Gas dispensing system with tank pressure and thermal management

Abstract

To provide a cryogenic delivery tank for supplying a gas to a use device, and the improved cryogenic delivery tank capable of keeping desired temperature and pressure in the cryogenic tank.SOLUTION: A cryogenic tank is configured to contain a gas in a headspace above a cryogenic liquid. First and second vaporizers and a use outlet are disposed, a first pipe is configured to transfer the gas from the headspace to the use outlet through the first vaporizer. A second pipe is configured to transfer a liquid from the tank through the first vaporizer so that a first vapor stream is directed to the use outlet. A third pipe is configured to transfer the liquid from the tank through the second vaporizer so that a second vapor stream is directed back to the headspace of the tank, and a pressure in the tank is increased.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001]

[0001] (Claim of Priority) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 009,614, filed April 14, 2020, the contents of which are hereby incorporated by reference.

[0002]

[0002] This disclosure relates generally to a cryogenic storage and delivery system for providing gas to a use device or process, and more specifically to a cryogenic storage and delivery system for providing gas to a use device or process while managing heat and pressure within a cryogenic tank. [Background technology]

[0003] Cryogenic tanks are an efficient way to store cryogenic fluids for use as gases. Gases are typically stored in a liquefied state because they take up much less volume when stored in a liquefied state. For example, liquefied natural gas takes up roughly 600 times less volume as a liquid than as a gas. Temperature and pressure control of cryogenic tanks is extremely important. Liquefied gases are stored in insulated cryogenic tanks to meet the low temperature requirements, and are typically stored at low pressures. Also, stored cryogenic liquids are typically saturated so that both gas and liquid states exist simultaneously at the desired temperature and pressure.

[0004]

[0004] A use device often requires that the gas be delivered from the cryogenic tank system at a specific temperature and pressure. While providing the gas to the use device, the pressure and temperature within the cryogenic tank may fluctuate. When the temperature and / or pressure increases too much, it may be necessary to vent the gas to the atmosphere, which may result in loss of the stored product. Therefore, it is desirable to have a cryogenic delivery tank system for providing the gas to the use device that can manage the internal temperature and pressure and prevent loss of the product.

[0005] 1, a prior art system for dispensing gas from a cryogenic liquid storage and delivery tank includes a cryogenic tank 100 having cryogenic liquid 110 and vapor 120 in a head space above a liquid level line 115. The cryogenic tank includes an inner shell 101 and an outer shell 102. The cryogenic tank system includes a vapor pipe or line 400 from the cryogenic tank 100 to a product vaporizer 12 and a distribution outlet valve 10. The pipe or line 400 may include a number of manual isolation valves, such as valve 30. The pipe or line 400 further includes an economizer regulator 6. A liquid line 300 leads from the liquid portion of the tank to the vaporizer 12 and the distribution outlet valve 10. In addition, the system includes a pressure boost line 500 that includes a pressure boost regulator 7 and runs from the liquid portion of the tank to a pressure boost vaporizer 13 and back to the tank 100.

[0006] When the distribution valve 10 is opened, gas from the system is taken for consumption by the use device or process. The regulator 7 is set to open at approximately 30 bar, while the economizer 6 is set to open at approximately 32 bar. Therefore, if the tank pressure is higher than 32 bar, gas vapor from the head space or head space of the tank should flow to the product vaporizer 12. However, the economizer 6 is a small regulator with a small capacity (kv or cv), and therefore only low flow rates can be accommodated without a large pressure drop across the economizer. As shown in FIG. 2 as path 401, when the economizer 6 is opened, gas flows through line 400. When the pressure in the head space of the tank drops below approximately 32 bar, the economizer 6 closes.

[0007] Regardless of whether the economizer 6 is open or closed, liquid from the bottom of the tank passes along path 301 through liquid line 300 to the vaporizer 12 as shown in FIG. 3 to meet consumption requirements when the dispensing or distribution valve 10 is opened.

[0008] If the tank pressure drops below the set point of pressure boost regulator 7, the regulator opens and liquid flows along line 501 as depicted in FIG. 4, using vapor from pressure boost vaporizer 13 to pressurize the tank.

