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Search Results: 1 - 10 of 3433 matches for " Tobias Mattisson "
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Materials for Chemical-Looping with Oxygen Uncoupling
Tobias Mattisson
ISRN Chemical Engineering , 2013, DOI: 10.1155/2013/526375
Abstract: Chemical-looping with oxygen uncoupling (CLOU) is a novel combustion technology with inherent separation of carbon dioxide. The process is a three-step process which utilizes a circulating oxygen carrier to transfer oxygen from the combustion air to the fuel. The process utilizes two interconnected fluidized bed reactors, an air reactor and a fuel reactor. In the fuel reactor, the metal oxide decomposes with the release of gas phase oxygen (step 1), which reacts directly with the fuel through normal combustion (step 2). The reduced oxygen carrier is then transported to the air reactor where it reacts with the oxygen in the air (step 3). The outlet from the fuel reactor consists of only CO2 and H2O, and pure carbon dioxide can be obtained by simple condensation of the steam. This paper gives an overview of the research conducted around the CLOU process, including (i) a thermodynamic evaluation, (ii) a complete review of tested oxygen carriers, (iii) review of kinetic data of reduction and oxidation, and (iv) evaluation of design criteria. From the tests of various fuels in continuous chemical-looping units utilizing CLOU materials, it can be established that almost full conversion of the fuel can be obtained for gaseous, liquid, and solid fuels. 1. Introduction In the last decade, chemical-looping combustion (CLC) has emerged as a viable and efficient alternative for combustion with carbon capture. The interest in CLC is mainly due to the intrinsic separation of from the rest of the flue gases during combustion, that is, nitrogen and unused oxygen, which means that no energy or equipment is needed for gas separation, which is in contrast to competing CCS technologies, that is, oxyfuel, postcombustion, and precombustion. An added advantage of CLC is the possibility to obtain 100% carbon capture, which is difficult to achieve in, for instance, post- or precombustion. Chemical-looping with oxygen uncoupling (CLOU) is very similar to CLC and has the same advantages with respect to efficiencies and degree of carbon capture, but the mechanism of fuel conversion is different, and this could result in significant advantages with respect to fuel conversion rates, which can have positive implications with respect to system performance. Below follows a description of both the CLC and CLOU technologies. This is followed by a simple thermodynamic analysis for some relevant metal oxides in Section 2. A detailed overview of the experimental research conducted on different oxygen carrier materials for CLOU is then carried out in Section 3. An overview of kinetic data
Examination of Perovskite Structure CaMnO3-δ with MgO Addition as Oxygen Carrier for Chemical Looping with Oxygen Uncoupling Using Methane and Syngas
Dazheng Jing,Tobias Mattisson,Henrik Leion,Magnus Rydén,Anders Lyngfelt
International Journal of Chemical Engineering , 2013, DOI: 10.1155/2013/679560
Abstract: Perovskite structure oxygen carriers with the general formula CaMnxMg1-xO3-δ were spray-dried and examined in a batch fluidized bed reactor. The CLOU behavior, reactivity towards methane, and syngas were investigated at temperature 900°C to 1050°C. All particles showed CLOU behavior at these temperatures. For experiments with methane, a bed mass corresponding to 57?kg/MW was used in the reactor, and the average CH4 to CO2 conversion was above 97% for most materials. Full syngas conversion was achieved for all materials utilizing a bed mass corresponding to 178?kg/MW. SEM/EDX and XRD confirmed the presence of MgO in the fresh and used samples, indicating that the Mg cation is not incorporated into the perovskite structure and the