Morphological Character of Blasted Talc Particles on Talc Flotation

Abstract -In this study, blasting method was applied to modify the morphology of particles. The extent of blasting was changed at different nozzle pressures through which shape factor and roughness of particles and their corresponding flotation recoveries were investigated. Performance of un-blasted and blasted particles in the system was measured by floating the particles of different characters in a micro-flotation cell. The results of these tests were correlated with shape factors and roughness values of particles that were analysed with Image Analysis, SEM and Optical Profilometer methods. It is shown that particles of higher angularity and roughness exhibited better floatability

Energy Optimization For Grinding Of Cement Raw Materials

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2006Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2006Bu tez kasamında, çimento üretim süreci ve özellikle öğütme kademesi incelenmiş, yapılan literatür çalışmalarından sonra, öğütme kademesinde gerçekleştirilebilecek bazı değişimlerin, sarf edilen enerji üzerindeki etkileri araştırılmış ve söz konusu öğütme işlemleri için optimum koşullara ulaşılmaya çalışılmıştır. Deneysel çalışmalar 2 farklı öğütme kademesi göz önüne alınarak 3 farklı aşamada yapılmıştır. 1.kademe öğütme, çimentonun ana hammeddesini oluşturan kireçtaşı, kil ve marn’ın yaklaşık -90 mikron boyutuna öğütülmesi (farin) kademesidir. Çalışmada iki tip “Marn” kullanılmıştır. Bu kademede besleme boyutunun, bilya yüklemesinin ve kompozisyonunun enerji sarfiyatı üzerindeki etkileri araştırılmıştır. 2. kademe öğütmede ise (çimento öğütme) “kompoze çimento” karışımı esas alınarak öncelikle klinkerin ve katkı maddelerinin (Curuf+Tras+Kireçtaşı+Alçıtaşı) ayrı ayrı Bond iş indeksleri bulunmuş daha sonra karışım çimentonun Bond iş indeksi bulunarak klinker ve katkı maddelerinin ayrı ayrı ve beraber öğütülmeleri durumunda sarf edilecek enerjiler karşılaştırılmıştır. Son aşamada karışım çimento, klinker ve katkı maddeleri, laboratuvar tipi bilyalı aktarmalı değirmende aynı koşullar altında öğütülmüş ve boyut analizleri yapılmıştır. Bu sayede malzemelerin ayrı ayrı ve birlikte bulunmaları halinde öğünme karakteristikleri anlaşılmaya çalışılmıştır. Yapılan deneyler sonucunda, bilya yükü %38-40 arasında olan değirmenlerin kullanılması durumunda, öğütmede kullanılan enerjide önemli bir tasarrufun sağlanacağı ve çimento öğütme kademesinde, klinker ve katkı maddelerinin ayrı ayrı öğütülmeleri yerine beraber öğütülmelerinin, daha az enerji sarfına neden olduğu saptanmıştır.In this thesis, cement production process, especially grinding stage of the process was investigated. Firstly, the literature surveys were completed and then some improvements made for grinding stage and their effects at the stages were investigated. At this point, optimum operating parameters were found. Considering two different stages of cement grinding, experimental studies were done at three different steps. Grinding of limestone, clay and marl which are the main components of the cement to approximately -90 micron is the first stage of the cement grinding. In this step, two types of marl were used. At this stage, effects of feed size, ball charge and ball composition were searched. At the second stage of this work, clinker’s and additives’ (slag, trass, limestone and gypsum) bond work index were found separately. After that, composite cement was formed with clinker and additives and this mixture’s bond work index was also determined, so that separate grinding and grinding of mixture were compared. Mixture’s bond work index was found as 13,59 kWh/t. The arithmetic mean of components’ bond work index values is 14,90 kWh/t. As a result of this investigation, it is stated that grinding as mixture of cement give better results than separate grinding. Finally, clinker and additives (slag, trass, limestone and gypsum) were ground under the same conditions. At this stage, laboratory type of ball mill was used. The aim of this study is to understand grinding characteristics of the cement components. As a result of the experiments, consumed energy at the grinding will be saved if mills with %38-40 ball charge are used in the grinding of cement. Moreover, grinding with mix form of clinker and additives has better results than separate grinding of these components considering consumed energy.Yüksek LisansM.Sc

