Multi-Scale Modelling of a Solar Reactor for the High-Temperature Step of a Sulphur-Iodine-Based Water Splitting Cycle

Abstract

The 3-step sulphur-iodine-based thermochemical cycle for splitting water is considered. The high-temperature step consists of the evaporation, decomposition, and reduction of H 2 SO 4 to SO 2 using concentrated solar process heat. This step is followed by the Bunsen reaction and HI decomposition. The solar reactor concepts proposed are based on a shell-and-tube heat exchanger filled with catalytic packed beds and on a porous ceramic foam to directly absorb solar radiation and act as reaction site. The design, modeling, and optimization of the solar reactor using complex porous structures relies on the accurate determination of their effective heat and mass transport properties. Accordingly, a multi-scale approach is applied. Ceramic foam samples are scanned using highresolution X-ray tomography to obtain their exact 3D geometrical configuration, which in turn is used in direct porelevel simulations for the determination of the morphological and effective heat/mass transport properties. These are incorporated in a volume-averaged (continuum) model of the solar reactor. Model validation is accomplished by comparing numerically simulated and experimentally measured temperatures in a 1 kW reactor prototype tested in a solar furnace. The model is further applied to analyze the influence of foam properties, reactor geometry, and operational conditions on the reactor performance.

Sulphur based thermochemical cycles: Development and assessment of key components of the process

“…These effective transport properties have been incorporated in a continuum reactor model developed by spatial averaging the governing equation in the fluid and solid phases. The model yielded temperature, velocity, pressure and species distribution in the absorbing foam, as well as the energetic and chemical conversion efficiencies [15].…”

Modeling of a Solar Receiver for Superheating Sulfuric Acid

“…Foundations of the current analysis have also been completed as part of the predecessor European Union project HycycleS [20]. Previous work included modeling direct radiation and LTNE in a receiver-reactor [21] and coupling of continuum models with pore-scale property determination [22]. As well, thermodynamic analysis was validated against test results and used to provide suggestions for scaled-up designs [23].…”