[0009] Depending on the amount of gas taken by 10 in the device or process used, the product vaporizer 12 will flood. Closing the distribution valve 10 will stop the gas take-off and the pressure will rise rapidly in the product vaporizer 12 due to the vaporization of the residual liquid remaining therein. The pressure created will push the steam and the heated liquid that has not yet vaporized back to the bottom of the tank. The economizer is then closed. During frequent cycles (gas consumption, pause, gas consumption, etc.), this process will rapidly heat up the liquid in the tank. After a while, the pressure in the tank will increase to the main relief valve set point. The safety valve, generally designated 600, will then open, resulting in the loss of some of the stored fluid.

[0010]

[0010] In this prior art design, the economization function has a very small working window. Economization only works if the pressure in the tank is high and the consumption through the distribution valve 10 by the used device or process is very low. At higher consumption, the flow rate drop and therefore the pressure drop across the economizer 6 increases, and mainly only liquid is taken from the tank 100. This causes the pressure to increase in the tank and may require the release of cryogen from the tank. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Provisional Patent Application No. 63 / 009,614 Summary of the Invention [Problem to be solved by the invention]

[0012] It would be desirable to provide a cryogenic delivery tank for supplying gas to a use device that has improved maintenance of a desired temperature and pressure within the cryogenic tank. [Means for solving the problem]

[0013]

[0012] Several aspects of the present subject matter may be embodied separately or collectively in the methods, devices, and systems described and claimed below. These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and describing these aspects as a group is not intended to exclude the use of these aspects separately, nor does it exclude claiming such aspects separately or in different combinations as set forth in the accompanying claims.

[0014] In one aspect, a system for cryogenic gas delivery includes a cryogenic tank containing a cryogenic liquid and gas in a head space above the cryogenic liquid. The system further includes a first vaporizer and a second vaporizer and a use outlet. A first tube is configured to move gas from the head space through the first vaporizer to the use outlet. A second tube is configured to move liquid from the tank through the first vaporizer such that a first vapor stream is directed to the use outlet. A third tube is configured to move liquid from the tank through the second vaporizer such that a second vapor stream is directed back to the head space of the tank, thereby increasing pressure in the tank. A first regulator valve is in fluid communication with the second tube. The first regulator valve is configured to open when pressure on the outlet side of the first regulator drops below a first predetermined pressure level. A second regulator valve is in fluid communication with the third tube. The second regulator valve is configured to open when pressure within the tank drops below a second predetermined pressure level, the first predetermined pressure level being greater than the second predetermined pressure level.

[0015] In another aspect, a method of providing gas from a cryogenic tank to a use device while maintaining a temperature and pressure in the cryogenic tank including a liquid stored in a delivery tank includes opening a dispense valve to initiate distribution of gas to the use device. At a first tank pressure, gas is directed through a first tube and a first vaporizer to the use device. At a second tank pressure, liquid is directed from the tank through a second tube and a first vaporizer to the use device. At a third tank pressure, liquid is directed from the tank through a third tube and a second vaporizer back to the tank. When the dispense valve is closed to stop distribution of gas to the use device, any remaining liquid or gas in the first vaporizer is returned to the top of the tank by the first tube. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of a prior art cryogenic delivery tank system. [Diagram 2] FIG. 2 is a schematic diagram of a first gas delivery function of the system of FIG. 1. [Diagram 3]

[0017] FIG. 2 is a schematic diagram of a second gas delivery function of the system of FIG. 1. [Figure 4]

[0018] FIG. 2 is a schematic diagram of the pressure boost function of the system of FIG. 1. [Diagram 5]

[0019] FIG. 1 is a schematic diagram of one embodiment of a delivery tank system of the current disclosure. [Figure 6]

[0020] FIG. 6 is a schematic diagram of a first gas delivery function of the system of FIG. 5. [Figure 7]

[0021] FIG. 6 is a schematic diagram of a second gas delivery function of the system of FIG. 5. [Figure 8]

[0022] FIG. 6 is a schematic diagram of the pressure boost function of the system of FIG. 5. [Figure 9]

[0023] FIG. 2 is a schematic diagram of another embodiment of a delivery tank system of the current disclosure. [Figure 10]

[0024] FIG. 2 is a schematic diagram of another embodiment of a delivery tank system of the current disclosure. [Figure 11]

[0025] FIG. 11 is a schematic diagram of a first gas delivery function of the system of FIG. [Figure 12]

[0026] FIG. 11 is a schematic diagram of a second gas delivery function of the system of FIG. [Figure 13]

[0027] FIG. 2 is a schematic diagram of another embodiment of a delivery tank system of the current disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017]

[0028] Certain disclosed embodiments provide a storage and delivery tank with thermal and pressure management capabilities.

