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Waste incineration residues: Persistent organic pollutants in flue gas and fly ash from waste incineration
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Organiska miljögifter i rökgas och flygaska från sopförbränning (Swedish)
Abstract [en]

Modern societies produce large quantities of municipal solid waste (MSW), which is commonly disposed of by incineration. This has several advantages: it reduces the waste’s volume and sterilizes it while also enabling energy recovery. However, MSW incineration has some notable disadvantages, the most widely debated of which is probably the production and release of persistent organic pollutants (POP) such as polychlorinated dibenzofurans (PCDF), dibenzo-p-dioxins (PCDD), biphenyls (PCB) and naphthalenes (PCN). Of the 210 PCDF and PCDD congeners, 17 are toxic, with hormone-disrupting and carcinogenic properties. Twelve of the 209 PCB congeners and at least 2 of the 75 PCN also exhibit such properties. These POP form in the post-combustion zones of MSW incineration plants and are removed from the flue gas using filtering devices that trap them in the fly ash

This thesis concerns the formation and degradation of POP in processes related to MSW incineration. The first paper describes a case study in which PCDD were forming in filters designed to remove them from flue gases, causing emission-related issues in a full-scale MSW incineration plant. It was shown that the PCDD formation was probably due to chlorophenol condensation on the filters’ surfaces.

The second paper describes the validation of a cooling probe designed to prevent POP formation during high temperature (>450 °C) flue gas sampling. The results obtained also confirmed that PCDF and PCDD formation takes place at temperatures below 600 °C.

In the third paper, three different fly ashes were subjected to thermal treatment under an inert atmosphere in a rotary kiln and in sealed ampoules at 400 °C. The concentrations, degrees of chlorination and congener profiles of the POP in the treated ashes and emitted gases were compared to those for the untreated ashes. The trends observed for PCDF mirrored those for PCN, while the trends for PCDD closely resembled those for PCB. The PCDF congener profiles of the kiln ash were similar regardless of the initial ash composition, suggesting that the mechanisms of PCDF formation were similar in all cases.

The fourth paper describes the surface characterization of the three fly ashes studied in paper three by SEM, EDX, XPS and XRD. In addition, the thermal desorption and subsequent degradation of POP from the ashes was studied at temperatures of 300-900 °C. The composition of the gases released as the temperature increased differed between the ashes and depended on their composition. Doping experiments using isotopically labelled PCDF and PCDD suggests that PCDD desorbed at lower temperatures than PCDF.

This thesis examines several problems relating to POP formation during MSW incineration, from sampling to the ultimate fate of incineration residues. The results obtained illustrate the wide range of processes that contribute to thermal POP formation and degradation during and after MSW incineration.

Abstract [sv]

Förbränning av hushållssopor är en vanlig metod för att hantera ett växande avfallsproblem. Metoden har flera fördelar, såsom minskning av volym och vikt, sterilisering och energiåtervinning. Sopförbränning har dock vissa nackdelar och det mest debatterade är sannolikt utsläpp av persistenta organiska föroreningar (POPs) som polyklorerad dibensofuran (PCDF), dibenso-p-dioxin (PCDD), bifenyl (PCB) och naftalen (PCN). Det finns totalt 210 PCDF- och PCDD- kongener, med mellan ett till åtta klor på kolskelettet, varav 17 är giftiga med hormonstörande och cancerframkallande egenskaper. Även tolv av totalt 209 PCB-kongener samt minst två av totalt 75 PCN-kongener uppvisar liknande egenskaper. Dessa klorerade organiska föroreningar bildas då rökgaserna kyls ner i sopförbränningsanläggningarna och avlägsnas från rökgaserna med hjälp av filter och hamnar i flygaskan. Denna avhandling handlar om bildning och nedbrytning av POPs i sopförbränningsrelaterade processer.

 

Den första artikeln är en fallstudie där PCDD bildas i filtren i en fullskalig sopförbränningsanläggning. Bildningen ledde till förhöjda halter organiska föroreningar i rökgaserna, vilket ledde till ökade utsläpp. Den funna bildningsvägen för PCDD i filtren befanns sannolikt bero på kondensation av klorfenoler på filterytorna.

Den andra artikeln är en valideringsstudie av en kylprob avsedd att användas vid rökgasprovtagning vid hög temperatur (> 450 °C) för att undvika bildning av POPs under provtagningen. Studien bekräftade att majoriteten av PCDF- och PCDD- bildning i rökgaser från sopförbränning sker vid temperaturer under 600 °C.

I den tredje artikeln berättas om behandling av tre olika flygaskor från olika sopförbränningsanläggningar. Askorna behandlades vid 400 °C i inert atmosfär i både en roterugn och i förseglade ampuller. De resulterande koncentrationerna, kloreringsgraderna och kongenprofilerna av de organiska föroreningarna jämfördes. Likheter hittades mellan PCDF och PCN, medan PCDD och PCB betedde sig på ett annat sätt. Studien fann också att PCDF kongenprofiler i aska som behandlats i roterugnen liknade varandra, oberoende av askornas sammansättning, vilket tyder på en liknande bildningsväg.

För den fjärde artikeln, genomfördes ytkarakterisering (SEM, EDX, XPS och XRD) på de tre flygaskorna från artikel tre som sedan hettades upp från 30 °C till 900 °C i vacuum. Det som frigjordes på grund av uppvärmningen samt nedbrytningsprodukter från askorna studerades med hjälp av masspektrometri och infraröd spektroskopi. Studien fann att de gaser som frigjordes när temperaturen ökade skilde mellan askorna, beroende på deras sammansättning. Studien fann också att när aska dopad med isotopmärkt PCDF och PCDD utsattes för samma behandling, frigjordes PCDD vid lägre temperatur än PCDF.

