The present invention relates to a method for production and supply of a densified liquid oxygen product for use in space vehicle applications.
Space vehicle launches require large quantities of liquid fuels and liquid oxygen to create the propulsion necessary to get the vehicle to space. Minimizing the volume and weight of the fuel/oxygen tanks is critically important to the viability of a rocket design. It is desired to fit all the necessary fuel into as small a volume as possible. Typically, cryogenic liquids are produced and stored in tanks in equilibrium with vapor at the liquid's boiling point temperature. Subcooling the liquids below their boiling points can create a denser fluid which requires smaller tanks to hold the same volume. The limit to the level of densification is solidification at the triple point of the material.
Depending on the size of the space vehicle, supply of the liquid oxygen to a launch platform at a launch facility typically requires in excess of 40 trailers of liquid oxygen to be trucked into the launch facility where the liquid oxygen is then densified. Similarly, liquid propellants such as liquid methane are also trucked to the launch facility
Cryogenic refrigeration systems have been used for decades in many rocket or space applications for purposes such as propellant or oxidant densification. For propellant or oxidant densification, the removal of sensible heat from a liquid propellant or oxidant, such as liquid oxygen, increases the density of the liquid, which is solely dependent on temperature since liquids are generally considered incompressible. Challenges facing the space industry related to propellant densification include reducing the operational and capital cost of propellant densification as well as reducing the time it takes to achieve the desired temperatures. Examples of cryogenic based liquid oxygen densification systems are shown and described in U.S. Pat. Nos. 10,808,967 and 11,293,671.
Another challenge in propellant and oxidant densification is that it typically is performed at the liquid storage location near the launch platform using liquid nitrogen as the densification refrigerant. Current oxidant densification typically require more trailers of liquid nitrogen to be trucked in from external sources than trailers of liquid oxygen are required to densify the liquid oxygen which increases the overall logistics burden of trucking in liquid cryogens to the launch facility. The liquid nitrogen densification refrigerant is used just for cooling and thus is a consumable within the process.
However, to further improve launch operations and reduce operating costs, there is a need to reduce or eliminate the transport of liquid oxygen via trucks to the launch facility and improve the supply arrangements for liquid propellants and oxidants. Thus, there is a continuing need to develop improved refrigeration cycles for liquefaction of gaseous oxygen and the densification of the resulting liquid oxygen as well as densification of other liquid propellants at the launch facility for use in launching space vehicles.
The present invention may be characterized as a method of supplying a densified, liquid oxygen stream for a space vehicle launch, the method comprising the steps of: (i) producing a gaseous oxygen stream in an air separation unit; (ii) directing the gaseous oxygen stream via a pipeline from the air separation unit to a space launch facility, the space launch facility having one or more launch platforms; (iii) liquefying and subcooling the gaseous oxygen stream in a first refrigeration stage to yield a subcooled, liquid oxygen stream; (iv) densifying the subcooled, liquid oxygen stream in a first refrigeration stage to yield a densified, liquid oxygen stream; (v) directing the densified, liquid oxygen stream to one or more storage tanks disposed at the launch facility; and (vi) suppling the densified, liquid oxygen from the one or more storage tanks to a space vehicle at least one of the one or more launch platforms.
In a preferred embodiment, the first refrigeration stage is a reverse Brayton cycle refrigeration system that is disposed at the launch facility and is configured to receive a first refrigerant and flow the first refrigerant through a first primary heat exchanger to cool the gaseous oxygen stream and then through a first subcooler to subcool and liquefy the cooled gaseous oxygen stream via indirect heat exchange with a residual portion the first refrigerant to yield the subcooled, liquid oxygen stream. In addition, the second refrigeration stage is disposed at the launch facility proximate the first refrigeration stage and is configured to flow a second refrigerant through a second heat exchanger to subcool the liquid oxygen stream and yield a densified, liquid oxygen stream. The first refrigerant is preferably nitrogen while the second refrigerant comprises a nitrogen and neon containing mixture.
