Method for processing a hydrogen BOG stream

Abstract

The invention provides a method for processing a hydrogen BOG (boil-off gas) stream, the method comprising at least the steps of: (a) providing a hydrogen feed stream (10) to be liquefied; (b) cooling the hydrogen feed stream (10) provided in step (a) using at least a first refrigerant (30) in a liquefaction unit (2) comprising a pre-cooling cold box (21) and a liquefaction cold box (22), thereby obtaining an at least partially liquefied hydrogen stream (20), wherein the first refrigerant (40) is compressed in a compressor (4) after leaving the liquefaction unit (2) to obtain a compressed first refrigerant (50), and is cooled in an external heat exchanger (3) before returning to the liquefaction unit (2); (c) providing a hydrogen BOG stream (60); (d) heating the hydrogen BOG stream (60) provided in step (c) using the compressed first refrigerant (50) in the external heat exchanger (3), thereby obtaining a heated hydrogen BOG stream (70); (e) compressing the heated hydrogen BOG stream (70), thereby obtaining a compressed heated hydrogen BOG stream (80); (f) combining the compressed heated hydrogen BOG stream (80) obtained in step (e) with the hydrogen feed stream (10) provided in step (a); and wherein the first refrigerant (30, 40, 50) is in a closed refrigerant circuit comprising the external heat exchanger (3), the compressor (4) and the liquefaction unit (2).

Description

Technical Field

[0001] This invention relates to a method for processing hydrogen BOG (evaporated gas) streams. Background Technology

[0002] Hydrogen is considered one of the most promising energy carriers for decarbonized energy systems. The efficient transport and storage of liquid hydrogen (LH2) is considered key to its large-scale adoption.

[0003] One of the main challenges in liquid hydrogen storage is dealing with hydrogen evaporation losses caused by cooling requirements, tank filling, heat ingress, and tank depressurization requirements.

[0004] Some evaporation gases will form continuously at a stable flow rate, such as those formed due to heat ingress during system pressurization mode. Other evaporation gases will form intermittently. Typically, these latter intermittent evaporation gas flows will have short durations (on the order of hours), relatively high peak flows (2 to 10 times the average daily processing rate of instantaneous flow), and low frequency (e.g., once to ten times per month).

[0005] Furthermore, some vapors can have temperatures significantly higher than the atmospheric boiling point of hydrogen, which is -253°C (20K). In this regard, A. Krenn's paper, "The safe removal of frozen air from the annulus of a liquid hydrogen storage tank," (which can be accessed via...) https: / / stars.library.ucf.edu / etd / 1382 (Check) Figure 6 The modeling results depict the temperature stratification of hydrogen in a steady-state, 50% filled LH2 tank are presented. The predicted temperature of the hydrogen vapor is above -34.65℃ (238.5K).

[0006] The aforementioned "intermittent" or "variable" nature of certain hydrogen evaporation flow rates makes them difficult to handle, for example, with mechanical equipment. If no suitable technical solution is available to handle these intermittent BOG flows, intermittent hydrogen BOG is emitted. Needless to say, such hydrogen BOG emissions are undesirable both economically and environmentally.

[0007] The article "Final test results for the ground operations demonstration unit for liquid hydrogen" by Notardonato et al., published in Cryogenics, Volume 88 (2017), pp. 147-155, describes the LH2 system using IRAS (Integrated Cooling and Storage) technology, which aims to achieve ZBO (Zero Evaporation) operation, i.e., avoiding the occurrence of hydrogen BOG.

[0008] The aforementioned IRAS technology suffers from high cost and complexity. Another issue is that while it reduces evaporation during operations such as cargo transfer, it cannot completely eliminate evaporation generation, thus requiring evaporation treatment. Furthermore, IRAS technology is not designed for reprocessing and recondensing intermittent evaporation gas flows.

[0009] Several methods for treating hydrogen BOG (rather than emissions) have recently been proposed in this field.

[0010] US 2023 / 0009727 A1 describes a method for liquefying hydrogen. The method includes the steps of: precooling a hydrogen feed stream in a precooling chamber equipped with a heat exchanger to form a cooled hydrogen stream, wherein the heat exchanger is configured to cool the feed stream within the precooling chamber via indirect heat exchange between the hydrogen feed stream and a precooling refrigerant; and drawing the cooled hydrogen stream from the precooling chamber; and introducing the cooled hydrogen stream into a plurality of liquefaction chambers, wherein the cooled hydrogen stream is liquefied within the plurality of liquefaction chambers via indirect heat exchange with a liquefying refrigerant to form a product hydrogen stream in each of the plurality of liquefaction chambers.

[0011] Paragraph

[0005] of US 2023 / 0009727 A1 states: "It is known in the art that the largest device within a cold box is a heat exchanger." US 2023 / 0009727 A1 thus makes a clear distinction between the heat exchanger device and the cold box in which the heat exchanger device is located, both of which form part of the liquefaction system.

[0012] In US 2023 / 0009727 A1, it will be readily understood by those skilled in the art that... Figure 1 The dashed rectangles 10 and 5 in the middle and Figure 3 and Figure 4 The dashed rectangles 10, 20, and 25 indicate which process equipment is enclosed in a precooling box or a liquefaction box.

[0013] As an example only, US 2023 / 0009727 A1 Figure 3 Paragraph

[0076] discloses the reheating of evaporation streams 42 and 43 drawn from liquid hydrogen storage tank 40 in one or two liquefaction zones, followed by combination and reheating in precooling zone 10. US 2023 / 0009727 A1 Figure 3 The simplified version is shown in this article as Figure 1 .

