Spinning Arc Plasma Reactor

Abstract

In recent years, the energy transition has led to increasingly higher installed capacities of intermittent renewable energy sources. This has sparked the interest in power-to-fuel technology to store excess renewable energy in the chemical bonds of synthetic fuels. As a highly reactive, turn-key process, plasma-chemical conversion offers a promising approach to power-to-fuel technology. However, recent studies have shown limitations in either energy efficiency, conversion or flow rate. The novel Spinning Arc Plasma Reactor (SAPR) developed by J. van Kranendonk stabilises the plasma by mechanical rotation with the potential to contain a liquid film for in-situ product removal. The aim of this thesis is to characterise this reactor by studying the effect of rotational confinement on the reactor performance. To this end, the prototype initially built by J. van Kranendonk was further developed. A wealth of recent studies on the plasma-chemical conversion of CO2 as a step in the formation of synthetic fuels serves as a benchmark to compare reactor performance of the SAPR concept against. A series of experiments with argon were performed to establish the relationship between the system variables (pressure, power, flow rate and rotational speed) and the plasma parameters (electron temperature and electron density). Based on this knowledge, a series of experiments with CO2 were performed to establish the relationship between the reactor performance measured by the conversion and energy efficiency and the system variables: pressure, power and flow rate. The maximum conversion of about 30% to 55% was obtained at an energy efficiency of approximately 0.25% and the maximum energy efficiency of about 3% was achieved at a conversion of approximately 8.5% conversion. Similarly to other studies, improvements to either one came at the expense of the other. The performance of the SAPR proved comparable to dielectric barrier and other glow discharges but was outperformed by microwave and gliding arc discharges. Especially energy efficiency was inferior to these configurations. Further analysis of the discharge emission spectra suggested that CO2 dissociation mainly occurred through electron impact excitation. This explains the large difference in energy efficiency as microwave and gliding arc configurations are able to exploit more energy efficient dissociation channels. Nonetheless, this study was able to further develop the concept and has laid the ground work to explore the potential effect of a liquid film and in-situ product removal on the reactor performance.