APPARATUS AND PROCESS FOR HYDROGEN RECYCLING TO AVOID LIQUEFIER SHUTDOWN DUE TO INSUFFICIENT FEED OF HYDROGEN

Description

FIELD OF THE INVENTION

The present innovation relates to processes and apparatuses for hydrogen liquefaction and processes and apparatuses for recycling of hydrogen for hydrogen liquefaction processing.

BACKGROUND OF THE INVENTION

Hydrogen can be produced via electrolysis of water. Examples of systems configured to help facilitate the production of hydrogen via electrolysis are disclosed in U.S. Pat. No. 11,929,613, and U.S. Patent Application Publication Nos. 2022/0033983 and 2024/0141524.

Hydrogen can be liquefied. Liquefaction for hydrogen gas can include use of one or more liquefiers. Examples of approaches used for liquifying hydrogen can be found in U.S. Patent Application Publication Nos. 2023/0175773 and U.S. Pat. Nos. 3,092,461 and 7,559,213.

SUMMARY OF THE INVENTION

Often hydrogen liquefaction occurs in processing that is desired for relatively steady state conditions. for example, a stream of hydrogen for liquefaction may be provided from a least one source of hydrogen production that operates using a reliable supply of hydrogen forming materials and a reliable supply of power that can be provided by conventional power sources (e.g. electricity generated from combustion of natural gas or other fossil fuel, hydrogen production provided by steam reforming that can be generated via use of fossil fuel sources, etc.).

In contrast to this type of approach to hydrogen production, green hydrogen production can be provided by use of renewable power to power production of hydrogen. Such systems can utilize electrolysis of water that is powered via renewable sources such as solar power and/or wind power to produce hydrogen gas. This type of production process, however, can be subject to significant production swings due to changing weather conditions that can greatly affect the power available to support the electrolysis of water. Often, the production of hydrogen can change significantly every day or every couple of days depending on various weather conditions (e.g. duration of daytime relative to the duration of nighttime, cloud coverage, wind availability, etc.). We have found that green hydrogen production system may often see a substantial change in outputs of hydrogen gas and that liquefiers that may be positioned to liquify hydrogen gas from such production systems may need to be shut down often due to the lack of a sufficient feed of hydrogen for supporting the liquefaction processing. The shutting down of liquefaction processing can involve a substantial cost in terms of lost production. The shutdown of such equipment also has other surprising costs. For example, it can take a relatively long time to start the liquefaction process back up, which can result in lost production that may occur when renewable power increases to support a sufficient output of hydrogen for feeding to the liquefaction system and the delay in start-up can affect the ability to efficiently utilize the produced hydrogen. Also, equipment degradation from the regular changes in operational states can result in equipment needing replaced more often or otherwise having a lesser operational life, which can increase maintenance costs as result in processing that is less flexible and more prone to having shutdowns or other problems due to equipment failures.

Conventionally, expensive storage units can be provided to provide a buffer between a hydrogen production system and a liquefaction system to help ensure that the liquefaction system can operate when a supply of hydrogen may be unavailable. This type of conventional approach, however, can require significant capital expense associated with the storage. And the storage of the hydrogen can result in losses due to having to control for over pressurization of stored hydrogen in storage and other storage related processing complications.

We have found that these types of issues can be better addressed by providing an apparatus and process for recycling of hydrogen output from a liquefaction unit so that the liquid hydrogen can be vaporized and subsequently recycled back to the feed of the liquefaction unit to account for an insufficient feed of hydrogen. We have surprisingly found that this type of approach in use of energy and process complexity related to the formed liquid hydrogen can be beneficial as it can avoid liquefaction unit shutdowns and also help mitigate or limit the amount of storage that may be desired to help support liquefaction operations during low hydrogen production rate occurrences.

We have surprisingly found this type of approach can be particularly beneficial in embodiments in which the feed of hydrogen is provided by a production system powered by renewable power sources that may experience variable hydrogen production rates due to weather conditions, daylight conditions (e.g. daytime as compared to nighttime, cloudy conditions, etc.), or other conditions that can affect the power available for the hydrogen production. Such systems may experience variable production often (e.g. at least 3 times a week, at least 12 times a month, at least 200 times in a year, etc.) in some situations, and we have surprisingly found that it can be beneficial to incur the cost and production complexity associated with recycling already liquified hydrogen back to a feed of a liquefaction unit for avoidance of the shutting down of a liquefier unit due to insufficient feed of hydrogen for a period of time (e.g. during nighttime, during a rainy day, etc.). This can be particularly challenging in situations where there is a short length of time of zero production (e.g. due to a transient weather condition issue affecting power availability that may be lost for between 2 hours and 12 hours of time, etc.). The duration of the power non-availability can be a much shorter time period than would typically be the case for providing a full liquefaction process shut-down and subsequent start-up, which may take a full 24 hours. We surprisingly found that it can be much more beneficial to keep the liquefaction process online in a full recycle mode of operation in such a situation to avoid a prolonged shutting down process so the liquefaction process can be more readily able to catch production after the power availability returns for supplying hydrogen to the liquefaction process while also avoiding venting of product (e.g. venting of hydrogen product).

We determined that refrigeration machinery that can produce refrigeration for liquefaction of hydrogen can require a heat load (e.g. feed hydrogen) to remain online and productive if the liquefaction process is to be kept running while hydrogen production is ceased or substantially slowed due to an unexpected loss of power. Without a heat load, the liquefaction process would over-cool all its equipment beyond their design temperatures, leading to a need to shut down the process. We surprisingly found that a replacement feed for the feed hydrogen can be provided in the form of a recycle stream that recycles hydrogen output from the liquefaction process to the feed of the process to replace the lost hydrogen feed that can occur when lack of power availability may result in a cessation of hydrogen production or a significant decrease in hydrogen production that can drastically lower (or cease) the providing of feed hydrogen for liquefaction.

For such recycling to be effective and to also avoid causing problems with refrigeration machinery limitations, refrigeration duties and cryogenic conditions in the liquefier unit that can output a liquid hydrogen having a content of at least 95 mole percent parahydrogen, we have also surprisingly found that the parahydrogen content and orthohydrogen content of the recycled hydrogen can be controlled to provide improved performance that also avoids processing problems that can damage equipment, degrade equipment, and/or create unexpected failures that may result in production problems or liquefaction shut down conditions arising from use of the recycled hydrogen.

For example, we have surprisingly found that the presence of parahydrogen content of over 25 mole percent (mol %) in the feed to a liquefaction unit for hydrogen liquefaction can require significant adjustments in refrigeration systems of the liquefaction unit. Typically, a feed of hydrogen fed for liquefaction has a parahydrogen content of about 25 mol %. The conversion of hydrogen from orthohydrogen to parahydrogen can release energy and as hydrogen is cooled for liquefaction, the parahydrogen content of the hydrogen can increase and the liquefaction unit's refrigeration system can be designed to absorb this heat created from the conversion of orthohydrogen to parahydrogen to facilitate cooling and liquefaction of the hydrogen. In the event a feed of hydrogen fed for liquefaction has a higher parahydrogen content than expected (e.g. significantly greater than 25 mol % parahydrogen content, over 25 mol % parahydrogen content, etc.), the heat released from conversion of orthohydrogen to parahydrogen can be lower than the liquefaction unit is designed to accommodate due to the decrease in orthohydrogen being available for conversion to parahydrogen. Such a decrease in heat can result in the refrigeration system over cooling, which can result in the temperature of the equipment falling below the temperature that may be required for stable capacity of cryogenic machinery utilized in the liquefaction unit. Such an occurrence could result in equipment tripping or other problems requiring the liquefaction process to have to be shut down. We have found that such an occurrence can be avoided by utilization of a parahydrogen to orthohydrogen conversion unit to help control the parahydrogen content in the hydrogen that is recycled to the liquefaction unit to better control the parahydrogen content in the feed of hydrogen that includes the recycled hydrogen. Such a conversion unit can help provide improved parahydrogen content control for the feed hydrogen that includes the hydrogen recycled from the liquefaction unit to avoid liquefaction shutdowns and equipment degradation from occurring while also avoiding processing delays and loss production efficiency that can occur from having to repeatedly cycle a liquefaction unit between shutdown and operational states.

In a first aspect, a process for recycling hydrogen is provided. The process can include feeding a feed of hydrogen to a liquefaction unit. The liquefaction unit can liquefy the hydrogen to output liquid hydrogen. The liquid hydrogen can have a parahydrogen content of between 80 mole percent (mol %) parahydrogen and 100 mol % parahydrogen. In response to determining that the feed of hydrogen has decreased to at or below a pre-selected threshold, the liquid hydrogen can be recycled to a feed of the liquefaction unit such that the liquid hydrogen is vaporized into a gaseous state and undergoes a parahydrogen to orthohydrogen conversion so that the parahydrogen content of the recycled hydrogen recycled to the feed of the liquefaction unit has a parahydrogen content of between 20 mol % parahydrogen and 30 mol % parahydrogen.

In some embodiments, the feed of hydrogen can have a pre-selected parahydrogen content. For instance, the feed of hydrogen can have a parahydrogen content within a pre-selected parahydrogen content range of between 20 mole percent parahydrogen and 30 mole percent parahydrogen (e.g. be at or about 25 mol % parahydrogen, be in a range of 23 mol % parahydrogen to 27 mol % parahydrogen, etc.)

In some embodiments, the feed of hydrogen can be provided by a hydrogen generation system that can be configured to operate via use of renewable power.

In a second aspect, the process can also include ceasing the recycling of the liquid hydrogen in response to determining that the feed of hydrogen has increased to at or above the pre-selected threshold. In some embodiments of the process, the recycling and cessation of recycling can occur in multiple different cycles of operation to account for a rate of feed of hydrogen being provided to the liquefaction unit, for example.