[0014] One problem with the aforementioned series in US 2023 / 0009727 A1 is that, particularly with variable flow rates and / or temperatures in the hydrogen BOG, this can lead to mechanical stress (and failure) in the heat exchanger equipment. Another problem with this series is that, particularly with high flow rates of hydrogen BOG, the flow capacity of the heat exchanger equipment may be exceeded.

[0015] US 3380809 A relates to a method for the liquefaction and conversion of hydrogen. Specifically, US 3380809 A provides a method for preparing liquid hydrogen with a high secondary hydrogen content, the method comprising:

[0016] - This involves countercurrent heat exchange between the compressed hydrogen feed and a relatively cold fluid, and catalytic conversion of orthohydrogen to secondary hydrogen to provide a high-secondary-hydrogen-content hydrogen feed at a relatively low temperature.

[0017] - Expand the high-secondary-hydrogen component hydrogen feed to a lower pressure to achieve partial liquefaction of the high-secondary-hydrogen component hydrogen feed.

[0018] - Separate the high-secondary-hydrogen component liquid hydrogen from the high-secondary-hydrogen component unliquefied hydrogen.

[0019] - Catalytic treatment of liquid hydrogen with high secondary hydrogen content to further increase the secondary hydrogen content of liquefied hydrogen.

[0020] - The unliquefied hydrogen of the high secondary hydrogen component is heated, and the hot high secondary hydrogen component hydrogen is compressed to a relatively high pressure.

[0021] - By subjecting the compressed, unliquefied hydrogen of the high-secondary hydrogen component to countercurrent heat exchange with a relatively cold fluid, the compressed, unliquefied hydrogen of the high-secondary hydrogen component is cooled to a low temperature without catalytic conversion to orthohydrogen.

[0022] - This causes the unliquefied hydrogen in the cold, high-hydrogen component to expand, and

[0023] - Catalytic treatment of expanded hydrogen with high secondary hydrogen content to further increase its secondary hydrogen content.

[0024] US 3380809 A Figure 1 A to Figure 1D illustrates a complex arrangement of equipment used in a liquefaction and refrigeration cycle. Clearly, the arrangement employed in US 3380809 A involves the recirculation of streams and results in close mixing (i.e., co-mixing) of various streams in the system, including a hydrogen feed stream, a hydrogen refrigerant stream, and a hydrogen BOG stream. Specifically, hydrogen BOG streams 200 and 201 are apparently guided through what is known in the system as a “hydrogen refrigeration and recirculation arrangement.” The hydrogen (e.g., refrigerant / BOG) stream in this arrangement is then recirculated back through the system, further compacting this stream with the hydrogen feed stream at various points in the system.

[0025] For example, in which compressed heated hydrogen BOG stream 151 is mixed with medium-pressure hydrogen stream 184 at the inlet of compressor 152, the medium-pressure hydrogen stream is used as a refrigerant in this arrangement. US 3380809 A explains in column 7, lines 67-70, that this medium-pressure hydrogen stream (181 / 182 / 183 / 184) "cools the hydrogen feed gas flowing through channels 46, 51, 55, 57, 61, 65 and 69 by means of the shell side of heat exchangers 47 and 58."

[0026] In another example, the combined BOG, along with medium-pressure hydrogen streams 151 and 184, is compressed in compressor 152, cooled in heat exchangers 158 and 178, and liquefied during expansion via valve 179 to produce a liquefied BOG-refrigerant stream 180, which mixes with the hydrogen feed gas in conduit 71 upstream of expansion valve 72.

[0027] In another example, the combined BOG, along with medium-pressure hydrogen streams 151 and 184, is compressed in compressor 152, cooled in heat exchangers 158, 47, and 58, and liquefied upon expansion via valve 169 to produce a liquefied BOG-refrigerant stream 170, which mixes with the hydrogen feed gas in duct 71 downstream of expansion valve 169.

[0028] Technicians will understand that, given the complex routing and recirculation arrangement described in US 3380809 A, the close mixing of various hydrogen feed, refrigerant, and BOG streams will require careful system balancing. In column 8, lines 52-64, US3380809 A discusses achieving “equilibrium conditions,” which is the operating state when the quality of some streams (combined) “substantially corresponds” to the quality of some other streams (combined). The system will encounter operational problems when large fluctuations in the flow rate and / or temperature of the hydrogen BOG must be addressed. This variability will lead to… Figure 1 A to Figure 1 The challenges and mechanical stresses (and failures) of the D arrangement. This arrangement will also struggle to cope with high-flow-rate hydrogen BOG events, exceeding the flow capacity of multiple heat exchangers, conduits, or phase separators in the arrangement.

[0029] As another example, WO 2023 / 046889 A1 discloses a method for recovering hydrogen BOG, wherein “based on the measurement of BOG pressure”, hydrogen BOG (“BOG1”) originating from a hydrogen transport truck (i.e., a relatively small volume hydrogen BOG) is processed (see page 1, lines 19-21 and claim 1).

[0030] Because WO 2023 / 046889 A1 focuses on relatively small hydrogen BOG volumes (derived from hydrogen transport trucks during truck loading / filling mode), it will not allow for the handling of larger hydrogen BOG volumes. Furthermore, WO 2023 / 046889 A1, on page 1, lines 24-32, discloses three different ways to maximize BOG recovery by using hydrogen molecules (including feeding BOG into the liquefier or upstream of the liquefier, and directly recycling cold BOG in the liquefier). In the case of feeding cold BOG directly into the liquefier, the same disadvantages as in US 2023 / 0009727 A1 are encountered. In the case of feeding evaporated hydrogen upstream of the liquefier, it is recommended to feed it "specifically at the compression column inlet" (see page 1, lines 29 / 30). As shown, in this case, a "BOG heater" is used. In this regard, it should be noted that on page 6, lines 23-24, it states that "BOG heaters typically use external fluids such as steam or water to heat the BOG." In this case, the resource utilization of the cold BOG is not achieved. Furthermore, in this situation, any leakage between the cold and hot fluids inside the BOG heater will result in the immediate formation of water ice and blockage.

