A study of reaction kinetics of a water plasma using a 0-D global kinetic model

Summary form only given. The need to reduce consumption of fossil fuels and a transition into an economy less dependent on hydrocarbons is urgently necessary. On this quest to find alternative energy sources, one proposed solution is to use another secondary energy source besides electricity - hydrogen. Hydrogen as an energy carrier can fulfill a portion of the energy demand, particularly in the transportation sector when used in fuel cells. However, less than four percent of the world's hydrogen is produced via renewable methods, primarily through "clean" electrolysis. The remaining 96% is produced from non-renewable methods including methane steam reformation and coal gasification, with an energy efficiency much higher than that of electrolysis. The experimental part of this project investigates the potential use of a radio-frequency (RF) plasma source to dissociate water molecules into their constituent parts, hydrogen and oxygen, for hydrogen production application. To supplement the experimental work, a global, zero-dimensional kinetic model is used to study reaction kinetics in dissociating water molecules in a plasma source. In this model, the plasma discharge is modeled as a cylinder, matching the geometry of the discharge in the experiment. Water flow rate into the chamber and discharge pressure are kept constant. Power deposited into the discharge is also kept constant with time. This simulation considers a total of 28 species and 283 gas phase and electron impact reactions. The main variables are deposited power, operating pressure, and water mass flow rate. The code outputs gas temperature, electron temperature, and species density. This work examines the theoretical energy efficiency for producing hydrogen by dissociating water molecules in a plasma source. Results indicate that the RF power required to break up water molecules is lower than that needed in the experiment. However, the maximum theoretical energy efficiency in this method as obtained from the kinetic model is still lower than the efficiency obtained from electrolysis.