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Thermal degradation of PCDD/F, PCB and HCB in municipal solid waste ash.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
2007 (Engelska)Ingår i: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 67, nr 3, s. 474-481Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

A thermal degradation procedure for reducing the concentrations of mono- to octa-chlorinated PCDD/Fs, PCBs and hexa-chlorobenzenes (HCB) in filter ash from incinerated municipal solid waste (MSW) is described. Thermal treatment of filter ash samples at 500 °C for 60 min in a closed system providing low oxygen conditions resulted in 97% and 99% reductions in the total and I-TEQ concentrations of PCDD/Fs, to 6.8 μg kg−1 ash and <0.05 μg I-TEQ kg−1 ash, respectively. Increasing the thermal treatment time to 480 min, at the same temperature, yielded 99% reductions in both total and I-TEQ concentrations of the mono- to octa-chlorinated PCDD/Fs. Similar effects were observed for HCB and PCBs. The data from this study indicate that PCDD/Fs and other toxic organic compounds in ash from incinerated MSW, can be effectively degraded by this procedure, which combines relatively low-temperatures, short treatment times, and low oxygen conditions.

Ort, förlag, år, upplaga, sidor
Oxford: Pergamon Press , 2007. Vol. 67, nr 3, s. 474-481
Nyckelord [en]
PCDD/F, PCB, HCB, Thermal degradation, MSW, Fly ash
Identifikatorer
URN: urn:nbn:se:umu:diva-10112DOI: 10.1016/j.chemosphere.2006.09.057PubMedID: 17109915OAI: oai:DiVA.org:umu-10112DiVA, id: diva2:149783
Tillgänglig från: 2007-03-02 Skapad: 2007-03-02 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
Ingår i avhandling
1. Formation and degradation of PCDD/F in waste incineration ashes
Öppna denna publikation i ny flik eller fönster >>Formation and degradation of PCDD/F in waste incineration ashes
2007 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The disposal of combustible wastes by incineration is a controversial issue that is strongly debated by both scientists and environmental activists due to the resulting emissions of noxious compounds, including (inter alia) polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), heavy metals and acid gases like sulfur dioxide. Currently available air pollution control devices are capable of effectively cleaning flue gases, and PCDD/F emissions to air from modern municipal solid waste (MSW) incinerators are low. However, the PCDD and PCDF end up in ash fractions that, in Sweden, are usually deposited in landfills.

The European Union has recently set a maximum permitted total concentration of 15 µg TEQ/kg for PCDD/F species in waste. Fly ash from municipal solid waste (MSW) incineration containing PCDD/Fs at concentrations above this limit will have to be remediated to avoid disposing of them in landfills; an expensive and environmentally unfriendly option. Therefore, effective, reliable and cost-effective methods for degrading PCDD/F in fly ash are required, and a better understanding of the behavior of PCDDs and PCDFs during thermal treatment will be needed to develop them.

In the studies this thesis is based upon both the formation and degradation of PCDDs and PCDFs in ashes from MSW incineration were studied.

The main findings of the investigations regarding PCCD/F formation were:

- The concentrations of PCDD and PCDF in fly ash increased with reductions in the temperature in the post-combustion zone.

- The homologue profile in the ash changed when the temperature in the post-combustion zone changed.

- The final amounts of PCDD and PCDF present were affected by their rates of both formation and degradation, and the mechanisms involved differ between PCDDs and PCDFs.

The main findings from the degradation studies were:

- The chemical composition of ash has a major impact on the degradation potential of PCDD and PCDF.

- The presence of oxygen during thermal treatment can enhance the degradation of PCDD and PCDF.

- Thermal treatment is a viable option for degrading PCDD and PCDF in ashes from MSW.

- Shifts in chlorination degree occur during thermal treatment.

- Rapid heat transfer into the ash is a key factor for ensuring fast degradation of PCDD and PCDF.

- Degradation of other chlorinated organic compounds, e.g. PCB and HCB, also occurs during thermal treatment of ash.

- Reductions in levels of PCDD and PCDF were not solely due to their desorption to the gas phase.

- Differences between the behavior of 2378-substituted congeners of PCDD and PCDF and the other congeners during thermal treatment were observed.

- Differences in isomer patterns of both PCDD and PCDF were observed between the ash and gas phases after thermal treatment at both 300 and 500 oC.

Overall, the results show that the formation and degradation mechanisms of PCDDs differ substantially from those of PCDFs. Thus these groups of compounds should be separately considered in attempts to identify ways to reduce their concentrations.

Ort, förlag, år, upplaga, sidor
Umeå: Kemi, 2007. s. 59
Nyckelord
MSW, fly ash, remediation, ash, PCDD, PCDF, formation, degradation, destruction, dechlorination, thermal treatment
Nationell ämneskategori
Miljövetenskap
Identifikatorer
urn:nbn:se:umu:diva-1395 (URN)978-91-7264-411-3 (ISBN)
Disputation
2007-11-09, N320, Naturvetarhuset, Umeå Universitet, Umeå, 13:00
Opponent
Handledare
Tillgänglig från: 2007-10-18 Skapad: 2007-10-18 Senast uppdaterad: 2011-03-10Bibliografiskt granskad

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