[0031] AU 2013 / 264212 A1 (also disclosed in WO 2013 / 175906 A1) discloses (see, for example,

[0011] ) the introduction of evaporated gas generated in a primary LH2 reservoir (e.g., an LH2 container of an LH2 transport ship) into a secondary LH2 reservoir, such that at least a portion of the BOG is liquefied by the cryogenic heat energy of the (supercooled) LH2 within the secondary LH2 reservoir. The problem with this setup is that it requires a large tank capable of reliquefying the hydrogen BOG, especially under intermittent peak flow conditions. Furthermore, this arrangement requires maintaining the LH2 tank in a filled (and supercooled) state even while waiting for the next batch of hydrogen BOG to be reliquefied. Keeping such a filled LH2 tank in a waiting mode is inefficient, as hydrogen BOG will inherently form in the waiting mode. Additionally, this will also contaminate the contents of the large secondary LH2 container if the hydrogen BOG fed to the secondary tank is of lower quality (e.g., contaminated).

[0032] The object of the present invention is to solve, minimize, or at least reduce one or more of the aforementioned problems associated with the handling of hydrogen evaporation gas, particularly in cases such as variable and large quantities of hydrogen BOG occurring during the filling of large hydrogen storage tanks.

[0033] Another object of the present invention is to provide a method for processing hydrogen BOG streams with varying or relatively high temperatures.

[0034] Another object of the present invention is to provide a method for processing a hydrogen BOG stream that does not depend on the measurement of the hydrogen BOG pressure.

[0035] Another object of the present invention is to provide an alternative method for processing hydrogen BOG. Summary of the Invention

[0036] According to the present invention, one or more of the above or other objectives can be achieved by providing a method for processing a hydrogen BOG (boiler gas) stream, the method comprising at least the following steps:

[0037] (a) Provide a feed stream of hydrogen to be liquefied;

[0038] (b) In a liquefaction unit comprising a precooling cold box and a liquefaction cold box, at least a first refrigerant is used to cool the hydrogen feed stream provided in step (a) to obtain a hydrogen stream that is at least partially liquefied, wherein the first refrigerant is compressed in a compressor after leaving the liquefaction unit to obtain a compressed first refrigerant, and is cooled in an external heat exchanger before returning to the liquefaction unit.

[0039] (c) Provide a hydrogen BOG stream;

[0040] (d) In an external heat exchanger, the hydrogen BOG stream provided in step (c) is heated using a compressed first refrigerant to obtain a heated hydrogen BOG stream.

[0041] (e) Compressing the heated hydrogen BOG stream to obtain a compressed heated hydrogen BOG stream; and

[0042] (f) Combine the compressed heated hydrogen BOG stream obtained in step (d) with the hydrogen feed stream provided in step (a); and

[0043] The first refrigerant is in a closed refrigerant circuit that includes an external heat exchanger, a compressor, and a liquefaction unit.

[0044] The present invention also provides an apparatus suitable for performing a method for processing a hydrogen BOG (boiler gas) stream, the apparatus comprising at least:

[0045] - A liquefaction unit, comprising a precooling cold box and a liquefaction cold box, the liquefaction unit being used to cool the hydrogen feed stream to be liquefied using at least a first refrigerant to obtain a hydrogen stream that is at least partially liquefied;

[0046] - Compressor, which is used to compress the first refrigerant after the first refrigerant has left the liquefaction unit;

[0047] - An external heat exchanger is used to cool the first refrigerant after it has left the compressor;

[0048] - One or more storage tanks, which are capable of being filled with liquefied hydrogen and capable of providing a hydrogen BOG stream;

[0049] In the external heat exchanger, the hydrogen BOG stream can be heated using the first refrigerant to obtain a heated hydrogen BOG stream.

[0050] - A compressor used to compress a heated hydrogen BOG stream to obtain a compressed heated hydrogen BOG stream; and

[0051] - Connector, which is used to combine a compressed heated hydrogen BOG stream with a hydrogen feed stream.

[0052] The first refrigerant is in a closed refrigerant circuit that includes an external heat exchanger, a compressor, and a liquefaction unit. Attached Figure Description

[0053] Figure 1 It is in US 2023 / 0009727 A1 Figure 3 A simplified version.

[0054] Figure 2This is a flowchart of a (advanced) first embodiment of the method for processing hydrogen BOG according to the present invention;

[0055] Figure 3 This is a flowchart of a second embodiment of the method for processing hydrogen BOG according to the present invention;

[0056] Figure 4 This is a flowchart of a third embodiment of the method for processing hydrogen BOG according to the present invention;

[0057] Figure 5 This is a flowchart of a fourth embodiment of the method for processing hydrogen BOG according to the present invention; and

[0058] Figure 6 This is a flowchart of a fifth embodiment of the method for processing hydrogen BOG according to the present invention.

[0059] While this disclosure allows for various modifications and alternatives, specific implementations have been shown in the figures and described in more detail herein.

[0060] However, it should be understood that the description of the specific embodiments is not intended to limit the invention to the particular forms disclosed, but rather, this disclosure will cover all modifications and equivalents exemplified in part by the appended claims. Detailed Implementation

[0061] According to the present invention, it has been surprisingly discovered that the processing of hydrogen BOG can be achieved in a simple manner by heating the hydrogen BOG stream with a compressed first refrigerant in an external heat exchanger (i.e., outside the liquefaction unit), the first refrigerant being in a closed refrigerant loop.

