| 1. |
- Klauser, Franziska, et al.
(author)
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Effect of Oxidizing Honeycomb Catalysts Integrated in a Firewood Room Heater on Gaseous and Particulate Emissions, Including Polycyclic Aromatic Hydrocarbons (PAHs)
- 2018
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In: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 32:11, s. 11876-11886
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Journal article (peer-reviewed)abstract
- Residential wood combustion is linked to a significant extent of emissions of polycyclic aromatic hydrocarbons (PAHs), which represent highly toxic, semivolatile pollutants. The use of catalysts reveals an effective measure to reduce emissions, especially gaseous flue gas compounds (carbon monoxide (CO) and organic gaseous compounds (OGC)). Their effect on toxicologically relevant PAHs is not clarified yet. In this work, the impact of two commercially available oxidizing platinum/palladium catalysts with either metallic or ceramic honeycomb carriers was examined under real-life operating conditions of a firewood room heater. The catalytic effect on CO and OGC, total suspended particles (TSP), total carbon (TC), elemental carbon (EC), organic carbon (OC), and 19 different PAHs, including 16 EPA PAHs (PAHs defined by the Environmental Protection Agency as priority pollutants) was evaluated by parallel measurements of catalytically treated and untreated flue gas from firewood combustion. The metallic catalyst, having a reaction surface that is 3.5 times greater than the ceramic catalyst, leads to a more-pronounced impact. Both types, the ceramic and the metallic catalyst, led to distinct reductions of CO (-69%, -88%) and OGC (-27%, -39%). In the test with the metallic catalyst, TSP increased (+17%) and PAHs were clearly reduced (-63%). This reduction was exclusively related to the higher-molecular-weight PAHs, such as the particularly toxic benzo(a)pyrene. Carbonaceous fractions (TC, EC, and OC) were not affected significantly. The toxicity of emissions arising from EPA PAHs can be clearly reduced by catalytic treatment. Moreover, the increase of TSP opens new questions, which must be clarified before the investigated catalysts are recommended as suitable secondary measure for emission abatement.
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| 2. |
- Klauser, Franziska, et al.
(author)
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Emission characterization of modern wood stoves under real-life oriented operating conditions
- 2018
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In: Atmospheric Environment. - : Elsevier. - 1352-2310 .- 1873-2844. ; 192, s. 257-266
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Journal article (peer-reviewed)abstract
- The quality of emission inventories substantially bases on the reliability of used emission factors (EFs). In this work EFs were studied according to recently published characterization methods, called “beReal”, reflecting real life operating conditions in Europe. EFs for four pellet stoves and nine firewood appliances (roomheaters and cookers) of carbon monoxide (CO), organic gaseous compounds (OGC), nitrogen oxides, total solid particles (TSP) of hot and of diluted flue gas, total, elemental and organic carbon (TC, EC, OC) and benzo(a)pyrene were determined.CO, OGC, TSPs, TC, EC and OC emissions from firewood appliances were significantly higher than for pellet stoves, indicating the high relevance of classifying appliances according to the operation type. TSP sampled from diluted flue gas at 40 °C (28 mg MJ−1 to 271 mg MJ−1 based on fuel input) was higher than TSP sampled from hot flue gas (2170 mg MJ−1 to 70 mg MJ−1). This reveals the high relevance of sampling conditions for the determination of real life emissions. Benzo(a)pyrene emissions scattered over a wide range (0.5 μg MJ−1 to 129.8 μg MJ−1) indicating high sensitivity to unfavorable combustion conditions. Therefore a higher number of experimentally determined emissions factors could improve the reliability of EFs for inventories. CO emissions measured in beReal tests were substantially higher than official type tests, thus showing that type testing results provide limited information for the determination of real life emissions.A systematic evaluation of EFs with defined real life methods like beReal would substantially improve the reliability of emission inventories.
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| 3. |
- Rebbling, Anders, 1980-, et al.
