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WO-2026093230-A1 - AN EXPANDER

WO2026093230A1WO 2026093230 A1WO2026093230 A1WO 2026093230A1WO-2026093230-A1

Abstract

The expander (3) comprises an outer casing (41) and an inner casing (51). A rotor (43) is housed in the inner casing (51) for rotation therein around a rotation axis. A plurality of generally cylindrical seats (101) are arranged around the rotation axis. Combustors (8) in a can-type arrangement project from the generally cylindrical seats (101) into an annular plenum, such that the transition pieces (113) thereof are located in the annular plenum and are supported by an annular structure (132), cantileverly mounted on the forward end of the inner casing (51).

Inventors

  • ZUCCA, Alessandro
  • PROVENZALE, Michele
  • CHECHI, Simone
  • GIUSTI, ENRICO
  • MENICHINI, Alessandro
  • MARIOTTI, MASSIMILIANO
  • BERTI, MATTEO
  • GAMBERI, Francesco

Assignees

  • NUOVO PIGNONE TECNOLOGIE - S.R.L.

Dates

Publication Date
20260507
Application Date
20251027
Priority Date
20241029

Claims (20)

  1. 1. An expander comprising a vertically-split outer casing, an inner casing, and a rotor housed in the inner casing and adapted to rotate therein around a rotation axis; wherein: the outer casing comprises a monolithic forward casing portion having an annular body developing around the rotation axis; the forward casing portion comprises a plurality of generally cylindrical seats entirely formed within the annular body of the forward casing portion and arranged side-by-side around the rotation axis; each generally cylindrical seat entirely houses a respective combustor; and each generally cylindrical seat is fluidly coupled with a first process gas inlet.
  2. 2. The expander of claim 1, wherein each combustor comprises: a tubular liner having a forward end, an aft end, and a side wall extending from the forward end to the aft end; transition piece at the aft end of the liner; and at least one burner at the forward end of the liner, the at least one burner being fluidly coupled with a fuel inlet and an oxidant inlet.
  3. 3. The expander of claim 2, further comprising a tubular sleeve arranged around the liner.
  4. 4. The expander of any preceding claim, wherein each generally cylindrical seat has a longitudinal axis converging towards the rotation axis of the rotor.
  5. 5. The expander of claim 3, wherein each sleeve projects in an aft direction from the respective generally cylindrical seat in the annular aft plenum.
  6. 6. The expander of any preceding claim, wherein each liner projects in an aft direction from the respective generally cylindrical seat in an annular aft plenum; and wherein the transition pieces are positioned in the annular aft plenum.
  7. 7. The expander of claim 6, wherein the annular aft plenum is fluidly coupled with at least one second process gas inlet.
  8. 8. The expander of any one of claims 1 to 6, comprising at least one second gas inlet for each combustor, fluidly coupled with the respective generally cylindrical seat.
  9. 9. The expander of claim 7, wherein the annular aft plenum is fluidly coupled with a respective outer annular space between each generally cylindrical seat and the respective sleeve housed therein.
  10. 10. The expander of any preceding claim, comprising an annular structure extending around the rotation axis, in which the transition pieces are housed.
  11. 11. The expander of claim 10, when depending upon any one of claims 3 to 6, wherein the annular structure is housed in the annular plenum.
  12. 12. The expander of claim 10 or 11, wherein the annular structure comprises a ring coaxial to the rotation axis and connected to a forward end of the inner casing.
  13. 13. The expander of claim 12, wherein the annular structure comprises a cylindrical member coaxial to the ring.
  14. 14. The expander of claim 13, wherein the ring and the cylindrical member are connected to one another by a plurality of struts, preferably radially extending struts.
  15. 15. The expander of claim 14, wherein a transition piece and an aft end of the respective liner are housed between each pair of sequentially arranged struts.
  16. 16. The expander of claim 14 or 15, wherein each transition piece is supported by one of said struts.
  17. 17. The expander of any one of claims 13 to 16, further comprising a thrust ring, engaged to the cylindrical member, wherein the thrust ring is connected to, or supports stationary blades of a first expansion stage of the expander.
  18. 18. The expander of any one of claims 1 to 15, wherein each transition piece is connected directly to a forward end of the inner casing.
  19. 19. The expander of any preceding claim, wherein each generally cylindrical seat forms a forward plenum surrounding the liner.
  20. 20. The expander of claim 19, wherein each forward plenum is fluidly coupled with an inner annular space between the liner and the sleeve housed in the corresponding generally cylindrical seat.

