Monitoring and Control of Toxic Organic Pollutant Emissions from Municipal Solid Waste Incinerators and Heavy-Duty Diesel Engines

Abstract

The monitoring and control of toxic organic pollutant emissions including persistent organic pollutants (POPs) and polyaromatic hydrocarbons (PAHs) from municipal solid waste incinerators (MSWIs) and heavy-duty diesel engines (HDDEs) were studied The aim was to address the key research gaps in the literature Specifically this included controlling the extreme POP emissions observed during the cold start-up of MSWIs Also for HDDEs having a comprehensive study on the effect of low to high petrodiesel-biodiesel blend on PAH and POP emissions and the effect of an air pollution control device (APCD) used to treat traditional pollutant on POP emissions The common start-up process adopted in MSWIs can generate extremely high concentrations of chlorinated and brominated POPs; for instance 130 ng WHO-TEQ Nm-3 for polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) 42 6 ng WHO-TEQ Nm-3 for polychlorinated biphenyls (PCBs) and 60 4 ng Nm-3 for polybrominated biphenyls (PBBs) as measured in this study Accordingly a two-day start-up process yields PCDD/F and PCB emission quantities around 20 times higher than those from an entire year’s normal operation In response this study proposed some control strategies including extensively cleaning the ash accumulated beneath the furnace beds of the combustion chambers and deposited on the wall of the superheaters and economizers and shortening the residence time of the flue gas at the POP formation window (250 ℃ – 450 ℃) in the combustion chambers Also advancing the injection time of activated carbon and lime to reduce POP emissions during the start-up processes Findings show that the control strategies were highly effective and reduced all the other POP emission quantities by > 96 % and PBDEs by 61 % The POP reductions were mostly attributed to strategies that reduced the potential for POP formation which were extensively cleaning the ash accumulated beneath the furnace beds of the combustion chambers and deposited on the wall of the superheaters and economizers and reducing the residence time of the flue gases in the combustion chamber within the POP formation temperature range Yet the effect of biodiesels on the emissions of PAHs and PCDD/Fs from HDDEs has only been studied using limited fuel blend ratios To clarify the influence of using higher fractions of biodiesel on the emissions of toxic organic pollutants from diesel engines in this research the emissions of PM PAHs and POPs from EURO IV and EURO III HDDEs fueled by low to high waste cooking oil (WCO)-based biodiesel-petrodiesel fuel blends were studied including D100 (0% biodiesel) B20 (20%) B40 (40%) B60 (60%) B80 (80%) and B100 (100%) The results for the EURO IV diesel engine showed that the PM and toxic organic pollutant emissions were reduced with increases in the blending ratio up until the B60 scenario when compared to the D100 scenario This is because biodiesel has higher oxygen content and no or lower aromatic content than petrodiesel Nevertheless during the B80 and B100 scenarios the PM and toxic organic pollutant emissions increased due to the high viscosity property of biodiesel which negatively affected the combustion process The biodiesel effect on the emissions from EURO III engine was more pronounced because of its lower combustion efficiency and therefore the improvement in combustion using biodiesel resulted in greater PCDD/F reductions Due to its thermal stability and lower potential of oxidizing SO2 Copper-zeolite selective catalytic reduction (CuZ-SCR) has been adopted in HDDEs to reduce NOx However because of the presence of Cu and the operating temperature coinciding with the temperature range optimal for POP formation there is a potential risk for increased emissions of POPs from HDDEs Therefore this study investigated the effect of CuZ-SCR on PCDD/F PCB PBDD/F and PBB emissions from a EURO I HDDE at 50% and 75% engine load Notably PCDD/F and PCB toxicity emissions increased by 78 4% and 201% respectively The dominant PCDD/F congeners were OCDD OCDF 1 2 3 4 6 7 8-HpCDD and 1 2 3 4 6 7 8-HpCDF and PCB-105 PCB-118 and PCB-77 for PCBs More PCDFs were formed compared to PCDDs and lower chlorinated congeners increased more than the higher chlorinated ones There was also an increase of PBDD/F concentrations from undetectable levels (ND) to 0 247 pg TEQ Nm–3 (4 00 pg TEQ L–1) after the CuZ-SCR However only 1 2 3 4 6 7 8-HpBDF and OBDF contributed to the concentrations PBBs was the only compound measured that reduced after the CuZ-SCR The only congener detected before and after the CuZ-SCR was PBB 15 The study is the first to show that the extreme emissions associated with the cold start-up of MSWIs can be reduced effectively and feasibly with no modifications to existing APCDs while having little influence on operational cost In addition the research presents a comprehensive understanding on the effect of petrodiesel-biodiesel ratio on emissions from HDDEs Finally we showed that CuZ-SCR could be a source of POPs under mid and high engine loads of a HDDE Further detailed research is needed to conclusively study the POP formation phenomenon in CuZ-SCR

Date of Award	2019
Original language	English
Supervisor	Wen-Che Hou (Supervisor)