dated 09 / 24 / 2025, page 24 / 197 10 / 22 reversible couplings. By reversible coupling means, it is understood coupling devices that allow the two or more parts that form the lining to be separated again without irreversible damage to them.

[0045] The high-pressure jacket 41.1 and the low-pressure exhaust jacket 41.2 can be connected to each other along a plane P that is orthogonal to an axis of rotation AA of a rotor 43 supported for rotation in the outer jacket 41. The outer jacket 41 is therefore a so-called vertically split jacket.

[0046] In some embodiments, the low-pressure exhaust jacket 41.2 forms a discharge plenum 41.3, through which the exhausted combustion gas is discharged from the expander 3.

[0047] Reference numbers 45, 47 indicate bearing arrangements that rotatably support the rotor 43. For example, bearing arrangement 45 on the opposite side to the combustor 7 may include a thrust or axial bearing in combination with a radial bearing or a bearing with an axial-radial bearing capacity. Bearing arrangement 47 on the combustor side may include a radial bearing. An inverted arrangement is also possible, with a bearing having axial load capacity arranged on the combustor side.

[0048] The output end 31 of the rotor 43 can be coupled in a driveable manner to the driven machine (electric generator 33) via flanges 49. The bearing arrangements 45, 47 can be arranged in bearing compartments, not shown in detail.

[0049] The rotor 43 is surrounded by an inner lining 51, which may be formed by a plurality of sections arranged sequentially in a forward-to-backward direction. In Figure 2, the inner lining 1 comprises two lining sections arranged sequentially in a forward-to-backward direction, i.e., parallel to the axis of rotation. The inner lining 51 may be divided horizontally, i.e., it may include two portions that are coupled to each other along a plane containing the axis of rotation of the rotor 43. If the inner lining comprises two lining sections arranged Petition 870250086194, dated 09 / 24 / 2025, page 25 / 197 11 / 22 sequentially in the axial direction, each section can, in turn, be divided into two portions along a plane containing the axis of rotation of the rotor 43.

[0050] The inner lining 51 is wholly or partially housed in the high-pressure lining 41.1. In some embodiments, as shown in Figure 2, the inner lining 51 projects into the low-pressure exhaust lining 41.2.

[0051] In some embodiments, the inner lining 51 is provided with cooling ducts, one of which is shown schematically in 51.1 in Figure 2. The cooling ducts provide a fluid coupling between one or each of the annular fluid chambers 42.1, 42.2 with the interior of the inner lining 51. A cooling duct, such as compressed recycled combustion gas consisting mainly of carbon dioxide, may flow from the annular fluid chambers into the interior of the inner lining 51 to cool or purge annular cavities within the inner lining 51. External cooling ducts may be provided in combination with, or as an alternative to, cooling ducts extending through the inner lining.

[0052] One or more annular fluid chambers 42 are formed between the inner lining 51 and the outer lining 41. Specifically, in the exemplary embodiment shown in Figure 2, the annular chamber 42 includes two sequentially arranged annular fluid chambers 42.1 and 42.2 separated by a septum 44. The fluid pressure within the two annular fluid chambers 42.1 and 42.2 may be different. For example, the front annular fluid chamber 42.1 may be at a higher pressure than the rear annular fluid chamber 42.2. In use, under steady-state equilibrium conditions, the rear fluid chamber 42.2 and the front fluid chamber 42.1 may be fed with freezing or cooling fluid, for example, with chilled and dehydrated combustion gas from the cooling line 27.

[0053] The septum 44 or other connecting member adapted to connect the inner lining 51 to the outer lining 41 is configured so as to allow differential thermal expansions of the inner lining 51 and the Petition 870250086194, dated 09 / 24 / 2025, page 26 / 197 12 / 22 outer coating 41 to take into account the different temperature conditions of the coatings in steady-state operating conditions and during temporary start-up and shutdown.