In a third aspect, the recycling of the liquid hydrogen can include feeding hydrogen having a parahydrogen content of between 80 mol % and 100 mol % stored in at least one storage tank towards a conversion unit positioned to convert the parahydrogen to orthohydrogen so that the parahydrogen content of the recycled hydrogen recycled to the feed of the liquefaction unit has the parahydrogen content of between 20 mol % parahydrogen and 30 mol % parahydrogen and/or feeding liquid hydrogen output from the liquefaction unit to a heater of a recycle loop to vaporize the liquid hydrogen and subsequently pass the vaporized hydrogen to the conversion unit positioned to convert the parahydrogen to orthohydrogen so that the parahydrogen content of the recycled hydrogen recycled to the feed of the liquefaction unit has the parahydrogen content of between 20 mol % parahydrogen and 30 mol % parahydrogen. In some embodiments, both of these steps can be performed. In other embodiments, only one of these steps may be performed.

In a fourth aspect, the process can include feeding the liquid hydrogen having the parahydrogen content of between 80 mol % parahydrogen and 100 mol % parahydrogen output from the liquefier to at least one storage tank of hydrogen storage in fluid communication with the liquefaction unit. In some embodiments, the recycling of the liquid hydrogen can include adjusting at least one valve so that the liquid hydrogen output from the liquefaction unit is not passable to the at least one storage tank and feeding liquid hydrogen output from the liquefaction unit to a heater of a recycle loop to vaporize the liquid hydrogen and subsequently pass the vaporized hydrogen to the conversion unit positioned to convert the parahydrogen to orthohydrogen so that the parahydrogen content of the recycled hydrogen recycled to the feed of the liquefaction unit has the parahydrogen content of between 20 mol % parahydrogen and 30 mol % parahydrogen.

In a fifth aspect, the process can also include feeding hydrogen stored in at least one storage tank towards a conversion unit positioned to convert the parahydrogen to orthohydrogen so that the parahydrogen content of the recycled hydrogen recycled to the feed of the liquefaction unit has the parahydrogen content of between 20 mol % parahydrogen and 30 mol % parahydrogen. After determining that sufficient hydrogen has been recycled to the liquefaction unit to account for the decrease of the feed of hydrogen, the feeding of the hydrogen stored in the at least one storage tank towards the conversion unit can be ceased, or stopped.

In a sixth aspect, the recycling of the liquid hydrogen can include compressing the hydrogen before the hydrogen is fed to a conversion unit positioned to convert the parahydrogen to orthohydrogen so that the parahydrogen content of the recycled hydrogen recycled to the feed of the liquefaction unit has the parahydrogen content of between 20 mol % parahydrogen and 30 mol % parahydrogen.

In a seventh aspect, the recycling of the liquid hydrogen can include feeding hydrogen having a parahydrogen content of between 80 mol % and 100 mol % stored in at least one storage tank towards a conversion unit positioned to convert the parahydrogen to orthohydrogen so that the parahydrogen content of the recycled hydrogen recycled to the feed of the liquefaction unit has the parahydrogen content of between 20 mol % parahydrogen and 30 mol % parahydrogen and/or feeding liquid hydrogen output from the liquefaction unit to a heater of a recycle loop to vaporize the liquid hydrogen and subsequently pass the vaporized hydrogen to the conversion unit positioned to convert the parahydrogen to orthohydrogen so that the parahydrogen content of the recycled hydrogen recycled to the feed of the liquefaction unit has the parahydrogen content of between 20 mol % parahydrogen and 30 mol % parahydrogen. Embodiments of the process can also include feeding liquid hydrogen stored in at least one storage tank to the liquefaction unit to facilitate operation of the liquefaction unit and cooling of the liquefaction unit to a cryogenic operational temperature and recycling the hydrogen output form the liquefaction unit during the start-up via the recycle loop in response to a start-up of the liquefaction unit when the liquefaction unit is at an ambient temperature.

In an eight aspect, the process can be configured to utilize a controller having a processor connected to a non-transitory memory. The controller can be positioned and configured to determine whether the feed of hydrogen has decreased to at or below the pre-selected threshold.

In a ninth aspect, the process of the first aspect can include one or more features of the second aspect, third aspect, fourth aspect, fifth aspect, sixth aspect, seventh aspect and/or eight aspect. Yet other embodiments can include other features as well. Examples of such other features include features of exemplary embodiments discuss herein, for instance.

In a tenth aspect, an apparatus for hydrogen recycling is provided. Embodiments of the apparatus can include a liquefaction unit configured to liquify a feed of hydrogen to output a first stream of liquid hydrogen to feed the liquid hydrogen to at least one storage tank. The liquid hydrogen can a parahydrogen content of between 80 mole percent (mol %) and 100 mol %). The apparatus can also include a conversion unit positioned to convert parahydrogen of hydrogen output by the liquefaction unit to orthohydrogen so hydrogen output from the liquefaction unit is recyclable to a feed inlet of the liquefaction unit with a parahydrogen content that is between 20 mol % and 30 mol %. Embodiments of the apparatus can be configured to implement an embodiment of the process for recycling hydrogen.

In an eleventh aspect, the apparatus can include a recycle loop conduit heater feed conduit connected between the liquefaction unit and a recycle loop conduit heater. The recycle loop conduit heater can be positioned to heat liquid hydrogen output from the liquefaction unit to vaporize the liquid hydrogen to gaseous hydrogen. The recycle loop conduit heater can be positioned to feed the gaseous hydrogen to the conversion unit.

In a twelfth aspect, the conversion unit includes at least one parahydrogen to orthohydrogen converter. In some embodiments, the conversion unit may include a single parahydrogen to orthohydrogen converter. In other embodiments, the conversion unit can include a plurality of parahydrogen to orthohydrogen converters. The converters can all operate in parallel in some embodiments. In other embodiments, some may operate in parallel while others operate in series. In yet other embodiments having multiple parahydrogen to orthohydrogen converters, the converters can be arranged to operate in series.

In a thirteenth aspect, the apparatus can include at least one storage tank positioned to output hydrogen stored therein to feed the hydrogen to the conversion unit. In some embodiments, the storage tank(s) can be also utilized to receive and store liquid hydrogen output from the liquefaction unit.

In a fourteenth aspect, the apparatus can include a recycle loop heater positioned to receive hydrogen from at least one storage tank and heat the hydrogen so the hydrogen output from the at least one storage tank to be fed to the conversion unit is fed to the conversion unit as gaseous hydrogen.

In a fifteenth aspect, a recycle loop conduit heater feed conduit can be connected between the liquefaction unit and a recycle loop conduit heater. The recycle loop conduit heater can be positioned to heat liquid hydrogen output from the liquefaction unit to vaporize the liquid hydrogen to gaseous hydrogen. The recycle loop conduit heater can be positioned to feed the gaseous hydrogen to the conversion unit. Alternatively (or additionally), a recycle loop heater can be positioned to receive hydrogen from at least one storage tank and heat the hydrogen so the hydrogen output from the at least one storage tank to be fed to the conversion unit is fed to the conversion unit as gaseous hydrogen.

In a sixteenth aspect, the apparatus can include a recycle loop conduit heater feed conduit connected between the liquefaction unit and a first recycle loop conduit heater. The first recycle loop conduit heater can be positioned to heat liquid hydrogen output from the liquefaction unit to vaporize the liquid hydrogen to gaseous hydrogen and the first recycle loop conduit heater can be positioned to feed the gaseous hydrogen to the conversion unit. A second recycle loop heater can be positioned to receive hydrogen from at least one storage tank and heat the hydrogen so the hydrogen output from the at least one storage tank to be fed to the conversion unit is fed to the conversion unit as gaseous hydrogen.

In a seventeenth aspect, the apparatus can include a compression system positioned upstream of the conversion unit to compress the hydrogen for feeding the hydrogen to the conversion unit. The compression system can include a single compressor or a train of compressors. In some embodiments, the compression system can include at least one multistage compressor or a single stage compressor.

In an eighteenth aspect, the apparatus of the tenth aspect can include one or more features of the eleventh aspect, twelfth aspect, thirteenth aspect, fourteenth aspect, fifteenth aspect, sixteenth aspect, and/or seventeenth aspect. Yet other embodiments can include other features as well. Examples of such other features include features of exemplary embodiments discuss herein, for instance.

For instance, in a nineteenth aspect, an apparatus for hydrogen recycling can include a liquefaction unit configured to liquify a feed of hydrogen to output a first stream of liquid hydrogen to feed the liquid hydrogen to at least one storage tank. The liquid hydrogen can have a parahydrogen content of between 80 mol % and 100 mol %. A conversion unit can be positioned to convert parahydrogen of hydrogen output by the liquefaction unit to orthohydrogen so hydrogen output from the liquefaction unit is recyclable to a feed inlet of the liquefaction unit with a parahydrogen content that is between 20 mol % and 30 mol %. The conversion unit can include at least one parahydrogen to orthohydrogen converter. At least one storage tank can be positioned to output hydrogen stored therein to feed the hydrogen to the conversion unit in response to the feed of hydrogen being at or below a pre-selected threshold. A recycle loop conduit heater feed conduit can be connected between the liquefaction unit and a first recycle loop conduit heater. The first recycle loop conduit heater can be positioned to heat liquid hydrogen output from the liquefaction unit to vaporize the liquid hydrogen to gaseous hydrogen. The first recycle loop conduit heater can be positioned to feed the gaseous hydrogen to the conversion unit. A second recycle loop heater can be positioned to receive hydrogen from the at least one storage tank and heat the hydrogen so the hydrogen output from the at least one storage tank to be fed to the conversion unit is feedable to the conversion unit as gaseous hydrogen.

