| 1. |
- Aurell, Johanna, et al.
(author)
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Effects of quench time profiles on PCDD/F formation in the postcombustion zone during municipal solid waste incineration
- 2009
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In: Environmental Engineering Science. - : Mary Ann Liebert. - 1092-8758 .- 1557-9018. ; 26:3, s. 541-550
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Journal article (peer-reviewed)abstract
- Effects of postcombustion zone temperatures and flue gas residence times on monochlorinated to octachlorinated dibenzo-p-dioxins and -furans (PCDD/F) in a laboratory-scale reactor combusting municipal solid waste were investigated. Four different quench time profiles were investigated, falling from 400°C to 200°C, 300°C to 100°C, 450°C to 200°C and 460°C to 260°C, with corresponding residence times of 1.4 to 4.4sec, 1.4 to 5.4sec, 1.3 to 4.3sec, and 1.3 to 4.0sec, respectively. Flue gas samples were collected simultaneously at three fixed sampling points, with an additional sampling of flue gas entering the postcombustion zone (640°C). The quench time profiles resulted in different total PCDD/F yields, as well as differences in homologue profiles and congener patterns. Thus, the formation pathways seem to be dependent on sufficient residence time within a specific temperature region. Formation of PCDD/F was shown to be rapid and mainly located to the 640°C to 400°C temperature region, with non-detectable levels at 640°C and concentrations at 400°C that did not increase or decrease significantly downstream. Furthermore, a prolonged residence time at and above 450°C/ 460°C showed low yields even downstream the postcombustion zone compared to the 400°C to 200°C and 300°C to 100°C profiles. The 460°C to 260°C profile resulted in increased abundance at the last two sampling points of PCDD congeners known to correlate with 2,4,6-trichlorophenols, suggesting that chlorophenol condensation reactions were promoted by this quench time profile.
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| 2. |
- Aurell, Johanna, et al.
(author)
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Effects of sulfur on PCDD/F formation under stable and transient combustion conditions during MSW incineration
- 2009
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In: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 76:6, s. 767-773
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Journal article (peer-reviewed)abstract
- SO2 levels in the flue gas from a laboratory-scale fluidized bed reactor combusting artificial municipal solid waste (MSW) were varied (resulting in four different SO2:HCl ratios 0, 0.2, 0.7 and 2.7 (by mass)) to study the effects of sulfur on the formation of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzothiophenes (PCDTs). Sampling was performed simultaneously at three fixed points in the post-combustion zone with temperatures of 400, 300 and 200 °C, under normal combustion conditions and both during and after transient combustion conditions. The findings indicate that sulfur has a greater inhibitory effect on PCDF formation than on PCDD formation and that the PCDD/PCDF ratio in the flue gas depends on both the SO2:HCl ratio in the flue gas and memory effects arising from transient combustion conditions. The results also indicate that the relative importance of different pathways shifts in the post-combustion zone; condensation products increasing with reductions in temperature and increases in residence time. However, these changes appear to depend on the SO2:HCl ratio in the flue gas and combustion conditions. Sulfur seems to inhibit the chlorination of PCDFs. A tendency for increased SO2 levels in the flue gas to increase levels of PCDTs was also detected, but the increases were much less significant than the reductions in PCDF levels.
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| 3. |
- Aurell, Johanna, et al.
(author)
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Effects of transient combustion conditions on the formation of polychlorinated dibenzo-p-dioxins, dibenzofurans, and benzenes, and polycyclic aromatic hydrocarbons during municipal solid waste incineration
- 2009
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In: Environmental Engineering Science. - : Mary Ann Liebert. - 1092-8758 .- 1557-9018. ; 26:3, s. 509-520
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Journal article (peer-reviewed)abstract
- This study investigated the effects of transient combustion conditions on formation of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) along the postcombustion zone. Polychlorinated benzenes (PCBz) and polycyclic aromatic hydrocarbons (PAH) were also studied. The study was conducted in a laboratory fluidized-bed reactor fed with an artificial municipal solid waste (MSW) under controllable but realistic combustion conditions. PCDD/Fs, PCBz, and PAHs were monitored under normal, transient, and posttransient combustion conditions and simultaneously sampled at three different sampling points/temperatures (400°C, 300°C, and 200°C). Substantially higher PCDD/F, PCBz, and PAH concentrations were found during transient combustion than during normal combustion. Elevated concentrations were found to decrease with time. PCDD/F concentrations were similar at all points during normal and transient combustion conditions, but were found in higher concentrations at 200°C than 400°C under the posttransient combustion periods. Higher concentrations of the sum PAH and PCBz were also found at 200°C than 400°C in the posttransient combustion periods. Transient combustion conditions induced changes in both PCDD/F homologue profile and PCDD/F congener patterns compared to normal combustion. PCDD/PCDF ratios indicated an increase of the de novo synthesis during transient combustion conditions. Although, the PCDD/F congeners found to be most strongly affected by the transient combustion conditions indicated different reactions pathways active for formation of PCDF and PCDD, de novo synthesis and precursors, respectively. The most strongly affected PCDD/F congeners of transient combustion were identified and are presented.
