METHOD OF OPERATING A COLD CRYOGENIC LIQUID SUPPLY CHAIN

Abstract

A cryogen storage vessel at an installation is filled with liquid cryogen from a liquid cryogen storage tank that has a pressure lower than that of the vessel. After headspaces of the vessel and tank are placed in fluid communication with another via a gas transfer vessel and are pressure-balanced, a pump in a liquid transfer line connected between the tank and the vessel is operated to transfer amounts of liquid cryogen from the tank to the vessel via the liquid transfer line and pump as amounts of gaseous cryogen are transferred, through displacement by the pumped cryogenic liquid, from the vessel to the tank.

Claims

1. A method of filling a liquid cryogen storage vessel installed at an installation with liquid cryogen from a liquid cryogen storage tank, the liquid cryogen preferably being liquid hydrogen or liquid helium and more preferably being liquid hydrogen, the method comprising the steps of: connecting a liquid transfer conduit from the liquid cryogen storage tank to the liquid cryogen storage vessel, the liquid transfer conduit having a first liquid cryogen pump disposed in-line, the connected liquid transfer conduit being in selectable fluid communication, via one or more valves, between a liquid cryogen space in the liquid cryogen storage tank, in which is stored an amount of liquid cryogen, and a liquid cryogen space in the liquid cryogen storage vessel, in which is stored an amount of the liquid cryogen, wherein, prior to said step of connecting a liquid transfer conduit, the liquid cryogen storage vessel has an initial pressure higher than an initial pressure of the liquid cryogen storage tank; connecting a gas transfer conduit between the liquid cryogen storage vessel and the liquid cryogen storage tank that is in selectable fluid communication between headspace of the liquid cryogen storage vessel, which contains an amount of the liquid cryogen in gaseous form, and a headspace of the liquid cryogen storage tank, which contains an amount of the gaseous cryogen, via one or more valves disposed in the gas transfer conduit; pressure-equalizing the liquid cryogen storage vessel and liquid cryogen storage tank headspaces by opening one or more of the valves in the gas transfer conduit, thereby allowing the cryogenic gas to be transferred from the liquid cryogen storage vessel headspace to the liquid cryogen storage tank headspace by virtue of a difference between their initial pressures; opening the one or more valves in the liquid transfer line thereby allowing fluid communication between the liquid cryogen spaces of the liquid cryogen storage tank and the liquid cryogen storage vessel; and pumping an amount of the liquid cryogen from the liquid cryogen space of the liquid cryogen storage tank to the liquid cryogen space of the liquid cryogen storage vessel via the liquid transfer line and first pump as amounts of the gaseous cryogen flow from the liquid cryogen storage vessel headspace to the liquid cryogen storage tank headspace caused by said pumping, wherein optionally, said step of pumping commences when a difference in pressure between the tank headspace and the vessel headspace, prior to initiating said pumping, reaches zero or a predetermined pressure of less than 1 bar.

2. The method of claim 1, wherein said pressure-equalization occurs without the use of a compressor or vacuum pump.

3. The method of claim 1, wherein the liquid cryogen is transferred from the liquid cryogen space of the liquid cryogen storage tank to the liquid cryogen space of the liquid cryogen storage vessel without the use of a pressure-building circuit.

4. The method of claim 1, further comprising the step of, prior to said pressure-equalization, purging the gas transfer conduit and/or the liquid transfer conduit with amounts of gaseous cryogen from the liquid cryogen storage vessel headspace.

5. The method of claim 1, further comprising the step of, prior to said pressure-equalization and optionally after any purging of the gas and liquid transfer conduits, precooling the gas transfer conduit and/or the liquid transfer conduit with amounts of gaseous cryogen from the liquid cryogen storage vessel headspace.

6. The method of claim 1, further comprising the step of, prior to said pressure-equalization and optionally after any precooling of the gas and liquid transfer conduits, cooling the gas transfer conduit and/or the liquid transfer conduit with amounts of liquid cryogen from the liquid cryogen space of the liquid cryogen storage tank.

7. The method of claim 1, wherein the first pump compresses the liquid cryogen from the liquid cryogen storage tank to a pressure that is a predetermined value above a pressure of the vessel.

8. The method of claim 1, wherein the predetermined value is less than 3 bar, preferably less than 2 bar, more preferably no more than 1 bar.

