The Direct Carbon Fuel Cell: Application to the Efficient Production of Electric Power
John F. Cooper
Lawrence Livermore National Laboratory
Tuesday, March 12, 2002 10:15 am
Ben Bandy Conference Center
Center for Applied Energy Research
John F. Cooper, Nerine Cherepy and John Ziagos
Lawrence Livermore National Laboratory, L-352, Livermore CA 94550
We introduce a concept for efficient conversion of fossil fuels to electricity that involves the production of carbon from fossil fuels followed by its conversion in a high temperature fuel cell. The carbon/air fuel cell has the advantages of nearly zero entropy change and associated heat loss (allowing the theoretical conversion efficiency to be 100%). The activities of the elemental C fuel and CO2 product are invariant with the extent of reaction. This results in a constant and uniform cell EMF and makes possible the full utilization of the carbon in single pass. The total electrochemical efficiency (80% of the heat of combustion at 0.5-1 kW/m2) is among the highest of any fuel cell.
Carbons useful as fuels typically have a high degree of disorder on the nanometer scale. These are found naturally among carbons derived from coal, lignite and petroleum coke, from charred biomass, and from the products of low-temperature pyrolysis of hydrocarbons. Cell voltages are typically 0.8 V at current densities of 30-100 mA/cm2 at 750-800 °C in molten carbonate electrolytes, the range reflecting structural differences in the carbon. Total system efficiencies range from 67% HHV for methane (with parallel conversion of the hydrogen in a SOFC) to 80% for direct utilization of petroleum coke. The cost of pyrolyzing hydrocarbons by the furnace black process is $7/GJ-thermal. Carbon-rich products from the mechanical cleaning of coal, or from the pyrolysis of hydrocarbons extracted by solvents from coal, are intriguing possibilities for efficient and clean utilization of coal.
This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.
About the Speaker:
John F. Cooper received his BA in chemistry from Pomona College and was awarded a PhD degree from University of California at Berkeley, in Physical Chemistry in 1975. Currently, Dr. Cooper is Scientific Capability Leader for Electrochemistry and Corrosion in the Chemistry and Materials Science Directorate at Lawrence Livermore National Laboratory. For 25 years, he has specialized in electrochemical science and engineering with particular emphasis on fuel cells, fuel batteries and power generation using reactive metals such as zinc, aluminum, lithium and elemental carbon together with air-depolarized cathodes. He led the DOE National Program to develop novel metal-air batteries for electric vehicle propulsion. Other research interests include the processes for production of optical crystals for the Laser Program, processes for electrowinning of metals, and molten-salt and chemical-oxidant based processes for demilitarization and radioactive waste treatment. He is the author of 120+ publications concerning electrochemical and chemical processes.