| 1. |
- Kong, Xiangrui, et al.
(författare)
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Phase recognition in SEM-EDX chemical maps using positive matrix factorization
- 2023
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Ingår i: Methodsx. - 2215-0161. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Images from scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spec- troscopy (EDX) are informative and useful to understand the chemical composition and mixing state of solid materials. Positive matrix factorization (PMF) is a multivariate factor analysis tech- nique that has been used in many applications, and the method is here applied to identify factors that can describe common features between elemental SEM-EDX maps. The procedures of con- verting both graphics and digital images to PMF input files are introduced, and the PMF analysis is exemplified with an open-access PMF program. A case study of oxygen carrier materials from oxygen carrier aided combustion is presented, and the results show that PMF successfully groups elements into factors, and the maps of these factors are visualized. The produced images provide further information on ash interactions and composition of distinct chemical layers. The method can handle all types of chemical maps and the method is not limited solely to SEM-EDX although these images have been used as an example. The main characteristics of the method are:center dot Adapting graphics and digital images ready for PMF analysis.center dot Conversion between 1-D and 2-D datasets allows visualization of common chemical maps of elements grouped in factors.center dot Handles all types of chemical mappings and large data sets.
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| 2. |
- Stanicic, Ivana, 1994, et al.
(författare)
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Combined manganese oxides as oxygen carriers for biomass combustion — Ash interactions
- 2019
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Ingår i: Chemical Engineering Research and Design. - : Elsevier BV. - 0263-8762 .- 1744-3563. ; 149, s. 104-120
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Institution of Chemical Engineers Carbon capture and storage (CCS) has been acknowledged as an important strategy for mitigation of climate change. Although highly applicable for fossil fuels, CCS with biomass could have the added advantage of resulting in negative emissions of carbon dioxide. One promising carbon capture technology is chemical-looping combustion (CLC). In CLC the reactors are filled with metal oxide bed material called oxygen carriers. Before CLC can be implemented for biomass combustion at a large scale, biomass ash components interaction with oxygen carriers needs to be further understood. Four combined manganese oxides Mn3O4-SiO2, Mn3O4-SiO2-TiO2, Mn3O4-Fe2O3 and Mn3O4-Fe2O3-Al2O3 were exposed to common biomass ash components K, Ca and P. The ash components can exist in many forms, but here the compounds CaCO3, K2CO3 and CaHPO4 were used. Exposures were performed at 900 °C for six hours in oxidising, reducing and inert conditions. Crystalline phases were analysed by XRD and morphology examined with SEM-EDX. Results show that oxygen carrier particles containing silicon were more likely to form agglomerates, especially in combination with potassium, whereas the particles including iron were more stable. MnFeAl was the oxygen carrier that showed least agglomerating behaviour while simultaneously showing a propensity to absorb some ash components. Some inconsistencies between thermodynamic predictions and experimental results is observed. This may be explained by lack of relevant data in the used databases, were only a few of the oxygen carrier-ash systems and subsystems have been optimised. Further optimisation related to manganese rich systems should be performed to obtain reliable results.
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| 3. |
- Andersson, Viktor, 1994, et al.
(författare)
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A Novel Method for On-Line Characterization of Alkali Release and Thermal Stability of Materials Used in Thermochemical Conversion Processes
- 2022
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 15:12
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Tidskriftsartikel (refereegranskat)abstract
- Alkali metal compounds are released during the thermal conversion of biofuels and fossil fuels and have a major impact on the efficiency of conversion processes. Herein, we describe a novel method for the simultaneous characterization of alkali release and mass loss from materials used in combustion and gasification processes including solid fuels, fluidized bed materials, and catalysts for gas reforming. The method combines the thermogravimetric analysis of selected samples with the on-line measurement of alkali release using a surface ionization detector. The technique builds on the careful treatment of alkali processes during transport from a sample to the downstream alkali monitor including the losses of alkali in the molecular form to hot walls, the formation of nanometer-sized alkali-containing particles during the cooling of exhaust gases, aerosol particle growth, and diffusion losses in sampling tubes. The performance of the setup was demonstrated using biomass samples and fluidized bed material from an industrial process. The emissions of alkali compounds during sample heating and isothermal conditions were determined and related to the simultaneous thermogravimetric analysis. The methodology was concluded to provide new evidence regarding the behavior of alkali in key processes including biomass pyrolysis and gasification and ash interactions with fluidized beds. The implications and further improvements of the technique are discussed.
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| 4. |
- Andersson, Viktor, 1983, et al.
