Cryogenic liquid conditioning and delivery system

Abstract

A cryogenic liquid conditioning system with flow driven by head pressure of liquid contained in a cryogenic storage tank, and a cryogenic liquid delivery system with flow driven by pressure in the vapor space of the cryogenic storage tank. A heat exchanger, coupled to the cryogenic storage tank located below the liquid level of the tank, operates as a portion of both the conditioning system and delivery system. A piping system moves cryogenic liquid to the heat exchanger where it is vaporized, and then moves vaporized liquid to the vapor space of the cryogenic tank and an application. The piping system includes a controller and valve(s) for controlling flow through the system. A sensor for measuring the saturated pressure of cryogenic liquid is coupled to the storage tank or piping system, and is in communication with the flow controller.

Claims

1. A method of conditioning cryogenic liquid onboard a transport vehicle, the method comprising the steps of: A) providing a conditioning system onboard the transport vehicle, the conditioning system comprising: (a) an insulated storage tank capable of storing a liquid at a cryogenic temperature and an initial pressure, wherein the stored liquid defines a liquid level and a vapor space of the storage tank; (b) a heat exchanger below the liquid level of the storage tank, wherein the heat exchanger converts cryogenic liquid to vapor; (c) a piping system connecting the storage tank to the heat exchanger, the piping system including: (i) a liquid flow path allowing cryogenic liquid to travel from the storage tank to the heat exchanger; (ii) a first vapor flow path allowing vapor to travel from the heat exchanger to an application; (iii) a second vapor flow path allowing vapor to travel from the heat exchanger to the vapor space of the storage tank; and (iv) at least one valve for selectively opening and closing the first vapor path and the second vapor path; (d) means for measuring saturated pressure of the cryogenic liquid in the storage tank; and (e) means for controlling the at least one valve based on the measured saturated pressure; B) controlling the at least one valve based on the measured saturated pressure such that: (a) when the measured saturated pressure is less than a first level for use of vapor by the application, the first vapor flow path is closed and the second vapor flow path is opened; (b) when the measured saturated pressure is equal to or greater than the first level and less than a second level, the first vapor flow path is opened and the second vapor flow path is opened; and (c) when the measured saturated pressure is equal to or greater than the second level, the first vapor flow path is opened and the second vapor flow path is closed; and C) agitating the storage tank to raise the saturated pressure of the cryogenic liquid in the storage tank to the second level, wherein the storage tank is agitated by operating the transport vehicle.

2. The method according to claim 1, wherein the piping system includes exactly one liquid flow path.

3. The method according to claim 1, wherein the piping system includes exactly one first vapor flow path.

4. The method according to claim 1, wherein the piping system includes exactly one second vapor flow path.

5. The method according to claim 1, wherein the at least one valve for selectively opening and closing the first vapor path and the second vapor path comprises a first valve in the first vapor path and a second valve in the second vapor path.

6. The method according to claim 1, wherein the liquid flow path includes means for maintaining a definitive liquid level within the piping system.

7. The method according to claim 6, wherein the means for maintaining a definitive liquid level within the piping system comprises a trap.

8. The method according to claim 6, wherein the means for maintaining a definitive liquid level within the piping system comprises a valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view of a cryogenic liquid conditioning and delivery system in accordance with a preferred embodiment of this disclosure.

(2) FIG. 2 is a schematic view of a cryogenic liquid conditioning and delivery system in accordance with a preferred embodiment of this disclosure.

(3) FIG. 3 is a schematic view of a cryogenic liquid conditioning and delivery system in accordance with a preferred embodiment of this disclosure.

(4) Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)

(5) Throughout the following description specific details are set forth in order to provide a more thorough understanding of the disclosure. However, the disclosure may be practiced without these particulars. In other instances, well known elements have not been showed or described in detail to avoid unnecessarily obscuring the present disclosure. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than restrictive sense.

(6) Generally, the subject disclosure relates to cryogenic liquid conditioning and delivery system, namely, a cryogenic tank assembly that incorporates a cryogenic storage tank, a combined liquid conditioning system to increase the saturated pressure of a cryogenic liquid within a storage tank, and a cryogenic liquid delivery system to deliver pressurized gas to an application such as a vehicular engine. The system described herein utilizes gravity or head pressure of the cryogenic liquid to move liquid through the conditioning system, and pressure in the vapor space of the tank to move cryogenic liquid through the delivery system.

(7) As illustrated in FIG. 1, a cryogenic liquid delivery system, indicated generally at 10, is shown in an example implementation in accordance with the disclosure. The system includes a conditioning system, indicated generally at 13, to maintain saturated pressure in a storage tank 14 at a minimum acceptable saturated pressure to move cryogenic liquid through the delivery system 10. The system utilizes one heat exchanger to supply vaporized cryogenic liquid to both the vapor space of the storage tank, and to an application. The cryogenic liquid conditioning system described herein utilizes head pressure to move cryogenic liquid into a heat exchanger 15 located below the liquid level 16 of the storage tank. The cryogenic liquid is vaporized in the heat exchanger 15 and returned to the vapor space 17 of the tank. The cryogenic tank is then agitated, and the vaporized material condenses into the cryogenic liquid, thereby raising the saturated pressure of the cryogenic liquid within the storage tank. When the saturated pressure of the cryogenic liquid reaches a sufficient level, the pressure in the vapor space of the storage tank will move liquid through the heat exchanger 15, where it will be vaporized, and deliver the resulting pressurized gas to an application.

