Browsing by Author "Cengizler H."
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Item Interactions between components in coking of coal blends; [KömüR Karişimlarinin Koklaştirilmasinda Bi̇leşenler Arasi Eti̇ki̇leşi̇mler](2004) Kemal M.; Arslan V.; Cengizler H.This study has been carried out for the purpose of determination of interactions among the components in coal blends during the coking process. For this purpose, the blends of cokable Zonguldak coal (ZK) with air-dried (TK), semicoked both at 550°C (TK550) and 900°C (TK900) Tunçbilek lignite were prepared. The plasticity, dilatation, contraction of these blends and the strength of the cokes produced from these blends were determined. The experimental data obtained were evaluated and it was determined that the lignite, when carbonised at about 500°C, completes its chemical breakdown, terminates the evolution of its volatile matter and contraction process, improves its surface wetting behavior and thus exhibits the most favorable properties as far as the cokability of coal blend is concerned.Item Formcoke production from char fines of hard brown coals by air curing(2006) Cengizler H.; Kemal M.The purpose of the present study was to explore the technical feasibility of formcoke production from non-coking bright hard brown coals and pitch as a binder by air curing. The briquettes obtained from the chars of Soma coals carbonised at 500, 600, 700, 800 and 900°C with 12% pitch were air cured in a streaming gas containing 16%O2 (air+N2) for 120 min at 270°C and the formcoke strength was found to be 10-40% higher than that of raw briquettes. Under the prevailing conditions, the formcoke strength and the apparent specific gravity of the green and formcoke briquettes increased as the carbonisation temperature increased, reaching a maximum at the optimum carbonisation temperature of 800°C. M40 and M10 values and the compressive strength of SK800 formcokes were determined to be 92·3, 7·7% and 23·5 MPa respectively being similar to those of conventional cokes produced at coke ovens. The optimum curing conditions (pitch content, curing time and temperature) were determined using TK800 char. The optimum curing time for TK800 briquettes at 220°C was determined to be 90 min. The formcoke strength of TK800 briquettes subjected to a thermal treatment at 220°C was lower than that of the briquettes air cured at the same temperature. The optimum curing temperature for TK800 briquettes with 10% pitch and cured in a gas stream containing 16%O2 in terms of formcoke strength was determined to be 285°C. M40 and M10 values and the compressive strength of TK800 formcokes were determined to be 91, 8·1% and 19·6 MPa respectively. The experimental results reveal the advantages of the method because the formcokes produced possess suitable properties for various metallurgical processes and smokeless fuel consumption. The gas and tar obtained during the carbonisation of raw coal are the added benefits. © 2006 Institute of Materials, Minerals and Mining and The AusIMM.Item Activity of MnO in MnO-CaO-MgO-SiO2-Al2O3 slags at 1500°C(Verlag Stahleisen GmbH, 2006) Cengizler H.; Eric R.H.A thermodynamic study was made on the MnO-CaO-MgO-SiO2-Al 2O3 slags that are typical of the production of ferromanganese in submerged arc furnaces. The Al2O3 content of the slags was kept constant at 5 per cent by mass. The activity-composition relationship in Pt-Mn binary alloys were re-determined for calibration purposes at 1300, 1400 and 1500°C and pO2 values between 5.40×10-6 and 4.54×10-13 atm. A linear regression equation was derived to predict the activity coefficients of manganese, in Pt-Mn alloys at 1500°C. The effect of concentration, basicity ratio and CaO-to-MgO ratio on MnO activities in above mentioned complex slags was investigated at 1500°C and at two different pO2 values of 4.76×10-7 and 5.80×10-8 atm. It was found that aMnO values increase with increasing MnO, and tend to increase with an increasing CaO-to-MgO ratio. The aMnO values also increase with increasing basicity ratio. The activity coefficient of MnO increases with an increase in its mole fraction in the slag. Quadratic multivariable regression model equations which represent the activity data successfully and which can be used to predict the MnO activities in the compositional range of this study were developed. The MnO activity data was interpreted in terms of a slag model which describes the thermodynamic properties of the slag successfully.Item Failure of welded radiator nipples caused by nonmetallic inclusions(2007) Elkoca O.; Cengizler H.A splitting phenomenon in the weld zone of the radiator nipples was encountered after a