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Bulunan: 19 Adet 0.001 sn
Koleksiyon [3]
Tam Metin [1]
Yayın Türü [1]
Yazar [20]
Yayın Yılı [13]
Konu Başlıkları [20]
Yayıncı [9]
Yayın Dili [2]
Dergi Adı [17]
Hydrogen sorption characteristics of Zonguldak region coal activated by physical and chemical methods

Kopac T. | Toprak A.

Article | 2009 | Korean Journal of Chemical Engineering26 ( 6 ) , pp.1700 - 1705

Hydrogen sorption characteristics of activated carbons (ACs) produced by physical and chemical activations from two coal mines (Kilimli and Armutcuk) in the Zonguldak region, Turkey were investigated by a volumetric technique at 77 K. H2 adsorption isotherms were obtained on the samples exposed to pyrolytic thermal treatments in a temperature range of 600-900 °C under N2 flow and chemical activation using different chemical agents such as KOH, NH4Cl, ZnCl2 from the two mines. Experimental hydrogen adsorption isotherm data at 77 K were used for the evaluation of the adsorption isotherm constants of the Brunauer-Emmett-Teller (BET) an . . .d the Langmuir models, and also the amount of hydrogen adsorbed on the various samples was evaluated by using the adsorption isotherm data. Higher hydrogen adsorption capacity values were obtained for all the heat and the chemically treated activated carbon samples from the Kilimli coal samples than Armutcuk. The amount of H2 adsorbed on the original Kilimli coal samples was 0.020 wt%, and it was increased to 0.89 wt% on the samples pyrolyzed at 800 °C. The highest value of hydrogen adsorption obtained was 1.2 wt% for the samples treated with KOH+NH4Cl mixture at 750 °C followed by oxidation with ZnCl2. It was shown that chemical activations were much more effective than physical activations in increasing the surface area, pore volume and the hydrogen sorption capacities of the samples. © 2009 Korean Institute of Chemical Engineers, Seoul, Korea Daha fazlası Daha az

Coal desulfurization using natural Ca-based sorbents

Sutcu H.

Article | 2004 | Coal Preparation24 ( 05.Jun ) , pp.249 - 259

Lignite with a high organic sulfur content was desulfurized by pyrolysis performed at temperatures ranging from 650 to 950°C. An investigation was carried out on the effect of calcium-based sorbents such as lime, limestone, and dolomite on removing sulfur during pyrolysis in the presence of N2 and CO2 gases. Limestone and dolomite proved more effective than lime and more sulfur was removed in an atmosphere of CO2 than in an atmosphere of N2.

Preparation of activated carbons from Zonguldak region coals by physical and chemical activations for hydrogen sorption

Kopac T. | Toprak A.

Article | 2007 | International Journal of Hydrogen Energy32 ( 18 ) , pp.5005 - 5014

Activated carbons were prepared by physical and chemical activations from coals collected from two mines (Kilimli and Armutcuk) in Zonguldak region, Turkey under different conditions. Ash content was reduced considerably by use of HCl and HF treatments. Pyrolytic thermal treatments in a temperature range of 600-900 {ring operator} C under N2 flow and chemical treatments using different chemical agents such as KOH, NH4Cl, ZnCl2 were applied to the coal samples from the two mines. N2 adsorption isotherms were obtained at 77.4 K for the thermally and the chemically treated samples and the data were used for the evaluation of the specif . . .ic surface area, total pore volumes and the average pore sizes of the samples. Higher surface area values were obtained from Kilimli coal samples than Armutcuk. The BET surface area of the Kilimli coal samples which were initially have a value of 1.20 m2/g were increased to 52.62 m2/g after pyrolytic heat treatments at 800 {ring operator} C and increased to a value of 830.5 m2/g by treating the coals with KOH + NH4 Cl mixture at 750 {ring operator} C followed by oxidation of the samples mixed with ZnCl2. The activated carbon samples were prepared for the purpose of their evaluation in hydrogen sorption studies. © 2007 International Association for Hydrogen Energy Daha fazlası Daha az

Examination of the effects of activated carbon produced from coal using single-step h3po4/n2+h2o vapor activation on the adsorption of bovine serum albumin at different temperatures and ph values

Toprak A. | Bozgeyik K.