[0062] A key advantage of the method according to the invention is that it can handle intermittent or variable amounts of hydrogen BOG without significantly affecting, for example, the heat exchanger equipment within the liquefaction unit (which would occur in cases where large amounts of hydrogen BOG are to be fed directly into the liquefaction unit).

[0063] Another advantage of the method according to the invention is that the resource utilization of cold BOG can be achieved by using an internal fluid to heat the hydrogen BOG (instead of an “external fluid” such as steam or water as used in WO 2023 / 046889 A1), resulting in higher energy efficiency of the liquefaction unit.

[0064] Another advantage of the method according to the invention is that it can handle a wide range of BOG temperatures and variations in BOG temperatures without significantly affecting, for example, the heat exchanger equipment inside the precooling cold box and / or liquefaction cold box.

[0065] In step (a) of the method according to the invention, a feed stream of hydrogen to be liquefied is provided.

[0066] Although there are no particular limitations on the hydrogen feed stream provided in step (a), it typically has a high hydrogen content and a low impurity content (otherwise, impurities would freeze in the conduit). Preferably, the hydrogen feed stream provided in step (a) comprises at least 99.0% by weight, preferably at least 99.8% by weight, and more preferably at least 99.9% by weight of hydrogen.

[0067] Preferably, the hydrogen feed stream provided in step (a) has a pressure in the range of 15 bara to 80 bara, preferably less than 50 bara, and more preferably less than 35 bara.

[0068] Typically, the hydrogen feed stream provided in step (a) will have a temperature in the range of -40°C to 55°C (233K to 328K), preferably in the range of -20°C to 55°C (253K to 328K), and more preferably in the range of -10°C to 40°C (263K to 313K).

[0069] In step (b) of the method according to the invention, at least a first refrigerant is used in the liquefaction unit to cool the hydrogen feed stream provided in step (a) to obtain a hydrogen stream that is at least partially liquefied, wherein the first refrigerant is compressed in a compressor after leaving the liquefaction unit to obtain compressed first refrigerant, and is cooled in an external heat exchanger before returning to the liquefaction unit.

[0070] As mentioned above, the first refrigerant is in a closed refrigerant circuit including an external heat exchanger, compressor, and liquefaction unit. As stated above, the liquefaction unit includes a precooling chamber and a liquefaction chamber. Those skilled in the art will understand that the liquefaction unit (and the precooling chamber and liquefaction chamber therein) may also include additional equipment, including valves, turboexpanders, compressors, phase separation vessels, adsorption vessels, interconnecting piping, and instrumentation. Therefore, the closed refrigerant circuit may also be connected to additional equipment included within the liquefaction unit. "Closed" as used herein means that the refrigerant circuit containing the first refrigerant is an isolated circuit such that the first refrigerant does not mix closely with other flows in the equipment (e.g., hydrogen feed flow, hydrogen BOG flow, heated hydrogen BOG flow, and compressed heated hydrogen BOG flow). However, those skilled in the art will understand that within a closed refrigerant circuit, the presence of equipment such as an expander and compressor can cause small amounts of the first refrigerant to leak from, for example, joints, valves, and seals within the circuit. Therefore, if desired, the closed refrigerant circuit may include one or more additional closable inlets ( Figures 2 to 6 (not shown in the image) to allow for optional replenishment of the first refrigerant.

[0071] Those skilled in the art will readily understand that the liquefaction unit can be varied in many ways.

[0072] The liquefaction unit includes a precooling box and a liquefaction box, wherein the first refrigerant passes through one or both of the precooling box and the liquefaction box.

[0073] In their article "Hydrogen liquefaction: a review of the fundamental physics, engineering practice and future opportunities," published in *Energy Environ. Sci.*, 2022, Vol. 15, pp. 2690–2731 (accessible via DOI: 10.1039 / d2ee00099g), S. Al Ghafri et al. point out that the purpose of the cold box is to "minimize heat leakage into the cryogenic equipment," which, in the view of those skilled in the art, refers to equipment at or below 120 K. In other words, the pre-cooling cold box and the liquefaction cold box in a hydrogen liquefaction unit are not part of its process system, but rather part of its mechanical insulation system. Al Ghafri et al. further described industrial cold boxes as: "cylindrical or rectangular containers designed to store key cryogenic equipment such as plate-fin heat exchangers; turboexpanders; adsorbers; and phase separation containers." These cold box containers are typically filled with insulating materials (such as perlite), often comprising multiple layers of super-insulation, and maintained inert or vacuum environments. When a hydrogen liquefaction unit comprises both an inert pre-cooling cold box and a vacuum liquefaction cold box, the pre-cooling cold box includes cryogenic equipment at temperatures above the atmospheric boiling point of the inert gas used. For example, this temperature is 77 K for nitrogen and 87 K for argon. The cryogenic equipment at the lower temperature then resides in the liquefaction cold box.

[0074] In this invention, the hydrogen feed stream provided in step (a) is cooled in a precooling box to obtain a precooled hydrogen stream with an intermediate temperature.

[0075] The precooled hydrogen stream, which has an intermediate temperature, remains gaseous. Typically, the precooled hydrogen stream has a temperature in the range of -203°C to -123°C (70K to 150K), preferably -198°C to -153°C (75K to 120K).

[0076] Those skilled in the art will readily understand that precooling boxes can be varied in many ways.

[0077] A precooling box may include one or more heat exchangers. Furthermore, the precooling box may include components capable of achieving isenthalpic and / or isentropic expansion. For example, examples of different precooling series have been described in the article "Hydrogen Liquefaction: A Review of Fundamental Physics, Engineering Practice and Future Opportunities" published by S. Al Ghafri et al. in *Energy & Environmental Science*, 2022, Vol. 15, pp. 2690–2731 (accessible via DOI: 10.1039 / d2ee00099g), which can be found in detail elsewhere. Figures 6 to 1 0 in.

