Adsorption of PCDD/F on MWI fly ash

Area of Science:

• Environmental Engineering
• Chemical Engineering
• Pollution Control

Background:

• Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) pose a significant challenge in waste incinerator off-gas treatment.
• Gaseous PCDD/F bypasses standard particle filters, necessitating additional removal strategies.
• Dioxin accumulation in equipment can create persistent emission sources.

Purpose of the Study:

• To investigate the adsorption of PCDD/F onto fly ash particles for simultaneous removal during filtration.
• To understand the influence of temperature and particle properties on PCDD/F gas-particle partitioning.
• To evaluate the efficiency of fly ash as a sink for gaseous PCDD/F.

Main Methods:

• Model calculations to determine gas/particle partitioning dependencies.
• Pilot-scale experiments (500 Nm3/h) using a hexachlorinated dioxin congener.
• Analysis of PCDD/F adsorption efficiency based on fly ash properties and temperature.

Main Results:

• At room temperature, approximately 90% of hexachlorinated dioxins (HxCDD) were in the particulate phase.
• At 135°C, only 10% of HxCDD remained in the particulate phase, deviating from sublimation equilibrium.
• Adsorption rate is not limiting; fly ash composition and temperature are key factors for PCDD/F capture.

Conclusions:

• Fly ash particles demonstrate potential as an effective sink for PCDD/F in flue gas.
• Temperature and fly ash chemical composition significantly impact PCDD/F adsorption efficiency.
• This approach offers a promising method for removing gaseous PCDD/F during waste incineration.