Article | 2018 | Journal of the Turkish Chemical Society, Section A: Chemistry5 ( 1 ) , pp.219 - 236

This study examined protein adsorption equilibrium and kinetics on activated carbon (AC) that we obtained from coal by single-step H3PO4 activation under N2+H2O vapor at 800 °C. Surface properties, pore size distribution, and volumes of AC were determined using volumetric method with N2 adsorption at 77 K. Also, the textural properties were characterized by SEM-EDAX and XRD. The zeta potential values were measured to elucidate the electrostatic interactions between the protein and AC. The obtained AC discrete system was also used as an adsorbent for adsorbing bovine serum albumin (BSA) from aqueous solution. The effects of pH (4.0, . . .5.0, and 7.4) and temperatures (20, 30 and 40 °C) on the adsorption of BSA on AC were examined. The surface area, micropore, mesopore and total pore volumes of AC were found to be 1175 m2/g, 0.477 cm3/g, 0.061 cm3/g and 0.538 cm3/g, respectively. The optimum temperature for AC in BSA adsorption was found to be 40 °C and the pH was found to be 4.0. The highest BSA adsorption was found to be 159 mg/g and pH to be 4.0. The experimental equilibrium data were compared with the Langmuir and Freundlich models and found to be compatible with both models. The adsorption process is best described by the pseudo-first-order kinetic model. As a result, it was found out that AC obtained by single step H3PO4/N2+H2O vapor activation is an effective adsorbent for the adsorption of BSA from aqueous solution. © 2018, Turkish Chemical Society. All rights reserved Daha fazlası Daha az

Structural characterization of oil component of high temperature pyrolysis tars

Sutcu H. | Toroglu I. | Piskin S.

Article | 2005 | Energy Sources27 ( 6 ) , pp.521 - 534

Tar samples obtained through high temperature carbonization of three different bituminous coals were separated into oil, asphaltene and preasphaltene fractions by soxhlet extraction. The oil fraction was further separated into parafinic, neutral aromatic and polar aromatic sub-fractions by silica gel chromatography. By means of the FT-IR spectroscopy of the sub-fractions, an attempt was made to define the existing functional groups, and through 1H-NMR spectroscopy, interpretations were made as to the aliphatic and aromatic hydrogen distribution as well as the location of the hydrogen atoms in the molecule and their position in relat . . .ion to each other. Copyright © Taylor & Francis Inc Daha fazlası Daha az

The effects of ash and maceral composition of Azdavay and Kurucasile (Turkey) coals on coking properties

Toroglu I.

Article | 2006 | Energy Sources, Part A: Recovery, Utilization and Environmental Effects28 ( 3 ) , pp.263 - 279

In this study, investigations were made as to the effect of the maceral compositions and mineral matter content of Azdavay and Kurucasile coals on the coking property. Chemical and maceral analyses and coking properties were determined for the products of the float-sink procedure. The coking properties were established on the basis of free swelling index and Ruhr dilatometer tests. Maceral analyses showed that as the ash content of a coal containing both high and medium volatile matter increases, its effective maceral proportion decreases, and the coking property is affected in an unfavorable way.

The role of coal in energy policy and sustainable development of Turkey: Is it compatible to the EU energy policy?

Baris K.

Article | 2011 | Energy Policy39 ( 3 ) , pp.1754 - 1763

This paper aims to assess the current and future role of coal in energy strategy of Turkey, and evaluates the compatibility of policies to the EU energy policy and strategy. Coal is regarded as the most important indigenous energy source in Turkey together with hydropower to strengthen the supply security of the country. Turkish government set targets to fully utilize coal reserves of the country in next decades. However, the country is also in the process of becoming an EU Member State, hence, it is expected that the energy policies have to comply with the EU. Moreover, Turkey ratified Kyoto Protocol in 2009, thus the country shoul . . .d limit CO2 emission together with other greenhouse gases. The probable obstacles that Turkey may face due to the utilization of coal were determined as CO2 emissions, lack of technology and application in Carbon Capture and Storage (CCS) and health and safety issues. It is concluded that coal is a very important domestic energy source for Turkey but new policies have to be developed and adopted immediately, and more realistic targets for the country should be set accordingly. © 2011 Elsevier Ltd Daha fazlası Daha az

Synthesis and characterization of KOH/boron modified activated carbons from coal and their hydrogen sorption characteristics

Kopac T. | Kırca Y. | Toprak A.

