223 research outputs found

    Qualitative and quantitative changes of essential composition in the flowers of some populations of Elaeagnus angustifolia

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    Background and aims: Elaeagnus angustifolia L. is a member of the Elaeagaceae family; different parts of it, especially fruits have been used for the treatment of several diseases in traditional medicine. The aim of this study was to isolate and determine essential oil composition of flowers of E. angustifolia collected from different ecological areas of East-Azarnayjan in Iran. Methods: In this experimental study, the essential oils of the flower were isolated by hydrodistillation method and analyzed by GC and GC/MS. Results: The number of compounds in the essential oil isolated from the population of Ahar, Marand and Hashtroud were 22, 17 and 14, respectively. The major component of all of the populations was ethylcinnamate; Ahar (47.59), Marand (69.99) and Hashtroud (85.49). It was observed that the oil number of E. angustifolia decreases from 22 to 14 when the altitude increases from 1344-1750 m. Conclusion:Chemical composition of the essential oils of E. angustifolia L. such as esters and aromatic acids contents were increased while the ketone content was decreased with increasing altitude

    Reaction Kinetics for High-Pressure Hydrogen and Methane Oxy-combustion in the Presence of High Levels of H2O and CO2

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    Continued use of fossil fueled heat and power generation calls for a multi-faceted approach to ensure their associated emissions, in particular CO2 emissions, are mitigated in an economically viable manner. A path to sustainable development, not only demands switching from carbon intensive fuels such as coal to the likes of natural gas or biofuels, it also requires equipping fossil-fueled systems with carbon capture, utilization and storage (CCUS) technologies. One promising carbon capture technology, is oxy-fuel combustion with cooling and compression CO2 capture. Oxy-fuel combustion entails reacting the fuel with nearly pure oxygen (95-99 mole %), producing a flue gas composed mostly of CO2 and H2O, with smaller quantities of N2 and Ar. As the flue gas is CO2-rich and is not diluted by large quantities of N2, it can be separated physicaly through compression, cooling, and auto-refrigeration steps. Pressurized variants of oxy-combustion technologies enable integration of CO2 capture and compression with the combustion process, and hold prospects for improved economics and reduced footprint. On the path for these promising technologies to reach their full potential, one of the knowledge gaps lies within the understanding of their combustion chemistry. This is due to the presence of high concentrations of H2O (up to 65%) and/or CO2 (up to 90%) in these systems. The impact of high H2O concentrations on pressurized oxy-combustion kinetics has not been explored. This research aims to fill this knowledge gap by generating new experimental data and developing experimentally-validated reaction mechanisms able to better characterize and model pressurized oxy-combustion kinetics behavior in presence of large quantities of H2O and CO2. To this end, novel shock tube experimental ignition delay time (IDT) test data were generated in collaboration with King Abdullah University of Science and Technology (KAUST) for reactive mixtures involving 4% H2, 0.48-3.44% CH4, at equivalence ratios (φ) of 0.93-1, to delineate the effect of high concentrations of H2O, CO2, and pressure on combustion kinetics. A hierarchical model development and validation approach is presented for high-pressure combustion kinetics in the presence of high levels of H2O and CO2. Two models, one for H2/CO and the other for CH4 high-pressure combustion kinetics were developed with particular attention to pressure- and bath gas-dependent reaction rates. High-pressure H2 IDT experiments were performed at temperatures of 1084-1242 K and pressures of 37-43.8 bar at φ of 1. IDT data for four different bath gases, namely: Ar, 45%H2O/Ar, 30%H2O/15%CO2/Ar, and 45%CO2/Ar are provided. Low-pressure H2 IDT experiments were also conducted across a temperature range of 917-1237 K, pressure range of 1.6-2.4 bar, at φ of 1 in Ar and 45%CO2/Ar bath gases. A minimally-tuned H2/CO reaction mechanism, CanMECH 1.0, targeting high-pressure combustion in the presence of large concentrations of H2O and CO2 is developed. CanMECH 1.0 is validated against both the shock tube IDT data of this work, and other H2 and H2/CO shock tube IDT datasets from literature. CanMECH 1.0 performance is compared to a well-cited incumbent syngas oxidation kinetics mechanism (Keromnes et al., Combust. Flame 160 (2013) 995-1011). It outperformed the incumbent for 16 out of 25 data subsets, and exhibited a similar performance for another two. CanMECH 1.0 improved model predictions of this work’s shock tube IDT data for H2O- and CO2- laden reactive mixtures, as well as all IDT data at pressures of 17-43.8 bar, which are of particular value to pressurized oxy-fuel combustion applications relevant to this work. Overall CanMECH 1.0 brought about a 26% improvement relative to the incumbent in predicting all the IDT validation data considered in this work. High-pressure CH4 IDT experiments were performed at CH4 concentrations of 0.48-0.5%, temperatures of 1536-1896 K, pressures of 37-53 bar, φ of 0.93-1, in the presence of Ar, 45%H2O/Ar, 30%H2O/15%CO2/Ar, and 45%CO2/Ar. Low-pressure IDT experiments were also conducted at temperatures of 1486-1805 K, pressures of 1.8-2.4 bar, CH4 concentrations of 3-3.44%, at φ of 1 in bath gases composed of Ar and 45%CO2/Ar. An improved CH4 reaction mechanism, CanMECH 2.0, is developed, by embedding CanMECH 1.0 (H2/CO mechanism) into a recent and well-validated C1-C4 detailed kinetics mechanism, AramcoMECH 2.0. CanMECH 2.0 performance is evaluated and compared with AramcoMECH 2.0, in addition to AramcoMECH 3.0, in predicting the shock tube IDT validation targets. CanMECH 2.0 is shown to improve the overall performance of the two incumbent mechanisms by 1% and 3%, respectively

