Microbubble-enhanced DBD plasma reactor: Design, characterisation and modelling

The emerging field of atmospheric pressure plasmas (APPS) for treatment of various solutions and suspensions has led to a variety of plasma reactors and power sources. This article reports on the design, characterisation and modelling of a novel plasma-microbubble reactor that forms a dielectric barrier discharge (DBD) at the gas-liquid interface to facilitate the transfer of short-lived highly reactive species from the gas plasma into the liquid phase. The use of microbubbles enabled efficient dispersion of long-lived reactive species in the liquid and UVC-induced oxidation reactions are triggered by the plasma radiation at the gas-liquid interface. A numerical model was developed to understand the dynamics of the reactor, and the model was validated using experimental measurements. Fluid velocities in the riser region of the reactor were found to be an order of magnitude higher for smaller bubbles ((5) over tilde mu m diameter) than for larger bubbles ((2) over tilde 500 mu m diameter); hence provided well-mixed conditions for treatment. In addition to other reactive oxygen species (ROS) and reactive nitrogen species (RNS), a dissolved ozone concentration of 3 mu M was recoded after a 15-min operation of the reactor, demonstrating the suitability of this design for various applications. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.