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Öğe A study on the physicochemical and thermal characterisation of dolomite and limestone samples for use in ironmaking and steelmaking(Taylor & Francis Ltd, 2018) Sivrikaya, OsmanLimestone and dolostone are used in industries depending on their physicochemical characteristics. They can be used in construction, agricultural, environmental industries and especially in ironmaking and steelmaking as flux. Dolomite is also used in the production of refractory materials. As the properties of products are significantly affected by physicochemical specifications of limestone or dolomite, the characterisation of those materials is important. This study was initiated to analyse the chemical, decrepitation, and degradation properties of dolomite and limestone samples to determine their suitability as flux. Since the degradation indices were found different for the chemically similar samples, the study was expanded to determine the reason. Complete physicochemical and thermal characterisation was performed via XRF, XRD, TG, FTIR, and thin section microscopic analyses. Although two dolomite samples were mineralogically similar, thermal behaviours were determined different. Microscopic analyses results showed that the crystal structures/sizes affect the thermal behaviour and degradation index of carbonate samples.Öğe Cleaning study of a low-rank lignite with DMS, Reichert spiral and flotation(Elsevier Sci Ltd, 2014) Sivrikaya, OsmanThe cleaning potential of a low-rank lignite coal has been evaluated via dense medium separation (DMS), Reichert spiral and flotation techniques. The washability characteristic of the lignite was investigated with laboratory sink and float tests. Solutions of zinc chloride (ZnCl2) with specific gravities ranging from 1.3 to 1.9 were used as dense medium liquid. The as-received raw lignite sample was sieved into three size fractions (-100 + 25 mm; -25 + 1.5 mm; -1.5 mm) and washability characteristics of the former two fractions were separately investigated. The latter fine fraction was cleaned using both DMS and Reichert spiral techniques under different operational parameters. Flotation tests were conducted using the -150 mu m fraction. Clean coal characteristics and recoveries were determined after each experiment. Elementary ash and +/- 0.1 relative specific gravity curves showed that this low-rank coal can be classified as difficult to clean'' due to its high content of near-gravity materials at specific gravities lower than 1.7. However, about 50% and 40% of the raw coal (3571 kcal/kg) can be obtained as clean coal with calorific values of 5400 kcal/kg for the coarse fraction and 5600 kcal/kg for the fine fraction, by DMS and Reichert spiral methods, respectively. The ash contents (14-18%) and calorific values (6022-5582 kcal/ kg) of the cleaned coarse and fine fractions are suitable for use in industry. Low calorific value (about 2500 kcal/kg) middling and tailing can be used in properly constructed thermal electric power plants. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Concentration study of a specularite ore via shaking table, reverse flotation, and microwave-assisted magnetic separation(Taylor & Francis Inc, 2023) Al-Dhubaibi, Ammar Mahdi Ahmed; Vapur, Huseyin; Top, Soner; Sivrikaya, OsmanDespite the difficulties in pelletizing specularite-type refractory iron ores, the utilization of these resources is indispensable for the steel industry due to the increasing need for iron. This study investigated Fe recovery from a refractory iron ore using gravity separation, reverse flotation, and two-stage magnetic separation. Tilt angle and particle size had a significant effect on the grade and recovery of concentrates in shaking table tests. Gravity concentration at optimum conditions resulted in an iron concentrate with 64.47% Fe grade and 90.73% Fe