Process and apparatus for the recovery of boil-off gas from the liquefaction of hydrogen

A hydrogen boil-off gas recovery method, the method comprising the steps of:

• cooling a hydrogen feed stream at a first pressure in a first cryogenic cold box to form a cooled hydrogen stream;
• further cooling the cooled hydrogen stream in a second cryogenic cold box by using a hydrogen refrigeration cycle to refrigerate the second cryogenic cold box;
• liquefying the hydrogen in the second cryogenic cold box or downstream thereof;
• providing liquefied hydrogen to a storage or a loading bay containing at least one hydrogen transport truck;
• sending boil-off gas from at least one hydrogen transport truck in the loading bay to which liquefied hydrogen has been provided to an indirect heat exchanger outside the first and second cryogenic cold boxes in order to warm the boil-off gas;
• measuring the pressure of the boil-off gas and if the boil-off gas stream from at least one hydrogen transport truck is below a previously determined pressure;
• and
• warming at least part of the boil-off gas stream in a first heater and mixing the at least part of the boil-off gas with a hydrogen refrigeration cycle stream,
• wherein if the boil-off gas stream from at least one hydrogen transport truck is above a previously determined pressure, at least part of the boil off gas stream from at least one hydrogen transport truck is warmed in the first heater or in a second heater and mixed with a hydrogen feed stream upstream of the first cryogenic cold box.

A hydrogen liquefier and boil-off gas recovery apparatus, the apparatus comprising:

• a liquefier configured to liquefy hydrogen, the liquefier comprising:
• a first cryogenic cold box for cooling a hydrogen feed stream at a first pressure and a second cryogenic cold box for further cooling the hydrogen so as to liquefy the hydrogen in the second cryogenic cold box or downstream thereof;
• a loading bay containing at least one hydrogen transport truck;
• means for providing liquefied hydrogen to a storage or a loading bay containing at least one hydrogen transport truck;
• a hydrogen refrigeration cycle used to provide refrigeration for the second cryogenic cold box;
• means for detecting the pressure of a boil-off gas stream from at least one hydrogen transport truck;
• first and second heaters outside the first and second cryogenic cold boxes;
• a controller comprising:
• one or more processors;
• and
• memory coupled to the one or more processors, the memory storing instructions that, when executed by the one or more processors, cause the one or more processors collectively to perform operations comprising:
• determining if the detected pressure is below or above a previously determined pressure;
• sending the boil-off gas stream from at least one hydrogen transport truck to the first heater if the detected pressure is below the previously determined pressure;
• sending the boil-off stream warmed in the first heater to be mixed with the hydrogen refrigeration cycle and sending the boil-off gas stream from at least one hydrogen transport truck to the second heater if the detected pressure is above the previously determined pressure;
• and
• sending the boil-off stream warmed in the first heater to be mixed with a hydrogen feed stream upstream of the first cryogenic cold box.