Fragmentation of particulate solids is an important process in many industrial activities, partic... more Fragmentation of particulate solids is an important process in many industrial activities, particularly in the mineral, cement and glass industries to comminute the raw materials to a required size. Understanding of processes and mechanisms responsible for fragmentation of particulate solids is a hard task. This may bring great precision for designing and controlling the comminution process. This work aims to contribute to understanding fragmentation of cement clinker particles under impact loading. For this purpose, six narrowsize classes of Portland clinker were fragmented with varying specific impact energy levels in a drop weight test apparatus. Then, breakage probabilities and functions of these size classes were determined from the product size distributions. The calculated breakage functions show evidences for the modes of breakage (meridian cracks to oblique cracks and shattering) given in the literature. Results of this study indicate that self-similarity of progeny size distributions can only be achieved, regardless of particle size and impact energy, if the particles have the same breakage probability, that is the same mode of breakage.
Liberation of the valuable minerals of an ore from its gangue is a prerequisite for the economic ... more Liberation of the valuable minerals of an ore from its gangue is a prerequisite for the economic recovery of the valuable minerals to concentrates. Mineral liberation is achieved by reducing the size of ore particles in various crushing and grinding devices. The fineness to which the ore must be ground, so as to yield sufficient degrees of liberation, increases if the valuable minerals with small grain sizes are disseminated throughout the gangue. Intensive fine grinding, however, increases energy costs and can lead to the loss of very fine untreatable particles into the tailings. Therefore, research should be oriented toward developing methods to foster breakage through the mineral grain boundaries to accomplish liberation at relatively coarser grinds. The purpose of this study is to determine if the pretreatment of the samples of a chromite ore with aqueous solutions of some salt and surfactant additives could improve the liberation by promoting preferential fracturing at the grain boundaries between the chromite and silicate minerals in the ore. For this purpose, untreated and pretreated samples of −9.53 + 6.35 mm size fraction of the ore were broken in a drop-weight tester, and the liberation spectra and the mass distribution of the resultant progenies were measured and compared. Optical and scanning electron microscope images and spectroscopic tools were used to find evidence for grain-boundary fracturing in the breakage progeny fragments. Results support the promoting effect of hydrolysis on grain-boundary fracturing. Aqueous salt and surfactant species enhance grain-boundary fracturing by forming surface complexes and dislocating aluminum atoms at the grain boundaries. Grain-boundary fracturing yields exposed chromite surfaces and enriched chromite content in the coarse progeny particles. The grain-boundary weakening is associated with slight hardness variation along the boundary.
Beneficiation process in the Kırka Borax Concentrator in Turkey generates a tailings effluent con... more Beneficiation process in the Kırka Borax Concentrator in Turkey generates a tailings effluent containing 3-10% solids that are composed mainly of colloidal particles of clay-rock-type gangue minerals and some unrecoverable borax fines. These colloidal particles form very stable aqueous suspensions in the tailings, hindering solid/liquid separation and clean water recovery. This leads to difficulties in the sustainable and environmentally acceptable operation of the concentrator. Flocculation studies on these colloidal suspensions had shown that the particles of the gangue minerals presented significant resistance to destabilization and remained in suspension forming high-turbidity supernatants in settling tests. For this reason, this study was undertaken to characterize the nature of such gangue particles with the intention of understanding the reason for their extreme colloidal stability and poor
Bu yazı bazt tane dağılımı formülleri ni ve tane dağılımı analizlerinin grafiksel sunulmaları ile... more Bu yazı bazt tane dağılımı formülleri ni ve tane dağılımı analizlerinin grafiksel sunulmaları ile ilgili yöntemleri özetle mektedir. Formüllerin kullanilmalanndaki sınırlamalar ve eğri uyumlaması acısından iyilik dereceleri de yer yer tartışılmıştır.
