Method and System for Forming and Dispensing a Compressed Gas

Abstract

A method and system for forming a compressed gas and dispensing it to a compressed gas receiver. The compressed gas is formed from a process fluid provided at a cryogenic temperature. The forming includes pressurizing the process fluid, feeding the pressurized process fluid at still a cryogenic temperature to a heat exchanger and heating it in indirect heat exchange with a thermal fluid which is provided in a reservoir at a thermal fluid temperature above the cryogenic temperature of the pressurized process fluid. Once heated to a suitable temperature the compressed gas may be dispensed to the compressed gas receiver or stored in one or more compressed gas storage vessels for later use.

Claims

1. A method for forming a compressed gas and dispensing it to a compressed gas receiver, the method comprising the following steps: (a) providing a process fluid at a cryogenic temperature; (b) pressurizing the process fluid and feeding the pressurized process fluid at still a cryogenic temperature to a first heat exchanger; (c) providing a thermal fluid, such as for example D-Limonene, in a thermal fluid reservoir at a thermal fluid temperature above the cryogenic temperature of the pressurized process fluid; (d) forming the compressed gas from the pressurized process fluid, wherein forming the compressed gas includes heating the pressurized process fluid in the first heat exchanger by indirect heat exchange with the thermal fluid; (e) optionally, providing one or more compressed gas storage vessels and feeding compressed gas from the one or more compressed gas storage vessels to a dispenser; (f) feeding compressed gas formed in step (d) to the dispenser and/or the one or more compressed gas storage vessels, if present; and (g) dispensing the compressed gas via the dispenser to the compressed gas receiver.

2. The method according to claim 1, wherein one of the pressurized process fluid and thermal fluid is conveyed in one or more fluid channels through the first heat exchanger and the other one surrounds the one or more fluid channels in direct contact thereby effecting the indirect heat exchange.

3. The method according to claim 1, wherein the thermal fluid of the thermal fluid reservoir is circulated in a thermal fluid circuit that comprises the thermal fluid reservoir, the first heat exchanger, and one or more pumps feeding the thermal fluid in the thermal fluid circuit.

4. The method according to claim 1, further comprising the step of cooling compressed gas formed in step (d) and/or from the compressed gas storage vessel, if present, by indirect heat exchange with the thermal fluid in a second heat exchanger and feeding the cooled compressed gas to the dispenser.

5. The method according to claim 4, wherein one of the pressurized process fluid and thermal fluid is conveyed in one or more fluid channels through the second heat exchanger and the other one surrounds the one or more fluid channels in direct contact thereby effecting the indirect heat exchange.

6. The method according to claim 4, wherein the first heat exchanger and the second heat exchanger are arranged in parallel with respect to the thermal fluid, and wherein a first pump feeds the thermal fluid of the thermal fluid reservoir through the first heat exchanger and a second pump feeds the thermal fluid of the thermal fluid reservoir through the second heat exchanger.

7. The method according to claim 1, wherein the one or more compressed gas storage vessels is/are provided, and at least a portion of the compressed gas formed in step (d) is fed to the one or more compressed gas storage vessels for intermediate storage.

8. The method according to claim 7, wherein the step of feeding compressed gas to the dispenser comprises or consists of feeding compressed gas from the one or more compressed gas storage vessels to the dispenser.

9. The method according to claim 1, wherein the one or more compressed gas storage vessels is/are provided, and at least a portion of the compressed gas formed in step (d) is fed to the dispenser while bypassing the one or more compressed gas storage vessels.

10. A system for forming compressed gas and dispensing it to a compressed gas receiver, the system comprising: (a) a source of a process fluid at a cryogenic temperature; (b) a cryogenic feeding device operatively disposed to receive process fluid from the source and configured to pressurize the process fluid and feed the pressurized process fluid at still a cryogenic temperature; (c) a process fluid treatment arrangement for forming a compressed gas from the pressurized process fluid, the process fluid treatment arrangement comprising a first heat exchanger operatively disposed to receive pressurized process fluid from the cryogenic feeding device at a cryogenic temperature and configured to heat the pressurized process fluid by indirect heat exchange with a thermal fluid; (d) a thermal fluid reservoir of the thermal fluid at a temperature above the cryogenic temperature of the pressurized process fluid, the thermal fluid reservoir operatively disposed to provide the thermal fluid for the first heat exchanger; (e) optionally, one or more compressed gas storage vessels operatively disposed to receive and configured to store compressed gas from the process fluid treatment arrangement; and (f) a dispenser operatively disposed to receive compressed gas from the process fluid treatment arrangement and/or operatively disposed to receive compressed gas from the one or more storage vessels, if present, and configured to dispense compressed gas to the compressed gas receiver.

