Method for filling liquid cryogen trailers

Abstract

In liquid cryogen storage, gaseous cryogen from a short trailer that is not completely filled is used to pressurize a jumbo trailer, and the pressure differential causes liquid cryogen to flow from the jumbo trailer into the empty trailer.

Description

[Technical Field]

[0001] The present invention relates to an optimized method for the delivery of liquid cryogen between a liquid cryogen reservoir and an end user. [Background technology]

[0002] Liquid cryogens such as hydrogen can be produced and stored by many means, but typically, liquid hydrogen is stored in cryogenic storage tanks on or near the hydrogen liquefaction source (i.e., liquefier), and often also at the original hydrogen source, such as an electrolyzer. From this cryogenic storage vessel, the liquid hydrogen is transferred by semi-truck to a cryogenic tube trailer that is transported to a location remote from the liquefier, such as a hydrogen filling station for fuel cell electric vehicles (FCEVs).

[0003] At the remote location, liquid hydrogen is transferred from the tube trailer through hoses to the end-user storage tanks by pressure differential. Because the pressure in the tube trailer is limited by regulatory agencies for safety reasons, the initial pressure in the tube trailer at the remote location is typically much lower than the pressure in the end-user tanks. Therefore, according to the prior art, the pressure in the tube trailer must be increased to a level sufficient to pump the liquid hydrogen from the tube trailer to the end-user tanks. The transfer of liquid hydrogen then proceeds until the pressures in the tube trailer and the end-user tanks are more or less equalized.

[0004] Because a significant portion of the final cost of liquid hydrogen consists of transportation costs between the liquefier and remote locations, it is desirable to reduce these transportation costs. One way to do this is to use so-called jumbo trailers, whose liquid hydrogen storage capacity substantially exceeds that of tube trailers. While the use of jumbo trailers can be advantageous, regulatory authorities may restrict their use in more densely populated areas for safety reasons.

[0005] Regardless of whether a tube trailer or jumbo trailer is used, if sufficient liquid hydrogen remains in the trailer after the initial fill, subsequent fills of other end user tanks at other remote locations can be performed. Once the tube trailer or jumbo trailer has been sufficiently depleted of liquid hydrogen, the liquid hydrogen can be returned to the liquefier and refilled for continued delivery to remote locations.

[0006] Prior to refueling, depending on the cost of hydrogen versus the cost of hydrogen compression, the gaseous hydrogen in the trailer may be vented to a location in the liquefaction process, typically until the pressure in the trailer reaches 2-4 psig (G. Petipas, “Boil-off losses along the LH2 pathway,” Lawrence Livermore National Laboratory, LLNL-TR-750685, May 2, 2018). Depending on the relative costs of refrigeration, compression, and hydrogen production, the hydrogen may instead be vented to the ambient air. This is because the hydrogen remaining in the trailer may be relatively warm and / or at a relatively low pressure when returned to the liquefier, making it difficult to take advantage of the thermodynamic advantages of its pressure and / or cryogenic energy when introducing the remaining hydrogen into the liquefaction process.

[0007] In view of the above, it would be advantageous to provide an improved method for delivering liquid hydrogen to one or more end-user sites that reduces the cost of transporting liquid hydrogen and avoids waste. Summary of the Invention [Means for solving the problem]

[0008] A method for delivering liquid cryogen to one or more end-user sites is disclosed. The method includes the following steps: first, second, and third liquid cryogen-containing trailers are provided; the first and third trailers have substantially the same storage capacity and are smaller than the second trailer's storage capacity; each trailer has a headspace filled with cryogen vapor above the liquid cryogen contained therein; and each trailer is located in a storage facility where the first trailer is at an initial pressure higher than the initial pressure of the second trailer, which is higher than the initial pressure of the third trailer. The headspaces of the first and second trailers are placed in flow communication, thereby equalizing the pressures of the first and second trailers to a pressure P1 between the initial pressures of the first and second trailers and higher than the initial pressure of the third trailer. Following pressure equalization of the first and second trailers, the liquid cryogen contained within the second trailer is placed in flow communication with the liquid cryogen contained within the third trailer, causing liquid cryogen to flow from the second trailer to the third trailer due to the pressure difference between the pressure P1 in the first and second trailers and the initial pressure of the third trailer. The flow of liquid cryogen between the second and third trailers is allowed to continue until the third trailer is substantially filled with liquid cryogen and the first and second trailers are each at pressure P2.