In some embodiments a compression system can be positioned upstream of the conversion unit to compress hydrogen for feeding the hydrogen to the conversion unit.

Embodiments of the apparatus and embodiments of the process can utilize liquefaction units that have different types of refrigeration systems. For instance, in some embodiments the liquefaction unit can have a closed loop refrigeration system. In other embodiments, the liquefaction unit can have an open loop refrigeration system.

It should be appreciated that embodiments of the process and apparatus can utilize various conduit arrangements and process control elements. The embodiments may utilize sensors (e.g., pressure sensors, temperature sensors, flow rate sensors, concentration sensors, etc.), controllers, valves, piping, and other process control elements. Some embodiments can utilize an automated process control system and/or a distributed control system (DCS), for example. Various different conduit arrangements and process control systems can be utilized to meet a particular set of design criteria.

Other details, objects, and advantages of the apparatus for recycling hydrogen, process for recycling hydrogen, hydrogen liquefaction apparatus, hydrogen liquefaction process, as well as an apparatus, process, and system for providing hydrogen recycling to avoid liquefier shutdown, and methods of making and using the same will become apparent as the following description of certain exemplary embodiments thereof proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of an apparatus for recycling hydrogen, process for recycling hydrogen, hydrogen liquefaction apparatus, hydrogen liquefaction process, as well as an apparatus, process, and system for hydrogen recycling that can avoid liquefier shutdown and methods of making and using the same are shown in the drawings included herewith. It should be understood that like reference characters used in the drawings may identify like components.

FIG. 1 (which can also be referred to as FIG. 1) is a block diagram of a first exemplary embodiment of an apparatus 1 for recycling hydrogen. Some optional elements of the exemplary embodiment of the apparatus are shown in broken line in FIG. 1. An exemplary embodiment of a process for recycling hydrogen is also illustrated in this Figure.

FIG. 2 (which can also be referred to as FIG. 2) is a block diagram of a first exemplary implementation of the first exemplary embodiment of an apparatus 1 for recycling hydrogen. An exemplary embodiment of a process for recycling hydrogen is also illustrated in this Figure.

FIG. 3 (which can also be referred to as FIG. 3) is a block diagram of a second exemplary implementation of the first exemplary embodiment of an apparatus 1 for recycling hydrogen. An exemplary embodiment of a process for recycling hydrogen is also illustrated in this Figure.

FIG. 4 (which can also be referred to as FIG. 4) is a block diagram of a second exemplary embodiment of an apparatus 1 for recycling hydrogen. Different compressors are shown in broken line in FIG. 4 as at least one such compressor may be optional for this particular embodiment. An exemplary embodiment of a process for recycling hydrogen is also illustrated in this Figure.

FIG. 5 (which can also be referred to as FIG. 5) is a block diagram of a first exemplary implementation of the second exemplary embodiment of an apparatus 1 for recycling hydrogen. An exemplary embodiment of a process for recycling hydrogen is also illustrated in this Figure.

FIG. 6 (which can also be referred to as FIG. 6) is a block diagram of a second exemplary implementation of the second exemplary embodiment of an apparatus 1 for recycling hydrogen. An exemplary embodiment of a process for recycling hydrogen is also illustrated in this Figure.

FIG. 7 (which can also be referred to as FIG. 7) is a flow chart illustrating an exemplary embodiment of a process for hydrogen recycling to prevent liquefier operation being shut down. Embodiments of the apparatus for hydrogen recycling can implement this exemplary embodiment of the process.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1-7, an apparatus 1 for recycling hydrogen can be utilized to recycle hydrogen output from a liquefaction unit 2 to feed that hydrogen back to the liquefaction unit 2. In some embodiments, the apparatus 1 can be configured to provide recycling of hydrogen in response to a feed of hydrogen 15 being provided to the liquefaction unit 2 for liquefaction of the hydrogen decreasing below a pre-selected feed rate (e.g. a pre-selected volumetric flow rate defining a threshold for actuation of the hydrogen recycling, a pre-selected mass flow rate defining a threshold for actuation of the hydrogen recycling, etc.). The recycling of the hydrogen can be actuated to help avoid shutting down of the liquefaction unit 2 in response to low feed rate conditions so that production delays associated with a liquefaction unit shutdown and subsequent start-up can be avoided as well as avoiding equipment degradation that can occur as a result of such operations that involve cycling between an activated operational condition and a shutdown operational condition.

We have surprisingly found this type of approach can be particularly beneficial in embodiments in which the feed of hydrogen 15 is provided by a production system powered by renewable power sources that may experience variable hydrogen production rates due to weather conditions, daylight conditions (e.g. daytime as compared to nighttime, cloudy conditions, etc.), or other conditions that can affect the power available for the hydrogen production. Such systems may experience variable production often (e.g. 200 or more than 200 times per year) in some situations, and we have surprisingly found that it can be beneficial to incur the cost and production complexity associated with use of already liquified hydrogen for recycling back to a feed of a liquefaction unit 2 for avoidance of the shutting down of a liquefier unit due to insufficient feed of hydrogen for a period of time (e.g. during nighttime, during a rainy day, etc.).

The liquefaction unit 2 that can be supported by the apparatus 1 for recycling of hydrogen can include one or more liquefiers or one or more trains of liquefiers for liquefaction of a feed of hydrogen 15. The liquefaction unit 2 can be configured as a hydrogen liquefaction system (HLS), for example, which can include one or more trains of liquefiers. The hydrogen liquefaction system (HLS) can include an array of expanders and hydrogen liquefaction heat exchangers. Some embodiments of the liquefaction system can also include orthohydrogen to parahydrogen conversion units as well to convert orthohydrogen of the hydrogen being liquefied to parahydrogen to increase the parahydrogen content of the hydrogen being liquefied.

The liquefaction unit 2 can be configured to output a liquid hydrogen stream that can have a relatively high parahydrogen content. In some embodiments, the parahydrogen content of the liquid hydrogen output from the liquefaction unit can be at least 80 mol % parahydrogen or at least 95 mol % parahydrogen (e.g. between 80 mol % parahydrogen and 100 mol % parahydrogen, between 95 mol % parahydrogen and 100 mol % parahydrogen, etc.). During operations in which a suitable supply of hydrogen feed is fed to the liquefaction unit 2, the liquid hydrogen stream output from the liquefaction unit 2 can be fed to storage 4 for storage and subsequent supply to one or more customers (e.g. via shipping of the liquid hydrogen, transport of the liquid hydrogen to another site or production facility, etc.). The storage 4 for the liquid hydrogen can include at least one tank or other vessel for the storage of liquid hydrogen at a cryogenic temperature to help maintain the liquid hydrogen in the liquid state.

The feed of hydrogen 15 supplied to the liquefaction unit 2 can include hydrogen that is entirely gaseous (e.g. 100% gaseous) or can include a mostly gaseous stream of hydrogen (e.g. a stream of gaseous hydrogen having between 0 vol % and 1 vol % liquid hydrogen, etc.). The feed of hydrogen 15 can be a normal hydrogen product that includes a concentration of 25 mol % parahydrogen and 75 mol % orthohydrogen, for example. The feed of hydrogen 15 can be provided via at least one hydrogen production system 20. The hydrogen production system 20 can include a hydrogen generation system (HGS), which can include one or more electrolyzers that can form hydrogen from electrolysis of water. In some embodiments, the electrolyzers of such a hydrogen production system 20 can be powered by at least one source of renewable power (e.g. solar power, wind power, hydropower, combinations thereof, etc.) for providing a feed of green hydrogen that is produced via renewable power.

The parahydrogen content of the feed of hydrogen provided by the hydrogen production system 20 can be about 25 mol % parahydrogen with the balance being orthohydrogen. For example, the feed of hydrogen 15 provided by the hydrogen production system 20 can have a parahydrogen content of between 20 mol % and 30 mol % (e.g. 25 mol % or about 25 mol %) and the orthohydrogen content of the hydrogen can be between 80 mol % and 70 mol % (e.g. 75 mol % or about 75 mol %).

The feed of hydrogen 15 that can be provided can be powered by renewable power sources that may experience variable hydrogen production rates due to weather conditions, daylight conditions (e.g. daytime as compared to nighttime, cloudy conditions, etc.), or other conditions that can affect the power available for the hydrogen production. Such systems may experience variable production often (e.g. at least 3 times a week, at least 12 times a month, at least 200 times in a year, etc.) by design in some situations, and we have surprisingly found that it can be beneficial to incur the cost and production complexity associated with recycling already liquified hydrogen output from the liquefaction unit 2 back to the feed of hydrogen 15 for providing a makeup flow of hydrogen for the feed of hydrogen 15 to support operation of the liquefaction unit 15 for avoidance of the shutting down of the liquefaction unit 2 due to insufficient feed of hydrogen for a period of time (e.g. during the night, during a rainy day, etc.). The recycling of the hydrogen can be via use of hydrogen within storage 4 and/or via routing of hydrogen output from the liquefaction unit so the hydrogen is passed back to the feed inlet of the liquefaction unit 2 instead of being routed to storage 4. This recycling can involve vaporization of the liquid hydrogen output from the liquefaction unit so the hydrogen that is recycled back to the feed inlet of the liquefaction unit 2 is in a gaseous state (e.g. is hydrogen gas instead of liquid hydrogen).

