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EP-4279748-B1 - ROTARY PRESSURE EXCHANGER

EP4279748B1EP 4279748 B1EP4279748 B1EP 4279748B1EP-4279748-B1

Inventors

  • Kus, Bartosz
  • De Raeve, Karel

Dates

Publication Date
20260506
Application Date
20230517

Claims (14)

  1. A rotary pressure exchanger for transferring pressure from a first fluid to a second fluid, comprising a housing (2) and a rotor (3) mounted within the housing (2) for rotation about an axis of rotation (D) defining an axial direction (A), wherein a plurality of channels (4) is provided inside the rotor (3) for transferring pressure from the first fluid to the second fluid, wherein each channel (4) extends parallel to the axis of rotation (D), wherein the housing (2) comprises a first inlet port (21) for supplying the first fluid to the channels (4) in the rotor (3), a first outlet port (22) for discharging the first fluid from the channels (4) in the rotor (3), a second inlet port (25) for suppling the second fluid to the channels (4) in the rotor (3), and a second outlet port (26) for discharging the second fluid from the channels (4) in the rotor (3) wherein the first inlet port (21) and the second inlet port (25) are configured as radial inlet ports, such that the first fluid and the second fluid enter the rotor (3) in a radial direction perpendicular to the axial direction (A), and in that the first outlet port (22) and the second outlet port (26) are configured as radial outlet ports, such that the first fluid and the second fluid leave the rotor (3) in the radial direction, characterized in that each channel (4) extends from a first axial end (41) to a second axial end (42), wherein at least one of the first axial end (41) and the second axial end (42) of each channel (4) is provided with a closing element (495).
  2. A rotary pressure exchanger in accordance with claim 1, wherein the rotor (3) extends from a first rotor end (31) in the axial direction (A) to a second rotor end (32), wherein the rotor (3) comprises a circumferential surface (33) delimiting the rotor (4) with respect to the radial direction, wherein each channel (4) comprises a first opening (45) and a second opening (46) for the fluids, and wherein each first opening (45) and each second opening (46) are arranged in the circumferential surface (33) of the rotor (3).
  3. A rotary pressure exchanger in accordance with anyone of the preceding claims, comprising a plurality of bearing flow passages (61, 62) for providing a hydrostatic support of the rotor (3).
  4. A rotary pressure exchanger in accordance with anyone of the preceding claims comprising a first end cover (5) and a second end cover (6), with each end cover (5, 6) arranged stationary with respect to the housing (2), wherein the rotor (3) is arranged between the first end cover (5) and the second end cover (6) regarding the axial direction (A).
  5. A rotary pressure exchanger in accordance with claim 4, wherein each end cover (5, 6) is made of a ceramic material.
  6. A rotary pressure exchanger in accordance with anyone of claims 4-5, wherein each rotor end (31, 32) comprises a bearing pin (35) extending in the axial direction (A) and configured coaxially with the axis of rotation (D), wherein each end cover (5, 6) comprises a bearing recess (56) configured for receiving one of the bearing pins (35), and wherein each bearing pin (35) engages with one of the bearing recesses (56).
  7. A rotary pressure exchanger in accordance with claim 6, wherein at each rotor end (31, 32) a radial bearing flow passage (61) and an axial bearing flow passage (62) are provided between the bearing recess (56) and the bearing pin (35) engaging with the bearing recess (56), wherein each radial bearing flow passage (61) is configured to provide hydrostatic radial support of the rotor (3), and wherein each axial bearing flow passage (62) is configured to provide hydrostatic axial support of the rotor (3).
  8. A rotary pressure exchanger in accordance with anyone of claims 6-7, wherein the rotor (3) comprises an axle (36) and a rotor body (37), wherein the axle (36) comprises both bearing pins (35) and extends from the bearing pin (35) at the first rotor end (31) to the bearing pin (35) at the second rotor end (32), wherein the rotor body (37) comprises all channels (4), and wherein the rotor body (37) is fixedly connected to the axle (36) in a torque proof manner.
  9. A rotary pressure exchanger in accordance with claim 8, wherein the axle (36) is made of a first material, preferably a ceramic material, wherein the rotor body (37) is made of a second material, preferably a metallic material, and wherein the first material is different from the second material.
  10. A rotary pressure exchanger in accordance with anyone of claims 8-9, wherein the axle (36) is configured as a hollow axle comprising a central opening (361) extending completely through the axle (36) in the axial direction, wherein each end cover (5, 6) comprises a central bore (80) aligned with the central opening (361), with each central bore (80) extending completely through the end cover (5; 6) in the axial direction (A), wherein a bolt (9) is provided extending in the axial direction (A) through each central bore (80) and through the central opening (361), and wherein the bolt (9) is secured to each end cover (5, 6).
  11. A rotary pressure exchanger in accordance with claim 10, wherein the bolt (9) comprises a central core (94) extending in the axial direction (A) along the entire length of the bolt (9), and a sleeve (93) arranged coaxially with the core (94) and abutting against the core (94), wherein the sleeve (93) is made of a first material, preferably a ceramic material, wherein the central core (94) is made of a second material, preferably a metallic material, and wherein the first material is different from the second material.
  12. A rotary pressure exchanger in accordance with anyone of claims 4-11, comprising a rotor sleeve (29) extending regarding the axial direction (A) from the first end cover (5) to the second end cover (6), with the rotor sleeve (29) arranged stationary with respect to the housing (2), wherein the rotor (3) is arranged within the rotor sleeve (29), so that the rotor sleeve (29) surrounds the circumferential surface (33) of the rotor (3).
  13. A rotary pressure exchanger in accordance with anyone of the preceding claims, wherein each first axial end (41) is provided with a first plug (491) for closing the first axial end (41), and wherein each second axial end (42) is provided with a second plug (492) for closing the second axial end (42).
  14. A rotary pressure exchanger in accordance with anyone of the preceding claims, wherein in each channel (4) a freely sliding separator (48) is provided for reducing a mixing of the first fluid and the second fluid.