threading operation. During the failure analysis, some oxide traces were macroscopically observed on the surfaces of unthreaded nipples. Subsequent scanning electron microscopy-x-ray spectrometer (SEM-EDS) examination through the surfaces of the unthreaded nipples and as-pickled steel sheet coupons that were used for nipple manufacturing revealed that the oxide traces were hot-rolling scale residuals. However, none of the traces of scale residuals were encountered on the cross sections of weld zone of unthreaded nipple samples. Contrarily, some cracks and inclusion residuals were observed through the interface between the protrusion and weld zone. EDS analysis and optical microscopy affirmed the presence of MnS-type inclusions. The same kind of inclusions was also observed when one of the unthreaded nipples was intentionally separated through the weld zone. In conclusion, the main cause for the failure was determined to be the adverse effect that the MnS inclusions in the steel had on the material ductility. © ASM International 2007.Item An efficient process for recovery of fine coal from tailings of coal washing plants(2008) Çiçek T.; Cöcen I.; Engin V.T.; Cengizler H.Gravity concentration of hard lignites using conventional jigs and heavy media separation equipment is prone to produce coal-rich fine tailings. This study aims to establish a fine coal recovery process of very high efficiency at reasonable capital investment and operational costs. The technical feasibility to upgrade the properties of the predeslimed fine refuse of a lignite washing plant with 35.9% ash content was investigated by employing gravity separation methods. The laboratory tests carried out with the combination of shaking table and Mozley multi-gravity separator (MGS) revealed that the clean coal with 18% ash content on dry basis could be obtained with 58.9% clean coal recovery by the shaking table stage and 4.1% clean coal recovery by MGS stage, totaling to the sum of 63.0% clean coal recovery from a predeslimed feed. The combustible recovery and the organic efficiency of the shaking table + MGS combination were 79.5% and 95.5%, respectively. Based on the results of the study, a flow sheet of a high-efficiency fine coal recovery process was proposed, which is also applicable to the coal refuse pond slurry of a lignite washing plant.Item Technical and economical applicability study of centrifugal force gravity separator (MGS) to Kef chromite concentration plant(2008) Çiçek T.; Cöcen I.; Engin V.T.; Cengizler H.; Şen S.The results of multigravity separator (MGS) upgrading tests on fine chromite gravity tailings using - 100 and -100 + 150 μm fractions of the initial sample (-1 mm) with 24-7%Cr2O3 grade were presented. The metal screen analysis revealed that 20·66% of the total Cr2O3 content was present in the -106 μm size fraction. Under optimal operational conditions, a concentrate with 43·7%Cr 2O3 content and 65·0% chromite yield for the size fraction of -100 μm and a concentrate with 30·5%Cr2O 3 and 83·3% yield for the size fraction of -100 + 150 μm could be produced. Shaking table test results revealed that the coarse fraction of the tailings could not be enriched any further owing to the high concentration of interlocked particles. However, a saleable concentrate could be obtained by MGS when the coarse tailings were ground down to - 100 μm and used as the feed. The results of the study suggested that multigravity separation of the Kef tailings was technically feasible and economically viable. The payback time of two alternatives suggested for the utilisation of MGS in Kef concentrator was calculated to be <7 months. © 2008 Institute of Materials, Minerals and Mining and The AusIMM.Item Cracking during cold forming process of rear brake component(2008) Elkoca O.; Cengizler H.The root cause for cracking of rear brake components occurred during cold forming process was investigated. Optical micrographs showed the abundance of extended inclusions with several rounded ones in the steel. SEM image revealed the fracture surface which contained many extended cavities formed by extended inclusions and dimples all indicating a ductile rupture. EDS analysis confirmed that the extended inclusions were MnS type while the rounded ones were formed as a result of Ca-treatment. The crack propagation along with inclusions was clearly observed on the polished planes and on the fracture surface. It was determined that MnS type inclusions were the root cause for the cracking phenomena. The abundance of extended MnS inclusions indicated insufficient inclusion modification through Ca-treatment and insufficient removal of these inclusions in failed steel. © 