The liquefaction unit 2 can output a liquid hydrogen having a content of at least 95 mole percent parahydrogen. For the recycling of the hydrogen output from the liquefaction unit 2, we have surprisingly found that the parahydrogen content and orthohydrogen content of the recycled hydrogen to be fed to a feed inlet of the liquefaction unit can be controlled to provide improved performance that also avoids processing problems that can damage equipment, degrade equipment, and/or create unexpected failures that may result in production problems or liquefaction shut down conditions arising from use of the recycled hydrogen. The parahydrogen content of the recycled hydrogen can be controlled via a conversion unit 11 so that the recycled hydrogen along with any low flow of hydrogen that may be provided as the feed of hydrogen 15 from a hydrogen production system 20 can have a pre-selected parahydrogen content that is at or below 25 mol % parahydrogen, at or below 30 mol % parahydrogen, or at or below another suitable parahydrogen content feed threshold that can be set to avoid over cooling of liquefaction equipment from cooling of the hydrogen that includes the recycled hydrogen.

We have surprisingly found that the presence of parahydrogen content of over 25 mole percent (mol %) or significantly over 25 mol % in the feed to a liquefaction unit for hydrogen liquefaction can require significant adjustments in refrigeration systems of the liquefaction unit. Typically, a feed of hydrogen fed for liquefaction has a parahydrogen content of about 25 mol %. The conversion of hydrogen from orthohydrogen to parahydrogen can release energy and as hydrogen is cooled for liquefaction, the parahydrogen content of the hydrogen can increase and the liquefaction unit's refrigeration system can be designed to absorb this heat created from the conversion of orthohydrogen to parahydrogen to facilitate cooling and liquefaction of the hydrogen.

In the event a feed of hydrogen fed to a liquefaction unit 2 for liquefaction has a higher parahydrogen content than expected (e.g. significantly greater than 25 mol % parahydrogen content, over 25 mol % parahydrogen content, etc.), the heat released from conversion of orthohydrogen to parahydrogen can be lower than the liquefaction unit is designed to accommodate due to the decrease in orthohydrogen being available for conversion to parahydrogen (which may only occur as a consequence of recycling of the hydrogen output from the liquefaction unit back to the feed of the liquefaction unit 2 in a sufficient quantity to significantly alter the parahydrogen content in the feed of hydrogen fed to the liquefaction unit 2). Such a decrease in heat can result in the refrigeration system over cooling the hydrogen during liquefaction, which can result in the temperature of the equipment falling below the temperature that may be required for stable capacity of cryogenic machinery utilized in the liquefaction unit. We determined that this type of occurrence can result in equipment tripping or other problems requiring the liquefaction process to have to be shut down.

We have found that such problems that may be caused by excessive refrigeration can be avoided by utilization of a parahydrogen to orthohydrogen conversion unit 11 (CVRT) to help control the parahydrogen content in the hydrogen that is recycled to the feed inlet of the liquefaction unit 2 to better control the parahydrogen content in the feed of hydrogen that includes the recycled hydrogen fed to the feed inlet of the liquefaction unit 2. Such a conversion unit 11 (CVRT) can include one or more parahydrogen to orthohydrogen converters to convert parahydrogen in the hydrogen being recycled to orthohydrogen to help provide improved parahydrogen content control for the feed hydrogen that includes the hydrogen recycled from the liquefaction unit to avoid liquefaction shutdowns and equipment degradation from occurring while also avoiding processing delays and loss production efficiency that can occur from having to repeatedly cycle a liquefaction unit between shutdown and operational states. This type of control of the parahydrogen content in the recycled hydrogen can help control the parahydrogen content of the hydrogen fed to the feed inlet of the liquefaction unit 2, in situations where the recycled hydrogen makes up all of the hydrogen being fed to the liquefaction unit 2 when there is no hydrogen feed 15 providable from a hydrogen production system 20 or there is a very low rate of feed of hydrogen from the hydrogen production system 20 such that the recycled hydrogen makes up a significant portion of the overall hydrogen fed to the liquefaction unit (e.g. at least 30% of the hydrogen is recycled hydrogen, at least 50% of the hydrogen of the feed of hydrogen is recycled hydrogen, between 50% and 100% of the hydrogen fed to the liquefaction unit 2 as the feed of hydrogen 15 is the recycled hydrogen, etc.). An example of a very low feed rate for the hydrogen feed 15 can be no feed at all or a feed that is so low that the heat load of the hydrogen feed 15 falls below a pre-selected minimum threshold required by the refrigeration system of the liquefaction process to keep the refrigeration machinery operating within its pre-defined temperature constraints.

The recycling of hydrogen may not occur all the time. Instead, the recycling of hydrogen can be provided in response to a determination that the feed of hydrogen 15 is at or below a pre-selected hydrogen feed rate or is expected to be at or below the pre-selected hydrogen feed rate for at least a pre-selected low hydrogen feed period of time. In response to the detection of such a condition, the recycling of hydrogen can be initiated or actuated. The recycled hydrogen can initially be provided via a long recycle loop LRP via use of hydrogen stored in the storage 4 and may thereafter be provided via a short recycle loop SRP for recycling of hydrogen output from the liquefaction unit 2 so that such hydrogen bypasses being fed to storage 4 and is instead directly recycled back to the feed inlet of the liquefaction unit 2. In other embodiments, the recycled hydrogen can be provided always via a short recycle loop SRP or always via a long recycle loop LRP (e.g. there may not be any switching of uses between loops and there may only be the short recycle loop SRP or the long recycle loop LRP). In yet other embodiments, the recycled hydrogen can initially be provided via the short recycle loop SRP and/or the long recycle loop LRP (e.g. a combination of stored hydrogen from storage as well as liquid hydrogen output from the liquefaction unit being recycled instead of sent to storage 4) and may thereafter be provided via the short recycle loop SRP.

After the feed of hydrogen 15 provided from the hydrogen production system 20 is detected as being at or above the pre-selected hydrogen feed rate or is expected to be at or above the pre-selected hydrogen feed rate for more than a pre-selected low hydrogen feed period of time, the recycling of hydrogen can be stopped or may be slowed until the feed rate of hydrogen provided from the hydrogen production system 20 is at or above the pre-selected hydrogen feed rate. This switching of operation between recycling and non-recycling of hydrogen can be provided repeatedly as low feed rates below a pre-defined threshold minimum needed for operation of the liquefaction unit 2 may be detected during the course of numerous different operational cycles as a result of changing weather conditions or other conditions that may affect hydrogen production at the hydrogen production system(s) 20 positioned to supply the feed of hydrogen 15 to the liquefaction unit 2.

The recycling of the hydrogen to account for a low feed rate of hydrogen from the hydrogen production system 20 can be dynamically adjusted to account for the low feed rate. For example, when there is no hydrogen provided by the hydrogen production system 20, the recycling of hydrogen can be provided at a higher capacity to provide sufficient hydrogen to the inlet of the liquefaction unit 2 to allow the unit to operate without having to shut down at a pre-selected minimum operational capacity. In the event the feed of hydrogen 15 is present, but is very low and below the pre-selected minimum threshold, the amount of hydrogen being recycled can vary to provide a makeup of hydrogen so that the feed of hydrogen fed to the inlet 15b of the liquefaction unit is at or above the pre-selected minimum threshold.

FIGS. 1-6 illustrate different exemplary implementations for different apparatuses for providing recycling of hydrogen. Embodiments of processes for hydrogen recycling can also be appreciated from these drawings. The first exemplary embodiment of FIGS. 1-3 illustrates exemplary recycling processing that may be provided in situations where the liquefaction unit 2 can utilize an open loop refrigeration system for liquefaction operations. The second exemplary embodiment of FIGS. 4-6 illustrate exemplary recycling processing that may be provided in situations where the liquefaction unit 2 can utilize a closed loop refrigeration system for liquefaction operations.

The feed of hydrogen 15 fed to the liquefaction unit 2 can be at a pre-selected feed pressure (e.g. between over 100 kPa and 4000 kPa or other suitable feed pressure) and a pre-selected feed temperature (e.g. between 0° C. and 100° C., a temperature of between ambient to less than 65°C., a temperature of between 0° C. and 65° C., or other suitable temperature). The parahydrogen content of the feed of hydrogen can also be in a pre-selected range of parahydrogen content (e.g. a parahydrogen content of between 20 mol % and 30 mol %).

The liquid hydrogen output from the liquefaction unit 2 can be at a pre-selected liquid hydrogen output pressure (e.g. a pressure of 200kPa, a pressure of between over 200 kPa and 500 kPa, a pressure of between 350 kPa and 425 kPa, or other suitable pressure) and a pre-selected liquid hydrogen output temperature (e.g. a temperature of between −230° C. and −250° C., a cryogenic temperature, etc.). For example, the hydrogen output pressure can be the inlet feed pressure of the hydrogen feed 15 minus the pressure drop of the liquefaction unit 2. The parahydrogen content of the liquid hydrogen that is output from the liquefaction unit 2 can also be within a pre-selected parahydrogen content range (e.g. a parahydrogen content of between 80 mol % and 100 mol %, a parahydrogen content of between 95 mol % and 100 mol %, etc.).

Referring to FIGS. 1-3, an apparatus 1 for recycling of hydrogen can be configured to recycle hydrogen output from a liquefaction unit 2 as at least one stream of liquid hydrogen to a feed inlet of the liquefaction unit 2 via a first recycle conduit arrangement and/or a second recycle conduit arrangement. The first recycle conduit arrangement can be a short recycle loop SRP or a long recycle loop LRP and the second recycle conduit arrangement can be the other loop (e.g. the second recycle conduit arrangement can be the long recycle loop LRP when the first recycle conduit arrangement is the short recycle loop SRP and the second recycle conduit arrangement can be the short recycle loop SRP when the first recycle conduit arrangement is the long recycle loop LRP.

