Proces and apparatus for recovering liquid hydrogen boiloff gas

Abstract

Processes and apparatus are provided for reducing and / or re-liquefying hydrogen boiloff from a liquid hydrogen product being stored and / or transported using a liquid hydrogen refrigerant having a higher carbon intensity to provide refrigeration duty to condense the boiloff gas and / or an onboard liquefier in which a single compression system is used for both the re-liquefication cycle and the refrigeration cycle.

Description

PROCES AND APPARATUS FOR RECOVERING LIQUID HYDROGEN BOILOFF GASCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] None.BACKGROUND OF THE INVENTION

[0002] As the hydrogen economy develops, large-scale storage and transport of liquid hydrogen will be required. Large liquid hydrogen storage and transport facilities, such as liquid hydrogen ships, are in the early stages of development. Liquid hydrogen product is valuable but is at very low temperature (20 K) and difficult and costly to reliquefy. "Green" hydrogen is particularly valuable due to its very low carbon intensity.

[0003] During shipping, heat leaks into the storage containers and some of the liquid hydrogen cargo is boiled off. This boiloff vapour can be vented (flared or combusted in a gas combustion unit), used as fuel, or reliquefied and returned to the storage containers.

[0004] Venting / flaring is undesirable as valuable product is lost. Fuel demand may not balance the boiloff rate and onboard reliquefication is inconvenient and costly because it requires additional machinery and consumes a significant amount of power.

[0005] The boiloff rate can be minimized by cooling the insulation of the storage containers to reduce heat leak, for example by warming the boiloff vapour itself, or vaporizing an external fluid, such as liquefied natural gas (LNG) used for fuel, or liquid nitrogen which is then vented.

[0006] The carbon intensity of liquid hydrogen may be different depending on the source and time of production. For example, "grey" hydrogen has a higher carbon intensity than "blue" hydrogen which in turn has a higher carbon intensity than green hydrogen. The carbon intensity of the final product will also be affected by power and / or fuel consumption of the liquefaction and transportation processes. For example, a liquid hydrogen transport ship may be fueled by oil, LNG or hydrogen, or the hydrogen may be liquefied with renewable electricity or electricity with a higher carbon intensity, for example from a national grid system or onboard power plant.

[0007] Depending on the regulations in particular geographies, liquid hydrogen product attracts financial incentives depending on its carbon intensity. It is therefore desirable to maximise the production of liquid hydrogen at the lowest carbon intensity, and to minimize boil-off losses during transport and storage. In many cases, some low level of carbon08430 wo emissions is permissible from the storage and transportation process, so that motive power and reliquefaction may produce some carbon emissions.

[0008] Direct mixing of liquid hydrogen from different sources, e.g., grey and green hydrogen, is not usually permitted to reach a carbon intensity target, but the Inventors have realized that using liquid hydrogen with a higher carbon intensity than the main liquid hydrogen product as a carrier of refrigeration and a supplementary fuel for transport or power production may be acceptable provided that its contribution to the carbon intensity of the final product is within allowed limits.

[0009] Power for onboard reliquefaction must be supplied from the ship’s power plant, which normally uses the same fuel as the propulsion engines with the associated carbon intensity, and would often contribute more to the carbon intensity than land-based liquefaction.

[0010] If a cryogenic liquid fuel is used, e.g., LNG or liquid hydrogen, the vaporization of that fuel may be used to reduce the power needed for reliquefaction by providing cooling in the reliquefier or by reducing boiloff by intercepting heat leak to the primary insulated storage container(s).

[0011] There are several patent applications that use liquid nitrogen (LIN), liquid oxygen (LOX) or LNG to minimize heat leak to liquid hydrogen tanks on ships, either for precooling a hydrogen reliquefier, cooling insulation around the liquid hydrogen tank or both. Examples of such patent applications include KR20230040142, KR102496987, KR102461340, CN217382515 and CN 114396563.

[0012] In a paper by Kim et al entitled "Hydrogen re-liquefaction process for boil-off gas handling on a large scale liquid hydrogen carrier1' (17thCryogenics 2023, HR Conference, Dresden, Germany, April 24-28, 2023), there is a described a system where hydrogen boiloff gas and expanded hydrogen gas are in two separate circuits and two separate multistage compressors are used, one for each circuit. It is mentioned that the use of hydrogen as a refrigerant enables the boiloff gas handling system (BHS) to conduct refrigerant makeup using boiloff gas.

[0013] There is a need for a more compact, flexible, and low-cost system to reduce boiloff losses of a liquid hydrogen product, ideally to zero.SUMMARY OF THE INVENTION

[0014] According to a first aspect of the present invention, there is provided a process for reducing and / or condensing boiloff during storage and / or transportation of a liquid hydrogen08430 wo product, said process comprising storing and / or transporting a liquid hydrogen product in a primary insulated storage container, the liquid hydrogen product having a first carbon intensity; storing a liquid hydrogen refrigerant in a secondary insulated storage container, said liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity; removing liquid hydrogen refrigerant from the secondary insulated storage container and, optionally after pressure reduction to control the flow by equalizing liquid / vapour pressure changes due to liquid head and vapour pressure drop, vaporizing the removed liquid hydrogen refrigerant by heat exchange against the liquid hydrogen product and / or against hydrogen boiloff gas produced therefrom to generate vaporised liquid hydrogen refrigerant, together with subcooled liquid hydrogen product and / or condensed hydrogen boiloff gas respectively; and where produced, returning the condensed hydrogen boiloff gas to the liquid hydrogen product in the primary insulated storage container. A part of the vaporised liquid hydrogen refrigerant is typically returned to the secondary insulated storage container in order to maintain the pressure therein.

[0015] This aspect of the invention enables a reduction in at least one, and typically all, of overall capital cost, power consumption and footprint, while optimizing the overall carbon intensity of the process. A reduction in carbon intensity typically comes from reliquefying the boiloff gas from liquid hydrogen product having a lower carbon intensity, e.g., green liquid hydrogen, using the refrigeration contained in the vaporizing liquid hydrogen refrigerant having a higher carbon intensity, e.g., blue liquid hydrogen or grey liquid hydrogen, which may then be used elsewhere, e.g., as fuel. This option is therefore particularly useful where the liquid hydrogen product is being transported by a ship driven by one or more engines that are at least partially or entirely fueled with hydrogen.

[0016] According to a second aspect of the present invention, there is provided a process for liquefying hydrogen boiloff gas during storage and / or transportation of liquid hydrogen product, said process comprising storing and / or transporting liquid hydrogen product in a primary insulated storage container; warming hydrogen boiloff gas removed from the primary insulated storage container to produce warmed hydrogen gas; compressing the warmed hydrogen gas, optionally combined with a warmed hydrogen recycle gas, in a hydrogen gas compressor to produce compressed hydrogen gas at a supercritical pressure; cooling the compressed hydrogen gas by heat exchange to produce cooled compressed hydrogen gas; and further cooling at least a first portion of the cooled compressed hydrogen gas by heat exchange to a critical temperature, i.e., a temperature at or below the critical temperature, to produce liquid hydrogen which is returned to the liquid hydrogen product in the primary insulated storage container after any necessary pressure adjustment, e.g., reduction, wherein the warming of08430 wo the hydrogen boiloff gas is achieved by heat exchange against the compressed hydrogen gas, thereby providing a first part of the refrigeration duty for cooling the compressed hydrogen gas to produce the liquid hydrogen being returned to the liquid hydrogen product in the primary insulated storage container.

[0017] A second portion of the cooled compressed hydrogen gas is typically expanded to produce expanded hydrogen gas which may be used to provide refrigeration for the process. The expanded hydrogen gas is typically warmed by heat exchange against the compressed hydrogen gas to produce the warmed hydrogen recycle gas for combining with the warmed hydrogen gas, thereby providing a second part of the refrigeration duty for cooling the compressed hydrogen gas to produce the liquid hydrogen being returned to the liquid hydrogen product in the primary insulated storage container.

[0018] Where the liquefier is provided onboard a ship, the process is a suitable solution in cases where the ship is not configured to operate with hydrogen as one of the fuels. The process enables recovery of a stream of high value hydrogen at the cost of capital and footprint on the ship.

[0019] Hybrid options combining the first and second aspects are also provided. Thus, in a process according to the second aspect, where the liquid hydrogen product being stored and / or transported has a first carbon intensity, the process may comprise storing a liquid hydrogen refrigerant in a secondary insulated storage container, said liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity; removing the liquid hydrogen refrigerant from the secondary insulated storage container and vaporizing the removed liquid hydrogen refrigerant by heat exchange against the liquid hydrogen product and / or against hydrogen boiloff gas produced therefrom to generate vaporised liquid hydrogen refrigerant, together with subcooled liquid hydrogen product and / or condensed hydrogen boiloff gas respectively; and where produced, returning the condensed hydrogen boiloff gas to the liquid hydrogen product in the primary insulated storage container. A part of the vaporised liquid hydrogen refrigerant is typically returned to the secondary insulated storage container in order to maintain the pressure therein.

[0020] In addition, there is provided a process for condensing boiloff during storage and / or transportation of liquid hydrogen product, said process comprising storing and / or transporting liquid hydrogen product in a primary insulated storage container, said liquid hydrogen product having a first carbon intensity; storing a liquid hydrogen refrigerant in a secondary insulated storage container, said liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity; removing liquid hydrogen refrigerant from the secondary08430 wo insulated storage container and vaporizing the removed liquid hydrogen refrigerant by heat exchange against hydrogen boiloff gas produced from the liquid hydrogen product in the primary insulated storage vessel to generate vaporised liquid hydrogen refrigerant and condensed hydrogen boiloff gas; returning the condensed hydrogen boiloff gas to the liquid hydrogen product in the primary insulated storage container; warming at least a (first) part of the vaporised liquid hydrogen refrigerant to produce warmed hydrogen gas; compressing the warmed hydrogen gas, optionally combined with a warmed hydrogen recycle gas, in a hydrogen gas compressor to produce compressed hydrogen gas at a supercritical pressure; cooling the compressed hydrogen gas by heat exchange to produce cooled compressed hydrogen gas; and further cooling at least a (first) portion of the cooled compressed hydrogen gas by heat exchange to a critical temperature to produce liquid hydrogen which is returned to the liquid hydrogen refrigerant in the secondary insulated storage container after any necessary pressure adjustment, e.g., reduction, wherein the warming of the vaporised liquid hydrogen refrigerant is achieved by heat exchange against the compressed hydrogen gas, thereby providing a first part of the refrigeration duty for cooling the compressed hydrogen gas to produce the liquid hydrogen being returned to liquid hydrogen refrigerant in the secondary insulated storage container.

