HIGH-GRADE HEAT-OF-COMPRESSION STORAGE SYSTEM, AND METHODS OF USE
20240240620 ยท 2024-07-18
Inventors
- Fahmi Osman AWALE (London, GB)
- Colm John Cochrane (London, GB)
- Cian QUINN (London, GB)
- Oliver James MCARDLE (London, GB)
Cpc classification
F25J1/0017
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25J2240/90
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F03G7/06
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25J1/0045
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25J1/004
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F01K25/10
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25J1/0012
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25J2205/60
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25J1/0015
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25J2230/04
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25J1/0251
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25J1/0202
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25J1/0242
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
Y02E60/16
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
F25J1/0022
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25J2235/02
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
International classification
Abstract
The present invention relates to cryogenic energy storage systems for storing using high-grade heat-of-compression. The system includes a liquefaction sub-system (100) and thermal energy storage device (300). The liquefaction sub-system (100) includes a first compressor (102), a first, second and third heat exchanger (104, 116, 112) and second compressor (114). The first and second heat exchangers (104, 116) are configured to transfer the high-grade heat of compression from the first and second compressors (102, 114) respectively to the thermal energy storage device (300). The third heat exchanger (112) is configured to recuperate the low-grade heat of compression from the second compressor (114) back into the second compressor (114) enabling the second compressor (114) to generate high-grade heat of compression. Further systems use compressors (124) and expanders (122). Further systems include power recovery sub-systems (400). The present disclosure also relates to methods of heat-of-compression storage in cryogenic energy storage systems.
Claims
1. A cryogenic energy storage system comprising: a liquefaction sub-system (100) comprising: a first compressor (102); a first heat exchanger (104); a second compressor (114); a second heat exchanger (116); a third heat exchanger (112); and a first arrangement of conduits (AB), having an upstream end (A) and a downstream end (B), and configured to pass a process stream from the first compressor (102) through the first heat exchanger (104), second compressor (114), second heat exchanger (116) and third heat exchanger (112); a thermal energy storage device (300) configured to store high-grade heat; and a second arrangement of conduits (C) forming a closed circuit and configured to pass a heat transfer fluid between the thermal energy storage device (300), the first heat exchanger (104) and the second heat exchanger (116); wherein the first heat exchanger (104) is positioned along the first arrangement of conduits (AB) downstream of the first compressor (102) and configured to transfer at least a portion of high-grade heat of compression of the process stream from the first compressor, via the heat transfer fluid, to the thermal energy storage device (300); wherein the second heat exchanger (116) is positioned along the first arrangement of conduits (AB) downstream of the second compressor (114) and configured to transfer at least a portion of high-grade heat of compression of the process stream from the second compressor, via the heat transfer fluid, to the thermal energy storage device (300); and wherein the third heat exchanger (112) is positioned along the first arrangement of conduits (AB) downstream of the second heat exchanger (116) and configured to transfer at least a portion of low-grade heat of compression of the process stream from the second heat exchanger to the second compressor (114), thereby transferring the at least portion of low-grade heat of compression back into the second compressor (114).
2. The cryogenic energy storage system of claim 1, wherein the liquefaction sub-system (100) further comprises an air purification unit positioned along the first arrangement of conduits (AB) downstream of the first heat exchanger (104), wherein the air purification unit is configured to purify the process stream.
3. The cryogenic energy storage system of claim 2, wherein the liquefaction sub-system (100) further comprises a first air conditioning unit positioned along the first arrangement of conduits (AB) between the air purification unit and the first heat exchanger (104), wherein the first air conditioning unit is configured to substantially or entirely remove the heat of compression of the process stream from the first compressor (102).
4. The cryogenic energy storage system of claim 2, wherein the liquefaction sub-system (100) further comprises a fourth heat exchanger positioned along the first arrangement of conduits (AB) between the first heat exchanger (104) and air purification unit and configured to transfer at least a portion of low-grade heat of compression of the process stream from the first heat exchanger to the process stream downstream of the air purification unit.
5. The cryogenic energy storage system of any of the preceding claims, wherein the third heat exchanger (112) being configured to transfer the at least portion of low-grade heat of compression of the process stream from the second heat exchanger to the second compressor (114) comprises transferring the at least portion of low-grade heat of compression of the process stream from the second heat exchanger to the process stream upstream of the second compressor (114).
6. The cryogenic energy storage system of any of the preceding claims, wherein the liquefaction sub-system (100) further comprises: a third arrangement of conduits, having an upstream end configured to be coupled to a cold box and a downstream end, wherein the third arrangement of conduits is configured to pass a return stream from the cold box to supplement the process stream upstream of the second compressor (114).
7. The cryogenic energy storage system of claim 6, wherein the third heat exchanger (112) being configured to transfer the at least portion of low-grade heat of compression of the process stream from the second heat exchanger to the second compressor (114) comprises transferring the at least portion of low-grade heat of compression of the process stream from the second heat exchanger to the return stream before it supplements the process stream.
8. The cryogenic energy storage system of claim 6, wherein the third heat exchanger (112) being configured to transfer the at least portion of low-grade heat of compression of the process stream from the second heat exchanger to the second compressor (114) comprises transferring the at least portion of low-grade heat of compression of the process stream from the second heat exchanger to the process stream after it is supplemented by the return stream.
9. A cryogenic energy storage system comprising: a liquefaction sub-system (100) comprising: a first compressor (102); a first heat exchanger (104); a second compressor (114); a second heat exchanger (117); and a first arrangement of conduits (AB), having an upstream end (A) and a downstream end (B), and configured to pass a process stream through the first compressor (102), first heat exchanger (104), second compressor (114) and second heat exchanger (117); a thermal energy storage device (300) configured to store high-grade heat; a first expander (122); a third compressor; and a second arrangement of conduits (C) forming a closed circuit and configured to pass a heat transfer fluid between the thermal energy storage device (300), the first heat exchanger (104), the first expander (122), the second heat exchanger (117) and the third compressor; wherein the first heat exchanger (104) is positioned along the first arrangement of conduits (AB) downstream of the first compressor (102) and configured to transfer at least a portion of high-grade heat of compression of the process stream from the first compressor, via the heat transfer fluid, to the thermal energy storage device (300); wherein the second heat exchanger (117) is positioned along the first arrangement of conduits (AB) downstream of the second compressor (114) and configured to transfer at least a portion of low-grade heat of compression of the process stream from the second compressor, via the heat transfer fluid, to the third compressor; and wherein the third compressor is positioned along the second arrangement of conduits (C) downstream of the second heat exchanger (117) and is configured to compress the heat transfer fluid and transfer at least a portion of high-grade heat of compression of the heat transfer fluid from the third compressor to the thermal energy storage device (300); and wherein the first expander (122) is positioned along the second arrangement of conduits (C) downstream of the thermal energy storage device (300) and configured to expand the heat transfer fluid and to extract work therefrom.
10. The cryogenic energy storage system of claim 9, wherein the liquefaction sub-system (100) further comprises: a third heat exchanger (105) positioned along the first arrangement of conduits (AB) downstream of the first heat exchanger (104); wherein the third heat exchanger (105) is configured to transfer at least a portion of low-grade heat of compression of the process stream from the first heat exchanger, via the heat transfer fluid, to the third compressor (124).
11. The cryogenic energy storage system of claim 9, wherein the liquefaction sub-system (100) further comprises an air purification unit positioned along the first arrangement of conduits (AB) upstream of the second compressor (114), wherein the first air purification unit is configured to purify the process stream.
12. The cryogenic energy storage system of claim 11, wherein the liquefaction sub-system (100) further comprises a first air conditioning unit positioned along the first arrangement of conduits (AB) upstream of the air purification unit, wherein the first air conditioning unit is configured to substantially or entirely remove the heat of compression of the process stream from the first compressor (102).
