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Öğe ALTERNATIVE BINDERS TO BENTONITE FOR IRON ORE PELLETIZING - PART I: EFFECTS ON PHYSICAL AND MECHANICAL PROPERTIES(Centro Federal Educacao Tecnologica Rio Grande Norte, 2014) Sivrikaya, O.; Arol, A. I.The use of conventional bentonite binder is favorable in terms of mechanical and metallurgical pellet properties, however, because of its acid constituents bentonite is considered as impurity especially for iron ores with high acidic content. Therefore, alternative binders to bentonite have been tested. Organic binders are the most studied binders and they yield pellets with good wet strength; they fail in terms of preheated and fired pellet strengths. This study was conducted to investigate how insufficient pellet strengths can be improved when organic binders are used as binder. The addition of a low-melting temperature and slag bonding/strength increasing constituent (free in acidic contents) into pellet feed was proposed. Addition of boron compounds such as colemanite, tincal, borax pentahydrate, boric acid together with organic binders such as CMC, starch, dextrin and some organic based binders, into iron oxide pellet was tested. Wet and thermally treated pellet physical-mechanical qualities (balling - moisture content - size - shape - drop number - compressive strengths porosity - dustiness) were determined. The results showed that good quality wet, dry, preheated and fired pellets can be produced with combined binders (an organic binder plus a boron compound) when compared with bentonite-bonded pellets. While organic binders provided sufficient wet and dry pellet strengths, the boron compounds provided the required preheated and fired pellet strengths at even lower firing temperature. Especially, the contribution of boron compound addition is most pronounced for hematite pellets which do not have strengthening mechanism through oxidation like magnetite pellets during firing. Therefore, addition of boron compound is beneficial to recover the low physical-mechanical qualities of pellets produced with organic binders through slag bonding mechanism. Furthermore, lowering the firing temperature thanks to low-melting boron compounds will be cost-effective for firing part of the pelletizing plants.Öğe ALTERNATIVE BINDERS TO BENTONITE FOR IRON ORE PELLETIZING - PART II: EFFECTS ON METALLURGICAL AND CHEMICAL PROPERTIES(Centro Federal Educacao Tecnologica Rio Grande Norte, 2014) Sivrikaya, O.; Arol, A. I.This study was started to find alternative binders to bentonite and to recover the low preheated and fired pellet mechanical strengths of organic binders-bonded pellets. Bentonite is considered as a chemical impurity for pellet chemistry due to acid constituents (SiO2 and Al2O3). Especially addition of silica-alumina bearing binders is detrimental for iron ore concentrate with high acidic content. Organic binders are the most studied binders since they are free in silica. Although they yield pellets with good wet strength; they have found limited application in industry since they fail to give sufficient physical and mechanical strength to preheated and fired pellets. It is investigated that how insufficient preheated and fired pellet strengths can be improved when organic binders are used as binder. The addition of a slag bonding/strength increasing constituent (free in acidic contents) into pellet feed to provide pellet strength with the use of organic binders was proposed. Addition of boron compounds such as colemanite, tincal, borax pentahydrate, boric acid together with organic binders such as CMC, starch, dextrin and some organic based binders, into magnetite and hematite pellet mixture was tested. After determining the addition of boron compounds is beneficial to recover the low pellet physical and mechanical qualities in the first part of this study, in this second part, metallurgical and chemical properties (reducibility - swelling index - microstructure mineralogy - chemical content) of pellets produced with combined binders (an organic binder plus a boron compound) were presented. The metallurgical and chemical tests results showed that good quality product pellets can be produced with combined binders when compared with the bentonite-bonded pellets. Hence, the suggested combined binders can be used as binder in place of bentonite in iron ore pelletizing without compromising the pellet chemistry.Öğe Determination of abrasion resistance of iron ore pellets by the scale-down tumbler test(Baski, 2019) Sivrikaya, O.; Arol, A.I.The tumbling-abrasion indices of iron ore pellets are measured according to instructions in ASTM E279- 97 (2010). This test measures the resistance of the product pellets under certain abrasive condition in a standard test drum. However, this test requires 11.3 kg pellet to carry out a single tumbling-abrasion test. This amount of pellet can be obtained from industrial-scale pellet production. However, it is impossible to produce this amount of pellet in laboratory-scale investigation since the capacities of laboratory equipment are low. Therefore, this test can not be applied in laboratory-scale pellet investigations. In this study, laboratory studies were carried out to determine the tumbling-abrasion indices of pellets in small quantities (500-1000 gram) via an alternative test method. Industrial-scaleproduced 4 different pellet samples were obtained from a company. Tumbling-abrasion tests were carried out with a scale-down test drum under different test conditions. It has been investigated whether the results of pellet abrasion in different test conditions are consistent and reproducible. According to the results, it was determined that the pellet abrasion values can be obtained consistently and reproducible by using the small quantities of pellet sample in a scale-down abrasion test drum. Copyright © IMCET 2019 International Mining Congress and Exhibition of Turkey. All rights reserved.