Experimental Investigation of the Carbothermal Reduction of ZnO Using a Beam-Down, Gravity-Fed Solar Reactor

Abstract

Carbothermal reduction of ZnO with beech charcoal has been performed in a directly irradiated, beam-down, continuously gravity-fed, 10 kW solar thermochemical receiver–reactor using a high-flux solar simulator. Upon reaching mean cavity temperatures between 1113 and 1446 K, a mixture of ZnO powder and charcoal particles was fed continuously from hoppers into the axisymmetric reactor to create a moving reactant bed along the inclined ceramic reaction tiles. Product gases including zinc vapor exited through a centrally located outlet before passing through a condenser and then into a filter battery for collection. Solar thermochemical energy conversion efficiencies of up to 12.4% were recorded, with reactant conversion as high as 14%. Products collected from the reactor indicated acceptably high Zn content, with product yield exceeding 75% on average. Peak Zn production rates were as high as 0.135 mol/min for a total reactant feed rate of 1.5 g/s and a reaction temperature of 1435 K.