13. The cryogenic energy storage system of any of claims 9 to 12, wherein the liquefaction sub-system (100) further comprises: a third arrangement of conduits, having an upstream end configured to be coupled to a cold box and a downstream end, wherein the third arrangement of conduits is configured to pass a return stream from the cold box to supplement the process stream upstream of the second compressor (114).
14. The cryogenic energy storage system of any of the preceding claims, wherein the liquefaction sub-system (100) further comprises a cold box positioned at the downstream end of the first arrangement of conduits (AB) and configured to at least partially liquefy the process stream, forming a liquefied product.
15. The cryogenic energy storage system of claim 14, wherein the liquefaction sub-system (100) further comprises a second air conditioning unit positioned along the first arrangement of conduits (AB) upstream of the cold box, wherein the second air conditioning unit is configured to substantially or entirely remove the heat of compression of the process stream from the second compressor (114).
16. The cryogenic energy storage system of claim 14, when dependent on claim 6 or 13, wherein the cold box is configured to pass the return stream, comprising at least a portion of any non-liquefied process stream, to the third arrangement of conduits.
17. The cryogenic energy storage system of claim 14, wherein the cold box is configured to pass at least a portion of the liquefied product to a cryogenic storage tank.
18. The cryogenic energy storage system of any preceding claim, wherein the heat transfer fluid is a first heat transfer fluid, and wherein the cryogenic energy storage system further comprises: a power recovery sub-system comprising: a pump; an evaporator; at least one heater; an expansion stage corresponding to each of the at least one heater; a fourth arrangement of conduits, having an upstream end and a downstream end, and configured to pass a working fluid from the pump through the evaporator and each of the at least one heater and corresponding expansion stage, wherein each heater is positioned upstream of its corresponding expansion stage; and a fifth arrangement of conduits forming a closed circuit and configured to pass a second heat transfer fluid between the thermal energy storage device (300) and each heater of the at least one heater; wherein each heater is configured to transfer at least a portion of high-grade heat of compression from the thermal energy storage device (300), via the second heat transfer fluid, to the working fluid; and wherein each expansion stage is configured to expand the working fluid and to extract work therefrom.
19. The cryogenic energy storage system of claim 18, wherein the power recovery sub-system further comprises: a pre-heater positioned along the fourth arrangement of conduits upstream of the first heater; wherein the pre-heater is configured to receive at least a portion of the exhaust from the final expansion stage and to transfer at least a portion of the heat from the exhaust of the final expansion stage to the working fluid upstream of the first heater.
20. The cryogenic energy storage system of claim 18, wherein the pump is configured to pump a liquefied product from a cryogenic storage tank and to pressurise it, forming the working fluid.
21. The cryogenic energy storage system of any claim 18, wherein the first and second heat transfer fluids are the same fluid and the second arrangement of conduits (C) and the fifth arrangement of conduits are fluidly connected and share the same heat transfer fluid.
22. The cryogenic energy storage system of any preceding claim, wherein the first and second heat transfer fluids comprise air, compressed air, water, glycol, a mixture of water and glycol, thermal oil, a mixture of thermal oils or molten salts.
23. A method for heat-of-compression storage in a cryogenic energy storage system, comprising: providing a liquefaction sub-system (100) comprising a first compressor (102) and a second compressor (114); providing a thermal energy storage device (300) configured to store high-grade heat; compressing a process stream in the first compressor (102); capturing at least a portion of high-grade heat of compression of the process stream from the first compressor and storing it, via a heat transfer fluid, in the thermal energy storage device (300); compressing the process stream in the second compressor (114); capturing at least a portion of high-grade heat of compression of the process stream from the second compressor and storing it, via the heat transfer fluid, in the thermal energy storage device (300); and capturing at least a portion of low-grade heat of compression of the process stream from the second compressor and transferring it back into the second compressor (114).
24. The method of claim 23, wherein the method comprises purifying the process stream after the at least portion of high-grade heat of compression of the process stream from the first compressor has been captured.
25. The method of claim 24, wherein the method comprises conditioning the process stream to substantially or entirely remove the heat of compression of the process stream from the first compressor (102) before the process stream is purified.
26. The method of claim 24, wherein the method comprises, after the at least portion of high-grade heat of compression of the process stream from the first compressor has been captured, capturing at least a portion of low-grade heat of compression of the process stream from the first compressor and transferring it to the process stream after it has been purified.
27. The method of claim 23, wherein transferring the at least portion of the low-grade heat of compression of the process stream from the second compressor back into the second compressor (114) comprises transferring the at least a portion of the low-grade heat of compression of the process stream from the second compressor to the process stream before the process stream is compressed in the second compressor (114).
28. The method of claim 23, wherein the method comprises supplementing the process stream with a return stream before the process stream is compressed in the second compressor (114).
29. The method of claim 28, wherein transferring the at least portion of low-grade heat of compression of the process stream from the second compressor back into the second compressor (114) comprises transferring the at least portion of low-grade heat of compression of the process stream from the second compressor to the process stream after the process stream has been supplemented by the return stream.
30. The method of claim 28, wherein transferring the at least portion of low-grade heat of compression of the process stream from the second compressor back into the second compressor (114) comprises transferring the at least portion of low-grade heat of compression of the process stream from the second compressor to the return stream before it supplements the process stream.
31. The method of claim 23, wherein the method comprises conditioning the process stream to substantially or entirely remove the heat of compression of the process stream from the second compressor (114) after the at least portion of low-grade heat of compression of the process stream from the second compressor has been captured.
32. A method for heat-of-compression storage in a cryogenic energy storage system, comprising: providing a liquefaction sub-system (100) comprising a first compressor (102), a second compressor (114), a third compressor (124) and an expander (122); providing a thermal energy storage device (300) configured to store high-grade thermal energy; compressing a process stream in the first compressor (102); capturing at least a portion of high-grade heat of compression of the process stream from the first compressor and storing it in the thermal energy storage device (300); compressing the process stream in the second compressor (114); capturing at least a portion of low-grade heat of compression of the process stream from the second compressor and transferring it, via a heat transfer fluid, to the third compressor (124); compressing the heat transfer fluid in the third compressor (124); capturing at least a portion of high-grade heat of compression of the heat transfer fluid from the third compressor and storing it in the thermal energy storage device (300); and expanding the heat transfer fluid in the expander (122) and extracting work therefrom.
33. The method of claim 32, wherein the method comprises, after the at least portion of high-grade heat of compression of the process stream from the first compressor has been captured, capturing at least a portion of low-grade heat of compression of the process stream from the first compressor and transferring it, via the heat transfer fluid, to the third compressor (124).
34. The method of claim 32, wherein the method comprises purifying the process stream before the process stream is compressed in the second compressor (114).
35. The method of claim 34, wherein the method comprises conditioning the process stream to substantially or entirely remove the heat of compression of the process stream from the first compressor (102) before the process stream is purified.
36. The method of claim 32, wherein the method comprises conditioning the process stream to substantially or entirely remove the heat of compression of the process stream from the second compressor (114) after the at least portion of low-grade heat of compression of the process stream from the second compressor has been captured.
37. The method of claim 32, wherein the method comprises supplementing the process stream with a return stream before the process stream is compressed in the second compressor (114).
38. The method of any of claims 23 to 37, wherein the method comprises at least partially liquefying the process stream, forming a liquified product.
39. The method of any of claim 38, wherein the method comprises passing at least a portion of the liquefied product to a cryogenic storage tank.
40. The method of claim 38, when dependent on claim 27 or 37, wherein the method comprises passing at least a portion of any non-liquefied process stream as the return stream to supplement the process stream.
41. The method of any of claim 23 or 32, wherein the method further comprises the steps of: heating a working fluid with at least a portion of high-grade heat of compression stored in the thermal energy storage device (300); and expanding the working fluid in an expansion stage and extracting work therefrom.