Description

The invention relates to a rotary pressure exchanger for transferring pressure from a first fluid to a second fluid in accordance with the preamble of the independent claim. Rotary pressure exchangers are used to transfer energy in the form of pressure from a first fluid available at a high pressure to a second fluid available at a low pressure. Usually the energy transfer takes place by a positive displacement of the fluids following Pascal's principle. Such rotary pressure exchangers are configured with a rotor which is driven by the fluids or by an external motor. A well-known application of rotary pressure exchangers is the field of reverse osmosis systems, for example Sea Water Reverse Osmosis (SWRO) for desalination of seawater or brackish water. Here, the rotary pressure exchanger is used as an efficient energy recovery device. In reverse osmosis systems a semipermeable membrane is used that can be passed by the water or the solvent but not by solutes like dissolved solids, molecules or ions. For reverse osmosis the membrane is supplied with a pressurized feed fluid for example seawater. Only the solvent, for example the water, can pass the membrane and will leave the membrane unit as permeate fluid, for example fresh water. The remaining part of the feed fluid that does not pass through the membrane is discharged from the membrane unit as concentrate fluid, for example brine. The feed fluid has to be supplied to the membrane with a high pressure to overcome the osmotic pressure. Thus, reverse osmosis typically is a process where a pressurized feed fluid is required and the concentrate fluid leaving the membrane unit still has a considerably large residual pressure that enables to recover a part of the pressurizing energy as mechanical energy. In seawater desalination, for example, the required pressure of the feed fluid (seawater) may be from 45 bar to 75 bar depending among others on the salinity and the temperature of the seawater. The pressure in the fresh water (permeate fluid) may be between zero and three bars, the pressure in the brine (concentrate fluid) is typically between 2 and 5 bars less than the feed pressure, i.e. 40-73 bar. Rotary pressure exchangers are used to transfer pressure from the brine, which is still at a considerably high pressure, to the feed fluid, thus recovering energy from the brine. The rotor of a rotary pressure exchanger is typically designed to include straight axially oriented ducts or channels, in which the pressure transfer takes place by positive displacement of the fluids. It is known to arrange the rotor between two stationary end covers which are used to supply the fluids to the rotor and to discharge the fluids from the rotor. For positioning and supporting the rotor it is known to use an axle which is arranged at the center of the rotor as it is disclosed for example in US 10,125,796. Another known solution is a sleeve positioning concept, where the rotor is surrounded by a stationary sleeve. During operation of the device the narrow gap between the rotor and the sleeve provides a hydrodynamic support of the rotor. In known rotary pressure exchangers, the fluids are supplied and discharged through the end covers and in axial direction into and from the rotor. Each end cover includes high and low pressure ports for the fluids. In each end cover the high and the low pressure port are separated by a sealing space formed between the stationary face between the ports and the end faces of the rotor. In order to limit the leakage between the ports extremely small clearances between the end covers and the rotor are required. This makes the manufacturing process complex and expensive and might require special materials. Due to the short distance between the high pressure port and the low pressure port the resulting leakage limits the efficiency of the device, despite using extremely narrow clearances (typically in the range of several micrometers). The document US2012/257991 A1 discloses a rotary pressure exchanger according to the preamble of claim 1, Starting from this state of the art, it is therefore an object of the invention to propose a rotary pressure exchanger having an improved efficiency. The subject matter of the invention satisfying this object is characterized by the features of the independent claim. Thus, according to the invention, a rotary pressure exchanger is proposed for transferring pressure from a first fluid to a second fluid, comprising a housing and a rotor mounted within the housing for rotation about an axis of rotation defining an axial direction, wherein a plurality of channels is provided inside the rotor for transferring pressure from the first fluid to the second fluid, wherein each channel extends parallel to the axis of rotation, wherein the housing comprises a first inlet port for supplying the first fluid to the channels in the rotor, a first outlet port for discharging the first fluid from the channels in the rotor, a second i