Process for Producing Liquefied Hydrogen

Abstract

A process for liquefying hydrogen gas comprising: cooling hydrogen gas to a temperature suitable for substantially complete conversion of its ortho-hydrogen content to para-hydrogen, passing the said cooled hydrogen over a catalyst which facilitates said substantially complete conversion of its ortho-hydrogen content to para-hydrogen, with provision of further cooling to remove the heat of reaction evolved, passing the resulting stream, essentially comprising para-hydrogen, in the form of a gas or vapour to an expander machine or turbine having an outlet stream consisting of vapor and liquid, separating the said outlet stream into vapor and liquid fractions, the liquid fraction constituting the liquefied hydrogen product of the process, and recycling the vapor fraction by means of one or more compressors having cryogenic inlet temperatures.

1 . A process for liquefying hydrogen gas comprising
 providing a first stream of pure hydrogen feed gas at a pressure of between 10 bar and 150 bar;   cooling the first stream in a hot passage of a first heat exchanger, having a first outlet stream with a temperature of between −150° C. and −210° C.;   admitting the first outlet stream to an assembly comprising a first catalyst for conversion of ortho-hydrogen to para-hydrogen with a second outlet stream and a second heat exchanger having a third outlet stream, the assembly comprising multiples of the first catalyst and the second heat exchanger, such that a composition of the third outlet stream is essentially para-hydrogen, with a temperature of between −210° C. and −250° C.;   providing a recycle stream of hydrogen having a composition essentially of para-hydrogen and having the same pressure as the third outlet stream;   combining the third outlet stream and the hydrogen recycle stream to form a combined stream;   admitting the combined stream to an expander machine having a fourth outlet stream with a pressure of between 10 bar and 1 bar and containing both liquid and vapor;   passing the fourth outlet stream to a vessel wherein a liquid fraction stream, comprising the liquid hydrogen product from the process, is separated from a vapor fraction stream;   providing the vessel with a catalyst which converts residual ortho-hydrogen in stream into para-hydrogen;   reheating the vapor fraction stream in a third heat exchanger to form a fifth outlet stream, having a temperature of between −100° C. and −240° C.;   admitting the fifth outlet stream to a compressor;   providing the compressor with a sixth outlet stream having a pressure between 10 bar and 150 bar; and,   cooling the sixth outlet stream in a fourth heat exchanger, having as a seventh outlet stream the hydrogen recycle stream.   
     
     
         2 . A process as claimed in  claim 1  in which the first catalyst in the assembly is incorporated in a hot passage of the second heat exchanger. 
     
     
         3 . A process as claimed in  claim 1 , wherein the expander machine is split into stages in series, whereby the third outlet stream streams and the hydrogen recycle stream are admitted at different pressures. 
     
     
         4 . A process as claimed in  claim 1 , wherein one or more additional heat exchangers are introduced between the stages of the expander machine. 
     
     
         5 . A process for liquefying hydrogen gas comprising
 providing a stream of pure hydrogen feed gas at a pressure of between 10 bar and 150 bar;   cooling the hydrogen feed gas stream stream in a hot passage of a first heat exchanger, having a first outlet stream with a temperature of between 0° C. to −150° C.;   further cooling the first outlet stream in a first hot passage of a second heat exchanger, having a second outlet stream with a temperature of between −150° C. and −210° C.;   admitting the second outlet stream to an assembly comprising a catalyst for conversion of ortho-hydrogen to para-hydrogen with a third outlet stream and a third heat exchanger provided with a first hot passage having a fourth outlet stream, the assembly comprising multiples of the catalyst and the third heat exchanger, such that the composition of the fourth outlet stream is essentially para-hydrogen, with a temperature of between −210° C. and −250° C.;   providing a hydrogen recycle stream having a composition essentially of para-hydrogen and having the same pressure as the fourth outlet stream;   combining the fourth outlet stream and the hydrogen recycle stream to form a hydrogen stream;   admitting the hydrogen stream to a first expander machine having a fifth outlet stream with a pressure of between 10 bar and 1 bar and containing both liquid and vapor;   passing the fifth outlet stream to a vessel wherein a liquid fraction stream, comprising a liquid hydrogen product from the process, is separated a vapor fraction stream;   providing the vessel with a catalyst which converts residual ortho-hydrogen in the fifth outlet stream into para-hydrogen;   reheating the vapor fraction stream successively in a first cold passage of the third heat exchanger to form a sixth outlet stream and in a first cold passage of the second heat exchanger to form a seventh outlet stream having a temperature of between −100° C. and −240° C.;   admitting the seventh outlet stream to a compressor as a first, lower pressure inlet stream;   providing a second stream of pure hydrogen gas having a composition essentially of para-hydrogen;   admitting the second hydrogen gas stream to the compressor as a second, higher pressure inlet stream;   providing the compressor with an eighth outlet stream having a pressure between 10 bar and 150 bar;   cooling the eighth outlet stream in a second hot passage of the second heat exchanger, having a ninth outlet stream and a same temperature as the second outlet stream;   dividing the ninth outlet stream into a tenth outlet stream and an eleventh outlet stream;   cooling the tenth outlet stream in a second hot passage of the third heat exchanger having as an outlet stream the hydrogen recycle stream;   passing the eleventh outlet stream to a second expander machine, having a twelfth outlet stream with a pressure of between 30 bar and 2 bar;   reheating the twelfth outlet stream successively in a second cold passage of the third heat exchanger to form a thirteenth outlet stream and in a second cold passage of the second heat exchanger to form the second, higher pressure inlet stream;   providing a first stream of refrigerant fluid [ 40 ], and passing the first refrigerant fluid stream [ 40 ]; through a cold passage of the first heat exchanger, having a fourteenth outlet stream; and,   providing a second refrigerant fluid stream, and passing said second refrigerant fluid stream through a third cold passage of the second heat exchanger [b], having a fifteenth outlet stream.