[0009] The method may include one or more of the following aspects. - Prior to the step of providing the first, second, and third refrigerated cryogen-containing trailers, the first trailer is transported to end user site A where liquid cryogen is transferred from the first trailer to a storage tank at end user site A, and following the transfer of the liquid cryogen to end user site A, the first trailer is transported to a storage facility where the second and third trailers are located, and at the storage facility the first trailer is at an initial pressure higher than the initial pressure of the second trailer which is higher than the initial pressure of the third trailer. - After the step of allowing the flow of liquid cryogen between the second trailer and the third trailer to continue until the third trailer is substantially filled, the third trailer is transported to end user site B where the liquid cryogen is transferred from the third trailer to a storage tank at end user site B which may be the same as or different from end user site A. - after the step of allowing the flow of liquid cryogen between the second trailer and the third trailer to continue until the third trailer is substantially filled, the gaseous cryogen is vented from the first trailer, thereby reducing the pressure of the first trailer to a predetermined pressure lower than P2, and a fourth liquid cryogen-containing trailer having substantially the same storage capacity as the first trailer and the third trailer is provided, the fourth trailer being located in the storage facility at an initial pressure and having a headspace filled with cryogen vapor above the liquid cryogen contained within the fourth trailer, the initial pressure of the fourth trailer being higher than P2, which is higher than the predetermined pressure of the first trailer, and the headspaces of the fourth trailer and the second trailer being placed in flow communication; This balances the pressures in the fourth trailer and the second trailer to an intermediate pressure between P2 and the initial pressure of the fourth trailer, the intermediate pressure in the fourth trailer and the second trailer being higher than the predetermined pressure of the first trailer, and following pressure balance in the fourth trailer and the second trailer, the liquid cryogen contained in the second trailer is placed in flow communication with the liquid cryogen contained in the first trailer, thereby allowing liquid cryogen to flow from the second trailer to the third trailer due to the pressure difference between the intermediate pressure in the first trailer and the second trailer and the predetermined pressure of the first trailer, and the flow of liquid cryogen between the second trailer and the first trailer to continue until the first trailer is substantially filled with liquid cryogen. - The first trailer is transported to end user site C where liquid cryogen is transferred from the first trailer to a storage tank at end user site C, end user site C being the same as or different from end user site A, which is the same as or different from end user site B, and the second trailer and fourth trailer being the same or different trailers. - after the step of allowing said flow of liquid cryogen between the second trailer and the third trailer to continue until the third trailer is substantially filled, gaseous cryogen is vented from the first trailer, thereby reducing the pressure of the first trailer to a predetermined pressure lower than P2, and a fourth liquid cryogen-containing trailer having substantially the same storage capacity as the first trailer and the third trailer is provided, the fourth trailer being located in the storage facility at an initial pressure and having a headspace filled with cryogen vapor above the liquid cryogen contained within the fourth trailer, the initial pressure of the fourth trailer being higher than P2, which is higher than the predetermined pressure of the first trailer, and the headspaces of the fourth trailer and the second trailer being placed in flow communication; This balances the pressure in the fourth trailer and the second trailer to an intermediate pressure between P2 and the initial pressure of the fourth trailer, the intermediate pressure in the fourth trailer and the second trailer being higher than the predetermined pressure of the first trailer, and following pressure equilibration in the fourth trailer and the second trailer, the liquid cryogen contained in the second trailer is placed in flow communication with the liquid cryogen contained in the first trailer, thereby allowing liquid cryogen to flow from the second trailer to the third trailer due to the pressure difference between the intermediate pressure in the first trailer and the second trailer and the predetermined pressure of the first trailer, and the flow of liquid cryogen between the second trailer and the first trailer to continue until the first trailer is substantially filled with liquid cryogen. - The first trailer is transported to end user site C where liquid cryogen is transferred from the first trailer to a storage tank at end user site C, end user site C being the same as or different from end user site A, which is the same as or different from end user site B, and the second trailer and fourth trailer being the same or different trailers. - after the step of allowing said flow of liquid cryogen between the second trailer and the third trailer to continue until the third trailer is substantially filled, gaseous cryogen is vented from the first trailer, thereby reducing the pressure of the first trailer to a predetermined pressure lower than P2, and a fourth liquid cryogen-containing trailer having substantially the same storage capacity as the first trailer and the third trailer is provided, the fourth trailer being located in the storage facility at an initial pressure and having a headspace filled with cryogen vapor above the liquid cryogen contained within the fourth trailer, the initial pressure of the fourth trailer being higher than P2, which is higher than the predetermined pressure of the first trailer, and the headspaces of the fourth trailer and the second trailer being placed in flow communication; This balances the pressure in the fourth trailer and the second trailer to an intermediate pressure between P2 and the initial pressure of the fourth trailer, the intermediate pressure in the fourth trailer and the second trailer being higher than the predetermined pressure of the first trailer, and following pressure equilibration in the fourth trailer and the second trailer, the liquid cryogen contained in the second trailer is placed in flow communication with the liquid cryogen contained in the first trailer, thereby allowing liquid cryogen to flow from the second trailer to the third trailer due to the pressure difference between the intermediate pressure in the first trailer and the second trailer and the predetermined pressure of the first trailer, and the flow of liquid cryogen between the second trailer and the first trailer to continue until the first trailer is substantially filled with liquid cryogen. The first trailer is transported to end user site C where liquid cryogen is transferred from the first trailer to a storage tank at end user site C, end user site C being the same as or different from end user site A, which may be the same as or different from end user site B, and the second trailer and fourth trailer being the same or different trailers. - After the step of allowing said flow of liquid cryogen between the second trailer and the third trailer to continue until the third trailer is substantially filled, the third trailer is transported to end user site B where the liquid cryogen is transferred from the first trailer to a storage tank at end user site B which may be the same as or different from end user site A. - The cryogen is hydrogen.