(författare)
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Alkali desorption from ilmenite oxygen carrier particles used in biomass combustion
- 2024
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Ingår i: Fuel. - 0016-2361 .- 1873-7153. ; 359
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen-carrying fluidized bed materials are increasingly used in novel technologies for carbon capture and storage, and to improve the efficiency of fuel conversion processes. Potassium- and sodium-containing compounds are released during biomass combustion and may have both negative and positive effects on conversion processes. Ilmenite is an important oxygen carrier material with the ability to capture alkali in the form of titanates. This is a desirable property since it may reduce detrimental alkali effects including fouling, corrosion, and fluidized bed agglomeration. This study investigates the interactions of alkali-containing compounds with ilmenite particles previously used in an industrial scale (115 MWth) oxygen carrier aided combustion system. The ilmenite samples were exposed to temperatures up to 1000 °C under inert and oxidizing conditions while the alkali release kinetics were characterized using online alkali monitoring. Alkali desorption occurs between 630 and 800 °C, which is attributed to loosely bound alkali at or near the surface of the particles. Extensive alkali release is observed above 900 °C and proceeds during extended time periods at 1000 °C. The release above 900 °C is more pronounced under oxidizing conditions and approximately 9.1 and 3.2 wt% of the alkali content is emitted from the ilmenite samples in high and low oxygen activity, respectively. Detailed material analyses using scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were conducted before and after temperature treatment, which revealed that the concentrations of potassium, sodium and chlorine decrease at the outermost surface of the ilmenite particles during temperature treatment, and Cl is depleted to a deeper level in oxidizing conditions compared to inert. The implications for ilmenite-ash interactions, oxygen carrier aided combustion and chemical looping systems are discussed.
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| 5. |
- Andersson, Viktor, 1994
(författare)
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Alkali Uptake and Release from Oxygen Carriers in Chemical Looping Applications: Development and Application of Reactor Systems and Measurement Techniques
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chemical looping combustion (CLC) of biomass is a heat and power generation technology with minimal associated costs for carbon capture, potentially resulting in negative CO2 emissions. The CLC technology utilizes fluidized beds of oxygen carrier (OC) particles to separate CO2 from the combustion air. The high content of potassium and sodium compounds in biomass fuels may cause detrimental problems during thermal conversion, including agglomeration, fouling and corrosion, while also enhancing conversion processes due to their catalytic abilities. Further knowledge about processes involving these alkali metals, including their uptake and release from OC materials and the control of alkali emission, is critical for the upscaling and commercialization of biomass CLC. The aim of this thesis is to improve the understanding of interactions between alkali compounds and OCs under conditions representative of biomass CLC. A novel technique based on temperature modulated surface ionization was developed to determine the contributions of alkali chlorides, hydroxides, and sulfates to the flux from different reactors. A novel laboratory-scale reactor was developed, facilitating continuous alkali vapor injection to a fluidized bed while monitoring the concentrations of alkali and gas in the reactor exhaust. An additional method was developed to monitor the real-time alkali release and mass loss from small, fixed bed samples, including OC particles and solid biomass. The type of OC material is observed to play a crucial role in alkali uptake, where fluidized beds of the promising CLC materials: calcium manganite, manganese oxide, and ilmenite, exhibiting varying levels of efficiency depending on the specific gas conditions present. Ilmenite showed near complete absorption of the injected alkali, especially during reducing conditions, making it a promising option to limit alkali emissions. The alkali speciation analysis revealed that NaCl and KCl were the predominant alkali species emitted during NaCl and KCl injection, and a similar pattern was observed for alkali sulfates. Alkali hydroxide injections resulted in highly efficient alkali uptake with emissions dominated by alkali hydroxides and chlorides. The study highlights the balance between alkali absorption efficiency and fuel conversion and oxidizing efficiency of the OC materials. While ilmenite demonstrated excellent alkali uptake, manganese oxide and calcium manganite exhibited superior fuel conversion and oxidizing efficiency. In addition, ilmenite previously used in an industrial process releases alkali in both inert and oxidizing environments at high temperatures. The described development and application of new methods are concluded to open new possibilities to understand and optimize biomass CLC.
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| 6. |
- Andersson, Viktor, 1994, et al.
(författare)
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Online Speciation of Alkali Compounds by Temperature-Modulated Surface Ionization: Method Development and Application to Thermal Conversion
- 2024
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Ingår i: ENERGY & FUELS. - 0887-0624 .- 1520-5029. ; 38:3, s. 2046-2057
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Tidskriftsartikel (refereegranskat)abstract
- A novel method for online speciation of potassium- and sodium-containing compounds has been described and demonstrated. The method is based on a temperature-modulated surface ionization (TMSI) technique and may be used to determine the concentrations of alkali chlorides, hydroxides, carbonates, and sulfates in high-temperature processes. The measurement device is a further development of a surface ionization detector (SID) commonly used for online alkali measurements in combustion, gasification, and pyrolysis research. Discrimination between sodium and potassium compounds is made possible by differences in their aerosol evaporation characteristics as a function of temperature combined with the desorption kinetics of alkali on a hot platinum filament. The method is evaluated in laboratory experiments with known alkali salt concentrations. An experimental procedure where the platinum filament in the SID is regularly shifted between three temperatures is concluded to provide sufficient selectivity and time resolution for common applications. The TMSI method is successfully applied to characterize the emission of alkali compounds during pyrolysis of pine wood. The emissions during low-temperature pyrolysis are dominated by KOH, while similar amounts of KOH and NaOH are subsequently emitted from the remaining char and ash. The ability of real-time characterization of individual sodium and potassium compounds opens up new means to understand and optimize solid fuel conversion of common fuels such as low-grade biomass, waste, and coal.
