Study of the two-step W/WO3 solar to fuel conversion cycle for syngas production

This work proposes syngas production by utilizing the W/WO3 redox system in a solar-powered two-step thermochemical cycle. Three chemical reactions occur in two chambers of a solar concentrator. A high temperature reaction reduces WO3 powder to metallic tungsten in both the chambers. Subsequently, the temperature of the first chamber is lowered and H-2(g) is produced via re-oxidation of the tungsten powder using H2O(g). The temperature of the second chamber is simultaneously lowered to an intermediate temperature, and CO2(g) oxidizes the tungsten powder to generate CO(g). The gas streams coming out of the two chambers will be combined, resulting in syngas production. Complete thermodynamic and kinetic analyzes of the system are described in this paper. The W/WO3 redox cycle offers greater gravimetric fuel productivity compared to previously proposed systems, and the entire cycle can be operated in the solid phase. Conditions to prohibit tungsten volatilization and tungsten carbide formation are also outlined. (C) 2013 Elsevier B.V. All rights reserved.