9. The method of claim 1, wherein the first pump is a centrifugal pump.

10. The method of claim 1, wherein a second cryogenic liquid pump is operatively associated with the vessel and said second pump and the vessel are adapted and configured to allow the second pump to pump amounts of the liquid cryogen from the liquid cryogen space of the vessel to a point of use at the installation.

11. The method of claim 1, wherein one or more of the gas transfer conduit, the liquid transfer conduit, and the first pump are vacuum jacketed.

12. The method of claim 1, a drive operatively associated with the first pump that is adapted and configured to drive the first pump is vacuum-jacketed or is located external from vacuum-jacketing of the first pump.

13. The method of claim 1, wherein the one or more valves of the gas transfer conduit comprises a first valve adjacent to the liquid cryogen storage tank and a second valve adjacent to the vessel, the one or more valves of the liquid transfer conduit comprises a first valve adjacent to the liquid cryogen storage tank and a second valve adjacent to the vessel, and said method further comprises the steps of: stopping operation of the first pump; closing the first and second valves of the gas transfer conduit; closing the first and second valves of the liquid transfer conduit; waiting an amount of time, optionally predetermined, for portions of the gas transfer conduit in between the first and second valves thereof to be warmed by the ambient and portions of the liquid transfer conduit in between the first and second valves thereof to be warmed by the ambient; and after said step of waiting, venting the portions of the gas transfer conduit between the first and second valves thereof of and the portions of the liquid transfer conduit between the first and second valves thereof.

14. The method of claim 1, wherein, prior to said step of pumping, the liquid cryogen in the liquid cryogen space of the vessel has an initial temperature higher than an initial temperature of the liquid cryogen in the liquid cryogen space of the liquid cryogen storage tank.

15. The method of claim 1, wherein: prior to said step of pumping, the liquid cryogen in the liquid cryogen space of the vessel has an initial saturation temperature; and after performance of said method, the liquid cryogen in the liquid cryogen space of the vessel has a saturation temperature lower than the initial saturation temperature.

16. The method of claim 1, wherein heat is removed from the vessel by performance of said method.

17. The method of claim 1, wherein a coupled system is made up of the liquid cryogen storage tank and vessel connected by the gas and liquid transfer conduits and no heat is added to the coupled system other than through heat leak from ambient and addition of heat from operation of the pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0184] For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

[0185] FIG. 1 is a graph of saturation pressure vs density for hydrogen a saturated conditions for both the liquid and vapor portions.

[0186] FIG. 2 is a graph of nitrogen density at saturated conditions for the liquid and vapor portions.

[0187] FIG. 3 is a graph of the proportion of vapor density as a portion of liquid density vs saturation pressure for both hydrogen and nitrogen.

[0188] FIG. 4 is a graph of volumetric heat content vs. saturation pressure for both liquid and vapor for hydrogen.

[0189] FIG. 5 is a graph of the vapor heat content (as a portion of the liquid heat content) vs saturation pressure for hydrogen.

[0190] FIG. 6 is a graph of the vapor heat content (as a portion of the liquid heat content) vs saturation pressure for hydrogen and nitrogen.

[0191] FIG. 7 is a flow chart of a conventional liquid hydrogen supply chain.

[0192] FIG. 8 is a graph of LH.sub.2 temperature vs time for a conventional delivery.

[0193] FIG. 9 is a schematic of the heat and mass transfer for a conventional delivery.

[0194] FIG. 10 is a schematic of a conventional liquid hydrogen delivery method.

[0195] FIG. 11 is a schematic of sources of heat at the final vessel.

[0196] FIG. 12 is a schematic of an embodiment of the invention.

[0197] FIG. 13 is a schematic of another embodiment of the invention utilizing automated control.

[0198] FIG. 14 is a graph of LH.sub.2 temperature vs time for subsequent deliveries according to an embodiment of the invention.

[0199] FIG. 15 is a schematic of the heat and mass transfer for an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0200] A major reason for the challenges described above is that the final vessel accumulates heat from the supply chain and the site operations. The LH.sub.2 delivered with the traditional method is warm (high heat content) and causes LH.sub.2 in the vessel to be warmer immediately after a delivery. More heat is added by the site operations. All this heat input causes increased amounts of venting, which results in a severe loss of product hydrogen, thereby reducing the operational economics of using hydrogen as a fuel source.

