CHARACTERIZATION OF TRACE ELEMENTS IN DRY FLUE GAS DESULFURIZATION (FGD) BY-PRODUCTS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Panuwat Taerakul, B.ENG., M.B.A., M.S. ***** The Ohio State University 2005 Dissertation Committee: Approved by Professor Harold Walker, Adviser Professor Linda Weavers Dr. Tarunjit Butalia Adviser Professor Yu-Ping Chin Civil Engineering Graduate Program ABSTRACT This study investigates the amount, distribution, variation and fate of trace elements in FGD by-product. Dry FGD by-product including lime spray dryer (LSD) ash have possible uses in agricultural and construction applications. However, the variability in the chemical properties, especially levels of trace elements, of LSD ash is a concern due to the possible release to the environment. Changes in levels of inorganic constituents in LSD ash collected from the McCracken Power Plant were measured. Variability of elemental composition in leachate and bulk chemical properties (i.e. available lime index (ALI), calcium carbonate equivalent (CCE), and total neutralization potential (TNP)) were also examined. Little variability over different time periods (e.g., daily to yearly) and little variability between samples collected from different particle collection hoppers were observed. Trace elements including As, Se, and Hg in LSD ash and in the leachate did not surpass limits for land application (EPA 503 Rule) or RCRA. Therefore, LSD ash is a consistent material which can be beneficially re-used in an environmentally sound manner. ii Further study of LSD ash samples was conducted to examine the distribution of trace elements in different fractions. LSD ash was fractionated using a 140-mesh (106 µm) sieve into two fractions: fly ash/unburned carbon-enriched fraction (>106 µm) and a calcium-enriched fraction (<106 µm). A lithium heteropolytungstate solution with a specific gravity of 1.84 g/mL was further used to separate unburned carbon and fly ash- enriched fractions from the >106 µm fraction. The results show that the concentration of As was consistently greater in the calcium-enriched fraction, while the Hg concentration was significant in all fractions. Specific surface area was found to be a factor controlling the levels of mercury in LSD ash fractions. The As concentration was also significant in economizer ash while Hg was undetected, suggesting that sorption of As on the surface of fly ash occurs at high temperature (600 °C) while sorption of Hg does not. As and Hg were also found to be more stable in the calcium-enriched fraction possibly due to the significant level of Ca and greater pH of the leachate. Results suggest that As and Hg are stable in LSD ash due to significant amounts of Ca. However, when LSD is disposed in a landfill, dissolution of Ca may lower the pH and calcium concentration in the leachate which may facilitate the release of As and Hg. The study of trace elements in LSD ash was used as a base-line for investigating trace elements in dry FGD by-product collected from the Ohio State Carbonation and Ash Reactivation (OSCAR) process. The OSCAR process is a pilot-plant of a new dry FGD system used on a slip stream of flue gas from the McCracken Power Plant. Two different sorbents (i.e., regenerated sorbent and supersorbent) were tested using the OSCAR process. Levels of trace elements, particularly As, Se and Hg, were found at greater levels compared to LSD ash. Higher concentrations of trace elements were found iii in OSCAR baghouse samples, compared to cyclone samples, due to lower temperature and high surface area of baghouse particles. Operational parameters, such as sorbent injection rate and flue gas flow rate, influenced levels of As and Se in the cyclone samples. For example, the As concentration increased as flue gas flow rate increased while the Se concentration increased as the sorbent injection rate increased. Based on the RCRA limits, leaching tests indicated that all cyclone samples are not hazardous. Results suggest that OSCAR sobents are effective for capturing trace elements, and the OSCAR by-product can be beneficially reused. iv ACKNOWLEDGMENTS I would like to thank, Dr. Harold Walker, for his advice and encouragement during my PhD research. He helped me stay focused on producing quality work. His patience, sincerity and kindness are greatly appreciated. I also thank Dr. Linda Weavers, Dr. Taranjit Butalia and Dr. Yu-Ping Chin for serving me as my committee members. I am grateful to Dr. Linda Weavers who gave suggestions and comments for my research and Dr. Taranjit Butalia who provided me a lot of information about coal combustion products. It has been a pleasure and I am thankful to work with the following lab members: