Method and unit for the production of hydrogen from a hydrogen-rich feed gas

Abstract

The invention relates to a method and unit for the production of hydrogen from a hydrogen-rich feed gas. According to the invention, N adsorbers are used and, at intervals, each of said adsorbers follows a cycle comprising: an adsorption phase at a high cycle pressure (PH); and a regeneration phase, consisting of a depressurization step, an elution step at a low cycle pressure (PB) and a repressurization step. During the depressurization step: partial pressure balancing is performed between an adsorber at the start of the cocurrent depressurization and an adsorber in the repressurization step until the pressure of the adsorber at the start of the cocurrent depressurization reaches a partial balancing pressure (P partial ); and the flow exiting the adsorber undergoing cocurrent depressurization, which has a pressure lower than the partial balancing pressure (P partial ), is sent to the adsorbers in the elution step. In addition, at least one part of the flows exiting the adsorbers in the regeneration phase is recycled by compressing said part until the high cycle pressure (PH) is reached and supplying the adsorbers in adsorption with said recycled part. The invention is suitable for purifying hydrogen and for recovering hydrogen from a low-pressure fuel network.

1 - 8 . (canceled)  
   
   
       9 . A method for producing hydrogen comprising producing said hydrogen from a main hydrogen rich feed mixture with at least one adsorber, wherein said adsorbers each follow, with a time lag, a cycle, wherein said cycle comprises: 
 a) an adsorption phase operating substantially at a high cycle pressure;    b) a regeneration phase, wherein said regeneration phase comprises: 
 1) a depressurization step to a low cycle pressure, wherein said depressurization step comprises a cocurrent depressurization substep;  
 2) an elution step at said low cycle pressure, wherein said elution step comprises receiving in said adsorber all flows exiting said adsorber during said depressurization substep; and  
 3) a repressurization step to said high cycle pressure; and  
   c) a recycle phase comprising: 
 1) forming a recycled gas part by compressing at least part of the flow leaving said adsorber during said regeneration phase to said high cycle pressure; and  
 2) feeding said absorber in said adsorption phase with said recycled part.  
   
   
   
       10 . The method of  claim 9 , wherein said adsorption phase further comprises: 
 a) treating by adsorption said main feed mixture at substantially said high cycle pressure; and    b) treating by adsorption said recycled part at substantially said high cycle pressure.    
   
   
       11 . The method of  claim 9 , wherein said depressurization step further comprises a countercurrent depressurization substep, wherein: 
 a) said countercurrent substep occurs after said cocurrent substep; and    b) the flow leaving said adsorber at the start of said countercurrent substep is at least partially recycled.    
   
   
       12 . The method of  claim 9 , wherein the flow leaving said adsorber at the end of said elution step is at least partially recycled.  
   
   
       13 . The method of  claim 11 , wherein: 
 a) the flow leaving said adsorber during the first third of said countercurrent substep is at least partially recycled; and    b) the flow leaving said adsorber during the last two thirds of said elution step is at least partially recycled.    
   
   
       14 . The method of  claim 10 , wherein said adsorption phase further comprises treating by adsorption, at said high cycle pressure, at least one supplementary feed gas, wherein said supplementary feed gas treating occurs after the treating of said recycled part in said regeneration phase and wherein said supplementary feed gas comprises a hydrogen content less than that of said feed mixture and said recycled part.  
   
   
       15 . The method of  claim 10 , wherein said adsorption phase further comprises treating by adsorption, at said high cycle pressure, at least one supplementary feed gas, wherein said supplementary feed gas treating occurs prior to the treatment of the second feed gas and wherein said supplementary feed gas comprises: 
 a) a hydrogen content less than that of said feed mixture; and    b) a hydrogen content greater than that of said recycled part.    
   
   
       16 . The method of  claim 9 , further comprising mixing a fuel gas with said recycled part leaving said adsorber during said regeneration phase, wherein said fuel gas comprises a hydrogen content less than that of said feed mixture.  
   
   
       17 . An apparatus for producing hydrogen from a main hydrogen-rich feed mixture comprising: 
 a) a line for recycling at least one of the flows leaving at least one adsorber during the regeneration phase;    b) a recycling compressor;    c) a line for providing part of said feed mixture to said recycling line; and    d) wherein, said hydrogen is produced with a least one said adsorber wherein said adsorbers each follow, with a time lag, a cycle, wherein said cycle comprises: 
 1) an adsorption phase operating substantially at a high cycle pressure;  
 2) said regeneration phase, wherein said regeneration phase comprises: 
 i) a depressurization step to a low cycle pressure, wherein said depressurization step comprises a cocurrent depressurization substep;  
 ii) an elution step at said low cycle pressure, wherein said elution step comprises receiving in said adsorber all flows exiting said adsorber during said depressurization substep; and  
 iii) a repressurization step to said high cycle pressure; and  
 
 3) a recycle phase comprising: 
 i) forming a recycled gas part by compressing at least part of the flow leaving said adsorber during said regeneration phase to said high cycle pressure; and  
 ii) feeding said absorber in said adsorption phase with said recycled part.  
 
   
   
   
       18 . The apparatus of  claim 17 , wherein said adsorption phase further comprises: 
 a) treating by adsorption said main feed mixture at substantially said high cycle pressure; and    b) treating by adsorption said recycled part at substantially said high cycle pressure.    
   
   
       19 . The apparatus of  claim 17 , wherein said depressurization step further comprises a countercurrent depressurization substep, wherein: 
 a) said countercurrent substep occurs after said cocurrent substep; and    b) the flow leaving said adsorber at the start of said countercurrent substep is at least partially recycled.    
   
   
       20 . The apparatus of  claim 17 , wherein the flow leaving said adsorber at the end of said elution step is at least partially recycled.  
   
   
       21 . The apparatus of  claim 19 , wherein: 
 a) the flow leaving said adsorber during the first third of said countercurrent substep is at least partially recycled; and    b) the flow leaving said adsorber during the last two thirds of said elution step is at least partially recycled.    
   
   
       22 . The apparatus of  claim 18 , wherein said adsorption phase further comprises treating by adsorption, at said high cycle pressure, at least one supplementary feed gas, wherein said supplementary feed gas treating occurs after the treating of said recycled part in said regeneration phase and wherein said supplementary feed gas comprises a hydrogen content less than that of said feed mixture and said recycled part.  
   
   
       23 . The apparatus of  claim 18 , wherein said adsorption phase further comprises treating by adsorption, at said high cycle pressure, at least one supplementary feed gas, wherein said supplementary feed gas treating occurs prior to the treatment of the second feed gas and wherein said supplementary feed gas comprises: 
 a) a hydrogen content less than that of said feed mixture; and    b) a hydrogen content greater than that of said recycled part.    
   
   
       24 . The apparatus of  claim 17 , further comprising mixing a fuel gas with said recycled part leaving said adsorber during said regeneration phase, wherein said fuel gas comprises a hydrogen content less than that of said feed mixture.