Dry Redox Reforming with Concentrated Solar Energy
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Date
2024
Publication Type
Doctoral Thesis
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Abstract
This thesis investigates the CeO2-CH4-CO2 redox reforming cycle, a promising
approach for producing sustainable aviation fuel via a solar thermochemical
route. The cycle utilizes non-stoichiometric ceria (CeO2−δ) in a
two-step isothermal process: an endothermic methanothermal reduction and
an exothermic oxidation with CO2, producing syngas (H2, CO)—a precursor
for Fischer-Tropsch liquid fuels. Employing methane (from biogenic) sources
facilitates high reduction extents (δ >> 0.05) and low operating temperatures
(< 1000 °C). Thermodynamic analyses indicate higher non-stoichiometries
improve syngas selectivity. Experiments in a tubular reactor at 5% educt concentrations
show that a pellet sintered at 1100 °C and made with a cylindrical
pore former proves optimal for high CH4 conversion due to enhanced kinetics.
A computational fluid dynamics model (porousRedoxFoam), developed
within OpenFOAM, is designed to solve a system of reversible heterogeneous
reactions involving fluid flow over a fixed-bed of a non-stoichiometric solid
metal oxide. The model is experimentally validated and used in a design
optimization case study, suggesting flow rates of 10 Ln/min using 7–10
cm diameter tubes. Various operating strategies such as high-δ cycling,
counter-current, and cycle priming are modeled. The process is demonstrated
using a directly-irradiated solar reactor (10 kWth) at a solar tower
concentrating facility, where the solar-to-fuel efficiency reached 16.4%. In
closing, a continuous operating mode, co-feeding, is presented.
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ETH Zurich
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Subject
Solar energy; Concentrated solar energy; Solar fuel; Syngas; Dry reforming of methane; Redox reaction; Thermochemical redox cycle; Metal oxide; Thermodynamic modeling; Experimental testing; Reactor; Ceramic structure; Computational fluid dynamics (CFD); OpenFOAM; Heat and mass transfer; Experimental validation; Design optimization; Solar reactor; Scale-up; Pilot plant; On-sun performance
Organisational unit
03530 - Steinfeld, Aldo (emeritus) / Steinfeld, Aldo (emeritus)