THE EFFECT OF COFIRING HIGH-SULFUR COAL WITH MUNICIPAL WASTE ON FORMATION OF POLYCHLORINATED DIBENZODIOXIN AND POLYCHLORINATED DIBENZOFURAN

The effect of cofiring minor amounts (5-10 wt %) of high-sulfur coal w ith municipal refuse-derived fuel (RDF) on emissions of polychlorinate d dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) was studied under a range of operating conditions. Through use of a 2(x) f actorial test matrix the program examined the effect of sulfur dioxide (SO2) concentration on preventing PCDD/F formation while accounting f or differences in hydrogen chloride concentration, sorbent slurry inje ction, and various furnace operating conditions such as quench rate, r esidence time, and RDF feed rate. An understanding of the effect of co al- and operating-related parameters on the postcombustion formation o f PCDD/F is expected to assist in developing strategies aimed at preve nting PCDD/F formation. The test facility was a 0.6-MWt (2 x 10(6) Btu /h) pilot scale, grate-fired combustor, designed to mimic the solid fu el handling and combustion rates of field units. Results were analyzed by examining comparative-run-averaged yields and through development of a model based on regression methods with stepwise parameter selecti on. The run-averaged yields and model show that higher SO2 concentrati ons due to cofiring with coal result in significant suppression of PCD D/F formation, even when controlling for changes in other operating pa rameters.