Mineralogy and geochemistry of feed coals and combustion residues of the Kangal power plant (Sivas, Turkey)

Rıza Görkem OSKAY,Ali İhsan KARAYİĞİT,Rod A. GAYER

doi:10.3906/yer-1811-7

Abstract

This study focuses on mineralogical and geochemical compositions of feed coal (FC) and combustion residues, namely fly ash (FA) and bottom ash (BA) samples, obtained from the Kangal coal-fired power plant in central Turkey. The X-ray powder diffraction data indicate that carbonate and clay minerals are dominant phases in the FC samples. In the FA samples, quartz, hematite, anhydrite, lime, and feldspar are generally dominant and abundant phases, whereas calcite, ettringite, and portlandite are generally more abundant in the BA samples. The elements Mo, Cs, and U are significantly enriched in the studied FC, FA, and BA samples. The statistical analysis and SEM-EDX data show that Ca, Ti, and the vast majority of trace elements are inorganically affiliated, and only Tl and U have prob-able organic affinity in the FC. In addition, the redox conditions in the paleomires presumably resulting in Mo and U enrichment in FC, whereas their enrichment in FA and BA is most likely related to retention by CaO and Ca-sulfate. The Cs enrichment in FA is due to retention by glass. The elements in the FA and BA are distinguished into four groups according to their volatility during combustion. The elements As, Mo, Cd, Tl, and U (Group I) are the most volatile elements during combustion and condensation in the FA. The elements Li, Zn, Ga, Rb, Nb, Cs, Ba, La, and Pb (Group IV) did not become more volatile or less volatile during combustion and are located in BA. Nevertheless, Zn and Pb in the BA seem to be related to the presence of unaffected pyrite and sphalerite, and are due to low combustion efficiency of the boiler during the sampling period. Overall, enriched elements and minerals in FA and BA suggest that their disposal should be undertaken with caution.

Highlights

Coal is a primary local energy resource in Turkey, and the country’s energy demand has increased remarkably during the last decade
The feed coal (FC) samples are characterized by high ash yields and total sulfur contents
The statistical analysis and SEM-EDX data show that Ca, Ti, Mg, and enriched trace elements such Li, Cr, Zn, Cs, Sr, and Pb are inorganically affiliated, and only Tl and U probably have organic affinity in FC

Summary

Introduction

Coal is a primary local energy resource in Turkey, and the country’s energy demand has increased remarkably during the last decade. Environmentally sensitive elements (e.g., B, Cr, As, and Ni) are enriched in these coals (Querol et al, 1997; Karayigit et al, 2000; Palmer et al, 2004) and have potential adverse effects on environment and human health Their total geological reserves and low calorific values make these coals suitable for energy generation. Considering their high ash yields, total sulfur contents, and elemental enrichment, emission of hazardous trace elements and disposal of combustion residues of the power plant will be problematic in the near future for the Turkish energy sector.

Methods

Findings

Discussion

Conclusion