| 1. |
- Hoshino, Yuichi, et al.
(författare)
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Quantitative evaluation of the pivot shift by image analysis using the iPad.
- 2013
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Ingår i: Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA. - : Springer Science and Business Media LLC. - 1433-7347. ; 21:4, s. 975-80
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Tidskriftsartikel (refereegranskat)abstract
- To enable comparison of test results, a widely available measurement system for the pivot shift test is needed. Simple image analysis of lateral knee joint translation is one such system that can be installed on a prevalent computer tablet (e.g. iPad). The purpose of this study was to test a novel iPad application to detect the pivot shift. It was hypothesized that the abnormal lateral translation in ACL deficient knees would be detected by the iPad application.
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| 2. |
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| 3. |
- Kuba, Matthias, et al.
(författare)
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A review on bed material particle layer formation and its positive influence on the performance of thermo-chemical biomass conversion in fluidized beds
- 2021
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Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 291
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Forskningsöversikt (refereegranskat)abstract
- Bed material particle layer formation plays a significant role in thermo-chemical conversion of biomass. The interaction between biomass ash and bed material in fluidized bed conversion processes has been described for a variety of different applications and spans from fundamental research of formation mechanisms to effects of this layer formation on long-term operation in industrial-scale. This review describes the current state of the research regarding the mechanisms underlying layer formation and the positive influence of bed material particle layer formation on the operation of thermo-chemical conversion processes. Thus, the main focus lies on its effect on the catalytic activity towards gasification reactions and the impact on oxygen transport in chemical looping combustion. The review focuses on the most commonly investigated bed materials, such as quartz, feldspar or olivine. While the most relevant results for both the underlying mechanisms and the subsequently observed effects on the operation are presented and discussed, knowledge gaps where further research is necessary are identified and described.
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| 4. |
- Kuba, Matthias, et al.
(författare)
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Deposit build-up and ash behavior in dual fluid bed steam gasification of logging residues in an industrial power plant
- 2015
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 139, s. 33-41
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Tidskriftsartikel (refereegranskat)abstract
- A promising way to substitute fossil fuels for production of electricity, heat, fuels for transportation and synthetic chemicals is biomass steam gasification in a dual fluidized bed (DFB). Using lower-cost feedstock, such as logging residues, instead of stemwood, improves the economic operation. In Senden, near Ulm in Germany, the first plant using logging residues is successfully operated by Stadtwerke Ulm. The major difficulties are slagging and deposit build-up. This paper characterizes inorganic components of ash forming matter and draws conclusions regarding mechanisms of deposit build-up. Olivine is used as bed material. Impurities, e.g., quartz, brought into the fluidized bed with the feedstock play a critical role. Interaction with biomass ash leads to formation of potassium silicates, decreasing the melting temperature. Recirculation of coarse ash back into combustion leads to enrichment of critical fragments. Improving the management of inorganic streams and controlling temperature levels is essential for operation with logging residues. (C) 2015 Elsevier B.V. All rights reserved.
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| 5. |
- Kuba, Matthias, et al.
