Experimental study of solar reactors for carboreduction of zinc oxide

The reduction of zinc oxide (ZnO) with pure carbon has been studied in the temperature range of 1200-1500 degreesC for converting solar thermal power into chemical energy in the form of metallic zinc. An experimental solar facility was set up to test different types of reactors, including a tube-type reactor and a quartz-windowed reactor, both operating in a batch-processing mode. The capabilities of the experimental facility included a 20-kW solar thermal concentrating system; portable cavity-type solar receivers; cooling system for gas quenching and excessive heat rejecting; solar power control; measuring and data acquisition systems. Characterization tests, which were carried out under solar peak flux ranging from I to 2 MW m(-2), demonstrated the feasibility of operating the tubular and windowed reactors at elevated temperatures, up to 1400 degreesC. Heat transfer simulation of the thermochemical process involving a kinetic global model to describe the windowed reactor is presented. The aspects discussed are the heating rate of reactants, the spatial temperature distribution and the effect of heat losses on reactor performance. (C) 2003 Elsevier Ltd. All rights reserved.