(8) The schematic diagram in FIG. 1 shows the overall mechanical interaction and operation of a preferred embodiment of the present disclosure. The schematic diagram also illustrates the flow paths for liquid and vapor. It will be appreciated that alternate designs and types of cryogenic storage tanks can be utilized without materially affecting the operation of the disclosure described herein. The configuration in FIG. 1 can be utilized in a number of applications, including vehicles with an engine designed to be powered by cryogenic fuel, or as a retrofit to existing vehicles, such as those with a diesel-powered engine. The system will have at least one insulated storage tank 14 capable of receiving and containing cryogenic liquid. Typically, the tank 14 will be a vacuum insulated cryogenic storage tank designed to contain cryogenic liquid such as liquefied natural gas. For clarity, other devices that are commonly installed on cryogenic storage tanks such as pressure safety valves, liquid fill circuits, liquid level gauges, and pressure gauges are not displayed in FIG. 1 since they are immaterial to the operation of the disclosure.

(9) A heat exchanger 15 is coupled to the storage tank, and located below the liquid level of the storage tank. A piping system 19 is coupled to the storage tank and heat exchanger 15. The piping system is sufficiently large to minimize pressure drop and resistance to flow. The piping system includes a liquid flow path 20 from the storage tank to the heat exchanger. The liquid flow path protrudes into the storage tank below the liquid level 16 of the tank, and may contain a means for maintaining a definitive liquid level within the piping system. The piping system further includes a vapor flow path 22 from the heat exchanger 15 to the vapor space 17 of the storage tank. The vapor flow path to the vapor space of the cryogenic tank contains a means for controlling vapor flow, such as a control valve 18b. Any type of control valve that, when open, would not increase flow restrictions, may be utilized without materially affecting the operation of this disclosure. The vapor flow path 22 to the vapor space 17 of the tank protrudes into the tank above the liquid level 16 of the tank. The piping system further includes a vapor flow path 21 from the heat exchanger to an application 11 that will utilize pressurized gas. The vapor flow path 21 to the application also contains a means for controlling vapor flow, such as a control valve 18a.

(10) In typical operating conditions, the liquid in the cryogenic tank must be saturated at a given pressure, meaning that the liquid in the tank must be warmed to a desired temperature and pressure equilibrium before it will move to an application 11. Liquid that has been warmed and saturated at a given pressure is known as conditioned liquid. If unconditioned liquid is dispensed into the storage tank, pressure head will move the liquid through the conditioning system 13 until it has been warmed to a desired temperature, and the cryogenic liquid is saturated at a given pressure.

(11) To condition cryogenic liquid, head pressure within the storage tank causes liquid to flow into the liquid flow path 20, and then into the heat exchanger 15. There are minimal flow restrictions in the liquid flow path and heat exchanger which allow cryogenic liquid to move through the conditioning system 13 with minimal head pressure in the storage tank 14, and pressure drop in the heat exchanger 15. The heat exchanger causes the cold cryogenic liquid to become warm, and quickly and completely vaporize before exiting. Any type of heat exchanger may be used including, but not limited to, a device that utilizes a hot liquid solution such as engine coolant. The heat exchanger is located below the liquid level 16, and in close proximity to the storage tank, so as to minimize pressure drop and resistance to flow in the liquid flow path 20 and heat exchanger 15.

(12) A means 26 for detecting the saturated pressure in the storage tank, communicates with the control valves 18a 18b in both vapor flow paths 21 22. Several measurement devices may be used including pressure sensors, thermocouples and other devices that are able to detect the saturated pressure of a cryogenic liquid. The device can communicate with the control valves in any way, including a programmable logic controller, mechanical relays, or solid state relays. When the saturated pressure of the cryogenic liquid in the storage tank is below a given level, the control valve 18a in the vapor flow path 21 to the application will close, and the control valve 18b in the vapor flow path 22 to the vapor space of the cryogenic tank will open. Liquid head pressure within the storage tank will then cause liquid to flow into the liquid flow path 20, and into the heat exchanger, where it will be vaporized. Vapor exiting the heat exchanger will then move through the conditioning system 13, and enter the vapor space of the cryogenic tank 17. Tank agitation will then cause the vapor to condense into the cryogenic liquid, raising the saturated pressure and temperature of the liquid within the storage tank 14.

(13) Once the saturated pressure of the cryogenic liquid within the storage tank has reached a given level, the control valve 18a in the vapor flow path to the application will open, and the control valve 18b in the vapor flow path to the cryogenic tank will close. The pressure in the vapor space of the cryogenic tank will then cause liquid to flow into the liquid flow path 20, and into the heat exchanger 15, where it will be vaporized. Vapor exiting the heat exchanger will then move through the vapor flow path 21 to the application.

(14) If the saturated pressure of the cryogenic liquid is sufficient for use in the application, but not elevated to a desired level, both control valves 18a 18b may be open simultaneously. When both valves are open, head pressure and pressure in the vapor space of the cryogenic tank will cause liquid to flow into the liquid flow path 20, and then into the heat exchanger 15, where it will be vaporized. Portions of the vapor exiting the heat exchanger will then move through both vapor flow paths 21 22 to the application 11 and the vapor space 17 of the cryogenic tank 14.

(15) Referring to FIG. 2, another system 10b is shown that is similar in most respects to that described above, but where the liquid flow path 20 contains a bend or trap 28 to maintain a definitive liquid level within the piping system.

(16) Referring to FIG. 3, another system 10c is shown that is similar in most respects to that described above, but where the liquid flow path 20 contains a valve 29 to maintain a definitive liquid level within the piping system.

(17) The cryogenic liquid conditioning system 13 and delivery system 10 may be enclosed in a shroud coupled to the cryogenic tank 14 to ease installation on an object such as a vehicle. However, failure to enclose the system will not materially affect the operation of this disclosure.

(18) While the foregoing examples are illustrative of the principles of the present disclosure in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the disclosure. Accordingly, it is not intended that the disclosure be limited, except as by the claims set forth below.