When the feed of hydrogen 15 fed to the liquefaction unit 2 is at or above a pre-selected feed rate, the liquid hydrogen output by the liquefaction unit 2 can be fed to storage 4 for being retained in one or more liquid hydrogen storage tanks. The liquid hydrogen fed therein may be retained at a pre-selected storage pressure (e.g. a pressure of between 100 kPa and 150 kPa or other suitable pressure). A liquid hydrogen storage feed conduit 3a can be connected between the storage 4 and the liquefaction unit 2 to route the liquid hydrogen to storage 4 for storage in one or more storage tanks. Liquid hydrogen retained in storage 4 can be fed to one or more trailers for transport to a customer via truck, railcar, or other type of vehicle or can be fed to another process element of an industrial facility at another location for use of the hydrogen. As noted above, the liquid hydrogen in the storage 4 can have a relatively high parahydrogen content of at least 80 mol % or at least 95 mol %.

During operation, the feed of hydrogen 15 may change significantly due to changed production conditions at the hydrogen production system 20 (e.g. changed weather conditions affecting available power for electrolysis of water, etc.). Such a change can result in the feed of hydrogen 15 decreasing significantly or no longer being provided by the hydrogen production system 20. At least some of the liquid hydrogen output from the liquefaction unit 2 can be recycled in response to a detection that no feed of hydrogen is being provided or that the feed of hydrogen is at or below a pre-selected threshold (e.g. a pre-selected volumetric flow rate defining a threshold for actuation of the hydrogen recycling, a pre-selected mass flow rate defining a threshold for actuation of the hydrogen recycling, etc.). The recycling may occur via utilization of the first recycling loop and/or second recycling loop (e.g. the short recycle loop SRP and/or the long recycle loop LRP).

For example, a short recycle loop SRP can be provided for routing of at least a portion of the liquid hydrogen output from the liquefaction unit 2 back to a feed conduit for the feed of hydrogen for feeding the hydrogen back to a feed inlet of the liquefaction unit 2. The short recycle loop can include a recycle loop conduit heater 5 that is positioned to heat liquid hydrogen output from the liquefaction unit to vaporize the hydrogen into a gaseous state and a recycle loop conduit heater feed conduit 5a that is connected between the liquefaction unit 2 and the recycle loop conduit heater 5. The heater 5 can be, in some embodiments, an ambient air vaporizer, an ambient air heat exchanger, a heat exchanger that utilizes water as a heating medium (e.g. ambient temperature water, heated water, etc.), or other suitable heat exchanger that may utilize a heating medium for heating of the liquid hydrogen to vaporize the hydrogen for outputting a vaporized hydrogen stream 5b from the heater for routing toward a conversion unit 11 that includes at least one parahydrogen to orthohydrogen converter for adjusting the orthohydrogen content and parahydrogen content of the hydrogen being recycled to be at about 25 mol % parahydrogen content.

For example, the heater 5 can be in fluid communication with a compression feed conduit 7b of the recycle conduit arrangement for the apparatus 1 to feed the vaporized hydrogen to at least one compressor (e.g. a first compressor C1, second compressor C2, and/or third compressor C3) of the compression system (CS). The compression system 9 can compress the hydrogen to a higher pressure for feeding to a feed inlet of the liquefaction unit 2 and to help pass the hydrogen through the conversion unit 11. The compression system 9 can output the hydrogen gas to feed the gas to at least one parahydrogen to orthohydrogen conversion device of the conversion unit 11 via a conversion unit feed conduit 9a positioned between the compression system 9 and the conversion unit 11. The conversion unit 11 can process the hydrogen gas to convert parahydrogen to orthohydrogen so that a parahydrogen content of the hydrogen gas output from the conversion unit 11 has a parahydrogen content of no more than 25 mol % or no more than 30 mol % (e.g. between 20 mol % and 30 mol % parahydrogen and between 80 mol % and 70 mol % orthohydrogen, etc.). The hydrogen gas having the modified parahydrogen content can be output from the conversion unit 11 for feeding to a feed conduit through which the feed of hydrogen 15 can pass for being fed to the feed inlet of the liquefaction unit. A conversion unit supply conduit 11a can be connected between the liquefaction unit 2 and the conversion unit 11 to feed the hydrogen output from the conversion unit to the liquefaction unit.

In some embodiments, the conversion unit supply conduit 11a can feed the hydrogen output from the conversion unit 11 to a feed conduit through which the feed of hydrogen 15 is passable for mixing in-line with the feed of hydrogen for being fed to the inlet of the liquefaction unit 2 with the feed of hydrogen 15 that can be output from the hydrogen production system 20. Alternatively, the conversion unit supply conduit 11a can pass the hydrogen to the feed inlet of the liquefaction unit for mixing with that hydrogen (if provided) from the hydrogen production system 20 at a feed inlet region of the liquefaction unit 2.

A long recycle loop LRP can be provided for routing of at least a portion of the liquid hydrogen output from the liquefaction unit 2 back to a feed conduit for the feed of hydrogen for feeding the hydrogen back to a feed inlet of the liquefaction unit 2 as well or as an alternative to use of the short recycle loop SRP. The long recycle loop LRP can include at least one storage tank of the storage 4 feeding hydrogen stored in the tank(s) to a heater 7 via a storage tank recycle conduit 4c positioned between the hydrogen storage 4 and the heater 7.

The hydrogen output from storage 4 can include vapor that may collect in the storage tank that can be output from a vapor conduit 4a that is connected between the storage tank recycle conduit 4c and the storage tank of the hydrogen storage 4. The hydrogen output from storage can also include liquid hydrogen that may be output from a liquid hydrogen conduit 4b that can be connected between the storage unit and a vaporizer 6 (VP) that can be positioned to vaporize the liquid hydrogen for feeding the gaseous hydrogen to the storage tank recycle conduit 4c via a vaporizer output conduit 4d connected between the vaporizer 6 and the storage tank recycle conduit 4c.

A recycle loop conduit heater 7 can be positioned to further heat the hydrogen output from the storage 4 to further heat the hydrogen so the hydrogen is gaseous hydrogen for feeding to at least one compressor of a compression system 9 via a recycle loop conduit heater output conduit 7a that is connected between the compression feed conduit 7b and the recycle loop conduit heater 7. The heater 7 can be, in some embodiments, an ambient air vaporizer, an ambient air heat exchanger, a heat exchanger that utilizes water as a heating medium (e.g. ambient temperature water, heated water, etc.), or other suitable heat exchanger that may utilize a heating medium for heating of the liquid hydrogen to vaporize the hydrogen for outputting gaseous hydrogen stream from the heater 7 for routing toward a conversion unit 11 that includes at least one parahydrogen to orthohydrogen converter for adjusting the orthohydrogen content and parahydrogen content of the hydrogen being recycled to be at about 25 mol % parahydrogen content.

The compression system 9 can receive the hydrogen from the heater 5 of the short recycle loop SRP and/or heater 7 of the long recycle loop LRP to compress the hydrogen and output the hydrogen to the conversion unit 11 (CVRT) via the conversion unit feed conduit 9a positioned between the compression system 9 and the conversion unit 11. The conversion unit 11 can process the hydrogen gas from the long recycle loop LRP and/or the combination of the hydrogen gas from the short recycle loop SRP and the long recycle loop LRP to convert parahydrogen to orthohydrogen so that a parahydrogen content of the hydrogen gas output from the conversion unit 11 has a parahydrogen content of no more than 25 mol % or no more than 30 mol % (e.g. between 20 mol % and 30 mol % parahydrogen and between 80 mol % and 70 mol % orthohydrogen, etc.). The hydrogen gas having the modified parahydrogen content can be output from the conversion unit 11 for feeding to a feed conduit through which the feed of hydrogen 15 can pass for being fed to the feed inlet of the liquefaction unit. A conversion unit supply conduit 11a can be connected between the liquefaction unit 2 and the conversion unit 11 to feed the hydrogen output from the conversion unit to the liquefaction unit.

In some implementations, the hydrogen being recycled may initially be provided via at least one storage tank of the hydrogen storage 4 and can subsequently be provided entirely via the short recycle loop SRP such that the recycled hydrogen bypasses being fed to storage 4 during such recycling after an initial providing of hydrogen from storage 4 occurs. In other implementations, the hydrogen being recycled can initially be provided via at least one storage tank of the hydrogen storage 4 as well as the routing of liquid hydrogen output from the liquefaction unit to the short recycle loop SRP. After a sufficient amount of hydrogen is provided for recycling, the recycling of hydrogen can be subsequently provided entirely via the short recycle loop SRP such that the recycled hydrogen bypasses being fed to storage 4 during such recycling after an initial providing of hydrogen from storage 4 occurs. In yet other implementations, a short recycle loop SRP may not be provided and only the long recycle loop LRP may be utilized for recycling of the hydrogen.

In embodiments that may utilize both the short recycle loop SRP and the long recycle loop LRP, the heater 5 of the short recycle loop SRP can be considered a first recycle loop heater of a first recycle loop and the heater 7 of the long recycle loop LRP can be considered a second heater of a second recycle loop. Alternatively, the heater 7 of the long recycle loop LRP can be considered a first heater of a first recycle loop and the heater 5 of the short recycle loop SRP can be considered a second recycle loop heater of a second recycle loop. Each heater can help heat hydrogen output from the liquefaction unit 2 (e.g. soon after being output or after the hydrogen is stored in hydrogen storage 4) so that gaseous hydrogen is feedable to the conversion unit 11 for the recycling of the hydrogen.

Embodiments of the apparatus 1 can be configured for use in conjunction with an open loop refrigeration system OLP of the liquefaction unit 2. the open loop refrigeration system OLP can include the liquefaction unit outputting at least one first stream of hydrogen 23 that may be at a lower pressure for feeding to the compression system for being compressed by at least one low pressure compressor of the compressions system 9. The liquefaction unit 2 can also output one or more second streams of hydrogen 25 that can each be at a pressure higher than a pressure of the first stream of hydrogen 23 for feeding to the compression system 9 for being compressed therein and subsequently being fed back to the liquefaction unit for use in refrigeration that is to occur during liquefaction as well. The utilization of the compression system 9 for the refrigeration system can be provided to facilitate an open loop refrigeration scheme in which hydrogen can be used as a refrigerant. The compressed hydrogen to be used as a refrigerant in the open loop refrigeration system OLP can be output from the compression system 9 for feeding to the liquefaction unit heat exchangers as a refrigerant via at least one refrigerant feed conduit 9b connected between the compression system 9 and the refrigeration system of the liquefaction unit 2.

