A hydrogen boil-off gas recovery method, comprises liquefying hydrogen by cooling a hydrogen feed stream in a first cryogenic cold box, further cooling the hydrogen in a second cryogenic cold box, liquefying the hydrogen in the second cryogenic cold box or downstream thereof, providing liquefied hydrogen 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 and mixing at least part of the warmed boil-off gas with the hydrogen feed stream upstream of the first cryogenic cold box or with hydrogen in a hydrogen refrigeration cycle used to provide refrigeration for the second cryogenic cold box as a function of the pressure of the boil-off gas.

A method of producing liquefied natural gas (LNG) is disclosed. A natural gas stream is provided from a supply of natural gas. The natural gas stream is compressed in at least two serially arranged compressors to a pressure of at least 2,000 psia to form a compressed natural gas stream. The compressed natural gas stream is cooled to form a cooled compressed natural gas stream. The cooled compressed natural gas stream is expanded in at least one work producing natural gas expander to a pressure that is less than 3,000 psia and no greater than the pressure to which the at least two serially arranged compressors compress the natural gas stream, to thereby form a chilled natural gas stream. The chilled natural gas stream is liquefied.

An apparatus and process for recycling hydrogen can be provided so that hydrogen is recycled during hydrogen liquefaction processing to account for an unexpected loss of feed of hydrogen so the recycled hydrogen can be provided to avoid liquefier operations having to be shut down. Embodiments can utilize a parahydrogen to ortho-hydrogen conversion unit to facilitate such recycling of hydrogen to avoid liquefaction processing problems in liquefaction of the recycled hydrogen included into the feed to account for the loss of fee hydrogen.