[0010] For a better 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 similar reference numerals, and in which: [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of an initial three trailer combination including a returning high pressure trailer, a jumbo trailer, and a low pressure trailer to be filled. [Figure 2] FIG. 2 is a schematic diagram of the steps of pressure balancing between the returning trailer and the jumbo trailer of FIG. [Figure 3] FIG. 3 is a schematic diagram of the steps for transferring liquid hydrogen from the jumbo trailer to the low-pressure trailer of FIG. [Figure 4] FIG. 4 is a schematic diagram of a continuation of the liquid hydrogen transfer step of FIG. [Figure 5] FIG. 5 is a schematic diagram of the results of the liquid hydrogen transfer step of FIG. [Figure 6] FIG. 6 is a schematic diagram of the steps for venting the returning trailer to reduce its pressure. [Figure 7] FIG. 7 is a schematic diagram of how an evacuated returning trailer goes to low pressure as it fills. [Figure 8] FIG. 8 is a schematic diagram of the initial state of the combination of the returned trailer and jumbo trailer of FIG. 5 with the now lower pressure returned trailer to be filled of FIG. [Figure 9] FIG. 9 is a schematic diagram of the steps of pressure balancing between the returning trailer and the jumbo trailer of FIG. [Figure 10] FIG. 10 is a schematic diagram of the liquid hydrogen transfer step from the jumbo trailer to the low-pressure trailer of FIG. [Figure 11] FIG. 11 is a schematic diagram of a continuation of the liquid hydrogen transfer step of FIG. [Figure 12]FIG. 12 is a schematic diagram of the results of the liquid hydrogen transfer step of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] The inventors have conceived an optimized method for delivering liquid cryogen (such as nitrogen, argon, helium, or hydrogen) to one or more end-user sites, which utilizes at least three, and often four (or even more) liquid cryogen-containing trailers, and includes steps performed at a liquid cryogen depot and steps performed at one or more end-user sites.

[0013] One of the trailers, a so-called jumbo trailer, has a substantially larger storage capacity and is located at the depot. Other trailers are filled with liquid cryogen from the jumbo trailer at the depot and then transported to the end user site so that these trailers can fill storage tanks located at the end user site. The types of cryogens include, but are not limited to, oxygen, nitrogen, argon, helium, krypton, neon, and preferably hydrogen.

[0014] After one of the other trailers is substantially depleted of liquid cryogen and is no longer available to fill end-user storage tanks, it is returned to storage. The interior of the trailer returned to storage may be at a relatively high pressure due to heat leaks that occur during the transport of one of the other trailers between the end-user site and the storage and / or the need to increase the pressure within that trailer to fill the end-user storage tanks. By equalizing the pressures of the returning trailer and the jumbo trailer, the relatively high pressure of the returning trailer is used to increase the pressure of the jumbo trailer. The pressure within the returning trailer and the pressure within the jumbo trailer are then used to pump liquid cryogen at a relatively low pressure from the jumbo trailer to another trailer to be filled.