[0201] Certain embodiments of the invention propose a method, system, and device that transfers hydrogen from a trailer to a final vessel (from one vessel to another) by allowing pressure to equalize—gas can flow between the final vessel and the trailer—and propelling the LH.sub.2 from the trailer to the final vessel with minimal power input to a pump. The combination of these actions results in a final temperature/saturation pressure in the final vessel that is greatly reduced from the traditional delivery method. In addition, the temperature/saturation pressure of LH.sub.2 within the trailer after a delivery increases less drastically than when using the traditional delivery method, which allows colder liquid to be delivered to subsequent final vessels.

[0202] By allowing gas to transfer from the final vessel to the trailer, the trailer does not need to add gas in order to stay at the appropriate pressure during a delivery. The gas from the final vessel raises the pressure in the trailer to the suitable pressure for delivery, and as liquid leaves the trailer and flows into the final vessel, gas from the final vessel can fill the space evacuated by LH.sub.2. The supply of gas from the final vessel uses heat that is already in the system to maintain pressure in the trailer, and no heat from outside the system is added to the trailer (pressure builder).

[0203] By allowing gas to transfer from the final vessel to the trailer, heat that has accumulated in the gaseous hydrogen in the final vessel is transferred to the trailer. Because this heat is removed from the final vessel, the final vessel is able to reach a much lower temperature/saturation pressure at the end of the delivery. Because the trailer and the final vessel are equalized throughout the delivery, the pressure in the trailer is also much lower at the end of a delivery. In addition to the equalized lower pressure, the advanced delivery does not require the trailer to be 1-2 bar higher than the final vessel at the end of the delivery. The pressure in the trailer at the end of an advanced delivery is much lower than the pressure in the trailer at the end of a traditional delivery. The lower pressure in the trailer equates to a lower density and heat content of the vapor phase in the trailer. When the trailer sloshes, the LH.sub.2 does not absorb nearly as much heat as compared with the traditional delivery method. The lower heat content allows subsequent deliveries of cold LH.sub.2.

[0204] The pump is only designed to provide the motive force to push liquid into the final vessel. Very little power input is required to push the LH.sub.2 from the trailer to the final vessel because the trailer and the final vessel are at the same pressure. In addition, the liquid provided to the pump is subcooled due to the pressure increase in the trailer when the trailer and final vessel are equalized. Subcooled liquid can be pumped efficiently because the pump does not cavitate the liquid during the pumping process.

[0205] The subcooling coil proposed one method for removing heat from a final vessel to improve pump performance. The subcooling coil is a slow process that removes heat from the final vessel by expanding LH.sub.2 within the vessel to create refrigeration. The cold cryogenic supply chain is another concept to reduce heat in the final vessel by removing vapor from the final vessel for utilization in the trailer. The cold cryogenic supply chain decreases the heat in the final vessel by delivering colder (lower heat content) LH.sub.2 into the final vessel and removing vapor, which has a high heat content, from the final vessel and sending this vapor to the trailer. The lower heat content in the final vessel after a delivery will improve pump performance and improve efficiency of the site by providing LH.sub.2 that has more capacity to accept heat.

Delivery Equipment

[0206] FIG. 12 provides a first embodiment for the advanced delivery device and method. This embodiment can include a liquid hose 2, a gas hose 4, and a centrifugal pump 6. A pressure builder is preferably not used. The liquid hose 2 connects the bottom of the trailer 10 to the final vessel 20. The gas hose 4 connects the top of the trailer 12 to the top of the final vessel 10. The centrifugal pump 6 can be placed anywhere along the liquid line 2: it can be placed on/in the trailer or at the site.

[0207] In a preferred embodiment, all parts of the process are insulated to minimize heat leak from ambient to the cryogenic liquid. For example, process lines and hoses can be vacuum jacketed including the gas hose and gas piping. The pump can be vacuum jacketed, and the drive can be installed within the vacuum jacket or the drive can be external to the cryogenic system with a method to reduce heat leak.

[0208] In certain embodiments, the pump is designed to only provide head to overcome resistance from the piping (1-2 bar of head). Due to the small amount of head provided by the pump, the pump inputs minimal power into the fluid and introduces little heat from inefficiency of the pump. Also, the pump can be designed to fit in a small footprint.

