Heat integration for generating carbon-neutral electricity

Abstract

Apparatus, means and methods of employing fuel cell power modules are disclosed for generating electricity by electrochemical conversion of hydrogen, which is provided by dehydrogenation of a liquid organic hydrogen carrier (LOHC) as a renewable fuel source. Also disclosed are fuel cell units that are energy balanced with a dehydrogenation unit, such that the fuel cell units are the sole source of heat for the dehydrogenation unit. Also disclosed are means of employing the liquid organic hydrogen carrier with carbon-neutral additives within improved fuel cells employing liquid heat transfer fluids and distribution means that efficiently repurpose generated heat to provide for overall net carbon-neutral and net zero carbon-based hydrogen emissions using the disclosed apparatus, means and methods.

What is claimed is: 
     
         1 . A method for operating a power module for generating electricity comprising:
 a) catalytically dehydrogenating a hydrogenated liquid organic hydrogen carrier (LOHC) to produce hydrogen by means of a dehydrogenation unit;   b) generating electricity by means of a fuel cell unit employing said hydrogen; and   c) redirecting heat generated by said fuel cell by means of thermal energy transfer employing a heat transfer fluid (HTF) in thermal communication with said dehydrogenation unit and said fuel cell unit;
 wherein said thermal energy produced by said fuel cell is the source of heat for operating said dehydrogenation unit. 
   
     
     
         2 . The method according to  claim 1 , further comprising:
 a) recovering thermal energy generated during a hydrogen electrochemical conversion reaction in said fuel cell unit by means of a first heat transfer fluid (first HTF) in thermal communication with said fuel cell unit; and   b) transferring said thermal energy to said dehydrogenation unit by means of said first HTF in thermal communication with said dehydrogenation unit;
 wherein said first HTF is circulated between said fuel cell and said dehydrogenation unit by means of a first HTF exchange loop; wherein said first HTF fluid exchange loop optionally includes a heat exchanger. 
   
     
     
         3 . The method according to  claim 2 , further comprising:
 a) recovering thermal energy generated during a hydrogen electrochemical conversion reaction within said fuel cell unit by means of a first heat transfer fluid (first HTF) in thermal communication with said fuel cell unit;   b) exchanging a portion of said thermal energy recovered by said first HTF with a second heat transfer fluid (second HTF) by means of said heat exchanger in fluid communication with said first HTF exchange loop and a second HTF exchange loop;
 wherein said second HTF is in thermal communication by means of a second HTF exchange loop with said dehydrogenation unit; wherein said first and said second HTF are in thermal communication with each other by means of said heat exchanger. 
   
     
     
         4 . The method according to  claim 3 , wherein said wherein said fuel cell unit is operated at a temperature higher than the temperature of said dehydrogenation unit. 
     
     
         5 . The method according to  claim 4 , wherein said fuel cell unit is operated within a temperature range of between 400 to 600° C.; and wherein said dehydrogenation unit is operated within a temperature range of between 250 to 450° C. 
     
     
         6 . The method according to  claim 2 , wherein at least 90% of said thermal energy recovered from said fuel cell unit is transferred to said dehydrogenation unit. 
     
     
         7 . The method according to  claim 5 , wherein said first HTF comprises a material that is a liquid within the fuel cell operating range and that maintains chemical stability at a temperature above said fuel cell unit operating temperature range. 
     
     
         8 . The method according to  claim 7 , wherein said second HTF comprises a material that is a liquid within the dehydrogenation unit operating temperature range and that maintains chemical stability at a temperature above said dehydrogenation unit operating temperature range. 
     
     
         9 . The method according to  claim 3 , further comprising:
 a) recovering thermal energy generated during said hydrogen electrochemical conversion reaction by means of said first HTF in thermal communication with a plurality of fuel cell elements located within said fuel cell unit;   b) exchanging said recovered thermal energy between said first HTF and said second HTF by means of said heat exchanger;   c) transferring at least a portion of said recovered thermal energy to said dehydrogenation reaction by means of said second HTF in thermal communication with a plurality of catalyst-containing vessels located within said dehydrogenation unit.   
     