recovery. In the reverse flotation tests, the frother and depressant substantially affected the Fe grade of concentrates while the collector influenced the Fe recovery. A 90% Fe recovery with 64.69% Fe grade was obtained within optimum flotation conditions. The Fe grades were raised to >67.5% in products after the first magnetic separation. The tailings of the first magnetic separation were subjected to the second magnetic separation after microwave-assisted roasting to increase the magnetic susceptibility. In the second magnetic separation, a concentrate containing 66.06% Fe was separated from the microwave-roasted non-magnetic material with 82.23% Fe recovery. To the best of our knowledge, the microwave-roasting method has been applied to a specularite-type refractory iron ore for the first time.Öğe Demir Cevheri Peletleri İçin Alternatif Tambur Aşınma Dayanımı Testi Belirlenmesi(2019) Sivrikaya, Osman; Arol, Ali İhsanDemir cevheri peletleri üretim, tasınma ve kullanım süreçlerinde hem basınç hem de asınma etkilerine maruz kalırlar. Bu etkiler neticesinde demir cevheri peletlerinin parçalanmadan saglam kalmaları gerekir. Demir cevheri peletlerinin saglamlıklarının göstergesi olarak pelet basma dayanımı testi yanı sıra pelet tambur asınma dayanımı testi uygulanmaktadır. Pelet tambur asınma dayanımı, ASTM E279-97(2010) standardına göre belirlenmektedir. Bu testte, mamul peletlerin, belirli özelliklere sahip standart bir tambur içinde olusturulan asındırma kosullarında asınmaya karsı dayanımları/dirençleri belirlenir. Bu standarda göre tek bir tambur asınma testi için 22.6 kg mamul pelet kullanmak gerekmektedir. Bu miktarda pelet, endüstriyel ölçekli üretimlerden temin edilebilmektedir. Fakat laboratuvar ölçekli arastırmalarda laboratuvar ekipmanlarının kapasiteleri göz önünde bulunduruldugunda bu miktarda peleti üretmek mümkün olamamaktadır. Bu arastırma projesinde bahsi geçen standarda alternatif, daha az pelet numunesi kullanılarak (500-1000 g) peletlerin tambur asınma dayanımlarını belirlemek için çalısmalar yapılmıstır. Bunun için 4 farklı endüstriyel mamul pelet numuneleri temin edilmistir. Dizayn parametreleri proje dâhilinde belirlenmis küçültülerek (scale down) ölçeklendirilmis ve sanayide imal ettirilmis iki farklı tambur ve iki farklı silindir boru pelet asındırma düzenekleri kullanılarak degisik deney kosullarında pelet asınma testleri gerçeklestirilmistir. Azaltılmıs pelet numunesi ile küçültülmüs pelet tambur veya silindir boru düzeneklerinde pelet tambur asınma testinin gerçeklestirilebilir, sonuçların tutarlı, karsılastırılabilir, tekrar üretilebilir ve güvenilir oldugu belirlenmistir. Böylece laboratuvar ölçekli arastırmalarda üretilen peletlerin pelet tambur asınma dayanımlarının küçültülmüs test düzeneklerinde belirlenmesinin mümkün oldugu ortaya konulmustur. Sonuçta, daha az numune ile pelet tambur testi uygulaması ile pelet konusunda çalısmalarda bulunacak arastırmacılara islemlerinde zaman kazandıracak bu testin laboratuvarda yapılabilirligi gösterilmistir. Ayrıca, test edilen peletlerin basma dayanımları ve tambur indeksleri arasında bir iliski olup olmadıgı da arastırılmıs ve peletlerin basma dayanımları ile tambur indeksleri arasında dogrusal bir iliski olmadıgı tespit edilmistir.Öğe Direct impregnation and characterization of Colemanite/Ulexite-Mg(OH)2 paraffin based form-stable phase change composites(Elsevier, 2019) Horpan, M. Safa; Sahan, Nurten; Paksoy, Halime; Sivrikaya, Osman; Gunes, MustafaParaffin is mainly preferred as an organic phase change material (PCM) in thermal energy storage (TES) systems especially for cooling and heating of buildings implementations. In order to develop form-stable and thermally stable blends natural minerals (Colemanite, Ulexite and Mg(OH)(2)) were used to prepare composites via direct impregnation method. These mineral compounds are abundant locally and known to