Inhibition of PCDD/F and PCB formation in co-combustion

Area of Science:

• Environmental Science and Engineering
• Combustion Chemistry
• Pollutant Emission Control

Background:

• Co-combustion of coal and solid waste generates toxic chlorinated hydrocarbons, including polychlorinated dibenzo-p-dioxins and furans (PCDD/F) and polychlorinated biphenyls (PCB).
• Effective monitoring and reduction strategies for these emissions are crucial for environmental protection and regulatory compliance.

Purpose of the Study:

• To investigate the efficacy of the primary measures technique for inhibiting PCDD/F and PCB formation during co-combustion.
• To evaluate the performance of twenty different inorganic compounds as fuel additives to reduce toxic emissions.

Main Methods:

• Co-combustion experiments were conducted using lignite coal, municipal solid waste, and polyvinyl chloride (PVC) mixtures in pilot and laboratory-scale combustors.
• Twenty thermally resistant inorganic compounds were added directly to the fuel as potential inhibitors.
• Principle component analysis (PCA) was employed to assess the effectiveness of inhibitors on PCDD/F and PCB formation.

Main Results:

• Metal oxides showed no significant inhibitory effect on PCDD/F and PCB formation.
• Single nitrogen (N)- and sulfur (S)-containing compounds exhibited limited inhibition.
• Other N- and S-containing substances effectively reduced PCDD/F and PCB emissions, with ammonium sulfate ((NH4)2SO4) and ammonium thiosulfate ((NH4)2S2O3) being the most potent.

Conclusions:

• Ammonium sulfate, at 3% of fuel weight, can reduce PCDD/F emissions by up to 90%.
• The study highlights the potential of specific N- and S-containing compounds as cost-effective and efficient inhibitors for large-scale combustion units.
• The primary measures technique using selected additives offers a viable strategy for controlling toxic emissions from waste co-combustion.