42. The method of claim 41, wherein the method comprises pre-heating the working fluid with an exhaust stream from the expansion stage before the working fluid is heated.
43. The method of claim 41, further comprising the step of pumping a liquefied product from a cryogenic storage tank and pressurising it to form the working fluid.
44. A cryogenic energy storage system substantially as described herein with reference to and as shown in the accompanying drawings.
45. A method for heat-of-compression storage substantially as described herein with reference to the accompanying drawings.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0131]
[0132]
[0133]
[0134]
[0135]
[0136]
[0137]
[0138]
DETAILED DESCRIPTION
[0139] The physical values such as pressures, temperatures and mass flow rates used in the following description are intended to illustrate the invention. A person skilled in the art will understand that a wide range of possible values of these physical quantities exist depending on the particular design of a CES system and requirement of the user.
[0140] In this description and the accompanying figures, the same or similar elements are denoted by the same reference numerals.
[0141]
[0142] In the charging phase of the CES system, the liquefaction sub-system 100 is configured to receive and liquefy ambient air through a series of compression and cooling stages. The stream of air or liquid air passing through the liquefaction sub-system 100 is herein referred to as the process stream of the liquefaction sub-system 100. The liquid air produced by the liquefaction sub-system 100, herein also referred to as cryogen, may then passed to the cryogenic storage tank 200 through a first cryogen conduit 710 of an arrangement of cryogen conduits 700. The liquefaction sub-system 100 may adopt any of the configurations depicted in
[0143] The high-grade TESD 300 is configured to receive the high-grade heat of compression of the process stream from the liquefaction sub-system 100 via a heat transfer fluid and store it in a storage medium. The heat transfer fluid is passed from the high-grade TESD 300 through the liquefaction sub-system 100 where it is embedded with the high-grade heat of compression generated as a result of the compression of the process stream of the liquefaction sub-system 100. The heat transfer fluid is then passed through the high-grade TESD 300 where the high-grade heat is transferred to a storage medium of the high-grade TESD 300.
[0144] During the storage phase of the CES system, the cryogen passed from the liquefaction sub-system 100 is stored in the cryogenic storage tank 200 and may be stored for an extended period under low pressure. It is understood that the cryogenic storage tank 200 may be formed of a plurality of cryogenic storage tanks with a common connection to the liquefaction sub-system 100 and/or the power recovery sub-system 400 and a common header in fluid communication. As is common practice in the safe design of all cryogenic energy storage systems, the pressure in the cryogenic storage tank 200 described herein may be prevented from rising above design value by means of a pressure relief valve (not shown).
[0145] In the discharging phase of the CES system, the cryogen is passed from the cryogenic storage tank 200 to the power recovery sub-system 400 through a second cryogen conduit 720 of the arrangement of cryogen conduits 700. The cryogen, liquid air or air passing through the power recovery sub-system 400 is herein referred to as the working fluid. The power recovery sub-system 400 is configured to pressurise, vaporise, heat, and expand the working fluid. The mechanical energy recovered from the expanding working fluid can then be converted to electrical energy. The exhaust from the power recovery sub-system 400 may be exhausted into atmosphere through a vent 500 or recycled into another system co-located to, or part of, the current CES system (e.g. any part of the power recovery sub-system, liquefaction sub-system or other part of the broader CES system). The power recovery sub-system 400 may adopt any of the configurations depicted in
[0146] The CES system may comprise any of the liquefaction sub-system 100 configurations depicted in
[0147] In the discharging phase, the CES system is configured to transfer the stored high-grade heat from the high-grade TESD 300 to the power recovery sub-system 400 via a heat transfer fluid. The heat transfer fluid, embedded with high-grade thermal energy, is passed from the high-grade TESD 300 through the power recovery sub-system 400. In the power recovery sub-system 400, the high-grade heat embedded in the heat transfer fluid is transferred to the working fluid before the working fluid is expanded which improves the power output of the power recovery sub-system during the discharging phase. This leads to an improvement of the round-trip efficiency of the CES system. The cool heat transfer fluid is then passed back to the high-grade TESD 300 for reheating.
[0148] The heat transfer fluid used to transfer the high-grade heat from the liquefaction sub-system 100 to the high grade TESD 300 may be passed through an arrangement of heat transfer conduits 610 forming a closed circuit configured to pass the heat transfer fluid between the liquefaction sub-system 100 and the high-grade TESD 300. The heat transfer fluid configured to transfer the high-grade heat from the high-grade TESD 300 to the power recover sub-system 400 may be passed through a further arrangement of heat transfer conduits 620 forming a closed circuit configured to pass the heat transfer fluid between the high-grade TESD 300 and the power recover sub-system 400. Alternatively, the above-mentioned heat transfer fluids may be the same heat transfer fluid and the above-mentioned arrangements of heat transfer conduits may be fluidly connected to make a single combined arrangement of heat transfer conduits 600 connecting the liquefaction sub-system 100, power recover sub-system 400 and the high-grade TESD 300. In this case, the combined arrangement of conduits 600 may share the same heat transfer fluid and pass the heat transfer fluid between the liquefaction sub-system 100, the high-grade TESD 300 and the power recover sub-system 400. The heat transfer fluid(s) circulating through the liquefaction sub-system 100, high-grade TESD 300 and power recover sub-system 400 may be gas such as air or compressed air, or liquid such as water or a mixture of water and glycol, or preferably thermal oil or a mixture of thermal oils (synthetic oils, natural oils, mineral oils) or molten salts.
[0149] Although liquid air, air or cryogen are used throughout this description, the present invention is not limited to producing and using only liquid air or air but may be used for producing and using other low temperature fluids such as liquid nitrogen, liquid oxygen, liquid natural gas (LNG).
[0150]
[0151] The liquefaction sub-system 100 may further comprise a first arrangement liquefaction of conduits 101, having an upstream end A and a downstream end B configured to pass the process stream of the liquefaction sub-system 100 from the MAC 102 going through the MAC HG HX 104, the MAC Recuperator 106, the MAC AC 108, the APU 110, the MAC Recuperator 106 a second time, the RAC Recuperator 112, the RAC 114, the RAC HG HX 116, the RAC Recuperator 112 a second time, the RAC AC 118, and to the cold box 120. The first arrangement of conduits is indicated by the line AB in
[0152] The first arrangement of conduits 101 of the embodiment of
[0153] The CES system may further comprise a second arrangement of heat transfer conduits 610, 600 forming a closed circuit and configured to pass a heat transfer fluid between the high-grade TESD 300, the MAC HG HX 104 and the RAC HG HX 116. The second arrangement of heat transfer conduits is indicated by closed circuit C in
[0154] The second arrangement of heat transfer conduits 610, 600 of the embodiment of
[0155] The liquefaction sub-system 100 may further comprise a third arrangement of liquefaction conduits 150, having an upstream end configured to be coupled to the cold box 120 and a downstream end and configured to pass a second process stream, herein referred to as a return process stream or return stream, from the cold box 120 at the upstream end to supplement the process stream of the first arrangement of conduits upstream of the RAC Recuperator 112 at the downstream end. The third arrangement of conduits is indicated by the line DE in
[0156] During the charging phase of the CES system, the MAC 102 compresses ambient air (i.e. air present in the atmosphere surrounding the CES system) from ambient air pressure to a first pressure, which may be approximately between two bar to tens of bar. As the ambient air is compressed it is significantly heated and its temperature may raise from ambient temperature to above approximately 400? C. depending on the ambient conditions as it is embedded with heat of compression. At such temperatures the process stream is embedded with high-grade heat of compression.
[0157] Downstream of the MAC 102, along the first arrangement of conduits, the MAC HG HX 104 receives the hot compressed process stream from the MAC 102. The MAC HG HX 104 also receives a stream of heat transfer fluid from the second arrangements of conduits. The MAC HG HX 104 is configured to transfer at least a portion of the high-grade heat of compression of the process stream to the heat transfer fluid. As a result, the process stream may be cooled to approximately 180-220? C., therefore the process stream may still be embedded with the residual low-grade heat of compression.
