| 1. |
- Bokrantz, Tove, et al.
(författare)
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Antihypertensive drug classes and the risk of hip fracture: results from the Swedish primary care cardiovascular database.
- 2020
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Ingår i: Journal of hypertension. - 1473-5598. ; 38:1, s. 167-175
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Tidskriftsartikel (refereegranskat)abstract
- Hypertension and fractures related to osteoporosis are major public health problems that often coexist. This study examined the associations between exposure to different antihypertensive drug classes and the risk of hip fracture in hypertensive patients.We included 59246 individuals, 50 years and older, diagnosed with hypertension during 2001-2008 in the Swedish Primary Care Cardiovascular Database. Patients were followed from 1 January 2006 (or the date of diagnosis of hypertension) until they had their first hip fracture, died, or reached the end of the study on 31 December 2012. Cox proportional hazards models were used to calculate the risk of hip fracture across types of antihypertensive medications, adjusted for age, sex, comorbidity, medications, and socioeconomic factors.In total, 2593 hip fractures occurred. Compared to nonusers, current use of bendroflumethiazide or hydrochlorothiazide was associated with a reduced risk of hip fracture (hazard ratio 0.86; 95% CI 0.75-0.98 and hazard ratio 0.84; 95% CI 0.74-0.96, respectively), as was use of fixed drug combinations containing a thiazide (hazard ratio 0.69; 95% CI 0.57-0.83). Current use of loop diuretics was associated with an increased risk of hip fracture (hazard ratio 1.23; 95% CI 1.11-1.35). No significant associations were found between the risk of hip fracture and current exposure to beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, aldosterone-receptor blockers or calcium channel blockers.In this large observational study of hypertensive patients, the risk of hip fracture differed across users of different antihypertensive drugs, results that could have practical implications when choosing antihypertensive drug therapy.
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| 2. |
- Falk, Joel, 1988-
(författare)
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The fate and ash transformations of phosphorus in combustion of biomass and sewage sludge
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The combustion of phosphorus (P)-rich biomass has a significant potential to increase the stock of biomass resources available for renewable heat and power production. In addition, the P-rich ashes have the potential as a fertilizer and could reduce the need for non-renewable P resources in agriculture. However, several technical challenges must be resolved to realize this potential.During combustion, the ash-forming matter in the fuel undergoes numerous chemical transformations, which can result in the formation of ash melts. Excessive melt formation can lead to durable ash deposits in and around the combustion zone and on heat exchangers, which can lower combustion performance and, in severe cases, lead to a complete shutdown of the process. Further, mono-combustion of P-rich residues such as sewage sludge results in the formation of phosphates with poor plant availability, which can significantly limit the value of the ash as a fertilizer. By co-combustion the sludge with K-rich biomass, it may be possible to alter the chemical speciation of P towards more plant-available phases while simultaneously managing the risk of ash-related operational issues. This work investigates the effect of combustion technology, fuel ash composition, and chemical association of P in the fuel on the fate, i.e., distribution and speciation, and ash transformations of P in combustion and co-combustion of biomass and sewage sludge.The basis of the study was experiments performed in three different combustion technologies, including a fluidized bed (5 kW, 730-800 °C), a fixed bed (20 kW, 950-1250 °C), and a powder burner (150 kW, ~1100°C). The fuels and fuel mixtures included P-rich and P-poor woody biomass, agricultural residues, and sewage sludge, which constitute a wide range of ash compositions in terms of K, Ca, Mg, Fe, Al, Si, and P. The residual ashes from the experiments were collected and chemically characterized with the original fuels and fuel mixtures to determine the ash transformation reactions of P. The experiments were complemented by thermodynamic equilibrium calculations (TECs), which aided the interpretation of experimental data and predicted the risk for operational issues related to the melting of coarse ash fractions.The major share of fuel P was found in coarse ash fractions such as bed ash particles, bottom ash, slag, cyclone ash, wind side deposits, and coarse fly ash. A low share of fuel P was found in fine ash fractions such as leeside deposits and PM1. This generally matched the predictions by TEC, which indicated that P was stable in condensed phases at the relevant compositions and conditions during the combustion experiments. The powder burner experiments produced the highest share of fuel P in PM1 (4-14 wt.%), followed by fixed bed combustion (<4 wt.%), with fluidized bed combustion having the lowest share (<0.6 wt.%). In addition, the experiments with sewage sludge indicated a significantly lower P share in PM1 for a given combustion technology than the other biomass fuels, ranging from <0.2 wt.% in the fluidized bed and <1.2 wt.% in the fixed bed.Combustion and co-combustion of woody biomass and agricultural residues resulted in the formation of a wide range of ortho-, pyro-, and metaphosphates associated with K, Ca, and Mg. Combustion of woody biomass generally resulted in a high share of Ca-orthophosphates, whereas agricultural residues had a higher share of K-rich ortho- and pyrophosphates. Irrespective of biomass assortment, the speciation of P in the ash from combustion and co-combustion followed general trends with respect to the fuel ash composition of the biomass mixture. The frequency and share of pyro- and metaphosphates identified in the coarse ash fractions tended to increase with the relative concentration of P to K, Ca, and Mg in the fuel mixture. A similar correlation was found between the share of K-rich phosphates and the relative concentration of K to Ca and Mg.The crystalline phosphate phases identified in the coarse ash fractions from sewage sludge and K-rich biomass experiments were mainly Fe-rich and Ca-rich orthophosphate. The frequency and share of Fe-rich orthophosphates decreased with the relative P to K, Ca, and Mg concentration in the fuel mixture. However, the sewage sludge mixtures