     
         10 . The method according to  claim 9 , further comprising:
 a) circulating said first HTF in thermal contact with said plurality of said fuel cell elements by means of said first heat exchanger and optionally a first pump located either internally or externally to said fuel cell unit;   b) circulating said second HTF in thermal contact with said plurality of catalyst-containing vessels located within said dehydrogenation unit by means of a second heat exchanger and optionally a second pump located either internally or externally to said dehydrogenation unit.   
     
     
         11 . The method according to  claim 3 , wherein a portion of thermal energy contained in either of said first HTF or said second HTF is redirected by means of a feed preheater to heat or vaporize an incoming LOHC feed stream prior to injection into said dehydrogenation unit. 
     
     
         12 . The method according to  claim 1 , further comprising:
 a) supplying an LOHC feed to said dehydrogenation unit that is operating at a dehydrogenation temperature and generating hydrogen;   b) conditioning said generated hydrogen to recover a purified hydrogen feed;   c) supplying said purified hydrogen feed to said fuel cell unit for electrochemical conversion of said purified hydrogen feed to produce electricity;   d) recovering a hydrogen-containing exhaust stream from said fuel cell unit; wherein said hydrogen-containing exhaust stream comprises unreacted hydrogen and hydrocarbon contaminants;   e) recycling a portion of said hydrogen-containing exhaust stream by combination with said purified hydrogen feed; and   f) venting a portion of said hydrogen-containing exhaust stream to the atmosphere;
 wherein the LOHC feed to the dehydrogenation reactor comprises an amount of carbon-neutral carbon that is at least as great as the amount of carbon contained in said vented portion of the hydrogen-containing exhaust stream. 
   
     
     
         13 . The method according to  claim 12 , wherein labile hydrogen contained in said LOHC feed is selected from renewable sources, carbon-neutral sources, carbon-neutral carbon sources, blue or green hydrogen sources, or combinations thereof. 
     
     
         14 . The method according to  claim 12 , wherein said fuel cell unit comprises a plurality of fuel cell elements located adjacent to one another within said fuel cell unit; wherein said fuel cell elements are separated by means of one or more auxiliary plates selected from an air flow plate, a heat exchange plate, and a hydrogen flow plate, and combinations thereof. 
     
     
         15 . The method according to  claim 14 , wherein said airflow plate operates to heat incoming air or an oxygen-enriched gas using thermal energy supplied by said HTF; wherein said hydrogen flow plate operates to recover heat from unreacted hydrogen recovered by said fuel cell unit; and wherein said heat exchange plate operates to recover and redistribute heat generated by the fuel cell unit. 
     
     
         16 . The method according to  claim 14 , wherein said auxiliary plate is a combination of said air flow plate, said heat exchange plate and said hydrogen flow plate. 
     
     
         17 . The method according to either  claim 15  or  16  wherein said heat exchange plate and said auxiliary plate further operate to exchange thermal energy between said HTF and a portion of HTF circulated externally to said fuel cell unit. 
     
     
         18 . The method according to  claim 17 , wherein said heat exchange plate and said auxiliary plate further operate to exchange thermal energy between an external portion of said HTF and a portion of said HTF internal to said fuel cell unit. 
     
     
         19 . The method according to  claim 17 , wherein said heat exchange plate and said auxiliary plate further operate to facilitate the exchange of thermal energy between said outgoing HTF and at least a portion of HTF circulated through said dehydrogenation unit by means of a heat transfer loop in fluid communication between said fuel cell unit and said dehydrogenation unit. 
     
     
         20 . The method according to  claim 17 , wherein said exchange of thermal energy between said fuel cell unit and said dehydrogenation unit is achieved by means of a second HTF in thermal communication with said outgoing HTF employing a heat exchange unit capable of proportioning thermal energy between said outgoing HTF and said second HTF.