| 1. |
- Aurell, Johanna, et al.
(author)
-
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
-
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)
-
Effects of sulfur on PCDD/F formation under stable and transient combustion conditions during MSW incineration
- 2009
-
In: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 76:6, s. 767-773
-
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)
-
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
-
In: Environmental Engineering Science. - : Mary Ann Liebert. - 1092-8758 .- 1557-9018. ; 26:3, s. 509-520
-
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
-
In: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 75:5, s. 667-673
-
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)
-
Effects of Varying Combustion Conditions on PCDD/F Formation
- 2008
-
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)
-
The effect of oils on PAH, PCDD, PCDF, and PCB emissions from a spark engine fueled with leaded gasoline
- 2000
-
In: Chemosphere. ; 41:12, s. 1905-11
-
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
-
In: Waste Management & Research. - : Wiley. - 0734-242X .- 1399-3070. ; 18:4, s. 358-66
-
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
-
In: Environmental Science and Technology. - 0013-936X. ; 40:4, s. 1263-9
-
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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| 11. |
- Cieplik, Mariusz K, et al.
(author)
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On Dioxin Formation in Iron Ore Sintering
- 2003
-
In: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 37:15, s. 3323-31
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Journal article (peer-reviewed)abstract
- Iron ore sintering is an important source of "dioxins", polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This paper reports on attempts to identify materials, conditions, and mechanisms responsible for PCDD/F formation (i) by investigating salient properties of ores (viz., with respect to oxidation, condensation, and chlorination of model organics) and (ii) by mimicking the industrial process on a microscale with real-life materials. Principles of Design of Experiments (DOE) are employed. The reactivities of iron ores differ greatly. Limonite/goethite "soft" ore is a very active oxidation catalyst (e.g., for benzene and phenol), a property that may be useful in cleaning up crude sintering process offgases, whereas hematite/magnetite "hard" ore is not. The latter, however strongly promotes condensation of phenol to dibenzofuran. A newly built lab-microscale sintering facility could satisfactorily imitate the large-scale process, in part or as a whole. Results obtained with realistic feed mixtures point at dioxin formation in the sinter bed at levels significant enough to explain a major part of the outputs observed in the real-life process. With ~8 ppm (wt) of chloride added as NaCl, the PCDD/F output doubled, but with the same proportion of chlorine administered as C2Cl4, the dioxin output was over 2 orders of magnitude larger. The use of process reverts, etc. containing chlorinated organics should therefore be avoided. PCDD/F congener patterns are also reported and compared with those observed in practice.
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| 12. |
- Duong Phan, Ngoc Chau, et al.
(author)
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Accurate sampling of PCDD/F in high temperature flue-gas using cooled sampling probes
- 2012
-
In: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 88:7, s. 832-836
-
Journal article (peer-reviewed)abstract
- In a laboratory-scale combustion reactor, flue-gas samples were collected at two temperatures in the post-combustion zone, 700 °C and 400 °C, using two different water-cooled sampling probes. The probes were the cooled probe described in the European Standard method EN-1948:1, referred to as the original probe, and a modified probe that contained a salt/ice mixture to assist the cooling, referred to as the sub-zero probe. To determine the efficiency of the cooling probes, internal temperature measurements were recorded at 5 cm intervals inside the probes. Flue-gas samples were analyzed for polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs). Samples collected at 700 °C using the original cooling probe showed higher concentrations of PCDD/Fs compared to samples collected using the sub-zero probe. No significant differences were observed between samples collected at 400 °C. The results indicated that artifact formation of PCDD/Fs readily occurs during flue-gas sampling at high temperatures if the cooling within the probe is insufficient, as found for the original probe at 700 °C. It was also shown that this problem could be alleviated by using probes with an enhanced cooling capacity, such as the sub-zero probe.Although this may not affect samples collected for regulatory purposes in exit gases, it is of great importance for research conducted in the high-temperature region of the post-combustion zone.