Article | 2017 | International Journal of Hydrogen Energy42 ( 37 ) , pp.23606 - 23616

Activated carbons from bituminous coal taken from the area of Zonguldak Kilimli region in Turkey were synthesized by chemical activation using a mixed combination of KOH and as a boron source borax decahydrate. The modification process consists of chemical activation of the demineralized coal with KOH (KOH/coal:4/1) and various concentrations of borax decahydrate solutions (0.025–0.1 M). Textural properties such as surface area and pore structure were studied by volumetric methods using N2 adsorption data at 77.4 K (P/P0 = 0–1). The samples obtained have high microporosity, in the form of irregular structures. The EDAX spectra indic . . .ate that Boron heteroatoms are attached to surface of AC41, and as BDH concentration increases from 0.025 M to 0.1 M, higher atomic percent of boron is accumulated at the surfaces. AC41 exhibits amorphous structures, whereas BDH modified AC41 consists of predominantly amorphous structure and disordered graphitic carbon. Among the synthesized boron modified samples, the highest surface area, total pore volume and average pore diameters were found for the 0.025 M_BDH-AC41 sample. As the BDH concentration increases, the volume of N2 adsorbed decreases. Surface area of CC and AC41 samples were 52.62 and 2228 m2/g, respectively, whereas surface area of the boron modified samples were found in the range of 2190–2704 m2/g. Hydrogen sorption capacities of the KOH/boron modified samples were found in the range between 2.08 and 3.74% wt. Hydrogen sorption capacity of AC41 obtained was 4.11% wt. Increasing boron concentration resulted in the decrease of hydrogen sorption capacities. Boron modified activated carbons were prepared successfully from coal samples by chemical activation using a mixed combination of KOH and BDH. © 2017 Hydrogen Energy Publications LL Daha fazlası Daha az

Effect of Surface Area and Micropore Volume of Activated Carbons from Coal by KOH, NaOH and ZnCl2 Treatments on Methane Adsorption

Toprak A. | Kopac T.

Article | 2019 | International Journal of Chemical Reactor Engineering17 ( 6 ) , pp.23606 - 23616

This paper investigates the methane adsorption characteristics of activated carbons produced from coal by activation with KOH, NaOH and ZnCl2 treatments at different agent to coal ratios (1:1-6:1) and temperatures (600-800°C) under N2 flow. CH4 adsorption capacities and desorption behaviors of the activated carbons were examined at 0°C and 25°C. The relationship between CH4 adsorption characteristics and surface properties of activated carbons, such as BET surface area determined by N2 adsorption at-196°C, and micropore volume determined by CO2 adsorption at 0°C were investigated. Optimal results for CH4 adsorption at 0°C and 25°C w . . .ere obtained for the activated carbon samples obtained with KOH treatment at 800°C at 4:1 ratio, as 2.67 and 1.12 mmol/g, respectively. The results have shown that CH4 adsorption increased proportionally with micropore volume of activated carbons, whereas BET surface area does not exhibit an exact consistency. CH4 adsorption-desorption isotherms at 25°C have shown that an increase in mesopore formation caused a decrease in adsorption; but allowed desorption to be reversible. Higher methane adsorption capacities were obtained from activated carbons produced from coal by various treatments in this study than most of the reported results in literature at the similar conditions, indicating the suitability of the evaluated materials for industrial applications of methane storage. © 2019 Walter de Gruyter GmbH, Berlin/Boston 2019 Daha fazlası Daha az

Emphysema and airflow obstruction in non-smoking coal miners with pneumoconiosis

Altınsoy B. | Öz İ.İ. | Erboy F. | Tor M. | Atalay F.

