The coal/Fe3O4 system for mixing of solar and fossil energies

The solar-driven endothermic reaction of coal and magnetite was studied for mixing solar and fossil energies. The overall reaction can be represented by CHx+Fe3O4 = CO + 3FeO + 1/2xH2, where x depends on the stoichiometry of the coal utilized (x≈0.2 in our study). Laboratory experimental studies with an equimolar mixture of anthracite coal and Fe3O4 powder using an infrared furnace showed rapid gas evolution above about 1473K and 1bar, producing FeO(s) and a gas mixture containing a CO/CO2 molar ratio at 4.5. Solar-driven experiments were conducted using a high-flux solar furnace. Pelleted samples were directly exposed for short time intervals to a solar flux irradiation of 300 W/cm2. The carbon content decreased rapidly after only 1 second exposure, suggesting efficient heat transfer and chemical conversion by direct absorption of concentrated solar energy at the reaction site. The proposed solar thermochemical process offers the possibility of performing simultaneously gasification of coal and reduction of iron oxide and also producing a fuel with an upgraded calorific value.