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| 13. |
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| 14. |
- Hedman, Björn, 1957-
(author)
-
Dioxin emissions from small-scale combustion of bio-fuel and household waste
- 2005
-
Doctoral thesis (other academic/artistic)abstract
- Denna avhandling behandlar rökgasutsläpp av persistenta organiska föroreningar, framförallt dioxiner, vid förbränning av fasta biobränslen och torrt hushållsavfall i relativt små anläggningar (5-600 kW) utan avancerad rökgasreningsteknik.Samförbränning av avfall och biobränsle i effektiva mindre biobränslepannor testades som en alternativ strategi till den vanligen förekommande storskaliga hanteringen och förbränningen fast hushållsavfall. Medan storskalig förbränning av avfall ger investeringsmässiga fördelar med rökgasreningsteknik etc. kan små lokala anläggningar ha transportmässiga fördelar och möjligheter till utnyttjande av lokala biobränsletillgångar. Källsorterat, torrt, brännbart hushållsavfall insamlades från hushåll i glesbygd och samförbrändes i brikettform med energigräset rörflen i 150-600 kW biobränslepannor. Endast undantagsvis understeg dioxinemissionerna gällande gränsvärden för avfallsförbränning och nivåerna av väteklorid i rökgas översteg gränsvärdena flerfaldigt. Det bedömdes att någon form av extra rökgasrening är nödvändig för att säkerställa nivågränserna. Dioxiner hittades också i det eldade avfallet, framförallt i textilfraktionen. Dioxinmängderna i rökgaserna var oftast lägre än i det ingående bränslet.Intermittent pelletseldning gav oväntat höga utsläpp av dioxiner med en emissionsfaktor på 28 ng(WHO-TEQ)/kg. Vedeldning i en modern miljömärkt villapanna gav betydligt lägre utsläpp av dioxiner än eldning i en gammal kombipanna och eldning med full lufttillförsel, som kan jämföras med användning av ackumulatortank, resulterade i upp till 90% minskning av utsläpp av dioxiner jämfört med eldning med reducerat lufttillskott (’pyreldning’). Eldning av plastavfall i en vedpanna gav höga utsläpp av dioxiner.Okontrollerad förbränning av trädgårdsavfall och hushålls avfall i tunna eller som öppen eld ’bakgårdsbränning’, gav stora variationer i utsläppsnivåer som bara delvis kunde kopplas till avfallsinnehåll. Resultaten visar att denna typ av förbränning kan vara en betydande källa till dioxiner i miljön, och ett emissionsfaktorintervall på 4-72 ng (WHO-TEQ)/kg föreslås för bedömningar av utsläpp från backgårdsbränning av avfall med låga eller måttliga klorhalter.En sammanfattande slutsats av alla försök är att dioxin utsläpp beror på komplicerade samband mellan bränsleinnehåll och förbränningsbetingelser. Bränslen med mycket höga klorhalter av ger oftast högre utsläpp av dioxiner än bränslen med låga klorhalter medan små skillnader döljs av variationer i förbränningsbetingelser.
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| 15. |
- Hedman, Björn, et al.
(author)
-
Emission of PCDD/F, PCB, and HCB from combustion of firewood and pellets in residential stoves and boilers
- 2006
-
In: Environmental Science and Technology. - Washington : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 40:16, s. 4968-4975
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Journal article (peer-reviewed)abstract
- To assess potential emissions of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and hexachlorobenzene (HCB) from residential combustion of biofuels, experiments were performed in which various types of pellets and firewood were combusted in four types of stoves and boilers, with both full and reduced rates of air supply. Intermittent combustion of wood pellets resulted in emissions of 11 ng-(WHO-TEQ)/kg combusted fuel (dry weight). A modern, environmentally certified boiler yielded somewhat lower emissions of PCCD/F and PCB than a wood stove. Both gave <0.1 ng(WHO-TEQ)/m3n (1.3-6.5 ng(WHO-TEQ)/kg) and considerably lower emissions than an old boiler (7.0-13 ng(WHO-TEQ)/kg). No positive effect on emissions could be observed in full air combustion (simulating the use of a heat storage tank) compared to combustion with reduced air. Two of the wood combustion experiments included paper and plastic waste fuels. Chlorine-containing plastic waste gave rise to high emissions: ca. 310 ng(WHO-TEQ)/ kg over the whole combustion cycle. The homologue profiles of PCDD/Fs show characteristic differences between ashes and flue gas from combustions with different levels of air supply. These differences do not, however, seem to have any correlation to the relative amount of toxic congeners.
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| 16. |
- Hedman, Björn, et al.