[0015] In this way, most of the pressurized gaseous cryogen remaining in the trailer after delivering the liquid cryogen to the end user site can be used during the filling of liquid cryogen from the jumbo trailer into another trailer, resulting in less cryogen being wasted.

[0016] A more detailed description of the method now follows.

[0017] As shown in FIG. 1, after delivery of liquid cryogen to an end-user site, designated End-User Site A, and transportation to a liquid cryogen storage facility, a liquid cryogen-containing tube trailer, designated Trailer 1, contains a relatively small amount of liquid cryogen and is at a relatively high pressure, e.g., 3.5-6 bara or about 3.8 bara. Also at the storage facility is another liquid cryogen-containing trailer, designated Trailer 2. Trailer 2, commonly referred to as a "jumbo trailer" in the liquefied gas field, has a higher liquid cryogen storage capacity than Trailer 1, commonly referred to as a "short trailer." For example, Trailer 1 typically has a capacity of about 36 m 3 whereas trailer 2 capacity is typically in the range of 75-80m 3 The depot also contains another liquid cryogen-containing trailer, called Trailer 3. Trailer 1, Trailer 2, and Trailer 3 each have a headspace filled with cryogen vapor above the liquid cryogen contained therein. In the depot, Trailer 1 is at a higher initial pressure than Trailer 2, which is higher than the initial pressure of Trailer 3. Trailer 1 and Trailer 3 have substantially the same capacity. This means that Trailer 1 and Trailer 3 are designed to contain the same amount of liquid cryogen, even if there are slight differences in their storage capacities.

[0018] Trailer 2 is typically used as the primary means of transporting the cryogen between the liquefaction plant where it is liquefied and storage, and for filling shorter trailers, including Trailer 1 and Trailer 3. As will be seen below, Trailer 3 is typically the trailer that has already fulfilled the role played by Trailer 1 in the following description of Figures 1-7. Trailer 1 is in storage because, after delivering liquid cryogen to End User Site A, it did not contain a sufficient quantity of liquid cryogen to deliver a practical amount of cryogen to another end user site.

[0019] As can be seen in FIG. 2 , after connecting a port formed in trailer 1 adjacent the headspace of trailer 1 to a port formed in trailer 2 adjacent the headspace of trailer 2 using suitable piping / conduit, the headspaces of trailer 1 and trailer 2 are placed in flow communication through the operation of one or more valves associated with the piping / conduit connecting the ports of trailer 1 and trailer 2. This brings trailers 1 and 2 into pressure equilibrium, which, of course, results in a common pressure between the initial pressures in trailer 1 and trailer 2 prior to pressure equilibrium. For example, if trailer 1 is at 3.8 bara and trailer 2 is at 1.7 bara prior to trailer 1 and trailer 2 reaching pressure equilibrium, the pressure in trailer 1 may decrease from 3.8 bara to 3.6 bara, while the pressure in trailer 2 may increase from 1.7 bara to 3.6 bara. This common pressure is also greater than the pressure in trailer 3.

[0020] As can be seen in Figure 3, a port formed in trailer 2 adjacent the bottom of trailer 2 is connected using suitable piping / conduit to a port formed in trailer 3 adjacent trailer 3, with trailer 2 and trailer 3 being placed in flow communication through the operation of one or more valves associated with the pipes / conduits connecting the ports of trailer 2 and trailer 3. It should be noted that at this point, the headspaces of trailer 1 and trailer 2 are in flow communication. This results in the flow of liquid cryogen from trailer 2 to trailer 3 due to the pressure difference between the pressure within trailers 1 and 2 on the one hand and the pressure within trailer 3 on the other. It should be noted that the gaseous cryogen within the headspace of trailer 3 is allowed to vent through the operation of one or more valves associated with the headspace of trailer 3 in order to maintain the pressure within trailer 3 to remain more or less constant, allowing the liquid cryogen to flow relatively unimpeded from trailer 2 to trailer 3 and preventing a pressure buildup within trailer 3. As liquid cryogen flows from trailer two into trailer three, a space is created in trailer two that must be filled with gaseous cryogen, which continues to flow from trailer one into trailer two.

