A 300 kW solar chemical pilot plant for the carbothermic production of zinc

In the framework of the EU-project SOLZINC, a 300-kW solar chemical pilot plant for the production of zinc by carbothermic reduction of ZnO was experimentally demonstrated in a beam-down solar tower concentrating facility of Casse grain optical configuration. The solar chemical reactor, featuring two cavities, of which the upper one is functioning as the solar absorber and the lower one as the reaction chamber containing a ZnO/C packed bed, was batch-operated in the 1300-1500 K range and yielded 50 kg/h of 95%-purity Zn. The measured energy conversion efficiency, i.e., the ratio of the reaction enthalpy change to the solar power input, was 30%. Zinc finds application as a fuel for Zn/air batteries and fuel cells, and can also react with water to form high-purity hydrogen. In either case, the chemical product is ZnO, which in turn is solar-recycled to Zn. The SOLZINC process provides an efficient thermochemical route for the storage and transportation of solar energy in the form of solar fuels.