[0021] A second part of the vaporised liquid hydrogen refrigerant may be returned to the secondary insulated storage container in order to maintain the pressure therein. Additionally or alternatively, a portion of the cooled compressed hydrogen gas may be expanded to produce expanded hydrogen gas which may be used to provide refrigeration for the process. The expanded hydrogen gas may be warmed by heat exchange against the compressed hydrogen gas to produce the warmed hydrogen recycle gas, thereby providing a second part of the refrigeration duty for cooling the compressed hydrogen gas to produce the liquid hydrogen being returned to liquid hydrogen refrigerant in the secondary insulated storage container.

[0022] The hybrid option is a suitable choice when some hydrogen is required for supplementing the primary fuel on a ship although the hydrogen fuel demand is such that the process according to the first aspect of the invention would not liquefy all of the boiloff gas produced. The selection across these options would be made on a case-by-case basis, taking into account various factors including the type of liquid hydrogen being shipped, the amount of boiloff gas as a result of heat leak (which depending on length / time of travel), the desired product carbon intensity, and space available on the ship.

[0023] According to a third aspect of the present invention, there is provided a storage and / or transportation installation for a liquid hydrogen product, said installation comprising a primary08430 wo insulated storage container for storing and / or transporting, e.g., containing, a liquid hydrogen product having a first carbon intensity; a secondary insulated storage container for storing and / or transporting, e.g., containing, a liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity, said secondary insulated storage container comprising an outlet for liquid hydrogen refrigerant in fluid flow communication with an inlet for vaporised liquid hydrogen refrigerant; and a heat exchange system located between the outlet and the inlet of the secondary insulated storage container and arranged to vaporize liquid hydrogen refrigerant from the secondary insulated storage container by heat exchange against liquid hydrogen product and / or hydrogen boiloff gas in the primary insulated storage container. The installation usually comprises an outlet for removing vaporized liquid hydrogen refrigerant for use, e.g., as fuel.

[0024] According to a fourth aspect of the present invention, there is provided a liquefier for liquefying hydrogen boiloff gas during storage and / or transportation of liquid hydrogen product, said liquefier comprising a primary insulated storage container for storing and / or transporting a liquid hydrogen product comprising an outlet for hydrogen boiloff gas and an inlet for liquid hydrogen; a compression system comprising a first inlet for warmed hydrogen gas in fluid flow communication with the outlet of the primary insulated storage container, and a first outlet for compressed hydrogen gas at supercritical pressure; a pressure reduction valve having an inlet for cooled compressed hydrogen at supercritical pressure and at a critical temperature in fluid flow communication with the outlet of the compression system, and an outlet for liquid hydrogen in fluid flow communication with the inlet of the primary insulated storage container; and a heat exchange system located between the outlet for hydrogen boiloff gas of the primary insulated storage container and the inlet of the compression system and between the outlet of the compression system and the inlet of the pressure reduction valve, and arranged to cool compressed hydrogen gas at supercritical pressure to a critical temperature by heat exchange with hydrogen boiloff gas.

[0025] Hybrid options combining the third and fourth aspects are also provided. Thus, in a process according to the fourth aspect, wherein the liquid hydrogen product has a first carbon intensity, said liquefier comprising a secondary insulated storage container for storing and / or transporting a liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity, said secondary insulated storage container comprising an outlet for liquid hydrogen refrigerant in fluid flow communication with an inlet for vaporised liquid hydrogen refrigerant; wherein the heat exchange system is also arranged to vaporize liquid hydrogen refrigerant from the secondary insulated storage container by heat exchange against hydrogen boiloff gas from the primary insulated storage container.08430 wo

[0026] In addition, there is also provided a storage and / or transportation installation for a liquid hydrogen product, said installation comprising a primary insulated storage container for storing and / or transporting a liquid hydrogen product having a first carbon intensity; a secondary insulated storage container for storing and / or transporting a liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity, said secondary insulated storage container comprising an outlet for liquid hydrogen refrigerant in fluid flow communication with an inlet for vaporised liquid hydrogen refrigerant, and an inlet for reliquefied liquid hydrogen refrigerant; a compression system comprising a first inlet for warmed hydrogen gas in fluid flow communication with the outlet of the secondary insulated storage container, and a first outlet for compressed hydrogen gas at supercritical pressure; a pressure reduction valve having an inlet for cooled compressed hydrogen at supercritical pressure and at a critical temperature in fluid flow communication with the outlet of the compression system, and an outlet for reliquefied hydrogen refrigerant in fluid flow communication with the inlet for reliquefied hydrogen refrigerant of the secondary insulated storage container; and a first heat exchange system located between the outlet and the inlet of the secondary insulated storage container and arranged to vaporize liquid hydrogen refrigerant from the secondary insulated storage container by heat exchange against liquid hydrogen product and / or hydrogen boiloff gas in the primary insulated storage container; and a second heat exchange system located between the outlet of the secondary insulated storage container and the inlet of the compression system and between the outlet of the compression system and the inlet of the pressure reduction valve, and arranged to cool compressed hydrogen gas at supercritical pressure to a critical temperature by heat exchange with vaporized liquid hydrogen refrigerant.

[0027] The storage and / or transportation installation (or the liquefier) are typically located onboard a ship.BRIEF DESCRIPTION OF DRAWINGS

[0028] FIG. 1 is a simplified flowsheet of one embodiment of the first aspect of the present invention in which grey liquid hydrogen refrigerant is used to condense boiloff gas generated from green liquid hydrogen product being transported on a ship.

[0029] FIG. 2 is a simplified flowsheet of an alternative embodiment of the first aspect of the present invention in which a portion of the vaporised liquid hydrogen refrigerant is compressed prior to being reliquefied or used as fuel.08430 wo

[0030] FIG. 3 is a simplified flowsheet of another embodiment of the first aspect of the present invention in which grey liquid hydrogen refrigerant is used to condense boiloff gas generated from green liquid hydrogen product being transported on a ship and vaporised liquid hydrogen refrigerant is used in a vapour-cooled insulation shield surrounding a primary insulated storage container to help cool the green liquid hydrogen product therein.

[0031] FIG. 4 is a simplified flowsheet of one embodiment of the second aspect of the present invention in which hydrogen boiloff gas generated from the liquid hydrogen product in the primary insulated storage container is reliquefied by heat exchange against expanded hydrogen gas derived from hydrogen boiloff gas and returned to the liquid hydrogen in the primary storage container.

[0032] FIG. 5 is a simplified flowsheet of a hybrid process combining elements from the embodiments depicted in FIGS. 1 and 4.

[0033] FIG. 6 is a simplified flowsheet of another hybrid process combining elements from the embodiments depicted in FIGS. 2 and 4.DETAILED DESCRIPTION OF THE INVENTION

[0034] Throughout the specification, any references to pressure are references to absolute pressure unless otherwise stated. In addition, all percentages are calculated on the basis of molarity, i.e., mol. %, unless otherwise stated or obvious from the context.

[0035] The expression "refrigeration duty" is intended to refer to the cooling duty provided by the transfer of latent heat and / or sensible heat between fluids at different temperatures.

[0036] The term "carbon intensity" in the context of the present invention refers to the equivalent amount of carbon dioxide emitted in the generation of the power used in operating a particular process and / or in generating a particular product, e.g., the liquid hydrogen being stored and / or transported and the liquid hydrogen being used as refrigerant. Carbon intensity may be calculated in terms of the number of kilograms carbon dioxide equivalent per MegaJoule of energy (kgCO2e / MJ) or per kilogram hydrogen (kgCO2e / kgH2) as appropriate.

[0037] Depending on how it is calculated, the carbon intensity of hydrogen may be negative, for example where the hydrogen is produced from biofuel with carbon capture. For the purpose of this disclosure, however, no credit is taken for fuels with negative carbon intensities (e.g., biomass, where the contained carbon has been "pre-captured" from the atmosphere or biomethane or coal bed methane that would otherwise be emitted to the atmosphere so are sometimes given credit for the CO2 equivalent of the avoided methane emissions).08430 wo

[0038] The term "green hydrogen" refers to hydrogen generated by electrolysis of water using renewable power. The term "green liquid hydrogen" will be interpreted accordingly.

[0039] The term "grey hydrogen" refers to hydrogen generated by reforming natural gas without the capture of carbon dioxide. The term "grey liquid hydrogen" will be interpreted accordingly.

[0040] The term "blue hydrogen" refers to hydrogen generated in the same way as grey hydrogen but with capture of carbon dioxide. The term "blue liquid hydrogen" will be interpreted accordingly.

[0041] The terms "brown hydrogen" and "black hydrogen" refer to hydrogen generated by the gasification of brown coal and black coal respectively without the capture of carbon dioxide. This hydrogen may be referred to as blue hydrogen if the carbon dioxide is captured. The terms "brown liquid hydrogen" and "black liquid hydrogen" will be interpreted accordingly.

[0042] The relative carbon intensities of the different hydrogens are generally as follows:Green hydrogen « Blue hydrogen < Grey hydrogen < Brown hydrogen » Black hydrogen

[0043] The term "supercritical pressure" refers to a pressure above the critical pressure of a gas, which is the pressure below which it is not possible to condense the gas at a critical temperature. For hydrogen, the critical pressure is about 13 bar. By way of example, hydrogen gas at a pressure in a range from about 20 bar to 70 bar would be considered to be at supercritical pressure.