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| 4. |
- Aurell, Johanna, et al.
(author)
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Effects of varying combustion conditions on PCDD/F emissions and formation during MSW incineration
- 2009
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In: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 75:5, s. 667-673
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Journal article (peer-reviewed)abstract
- Process, combustion and fuel parameters were varied to elucidate factors that substantially affect the formation and emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) arising from municipal solid waste (MSW) incineration. The combustion conditions were varied by changing the: freeboard temperatures; quench time in the post-combustion zone; fuel load; chlorine and copper levels in the fuel; and the water, sulfur dioxide, carbon monoxide and oxygen levels in the combustion gases. The study was performed using a 5 kW laboratory-scale fluidized-bed reactor and PCDD/Fs were sampled at a point at 300 °C in the post-combustion zone. The results showed that increasing the SO2 level (from 0 to 130 ppm) substantially reduced the PCDD/F emissions, by up to 60%. In contrast, increasing the CO levels (due to transient combustion conditions), raising the Cl level (from 0.7% to 1.7%) and reducing the freeboard temperature (from 800 °C to 660 °C) all substantially increased the emission levels (more than 3-fold). Changes in PCDD/F profiles associated with increases in Cl, SO2 or CO levels and increasing the freeboard temperature (from 800 °C to 950 °C) indicate that the PCDFs were mainly formed by chlorination. In addition, increasing the Cl level increased the chlorination activity in the formation of PCDDs. Increasing the SO2 level appeared to be less effective in reducing the amount of PCDDs formed via the precursor pathway. While increased CO levels induced PCDD formation via the precursor pathway, although this was found to depend on the O2 level in the flue gas.
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| 5. |
- Aurell, Johanna, 1972-
(author)
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Effects of Varying Combustion Conditions on PCDD/F Formation
- 2008
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Doctoral thesis (other academic/artistic)abstract
- Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are by-products emitted from combustion sources such as municipal solid waste (MSW) incineration plants. These organic compounds are recognized as toxic, bioaccumulative and persistent in the environment. PCDD/Fs are removed from flue gases before released from MSW incineration. However, the PCDD/Fs are not destroyed but retained in the residues, thus in the environment. Understanding the pathways that lead to their formation is important in order to develop ways to suppress their formation and prevent their release into the environment. Suppressing the formation can also allow less expensive air pollution control system to be used, and/or the costs of thermally treating the residues to be reduced. The main objective of the studies underlying this thesis was to elucidate process, combustion and fuel parameters that substantially affect the emission levels and formation of PCDD/Fs in flue gases from MSW incineration. The experiments were conducted under controllable, realistic combustion conditions using a laboratory-scale reactor combusting artificial MSW. The parameter found to most strongly reduce the PCDD/F emissions, was prolonging the flue gas residence time at a relatively high temperature (460°C). Increasing the sulfur dioxide (SO2) to hydrogen chloride (HCl) ratio to 1.6 in the flue gas was also found to reduce the PCDF levels, but not the PCDD levels. Fluctuations in the combustion process (carbon monoxide peaks), high chlorine levels in the waste (1.7%) and low temperatures in the secondary combustion zone (660°C) all tended to increase the emission levels. The PCDD/PCDF ratio in the flue gas was found to depend on the chlorine level in the waste, fluctuations in the combustion process and the SO2:HCl ratio in the flue gas. The formation pathways were found to be affected by the quench time profiles in the post-combustion zone, fluctuations in the combustion process and addition of sulfur. In addition, increased levels of chlorine in the waste increased the chlorination degrees of both PCDDs and PCDFs. A tendency for increased SO2 levels in the flue gas to increase levels of polychlorinated dibenzothiophenes (sulfur analogues of PCDFs) was also detected, however the increases were much less significant than the reduction in PCDF levels.
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| 6. |
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| 7. |
- Avakian, Maureen D., et al.
