Heavy metal vaporization and abatement during thermal treatment of modified wastes.

This study examines the vaporization percentage and partitioning of heavy metals Cd, Pb and Zn during thermal treatment of wastes with added PVC, heavy metals or phosphate, and the efficiency of sorbents for removal of these metallic compounds in flue gas of an industrial solid waste incinerator. Firstly, vaporization experiments were carried out to determine the behavior of heavy metals during combustion under various conditions (type of waste, temperature, presence of chloride or phosphate ...). The experimental results show relatively high vaporization percentage of metallic compounds within fly ash and limestone matrix while heavy metals within sediments treated with phosphoric acid are less volatile. Vaporization of metals increases with increasing temperature and with chloride addition. The thermal behavior of the selected heavy metals and their removal by sorbents (sodium bicarbonate, activated carbon) was also studied in an industrial solid waste incinerator. These pilot scale experiments confirm that heavy metals are concentrated in fly ashes and cyclone residues, thus effectively controlling their release to the atmosphere.