Alternatively, the present invention may be characterized as a method of supplying a densified, liquid oxygen stream for a space vehicle launch, the method comprising the steps of: (i) producing a liquid oxygen stream and a nitrogen refrigerant from an air separation unit; (ii) cooling the nitrogen refrigerant in a first refrigeration stage comprising a first heat exchanger; (iii) cooling a helium or neon containing second refrigerant in a second heat exchanger in a second refrigeration stage via indirect heat exchange with one or more streams of the cooled nitrogen refrigerant; (iv) subcooling and densifying the liquid oxygen stream in a densification heat exchanger in the second refrigeration stage via indirect heat exchange with the cooled second refrigerant to yield a densified, liquid oxygen stream; and (v) transporting the densified, liquid oxygen stream to a launch facility via truck.
It is believed that the claimed system and method will be better understood when taken in connection with the accompanying drawings in which:
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Alternatively, the oxygen stream originating from the air separation unit could be gaseous oxygen that, together with the nitrogen stream are directed to a combined liquefaction and densification system where the gaseous oxygen stream is liquefied and the resulting liquid oxygen is then densified, as described in more detail below with reference to
In both improved supply arrangements depicted in
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The first refrigeration stage uses a high pressure nitrogen refrigerant stream 55 at a pressure of about 50 bar(a) that is cooled a first heat exchanger 50 that can be segmented into a plurality of heat exchange sections, E1, E2, E3. To cool the high pressure nitrogen refrigerant stream 55, the first heat exchanger 50 is configured to include a first warm refrigeration circuit 52, a second cold refrigeration circuit 54, a residual refrigeration circuit 56, and one or more recycle circuits 58,59.
The nitrogen refrigerant stream 55 is referred to as a first refrigerant stream and is preferably split into three portions as it traverses the first heat exchanger 50, namely a first warm portion 62 of the first refrigerant stream that traverses through the first warm refrigeration circuit 52, a second cold portion 64 of the first refrigerant stream that traverses through the second cold refrigeration circuit 54, and a residual portion 66 of the first refrigerant stream that traverses through the residual refrigeration circuit 56. Upon exiting the first warm refrigeration circuit, the second cold refrigeration circuit, or the residual refrigeration circuit, the respective portions of the first refrigerant stream are recycled in one or more recycle circuits 58, 59.
The first refrigeration stage also preferably includes a warm turbine 63 configured to expand the first warm portion 62 the first refrigerant stream to yield an intermediate pressure warm exhaust 72 at a pressure of about 6 bar(a) and a cold turbine 65 configured to expand the second cold portion 64 the first refrigerant stream to yield an intermediate pressure cold exhaust 74 also at a pressure of about 6 bar(a). The warm exhaust 72 and the cold exhaust 74 are recycled in the one or more recycle circuits 58 to cool the low pressure gaseous oxygen stream 30 and the nitrogen refrigerant stream 55.
More specifically, the intermediate pressure cold exhaust 74 is mixed with an intermediate pressure recycle stream 77 before being fed into the cold end of exchanger section E3 where the mixed stream (with cold exhaust) is warmed to provide refrigeration for the cooling of the gaseous oxygen stream 30 and the nitrogen refrigeration stream 55. Similarly, the intermediate pressure warm exhaust 72 is also mixed with intermediate pressure recycle stream 78 before being fed into the cold end of exchanger section E2 where it also provides refrigeration for the cooling of the gaseous oxygen stream 30 and nitrogen refrigeration stream 55. The combined intermediate pressure recycle stream 79 (including the cold exhaust and warm exhaust) is further warmed in heat exchange section E1 to yield a fully warmed, intermediate pressure nitrogen recycle stream 81, which is then compressed in one or more recycle compressors 95.
The residual portion 66 of the first refrigerant stream is further cooled in heat exchange section E3 of the first heat exchanger and then expanded preferably using one or more expansion valves, including a first expansion valve 75. Prior to expansion, the residual portion 66 of the high pressure first refrigerant stream is at a temperature above its critical point, so that no phase transition occurs. However, once the residual portion 66 of the first refrigerant stream is expanded or ‘flashed’ to an intermediate pressure it may exist in the liquid phase. The pseudo-liquefaction is advantageous because it eliminates the constant temperature phase transition that can create a large ‘Delta-T’ in the first heat exchanger composite curve. A large ‘Delta-T’ represents an inefficiency and an increase in power consumption.