[0044] The term "critical temperature" refers to the temperature of a gas above which the gas cannot be liquefied. The critical temperature of hydrogen gas is about 33 K. For the avoidance of doubt, the term "a critical temperature" includes sub-critical temperatures.

[0045] The expression "in fluid flow communication" will be understood to mean that piping or other suitable conduits will be used to convey fluid from one specified location to another. During passage between the two locations, the fluid may flow through one or more other units which may be designed and / or arranged to alter the physical condition, e.g., temperature (e.g., a heat exchanger) and / or pressure (e.g., a compressor, a pump, a pressure reduction valve or an expander) of the fluid, or the composition of the fluid through reaction of components within the fluid (e.g., a catalytic reactor).

[0046] The term "downstream" will be understood to mean in the direction of flow of a fluid under normal operation. The term "upstream" is to be interpreted accordingly.08430 wo

[0047] The expression "located between" in the context of a heat exchanger being located between two other apparatus units in fluid flow communication with each other will be understood to mean that the heat exchanger is provided at a position intermediate to the positions of the other apparatus units where it is able to alter the temperature of a process fluid flowing from one apparatus unit to the other by heat exchange with another fluid. For the avoidance of doubt, the fluids within the heat exchanger are not mixed and remain independent of each other.

[0048] Heat exchange systems of the present invention may comprise a plurality of heat exchangers. One or more of the heat exchangers may be individual heat exchangers such as shell-and-tube style heat exchangers. Alternatively, two or more of the heat exchangers may be adjacent passages within a single heat exchanger having multiple passages in which various process streams are cooled by heat exchange with one or more of the "cold" process streams and / or external refrigerant streams.

[0049] Refrigeration swap system

[0050] Liquid hydrogen produced with lower carbon intensity is more valuable than liquid hydrogen with higher carbon intensity, so it is especially important to reduce losses of lower carbon intensity hydrogen during transport and storage.

[0051] Boiloff re-liquefaction is power-intensive and, when re-liquefaction takes place on a ship, increases the onboard power generation demand. Onboard liquefaction may have significantly higher carbon intensity than land-based liquefaction depending on the fuel used.

[0052] Other cryogenic liquids, e.g., LNG and LIN, may be used to cool the insulation of the liquid hydrogen container and reduce boiloff, but boiloff will still occur, and must be reliquefied or otherwise consumed, for example as fuel.

[0053] Using low carbon intensity (e.g., green) liquid hydrogen boiloff as fuel consumes some of the valuable product, but avoids additional power demand. However, it is a very costly fuel and it may not enable keeping the carbon intensity within allowable limits.

[0054] If instead higher carbon intensity (e.g., blue, grey, brown or black) liquid hydrogen is used as fuel, it must be evaporated first, but lower carbon intensity boiloff can be recondensed during the evaporation. The Inventors have realized that the carbon intensity associated with the liquefaction of higher carbon intensity hydrogen can be lower than the carbon intensity of re-liquefaction using power generated with an alternative onboard fuel, for example if renewable power is used. io

[0055] In the first aspect, the present invention is a process for reducing and / or condensing boiloff during storage and / or transportation of a liquid hydrogen product. Processes according to this aspect (or indeed any other aspect of the invention) may be applied to static installations storing liquid hydrogen on land. Alternatively, the processes of any aspect may be applied to mobile installations storing liquid hydrogen during transportation, e.g., onboard a ship.

[0056] The process comprises storing and / or transporting a liquid hydrogen product having a first carbon intensity in a primary insulated storage container. The liquid hydrogen product is typically stored at a first pressure of at least about 1 bar, e.g., at least 1.05 bar or at least 1 .2 bar. The first pressure may be in a range from at least about 1 bar to about 10 bar or in a range from at least about 1 bar to about 5 bar.

[0057] A liquid hydrogen refrigerant is stored in a secondary insulated storage container, typically at a pressure of at least about 1 bar, e.g., at least 1.05 bar or at least 1.2 bar. The pressure may be in a range from at least about 1 bar to about 10 bar or in a range from at least about 1 bar to about 5 bar.

[0058] In some embodiments, the liquid hydrogen refrigerant is stored at a second pressure that is less than the first pressure of the liquid hydrogen product. In this regard, the second pressure is typically at least about 0.01 bar, e.g., from about 0.01 bar to about 2 bar or from about 0.1 bar to 1 bar, less than the first pressure. The vaporization may therefore take place below the pressure of the primary insulated storage container, followed by compression for reliquefaction and / or use as fuel.

[0059] In other embodiments, the liquid hydrogen refrigerant is stored at a second pressure that is greater than the first pressure of the liquid hydrogen product. In this regard, the second pressure may be at least 0.01 bar, e.g., from about 0.01 bar to about 10 bar or from about 0.1 bar to about 5 bar, greater than the first pressure. The vaporization may therefore take place above the pressure of the primary insulated storage container against boil-off vapour compressed for direct condensation or as part of a reliquefaction cycle.

[0060] A key feature of this aspect of the present invention is that the liquid hydrogen refrigerant has a second carbon intensity that is greater than the first carbon intensity of the liquid hydrogen product being stored and / or transported. In this regard, the second carbon intensity is typically greater than the first carbon intensity by at least about 0.4 kgCO2e / kgH2, by at least about 0.5 kgCC>2e / kgH2, by at least about 1 kgCC>2e / kgH2, by at least about 2.5 kgCC>2e / kgH2, by at least about 5 kgCC>2e / kgH2, by at least about 7.5 kgCC>2e / kgH2, by at least about 10 kgCC>2e / kgH2, by at least about 12.5 kgCC>2e / kgH2, or by at least about 1508430 wo kgCC>2e / kgH2. As would be appreciated by the skilled person, there is no absolute upper limit to the difference in the carbon intensities as the difference depends solely on the respective values of the first and second carbon intensities. However, the Inventors suggest that a practical upper limit for the difference in carbon intensities may be 50 kgCO2e / kgH2, or perhaps less, e.g., 35 kgCO2e / kgH2.

[0061] The first carbon intensity of the liquid hydrogen product is typically at least 0 kgCC>2 / kgH2, e.g., in a range from 0 kgCO2e / kgH2 to about 10 kgCO2e / kgH2, or in a range from 0 kgCC>2e / kgH2 to about 4 kgCO2e / kgH2, or in a range from 0 kgCC>2e / kgH2 to about 2.5 kgCC>2e / kgH2, or in a range from 0 kgCO2e / kgH2 to about 1.5 kgCO2e / kgH2, or in a range from about 0 kgCC>2e / kgH2 to about 0.45 kgCO2e / kgH2. In this regard, the liquid hydrogen product is typically either blue liquid hydrogen or, in preferred embodiments, green liquid hydrogen.

[0062] The second carbon intensity of the liquid hydrogen refrigerant is typically at least about 0.45 kgCC>2e / kgH2, e.g., at least about 1.5 kgCO2e / kgH2, at least about 2.5 kgCC>2e / kgH2, at least about 4 kgCO2e / kgH2, at least about 10 kgCC>2e / kgH2, or at least about 15 kgCC>2e / kgH2. In this regard, the liquid hydrogen refrigerant is typically blue liquid hydrogen or grey liquid hydrogen but may be brown liquid hydrogen or even black liquid hydrogen. As would be appreciated by the skilled person, there is no absolute upper limit to the second carbon intensity. However, the inventors suggest that a practical upper limit for the second carbon intensity may be 50 kgCO2e / kgH2, or perhaps less, e.g., 35 kgCO2e / kgH2.

[0063] Generally speaking, the primary benefit of the present invention increases as the difference in the first and second carbon intensities increases, provided the second carbon intensity does not contribute too much to the first carbon intensity to push it into a lower incentive band. Therefore, in preferred embodiments, the liquid hydrogen product has a low first carbon intensity, e.g., less than 0.45 kgCO2e / kgH2 such as 0 kgCO2e / kgH2for green hydrogen, and the liquid hydrogen refrigerant has a significantly higher second carbon intensity, e.g., at least about 10 kgCO2e / kgH2Such as about 16 kgCO2e / kgH2 for grey hydrogen liquefied with natural gas power or about 12 kgCO2e / kgH2 for grey hydrogen liquefied with renewable power.

[0064] The liquid hydrogen refrigerant is removed from the secondary insulated storage container and vaporised by heat exchange against either the liquid hydrogen product or the hydrogen boiloff gas (produced from the liquid hydrogen product) or both, to generate vaporised liquid hydrogen refrigerant.08430 wo

[0065] The volume of the extracted liquid needs to be replaced in the secondary insulated storage container in order to maintain the pressure therein. This volume is typically replaced with an equivalent volume of a gas or vapour. In this regard, a part of the vaporised liquid hydrogen refrigerant is typically fed to the secondary insulated storage container. This part of the vaporized liquid hydrogen refrigerant is typically very small as the volume of the vapour replaces the volume of the extracted liquid and the volume ratio is only about 2% at 1 bar although increases with pressure up to about 30% at 10 bar.

[0066] Vaporizing the refrigerant against the liquid hydrogen product subcools the liquid hydrogen product, thereby producing subcooled liquid hydrogen product. The rate at which boiloff gas is produced is thereby reduced or eliminated, resulting in less or no boiloff gas over a given period of time.

[0067] Vaporizing the refrigerant against hydrogen boiloff gas condenses the boiloff gas to produce reliquefied hydrogen. Where produced, the condensed (or reliquefied) hydrogen is returned to the liquid hydrogen product in the primary insulated storage container.

[0068] A first part of the vaporised liquid hydrogen refrigerant is typically returned to the secondary insulated storage container in order to maintain the pressure in the container, e.g., within an allowable range without the need for venting. A second part, e.g., the remainder, of the vaporized liquid hydrogen refrigerant may be compressed before being reliquefied or used as fuel, e.g., in a fuel cell or combustion engine, for transport, power generation, compression, liquefaction, or other purpose.