11. The system according to claim 10, wherein the first heat exchanger is disposed in a thermal fluid circuit which comprises the thermal fluid reservoir and one or more pumps operatively disposed and configured to circulate the thermal fluid of the thermal fluid reservoir through the first heat exchanger and the thermal fluid reservoir.

12. The system according to claim 10, wherein the thermal fluid reservoir comprises a reservoir container which contains a bath of the thermal fluid, the thermal fluid reservoir operatively disposed to provide the thermal fluid for the first heat exchanger from the bath.

13. The system according to claim 11, wherein the thermal fluid circuit contains a total mass M.sub.11 of thermal fluid and the reservoir container contains a mass m.sub.12 of thermal fluid out of this total mass, and wherein the ratio m.sub.12/M.sub.11 fulfills the relation m.sub.12/M.sub.11≥0.5 or m.sub.12/M.sub.11≥0.6 or m.sub.12/M.sub.11≥0.7.

14. The system according to claim 10, wherein the first heat exchanger comprises: a casing with an inlet and an outlet for a casing-side fluid, which is one of the thermal fluid and the pressurized process fluid, and one or more fluid channels mounted within the casing and operatively disposed to receive a channel-side fluid and configured to convey the channel fluid through the casing, the channel-side fluid being the other one of the pressurized process fluid and the thermal fluid; wherein the first heat exchanger is configured to bring the casing-side fluid in direct contact with the one or more fluid channels for the channel-side fluid.

15. The system according to claim 10, wherein the first heat exchanger is a helically coiled heat exchanger which comprises a casing for one of the thermal fluid and the pressurized process fluid as a casing-side fluid and one or more helically coiled fluid channels mounted within the casing for conveying the other one of the pressurized process fluid and the thermal fluid as a channel-side fluid through the casing.

16. The system according to claim 10, comprising a second heat exchanger operatively disposed to receive compressed gas from the process fluid treatment arrangement and/or operatively disposed to receive compressed gas from the one or more compressed gas storage vessels, if present, wherein the second heat exchanger is configured to cool the received compressed gas by indirect heat exchange with the thermal fluid, and wherein the thermal fluid reservoir is operatively disposed to provide the thermal fluid for the second heat exchanger.

17. The system according to claim 16, comprising a thermal fluid circuit with a first branch and a second branch arranged in parallel to the first branch with respect to the thermal fluid, wherein the first branch comprises the thermal fluid reservoir, the first heat exchanger and a first pump operatively disposed and configured to circulate the thermal fluid of the thermal fluid reservoir in the first branch through the thermal fluid reservoir and the first heat exchanger, and wherein the second branch comprises the thermal fluid reservoir, the second heat exchanger and a second pump operatively disposed and configured to circulate the thermal fluid of the thermal fluid reservoir in the second branch through the thermal fluid reservoir and the second heat exchanger.

18. The system according to claim 16, wherein the second heat exchanger comprises: a casing with an inlet and an outlet for a casing-side fluid, which is one of the thermal fluid and the pressurized process fluid; and one or more fluid channels mounted within the casing and operatively disposed to receive a channel-side fluid and configured to convey the channel fluid through the casing, the channel-side fluid being the other one of the pressurized process fluid and the thermal fluid; wherein the second heat exchanger is configured to bring the casing-side fluid in direct contact with the one or more fluid channels for the channel-side fluid.

19. The system according to claim 10, wherein the process fluid treatment arrangement comprises a heater operatively disposed to receive pressurized process fluid from the first heat exchanger and configured to heat this process fluid further.