[0054] The expander can be adapted to expand the combustion gas through the gas expansion flow path with a pressure drop of at least 150 bar, preferably at least 250 bar, more preferably between 250 and 400 bar. To expand the combustion gas generated in the combustor 7, a high number of expansion stages is preferred. In the exemplary embodiment of Figure 2, the expander 3 includes eight stages, each configured as an axial expansion stage. In other embodiments, a different number of expansion stages may be provided, preferably equal to or greater than four, more preferably equal to or greater than five. In some embodiments, the number of expansion stages may be greater than eight, for example, nine, ten, eleven or more.

[0055] Each expansion stage includes an annular row of stationary blades or stationary vanes 53 that are stationarily arranged in the inner casing 51. Each expansion stage further includes a respective annular row of rotor blades 55, arranged downstream of the respective annular row of stationary blades 53 along an expansion flow path that extends from the combustor 7 through the expansion section 5 to the discharge-filled space 41.3 in a front-to-back direction.

[0056] The rotor blades 55 are part of the rotor 43, that is, they are connected to it for co-rotation with the rotor shaft. In some embodiments, each annular row of rotor blades 55 is connected to a respective rotor disc, not shown in detail. The structure of the rotor and rotor discs is not relevant and is not shown in detail.

[0057] In embodiments, the rotor 43 further comprises a front shaft portion 65 and a rear shaft portion 67. In embodiments, the combustor 7 extends around the front shaft portion 65. In some embodiments, the discharge plenum 41.3 extends around the rear shaft portion 67. Petition 870250086194, dated 09 / 24 / 2025, p. 27 / 197 13 / 22

[0058] A balancing drum 69 can be restricted to the rotor 43 for co-rotation with it. In the embodiment of Figure 2, the balancing drum 69 includes a first balancing drum portion 69A and a second balancing drum portion 69B connected to each other by tie rods 70.

[0059] In the embodiment of Figure 2, the expander 3 is configured so that the rotor 43 is mounted on the outer casing 41 from the rear side, i.e., from the low-pressure side of the expander. In some embodiments, a beam comprising the inner casing 51 and the rotor 43 is mounted and axially introduced from the rear side into the high-pressure casing 41.1. Finally, the low-pressure exhaust casing 41.2 is mounted on the high-pressure casing 41.1.

[0060] In some embodiments, the low-pressure exhaust jacket 41.2 may include a plurality of exhaust openings, rather than a single exhaust opening. The provision of multiple exhaust openings results in a structure of the low-pressure exhaust jacket 41.2 that is better suited to withstand the high pressure and temperature values ​​involved. The total cross-sectional area of ​​the multiple exhaust openings may be the same as if a single opening were provided, but the overall structure is mechanically more robust.

[0061] Figures 3, 4, 5 and 6 show axonometric views of the low-pressure exhaust jacket 41.2 in various embodiments, each including multiple exhaust ports.

[0062] Figure 3 illustrates an axonometric view of the rear side of the low-pressure exhaust casing 41.2 in an embodiment comprising two exhaust openings 46.1, 46.2 oriented radially with respect to the axis of the expander 3, i.e., the axis of rotation of the rotor 43. In the embodiment of Figure 3, the two exhaust openings 46.1, 46.2 are arranged symmetrically around the axis of rotation and with respect to a plane containing the axis of rotation.

[0063] Figure 4 illustrates an axonometric view of the rear side of the low-pressure exhaust casing 41.2 in an embodiment comprising two exhaust openings 46.3, 46.4 oriented tangentially with respect to Petition 870250086194, dated 09 / 24 / 2025, page 28 / 197 14 / 22 to the expander axis 3, that is, the axis of rotation of the rotor 43. In the embodiment of Figure 4, the two exhaust ports 46.3, 46.4 are symmetrical with respect to the axis of rotation.

[0064] Figure 5 illustrates an axonometric view of the rear side of the low-pressure exhaust casing 41.2 in an embodiment comprising four exhaust ports 46.5, 46.6, 46.7, 46.8 oriented radially with respect to the axis of the expander 3, i.e., the axis of rotation of the rotor 43. In the embodiment of Figure 5, the four exhaust ports 46.1, 46.2 are arranged symmetrically around the axis of rotation and with respect to a plane containing the axis of rotation.

