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The efficient combustion of o-xylene in a Knudsen controlled catalytic membrane reactor

Yıldırım, Yılmaz | Hughes, Ronald

Article | 2002 | PROCESS SAFETY AND ENVIRONMENTAL PROTECTION80 ( B3 ) , pp.159 - 164

Catalytic inorganic membrane preparation and the catalytic oxidation of o-xylene contained in air streams on catalytic membrane tubes are presented in this study. Boehmite prepared sols were deposited onto porous alumina tubes from the outside using a filtration coating technique. The coatings were characterized by nitrogen gas permeations at the same temperatures used for the o-xylene experiments. Single gas permeabilities indicated a best separation factor for the modified membrane for H-2/N-2 of 3.6, which is very close to the Knudsen value. Pt loading was estimated as 1.6%w/w based on membrane material weight by using both weigh . . .ing and atomic absorption spectrophotometry (AAS) methods. O-ylene catalytic oxidation of o-xylene contained in air streams with concentrations between 0.146-0.220% (v/v) was carried out in a catalytic membrane reactor at temperatures between 150-290degreesC and 97% conversion was achieved for 0.146% o-xylene in air at a temperature of 285degreesC Daha fazlası Daha az

Experimental studies on the effect of electrode configuration in electrofiltration

Genç, Ayten | Tosun, İbrahim

Article | 2002 | Separation Science and Technology37 ( 13 ) , pp.3053 - 3064

Results from the electrofiltration of anatase (TiO2) particles in a water suspension and using three different electrode configurations are presented. The three electrode configurations studied were spot, foil, and mesh. For the first two configurations, the electric field was perpendicular to the direction of flow while for the mesh configuration it was opposite to the direction of flow. The percent gain volume filtrate and power consumption were measured for each electrode configuration. For a given percent gain volume filtrate, it was observed that the foil electrode configuration consumes the least power.

Membrane potentials for linearly varying fixed charges

Genç, Ayten

Article | 2009 | Turkish Journal of Engineering and Environmental Sciences33 ( 1 ) , pp.73 - 81

The membrane potentials for asymmetric membranes where fixed charges varied linearly with position were evaluated from the numerical solutions of Nernst-Planck flux and Donnan potential equations. The evaluated membrane potentials were compared with the results obtained from the conventional TMS theory where the fixed charge concentration in the membrane was assumed to be uniform. In the comparison, the number of fixed charges was kept constant by defining an average for the fixed charge concentration. The numerical results showed that the membrane potential increased in magnitude when the distributions of fixed charges at the membr . . .ane-solution interfaces were unequal. In addition, the deviation from TMS theory increased more as the charge difference at the interfaces increased. © TÜBİTAK Daha fazlası Daha az

Analysis of the electrofiltration mechanism based on multiphase filtration theory

Genç, Ayten | Tosun, İsmail

Article | 2004 | Chemical Engineering Communications191 ( 1 ) , pp.125 - 136

A mathematical model based on multiphase filtration theory is developed to describe the electrofiltration process. The model takes both electrophoretic and electroosmotic effects into account. The electrophoretic migration velocity of solid particles is predicted from the model using the filtrate volume time data obtained from electrofiltration experiments.

The Evaluation of Kurtbogazi Dam (Ankara, Turkey) from Hydro-Geochemical and Environmental Aspects

Altın, Ahmet | Bakır, Fatma | Özölçer, İsmail Hakkı

Article | 2010 | WATER RESOURCES MANAGEMENT24 ( 4 ) , pp.747 - 759

KurtbogazA +/- Dam is one of the most significant sources of drinking water sources for Ankara City. In this study, hydro-geochemical properties and pollution sources of surface waters feeding into the dam are determined. In addition, important environmental problems such as squatter's houses and wastewater discharges within protection zones of watershed of the dam are defined and appropriate precautions are discussed. The long-term trend (1998-2007) in water quality results of the dam and the surface waters in the KurtbogazA +/- watershed were studied, utilizing data provided by General Directorate of State Water Works (DSI). The r . . .esults indicate that waters in the watershed can be classified as waters with calcium-bicarbonate. Due to the drought conditions experienced in recent years, the concentrations of the organic materials and nitrogen and phosphorus compounds in the surface waters have increased dramatically since 2005. It is thought that wastewaters discharged by the settlements within the watershed (especially Pazar Township) are responsible for these increases. Preventing wastewater discharges from the squatter's houses and agricultural activities on the absolute and the proximate zones of the watershed and the constructing of a sewerage and treatment plant are the first challenges for the protection of the watersheds Daha fazlası Daha az