Delivery Process

[0209] In certain embodiments, the delivery can include several major steps: connecting, purging and cool down, pumping to deliver LH.sub.2, and disconnecting. First, the liquid hose 2 and the gas hose 4 (both vacuum jacketed) are connected from the trailer 10 to the final vessel 12. Next, the hoses are purged with a flow of warm GH.sub.2 from the vapor space of the final vessel 12. Next, the hoses are purged with several pressure pulses of GH.sub.2 from the vapor space of the final vessel. After purging, gaseous hydrogen from the final vessel 12 is circulated through the piping and hoses to cool the system. Next, a small amount of liquid hydrogen from the trailer 10 flows through the pump 6 and liquid hose 2 to achieve the final cooling. For the advanced delivery, gaseous hydrogen from the final vessel 12 is used for most of the purging and cool down steps instead of gaseous hydrogen from the trailer 10. The gas in the final vessel 12 has the highest heat content as compared to the other fluids in the system.

[0210] After purging and cool down, the valves around the gas hose 4 are opened to allow the trailer and the final vessel to equalize. Next, the valves around the liquid hose 2 are opened to allow communication between the liquid phase of the trailer and the final vessel. Next, the pump 6 is turned on, and liquid begins to flow from the trailer 10 to the final vessel 12. While liquid is flowing from the trailer 10 to the final vessel 12, gas hydrogen flows from the final vessel back to the trailer via gas hose 4.

[0211] After the delivery, the hoses are warmed using GH2 from the vessel 12 that has been heated in a heater, which can be heated by ambient conditions, and then the hoses are disconnected. The driver does not need to decrease pressure in the trailer 10 because the pressure is within an acceptable range for driving. As the trailer is hauled down the road, the fluid will naturally slosh and the vapor and liquid will mix and reach thermodynamic equilibrium.

Detailed Delivery Equipment and Process

[0212] The delivery can take place as a simple system as shown in FIG. 12. However, those of ordinary skill in the art will understand that additional complexities can be included to improve the overall concept. For example, FIG. 13 provides an embodiment that is an improvement over the embodiment shown in FIG. 12. In this embodiment, the concept for the actual implementation of the advanced delivery method is more complex with additional steps and can include an automated delivery. The delivery process can be automated with a controller that operates valves and the pump and monitors many sensors. Automation will make the delivery safer and faster by reducing tasks for the driver.

[0213] In the embodiment shown, the delivery steps can include: [0214] all valves should start in the closed position; [0215] open vent valves VV1 and VV2, and then connect gas hose 4; [0216] close vent valves VV1 and VV2; [0217] open vent valves VV3 and VV4, and then connect liquid hose 2; [0218] close vent valves VV3 and VV4; [0219] purge gas hose 4 by opening valves VG1 and VG2, this will allow for gas flow from vessel 12 up through heater 5, through VG2, then line 4 before venting out VG1; [0220] close VG1 and VG2; [0221] open manual flow valves V1 and V2 on trailer and confirm that liquid hose holds pressure, [0222] begin purging liquid line 2 by opening bypass valve 15, along with VG2 and VL2; [0223] close valves 15, VG2, and VL2; [0224] open manual vessel gas valve V3 (along with valves V1 and V2) and instruct controller to cooldown system; [0225] system cooldown includes: [0226] cooldown of hoses and pump using GH.sub.2 from vessel 12, which includes automatic opening of valve 15, valve 17, and valve VL2; [0227] cooldown of pump with LH2 from tank 10 by closing valve 15, opening valve 19, and opening valve 21 (valves V3, 17, V2, and VL2 also remain open), with valve 21 open, the gas can balance between vessel 12 and tank 10; [0228] once cooldown is complete, valve VL2 is closed, and then fill valve 23 is opened; [0229] PLC command to start pump 6; [0230] Filling vessel while pump 6 is still running, gas flows via V3 through 4 to top of tank 10, which keeps the pressures of the two tanks similar, while pump 6 provides head to push liquid hydrogen from tank 10 to vessel 12; [0231] After vessel 12 is filled, pump 6 is stopped and vessel valves 23 and V3, along with valve 19 are closed; [0232] Hoses are warmed and pressure in hoses is vented [0233] To warmopen valves 21, 15, V2, V1, and 17, while all other valves are in the closed position, before opening valve VG2 and valve VL2 (this allows gaseous H2 from vessel 12 to be warmed in heater 5 before traveling to remaining conduits); [0234] To vent—close valve VG2 (which stops GH2 from vessel 12) such that the remaining gas vents out VL2; [0235] Hose removal— [0236] all valves closed except for valves V1, V2 and VL2, which are open; [0237] close trailer valves V1 and V2; [0238] vent liquid hose by opening vent valve VV4 and then disconnect liquid hose 2; [0239] vent gas hose by opening vent valve VV2 and then disconnect gas hose 4; [0240] PLC confirm hoses are disconnected
In a preferred embodiment, the PLC commands can include the steps of: [0241] Once hoses are connected, purge gas hose; [0242] Once manual valves on the trailer are open, purge the LH2 hose; [0243] Once gas valve on the vessel is open, cooldown and gas balance; [0244] Once fill valve is open on the vessel, start the pump; [0245] Once fill is complete, stop the pump; [0246] Once manual valves are closed on the tank, hoses are warmed and pressure vented on the hoses; and [0247] Confirm hoses are disconnect.
In a further embodiment, the method and apparatus can include additional details, which are outlined below:

