CO2 Decomposition in CO2 and CO2/H2 Spark‐like Plasma Discharges at Atmospheric Pressure. Issue 16 (25th July 2019) - Kelly, Seán
Abstract: In this work, a spark‐like plasma discharge is ignited in pure CO2 and in CO2 /H2 mixtures to investigate CO formation. Power pulsing is used to limit arc formation to sustain a high current transient "spark‐like" plasma consisting of a mixed mode discharge comprising an initial current pulse ("spark") followed by a longer‐lived glow mode thorough each half cycle of the applied voltage. In pure CO2, the efficiency ranged between 20–50 % for CO2 conversions between 9–18 % for gas residence times of 100–600 ms. Adding H2 as a co‐reactant was investigated for a wide range of mixture ratios. The outlet gas was found to produce O2 ‐free mixtures of CO/H2 /CO2 . Conversion rates in CO2 /H2 mixtures are found to be similar to pure CO2 at equivalent residence times. The primary role of H2 as a co‐reactant is therefore found to be the removal of O2 formed during dissociation of CO2 . The energy cost of this dilution resulted in reduced efficiency for CO2 conversion (from 41 to 18 %), which is correlated to the efficiency drop found for pure CO2 conversion at lower flows. Opportunities for optimising this small volume "unit‐cell" spark reactor are encouraged by the results presented. This approach could enable deployment of serial or parallel combinations of such reactors capable of dealing cost‐effectively with the conversion of the larger CO2 and CO2 /H2 volumes required in future industry applications. Abstract : A bright spark : A spark‐like atmospheric pressure plasma discharge is ignited in pure CO2 and in CO2 /H2 mixtures to investigate CO formation. In pure CO2, the efficiency ranged between 20–50 % for CO2 conversions between 9–18 % for gas residence times of 100–600 ms. Conversion rates in CO2 /H2 mixtures are found to be similar to pure CO2 at equivalent residence times. However, the outlet gas was found to produce O2 ‐free mixtures of CO/H2 /CO2 when H2 was present.