Assessment of mineral liberation spectrum with all its aspects is essential for plant control and... more Assessment of mineral liberation spectrum with all its aspects is essential for plant control and optimization. This paper aims to estimate 2D mineral map and its associated liberation spectrum of a particular chromite sample from optical micrographs by using Random Forest Classification, a powerful machine-learning algorithm implemented on a user-friendly and an open-source software. This supervised classification method can be used to accurately generate 2D mineral map of this chromite sample. The variation of the measured spectra with the sample size is studied, showing that images of 200 particles randomly selected from the optical micrographs are sufficient to reproduce liberation spectrum of this sample. In addition, the 2D spectrum obtained with this classification method is compared with the one obtained from the Mineral Liberation Analyzer (MLA). Although 2D mineralogical compositions obtained by the two methods are quite similar, microscopic analysis estimates poorer liberation than MLA due to the residual noise (misclassified gangue) generated by the classification. Nevertheless, we cannot compare the reliabilities of the two methods, as there is not a standard produce yet to quantify the accuracy of MLA analysis.
Constant pressure filtration of kaolin slurries is studied by directly measuring the pressure dro... more Constant pressure filtration of kaolin slurries is studied by directly measuring the pressure drop across the filter medium under conditions leading to various extents of medium clogging. Experimental data are analyzed in terms of the conventional filtration theory based on the two-resistances-in-series model. The filter medium resistance and the cake resistance values obtained by the conventional data interpretation techniques, which require only the measurement of total filtration pressure, are compared withthose calculated from directly measured pressure drops across the filter medium and the cake. The results show that the conventional analysis yieldsunrealistic filter medium resistances if the medium clogging is significant and continues throughout the course of filtration. The medium resistanceis a significant part of the total filtration resistance even at long filtration times. The average specific cake resistance obtained by the conventional methodology does not appear to be in error when compare...
International Journal of Mineral Processing, May 1, 2009
Packing characteristics of particle beds, determined mainly by the particle size distribution, ex... more Packing characteristics of particle beds, determined mainly by the particle size distribution, exert a critical influence on the interparticle breakage of minerals in confined beds under compression. This paper is concerned with the effects of feed size distribution on characteristic phenomena of confined-bed comminution. Minus 3.35-mm quartz and calcite feeds were prepared by proportionately mixing previously classified narrow-size fractions so as to construct particle size distributions having the Gaudin-Schuhmann functional form with distribution modulus values of 0.5, 0.7, and 0.9. These feeds were comminuted in a piston-die press at five levels of applied pressure ranging between 26.5 MPa and 283 MPa, generating specific energy inputs in the range 0.65 J/g to 8 J/g depending on the material and feed size distribution. The size distributions of the comminuted solids were analyzed for self-similarity, comminution kinetics and reduction ratios. Force-displacement data were analyzed for bed compaction, energy absorption and energy utilization phenomena. The results showed definite effects of feed size distribution on these latter phenomena and product particle size distributions. The relationship between the specific energy absorbed and applied pressure is linear. Self-similarity does not hold for the coarse-size range of the products, indicating greater deviations for feeds with greater proportions of the coarse material. Breakage fraction of the top-size class (3.35 × 2.36 mm) particles and production of fines (minus 75 μm) are significantly high with feeds having the size distribution modulus of 0.9. Reduction ratio-specific energy input relationship is curvi-linear; energy utilization becomes better with increasing value of the distribution modulus. The observed effects are explicable in terms of the packing density of particle beds and the amount of fines in the feeds.
Samples of a chromite ore were ground by conventional rod mill and by piston-die press. Five size... more Samples of a chromite ore were ground by conventional rod mill and by piston-die press. Five size fractions of products from the two commination devices having different modes of breakage were analyzed for the percent degree of chromite liberation and particle shape by an image analysis software. Results confirmed enhanced liberation in particle bed breakage achieved in the piston-die press. Particles ground in the rod mill had no shape differences as a function of particle size. Particle bed breakage generated particle profiles with less circularity at the finer end of the investigated size spectrum.
An alternative analytical exact solution for the discrete-size kinetic equation of grinding in cu... more An alternative analytical exact solution for the discrete-size kinetic equation of grinding in cumulative-fraction-passing mode was formulated as a matrix equation and tested successfully for predicting the transient evolution of the cumulative particle-size distribution and also for back-calculating the selection and breakage function parameters. The compact matrix form of the equation makes it computationally simple, and easy to extend the treatment to continuous mills. The solution should be particularly useful for parameter estimation purposes as it is expected to reduce the variability of the estimates because of the monotonic nature of the cumulative size distributions.
