Mass Balance of Major and Trace Elements in a Coal-Fired Power Plant

Abstract

The Soma power plant in western Turkey consists of six 165-MW units (B1–4 and B5–6), of which the first four units (B1–4) burn Early-Middle Miocene feed coals from the lower seam in central mines (southern Soma village), and later, two units (B5–6) use Early-Middle Miocene and Upper Miocene feed coals from the lower and upper seams in Denis mines (northern Soma village). A total of 48 samples, feed coals (FCs), fly ashes (FAs) and bottom ashes (BAs), which were systematically collected once a week over an eight-week period from both group boiler units, B1–4 with 660 MW and B5–6 with 330 MW capacity from Soma power plant, have been evaluated for major and trace elements (Al, Ca, Fe, K, Mg, Mn, Na, Ti, S, As, B, Ba, Be, Bi, Cd, Co, Cr, Cu, Cs, Ga, Ge, Hf, Hg, Li, Mo, Nb, Ni, P, Pb, Rb, Sb, Sc, Se, Sn, Sr, Ta, Th, Tl, U, V, Y, Zn, Zr, and REEs) to get information on behavior during coal combustion. This study indicates that some elements such as Hg, Bi, Cd, As, Pb, Ge, Tl, Sn, Zn, Sb, B show enrichments in FAs relative to the BAs in both group boiler units. In addition to these, Cs, Lu, Tm, and Ga in Units B1–4 and S in Units B5–6 also have enrichments in FAs. Elements showing enrichments in BAs in both group boiler units are Ta, Mn, Nb. In addition to these, Se, Ca, Mg, Na, Fe in Units B1–4 and Cu in Units B5–6 also have enrichments in BAs. The remaining elements investigated in this study have no clear segregation between FAs and BAs. Mass balance calculations with the two methods show that some elements, S, Ta, Hg, Se, Zn, Na, Ca in Units B1–4, and Hg, S, Ta, Se, P in Units B5–6, have volatile behavior during coal combustion in the Soma power plant. This study also implies that some elements, Sb and Tb in Units B1–4 and Sb in Units B5–6, have relatively high retention effects in the combustion residues from the Soma power plant.

Keywords:

• bottom ash
• coal
• fly ash
• mass balance
• Soma
• trace element
• Turkey

Acknowledgments

This study is part of a research project on environmental implications of power plant feed coal and ash geochemistry under NATO Collaborative Linkage Grant (EST.CLG.979151). The authors gratefully acknowledge this NATO grant for the financial support, Prof. Dr. J. Hower for Hg analysis, and Ms. S. Rico, S. Toro, and S. Martinez (IES-CSIC) for sample digestion and ICP analysis.