Denna avhandling berör flera aspekter av problematiken kring klorerade organiska föroreningar som bildas vid sopförbränning, från provtagning till hur man ska hantera flygaskan. Avhandlingen belyser även olika typer av bildning och nedbrytning av POPs i varma processer kopplade till sopförbränning.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet , 2014. , 75 p.
Keyword [en]
MSW, PCDD, PCDF, PCN, PCB, POP, formation, degradation, case study, flue gas sampling thermal treatment, fly ash, surface characterization
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:umu:diva-92765ISBN: 978-91-7601-113-3 (print)OAI: oai:DiVA.org:umu-92765DiVA: diva2:742941
Public defence
2014-09-26, Umeå universitet, KBC-huset, KB3B1, Linneaus väg 6, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2014-09-05 Created: 2014-09-03 Last updated: 2016-05-03Bibliographically approved
List of papers
1. In-filter PCDF and PCDD formation at low temperature during MSWI combustion
Open this publication in new window or tab >>In-filter PCDF and PCDD formation at low temperature during MSWI combustion
2014 (English)In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 102, 12-17 p.Article in journal (Refereed) Published
Abstract [en]

This case study investigated PCDF and PCDD emissions from a 65 MW waste-to-energy plant to identify why an air pollution control system remodeling to accommodate increased production resulted in increased TEQ concentrations. Pre- and post-filter gases were collected simultaneously in four sample sets with varying filter temperatures and with/without activated carbon injection. Samples were analyzed to determine total PCDF and PCDD concentrations, as well as homologue profiles, and concentrations of individual congeners (some remained co-eluted). The total post filter PCDD concentrations where found to increase while the concentrations of PCDF and 2,3,7,8-substituted congeners declined. An investigation of the individual congener concentrations revealed that the increase of PCDD concentrations were due to a few congeners, suggesting a single formation route. The study also concludes that vital information about the formation could be obtained by not restricting the analysis to just the 2,3,7,8-substituted congeners. 

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
full scale, MSWI, PCDD, PCDF, fabric filters, case study
National Category
Chemical Sciences Biological Sciences
Identifiers
urn:nbn:se:umu:diva-88378 (URN)10.1016/j.chemosphere.2013.11.068 (DOI)000333496800003 ()
Available from: 2014-05-05 Created: 2014-05-05 Last updated: 2017-12-05Bibliographically approved
2. Accurate sampling of PCDD/F in high temperature flue-gas using cooled sampling probes
Open this publication in new window or tab >>Accurate sampling of PCDD/F in high temperature flue-gas using cooled sampling probes
Show others...
2012 (English)In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 88, no 7, 832-836 p.Article in journal (Refereed) Published
Abstract [en]

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. 

Place, publisher, year, edition, pages
Elsevier, 2012
Keyword
Polychlorinated dibenzo-p-dioxins, Polychlorinated dibenzofurans, Quenching, Sub-zero cooling probe, Waste combustion
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-54601 (URN)10.1016/j.chemosphere.2012.03.090 (DOI)
Note

Available online 28 April 2012

Available from: 2012-05-02 Created: 2012-05-02 Last updated: 2017-12-07Bibliographically approved
3. Behavior of PCDF, PCDD, PCN and PCB during low temperature thermal treatment of MSW incineration fly ash
Open this publication in new window or tab >>Behavior of PCDF, PCDD, PCN and PCB during low temperature thermal treatment of MSW incineration fly ash
2015 (English)In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 279, 180-187 p.Article in journal (Refereed) Published
Abstract [en]

For both economic and ecological reasons better knowledge of effects of incinerating waste on its persistent organic pollutant (POP) contents is needed. Thus, ash from three municipal solid waste incineration (MSWI) plants was collected and analyzed for elemental composition, carbon speciation and POP (PCDF, PCDD, PCN and PCB) contents. The ash was then subjected to two thermal treatments: a small batch treatment (3 g) in sealed glass ampoules and a large batch treatment (0.7 kg, in a kiln) under oxygen-deficient conditions. The POP contents of the ash (and the gas phase generated by the large batch treatment) were subsequently re-analyzed. Finally, principal component analysis of congener profiles were used to clarify the POPs' behavior in the treated ash. The results indicate that the thermal treatments had similar effects on PCDDs and PCBs, which apparently degraded but did not reform. They also had similar effects on PCDFs and PCNs, which were degraded but selectively reformed (both during and after the treatment). Furthermore, the ash composition did not significantly influence the homologue-specific congener patterns of the formed PCDFs and PCNs, but they had markedly lower chlorination degrees than those in the untreated ash and their overall toxicity was reduced by the kiln treatment, regardless of post-kiln concentrations and ash composition. (C) 2015 Elsevier B.V. All rights reserved.

Keyword
PCDD/PCDF, PCN, PCB, MSWI ash, Homologue specific congener patterns
National Category
Organic Chemistry
Identifiers
urn:nbn:se:umu:diva-108447 (URN)10.1016/j.cej.2015.05.015 (DOI)000359873500021 ()
Note

Originally published in manuscript form with title "Behavior of PCDF, PCDD, PCN and PCB during thermal treatment of MSW incineration fly ash".

Available from: 2015-09-29 Created: 2015-09-11 Last updated: 2017-12-01Bibliographically approved
4. Thermal desorption and degradation of municipal solid waste incineration fly ash
Open this publication in new window or tab >>Thermal desorption and degradation of municipal solid waste incineration fly ash
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-92730 (URN)
Available from: 2014-09-03 Created: 2014-09-02 Last updated: 2014-09-03Bibliographically approved

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Weidemann, Eva

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