[0158] The MAC Recuperator 106 is configured to receive the process stream at two different locations and transfer the low-grade heat of compression of the process stream at a first location to the process stream at a second location. Essentially, forming a recuperation loop for the low-grade heat of compression where the heat is transferred from one location to another. The two portions of the process stream passing through the MAC Recuperator 106 may pass through two independent fluid pathways within the MAC Recuperator 106 to prevent mixing.
[0159] Downstream of the MAC HG HX 104, along the first arrangement of conduits, the MAC Recuperator 106 receives the process stream from the MAC HG HX 104. The MAC Recuperator 106 also receives the process stream downstream of the APU 110 (described below). The MAC Recuperator 106 is configured to transfer at least a portion of the low-grade heat of compression from the process stream passing from the MAC HG HX 104 to the process stream passing from the APU 110. The process stream passing from the MAC HG HX 104 may be cooled from approximately 210? C. to 60? C. using the outlet stream to the APU 110. The part of the process stream passing from the MAC HG HX 104 and cooled in the MAC Recuperator 106 is then passed to the MAC AC 108, whereas the part of the process stream passing from the APU 110 and heated in the MAC Recuperator 106 is then passed to the RAC Recuperator 112 (described below).
[0160] Downstream of the MAC Recuperator 106, along the first arrangement of conduits, the MAC AC 108 receives the process stream from the MAC Recuperator 106 and is configured to substantially or entirely remove the final heat of compression from the process stream. The cooling provided by the MAC AC 108 determines the final temperature of the process stream before it is passed to the APU 110, and therefore determines the inlet temperature for the APU 110. The MAC AC 108 may cool the process stream down to approximately ambient temperature. The MAC AC 108 may also remove a significant portion of the moisture from the process stream due to condensation.
[0161] Downstream of the MAC AC 108, along the first arrangement of conduits, the APU 110 receives the process stream from the MAC AC 108 and is configured to purify it by removing water and CO.sub.2 which would otherwise freeze and block the liquefaction sub-system during operation. The APU 110 may purify the process stream through molecular adsorption, Temperature Swing Adsorption (TSA), Pressure Swing Adsorption (PSA), or a combination of both. Specific adsorbents may be employed within the APU that preferentially remove the CO.sub.2 and water from the process stream. The process stream may leave the APU 110 at approximately ambient temperature or slightly above due to possible exothermic processes in the APU 110.
[0162] As noted above, the process stream is then passed through the MAC Recuperator 106 again. Downstream of the APU 110, along the first arrangement of conduits, the MAC Recuperator 106 receives the process stream from the APU 110 and also receives the process stream from the MAC HG HX 104. The cool process stream leaving the APU 110 may be at approximately ambient temperature and is used in the MAC Recuperator 106 to cool the hotter process stream leaving the MAC HG HX 104 which may be at approximately 190-230? C. The process stream passing from the APU 110 may be heated in the MAC Recuperator 106 to approximately 180-225? C. using the outlet stream from the MAC HG HX 104. The part of the process stream passing from the APU 110 and heated in the MAC Recuperator 106 is then passed to the RAC Recuperator 112. The MAC AC 108 or APU 110, or combination of both, may comprise further refrigeration systems such as coolers, or chiller systems to further aid removing water from the process stream.
[0163] Downstream of the MAC Recuperator 106, along the first arrangement of conduits, the RAC Recuperator 112 receives the process stream passing from the MAC Recuperator 106. The RAC Recuperator 112 also receives the process stream passing from the RAC HG HX 116 (described below). Similar to the MAC Recuperator 106, the RAC Recuperator 112 is configured to receive the process stream at two different locations, capture the heat from the process stream at a first location, and transfer it to another part of the process stream at a second location. Essentially, forming a recuperation loop for the heat of the process stream where the heat is transferred from one location to another. The two portions of the process stream passing through the RAC Recuperator 112 may pass through two independent fluid pathways within the RAC Recuperator 112 to prevent mixing.
[0164] As described in the background section above, in a typical CES system, the compression of the process stream in the recycle air compressor will generate heat of compression. However, the outlet temperature of such a recycle air compressor may have a temperature of approximately 190? C., therefore the heat of compression of the output stream is typically of low-grade only.
[0165] The RAC Recuperator 112 is configured to transfer at least a portion of the low-grade heat of compression from the process stream passing from the RAC HG HX 116 (described below), to the process stream passing from the MAC Recuperator 106 and into the RAC 114. The process stream passing from the MAC Recuperator 106 may therefore be heated to above 190? C. using the outlet stream of the RAC HG HX 116. As a result, the inlet temperature of the RAC 114 is much higher than a typical recycle air compressor which causes the discharge temperature of the RAC 114 to be significantly higher and may match the MAC 102 outlet temperature of above approximately 400? C. The process stream passing from the MAC Recuperator 106 and heated in the RAC Recuperator 112 is then passed to the RAC 114 (described below), whereas the process stream passing from the RAC HG HX 116 and cooled in the RAC Recuperator 112 is then passed to the RAC AC 118 (described below).
[0166] Downstream of the RAC Recuperator 112, along the first arrangement of conduits, the RAC 114 receives the process stream passing from the RAC Recuperator 112. During the previously described stages the pressure of the process stream may drop slightly due to leaks or other environmental factors. The RAC 114 may however compress the process stream from approximately the first pressure (accounting for any pressure drops) to a second pressure, which may be approximately several tens of bar. As the process stream is compressed its temperature significantly increases as heat of compression is generated in the stream. Due to the increased inlet temperature of the RAC 114, the outlet temperature of above approximately 400-440? C. In comparison to the outlet process stream of a typical recycle air compressor the outlet process stream of RAC 114 may now be embedded with high-grade thermal energy.
[0167] Downstream of the RAC 114, along the first arrangement of conduits, the RAC HG HX 116 receives the process stream passing from the RAC 114. The RAC HG HX 116 also receives a stream of heat transfer fluid from the second arrangements of conduits. The RAC HG HX 116 is configured to transfer at least a portion of the high-grade heat of compression from the process stream to the heat transfer fluid. As a result, the process stream may be cooled to approximately 210? C., and therefore may still be embedded with the residual low-grade heat of compression.
[0168] As mentioned above, downstream of the RAC HG HX 116 along the first arrangement of conduits, the RAC Recuperator 112 receives the process stream passing from the RAC HG HX 116 as well as the process stream passing from the MAC Recuperator 106. The RAC Recuperator 112 is configured to transfer a least a portion of the low-grade heat of compression from the process stream passing from the RAC HG HX 116 to the process stream passing from the MAC Recuperator 106. The process stream passing from the RAC HG HX 116 and cooled in the RAC Recuperator 112 is then passed to the RAC AC 118.
[0169] Downstream of the RAC Recuperator 112 along the first arrangement of conduits, the RAC AC 118 receives the process stream passing from the RAC Recuperator 112. The RAC AC 118 is configured to remove the residual heat of compression from the process stream before it is passed to the cold box 120. The RAC AC 118 may cool the process stream down to approximately ambient temperature.
[0170] Downstream of the RAC AC 118, along the first arrangement of conduits, the cold box 120 may receive the process stream passing from the RAC AC 118. The cold box 120, as described in the background section above, is configured to cool the process stream until it substantially condenses to liquid. The liquid product is separated from the vapour phase and at least a portion is passed to the cryogenic storage tank 200 for storage. At least a portion of the vapour phase (i.e., any non-liquefied process stream) may to used cool the process stream entering the cold box 120 to aid liquefaction. This is done by passing the vapour phase through the cold box 120 in a counter-flow direction to the process stream entering the cold box 120. The return stream is formed of the vapour phase after it has been passed through the cold box 120 and is passed through the third arrangement of conduits to supplement the process stream upstream of the RAC Recuperator 112.