Destabilization and treatment of emulsified oils in wastewaters by electrocoagulation

Genç, Ayten | Bakırcı, Büşra

Article | 2016 | Water Environment Research88 ( 11 ) , pp.2008 - 2014

In this study, the optimum operating conditions for the treatment of emulsified oils by electrocoagulation were determined depending on droplet stability analysis. Zeta potential measurements were used as the indication of oil droplet charges. In addition, the effects of pH and ionic conductivity on the droplet sizes and surface charges were investigated. The studied emulsified oil droplet sizes were more sensitive to changes in pH rather than salt concentration. The droplets became larger and unstable in alkaline conditions. As the initial pH of wastewaters increased, the oil removal efficiency increased during the electrocoagulati . . .on experiments as well. The use of iron or aluminum electrodes resulted in higher removal efficiencies in comparison to stainless steel electrodes. In addition, the energy consumption for aluminum electrodes was much lower than iron electrodes. To obtain 98% oil removal efficiency, distance between the electrodes was recommended to be less than or equal to 1 cm. © 2016, Water Environment Federation. All rights reserved Daha fazlası Daha az

Sorption of acid dyes from aqueous solution by using non-ground ash and slag

Genç, Ayten | Oğuz, Aşkın

Article | 2010 | Desalination264 ( 01.Feb ) , pp.78 - 83

The sorption of two acid dyes (Acid Yellow 99 and Acid Red 183) into locally available industrial waste materials, namely, Granulated Blast Furnace Slag (GBFS) and Furnace Bottom Ash (FBA), has been investigated by performing batch equilibrium experiments with pH, ionic conductivity, initial dye concentration and temperature as variables. The kinetic sorption data indicated that the sorption capacity of GBFS for these dyes was almost zero. On the other hand, the color removal efficiency for FBA could reach 50% depending on the initial dye concentration. It was also found that the kinetics of sorption of Acid Yellow 99 and Acid Red 1 . . .83 onto the surface of FBA at different operating conditions were best described by the Elovich kinetic model. In addition, the adsorption equilibrium data were analyzed using various adsorption isotherm models and the results have shown that the sorption behaviors of the studied dyes could be best described by the Langmuir model. © 2010 Elsevier B.V Daha fazlası Daha az

Transport of Lead (Pb2+) Ions through silty-clayey soils under acidic conditions

Genç, Ayten | Ulupınar, Elif

Article | 2010 | Transport in Porous Media84 ( 3 ) , pp.699 - 709

This study aimed to identify effects of pH on the transport of Pb2+ ions through a saturated silty-clayey soil layer by using advection-dispersion equation (ADE). The predictive accuracy of the solution of ADE depends on the proper determination of the retardation by adsorption and, therefore, the adsorption mechanism of lead onto silty-clayey soil was investigated first by performing batch equilibrium experiments. These results showed that the sorption mechanism of lead onto silty-clayey soil depended on pH and could be best described by the Langmuir isotherm. Based on the results of the sequential experiments, it was also conclude . . .d that the pH dependent charges in silty-clayey soil were mainly associated with the surfaces of carbonates and the specific adsorption of lead ions. The numerical solutions of the combined form of ADE with the Langmuir isotherm indicated that the migration profiles of lead in silty-clayey soil were a strong function of the parameters of the Langmuir isotherm rather than the infiltration velocity. © 2010 Springer Science+Business Media B.V Daha fazlası Daha az

An alternative type of photoelectro-Fenton process for the treatment of landfill leachate