GH.SUB.2 .Hose Purging

[0248] Open the warm GH.sub.2 supply valve VG2 for a short, specified period. The pressure on PT3 should be greater than a specified pressure. Preferably allow a specified time for the pressure to settle. Next monitor the pressure, and if the pressure does not decay less than a specified amount in a specified period, the GH.sub.2 hose is not leaking. Open the gas return vent valve VG1 until the pressure decreases below a specified pressure. If the pressure decreases as expected then the vent valve is functioning.

[0249] Flow purge by opening the warm GH.sub.2 supply valve VG2 and the gas return vent valve VG1 on the trailer. Purge continues until timer expires.

[0250] Pressure purge: Open the warm GH.sub.2 supply valve until the hose meets a specified pressure. Close the warm GH.sub.2 supply valve. Open the gas return vent valve on the trailer until the pressure is below a specified pressure. Close gas return vent valve. Repeat for a specified count.

LH2 Hose Purging

[0251] Open the warm GH2 supply valve VG2 for a short, specified period. The pressure on PT1 and PT3 should be greater than a specified pressure. Allow a specified time for the pressure to settle. Next monitor the pressure, and if the pressure does not decay less than a specified amount in a specified period, the LH2 hose 2 is not leaking. Open the LH2 hose vent valve VL2 until the pressure decreases below a specified pressure. If the pressure decreases as expected then the vent valve is functioning.

[0252] Flow purge by opening the warm GH2 supply valve VG2 on the final vessel, the crossover valve 15 on the trailer, and the LH2 hose vent valve VL2 on the final vessel. Purge continues until timer expires.

[0253] Pressure purge by opening the warm GH2 supply valve until the hose meets a specified pressure. Open the LH2 hose vent valve VL2 on the final vessel until the pressure is below a specified pressure. Repeat for a specified count.

GH2 Cool Down

[0254] Open GH2 valve V3 on the final vessel, crossover valve on the trailer 15, and LH2 hose vent valve VL2 on the final vessel. [0255] Option 1: Cool down for a specified time. If TT1 is less than a specified temperature at the end of the timer, continue to the next step. [0256] Option 2: Cool down until TT1 reaches a specified temperature. (Show a warning if the cool down exceeds a specified time.) Continue to the next step.

Equalization and LH2 Cool Down

[0257] Open the GH2 valve 21 on the trailer and the GH2 valve 17 on the final vessel so that the final vessel and the trailer can equalize. [0258] Option 1: Open the LH.sub.2 valve 19 on the trailer and the LH.sub.2 hose vent valve VL2 on the final vessel for a specified time. If TT1 is less than a specified temperature at the end of the timer, continue to the next step. [0259] Option 2: Open the LH.sub.2 valve on the trailer and the LH.sub.2 hose vent valve on the final vessel until TT1 reaches a specified temperature. (Show a warning if the cool down exceeds a specified time.) Continue to the next step.

Pump Permissive to Start

[0260] If TT1 is less than a specified temperature, the pump 6 can start.

Running the Pump

[0261] While running the pump, several sensors are monitored to determine if there is a problem. The temperature at the pump TT1 should remain below a specified value or the pump will stop. Beginning at a specified period after startup, the differential pressure between PT1 and PT2 must be greater than a specified value or the pump will stop. Beginning at a specified period after startup, the flow rate FT1 through the pump should be greater than a specified value or the pump will stop.

[0262] If the level in the final vessel level meets/exceeds the maximum level, then the pump is stopped.

Stop the Pump

[0263] At pump stop, turn off the pump. After a specified period, close the LH.sub.2 valve 19 on the trailer and open the crossover valve 15 on the trailer.

