Process for precooling hydrogen for liquefaction with supplement liquid nitrogen

Abstract

A hydrogen feed stream is introduced into a primary refrigeration system of a precooling system and cooling the hydrogen stream to a first precooling temperature. From there, the precooled hydrogen stream is then introduced to a secondary refrigeration system of the precooling system and cooling the precooled hydrogen stream to a second temperature. Next, the cooled hydrogen stream is then liquefied in the liquefaction system to produce liquid hydrogen.

What is claimed is: 
     
         1 . A method for liquefaction of hydrogen in a hydrogen liquefaction unit, the method comprising the steps of:
 introducing a hydrogen stream into a precooling system under conditions effective for cooling the hydrogen stream to a temperature of between about 75K and about 100K, more preferably between about 80K and about 90K to produce a cooled hydrogen stream, wherein the precooling system comprises a primary refrigeration system and a secondary refrigeration system;   introducing the cooled hydrogen stream to a liquefaction system under conditions effective for liquefying the cooled hydrogen stream to produce liquid hydrogen; and   withdrawing the liquid hydrogen from the liquefaction system.   
     
     
         2 . The method as claimed in  claim 1 , wherein the hydrogen stream is sourced from a hydrogen generation unit. 
     
     
         3 . The method as claimed in  claim 1 , wherein the primary refrigeration system is configured to provide cooling within the precooling system to a first temperature between about 100K and about 120K. 
     
     
         4 . The method as claimed in  claim 3 , wherein the first temperature is within about 30K of a vaporization temperature of liquid nitrogen used within the secondary refrigeration system. 
     
     
         5 . The method as claimed in  claim 1 , wherein the primary refrigeration system uses refrigeration produced by a refrigerant selected from the group consisting of a hydrocarbon refrigerant, a mixed hydrocarbon refrigerant, nitrogen as part of a closed loop refrigeration cycle, argon, fluorocarbons, vaporization of liquid nitrogen, ammonia, and combinations thereof 
     
     
         6 . The method as claimed in  claim 1 , wherein the secondary refrigeration system is configured to provide cooling within the precooling system to a temperature of between about 75K and about 100K. 
     
     
         7 . The method as claimed in  claim 1 , wherein the secondary refrigeration system comprises vaporization of liquid nitrogen, wherein the liquid nitrogen is received from an air separation unit. 
     
     
         8 . The method as claimed in  claim 7 , wherein the vaporization of liquid nitrogen in the secondary refrigeration system occurs at a vaporization pressure that is less than a discharge pressure of a cold turbine used within the primary refrigeration system. 
     
     
         9 . The method as claimed in  claim 1 , further comprising the step of providing an air separation unit and a hydrogen generation unit, wherein the air separation unit is configured to produce an oxygen stream and a liquid nitrogen stream, wherein the air separation unit is in fluid communication with the hydrogen generation unit and the secondary refrigeration system, such that the air separation unit is configured to send the oxygen stream to the hydrogen generation unit and the liquid nitrogen to the secondary refrigeration system. 
     
     
         10 . The method as claimed in  claim 9 , wherein the liquid nitrogen has a flow rate between about 5% to about 50% of a flow rate of the oxygen stream sent to the hydrogen generation unit. 
     
     
         11 . The method as claimed in  claim 9 , further comprising recycling a vaporized nitrogen stream from the hydrogen liquefaction unit to the air separation unit. 
     
     
         12 . The method as claimed in  claim 9 , wherein the air separation unit comprises a high pressure feed air compressor. 
     
     
         13 . The method as claimed in  claim 12 , wherein the air separation unit is a GOK type air separation unit. 
     
     
         14 . A method for liquefaction of hydrogen in a hydrogen liquefaction unit, the method comprising the steps of:
 introducing a hydrogen stream into a precooling system under conditions effective for cooling the hydrogen stream to a temperature of between 100K and 75K, to produce a cooled hydrogen stream, wherein the precooling system comprises a primary refrigeration system and a secondary refrigeration system;   introducing the cooled hydrogen stream to a liquefaction system under conditions effective for liquefying the cooled hydrogen stream to produce liquid hydrogen; and   withdrawing the liquid hydrogen from the liquefaction system. wherein the primary refrigeration system comprises compression and expansion of a primary refrigerant with expansion outlet pressure of P 1  and a secondary refrigeration system comprises vaporization of liquid nitrogen at pressure P 2 . wherein the primary and secondary refrigerants are not in fluid communication.   
     
     
         15 . The method as claimed in 14 wherein P 1  is at least 0.5 bar greater than P 2 . 
     
     
         16 . The method as claimed in 14, further comprising the step of providing an air separation unit and a hydrogen generation unit, wherein the air separation unit is configured to produce an oxygen stream and a liquid nitrogen stream, wherein the air separation unit is in fluid communication with the hydrogen generation unit and the secondary refrigeration system, such that the air separation unit is configured to send the oxygen stream to the hydrogen generation unit and the liquid nitrogen to the secondary refrigeration system. 
     
     
         17 . The method as claimed in  claim 16 , wherein the liquid nitrogen has a flow rate of about 5% to about 50% of a flow rate of the oxygen stream sent to the hydrogen generation unit.