(author)
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Prediction of slag related problems during fixed bed combustion of biomass by application of a multivariate statistical approach on fuel properties and burner technology
- 2020
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In: Biomass and Bioenergy. - : Elsevier. - 0961-9534 .- 1873-2909. ; 137
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Journal article (peer-reviewed)abstract
- Slag is related to the melting properties of ash and is affected by both the chemical composition of the fuel ash and the combustion parameters. Chemical analysis of slag from fixed bed combustion of phosphorus-poor biomass show that the main constituents are Si, Ca, K, O (and some Mg, Al, and Na), which indicates that the slag consists of different silicates. Earlier research also points out viscosity and fraction of the ash that melts, as crucial parameters for slag formation. To the authors’ knowledge, very few of the papers published to this day discuss slagging problems of different pelletized fuels combusted in multiple combustion appliances. Furthermore, no comprehensive classification of both burner technology and fuel ash parameters has been presented in the literature so far. The objective of the present paper was therefore to give a first description of a qualitative model where ash content, concentrations of main ash forming elements in the fuel and type of combustion appliance are related to slagging behaviour and potential operational problems of a biomass fuel in different small- and medium scale fixed bed appliances.Based on the results from the combustion of a wide range of pelletized biomass fuels in nine different burners, a model is presented for amount of slag formed and expected severity of operational problems. The model was validated by data collected from extensive combustion experiments and it can be concluded that the model predicts qualitative results.
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| 4. |
- Schoen, Claudia, et al.
(author)
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New evaluation strategies regarding slag prediction in pellet boilers
- 2014
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In: Papers of the 22nd european biomass conference. ; , s. 368-372
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Conference paper (peer-reviewed)abstract
- Pellet boilers are widely used for heat production. In most cases only wood pellets with low ash content are suitable for these appliances due to the increased risk of slagging. The ash fusion test (AFT) is the only standardized method currently available for the prediction of slagging but it frequently failed when solid biofuels were investigated. Therefore different laboratory methods for the prediction of slagging were applied in order to identify the most suitable method for reliable prediction of slagging tendencies. Three laboratory test methods were considered in this investigation: a rapid slag test (1), the so-called "CIEMAT method" (2) and the "slag analyser" (3). The suitability of the obtained results was validated by practical combustion tests in up to nine different pellet boilers. As the most promising method the slag analyser was identified. It will be further developed with the aim to be proposing as an additional standard method for determination of slag related problems in fixed bed combustion systems.
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| 5. |
- Schön, Claudia, et al.
(author)
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New Experimental Evaluation Strategies Regarding Slag Prediction of Solid Biofuels in Pellet Boilers
- 2019
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In: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 33:11, s. 11985-11995
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Journal article (peer-reviewed)abstract
- Pellet boilers and pellet stoves are widely used for heat production. But in most cases, only specific wood pellets with a low ash content are approved due to the increased risk of slagging and limited deashing capacity. The ash fusion test (AFT), according to prCEN/TS 15370-1, is currently the only standard method for the prediction of slagging. This method is not feasible for all biomass fuel types, since sometimes the characteristic temperatures cannot be determined or the characteristic shapes do not occur for temperature determination. Furthermore, the method is costly and requires complex instrumental infrastructure. Hence, a demand for more expressive or more rapid methods to characterize slag formation potential of fuels is often claimed. Based on a literature study, four such laboratory test methods were chosen, partly adapted, and then experimentally investigated. These methods included thermal treatment of the fuel itself or the ashes of the fuel and were the rapid slag test, CIEMAT, the slag analyzer, and the newly developed pellet ash and slag sieving assessment (PASSA) method. Method performance was practically assessed using 14 different biomass fuel pellets, which were mainly from different assortments of wood, but also herbaceous or other nonwoody fuels. The results from the tests with these four alternative methods were evaluated by comparing to both results from standard AFT and results from full-scale combustion tests performed over a maximum of 24 h. Seven different pellet boilers were assessed, of which one boiler was used to apply all 14 test fuels. According to the granulometric ash analysis (i.e., the ratio of >1 mm-fraction toward total ash formed), the sensitivity of the new test methods to depict slagging phenomena at a suitable level of differentiation was assessed. Satisfactory conformity of the boiler ash assessment (reference) was found for both, the slag analyzer and the PASSA method. The latter may, in particular, be seen as a promising and relatively simple low-input procedure, which can provide more real-life oriented test results for fixedbed combustion. The standardized AFT could, however, not sufficiently predict the degree of slag actually formed in the reference boiler, particularly when only wood fuels are regarded.
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