Observations on the effect of process parameters on dioxin/furan yield in municipal waste and coal systems

Effects of fly ash loading; ash-borne, extractable organics; sulfur dioxide (SO2) and hydrogen chloride (HCl) concentration; and combustion quality on the formation of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/F) were evaluated in pilot scale tests simulating municipal waste combustion and coal/waste co-combustion testing. Similar PCDD/F yields from reinjection of as-received and extracted fly ash injection along with testing under “poor combustion” conditions show the importance of combustion quality on minimizing precursors. Co-firing coal and municipal solid waste ash leads to increased formation from that of firing coal alone, indicating that the municipal solid waste ash provides additional reactants and/or catalytic sites for formation. Finally, tests with elevated SO2 levels found that, at sufficiently high sulfur/chlorine levels, formation of PCDD/F is prevented in both simulated municipal waste combustion and coal/waste co-firing.