Flame bands: CO + O chemiluminescence as a measure of gas temperature

Carbon monoxide flame band emission (CO+O → CO2+hV) in CO2 microwave plasma is quantified by obtaining absolute calibrated emission spectra at various locations in the plasma afterglow while simultaneously measuring gas temperatures using rotational Raman scattering. Comparison of our results to literature reveals a contribution of O2 Schumann-Runge UV emission at T &gt; 1500 K. This UV component likely results from the collisional exchange of energy between CO2(1B) and O2. Limiting further analysis to T &lt; 1500 K, we demonstrate the utility of CO flame band emission by analyzing afterglows at different plasma conditions. We show that the highest energy efficiency for CO production coincides with an operating condition where very little heat has been lost to the environment prior to ∼3 cm downstream, while simultaneously, T ends up below the level required to effectively freeze in CO. This observation demonstrates that, in CO2 plasma conversion, optimizing for energy efficiency does not require a sophisticated downstream cooling method.</p

Post-plasma Quenching to Improve Conversion and Energy Efficiency in a CO2 Microwave Plasma

Transforming CO2 into value-added chemicals is crucial to realizing a carbon–neutral economy, and plasma-based conversion, a Power-2-X technology, offers a promising route to realizing an efficient and scalable process. This paper investigates the effects of post-plasma placement of a converging–diverging nozzle in a vortex-stabilized 2.45 GHz CO2 microwave plasma reactor to increase energy efficiency and conversion. The CDN leads to a 21% relative increase in energy efficiency (31%) and CO2 conversion (13%) at high flow rates and near-atmospheric conditions. The most significant performance improvement was seen at low flow rates and sub-atmospheric pressure (300 mbar), where energy efficiency was 23% and conversion was 28%, a 71% relative increase over conditions without the CDN. Using CFD simulations, we found that the CDN produces a change in the flow geometry, leading to a confined temperature profile at the height of the plasma, and forced extraction of CO to the post-CDN region

Characteristics, management, and outcomes of patients with left‐sided infective endocarditis complicated by heart failure: a substudy of the ESC‐EORP EURO‐ENDO (European infective endocarditis) registry

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