System for hydrogen generation

Abstract

The present invention relates to an improvement in a system for the generation of hydrogen by contacting an aqueous solution of a metal hydride salt with a hydrogen generation catalyst. In particular, the present invention relates to the incorporation within the system of a recycle line of water condensed from the fluid product to the feed line to be contacted with the catalyst. The internal recycle line permits the use of a more concentrated solution of metal hydride as it is diluted by the recycle line prior to contact with the catalyst.

1 - 18 . (canceled)  
   
   
       19 . A method of generating hydrogen, comprising: 
 providing an aqueous composition containing at least one metal hydride;    contacting the metal hydride with a hydrogen generation catalyst to generate a fluid product stream comprising hydrogen, water and a metal salt; and    mixing at least part of the water of the fluid product stream with the metal hydride prior to contacting the metal hydride with the catalyst.    
   
   
       20 . The method of  claim 19 , wherein the metal hydride is provided in the form of an aqueous solution.  
   
   
       21 . The method of  claim 19 , further comprising separating the fluid product stream into a gaseous product comprising hydrogen and water vapor, and a liquid product comprising water and the metal salt.  
   
   
       22 . The method of  claim 21 , further comprising condensing water from the gaseous product recovering the condensed water.  
   
   
       23 . The method of  claim 22 , further comprising combining the condensed water with the metal hydride composition prior to contacting the metal hydride with the hydrogen generation catalyst.  
   
   
       24 . The method of  claim 22 , further comprising providing a pump for withdrawing the condensed water from a condensate recovery zone and introducing it into a mixing zone.  
   
   
       25 . The method of  claim 19 , further comprising withdrawing the aqueous composition containing a metal hydride from a fuel supply reservoir before contacting with the catalyst.  
   
   
       26 . The method of  claim 25 , wherein the withdrawing is conducted using a fuel pump.  
   
   
       27 . The method of  claim 26 , wherein the fuel pump is located upstream of a mixing zone for mixing at least part of the water of the fluid product stream with the aqueous composition containing a metal hydride.  
   
   
       28 . The method of  claim 27 , wherein the mixing zone is located in fluid communication with the fuel pump and the hydrogen generation catalyst.  
   
   
       29 . The method of  claim 28 , further comprising providing a valve upstream of the mixing zone and permitting alternative flow of the metal hydride composition and condensed water from a condensate zone into the mixing zone.  
   
   
       30 . The method of  claim 24 , wherein the concentration of metal hydride in the fuel supply reservoir is above the maximum solubility of the hydride and a portion thereof is in suspension.  
   
   
       31 . The method of  claim 30 , wherein sufficient condensed water is added to the mixing zone so that all of the metal hydride is in solution when it contacts the hydrogen generation catalyst.  
   
   
       32 . The method of  claim 30 , further comprising maintaining uniformity of the suspension.  
   
   
       33 . The method of  claim 19 , further comprising providing a sufficient amount of an alkaline stabilizing agent to the aqueous composition containing a metal hydride to provide a pH thereof at about 7.  
   
   
       34 . The method of  claim 33 , wherein the alkaline stabilizing agent is an hydroxide.  
   
   
       35 . The method of  claim 33 , wherein the cation portion of the alkaline stabilizing agent is the same as the cation portion of the metal hydride.  
   
   
       36 . The method of  claim 35 , wherein the cation is a sodium ion.  
   
   
       37 . The method of  claim 33 , wherein the alkaline stabilizing agent is sodium hydroxide and the metal hydride is sodium borohydride.  
   
   
       38 . The method of  claim 19 , further comprising providing a containment system for the catalyst.  
   
   
       39 . The method of  claim 38 , wherein the containment system comprises a cylinder having the catalyst therein.  
   
   
       40 . The method of  claim 19 , wherein the hydrogen generation catalyst comprises a transition metal selected from the group consisting of ruthenium, iron, cobalt, nickel, copper, manganese, rhodium, rhenium, platinum, palladium, chromium, silver, osmium, iridium, borides thereof, alloys thereof, and mixtures thereof.  
   