[0018]

[0029] 5 illustrates a cryogenic delivery tank system 200 of the present disclosure that includes a cryogenic tank 203. The cryogenic tank 203 is employed to store a cryogenic liquid. By way of example only, the cryogenic liquid may be nitrogen, helium, oxygen, or any other known cryogenic fluid.

[0019]

[0030] In the illustrated embodiment, the cryogenic tank 203 has an inner shell 201 and an outer shell 202, the inner shell defining the interior of the tank. Stored within the interior of the inner shell 201 is a cryogenic liquid 210. The cryogenic liquid 210 occupies a certain volume of the cryogenic tank 203, with the remaining volume being occupied by a cryogenic gas or vapor 220. A liquid level 215 is included for illustrative purposes, although the liquid level may change, particularly upon each event (after delivery of gas by the system, refilling of the tank with liquid, etc.).

[0020]

[0031] In the illustrated embodiment, the cryogenic tank 203 is a vertical tank. In other embodiments, the tank 203 may be a horizontal tank.

[0021]

[0032] The cryogenic tank 203 of the current invention is shown as being double walled, but may also be single or triple walled. The cryogenic tank may be made from copper alloys, nickel alloys, carbon, stainless steel, or any other material known in the art.

[0022]

[0033] The cryogenic delivery tank 203 may have insulation between the inner wall (inner shell) and the outer wall (outer shell) and / or may be vacuum insulated. Single or multiple layers of insulation of any known material for insulation may be utilized.

[0023]

[0034] The inner container 201 can be joined to the outer container 202 by one or more inner container support members. For example, the inner container support members may connect the neck and base of the inner container to the outer container, as known in the art.

[0024]

[0035] The cryogenic delivery system 200 includes at least one vaporizer, preferably at least two vaporizers, for converting liquefied gas to gas for use by a use device or process. Various types of vaporizers can be used as disclosed herein, such as atmospheric, hydronic, electric, fuel-fired, steam, or water bath vaporizers. In one embodiment, an atmospheric vaporizer is utilized. The cryogenic delivery system 200 includes at least one first vaporizer 12 and a second vaporizer 13. The vaporizer 12 acts as a product vaporizer, converting liquid from the tank to vapor and warming the vapor or warming vapor from the headspace of the tank to the appropriate pressure and temperature for the use device. The vaporizer 13 acts as a pressure boost vaporizer to increase the pressure of the cryogenic tank by taking liquid from the tank, forming a gas, and returning it to the headspace of the tank. Although three vaporizers are shown, one for the product and one for the pressure boost, cryogenic delivery system 200 may include more or fewer vaporizers.

[0025]

[0036] A number of connected transfer tubes or lines serve different functions with respect to the tank and the use device as part of the cryogenic delivery system 200. The cryogenic delivery system 200 includes a liquid line 350 from the liquid portion of the tank, which provides liquid for conversion to gas through the vaporizer 12 and to a use outlet 250 that connects to a use device or process. A vapor line 450 provides vapor from the tank 203 for passage through the vaporizer 12 and then distribution to the use device through the use outlet 250. A pressure boost line 550 directs liquid from the tank 203 to the pressure boost vaporizer 13 to circulate the resulting vapor stream back into the tank 203 so that the pressure within the tank is increased. Although specific details are not shown in the figures, both ends of each transfer tube can feature a number of specific fittings. For example, each may include a removable reusable seal. Each tube end may further include a valve or vent. The cross-sections of the tubes and other structures can have a variety of shapes, such as circular, oval, square, triangular, pentagonal, hexagonal, polygonal, or other shapes.

[0026]

[0037] The transfer lines of cryogenic delivery tank system 200 may have multiple valves. Line 450 has isolation valve 32 while line 350 has valve 10, which in the embodiment of Figure 5 is an isolation valve. Line 550 has isolation valve 8. Use outlet 250 may have a dispense valve that is opened to provide gas to a use device or process.

