In-filter PCDF and PCDD formation at low temperature during MSWI combustion

• Case study of remodeled MSWI with PCDD/F emission problems.
• Analysis of all PCDD/F congeners before and after fabric filters in MSWI plant.
• PCDD formation within the fabric filters at 220 °C was observed.
• PCDD/F TEQ concentrations and total PCDD/F are independent of each other.

This case study investigated PCDF and PCDD emissions from a 65 MW waste-to-energy plant to identify why an air pollution control system remodeling to accommodate increased production resulted in increased TEQ concentrations. Pre- and post-filter gases were collected simultaneously in four sample sets with varying filter temperatures and with/without activated carbon injection. Samples were analyzed to determine total PCDF and PCDD concentrations, as well as homologue profiles, and concentrations of individual congeners (some remained co-eluted). The total post filter PCDD concentrations where found to increase while the concentrations of PCDF and 2,3,7,8-substituted congeners declined. An investigation of the individual congener concentrations revealed that the increase of PCDD concentrations were due to a few congeners, suggesting a single formation route. The study also concludes that vital information about the formation could be obtained by not restricting the analysis to just the 2,3,7,8-substituted congeners.