EFFECT OF CALCINATED MAGNESITE ON RHEOLOGY OF BENTONITE SUSPENSIONS. MAGNESIA-BENTONITE INTERACTION

In this study, the effect of calcination temperature and time on the structure of calcinated magnesite was investigated. In addition, the effect of calcinated magnesite on rheology when added into bentonite suspension was also examined. Electrokinetic, rheological and stabilization studies including coagulation and gelation tests were performed to explain the mechanism of viscosity increase in bentonite suspension upon addition of the calcinated products. FTIR, SEM, BET analyses and rheological data were used to determine the transition degree of MgCO3 to MgO, and evaluate the structure of MgO and bentonite suspensions. The results from this study showed that specific surface area (SSA) and mean pore radius (MPR) values for the calcinated products were directly affected by the calcination temperature and time. According to the ignition loss and transition ratio from MgCO3 to MgO of the calcinated samples, it was found that the calcination was completed above 800 degrees C. In order to obtain a bentonite suspension with higher viscosity, interaction of the sufficient amount of MgO particles with bentonite particles were necessary. Based on these results, the formation of gelation and heterocoagulation between MgO and bentonite particles were found to be responsible for these effects

Three dimensional frame element formulation for nonlinear analysis of semi rigid steel structures

In this paper, a force-based three-dimensional frame finite element formulation with spread of inelasticity through the element and localized nonlinear semi-rigid connections is developed. The proposed model utilizes Euler-Bernoulli beam theory assumptions, and adopts fiber discretization of monitored sections along element length and section depth for the spread of inelasticity in order to capture axial force and biaxial bending moment interaction. Defining any type of semi-rigid either linear or nonlinear connection behavior along element length does not necessitate any increase in number of degrees of freedom. The element is modelled with option of capturing nonlinear geometric effects. The proposed element is designated for the biased analysis of steel structures, since considering the presence of beam to column semi-rigid connections through analyses provides true behavior. The formulated element can also consider the presence of any type of connection that may be present in a steel structure; such as beam to column, column base, brace end connections. Specific to this study, moment-rotation response of beam to column connections is implemented for both the strong axis and weak axis bending directions. Numerical examples are considered to verify the results obtained from the developed finite element models with regards to other available structural analysis programs

Changes on montmorillonite characteristics through modification

Since montmorillonite (Mt) and organomontmorillonite (O-Mt) are widely used in many different areas from ordinary to high technological applications, there are lots of studies about them in the literature. However, its unique characteristic and different interaction mechanism with additives make those studies continue in order to explain much more detail on it In this study effect of hexadecyltrimethylammonium bromide (HDTMA) on Mt through modification process has revealed in detail. Adsorption, electrokinetic, rheology and structural aspects of the system were considered in together to explain the interaction mechanism between Na-Mt and HDTMA. Mt suspensions show four different characteristics that are dependent on the HDTMA concentration as dispersion, coagulation-precipitation, coagulation-flotation and re-dispersion. It is found that sedimentation behavior at this regions are in a good agreement with adsorption isotherm, zeta potential, apparent viscosity, X-ray diffraction patterns, swelling index and filtration losses

Çelik Yapılarda Yarı-Rijit Bağlantıların Doğrusal Olmayan Davranışının Modellenmesi ve Üç Boyutlu Yapısal Çözümlemelere Olan Etkisinin Araştırılması