be thermally stable as they show multi-step thermal decompositions. Thermal, morphological and chemical properties of these composites were characterized by thermogravimetric analysis (TGA), the differential scanning calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM). Results of analyses indicate that the introduction of mineral phase to the paraffin is achieved adequately despite of minor mixing problems that show a form-stable behaviour. Comparing energy storage abilities of these composites, Mg(OH)(2) or Colemanite containing blends are found to be the promising composites.Öğe ENERJİ KAYNAĞI OLARAK ASFALTİT: OLUŞUMU, İÇERİĞİ, TÜRKİYE REZERVLERİ, TEMİZLENMESİ(2019) Demirci, Seda; Sivrikaya, Osman; Vapur, HüseyinPetrolün tektonik hareketler sonucu kendi yatağından ayrılarak çevredeki yarık ve çatlaklara yerleşereksıcaklık ve basıncın etkisi ile metamorfizmaya uğramış maddelere asfaltit denir. Petrol kökenli olması,kalorisinin yüksek olması ve içerisinde nikel, molibden, vanadyum gibi elementleri bulundurması nedeniyleönemli bir kaynak olarak görülmektedir. Türkiye’de Şırnak ve Hakkari illerinde 13 filon halinde bulunan asfaltityatakları tespit edilmiştir. Kalori değerinin yüksek olması Şırnak-Silopi’de bulunan asfaltit kaynağının, 405 MWgücünde akışkan yataklı kazan teknolojili termik santral kurulmasına olanak sağlamıştır. Mineral madde vekükürt asfaltitin yakıt olarak kullanılmasında büyük bir sorundur. Bu yüzden yerleşim merkezlerinde evselısıtmalarda kullanılması sakıncalıdır. Asfaltitleri çevreye uyumlu bir enerji kaynağı haline getirmek için çeşitlitemizleme çalışmaları yapılmıştır. Yapılan çalışmalar sonucunda kül oranında düşüş saptanmasına rağmenkükürt değerlerinde istenilen oranda düşüş gözlemlenememiştir. Bu çalışmada asfaltit hakkında bilgilerTürkiye’nin asfaltit kaynakları ile birlikte verilirken asfaltitin enerji kaynağı olarak kullanımından kaynaklanançevresel zararlarını azaltmak için yapılan çalışmalar hakkında kapsamlı bilgiler sunulmuştur.Öğe Evaluation of a Turkish Lignite Coal Cleaning by Conventional and Enhanced Gravity Separation Techniques(Taylor & Francis Inc, 2018) Tozsin, Gulsen; Acar, Cemil; Sivrikaya, OsmanThe use of low-rank coals as an energy source may cause environmental problems. Washability of a Turkish lignite sample was evaluated by conventional methods with sink-and-float tests and a Reichert spiral. Also, the fine size fractions were cleaned with enhanced gravity separation techniques, a multigravity separator (MGS), and a Falcon concentrator. The as-received lignite sample was sieved into five size fractions (-100 +25.4 mm; -25.4 +12.7 mm; -12.7 +1.2 mm; -1.2 +0.15 mm; -0.15 mm) and the washability characteristics of the first three fractions were separately investigated with sink-float tests. The -1.2 +0.15 mm size fraction was cleaned using a Reichert spiral. Tests with the MGS and the Falcon concentrator were conducted with a -0.15 mm fine size fraction. Sink-float tests results showed that the tested coal can be classified as difficult-to-clean coal due to the presence of high near-gravity material at lower separation densities than 1.7 g/cm(3). However, the production of cleaner coal was easier at finer size fractions due to further liberation. Enhanced gravity separation techniques presented better results in terms of combustible recoveries.