ROLE OF COMBUSTION AND SORBENT PARAMETERS IN PREVENTION OF POLYCHLORINATED DIBENZO-P-DIOXIN AND POLYCHLORINATED DIBENZOFURAN FORMATION DURING WASTE COMBUSTION

This research uses experimental data and a statistical approach to det ermine the effect of combustion- and sorbent-injection-related paramet ers on the mechanism of polychlorinated dibenzo-p-dioxin and polychlor inated dibenzofuran (PCDD and PCDF, respectively) formation and preven tion in waste combustors. The operation of a pilot-scale combustor was varied to effect different regimes of oxygen (O2), hydrogen chloride (HCl), and chlorine (Cl2) concentration, temperature; residence time; quench rate; and sorbent injection. The fly ash loading of a municipal waste combustor was simulated by postcombustion injection of fly ash collected from a full-scale facility. Downstream sampling and analysis indicated significant PCDD and PCDF formation, beyond concentrations on the preinjected fly ash, at rates conducive to explaining formation in full-scale facilities at particle/gas residence times < 5 s. Stepw ise regression analyses determined the predictive parameters for four models of PCDD, PCDF, the total of PCDD and PCDF yield, and the partit ioning between PCDD and total yield. Substantial prevention of PCDD an d PCDF formation can be brought about with upstream sorbent injection for HCl and Cl2 reduction, control of excess air, and increased quench rate.