| 1. |
- Carvalho, Lara, et al.
(författare)
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Performance of a pellet boiler fired with agricultural fuels
- 2013
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 104, s. 286-296
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Tidskriftsartikel (refereegranskat)abstract
- The increasing demand for woody biomass increases the price of this limited resource, motivating the growing interest in using woody materials of lower quality as well as non-woody biomass fuels for heat production in Europe. The challenges in using non-woody biomass as fuels are related to the variability of the chemical composition and in certain fuel properties that may induce problems during combustion. The objective of this work has been to evaluate the technical and environmental performance of a 15 kW pellet boiler when operated with different pelletized biomass fuels, namely straw (Triticum aestivum), Miscanthus (Miscanthus × giganteus), maize (Zea mays), wheat bran, vineyard pruning (from Vitis vinifera), hay, Sorghum (Sorghum bicolor) and wood (from Picea abies) with 5% rye flour. The gaseous and dust emissions as well as the boiler efficiency were investigated and compared with the legal requirements defined in the FprEN 303-5 (final draft of the European standard 303-5). It was found that the boiler control should be improved to better adapt the combustion conditions to the different properties of the agricultural fuels. Additionally, there is a need for a frequent cleaning of the heat exchangers in boilers operated with agricultural fuels to avoid efficiency drops after short term operation. All the agricultural fuels satisfied the legal requirements defined in the FprEN 303-5, with the exception of dust emissions during combustion of straw and Sorghum. Miscanthus and vineyard pruning were the best fuels tested showing comparable emission values to wood combustion.
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| 2. |
- Klauser, Franziska, et al.
(författare)
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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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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 32:11, s. 11876-11886
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Klauser, Franziska, et al.
(författare)
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Emission characterization of modern wood stoves under real-life oriented operating conditions
- 2018
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Ingår i: Atmospheric Environment. - : Elsevier. - 1352-2310 .- 1873-2844. ; 192, s. 257-266
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Moser, Konstantin, et al.
(författare)
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Screw reactors and rotary kilns in biochar production – A comparative review
- 2023
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Ingår i: Journal of Analytical and Applied Pyrolysis. - : Elsevier. - 0165-2370 .- 1873-250X. ; 174:September 2023
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Tidskriftsartikel (refereegranskat)abstract
- One promising technology in the field of residue valorization is the pyrolytic conversion of biomass to biochar. There are a lot of proven technologies for this task, with many of them being quite distinctive. Biochar has a lot of valuable properties and it shows potential to be applicated in many different fields of industry as a green carbon resource. Thus, as the demand for its production rises, more and more people from different fields share interest in the same technologies and the demand for guidance in form of readily available information increases. Two prominent technologies rather similar in appearance are rotary kilns and screw reactors. Both technologies consist of a long, hollow cylinder and both technologies use some form of longitudinal rotation as a means to transport feedstock. In this review, both technologies are described and their biggest differences and similarities are discussed, all under the aspect of biochar production. In total, 21 unique rotary kilns and 58 unique auger reactors were identified. The paper addresses process specific aspects, like heat supply or residence time, but it also gives an overview on current research and general aspects like scale-up considerations. Differences between both technologies were found in all of these aspects, with some of the most pronounced being the bigger maximum capacities and the greater residence time distributions in rotary kiln pyrolysis. Both technologies are viable candidates for producing biochar on a commercial level, however, literature comparing the influence of the reactor type on biochar properties was very scarce. As a future outlook it is recommended to produce data that can be compared on a quantitative level, so a more accurate assessment of each technologies up- and downsides can be made.
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| 5. |
- Rebbling, Anders, 1980-, et al.
(författare)
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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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Ingår i: Biomass and Bioenergy. - : Elsevier. - 0961-9534 .- 1873-2909. ; 137
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Reichert, G., et al.
