| 1. |
- Kozyatnyk, Ivan, 1982-, et al.
(författare)
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Influence of hydrothermal carbonization conditions on the porosity, functionality, and sorption properties of microalgae hydrochars
- 2023
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Green microalgae is a possible feedstock for the production of biofuels, chemicals, food/feed, and medical products. Large-scale microalgae production requires large quantities of water and nutrients, directing the attention to wastewater as a cultivation medium. Wastewater-cultivated microalgae could via wet thermochemical conversion be valorised into products for e.g., water treatment. In this study, hydrothermal carbonization was used to process microalgae polycultures grown in municipal wastewater. The objective was to perform a systematic examination of how carbonization temperature, residence time, and initial pH affected solid yield, composition, and properties. Carbonization temperature, time and initial pH all had statistically significant effects on hydrochar properties, with temperature having the most pronounced effect; the surface area increased from 8.5 to 43.6 m2 g−1 as temperature was increased from 180 to 260 °C. However, hydrochars produced at low temperature and initially neutral pH generally had the highest capacity for methylene blue adsorption. DRIFTS analysis of the hydrochar revealed that the pH conditions changed the functional group composition, implying that adsorption was electrostatic interactions driven. This study concludes that un-activated hydrochars from wastewater grown microalgae produced at relatively low hydrothermal carbonization temperatures adsorb methylene blue, despite having low surface area.
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| 2. |
- Björklund, Sofie, et al.
(författare)
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Emission of per- and polyfluoroalkyl substances from a waste-to-energy plant-occurrence in ashes, treated process water, and first observation in flue gas
- 2023
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 57:27, s. 10089-10095
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Tidskriftsartikel (refereegranskat)abstract
- Per- and polyfluoroalkyl substances (PFASs) are a large group of compounds commonly used as industrial chemicals and constituents of consumer products, e.g., as surfactants and surface protectors. When products containing PFASs reach their end of life, some end up in waste streams sent to waste-to-energy (WtE) plants. However, the fate of PFASs in WtE processes is largely unknown, as is their potential to enter the environment via ash, gypsum, treated process water, and flue gas. This study forms part of a comprehensive investigation of the occurrence and distribution of PFASs in WtE residues. Sampling was performed during incineration of two different waste mixes: normal municipal solid waste incineration (MSWI) and incineration of a waste mix with 5-8 wt % sewage sludge added to the MSWI (referred to as Sludge:MSWI). PFASs were identified in all examined residues, with short-chain (C4-C7) perfluorocarboxylic acids being the most abundant. Total levels of extractable PFASs were higher during Sludge:MSWI than during MSWI, with the total annual release estimated to be 47 and 13 g, respectively. Furthermore, PFASs were detected in flue gas for the first time (4.0-5.6 ng m-3). Our results demonstrate that some PFASs are not fully degraded by the high temperatures during WtE conversion and can be emitted from the plant via ash, gypsum, treated process water, and flue gas.
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| 3. |
- Björklund, Sofie, 1992-
(författare)
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Exploring the occurrence, distribution and transport of per- and polyfluoroalkyl substances in waste-to-energy plant
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Efficient municipal solid waste (MSW) management promotes resource conservation, climate-change mitigation, public health, and environmental protection. A key aspect of environmental protection within MSW management is ensuring that potential pollutants are not released into the environment. One group of environmental pollutants of global concern is per- and polyfluoroalkyl substances (PFAS). Also known as “forever chemicals”, these are used in a wide variety of consumer products and industrial processes, and are known for their persistence. The fate of PFAS in waste-management processes, such as Waste-to-Energy (WtE), is largely unknown. This thesis aimed to investigate the fate of PFAS in a WtE plant.Comprehensive sampling was performed to provide a synoptic overview of the occurrence and distribution of PFAS in residual streams, and to investigate the potential emission of PFAS from the WtE process to the environment.Short-chain (C ≤ 7) perfluorocarboxylic acids were the dominant class of PFAS across all matrices analysed. PFAS was found in leachate from the temporary MSW stockpile located at the WtE plant, as well as in most incineration residues (e.g., bottom ash, condensate, and flue gas) during the incineration of MSW. Co-incineration of sewage sludge from a wastewater treatment plant and MSW (with the former added at 5–8 wt.% of the latter) led to an increase in the concentration of PFAS in all matrices, with the exception of filter ash and stack flue gas.In general, the wet flue-gas treatment was able to capture some PFAS and transfer them to the in-house process-water treatment; however, further optimisation is required to increase the ability of this treatment to capture the shortest PFAS investigated (perfluorobutanoic acid).Overall, these findings highlight that some PFAS are not fully degraded during WtE conversion, and that PFAS could enter the environment via both leaching from unburnt MSW and incineration residues.