20. The system according to claim 10, further comprising a thermal fluid heater operatively disposed, as for example in the thermal fluid reservoir, and configured to heat the thermal fluid.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0044] The FIGURE illustrates a method and system for forming compressed gas from a process fluid provided at a cryogenic temperature and dispensing the compressed gas to a compressed gas receiver.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0045] The ensuing detailed description provides a preferred exemplary embodiment only, and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the ensuing detailed description of the preferred exemplary embodiment will provide those skilled in the art with an enabling description for implementing the preferred exemplary of the invention, it being understood that various changes may be made in the function and arrangement of elements without departing from the scope of the invention as defined by the claims.

[0046] The FIGURE shows a system for forming a compressed gas and dispensing the compressed gas to a compressed gas receiver as in particular a fuel tank of a combustion engine or fuel cell vehicle, or some other pressure rated receiving vessel. The FIGURE also illustrates a method for forming the compressed gas from a cryogenic process fluid, i.e. a process fluid provided at a cryogenic temperature. Forming the compressed gas includes at least pressurizing and heating the cryogenic process fluid. Where the compressed gas is compressed hydrogen, compressed natural gas, or a mixture thereof, the cryogenic process fluid, as provided, is hydrogen, natural gas, or a mixture thereof in the liquid or mixed-liquid-gaseous phase.

[0047] The system comprises a source of the cryogenic process fluid as for example a supply vessel 2 filled with the cryogenic process fluid 1, for example, liquid or mixed-phase hydrogen. The system furthermore comprises a cryogenic feeding device 3 operatively disposed to receive cryogenic process fluid 1 from the supply vessel 2. The cryogenic feeding device 3 is configured to pressurize the cryogenic process fluid 1 which leaves the cryogenic feeding device 3 as a pressurized process fluid 4 which is still at a cryogenic temperature. The cryogenic feeding device 3 may be configured to increase the pressure of the cryogenic process fluid 1 from about 0.5 MPa to pressures useful for filling a vehicle fuel tank, normally from 20 to 100 MPa, and typically around 80 MPa. The pressurized process fluid 4 is still very cold, for example −150° C., when it leaves the cryogenic feeding device 3.

[0048] The system therefore comprises a process fluid treatment arrangement for transforming at least a portion of the pressurized cryogenic process fluid 4 leaving the cryogenic feeding device 3 into a compressed gas 7 suitable to be dispensed to a compressed gas receiver 26 via a dispenser 25 and/or sent to intermediate storage, if provided for. The process fluid treatment arrangement comprises a first heat exchanger 5. It may comprise one or more further components arranged in-line with the first heat-exchanger 5 and/or one or more further components arranged in parallel to the first heat-exchanger 5, those optional further components configured to heat and/or vaporize the pressurized process fluid 4 from the cryogenic feeding device 3 should further treatment be necessary to form the compressed gas 7 suitable for filling a receiving vessel.

[0049] Pressurized cryogenic process fluid 4 from the cryogenic feeding device 3 is heated in the first heat exchanger 5 operatively disposed to receive at least a portion of the cryogenic process fluid 4 pressurized and fed by the cryogenic feeding device 3. In the example embodiment the first heat exchanger 5 is operatively disposed to receive all of the cryogenic process fluid 4 pressurized and fed by the cryogenic feeding device 3. The pressurized cryogenic process fluid 4 is heated in the first heat exchanger 5 by indirect heat exchange with a thermal fluid 11 provided in a thermal fluid reservoir 12.

[0050] The thermal fluid reservoir 12 is a reservoir container filled with the thermal fluid 11 at a thermal fluid temperature above the cryogenic temperature of the pressurized process fluid 4 at a process fluid inlet of the first heat exchanger 5. The thermal fluid 11 is circulated in a thermal fluid circuit comprising the thermal fluid reservoir 12, the first heat exchanger 5, and a first thermal fluid pump 14 configured to circulate the thermal fluid 11 from the thermal fluid reservoir 12 to and through the first heat exchanger 5 and from there back into and through the thermal fluid reservoir 12.

[0051] The thermal fluid 11 may advantageously be provided as a liquid. The thermal fluid reservoir 12 may accordingly comprise or consist of a bath of liquid thermal fluid 11 contained in the reservoir container. Circulating the thermal fluid 11 in the thermal fluid circuit involves removing thermal fluid 11 from the bath and re-introducing thermal fluid 11 into the bath. In advantageous embodiments the thermal fluid 11 is chosen to have a standard boiling point above 50° C. or above 80° C., preferably above 100° C., at 1 bar. It may have a standard freeze point below −50° C. or below −70° C., at 1 bar.