[0021] As can be seen in Figures 4-5, this transfer of liquid cryogen from trailer 2 to trailer 3 is allowed to continue until the third trailer is substantially filled with liquid cryogen and trailers 1 and 2 are each at pressure P2. If the pressure differential between trailers 1 and 2 on the one hand and trailer 3 on the other is not sufficient to allow trailer 3 to be filled with liquid cryogen to the desired level, the pressure establishing circuit associated with trailer 1, the pressure establishing circuit associated with trailer 2, or each of the aforementioned pressure establishing circuits can be operated to increase the pressure in trailers 1 and 2 sufficient to force sufficient liquid cryogen into trailer 3. Typically, the flow of liquid cryogen continues until trailers 1, 2, and 3 each reach a state of pressure equilibrium. Alternatively, the flow of liquid cryogen can continue until the amount of liquid cryogen in trailer 3 reaches a desired level, as confirmed by any suitable technique in the field of industrial gases, such as a level sensor or weigh scale. For example, if the pressure in trailer 1 and trailer 2 is 3.6 bara and the pressure in trailer 3 is 1.1 bara before operation of one or more valves associated with the pipe / conduit connecting trailer 2 and trailer 3, after trailer 3 is substantially filled with liquid cryogen from trailer 2, the pressure in trailer 1 and trailer 2 will drop from 3.6 bara to 2.7 bara and the pressure in trailer 3 will remain at 1.1 bara.

[0022] Once substantially filled, one or more valves associated with the pipe / conduit connecting trailer 2 and trailer 3 are operated to prevent flow communication between trailer 2 and trailer 3. Also, operating one or more valves associated with the headspace of trailer 3 prevents the discharge of gaseous cryogen from the headspace of trailer 3. The pipe / conduit connecting trailer 2 and trailer 3 is then disconnected. Trailer 3 can now be transported to end user site B, where the liquid cryogen is transferred from trailer 3 to a storage tank at end user site B, which may be the same as or different from end user site A.

[0023] Optionally, as can be seen in Figure 6, the pressure in the headspace of trailer 1 can be vented to a suitable level so that it can be more easily filled by pressure differential with liquid cryogen from trailer 2 in the same manner as described above with respect to filling trailer 3. For example, if trailer 1 is at 1.8 bara after filling trailer 3 with liquid cryogen from trailer 2, the gaseous cryogen in the headspace of trailer 1 can be vented until the pressure in trailer 1 reaches 1.1 bara. This reduced pressure allows trailer 1 to be filled with liquid cryogen due to the aforementioned pressure differential without necessarily using the pressure-establishing circuit, or to such a great extent compared to filling without prior venting.

[0024] Optionally, as can be seen in Figures 7-12, Trailer 1 takes on the role already played by Trailer 3 and is also substantially filled with liquid cryogen.

[0025] As can be seen in FIG. 8, after delivery of liquid cryogen to an end-user site, designated End-User Site C (which may be the same as or different from Site A and the same as or different from Site B), and transportation to a liquid cryogen storage facility, a liquid cryogen-containing tube trailer, designated Trailer 4, contains a relatively small amount of liquid cryogen and is at a relatively high pressure, e.g., 3.5-6 bara or about 3.8 bara. Also present in the storage facility are Trailer 2 and Trailer 1. Like Trailer 2 and Trailer 1, Trailer 4 has a headspace filled with cryogen vapor above the liquid cryogen contained therein. At the storage facility, Trailer 4 is at a higher initial pressure than Trailer 2, which is higher than the initial pressure of Trailer 1. Trailers 4 and 1 have substantially the same capacity. This means that Trailer 4 and Trailer 1 are designed to contain the same amount of liquid cryogen, even if there are slight differences in their storage capacities.

[0026] As seen above, trailer 1 has already fulfilled the role that trailer 4 will fulfill in the following description of Figures 8-12. Trailer 4 is in storage because, after delivering liquid cryogen to end user site C, it did not contain a sufficient quantity of liquid cryogen to deliver a practical amount of cryogen to another end user site.

[0027] As can be seen in FIG. 9 , after connecting a port formed in trailer 4 adjacent to the headspace of trailer 4 to a port formed in trailer 2 adjacent to the headspace of trailer 2 using suitable piping / conduit, the headspaces of trailer 4 and trailer 2 are placed in flow communication through the operation of one or more valves associated with the piping / conduit connecting the ports of trailer 4 and trailer 2. This brings trailers 4 and 2 into pressure equilibrium, which, of course, results in a common pressure between the initial pressures in trailer 4 and trailer 2 prior to pressure equilibrium. For example, if trailer 4 is at 3.8 bara and trailer 2 is at 1.8 bara prior to pressure equilibrium between trailer 4 and trailer 2, the pressure in trailer 4 may decrease from 3.8 bara to 2.8 bara, while the pressure in trailer 2 may increase from 1.8 bara to 2.8 bara. This common pressure is also greater than the pressure in trailer 1.