[0171] The return stream from the cold box 120 may be at ambient temperature and it may have a much larger mass flow rate than the process stream passing from the outlet to the MAC Recuperator 106. Therefore the return stream can have a greater influence on the temperature of the inlet of the RAC 114. The mass flow rate of the return stream is typically larger than the process stream passing from the MAC Recuperator 106 because of the use of expansion turbines in the cold box 120 to liquefy the process stream. For example, the ratio of the mass flow rate of the mass flow rate of the return stream to the process stream before being joined by the return stream may be between approximately 11:7 to 13:5. While the process stream passing from the MAC Recuperator 106 has been sufficiently heated, the return stream passing from the Cold Box 120 may not yet be heated. The RAC Recuperator 112 therefore recuperates at least a portion of the low-grade heat of compression from the RAC 114 back into the inlet of the RAC 114, thus increasing the outlet temperature of the RAC 114 and enabling high-grade heat of compression to be extracted from the outlet of the RAC 114. This also counteracts the cooling of the process stream after it has been supplemented by the return stream from the cold box 120.
[0172] The high-grade TESD 300 is configured to store the high-grade heat of compression embedded in the process stream as a result of its compression in the MAC 102 and the RAC 114. The high-grade heat is transferred to the high-grade TESD 300 from the process stream by the MAC HG HX 104, RAC HG HX 116 and the heat transfer fluid of the second arrangement of conduits. The high-grade TESD 300 may be a packed bed TESD, a stationary liquid phase-based TESD or preferably a two-reservoir TESD as described in the background section above. The heat transfer fluid may be a gas such as air or compressed air, or a liquid such as water, glycol, a mixture of water and glycol, thermal oil, a mixture of thermal oils or preferably molten salts.
[0173] As the process stream of liquefaction sub-system 100 is compressed in the MAC 102, it is embedded with high-grade heat of compression. It then passes through the MAC HG HX 104 where at least a portion of the high-grade heat of compression is transferred to the heat transfer fluid of the second arrangement of conduits. The heat transfer fluid is then pumped through the second arrangement of conduits to the high-grade TESD 300. In the high-grade TESD 300, the high-grade heat is transferred to a storage medium from the heat transfer fluid. The cool heat transfer fluid is then recirculated back to the MAC HG HX 104 or RAC HG HX 116 to repeat the heat transfer process.
[0174] In a similar process, as the process stream of liquefaction sub-system 100 is compressed in the RAC 114, it is embedded with high-grade heat of compression due to the recuperation of the process stream heat by the RAC Recuperator 112 as described above. The process stream then passes through the RAC HG HX 116 where at least a portion of the high-grade heat of compression is transferred to the heat transfer fluid of the second arrangement of conduits. The heat transfer fluid is then pumped through the second arrangement of conduits to the high-grade TESD 300. In the high-grade TESD 300, the high-grade heat is transferred to a storage medium. The cool heat transfer fluid is then pumped back to the MAC HG HX 104 or RAC HG HX 116 to repeat the heat transfer process. The storage medium of the high-grade TESD 300 may preferably be molten salt.
[0175] As described above, the process stream passing from the MAC Recuperator 106 to the RAC Recuperator 112 is supplemented by the return stream from the cold box 120 before it passes into the RAC Recuperator 112. Therefore, the mass flow through the RAC Recuperator 112 may be significantly higher than the mass flow through the MAC Recuperator 106. For example, the ratio of the mass flow rate through the RAC Recuperator 112 to the mass flow rate through the MAC Recuperator 106 may be between approximately 17:7 to 19:5. Generally, in heat exchangers, the rate of heat transfer is proportional to mass flow rate. As the mass flow of a fluid increases through a heat exchanger more molecules are able to interact with the internal surfaces of the heat exchanger and so more heat is able to conduct through its surface, enabling the heat exchanger to transfer more thermal energy. The increased mass flow rate through the RAC Recuperator 112 means that it can have significantly more heat available to exchange than the MAC Recuperator 106 and so can play a larger role in heating the process stream prior to it entering the RAC 114. Therefore, the MAC Recuperator 106 may be removed in favour of keeping only the RAC Recuperator 112.
[0176]
[0177] The CES system comprises a liquefaction sub-system 100 and a high-grade TESD 300. The liquefaction sub-system 100 may similarly comprise a main air compressor (MAC) 102, a main air compressor high-grade heat exchanger (MAC HG HX) 104, a main air compressor air conditioner (MAC AC) 108, an air purification unit (APU) 110, a recycle air compressor recuperator heat exchanger (RAC Recuperator) 112, a recycle air compressor (RAC) 114, a recycle air compressor high-grade heat exchanger (RAC HG HX) 116, a recycle air compressor air conditioner (RAC AC) 118, a cold box 120, a first arrangement of conduits, a second arrangement of conduits and a third arrangement of conduits in a similar configuration to the CES system of
[0178] The CES system of
[0179] The MAC HG HX 104 is configured to transfer the high-grade heat of compression embedded in the process stream as a result of its compression in the MAC 102 to the heat transfer fluid of the second arrangement of conduits. The process stream is then passed directly to the MAC AC 108. However, the process stream received by the MAC AC 106 may still be embedded with the residual low-grade heat of compression. It is understood that the APU 110 operates optimally when the process stream is at approximately ambient temperature. Therefore, the MAC AC 108 may be configured to dump the excess heat into the atmosphere to cool the process stream to approximately ambient temperature. Alternatively, the MAC AC 108 may be configured to transfer at least a portion of the residual low-grade heat of compression to another system (e.g., any part of the power recovery sub-system, liquefaction sub-system or other part of the broader CES system) co-located to, or part of, the current CES system. As a further alternative, the MAC AC 108 may transfer at least a portion of the residual low-grade heat of compression to an external process or system that requires additional heat (e.g., heating facilities, boilers, air-conditioners, etc.).
[0180] The APU 110 receives the process stream from the MAC AC 108 and is configured to purify the process stream by removing water and CO.sub.2. The process stream is then passed from the APU 110 to the RAC Recuperator 112. The process stream leaving the APU 110 may be at approximately ambient temperature and since the process stream is not passed through an MAC Recuperator 106, it may not be embedded with the residual low-grade heat of compression from the MAC 102.
[0181] Downstream of the APU 110, along the first arrangement of conduits, the RAC Recuperator 112 receives the process stream passing from the APU 110 as well as the process stream passing from the RAC HG HX 116. The RAC Recuperator 112 is configured to transfer at least a portion of the low-grade heat of compression from the process stream passing from the RAC HG HX 116 (described below) to the process stream passing from the APU 110. The process stream passing from the APU 110 is heated in the RAC Recuperator 112 and then passed to the RAC 114, whereas the process stream passing from the RAC HG HX 116 is cooled in in the RAC Recuperator 112 and then passed to the RAC AC 118. The remaining components of the CES system perform similar operations to those of the CES system illustrated in
[0182] The return stream passing from the cold box 120 joins the process stream downstream of the APU 110. As noted above, the return stream may be at approximately ambient temperature. The process stream passing from the APU 110 may also be at approximately ambient temperature. Therefore, the RAC Recuperator 112 may be configured to transfer sufficient thermal energy to the process stream after it has been supplemented by the return stream to ensure it is embedded with high-grade thermal energy after compression in the RAC 114.