[0065] Figure 6 illustrates an axonometric view of the rear side of the low-pressure exhaust casing 41.2 in an embodiment comprising four exhaust ports 46.9, 46.10, 46.11, 46.12, oriented tangentially with respect to the axis of the expander 3, i.e., the axis of rotation of the rotor 43. In the embodiment of Figure 6, the two exhaust ports 46.9, 46.10 and the two exhaust ports 46.11, 46.12 are symmetrical with respect to a plane containing the axis of rotation.

[0066] In other embodiments, the low-pressure exhaust casing 41.2 may comprise a different number or a different arrangement of exhaust openings. For example, in some embodiments, the low-pressure exhaust casing 41.2 may include three exhaust openings.

[0067] For example, in some embodiments, the exhaust openings may be arranged at a constant pitch in a tangential direction. Figure 24 shows such an arrangement with four exhaust openings 46 at a constant pitch of 90° from each other. Figure 26 illustrates a similar arrangement with only three exhaust openings 46 at 120° from each other in a tangential direction.

[0068] In Figure 27, the three exhaust ports 46 are at a constant pitch of 120° from each other, but are oriented radially instead of tangentially as in Figure 26. Petition 870250086194, dated 09 / 24 / 2025, page 29 / 197 15 / 22

[0069] In Figure 25, two exhaust openings 46 (in the lower part of the low-pressure exhaust jacket in this embodiment) are arranged parallel to each other and two exhaust openings 46 (in the upper part of the low-pressure exhaust jacket) are oriented with an inclination about the horizontal, but neither parallel to each other nor coaxial with the opposite exhaust openings on the lower side of the low-pressure exhaust jacket. In other embodiments, not shown, the upper openings may be coaxial.

[0070] In some embodiments, the exhaust openings may have the same cross-sectional area. In other embodiments, the exhaust openings may have different cross-sectional areas.

[0071] In some embodiments, the low-pressure exhaust jacket 41.2 may be made of a metal alloy adapted to withstand the high temperatures of the exhaust combustion gas after expansion. In this case, the low-pressure exhaust jacket 41.2 may be devoid of any thermal shielding, as shown schematically in Figure 7. In some embodiments, the low-pressure exhaust jacket 41.2 of Figure 7 is made of a cast nickel-based alloy, adapted to withstand temperatures in the range of 600°C in a continuous operating mode of the expander 3. In other embodiments, the low-pressure exhaust jacket may be made of austenitic steels or Fe-based alloys, or any other metal alloy adapted to withstand the operating conditions in terms of chemical and thermal resistance.

[0072] In other embodiments, the exhaust port(s) of the low-pressure exhaust jacket 41.2 may be provided with an internal thermal protection, adapted to reduce heat exchange between the exhaust combustion gas and the inner surface of the low-pressure exhaust jacket, specifically the inner surface of the ducts forming the exhaust port(s). Figures 8 and 9 show a cross-sectional view of a single exhaust port of the low-pressure exhaust jacket 41.2 in two embodiments. Petition 870250086194, dated 09 / 24 / 2025, page 30 / 197 16 / 22

[0073] In Figure 8, a heat shield or heat jacket 48 is disposed within a generic exhaust port 46. The heat shield 48 can be manufactured from a metal alloy capable of withstanding high temperatures for a long period of time, thus allowing continuous operation of the expander 3. In some embodiments, the heat shield 48 can be made of a nickel-based alloy, while the low-pressure exhaust jacket 41.2 can be made of ferritic-martensitic steel provided with a suitable protective weld overlay or austenitic steel.

[0074] In some embodiments, additional thermal insulation 48.2 may be provided between the thermal shield 48 and the inner surface of the low-pressure exhaust jacket 41.2.