were less prone to form K-rich orthophosphates than the biomass mixtures for a given composition in terms of P to K, Ca, and Mg.Based on TECs, it was possible to qualitatively predict ash-related issues related to the melting behavior of coarse ash fractions, such as slag formation, for woody biomass and agricultural residues by considering the K, Ca, Mg, Si, and P content in the fuel. The share of network formers (SiO2, PO2.5) to total ash oxides had the largest overall influence on the melting tendency of the ash mixture, followed by the ratio of K2O to total network modifiers (K2O, CaO, MgO), which had a high impact on ash mixtures with high relative shares of SiO2. The slagging tendency of fuel mixtures with a high share of sewage sludge could not be predicted based on the melting behavior of the K-Ca-Mg-Si-P-O system due to the high relative share of Fe and Al. The experimental results indicated that the slagging tendency of the sewage sludge was significantly improved by co-combustion with moderate amounts of wheat straw or sunflower husk.Based on the combined results, it was possible to establish four fuel ash molar ratios correlated with the speciation of P in the produced coarse ash fractions and the risk of slag formation in fixed-bed combustion. These ratios were used to recommend practical fuel mixing strategies that could enable the production of combustion ashes with high P-plant availability while simultaneously managing the risk of severe slag formation.
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| 3. |
- Rebbling, Anders, 1980-, et al.
(författare)
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Demonstrating Fuel Design To Reduce Particulate Emissions and Control Slagging in Industrial-Scale Grate Combustion of Woody Biomass
- 2020
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Ingår i: Energy & Fuels. - : AMER CHEMICAL SOC. - 0887-0624 .- 1520-5029. ; 34:2, s. 2574-2583
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Tidskriftsartikel (refereegranskat)abstract
- The demand for increased overall efficiency, improved fuel flexibility, and more stringent environmental legislations promotes the development of new fuel- and technology-related concepts for the bioenergy sector. Previous research has shown that careful consideration of the fuel ash composition and the adjustment of the same via various routes, i.e., fuel design, have the potential to alter the ash transformation reactions, leading to, e.g., a reduction of the formation of slag or entrained inorganic ash particles. The objective of the present work was, therefore, to demonstrate the use of fuel design as a primary measure to reduce the emission of PM1 during combustion of woody biomass in medium-scale grate-fired boilers while keeping the slag formation at a manageable level. This was achieved by designing fuel blends of woody biomass with carefully selected Scandinavian peats rich in Si, Ca, and S. The work includes results from three experimental campaigns, performed in three separate grate-fired boilers of different sizes, specifically 0.2 MWth, 2 MWth, and 4 MWth. In one of the campaigns, softwood-based stemwood pellets were copelletized with different additions of peat (5 and 15 wt %) before combustion. In the other campaigns, peat was added in a separate fuel feed to Salix chips (15 wt % peat) and softwood-based stemwood pellets (10 and 20 wt % peat). Particulate matter and bottom ashes were characterized by scanning electron microscopy-energy-dispersive X-ray spectroscopy for morphology and elemental composition as well as by powder X-ray diffraction for crystalline phase composition. The results show that the fuel design approach provided PM1 reduction for all fuel blends between 30 and 50%. The PM1 reduction could be achieved without causing operational problems due to slagging for any of the three commercial boilers used, although an expected increased slagging tendency was observed. Overall, this paper illustrates that fuel design can be implemented on an industrial scale by achieving the desired ash transformation reactions, in this case, leading to a reduction of fine particulate emissions by up to 50% without any operational disturbances due to slag formation on the grate.
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| 4. |
- 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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| 5. |
- Söderlund, Henrik, 1994, et al.
(författare)
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The Creation of a Multi-User Virtual Training Environment for Operator Training in VR
- 2024
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Ingår i: Advances in Transdisciplinary Engineering. ; 52, s. 173-184
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Konferensbidrag (refereegranskat)abstract
- Many industries are today heavily exposed to competition which increases the demand for continuous innovations, faster product changes and continued improvements, this is especially true for the automotive industry. Such demands raise the complexity and set a need for continuous training and development of our operators and assembly personnel to keep up with new designs and product changes. This, in combination with an aging population and a growing shortage of experienced assembly workers, increases the need for efficient training capabilities.Today most of the operator training is supervisor driven and takes place in the live production environment working with real products. This approach might introduce uncertainties and a risk to the production system as less experienced workers, still in training, might jeopardize quality, ramp ups and takt time. With the rise of virtual reality there are growing possibilities to carry out these training sessions in a more secure, non-disruptive, virtual environment without jeopardizing ramp ups, takt time or quality. This paper evaluates the possibility to introduce virtual multi-user operator training as an alternative to traditional supervised “on-site” training for assembly workers. Recreation of different assembly task from an automotive case company was created in virtual reality while introducing multi-user functionality to allow multiple operators and supervisors to observe, instruct and evaluate the performance of the operator in training. The developed demonstrator is used as the discussion basis throughout a focus group interview study with selected participants from an OEM case company and the potential of a multi-user virtual reality application as a complement for traditional operator training in operator training is discussed and future research directions for multi-user virtual reality trainings at OEMs is presented.
