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

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 probable 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.

Geological Controls on Enrichment of Rare Earth Elements and Yttrium (REY) in Late Permian Coals and Non-Coal Rocks in the Xian’an Coalfield, Guangxi Province

“…In Horizon I, the REY, Se, Pb, Mo, and U contents are up to 1013, 38, 123, 72, and 81 µg/g, respectively; the REY negatively correlates with ash yield (r = −0.99) and show essentially no correlations with Al 2 O 3 (Figure 9), P 2 O 5 , and Zr, thereby appearing to indicate an organic association; this result differs from previous studies showing that the REY in some REY-rich coals is mostly likely hosted by phosphates, heavy minerals, and clay minerals [5,7,56]. Moreover, Horizon I is characterized by a high degree of REY enrichment and normal levels of Zr, Hf, Nb, and Ta, appearing to exclude the possibility of the input of alkaline volcanic ash due to them being enriched in the REY-Zr (Hf)-Nb (Ta) assemblage [5,7,[60][61][62][63][64]. Furthermore, the highly elevated concentrations of REY in Horizon I, however, are accompanied by elevated contents of Se, U, Mo, and Pb; this assemblage most commonly represents the influx of metal-bearing solutions [7].…”

Assessment of the Enrichment of Heavy Metals in Coal and Its Combustion Residues

“…Kangal LC has high humidity (43.1–55.8%) and volatile matter content (37.7–46.2%). 35 Kangal LS generally has a uniform grain size (0.5–0.5 mm) and a smooth surface texture. Kangal FA is classified as calcareous FA because its reactive lime is over 10%.…”

“…Ten samples of LC, LS, and FA were collected from different parts of the lignite basin, the slag storage field, and the ash mountain of Kangal LFTPP, respectively. Kangal LC has high humidity (43.1–55.8%) and volatile matter content (37.7–46.2%) . Kangal LS generally has a uniform grain size (0.5–0.5 mm) and a smooth surface texture.…”

Impacts of coal-fired power plants for energy generation on environment and future implications of energy policy for Turkey

“…Radioactive elements and heavy metals are also present in bottom ashes, resulting from the combustion of coal. Enrichment of toxic elements such as Mo, Cs, U, Zn, Pb, S, B, V, Zn, As, Cu, Co, and Hg were reported in CFPP ashes in Sivas (Karayiğit et al 2019b ), Kütahya (Karayiğit et al 2019a ), and Çanakkale (Baba et al 2016 ), where caution with their disposal was advised. These radionuclides can spread from uncontrolled open storage areas, causing a great deal of land pollution (Avcı 2005).…”