[0052] A shell and tube design may be chosen for the first heat exchanger 5. In such a design, the first heat exchanger 5 comprises a casing with an inlet and an outlet for the casing-side fluid. The other one of the two heat exchanging fluids is conveyed through the casing in one or more fluid channels formed as one or more helically coiled tubes. In the example embodiment the pressurized cryogenic process fluid 4 is the channel-side fluid conveyed in the fluid channels and the thermal fluid 11 is the casing-side fluid which surrounds the fluid channels in direct contact with the fluid channels (tubes). Advantageously, the first heat exchanger 5 is a coiled-tube heat exchanger. If the first heat exchanger 5 is designed as a helically coiled-tube heat exchanger, both heat exchanging fluids 4 and 11 are circulated through the first heat exchanger 5 in a helical or spiral flow path, preferably in counter flow or cross-flow, to intensively transfer heat from the thermal fluid 11 to the pressurized cryogenic process fluid 4.

[0053] The thermal fluid 11 cooled in the first heat exchanger 5 is fed back into the thermal fluid reservoir 12. The pressurized process fluid 4 leaving the first heat exchanger 5 may directly be sent to the compressed gas receiver 26, as for example a receiving vessel such as a vehicle tank and/or an on-site storage vessel, if its temperature allows for.

[0054] The pressurized process fluid 4 may however leave the first heat exchanger 5 at a temperature that is still too cold for dispensing it to the compressed gas receiver 26 or feeding it to intermediate storage. The process fluid treatment arrangement may therefore comprise a heater 6, for example an electric resistance heater, to heat a portion of or all the pressurized process fluid 4 leaving the first heat exchanger 5. The heater 6 may serve as an in-line electric trim heater. The heater 6, if present, is operatively disposed to receive at least a portion of the warmed process fluid 4 from the first heat exchanger 5 and configured to heat this a least a portion of the warmed process fluid 4 further, expediently to a temperature allowing to fill the pressurized and tempered process fluid leaving the heater 6 as the compressed gas 7 directly into a receiving vessel such as a vehicle tank and/or an on-site storage vessel.

[0055] The system may comprise one or more compressed gas storage vessels 20 for intermediate storage of compressed gas 7 formed in the process fluid treatment arrangement. The one or more compressed gas storage vessels 20 may operatively be disposed to receive at least a portion 21 of the compressed gas 7 from the process fluid treatment arrangement. In the example embodiment the one or more compressed gas storage vessels 20 are operatively disposed to receive compressed gas 7 from the heater 6. The one or more compressed gas storage vessels 20 may be arranged stationary, i.e. fixed on-site, or on a mobile compressed gas storage trailer to allow for quick replacement, or may comprise a combination of one or more stationary compressed gas storage vessels 20 and one or more mobile compressed gas storage vessels 20.

[0056] The dispenser 25 may operatively be disposed to receive compressed gas 8 by-passing the one or more compressed gas storage vessels 20, and in this sense directly from the process fluid treatment arrangement, here, from the heater 6. All or only a portion of the compressed gas 7 formed in the process fluid treatment arrangement may be conveyed directly, as formed, to the dispenser 25 and dispensed via the dispenser 25 to the compressed gas receiver 26 as for example a vehicle fuel tank.

[0057] If the system comprises the one or more compressed gas storage vessels 20, all or only a portion of the compressed gas 7 formed in the process fluid treatment arrangement may be directed to the one or more compressed gas storage vessels 20 and stored therein for later use. The dispenser 25 may operatively be disposed, at least in principle, to receive compressed gas 22 only from the one or more compressed gas storage vessels 20 for dispensing it to the compressed gas receiver 26. All of the compressed gas 7 formed in the process fluid treatment arrangement may be sent, under this premise, to the one or more compressed gas storage vessels 20. In the example embodiment, however, the one or more compressed gas storage vessels 20 is/are operatively disposed to receive at least a portion 21 of the compressed gas 7, and the dispenser 25 is operatively disposed to receive compressed gas 8 by-passing the one or more compressed gas storage vessels 20 and to receive compressed gas 22 from the one or more compressed gas storage vessels 20. The system may comprise flow regulating means, e.g. valves, for directing the compressed gas fractions 8 and 22 selectively to the dispenser 25, i.e. one at a time. The flow regulating means may furthermore enable conveying both compressed gas fractions 8 and 22 concurrently to the dispenser 25, for example as a mixture.