[0069] The vaporised liquid hydrogen refrigerant is still a cold vapour, e.g., at a temperature in a range from about 20 K to about 32 K. Thus, in embodiments in which the primary insulated storage container comprises a gas-cooled insulation shield, the process may further comprise passing vaporised liquid hydrogen refrigerant through the gas-cooled insulation shield of the primary insulated storage container to cool the insulation and reduce heat leak into the liquid hydrogen. Indeed, the vaporised liquid hydrogen refrigerant may be subjected to para-ortho conversion to provide further refrigeration.

[0070] The primary insulated storage container may comprise a liquid-cooled insulation shield and the process may comprise passing a second liquid refrigerant, e.g., liquid nitrogen (LIN), liquefied natural gas (LNG) or other suitable cryogenic liquid, through the liquid-cooled insulation shield of the primary insulation storage container to reduce heat leak to the liquid hydrogen product therein. In these embodiments, the second liquid refrigerant is typically stored in a further secondary insulated storage container which may comprise a gas-cooled08430 wo insulation shield. Vaporised liquid hydrogen refrigerant may be passed through the gas- cooled insulation shield of the further secondary insulated storage container to reduce heat leak into the second liquid refrigerant stored therein.

[0071] The process of the first aspect of the present invention reduces, minimizes or even eliminates material losses from a higher value liquid hydrogen product in a large primary insulated storage container that is either static or located on a means of transport, e.g. , a ship.

[0072] The cost, equipment count, and plot space requirements of a boiloff re-liquefier may therefore be avoided, but losses of the low carbon intensity product are eliminated. Onshore liquefaction of the higher carbon intensity hydrogen can use renewable power at lower carbon intensity than higher carbon intensity power generated, for example, on board a vessel. The contribution from the carbon intensity of using the higher-carbon intensity product as fuel to the carbon intensity of the low-carbon intensity product typically will therefore be minimal.

[0073] Onboard Liquefier

[0074] In a conventional hydrogen liquefier, a warm, pressurised feed of molecular hydrogen (preferably about 75% ortho-hydrogen and 25% para-hydrogen) is cooled, cleaned, and converted over a catalyst to para-hydrogen during cooling. Precooling to around 80 K is normally accomplished by evaporating LIN or in a nitrogen-based refrigeration cycle. It is also known to replace or supplement the precooling by vaporizing LNG or using a methane-based refrigeration cycle. Final cooling to liquid hydrogen temperatures typically takes place with a hydrogen expansion cycle.

[0075] Four elements of refrigeration are usually required - sensible cooling of the feed, removal of heat of reaction during ortho-para conversion, latent heat of condensation of the liquid hydrogen, and refrigeration - to overcome irreversibilities in the heat recovery system, e.g., the main heat exchangers.

[0076] Where liquid hydrogen is to be stored for an extended period, particularly for example during transport, it may be required to recondense cold para-hydrogen boiloff vapour from the tank. This recondensation does not require two of the refrigeration elements - sensible cooling or catalytic conversion of the feed. Therefore, for a particular flow of liquid hydrogen produced, the refrigeration duty and therefore power consumption of the process may be significantly reduced compared to one with a warm feed. A simplified process is required that is well-suited to installation on a ship.08430 wo

[0077] The process of the second aspect is concerned with liquefying hydrogen boiloff gas during storage and / or transportation of liquid hydrogen product, but has particular application onboard a ship. At vapour-liquid equilibrium at 1 bar and 20K, the liquid hydrogen is at least 90%, e.g., at least 95%, up to an upper limit of 99.8%, para-hydrogen. On this basis, the liquid hydrogen is generally considered to be essentially para-hydrogen.

[0078] In this process, liquid hydrogen product is stored and / or transported in a primary insulated storage container. The liquid hydrogen product in the primary insulated storage container is typically at a pressure of at least about 1 bar, e.g., in a range from about 1 bar to about 10 bar or in a range from about 1 bar to about 5 bar.

[0079] Hydrogen boiloff gas (which is typically essentially para-hydrogen) removed from the primary insulated storage container and used to provide refrigeration duty by heat exchange, thereby becoming warmed to produce warmed hydrogen gas. The hydrogen boiloff gas typically includes flash vapour generated as a result of the reduction in pressure of liquid hydrogen being returned to the primary insulated storage container.

[0080] Warmed hydrogen gas is compressed, together with a warmed hydrogen recycle gas, in a hydrogen gas compressor to produce compressed hydrogen gas at a supercritical pressure, e.g., at a pressure in a range from about 20 bar to about 70 bar or in a range from about 30 bar to about 50 bar, e.g., at a pressure of about 40 bar.

[0081] The hydrogen gas compressor may be a single stage compressor but is typically a combined compressor comprising two or more process sections, each of which contains one or more stages. Each section could be a separate compressor or they could be combined into a single machine, or multistage compressor. Flow variability may be handled using parallel compression.

[0082] In embodiments involving a combined compressor, the warmed hydrogen gas is typically compressed in at least the first section of the compressor to produce intermediate compressed hydrogen gas which may be at a pressure of at least about 3 bar, e.g., in a range from about 3 bar to about 12 bar.

[0083] The intermediate compressed hydrogen gas may then be combined with a warmed hydrogen recycle gas to form a combined hydrogen gas. At least a portion of the combined hydrogen gas is then typically compressed in the remaining section(s) of the combined compressor to form the compressed hydrogen gas, although some of the combined hydrogen gas may be removed at this point and used a fuel, e.g., in a fuel cell or combustion engine, for transport, power generation, compression, liquefaction, or other purpose.08430 wo

[0084] In high-pressure storage options, the warmed hydrogen recycle gas may be combined with the warmed hydrogen gas at the feed end of the combined compressor rather than at an intermediate point in the compression system.

[0085] The compressed hydrogen gas is typically passed through an oil adsorption unit comprising carbon beds to remove any oil entrained within the gas to very low levels following passage through the oil removal separators of the combined compressor.

[0086] The compressed hydrogen gas is cooled by heat exchange to produce cooled compressed hydrogen gas which may be divided into two portions.

[0087] The cooled compressed hydrogen gas (or at least a first portion thereof) is further cooled by heat exchange to below the critical temperature by heat exchange to produce condensed (or liquid) hydrogen which is returned to the primary insulated storage container as liquid hydrogen product after any necessary pressure adjustment, e.g., reduction.

[0088] If the cooled compressed hydrogen gas is divided, then a second portion of the cooled compressed hydrogen gas may be expanded to produce expanded hydrogen gas. The expanded hydrogen gas is typically at a pressure of at least about 2 bar, e.g., in a range from about 2 bar to about 12 bar.

[0089] The first portion of the cooled compressed hydrogen gas may be from about 30 % (for full liquefaction) to about 100 % (in the limit if no expanders and full secondary liquid injection) of the total mass flow of cooled compressed hydrogen gas with the second portion being typically formed from the remainder, if any.

[0090] Prior to being further cooled, compressed hydrogen gas that has been cooled may be passed through an adsorption unit to remove any impurities that may inadvertently have been entrained in the gas from the process to this point. The purified gas would then be divided into the two portions.

[0091] Warming of the hydrogen boiloff gas is achieved by heat exchange against the compressed hydrogen gas, thereby providing a first part of the refrigeration duty for cooling the compressed hydrogen gas to produce the liquid hydrogen being returned to the liquid hydrogen product in the primary insulated storage container. The first part may be about 25% to 35%, e.g., 30% (or about 30% to 40%, e.g., about 35%, including flash gas) of the refrigeration duty required for cooling the compressed hydrogen gas.

[0092] The expanded hydrogen gas is typically warmed by heat exchange against the compressed hydrogen gas to produce the warmed hydrogen recycle gas, thereby providing asecond part of the refrigeration duty for cooling the compressed hydrogen gas to produce the liquid hydrogen being returned to the liquid hydrogen product in the primary insulated storage container. The second part may be about 60% to about 70%, e.g., about 65%, of the refrigeration duty required for cooling and condensing the compressed hydrogen gas.

[0093] The second portion of the cooled compressed hydrogen gas may be expanded in a single expander. However, in preferred embodiments, the gas is expanded in at least two, e.g., three, expanders in series. In these embodiments, the intermediate expanded gas from one expander may be cooled by heat exchange against hydrogen boiloff gas and / or expanded hydrogen gas before being fed to the next expander in the series. A portion of an intermediate expanded gas may be removed and used as fuel, e.g., in a fuel cell or combustion engine, for transport, power generation, compression, liquefaction, or other purpose. In other embodiments, there may be two or more expanders in parallel.

[0094] The hydrogen boiloff gas may include flash vapour generated as a result of the reduction in pressure of the liquid hydrogen being returned to the primary insulated storage container.

[0095] The process of the second aspect of the invention uses the hydrogen boiloff vapour as refrigerant, and therefore only needs a single hydrogen compression system for boiloff compression and refrigeration. No warm refrigerant cycle is required. The process may also provide a warm, pressurised hydrogen stream to be used as fuel.

[0096] Cooling above 80 K may be provided by the hydrogen refrigeration cycle, and / or by vaporization of a supplementary stored liquid refrigerant, in liquid nitrogen (LIN) or liquefied natural gas (LNG) which may be the primary fuel for the ship. Refrigerant from the main hydrogen cycle, or the supplementary refrigerant, may also be used to cool the insulation of the primary insulated storage container to reduce the liquid hydrogen boiloff.

[0097] The process is able to reliquefy hydrogen with a specific power of about 4.5 kWh / kg, compared to around 12 kWh / kg for a warm hydrogen liquefier ( / .e., one with a feed around ambient temperature). In this solution, various improvements are possible to ensure that the on-board liquefier is suitable for floating service, for instance, plot space comes at a premium on shipboard, hence some equipment may be stacked vertically, all compression equipment may be co-located, and flammable chemicals may be avoided as refrigerant selection.