At least one storage tank of the hydrogen storage 4 can be fluidly connected to the refrigeration system of the liquefaction unit 2 to provide hydrogen as a refrigerant as well. For example, a hydrogen refrigerant feed conduit 21 can be connected between the storage tank of the hydrogen storage 4 and the refrigeration system of the liquefaction unit 2 to feed hydrogen from the hydrogen storage 4 to the refrigeration system of the liquefaction unit 2.

The apparatus 1 can also be configured to facilitate venting via at least one vent conduit VT. For example, in situations where hydrogen that has been output from the liquefaction unit 2 fails to meet a pre-selected hydrogen content specification, the hydrogen can be vented. Such venting may occur downstream of at least one heater (e.g. heater 5 of the short recycle loop SRP, heater 7 of the long recycle loop LRP, an ambient air heater of the venting conduit, etc.) so that the vented hydrogen is warmed to a suitable venting temperature for venting to the external atmosphere in some embodiments.

In some embodiments, the liquefaction unit 2 can be configured to output more than one stream of liquid hydrogen. For example, the liquefaction unit 2 can output a first stream of liquid hydrogen 2a as well as a second stream 2b of liquid hydrogen. These streams of liquid hydrogen can be mixed together via a mixing device (e.g. inline mixer, mixing vessel, etc.) in some embodiments for feeding to the short recycle loop SRP or to hydrogen storage 4.

Some embodiments can utilize a phase separation system PS for providing liquid hydrogen to storage 4 and/or the short recycle loop SRP and returning hydrogen gas that may be output from the liquefaction unit 2 back to the liquefaction unit 2 for use as a refrigerant in the refrigeration system and/or for returning to the liquefaction unit for being liquified. For example, the phase separation system PS can output a hydrogen gas stream 3c for providing to the liquefaction unit via a hydrogen gas return conduit connected between the phase separation system PS and the liquefaction unit 2. In some embodiments, a portion of the liquid hydrogen output from the phase separation system PS for feeding to hydrogen storage 4 can be returned to the phase separation system PS for use as a refrigerant or to otherwise assist in the phase separation processing via a phase separation conduit 3d connected between the phase separation system and the liquid hydrogen storage feed conduit 3a.

The phase separation system PS can be positioned to facilitate Joule-Thomson cooling of liquid hydrogen via pressure reduction in some embodiments. Partial flashed cold vapor (e.g. hydrogen gas) that may be formed can be output as the hydrogen gas stream 3c and sent to an open loop refrigeration system, for example. Alternatively, the hydrogen vapor can be routed from the phase separation system to the compression system 9 as a low pressure hydrogen vapor stream LPV for being recycled back to the feed inlet of the liquefaction unit 2 or the refrigeration system of the liquefaction unit 2 via the compression system 9.

In some embodiments, at least one trailer 8 can be connected to the long recycle loop LRP. The trailer 8 can be positioned to receive hydrogen from storage for supplying the hydrogen to another site. The trailer (TRLR) can alternatively include hydrogen gas and be positioned to feed hydrogen to a recycle loop in the event makeup hydrogen is needed and there is an insufficient supply of liquid hydrogen in hydrogen storage 4 to provide for recycling to the liquefaction unit 2 to provide sufficient hydrogen makeup to account for the decreased flow of the feed of hydrogen 15 that may actuate recycling of hydrogen. For example, the trailer 8 can be in fluid connection with the short recycle loop SRP or the long recycle loop LRP for providing hydrogen for feeding the hydrogen to the conversion unit 11 for adjustment of the parahydrogen and orthohydrogen content of the hydrogen to be recycled to a feed inlet of the liquefaction unit 2.

FIG. 2 illustrates an exemplary implementation of the apparatus 1 shown in FIG. 1. The compression system 9 can include a first compressor C1 and a second compressor C2 and the hydrogen gas output from the liquefaction unit 2 as part of the open loop refrigeration system can include a first stream of hydrogen 23 that may be at a lower pressure for feeding to the compression system 9 for being compressed by a first compressor C1 of the compression and subsequently undergoing further compression via a second compressor C2 of the compression system 9. The liquefaction unit 2 can also output a second stream of hydrogen 25 that can at a pressure higher than the pressure of the first stream of hydrogen 23 for feeding to the second compressor C2 of the compression system 9 for being compressed therein and subsequently being fed back to the liquefaction unit for use in refrigeration that is to occur during liquefaction as well and/or the conversion unit 11 for recycling (in the event use of a recycling loop is utilized due to a low level of hydrogen feed being provided to the liquefaction unit 2).

As can be appreciated from the example implementation illustrated in FIG. 2, the apparatus 1 for recycling of hydrogen may not utilize a phase separation system PS. First and second streams of liquid hydrogen 2a, 2b can be output from the liquefaction unit 2 and subsequently merged to be fed to hydrogen storage 4 via the liquid hydrogen storage feed conduit 3a. In response to a feed rate of hydrogen decreasing, at least some of this liquid hydrogen can also be routed to a short recycle loop via the recycle loop conduit heater feed conduit 5a that can be connected to the liquid hydrogen storage feed conduit 3a and/or can be connected between the liquefaction unit 2 and the heater 5 of the recycle loop conduit heater feed conduit 5a.

In other configurations, the short recycle loop SRP may not be provided. Instead, only a long recycle loop LRP may be utilized. In such an embodiment, liquid hydrogen from at least one storage tank of the hydrogen storage 4 can output hydrogen for feeding to the conversion unit via the long recycle loop LRP conduit arrangement. Hydrogen from at least one trailer 8, may also be utilized to help provide a stream of hydrogen to the liquefaction unit for recycling of the hydrogen to support operation of the liquefaction unit while the feed of hydrogen to be provided by the hydrogen production system 20 is too low or is non-existent.

As may best be seen from the example implementation shown in FIG. 3, the compression system 9 can include a first compressor C1 as a low pressure compressor, a second compressor C2 as an intermediate pressure compressor, and a third compressor C3 as a high pressure compressor. Such a configuration may be utilized for a high pressure liquefaction unit 2 that can utilize high, low, and intermediate pressure refrigeration elements of its refrigeration system for liquefaction of hydrogen. The liquefaction unit 2 can output a first stream of hydrogen 23 that may be at a lower pressure for feeding to the compression system 9 for being compressed by a first compressor C1 of the compression and subsequently undergoing further compression via the second compressor C2 and the third compressor C3 of the compression system 9. The liquefaction unit 2 can also output a second stream of hydrogen 25 that can at an intermediate pressure that is higher than the pressure of the first stream of hydrogen 23 for feeding to the second compressor C2 of the compression system 9 for being compressed therein and subsequently being compressed by the third compressor C3 for subsequently being fed back to the liquefaction unit for use in refrigeration that is to occur during liquefaction as well and/or the conversion unit 11 for recycling (in the event use of a recycling loop is utilized due to a low level of hydrogen feed being provided to the liquefaction unit 2). Another second stream of hydrogen 25 can be output from the refrigeration system of the liquefier 2 that can at a high pressure that is higher than the pressure of the first stream of hydrogen 23 and also higher than the intermediate pressure of the other second stream of hydrogen 25 for feeding to the third compressor C3 of the compression system 9 for being compressed therein for subsequently being fed back to the liquefaction unit for use in refrigeration that is to occur during liquefaction as well and/or the conversion unit 11 for recycling (in the event use of a recycling loop is utilized due to a low level of hydrogen feed being provided to the liquefaction unit 2).

The phase separation system PS can include a phase separator PH and a subcooler 3 (SC). In other embodiments, the phase separation system may only include a single phase separator PH or may include only a subcooler 3 without use of an upstream phase separator.

For example, the liquefaction unit can output a liquid hydrogen stream that also includes hydrogen gas (e.g. between 3 volume percent (vol %) hydrogen gas and 10 vol % hydrogen gas, between 5 vol % hydrogen gas and 25 vol % hydrogen gas, between greater than 0 vol % gas and 40 vol % gas, etc.). The liquid hydrogen stream that also includes hydrogen gas can be fed to the phase separation system PS so that it is passed through a phase separator PH and a significant amount of the hydrogen gas can be separated from the liquid hydrogen and returned to the liquefier unit 2 via a vapor return conduit 2v connected between the liquefaction unit 2 and the phase separator PH. This hydrogen vapor can be returned to the liquefaction unit as a low pressure hydrogen vapor stream LPV for being recycled back to the feed inlet of the liquefaction unit 2 or for being fed to the refrigeration system of the liquefaction unit via feeding of this stream to the compression system 9 for being routed to the inlet of the liquefaction unit 2, for example. Such routing can occur when the apparatus has insufficient feed of hydrogen from the hydrogen generation system and can also occur while the feed of hydrogen from the hydrogen production system 20 is at or above a pre-selected feed rate for normal operation of the liquefaction unit without recycling of the hydrogen.