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| 7. |
- Andersson, Viktor, 1994, et al.
(författare)
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Relating person-centredness to quality-of-life assessments and patient-reported outcomes in healthcare: A critical theoretical discussion
- 2022
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Ingår i: Nursing Philosophy. - : Wiley. - 1466-7681 .- 1466-769X. ; 23:3
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Tidskriftsartikel (refereegranskat)abstract
- Engagement with the historical and theoretical underpinnings of measuring quality of life (QoL) and patient-reported outcomes (PROs) in healthcare is important. Ideas and values that shape such practices—and in the endgame, people's lives—might otherwise remain unexamined, be taken for granted or even essentialized. Our aim is to explicate and theoretically discuss the philosophical tenets underlying the practices of QoL assessment and PRO measurement in relation to the notion of person-centredness. First, we engage with the late-modern history of the concept of QoL and the act of assessing and measuring it. Working with the historical method of genealogy, we describe the development of both QoL assessments and PRO measures (PROMs) within healthcare by accounting for the contextual conditions for their possibility. In this way, the historical and philosophical underpinnings of these measurement practices are highlighted. We move on to analyse theoretical and philosophical underpinnings regarding the use of PROMs and QoL assessments in clinical practice, as demonstrated in review studies thereof. Finally, we offer a critical analysis regarding the state of theory in the literature and conclude that, although improved person-centredness is an implied driver of QoL assessments and PROMs in clinical practice, enhanced theoretical underpinning of the development of QoL assessments is called for.
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| 8. |
- Argyri, Smaragda Maria, 1994, et al.
(författare)
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Customized and high-performing acoustic levitators for contact-free experiments
- 2024
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Ingår i: Journal of Science: Advanced Materials and Devices. - 2468-2284 .- 2468-2179. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Acoustic levitators are becoming an increasingly common research instrumentation for contact-free, lab-in-a-droplet studies. Recently, levitators that employ multiple, small, ultrasonic transducers have gained popularity, given their low price, temperature and spatial stability, low voltage, and accessibility. Yet, the current state-of-the-art device, TinyLev, presents limitations for certain applications in terms of stability, strength, and compactness. Herein, we developed three new levitators and evaluated the effect of the construction parameters (e.g., distance of opposing arrays, number and arrangement of transducers, etc.) on their performance. Compared to TinyLev, the best performing levitator from this work had half the number of transducers while presenting 1.7 and 3.5 times higher levitation capacity along the horizontal and vertical configurations, respectively, while the horizontal and vertical stability of a levitated object was improved 4.7 and 2.0 times, respectively. Additionally, we present a direct means to evaluate the acoustic radiation net force acting on a deformable object for uniaxial levitators, without the use of a microphone or a schlieren deflectometer for this type of levitators. The theoretical and experimental observations provide insights for adapting the acoustic levitator design for specific applications. Finally, we developed an open-source software which allows the evaluation of the acoustic pressure field generated by customized designs and provides the necessary files for 3D printing the scaffold of the levitator. This study aims to increase accessibility and promote further developments in contact-free experiments.
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| 9. |
- Feldthusen, Caroline, 1977, et al.
(författare)
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Centredness in health care: A systematic overview of reviews
- 2022
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Ingår i: Health Expectations. - : Wiley. - 1369-6513 .- 1369-7625. ; 25:3, s. 885-901
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Tidskriftsartikel (refereegranskat)abstract
- Introduction The introduction of effective, evidence-based approaches to centredness in health care is hindered by the fact that research results are not easily accessible. This is partly due to the large volume of publications available and because the field is closely linked to and in some ways encompasses adjoining fields of research, for example, shared decision making and narrative medicine. In an attempt to survey the field of centredness in health care, a systematic overview of reviews was conducted with the purpose of illuminating how centredness in health care is presented in current reviews. Methods Searches for relevant reviews were conducted in the databases PubMed, Scopus, Cinahl, PsychINFO, Web of Science and EMBASE using terms connected to centredness in health care. Filters specific to review studies of all types and for inclusion of only English language results as well as a time frame of January 2017-December 2018, were applied. Results The search strategy identified 3697 unique reviews, of which 31 were included in the study. The synthesis of the results from the 31 reviews identified three interrelated main themes: Attributes of centredness (what centredness is), Translation from theory into practice (how centredness is done) and Evaluation of effects (possible ways of measuring effects of centredness). Three main attributes of centeredness found were: being unique, being heard and shared responsibility. Aspects involved in translating theory into practice were sufficient prerequisites, strategies for action and tools used in safeguarding practice. Further, a variety and breadth of measures of effects were found in the included reviews. Conclusions Our synthesis demonstrates that current synthesized research literature on centredness in health care is broad, as it focuses both on explorations of the conceptual basis and the practice, as well as measures of effects. This study provides an understanding of the commonalities identified in the reviews on centredness in healthcare overall, ranging from theory to practice and from practice to evaluation. Patient or Public Contribution Patient representatives were involved during the initiation of the project and in decisions about its focus, although no patient or public representatives made direct contributions to the review process.
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| 10. |
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