(author)
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Emissions from small-scale energy production using co-combustion of biofuel and the dry fraction of household waste
- 2005
-
In: Waste Management. - New York, N.Y. : Pergamon. - 0956-053X .- 1879-2456. ; 25:3, s. 311-321
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Journal article (peer-reviewed)abstract
- In sparsely populated rural areas, recycling of household waste might not always be the most environmentally advantageous solution due to the total amount of transport involved. In this study, an alternative approach to recycling has been tested using efficient small-scale biofuel boilers for co-combustion of biofuel and high-energy waste. The dry combustible fraction of source-sorted household waste was mixed with the energy crop reed canary-grass (Phalaris Arundinacea L.), and combusted in both a 5-kW pilot scale reactor and a biofuel boiler with 140–180 kW output capacity, in the form of pellets and briquettes, respectively. The chlorine content of the waste fraction was 0.2%, most of which originated from plastics. The HCl emissions exceeded levels stipulated in new EU-directives, but levels of equal magnitude were also generated from combustion of the pure biofuel. Addition of waste to the biofuel did not give any apparent increase in emissions of organic compounds. Dioxin levels were close to stipulated limits. With further refinement of combustion equipment, small-scale co-combustion systems have the potential to comply with emission regulations.
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| 17. |
- Hedman, Björn, et al.
(author)
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Emissions of polychlorinated dibenzodioxins and dibenzofurans and polychlorinated biphenyls from uncontrolled burning of garden and domestic waste (backyard burning)
- 2005
-
In: Environmental Science and Technology. - Washington : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 39:22, s. 8790-8796
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Journal article (peer-reviewed)abstract
- To assess emissions of dioxins (chlorinated dibenzodioxins and dibenzofurans) and PCB from uncontrolled domestic combustion of waste ("backyard burning"),test combustions in barrels and open fires were monitored. The waste fuels used were garden waste, paper, paper and plastic packaging, refuse-derived fuel (RDF), PVC, and electronic scrap. Combustions including PVC and electronic scrap emitted several orders of magnitude more dioxins than the other waste fuels. Emissions from the other fuels had considerable variations, but the levels were difficult to relate to waste composition. Emission factors of PCDD/F and PCB from the backyard burning ranged from 2.2 to 13 000 ng (WHO-TEQ)/kg. The levels found in ash usually were less than 5% of the total. For assessment of total emissions of dioxins and PCB from backyard burning of low and moderately contaminated wastes, an emission factor range of 4-72 ng (WHO-TEQ)/kg is suggested. These figures imply that combusting waste in the backyard could contribute substantially to total emissions, even if the amounts of fuel involved are equivalent to just a few tenths of a percent of the amounts combusted in municipal waste incinerators.
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| 18. |
- Hedman, Björn, et al.
(author)
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PCDD/F in source-sorted waste fractions and emissions from their co-combustion with reed canary-grass
- 2007
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In: Waste Management. - Oxford : Pergamon Press. - 0956-053X .- 1879-2456. ; 27:11, s. 1580-1592
-
Journal article (peer-reviewed)abstract
- The dry combustible fraction of source-sorted household waste, including material that would otherwise be recycled, was mixed with the energy crop reed canary-grass (Phalaris arundinacea L.), and combusted as briquettes in 150 and 600 kW biofuel-boilers without advanced cleaning systems. The source-sorted waste was further sorted and characterized according to its material and chemical contents. The bulk of the waste’s chlorine content came from the non-package plastic fraction, whereas 90–95% of ∑PCDD/F (74–90% of WHO-TEQ) originated from the textile fraction. The sources of the dioxins in the waste fractions are discussed. The balance of dioxin levels was negative, i.e., the amounts of dioxins output in the flue gas were lower than those input in the fuel, except when there were operational disturbances in the combustion. In one of the combustion trials the total levels of dioxins in the flue-gas and ashes were also lower than the input levels. The use of additional cleaning equipment will be needed to ensure that emissions of dioxins and hydrochloric acid will be below legal limits.
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| 19. |
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| 20. |
- Jansson, Stina, et al.