(författare)
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Impact of oxidizing honeycomb catalysts integrated in firewood stoves on emissions under real-life operating conditions
- 2018
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Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 177, s. 109-118
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Tidskriftsartikel (refereegranskat)abstract
- Catalytic systems integrated in firewood stoves represent a secondary measure for emission reduction. This study evaluates the impact on emissions of two types of honeycomb catalysts integrated in different firewood stoves. The tests were conducted under real-life related testing conditions. The pressure drop induced by the catalyst's carrier geometry affects primary combustion conditions which can influence the emissions. A negative primary effect reduces the catalytic efficiency and has to be considered for developing catalyst integrated solutions. However, a significant net emission reduction was observed. The ceramic catalyst reduced CO emissions by 83%. The metallic catalyst reduced CO emissions by 93% which was significantly better compared to the ceramic catalyst. The net emission reduction of OGC (~30%) and PM (~20%) was similar for both types of catalysts. In most cases, the “Ecodesign” emission limit values, which will enter into force in 2022 for new stoves, were met although the ignition and preheating batches were respected. PM emission composition showed a lower share of elemental (EC) and organic carbon (OC) with integrated catalyst. However, no selectivity towards more reduction of EC or OC was observed. Further investigations should evaluate the long term stability under real-life operation in the field and the effect of the catalyst on polycyclic aromatic hydrocarbon (PAH) emissions.
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| 7. |
- Sedlmayer, Irene, et al.
(författare)
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Determination of off-gassing and self-heating potential of wood pellets – Method comparison and correlation analysis
- 2018
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 234, s. 894-903
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Tidskriftsartikel (refereegranskat)abstract
- Several methods for identifying the phenomena of self-heating and off-gassing during production, transportation and storage of wood pellets have been developed in recent years. Research focused on the exploration of the underlying mechanisms, influencing factors or the quantification of self-heating or off-gassing tendencies. The present study aims at identifying a clear correlation between self-heating and off-gassing. Thus, different methods for determining self-heating and off-gassing potentials of wood pellets are compared. Therefore, eleven wood pellet batches from the European market were analyzed. For this investigation, three methods for the determination of self-heating, like isothermal calorimetry, oxi-press and thermogravimetric analysis, and four methods for off-gassing, like volatile organic compound (VOC) emissions measurements, gas phase analysis of stored pellets in a closed container by offline and by glass flask method and determination of fatty and resin acids content, were performed. Results were ranked according to the self-heating and off-gassing tendency providing a common overview of the analyzed pellets batches. Relations between different methods were investigated by Spearman's correlation coefficient. Evaluation of the results revealed an equal suitability of offline and glass flask methods to predict off-gassing tendency and indicated a very significant correlation with isothermal calorimetry for the identification of self-heating tendency. The thermogravimetric analysis as well as the fatty and resin acids determination proved to be insufficient for the exclusive assessment of self-heating and off-gassing tendency, respectively.
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| 8. |
- Sedlmayer, Irene, et al.
(författare)
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Off-gassing reduction of stored wood pellets by adding acetylsalicylic acid
- 2020
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Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 198
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Tidskriftsartikel (refereegranskat)abstract
- During transportation and storage of wood pellets various gases are formed leading to toxic atmosphere. Various influencing factors and measures reducing off-gassing have already been investigated. The present study aims at applying an antioxidant, acetylsalicylic acid (ASA), to reduce off-gassing from wood pellets by lowering wood extractives oxidation. Therefore, acetylsalicylic acid was applied in industrial and laboratory pelletizing processes. Pine and spruce sawdust (ratio 1:1) were pelletized with adding 0-0.8% (m/m) ASA. Glass flasks measurements confirmed off-gassing reduction by adding ASA for all wood pellets investigated.The biggest effect was achieved by adding 0.8% (m/m) ASA in the industrial pelletizing experiments where the emission of volatile organic compounds (VOCtot) was reduced by 82% and a reduction of carbon monoxide (CO) and carbon dioxide (CO2) emissions by 70% and 51%, respectively, could be achieved. Even an addition of 0.05% (m/m) ASA led to off-gassing reduction by >10%. A six week storage experiment to investigate the long-term effectivity of ASA addition revealed, that antioxidant addition was effective in reducing CO-, CO2- and VOCtot-release, especially during the first four weeks of the storage experiment, after which time the relative reduction effect was significantly decreased.
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