[0098] Hybrid options08430 wo

[0099] The processes of the first and second aspects may also be combined into a hybrid process. For example, liquid hydrogen refrigerant having a higher carbon intensity may be used to provide refrigeration duty in the re- liquefaction cycle of the hydrogen boiloff gas.

[0100] In these embodiments of the process of the second aspect, the liquid hydrogen product being stored and / or transported has a first carbon intensity and the process comprises storing a liquid hydrogen refrigerant having a second carbon intensity that is higher than the first carbon intensity in a secondary insulated storage container. Liquid hydrogen refrigerant is removed from the secondary insulated storage container and vaporized by heat exchange against either the liquid hydrogen product or hydrogen boiloff gas produced therefrom or both, to generate vaporised liquid hydrogen refrigerant, together with subcooled liquid hydrogen product and / or condensed hydrogen boiloff gas respectively. Where produced, condensed hydrogen boiloff gas is returned to the liquid hydrogen product in the primary insulated storage container. A first part, e.g., 2% for low pressure storage up to 30% for 10 bar storage, of the vaporised liquid hydrogen refrigerant is typically returned to the secondary insulated storage container in order to maintain the pressure therein.

[0101] The proportion of the total refrigeration duty provided by the liquid hydrogen refrigerant depends on the design ratio of the refrigerant consumption to reliquefaction rate but may be in the range from about 30% to about 40%.

[0102] The hybrid option may further comprise any of the optional or preferred features described above in respect of the second aspect of the process of the present invention.

[0103] In a different hybrid option, the vaporised liquid hydrogen refrigerant is reliquefied using the process of the second aspect.

[0104] In this process, a liquid hydrogen product having a first carbon intensity is stored and / or transported in a primary insulated storage container, and a liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity is stored in a secondary insulated storage container.

[0105] Liquid hydrogen refrigerant is removed from the secondary insulated storage container and vaporized by heat exchange against hydrogen boiloff gas produced from the liquid hydrogen product in the primary insulated storage vessel to generate vaporised liquid hydrogen refrigerant and condensed hydrogen boiloff gas which is returned to the liquid hydrogen product in the primary insulated storage container.08430 wo

[0106] At least part of the vaporized liquid hydrogen refrigerant is warmed to produce warmed hydrogen gas. The warmed hydrogen gas is compressed in combination with a warmed hydrogen recycle gas in a hydrogen gas compressor to produce compressed hydrogen gas which is then cooled by heat exchange to produce cooled compressed hydrogen gas.

[0107] At least a portion of the cooled compressed hydrogen gas is further cooled by heat exchange to a critical temperature to produce liquid hydrogen which is returned to the liquid hydrogen refrigerant in the secondary insulated storage container after any necessary pressure adjustment, e.g., reduction.

[0108] The warming of the vaporised liquid hydrogen refrigerant is achieved by heat exchange against the compressed hydrogen gas, thereby providing a first part of the refrigeration duty for cooling the compressed hydrogen gas to produce the liquid hydrogen refrigerant being returned to the second insulated storage container.

[0109] A second portion of the cooled compressed hydrogen gas is typically expanded to produce expanded hydrogen gas. Expanded hydrogen gas may be warmed by heat exchange against the compressed hydrogen gas to produce the warmed hydrogen recycle gas, thereby providing a second part of the refrigeration duty for cooling the compressed hydrogen gas to produce the liquid hydrogen refrigerant being returned to the second insulated storage container.

[0110] The hybrid option may further comprise any of the optional or preferred features described above in respect of the first or second aspects of the process of the present invention.

[0111] At least part, optionally all, of the balance of the refrigeration duty for cooling the compressed hydrogen gas in any of the processes is typically provided by a second liquid refrigerant, e.g., LIN or LNG or another suitable cryogenic liquid.

[0112] Thus, in summary, the refrigerant swap system is a low capital expense and plot space option if the ship uses hydrogen as one of the fuels. If the ship is not fueled at least partly by hydrogen, then the on-board liquefier is needed to liquefy boiloff gas but leads to more equipment and higher overall cost. The hybrid option allows optimization of cost but again, the ship would need to be fueled at least partly by hydrogen.

[0113] The invention will now be described by way of example only with reference to the figures.08430 wo

[0114] In FIGS. 1 and 2, a primary insulated storage container 10 located onboard a ship 14 contains liquid hydrogen product 15 (typically over 95% para-hydrogen) having a carbon intensity of about 0 kgCCh / kgbk (when loaded onto the ship). The liquid hydrogen product has been produced by electrolysis of water and liquefaction using renewable energy and hence may be described as green liquid hydrogen.

[0115] A secondary insulated storage container 20 contains liquid hydrogen refrigerant 25 having a carbon intensity of about 16 kgCO2 / kgH2. The liquid hydrogen refrigerant has been produced by reforming natural gas without carbon capture and liquefied using power generated by natural gas and hence is grey liquid hydrogen.

[0116] Heat leaks through the walls of container 10 over time resulting in generation of hydrogen boiloff gas from the liquid hydrogen product contained therein. Liquid hydrogen refrigerant passes through lines 200 and 205 to heat exchanger 40. The flow of liquid refrigerant from the insulated storage container 20 to the heat exchanger 40 is controlled by valve 30 in response to a signal from pressure indicating control (PIC) sensor 35 located within the vapour space of the insulated storage container 10.

[0117] Hydrogen boiloff gas is condensed by heat exchange with the liquid hydrogen refrigerant in the heat exchanger 40, generating vaporised hydrogen refrigerant. The condensed boiloff gas is returned to the liquid hydrogen product in the container 10 and the vaporised hydrogen refrigerant is removed in line 210 and divided into two parts. A first part is returned to the secondary insulated storage container 20 through line 215 to maintain the pressure in the storage container 20, and the remaining is removed in lines 220 and 225 and used as a fuel (not shown). The flow of the remaining part is controlled by valve 50 in response to a signal from PIC sensor 55 located on line 215 (or in the vapour space of tank 20).

[0118] The vaporised hydrogen refrigerant in line 225 may be further processed, for example by warming (not shown) and / or compression (see compressor 60 and aftercooler 65 in FIG. 2) to produce compressed hydrogen gas in line 230.

[0119] FIG. 3 depicts a modified version of the embodiment depicted in FIG. 2 in which the amount of boiloff gas generated from the liquid hydrogen in the primary insulated storage vessel is reduced using refrigeration provided by the vaporised hydrogen refrigerant. The common features in FIGS. 2 and 3 have been given the same reference numerals. The following is a discussion of the distinguishing features in FIG. 3.

[0120] The primary insulated storage container 10 has a gas-cooled insulation shield 11 and an outer envelope 12. Vaporised hydrogen refrigerant is fed via line 225 to the shield 11. The08430 wo cold gas circulates around the shield, cooling the insulation and reducing heat leak into the liquid hydrogen product within the storage container 10. The amount of boiloff gas generated is thereby reduced. The vaporised refrigerant is removed from the shield 11 in line 227, compressed in compressor 60 and the compressed gas is then cooled in aftercooler 65 before being used as fuel (not shown) from line 230.

[0121] In FIG. 4, hydrogen boiloff gas (containing flash vapour) is removed in line 122 from the primary insulated storage container 10, warmed by heat exchange in a "cold" main heat exchanger 4 and transferred in line 128 to a "warm" main heat exchanger where it is further warmed by heat exchange to produce warmed hydrogen gas in line 129. The warmed hydrogen gas is compressed in a first section 17 of a combined compressor 17, 21 to an intermediate pressure, e.g., about 4 bar. The intermediate compressed hydrogen gas in line 130 is cooled in an aftercooler 18 and the cooled gas in line 131 is combined with warmed hydrogen recycle gas in line 142. At least a portion of the combined hydrogen gas is then fed in line 143 to a second section 21 of the combined compressor 17, 21 where it is compressed to form compressed hydrogen gas in line 144 at a supercritical pressure, e.g., about 30 bar, and cooled in aftercooler 22.

[0122] The combined compressor has process sections 17, 21 , each of which could contain several stages. Each section could be a separate compressor, or they could be combined into a single machine. Parallel compression is also an option to handle flow variability.

[0123] A portion of the combined hydrogen gas may be removed in line 135 and used as fuel, e.g., to help power the engines (not shown) of ship 14 or to generate power in a fuel cell (not shown).

[0124] The compressed hydrogen gas is fed in line 145 to the warm main heat exchanger 1 where it is cooled by heat exchange to produce cooled compressed hydrogen gas which is passed through a guard adsorber 23 to remove any impurities that may be inadvertently introduced into the system.

[0125] The cooled compressed hydrogen gas in line 147 is then cooled in the cold main heat exchanger 4 and divided into two portions. The first portion is further cooled to a critical temperature by heat exchange. The hydrogen in line 154 is reduced in pressure in valve 27 to produce liquid hydrogen before being fed back to the primary insulated storage container 10.

[0126] The second portion is fed in line 148 to a first hydrogen expander 24 where it is expanded. The discharge from the first expander 24 is fed in line 149 back to the cold main08430 wo heat exchanger where it is cooled before being fed in line 150 to a second hydrogen expander 26 where it is expanded further. The discharge from the second expander 26 is fed in line 151 back to the cold main heat exchanger 4 where it is further cooled before being fed in line 152 to a third hydrogen expander 28 where it is expanded even further.

[0127] The discharge from the third expander 28 is fed in line 153 back to the cold main heat exchanger 4 wherein it provides refrigeration duty for cooling and condensing the compressed hydrogen gas. Intermediate warmed hydrogen gas is then fed in line 141 to the warm main heat exchanger 1 where it provides further refrigeration duty for cooling the compressed hydrogen gas. The resultant warmed hydrogen recycle gas in line 142 is then combined with the intermediate compressed hydrogen gas in line 131 as described above.

