High Efficiency Direct Carbon and Hydrogen Fuel Cells for Fossil Fuel Power Generation

摘要

Hydrogen fuel cells have been under advanced development for a number of years andare now nearing commercial applications. Direct carbon fuel cells have, heretofore, not reachedpractical development because of difficulties in fuel and electrolyte configuration. Thecarbon/air fuel cell has the advantage of near zero entropy change allowing 100% theoreticalthermodynamic efficiency at temperatures to 1000°C. The activities of the C fuel and CO2product are invariant allowing constant EMF and full utilization of fuel in a single pass mode ofoperation. The hydrogen fuel cell has a theoretical thermodynamic efficiency of only 70% at1000°C and the activity of the H2 fuel and H2O product limit utilization to 80% in a single pass.A direct carbon fuel cell is currently being developed which utilizes clean reactive carbonparticulates in a molten carbonate salt slurry. Concentrated CO2 is evolved at the anode andoxygen from air is consumed at the cathode. At temperatures of 750°C to 850°C, a voltageefficiency of 80% has been achieved at a power density of 1Kw/sqM. The clean carbon andhydrogen fuel is produced from (1) natural gas, by thermal decomposition, (2) petroleum, bypyrolysis coking, (3) coal, by sequential hydrogasification and thermal pyrolysis, and (4)biomass, by sequential hydro- and thermal-pyrolysis, and are integrated with direct C and H2 fuelcells for power cycle estimates. Thermal to electric efficiencies indicate 80% (HHV), 85%(LHV) for petroleum, 75.5% (HHV), 83.4% (LHV) for natural gas and 68.3% (HHV), 70.8%(LHV) for lignite coal. The benefits of integrated combined carbon and hydrogen fuel cellpower generation cycles include, (1) more than twice the efficiency of conventional fossil fuelsteam plants, (2) reduced power generation cost, especially for increasing fossil fuel cost, (3)reduced CO2 emission by a factor of 2 or more, and (4) capability for direct sequestration orutilization of the concentrated CO2 from the direct carbon fuel cell effluent.