The intermediate pressure liquid nitrogen stream 76 is then subcooled in a nitrogen subcooler E4. A first portion 82 of the subcooled, intermediate pressure liquid nitrogen is further expanded or ‘flashed’ in expansion valve 85 to form a low pressure nitrogen refrigerant stream 83 at a pressure of about 1.5 bar(a) that is used to subcool the intermediate pressure liquid nitrogen 76 in the nitrogen subcooler E4. The now boiled, low pressure nitrogen refrigerant stream 83 is recycled via recycle circuit 59 through heat exchanger sections E3, E2, and E1 where it is further warmed to about ambient temperatures. Upon exiting the heat exchanger sections, the warmed, low pressure return stream 86 is compressed in a multi-stage feed compressor 85 and mixed with the fully warmed, intermediate pressure nitrogen recycle stream 81. The combined recycle stream 87 is further compressed in a multi-stage recycle compressor 95 to form the high pressure nitrogen refrigerant stream 55. Make up nitrogen 99, preferably from the nearby air separation unit, can be supplied at various points in the process depending on the pressure and phase of the nitrogen source.
The first refrigeration stage also includes a subcooler E5 that is configured to receive a second portion 84 of the subcooled, intermediate pressure liquid nitrogen which provides the refrigeration necessary to subcool and liquefy the cooled, low pressure gaseous oxygen stream 30 via indirect heat exchange between the two streams to yield the low pressure liquid oxygen stream 40. The warmed or boiled, intermediate pressure recycle stream 77 is then recycled via one or more recycle circuits 58 and further warmed in heat exchanger sections E3, E2, and E1.
The gaseous oxygen stream 30, preferably piped in from the nearby air separation unit, enters combined liquefaction and densification system at a relatively low pressure that will allow its boiling point to match up well with the condensation of the intermediate pressure liquid nitrogen 76. In the current embodiments, the low pressure gaseous oxygen stream 30 is at a pressure of between 1.5 bar(a) and 3.0 bar(a), or higher, and more preferably at a pressure of about 2.3 bar(a). The low pressure gaseous oxygen stream 30 is then cooled to near its condensation temperature in heat exchanger sections E1, E2, and E3 of the first heat exchanger 50. The cooled, low pressure gaseous oxygen stream 35 is then liquefied and subcooled in subcooler E5 via indirect heat exchange against the subcooled, intermediate pressure liquid nitrogen stream 84. While the current drawings depict subcooler E5 as a single heat exchange vessel, the use of multiple heat exchange vessels could be considered in this approach such as a first vessel configured as an evaporator section and a second vessel configured as a sensible heat section. As indicated above, the resulting liquid oxygen stream 40 is at a temperature of 81 Kelvin.
The subcooled liquid oxygen stream 35 is cooled even further, and thus densified, to a temperature of between about 54 Kelvin and 57 Kelvin in a densification heat exchanger E6. The cooling occurs against a second mixed refrigerant stream 95 comprising helium, neon, or combinations of helium and neon. The second mixed refrigerant stream 95 may also include small amounts of other gases such as nitrogen and oxygen.
The densification heat exchanger E6 and second mixed refrigerant stream 95 form part of the second refrigeration stage, which is preferably a closed loop refrigeration stage. As shown in the drawings, the second refrigeration stage is configured to flow the neon and/or helium containing second mixed refrigerant 95 through a second heat exchanger 90 and the densification heat exchanger E6. The second refrigeration stage also includes a second refrigerant recycle compressor 91 disposed downstream of the second heat exchanger 90 and configured to compress the second mixed refrigerant feed 92 to yield the compressed second mixed refrigerant 93 and an aftercooler 98 configured to cool the compressed second mixed refrigerant 93 to ambient temperature.
The second refrigeration stage also includes a second refrigerant turbine 96 disposed downstream of the second heat exchanger 90 and upstream of the densification heat exchanger E6. The second refrigerant turbine 96 is configured to expand the compressed second mixed refrigerant 93 to yield an exhaust stream 97 that provides the refrigeration for the densification heat exchanger E6 necessary to the further subcool the liquid oxygen stream 40 and yield a densified, liquid oxygen stream 45. The partially warmed second mixed refrigerant 95 exiting the densification heat exchanger E6 is further warmed in second heat exchanger 90 to create the second mixed refrigerant feed 92 to the second refrigerant recycle compressor 91. The partially warmed second mixed refrigerant can be further warmed to ambient temperature or be left somewhat below ambient temperature to take advantage of the power savings from cold compression in the second refrigerant recycle compressor 91. The process would have a make-up system on site to account for potential refrigerant losses over time and/or utilize liquid nitrogen from a storage tank for liquid assist or backup densification.