active compound is likely pure CaMnO3-δ. The very high reactivity with fuel gases, comparable to that of baseline oxygen carriers of NiO, makes these perovskite particles highly interesting for commercial CLC application. Contrary to NiO, oxygen carriers based on CaMnO3-δ have no thermodynamic limitations for methane oxidation to CO2 and H2O, not to mention that the materials are environmentally friendly and can utilize much cheaper raw materials for production. The physical properties, crystalline phases, and morphology information were also determined in this work. 1. Introduction Carbon dioxide is the greenhouse gas which contributes most to anthropogenic climate change. A significant amount of CO2 is emitted into the atmosphere each year, of which combustion of fossil fuels was responsible for over 30000 million tons of CO2 in 2010 [1]. The increasing energy demand of a globally growing economy will likely make fossil fuels the main energy source in the foreseeable future. Hence, reducing CO2 emission from combustion of fossil fuels is a key point in reducing the impact of global warming. CO2 capture and storage (CCS) is one important option to reduce CO2 emission. In this concept, CO2 produced from combustion or industrial processes is captured and stored in closed geological formations where it is stored for long periods of time before being converted to carbonate minerals or other stable phases by natural processes. Some of the carbon dioxide may actually leak to the atmosphere, but if the leakage rate is low enough, this may not be of significant importance as natural mechanisms could sequester the carbon. CO2 capture can be achieved by different technologies and the most discussed are postcombustion, precombustion and oxyfuel combustion. Unfortunately, a substantial energy penalty is required for gas separation in these
The neglected story of non-combatants at war. Modern British fiction on World War One
Jane Mattisson
Oceánide , 2012,
Abstract: Literature has a special power to reveal the complex story of war. It is private soldiers and officers rather than non-combatants, civilians, conscientious objectors, clergymen and chaplains who are usually the focus of attention in historical studies and fiction. In my article, I focus on the situation of clergymen and army chaplains as they offer a unique opportunity to explore the ethical and emotional aspects of war, involving the reader in a series of moral choices to which it is impossible to remain neutral.
Sex Differences in Drug Development
Mattisson DR,Mattison Faye AC
Blickpunkt der Mann , 2008,
Abstract: The premise of individualized or personalized medicine is that the intervention is tailored to the individual. Individualized therapy will accommodate differences in body size, differences in metabolism and elimination, as well as differences in response. One appropriate starting point for individualized therapy is to focus on sex differences. Men and women differ in critical molecular, genetic, cellular, and physiological aspects. One important consequence of these differences is how sex influences drug disposition and impact. While, historically, women were excluded from most clinical studies, more recently there have been attempts to include them as subjects in all aspects of drug development. Additionally, more attention is being directed to sexappropriate diagnosis and treatment of disease as a component of individualized medicine. Despite this increased attention to sex differences, there remain substantial gaps in our understanding of sex differences in drug development, the focus of this review. This review was adapted from a talk presented at the Second International Congress of Gender Medicine in Vienna in 2007.
Chemical Looping Combustion of Solid Fuels in a Laboratory Fluidized-bed Reactor Combustion de charges solides avec la boucle chimique dans un lit fluidisé de laboratoire
Leion H.,Mattisson T.,Lyngfelt A.
