Geochemistry, mineralogy, and technological properties of the main Stephanian (Carboniferous) coal seams from the Puertollano Basin, Spain

This study is focused on the occurrence and distribution of mineral matter and major and trace elements in the high volatile bituminous coal from Puer tollano (south-central Spain). The relationship between ash behaviour and i norganic composition, as well as the possible formation of fouling and slag ging deposits in boilers during the conversion process, were investigated. The Puertollano coals do not exhibit plastic properties, despite their rank , probably because of their high ash and inertinite contents. The Puertollano coal has medium to low total S content (0.48% to 1.63% db, with a mean of 1.0% db) and is characterised by relatively high contents of Si, Pb, Sb, and Cs. Some elements such as As, Cd, Co, Cr, Cu, Ge, Li, Mn, Ni, W, and Zn are also present in relatively high contents. The enrichment in a number of heavy metals could be attributed to the common sulphide ores occurring near the Puertollano coal deposit. The following trace elements affinities are deduced: (a) sulphide affinity: As, Co, Cd, Cu, Ni, Sb, Tl, and Zn; (b) aluminum-silicate affinity: K, Ti, B, Co, Cr, Cs, Cu Ga, Hf, Li, Nb, Rb, Sn, Ta, Tn, V, Zr, and LREE; (c) Car bonate affinity: Ca, Mg, Mn, and B; (d) organic affinity: B. The very high Si levels and the anomalous enrichment in Cs, Ge, Pb, Sb, and Zn shown by the Puertollano coals account for the high contents of these e lements in the Puertollano fly ash when compared with the other Spanish coa l fly ashes. The chemical composition of the high temperature ash (HTA) is consistent wi th the trend shown by the ash fusion temperatures (AFT) and also with the p redictive indices related to slagging and fouling propensities. Thus, the a sh fusion temperatures increase with high values of Al2O3 as well as with t he decrease in Fe2O3, CaO, and MgO. (C) 2001 Elsevier Science B.V. All righ ts reserved.