Article | 2016 | Medical Science Monitor22 , pp.4887 - 4893

Background: Accumulating evidence shows that functional impairment in subjects with coal workers’ pneumoconiosis (CWP) is principally due to emphysema and airflow obstruction, rather than underlying restrictive mechanisms. However, cigarette smoking has remained a major confounder. The aim of this study was to assess whether coal dust exposure was associated with emphysema and/or airflow obstruction in the absence of smoking history. Material/Method: The subjects evaluated for possible pneumoconiosis between 2013 and 2015 were retrospectively enrolled into this study. After excluding those with history of smoking, tuberculosis, or l . . .ung cancer, the study population was a total of 57 subjects. The emphysema severity and airflow obstruction were quantified by computed tomographic densitometry analysis and spirometry, respectively. For comparability regarding emphysema, 9 age- and sex-matched nonsmoker (n=9) control subjects without known lung disease were randomly selected from a radiology database. Results: Emphysema severity was significantly higher in the CWP group compared with the control group (15% vs. 4%, p<0.001). The median percent emphysema and percentage of those with FEV1/FVC <0.7 was 13% and 37% in subjects with simple CWP and 18% and 67% in subjects with complicated CWP, respectively. Percent emphysema and Perc15 (15th percentile of the attenuation curve) was correlated with FEV1/FVC (r=–0.45, r=–0.47) and FEF25–75 (r=–0.36, r=–0.56), respectively, but not with perfusion score. A linear regression analysis showed that factors associated with emphysema were FEV1/FVC (b=–0.24, p=0.009) and large opacity (ß=–3.97, p=0.079), and factors associated with FEV1/FVC were percent emphysema (ß=–0.51, p=0.018) and tenure (ß=–0.63, p=0.044). Conclusions: Our results support the observation that coal dust exposure is associated with emphysema and airflow obstruction, independent of smoking status. © Med Sci Monit, 2016 Daha fazlası Daha az

Optimization of some parameters in column flotation and a comparison of conventional cell and column cell in terms of flotation performance

Hacifazlioglu H. | Sutcu H.

Article | 2007 | Journal of the Chinese Institute of Chemical Engineers38 ( 03.Apr ) , pp.287 - 293

In this study, a comparative evaluation was made between column and mechanical flotation cells for fine coal cleaning. In addition, the optimum values of operating parameters were examined, which are important to achieve a desired separation performance in column flotation, such as the frother concentration, the collector dosage, the froth thickness, the wash water rate, the air rate and the feeding rate. The coal sample was collected from a classifying cyclone overflow stream consisting of nominally - 130 µm material. Ash, volatile mater, fixed carbon and total sulfur contents of the sample were found to be 47.50%, 20.80%, 31.70% a . . .nd 0.75%, respectively. Comparison of the column and mechanical flotation results indicated that column flotation was considerably more efficient than mechanical flotation for fine coal cleaning. High froth thickness and wash water addition during column flotation made it possible to obtain cleaner coals. The column flotation produced a 15.60% product ash with a 50.92% clean coal yield and 81.85% combustible recovery. © 2007 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved Daha fazlası Daha az

Working conditions and pneumoconiosis in Turkish coal miners between 1985 and 2004: A report from Zonguldak coal basin, Turkey

Tor M. | Öztürk M. | Altin R. | Çimrin A.H.

Article | 2010 | Tuberkuloz ve Toraks58 ( 3 ) , pp.252 - 260

In Turkey, bituminous coal mining is performed only in Zonguldak coal basin since 1940. Pneumoconiosis surveillance programs and dust control measures are in effect, but published pneumoconiosis data from this area is lacking. In this study, we aimed to evaluate the change in prevalence and case detection between 1985 and 2004 and assess the correlation between the dust concentration in workplaces and the prevalence of pneumoconiosis. Data on respirable dust concentrations and number of workers diagnosed as pneumoconiosis between 1985 and 2004 were obtained from Turkish Coal Enterprises authorities. Mean respirable dust concentratio . . .ns in workplaces underground and on the ground were 1.66 mg/m3 and 0.73 mg/m3 respectively. Total number of workers decreased from 38.231 in 1985 to 12.261 in 2004 including 8932 underground workers. In this period, pneumoconiosis has not been reported in the ground workers. Incidence of pneumoconiosis ranged between 0.17-2.8 percent and prevalence ranged between 1.23-6.23 percent between 1985 and 2004. Radiologic opacities compatible with pneumoconiosis were predominantly small opacities. This is the first report about the incidence and prevalence rate of coal worker's pneumoconiosis in the main coal mining area of Turkey. Dust measurement and screening standards should be improved and adapted to international standards and we conclude that surveillance data should be closely monitored in this region and further epidemiologic studies in this area are warranted Daha fazlası Daha az

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