2007 Elsevier Ltd. All rights reserved.Item Enrichment of a low grade chromite ore(Grup Matbaacilik, 2009) Çiçek T.; Cöcen I.; Cengizler H.The applicability of Mozley centrifugal force gravity separator (MGS) to fine fractions (-0.1 mm) of a low grade chromite ore (9.3 % Cr2O3) was investigated. The metal-screen analysis revealed that 83.9 % of the material ground under 1 mm for tests was in the +0.106 mm fraction containing 8 % Cr2O3. On the other hand, 16.1 % was in the-0.106 mm size fraction containing 16.12 % Cr2O3. The +0.1 and -0.1 mm fractions were used as feed for shaking table and MGS tests respectively. A saleable shaking table concentrate with low chromite recovery was obtained by shaking table tests. However, after some of the shaking table products were ground under-100 μm and concentrated with MGS, a chromite concentrate with 46.22 % Cr2O3 grade and 66.1 % Cr2O3 wt. recovery was obtained by the combination of shaking table and MGS. It was seen that MGS was an applicable beneficiation method at fine fractions for concentration of a low grade chromite ore. A principal flowsheet for the concentration plant was proposed.Item Evaluation of leachability of potentially toxic elements from fly ash bricks(Grup Matbaacilik, 2009) Cengizler H.Batch leach tests were carried out to investigate the leachability of some toxic elements from fly ash bricks. The tests simulating the acid rain environment and natural rain water were conducted to gain insight regarding the behavior of the elements during weathering and to determine their toxicity characteristics. In the tests using TCLP method, the solubility levels of Fe, Zn and Mn detected in the leachate of the whole brick pieces were in agreement with the drinking water standards. In the tests using ASTM method, no detectable level of any element was found in the leachates of the whole brick pieces and of ground brick. In the tests using TCLP method, the solubility concentrations of the elements such as Fe, Zn, Cu, Cr, Ni, and Mn from the leachate of the ground brick were higher than those of the whole brick pieces. However, only Fe, Ni and Mn concentrations were determined to be higher than those allowed in the drinking water standards.Item Variation in coal surface wettability with carbonization temperature and effect of pitch on coal fluidity(Grup Matbaacilik, 2009) Cengizler H.; Kemal M.The effect of pitch (Z) ratio on the fluidity of coal and of carbonization temperature on the wetting behaviour of coal surface in the binary mixtures have been investigated with the experimental runs performed by the constant-torque Gieseler plastometer. The binary mixtures consisted of Tunçbilek brown coal (TK) or its semicokes and Z in different ratios. TK200, TK400, TK600, TK800 and TK1000 semicokes were obtained at 200°, 400 °, 600 °, 800 ° and 1000 °C carbonization temperatures respectively. It was found that the maximum fluidity values of the binary mixtures increases with increasing Z ratios. The lowest maximum fluidity values were obtained in TK400+Z binary mixture and it was shown that TK400 is the semicoke which has the optimum surface wetting behaviour. It was determined that the maximum fluidity values increase in the order of TK400, TK200, TK, TK600, TK800 and TK1000. The surface wettability also decreases in the same order.Item Toxic elements leachability tests on light weight fly ash bricks(Chemical Publishing Co., 2009) Cengizler H.In present work, a series of batch leach tests were carried out to investigate the leachability of some toxic elements contained in the light weight fly ash bricks. The primary aim of these tests was to find out whether the light weight fly ash bricks were environmentally safe. The tests simulating the acid rain environment and natural rain water were conducted to gain insight regarding the behaviour of the elements during weathering. The light weight fly ash bricks were tested using the TCLP method and ASTM method A extraction to determine their toxicity levels.Item An efficient process for the beneficiation of a low grade chromite ore(2010) Çiçek T.; Cengizler H.; Cöcen I.The applicability of centrifugal force multigravity separator (MGS) to concentrate fine fractions (-0.1 mm) of a low grade chromite ore assaying 9.3%Cr2O3 was investigated. The metal screen analysis revealed that 83.92% of the material prepared for tests was in the +0.106 mm fraction containing 8%Cr2O3 and that 16.08% was in the -0.106 mm size fraction containing 16.12%Cr2O3. The +0.1 and -0.1 mm fractions of the ore was used as feed for shaking table and MGS tests respectively. The results gathered from shaking table test were not satisfactory due to low Cr2O3 