Process for Producing Liquefied Hydrogen

Abstract

A process for liquefying hydrogen gas including the following is disclosed: cooling the hydrogen gas to an intermediate temperature by heat exchange with a refrigerant circulating in a refrigeration loop provided with a higher temperature expander and a lower temperature expander, wherein the outlet stream from the lower temperature expander contains some condensed refrigerant; a means is provided of separating the condensate from the circulating refrigerant; and further cooling of the hydrogen gas by heat exchange with evaporation and reheating of the said condensate. The fluid in the refrigeration loop is typically methane (such as natural gas after removal of carbon dioxide, water vapor and other impurities), or nitrogen, or a mixture thereof.

1 .- 13 . (canceled) 
     
     
         14 . A process for liquefying hydrogen gas, the process comprising:
 providing a stream of hydrogen feed gas;   providing a stream of recycled hydrogen gas at a pressure of from 1 bar to 50 bar;   admitting the stream of hydrogen feed gas and the stream of recycled hydrogen gas to a first hydrogen compressor, the first hydrogen compressor having a combined discharge stream with a pressure of between 10 bar and 200 bar;   cooling said combined discharge stream in a first hot passage of a first heat exchanger, said first hot passage having a first outlet stream;   cooling said first outlet stream in a second hot passage of a second heat exchanger, said second hot passage having a second outlet stream;   cooling said second outlet stream in a third hot passage of a third heat exchanger, said third hot passage having a third outlet stream;   passing the third outlet stream to a hydrogen liquefier unit comprising one or more hydrogen gas expanders, one or more further heat exchangers, and one or more stages of catalytic conversion of ortho-hydrogen to para-hydrogen;   the hydrogen liquefier unit having a first liquefier outlet stream of liquid hydrogen with a temperature of between −240° C. and −255° C. and a second liquefier outlet stream of gaseous hydrogen having a pressure between 1 bar and 20 bar;   reheating the stream of gaseous hydrogen in a first cold passage of the third heat exchanger to provide a first reheated outlet stream, then in a first cold passage of the second heat exchanger to provide a second reheated outlet stream, then in a first cold passage of the first heat exchanger to provide a third reheated outlet stream from the first heat exchanger to form a stream of recycled hydrogen gas;   providing a stream of refrigerant gas at a pressure of from 10 bar to 150 bar;   dividing the stream of refrigerant gas into first and second parts;   passing said first part to a first refrigerant gas expander to provide an outlet stream from said first refrigerant gas expander having a pressure between 5 bar and 50 bar;   reheating the first refrigerant gas expander outlet stream in a second cold passage of the first heat exchanger to form a reheated refrigerant gas stream;   compressing the reheated refrigerant gas stream in a second compressor to a pressure of from 10 to 150 bar to form a first constituent of the refrigerant gas;   passing the second part of the refrigerant gas to a second hot passage of the first heat exchanger to provide a cooled outlet stream;   passing said cooled outlet stream to a second refrigerant gas expander to provide an outlet stream from said second refrigerant gas expander having a pressure of between 3 bar and 50 bar and comprising a mixture of vapor and liquid;   separating the outlet stream of the second gas expander in a vapor/liquid separator to form a vapor stream and a liquid stream;   depressurizing said liquid stream in valve to form a depressurized stream with a pressure of between 0.5 bar and 10 bar;   evaporating and reheating said depressurized liquid stream in a second cold passage of third heat exchanger to form an outlet vapor stream;   compressing the outlet vapor stream to a same pressure as the pressure of the vapor stream from the vapor liquid separator by a low pressure refrigerant compressor having a compressor outlet stream;   combining the vapor stream and the compressor outlet stream to form a combined vapor stream;   reheating the combined vapor stream in the second cold passage of the second heat exchanger to form a third reheated outlet stream and then in a third cold passage of the first heat exchanger to form a fourth reheated outlet stream; and,   compressing the fourth reheated outlet stream in the second compressor to a pressure of from 10 to 150 bar to form a second constituent of the refrigerant gas.   
     
     
         15 . A process according to  claim 14  in which the combined discharge stream from the first compressor has a pressure of between 20 bar and 100 bar. 
     
     
         16 . A process according to  claim 14  in which the pressure of the depressurized stream is between 1 bar and 3 bar. 
     
     
         17 . A process according to  claim 14  in which the refrigerant gas is methane or a methane-rich gas. 
     
     
         18 . A process according to  claim 17  in which the pressure of the outlet stream from second gas expander is between 10 bar and 50 bar. 
     
     
         19 . A process according to  claim 14  in which the refrigerant gas is nitrogen. 
     
     
         20 . A process according to  claim 19  in which the pressure of the outlet stream from second gas expander is between 3 bar and 30 bar. 
     
     
         21 . A process according to  claim 14  in which the refrigerant gas is a mixture of methane and nitrogen. 
     
     
         22 . A process according to  claim 14  in which the refrigerant gas flowing in first refrigerant gas expander is methane or a methane-rich gas, while the cooled outlet stream flowing in the second refrigerant gas expander, in the separator, and the valve is nitrogen. 
     
     
         23 . A process according to  claim 14  in which the temperature the inlet stream of compressor is between −200° C. and 40° C. 
     
     
         24 . A process according to  claim 23 , in which the inlet stream to the first compressor is taken directly from the outlet stream of the hydrogen liquefier unit or from the outlet of the first cold passage of the third heat exchanger or the second heat exchanger. 
     
     
         25 . A process according to  claim 14 , further providing a stream of a second refrigerant gas at near-ambient temperature;
 cooling said second refrigerant gas stream in a third hot passage of the first heat exchanger to form a fourth outlet stream;   cooling said fourth outlet stream in a second hot passage of the second heat exchanger to form a fifth outlet stream;   cooling said fifth outlet stream in a second hot passage of the third heat exchanger to form a sixth outlet stream;   passing said sixth outlet stream into the hydrogen liquefaction unit, in which the sixth outlet stream passes through one or more stages of expansion to provide refrigeration, before leaving the liquefier unit as a seventh outlet stream;   reheating the seventh outlet stream in a third cold passage of the third heat exchanger to form an eighth outlet stream;   further reheating the eighth outlet stream in a third cold passage of the second heat exchanger to form a ninth stream;   further reheating the ninth outlet stream in a fourth cold passage of the first heat exchanger to form a tenth outlet stream; and,   recompressing the tenth outlet stream in a third compressor to form said second refrigerant gas stream.   
     
     
         26 . A process according to  claim 25  in which the said second part of the refrigerant gas is hydrogen, helium, or a mixture of hydrogen or helium with neon.