The mostly liquid hydrogen (e.g. at least 95 vol % liquid hydrogen) or entirely liquid hydrogen can be output from the phase separator PH for feeding to a subcooler 3 via a phase separator output conduit 3b connected between the phase separator PH and the subcooler 3. Additional hydrogen gas may be output from the subcooler 3 as a hydrogen gas stream 3c for providing to the liquefaction unit via a hydrogen gas return conduit connected between the subcooler 3 and the liquefaction unit 2. As noted above, such a flow of hydrogen gas can be fed to a refrigeration system of the liquefaction unit or can be routed back to the liquefaction unit as a low pressure hydrogen vapor stream LPV for being recycled back to the feed inlet of the liquefaction unit 2 (e.g. by being fed to the compression system 9 for subsequently being fed to the feed inlet of the liquefaction unit 2 or the refrigeration system of the liquefaction unit 2). Such routing can occur when the apparatus has insufficient feed of hydrogen from the hydrogen generation system, for example. Such routing can also occur when the apparatus has a sufficient feed of hydrogen form the hydrogen production system 20 that is at or above a pre-selected feed rate for normal operation of the liquefaction unit without recycling of the hydrogen.

The cooled liquid hydrogen can be output from the subcooler 3 for being fed toward hydrogen storage 4 and/or the short recycle loop SRP via a subcooler output conduit connected between the subcooler 3 and the liquid hydrogen storage feed conduit 3a. A portion of the liquid hydrogen passing through the hydrogen storage feed conduit 3a can be returned to the subcooler 3 via the phase separation conduit 3d connected between the phase separation system and the liquid hydrogen storage feed conduit 3a to facilitate subcooling of the hydrogen.

As may be appreciated from FIGS. 4-6, embodiments of the apparatus 1 for hydrogen recycling can also be utilized in conjunction with liquefaction units 2 that may utilize a closed loop refrigeration system CLP. Such a closed loop refrigeration system CLP may have a dedicated closed loop compressor 31 (CP) to help drive a flow of refrigerant in a closed loop arrangement for liquefaction of the hydrogen. In such a configuration, the liquefaction unit 2 may not receive hydrogen from hydrogen storage 4 and/or a compressor of a recycle conduit through which other hydrogen may also pass as refrigerant for the refrigeration system. Instead, the utilized refrigerant for the refrigeration system of the liquefaction unit can be provided in a close loop arrangement.

In such a closed loop refrigeration system environment, the recycling conduit arrangement for hydrogen recycling can utilize a different compression system arrangement. For example, there can be a compressor 41 positioned upstream of the conversion unit 11 to compress hydrogen for feeding to the conversion unit 11 and subsequently being recycled to the feed inlet of the liquefaction unit 2. As another example, there can be a compressor 43 that is positioned downstream of the heater 7 through which hydrogen from at least one storage tank of the hydrogen storage 4 may pass for being heated for recycling to the feed inlet of the liquefaction unit 2 via the conversion unit 11. In embodiments that may utilize multiple such compressors, the compressor 43 can be a low pressure compressor LC and additional compressor 41 downstream of this compressor can be a higher pressure compressor (HC) that can further compress the hydrogen to a second higher pressure for being recycled (e.g. a high pressure or a moderate pressure).

In yet other arrangements, the feed conduit for the feed of hydrogen 15 being supplied to the liquefaction unit 2 can include a feed compressor. In such a configuration, the excess capacity of the feed compressor that may exist due to the decreased feed of hydrogen from the hydrogen production system 20 can be utilized to help drive the flow of the hydrogen being recycled via the short recycle loop SRP and/or the long recycle loop LRP.

In some exemplary implementations such as the exemplary implementation shown in FIG. 5, a low pressure compressor LC can be utilized downstream of a heater 7 for receipt of hydrogen from hydrogen storage 4 and/or at least one trailer 8 for feeding to the conversion unit 11 for recycling of the hydrogen to the liquefaction unit 2. The recycle loop conduit heater output conduit 7a can be connected between the recycle loop conduit heater 7 and the compressor 43 to feed the hydrogen to the compressor for being output for feeding to the conversion unit 11 via a conversion unit feed conduit 9a positioned between the compressor 43 and the conversion unit 11.

Hydrogen that may be recycled via a short recycle loop SRP can be output from the heater 5 of the conduit arrangement for that loop and fed to the conversion unit 11 via a conduit connection between the heater 5 and the conversion unit feed conduit 9a so that the vaporized hydrogen stream 5b output from the heater 5 can be routing to the conversion unit 11.

In other exemplary implementations such as the exemplary implementation of FIG. 6, the higher pressure compressor HC can be positioned to receive hydrogen from the short recycle loop SRP and/or the long recycle loop LRP via the compression feed conduit 7b that can be connected between this compressor 41 and the heater 5 of the short recycle loop SRP and/or the heater 7 of the long recycle loop LRP. In such a configuration, the higher pressure compressor HC can be positioned as a compressor system 9 similar to positioning of the compression system 9 in the open loop refrigeration embodiment of FIG. 1 (but without receipt of hydrogen stream(s) from the refrigeration system of the liquefaction unit 2 for compression of those streams).

As noted above, the different exemplary embodiments and implementations of the apparatus 1 can be configured to provide recycling of hydrogen in response to a feed of hydrogen 15 being provided to the liquefaction unit 2 for liquefaction of the hydrogen decreasing below a pre-selected feed rate (e.g. a pre-selected volumetric flow rate defining a threshold for actuation of the hydrogen recycling, a pre-selected mass flow rate defining a threshold for actuation of the hydrogen recycling, etc.). The recycling of the hydrogen can be actuated to help avoid shutting down of the liquefaction unit 2 in response to low feed rate conditions so that production delays associated with a liquefaction unit shutdown and subsequent start-up can be avoided as well as avoiding equipment degradation that can occur as a result of such operations that involve cycling between an activated operational condition and a shutdown operational condition.

As shown in FIGS. 1-6, A controller CTRL can be provided to detect such a condition for actuation of hydrogen recycling via one or more sensors that can be positioned to monitor or measure a flow of the feed of hydrogen 15 at a position 15a upstream of where a recycle flow may be fed to the inlet of the liquefaction unit 2 via the conversion unit supply conduit 11a and/or a flow of the feed of hydrogen at the inlet 15b of the liquefaction unit 2. The one or more sensors can be flow sensors and/or pressure sensors, for example. The controller CTRL can be communicatively connected to the sensors to receive data from the sensors to determine whether the feed of hydrogen is at or below a pre-selected threshold for actuation of the recycling of hydrogen. The controller CTRL may also, or alternatively, receive data from one or more sensors or other element of the hydrogen production system 20 that can provide input indicating when the feed of hydrogen may decrease to the pre-selected threshold for actuation of the recycling of hydrogen.

The controller CTRL can also be communicatively connected to one or more sensors positioned to monitor or measure a flow of liquid hydrogen output from the liquefaction unit 2 for use in controlling valves V for actuation of the recycling of hydrogen to the inlet of the liquefaction unit. The controller can utilize such flow data to communicate with valves of one or more recycle loops for recycling of an appropriate portion of the liquid hydrogen to account for the lack of sufficient feed of hydrogen being provided by the hydrogen production system 20. Valves V can be dynamically adjusted to account for changing feed of hydrogen 15 conditions so that the portion of hydrogen being recycled can be adjusted from no recycling of hydrogen to a full recycling of output hydrogen to account for the detected flow rate of the feed of hydrogen 15 being provided by the hydrogen production system 20.

The controller CTRL can be a computer device that includes a processor connected to non-transitory memory and at least one transceiver. The controller CTRL can also be communicatively connected to valves to actuate valve adjustment for the recycling of the hydrogen.

The controller CTRL can be configured to respond to the determination that the feed of hydrogen is too low (e.g. is decreasing below a pre-selected feed rate, is decreasing below a pre-selected feed rate and may be at that lower rate for at least a pre-selected hydrogen recycling time period, etc.) by communicating with different valves V to adjust the flow of hydrogen output from the liquefaction unit 2 for passing through the short recycle loop SRP and/or the long recycle path LRP. Such a configuration of the controller CTRL can be implemented via automated process control logic that is defined in code of the non-transitory memory of the controller that can be executed by the processor of the controller.

For example, in some embodiments, the controller CTRL can communicate with a valve V of the liquid hydrogen storage feed conduit 3a to close this valve V and open a valve V of the recycle loop conduit heater feed conduit 5a that is connected between the liquefaction unit 2 and the recycle loop conduit heater 5 to initiate the recycling of hydrogen output from the liquefaction unit to the conversion unit 11 for the hydrogen to be recycled back to the feed inlet for the liquefaction unit with a decreased parahydrogen content. The controller CTRL can also communicate with a valve V of the storage tank recycle conduit 4c positioned between the hydrogen storage 4 and the heater 7 to open this valve V to supply hydrogen from hydrogen storage 4 to the conversion unit 11 for the hydrogen to be recycled back to the feed inlet for the liquefaction unit with a decreased parahydrogen content. The controller CTRL can also communicate with a valve V of the conversion unit supply conduit 11a to open this valve V to facilitate the feeding of hydrogen to the feed inlet of the liquefaction unit for recycling of the hydrogen after the parahydrogen content of the hydrogen is adjusted via the conversion unit 11. After a sufficient amount of hydrogen is provided from the storage tank 4 to make up for the decreased amount of hydrogen that is being received from the hydrogen production system 20, the controller CTRL can communicate with the valve V of the storage tank recycle conduit 4c to close that valve V such that the short recycle loop SRP can then be exclusively used for recycling of the hydrogen until the feed of hydrogen from the hydrogen production system 20 is increased to a desired level.

In other arrangements in which a short recycle loop SRP may not be provided, the controller CTRL can communicate with the valve V of the storage tank recycle conduit 4c positioned between the hydrogen storage 4 and the heater 7 to open this valve V to supply hydrogen from hydrogen storage 4 to the conversion unit 11 for the hydrogen to be recycled back to the feed inlet for the liquefaction unit with a decreased parahydrogen content. The controller CTRL can also communicate with a valve V of the conversion unit supply conduit 11a to open this valve V to facilitate the feeding of hydrogen to the feed inlet of the liquefaction unit for recycling of the hydrogen after the parahydrogen content of the hydrogen is adjusted via the conversion unit 11. The controller CTRL can communicate with the valve V of the storage tank recycle conduit 4c to close that valve V and also communicate with the valve V of the conversion unit supply conduit 11a to close that valve V after the feed of hydrogen from the hydrogen production system 20 is increased to a desired level to facilitate cessation of the recycling of hydrogen as well.