[0183] As described above, the return stream from the cold box 120 may have a mass flow rate significantly higher than the process stream passing from the MAC Recuperator 106 in the CES system of
[0184]
[0185] The CES system of
[0186] The CES system comprises a liquefaction sub-system 100 and a high-grade TESD 300. The liquefaction sub-system 100 may similarly comprise a main air compressor (MAC) 102, a main air compressor high-grade heat exchanger (MAC HG HX) 104, a main air compressor recuperator heat exchanger (MAC Recuperator) 106, a main air compressor air conditioner (MAC AC) 108, an air purification unit (APU) 110, a recycle air compressor recuperator heat exchanger (RAC Recuperator) 112, a recycle air compressor (RAC) 114, a recycle air compressor high-grade heat exchanger (RAC HG HX) 116, a recycle air compressor air conditioner (RAC AC) 118, a cold box 120, a first arrangement of conduits, a second arrangement of conduits and a third arrangement of conduits in a similar configuration to the CES system illustrated in
[0187] The process stream from the MAC recuperator 106, which may be embedded with low-grade heat of compression, is passed to the RAC 114. Before passing to the RAC 114 the process stream is supplemented by the return stream from the cold box 120. The process stream is then compressed in the RAC 114 and passed to the RAC HG HX 116 where the high-grade heat of compression is transferred to the high-grade TESD 300 via the heat transfer fluid of the second arrangement of conduits. The process stream is then passed to the RAC Recuperator 112.
[0188] The RAC Recuperator 112 is configured to receive the process stream passing from the RAC HG HX 116 as well as the return stream from the cold box 120 before it supplements the process stream passing from the MAC Recuperator 106 to the RAC 114. The RAC Recuperator 112 is configured to transfer at least a portion of the low-grade heat of compression of the process stream leaving the RAC HG HX 116 to the return stream. The return stream from the cold box 120 may be heated in RAC Recuperator 112 to the approximate temperature of the process stream passing from the MAC Recuperator 106 to the RAC 114. The process stream passing from the RAC HG HX 116 to the RAC Recuperator 112 may be cooled in the RAC Recuperator 112 then passed to the RAC AC 118 and follows the same onward process as described in relation to the CES system illustrated in
[0189] The return stream from the cold box 120 is therefore embedded with at least a portion of the low-grade heat of compression in the RAC Recuperator 112. Since the process stream passing from the MAC Recuperator 106 to the RAC 114 is also embedded with at least a portion of the low-grade heat of compression in the MAC Recuperator 106, when these streams combine, they may not experience significant mixing at different temperatures. Furthermore, since both streams have been heated, when combined and compressed in the RAC 114, the process stream will be embedded with high-grade heat of compression. This enables the present system the transfer at least a portion of this high-grade heat to the high-grade TESD 300 through the RAC HG HX 116 and the seat transfer fluid of the second arrangement of conduits.
[0190] As previously noted, in the CES system of
[0191]
[0192] The CES system comprises a liquefaction sub-system 100 and a high-grade TESD 300. The liquefaction sub-system 100 may similarly comprise a main air compressor (MAC) 102, a main air compressor high-grade heat exchanger (MAC HG HX) 104, a main air compressor air conditioner (MAC AC) 108, an air purification unit (APU) 110, a recycle air compressor recuperator heat exchanger (RAC Recuperator) 112, a recycle air compressor (RAC) 114, a recycle air compressor high-grade heat exchanger (RAC HG HX) 116, a recycle air compressor air conditioner (RAC AC) 118, a cold box 120, a first arrangement of conduits, a second arrangement of conduits and a third arrangement of conduits in a similar configuration to the CES system of
[0193] The CES system of
[0194] The process stream leaving the MAC HG HX 104 may be embedded with the residual low-grade heat of compression and is then passed to the MAC AC 108. The MAC AC 108 may be configured to dump the excess heat into the atmosphere to cool the process stream to approximately ambient temperature. Alternatively, the MAC AC 108 may be configured to transfer at least a portion of the residual low-grade heat of compression to another system (e.g., any part of the power recovery sub-system, liquefaction sub-system or other part of the broader CES system) co-located to, or part of, the current CES system. As a further alternative, the MAC AC 108 may transfer at least a portion of the residual low-grade heat of compression to an external process or system that requires additional heat (e.g., heating facilities, boilers, air-conditioners, etc.).
[0195] The APU 110 receives the process stream from the MAC AC 108 and is configured to purify the process stream by removing water and CO.sub.2. The process stream is then passed from the APU 110 to the RAC 114. The process stream passing from the APU 110 may be at approximately ambient temperature since it is not passed through an MAC Recuperator 106 and does not receive the low-grade heat from the MAC 102. The process stream passing from the APU 110 is supplemented by the return stream from the cold box 120 before it is passed to the RAC 114. The remaining components of this CES system perform similar operations to those of the CES system of
[0196] Downstream of the RAC HG HX 116, along the first arrangement of conduits, the RAC Recuperator 112 receives the process stream passing from the RAC HG HX 116 as well as the return stream passing from the cold box 120. The RAC Recuperator 112 is configured to transfer at least a portion of the low-grade heat of compression of the process stream downstream of the RAC HG HX 116 to the return stream from the cold box 120. The return stream leaving the cold box 120 and the process stream passing from the APU 110 may be at approximately ambient temperature. Therefore, the RAC Recuperator 112 may be configured to transfer sufficient thermal energy to the return stream before it supplements the process stream to ensure the process stream is embedded with high-grade thermal energy after compression in the RAC 114.
[0197]
[0198] The liquefaction sub-system 100 may comprise a main air compressor (MAC) 102, a main air compressor high-grade heat exchanger (MAC HG HX) 104, a main air compressor low-grade heat exchanger (MAC LG HX) 105, a main air compressor air conditioner (MAC AC) 108, an air purification unit (APU) 110, a recycle air compressor (RAC) 114, a recycle air compressor low-grade heat exchanger (RAC LG HX) 117, a recycle air compressor air conditioner (RAC AC) 118 and a cold box 120. The CES system may further comprise a heat transfer fluid expander (HTF Expander) 122 and a heat transfer fluid compressor (HTF Compressor) 124. The HTF Expander 122 and HTF Compressor 124 may be comprised within the liquefaction sub-system 100 or separate from the liquefaction sub-system 100. The CES system may further comprise the cryogenic storage tank 200.
[0199] The liquefaction sub-system 100 may further comprise a first arrangement of conduits, having an upstream end and a downstream end and configured to pass the process stream of the liquefaction sub-system 100 from the MAC 102 going through the MAC HG HX 104, the MAC LG HX 105, the MAC AC 108, the APU 110, the RAC 114, the RAC LG HX 117, the RAC AC 118, and to the cold box 120. The first arrangement of conduits is indicated by the line AB in
[0200] The first arrangement of conduits 101 of the CES of
[0201] The second arrangement of Heat transfer conduits 610 of the CES of
[0202] During the charging phase of the CES system, the MAC 102 compresses ambient air (i.e. air present in the atmosphere surrounding the CES system) from ambient air pressure to a first pressure, which may be approximately between two bar to tens of bar. As the ambient air is compressed it is significantly heated, its temperature may raise from ambient temperature to above approximately 400? C. depending on the ambient conditions as it is embedded with heat of compression. At such temperatures the process stream is embedded with high-grade heat of compression.
[0203] Downstream of the MAC 102 along the first arrangement of conduits, the MAC HG HX 104 receives the hot compressed process stream from the MAC 102. The MAC HG HX 104 also receives a stream of heat transfer fluid from the second arrangements of conduits. The MAC HG HX 104 is configured to transfer at least a portion of the high-grade heat of compression of the process stream to the heat transfer fluid. As a result, the process stream may be cooled to approximately 180-220? C., therefore the process stream may still be embedded with the residual low-grade heat of compression.
[0204] Downstream of the MAC HG HX 104 along the first arrangement of conduits, the MAC LG HX 105 receives the process stream from the MAC HG HX 104. The MAC LG HX 105 also receives a stream of heat transfer fluid from the second arrangements of conduits downstream of the HTF Expander 122 (described below). The MAC LG HX 105 is configured to transfer at least a portion of the residual low-grade heat of compression of the process stream to the heat transfer fluid of the second arrangement of conduits upstream of the HTF Compressor 124 (described below). The heat transfer fluid, now embedded with low-grade heat of compression from the MAC 102, then passes to the HTF Compressor 124 (described below) through the second arrangement of conduits.