Öğe Investigation of spontaneous combustion of coal in a longwall panel(International Pittsburgh Coal Conference, 2014) Ozdeniz, Hadi; Sivrikaya, Osman; Berberoglu, SezginSpontaneous combustion of coal is pretty important especially for underground collieries for safety of workers and equipment. The temperature of colliery air increases due to some reasons during coal production and the main reason is oxidation of coal. Coal reacts with oxygen during production and is subject to spontaneous combustion. Coal oxidation is an exothermic reaction and coal generates heat in colliery atmosphere. If the heat is not removed from the colliery air, spontaneous combustion may start and then turn into combustion. In addition, explosive, flammable and toxic gases are other potential risks for safety in underground collieries. Those are not desired and cause problems. In order to avoid those problems, a proper mining method should be applied with a good ventilation system. If the problem cannot be solved, the longwall panel must be packed to prevent oxidation of coal. In this study, the temperatures changes of a longwall panel were monitored by a temperature sensor to predict spontaneous combustion. In addition, the temperature of the fresh air entering the longwall panel, exhaust air leaving the longwall panel and concentration of colliery gases (CO, CH4, O2 and CO2) were monitored. Graham's ratios were then calculated and used to predict of spontaneous combustion. When the temperature of the longwall panel and CO concentration were greater than the average values, the longwall panel was packed. In time, temperature of longwall panel started to decrease continuously after packing.Öğe Okyanus ve Deniz Altı Madenciliğinin Kısa Tarihçesi(2018) Ehsani, Arman; Sivrikaya, OsmanBu çalışmada okyanus ve deniz altı madenciliğinin tarihsel gelişimine kısa ve özet bir şekilde değinilmiştir. Okyanuslar ve denizlerdünyamızın yaklaşık % 71’ini kapsamaktadır. Deniz altı ve okyanus maddeciliğinin gelişimi deniz-okyanus bilimi (oşinografi)çalışmaları kapsamında hayata geçmiştir. Deniz ve deniz altı ile ilgili ilk araştırmalar M.Ö. 2000 yıllarında Giritliler ve Fenikelilertarafından gerçekleştirilmiştir. Oşinografi dalında modern teknikler ile yapılan ilk araştırma, 1855 yılında okyanusların derinliğininölçülmesi (bathymetric) çalışmaları olarak göze çarpmaktadır. British Challenger gemisi ile 1872 yılında 4 yıl süren bir araştırmaseyahatinde Kuzey Kutbu Denizi hariç bütün okyanus ve denizler gezilerek mangan içeren yumrulu yataklar saptanmıştır. 1968 yılındaGolmar Challenger denizaltı aracı, deniz altı ve okyanus tabanı hakkında inceleme çalışmalarına başlamıştır. 2005 yılında ise ilkokyanus-deniz altı madenciliği uygulaması olan Solwara projesinin ilk sondaj çalışmaları Papua Yeni Gine açıklarında başlamıştır.Öğe Prediction of gross calorific value of coal based on proximate analysis using multiple linear regression and artificial neural networks(Tubitak Scientific & Technological Research Council Turkey, 2018) Acikkar, Mustafa; Sivrikaya, OsmanGross calorific value (GCV) of coal was predicted by using as-received basis proximate analysis data. Two main objectives of the study were to develop prediction models for GCV using proximate analysis variables and to reveal the distinct predictors of GCV. Multiple linear regression (MLR) and artifcial neural network (ANN) (multilayer perceptron MLP, general regression neural network GRNN, and radial basis function neural network RBFNN) methods were applied to the developed 11 models created by different combinations of the predictor variables. By conducting 10fold cross-validation, the prediction accuracy of the models has been tested by using R-2, RMSE, MAE, and MAPE. In this study, for the first time in the literature, for a single dataset, maximum number of coal samples were utilized and GRNN and RBFNN methods were used in GCV prediction based on proximate analysis. The results showed that moisture and ash are the most discriminative predictors of GCV and the developed RBFNN-based models produce high performance for GCV prediction. Additionally, performances of the regression methods, from the best to the worst, were RBFNN, GRNN, MLP, and MLR.