[0058] Compressed gas 22 from the one or more compressed gas storage vessels 20 may be directed to the dispenser 25 e.g. if the cryogenic feeding device 3 is not ready to send product to the dispenser 25. The dispenser 25 may dispense the compressed gas directly to the compressed gas receiver 26 if the gas is cold enough. More commonly, the compressed gas 22 is too warm to be dispensed directly. Likewise, the compressed gas 8 may be too warm for being dispensed directly. The compressed gas 8 in the conveying line by-passing the one or more compressed gas storage vessels 20 may have been warmed after a longer rest time.

[0059] The system may comprise a second heat exchanger 10 operatively disposed to receive at least a portion 23 of the compressed gas 8 and/or 22 and configured to cool this at least a portion 23 by indirect heat exchange with the thermal fluid 11 before sending it to the dispenser 25. The second heat exchanger 10 is configured to cool the at least a portion 23 of the compressed gas 8 and/or 9 by indirect heat exchange with the thermal fluid 11 to a temperature within a temperature range suitable for dispensing, for example, to a temperature within the range from −17.5° C. to −40° C., preferable to below −33° C.

[0060] The system, for example the dispenser 25, may furthermore comprise a temperature sensor for measuring a temperature representative for the compressed gas 8 and/or 22 directed to the dispenser 25 and a distributor 24 operatively disposed to receive the compressed gas 8 and/or 22. The dispenser 25 is operatively disposed to receive compressed gas via the distributor 24. The distributor 24, if present, is configured for sending the compressed gas 8 and/or 22 directly via the dispenser 25 to the compressed gas receiver 26, if the measured temperature allows for, and is furthermore configured for sending the at least a portion 23 of the compressed gas 8 and/or 22 to the second heat exchanger 10, if the measured temperature is too high. If sent to the second heat exchanger 10, at least a portion 23 is cooled against the thermal fluid 11 to a temperature within a temperature range suitable for dispensing, as mentioned above. The compressed gas suitably cooled then gets dispensed via the dispenser 25.

[0061] The second heat exchanger 10 is a component of the thermal fluid circuit and is operatively disposed to receive thermal fluid 11 from the thermal fluid reservoir 12. Thermal fluid 11 may accordingly be circulated from the thermal fluid reservoir 12 also to and through the second heat exchanger 10 and from there back to and through the thermal fluid reservoir 12.

[0062] A shell and tube design may be chosen for the second heat exchanger 10. In such a design, the second heat exchanger 10 comprises a casing with an inlet and an outlet for the casing-side fluid. The other one of the two heat exchanging fluids is conveyed through the casing in one or more fluid channels formed as one or more helically coiled tubes. In the example embodiment the compressed gas 23 is the channel-side fluid conveyed in the fluid channels and the thermal fluid 11 is the casing-side fluid which surrounds the fluid channels in direct contact with the fluid channels (tubes). Advantageously, the second heat exchanger 10 is a coiled-tube heat exchanger. If the second heat exchanger 10 is designed as a helically coiled-tube heat exchanger, both heat exchanging fluids 23 and 11 are circulated through the second heat exchanger 10 in a helical or spiral flow path, preferably in counter or cross-flow, to intensively transfer heat from the thermal fluid 11 to the compressed gas 23.

[0063] The first heat exchanger 5 and the second heat exchanger 10 could be arranged in series with respect to the circulating thermal fluid 11. In a sequential flow arrangement, the thermal fluid reservoir 12 could be circulated from the thermal fluid reservoir 11 to and through the first heat exchanger 5 where it warms the pressurized process fluid 4. The cooled thermal fluid 11 could then be circulated further to and through the second heat exchanger 10 where it cools the compressed gas 23 and gets in-turn warmed again before it is circulated back to the thermal fluid reservoir 12 to complete a full circle. The sequential flow arrangement could be modified with respect to the flow direction of the thermal fluid. One or more pumps may be arranged in the serial thermal fluid circuit to circulate the thermal fluid 11.