(author)
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The origin, fate, and health effects of combustion by-products : A research framework
- 2002
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In: Journal of Environmental Health Perspectives. - : National Institute of Environmental Health Sciences. - 0091-6765 .- 1552-9924. ; 110:11, s. 1155-1162
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Journal article (peer-reviewed)abstract
- Incomplete combustion processes can emit organic pollutants, metals, and fine particles. Combustion by-products represent global human and environmental health challenges that are relevant not only in heavily industrialized nations, but also in developing nations where up to 90% of rural households rely on unprocessed biomass fuels for cooking, warmth, and light. These issues were addressed at the Seventh International Congress on Combustion BY-Products, which convened 4-6 June 2001 in Research Triangle Park, North Carolina. This congress included a diverse group of multidisciplinary researchers and practitioners who discussed recent developments and future goals in the control of combustion by-products and their effects of exposure on human and ecologic health. Participants recommended that interdisciplinary, coordinated research efforts should be focused to capitalize on the important potential synergisms between efforts to reduce the adverse human health effects linked to exposures to combustion by-products and broader efforts to reduce greenhouse gas emissions and save energy through efficiency. In this article we summarize the principal findings and recommendations for research focus and direction.
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| 8. |
- Broz, J, et al.
(author)
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The effect of oils on PAH, PCDD, PCDF, and PCB emissions from a spark engine fueled with leaded gasoline
- 2000
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In: Chemosphere. ; 41:12, s. 1905-11
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Journal article (peer-reviewed)abstract
- The effect of synthetic and mineral oils on the formation of polyaromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) in emissions from a spark ignition engine was studied on a Skoda Favorit engine fueled with leaded gasoline. The test cycle simulated urban traffic conditions on a chassis dynamometer, in accordance with the ECC 83.00 test. The data for selected PAHs as well as PCDDs, PCDFs, and PCBs congener profiles are presented. PCDD/Fs emissions for an unused oil and the oil after 10000-km operation varied from 300 to 2000 fmol/m3, PCBs emissions from 75 to 178 pmol/m3, and PAHs emissions from 150 to 420 g/m3. The content of PCBs in oils varied from 2 to 920 mg/kg.
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| 9. |
- Börjeson, L, et al.
(author)
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Characterization of automotive shredder residues from two shredding facilities with different refining processes in Sweden
- 2000
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In: Waste Management & Research. - : Wiley. - 0734-242X .- 1399-3070. ; 18:4, s. 358-66
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Journal article (peer-reviewed)abstract
- Strict legislation imposing producer responsibility on car manufacturers, introduced in 1998 in Sweden, has prompted a search for new alternatives for recycling organic materials In end-of-life vehicles (ELVs), i.e. the automotive shredder residue (ASR). The recovery of materials from ELVs must increase from the present 70 to 75%, to 95% by 2015. The aim of this study was to characterize material other than ferrous components, i.e. the (automotive) shredder residue [(A)SR] and the non-ferrous (NF), material in order to investigate its suitability for energy recovery. The results show that the good heat value of the material gives it potential, but high levels of metals and chlorinated compounds may cause problems. Levels of elements, metals and polychlorinated dibenzodioxins/furans (PCDD/F), polychlorinated biphenyls (PCB) and polychlorinated benzenes (PCBz) in the ASR were also analysed, and the results are described and discussed.
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| 10. |
- Cieplik, M.K., et al.
(author)
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Formation of dioxins from combustion micropollutants over MSWI fly ash.
- 2006
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In: Environmental Science and Technology. - 0013-936X. ; 40:4, s. 1263-9
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Journal article (peer-reviewed)abstract
- Formation of polychlorinated dibenzofurans and dibenzo-p-dioxins (PCDD/Fs) from a model mixture of products of incomplete combustion (PICs) representative of municipal solid waste incineration (MSWI) flue gases, over a fixed bed of MSWI fly ash has been investigated. For comparison, a single model compound (chlorobenzene) was also briefly studied. A newly developed lab-scale system enabled the application of (very) low and stable concentrations of organic substances--of 10(-6) M or less-to approach realistic conditions. Samples taken at several time intervals allowed the observation of changes in rates and patterns due to depletion of the carbon in fly ash. The model flue gas continuously produced PCDDs and PCDFs after the de novo reaction had ceased to occur. Dioxin output levels are comparable to those of "old" MSW incinerators. Replacing the PIC trace constituent phenol by its fully 13C-labeled analogue led to, e.g., PCDD with one labeled ring as prominent product, meaning that the formation is about first order in phenol, contrary to earlier assumptions. The meaning of the results for the formation of dioxins in the MSWI boiler is discussed.
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