Warm Hoses

[0264] Open the warm gas valve on the final vessel, the crossover valve on the trailer, and the LH.sub.2 vent valve on the final vessel. [0265] Option 1: Allow warm up for a specified time. If TT1 is greater than a specified temperature at the end of the timer, continue to the next step. [0266] Option 2: Warm up until TT1 is greater than a specified temperature. (Show a warning if the warm up exceeds a specified time.) Continue to the next step.

Vent Hoses

[0267] Open the crossover valve on the trailer and the LH.sub.2 vent valve on the final vessel for a specified period. If the PT2 and PT3 are less than a specified value, continue to the next step.

[0268] In certain embodiments, the controller (PLC) will preferably communicate with the final vessel 12 for the following points:

[0269] Operation of the warm GH.sub.2 valve VG2 on the final vessel,

[0270] Operation of the GH.sub.2 valve 17 on the final vessel,

[0271] Operation of the LH.sub.2 hose vent valve VL2 on the final vessel,

[0272] Tank level so that the trailer knows when the final vessel is full and the pump can be stopped,

[0273] Emergency stop conditions activated by the site and sent to the trailer, and

[0274] Emergency stop activated by the trailer and sent to the site.

[0275] Communication between the trailer 10 and the final vessel 12 can be through several methods: pneumatic signal, electronic signal (24V on/off), communication protocol, or other means.

[0276] An automated delivery improves safety of the delivery by removing human factors that may lead to error, by performing a leak check on the hoses, and by warming the hoses after the delivery. An automated delivery also minimizes the amount of venting by precisely controlling the amount of hydrogen used for purging, cool down and warm up steps instead of using rules of thumb that are typical for the traditional delivery method. Finally, an automated delivery reduces the duration of a delivery because the controller automatically conducts the purging, cool down and warm up steps. As compared to the traditional delivery method, the advanced delivery method decreases the delivery duration by avoiding the time needed to pressure build at the start of the delivery and avoiding time for the LH.sub.2 hose to warm by natural heat leak after the delivery. Additionally the advanced delivery will not require the trailer to be vented after a delivery because the pressure in the trailer will be quite low as compared to a traditional delivery.

[0277] Warming the hoses improves safety of the delivery by ensuring that there is no LH.sub.2 in the hose when it is disconnected. The warming step also improves the quality assurance by reducing the likelihood that impurities such as water will condense/solidify in the corrugations of the cold hose.

[0278] The device and/or method disclosed in U.S. patent application Ser. No. 17/322,441, filed May 17, 2021, and whose contents are incorporated herein by reference, may be used in performance of the invention. Those skilled in the art will recognize that the cryogen storage vessel or trailer of described in the instant Specification corresponds to the first tank of the '441 Application and the cryogen storage vessel or final vessel described in the instant Specification corresponds to the second tank of the '441 Application.

Heat in the Trailer

[0279] During the advanced delivery, gas flows from the final vessel to the trailer. First, the gas flows from the final vessel to the trailer in order to equalize the pressure between the vessels. Once the pump starts transferring LH.sub.2, more gas flows from the final vessel to the trailer to fill the space that is evacuated as the LH.sub.2 flows into the final vessel. With the final vessel as the source for gas, there is no need to pressure build (add heat) during the delivery to create gas and maintain a specific pressure within the trailer. The fluid communication between the final vessel and the trailer ensures that the vessels are equalized throughout the delivery.

[0280] Along with the mass transfer of vapor, the heat content of this vapor moves from the final vessel into the trailer. Because heat is removed from the final vessel, the saturation pressure in the final vessel after a delivery is much lower than a delivery from the traditional supply chain. The lower saturation pressure/temperature in the final vessel results in a lower pressure in the vapor space of the trailer and a smaller heat content in the vapor space of the trailer. When the trailer is sloshed after the delivery much less heat is added to the LH.sub.2 that remains in the trailer.

[0281] FIG. 14 provides a graphical representation showing temperature of LH2 as a function of time in accordance with an embodiment of the present invention.

[0282] With the advanced delivery, the temperature of the LH.sub.2 warms by 2.3 K (16.2 psi saturation pressure) after the first delivery to a typical vessel (120 psig operating pressure). With the smaller increase in temperature, the advanced delivery is able to transfer colder liquid to subsequent deliveries, and the average temperature of a delivery is 23.2 K (22.2 K for the first delivery and 24.2 K for the second delivery). When more deliveries are made, the effect of colder LH.sub.2 is more noticeable as compared to the traditional delivery method.