Öğe Prediction of gross calorific value of coal based on proximate analysis using multiple linear regression and artificial neural networks(2018) Açıkkar, Mustafa; Sivrikaya, OsmanGross calorific value (GCV) of coal was predicted by using as-received basis proximate analysis data. Twomain objectives of the study were to develop prediction models for GCV using proximate analysis variables and toreveal the distinct predictors of GCV. Multiple linear regression (MLR) and artifcial neural network (ANN) (multilayerperceptron MLP, general regression neural network GRNN, and radial basis function neural network RBFNN) methodswere applied to the developed 11 models created by different combinations of the predictor variables. By conducting 10-fold cross-validation, the prediction accuracy of the models has been tested by using R2, RMSE , MAE , and MAP E .In this study, for the first time in the literature, for a single dataset, maximum number of coal samples were utilizedand GRNN and RBFNN methods were used in GCV prediction based on proximate analysis. The results showed thatmoisture and ash are the most discriminative predictors of GCV and the developed RBFNN-based models produce highperformance for GCV prediction. Additionally, performances of the regression methods, from the best to the worst, wereRBFNN, GRNN, MLP, and MLRÖğe The use of colemanite and ulexite as novel fillers in epoxy composites: Influences on thermal and physico-mechanical properties(Elsevier Sci Ltd, 2016) Guzel, Gulcihan; Sivrikaya, Osman; Deveci, HuseyinBoron compounds such as colemanite, tincal and ulexite are of interest in many application areas due to their great properties. Colemanite and ulexite was used individually as fillers to prepare epoxy composites in this study. The influences of amount of filler, type of hardener and plasticizer addition on the properties of the novel composites were investigated with instrumental analyses and tests. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses showed good dispersion of filler in the epoxy matrix. Improvement in tensile properties was obtained up to 5 wt% filler content in the composites. Water sorption reduced dramatically with increasing amount of filler compared to neat epoxy. Excellent corrosion resistance and strong adhesion properties were observed in all composites. Thermogravimetric analyses (TGA) and vicat softening temperature (VST) tests indicated that colemanite had better synergistic effect on the thermal properties of the neat epoxy than ulexite. Resistance to cold environment of the composites was quite high. It was thought that the composites can be evaluated successfully with the mentioned advantages in many industrial fields such as construction, coating, flooring, and so on. (C) 2016 Elsevier Ltd. All rights reserved.Öğe Yıkanmış Türk Linyit Kömürlerinin Üst Isıl Değerinin Destek Vektör Regresyonu ile Tahmini(2020) Açıkkar, Mustafa; Sivrikaya, OsmanBu çalışmada yıkanmış Türk linyit kömürlerinin üst ısıl değeri (GCV), makine öğrenmesi yöntemleri ile kömür numunelerinin kuru bazkısa analiz sonuçları kullanılarak tahmin edilmiştir. Laboratuvar kömür analiz sonuçlarından elde edilen kül (A), uçucu madde (VM),kükürt (S) ve GCV değişkenleri kullanılarak veri kümesi oluşturulmuştur. Veri kümesine, Destek Vektör Regresyonu (SVR) ile ÇokKatmanlı Algılayıcı (MLP), Genel Regresyon Sinir Ağı (GRNN) ve Radyal Temelli Fonksiyon Sinir Ağı (RBFN) olmak üzere üç farklıYapay Sinir Ağı (ANN) uygulanarak GCV tahmin modelleri geliştirilmiştir. Geliştirilen modellerin performans genelleştirme kabiliyeti10-katlı çapraz-doğrulama kullanılarak sağlanmış ve modellerin tahmin doğruluğu, performans ölçütleri Çoklu Korelasyon Katsayısı(R), Kök Ortalama Kare Hatası (RMSE), Ortalama Mutlak Hata (MAE) ve Ortalama Mutlak Yüzde Hata (MAPE) kullanılarakhesaplanmıştır. Sonuçlar, GCV tahmini için, tüm modeller arasında SVR tabanlı modelin ANN tabanlı modellere göre biraz daha iyi,ANN tabanlı modeller arasında ise RBFN tabanlı modelin MLP ve GRNN tabanlı modellere göre daha iyi performans gösterdiğiniortaya koymuştur.
