Charakterizace paliv z biomasy v IPFR reaktoru

Combustion of fossil fuels is one of the most important source of energy. However low carbon politics and environmental commitments, affects developing combustion and co – combustion technologies. Utilization of biomass fuels can be answer for new challenges, although more research on effective utilization of these fuels are needed. Nowadays, combustion of biomass fuels, especially straw, causes many technical problems, mainly slagging formation, fouling of heat exchangers inside combustion chamber and insufficient fuel burnout. This paper focuses on analysis of biomass combustion. Better knowledge of behavior during biomass combustion may help to optimization of PF (Pulverized Fuel) boiler of and avoid some technical problems. The results of investigation shows that temperature and oxygen concentration in reactor play significant role in process of devolatilization and char burnout. For instance during char burnout experiments at temperature 850⁰C at 14% oxygen concentration after 200 ms more than 80% of mass loss were achieved. Compared to 700⁰C at 14% oxygen concentration this same level of mass loss were completed after 500 ms. Experiments performed on Isothermal Plug Flow Reactor (IPFR) at Institute of Energy Process Engineering and Fuel Technology (IEVB) at TU Clausthal were a part of project between IEVB and the Karlsruhe Institute of Technology (KIT) in Germany.Spalování fosilních paliv je jedním z nejdůležitějších zdrojů energie. Nicméně nízkouhlíková politika a environmentální závazky ovlivňují vývoj spalovacích a spolu-spalovacích technologií. Využívání paliv z biomasy může být odpovědí na nové výzvy, i když je zapotřebí více výzkumu o efektivním využití těchto paliv. V současné době spalování paliv z biomasy, zejména slámy, způsobuje řadu technických problémů, zejména tvorbu strusky, zanášení výměníků tepla uvnitř spalovací komory a nedostatečné vyhoření paliva. Tento příspěvek se zaměřuje na analýzu spalováníbiomasy. Lepší znalost chování procesů při spalování biomasy může přispět k optimalizaci návrhu práškového kotle a vyhnout se tím technickým problémům. Výsledky výzkumu ukazují, že teplota a koncentrace kyslíku v reaktoru hrají významnou roli v procesu tvorby prchavé hořlaviny a vyhoření tuhého zbytku. Například během experimentů s vyhořelým tuhým zbytkem při teplotě 850 ° C při 14% koncentraci kyslíku po 200 ms bylo dosaženo více než 80% úbytku hmotnosti. Ve srovnání se 700 ° C při 14% koncentraci kyslíku byla stejná úroveň úbytku hmotnosti dosažena po 500 ms. Experimenty provedené na izotermickém reaktoru (IPFR) v Institutu energetických procesů a technologií paliv (IEVB) na TU Clausthal byly součástí projektu mezi IEVB a „Karlsruhe Institute of Technology (KIT)“ v Německu

Thermodynamic Evaluation of the system Ta–O and Preliminary Assessment of the Systems Al–Nb–O and Al–Ta–O

The binary tantalum–oxygen system is assessed using the CALculation of PHase Diagrams (CALPHAD) method with experimental data from the literature. The oxygen solubility in the Ta solid-solution phase is discussed and modeled. The low- and high-temperature modifications of Ta₂O₅ are described as stoichiometric compounds. This dataset is extended into the ternary Al–Ta–O system by complementing it with binary datasets for Al–O and Al–Ta from the literature and adding mixed-oxide AlTaO₄. The dataset for the ternary system Al–Nb–O is created by combining the three corresponding binary datasets from the literature and by assessing the quasibinary section Al₂O₃–Nb₂O₅. The ternary aluminum niobates are described as stoichiometric compounds. Phase equilibria between refractory metals and alumina at high temperature are discussed

The use of mobile devices for physical activity tracking in older adults’ everyday life

Objective: The tracking of one’s own physical activity with mobile devices is a way of monitoring and motivating oneself to remain healthy. Older adults’ general use of mobile devices for physical activity tracking has not yet been examined systematically. The study aimed to describe the use of physical activity trackers, smartwatches and smartphones, or tablets for tracking physical activity and to examine the reasons for the use of these technologies. Methods: Participants aged ≥50 years (N = 1013) living in Switzerland were interviewed in a telephone survey. To address the research questions, we calculated descriptive frequency distributions, tested for differences between groups, and performed logistic regression analyses. Results: Descriptive and multivariate analyses showed that (a) 20.5% of participants used mobile devices for physical activity tracking; (b) men, younger individuals, those with a strong interest in new technology, and those who frequently exercised had a higher likelihood of using mobile devices for physical activity tracking; and (c) participants more often agreed with reasons for use relating to tracking physical activity and motivating oneself to remain healthy than they did with reasons relating to social factors. Conclusions: The study presented representative data about the actual use of mobile tracking technology in persons over 50 years of age. Today, mainly active and younger elderly (mostly men) with a high interest in technology are using tracking technologies. Results indicate a need for further studies on motivational and usability aspects regarding the use of mobile health tracking devices by older adults

Modeling and Simulation the Thermal Runaway Behavior of Cylindrical Li-Ion Cells—Computing of Critical Parameter

The thermal behavior of Li-ion cells is an important safety issue and has to be known under varying thermal conditions. The main objectives of this work is to gain a better understanding of the temperature increase within the cell considering different heat sources under specified working conditions. With respect to the governing physical parameters, the major aim is to find out under which thermal conditions a so called Thermal Runaway occurs. Therefore, a mathematical electrochemical-thermal model based on the Newman model has been extended with a simple combustion model from reaction kinetics including various types of heat sources assumed to be based on an Arrhenius law. This model was realized in COMSOL Multiphysics modeling software. First simulations were performed for a cylindrical 1860 cell with a -cathode to calculate the temperature increase under two various simple electric load profiles and to compute critical system parameters. It has been found that the critical cell temperature [Math Processing Error] , above which a thermal runaway may occur is approximately [Math Processing Error] , which is near the starting temperature of the decomposition of the Solid-Electrolyte-Interface in the anode at [Math Processing Error] . Furthermore, it has been found that a thermal runaway can be described in three main stages

Laser-assisted post-processing of additive manufactured metallic parts

Laser-assisted additive manufacturing (AM) is the process of successively melting thin layers of material using a laser source to produce a three dimensional device or product. From the many technologies available, only a few can produce metallic parts that fulfil the requirements of industrial applications. Ultrafast laser machining is a new and promising technical approach for post-processing AM parts since laser ablation and surface modification processes could be applied with high accuracy for trimming shape and functionality, i.e., edge quality and wettability. The impact of different ultrafast laser parameters is evaluated for AM samples, which are examined for surface roughness before and after the laser-assisted post-processes. For all the parameters tested, the use of ultrafast laser resulted in a homogeneous material ablation of the samples’ surfaces. For the investigated parameter range, the AM building tracks were still maintained even after ultrafast laser post-processing. The achieved results showed the formation of self-organized porous structures at low laser scan velocities leading to an enhanced surface roughness. For higher scan velocities characteristic nano ripples might be induced having no significant impact on the measured surface roughness