[0075] In Figure 9, a thermal shield 48 is provided within the exhaust opening 46 and a cooling chamber or jacket 48.1 is formed between the thermal shield 48 and the low-pressure exhaust jacket 41.1. A cooling gas at a suitable temperature, for example, recycled combustion gas consisting mainly of carbon dioxide, can be circulated in the cooling chamber or jacket 48.1. The thermal shield 48 of Figure 9 can be made of a nickel-based alloy and the low-pressure exhaust jacket 41.2 can be made of ferritic-martensitic steel or austenitic steel, similarly to the embodiment of Figure 8.

[0076] Efficient connection between the high-pressure jacket 41.1 and the low-pressure exhaust jacket 41.2 can be achieved through suitably shaped flanges and relevant connection means. In Figure 2, the high-pressure jacket 41.1 comprises a high-pressure closing flange 41.5 and the low-pressure exhaust jacket comprises a low-pressure closing flange 41.6. The high-pressure closing flange 41.5 and the low-pressure closing flange 41.6 are coupled to each other by a set of pins or bolts shown in more detail and various embodiments in Figures 10 to 21.

[0077] With continued reference to Figures 2 to 9, Figure 10 shows a cross-sectional view of a portion of the outer cladding 41 in one embodiment. Petition 870250086194, dated 09 / 24 / 2025, page 31 / 197 17 / 22 high-pressure shut-off flange 41.5 and low-pressure shut-off flange 41.6 are coupled to each other by pins 81, each having a first threaded end screwed into a respective threaded blind hole 82 in the low-pressure shut-off flange 41.6. The pins 81 extend through the respective holes in the high-pressure shut-off flange 41.5 and a second threaded end of each pin 81 is engaged by a respective nut 83.

[0078] In some embodiments, one of the low-pressure closing flange 41.6 and the high-pressure closing flange 41.5 may have at least one fitting that acts in conjunction with the other flange. Fittings are particularly useful in embodiments where the high-pressure lining is made of a heat-resistant alloy generally characterized by a coefficient of thermal expansion that is greater than the coefficient of thermal expansion of the high-pressure lining, which may be made, for example, of a martensitic alloy.

[0079] In general terms, the fitting can be internal, that is, located on the inside of the outer casing, external, that is, located on the outside of the outer casing, or intermediate. In some embodiments, more than one fitting can be provided at the interface between flanges 41.6, 41.5 and can be located on the high-pressure flange, the low-pressure flange, or both.

[0080] In Figure 10, the low-pressure shut-off flange has an internal fitting 85. During operation, the fitting is engaged by the greater radial displacement of the exhaust liner relative to the high-pressure liner.

[0081] With continued reference to Figures 2 to 10, Figure 11 illustrates a further embodiment of the low-pressure shut-off flange 41.6 and the high-pressure shut-off flange 41.5. In this embodiment, both the low-pressure shut-off flange 41.6 and the high-pressure shut-off flange 41.5 comprise a through hole; a set of bolts Petition 870250086194, dated 09 / 24 / 2025, page 32 / 197 18 / 22 and their respective nuts 88 connect the low-pressure exhaust liner 41.2 and the high-pressure liner 41.1 to each other.

[0082] With continued reference to Figures 2 to 11, Figure 12 illustrates a further embodiment of the low-pressure shut-off flange 41.6 and the high-pressure shut-off flange 41.5. The low-pressure shut-off flange 41.6 and the high-pressure shut-off flange 41.5 are coupled to each other by a set of bolts 87 that extend through holes in the low-pressure shut-off flange 41.6 and the high-pressure shut-off flange 41.5. The external nuts 91 are bolted onto the respective first ends of the bolts 87, which are positioned outside the outer casing 41. The internal nuts 93 are bolted onto the opposite ends of each bolt 87. Each internal nut 93 is housed in a seat 95 facing inwards within the discharge-filled space 41.3. This embodiment results in a reduced outside diameter of the flanges, while still allowing the use of standard bolts and nuts.

[0083] The low-pressure shut-off flange 41.6 also includes an internal fitting 97 that works in conjunction with the high-pressure shut-off flange 41.5.

