A Receiver-Reactor for the Solar Thermal Dissociation of Zinc Oxide

Abstract

An improved engineering design of a solar chemical reactor for the thermal dissociation of ZnO at above 2000K is presented. It features a rotating cavity receiver lined with ZnO particles that are held by centrifugal force. With this arrangement, ZnO is directly exposed to concentrated solar radiation and serves simultaneously the functions of radiant absorber, chemical reactant, and thermal insulator. The multilayer cylindrical cavity is made of sintered ZnO tiles placed on top of a porous 80%Al2O3–20%SiO2 insulation and reinforced by a 95%Al2O3–5%Y2O3 ceramic matrix composite, providing mechanical, chemical, and thermal stability and a diffusion barrier for product gases. 3D computational fluid dynamics was employed to determine the optimal flow configuration for an aerodynamic protection of the quartz window against condensable Zn(g). Experimentation was carried out at PSI’s high-flux solar simulator with a 10kW reactor prototype subjected to mean radiative heat fluxes over the aperture exceeding 3000suns (peak 5880suns). The reactor was operated in a transient ablation mode with semicontinuous feed cycles of ZnO particles, characterized by a rate of heat transfer—predominantly by radiation—to the layer of ZnO particles undergoing endothermic dissociation that proceeded faster than the rate of heat transfer—predominantly by conduction—through the cavity walls.

CO2 reduction with Zn particles in a packed‐bed reactor

“…The ZnO particles were identical to those employed to study ZnO thermolysis in a solar chemical reactor, while the Zn particles were similar in size to products collected from the filter resulting from experimentation to thermolyze ZnO with concentrated solar irradiation. [4][5][6]30 The initial amount of Zn was 500 mg at Zn mass fractions of 67, 75, and 100 wt %. The composition of reacting flow was 25, 50, and 75% CO 2 -Ar and 100% CO 2 .…”

Syngas production from H2O and CO2 over Zn particles in a packed‐bed reactor

“…4,5 Solar Zn can also be produced via solar thermal electrolysis of ZnO, 6 and solar carbothermal reduction of ZnO. 7 The second, nonsolar step is the exothermic reaction of CO 2 and H 2 O with Zn, given as…”

Tomography-Based Determination of Effective Transport Properties for Reacting Porous Media

“…Of interest are packed-bed reactors for producing solar fuels, which make use of concentrated solar radiation as the energy source of process heat [1]. Examples of these high-temperature solar-driven processes are the thermal reduction of ZnO as part of a H 2 O-splitting cycle and the thermal gasification of carbonaceous material for producing syngas [2,3]. The design, optimization, and scale-up of packed-bed reactors require modeling the transport phenomena across porous media.…”