[0027]

[0038] The valves of the system may be, but are not limited to, globe valves, ball valves, check valves, gate valves, tilting disk check valves, swing check valves, or stop check valves.

[0028]

[0039] The valve may also be an electromechanical valve, such as a solenoid valve. In one embodiment, the dispensing valve of the usage outlet 250 is a solenoid valve.

[0029]

[0040] Pressure boost line 550 contains pressure boost regulator 16 and liquid line 350 contains liquid regulator 17. In the embodiment illustrated in Figure 5, vapor line 450 does not have a regulator valve or economizer.

[0030]

[0041] The cryogenic tank system 200 may include devices or gauges for reading different characteristics of the tank system. These devices or gauges may indicate pressure, temperature, differential pressure, liquid level, etc.

[0031]

[0042] The cryogenic tank system 200 may further include a control system. The control system may include a controller and optionally various sensors (e.g., pressure and temperature sensors, etc.) located on or within the system. The controller may be utilized to control various portions of the cryogenic tank system, such as the valves of the cryogenic tank system 200. The controller may be wired or wireless and may be in communication with the optional sensors and with those valves and other portions of the system that it controls. The controller may include a processor or other computing device and may be programmable to regulate or initiate processes upon certain events or status information, including placing the system in the configurations described below. The controller may also provide information to a user, such as historical data or various types of instructions.

[0032]

[0043] In the embodiment of FIG. 5 or any other embodiment of the current disclosure, the cryogenic tank system 200 includes at least one tube for filling the tank with cryogenic liquid. In one embodiment, a separate fill tube and a separate withdrawal tube are provided. There may also be other paths leading out of the inner vessel for filling and withdrawing liquid. The fill tube and withdrawal tube may be any suitable conduit for carrying or allowing the flow of fluid therethrough.

[0033]

[0044] FIG. 6 illustrates a first gas delivery function by the cryogenic tank system 200. The valve 32 in line 450 is opened and remains open throughout the operation described below. When a use device or use process is connected and the dispense valve is opened at the use outlet 250, gas is transferred from the headspace of the cryogenic tank 203 as long as the pressure in line 450, and therefore the pressure on the outlet side of the liquid regulator 17, is above a specific pressure. In one embodiment, the specific pressure is 30 bar. In other words, the liquid regulator 17 is closed when the pressure on the outlet side (i.e., the pressure in line 450) is above approximately 30 bar. Gas proceeds from the headspace of the cryogenic tank through the tube 450, through the product vaporizer 12 (which may be heated) to the use outlet 250, as generally represented by arrow 451. Taking vapor from the tank headspace significantly improves the overall heat management because the removal of gas removes a large amount of heat from the tank. Unlike conventional systems, there is no economizer or regulator on line 450 that interferes with the gas moving out of the tank headspace.

[0034]

[0045] FIG. 7 illustrates a second gas delivery function by the cryogenic tank system 200. As previously mentioned, the liquid regulator 17 on line 350 is set to a specific pressure of approximately 30 bar. When the pressure in the headspace of the cryogenic tank drops due to gas / vapor withdrawal from the headspace, the pressure in line 450 drops below 30 bar and the liquid regulator 17 opens. Liquid then flows from the tank through line 350 and regulator 17 to the product vaporizer 12. The resulting vapor then flows through the use outlet 250 to the use device or process. The fluid path is generally indicated by arrow 351 in FIG. 7.

[0035]

[0046] FIG. 8 illustrates the pressure build-up function of the cryogenic tank system 200. The pressure build-up regulator 16 on line 550 is set to open when the pressure in the tank drops to a specific pressure. In one embodiment, the specific pressure is approximately 29 bar. When the pressure in the cryogenic tank drops to that specific pressure due to gas / vapor withdrawal from the headspace of the tank and / or liquid withdrawal from the bottom of the tank, liquid flows from the tank through line 550 to the pressure build-up vaporizer 13. The resulting vapor flows back to the cryogenic tank 203 and enters the vapor headspace. The fluid path is generally indicated by arrows 551 in FIG. 8. The pressure build-up regulator 16 closes when the pressure in the tank rises above approximately 29 bar. This maintains the desired pressure in the tank and to the product vaporizer 12.