[0028] As can be seen in Figure 10, a port formed in trailer 2 adjacent the bottom of trailer 2 is connected using suitable piping / conduit to a port formed in trailer 1 adjacent the bottom of trailer 1, with trailer 2 and trailer 1 being placed in flow communication through the operation of one or more valves associated with the pipe / conduit connecting the ports of trailer 2 and trailer 1. It should be noted that at this point, the headspaces of trailer 4 and trailer 2 are in flow communication. This results in the flow of liquid cryogen from trailer 2 to trailer 1 due to the pressure difference between the pressure within trailer 4 and trailer 2 on the one hand and the pressure within trailer 1 on the other. It should be noted that the gaseous cryogen within the headspace of trailer 1 is allowed to vent through the operation of one or more valves associated with the headspace of trailer 1 in order to maintain the pressure within trailer 1 to remain more or less constant, allowing the liquid cryogen to flow relatively unimpeded from trailer 2 to trailer 1 and preventing a pressure buildup within trailer 1. As liquid cryogen flows from trailer 2 into trailer 1, a space is created in trailer 2 that must be filled with gaseous cryogen, which continues to flow from trailer 4 into trailer 2.

[0029] As can be seen in Figures 11-12, this transfer of liquid cryogen from trailer 2 to trailer 1 is allowed to continue until the third trailer is substantially filled with liquid cryogen and trailer 4 and trailer 2 are each at pressure P2. If the pressure differential between trailer 4 and trailer 2 on the one hand and trailer 1 on the other hand is not sufficient to allow trailer 1 to fill with liquid cryogen to the desired level, the pressure establishing circuit associated with trailer 4, the pressure establishing circuit associated with trailer 2, or each of the aforementioned pressure establishing circuits can be operated to increase the pressure within trailer 4 and trailer 2 sufficient to force sufficient liquid cryogen into trailer 1. Typically, the flow of liquid cryogen continues until trailer 4, trailer 2, and trailer 1 each reach a state of pressure equilibrium. Alternatively, the flow of liquid cryogen can continue until the amount of liquid cryogen within trailer 1 reaches a desired level, as confirmed by any suitable technique in the field of industrial gases, such as a level sensor or weigh scale. For example, if the pressure in trailer 4 and trailer 2 is 2.8 bara and the pressure in trailer 1 is 1.1 bara before operation of one or more valves associated with the pipe / conduit connecting trailer 2 and trailer 1, after trailer 1 is substantially filled with liquid cryogen from trailer 2, the pressure in trailer 2 and trailer 4 will drop from 2.8 bara to 2.3 bara and the pressure in trailer 1 will remain at 1.1 bara.

[0030] Once substantially filled, one or more valves associated with the pipe / conduit connecting trailer 2 and trailer 1 are operated to prevent flow communication between trailer 2 and trailer 1. Also, operating one or more valves associated with the headspace of trailer 1 prevents the discharge of gaseous cryogen from the headspace of trailer 1. The pipe / conduit connecting trailer 2 and trailer 1 is then disconnected. Trailer 1 can now be transported to end user site D, which may be the same as or different from end user site A, end user site B, and end user site C, where the liquid cryogen will be transferred from trailer 3 to a storage tank at end user site D.

[0031] Optionally, those skilled in the art will recognize that the above method can be repeated as necessary, with the initially high pressure trailer being evacuated to a suitable level to allow the trailer to fill with liquid cryogen from trailer 2 by pressure differential.

[0032] Embodiments of the present invention provide many advantages.

[0033] Without the present invention, the jumbo trailer would need to be pressurized to push the liquid cryogen from the jumbo trailer into the short trailer. Those skilled in the art will appreciate that this pressurization occurs conventionally by vaporizing the liquid cryogen within the jumbo trailer. In contrast, embodiments of the present invention utilize gaseous cryogen from the short trailer to pressurize the jumbo trailer. By avoiding the vaporization of liquid cryogen for pressurization, more cryogen (e.g., approximately 170 kg for cryogenic hydrogen) is available to be transferred to the short trailer. Utilizing this liquid cryogen increases supply chain efficiency and reduces losses because it has a lower heat content than liquid cryogen loaded into a short trailer using conventional technology. This step transfers the entire amount of liquid cryogen, increasing supply chain efficiency. Another way to look at this is that losses are reduced (by approximately 170 kg using the cryogenic hydrogen example above). Because gas within the short trailer is vented, capturing the gas to pressurize the jumbo trailer prevents additional gas from being created within the jumbo trailer that needs to be vented.

