The release of heavy metals from the combustion of hazardous wastes is an environmental issue of in-creasing concern.The species transformation characteristics of toxic heavy metals and their distribution are consid-ered to be a complex problem of mechanism.The behavior of hazardous dyestuff residue is investigated in a tubular furnace under the general condition of hazardous waste pyrolysis and gasfication.Data interpretation has been aided by parallel theoretical study based on a thermodynamic equilibrium model based on the principle of Gibbs free en-ergy minimization.The results show that Ni,Zn,Mn,and Cr are more enriched in dyestuff residue incineration than other heavy metals(Hg,As,and Se)subjected to volatilization.The thermodynamic model calculation is used for explaining the experiment data at 800℃ and analyzing species transformation of heavy metals.These results of species transformation are used to predict the distribution and emission characteristics of trace elements.Although most trace element predictions are validated by the measurements,cautions are in order due to the complexity of incineration systems.
Dyestuff residue, a type of hazardous waste, is incinerated in the tub ular furnace, and thermodynamic equilibrium model is used to calculate and analy ze the chlorine behavior. The HCl emission and its effects on the behaviors of h eavy metals are studied. Meanwhile, the effects of three dechlorine reagents are predicted at a high temperature. Results show that HCl emission is dependent on incineration temperature. The HCl evaporated mainly derives from the organic ch lorine. Under the working condition of 500—900℃, the main products of Hg, Pb, Cu, Ni, Zn, and Mn in reaction with HCl are HgCl2 (g), PbCl4 (g), PbCl2 (g), (Cu Cl)3 (g), NiCl2 (s), NiCl2 (g), ZnCl2 (s), ZnCl2 (g), Zn (g), MnCl2 (s), and MnC l2 (g), respectively. Among the three dechlorine reagents, CaCO3 is optimal to r emove chlorine at high temperature, little of HCl is released below 800℃, where as Fe3O4 is unstable at high temperature.
YAN Jian-hua TAN Zhong-xin JIANG Xue-guang CHI Yong CEN Ke-fa
