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- Löthgren, Carl-Johan, 1968-
(författare)
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Mercury and dioxins in a MercOx-scrubber
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The removal of mercury and the absorption of dioxins in an acid wet scrubber have been studied in industrial scale. Hydrogen peroxide is added as an oxidizing agent to the scrubber liquid with the purpose to remove SO2 and enhance the removal of mercury. The scrubber is operating as the final flue gas cleaning stage at the SAKAB plant, a hazardous waste incinerator in Sweden. Mercury speciation was measured in flue gases upstream and downstream of the scrubber with three different techniques: Impingers, solid phase absorbents and a continuous emission monitor. During the flue gas sampling periods also the scrubber liquid was sampled. It was found that mercury entering the scrubber is efficiently oxidized at normal operating conditions. An increased fraction of elemental gaseous mercury was found in flue gases after the scrubber at redox potentials below 700 mV and pH below 1. The mercury emissions were more dependent on the scrubber liquid composition than on the inlet concentrations. Equilibrium calculations of the mercury speciation in the scrubber liquid and flue gases after the scrubber showed that mercury is normally emitted as HgBr2 or HgCl2. Elemental bromine and chlorine are formed in the scrubber. Both species probably take part in the mercury oxidation process. Results from 18 months of dioxin sampling, using a continuous long term sampling device (the AMESA system) were evaluated by multivariate data analyses. It was shown that the elevated emissions observed were caused by a memory effect in the scrubber due to high start-up concentrations. The memory effect was modelled in a diffusion model where the dioxins were considered to be physically absorbed in and desorbed from the polypropylene fillings of the scrubber. From the diffusion model, the diffusivities for tetra to hexa chlorinated dioxins in polypropylene were calculated. The diffusivity of tetra chlorinated dioxins was calculated to be 10-14 m2/s. The diffusivity decreases with increasing chlorination. For hexa chlorinated dioxins it was calculated to be 10-16 m2/s. Brominated dioxins were measured before and after a fabric filter. The fraction of brominated dioxins increased after the filter. Di brominated furans were the most abundant homologue.
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| 2. |
- Malmvärn, Anna, 1966-
(författare)
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Brominated natural products at different trophic levels in the Baltic Sea : Identification of polybrominated dioxins, hydroxylated and methoxylated diphenyl ethers
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Over time, the Baltic Sea has been contaminated by increasing discharges of pollutants from human activities. Persistent organic pollutants (POPs) have caused toxic effects in wildlife and excess of nutrients have led to eutrophication. Furthermore, there are indications that certain polyhalogenated compounds similar in structure to man-made POPs are produced by the biota present in this sea. In the late 1990’s both methoxylated polybrominated diphenyl ethers (MeO-PBDEs) and hydroxylated-PBDEs (OH-PBDEs) were identified in fish and seals living in this environment. OH-PBDEs can originate from metabolism of PBDEs, but both OH- and MeO-PBDEs are also known to be natural products in marine environments. Another group of POPs, the polybrominated dibenzo-p-dioxins (PBDDs), are not produced commercially, but are known to be by-products of chemical industry and of the combustion of, e.g., brominated flame retardants (BFRs). In contrast to the OH- and MeO-PBDEs, PBDDs have not previously been shown to be natural products, although certain related compounds have been indicated to have a natural origin.This thesis describes the identification of PBDDs, OH-PBDEs and MeO-PBDEs in algae, blue mussels and fish living in the Baltic Sea. Several of these compounds were also detected in cyanobacteria. Moreover, PBDDs were present in fish, mussels, shrimp and crabs from different regions of the Baltic Sea and from the west coast of Sweden, but not in organisms from freshwater environments. The levels of these compounds in Baltic fish generally exceeded those of their chlorinated analogues. The origin of the PBDDs identified is somewhat unclear, but the high levels present in blue mussels and the pattern of congeners observed indicate natural production. The presence of PBDDs, OH-PBDEs and MeO-PBDEs in fish and shellfish constitutes a potential risk to both humans and wildlife and requires further investigation.
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