This paper presents a study on the reactivity of natural limestones from five deposits in Turkey.... more This paper presents a study on the reactivity of natural limestones from five deposits in Turkey. The conversion rates of carbonates in size fractions of the samples were measured in a stirred suspension of 2.5 l at 20°C and a constant-pH value of 5 obtained with the addition of HCl solutions by a pH control pump. Particle size and the dolomite content of the limestones were found to be the most influential parameters in the reactivity measurements.
Physicochemical Problems of Mineral Processing, 2001
Single-mineral floatability of pure, heavy sand rutile and zircon minerals using sodium oleate an... more Single-mineral floatability of pure, heavy sand rutile and zircon minerals using sodium oleate and hydrogenated tallow amine acetate as collectors was studied by a micro-flotation device over a wide pH range from 2 to 12, at three levels of the collectors and two levels of a polypropylene glycol type frother. Rutile yielded a peak foatability at pH 6 with sodium oleate, and floated reasonably well over a wide pH range from 2 to 8 with the amine collector. An abrupt deterioration of the floatability of rutile was observed at pH>8. The maximal floatability range for zircon was from pH 6 to 10, followed by a sharp decrease at pH>10, with both of the collectors. The floatability of zircon decreased sharply with decreasing pH in the acidic medium, below pH 6. The results were discussed in view of collector species distribution as a function of pH to suggest adsorption mechanisms for the collectors. The upper critical flotation pH values for the minerals seemed to be sufficiently distinct to suggest a potential for the differential flotation of the minerals in the alkaline medium with both of the collectors tested.
The Bond method of grindability was applied to ceramic raw materials (quartz, kaolin and feldspar... more The Bond method of grindability was applied to ceramic raw materials (quartz, kaolin and feldspar) and to their binary and ternary mixtures. The Bond work indices of the admixtures containing a softer component (kaolin) were found to be greater than the weighted average of the work indices of the individual components in the mixture. As a result, separate grinding of ceramic raw materials seems to require less specific energy input than grinding them in admixtures.
The irreducible equilibrium saturation and dewatering kinetics of vacuus-dewatered filter cakes a... more The irreducible equilibrium saturation and dewatering kinetics of vacuus-dewatered filter cakes are studied. Limitations of available empirical correlations for cake dewatering characteristics are presented. The mechanisms of air displacement dewatering are delineated as no-air-flow and air-flow dewatering regimes, and new nondimensional groups combining the pertinent parameters in each regime are proposed for correlating the equilibrium saturation. On the basis of the capillary flow dynamics, a nondimensional group is formulated for the correlation of dewatering kinetics in the absence of air flow rate data. The correlations are verified with the experimental data obtained from the filtration of hematite slurries and an empirical equation based on the same data is suggested for equilibrium saturation predictions.
Batch experiments were carried out on the dry ball milling of commonly used ceramic raw materials... more Batch experiments were carried out on the dry ball milling of commonly used ceramic raw materials quartz, kaolin and feldspar, singly and as ternary mixtures. The modified form of the Charles energy-size reduction equation was used to calculate the energy consumed by each of the components in the mixture. The results confirmed the validity of the mass fraction hypothesis for energy split between the components that had been defined and verified for the binary mixtures of equal-density minerals. The distribution and size module of the minerals remained the same whether they were ground separately or in a ternary mixture.
Conventional drum pelletization circuits exhibit undesirable surging behavior that is known to re... more Conventional drum pelletization circuits exhibit undesirable surging behavior that is known to result from uncontrolled occurrence of the mechanisms of nucleation, coalescence and layering. This study was undertaken to investigate the mechanism of pellet growth by layering. Several laboratory experiments were carried out to delineate the effect of feed moisture content and feed quantity. This paper presents an analysis of the experimental results and a simple model to describe the layering process.