[0128] The balance of the refrigeration duty required for cooling the compressed hydrogen gas is provided by a second (or supplemental) liquid refrigerant, in this case LIN provided in line 210 from a secondary insulated storage container (not shown). The LIN is reduced in pressure in valve 42 and fed in line 214 to a separator 41. Nitrogen vapour from the separator 41 is fed in line 218 to the warm main heat exchanger 1. Additionally, LIN from the separator 41 is fed in lines 215 and 217 to the warm main heat exchanger 1. The nitrogen refrigerant helps cool the compressed hydrogen gas by heat exchange and the resultant warmed nitrogen vapour is then removed from the warm main heat exchanger 1 in line 219.

[0129] It should be noted that the required flow of the supplementary refrigerant is much less than that for a warm hydrogen liquefier, and it may be totally eliminated.

[0130] In addition, it should be noted that the cooling between expanders is optional. Indeed, the number of expanders and cooling therebetween may be optimized in a particular case according to the availability of supplementary refrigerant and the value of power saving relative to capital cost. In this regard, more expanders with more cooling leads to lower power but at increased capital cost.

[0131] In other embodiments, the fuel stream may be divided from the discharge from expander 28 in line 153 and warmed in the main heat exchangers 4, 1 separately from the recycle gas in lines 141 , 142. In addition, the expander discharge may undergo catalytic paraortho conversion to help supplement refrigeration.

[0132] FIG. 5 depicts a modified version of the embodiment depicted in FIG. 4 in which liquid hydrogen having a greater carbon intensity than the liquid hydrogen product being stored and / or transported is used to provide refrigeration duty. The common features in FIGS. 4 and5 have been given the same reference numerals. The following is a discussion of the distinguishing features in FIG. 5.

[0133] A secondary insulated storage container 52 contains grey liquid hydrogen refrigerant having a carbon intensity of about 16 kgCCh / kgbk which is greater than the carbon intensity (about 0 kgCCh / kgbh) of the green liquid hydrogen product in the primary insulated storage container 10. The liquid hydrogen refrigerant is stored at pressure, e.g., from about 5 bar to about 10 bar.

[0134] Liquid hydrogen refrigerant in line 300 is reduced in pressure in valve 44 (to offset liquid head) and then fed in line 302 to the cold main heat exchanger 4 where it is used to help cool and condense compressed hydrogen gas.

[0135] Vaporised refrigerant leaves the cold main heat exchanger 4 and is divided in two parts. A first part is returned in line 304 to the secondary insulated storage container 52 to maintain the pressure therein. The second part is fed in line 305 to the warm main heat exchanger 1 where it helps to cool the compressed hydrogen gas. The warmed hydrogen refrigerant is then removed from the warm main heat exchanger 1 in line 310 and used as fuel.

[0136] FIG. 6 depicts a modified version of the embodiment depicted in FIG. 2 in which the process of FIG. 4 is used to reliquefy vaporised hydrogen refrigerant after condensing hydrogen boiloff gas from the primary insulated storage container 10. The common features in FIGS. 2, 4 and 6 have been given the same reference numerals. The following is a discussion of the distinguishing features in FIG. 6.

[0137] Cooled hydrogen in line 154 is reduced in pressure in valve 27 and the reduced pressure liquid hydrogen is fed in line 155 back to the secondary insulated storage container 20.

[0138] EXAMPLES

[0139] The invention will now be illustrated by the following non-limiting examples. These examples are based on the ship design in Alkheledi et al 2022 ("A hydrogen fuelled LH2tanker ship design", Ships and Offshore Structures, 17:7, 1555-1564, DOI:10.1080 / 17445302.2021.1935626) at minimum propulsion power with voyage details from Ahn et al 2017 ("Strategy for selecting an optimal propulsion system of a liquefied hydrogen tanker", Int. J. Hydrogen Energy, 42 (8), pp. 5366-5380 DOI: 10.1016 / j.ijhydene.2017.01.037)08430 wo from the Red Sea to Rotterdam. The reliquefaction was simulated using AspenPlus (ver. 12.1).

[0140] Each of the examples is based on a ship transporting 20,000 tonnes of liquid hydrogen on a 20-day return voyage (assuming same heat leak / boiloff rate both ways). The ship is assumed to have a 27 megaWatt (MW) main engine with 50% efficiency, thus having an energy requirement of 12960 megaWatt hours (MWh) or 0.65 kiloWatt hours per kilogram (kWh / kg) of liquid hydrogen transported. Boiloff rate is assumed to be 0.1% per day, thus 400 tonnes in total over the course of the voyage. Reliquefaction is assumed to have an energy requirement of 1800 MWh or 4.5 kWh / kg of hydrogen boiloff (or 0.09 kWh / kg of liquid hydrogen transported). Thus, the total energy requirement (for shipping and onboard reliquefaction) is assumed to be 0.74 kWh / kg of liquid hydrogen transported.

[0141] Example 1

[0142] In this example, the process illustrated in the flowsheet of Fig. 4 is exemplified with an onboard reliquefier and using LNG for propulsion and to power the reliquefaction of the boiloff gas. In this example, no supplementary refrigerant 210, such as LIN, is used.

[0143] For CO2 emissions from LNG-fuelled power production of 0.5 kilograms carbon dioxide per kilowatt hour (kgCO2 / kWh), the hydrogen shipping carbon intensity is 0.37 kilograms carbon dioxide per kilogram of liquid hydrogen transported (kgCO2 / kgH2) or 0.0031 kilograms carbon dioxide per megaJoule (kgCO2 / MJ), all as direct carbon dioxide emissions from the ship.

[0144] Example 2

[0145] In this example, the process illustrated in the flowsheets of Figs. 1 and 2 is exemplified using grey hydrogen liquefied onshore with renewable power as the refrigerant to condense boiloff and then using the vaporised hydrogen as fuel with LNG providing the balance of fuel requirement.

[0146] Hydrogen fuel requirement for all the propulsion would be 800 tonnes (48.5% thermal efficiency of propulsion system), i.e., double the available boiloff, so use, e.g., 50% liquid hydrogen and 50% LNG as fuel (no onboard reliquefaction). The energy requirement for the onshore liquefaction of 400 tonnes of hydrogen fuel is 4800 MWh (at 12 kWh / kg), which is higher than onboard reliquefaction due to the warm feed onshore. For grey hydrogen with renewable liquefaction, the carbon intensity is e.g., 0.68 kgCO2 / kWh, so the carbon intensity of the combined fuel is 0.59 kgCO2 / kWh and the carbon intensity of hydrogen shipping is 0.3808430 wo kgCC>2 / kgH2 (0.0032 kgCCh / MJ). However, direct carbon dioxide emissions from the ship are only from the LNG combustion that provides half the power, i.e., 0.16 kgCO2 / kgH2.

[0147] Example 3

[0148] In this example, the process illustrated in Fig. 3 is exemplified using grey hydrogen liquefied onshore with renewable power as the refrigerant to condense boiloff, then using vaporised hydrogen to cool the insulation shields of the insulated storage container and then using the resultant warmed hydrogen gas as fuel with LNG providing the balance of fuel requirement.

[0149] A single vapour-cooled shield (VCS) reduces actual boiloff by 50%, thus in this case reducing the daily boiloff rate to 0.05% per day or 200 tonnes for the voyage. The fuel requirement is met using about 25% liquid hydrogen and about 75% LNG (no onboard reliquefaction). The energy requirement for the onshore liquefication of 200 tonnes of hydrogen fuel is 2400MWh (at 12 kWh / kg) which is higher than onboard reliquefaction of 400 tonnes due to the warm feed onshore. The carbon intensity of the combined fuel is 0.545 kgCO2 / kWh and the carbon intensity of hydrogen shipping is 0.35 kgCO2 / kgH2 (0.0029 kgCO2 / MJ). Direct carbon dioxide emissions from the ship are from the 75% of power provided by LNG, i.e., 0.24 kgCO2 / kgH2.

[0150] Example 4

[0151] In this example, the process illustrated in Fig. 5 is exemplified, where an onboard reliquefaction cycle condenses the boiloff gas with injection of grey hydrogen liquefied onshore with renewable power as the refrigerant with a flow of 50% of the boiloff, then using the resultant warmed hydrogen gas as fuel with LNG providing the balance of fuel requirement. In this example, the liquid hydrogen refrigerant is produced and consumed at 10 bara pressure.

[0152] The daily boiloff rate is 0.1 % per day so the total boiloff is 400 tonnes for the voyage. The 200 tonnes of refrigerant provides about 25% of the propulsion fuel as liquid hydrogen and about 75% is from LNG. The energy requirement for the onshore liquefication of 200 tonnes of hydrogen fuel at 10 bar is 1600MWh (at 8 kWh / kg), which is less than producing it at low pressure because the higher pressure corresponds to a higher saturation temperature. But this does not contribute to the carbon intensity, as renewable power is used. The onboard reliquefier power is simulated to be 1560kWfor a net 10TPD liquefaction rate, consuming 750 MWh to reliquefy 200 tonnes during the voyage, that is 5.8% of the propulsion power. The carbon intensity of the combined fuel is 0.543 kgCO2 / kWh and the carbon intensity of hydrogen08430 wo shipping is 0.372 kgCO2 / kgH2 (0.0031 kgCO2 / MJ). Direct carbon dioxide emissions from the ship are from the LNG, i.e., 0.262 kgCO2 / kgH2. In this case, the flow through the expander circuit of the reliquefaction process is zero, so the expanders are not required and the capital cost of the reliquefier is reduced.

[0153] Example 5

[0154] In this example, the process illustrated in Fig. 6 is exemplified, where grey hydrogen liquefied onshore with renewable power is used as the refrigerant with a net consumption of 50% of the boiloff, then using the resultant warmed hydrogen gas as fuel with LNG providing the balance of fuel requirement. The remaining refrigerant evaporated by condensing the boiloff is reliquefied and returned to the refrigerant tank. In this example, the liquid hydrogen refrigerant is produced and consumed at approximately 1 bara pressure.