Heat in the Final Vessel During a Delivery

[0283] The amount of heat in the final vessel after a delivery is based on the amount of heat in the final vessel before the delivery and the heat content of the LH.sub.2 delivered to the final vessel. The interaction of heat and mass during the advanced delivery process will be explored further in this section.

[0284] Prior to a delivery, the final vessel is usually at or near the maximum operating pressure due to the large amount of heat introduced to the final vessel during operation. When a trailer arrives, the trailer will have LH.sub.2 that is at a colder condition than LH.sub.2 delivered by the traditional delivery. Also the advanced delivery process will ensure the lowest heat content in the final vessel at the end of the delivery.

[0285] As is typical, the driver will fill from the top of the final vessel. As the liquid flows into the final vessel, it mixes with the gaseous hydrogen in the vessel and the contents of the final vessel reach equilibrium. Also the gas transferred from the top of the final vessel back to the trailer is in equilibrium with the final vessel contents. Because the trailer accepted some of the vapor from the final vessel, heat was removed from the final vessel, and heat from this vapor does not have to be absorbed by the cold liquid coming into the final vessel. The final heat content in the final vessel is much lower than the traditional delivery.

[0286] FIG. 15 provides simulation results of heat and mass transferred to the final vessel in accordance with an embodiment of the present invention. The cold cryogenic supply chain ensures that all final vessels achieve a low heat content. Due to the improved condition, the final vessel can absorb substantially more heat before venting occurs.

Heat in the Final Vessel After a Delivery

[0287] Now that the heat content in the final vessel is low, the final vessel can absorb substantially more heat before venting occurs. Additionally, the pump performs better with cold liquid because the liquid at the pump can absorb more heat before vaporizing which allows heat to be rejected out the discharge of the pump instead of immediately vaporizing and sending the vapor back to the vessel. The combination of the low initial heat content and the improved pump performance result in much lower losses at the site.

Supply Chain

[0288] A cold cryogenic supply chain improves the distribution and delivery of molecules and improves the yield of product through the final vessel. This is a unique system to minimize heat input and preserve refrigeration.

[0289] In certain embodiments of the present invention, most, preferably all, of the LH.sub.2 that is in the trailer is transferred to the final vessel. After the LH.sub.2 molecules are transferred to the final vessel, the final vessel adds heat through its normal operation. When a trailer returns for another delivery, the heat and mass of the gas phase of the final vessel is transferred to the trailer. Due to certain embodiments of the present invention, much more hydrogen is transferred from the trailer to the final vessel. Also, much more hydrogen is transferred from the final vessel to the end use (dispensed). In total, significantly more of the hydrogen that enters the supply chain can be dispensed.

Preserving Refrigeration of a Cold Cryogenic Supply Chain

[0290] The supply chain functions as a conduit for refrigeration as well as molecule transfer. The only significant heat input is added by the pump in the final vessel. (Other inputs such as natural heat leak and the transfer pump are miniscule.) The heat input from the pump in the final vessel generates gas. When the trailer arrives for a delivery, the trailer takes the heat and mass of gas molecules from the final vessel and transports it back to the liquefier. By implementing a system that avoids heat input, the supply chain that functions to transport refrigeration to the final vessel, which is the heat source, instead of the traditional supply chain that functions primarily to transport molecules with little regard to the refrigeration of the supply chain.

[0291] In order to preserve the cold of the cryogenic liquid, all designs and processes avoid adding heat. Heat is not added by the pressure builder. Heat is not added by pumping to unnecessary pressure (adding extra work to the fluid). Heat leak is minimized with vacuum insulation. All the heat of the vapor in the final vessel is not absorbed by incoming liquid because some of the vapor is provided to the trailer. Also cold is not wasted for cool down or purging. The cold conservation allows more cold product to be delivered to final vessels. All final vessels receive cold liquid.

[0292] Instead of adding heat to create pressure, certain embodiments of the present invention use heat that is already in the supply chain to balance pressure and fill the trailer. This prevents additional heat from being added and leading to losses in the supply chain.

[0293] Benefits of a cold cryogenic supply chain is that it provides more value for each molecule delivered to the final vessel because the cryogenic liquid has the ability to receive more heat before vaporizing. In addition, a cold cryogenic supply chain is more efficient at transferring molecules from the trailer to the final vessel. Because minimal heat is added to the trailer at each delivery, the cryogenic liquid in the trailer remains cold and all LH.sub.2 delivered to the final vessel is cold. Because of the cold incoming liquid and the removal of heat from the final vessel, the final vessel is much colder after the delivery.

