Date of Award

5-1-1999

Degree Type

Thesis

University or Center

Clark Atlanta University(CAU)

Degree Name

Ph.D.

Department

Chemistry

First Advisor

Kofi B. Bota

Second Advisor

Yaw D. Yeboah

Comments

Nitrogen oxides (NOx) contribute to the formation of acid rain and ground-level ozone. Cost-effective technologies that destroy NOx from gas streams are needed. Of particular interest are Non-thermal plasma technologies that offer an innovative approach to the solution of NOx emission control.

This study investigates the use of a particular electrical discharge technique, the barrier discharge. Experiments were conducted in double dielectric barrier discharge (DDBD) reactors to elucidate the effects of physical and chemical variables on the NOx removal efficiencies. Analysis instruments included a FT-IR with a length adjustable gas cell, a GC-MS, several gas analyzers and an emission spectrometer.

The variables investigated include input power, chemical composition, residence time, and gap spacing. Through this investigation, an overall optimization of DDBD performance was obtained. Of these, we primarily investigated the effect of discharge gap spacing on the electrical and chemical processes that occur in non-thermal plasma discharge (NTPD). A numerical model was developed to simulate the physical and chemical processes during the oxidation and reduction of NOx. Experiments and 1 calculations were performed to investigate the effects of the above-mentioned variables on breakdown electric field, free electron energy distribution, electron impact kinetic rates, and chemical reactions. Results from the calculations and experiments demonstrated the complex relations between NOx removal efficiency and the tested variables. A mechanism of NOx destruction in a NTPD was proposed.

This study revealed that the characteristics of microdischarges are the key to understanding the NTPD process. Optical measurements, by means of a high speed intensified imager, provided important information on the microdischarge. This information helped to develop the numerical model, which established the relation between surface charge and charge density within a microdischarge. Results of this study should provide a basis for developing a potential solution for the reduction of NOx emission from off-gas sources, such as diesel-powered aerospace ground equipment used on the Air Force.

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