Reduction of carbon dioxide particles to carbon monoxide by nonthermal plasma

Haruhiko Yamasaki^*, Takafumi Kida, Tomoyuki Kuroki, Masaaki Okubo

^* The author to whom correspondence should be addressed.

Department of Mechanical Engineering, Osaka Metropolitan University, Japan

Abstract

Nonthermal plasma reduces carbon dioxide to carbon monoxide, which can be converted into fuels and organic compounds, and is used as a raw material for gas synthesis. However, the energy efficiency is currently too low for practical use, and innovative ideas are required. This study proposes a CO₂ fuel conversion technology using solid CO₂ in a nonthermal plasma reactor. The advantages of using solid CO₂ are the suppression of the CO re-oxidation reaction at low temperatures and the improvement in energy efficiency at high CO₂ concentrations. In the experiment, the plasma reduction of gaseous and solid CO₂ is performed using a dielectric barrier discharge plasma reactor, and the conversion and energy efficiencies are compared. The concentration of generated CO is found to be dependent on the concentration of CO₂. When nonthermal plasma is applied to solid CO₂, Joule heating causes CO₂ sublimation, which reduces gaseous CO₂ to CO. The solid CO₂ in the plasma reactor increases the impedance and decreases the discharge power. The introduction of solid CO₂ upstream of the reactor increases the discharge power and improves the CO conversion efficiency. At a specific energy of 1.8 eV/molecule, the reduction of solid CO₂ increases the conversion efficiency from 1.4% to 1.8% and the energy efficiency from 2.3% to 2.7%, compared to the reduction of gaseous CO₂.

Keywords - Nonthermal plasma, carbon dioxide, carbon monoxide, solid-phase of CO₂, dielectric barrier discharge.

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