Phase-mineral and chemical composition of composite samples from feed coals, bottom ashes and fly ashes at the Soma power station, Turkey

摘要

The phase-mineral and chemical composition of feed coals (PCs) and their bottom ashes (BAs) and fly ashes (FAs) produced in the Soma thermo-electric power station (TPS), Turkey, was characterized. PCs are high-ash Soma subbituminous coals abundant in moisture and Ca, and depleted in S. The inorganic composition (in decreasing order of significance) of PCs includes calcite, quartz, kaolinite, illite+muscovite, chlorite, plagioclase, gypsum, pyrite, montmorillonite, K-feldspar, dolomite, siderite, ankerite, opal, and volcanic glass. The results for 57 elements studied show that Ca>Nb>Cs>(V, Li) have significantly higher contents in PC ashes than the respective Clarke values for coal ashes. The water-soluble residues isolated from PCs include gypsum, calcite, inorganic amorphous matter, Ca-Mg-Na-K phase, and opal. These residues are enriched in Na>Se>S>B>Mg>Mo>Sr>Ca>K. The phase-mineral composition of BAs and FAs includes mainly glass, quartz, char, mullite, plagioclase, calcite, and portlandite; and, to a lesser extent, illite+muscovite, melilite, hematite, anhydrite, lime, cristobalite, kaolinite, and magnetite. Minor amounts of K-feldspar, dolomite, ankerite, Fe-spinel, gypsum, and Ca-K-Na phase also occur in BAs and FAs. FAs are enriched in inorganic matter, glass, cristobalite, mullite, Fe oxides, lime, and anhydrite, and depleted in mineral matter, char, quartz, clay minerals, melilite, portlandite, and carbonates in comparison with BAs. Only Se is significantly enriched in BAs and FAs compared to PC ashes. Most of the trace elements (in particular As, Bi. Cd, Ge, Pb, Sn. Tl, and W) are more abundant in FAs, while BAs are more enriched in Ca, Cs, Fe, Ho, Mn, P, Sc, Se and Tb. Significant percentages (11-59 percent) of elements initially present in PCs, namely S>Sb>Sn>Ta>Mo>Bi>Zn>Ni>Na>(Lu, Tm)>B, were emitted by stack emissions and not captured by the cleaning equipment in the Soma TPS. Some genetic features, properties, possible environmental concerns, and potential utilization directions related to PCs. BAs, and FAs are also discussed.