(author)
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Formation and chlorination of polychlorinated naphthalenes (PCNs) in the post-combustion zone during MSW combustion
- 2008
-
In: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 72:8, s. 1138-1144
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Journal article (peer-reviewed)abstract
- Non- to octa-chlorinated naphthalenes (PCNs) were analyzed in flue gas samples collected simultaneously at three different temperatures (450 °C, 300 °C and 200 °C, respectively) in the post-combustion zone during waste combustion experiments using a laboratory-scale fluidized-bed reactor. PCN homologue profiles in all samples were dominated by the lower chlorinated homologues (mono- to triCN), with successive reductions in abundance with each additional degree of chlorination. The isomer distribution patterns reflected ortho-directionality behavior of the first chlorine substituent, and the β-positions, i.e. the 2,3,6,7-substitution sites, seemed to be favored for chlorination. Injection of naphthalene into the post-combustion zone resulted in increased PCN levels at 200 °C, demonstrating the occurrence of chlorination reactions in the post-combustion zone. However, the increases were restricted to the least-chlorinated homologue (monoCN), probably because there was insufficient residence time for further chlorination. In addition, an episode of poor combustion (manifested by high CO levels) was accompanied by extensive formation of 1,8-diCN, 1,2,3- and 1,2,8-triCN; congeners with substitution patterns that are not thermodynamically favorable. These are believed to be products of PAH breakdown reactions and/or chlorophenol condensation. Overall, PCN formation is likely to occur via more than one pathway, including chlorination of naphthalene that is already present, de novo synthesis from PAHs and, possibly, chlorophenol condensation.
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| 21. |
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| 22. |
- Jansson, Stina, et al.
(author)
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Multivariate Relationships between Molecular Descriptors and Isomer Distribution Patterns of PCDD/Fs Formed during MSW Combustion
- 2009
-
In: Environmental Science & Technology. - : American Chemical Society. - 0013-936X .- 1520-5851. ; 43:18, s. 7032-8
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Journal article (peer-reviewed)abstract
- The isomer distribution patterns of mono- to hepta-chlorinated dibenzo-p-dioxins (PC1−7DD) and dibenzofurans (PC1−7DF) in postcombustion zone flue gas during incineration of an artificial municipal solid waste in a laboratory-scale fluidized-bed reactor were evaluated. Bidirectional orthogonal projections to latent structures (O2PLS) was used to correlate a set of physicochemical properties and chlorine substitution descriptors with the objective to identify parameters correlated with postcombustion zone PCDD and PCDF formation. The most influential variable for the distribution of PCDD congeners was chlorine substitution in positions 1 and 3 (Cl1 + 3), and overall the chlorine substitution descriptors exerted a larger impact on PCDDs than on PCDFs. For the PCDF, chlorination of the 9-position was the most influential X-variable. Distinct clustering was observed and was most pronounced for PCDFs, dividing most of the homologues into two or three subgroups of congeners. These subgroups seemed to correspond to the probability of formation by chlorophenol condensation. The sterically crowded dibenzofuran bay-sites (1- and 9-positions) were found to negatively influence PCDF formation, with chlorination of the 9-position having the greatest impact. Since PCDD/F toxicity is related to the lateral positions, elucidating the factors governing chlorination may be of great importance for detoxification of incineration byproducts.
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| 23. |
- Jansson, Stina, et al.
(author)
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Post-combustion formation of PCDD, PCDF, PCBz, and PCPh in a laboratory-scale reactor : Influence of dibenzo-p-dioxin injection
- 2009
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In: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 76:6, s. 818-25
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Journal article (peer-reviewed)abstract
- Formation of polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF), benzenes (PCBz), and phenols (PCPh) was studied during combustion of an artificial municipal solid waste (MSW) in a laboratory-scale fluidized-bed reactor with simultaneous collection of flue gas samples at three different temperatures in the post-combustion zone (450 degrees C, 300 degrees C, and 200 degrees C). PCDF, PCBz, and PCPh were predominantly formed at or above the first sampling point (450 degrees C) with a dominance of the lower chlorinated homologues. PCDDs, on the other hand, were dominated by the intermediately chlorinated homologues with concentrations peaking at 300 degrees C. The dominating PCPh congeners clearly displayed the ortho-para directionality, which is indicative of electrophilic aromatic substitution, as did the PCBz isomer distribution patterns to some extent. Comparison of the observed PCBz isomer distribution patterns to prior work may indicate coupling of aliphatic species in chlorobenzene formation. The PCDDs seemed to be largely influenced by chlorophenol condensation reactions and to some extent chlorination reactions, while the PCDFs displayed a chlorination-oriented pattern for the mono- to tri-chlorinated homologues and a PCPh condensation pattern for the higher chlorinated homologues. Injection of non-chlorinated dibenzo-p-dioxin at 650 degrees C resulted in increased formation of Tri-HxCDD and a decrease in the dibenzofuran levels. The affected PCDD and PCDF congeners were not products expected to form from chlorine substitution, but instead are well known chlorophenol condensation products.