In addition to the work supplied by the warm turbine and cold turbine, the external power required to drive the multi-stage compressors are preferably obtained from renewable energy sources, such as solar power sources, located or disposed at the launch facility. As the need for densified liquid oxygen at the launch facility is typically an intermittent requirement at or near a space vehicle launch window, the use of renewable power sources, such as solar power, for the present system and methods is ideal. Also, in some embodiments may optionally be configured to operate as a nitrogen liquefaction system that takes gaseous nitrogen via the pipeline from the nearby air separation unit and produces and stores liquid nitrogen for other uses at the launch facility or in the surrounding liquid nitrogen merchant markets or the liquid nitrogen can be stored and subsequently used as an alternate source of power via a Liquid Nitrogen Energy Storage (LNES) system. Whatever the use, the production of liquid nitrogen could make economic sense during periods when there are no scheduled space vehicle launches from the launch platforms at the launch facility and the requirement for densified liquid oxygen at the launch facility is reduced.
The process flow diagrams depicted in
In the embodiment depicted in
Turning to
The first refrigeration stage uses a high pressure nitrogen refrigerant stream 555 at a pressure of about 50 bar(a) that is cooled a first heat exchanger 550 that can be segmented into a plurality of heat exchange sections, E1, E2, E3. To cool the high pressure nitrogen refrigerant stream 555, the first heat exchanger 550 is configured to include a first warm refrigeration circuit 552, a second cold refrigeration circuit 554, a residual refrigeration circuit 56, and one or more recycle circuits 558,559.
The nitrogen refrigerant stream 555 is referred to as a first refrigerant stream and is preferably split into three portions as it traverses the first heat exchanger 550, namely a first warm portion 562 of the first refrigerant stream that traverses through the first warm refrigeration circuit 552, a second cold portion 564 of the first refrigerant stream that traverses through the second cold refrigeration circuit 554, and a residual portion 566 of the first refrigerant stream that traverses through the residual refrigeration circuit 556. Upon exiting the first warm refrigeration circuit, the second cold refrigeration circuit, or the residual refrigeration circuit, the respective portions of the first refrigerant stream are recycled in one or more recycle circuits 558, 559.
The first refrigeration stage also preferably includes a warm turbine 563 configured to expand the first warm portion 562 the first refrigerant stream to yield an intermediate pressure warm exhaust 572 at a pressure of about 6 bar(a) and a cold turbine 565 configured to expand the second cold portion 564 the first refrigerant stream to yield an intermediate pressure cold exhaust 574 also at a pressure of about 6 bar(a). The warm exhaust 572 and the cold exhaust 574 are recycled in the one or more recycle circuits 558 to cool the nitrogen refrigerant stream 555.
More specifically, the intermediate pressure cold exhaust 574 is mixed with an intermediate pressure recycle stream 577 before being fed into the cold end of exchanger section E3 where the mixed stream (with cold exhaust) is warmed to provide refrigeration for the cooling of the nitrogen refrigeration stream 555. Similarly, the intermediate pressure warm exhaust 572 is also mixed with intermediate pressure recycle stream 578 before being fed into the cold end of exchanger section E2 where it also provides refrigeration for the cooling of the nitrogen refrigeration stream 555. The combined intermediate pressure recycle stream 579 (including the cold exhaust and warm exhaust) is further warmed in heat exchange section E1 to yield a fully warmed, intermediate pressure nitrogen recycle stream 581, which is then compressed in one or more recycle compressors 695.
The residual portion 566 of the first refrigerant stream is further cooled in heat exchange section E3 of the first heat exchanger and then expanded preferably using one or more expansion valves, including a first expansion valve 575. Prior to expansion, the residual portion 566 of the high pressure first refrigerant stream is at a pressure above its critical point, so that little or no phase transition occurs. However, once the residual portion 566 of the first refrigerant stream is expanded or ‘flashed’ to an intermediate pressure it may exist in the liquid phase or in a dual phase. As explained above, the pseudo-liquefaction is advantageous.
