Nitric acid regeneration fuel cell systems

Abstract

Methods and systems for regenerating a fuel cell are disclosed, comprising sparging a catholyte liquid with a gaseous oxygen-containing flow stream. In addition, the gaseous byproducts in the catholyte can be collected and then converted to liquid forms for easy disposal. In some embodiments, the regeneration process comprises intermittently regenerating an oxidant flow stream, for example, based on detected conditions. In some embodiments, the regeneration process comprises switching between different modes of oxidant regeneration, for example, based on detected conditions.

What is claimed is: 
     
         1 . A nitric acid regeneration fuel cell system, comprising:
 an anode;   anode conduits fluidly connected to the anode,
 wherein the anode conduits comprises an inlet anode conduit for providing an anolyte flow stream to the anode, 
 wherein the anode conduits comprises an outlet anode conduit for delivering an anolyte effluent flow stream from the anode, 
 wherein the anolyte flow stream comprises a fuel for reacting at the anode; 
   a cathode;   cathode conduits fluidly connected to the cathode,
 wherein the cathode conduits comprises an inlet cathode conduit for providing a catholyte flow stream to the cathode, 
 wherein the cathode conduits comprises an outlet cathode conduit for delivering a catholyte effluent flow stream from the cathode, 
 wherein the catholyte flow stream comprises nitric acid for reacting at the cathode, 
 wherein the catholyte flow stream reacts at the cathode to yield gaseous nitrogen oxide in the catholyte effluent flow stream; 
   a regeneration conduit fluidly connected to the catholyte effluent flow stream,
 wherein the regeneration conduit is configured to deliver an oxygen-containing flow stream for bubbling through the catholyte effluent flow stream. 
   
     
     
         2 . A system as in  claim 1   a conduit fluidly connected to the catholyte effluent flow stream,
 wherein the conduit is configured to accept a portion of the gaseous nitrogen oxide in the catholyte effluent flow stream. 
   
     
     
         3 . A system as in  claim 1   a liquid oxidant reservoir fluidly connected to the conduit,
 wherein the liquid oxidant reservoir is configured to react with portions of the gaseous nitrogen oxide in the conduit. 
   
     
     
         4 . A system as in  claim 1   wherein the oxygen-containing flow stream is configured to contact and react with the gaseous nitrogen oxide of the catholyte effluent flow stream.   
     
     
         5 . A nitric acid regeneration fuel cell system, comprising:
 an anode;   anode conduits fluidly connected to the anode,
 wherein the anode conduits comprises an inlet anode conduit for providing an anolyte flow stream to the anode, 
 wherein the anode conduits comprises an outlet anode conduit for delivering an anolyte effluent flow stream from the anode, 
 wherein the anolyte flow stream comprises a fuel for reacting at the anode; 
   a cathode;   cathode conduits fluidly connected to the cathode,
 wherein the cathode conduits comprises an inlet cathode conduit for providing a catholyte flow stream to the cathode, 
 wherein the cathode conduits comprises an outlet cathode conduit for delivering a catholyte effluent flow stream from the cathode, 
 wherein the catholyte flow stream comprises nitric acid for reacting at the cathode, 
 wherein the catholyte flow stream reacts at the cathode to yield gaseous nitrogen oxide in the catholyte effluent flow stream; 
   a regeneration conduit fluidly connected to the catholyte effluent flow stream,
 wherein the regeneration conduit is configured to deliver an oxygen-containing flow stream for bubbling through the catholyte effluent flow stream, 
 wherein the oxygen-containing flow stream is configured to contact and react with the gaseous nitrogen oxide of the catholyte effluent flow stream. 
   
     
     
         6 . A system as in  claim 5   a conduit fluidly connected to the catholyte effluent flow stream.   
     
     
         7 . A system as in  claim 5   wherein the conduit is configured to accept a portion of the gaseous nitrogen oxide in the catholyte effluent flow stream.   
     
     
         8 . A system as in  claim 5   a liquid oxidant reservoir fluidly connected to the conduit.   
     
     
         9 . A system as in  claim 5   wherein the liquid oxidant reservoir is configured to react with portions of the gaseous nitrogen oxide in the conduit.   
     
     
         10 . A system as in  claim 5   wherein the oxygen-containing flow stream comprises air, and   wherein the oxidant reservoir comprises hydrogen peroxide.   
     
     
         11 . A system as in  claim 5   wherein the anolyte flow stream contacting and passing the anolyte.   
     
     
         12 . A system as in  claim 5   wherein the catholyte flow stream flowingly by the cathode.   
     
     
         13 . A system as in  claim 5   wherein the liquid oxidant reservoir reacts with the portion of the nitrogen oxide to yield nitric acid.   
     
     
         14 . A system as in  claim 5   wherein a portion of the anode conduits, the cathode conduits and the regeneration conduit comprise a microfluidic conduit disposed within a plate sandwiched between other plates.   
     
     
         15 . A system as in  claim 5   wherein the regeneration conduit is coupled to the outlet cathode conduit or a reservoir of the catholyte flow stream.   
     
     
         16 . A system as in  claim 5   wherein the regeneration conduit is coupled to the catholyte effluent flow stream through a porous element.   
     
     
         17 . A system as in  claim 5   wherein the regeneration conduit is coupled to the catholyte effluent flow stream through a membrane, wherein the membrane allows gaseous oxygen-containing flow stream to enter the catholyte effluent flow stream while preventing the liquid catholyte effluent flow stream from entering the oxygen-containing flow stream.   
     
     
         18 . A system as in  claim 5   further comprising a flow restrictor coupled to the catholyte effluent flow stream.   
     
     
         19 . A system as in  claim 5  further comprising a catholyte reservoir,
 wherein the catholyte reservoir is fluidly connected to the catholyte inlet conduit and the catholyte outlet conduit. 
 
     
     
         20 . A system as in  claim 5  further comprising a catholyte reservoir,
 wherein the catholyte flow stream forms a close-loop from the catholyte reservoir to the catholyte inlet conduit to the cathode to the catholyte outlet conduit and back to the catholyte reservoir.