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MODELING SUPPRESSION OF DIOXIN FORMATION DURING COAL COMBUSTION
Citation:
Telfer*, M. A. AND B K. Gullett*. MODELING SUPPRESSION OF DIOXIN FORMATION DURING COAL COMBUSTION. Presented at Pittsburgh Coal Conference, Newcastle, New South Wales, Australia, 12/4-7/01.
Description:
The paper discusses a homogeneous, gas-phase reaction mechanism that has been developed to explain sulfur (S) and chlorine (Cl) interactions in an industrial, fire-tube boiler, using No. 2 fuel oil (0.03%S) doped with copper naphthenate (CuNA) and 1,2-dichlorobenzene (1,2-diClBz). The experiments were intended primarily for the investigation of polychlorinated dibenzodioxin and furan (PCDD/F) formation. However, significant reduction of sulfur dioxide (SO2) from combustion of No.2 fuel oil was also observed upon injection of 1,2-diClBz. Interaction between S and Cl has been of significant interest due to the potential of S to suppress the formation of PCDDs/Fs during cofired combustion of high-S coal with municipal waste (MW). A suggested mechanism is the gas-phase reaction SO2 + Cl2 + H2O = SO3 + 2HCl that converts active molecular chlorine (Cl2)--formed in the post-flame zone by the metal-catalyzed Deacon process--to inactive hydrogen chloride (HCl). In this study, the gas-phase suppression reaction is represented by a series of elementary reaction steps compiled from previously validated reaction mechanisms. The model was able to explain the observed rapid conversion of SO2 to SO3 in the boiler experiments upon injection of 1,2-diClBz to a HCl conversion of 60%. These results present a possible mechanism for gas-phase S and Cl interactions and a potential means of elucidating the SO2 suppression mechanisms of PCDD/F formation during cofired combustion of high-S coal and MW.