TÜBİTAK MAG Proje15.09.2016Bu proje kapsamında, yarı-rijit bağlantılı çelik çerçeve yapı sistemlerinde, doğrusal ve doğrusal olmayan analizler yürütülebilmesi için bir çerçeve elemanı geliştirilmiştir. Geliştirilen eleman Timoshenko kiriş teorisine dayanmakta, kolon ve kiriş elemanları boyunca I-kesitlerde oluşan kesme deformasyonlarını yakalanabilmektedir. Elemanın formülasyonu kuvvet-bazlı fonksiyonlar kullanmasıyla doğrusal olmayan davranışlar altında da gerçekçi sonuçlar sunabilmektedir. Geliştirilen elemanla kolon ve kirişler boyunca ve derinliğinde oluşan yayılı plastisite yakalanabilmekte ve böylece örneğin eksenel kuvvet ve moment arasındaki etkileşim elde edilebilmekte, ayrıca düğüm noktalarında (yani serbestlik derecesinde) herhangi bir artış yapmadan kolon-kiriş, kolon taban ve ayrıca çaprazların uçlarındaki bağlantılar eleman formülasyonuna katılabilmektedir. Bu sayede sistem seviyesinde çözülecek olan denklemlerin boyutu ciddi anlamda azaltılabilmekte ve ayrıca modelleme açısından da daha stabil çözüm yöntemi sunulabilmektedir. Geliştirilen elemanda ayrıca tutarlı kütle matrisi kuvvet-bazlı formülasyona dayanarak türetilmiştir. Bağlantı davranışı açısından hem doğrusal elastik, hem de pek çok farklı doğrusal olmayan bağlantı davranışı modellerinin uygulaması başarıyla gerçekleştirilmiştir ve ayrıca çevrimsel hareket sırasında oluşabilecek bağlantı dayanımında azalmalar ve bağlantının enerji harcama kapasitesinde düşüşe sebep olan daralma (pinching) etkisi de dikkate alınmıştır. Geliştirilen çerçeve elemanı ve ayrıca bağlantı modeli davranışları, literatürde mevcut olan deneysel ve analitik sonuçlar ve ayrıca farklı çözüm platformlarından elde edilen sonuçlarla karşılaştırılmış ve geliştirilen modellerin yüksek doğrulukta tepkileri farklı yüklemeler ve sınır şartları altında sunduğu görülmüştür. Ayrıca parametrik analizler yürütülerek yarı-rijit bağlantıların modellenmesinin önemi vurgulanmıştı

Comparative Analysis of Residents' Attitudes Toward Sustainable Tourism Development Using a Multi-Criteria Decision-Making Technique

The main purpose of this study was to comparatively examine the factors that affect the attitudes of different resident groups (local and foreign) toward sustainable tourism development. In the study, the cause and effect relationship between contextual factors that affect residents' attitudes toward sustainable tourism development have been analyzed using a multi-criteria decision-making technique for the first time. Moreover, the sub-criteria specifying the environmental, social, economic, and cultural impacts of sustainable tourism were analyzed with the DEMATEL technique. According to the study results, while seasonality was the most affecting factor for the locals, the environmental benefit was the most affecting factor for foreign residents. The factors most affected for the locals were environmental, cultural, and social benefits, and the most affected factors for foreign residents were cultural and social benefits. The results of the study provide important insights for destination planners.WOS:00065990450000

Rheological, Electrokinetic, and Morphological Characterization of Alginate-Bentonite Biocomposites

We prepared biocomposite gel dispersions involving sodium alginate (Na-Alg) and calcium bentonite (Ca-B) with various solid concentrations and characterized their rheological, electrokinetic, and morphological properties. The flow properties, such as the apparent and plastic viscosities, shear stress, and yield value point, changed with increasing clay dosage. The viscosities of the homogeneous dispersions were represented by the Herschel-Bulkley model. The zeta-potential results were examined in the light of different characterization methods (X-ray diffraction, Fourier transform infrared spectroscopy, and atomic force microscopy) to understand the interactions between the Na and Ca ions of the alginate biopolymer and bentonite clay. A plausible structural model for the alginate-bentonite composite gel, known as the egg-box model, is proposed. The presence of Ca ions in the Ca-B partially crosslinked Na-Alg may be regarded as an excellent example of a self-assembling process. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 19-28, 201

Effect of Coal Moisture on the Treatment of a Lignitic Coal through a Semi-Pilot-Scale Pneumatic Stratification Jig

Dry processing methods are well known to be sensitive to the moisture content of the processed material. It is well known that cohesive forces among the particles originating from the surface moisture hinder the individual movement or appropriate stratification of particles during separation. Furthermore, high surface moisture also hampers the flow of feed material. In this study, the effect of total/surface moisture on separation of lignitic coals was investigated by using Allair stratification jig with the aim of finding possible critical surface moisture content for optimum separation. Coal samples in the size of -13 +4 and -4 mm were processed at different particle total/surface moisture levels to recover as clean coal concentrate as possible along with obtaining tailings with minimum levels of combustibles. It is envisaged that a critical surface moisture on both classification (effective screening) and separation is available around 5.5% surface moisture (corresponding to 15% total moisture) for -13 +4 mm whereas effective separation is not possible for the -4 mm size range even at minor changes in surface moisture of particles