recoveries. However, a chromite concentrate with 46.22%Cr2O3 grade and 66.1 wt-%Cr2O3 recovery was obtained by the combination of shaking table and MGS. It was clearly demonstrated that MGS is an ideal beneficiation equipment for fine fractions of a low grade Cr2O 3 ore. Based on the experimental results, a principal flowsheet for the enrichment plant was proposed. © 2010 Maney Publishing.Item Fly ash microspheres; [Uçucu kül mikrosferleri](Chamber of Mining Engineers of Turkey, 2013) Cengizler H.Types of microspheres which are valuable components of fly ashes produced in coal fired power plants, their formation, contents in fly ashes, mineralogical and chemical compositions, particle size distribution and specific gravity, physical structure and other physical properties, beneficiation methods, utilization and potential utilization areas were studied. To develop technologies to increase and optimize the production of microspheres and to carry out research in this direction are of importance. Extensive usage of microspheres which have properties to be utilized effectively in many new technologies will contribute to the efforts to valuate fly ash waste and to eliminate the environmental pollution in global and local basis. Besides, re-introducing this fly ash component having a high added-value to our country's economy as an input will be ensured.Item Effect of Silver Oxide on Colour Variation and Gloss of an Opaque Glaze(I N S I O Scientific Books and Periodicals, 2014) Israil L.I.; Köseoglu K.; Cengizler H.The most important point of whitening frit glazes is the elimination of transperancy. For that purpose, opacifiers are used. In this work, the effect of Ag2O additive on colour variation and gloss of a white opaque glaze, used commonly in ceramic ware production, were investigated at the temperatures of 1040°, 1090° and 1140°C. It was found that colour and gloss of an opaque glaze did not vary significantly with Ag2O addition. Furthermore, Ag2O addition was found to be a viable alternative for reducing the sintering temperature of opaque glaze from 1090° to 1040°C. © 2014 © 2014 The Indian Ceramic Society.Item Silicon and manganese partition between slag and metal phases and their activities pertinent to ferromanganese and silicomanganese production(Springer International Publishing AG, 2016) Cengizler H.; Eric R.H.Equilibrium between MnO-CaO-MgO-SiO2-Al2O3 slags and carbon saturated Mn-Si-Fe-C alloys was investigated under CO at 1500oC. Manganese and silicon activities were obtained by using the present data and the previously determined MnO and SiO2 activities of the slag. Quadratic multi-coefficient regression equations were developed for activity coefficients of manganese and silicon. The conclusions of this work are:(i)increase in the basicity and the CaO/Al2O3 ratios decreases the Mn distribution ratio,(ii)increase in the silica concentration and the MgO/CaO ratio increases the Mn distribution ratio, iii)carbon and manganese as well as carbon and silicon of the metal phase are inversely proportional,(iv)as Mn/Fe and Mn/Si ratio increases in the metal the carbon solubility increases,(v)decrease in the basicity increases the silicon content of the metal and (vi)increase in the silica content of the slag increases the silicon content of the metal and this effect is more pronounced at the higher Mn/Fe and Mn/Si ratios. © 2016 by The Minerals, Metals & Materials Society.Item Tannery wastewater sediments produced by clinoptiolite/polyacrylamide-aided flocculation as a clay additive in brick making(Springer International Publishing, 2017) Köseoglu K.; Cengizler H.; Israil L.I.; Polat H.Toxic tannery wastewater(s) (TWW) pose(s) a great risk to the environment. This study explores the potential of mitigating the harmful effects of TWW through sedimentation using clinoptiolite in the presence of various anionic, cationic and non-ionic flocculants with different molecular weights and charge densities followed by encapsulation in a brick structure for stability. Compressive strength (CS), size reduction after firing (SRAF), water absorption (WA) and colouring parameters of bricks were determined. X-Ray diffraction (XRD) and scanning electron microscopy (SEM)-energy dispersive X-ray (EDX) analyses were conducted on brick bodies. Kinetic leaching experiments were conducted for possible heavy metal release from the bricks. Bricks containing 10 wt% leather waste and 5 wt% clinoptiolite sintered at 800 °C instead of 920 °C possessed similar properties to the standard brick (SB). © 2017 Australian Ceramic Society.Item Production of porous ceramic from clinoptilolite incorporating aluminum powder(Elsevier Ltd, 2019) Şan O.; Koç