Final Report: Characterization and Minimization of Fine Particulate Emissions from Waste Incinerators by Real-Time Monitoring of Size-Resolved Mass and Chemical CompositionEPA Grant Number: R828192
Title: Characterization and Minimization of Fine Particulate Emissions from Waste Incinerators by Real-Time Monitoring of Size-Resolved Mass and Chemical Composition
Investigators: Smith, Kenneth A. , Boudries, Hacene , Worsnop, Douglas R.
Institution: Massachusetts Institute of Technology , Aerodyne Research Inc.
EPA Project Officer: Shapiro, Paul
Project Period: June 1, 2000 through May 1, 2003
Project Amount: $335,000
RFA: Combustion Emissions (1999) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
The goal of this research project was to perform a real-time analysis and quantification of particulate pollutants in the exhaust of waste incinerators. All pollutants that we proposed to measure are known to be either toxic or carcinogenic. Our approach involved using two instruments: a laser-based aerosol mass spectrometer (REMPI-AMS) for selective and sensitive detection of toxic organics (specifically, chlorinated polycyclic hydrocarbons) and an aerosol mass spectrometer (AMS; Aerodyne Research, Inc.) for volatile and semivolatile compounds. This program was a collaborative effort between the research groups led by Professor Kenneth A. Smith at Massachusetts Institute of Technology, Department of Chemical Engineering, and Dr. Douglas R. Worsnop at Aerodyne Research, Inc.
A resonance enhanced multiphoton ionization time-of-flight aerosol mass spectrometer (REMPI-TOF) and an AMS developed at Aerodyne Research, Inc., were used to measure in real-time the chemical and size distribution of submicron particulate (PM1.0) emissions from incinerators. The experimental results reported here summarize three different types of major municipal incinerators: a sewage sludge fluid bed incinerator, a municipal solid waste combustor, and a multiple-hearth municipal sewage sludge incinerator.
Sampling and Analysis
The REMPI-AMS, an AMS-Quadrupole (Jayne, et al., 2000), a condensation particle counter, (CPC; TSI Model 3010), a differential mobility analyzer (TSI Model 3071), and an atomizer (TSI Model 3076) were deployed to each waste incinerator for particle sampling and analysis. All particulate sampling was performed in the stack just before being emitted into the atmosphere. A sampling line (copper tube, 1/2 inch OD, 5 m long) and a cyclone (URG-200-30EN) were used to sample aerosol particles below 2.5 μm at a flow rate of 10 L min-1. Both the sampling line and the cyclone were heated to the temperature of the gas inside the stack to avoid water vapor condensation in the sampling line. The sampling line also was kept as short as possible by sampling very close to the stack. Both aerosol mass spectrometers and the CPC were connected to iso-kinetically sample through the sampling line. During this experiment, the CPC, REMPI-AMS, and AMS were set to sample at 1.5, 0.1, and 0.1 L min-1, respectively.
Aerosols were sampled into the AMS at a flow rate of 0.1 L min-1 and focused in an aerodynamic lens (Zhang, et al., 2002). The focused particle beam exiting the lens is directed toward a heated tungsten surface (vaporizer) that is normally maintained at about 600°C for volatile and semi-volatile species, but was varied during this experiment between 500°C and 1,100°C. All but the most refractory chemical components present in particles that hit the vaporizer are flash vaporized, ionized at standard 70 eV electron impact, and analyzed by a quadrupole mass spectrometer (Balzers Model QMA 410) (Jayne, et al., 2000; Jimenez, et al., 2003; Boudries, et al., 2004).
Fluid Bed Incineration System. The experiment at the fluid bed sewage sludge incinerator was conducted August 14-18, 2002. Submicron particles were sampled in the stack and analyzed in real-time by the AMS. During this experiment, submicron aerosols were sampled in the stack by the AMS through a 5 m heated transfer line at a flow rate of about 10 L min-1.
Figure 1 shows the temporal trend of total mass loadings of major organic and inorganic components present in/on aerosols. A significant variability was observed in the aerosol mass loadings, whereas the feeding rates (wet sludge~7,000 kg/hr; dry sludge~1,600 kg/hr; wet scum~100kg/hr; dry scum~50 kg/hr) and combustion conditions (temperature ~ 700°C) remained stable. The total mass loading measured at the incinerator varied between 9 and 380 μg m-3, with an average concentration of 84 μg m-3. This variability in mass loadings could be attributed to the variability in the composition of the sludge.
Figure 1. Distribution of Total Mass Loadings, Organics, Chloride, Sulfate, Nitrate, and Ammonium, Measured in the Stack of Fluid Bed Incinerator
The average size distributions for these compounds varied between 130 and 200 nm. Both ammonium and sulfate exhibit the same average aerodynamic diameter of about 130 nm. Organics and chloride are found to be associated with a higher and similar diameter of about 200 nm, and nitrate is found to be associated with an aerodynamic diameter of about 160 nm. These results suggest that the aerosols emitted from the incinerator are externally mixed, and consist of ammonium sulfate, ammonium nitrate, ammonium chloride, organics, and chlorinated organics.