The intermediate pressure liquid nitrogen stream 576 is then subcooled in a nitrogen subcooler E4. A first portion 582 of the subcooled, intermediate pressure liquid nitrogen is further expanded or ‘flashed’ in expansion valve 585 to form a low pressure nitrogen refrigerant stream 583 at a pressure of about 1.5 bar(a) that is used to subcool the intermediate pressure liquid nitrogen 576 in the nitrogen subcooler E4. The now boiled, low pressure nitrogen refrigerant stream 583 is recycled via recycle circuit 559 through heat exchanger sections E3, E2, and E1 where it is further warmed to about ambient temperatures. Upon exiting the heat exchanger sections, the warmed, low pressure return stream 586 is compressed in a multi-stage feed compressor 685 and mixed with the fully warmed, intermediate pressure nitrogen recycle stream 581. The combined recycle stream 587 is further compressed in a multi-stage recycle compressor 695 to form the high pressure nitrogen refrigerant stream 555. Make up nitrogen 599 can be supplied at various points in the process depending on the pressure and phase of the nitrogen source.
The liquid oxygen stream 540, preferably taken from a storage tank or directly from an air separation unit, enters densification system at a relatively low pressure that will allow its boiling point to match up well with the condensation of the intermediate pressure liquid nitrogen 576. In the current embodiments, the liquid oxygen stream 540 is at a pressure of between about 1.3 bar(a) and 25.0 bar(a), and more preferably between 1.3 bar(a) and about 3.0 bar(a) and still more preferably at a pressure of about 2.3 bar(a). The liquid oxygen stream 540 is likely at a temperature of around 81 Kelvin.
The liquid oxygen stream 540 is subcooled and thus densified, to a temperature of between about 70 Kelvin and between about 54 Kelvin to 57 Kelvin in a densification heat exchanger E6. The cooling occurs against a second refrigerant stream 595 comprising helium, neon, or combinations of helium and neon. The second refrigerant stream 595 may also include small amounts of other gases such as nitrogen and oxygen. As indicated above, the densified liquid oxygen product at this temperature represents between about 10% to about 14% increase in density compared to a conventional liquid oxygen product and about 4% increase in density compared to conventional oxygen densification processes.
The densification heat exchanger E6 and second refrigerant stream 595 form part of the second refrigeration stage. As shown in the drawings, the second refrigeration stage is configured to flow the neon and/or helium containing second refrigerant stream 595 through a second heat exchanger 590 and the densification heat exchanger E6. The second refrigeration stage also includes a second refrigerant recycle compressor 591 disposed downstream of the second heat exchanger 590 and configured to compress the second refrigerant feed 592 to yield the compressed second refrigerant 593 and an aftercooler 598 configured to cool the compressed second refrigerant 593 to ambient temperature.
The second refrigeration stage also includes a second refrigerant turbine 596 disposed downstream of the second heat exchanger 590 and upstream of the densification heat exchanger E6. The second refrigerant turbine 596 is configured to expand the compressed second refrigerant 593 to yield an exhaust stream 597 that provides the refrigeration for the densification heat exchanger E6 necessary to the further subcool the liquid oxygen stream 540 and yield a densified, liquid oxygen stream 545. The partially warmed second refrigerant stream 595 exiting the densification heat exchanger E6 is further warmed in second heat exchanger 590 to create the second refrigerant feed 592 to the second refrigerant recycle compressor 591. The partially warmed second refrigerant can be further warmed to ambient temperature or be left somewhat below ambient temperature to take advantage of the power savings from cold compression in the second refrigerant recycle compressor 591. The process would have a make-up system on site to account for potential refrigerant losses over time and/or utilize liquid nitrogen from a storage tank for liquid assist or backup densification.
The embodiment depicted in
The embodiment depicted in
While the present systems and methods for the production and supply of a densified liquid oxygen product have been described with reference to one or more preferred embodiments, it is understood that numerous additions, changes, and omissions can be made without departing from the spirit and scope of the present systems and methods as set forth in the appended claims.
This application claims the benefit of and priority to U.S. provisional patent application Ser. Nos. 63/478,547 filed on Jan. 5, 2023 and 63/493,111 filed on Mar. 30, 2023, the disclosures of which are incorporated by reference.
Number | Date | Country | |
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63493111 | Mar 2023 | US | |
63478547 | Jan 2023 | US |