    Economic Evaluation of an Advanced Super Critical Oxy-Coal Power Plant with CO2 Capture

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    Today’s carbon constrained world with its increasing demand for cheap energy and a fossil fuel intensive fleet of power producers is making carbon capture and storage (CCS) desirable. Several CCS technologies are under investigation by various research and development groups globally. One of the more promising technologies is oxy-fuel combustion, since it produces a CO2 rich flue gas which requires minor processing to meet storage condition requirements. In this study the economics of an advanced super critical oxy-coal power plant burning lignite, simulated in-house was assessed. A robust and user-friendly financial tool box has been developed with commonly acceptable default parameter settings. Capital, operation and maintenance costs were estimated along with corresponding levelized cost of electricity and CO2 avoidance costs calculated using the detailed financial model developed. A levelized cost of electricity of 131 /MWhrnetalongwithalevelizedCO2avoidancecostof64/MWhrnet along with a levelized CO2 avoidance cost of 64 /tonne was estimated for an ASC oxy-coal power plant with CO2 capture. Also a levelized cost of electricity of 83 /MWhrnetwasestimatedforanASCair−firedcoalpowerplantwithoutCO2capturecapabilitiesasthebaseplant.Thepriceofelectricitywasobservedtoincreasefrom83/MWhrnet was estimated for an ASC air-fired coal power plant without CO2 capture capabilities as the base plant. The price of electricity was observed to increase from 83 /MWhrnet to 131 $/MWhrnet translating into a 57% increase. The sensitivity of the overall economics of the process was assessed to several parameters. The overall economics was found sensitive to the choice chemical engineering plant cost index (CEPCI), capacity factor, size of power plant, debt ratio, fuel price, interest rate, and construction duration

    A Novel Fuzzy Theory-Based Differential Protection Scheme for Transmission Lines

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    Abstract- Ever-increasing consumption of electrical energy has forced extension of power systems to wider regions, which will augment concerns about the stability and reliability of power systems. Therefore, a special attention has been given to protection systems and protection relays to improve these concerns. By appropriate design of protection systems and proper function of protection relays, it is possible to reduce the adverse effects of undesirable faults. A fuzzy logic-based algorithm is presented to improve differential relay performance. The algorithm is employed for protection of short transmission lines against internal faults with/without resistance. By using fuzzy logic and selecting the best stability characteristics, the possibility of malfunction of protection relays will be negligible. In this algorithm, sensitivity, reliability and speed of the relay performance are preserved at suitable levels. The proposed algorithm is also very beneficial for external faults accompanied with the saturation of current transformers (CTs). The purpose of this study is to present an algorithm based on the fuzzy logic, which can decide on the slope of stability characteristics of a differential relay in the best way during various conditions. The performance of the presented algorithm is analyzed in PSCAD/EMTDC program and compared to conventional methods

    Medical professionalism: teaching and assessment tools

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    Establishing a structured curriculum for professionalism by adopting new methods and evaluation tools within an educational environment is important in the light of the vicissitudes of changing world and medical profession. By incorporating such tools of teaching and assessing, medical students will be abreast and gain a mastery over competencies such as collaboration, communication, teamwork, and rapport skills to deal with doctors, patients, peers, and the healthcare team
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