In yet other arrangements in which a long recycle loop LRP may not be utilized, the controller CTRL can communicate with a valve of the liquid hydrogen storage feed conduit 3a to close this valve V and open a valve V of the recycle loop conduit heater feed conduit 5a that is connected between the liquefaction unit 2 and the recycle loop conduit heater 5 to initiate the recycling of hydrogen output from the liquefaction unit to the conversion unit 11 for the hydrogen to be recycled back to the feed inlet for the liquefaction unit with a decreased parahydrogen content. The controller CTRL can communicate with the valve V of the recycle loop conduit heater feed conduit 5a to close that valve V and also communicate with the valve V of the conversion unit supply conduit 11a to close that valve V after the feed of hydrogen from the hydrogen production system 20 is increased to a desired level to facilitate cessation of the recycling of hydrogen as well.

The controller CTRL can communicate with the different valves to adjust their position to a more or less open position and/or closed position to account for the flow rate of the feed of hydrogen 15 being provided by the hydrogen production system 20 and how that flow rate compares to a pre-selected minimum threshold flow rate. In a situation where there is no feed of hydrogen, the valve(s) V for recycling of hydrogen can be fully opened, for example to provide a recycle flow of hydrogen to provide a makeup for the lack of the feed of hydrogen form the hydrogen production system 20. In a situation where the feed of hydrogen is present, but significantly below the pre-selected minimum threshold flow rate, the valve(s) for recycling of hydrogen may be partially opened (but less opened as compared to when there is no feed of hydrogen being provided), but not necessarily in a full opened position, to provide a recycle flow of hydrogen that can provide a makeup flow of hydrogen to account for the deviation from the pre-selected minimum threshold flow rate. In a situation where the feed of hydrogen is only slightly below the pre-selected minimum threshold flow rate the valve(s) for recycling of hydrogen may be partially open to a lesser extent to provide a recycle flow of hydrogen that can provide a makeup for this slight deviation from the pre-selected minimum threshold flow rate.

We have also surprisingly found that utilization of the short recycle loop SRP and the long recycle loop LRP can provide some other benefits. For example, during starting up of a liquefaction unit that is initially at ambient temperature, the long recycle loop LRP can provide pure hydrogen for use in the cooling down of the liquefaction unit equipment and the short recycle loop SRP can be utilized to help speed up cooling of the liquefaction equipment of the liquefaction unit 2. This type of approach for cooling of liquefaction unit upon start-up of operation of the liquefaction unit can permit such cooling to occur without venting or with minimal venting (e.g. due to lack of impurities in the hydrogen utilized to facilitate the cooling of the liquefaction unit 2).

Embodiments of the apparatus 1 can provide flexibility in operation in response to turndowns or other low hydrogen production situations. For example, the liquefaction unit 2 can be kept at cryogenic temperatures via use of the apparatus 1 for recycling of hydrogen via the long recycle loop LRP and/or the short recycle loop SRP to avoid the liquefaction unit 2 having to be shutdown. This type of operation can occur even when no feed of hydrogen may be present to allow the liquefaction unit to be quickly transitioned for processing hydrogen when production of hydrogen via the hydrogen production system is increased due to an increase in available power or other situation without significant lags in operation that may affect yield or production efficiency.

Embodiments can be configured so that the liquefaction unit can utilize minimal power or relatively low power when recycling of hydrogen is being utilized. For example, spare capacity of refrigeration compressors can be utilized to help run the liquefaction unit while the feed of hydrogen from the production system 20 is low and can also re-compress the liquid hydrogen when it is flashed to near atmospheric pressure to help keep the power draw for liquefaction operations low. This can occur while the recycling of the hydrogen can provide a heat load that can soak up the refrigeration produced by the operating liquefaction unit refrigeration system to allow the liquefaction unit 2 to maintain a cryogenic temperature with low feed (e.g. a feed of hydrogen from the hydrogen generation system (HGS) that is below a pre-selected minimum flow rate or a pre-selected minimum threshold flow rate) or no feed of hydrogen from the hydrogen production system 20.

Referring to FIG. 7, a process for recycling of hydrogen is illustrated. Embodiments of the apparatus 1 can be implemented and operated to utilize an embodiment of this process.

For example, in a first step S1, a feed of hydrogen from a hydrogen production system 20 can be determined to be below a pre-selected threshold (e.g. a feed of hydrogen that is 30% of a pre-selected feed rate of hydrogen that is to be provided to the liquefaction unit, a feed of hydrogen that is 20% of a pre-selected feed rate of hydrogen that is to be provided to the liquefaction unit 2, etc.). This feed of hydrogen can be a feed of hydrogen that is being passed to a liquefaction unit 2 to liquify the hydrogen. A controller CTRL may make such a determination as discussed above, for example. Such a determination can be based on sensor data or other data related to production of the hydrogen and feeding of that hydrogen to the liquefaction unit 2.

In a second step S2, a flow of liquid hydrogen output from the liquefaction unit 2 can be adjusted to recycle the hydrogen to the feed inlet of the liquefaction unit. The recycling can occur so that the hydrogen undergoes a parahydrogen to orthohydrogen conversion to decrease the parahydrogen content of the hydrogen being recycled as discussed above. The recycling can occur via a first recycle loop and/or a second recycle loop as discussed above (e.g. use of only a short recycle loop SRP, use of only a long recycle loop LRP, utilization of both loops, etc.). The recycling of the hydrogen can be actuated and controlled so that the amount of recycled hydrogen provides a sufficient makeup flow of hydrogen to account for the deviation between the flow of the feed of hydrogen being provided by the hydrogen production system 20 and the pre-selected minimum threshold. For example, as the flow rate of hydrogen from the hydrogen production system 20 may increase (but still be below the pre-selected minimum threshold), the recycling of hydrogen can be adjusted to account such changes as discussed above via controls of one or more valves, compressor operation, or other parameters. Similarly, as the flow rate of hydrogen from the hydrogen production system 20 may decrease (e.g. to a flow rate that is further below the pre-selected minimum threshold), the recycling of hydrogen can be adjusted to account such changes as discussed above via controls of one or more valves, compressor operation, or other parameters.

In a third step S3, the feed of hydrogen can be determined to be at or above a pre-selected threshold such that recycling of hydrogen is no longer warranted. In response to such a detection, the recycling of hydrogen can be stopped. Examples of such cessation of hydrogen recycling can be appreciated from the above. A controller CTRL can be utilized to actuate such a cessation of recycling of hydrogen as noted above, for example.

The process may then return to the first step S1 when the feed of hydrogen may again decrease below the pre-selected threshold. This processing may occur multiple times a week or more often in some embodiments in which hydrogen production is powered by renewable power sources such as solar power and/or wind power, for example.

The storage 4 for the liquid hydrogen can be positioned to receive hydrogen from multiple different liquefaction units 2 or only a single unit. In embodiments in which the storage 4 can receive liquid hydrogen from multiple different liquefaction units, the hydrogen stored therein can be provided for recycling hydrogen to one or more of the different liquefaction units in response to the feed of the hydrogen being fed to a liquefaction unit decreasing to or below a pre-selected threshold.

Embodiments can provide flexibility in operation in response to turndowns or other low hydrogen production situations. For example, embodiments of the process can permit a liquefaction unit 2 to be kept at cryogenic temperatures via the recycling of hydrogen via a first recycle loop and/or a second recycle loop to avoid the liquefaction unit 2 having to be shutdown. This type of operation can occur even when no feed of hydrogen may be present to allow the liquefaction unit to be quickly transitioned for processing hydrogen when production of hydrogen via the hydrogen production system is increased due to an increase in available power or other situation without significant lags in operation that may affect yield or production efficiency.

Embodiments of the process can be implemented so that the liquefaction unit 2 can utilize minimal power or relatively low power when recycling of hydrogen is occurring as well. For example, spare capacity of refrigeration compressors can be utilized to help run the liquefaction unit while the feed of hydrogen from the production system is low and hydrogen recycling is occurring. This excess compression capacity can be utilized to help re-compress the liquid hydrogen when it is flashed to near atmospheric pressure to help keep the power draw for liquefaction operations low. This can occur while the recycling of the hydrogen can provide a heat load that can soak up the refrigeration produced by the operating liquefaction unit refrigeration system to allow the liquefaction unit 2 to maintain a cryogenic temperature with low feed or no feed of hydrogen from the hydrogen production system 20.

It should also be appreciated that modifications to embodiments of the apparatus 1 and process can also be made to meet a particular set of criteria for different embodiments of the apparatus or process. For instance, the arrangement of valves, sensors, piping, and other conduit elements (e.g., conduit connection mechanisms, tubing, seals, valves, etc.) for interconnecting different units of the apparatus for fluid communication of the flows of fluid between different elements can be arranged to meet a particular facility layout design that accounts for available area of the apparatus, sized equipment of the apparatus, a preferred type of automated process control scheme and/or distributed control scheme, and other design considerations. The size or type of the equipment can be modified to meet a particular set of design criteria as well.

As yet another example, it is contemplated that a particular feature described, either individually or as part of an embodiment, can be combined with other individually described features, or parts of other embodiments. The elements and acts of the various embodiments described herein can therefore be combined to provide further embodiments. Thus, while certain exemplary embodiments of the process, apparatus, system, and methods of making and using the same have been shown and described above, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.