M.; Cengizler H.In this study, production of porous ceramic from clinoptilolite incorporating aluminum powder at various sintering temperatures was investigated. The mixtures were sintered at 1150, 1200, 1250 and 1300 °C for 1 h in air atmosphere. SEM and XRD analyzes were conducted to observe the microstructural evolution and the phase composition, respectively. The DSC/TG analyzes of the clinoptilolite and aluminum powder mixture indicated that 1150 °C was a significant temperature at which oxidation of molten aluminum enhanced and the softening of the clinoptilolite began. The progress in oxidation of aluminum with increasing temperature led to corundum phase crystallization while the amount of cristobalite decreased. Aluminum distribution in the ceramic matrix began at 1200 °C but pore channels with very smooth surfaces were obtained at 1250 °C. At this temperature, the pores interconnected to each other had narrow pore size distribution (4–180 μm) with low friction coefficient of 0.64 resulting from enhanced corundum phase formation in the structure. Results showed that the porous ceramic sintered at 1250 °C with 32.8% apparent porosity and a pure water permeability of ~2050 L/(m2•hr•bar) promises great potential for use as a filtering media and/or support. © 2019Item Production of ceramic glass foam of low thermal conductivity by a simple method entirely from fly ash(Elsevier Ltd, 2021) Cengizler H.; Koç M.; Şan O.Ceramic glass foam/foams (CGF) from two different F-class fly ashes were produced via a well-known simple conventional sintering method using sodium silicate (Na2SiO3) as a foaming and fluxing agent. The research aimed to understand the effects of each fly ash, Na2SiO3 ratio, and sintering conditions on the properties and microstructure to produce a commercial CGF of low thermal conductivity. The chemical composition of fly ash from the thermal power plants of Tunçbilek and Seyitömer were quite similar but had different melting temperatures and microstructures. While the foam structure was successfully obtained at 1100 °C with 30 wt.% Na2SiO3 from Tunçbilek fly ash, a similar structure was obtained at 1150 °C from the Seyitömer fly ash. The effects of Na2SiO3 content and sintering temperature on the properties and microstructure of the CGF from the Tunçbilek fly ash of a lower melting point, in particular, were investigated systematically. The optimal sintering temperatures were determined to be 1200, 1150, and 1100 °C at the highest fly ash ratios of 90, 80 and 70 wt.%, respectively. The CGF were produced with 69.76–75.43% porosity, 0.55–0.69 gr/cm3 bulk density, 3.2–5.35 MPa compressive strength and 0.10–0.21 W/(m K) of low thermal conductivity. XRD results showed that optimal CGF samples mainly contained spinel, quartz and hematite crystal phases and amorphous phase. In this research, a thermal insulation material was successfully produced using an industrial waste completely with a well-known simple method. It is thought that this will contribute beneficially to the environment and the economy. © 2021 Elsevier Ltd and Techna Group S.r.l.Item Effect of calcination temperature on use of high-boron-content waste for low-temperature wall tile production(Elsevier Ltd, 2022) Cengizler H.The effects of the calcination temperature on raw-colemanite-waste properties and calcined waste content on wall tile production were investigated. Waste containing 11.24% B2O3 calcined between 500 and 800°C was added to wall tile granules in various ratios (0–100 wt.%) to produce a low-temperature-sintered wall tile by adding the maximum content of boron waste, as determined through optimal calcination. The low-temperature (850–1000°C) sinterability of the samples and the effect of the calcined colemanite-waste content on the wall tile properties were investigated. The samples were characterised using X-ray fluorescence, X-ray powder diffraction, differential thermal analysis, thermogravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, and colourimetry. The waste calcined at 800°C exhibited a substantially different phase distribution, bond structure, morphology, and colour. The wall tile produced using 40 wt.% colemanite waste calcined at 800°C and subsequently sintered at 950°C exhibited the optimal properties. The linear firing shrinkage, water absorption, and flexural strength of the optimised wall tile were 0.88%, 16.04%, and 36.07 MPa, respectively. The optimised wall tile exhibited major albite, quartz, and diopside phases and 64% higher strength. The sample calcined at 800°C showed that high colemanite-waste content could be incorporated into ceramic bodies. © 2021 Elsevier Ltd and Techna Group S.r.l.