Design and operation of a solar-driven thermogravimeter for high temperature kinetic analysis of solid-gas thermochemical reactions in controlled atmosphere

A novel solar-driven thermogravimeter has been developed for on-sun kinetic analysis of solid-gas thermochemical reactions at high temperature in controlled atmosphere. The proposed concept includes a cavity-type solar receiver and a separate tubular reaction chamber that aims at ensuring a reliable reaction temperature measurement during thermochemical processing while enabling on-line gas analysis. Other features include high temperature and heating rate capabilities (1600 °C, up to 150 K min−1), controlled atmosphere including reduced pressure or vacuum conditions or different flowing gas atmospheres, and precise measurement of mass variations (resolution of 10−5 g over the whole range, capacity 220 g). Since the available incident solar power absorbed by the reactor was determined by the size of the parabolic dish concentrator (about 1 kW), a thermal analysis was performed to design properly the cavity size for reaching the desired temperature level. Limestone calcination and ZnO thermal reduction were successfully performed to validate the set-up reliability. The temperature- and pressure-dependent drift was determined and corrected using the mass variation observed during the heating period of the reactant. The device was finally operated to investigate the kinetics of ZnO and SnO2 solar thermal dissociation.