Öğe Effects of grinding time on morphology and collectorless flotation of coal particles(Elsevier, 2022) Guven, O.; Kaymakoglu, B.; Ehsani, A.; Hassanzadeh, A.; Sivrikaya, O.The impact of particle shape and surface properties has been mainly overlooked in the literature for different mineral systems. In this study, to investigate the effects of morphological variations, samples of clean coal parti-cles (-0.212 + 0.075 mm) were used and the flotation experimental in a batch condition (2 L Denver cell) were conducted in the absence of collectors by keeping the particle size constant. Binocular microscopic images were used to determine the shape factors of coal particles. A dry ball milling process was carried out as a function of grinding time (60-960 s) and representative samples were taken for determining both shape and floatability of particles. Further, particle-bubble attachment, zeta potential, roundness, surface roughness values and flotation kinetics were measured. It was indicated that by increasing milling duration from 60 s to 960 s, the round-ness and roughness increased from 0.792 to 0.809 and 23 nm to 57 nm, respectively. This led to increasing flotation rate constant from 0.4482 +/- 0.02 to 0.4856 +/-& nbsp;& nbsp;0.03 1/min. In addition, the theoretical calculations for energy barrier showed that upon increasing the roughness degree from 0 to 57 nm, the energy barrier signifi-cantly decreased from 2.79E-16 to 6.51E-17 J/m(2), which also proved our findings from a theoretical point of view. Thus, it was finally concluded that the more the roughness, the higher the flotation kinetics and the lower the energy barrier.(c) 2021 Elsevier B.V. All rights reserved.Öğe Flotation performance analysis on coal washery rejects(Keai Publishing Ltd, 2021) Kumar, P. S.; Sivrikaya, O.; Pradhan, S.; Nagannor, P. C.The coal washery rejects cause major environmental problems in various parts of the globe. Nearly 1 Mt of coal rejects discarded as waste, is accumulated per annum in India, during washing or cleaning of raw coal. Cleaning coal, especially washery rejects, has posed a major challenge to the recovery of fine coal. Froth flotation is a better choice for processing coal washery rejects. In this study, flotation studies are attempted on the coal slurry received from Sudamdih coal washery, Jharkhand, India. A statistical design package (Minitab V17) was used to study the effect of process variables like collector and frother dosages on the responses. Regression equations for froth height, froth density, recovery and ash content of clean coal were developed. The coefficient of correlation (R2) values between the experimental and the predicted values of the flotation responses was found to be greater than 0.98 for all the models. Clean coal product was analyzed for recovery, froth height, and ash content by varying pulp densities. Results show that the coal slurry sample could be evaluated with acceptable recovery via flotation. Clean coal with an ash content of 17.2% is obtained with a 70% recovery from 35.5% ash. The cleaned coal can be used in powder coal-consuming industries. (c) 2021 Sinopec Petroleum Exploration and Production Research Institute. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Öğe Image processing for characterization of iron ore pellets using geostatistical instruments(TMMOB Maden Muhendisleri Odasi, 2017) Yunsel, T.Y.; Sivrikaya, O.Approximately in the last 20 years, the computational methods have advanced very fast and affected a vast range of discipline. Also, new dimensions in the applications have appeared as parallel to development of computing technology. One of the study methods requiring exhaustive data processing in the earth related science is geostatistics. Iron ore pellets are produced by using magnetite or hematite concentrate together with a binder and water addition. The raw pellets are sintered to produce the sufficiently strong pellets. Some parameters such as type of the binder, addition amount of the binder and sintering conditions affect the quality of the product pellets. The physical quality of the product pellets can be determined by physical pellet testing methods. Physical quality of pellets can be considered as function of sintering conditions. In this study, sintering properties of magnetite pellets produced with bentonite binder are examined by geostatistical image processing method. Polished samples of the pellets were prepared and micro images were taken by a stereomicroscope. The micro images are processed by ISATIS software and converted to digitised images. Models are analysed using geostatistical instruments like kriging and image filtering. The obtained data are used to examine the sintering properties of the pellet matrix. The differences in the pellet matrix (core, inner shell and outer shell) may be used to understand the sintering properties of the pellets. The results may be correlated with the physical quality parameter of the pellets.Öğe Statistical Modeling of Spontaneous Coal Combustion Due to the Effect of the Sun's Rays(Taylor & Francis Inc, 2015) Ozdeniz, A. H.; Sivrikaya, O.; Kelebek, S.Spontaneous combustion occurs in stockpiles in coal managements and causes interruptions in production and economical and environmental problems. This work was performed on an industrial-scale stockpile formed with +18-mm clean coal. The temperature changes of the stockpile exposed to sun's rays were measured. Concurrently, the values of solar intensity, air temperature, air pressure, air humidity, wind speed, and wind direction affecting the stockpile were measured continuously. A statistical model to predict spontaneous combustion was developed by multi-nonlinear-regression analyses. The correlation coefficients were calculated around 0.95 levels. With this model, the effects of atmospheric conditions on spontaneous combustion of coal stockpiles can be predicted.Öğe The Study of Pelletizing of Mixed Hematite and Magnetite Ores(Int Inst Science Sintering (I I S S), 2019) Kumar, P. S.; Ravi, B. P.; Sivrikaya, O.; Nanda, R. K.The present study aims to investigate the use of mixed hematite and magnetite ores in iron ore pellet production. Pelletizing tests were carried out on the hematite and magnetite premixed pellet feed. Drop number and compressive strength tests for green and dry pellets; porosity, compressive strength and reducibility tests for fired pellets were carried out to determine the influence of mixing ratios of both iron oxides on those pellet properties. Experimental results showed that as the hematite content in the mix pellets is increased, the green drop number decreased from 6.5 to 5.2, the green compressive strength decreased from 1.51 to 1.28 kg/pellet and the dry compressive strength decreased from 2.50 to 1.60 kg/pellet. It was determined that fired compressive strength of mix pellets decreased from 380 to 230 kg/pellet when the hematite content in the mixed pellet is increased. The reducibility of mix pellets had almost the same trend and it was faster up to 40 min reduction time. The results showed that the use of hematite together with magnetite is possible to produce pellets with sufficiently good quality in terms of wet, dry and fired mechanical strengths. The porosity and reducibility values of mix pellets were also found to be adequate to use as feed for the blast furnace.