Oil & Gas Science and Technology , 2011, DOI: 10.2516/ogst/2010026
Abstract: When using solid fuel in a chemical looping system, the char fraction of the fuel needs to be gasified before syngas react with the oxygen carrier. This can be done inside the fuel reactor with fuel and oxygen carriers well mixed, and, since this gasification is comparably slow, this will be the time limiting step of such a system. An option is to use an oxygen carrier that is able to release gas-phase oxygen which can react with the fuel by normal combustion giving a significantly faster overall fuel conversion. This last option is generally referred to as Chemical Looping combustion with Oxygen Un-coupling (CLOU). In this work, an overview is given of parameters that affect the fuel conversion in laboratory CLC and CLOU experiments. The main factor determining the fuel conversion, in both CLC and CLOU, is the fuel itself. High-volatile fuels are generally more rapidly converted than low volatile fuels. This difference in fuel conversion rate is more pronounced in CLC than in CLOU. However, the fuel conversion is also, both for CLC and CLOU, increased by increasing temperature. Increased steam and SO2 fraction in the surrounding gas will also enhance the fuel conversion in CLC. CO2 gasification in CLC appears to be very slow in comparison to steam gasification. H2 can inhibit fuel gasification in CLC whereas CO did not seem to have any effect. Possible deactivation of oxygen carriers due to SO2 or ash also has to be considered. Lorsque l’on utilise des combustibles solides dans la boucle chimique (CLC pour Chemical Looping Combustion), il est nécessaire de gazéifier le char avant de faire la combustion du gaz de synthèse au contact du transporteur d’oxygène. Ces réactions peuvent s’effectuer dans le réacteur fuel, dans lequel le combustible et le transporteur d’oxygène sont bien mélangés. Cependant, la gazéification du charbon est lente et reste l’étape limitante du processus de combustion dans ces conditions. Une alternative consiste à utiliser un matériau transporteur d’oxygène capable de relarguer l’oxygène directement dans la phase gazeuse, cet oxygène pouvant ensuite réagir directement avec le combustible. Cela permet alors d’avoir des vitesses de combustion plus rapides. Cette alternative est couramment appelée CLOU (pour Chemical Looping combustion with Oxygen Un-coupling). Dans cet article, on présente une synthèse sur les paramètres qui influencent la conversion du combustible dans les modes CLC et CLOU à partir de résultats obtenus en laboratoire. Le paramètre le plus important est la nature du combustible. Les combustibles contenant plus de
E-Commerce Business Models and Search Engine Dependency  [PDF]
Tobias Klatt
iBusiness (IB) , 2013, DOI: 10.4236/ib.2013.53B041
Abstract:

E-Commerce business models attracted a great deal of attention in the last years. An increasing number of bargains are realized via online transactions. However, some business models suffer distinctly under changes of search engine algorithms while others experience continuous stable traffic. This paper sheds light on the drivers of the unpunished e-commerce businesses based on a case-by-case analysis of 43 business models in the German Internet market. The analysis reveals that more stable business models are characterized by diversified customer arrivals which are obtained by a focused product management, multiple marketing channeling, freemium registration strategies and a subtle way to attract customer trust.

The Generalized wH Value  [PDF]
Tobias Hiller
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.43034
Abstract:

In this note, we generalize the wHSh value [1] [2] for CO values.

Chemical Looping Combustion of Solid Fuels in a 10 kWth Unit Combustion de charge solide en boucle chimique dans une unité de 10 kWth
Berguerand N.,Lyngfelt A.,Mattisson T.,Markstr?m P.
Oil & Gas Science and Technology , 2011, DOI: 10.2516/ogst/2010023
Abstract: The present study is based on previous results from batch experiments which were conducted in a 10 kWth chemical looping combustor for solid fuels using ilmenite, an iron titanium oxide, as the oxygen carrier with two solid fuels: a Mexican petroleum coke and a South African bituminous coal. These experiments involved testing at different fuel reactor temperatures, up to 1030°C, and different particle circulation rates between the air and fuel reactors. Previous results enabled modeling of the reactor system. In particular, it was possible to derive a correlation between measured operational data and actual circulation mass flow, as well as a model that describes the carbon capture efficiency as a function of the residence time and the char reactivity. Moreover, the kinetics of char conversion could be modeled and results showed good agreement with experimental values. The purpose of the present study was to complete these results by developing a model to predict the conversion of syngas with ilmenite in the fuel reactor. Here, kinetic data from investigations of ilmenite in TGA and batch fluidized bed reactors were used. Results were compared with the actual conversions during operation in this 10 kWth unit. Cette étude est basée sur des résultats antérieurs obtenus dans une unité de combustion de charges solides en boucle chimique d’une puissance de 10 kWth. Le transporteur d’oxygène utilisé est de l’ilménite, un minerai de fer et de titane, et les charges solides étudiées sont, d’une part, un coke de pétrole mexicain et, d’autre part, un charbon bitumineux sud africain. Les résultats expérimentaux ont été obtenus à des températures allant jusqu’à 1030°C avec différents débits de transporteur d’oxygène entre les réacteurs d’oxydation et de réduction. La modélisation de la combustion en boucle chimique de charges solides a déjà permis d’établir une corrélation entre le débit de circulation de transporteur d’oxygène et les données expérimentales mesurées puis de modéliser le taux de captage en fonction du temps de séjour du charbon et de sa réactivité. La cinétique de conversion du charbon a de plus été établie et permet de représenter les résultats expérimentaux de manière satisfaisante. Cette étude vise à compléter la modélisation entreprise pour prédire la conversion du gaz de synthèse résultant de la gazéification du charbon au contact de l’ilménite, en s’appuyant sur des données obtenues par ATG et dans un lit fluidisé en batch. Les résultats obtenus par modélisation sont comparés aux conversions mesurées expérimentalement dans l’unité de 10 kWth.
