Date of Award

2017

Document Type

Open Access Dissertation

Department

Chemical Engineering

Sub-Department

College of Engineering and Computing

First Advisor

Bihter Padak

Abstract

With the increasing levels of carbon dioxide (CO2) in the atmosphere, researchers are driven to seek cleaner combustion techniques to burn coal for power generation. Oxy-coal combustion is a promising technique to cut down CO2 emissions. This technology requires the introduction of a pure oxygen (O2) stream and a recycled flue gas stream into the boiler instead of air. Flue gas stream generated from the system will be low in volume and highly concentrated in CO2. Thus, the capture and sequestration process will be facilitated. But, one of the concerns of adopting this technology is the altered chemistry of pollutants due to the changes in the combustion medium and operating mode. Chemistry of the species such as sulfur, nitrogen, mercury (Hg) and chlorine (Cl) can be significantly affected under this CO2-rich operating mode. So, before retrofitting the existing power plants, comprehensive studies are necessary to enhance the current understanding of nitrogen oxides (NOx), sulfur oxides (SOx), Hg and Cl chemistry in oxy-combustion environments.

The need for better understanding of the combustion chemistry in an oxy-combustion environment inspired this unique and comprehensive research project. In the course of this study, a lab-scale combustion setup was designed and built. A stable oxy-combustion environment was created in the reactor and the system was subjected to a time-temperature profile representative of an actual plant boiler. To capture the speciation profiles of NOx and SOx, samples were collected from the different temperature points of the reactor. In addition to the experimental efforts, kinetic simulations were conducted to gain deeper understanding of the NOx, SOx, Hg and Cl chemistry, and the dominating reaction pathways were revealed. Such a detailed study employing the combinatorial approach of experimental analysis and kinetic simulation will be valuable to predict the emissions from power plants and to determine suitable emission control strategies.

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