Thermal behaviors and heavy metal vaporization of phosphatized tannerysludge in incineration process
TANG Ping , ZHAO Youcai , XIA Fengyi
DOI:
Received November 14, 2007,Revised January 09, 2008, Accepted , Available online
Volume 20,2008,Pages 1146-1152
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The high concentration of heavy metal (Cu, Cr, Zn, Pb) in tannery sludge causes severe heavy metal emissions in the process of
incineration. In the present investigation, the tannery sludge was treated with 85% phosphoric acid before the incineration process
in the tube furnace to control the heavy metal emissions. The thermal behavior and heavy metal vaporization of pre-treated tannery
sludge were investigated, and X-ray di raction (XRD) and scanning electron microscopy (SEM) analysis were also implemented to
elucidate the chemical mechanisms responsible for the thermal behavior and weakening of heavy metal vaporization of pre-treated
tannery sludge. The results obtained show that the di erences in thermal behaviors between untreated and pre-treated tannery sludge
are caused by the reaction of phosphoric acid and calcium carbonate. The vaporization percentage of heavy metal decreased e ciently
with the increasing volumes of H3PO4, which indicated the important thermal stability of the water-insoluble metallic phosphates
(Ca18Cu3(PO4)14, Ca9Cr(PO4)7, Ca19Zn2(PO4)14, PbMgP2O7) formed during tannery sludge phosphatation.
