Abstract
Mitigation of dilute methane in outdoor air is challenging because of its low concentration and high chemical stability. This study proposed a solar chimney-driven honeycomb photocatalytic reactor (SC-HPCR) to couple solar-induced buoyancy, methane transport, and photocatalytic oxidation. An HPCR coated with 18 g of Ag/ZnO was integrated into a SC and tested outdoors in Wuhan under natural solar irradiation. During the main operating period, the inlet methane concentration was approximately 15 to 25 ppm. A three-dimensional numerical model was developed to reveal the coupled airflow, heat transfer, methane diffusion, and reaction behavior inside the system. The results showed that solar radiation generated a non-uniform thermal response on the absorber wall and drove measurable passive airflow through the HPCR. During the main irradiation period, the methane photocatalytic efficiency was generally 8–14%, with transient peaks of 16–18%. The apparent rate constant of the overall reactor reached approximately 0.30 min−1. The maximum methane removal rate reached 105.70 μg/s, and the total methane removal was 1.395 g. Under the complete oxidation assumption, the corresponding operational climate credit was 113.35 g CO2-eq using GWP20 = 84. The numerical model reproduced the measured outlet air temperature and methane concentration with root mean square deviation (RMSD) values of 0.71% and 10.66%, respectively. A global area-normalized assessment further yielded an annual operational CO2-equivalent climate credit of 0.38–2.98 kg CO2 eq m−2·yr−1. The results provide an outdoor proof of concept for passive treatment of dilute methane in methane enriched air near emission sources.
Abstract by the authors, reproduced under the CC BY 4.0 licence. Original publication via the link below.