[0078] In the liquefaction cold box, the pre-cooled hydrogen gas stream with an intermediate temperature is further cooled to obtain at least partially liquefied hydrogen gas stream (and preferably fully liquefied hydrogen gas stream).

[0079] Similarly, those skilled in the art will readily understand that liquefaction cold boxes can vary in many ways. A liquefaction cold box may include one or more heat exchangers. Furthermore, a liquefaction cold box may include components capable of achieving isenthalpic and / or isentropic expansion, such as valves or expanders. Additionally, a portion of the cooling in the liquefaction cold box may (and typically will) be achieved by the expansion of the hydrogen feed stream. Suitable, non-limiting examples of liquefaction series are, for instance, already described in the aforementioned article by S. Al Ghafri et al. Figures 6 to 1 0 is publicly available.

[0080] According to a preferred embodiment of the method of the invention, the liquefaction unit uses a second refrigerant, and the second refrigerant is supplied through one or both of the precooling cold box and the liquefaction cold box.

[0081] Those skilled in the art will readily understand that the first and second refrigerants can be varied in many ways and are not particularly limited. Furthermore, in addition to the first and second refrigerants, other refrigerants may be present. The composition of the first, second, and other refrigerants will depend particularly on where the refrigerants will be used in the liquefaction unit.

[0082] According to a preferred embodiment of the method of the present invention, the first refrigerant is selected from the group consisting of nitrogen, one or more hydrocarbons, argon, hydrogen, helium, neon or a mixture thereof, and preferably from the group consisting of hydrogen, helium, neon or a mixture thereof.

[0083] Furthermore, preferably, the second refrigerant is selected from the group consisting of nitrogen, one or more hydrocarbons, argon, hydrogen, helium, neon, or mixtures thereof, and more preferably from the group consisting of nitrogen, one or more hydrocarbons, argon, or mixtures thereof. Typically, the second refrigerant will include nitrogen or a mixture of nitrogen and other components. Suitable refrigerant compositions that can be used as a second refrigerant have been disclosed, for example, in WO 2017 / 072221 A1 (also disclosed as EP 3368630 A1).

[0084] According to an embodiment of the method of the present invention, the first refrigerant does not pass through the liquefaction cold box.

[0085] According to an embodiment of the method of the present invention, the second refrigerant does not pass through the liquefaction cold box.

[0086] Those skilled in the art will understand that there are no particular restrictions on the external heat exchanger (in which the compressed first refrigerant is cooled after leaving the liquefaction unit), as long as the external heat exchanger is outside the liquefaction unit (i.e., does not form part of the liquefaction unit).

[0087] In step (c) of the method according to the invention, a hydrogen BOG stream is provided.

[0088] Typically, the hydrogen BOG stream provided in step (c) is derived from the hydrogen BOG stream of liquid hydrogen processing and storage operations, and therefore has a high hydrogen content and low impurity content (otherwise, impurities would freeze in the conduit leading to the storage tank). The hydrogen BOG stream can originate from a variety of sources (combinations), such as hydrogen BOG generated during hydrogen cooling, heat entering several parts of the hydrogen supply chain, depressurization of the storage tank, etc. Preferably, the hydrogen BOG originates from a liquid hydrogen storage tank, and more preferably from a liquid hydrogen storage tank filled with liquid hydrogen (thus generating hydrogen BOG).

[0089] Preferably, the hydrogen BOG stream provided in step (c) originates from one or more storage tanks filled with the liquid hydrogen obtained in step (b).

[0090] These storage tanks can be “portable” tanks for storing liquid hydrogen (which can be transported to different locations) or “static” or “immovable” tanks for storing liquid hydrogen (which will not be transported to different locations but will remain with the hydrogen liquefaction process unit).

[0091] In the following text, the movable tank will be referred to as the "first storage tank" and the static tank will be referred to as the "second storage tank".

[0092] According to a preferred embodiment of the method of the present invention, the liquefied hydrogen gas obtained in step (b) is temporarily stored in a (static) second storage tank, and one or more (removable) first storage tanks are filled with liquid hydrogen from the second storage tank.

[0093] Typically, if both a first storage tank and a second storage tank exist, the volume of the second storage tank is greater than the volume of the first storage tank.

[0094] According to a preferred embodiment of the method of the invention (and to reflect the typical large BOG volume processed by the method of the invention), during the filling with liquid hydrogen, the amount of hydrogen BOG from one or more storage tanks is at least 1000 kg / day for at least one storage tank, preferably each individual storage tank.

[0095] Furthermore, preferably, the second storage tank has a capacity of at least 1000m³. 3 Preferably at least 1500m 3 More preferably at least 2000m 3 or even more preferably at least 2500m 3 The volume.

[0096] Preferably, the hydrogen BOG stream provided in step (c) comprises at least 99.0% by weight, preferably at least 99.8% by weight, and more preferably at least 99.9% by weight of hydrogen. Furthermore, it is preferred that the hydrogen BOG stream provided in step (c) comprises at least 90% by weight, preferably at least 95% by weight of secondary hydrogen.

[0097] Although there is no particular limitation on the temperature of the hydrogen BOG stream provided in step (c), and it can range from low temperatures of ~-259°C (~14K) to ambient temperatures (~25°C (298K)), the hydrogen BOG stream provided in step (c) preferably has a temperature in the range of -259°C to -213°C (14K to 60K), and preferably below -233°C (below 40K). This reflects the typical temperature of the hydrogen BOG stream from the liquid hydrogen storage tank, especially when generated during the filling / loading of the liquid hydrogen storage tank.