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| 24. |
- Jansson, Stina, 1975-
(author)
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Thermal formation and chlorination of dioxins and dioxin-like compounds
- 2008
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Doctoral thesis (other academic/artistic)abstract
- This thesis contributes to an increased understanding of the formation of dioxins and dioxin-like compounds in combustion processes. Although emissions to air from waste incineration facilities have been greatly reduced by the use of efficient air pollution control measures, the resulting residues (ashes and filters) are highly toxic and are classified as hazardous waste. The main objective of the work underlying this thesis was to elucidate the formation and chlorination pathways of dioxins and dioxin-like compounds in waste combustion flue gases in the temperature range 640-200°C in a representative, well-controlled laboratory-scale reactor using artificial municipal solid waste. This could contribute to the reduction of harmful emissions to air and also reduce the toxicity of waste incineration residues, thus reducing or even eliminating the need for costly and potentially hazardous after-treatment. A comparison of four different quenching profiles showed that the formation of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) was rapid and mainly occurred in the 640-400°C temperature region, with high dependency on sufficient residence time within a specific temperature region. Prolonged residence time at high temperatures (450/460°C) reduced the PCDD yields, even at lower temperatures along the post-combustion zone. PCDD, PCDF and PCN (polychlorinated naphthalene) isomer distribution patterns indicated contributions from chlorophenol condensation as well as chlorination reactions for all three classes of compounds. The formation of PCDDs was largely influenced by chlorophenol condensation and to some extent by chlorination reactions. For the PCDFs, chlorine substitution adjacent to the oxygen bridges was unfavoured, as demonstrated by the notably lower abundance of 1,9-substituted congeners. This was supported by bidirectional orthogonal partial least squares (O2PLS) modelling. The variable with the greatest influence on the distribution of PCDD congeners was the relative free energy (RΔGf). The O2PLS models displayed distinct clusters, dividing most of the homologues into two or three sub-groups of congeners which seemed to correspond to the probability of origination from chlorophenol condensation. The effects of injection of aromatic structures into the flue gas differed for each class of compounds. Injection of naphthalene increased the formation of monochlorinated naphthalene but the remaining homologues appeared to be unaffected. This was probably due to insufficient residence time at temperatures necessary for further chlorination. Injected dibenzo-p-dioxin was decomposed, chlorinated and re-condensated into PCDDs and PCDFs, whereas injection of dibenzofuran and fluorene reduced the PCDD levels in the flue gas.
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| 25. |
- Liljelind, Per, et al.
(author)
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Method for Multiresidue Determination of Halogenated Aromatics and PAHs in Combustion-Related Samples
- 2003
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In: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 37:16, s. 3680-6
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Journal article (peer-reviewed)abstract
- Flue gas and fly ash samples have a complex composition. Thus, thorough extraction and selective cleanup prior to analysis are essential. This paper presents an evaluated method for determining halogenated dibenzo-p-dioxins (PXDD), halogenated dibenzofurans (PXDF), chlorinated biphenyls (PCB), chlorobenzenes (CBz), -phenols (CPh), dibenzo-p-dioxins (DD), dibenzofurans (DF), and polycyclic aromatic hydrocarbons (PAH) in a single sample. Since these combustion byproducts are ubiquitous, harmful environmental contaminants it is very important to obtain reliable assessments of them: especially specific PCDD/F and PCB congeners with Ah-receptor mediated toxicity. The reported method for this purpose includes techniques such as solid-phase extraction, Soxhlet-Dean-Stark extraction, cleanup using open liquid chromatographic columns, and finally GC/MS analysis/determination with quantification by the isotope dilution technique. The validation results presented here show good reproducibility for PXDD/F and PCB and are satisfactory for CPh, CBz, and PAH. An extraction efficiency test revealed that a nonpolar solvent did not completely extract a few analytes, i.e., diCPh and fluorene, which appear to require a more polar extraction agent. To pinpoint and minimize the loss of analytes, specific studies on reductions of their amounts during sample concentration were performed, showing that traditional rotary evaporation and nitrogen blow-down produce equally good results as a novel technique.
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