| A new kind of receiver-reactor for high temperature solar furnaces is proposed. The reactor component, a crucible, is placed at the focal point of the concentrator. The receiver, a cavity, is a sphere concentric with the reactor with specularly reflecting inner walls. Reactor and aperture sizes are chosen so that virtually all the incoming radiation from the concentrator enters the cavity through the aperture and reaches the reactor directly. An analysis of the energy exchange among the surfaces is formulated and a simulation model is developed to calculate its collection efficiency and provide a tool for a parametric study and optimization of the design. A prototype is fabricated and experimentation is carried out to demonstrate its potential applicability and investigate practical problems associated with its use. It is found that, in contrast to conventional insulated cavity-receivers, it has an excellent thermal shock resistance and an extremely low thermal inertia.; The feasibility of producing light metals (aluminum, magnesium, and zinc) and metallic carbides (titanium carbide, silicon carbide, and calcium carbide) by carbothermic reduction of their metallic oxides, using solar energy as the sole source of high temperature process heat, is explored. The thermodynamics of each reaction is examined to determine the necessary operating temperatures. The experiments were conducted on the new receiver/reactor. The nature of the products was determined by x-ray powder diffraction and chemical analyses. It is found that the production of aluminum is hindered by the formation of two oxycarbides (Al{dollar}sb4{dollar}O{dollar}sb4{dollar}C and Al{dollar}sb2{dollar}OC) and a carbide (Al{dollar}sb4{dollar}C{dollar}sb3{dollar}). No carbides or other undesirable products were found from the production of magnesium and zinc. In general, in order to obtain the maximum metal yield it is necessary to rapidly condense the metal vapor before it recombines with carbon monoxide to form back the oxide. Titanium carbide and a lower titanium oxide (Ti{dollar}sb2{dollar}O{dollar}sb3{dollar}) were produced from the carburization of TiO{dollar}sb2{dollar}; silicon carbide and {dollar}alpha{dollar}-SiO{dollar}sb2{dollar} were obtained from the carburization of {dollar}beta{dollar}-SiO{dollar}sb2{dollar}; small amounts of calcium carbide were obtained from calcium oxide using calcium fluoride as a flux. |