[0036]

[0047] When consumption by the use device or process is stopped, the liquid remaining in the product vaporizer 12 will vaporize. The pressure created by this action will push back the heated liquid and residual vapor that could not yet be vaporized. The liquid and vapor will travel through line 450 and back into the headspace of the cryogenic tank 203. The liquid regulator 17 will close due to the higher pressure in the product vaporizer 12. The pressure inside the tank should rise again above 29 bar, so the pressure increase regulator 16 will close. The excess heat in the form of vapor will build up again at the top of the tank, allowing the removal of gas / vapor from the top of the tank before switching to liquid withdrawal during the next gas delivery or dispensing cycle.

[0037]

[0048] This improvement in design ensures that the cold liquid at the bottom of the tank stays in the tank and does not warm up as it would in the prior art system of Figure 1. By keeping the liquid cold in the tank, the heat capacity of the stored liquid is also maintained. Therefore, even if there is frequent cycling (gas consumption, interruption, gas consumption, etc.), the impact should be limited, resulting in less frequent opening of the relief valve and lower loss of stored liquid.

[0038]

[0049] 9 illustrates an additional embodiment of the current disclosure in which a cryogenic tank system 225 employs a check valve 18 along liquid line 350. Cryogenic tank system 225 can include all of the features of cryogenic tank system 200, but with the additional check valve 18. As a one-way valve, check valve 18 prevents liquid backflow from product vaporizer 12 to the bottom of the cryogenic tank after gas consumption has stopped if the pressure in the product vaporizer is below the seating point of liquid regulator 17 (and therefore liquid regulator 17 is open).

[0039]

[0050] Alternatively, valve 10 in FIG. 9 may be a globe check valve that prevents liquid backflow from product vaporizer 12 to the bottom of the cryogenic tank after gas consumption has stopped if the pressure in the product vaporizer is below the installation point of liquid regulator 17 (and therefore liquid regulator 17 is open) (check valve 18 may be omitted).

[0040]

[0051] FIG. 10 illustrates an additional embodiment of the current disclosure in which a cryogenic tank system 226 employs a loop 19 prior to the product vaporizer 12. The cryogenic tank system 226 can include all of the features of the cryogenic tank system 200, but further includes a loop prior to the product vaporizer 12. Of note, in the embodiment of FIG. 10, the loop 19 features a physically elevated ridge above the product vaporizer 12. As depicted in FIG. 10, a vapor line 450 is attached to this ridge of the loop. This embodiment, which may be desirable in some applications of the disclosed technology, prevents a portion of the liquid from the tank and line 350 from flowing into line 450 at the same time that the remainder of the liquid proceeds to the product vaporizer 12. Such flow into line 450 would result in flow into the headspace of the tank, causing line 450 to undesirably function as a pressure buildup circuit.

[0041]

[0052] 11 and 12 illustrate the first and second gas delivery functions for the cryogenic tank system 226. FIG. 11 shows a gas path, generally represented by arrow 452, from the headspace of the cryogenic tank 203 when the liquid regulator 17 is closed to the use outlet 20 and the use device or process. FIG. 12 shows a liquid path, generally represented by arrow 352, from the cryogenic tank 203 through the open liquid regulator 17 and vaporizer 12 to the use outlet 250 and the use device or process. As previously noted, the loop 19 provides additional structure to ensure that liquid drawn from the cryogenic tank through line 350 does not flow through valve 32 into gas line 450.

[0042]

[0053] Figure 13 illustrates an additional embodiment of the current disclosure in which a cryogenic tank system 227 uses a check valve 18 along line 350 in conjunction with the loop arrangement 19 of Figures 10-12. The cryogenic tank system 227 can include all of the features and functionality of the cryogenic tank system 226 of Figures 10-12, but also includes a check valve 18, the functionality of which is described above with respect to Figure 9. As further described with respect to Figure 9, in another alternative embodiment of the disclosed system, the valve 10 of Figure 13 can be a globe check valve (and the check valve 18 can be omitted).