[0098] Furthermore, although there is no particular limitation on the pressure of the hydrogen BOG stream provided in step (c), it is preferred that the hydrogen BOG stream provided in step (c) has a pressure in the range of 1.0 bara to 6.0 bara, preferably up to 3.0 bara.

[0099] The hydrogen BOG stream provided in step (c) is fed to an external heat exchanger. Preferably, the hydrogen BOG stream is fed directly to the external heat exchanger. "Directly" means that the hydrogen BOG stream provided in step (c) does not pass through any liquefaction unit heat exchanger, precooling box, or liquefaction box before reaching the external heat exchanger.

[0100] In step (d) of the method according to the invention, the hydrogen BOG stream provided in step (c) is heated in an external heat exchanger using a compressed first refrigerant, thereby obtaining a heated hydrogen BOG stream. If desired, the hydrogen BOG stream can also be heated using other streams besides the compressed first refrigerant. This additional heating can be performed in an external heat exchanger or in one or more separate heat exchangers. However, according to a particularly preferred embodiment of the invention, the hydrogen BOG stream is not heated in a pre-cooling cold box or a liquefaction cold box.

[0101] Typically, the heated hydrogen BOG stream has a temperature of -150°C to 55°C (123K to 328K), preferably -40°C to 55°C (233K to 328K), and more preferably -20°C to 40°C (253K to 313K).

[0102] In addition, the heated hydrogen BOG stream typically has a pressure of 1.0 bara to 6.0 bara.

[0103] In step (e) of the method according to the invention, the heated hydrogen BOG stream is compressed to obtain a compressed heated hydrogen BOG stream. Typically, the compressed heated hydrogen BOG stream has a pressure in the range of 15 bara to 80 bara, preferably below 50 bara, and more preferably below 35 bara.

[0104] In step (f) of the method according to the invention, the compressed heated hydrogen BOG stream obtained in step (e) is combined with the hydrogen feed stream provided in step (a). Preferably, the compressed heated hydrogen BOG stream and the hydrogen feed stream are combined upstream of the liquefaction unit (pre-cooling box) and enter the liquefaction unit as a combined stream.

[0105] As described above, in another aspect, the present invention provides an apparatus suitable for performing a method according to the invention for processing a hydrogen BOG (boiler gas) stream, the apparatus comprising at least:

[0106] - A liquefaction unit, comprising a precooling cold box and a liquefaction cold box, the liquefaction unit being used to cool the hydrogen feed stream to be liquefied using at least a first refrigerant to obtain a hydrogen stream that is at least partially liquefied;

[0107] - Compressor, which is used to compress the first refrigerant after the first refrigerant has left the liquefaction unit;

[0108] - An external heat exchanger is used to cool the first refrigerant after it has left the compressor;

[0109] - One or more storage tanks, which are capable of being filled with liquefied hydrogen and capable of providing a hydrogen BOG stream;

[0110] In the external heat exchanger, the first refrigerant can be used to heat the hydrogen BOG stream, thereby obtaining a heated hydrogen BOG stream.

[0111] - A compressor used to compress a heated hydrogen BOG stream to obtain a compressed heated hydrogen BOG stream; and

[0112] - Connector, used to combine a compressed heated hydrogen BOG stream with a hydrogen feed stream.

[0113] The first refrigerant is in a closed refrigerant circuit that includes an external heat exchanger, a compressor, and a liquefaction unit.

[0114] Preferably, the device further includes a second storage tank for temporarily storing liquefied hydrogen obtained in the liquefaction unit, wherein one or more first storage tanks may be filled with liquid hydrogen from the second storage tank.

[0115] The invention will be further illustrated below with reference to the following non-limiting drawings: Figures 2 to 6 .

[0116] For the purposes of this description, the same reference numerals denote the same or similar parts.

[0117] Figure 2 The flowchart is generally indicated by reference numeral 1 in the attached diagram, showing the liquefaction unit 2, external heat exchanger 3, compressor 4 and compressor 5, several (movable) first storage tanks 6 for storing liquefied hydrogen, and connector 9.

[0118] In use Figure 2 During the series, a hydrogen feed stream 10 to be liquefied is provided. The hydrogen feed stream 10 (as stream 15) is fed into the liquefaction unit 2. In the liquefaction unit 2, at least a first refrigerant 30 is used to cool the hydrogen feed stream, thereby obtaining a stream 20 that is at least partially liquefied.

[0119] The liquefaction unit 2 uses at least the first refrigerant 30 that circulates in the first refrigerant cycle. The compressor 4 forms part of the first refrigerant cycle. The first refrigerant cycle will typically include other components that are also capable of achieving isenthalpic and / or isentropic expansion.

[0120] After leaving the liquefaction unit 2 (as flow 40), the first refrigerant is compressed in the compressor 4 to obtain compressed first refrigerant 50. The compressed first refrigerant 50 is cooled in an external heat exchanger 3 (which is not part of the liquefaction unit 2) before returning (as flow 30) to the liquefaction unit 2.

[0121] exist Figure 2 In this embodiment, the liquefied hydrogen gas stream 20 is used to directly fill the movable first storage tank 6. During the filling of the movable first storage tank 6, a relatively large amount of hydrogen BOG (BoG) is generated. Figure 2 (60 in the middle).

[0122] After the first hydrogen storage tank 6 is filled, these tanks (which may be placed, for example, on a ship) can be transported to their intended destination.

[0123] In the external heat exchanger 3, the hydrogen BOG stream 60 is heated by the compressed first refrigerant 50 to obtain a heated hydrogen BOG stream 70. The heated hydrogen BOG stream 70 is compressed in the compressor 5 to obtain a compressed heated hydrogen BOG stream 80. Then, the compressed heated hydrogen BOG stream 80 is combined with the hydrogen feed stream 10 at the connector 9 and then delivered to the liquefaction unit 2 as a combined stream 15.