[0084] Figure 13 illustrates an embodiment of the high-pressure and low-pressure closing flanges 41.5 and 41.6 in an additional embodiment, similar to the embodiment in Figure 10. The same reference numbers from Figure 10 are used in Figure 13 to designate the same or equivalent components. The main difference between Figures 13 and 10 concerns the position of the centering fitting. In the embodiment of Figure 13, an external fitting 86 is integrally formed with the high-pressure closing flange 41.5 and replaces the internal fitting 85 which in Figure 10 is integrally formed with the low-pressure closing flange 41.6.

[0085] For improved sealing between the low-pressure shut-off flange 41.6 and the high-pressure shut-off flange 41.5, energized seals may be provided in some embodiments. Figures 14 and 15 illustrate a cross-sectional view of the outer casing 41 including a seal. Petition 870250086194, dated 09 / 24 / 2025, page 33 / 197 19 / 22 radial working energized seal 101 and an axial working energized seal 103, respectively.

[0086] In some embodiments, to provide a more rigid structure of the low-pressure exhaust jacket 41.2, ribs may be provided in the discharge plenum 41.3. An embodiment with reinforcing ribs 105 in the discharge plenum 41.3 is shown in Figures 16, 17, 18, wherein Figure 16 illustrates a cross-sectional view of the outer jacket and Figures 17 and 18 illustrate detailed axonometric cross-sectional views of the low-pressure exhaust jacket. The reinforcing ribs 105 reduce bending deformations of the low-pressure exhaust jacket 41.2 caused by the internal pressure of the exhaust combustion gas. In addition, the reinforcing ribs 105 can improve the distribution of the exhaust combustion gas towards the exhaust ports 46.

[0087] In some embodiments, the interface between the low-pressure closing flange 41.6 and the high-pressure closing flange 41.5 may be provided with locking teeth engaged in recesses provided on the opposite side. One embodiment of locking teeth and recesses is shown in Figures 19, 20 and 21. In this embodiment, on a surface of the high-pressure closing flange 41.5, which is in pressure contact with a corresponding surface of the low-pressure closing flange 41.6, locking teeth 107 are provided that engage in recesses 109 on the opposite surface of the low-pressure closing flange 41.6. An opposite arrangement, with recesses in the high-pressure closing flange 41.5 and locking teeth in the low-pressure closing flange 41.6, is also possible.

[0088] While in the embodiments disclosed above the outer casing 41, the inner casing 5 and the rotor 43 of the expander 3 are adapted to introduce the inner casing 51 and the rotor 43 in a back-to-front direction, in other embodiments the beam including the inner casing 51 and the rotor 43 can be introduced into the outer casing 41 in a front-to-back direction. Figure 22 illustrates a schematic cross-sectional view of an expander 3 adapted for front insertion of the expander beam, i.e., in a Petition 870250086194, dated 09 / 24 / 2025, page 34 / 197 20 / 22 front-to-back direction. The same reference numbers used in the previous figures designate the same or equivalent components in Figure 22, which are not described in detail again.

[0089] To allow the beam to be introduced in a front-to-back direction (i.e., in the direction of arrow f in Figure 22), the front end of the outer casing 41 comprises an opening, the diameter of which is sufficiently large to accommodate the inner casing 51. The combustion chambers 7.1 of the combustor 7 are introduced into their respective seats 41.4 once the beam 51, 43 has been accommodated in the outer casing 41. The front end of the outer casing 41 is then closed by a closing member 111 disposed opposite the low-pressure exhaust casing 41.2.

[0090] In some embodiments, if the combustor comprises a plurality of combustion chambers 7.1 at least partially housed in the outer casing, two or more combustion chambers 7.1 may be connected to each other by cross-fire ducts housed in the outer casing body, specifically in the high-pressure casing 41.1. One embodiment of a cross-fire duct connecting two adjacent combustion chambers 7.1 is shown in the cross-sectional view of Figure 23. This cross-sectional view shows the combustion chambers 7.1 and a cross-fire duct 7.2. The cross-fire duct seamlessly couples the interior of the combustion chambers 7.1 and propagates the flame from one chamber to another, if necessary, for example, at startup. More uniform operating conditions are maintained in the various combustion chambers 7.1 coupled by the respective cross-fire ducts 7.2, and the risk of flame extinction in one of the combustion chambers is avoided.