[0155] As before, the daily boiloff rate is 0.1% per day so the total boiloff is 400 tonnes for the voyage. The 200 tonnes of net refrigerant provides about 25% of the propulsion fuel as liquid hydrogen and about 75% is from LNG. The energy requirement for the onshore liquefication of 200 tonnes of hydrogen fuel is 2400MWh (at 12 kWh / kg), but this does not contribute to the carbon intensity, as renewable power is used. The onboard reliquefier power is simulated to be 1040kW for a net 10TPD liquefaction rate, consuming 500 MWh to reliquefy 200 tonnes during the voyage, that is 3.9% of the propulsion power. This is less than example 4 because the low pressure refrigerant liquid is colder in this case. The carbon intensity of the combined fuel is 0.543 kgCO2 / kWh and the carbon intensity of hydrogen shipping is 0.366 kgCO2 / kgH2 (0.0031 kgCO2 / MJ). Direct carbon dioxide emissions from the ship are from the LNG, i.e., 0.256 kgCO2 / kgH2. In this case, the flow through the expander circuit of the reliquefaction process is also zero, so the expanders are not required and the capital cost of the reliquefier is reduced.

[0156] Example 6

[0157] In this example, the process illustrated in Fig. 6 is exemplified, where the reliquefier consumes some grey hydrogen liquefied onshore with renewable power as the refrigerant, then the resultant warmed hydrogen gas is used as fuel to power only the reliquefier, with LNG providing all the fuel for propulsion. The liquid hydrogen refrigerant is again produced and consumed at approximately 1 bara pressure.

[0158] As before, the daily boiloff rate is 0.1% per day so the total boiloff is 400 tonnes for the voyage. From a simulation, 18.4% of this net boiloff (74 tonnes) is consumed to power the reliquefier. The energy requirement for the onshore liquefication of 74 tonnes of hydrogen08430 wo fuel is 888MWh (at 12 kWh / kg), but this does not contribute to the carbon intensity, as renewable power is used. The onboard reliquefier power is simulated to be 2500kWfor a net 16.3TPD reliquefaction rate, consuming 1200 MWh to reliquefy 326 tonnes during the voyage, that is 9.3% of the propulsion power. The carbon intensity of the combined fuel is 0.515 kgCC>2 / kWh and the carbon intensity of hydrogen shipping is 0.365 kgCO2 / kgH2 (0.0031 kgCC>2 / MJ). Direct carbon dioxide emissions from the ship are from the LNG, / .e., 0.324 kgCC>2 / kgH2. In this case, about 57% of the recycle flow is sent through the expander circuit of the reliquefaction process.

[0159] While the invention has been described with reference to the preferred embodiments depicted in the figures, it will be appreciated that various modifications are possible within the spirit or scope of the invention as defined in the following claims.

[0160] In this specification, unless expressly otherwise indicated, the word "or" is used in the sense of an operator that returns a true value when either or both of the stated conditions are met, as opposed to the operator "exclusive or" which requires only that one of the conditions is met. The word "comprising" is used in the sense of "including" and incorporates "consisting of" rather than meaning "consisting of' exclusively.

[0161] All prior teachings above are hereby incorporated herein by reference. No acknowledgement of any prior published document herein should be taken to be an admission or representation that the teaching thereof was common general knowledge in Australia or elsewhere at the date thereof.T1

Claims

08430 woCLAIMS1. A process for reducing and / or condensing boiloff during storage and / or transportation of a liquid hydrogen product, said process comprising: storing and / or transporting a liquid hydrogen product in a primary insulated storage container, the liquid hydrogen product having a first carbon intensity; storing a liquid hydrogen refrigerant in a secondary insulated storage container, said liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity; removing liquid hydrogen refrigerant from the secondary insulated storage container and vaporizing the removed liquid hydrogen refrigerant by heat exchange against the liquid hydrogen product and / or against hydrogen boiloff gas produced therefrom to generate vaporised liquid hydrogen refrigerant, together with subcooled liquid hydrogen product and / or condensed hydrogen boiloff gas respectively; and where produced, returning the condensed hydrogen boiloff gas to the liquid hydrogen product in the primary insulated storage container.

2. A process according to Claim 1 , wherein the second carbon intensity is greater than the first carbon intensity by at least about 0.4 kgCO2e / kgH2 or by at least about 0.5 kgCC>2e / kgH2 or by at least about 1 kgCO2e / kgH2 or by at least about 2.5 kgCO2e / kgH2 or by at least about 5 kgCO2e / kgH2 or by at least about 7.5 kgCO2e / kgH2 or by at least about 10 kgCC>2e / kgH2 or by at least about 15 kgCO2e / kgH2.

3. A process according to Claim 1 or Claim 2, wherein the first carbon intensity of the liquid hydrogen product is at least about 0 kgCO2e / kgH2, e.g., in a range from about 0 kgCC>2e / kgH2 to about 4 kgCO2e / kgH2.

4. A process according to any of the preceding claims, wherein the second carbon intensity of the liquid hydrogen refrigerant is at least about 0.45 kgCO2e / kgH2 or at least about 1.5 kgCC>2e / kgH2 or at least about 2.5 kgCO2e / kgH2 or at least about 4 kgCO2e / kgH2 or at least about 10 kgCC>2e / kgH2 or at least about 15 kgCO2e / kgH2.

5. A process according to any of the preceding claims, wherein the liquid hydrogen product is either green liquid hydrogen or blue liquid hydrogen.08430 wo6. A process according to any of the preceding claims, wherein the liquid hydrogen refrigerant is selected from the group consisting of blue liquid hydrogen, grey liquid hydrogen, brown liquid hydrogen and black liquid hydrogen.

7. A process according to any of the preceding claims, wherein the primary insulated storage container comprises a gas-cooled insulation shield, the process comprising: passing vaporised liquid hydrogen refrigerant through the gas-cooled insulation shield of the primary insulated storage container to reduce heat leak into the liquid hydrogen product.

8. A process according to Claim 7, wherein the vaporised liquid hydrogen refrigerant is subjected to para-ortho conversion to provide further cooling to the liquid hydrogen product in the primary insulated storage container.

9. A process according to any of the preceding claims, wherein the primary insulated storage container comprises a liquid-cooled insulation shield, the process comprising: storing a second liquid refrigerant, e.g., liquid nitrogen (LIN) or liquefied natural gas (LNG), in a further secondary insulated storage container comprising a gas-cooled insulation shield; and passing a second liquid refrigerant from the further secondary insulated storage container through the liquid-cooled insulation shield of the primary insulated storage container to reduce heat leak into the liquid hydrogen product therein, wherein vaporised liquid hydrogen refrigerant is passed through the gas-cooled insulation shield of the further secondary insulated storage container to reduce heat leak into the second liquid refrigerant therein.

10. A process according any of the preceding claims, wherein a second part, e.g., the remainder, of the vaporized liquid hydrogen refrigerant is compressed before being reliquefied or used as fuel.

11. A process for liquefying hydrogen boiloff gas during storage and / or transportation of liquid hydrogen product, said process comprising: storing and / or transporting liquid hydrogen product in a primary insulated storage container; warming hydrogen boiloff gas removed from the primary insulated storage container to produce warmed hydrogen gas;08430 wo compressing the warmed hydrogen gas combined with a warmed hydrogen recycle gas in a hydrogen gas compressor to produce compressed hydrogen gas at a supercritical pressure; cooling the compressed hydrogen gas by heat exchange to produce cooled compressed hydrogen gas; and further cooling at least a first portion of the cooled compressed hydrogen gas to a critical temperature by heat exchange to produce liquid hydrogen which is returned to the liquid hydrogen product in the primary insulated storage container after any necessary pressure adjustment, wherein the warming of the hydrogen boiloff gas is achieved by heat exchange against the compressed hydrogen gas, thereby providing a first part of the refrigeration duty for cooling the compressed hydrogen gas to produce the liquid hydrogen being returned to the liquid hydrogen product in the primary insulated storage container.

12. A process according to Claim 11 , wherein the hydrogen gas compressor is a combined compressor, said process comprising: compressing the warmed hydrogen gas in at least the first section of the combined compressor to produce intermediate compressed hydrogen gas; combining the intermediate compressed hydrogen gas with the warmed hydrogen recycle gas to form a combined hydrogen gas; and compressing at least a portion of the combined hydrogen gas in the remaining section(s) of the combined compressor to form the compressed hydrogen gas.

13. A process according to Claim 12, wherein intermediate compressed hydrogen gas is at a pressure of at least about 2 bar, e.g., in a range from about 2 bar to about 12 bar.

14. A process according to Claim 12 or Claim 13, wherein a portion of the combined hydrogen gas is removed and used a fuel.

15. A process according to any of Claims 12 to 14 comprising passing the cooled compressed hydrogen gas through an adsorption unit to remove any impurities.

16. A process according to any of Claim 12 to 15, wherein a second portion of the cooled compressed hydrogen gas is expanded in at least two expanders in series to produce expanded hydrogen gas.08430 wo17. A process according to Claim 16, wherein the expanded hydrogen gas is warmed by heat exchange against the compressed hydrogen gas to produce the warmed hydrogen recycle gas, thereby providing a second part of the refrigeration duty for cooling the compressed hydrogen gas to produce the liquid hydrogen being returned to the liquid hydrogen product in the primary insulated storage container18. A process according to Claim 16 of Claim 17, wherein the pressure of the expanded hydrogen gas is in a range from about 2 bar to about 12 bar.

19. A process according to any of Claims 16 to 18, wherein intermediate expanded gas from one expander is cooled by heat exchange against hydrogen boiloff gas and / or expanded hydrogen gas before being fed to the next expander.

20. A process according to any of Claims 16 to 19, wherein a portion of an intermediate expanded gas is removed and used as fuel.21 . A process according to any of Claims 12 to 20, wherein the compressed hydrogen gas is at a pressure in a range from about 20 bar to about 70 bar, e.g., in a range from about 30 bar to about 40 bar.

22. A process according to any of Claims 12 to 21 , wherein the first portion of the cooled compressed hydrogen gas is from about 30 % to about 100 % of the total mass flow of cooled compressed hydrogen gas.