Mineral Processing and Extractive Metallurgy Review, 2015
ABSTRACT The use of high-pressure grinding rolls (HPGR) prior to ball mills has become a common p... more ABSTRACT The use of high-pressure grinding rolls (HPGR) prior to ball mills has become a common practice in cement clinker grinding due to significant energy savings in comparison to ball milling alone. The energy savings has been attributed to higher energy efficiency of the HPGR at low reduction ratios, smaller particle top sizes in the ball mill feed, and the weakening of particles resulting from compression of particle bed by HPGR. This study attempts to show how the weakening effect changes the kinetic breakage parameters of HPGR-treated clinker. For this purpose, batch ball mill experiments were conducted with three narrow-size fractions (−3.35 + 2.36 mm, −1.70 + 1.18 mm, and −0.85 + 0.60 mm) of the feed and product samples of an industrial HPGR, and the breakage rate and breakage distribution parameters of the samples were compared. The results show that the weakening effect leads to non-linear breakage rates for all sizes, coupled with abnormal breakage at the two coarsest sizes. The weakening effect leads to increased breakage rates of the HPGR product relative to particles of the HPGR feed. The increased breakages rates are accompanied by coarser progeny distributions for the two coarsest size ranges relative to that of the HPGR feed. The progeny distribution of the finest size of the HPGR product, however, is finer than that of the HPGR feed. Ball milling of size-distributed feeds prepared from the HPGR product and feed samples for the same grind time produces self-similar size distributions when the size is normalized with respect to the median size.
Flocculation behavior of two clay rock samples with different dolomite and clay mineral (smectite... more Flocculation behavior of two clay rock samples with different dolomite and clay mineral (smectite) contents was examined using a non-conventional, medium-anionic polyacrylamide-based flocculant in borax solutions. The samples were representative of two major types of gangue material discarded from the borax processing plant at Kirka/Turkey as borax-saturated tailings stream which present serious disposal problems from technical and environmental points of view. The effect of the dissolved borax concentration by itself, and the effects of Ca 2+ and Mg 2+ ions at a constant borax concentration of 3% w/v were investigated with dispersions flocculated at the buffered pH 9.4. Flocculation efficiency was mainly assessed by the supernatant turbidity. Increasing the borax concentration decreased the supernatant turbidity. The effect was attributed to the reduced negative electric field around the dolomite and clay mineral particles due to the high ionic strength and the adsorption of sodium cations on the surfaces of the clay mineral particles, facilitating the hydrogen bonding of the amide groups of the flocculant. Ca 2+ ions were essential for improving the floc formation and obtaining clear supernatants, but Mg 2+ ions were detrimental to floc formation and turbidity removal. Positively-charged adsorbed calcium-hydroxo species on the particles should have promoted stronger salt linkages with the negative pendant groups of the flocculant. The adverse effect of Mg 2+ was attributed to its higher hydration energy and the likely precipitation of Mg(OH) 2 on particle surfaces. FTIR studies provided some supporting evidence for the suggested mechanisms of flocculant adsorption.
Fragmentation of particulate solids is an important process in many industrial activities, partic... more Fragmentation of particulate solids is an important process in many industrial activities, particularly in the mineral, cement and glass industries to comminute the raw materials to a required size. Understanding of processes and mechanisms responsible for fragmentation of particulate solids is a hard task. This may bring great precision for designing and controlling the comminution process. This work aims to contribute to understanding fragmentation of cement clinker particles under impact loading. For this purpose, six narrowsize classes of Portland clinker were fragmented with varying specific impact energy levels in a drop weight test apparatus. Then, breakage probabilities and functions of these size classes were determined from the product size distributions. The calculated breakage functions show evidences for the modes of breakage (meridian cracks to oblique cracks and shattering) given in the literature. Results of this study indicate that self-similarity of progeny size distributions can only be achieved, regardless of particle size and impact energy, if the particles have the same breakage probability, that is the same mode of breakage.
Liberation of the valuable minerals of an ore from its gangue is a prerequisite for the economic ... more Liberation of the valuable minerals of an ore from its gangue is a prerequisite for the economic recovery of the valuable minerals to concentrates. Mineral liberation is achieved by reducing the size of ore particles in various crushing and grinding devices. The fineness to which the ore must be ground, so as to yield sufficient degrees of liberation, increases if the valuable minerals with small grain sizes are disseminated throughout the gangue. Intensive fine grinding, however, increases energy costs and can lead to the loss of very fine untreatable particles into the tailings. Therefore, research should be oriented toward developing methods to foster breakage through the mineral grain boundaries to accomplish liberation at relatively coarser grinds. The purpose of this study is to determine if the pretreatment of the samples of a chromite ore with aqueous solutions of some salt and surfactant additives could improve the liberation by promoting preferential fracturing at the grain boundaries between the chromite and silicate minerals in the ore. For this purpose, untreated and pretreated samples of −9.53 + 6.35 mm size fraction of the ore were broken in a drop-weight tester, and the liberation spectra and the mass distribution of the resultant progenies were measured and compared. Optical and scanning electron microscope images and spectroscopic tools were used to find evidence for grain-boundary fracturing in the breakage progeny fragments. Results support the promoting effect of hydrolysis on grain-boundary fracturing. Aqueous salt and surfactant species enhance grain-boundary fracturing by forming surface complexes and dislocating aluminum atoms at the grain boundaries. Grain-boundary fracturing yields exposed chromite surfaces and enriched chromite content in the coarse progeny particles. The grain-boundary weakening is associated with slight hardness variation along the boundary.
