Effects of combustion parameters on polychlorinated dibenzodioxin and dibenzofuran homologue profiles from municipal waste and coal co-combustion

Variation in polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofu ran (PCDD and PCDF) homologue profiles from a pilot scale (0.6 MWt, 2 x 10( 6) Btu/h), co-fired-fuel [densified refuse derived fuel (dRDF) and high-sul fur Illinois coal] combustion system was used to provide insights into effe cts of combustion parameters on PCDD and PCDF pollutant formation. A 24-run , statistically designed test matrix varied dRDF and/or coal firing rates ( at a constant targeted energy release rate) along with a range of process v ariables including calcium hydroxide injection, hydrogen chloride (HCl) con centration, flue gas temperature, quench, and residence time such that the results would be relatable to a wide variety of combustion conditions. Stat istical analysis of the molar homologue profiles enabled interpretation bas ed on non-confounding variables. A multivariate, generalized additive model , based on transformations of the design variables, described 83% of the va riation of the profiles characterized by log ratios of the homologue molar concentrations. This method identifies the operating parameters that are mo st significant in determining the PCDD/F homologue profiles. The model can be exercised to predict homologue profiles through input of these system-sp ecific operating parameters. For example, both higher HCl and sulfur dioxid e concentrations favor higher relative formation of the lower chlorinated P CDF homologues. (C) 1999 Elsevier Science Ltd. All rights reserved.