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| 6. |
- Thyrel, Mikael, et al.
(författare)
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Phase transitions involving Ca - The most abundant ash forming element - In thermal treatment of lignocellulosic biomass
- 2021
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Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 285
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Tidskriftsartikel (refereegranskat)abstract
- Torrefaction, pyrolysis and gasification are of interest to convert lignocellulosic biomass into fuels and chemicals. These techniques involve thermal treatment at low partial pressures of oxygen. However, little is known about the transformation of ash elements during these processes. The phase transition of the major ash element calcium (Ca) was therefore studied with powder from pine as biomass model treated at temperatures 300-800 degrees C under atmospheres of 100% N-2, 3% O-2 and 6% O-2 and thermodynamic equilibrium modelling. For evaluation, Xray powder diffraction and synchrotron Ca K-edge X-ray absorption near edge structure (XANES) spectroscopy in combination with linear combination fitting and reference compounds was used. The results indicated that the most abundant Ca-containing species in the untreated material was thermally unstable Ca oxalate (CaC2O4) primarily decomposing into Ca phases dominated by carbonates at temperatures up to 600 degrees C. Double carbonates of calcium and potassium were observed in the form of fairchildiite/butscheliite (K2Ca(CO3)(2)), and these phases were stable over the low temperature range studied. Hydroxyapatite (Ca-5(PO4)(3)OH) was expected to be present and thermally stable over the entire temperature interval and was found in untreated material. At temperatures above 600 degrees C calcium oxide (CaO) was formed. The amount of oxygen had little effect on the phase transitions. The results of thermodynamic modeling were in agreement with XANES showing that this is a versatile technique that can be applied to systems as complex as Ca phase transitions in thermally treated lignocellulosic biomass at low partial pressures of oxygen.
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| 7. |
- Viggh, Erik, 1957-
(författare)
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Modeling the influence of magnesium from alternative raw materials on the chemistry of Portland cement clinker
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The methods used in this thesis work were a combination of computational and modeling based laboratory experiments.Thermodynamic process modeling of the cement clinker process offers a tool for evaluating how changes in raw materials and process parameters affect the clinker quality. Work with finding suitable replacement raw materials involves investigating the chemical compatibility of potential alternative materials. Such replacement materials may be metallurgical slags, although there are some unsolved issues with the quantities of certain metals and particularly Mg in these materials.For predicting the formation of clinker mineral phases, cooling calculations are used in order to reproduce the temperature history in the full scale process. A chemistry model including a solid solution phase based on C2S and phosphate was developed along with the recommendation for continued work on clinker phases with solid solutions to include MgO. A thermodynamic database for phase chemistry calculations of clinkering reactions was created and evaluated. Suitable compounds and solution species were selected from the thermochemical database included in FactSage software. The extent and quality of the required thermodynamic data via available databases is generally satisfactory, except for certain properties of some of the main clinker phases. One example is the lack of a thermodynamic model for the alite solid solution. That is, the composition of the phase available in the database representing alite does not contain the minor elements Al, Fe and Mg. Therefore, it is difficult to predict the quantity and distribution of Mg in the clinker, with varying total content of MgO. Thus, one of the goals/objectives was to improve thethermodynamic model of alite as a solid solution of 3CaO-SiO2-xAl2O3-yFe2O3-zMgO. To achieve this, it was assumed that a mix of compounds with adjusted Henrian coefficients representing the solid solution clinker phase alite was in equilibrium with the clinker melt.The distribution of MgO was studied in synthetic clinker compositions with quantities ranging from 0.5 to 10 wt-%. Synthetic clinker mixes were heated to 1450°C and studied with Rietveld refinements of X-ray diffraction data and SEM-EDS analysis. In addition, the mechanisms of how slag and lime particles react facilitating the diffusion of MgO into the developing clinker melt and the formation of incipient belite were studied.The calculated results provide a good prediction of the quantities and composition of the clinker phases formed during heating and non-equilibrium cooling. The solubility of MgO in the clinker and the quantity of periclase formed is in fair agreement with published data. Thus, this thesis work shows that using a mix of compounds with adjusted activities in alite together with available standard thermodynamic data and the Scheil cooling method had good potential for evaluating alternative raw materials.Also, the work has identified weak points in the process modeling and suggest improvements to be made in future research work.
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