Thermal dissociation of compressed ZnO and SnO₂ powders in a moving‐front solar thermochemical reactor

Abstract

The high-temperature thermal dissociation reaction of ZnO and SnO 2 was investigated, as part of a two-step thermochemical water-splitting cycle for H 2 production. A lab-scale solar reactor (1 kW) was designed, built, and operated for continuous dissociation of volatile oxides under reduced pressure. In this reactor, compressed oxide powders placed in a vertical ceramic cavity are irradiated by highly concentrated solar energy. The reactor design allows moving the reaction front for achieving continuous reactant feeding. ZnO and SnO 2 thermal dissociations were successfully performed at about 1900 K, with the recovery of up to 50% of products as nanopowders with high specific surface area (in the range 20-60 m 2 /g) and with mass fractions of reduced species up to 48 wt % for Zn and 72 wt % for SnO. The performed O 2 measurements confirmed the kinetics of ZnO dissociation and gave an activation energy of 380 AE 16 kJ/mol, based on an ablation regime of the ZnO surface.

A review on solar thermal syngas production via redox pair-based water/carbon dioxide splitting thermochemical cycles

“…In the other hand, a pressed cylinder of ZnO could be continuously advanced to the focal point from the back of the reactor. This is exactly the principle that the research group of PROMES has adopted in a recent study where they proposed, built and tested a "moving front" reactor suitable for both the SnO 2 /SnO and ZnO/Zn cycles [180]. The reactor (Fig.…”

“…Moving front solar reactors for the solar thermal dissociation of ZnO (or SnO 2 ): (a) the solar reactor of PSI/ETH tested and (b) its irradiation principle (from[179]); (c) schematic of the experimental setup of the solar reactor of PROMES; (d) photographs of ZnO oxide pellets before (left) and after (right) high-temperature heating in PROMES's solar reactor (from[180]). …”

Review of experimental investigation on directly irradiated particles solar reactors

“…As a part of the two-step thermochemical water splitting cycle the high-temperature thermal reaction of ZnO and SnO 2 was also investigated by Chambon et al [54] in a 1 kW solar fixed reactor. It was composed of a cylindrical water-cooled shell (depth: 76 mm, diameter: 88 mm) made of stainless steel.…”

“…Fixed solar reactor developed by Chambon et al[54] to investigate the high-temperature thermal reaction of ZnO and SnO 2 .…”

Radiative heat transfer analysis of a directly irradiated cavity-type solar thermochemical reactor by Monte-Carlo ray tracing

“…The reactant is located at the bottom of the reactor and it consists of an ascending rod made of stacked 5 mm thick oxide pellets. 8 The developed radiation model uses the Monte Carlo (MC) method and takes into account the radiative properties of the compressed oxide particles and of the alumina cavity walls, as well as the angular dependence of the intensity distribution of the incoming concentrated solar energy, which is calculated by the ray tracing code TONALLI. 9 In addition, the conduction heat transfer through the reactor walls and the chemical reaction are included into the model by using standard expressions.…”