Volatilisation of trace elements for coal-sewage sludge blends during their combustion

The influence of sewage sludge addition on the volatility of 37 trace elements (Ag, As, An, B, Ba, Bi, Cd, Ce, Co, Cr, Cs, Cu, Ga, Hf, Hg, La, Li, Mn, Mo, Nb, Ni, Pb, Rb, Sb, Sc, Se, Sn, Sr, Ta, Te, Th, Tl, U, V, Y, Zn, Zr) during coal combustion was studied. For this purpose, a bituminous coal from the Asturian Central Basin and sewage sludge treated with Ca(OH)(2) and FeCl3, as well as 10 and 50 wt% sludge-coal blends were used. Combustion experiments were performed in a laboratory electric furnace at 800, 900, 1000 and 1100 degreesC. The results have confirmed that the high Cl contents of the sludge can produce a pronounced effect on the volatilisation of some trace elements (Ag, Cd, Cs, Cu, Li, Pb, Rb and TI) due to the probable formation of volatile chlorides, while the high CaO concentrations increase the retention of some elements in ash as As, Se and Te. The above opposite effects of Cl and CaO on trace element volatilisation were generally inappreciable for the 10 wt% blend, while they were more significant, but not as noticeable as expected, for the 50 wt% blend. (C) 2003 Elsevier Ltd. All rights reserved.