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

Area of Science:

• Environmental Science
• Chemical Engineering
• Pollution Control

Background:

• A 65 MW waste-to-energy plant underwent air pollution control system remodeling to increase production capacity.
• This remodeling unexpectedly resulted in elevated Toxic Equivalency (TEQ) concentrations in emissions.
• Investigating the cause of increased emissions was crucial for environmental compliance and public health.

Purpose of the Study:

• To investigate polychlorinated dibenzodioxin (PCDD) and polychlorinated dibenzofuran (PCDF) emissions from a waste-to-energy plant.
• To identify the specific reasons for increased TEQ concentrations after air pollution control system remodeling.
• To understand the formation pathways of PCDD/Fs under modified operational conditions.

Main Methods:

• Simultaneous collection of pre- and post-filter gases in four sample sets.
• Varied filter temperatures and activated carbon injection were tested.
• Analysis of total PCDF and PCDD concentrations, homologue profiles, and individual congener concentrations.

Main Results:

• Total post-filter PCDD concentrations increased, while PCDF and 2,3,7,8-substituted congener concentrations decreased.
• The increase in PCDD was attributed to a few specific congeners, suggesting a singular formation route.
• Analysis of individual congeners provided insights beyond the commonly monitored 2,3,7,8-substituted compounds.

Conclusions:

• The remodeling of the air pollution control system led to an increase in specific PCDD congeners.
• A single formation route is likely responsible for the observed increase in PCDD emissions.
• Expanding analytical focus beyond 2,3,7,8-substituted congeners is vital for a comprehensive understanding of PCDD/F formation.