Systems and methods for delivering hydrogen and separation of hydrogen from a carrier medium

Abstract

Methods and systems are provided for the transportation of hydrogen including the use of a carrier medium and the subsequent separation of the hydrogen from the carrier medium upon delivery of the mixed gas stream to a desired location. In one example, up to approximately 20% hydrogen (molar fraction) may be mixed with natural gas and transported through a natural gas pipeline. The hydrogen may be separated from the natural gas by liquefying the natural gas and separating the liquid and vapor components in a gas-liquid separator to form a natural gas stream and a hydrogen stream. One or both of the separated streams may be used in cooling of the mixed stream. Precompression and expansion pressure of the various streams may be used to influence the purity level of the hydrogen. Other constituents, or impurities, present in the mixed gas stream may also be removed as may be desired.

1 . A method of transporting hydrogen, the method comprising: 
 adding a volume of hydrogen to a volume of natural gas to form a mixed gas volume;    flowing the mixed gas volume as a mixed gas stream from a first location to a second location;    cooling the mixed gas stream and liquefying a substantial portion of the volume of natural gas;    substantially separating the liquefied natural gas from the volume of hydrogen to provide a natural gas stream and a hydrogen stream; and    using at least one of the natural gas stream and the hydrogen stream to cool the mixed gas stream.    
   
   
       2 . The method according to  claim 1 , further comprising compressing the mixed gas stream prior to cooling the mixed gas stream.  
   
   
       3 . The method according to  claim 2 , wherein compressing the mixed gas stream includes compressing the mixed gas stream to a pressure of approximately 300 pounds per square inch absolute or greater.  
   
   
       4 . The method according to  claim 2 , wherein cooling the mixed gas stream includes flowing the mixed gas stream sequentially through a first heat exchanger and a second heat exchanger.  
   
   
       5 . The method according to  claim 4 , wherein flowing the mixed gas stream through the first heat exchanger includes cooling the mixed gas stream to a temperature of approximately 60° F.  
   
   
       6 . The method according to  claim 5 , wherein flowing the mixed gas stream through the second heat exchanger includes cooling the mixed gas stream to a temperature of approximately −265° F.  
   
   
       7 . The method according to  claim 4 , wherein substantially separating the liquefied natural gas from the volume of hydrogen to provide a natural gas stream and a hydrogen stream includes flowing the mixed gas stream from the second heat exchanger into a gas-liquid separator.  
   
   
       8 . The method according to  claim 4 , wherein using at least one of the natural gas stream and the hydrogen stream to cool the mixed gas stream includes expanding at least one of the natural gas stream and the hydrogen stream and flowing the expanded stream through the second heat exchanger.  
   
   
       9 . The method according to  claim 4 , wherein using at least one of the natural gas stream and the hydrogen stream to cool the mixed gas stream includes expanding the natural gas stream, expanding the hydrogen stream, and flowing both the expanded natural gas stream and the expanded hydrogen stream through the second heat exchanger.  
   
   
       10 . The method according to  claim 9 , further comprising compressing the expanded natural gas stream.  
   
   
       11 . The method according to  claim 10 , further comprising compressing the expanded hydrogen stream.  
   
   
       12 . The method according to  claim 9 , further comprising controlling a purity of the hydrogen stream, at least in part, by selecting the pressure to which at least one of the hydrogen stream and the natural gas stream is expanded.  
   
   
       13 . The method according to  claim 12 , further comprising expanding the at least one of the hydrogen stream and the natural gas stream to a pressure of approximately 65 pounds per square inch absolute (psia) or lower.  
   
   
       14 . The method according to  claim 15 , further comprising controlling a purity of the hydrogen stream, at least in part, by selecting the pressure to which the mixed gas stream is compressed.  
   
   
       15 . The method according to  claim 1 , further comprising expanding at least one of the hydrogen stream and the natural gas stream and controlling a purity of the hydrogen stream, at least in part, by selecting the pressure to which the at least one of the hydrogen stream and the natural gas stream is expanded.  
   
   
       16 . The method according to  claim 15 , further comprising expanding the at least one of the hydrogen stream and the natural gas stream to a pressure of approximately 65 pounds per square inch absolute (psia) or lower.  
   
   
       17 . The method according to  claim 16 , further comprising compressing the mixed gas stream prior to cooling the mixed gas stream and controlling a purity of the hydrogen stream, at least in part, by selecting the pressure to which the mixed gas stream is compressed.  
   
   
       18 . The method according to  claim 1 , further comprising removing impurities from the natural gas.  
   
   
       19 . The method according to  claim 18 , wherein removing impurities from the natural gas further includes removing water from the natural gas.  
   
   
       20 . The method according to  claim 19 , wherein removing water from the natural gas includes injecting methanol into the mixed gas stream, liquefying the water and methanol, and separating the water and methanol from the mixed gas stream.  
   
