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Progress in Plasma Processing of Materials, 1997

ISBN:
1-56700-093-2 (Print)

COMBINED EFFECTS OF OXYGEN, CHWRINE AND WATER VAPOR ON THE VAPORIZATION OF HEAVY METALS DURING FLY ASHES VITRIFICATION BY PLASMA

J. M. Badie
C. N. R. S., Institut de Science et de Genie des Materiaux et Procedes B. P. 5, Odeillo, F-66125 Font-Romeu Cedex

X. Chen
Institut de Science et de Genie des Materiaux et Precedes - CNRS BP. 5 - ODEILLO - 66125 FONT-ROMEU CEDEX - France

Gilles Flamant
Laboratoire des Procedes, Materiaux et Energie Solaire, PROMES-CNRS UPR 8521, 7 rue du Four solaire, 66120 Font Romeu-Odeillo, France

D. Gauthier
Institut de Science et de Genie des Materiaux et Precedes - CNRS BP. 5 - ODEILLO - 66125 FONT-ROMEU CEDEX - France

Abstract

The vaporization of fly ash from municipal waste incinerators during vitrification by plasma is the result of the complex interaction of 02, Cl2, H20 with a multicompounds molten bath at different temperatures. It is shown theoretically that vaporization rate decreases with 02 partial pressure and that H20 affects mainly the equilibrium pressure of alkali (Na,K). The influence of Cl2, is proved to be temperature dependent. At low temperature (1500K) the Cl2 pressure increase causes the enhancement of the heavy metals vaporization (Pb and Zn), whereas the effect is negligible at high temperature. The main part of chlorine is associated with Na and K in the fumes.
Concerning the interest of chlorine elimination by ash washing, the theoretical analysis shows the possible decrease of heavy metal evaporation, but it is not observed experimentally due to the modification of electric arc characteristics and bath temperature with and without chlorine.