[0034] While the present invention has been described in conjunction with specific embodiments thereof, it is evident that many changes, 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 changes, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist of, or consist essentially of disclosed elements, or may be practiced without elements not disclosed. Furthermore, when there are sequence references such as "first" and "second," they should be understood in an illustrative sense, not a limiting sense. For example, one skilled in the art may recognize that certain steps can be combined into a single step.

[0035] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0036] "Comprising" in the claims is an open-ended transitional phrase meaning that the claim elements specified thereafter are a non-exclusive recitation, i.e., others may additionally be included and fall within the scope of the "comprising." "Comprising" is defined herein as necessarily encompassing the more restrictive transitional phrases "consisting essentially of" and "consisting of," and "comprising" may therefore be replaced with "consisting essentially of" or "consisting of" and fall within the expressly defined scope of "comprising."

[0037] "Providing" in the claims is defined to mean furnishing, supplying, making available, or preparing something. Steps may be performed by any actor, absent express language to the contrary in the claims.

[0038] Optional or optional means that the described event or circumstance may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0039] 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 should be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said ranges.

[0040] All references set forth herein are incorporated by reference in their entirety and individually for the specific information for which each is cited.

Claims

1. 1. A method for delivering liquid cryogen to one or more end user sites, comprising: providing first, second, and third liquid cryogen storage trailers, the first trailer and the third trailer having a storage capacity substantially equal to but less than the storage capacity of the second trailer, each trailer having a headspace filled with cryogen vapor above the liquid cryogen contained therein, each trailer located in a depot with the first trailer at an initial pressure higher than the initial pressure of the second trailer, which is higher than the initial pressure of the third trailer; placing the headspaces of the first trailer and the second trailer in flow communication, thereby equalizing the pressures of the first trailer and the second trailer to a pressure P1 that is between the initial pressure of the first trailer and the initial pressure of the second trailer, the pressure P1 being higher than the initial pressure of the third trailer; following the pressure equalization of the first trailer and the second trailer, placing the liquid cryogen contained within the second trailer in flow communication with the liquid cryogen contained within the third trailer, thereby allowing liquid cryogen to flow from the second trailer to the third trailer due to the pressure difference between the pressure P1 of the first trailer and the second trailer and the initial pressure of the third trailer, and the flow of liquid cryogen between the second trailer and the third trailer to continue until the third trailer is substantially filled with liquid cryogen and the first trailer and the second trailer are each at pressure P2; A method comprising:

2. before the step of providing first, second, and third liquid cryogen-containing trailers, transporting the first trailer to end user site A where liquid cryogen is transferred from the first trailer to a storage tank at end user site A; following the transfer of liquid cryogen to the end user site A, transporting the first trailer to the depot where the second trailer and the third trailer are located, wherein at the depot, the first trailer is at an initial pressure higher than the initial pressure of the second trailer, which is higher than the initial pressure of the third trailer; The method of claim 1 further comprising:

3. 3. The method of claim 2, further comprising, after the step of allowing the flow of liquid refrigerant between the second trailer and the third trailer to continue until the third trailer is substantially filled, transporting the third trailer to an end user site B where liquid refrigerant is transferred from the third trailer to a storage tank at an end user site B that is the same as or different from end user site A.

4. After the step of allowing the flow of liquid cryogen between the second trailer and the third trailer to continue until the third trailer is substantially filled, venting gaseous cryogen from the first trailer until a predetermined pressure lower than P2 is reached; providing a fourth liquid cryogen storage trailer having substantially the same storage capacity as the first trailer and the third trailer, the fourth trailer being positioned at the depot at an initial pressure and having a headspace filled with cryogen vapor above the liquid cryogen contained within the fourth trailer, the initial pressure of the fourth trailer being greater than P2, which is greater than the predetermined pressure of the first trailer; placing the headspaces of the fourth trailer and the second trailer in flow communication, thereby equalizing the pressures of the fourth trailer and the second trailer to an intermediate pressure between P2 and the initial pressure of the fourth trailer, the intermediate pressure of the fourth trailer and the second trailer being higher than the predetermined pressure of the first trailer; following the pressure equalization of the fourth trailer and the second trailer, placing the liquid cryogen contained within the second trailer in flow communication with the liquid cryogen contained within the first trailer, thereby allowing liquid cryogen to flow from the second trailer to the third trailer due to the pressure difference between the intermediate pressure of the first trailer and the second trailer and the predetermined pressure of the first trailer, and the flow of liquid cryogen between the second trailer and the first trailer to continue until the first trailer is substantially filled with liquid cryogen; The method of claim 3 further comprising:

