Hydrogen liquefaction system and hydrogen liquefaction method

A hydrogen liquefaction system, comprising:

• a hydrogen pipe, where gaseous hydrogen is introduced at a front end, heat exchange occurs in a first heat exchange unit leading to liquefaction of gaseous hydrogen into liquid hydrogen, and liquefied liquid hydrogen can be discharged at a rear end;
• a pre-cooling device formed between the front end of the hydrogen pipe and the first heat exchange unit, pre-cooling gaseous hydrogen;
• an oxygen pipe, where gaseous oxygen is introduced at a front end, heat exchange occurs in the pre-cooling device leading to liquefaction of gaseous oxygen into liquid oxygen, and liquefied liquid oxygen can be discharged at a rear end;
• and
• a heat exchange device, which is in thermal contact with the first heat exchange unit of the hydrogen pipe so as to perform heat exchange with the first heat exchange unit of the hydrogen pipe such that pre-cooled gaseous hydrogen can be liquefied into liquid hydrogen;
• wherein the pre-cooling device comprises:
• a heat exchange tank that uses low-temperature liquid nitrogen, or latent heat that is generated when liquid nitrogen is vaporized into gaseous nitrogen, to pre-cool gaseous hydrogen and liquefy gaseous oxygen into liquid oxygen, is formed to surround at least a part of the hydrogen pipe and the oxygen pipe so as to perform heat exchange with the hydrogen pipe and the oxygen pipe, and has an accommodation space therein so as to accommodate liquid nitrogen;
• a nitrogen circulating line that connects a lower side and an upper side of the heat exchange tank in a form of a closed loop, and performs heat exchange in a second heat exchange unit leading to liquefaction of gaseous nitrogen into liquid nitrogen such that liquid nitrogen can be supplied to the lower side of the heat exchange tank and gaseous nitrogen can be discharged to the upper side of the heat exchange tank;
• an oxygen liquefaction tank formed in the oxygen pipe in the accommodation space of the heat exchange tank, forming a liquefaction space where gaseous oxygen can be liquefied into liquid oxygen by heat exchange with liquid nitrogen that is accommodated in the accommodation space;
• a pressure regulator that regulates internal pressure of the accommodation space of the heat exchange tank and internal pressure of the liquefaction space of the oxygen liquefaction tank;
• a liquid nitrogen supply pipe formed to penetrate the upper side of the heat exchange tank and extend toward the lower side of the heat exchange tank in the accommodation space, supplying liquid nitrogen to the heat exchange tank from outside;
• an on-off valve formed in the liquid nitrogen supply pipe so as to control a supply amount of liquid nitrogen that is supplied through the liquid nitrogen supply pipe;
• and
• an Ortho-Para (O-P) converter formed in the hydrogen pipe in the accommodation space of the heat exchange tank, converting a ratio of ortho-hydrogen to para-hydrogen in a process of pre-cooling gaseous hydrogen;
• and
• wherein at least a part of the hydrogen pipe is formed in a spiral shape within the accommodation space so as to increase a thermal contact area in contact with liquid nitrogen that is accommodated in the accommodation space of the heat exchange tank, and
• the heat exchange device is in thermal contact with the second heat exchange unit of the nitrogen circulating line so as to perform heat exchange with the second heat exchange unit of the nitrogen circulating line leading to liquefaction of gaseous nitrogen into liquid nitrogen, and performs heat exchange with the first heat exchange unit of the hydrogen pipe and the second heat exchange unit of the nitrogen circulating line by a recuperative cycle and a regenerative cycle.

A hydrogen liquefaction method, comprising:

• (a) preparing a hydrogen pipe, where gaseous hydrogen is introduced at a front end, heat exchange occurs in a first heat exchange unit leading to liquefaction of gaseous hydrogen into liquid hydrogen, and liquefied liquid hydrogen can be discharged at a rear end;
• (b) preparing an oxygen pipe, where gaseous oxygen is introduced at a front end, heat exchange occurs in a pre-cooling device leading to liquefaction of gaseous oxygen into liquid oxygen, and liquefied liquid oxygen can be discharged at a rear end;
• (c) pre-cooling gaseous hydrogen between the front end of the hydrogen pipe and the first heat exchange unit by using the pre-cooling device, and liquefying gaseous oxygen into liquid oxygen;
• and
• (d) liquefying gaseous pre-cooled hydrogen, which is pre-cooled by performing heat exchange with the first heat exchange unit of the hydrogen pipe by using a heat exchange device that is in thermal contact with the first heat exchange unit of the hydrogen pipe, into liquid hydrogen.