Description

AN EXPANDER DESCRIPTION TECHNICAL FIELD [0001] The present disclosure pertains to turbomachines and parts thereof. Embodiments disclosed herein specifically refer to oxyfuel combustion expanders, such as supercritical carbon dioxide expanders (sCO2 expanders). [0002] As understood herein a SCO2 expander is an expander wherein carbon dioxide in a supercritical state is present in at least a portion of the process gas flow path inside the expander. BACKGROUND ART [0003] Fossil fuels are a major source of chemical energy used for the generation of mechanical power. Fossil fuels are mixed with air and combusted to generate a combustion gas at high pressure and temperature, which expands in an expander. The expander converts combustion gas enthalpy into mechanical power available on the output shaft of the expander and used to drive a load, such as a compressor or compressor train, or to rotate an electric generator and convert mechanical power into electric power. [0004] One of the major concerns regarding combustion of fossil fuels relates to the production of carbon dioxide, a greenhouse gas which is considered one of the main contributors of global warming and climate changes. [0005] To reduce the environmental impact of power generation through combustion of fossil fuels, the option of post combustion capture of carbon dioxide has been investigated. Carbon dioxide capture facilities have been developed, to process flue gas exhausted from gas turbines and remove carbon dioxide therefrom, prior to discharging the flue gas in the environment. The cost of a carbon dioxide capturing facility are high, both in term CAPEX, as well as in terms of energy required to run the facility, which reduces the overall thermodynamic efficiency of the system. The percentage of carbon dioxide in flue gas is low. This requires large volumes of flue gas to be processed through the carbon dioxide capturing facility and renders the capturing process particularly inefficient. [0006] In recent years oxy-combustion cycles, also known as oxy-fuel cycles or oxyfuel combustion cycles, have been developed, wherein fuel, such as natural gas or another fossil fuel, is blended into a mixture of an oxidant consisting mainly of oxygen (O2) and carbon dioxide (CO2) at high pressure. The blend of fuel, oxidant and carbon dioxide bums in a combustor assembly of an expander producing a pressurized flue gas consisting exclusively or almost exclusively of carbon dioxide and water. [0007] The flue gas is expanded in the expander to generate mechanical power. The exhaust flue gas discharged at the discharge side of the expander is cooled in a regenerative heat exchanger and further chilled to condensate water which can thus be removed from the chilled flue gas. The low-temperature flue gas, consisting mainly or exclusively of carbon dioxide is pressurized and recycled through the regenerative heat exchanger towards the combustor assembly of the expander. [0008] Oxygen supplied to the combustor assembly of the expander can be obtained by separation from ambient air, removing nitrogen therefrom, such that the working fluid supplied to the combustor assembly mainly consists of oxygen and carbon dioxide and does not include nitrogen. The resulting flue gas mainly consists of water and carbon dioxide. Water is removed from the flue gas by condensation and the part of water-free flue gas, which is not recycled to the combustor assembly, can be efficiently processed in a carbon dioxide capturing unit. [0009] The oxy-fuel cycle summarized above is a semi-closed cycle, in that only a fraction of the flue gas exits the cycle after water has been removed therefrom. [0010] Oxy-fuel combustion cycles, such as those described above, are particularly interesting in terms of efficiency, reduction of noxious emissions and ease of CO2 sequestration. However, they operate under CO2 supercritical conditions at the inlet of the expander and are characterized by extremely high pressure and high temperature inside the expander and specifically inside the combustor assembly. These operating conditions pose difficult constraints in the casing design. [0011] Improvements in the design of the expanders adapted for supercritical carbon dioxide cycles, or other cycles operating in similar conditions are highly desirable. SUMMARY [0012] The invention concerns an expander according to claim 1. Further features and embodiments are set forth in the dependent claims. [0013] As used herein “forward” and “aft” are referred to the direction of flow of the process gas through the combustor assembly and through the expander, and therefore the forward end of a component is the end upstream of the aft end of the same component, with regard to the direction of flow of the gas stream processed through the expander or components thereof. [0014] If not differently indicated, the terms “upstream” and “downstream” refer to the direction of flow of the process gas in the combustor assembly and