[0205] Downstream of the MAC LG HX 105 along the first arrangement of conduits, the MAC AC 108 receives the process stream from the MAC LG HX 105 and is configured to remove the final heat of compression from the process stream. The cooling provided by the MAC AC 108 determines the final temperature of the process stream before being passed to the APU 110, and therefore determines the inlet temperature for the APU 110. The MAC AC 108 may cool the process stream down to approximately ambient temperature. The MAC AC 108 may also remove a significant portion of the moisture from the process stream due to condensation.
[0206] Downstream of the MAC AC 108, along the first arrangement of conduits, the APU 110 receives the process stream from the MAC AC 108 and is configured to purify the process stream by removing water and CO.sub.2 which would otherwise freeze and block the liquefaction sub-system during operation. The APU 110 may purify the process stream through molecular adsorption, Temperature Swing Adsorption (TSA), Pressure Swing Adsorption (PSA), or a combination of both. Specific adsorbents may be employed within the APU that preferentially remove the CO.sub.2 and water from the process stream. The process stream may leave the APU 110 at approximately ambient temperature or slightly above due to possible exothermic processes in the APU 110.
[0207] Downstream of the APU 110, the process stream is supplemented by the return stream from the cold box 120 similar to the CES systems of
[0208] Downstream of the APU 110, along the first arrangement of conduits, the RAC 114 receives the process stream passing from the APU 110 after it has been supplemented by the return stream. During the previously described stages the pressure of the process stream may drop slightly, however, the RAC 114 may compress the process stream from approximately the first pressure (accounting for any pressure drops) to a second pressure, which may be approximately several tens of bar. As the process stream is compressed its temperature significantly increases as heat of compression is generated. Compared to the CES systems of
[0209] Downstream of the RAC 114, along the first arrangement of conduits, the RAC LG HX 117 receives the process stream from the RAC 114. The RAC LG HX 117 also receives a stream of heat transfer fluid from the second arrangements of conduits downstream of the HTF Expander 122 (described below). The RAC LG HX 117 is configured to transfer at least a portion of the low-grade heat of compression of the process stream to the heat transfer fluid of the second arrangement of conduits upstream of the HTF Compressor 124. The heat transfer fluid, now embedded with the low-grade heat of compression from the RAC 114, then passes to the HTF Compressor 124 (described below) through the second arrangement of conduits.
[0210] Downstream of the RAC LG HX 117, along the first arrangement of conduits, the RAC AC 118 receives the process stream passing from the RAC LG HX 117. The RAC AC 118 is configured to remove the residual heat of compression from the process stream before it is passed to the cold box 120. The RAC AC 118 may cool the process stream down to approximately ambient temperature.
[0211] Downstream of the RAC AC 118 along the first arrangement of conduits, the cold box 120 receives the process stream passing from the RAC AC 118. The cold box 120, as described in the background section above, is configured to cool the process stream until it substantially condenses to liquid. At least a portion of the liquid product is separated from the vapour phase and passed to the cryogenic storage tank 200 for later use. At least a portion of the vapour phase (i.e., any non-liquefied process stream) may to used cool the process stream entering the cold box 120 to aid liquefaction. This is done by passing the vapour phase through the cold box 120 in a counter-flow direction to the process stream entering the cold box 120. The return stream is formed of the vapour phase after it has been passed through the cold box 120 and is passed through the third arrangement of conduits to supplement the process stream upstream of the RAC 114.
[0212] As described above, the MAC HG HX 104 is configured transfer at least a portion of the high-grade heat of compression from the process stream to the heat transfer fluid. The heat transfer fluid is then pumped through the second arrangement of conduits to the high-grade TESD 300. The MAC LG HX 105 and RAC LG HX 117 on the other hand are configured transfer at least a portion of the residual low-grade heat of compression from the process stream to the heat transfer fluid. The heat transfer fluid is then pumped through the second arrangement of conduits to the HTF Compressor 124.
[0213] The HTF Compressor 124 is configured to receive the heat transfer fluid from both the MAC LG HX 105 and the RAC LG HX 117. The HTF Compressor 124 then compresses the heat transfer fluid, which may raise its temperature to approximately that of the high-grade TESD 300 and/or that of the heat transfer fluid passing from the MAC HG HX 104. As a result of the generation of additional heat of compression, the heat transfer fluid passing from the HTF Compressor 124 may be embedded with high-grade heat of compression. The heat transfer fluid is then pumped through the second arrangement of conduits to the high-grade TESD 300.
[0214] The high-grade TESD 300 may be configured to store the high-grade heat of compression embedded in the heat transfer fluid in a storage medium. The storage medium of the high-grade TESD 300 may preferably be molten salt. The high-grade TESD 300 may be a packed bed TESD, a stationary liquid phase-based TESD or preferably a two-reservoir TESD as described in the background section above. The heat transfer fluid may preferably be gas or compressed gas. In the high-grade TESD 300, the high-grade heat of compression embedded in the heat transfer fluid is transferred to the storage medium from the heat transfer fluid. The cool heat transfer fluid is then recirculated back to MAC HG HX 104 and/or HTF Expander 122. As described above, the MAC HG HX 104 is configured to receive at least a portion of the cooled heat transfer fluid and to transfer at least a portion of the high-grade heat of compression from the process stream generated from its compression in the MAC 102 to the heat transfer fluid.
[0215] The HTF Expander 122 is configured to receive at least a portion the cool heat transfer fluid passing from the high-grade TESD 300. The heat transfer fluid passing from the high-grade TESD 300 may still have a relatively high temperature compared to the process stream passing from the MAC HG HX 104 or the RAC 114. The HTF Expander 122 may therefore expand the heat transfer fluid, which cools the heat transfer fluid and also allows work to be extracted from the expanding heat transfer fluid. The HTF Expander 122 may be mechanically coupled to a generator for generating electricity. The heat transfer fluid is then passed to the MAC LG HX 105 and the RAC LG HX 117, for receiving the low-grade heat of compression from the process stream as described above.
[0216] For compressors in general, as the inlet fluid temperature increases the amount of work required to compress the fluid also increases due to the higher internal kinetic energy of the fluid molecules. In the present CES system, the inlet fluid temperature of the RAC 114 may be much lower than the CES systems of
[0217] In a similar manner to the CES systems of
[0218]
[0219] The at least one heater is represented in
[0220] The power recovery sub-system 400 may further comprise a first arrangement of power recovery conduits 401 configured to pass a working fluid of the power recovery unit 400 from the pump 402 going through the evaporator 404 and each of the at least one heater 406 and corresponding expansion stage 408 to the final expansion stage 408j. The first arrangement of conduits is indicated by the line AB in
[0221] The first arrangement of power recovery conduits 401 may include the following fluidly connected power recovery conduits: a first conduit 431 connected to the pump 402 and the evaporator 404, a second conduit 432 connected to the evaporator 404 and at least one of the at least one heater 406n, one or more third conduits 433 connected between each of the at least one heater 406n and the corresponding expansion stage 408n, one or more fourth conduits 434 connected to each of the at least one expansion stage 408n to the next of the at least one heater 406n+1 if included and a fifth conduit 435 connected to the final expansion stage 408j and to the vent 500. It will be understood that there could be any number of heaters 406n an expansion stages 408n and j does not indicate a maximum or required number of stages.
[0222] The CES system may further comprise a second arrangement of heat transfer conduits 620, 600 forming a closed circuit and configured to pass a heat transfer fluid between the high-grade TESD 300 and each of the at least one heater 406. The second arrangement of conduits is indicated by closed circuit C in
[0223] The second arrangement of heat transfer conduits 620, 600 includes heat transfer conduits fluidly connected as follows: one or more first conduits 461 each connected to the high-grade TESD 300 and each of the at least one heaters 406 and one or more second conduits 462 each connected to the at least one heaters 406 and the high-grade TESD 300.