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| 4. |
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| 5. |
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| 6. |
- Björklund, Sofie, et al.
(författare)
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Occurrence of per- and polyfluoroalkyl substances and unidentified organofluorine in leachate from waste-to-energy stockpile : A case study
- 2021
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Ingår i: Chemosphere. - : Pergamon Press. - 0045-6535 .- 1879-1298. ; 278
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Tidskriftsartikel (refereegranskat)abstract
- Per- and polyfluoroalkyl substances (PFASs) are a diverse group of chemicals used in consumer products, which will inevitably end up in waste streams. Landfills are widely recognized secondary point sources of PFASs, but other types of waste management sites have received less attention. Therefore, in a case study presented here we investigated releases of PFASs from temporarily stored waste by determining quantities of 34 PFASs in leachate from a Waste-to-Energy stockpile (45 000 ± 2000 tonnes) during five months in 2019. We also measured extractable organofluorine (EOF) to account for PFASs not included in the target list. The mean total concentration of the 34 PFAS (Σ34PFAS) was 211 ± 31 ng/L, and short-chain (C4–C7) perfluorocarboxylic acids (PFCAs) accounted for 56–60% of the total. Moreover, we found that Σ34PFAS only accounted for 12% ± 4% of EOF detected in the leachate. Our results demonstrate that waste stockpiles are previously unexplored sources of PFASs in the environment, and the dominance of short-chain PFCAs is consistent with observed profiles of contaminants in landfill leachates.
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| 7. |
- Duong Phan, Ngoc Chau, et al.
(författare)
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Accurate sampling of PCDD/F in high temperature flue-gas using cooled sampling probes
- 2012
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 88:7, s. 832-836
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Wang, Dong, et al.
(författare)
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A novel data mining framework to investigate causes of boiler failures in waste-to-energy plants
- 2024
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Ingår i: Processes. - : MDPI. - 2227-9717. ; 12:7
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Tidskriftsartikel (refereegranskat)abstract
- Examining boiler failure causes is crucial for thermal power plant safety and profitability. However, traditional approaches are complex and expensive, lacking precise operational insights. Although data-driven approaches hold substantial potential in addressing these challenges, there is a gap in systematic approaches for investigating failure root causes with unlabeled data. Therefore, we proffered a novel framework rooted in data mining methodologies to probe the accountable operational variables for boiler failures. The primary objective was to furnish precise guidance for future operations to proactively prevent similar failures. The framework was centered on two data mining approaches, Principal Component Analysis (PCA) + K-means and Deep Embedded Clustering (DEC), with PCA + K-means serving as the baseline against which the performance of DEC was evaluated. To demonstrate the framework’s specifics, a case study was performed using datasets obtained from a waste-to-energy plant in Sweden. The results showed the following: (1) The clustering outcomes of DEC consistently surpass those of PCA + K-means across nearly every dimension. (2) The operational temperature variables T-BSH3rm, T-BSH2l, T-BSH3r, T-BSH1l, T-SbSH3, and T-BSH1r emerged as the most significant contributors to the failures. It is advisable to maintain the operational levels of T-BSH3rm, T-BSH2l, T-BSH3r, T-BSH1l, T-SbSH3, and T-BSH1r around 527 °C, 432 °C, 482 °C, 338 °C, 313 °C, and 343 °C respectively. Moreover, it is crucial to prevent these values from reaching or exceeding 594 °C, 471 °C, 537 °C, 355 °C, 340 °C, and 359 °C for prolonged durations. The findings offer the opportunity to improve future operational conditions, thereby extending the overall service life of the boiler. Consequently, operators can address faulty tubes during scheduled annual maintenance without encountering failures and disrupting production.
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| 9. |
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| 10. |
- Weidemann, Eva, 1982-, et al.
(författare)
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In-filter PCDF and PCDD formation at low temperature during MSWI combustion
- 2014
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 102, s. 12-17
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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