SOLAR CARBOTHERMIC PRODUCTION OF ZINC AND POWER PRODUCTION VIA A ZnO-Zn-CYCLIC PROCESS

摘要

The reduction of ZnO with a carbonaceous material using concentrated solar radiation as energy source is an innovative concept (1) for the storage of solar energy in Zn as a "solar fuel" prior to its use for the production of electricity in Zn-air fuel cells or of hydrogen by splitting water with Zn. In both cases ZnO is formed, which can be reprocessed to Zn in the solar plant, creating a cyclic process (2) for the production of metallic Zn as a commodity with drastically reduced CO{sub}2-emissions compared to conventional fossil-fuel based Zn-production. This paper gives an overview over the SOLZINC-project, in which we investigate the scientific and technological problems of scaling up this novel technology. Based on the small scale investigations a batch process (1 batch per day) using a concentrated beam down radiation heating the ZnO-C mixture has been selected for upscaling. The choosen furnace concept using concentrated solar irradiation to react ZnO and a solid carbon material to produce gaseous Zn has been further optimized on 5-10 kW scale. The necessary input data for upscaling have been generated. The results with respect to operation temperature requirements, overall reaction rates, choice of specific C-material for reduction and of construction materials of the furnace are used to design and build a pilot plant at a scale of several hundred kW. The use of Zn-dust as to be produced from the offgas of the solar reactor for mechanically rechargable Zinc-air fuel cells has been demonstrated.