In Optional Embodiments

[0294] Addition of a check valve in the gas line to only allow vapor to flow from the final vessel to the trailer. The check valve would prevent gas from flowing backward from the trailer to the final vessel.

[0295] Addition of analysis for the vapor flowing from the final vessel to the trailer to prevent contamination. Analysis can be as simple as a passive device that activates (changes color for example) when an impurity is detected.

Advantages of Certain Embodiments of the Present Invention

[0296] Those of ordinary skill in the art will readily recognize that certain embodiments of the present invention provide many distinct advantages, such as:

[0297] Introduction of heat into the tanker and the final vessel is minimized since the gaseous cryogen from the final vessel is used to decrease the initial pressure imbalance between the tanker and the final vessel. Since the pump does not need to overcome a significant pressure difference between the tanker and the final vessel, the pump does not have to be operated at significant head and thus adds little heat to the coupled system. Indeed, the pump provides only a small pressure differential (e.g., only a few bar or as little as 1-2 bar). Because introduction of heat into the either the tanker and the final vessel is minimized, boil-off loss in each of the tanker and the final vessel is similarly minimized. The gaseous cryogen in the final vessel headspace is put to profitable use and not vented.

[0298] For a given amount of liquid cryogen dispensed to the tanker of the liquid cryogen production facility, more of the liquid cryogen is transferred to the final vessel (or in the case of multiple deliveries with a single tanker, multiple final vessels). This is because none of the high quality, low-temperature, low-saturation pressure cryogenic liquid from the tanker is used to perform purging and pre-cooling. More importantly, none of this higher quality liquid cryogen is consumed in a pressure building circuit.

[0299] The quality of the molecules delivered by the tanker to the final vessel is improved because performance of the invention removes heat from the final vessel and lowers its saturation temperature. This is important because a lower saturation temperature provides for a greater buffer of heating of the cryogenic liquid over time in the final vessel before it must be vented or before an efficiency of a pump associated with the final vessel is degraded. In contrast, heat is actually added to the final vessel during a delivery according to conventional techniques.

[0300] The quality of the molecules remaining in the tanker after a first delivery and fill is improved. Because less heat is added to the tanker in performance of the invention in comparison to conventional techniques utilizing a pressure building circuit, the temperature and saturation temperature of the liquid cryogen remaining in the tanker following the first delivery is lower in comparison to the same liquid cryogen remaining in the tanker following a first delivery according to the conventional technique. This effect is additive as the same tanker is used to subsequently fill other final vessels. Thus, multiple deliveries with a single tanker are more efficient.

[0301] The overall fill time realized in performance of the invention is decreased in comparison to final vessel fills utilizing conventional techniques. This is because the invention does not require the lengthy period of time necessary to build pressure in the tanker using a pressure building circuit.

[0302] Certain embodiments of the invention allow for a possible increase in the transfer flow rate while at the same time maintaining relatively stable pumping conditions. In addition, the transfer flow rates can be independent of the weather conditions. Certain embodiments also substantially reduce or eliminate the cryogenic cloud and the condensation of liquid oxygen under the tanker.

[0303] In addition, the procedures for the delivery operators are simplified.

[0304] In comparison to conventional techniques, the tanker and the final vessel are at relatively lower pressures during a fill. This potentially makes it possible to reduce the mechanical size constraints (saving in terms of weight, material, cooling time and cost).

[0305] It is thus no longer necessary to equip the tanker with pressure building circuit.

[0306] The electrical consumption of the liquid cryogen pump in the liquid transfer line is markedly lower than the electrical consumption of a gas compressor that could be used on the gas transfer line utilized by a prior art technique. This is notable since the pressure and especially temperature at the inlet of a compressor are much more variable than those at the inlet of a liquid cryogen pump.

[0307] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0308] The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.

[0309] “Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing i.e. anything else may be additionally included and remain within the scope of “comprising.” “Comprising” is defined herein as necessarily encompassing the more limited transitional terms “consisting essentially of” and “consisting of”; “comprising” may therefore be replaced by “consisting essentially of” or “consisting of” and remain within the expressly defined scope of “comprising”.

[0310] “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0311] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0312] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

[0313] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.