(författare)
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Thermal stability of bed particle layers on naturally occurring minerals from dual fluid bed gasification of woody biomass
- 2016
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Ingår i: Energy & Fuels. - Washington : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 30:10, s. 8277-8285
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Tidskriftsartikel (refereegranskat)abstract
- The use of biomass as feedstock for gasification is a promising way of producing not only electricity and heat but also fuels for transportation and synthetic chemicals. Dual fluid bed steam gasification has proven to be suitable for this purpose. Olivine is currently the most commonly used bed material in this process due to its good agglomeration performance and its catalytic effectiveness in the reduction of biomass tars. However, as olivine contains heavy metals such as nickel and chromium, no further usage of the nutrient-rich ash is possible, and additional operational costs arise due to necessary disposal of the ash fractions. This paper investigates possible alternative bed materials and their suitability for dual fluid bed gasification systems focusing on the behavior of the naturally occurring minerals olivine, quartz, and K-feldspar in terms of agglomeration and fracturing at typical temperatures. To this end, samples of bed materials with layer formation on their particles were collected at the industrial biomass combined heat and power (CHP) plant in Senden, Germany, which uses olivine as the bed material and woody biomass as feedstock. The low cost logging residue feedstock contains mineral impurities such as quartz and K-feldspar, which become mixed into the fluidized bed during operation. Using experimental and thermochemical analysis, it was found that the layers on olivine and K-feldspar showed a significantly lower agglomeration tendency than quartz. Significant fracturing of particles or their layers could be detected for olivine and quartz, whereas K-feldspar layers were characterized by a higher stability. High catalytic activity is predicted for all three minerals once Ca-rich particle layers are fully developed. However, quartz may be less active during the buildup of the layers due to lower amounts of Ca in the initial layer formation.
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| 6. |
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| 7. |
- Priščák, Juraj, et al.
(författare)
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Effect of time-dependent layer formation on the oxygen transport capacity of ilmenite during combustion of ash-rich woody biomass
- 2023
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Ingår i: Fuel. - : Elsevier Ltd. - 0016-2361 .- 1873-7153. ; 353
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen carrier aided combustion (OCAC) is a novel technology that aims to enhance combustion of heterogenous fuels by replacing the inert bed material with an active oxygen carrier. One of the promising oxygen carriers is natural ilmenite which shows decent oxygen transport capacity and mechanical stability under OCAC operating conditions. However, interactions between ilmenite and woody biomass ash lead to the formation of a calcium-rich ash layer, which affects the ability of the oxygen carrier (OC) to transfer oxygen throughout the boiler and subsequently decreases the combustion efficiency. This paper focuses on the time-dependent morphological and compositional changes in ilmenite bed particles and the consequence effects on the oxygen transport capacity and reactivity of ilmenite. Ilmenite utilized in this study was investigated in a 5 kW bubbling fluidized bed combustion unit, utilizing ash-rich bark pellets as fuel. A negative effect of iron migration on the oxygen transport capacity was observed in ilmenite bed particles after 6 h of operation in the bubbling fluidized bed reactor. The decrease in the oxygen transport capacity of ilmenite was found to correlate with the increased exposure time in the fluidized bed reactor and was caused by the migration and subsequent erosion of Fe from the ilmenite particles. On the other hand, the older bed particles show an increase in reaction rate, presumably due to the catalytic activity of the calcium-enriched outer layer on the bed particle surface.
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| 8. |
- Wagner, Katharina, et al.
(författare)
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Influence of Phosphorus on the Layer Formation on K-feldspar during Fluidized Bed Combustion and Gasification
- 2018
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Ingår i: European Biomass Conference and Exhibition Proceedings. - : ETA-Florence Renewable Energies. - 9788889407189 ; 26thEUBCE, s. 486-492
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Konferensbidrag (refereegranskat)abstract
- Today, mainly wood-based feedstocks are used in thermo-chemical biomass conversion since they have a comparably high heating value and contain a small amount of ash. Fluidized beds allow a greater variety of fuels to be used, since they are rather flexible regarding their fuel input. The use of biogenic waste streams (chicken manure, horse manure, etc.) and sewage sludge would not only increase the fuel diversity in fluidized beds but might also enhance the usability of side products. The contained essential nutrients like phosphorus, potassium, calcium, etc. in these fuels are enriched in the ash after thermochemical conversion. Thus, in the near future it may be possible to apply this ash as secondary resource for fertilizer. Especially the recovery of phosphorus is of importance due to the imminent phosphorus scarcity. Due to its tendency to react with ash forming elements in fuels, phosphorus influences the ash chemistry severely. Especially the agglomeration and layer formation on bed materials during biomass combustion and gasification is highly dependent on the predominant ash forming elements. Phosphorus therefore has a significant impact on those mechanisms. Until now, the behavior of phosphorus-rich fuels in fluidized beds has not been studied in much detail. To develop a basic understanding of the behavior, phosphorus-rich feedstock was combusted in a bench-scale fluidized bed reactor. Ash layers on bed particles, which were formed during these experiments, were studied and compared to results with phosphorus-lean fuels. Furthermore, layer formation of phosphorus-rich and phosphorus-lean fuels from dual fluid bed gasification were compared to those from fluidized bed combustion. The studied layers on bed materials showed significant amounts of phosphorus. The data also indicates a change in layer formation as soon as phosphorus is present. An increased catalytic activity due ash-layer formation was observed for both phosphorus-rich and phosphorus-lean feedstock, independent from the presence of phosphorus in the ash layer.