   
       41 . The method of  claim 19 , wherein the metal hydride is selected from the group consisting of sodium borohydride, lithium borohydride, potassium borohydride, ammonium borohydride, and mixtures thereof.  
   
   
       42 . The method of  claim 19 , wherein the catalyst is a supported catalyst.  
   
   
       43 . A method of generating hydrogen, comprising: 
 providing a fuel supply reservoir containing an aqueous solution of at least one metal hydride;    withdrawing the aqueous solution from the reservoir and contacting the aqueous solution with a hydrogen generation catalyst to generate a fluid product stream comprising hydrogen, water and a salt of the metal;    separating the fluid stream into a gaseous product comprising hydrogen and water vapor, and a liquid product comprising water and the metal salt;    recovering at least part of the water vapor to obtain recovered water; and    mixing the recovered water with the aqueous solution of metal hydride prior to contacting the catalyst.    
   
   
       44 . The method of  claim 43 , wherein mixing is conducted in a separate mixing zone prior to contacting the metal hydride with the hydrogen generation catalyst.  
   
   
       45 . The method of  claim 43 , wherein withdrawing the solution from said fuel supply reservoir is conducted with a fuel pump.  
   
   
       46 . The method of  claim 45 , wherein the fuel pump is located upstream of the mixing zone.  
   
   
       47 . The method of  claim 43 , wherein the mixing zone is located in fluid communication with the fuel pump and the hydrogen generation catalyst.  
   
   
       48 . The method of  claim 43 , further comprising providing a pump for withdrawing the recovered water from a recovery zone and introducing it into the mixing zone.  
   
   
       49 . The method of  claim 43 , further comprising providing a valve upstream of the mixing zone for permitting alternative flow of the metal hydride solution and the recovered water into the mixing zone.  
   
   
       50 . The method of  claim 43 , wherein the concentration of the metal hydride in the fuel supply reservoir is above the maximum solubility of the hydride and a portion thereof is in suspension.  
   
   
       51 . The method of  claim 50 , further comprising adding sufficient recovered water to the mixing zone so that all of the metal hydride is in solution when it contacts the hydrogen generation catalyst.  
   
   
       52 . The method of  claim 50 , further comprising agitating the fuel supply to maintain uniformity of the suspension.  
   
   
       53 . The method of  claim 50 , further comprising providing a sufficient amount of an alkaline stabilizing agent to the aqueous solution of metal hydride to provide a pH thereof at about 7.  
   
   
       54 . The method of  claim 53 , wherein the alkaline stabilizing agent is an hydroxide.  
   
   
       55 . The method of  claim 53 , wherein the cation portion of the alkaline stabilizing agent is the same as the cation portion of the metal hydride.  
   
   
       56 . The method of  claim 55 , wherein the cation is a sodium ion.  
   
   
       57 . The method of  claim 53 , wherein the alkaline stabilizing agent is sodium hydroxide and the metal hydride is sodium borohydride.  
   
   
       58 . The method of  claim 43 , further comprising providing a containment system for the catalyst.  
   
   
       59 . The method of  claim 58 , wherein the containment system comprises a cylinder having the catalyst therein.  
   
   
       60 . The method of  claim 43 , wherein the hydrogen generation catalyst comprises a transition metal selected from the group consisting of ruthenium, iron, cobalt, nickel, copper, manganese, rhodium, rhenium, platinum, palladium, chromium, silver, osmium, iridium, borides thereof, alloys thereof, and mixtures thereof.  
   
   
       61 . The method of  claim 43 , wherein the metal hydride is selected from the group consisting of sodium borohydride, lithium borohydride, potassium borohydride, ammonium borohydride, and mixtures thereof.  
   
   
       62 . The method of  claim 43 , wherein the catalyst is a supported catalyst.