[0064] In more preferred embodiments, one of which is illustrated in the FIGURE, the first heat exchanger 5 and the second heat exchanger 10 are arranged in parallel with respect to the thermal fluid 11. The thermal fluid circuit comprises a first branch 13 and a second branch 15 in parallel to the first branch 13. The first branch 13 comprises the thermal fluid reservoir 12, the first heat exchanger 5, and the first thermal fluid pump 14 configured to circulate the thermal fluid 11 in the first branch 13. The second branch 15 comprises the thermal fluid reservoir 12, the second heat exchanger 10, and a second thermal fluid pump 16 configured to circulate the thermal fluid 11 in the second branch 15.

[0065] The thermal fluid circuit splits into the two branches 13 and 15 upstream of the pumps 14 and 15 and heat exchangers 5 and 10, and the two branches 13 and 15 are united again downstream of the pumps 14 and 15 and heat exchangers 5 and 10. The thermal fluid circuit may split into the two branches 13 and 15 downstream of a thermal fluid outlet of the thermal fluid reservoir 12 and/or the two branches 13 and 15 may be united again upstream of a thermal fluid inlet of the thermal fluid reservoir 12. In the example embodiment, the thermal fluid outlet and the thermal fluid inlet are common to both branches 13 and 15.

[0066] The thermal fluid pumps 14 and 16 may be configured to operate independently from one another. Thermal fluid 11 may accordingly be circulated in the first branch 13 only or in the second branch 15 only or, with both pumps 14 and 16 operating, in both branches 13 and 15 at the same time. Providing a first thermal fluid pump 14 in the first branch 13 for the first heat exchanger 5 and a further, second pump 16 in the second branch 15 for the second heat exchanger 10 increases the flexibility with respect to heat management. The flow rates of the thermal fluid 11 can be optimized for each of the heat exchangers 5 and 10 individually.

[0067] The first pump 14 may turn on any time the cryogenic feeding device 3 is running, as well as when venting to either cool the cryogenic feeding device 3 or venting to keep pressure from building too high in the supply vessel 2. The second thermal fluid pump 16 circulates the thermal fluid 11 as required to keep the second heat exchanger 10 at the correct temperature, typically about −40 C.

[0068] The system may comprise a variable drive configured for driving the first pump 14 and/or the second pump 16 at varying speed(s). The variable drive may comprise a first electric drive motor driving the first pump 14 and/or a second electric drive motor driving the second pump 16. The variable drive may advantageously be a variable frequency drive (VFD) for varying the speed of the respective pump by varying the input frequency of the respective electric drive motor. The speed of the first pump 14 may be varied to keep the temperature of the thermal fluid exiting the first heat exchanger 5 within a predetermined temperature range. The speed of the second pump 16 may be varied to keep the temperature of the thermal fluid exiting the second heat exchanger 10 within a predetermined temperature range and/or to keep the temperature of the compressed gas exiting the second heat exchanger 10 within a predetermined temperature range.

[0069] The thermal fluid reservoir 12 contains the thermal fluid 11 in an amount exceeding an amount necessary to sustain circulation in the thermal fluid circuit. If the thermal circuit, including both branches 13 and 15, contains a total mass M.sub.11 of thermal fluid 11 and the reservoir container contains a mass m.sub.12 out of this total mass, the ratio m.sub.12/M.sub.11 may advantageously fulfill the relation m.sub.12/M.sub.11≥0.5 or, more preferably, m.sub.12/M.sub.11≥0.6, or m.sub.12/M.sub.11≥0.7.

[0070] The thermal fluid circuit may comprise a thermal fluid heater 18, as in particular an electric resistance heater, for heating the thermal fluid 11. The thermal fluid heater 18 may serve to compensate for any shortfall of heat, for example, if the cold accumulated by the thermal fluid 11 in the first heat exchanger 5 cannot be fully compensated by the transfer of heat to the thermal fluid 11 in the second heat exchanger 10. The thermal fluid heater 18 may be arranged in a conveying line conveying the thermal fluid 11 to the first heat exchanger 5 or in a conveying line conveying the thermal fluid 11 back to the thermal fluid reservoir 12. In the example embodiment, the thermal fluid heater 18 is disposed in the reservoir container and immersed in the thermal fluid 11 of the thermal fluid reservoir 12.