[0124] Figure 3 A (more detailed) flowchart of a second embodiment of the method according to the invention is shown schematically.

[0125] exist Figure 3 In one embodiment, the liquefaction unit 2 includes a pre-cooling cold box 21 and a liquefaction cold box 22. The liquefaction unit 2 uses both a first refrigerant 30 and a second refrigerant 200.

[0126] The first refrigerant 30 passes through both the pre-cooling cold box 21 and the liquefaction cold box 22, while the second refrigerant 200 passes through the pre-cooling cold box 21 but not through the liquefaction cold box 22.

[0127] exist Figure 3 In the embodiments, the first refrigerant 30 is preferably selected from the group consisting of hydrogen, helium, neon or a mixture thereof, while the second refrigerant 200 is preferably selected from the group consisting of nitrogen, one or more hydrocarbons, argon or a mixture thereof.

[0128] In use Figure 3 During the series, the hydrogen feed stream 10 (as feed stream 15 to liquefaction unit 2) is cooled in precooling box 21 to obtain a precooled hydrogen stream 15' with an intermediate temperature.

[0129] The pre-cooled cold box 21 uses a first refrigerant 30 circulating in a first refrigerant cycle and a second refrigerant 200 circulating in a second refrigerant cycle. Compressor 4 forms part of the first refrigerant cycle. Compressor 7 forms part of the second refrigerant cycle. The first and second refrigerant cycles typically include other components also capable of achieving isenthalpic and / or isentropic expansion.

[0130] After leaving the precooling cold box 21, the precooled hydrogen gas stream 15' is further cooled in the liquefaction cold box 22 to obtain at least partially liquefied hydrogen gas stream 20.

[0131] Figure 4 A (more detailed) flowchart of a third embodiment of the method according to the invention is shown schematically.

[0132] exist Figure 4 In the implementation scheme, liquefaction unit 2 again acts like Figure 3 It also includes a pre-cooling cold box 21 and a liquefied cold box 22, as well as a first refrigerant 30 and a second refrigerant 200.

[0133] However, in Figure 4 In this process, the second refrigerant 200 passes through both the pre-cooling cold box 21 and the liquefaction cold box 22, while the first refrigerant 30 passes through the pre-cooling cold box 21 but not through the liquefaction cold box 22.

[0134] exist Figure 4 In the embodiments, the second refrigerant 200 is preferably selected from the group consisting of hydrogen, helium, neon or a mixture thereof, while the first refrigerant 30 is preferably selected from the group consisting of nitrogen, one or more hydrocarbons, argon or a mixture thereof.

[0135] Figure 5 A flowchart illustrating a fourth embodiment of the method according to the invention is shown schematically.

[0136] exist Figure 5 In this embodiment, the liquefied hydrogen stream 20 is temporarily stored in (static or immovable) second storage tanks 8. These second storage tanks 8 will not be transported to different locations but will remain with the hydrogen liquefaction process unit 1. The second storage tanks 8 are larger than the first storage tanks 6 (e.g., having a larger internal volume). One or more first storage tanks 6 are filled with liquid hydrogen from the second storage tanks 8. Those skilled in the art will understand that filling the second storage tanks 8 may also result in the generation of hydrogen BOG streams; these hydrogen BOG streams ( Figure 5 (Not shown in the image) can also be processed by passing it to pipeline 60.

[0137] Those skilled in the art will understand that using, as Figure 5 The concept of the (static or immovable) second storage tank 8 shown also applies to, for example... Figure 3 and Figure 4 The implementation scheme shown.

[0138] Figure 6 A flowchart illustrating a fifth embodiment of the method according to the invention is shown schematically. Figure 6In this implementation, the liquefied hydrogen stream 20 is used to fill the static second storage tank 8. Similarly, during the filling of the static second storage tank 8, a hydrogen BOG stream 60 is generated, which is passed via an external heat exchanger 3 and a compressor 5 to combine with the hydrogen feed stream 10 at a connector 9. The movable first storage tank 6 is filled with liquid hydrogen from the static second storage tank 8. Any hydrogen BOG generated during the filling of the first storage tank 6 is returned to the second storage tank 8 and passed along with the hydrogen BOG stream 60 generated in the second storage tank 8. If necessary, a portion of the hydrogen BOG stream from the first storage tank 6 can be recondensed in the second storage tank 8.

[0139] Similarly, those skilled in the art will understand that using, as Figure 6 The concept of the (static or immovable) second storage tank 8 shown also applies to, for example... Figure 3 and Figure 4 The implementation scheme shown.

[0140] discuss

[0141] from Figures 2 to 6 It can be seen that the method according to the invention allows for a surprisingly simple and efficient way of processing hydrogen BOG streams.

[0142] A key advantage of this invention is that it can handle intermittent or variable quantities and / or temperatures of hydrogen BOG without significantly impacting heat exchanger equipment in, for example, precooling and / or liquefaction boxes (which would occur if the hydrogen BOG were to be fed directly into the precooling and / or liquefaction boxes).

[0143] Furthermore, the method according to the invention is not limited by the pressure of the BOG flow 60 (there is no specific pressure limit to be met).

[0144] Furthermore, there is no need to build / operate large (subcooled) LH2 tanks for BOG recondensation.

[0145] Furthermore, the present invention reduces or even eliminates the need for large-scale BOG emissions, which are undesirable both environmentally and economically.

[0146] Those skilled in the art will readily understand that many modifications can be made without departing from the scope of the invention. Furthermore, those skilled in the art will readily understand that while the invention may have been exemplified in some instances with reference to specific combinations of features and measures, many of these features and measures are functionally independent of other features and measures given in the respective embodiments, such that they can be applied equally or similarly independently in other embodiments.