Beneficiation process in the Kırka Borax Concentrator in Turkey generates a tailings effluent con... more Beneficiation process in the Kırka Borax Concentrator in Turkey generates a tailings effluent containing 3-10% solids that are composed mainly of colloidal particles of clay-rock-type gangue minerals and some unrecoverable borax fines. These colloidal particles form very stable aqueous suspensions in the tailings, hindering solid/liquid separation and clean water recovery. This leads to difficulties in the sustainable and environmentally acceptable operation of the concentrator. Flocculation studies on these colloidal suspensions had shown that the particles of the gangue minerals presented significant resistance to destabilization and remained in suspension forming high-turbidity supernatants in settling tests. For this reason, this study was undertaken to characterize the nature of such gangue particles with the intention of understanding the reason for their extreme colloidal stability and poor
Bu yazı bazt tane dağılımı formülleri ni ve tane dağılımı analizlerinin grafiksel sunulmaları ile... more Bu yazı bazt tane dağılımı formülleri ni ve tane dağılımı analizlerinin grafiksel sunulmaları ile ilgili yöntemleri özetle mektedir. Formüllerin kullanilmalanndaki sınırlamalar ve eğri uyumlaması acısından iyilik dereceleri de yer yer tartışılmıştır.
Assessment of mineral liberation spectrum with all its aspects is essential for plant control and... more Assessment of mineral liberation spectrum with all its aspects is essential for plant control and optimization. This paper aims to estimate 2D mineral map and its associated liberation spectrum of a particular chromite sample from optical micrographs by using Random Forest Classification, a powerful machine-learning algorithm implemented on a user-friendly and an open-source software. This supervised classification method can be used to accurately generate 2D mineral map of this chromite sample. The variation of the measured spectra with the sample size is studied, showing that images of 200 particles randomly selected from the optical micrographs are sufficient to reproduce liberation spectrum of this sample. In addition, the 2D spectrum obtained with this classification method is compared with the one obtained from the Mineral Liberation Analyzer (MLA). Although 2D mineralogical compositions obtained by the two methods are quite similar, microscopic analysis estimates poorer liberation than MLA due to the residual noise (misclassified gangue) generated by the classification. Nevertheless, we cannot compare the reliabilities of the two methods, as there is not a standard produce yet to quantify the accuracy of MLA analysis.
Constant pressure filtration of kaolin slurries is studied by directly measuring the pressure dro... more Constant pressure filtration of kaolin slurries is studied by directly measuring the pressure drop across the filter medium under conditions leading to various extents of medium clogging. Experimental data are analyzed in terms of the conventional filtration theory based on the two-resistances-in-series model. The filter medium resistance and the cake resistance values obtained by the conventional data interpretation techniques, which require only the measurement of total filtration pressure, are compared withthose calculated from directly measured pressure drops across the filter medium and the cake. The results show that the conventional analysis yieldsunrealistic filter medium resistances if the medium clogging is significant and continues throughout the course of filtration. The medium resistanceis a significant part of the total filtration resistance even at long filtration times. The average specific cake resistance obtained by the conventional methodology does not appear to be in error when compare...