[0091] The exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions, and additions may be made to what is specifically disclosed in the present invention without departing from the scope of the invention, as defined in the following claims. Petition 870250086194, dated 09 / 24 / 2025, page 35 / 197 21 / 22

[0092] Some features disclosed in combination with embodiments of the expander described in this document may be used in a power-generating turbomachine with a different structure. According to one aspect, for example, the low-pressure exhaust casing may be used in an expander or in a turbine having a different casing structure, such as a horizontally split structure, instead of a drum structure as described above.

[0093] Another matter of the present disclosure is, therefore, a casing for a power-generating turbomachine comprising: a discharge-filled space; and a plurality of discharge openings.

[0094] Although in the embodiments described above the outer casing of the expander comprises a high-pressure casing and a low-pressure exhaust casing, the novel feature of a plurality of exhaust ports may be incorporated into a turbomachine wherein the outer casing comprises two or more sections coupled along a plane containing the axis of rotation, i.e. a horizontally divided casing, wherein the rear part of the casing has the full discharge space and the plurality of exhaust ports.

[0095] Exhaust openings may be arranged in a radial or tangential direction. In some embodiments, the exhaust openings may be arranged symmetrically around the axis of rotation or with respect to a plane containing the axis of rotation.

[0096] In some embodiments, the discharge-filled space may include reinforcing ribs, such as ribs 105.

[0097] The lining containing the discharge plenum and having multiple exhaust openings may be monolithic, that is, formed as a single body. In other embodiments, the lining may be divided into two or more components, parts or sections that may be coupled to each other by bolts, tie rods or other reversible coupling means. When the lining is divided into two or more portions, the portions may Petition 870250086194, dated 09 / 24 / 2025, page 36 / 197 22 / 22 to be coupled to each other along a plane containing the axis of rotation of the turbomachine or parallel to said axis.

[0098] In some embodiments, the casing containing the discharge-filled space may be a portion of an outer casing of the turbomachine, for example, it may form a low-pressure exhaust casing or a rear casing of the power-generating turbomachine. The low-pressure exhaust casing or rear casing may include a flange for connection to a high-pressure casing or forward casing of the turbomachine. Petition 870250086194, dated 09 / 24 / 2025, page 37 / 197

Claims

1 / 5 CLAIMS 1.Supercritical expander comprising: an outer casing; a rotor housed in the outer casing for rotation around an axis of rotation; and at least one combustor; characterized in that the outer casing is formed by fewer than four annular components flanged together along planes orthogonal to the axis of rotation; the outer casing comprising a high-pressure casing and a low-pressure exhaust casing coupled to each other with a flange connection along a plane orthogonal to the axis of rotation; each annular component of the high-pressure casing being monolithic; the flow path being entirely contained within the outer casing; and the low-pressure exhaust casing comprising a discharge-filled space, adapted to collect expanded combustion gas along a gas expansion flow path; the low-pressure exhaust casing comprising at least one exhaust port.

2. Expander, according to claim 1, characterized in that at least one combustor is at least partially housed in a seat in the high-pressure jacket.

3. Expander, according to claim 2, characterized in that at least one combustor comprises a plurality of combustion chambers; wherein the expander further comprises a plurality of seats in the high-pressure jacket, wherein said seats are positioned around the axis of rotation; wherein each seat houses a respective combustion chamber; and wherein, preferably, the adjacent combustion chambers are in fluid communication with each other by their respective cross-fire ducts. Petition 870250087369, dated 09 / 26 / 2025, page 9 / 13 2 / 5 4. Expander, according to claim 1, characterized in that the outer casing is formed by two annular components flanged to each other along a plane orthogonal to the axis of rotation; wherein one of said annular components is a monolithic annular component that forms the high-pressure casing; and wherein the other of said annular components forms the low-pressure discharge casing.

