Water Spray in Atmospheric Pressure Electrical Discharge Plasma

Florida State University, Tallahassee FL

Investigators

Abstract

0932481 Locke This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The interaction of liquid (e.g., water) with plasma (typically an ionized gas) occurs in a wide range of technological applications and natural phenomena including liquid-phase electrical discharge for arthroscopic surgery, lithotripsy for kidney stone treatment, wound healing and disinfection, synthesis of nanoparticles, plasma-assisted combustion, microsensors for chemical analysis, lightning discharges, corrosion in high-voltage electrical transmission and air flow control using plasma actuators. The relatively unexplored field of plasma-chemical reactions in gas-liquid plasma may also have a broad impact in industrially important applications where gas-liquid chemical reactions are important (e.g., air pollution study and control and the production of useful chemicals such as methanol or hydrogen and other fuels). This work will focus on studying a gas-phase electrical discharge with a spray of small micron-size water droplets into the plasma because this approach has been shown to be potentially very energy efficient for initiating a variety of chemical reactions, including the formation of hydrogen peroxide. Analysis of plasma interactions, particularly the chemical reactions initiated in such systems with small droplets of water, is vital to developing our understanding of plasma with condensed liquids in general. This work will focus on two general cases of 1) reaction products, including hydrogen peroxide, oxygen, and hydrogen, from pure water with Ar and O2 carrier gases and 2) formation of methanol from methane and water droplets with Ar carrier. The first case is of fundamental importance for all hydroxyl radical reactions initiated in the plasma and the second, while of significant importance in the energy field for production of liquid fuels, provides an example of gas-liquid reactions with reasonably well characterized reaction pathways and mechanisms. The proposed work will use a range of experimental techniques including aerosol particle size measurements, flow visualization, emissions spectroscopy, and chemical analysis to develop our understanding of how reactive chemical species like hydroxyl radicals are formed by water droplets flowing into a plasma reactor. Mathematical modeling of the transport coupled to the plasma chemical reactions will be conducted. Fundamental analysis using molecular dynamics will also be conducted to study the basic interactions of electrons with condensed water surfaces and to assist in interpretation of the experimental studies. This project is expected to lead to the development of fundamental knowledge on how plasma in gas-liquid environments leads to the formation of reactive species and how it affects some of the applications mentioned above. Advanced education and training of undergraduate students, PhD students, and a postdoctoral researcher in chemical, mechanical, and electrical engineering in an interdisciplinary and international environment will be conducted, and the mentoring of a young faculty member in chemical engineering will be accomplished.