Co-combustion of Bituminous Coal and Pickling Sludge in a Drop-Tube Furnace: Thermodynamic Study and Experimental Data on the Distribution of Cr, Ni, Mn, As, Cu, Sb, Pb, Cd, Zn, and Sn

Abstract

The effect of bituminous coal and pickling sludge co-combustion on the distributions of Cr, Ni, Mn, As, Cu, Sb, Pb, Cd, Zn, and Sn in flue gas, fly ash, and bottom ash were studied in a drop-tube furnace. To simulate combustion conditions in suspension-firing boilers, experiments were carried out at temperatures ranging from 1100 to 1400 °C, with sludge amounts ranging from 0% to 10% by weight. The results show that the 10 selected heavy metals could be divided into three distinct classes according to bottom ash mass percentage, except for Sn, which showed an irregularity. Class I included Cr, Ni, Mn, and As and were identified as less volatile heavy metals because more than 95% was retained in the bottom ash; these heavy metals exhibit high-temperature stability. Class II contained Cu, Sb, Pb, and Cd and were identified as semivolatile heavy metals; nearly 20–40% was distributed among flue gas and fly ash. In addition, the bottom ash heavy metal percentage decreased markedly with increasing temperature. ...