Altın, Ahmet

Article | 2008 | Separation and Purification Technology61 ( 3 ) , pp.391 - 397

An alternative type of photoelectro-Fenton (PEF) process has been proposed to remove COD, color and phosphate from the landfill leachates. The process was improved by combining the different type of electro-Fenton (EF) process with UV irradiation. The efficiency of the process and settling characteristics of waste sludge produced from the process were investigated by changing some operating parameters such as initial pH, H2O2 and current. In addition, the proposed process was compared with other treatment processes such as electro-coagulation (EC), electro-Fenton and UV/H2O2 in terms of treatment efficiency. The high removal efficie . . .ncies were observed at the initial pH 3, initial H2O2 concentration, 3000 mg L-1; current, 2.5 A; and treatment time, 20 min. Removal of COD, color and phosphate under the reported conditions were 94%, 97%, 96%, respectively. The obtained results from the comparative experiments revealed that the proposed PEF process is more effective than the other treatment processes for the landfill leachate. © 2007 Elsevier B.V. All rights reserved Daha fazlası Daha az

Prediction of the bottom ash formed in a coal-fired power plant using artificial neural networks

Bekat, Tuğçe | Erdoğan, Muharrem | İnal, Fikret | Genç, Ayten

Article | 2012 | Energy45 ( 1 ) , pp.882 - 887

The amount of bottom ash formed in a pulverized coal-fired power plant was predicted by artificial neural network modeling using one-year operating data of the plant and the properties of the coals processed. The model output was defined as the ratio of amount of bottom ash produced to amount of coal burned (Bottom ash/Coal burned). The input parameters were the moisture contents, ash contents and lower heating values of the coals. The total 653 data were divided into two groups for the training (90% of the data) and the testing (10% of the data) of the network. A three-layer, feed-forward type network architecture with back-propaga . . .tion learning was used in the modeling study. The activation function was sigmoid function. The best prediction performance was obtained for a one hidden layer network with 29 neurons. The learning rate and the tolerance value were 0.2 and 0.05, respectively. R2 (coefficient of determination) values between the actual (Bottom ash/Coal burned) ratios and the model predictions were 0.988 for the training set and 0.984 for the testing set. In addition, the sensitivity analysis indicated that the ash content of coals was the most effective parameter for the prediction of the ratio of bottom ash to coal burned. © 2012 Elsevier Ltd Daha fazlası Daha az

Effects of coal properties on the production rate of combustion solid residue

Durgun D. | Genç, Ayten

Article | 2009 | Energy34 ( 11 ) , pp.1976 - 1979

The production rates of furnace bottom ash in a pulverized coal-fired power plant were monitored for a two-year period and its variations with respect to coal properties were analyzed. The power plant was originally designed to fire the coal sludge generated from a washing process; however, the coal sludge and its mixture with low-rank bituminous coal have been started to be used as the main fuel with time. The results of the hardgrove grindability measurements have shown that the grinding properties of sludge or its mixtures could not be predicted based on proximate analysis (moisture, ash, carbon and volatile contents); it could o . . .nly be determined by experiments. The production rate of bottom ash in this particular power plant remained relatively insensitive to the high ash and moisture contents and could be estimated almost only by knowing the calorific value of the source coal. The evaluated dependency was linear. © 2009 Elsevier Ltd. All rights reserved Daha fazlası Daha az

Industrial noise and its effects on humans

Atmaca, Eyüp | Peker, İ. | Altın, Ahmet

Article | 2005 | Polish Journal of Environmental Studies14 ( 6 ) , pp.721 - 726

The problem of noise in the industries around Sivas has been examined in this study; and noise measurement and survey studies have been carried out at concrete traverse, cement, iron and steel and textile factories located in this region. A questionnaire was completed by 256 workers during this study in order to determine the physical, physiological, and psycho-social impacts of the noise on humans and to specify what kind of measurements have been taken both by the employers and workers for protection from the effects of noise. It has been specified, during the surveys, that the noise levels detected in all the industries are much . . .above the 80 dBA that is specified in the regulations: 73.83% of the workers in these industries are disturbed from the noise in their workplaces, 60.96% of them have complaints about their nervous situations, 30.96% of these workers are suffering hearing problems although they had not had any periodical hearing tests and they are not using ear protection equipment Daha fazlası Daha az

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