Steam-carbon cell for hydrogen production

Abstract

This invention relates to high purity hydrogen production in a steam-carbon cell, which may be operated either in fuel cell mode thus generating electricity at the same time, or in electrolysis mode where the hydrogen production rate is augmented by an externally applied voltage. Introduction of a solid carbonaceous fuel at the anode eliminates the uphill barrier of the open circuit voltage for the reduction of H 2 O to hydrogen. This novel concept nearly doubles the conversion efficiency of conventional electrolysis and offers near-zero emissions. The improved efficiency would mean that nearly half the greenhouse gases and other pollutants are produced. The product stream from the anode compartment primarily consists of CO 2 and, hence, it is easier and cheaper to capture and mineralize the CO 2 .

1 . A system that produces hydrogen, the system comprising:
 an anode;   an anode compartment;   a solid oxide electrolyte that selectively transports oxygen ions; and   a cathode,   where the system uses a solid carbon-containing fuel,   where electrical current is generated by oxidation of the carbon-containing fuel,   where the oxygen and hydrogen are produced by dissociation of steam,   where steam is introduced proximate the cathode, and   where the carbon-containing fuel is introduced into the anode compartment.   
   
   
       2 . The system of  claim 1 , where there is sequestration of carbon dioxide achieved by an inorganic compound introduced into the anode compartment. 
   
   
       3 . The system of  claim 1 , where there is sequestration of CO 2  and SO 2  achieved by introducing into an anode compartment a gettering agent selected from a group consisting of calcium oxide, magnesium oxide, dolomite, olivine, serpentine, talc, mica, clay, and zeolite. 
   
   
       4 . The system of  claim 1 , where there is direct physical contact of a surface of the anode with the carbon-containing fuel. 
   
   
       5 . The system of  claim 1 , where there is direct physical contact of a surface of the cathode with the steam. 
   
   
       6 . The system of  claim 1 , where the oxidation of carbon-containing fuel is by lattice oxygen provided through the solid oxide electrolyte to the anode. 
   
   
       7 . The system of  claim 1 , where the oxidation of carbon-containing fuel is by lattice oxygen, the lattice oxygen being extracted from splitting the steam at the cathode surface, and where the lattice oxygen is provided through the solid oxide electrolyte to the anode. 
   
   
       8 . The system of  claim 1 , where the anode compartment comprises a fixed bed of carbon-fuel with no gas flow. 
   
   
       9 . The system of  claim 1 , where the anode compartment comprises a carbon-fuel containing bed agitated by gas flow. 
   
   
       10 . The system of  claim 1 , where the anode compartment comprises a carbon-fuel containing bed fluidized by gas flow. 
   
   
       11 . The system of  claim 1 , where there is a shell-and-tube type design, where there is a bed of pulverized carbon-containing material that is outside of the tube and in contact with the anode. 
   
   
       12 . The system of  claim 1 , where there is a shell-and-tube type design, where there is a bed of pulverized carbon-containing material that is inside of the tube and in contact with the anode. 
   
   
       13 . The system of  claim 1 , where there is a flat plate design with alternating compartments of carbon-fuel bed and steam flow space,
 where the compartments are separated by flat or corrugated ceramic membrane assemblies, and   where there is a bed of pulverized carbon-containing material that is in contact with the anode.   
   
   
       14 . The system of  claim 1 , where the system has an operating temperature in the range 500 to 1300 degrees Centigrade. 
   
   
       15 . The system of  claim 14 , where the operating temperature is in the range 600 to 1100 degrees Centigrade. 
   
   
       16 . The system of  claim 15 , where the operating temperature is in the range 700 to 1000 degrees Centigrade. 
   
   
       17 . The system of  claim 1 , where an external voltage is applied between the anode and cathode, the external voltage increasing the oxygen transport rate through the solid oxide electrolyte and driving a rate for hydrogen production higher. 
   
   
       18 . The system of  claim 1 , where the solid carbon-containing fuel is selected from a group consisting of pulverized coal, charcoal, peat, coke, char, petroleum coke, oil sand, tar sand, waste plastics, biomass, and carbon produced by pyrolysis of carbonaceous substance.