Claims

1. A method for processing a hydrogen BOG (boiler gas) stream, the method comprising at least the following steps: (a) Provide a feed stream of hydrogen to be liquefied (10); (b) In a liquefaction unit (2) comprising a precooling cold box (21) and a liquefaction cold box (22), at least a first refrigerant (30) is used to cool the hydrogen feed stream (10) provided in step (a) to obtain a hydrogen stream (20) that is at least partially liquefied, wherein the first refrigerant (40) is compressed in a compressor (4) after leaving the liquefaction unit (2) to obtain a compressed first refrigerant (50) and is cooled in an external heat exchanger (3) before returning to the liquefaction unit (2); (c) Provide hydrogen BOG flow (60); (d) In the external heat exchanger (3), the compressed first refrigerant (50) is used to heat the hydrogen BOG stream (60) provided in step (c) to obtain a heated hydrogen BOG stream (70). (e) The heated hydrogen BOG stream (70) is compressed to obtain a compressed heated hydrogen BOG stream (80); and (f) The compressed heated hydrogen BOG stream (80) obtained in step (e) is combined with the hydrogen feed stream (10) provided in step (a); and The first refrigerant (30, 40, 50) is in a closed refrigerant circuit including the external heat exchanger (3), the compressor (4) and the liquefaction unit (2).

2. The method according to claim 1, wherein the first refrigerant (30) is supplied through one or both of the precooling box (21) and the liquefaction box (22).

3. The method according to claim 1 or 2, wherein the liquefaction unit (2) uses a second refrigerant (200), and wherein the second refrigerant (200) is supplied by one or both of the precooling box (21) and the liquefaction box (22).

4. The method according to any one of the preceding claims, wherein the first refrigerant (30) is selected from the group consisting of nitrogen, one or more hydrocarbons, argon, hydrogen, helium, neon or a mixture thereof, preferably selected from the group consisting of hydrogen, helium, neon or a mixture thereof.

5. The method according to claim 3 or 4, wherein the second refrigerant (200) is selected from the group consisting of nitrogen, one or more hydrocarbons, argon, hydrogen, helium, neon or a mixture thereof, preferably selected from the group consisting of nitrogen, one or more hydrocarbons, argon or a mixture thereof.

6. The method according to any one of claims 2 to 5, wherein the first refrigerant (30) does not pass through the liquefied cold box (22).

7. The method according to any one of claims 2 to 5, wherein the second refrigerant (200) does not pass through the liquefied cold box (22).

8. The method according to any one of the preceding claims, wherein the hydrogen BOG stream (60) provided in step (c) originates from one or more storage tanks (6, 8) filled with the liquid hydrogen (20) obtained in step (b).

9. The method of claim 8, wherein the liquefied hydrogen gas obtained in step (b) is temporarily stored in a second storage tank (8), and wherein one or more first storage tanks (6) are filled with liquid hydrogen from the second storage tank (8).

10. The method according to claim 8 or 9, wherein during filling with liquid hydrogen, the amount of hydrogen BOG originating from at least one storage tank (6, 8) is at least 1000 kg / day.

11. The method according to any one of claims 9 or 10, wherein the second storage tank (8) has a capacity of at least 1000 m³. 3 Preferably at least 1500m 3 More preferably at least 2000m 3 or even more preferably at least 2500m 3 The volume.

12. The method according to any one of the preceding claims, wherein the hydrogen BOG stream (60) provided in step (c) comprises at least 99.0% by weight, preferably at least 99.8% by weight, more preferably at least 99.9% by weight of hydrogen.

13. The method according to any one of the preceding claims, wherein the hydrogen BOG stream (60) provided in step (c) has a temperature in the range of -259°C to -213°C (14K to 60K), preferably below -233°C (40K).

14. The method according to any one of the preceding claims, wherein the hydrogen BOG stream (60) provided in step (c) has a pressure in the range of 1.0 bara to 6.0 bara, preferably up to 3.0 bara.

15. An apparatus (1) suitable for performing a method for processing a hydrogen BOG (boiler gas) stream according to any one of claims 1 to 14, said apparatus (1) comprising at least: - Liquefaction unit (2), the liquefaction unit includes a precooling cold box (21) and a liquefaction cold box (22), the liquefaction unit is used to cool the hydrogen feed stream (10) to be liquefied using at least a first refrigerant (30) to obtain at least a partially liquefied hydrogen stream (20). - Compressor (4), the compressor being used to compress the first refrigerant (40) after it has left the liquefaction unit (2); - An external heat exchanger (3) is used to cool the first refrigerant (50) after it has left the compressor (4); - One or more storage tanks (6, 8), said one or more storage tanks being able to be filled with liquefied hydrogen and being able to provide a hydrogen BOG stream (60). In the external heat exchanger (3), the first refrigerant (50) can be used to heat the hydrogen BOG stream (60) to obtain a heated hydrogen BOG stream (70). - Compressor (5), the compressor being used to compress the heated hydrogen BOG stream (70) to obtain a compressed heated hydrogen BOG stream (80); and - Connector (9), the connector being used to combine the compressed heated hydrogen BOG stream (80) with the hydrogen feed stream (10), The first refrigerant (30, 40, 50) is in a closed refrigerant circuit including the external heat exchanger (3), the compressor (4) and the liquefaction unit (2).

16. The apparatus of claim 15, further comprising a second storage tank (8) for temporarily storing the liquefied hydrogen (20) obtained in the liquefaction unit (2), wherein one or more first storage tanks (6) are capable of being filled with liquid hydrogen from the second storage tank (8).

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