Integration process principles for maximizing the boil off recovery on a h2 liquefier plant

Abstract

A method for recovering boil-off gas from a system including one or more liquefaction trains including transport trucks or loading bays, a gaseous hydrogen feed stream, a lower-temperature cold box, and a low-pressure hydrogen compressor. The method including collecting a boil-off gas stream from the transport trucks or loading bays, determining the pressure of the boil-off gas stream, and depending on the pressure, recycling the boo-off gas stream to predetermined destinations. Wherein the boil-off gas stream has either a low-pressure, having a pressure of less than 2 bara, or a medium-pressure, having a pressure equal to or greater than 2 bara.

What is claimed is: 
     
         1 . A method for recovering boil-off gas from a system comprising one or more liquefaction trains, the one or more liquefaction trains comprising:
 transport trucks or loading bays,   a gaseous hydrogen feed stream,   a lower-temperature cold box, and   a low-pressure hydrogen compressor;   
       the method comprising:
 collecting a boil-off gas stream from the transport trucks or loading bays, 
 determining the pressure of the boil-off gas stream, and 
 depending on the pressure, recycling the boil-off gas stream to predetermined destinations, 
 
       wherein the boil-off gas stream has either a low-pressure, having a pressure of less than 2 bara, or a medium-pressure, having a pressure equal to or greater than 2 bara. 
     
     
         2 . The method of  claim 1 , wherein at least a portion of the low-pressure boil-off gas stream is recycled to the lower-temperature cold box. 
     
     
         3 . The method of  claim 1 , wherein at least a portion of the low-pressure boil-off gas stream is recycled to the low-pressure hydrogen compressor. 
     
     
         4 . The method of  claim 1 , wherein at least a portion of the medium-pressure boil-off gas stream is recycled to the gaseous hydrogen feed stream, thereby forming a compressor feed stream. 
     
     
         5 . The method of  claim 4 , further comprising:
 a hydrogen generation unit configured to produce a gaseous hydrogen stream,   a hydrogen stream flow control valve, and   a first boil-off gas flow indicator,   
       wherein the first boil-off gas flow indicator detects the flowrate of medium-pressure boil-off gas stream, and sends a signal to the hydrogen stream flow control valve, thereby adjusting the flowrate of the gaseous hydrogen stream such that the flowrate of the compressor feed stream remains constant. 
     
     
         6 . The method of  claim 1 , further comprising a liquid hydrogen storage unit, wherein the liquid hydrogen storage unit provides liquid hydrogen to the transport trucks or loading bays and collecting a second boil-off gas stream from the liquid hydrogen storage unit and recycling the second boil-off gas stream to the lower-temperature cold box. 
     
     
         7 . The method of  claim 1 , wherein the boil-off gas is hydrogen. 
     
     
         8 . A method for recovering boil-off gas from a system comprising one or more liquefaction trains, the one or more liquefaction trains comprising:
 transport trucks or loading bays,   a gaseous hydrogen feed stream, and   a low-pressure hydrogen compressor;   
       the method comprising:
 collecting a boil-off gas stream from the transport trucks or loading bays, and 
 recycling at least a portion of the boil-off gas stream to either the low-pressure hydrogen compressor or the gaseous hydrogen feed stream, or both. 
 
     
     
         9 . The method of  claim 8 , further comprising a liquid hydrogen storage unit, and a lower-temperature cold boxy, wherein the liquid hydrogen storage unit provides liquid hydrogen to the transport trucks or loading bays and collecting a second boil-off gas stream from the liquid hydrogen storage unit and recycling the second boil-off gas stream to the lower-temperature cold box. 
     
     
         10 . The method of  claim 8 , wherein the boil-off gas is hydrogen.