Properties of Heavy Metals Transmission to Bed Ash in the Sludge Incineration

Most of the metal-based phases formed in the process of sludge incineration are toxic and their emissions need to be strictly controlled. The sludge incineration tests using tubular furnace were carried out to study the distribution of heavy metals under different operating conditions. The emphasis has been on the study of the behavior of the potentially most harmful metals present in the sludge in trace quantities; data for Cu, Pb, Ni, Cd, Cr, Zn, Mn are reported. The contents of heavy metals in the residues were quantified and their transmission behaviors were intensively investigated. The tests indicate that all kinds of heavy metal elements have different remaining percentages in bed ash in different condition, depending on the chemical and physical reactions happened during the incineration. The optimum excess air coefficient (α=Va/V0) and temperature for the remaining percentages were 1.1 to 1.5 times of α and 900°C respectively. Metals have higher melting points like Ni, Cr were apt to be trapped by the bed ash in the incineration process with variable residence time, α and the incineration temperature.