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| 9. |
- Wagner, Katharina, et al.
(författare)
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Layer formation mechanism of K-feldspar in bubbling fluidized bed combustion of phosphorus-lean and phosphorus-rich residual biomass
- 2019
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 248, s. 545-554
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Tidskriftsartikel (refereegranskat)abstract
- The use of phosphorus-rich fuels in fluidized bed combustion is one probable way to support both heat and power production and phosphorus recovery. Ash is accumulated in the bed during combustion and interacts with the bed material to form layers and/or agglomerates, possibly removing phosphorus from the bed ash fraction. To further deepen the knowledge about the difference in the mechanisms behind the ash chemistry of phosphorus-lean and phosphorus-rich fuels, experiments in a 5 kW bench-scale-fluidized bed test-rig with K-feldspar as the bed material were conducted with bark, wheat straw, chicken manure, and chicken manure admixtures to bark and straw. Bed material samples were collected and studied for layer formation and agglomeration phenomena by scanning electron microscopy combined with energy dispersive X-ray spectrometry. The admixture of phosphorus-rich chicken manure to bark changed the layer formation mechanism, shifting the chemistry to the formation of phosphates rather than silicates. The admixture of chicken manure to straw reduced the ash melting and agglomeration risk, making it possible to increase the time until defluidization of the fluidized bed occurred. The results also highlight that an increased ash content does not necessarily lead to more ash melting related problems if the ash melting temperature is high enough.
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| 10. |
- Wagner, Katharina, et al.
(författare)
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Layer formation on K-feldspar in fluidized bed combustion and gasification of bark and chicken manure
- 2019
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Ingår i: Biomass and Bioenergy. - : Elsevier. - 0961-9534 .- 1873-2909. ; 127
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Tidskriftsartikel (refereegranskat)abstract
- Understanding layer formation on bed materials used in fluidized beds is a key step for advances in the application of alternative fuels. Layers can be responsible for agglomeration-caused shut-downs but they can also improve the gas composition in fluidized bed gasification. Layers were observed on K-feldspar (KAlSi3O8) impurities originating from the combined heat and power plant Senden which applies the dual fluidized bed (DFB) steam gasification technology. Pure K-feldspar was therefore considered as alternative bed material in DFB steam gasification. Focusing on the interactions between fuel ash and bed material, K-feldspar was tested in combustion and DFB steam gasification atmospheres using different fuels, namely Ca-rich bark, Ca- and P-rich chicken manure, and an admixture of chicken manure to bark. The bed particle layers formed on the bed material surface were characterized using combined scanning electron microscopy and energy-dispersive X-ray spectroscopy; area mappings and line scans were carried out for all samples. The obtained data show no essential influence of operational mode on the layer-formation process. During the combustion and DFB steam gasification of Ca-rich bark, a layer rich in Ca formed while K was diffusing out of the layer. The use of Ca- and P-rich chicken manure inhibited the diffusion of K, and a layer rich in Ca and P formed. The addition of P to bark via chicken manure also changed the underlying layer-formation processes to reflect the same processes as observed for pure chicken manure.
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