[0043]

[0054] While preferred embodiments of the disclosure have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the disclosure, the scope of which is defined by the appended claims. [Explanation of symbols]

[0044] 8 Isolation valve 10 Isolation valve 12 First vaporizer, product vaporizer 13 Second carburetor, pressure boost carburetor 16 Pressure boost regulator 17 Liquid regulator 18 Check valve 19 Loop 32 Isolation valve 200 Cryogenic Delivery Tank System 201 Inner shell 202 Outer shell 203 Cryogenic Tank 210 Cryogenic Liquids 215 Liquid level 220 Cryogenic gas or steam 225, 226, 227 Cryogenic Tank Systems 250 use outlet 350 Fluid Line 351 Fluid Path 352 Liquid Path 450 Steam Line 451 Gas Path 452 Gas Path 550 Pressure Increase Line 551 Fluid Path

Claims

1. a cryogenic tank comprising an inner shell and an outer shell, the inner shell defining an interior configured to contain a cryogenic liquid and a gas in a headspace above the cryogenic liquid; A first vaporizer; A second vaporizer; Use outlet, a first conduit configured to move gas from the headspace through the first vaporizer to the outlet; a second tube configured to move liquid from the tank through the first vaporizer such that a first vapor stream is directed to the use outlet; and a third conduit configured to move liquid from the tank through the second vaporizer such that a second vapor stream is directed back to the headspace of the tank, thereby increasing pressure within the tank; and a first regulator valve in fluid communication with the second conduit, the first regulator valve configured to open when pressure on an outlet side of the first regulator valve drops below a first predetermined pressure level; a second regulator valve in fluid communication with the third line, the second regulator valve configured to open when pressure within the tank drops below a second predetermined pressure level; 1. A system for cryogenic gas delivery comprising: the first predetermined pressure level is greater than the second predetermined pressure level; A system for cryogenic gas delivery.

2. 10. The cryogenic tank delivery system of claim 1, wherein the system further comprises a piping loop upstream of the first vaporizer.

3. The cryogenic tank delivery system of claim 2 , wherein the loop includes a physically raised ridge above the first vaporizer.

4. 4. The cryogenic tank delivery system of claim 1, further comprising a valve on the second line between the first regulator valve and the first vaporizer.

5. The cryogenic tank delivery system of claim 4 , wherein the valve is a check valve.

6. 5. The cryogenic tank delivery system of claim 4, wherein the valve is a globe check valve.

7. 7. The cryogenic tank delivery system of claim 1, wherein the first line does not have a regulator valve.

8. 8. A cryogenic tank delivery system as claimed in any one of claims 1 to 7, wherein the first predetermined pressure level is 3.0 MPa (30 bar).

9. 9. A cryogenic tank delivery system as claimed in any one of claims 1 to 8, wherein the second predetermined pressure level is 2.9 MPa (29 bar).

10. 10. The cryogenic tank delivery system of claim 1, wherein the first vaporizer is an atmospheric vaporizer.

11. 11. The cryogenic turbine according to claim 1, wherein the second vaporizer is an atmospheric vaporizer. Ink delivery system.

12. 12. The cryogenic tank delivery system of claim 1, wherein the first pipe includes an isolation valve.

13. 1. A method for providing gas from a cryogenic tank to a use device while maintaining a temperature and pressure within said tank, comprising: opening a dispensing valve to initiate delivery of gas to the use device; directing gas at a first tank pressure through a first tube and a first vaporizer to the use device; directing liquid from the tank through a second line and the first vaporizer to the use device at a second tank pressure; directing liquid from the tank through a third line and a second vaporizer back to the tank at a third tank pressure; closing the dispensing valve to stop delivery of gas to a use device; returning any residual liquid or gas in said first vaporizer to the top of said tank via said first pipe; Equipped with The method, wherein the first tank pressure is greater than the second tank pressure, and the second tank pressure is greater than the third tank pressure.

14. 14. The method of claim 13, wherein the first tank pressure is approximately 30 bar or greater.

15. 15. The method of claim 13 or claim 14, wherein the second tank pressure is approximately 30 bar or less.

16. 16. The method of any one of claims 13 to 15, wherein the third tank pressure is approximately 2.9 MPa (29 bar) or below.

17. 17. The method of any one of claims 13 to 16, further comprising directing liquid or gas through a loop prior to the first vaporizer.

18. 18. The method of any one of claims 13 to 17, wherein the second line further comprises a regulator that opens at the second tank pressure to allow liquid to flow through the second line to the first vaporizer.

19. 19. The method of any one of claims 13 to 18, wherein the third line further comprises a regulator that opens at the third tank pressure to allow liquid to flow through the third line to the second vaporizer.

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