   
       21 . The method according to  claim 18 , wherein removing impurities from the natural gas includes removing carbon dioxide from the natural gas.  
   
   
       22 . The method according to  claim 21 , wherein removing carbon dioxide from the natural gas includes producing a slurry of solid carbon dioxide and natural gas and substantially separating the solid carbon dioxide from the natural gas.  
   
   
       23 . The method according to  claim 22 , further comprising subliming the solid carbon dioxide.  
   
   
       24 . The method according to  claim 1 , wherein adding a volume of hydrogen to a volume of natural gas to provide a mixed gas stream includes providing a mixed gas stream with up to approximately 20% molar fraction of hydrogen.  
   
   
       25 . A method of separating hydrogen from natural gas contained in a mixed gas stream, the method comprising: 
 cooling the mixed gas stream and liquefying a substantial portion of the volume of natural gas;    substantially separating the liquefied natural gas from the volume of hydrogen to provide a natural gas stream and a hydrogen stream; and    using at least one of the natural gas stream and the hydrogen stream to cool the mixed gas stream.    
   
   
       26 . The method according to  claim 25 , further comprising compressing the mixed gas stream prior to cooling the mixed gas stream.  
   
   
       27 . The method according to  claim 26 , wherein cooling the mixed gas stream includes flowing the mixed gas stream sequentially through a first heat exchanger and a second heat exchanger.  
   
   
       28 . The method according to  claim 27 , wherein using at least one of the natural gas stream and the hydrogen stream to cool the mixed gas stream includes expanding the natural gas stream, expanding the hydrogen stream, and flowing both the expanded natural gas stream and the expanded hydrogen stream through the second heat exchanger.  
   
   
       29 . The method according to  claim 28 , further comprising compressing the expanded natural gas stream.  
   
   
       30 . The method according to  claim 29 , further comprising compressing the expanded hydrogen stream.  
   
   
       31 . The method according to  claim 28 , further comprising controlling a purity of the hydrogen stream, at least in part, by selecting the pressure to which at least one of the hydrogen stream and the natural gas stream is expanded.  
   
   
       32 . The method according to  claim 31 , further comprising expanding the at least one of the hydrogen stream and the natural gas stream to a pressure of approximately 65 pounds per square inch absolute (psia) or lower.  
   
   
       33 . The method according to  claim 25 , further comprising expanding at least one of the hydrogen stream and the natural gas stream and controlling a purity of the hydrogen stream, at least in part, by selecting the pressure to which the at least one of the hydrogen stream and the natural gas stream is expanded.  
   
   
       34 . The method according to  claim 25 , further comprising compressing the mixed gas stream prior to cooling the mixed gas stream and controlling a purity of the hydrogen stream, at least in part, by selecting the pressure to which the mixed gas stream is compressed.  
   
   
       35 . The method according to  claim 25 , further comprising removing impurities from the natural gas.  
   
   
       36 . The method according to  claim 25 , wherein adding a volume of hydrogen to a volume of natural gas to provide a mixed gas stream includes providing a mixed gas stream with up to approximately 20% molar fraction of hydrogen.  
   
   
       37 . A system for separating hydrogen from natural gas contained in a mixed stream, the system comprising: 
 a first compressor;    a first heat exchanger;    a second heat exchanger;    a gas-liquid separator;    at least one expansion device;    a first flow path defined and configured to deliver a mixed gas stream sequentially through the first compressor, the second compressor, and into the gas-liquid separator; and    a second flow path defined and configured to deliver at least one of liquid natural gas and hydrogen gas from the gas liquid separator, through the at least one expansion device and through the second heat exchanger.    
   
   
       38 . The system of  claim 37 , wherein the second flow path is defined and configured to deliver liquid natural gas from the gas liquid separator, through a first expansion device of the at least one expansion device and through the second heat exchanger, and wherein the system further comprises a third flow path defined and configured to deliver hydrogen from the gas liquid separator, through a second expansion device of the at least one expansion device and through the second heat exchanger.  
   
   
       39 . The system of  claim 38 , wherein first and second expansion devices each include Joule-Thomson valves.  
   
   
       40 . The system of  claim 38 , further comprising a second compressor, and wherein the second flow path extends from the second heat exchanger to the second compressor.  
   
   
       41 . The system of  claim 40 , further comprising a third compressor, and wherein the third flow path extends from the second heat exchanger to the third compressor.  
   
   
       42 . The system of  claim 41 , further comprising a source of methanol coupled with the first flow path and configured to introduce a volume of methanol thereinto.  
   
   
       43 . The system of  claim 42 , further comprising a separating system coupled with the first flow path and configured to remove water and methanol from the mixed stream of gas at a location between the first heat exchanger and the gas-liquid separator.  
   
   
       44 . The system of  claim 43 , further comprising another separating system coupled with second flow path and configured to remove carbon dioxide from the liquid natural gas.