Mikko, Sunny, Jason, Yi-Fang, Jing, Eun-Kyoung, Maggi, Julie, Mike, Eric, Dong, Li- Mei, Ziqi, Yu-sik, Aaron, Hiong, Mustafa, Vibhash, Laura, Sindhu, Dawn, Clayton, and Ya-ning. Everybody has been very helpful to me and I have learned so much from working with others. Our lunch break is always fun for many of us to go out and experience new food. Getting together outside of the lab allows me to connect to our personal lives. I thank Dr. Danold Golightly for his kind suggestions on the operation of ICP- OES. I appreciate Doug Beak and Kevin Jewel for providing me acid digestion techniques and Ray Hunter for his design of a tool used for sampling in the power plant. I v also would like to thank staff at the McCracken Power Plant for their assistance during the sampling of LSD ash and OSCAR samples. Finally, I am fortunate to have a strong support and an encouragement from my family and my girlfriend. Especially my parents, I could not imagine how much love and support that they give me. Without them, it would be so hard for me to bounce back when I am in tough times. vi VITA December 5, 1971 ………………………... Ratchaburi, Thailand 1993 ………………………………………. B.ENG., Environmental Engineering, Chulalongkorn University, Thailand 1993-1994………………………………… Environmental Engineer, Progress Technology Consultant, Bangkok, Thailand 1997 ………………………………............. M.B.A., Finance, Wright State University , Dayton, Ohio 2000………………………………………. M.S., Environmental Engineering, The Ohio State University 1998-present ……………………………… Graduate Research Associate, The Ohio State University PUBLICATIONS Research Publication 1. Taerakul, Panuwat, Lamminen, Mikko, He, Yongtian, Walker, Harold W., Tranina, Samuel J., Whitlatch, Earl, “Long-Term Behavior of Fixated Flue Gas Desulfurization Material Grout in Mine Drainage Environments”, Journal of Environmental Engineering 130(7), 816, (2004). vii 2. Harold W. Walker, Panuwat Taerakul, Tarunjit Butalia, William E. Wolfe, and Warren A. Dick, Minimize and Use of Coal Combustion By-Products (CCBs): Concept and Applications. In: Ghassemi A. editors. The Handbook of Pollution Control and Waste Minimization, New York: Marcel Dekker, 2002. FIELDS OF STUDY Major Field: Civil Engineering viii TABLE OF CONTENTS Page Abstract……………………………………………………………………………………ii Acknowledgments ………………………………………………………………………...v Vita ……………………………………………………………………………………....vii List of Figures …………………………………………………………………………...xiv List of Tables ……………………………………………………………………………xvi Chapters 1. INTRODUCTION AND BACKGROUND.................................................................1 1.1. Flue Gas Desulfurization (FGD) Process...............................................................1 1.2. Production and Utilization of FGD By-Product.....................................................5 1.3. Trace Elements in FGD By-Product......................................................................6 1.4 Trace Element Characterization of Dry FGD Materials ..........................................9 1.5. Dissertation Overview.........................................................................................11 2. VARIABILITY OF INORGANIC CONSTITUENTS IN LIME SPRAY DRYER ASH15 2.1 Abstract ...............................................................................................................15 2.2 Introduction .........................................................................................................16 2.3 Experimental........................................................................................................18 2.3.1 Sample Collection .........................................................................................18 ix 2.3.2 LSD Ash Characterization.............................................................................19 2.3.3 Inorganic Analysis ........................................................................................20 2.3.4 Coal Sample Analysis ...................................................................................21 2.4 Results and Discussion.........................................................................................21 2.4.1 Variability in Inorganic Composition of LSD Ash.........................................21 2.4.2 Variability in Leaching of Inorganic Elements and Bulk Chemical Properties of LSD Ash............................................................................................................28 2.5 Conclusions .........................................................................................................30 3. DISTRIBUTION OF ARSENIC AND MERCURY IN LIME SPRAY DRYER ASH41 3.1 Abstract ...............................................................................................................41