Optical and experimental evaluation of a directly irradiated solar reactor for the catalytic dry reforming of methane

Dry reforming of methane is a process to produce syngas which is a major precursor for many chemicals and ultra-clean fuels. It is a CO₂-assisted process that leads to the conversion of CO₂ to higher-value products but is also a highly endothermic process that requires significant amounts of energy in the form of CO₂ emitting fuels. For these reasons, this study focused on the direct utilization of concentrated solar energy by irradiating the catalyst directly rather than via a heat transfer fluid or conductive heat transfer. In addition, it uniquely adopts a tubular reactor with transparent (quartz) walls configuration, which allows extending the length of the irradiated (hot) zone to control the residence time. The new reactor was designed using Monte-Carlo ray-tracing modeling and evaluated experimentally using a commercial Ni-based catalyst. In brief, the reacting gas mixture (CH₄:CO₂ − 5 %: 5 %) was fed into the reactor at weight gas hourly space velocities of around 17–58 l h⁻¹ g⁻¹ and three different temperature levels (550 °C, 650 °C, and 800 °C). Although the non-conventional mode of heating, the achieved methane conversions (∼93 % at 800 °C to ∼ 53 % at 550 °C) and H₂ / CO ratios (∼0.9 at 800 °C to ∼ 0.4 at 550 °C) were similar to literature studies with the same catalyst. At the same time, the quartz walls showed no degradation after more than 80 h of intermittent testing. On the other hand, the overall energy efficiency was estimated to be less than 1 %, considering the radiation intercepted by the reactor system. However, it rose to 5 % − 25 % when correcting for the actual amount of irradiance on the catalytic bed.

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Published in: Chemical Engineering Journal
License: http://creativecommons.org/licenses/by/4.0/
See article on publisher's website: https://dx.doi.org/10.1016/j.cej.2022.139190