5. Expander, according to claim 1, characterized in that the low-pressure exhaust compartment comprises a main body configured as a monolithic block.

6. Expander, according to claim 1, characterized by further comprising a closing member connected to the outer casing, opposite the low-pressure exhaust casing.

7. Expander, according to claim 1, characterized by further comprising an inner lining, stationarily housed in the outer lining; wherein the rotor is housed in the inner lining for rotation therein.

8. Expander, according to claim 7, characterized by a plurality of annular rows of stationary blades being housed in the inner lining; wherein a respective annular row of rotor blades is positioned downstream of each annular row of stationary blades, forming with it an axial expanding stage; and wherein the sequentially arranged annular rows of stationary blades and rotor blades form the gas expansion flow path; wherein the gas expansion flow path is preferably entirely contained within the inner lining.

9. Expander, according to claim 7, characterized in that the inner lining is mechanically coupled to the outer lining by at least one connecting member disposed between a front end and a rear end of the inner lining.

10. Expander, according to claim 7, characterized in that the inner lining is entirely housed in the high-pressure lining and surrounded by it, or partially housed in the high-pressure lining and projecting into the low-pressure exhaust lining.

11. Expander, according to claim 7, characterized in that the outer casing and an assembly comprising the inner casing and the rotor housed therein are configured such that the assembly is adapted to be introduced into the high-pressure casing in a back-to-front direction; and wherein the low-pressure exhaust casing comprises a stop against which the assembly is pushed during the operation of the expander by a thrust generated by the expanding gas in the expander.

12. Expander, according to claim 7, characterized by comprising a plurality of annular fluid chambers between the inner lining and the high-pressure lining; wherein the plurality of annular fluid chambers are arranged sequentially in a front-to-back direction and are adapted to receive a pressurized cooling fluid at a gradually decreasing pressure from the most upstream annular fluid chamber to the most downstream annular fluid chamber.

13. Expander, according to claim 12, characterized in that at least two sequentially arranged annular fluid chambers are separated from each other by a pressure-reducing device or a sealing device.

14. Expander, according to claim 1, characterized in that the low-pressure exhaust compartment comprises a plurality of exhaust openings.

15. Expander, according to claim 1, characterized in that the low-pressure exhaust jacket comprises an internal thermal shield, adapted to reduce heat exchange between an exhaust stream and an internal surface of the low-pressure exhaust jacket.

16. Expander, according to claim 15, characterized in that the internal thermal protection comprises a thermal shield covering at least partially an internal surface of the low-pressure exhaust lining.

17. Expander, according to claim 16, characterized in that the internal thermal protection comprises a cooling chamber defining a flow passage for a cooling fluid between the thermal shield and an inner surface of the low-pressure exhaust jacket.

18. Expander, according to claim 16, characterized in that the internal thermal protection comprises a layer of a solid thermal insulation material between the thermal shield and the inner surface of the low-pressure exhaust jacket.

19. Expander, according to claim 1, characterized in that the high-pressure liner comprises a high-pressure closing flange and the low-pressure exhaust liner comprises a low-pressure closing flange, wherein the high-pressure closing flange and the low-pressure closing flange are coupled to each other by a set of pins or bolts; comprising at least one of the following features: bolts engaging nuts disposed in the low-pressure exhaust liner or high-pressure liner; at least one fitting in at least one of said low-pressure closing flange and high-pressure closing flange; a radially operating energized seal; an axially operating energized seal; reinforcing ribs extending from the low-pressure closing flange into a discharge-filled space formed in the low-pressure exhaust liner;Locking teeth projecting from a sealing surface of one of said low-pressure closing flanges and high-pressure closing flanges and engaging in recesses formed in a sealing surface of another of said low-pressure closing flanges and high-pressure closing flanges. Petition 870250087369, dated 09 / 26 / 2025, page 12 / 13 5 / 5; 20. Oxy-fuel combustion system, characterized by comprising an expander as defined in claim 1 and a compression system adapted to provide a flow of compressed process gas to the expander. Petition 870250087369, dated 09 / 26 / 2025, page 13 / 13

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