Municipal Solid Waste Combustor. Three major field experiments were conducted at a municipal solid waste combustor August 27-31, 2002. Temporal variations of major chemical compounds emitted from the municipal solid waste incinerator during the first deployment are presented in Figure 2. It can be seen that transition metals represent the dominant fraction, followed by sulfate and chloride. As shown in Figure 2, no significant variability was observed in the aerosol mass loading when measured at a constant vaporization temperature.
Figure 2. Distribution of Metals, Organics, Sulfate, Nitrate, Ammonium and Chloride Measured in the Stack of a Municipal Solid Waste Incinerator
During this campaign, the total mass loadings in aerosols were in a range of 20-140 μg m-3, with an average value of about 80 μg m-3 at a vaporizer temperature over 800°C, and averaging 15 μg m-3 at a vaporizer temperature of about 600°C. Here again, the PAH level was determined to be below the detection limit of the REMPI-AMS instrument. The size distributions of all measured species are found to be monomodal and internally mixed with an average aerodynamic diameter of about 600-700 nm.
Municipal Multi-Hearth Sludge Incinerator. The experiment at the municipal multi-hearth sewage sludge incinerator was conducted September 29 to October 3, 2003. Figure 3 shows the temporal trend of total mass loadings of major organic and inorganic components present in aerosols in the stack. Contrary to the results obtained at the solid waste incinerator, here the inorganic fraction (sulfate and ammonium) represents the dominant fraction of total mass loadings, followed by the total organic fraction. The total mass loadings measured at this multi-hearth sewage sludge incinerator varied between 60 and 10,000 μg m-3 at a vaporizer temperature over 800°C, and varying between 15 and 5,000 μg m-3 with an average concentration of 1,150 μg m-3 at a vaporizer temperature of about 600°C.
The analysis of the size distribution shows that all species are internally mixed with an average aerodynamic diameter of about 200 nm, slightly higher than the average size distribution measured at the sewage fluid bed incinerator.
Figure 3. Distribution of Total Mass Loadings, Organics, Sulfate, Chloride Measured in the Stack of a Municipal Solid Waste Incinerator
Conclusion. In this study, a REMPI-AMS and an AMS were used to monitor, in real time, the size-resolved chemical composition of particulate emissions from a fluid bed sewage sludge incinerator, a solid waste combustor, and a multi-hearth sewage sludge incinerator.
At the fluid bed sewage sludge incinerator, the size-resolved distribution shows that the aerosols in the stack are externally mixed, with an aerodynamic diameter varying between 140 and 220 nm. The mass loading ranged from 10 to 380 μg/m3 with an average concentration of 85 μg/m3 and a standard deviation of 84 μg/m3, mostly composed of ammonium, sulfate, ammonium chloride, organics, chlorinated organics, and nitrates.
At the solid municipal waste incinerator, the mass loading varied between 20 and 141 μg/m3 with an average concentration of 80 μg/m3 and a standard deviation of 29 μg/m3 when the AMS was operated at high vaporization temperature above 650ºC. There was aclear presence of refractory compounds such as mercury and lead. The size distribution analysis shows that the aerosols in the stack are internally mixed and exhibit higher average vacuum aerodynamic diameters of about 600 to 700 nm. The emission level of PAH is below the level of the current REMPI-AMS detection limit, though quantitatively it was shown that the pyrene level is on the order of 20 ng m-3. The majority of aerosol mass was inorganic sulfate, transition metals, and chlorine-containing compounds. Transition metals represent the dominant fraction, contributing 43 percent of total mass loadings.
At the multiple-hearth sewage sludge incinerator, the mass loadings were in a range of 14-4,983 μg m-3 with an average concentration of 1,153 μg/m3 and a standard deviation of 883 μg m-3. The aerosol compositions were dominated by sulfates and ammonium, representing about 73 percent and 22 percent, respectively. Chlorides, organics, and nitrates also were present but at very low concentrations. Aerosols were found internally mixed with average vacuum aerodynamic diameters of particles at 200nm.
A paper summarizing all findings and results performed under this grant is in preparation (to be submitted for publication in a peer-reviewed journal in 2005).
Boudries H, Canagaratna MR, Jayne JT, Alfarra MR, Allan JA, Bower KN, Coe H, Pryor SC, Jimenez JL, Brook JR, et al. Chemical and physical processes controlling the distribution of aerosol in the Lower Fraser Valley, Canada, during the Pacific 2001 field campaign. Atmospheric Environment 2004;38(34):5759-5774.
Jayne JT, Leard DC, Zhang X, Davidovits P, Smith KA, Kolb CE, Worsnop DR. Development of an aerosol mass spectrometer for size and composition analysis of submicron particles. Aerosol Science and Technology 2000;33(1-2):49-70.
Jimenez JL, Jayne JT, Shi Q, Kolb CE, Worsnop DR, Yourshaw I, Seinfeld JH, Flagan RC, Zhang X, Smith K, et al. Ambient aerosol sampling using the aerodyne aerosol mass spectrometer. Journal of Geophysical Research 2003;108(D7):8425.
Zhang X, Smith KA, Worsnop DR, Jiménez J, Jayne JT, Kolb CE. A numerical characterization of particle beam collimation by an aerodynamic lens-nozzle system. Part 1. An individual lens or nozzle. Aerosol Science and Technology 2002;36(5):617-631.