[0224] During the discharging phase of the CES system, the cryogenic pump 402 is configured to extract a stream of liquid product from the storage tank 200, such as the cryogen or liquid air, and to pressurise said stream, forming the working fluid. The pump 200 is configured to control the flow of cryogen withdrawn from the storage tank 200.
[0225] Downstream of the pump 402, along the first arrangement of conduits, the evaporator 404 is configured to receive the working fluid from the pump 402 and substantially or entirely vaporise the working fluid.
[0226] Downstream of the evaporator 404, along the first arrangement of conduits, the first heater 406a of the at least one heater 406 receives the working fluid from the evaporator 404. The first heater 406a is also receives the heat transfer fluid from the high-grade TESD 300 via the second arrangement of conduits. The heat transfer fluid passing from the high-grade TESD 300 may be embedded with high-grade heat originating from the liquefaction sub-system 100. The first heater 406a is configured to transfer at least a portion of the high-grade heat from the heat transfer fluid to the working fluid.
[0227] Downstream of the first heater 406a, along the first arrangement of conduits, the first expansion stage 408a of the at least one expansion stage 408 receives the working fluid from the first heater 406a. The first expansion stage 408a is configured to expand the working fluid and to extract work therefrom. The first expansion stage 408 may be mechanically coupled an electric generator (not shown) which converts the mechanical energy to electrical energy.
[0228] In the case where there is more than one heater and expansion stage, downstream of the first expansion stage 408a, a second heater 406n receives the working fluid from the first expansion stage 408a and a second expansion stage 408n receives the working fluid from the second heater 406n. The second heater 406n and expansion stage 408n may perform the same process of heating and expanding the working fluid as the first heater and first expansion stage as described above. This also applies to any number of heaters and corresponding expansion stages. Namely, each heater 406 is configured to transfer the high-grade heat from the heat transfer fluid to the working fluid, and each expansion stage 408 is configured to expand the working fluid to generate mechanical energy that can be used to generate electrical energy. Each expansion stage 408 may be coupled to a common shaft which may be ultimately mechanically coupled to a common electric generator, this allows each the expansion stage 408 to contribute to the electrical energy generated in the generator.
[0229] Downstream of the final expansion stage 408j (which may be the first expansion stage as noted above), along the first arrangement of conduits, the exhaust from the final expansion stage 408j may be exhausted into atmosphere through the vent 500 or recycled into another part of the CES system (e.g. liquefaction sub-system, TESD, etc.) or another system (e.g. refrigeration system, air-conditioning system, air liquefier, etc.) co-located to the current CES system.
[0230] The high-grade TESD 300 may be configured to store, in a storage medium, the high-grade heat of compression generated in the process stream of the liquefaction sub-system 100 during the charging phase as described in relation to the CES systems of
[0231] In general, the power generated by an expansion turbine is a function of the pressure ratio across the turbine, the mass flow rate through the turbine and the inlet temperature. In power recovery systems of known in the art (for example WO2019158921A1 described in the background section above), some expansion stages of the power recovery sub-system are specified to generate power from the working fluid heated by the low-grade heat of compression, whereas some expansion stages are specified to generate power from the working fluid heated by the high-grade heat of compression. This means that at least some of the expansion stages operate at a lower temperature and therefore a lower specific output.
[0232] On the other hand, the expansion turbines 408 of the present CES system may all be configured to generate power from the working fluid heated by the high-grade heat of compression from the high-grade TESD 300. This means the inlet temperature of the expansion turbines may be higher, so they may operate at a higher temperature and can extract more work from the hotter working fluid, resulting in a higher specific output. This means that the present CES system operates at a higher average temperature and, therefore, is more energy dense meaning it can produce more energy per unit of working fluid. Furthermore, building and maintaining a CES plant with expansion stages that operate at similar temperatures allows for more efficient construction, easier maintenance and lower capital expenditure due to the ability to procure all expansion turbines of the same, similar or comparable specifications. This leads to a simplification of the system and may result in an overall reduction in plant component cost.
[0233]
[0234] Therefore the CES of
[0235] The CES system comprises a power recovery sub-system 100 and a high-grade TESD 300. The power recovery sub-system 400 may similarly comprise a cryogenic pump 402, an evaporator 404, at least one heater 406, at least one expansion stage 408, a first arrangement of conduits and a second arrangement of conduits in a similar configuration to the CES system of
[0236] Downstream of the evaporator 404, along the first arrangement of conduits, the pre-heater 405 receives the working fluid from the evaporator 404. The pre-heater also receives at least a portion of the exhaust passing from the final expansion turbine 408j. The pre-heater is configured to transfer at least a portion of the heat embedded in the exhaust to the working fluid. The heated working fluid is then passed to the first heater 406a and follows the same onward process through the first arrangement of conduits as described in relation to the CES system of
[0237] By pre-heating the working fluid, this system may prevent the heat transfer fluid from freezing as a result of being cooled in the first heater 406a by the working fluid passing from the evaporator 404. For example, after evaporation in the evaporator 404, the working fluid may have a temperature at approximately ambient temperature whereas the temperature of the heat transfer fluid passing from the high-grade TESD 300 and into the first heater 406a, may be approximately 350-400? C. depending on the fluid used. Without the pre-heater 405, some types of heat transfer fluid may freeze, such as some typical molten salts which have a freezing temperature below 190? C. as described above. If these types of molten salts, acting as the heat transfer fluid, fall below 190? C. in the first heater 406a they may be at risk of freezing which will block the second arrangement of conduits. Additionally, when being significantly cooled or approaching its freezing temperature the heat transfer fluid may become more viscous leading to additional work required by the pumps responsible for pumping it through the second arrangement of conduits. The working fluid may be heated from approximately ambient temperature to approximately 50-150? C. before entering the first heater 406a whereas the exhaust passing from the final expansion turbine 408j may be cooled from approximately 210? C. to 125? C. by the outlet to the evaporator 404.
[0238] The CES systems described above are considered to be high energy density systems. This is because the heat of compression captured during the liquefaction of the process fluid is hotter than traditional CES systems as only high grade heat is captured, therefore the specific work of the liquefaction sub-system 100 is higher. In the power recover sub-system, said captured heat energy can be applied to the working fluid, resulting in higher expansion turbine operating temperatures. Therefore, the power recovery sub-system can extract more energy from the expanding working fluid, meaning the specific work of the power recover sub-system also increases because it produces more energy per unit of working fluid. Therefore, these systems have more energy being discharged and charged. As a result of this, less cryogen is required to produce a MWh of electricity. This means that the cryogenic storage tank and consequently the CES system can be significantly smaller for a given plant energy size (e.g., a 300 MWh plant) on a volume basis. Furthermore, the charging time required to store a given amount of energy may be reduced as well due to the reduced cryogen use.
[0239] Additionally, as mentioned above, the disclosed CES systems can efficiently store the heats of compression from the MAC 102 and RAC 114 in a single high-grade TESD 300, which means that a low-grade TESD is not required, which reduces the plant complexity and capital expenditure required to build said plant. Furthermore, the removal of the low-grade TESD avoids the issues associated with them as described above, such as thermal mixing on the stratification boundary of a thermocline based low-grade TESD system, and therefore the associated losses and inefficiency associated with low-grade TESD systems. Also, capturing high-grade heat enables the use of molten salt as a heat transfer fluid or storage medium which is advantageous due to their availability, low costs, non-toxicity, non-flammability, high thermal stabilities and low vapor pressures. The low vapor pressure means the salts are a liquid at atmospheric pressures which results in storage system designs without the need for pressurized tanks.
[0240] As noted above the CES system of the present invention may comprise any of the liquefaction sub-system 100 configurations depicted in