5. 5. The method of claim 4, further comprising the step of transporting the first trailer to an end user site C where liquid cryogen is transferred from the first trailer to a storage tank at end user site C, wherein end user site C is the same as or different from end user site A and the same as or different from end user site B, and the second trailer and the fourth trailer are the same or different trailers.

6. After the step of allowing the flow of liquid cryogen between the second trailer and the third trailer to continue until the third trailer is substantially filled, venting gaseous cryogen from the first trailer until a predetermined pressure lower than P2 is reached; providing a fourth liquid cryogen storage trailer having substantially the same storage capacity as the first trailer and the third trailer, the fourth trailer being positioned at the depot at an initial pressure and having a headspace filled with cryogen vapor above the liquid cryogen contained within the fourth trailer, the initial pressure of the fourth trailer being greater than P2, which is greater than the predetermined pressure of the first trailer; placing the headspaces of the fourth trailer and the second trailer in flow communication, thereby equalizing the pressures of the fourth trailer and the second trailer to an intermediate pressure between P2 and the initial pressure of the fourth trailer, the intermediate pressure of the fourth trailer and the second trailer being higher than the predetermined pressure of the first trailer; following the pressure equalization of the fourth trailer and the second trailer, placing the liquid cryogen contained within the second trailer in flow communication with the liquid cryogen contained within the first trailer, thereby allowing liquid cryogen to flow from the second trailer to the third trailer due to the pressure differential between the intermediate pressure of the first trailer and the second trailer and the predetermined pressure of the first trailer, and the flow of liquid cryogen between the second trailer and the first trailer to continue until the first trailer is substantially filled with liquid cryogen; The method of claim 2 further comprising:

7. 7. The method of claim 6, further comprising the step of transporting the first trailer to an end user site C where liquid cryogen is transferred from the first trailer to a storage tank at end user site C, end user site C being the same as or different from end user site A and the same as or different from end user site B, and the second trailer and the fourth trailer being the same or different trailers.

8. After the step of allowing the flow of liquid cryogen between the second trailer and the third trailer to continue until the third trailer is substantially filled, venting gaseous cryogen from the first trailer until a predetermined pressure lower than P2 is reached; providing a fourth liquid cryogen storage trailer having substantially the same storage capacity as the first trailer and the third trailer, the fourth trailer being positioned at the depot at an initial pressure and having a headspace filled with cryogen vapor above the liquid cryogen contained within the fourth trailer, the initial pressure of the fourth trailer being greater than P2, which is greater than the predetermined pressure of the first trailer; placing the headspaces of the fourth trailer and the second trailer in flow communication, thereby equalizing the pressures of the fourth trailer and the second trailer to an intermediate pressure between P2 and the initial pressure of the fourth trailer, the intermediate pressure of the fourth trailer and the second trailer being higher than the predetermined pressure of the first trailer; following the pressure equalization of the fourth trailer and the second trailer, placing the liquid cryogen contained within the second trailer in flow communication with the liquid cryogen contained within the first trailer, thereby allowing liquid cryogen to flow from the second trailer to the third trailer due to the pressure differential between the intermediate pressure of the first trailer and the second trailer and the predetermined pressure of the first trailer, and the flow of liquid cryogen between the second trailer and the first trailer to continue until the first trailer is substantially filled with liquid cryogen; The method of claim 1 further comprising:

9. 9. The method of claim 8, further comprising the step of transporting the first trailer to an end user site C where liquid cryogen is transferred from the first trailer to a storage tank at end user site C, end user site C being the same as or different from end user site A and the same as or different from end user site B, and the second trailer and the fourth trailer being the same or different trailers.

10. 10. The method of claim 9, further comprising, after the step of allowing the flow of liquid cryogen between the second trailer and the third trailer to continue until the third trailer is substantially filled, transporting the third trailer to an end user site B where liquid cryogen is transferred from the first trailer to a storage tank at an end user site B that is the same as or different from end user site A.

11. The method of claim 1 , wherein the cryogen is hydrogen.

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