23. A process according to any of Claims 12 to 22, wherein the liquid hydrogen product being stored and / or transported has a first carbon intensity, the process comprising: storing a liquid hydrogen refrigerant in a secondary insulated storage container, said liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity; removing the liquid hydrogen refrigerant from the secondary insulated storage container and vaporizing the removed liquid hydrogen refrigerant by heat exchange against the liquid hydrogen product and / or against hydrogen boiloff gas produced therefrom to generate vaporised liquid hydrogen refrigerant, together with subcooled liquid hydrogen product and / or condensed hydrogen boiloff gas; and where produced, returning the condensed hydrogen boiloff gas to the liquid hydrogen product in the primary insulated storage container.08430 wo24. A process for condensing boiloff during storage and / or transportation of liquid hydrogen product, said process comprising: storing and / or transporting liquid hydrogen product in a primary insulated storage container, said liquid hydrogen product having a first carbon intensity; storing a liquid hydrogen refrigerant in a secondary insulated storage container, said liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity; removing liquid hydrogen refrigerant from the secondary insulated storage container and vaporizing the removed liquid hydrogen refrigerant by heat exchange against hydrogen boiloff gas produced from the liquid hydrogen product in the primary insulated storage vessel to generate vaporised liquid hydrogen refrigerant and condensed hydrogen boiloff gas; returning the condensed hydrogen boiloff gas to the liquid hydrogen product in the primary insulated storage container; warming at least a part of the vaporised liquid hydrogen refrigerant to produce warmed hydrogen gas; compressing the warmed hydrogen gas, optionally combined with a warmed hydrogen recycle gas, in a hydrogen gas compressor to produce compressed hydrogen gas; cooling the compressed hydrogen gas by heat exchange to produce cooled compressed hydrogen gas; and further cooling at least a first portion of the cooled compressed hydrogen gas by heat exchange to a critical temperature to produce liquid hydrogen which is returned to the liquid hydrogen refrigerant in the secondary insulated storage container after any necessary pressure adjustment, wherein the warming of the vaporised liquid hydrogen refrigerant is achieved by heat exchange against the compressed hydrogen gas, thereby providing a first part of the refrigeration duty for cooling the compressed hydrogen gas to produce the liquid hydrogen being returned to the liquid hydrogen refrigerant in the secondary insulated storage container.

25. A process according to Claim 24 comprising expanding a second portion of the cooled compressed hydrogen gas to produce expanded hydrogen gas,08430 wo wherein the expanded hydrogen gas is warmed by heat exchange against the compressed hydrogen gas to produce the warmed hydrogen recycle gas for combination with the warmed hydrogen gas, thereby providing a second part of the refrigeration duty for cooling the compressed hydrogen gas to produce the liquid hydrogen being returned to the liquid hydrogen refrigerant in the secondary insulated storage container.

26. A storage and / or transportation installation for a liquid hydrogen product, said installation comprising: a primary insulated storage container for storing and / or transporting a liquid hydrogen product having a first carbon intensity; a secondary insulated storage container for storing and / or transporting a liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity, said secondary insulated storage container comprising an outlet for liquid hydrogen refrigerant in fluid flow communication with an inlet for vaporised liquid hydrogen refrigerant; and a heat exchange system located between the outlet and the inlet of the secondary insulated storage container and arranged to vaporize liquid hydrogen refrigerant from the secondary insulated storage container by heat exchange against liquid hydrogen product and / or hydrogen boiloff gas in the primary insulated storage container.

27. A storage and / or transportation installation according to Claim 26 wherein the primary insulated storage container comprises a gas-cooled insulation shield for vaporised liquid hydrogen refrigerant from the heat exchanger.

28. A storage and / or transportation installation according to Claim 26 or Claim 27 comprising an ortho-para conversion unit for vaporised liquid hydrogen refrigerant from the heat exchange system.

29. A storage and / or transportation installation according to any of Claims 26 to 28 comprising: a further secondary insulated storage container for a second liquid refrigerant, said further secondary insulated storage container comprising a gas-cooled insulation shield for vaporised liquid hydrogen refrigerant from the heat exchanger, wherein the primary insulated storage container comprises a liquid-cooled insulation shield for second liquid refrigerant from the further secondary insulated storage container.

30. A storage and / or transportation installation as claimed in any of Claims 26 to 29 comprising a hydrogen compression system for compressing vaporized liquid hydrogen refrigerant.

31. A liquefier for liquefying hydrogen boiloff gas during storage and / or transportation of liquid hydrogen product, said liquefier comprising: a primary insulated storage container for storing and / or transporting a liquid hydrogen product comprising an outlet for hydrogen boiloff gas and an inlet for liquid hydrogen; a compression system comprising a first inlet for warmed hydrogen gas in fluid flow communication with the outlet of the primary insulated storage container, and a first outlet for compressed hydrogen gas at supercritical pressure; a pressure reduction valve having an inlet for cooled compressed hydrogen at supercritical pressure and at a critical temperature in fluid flow communication with the outlet of the compression system, and an outlet for liquid hydrogen in fluid flow communication with the inlet of the primary insulated storage container; and a heat exchange system located between the outlet for hydrogen boiloff gas of the primary insulated storage container and the inlet of the compression system and between the outlet of the compression system and the inlet of the pressure reduction valve, and arranged to cool compressed hydrogen gas at supercritical pressure to a critical temperature by heat exchange with hydrogen boiloff gas.

32. A liquefier according to Claim 31 comprising an adsorption unit to remove impurities from cooled compressed hydrogen gas at an intermediate point in the heat exchange system.

33. A liquefier according to Claim 31 or Claim 32, wherein the compression system is a combined compressor comprising at least two sections and a second inlet at an intersection within the compression system for warmed hydrogen recycle gas.

34. A liquefier according to Claim 32, wherein the compression system comprises a second outlet at an intersection within the compression system for intermediate compressed hydrogen gas.

35. A liquefier according to Claim 33 or Claim 34 comprising:08430 wo an expander system comprising an inlet for cooled compressed hydrogen gas and an outlet for expanded hydrogen gas in fluid flow communication with the second inlet of the compression system, wherein the heat exchange system is also arranged to cool compressed hydrogen gas at supercritical pressure to a critical temperature by heat exchange with expanded hydrogen gas.

36. A liquefier according to Claim 35 wherein the expander system comprises at least two expanders in series and wherein the heat exchanger system is also arranged to cool intermediate expanded gas between the two expanders by heat exchange with hydrogen boiloff gas and / or expanded hydrogen gas.

37. A liquefier according to any of Claims 31 to 36 wherein the liquid hydrogen product has a first carbon intensity, said liquefier comprising: a secondary insulated storage container for storing and / or transporting a liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity, said secondary insulated storage container comprising an outlet for liquid hydrogen refrigerant in fluid flow communication with an inlet for vaporised liquid hydrogen refrigerant; wherein the heat exchange system is also arranged to vaporize liquid hydrogen refrigerant from the secondary insulated storage container by heat exchange against hydrogen boiloff gas from the primary insulated storage container.

38. A liquefier according to any of Claims 31 to 37 located onboard a ship.

39. A storage and / or transportation installation for a liquid hydrogen product, said installation comprising: a primary insulated storage container for storing and / or transporting a liquid hydrogen product having a first carbon intensity; a secondary insulated storage container for storing and / or transporting a liquid hydrogen refrigerant having a second carbon intensity that is greater than the first carbon intensity, said secondary insulated storage container comprising an outlet for liquid hydrogen refrigerant in fluid flow communication with an inlet for vaporised liquid hydrogen refrigerant, and an inlet for reliquefied liquid hydrogen refrigerant; and08430 wo a compression system comprising a first inlet for warmed hydrogen gas in fluid flow communication with the outlet of the secondary insulated storage container, and a first outlet for compressed hydrogen gas at supercritical pressure; a pressure reduction valve having an inlet for cooled compressed hydrogen at supercritical pressure and at a critical temperature in fluid flow communication with the outlet of the compression system, and an outlet for reliquefied hydrogen refrigerant in fluid flow communication with the inlet for reliquefied hydrogen refrigerant of the secondary insulated storage container; and a first heat exchange system located between the outlet and the inlet of the secondary insulated storage container and arranged to vaporize liquid hydrogen refrigerant from the secondary insulated storage container by heat exchange against liquid hydrogen product and / or hydrogen boiloff gas in the primary insulated storage container; and a second heat exchange system located between the outlet of the secondary insulated storage container and the inlet of the compression system and between the outlet of the compression system and the inlet of the pressure reduction valve, and arranged to cool compressed hydrogen gas at supercritical pressure to a critical temperature by heat exchange with vaporized liquid hydrogen refrigerant.

40. A storage and / or transportation installation according to Claim 39 comprising an adsorption unit to remove impurities from cooled compressed hydrogen gas at an intermediate point in the second heat exchange system.41 . A storage and / or transportation installation according to Claim 39 or Claim 40, wherein the compression system is a combined compressor comprising at least two sections and a second inlet at an intersection within the compression system for warmed hydrogen recycle gas.

42. A storage and / or transportation installation according to Claim 41 , wherein the compression system comprises a second outlet at an intersection within the compression system for intermediate compressed hydrogen gas.

43. A storage and / or transportation installation according to Claim 41 or Claim 42 comprising: an expander system comprising an inlet for cooled compressed hydrogen gas and an outlet for expanded hydrogen gas in fluid flow communication with the second inlet of the compression system,08430 wo wherein the second heat exchange system is also arranged to cool compressed hydrogen gas at supercritical pressure to a critical temperature by heat exchange with expanded hydrogen gas.

44. A storage and / or transportation installation according to Claim 43 wherein the expander system comprises at least two expanders in series and wherein the second heat exchanger system is also arranged to cool intermediate expanded gas between the two expanders by heat exchange with vaporized liquid hydrogen refrigerant.

45. A storage and / or transportation installation as claimed in any of Claims 26 to 30 or Claims 39 to 44 located onboard a ship.

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