How Safe Is Conversion from Tacrolimus to Its Generic Drug?—A Single Center Experience  [PDF]
Tobias A. Marsen
Open Journal of Nephrology (OJNeph) , 2012, DOI: 10.4236/ojneph.2012.24012
Abstract: Background: Generically produced cyclosporine has long been approved in the treatment of organ transplant recipients and several publications have dealt with its use. For tacrolimus, however, very few data exist for safety and efficacy after conversion to its generic in kidney transplant recipients. Methods: In this single-center observational study, 14 kidney transplant carriers were converted to generic tacrolimus as part of aftercare, and graft function, fasting tacrolimus levels and the daily tacrolimus dose was pursued for up to 95 weeks. Results: Average drug doses changed from 3.64 ± 1.88 mg/day with the original to 3.33 ± 1.72 mg/day after conversion to generic tacrolimus (p = 0.33). Tacrolimus fasting levels were 6.23 ± 1.68 ng/ml before and 5.89 ± 1.15 ng/ml after conversion (p = 0.66). Average serum creatinine values of 2.26 ± 1.08 mg/dl after conversion did not differ from previous values of 1.99 ± 0.74 mg/dl (p = 0.15). Conclusions: These data support the assumption, that it is safe to convert stable kidney transplant patients from the original galenic formulation under close scrutiny to the generically produced substance. Conversion is easy to be implemented in the routine follow-up and thus represents an option in the therapy with calcineurin inhibitors, which will contribute to cost reduction in the health system.
Herbicidal Effects of Fungicides on Arable Weeds  [PDF]
Henning Nordmeyer, Tobias Koch
American Journal of Plant Sciences (AJPS) , 2014, DOI: 10.4236/ajps.2014.51006
Abstract:

In the present study, the herbicidal effects of two fungicides with the active ingredients expoxiconazole, fluxapyroxad, pyraclostrobin and fenpropimorph on the two arable weeds Lamium purpureum L. and Chenopodium album L. were investigated. The experiments were conducted in a climate chamber under defined conditions. Sowing pods were prepared and plants at the cotyledon leaf stage were pricked out in test pods. Fungicides were applied at six application rates: 0%, 12.5%, 25%, 50%, 100% and 200% of the maximum registered dose rate in Germany. Seven days after application, the first assessment was conducted, regarding growth stage, quantity of plants and visible plant damage. Fourteen days after application, the second and final assessment was conducted, regarding growth stage, quantity of plants, visible plant damage and the fresh weight of the plants. There were herbicidal effects of the fungicides, which were presumably due to the active ingredient epoxiconazole. Epoxiconazole has effects on enzymes that are dependent on cytochrome P-450 and inhibits sterol biosynthesis and probably gibberellin synthesis. By doing so, these fungicides have similar effects to plant growth regulators. Weed species showed differential sensitivities, contractions and growth inhibition and ED50-values were calculated. Notwithstanding the probably minor relevance of the present results in agricultural practice, some effects on arable weeds might result if fungicides are applied at an early growth stage in the field. In some cases, the crop-weed competition could be shifted to the benefit of the crop. Nevertheless, the results are interesting for the field of weed research and for the assessment of the ecotoxicology of fungicides.

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