International Journal of Mineral Processing, May 1, 2009
Packing characteristics of particle beds, determined mainly by the particle size distribution, ex... more Packing characteristics of particle beds, determined mainly by the particle size distribution, exert a critical influence on the interparticle breakage of minerals in confined beds under compression. This paper is concerned with the effects of feed size distribution on characteristic phenomena of confined-bed comminution. Minus 3.35-mm quartz and calcite feeds were prepared by proportionately mixing previously classified narrow-size fractions so as to construct particle size distributions having the Gaudin-Schuhmann functional form with distribution modulus values of 0.5, 0.7, and 0.9. These feeds were comminuted in a piston-die press at five levels of applied pressure ranging between 26.5 MPa and 283 MPa, generating specific energy inputs in the range 0.65 J/g to 8 J/g depending on the material and feed size distribution. The size distributions of the comminuted solids were analyzed for self-similarity, comminution kinetics and reduction ratios. Force-displacement data were analyzed for bed compaction, energy absorption and energy utilization phenomena. The results showed definite effects of feed size distribution on these latter phenomena and product particle size distributions. The relationship between the specific energy absorbed and applied pressure is linear. Self-similarity does not hold for the coarse-size range of the products, indicating greater deviations for feeds with greater proportions of the coarse material. Breakage fraction of the top-size class (3.35 × 2.36 mm) particles and production of fines (minus 75 μm) are significantly high with feeds having the size distribution modulus of 0.9. Reduction ratio-specific energy input relationship is curvi-linear; energy utilization becomes better with increasing value of the distribution modulus. The observed effects are explicable in terms of the packing density of particle beds and the amount of fines in the feeds.
Samples of a chromite ore were ground by conventional rod mill and by piston-die press. Five size... more Samples of a chromite ore were ground by conventional rod mill and by piston-die press. Five size fractions of products from the two commination devices having different modes of breakage were analyzed for the percent degree of chromite liberation and particle shape by an image analysis software. Results confirmed enhanced liberation in particle bed breakage achieved in the piston-die press. Particles ground in the rod mill had no shape differences as a function of particle size. Particle bed breakage generated particle profiles with less circularity at the finer end of the investigated size spectrum.
An alternative analytical exact solution for the discrete-size kinetic equation of grinding in cu... more An alternative analytical exact solution for the discrete-size kinetic equation of grinding in cumulative-fraction-passing mode was formulated as a matrix equation and tested successfully for predicting the transient evolution of the cumulative particle-size distribution and also for back-calculating the selection and breakage function parameters. The compact matrix form of the equation makes it computationally simple, and easy to extend the treatment to continuous mills. The solution should be particularly useful for parameter estimation purposes as it is expected to reduce the variability of the estimates because of the monotonic nature of the cumulative size distributions.
This paper presents a study on the reactivity of natural limestones from five deposits in Turkey.... more This paper presents a study on the reactivity of natural limestones from five deposits in Turkey. The conversion rates of carbonates in size fractions of the samples were measured in a stirred suspension of 2.5 l at 20°C and a constant-pH value of 5 obtained with the addition of HCl solutions by a pH control pump. Particle size and the dolomite content of the limestones were found to be the most influential parameters in the reactivity measurements.
Physicochemical Problems of Mineral Processing, 2001
Single-mineral floatability of pure, heavy sand rutile and zircon minerals using sodium oleate an... more Single-mineral floatability of pure, heavy sand rutile and zircon minerals using sodium oleate and hydrogenated tallow amine acetate as collectors was studied by a micro-flotation device over a wide pH range from 2 to 12, at three levels of the collectors and two levels of a polypropylene glycol type frother. Rutile yielded a peak foatability at pH 6 with sodium oleate, and floated reasonably well over a wide pH range from 2 to 8 with the amine collector. An abrupt deterioration of the floatability of rutile was observed at pH>8. The maximal floatability range for zircon was from pH 6 to 10, followed by a sharp decrease at pH>10, with both of the collectors. The floatability of zircon decreased sharply with decreasing pH in the acidic medium, below pH 6. The results were discussed in view of collector species distribution as a function of pH to suggest adsorption mechanisms for the collectors. The upper critical flotation pH values for the minerals seemed to be sufficiently distinct to suggest a potential for the differential flotation of the minerals in the alkaline medium with both of the collectors tested.
The Bond method of grindability was applied to ceramic raw materials (quartz, kaolin and feldspar... more The Bond method of grindability was applied to ceramic raw materials (quartz, kaolin and feldspar) and to their binary and ternary mixtures. The Bond work indices of the admixtures containing a softer component (kaolin) were found to be greater than the weighted average of the work indices of the individual components in the mixture. As a result, separate grinding of ceramic raw materials seems to require less specific energy input than grinding them in admixtures.
The irreducible equilibrium saturation and dewatering kinetics of vacuus-dewatered filter cakes a... more The irreducible equilibrium saturation and dewatering kinetics of vacuus-dewatered filter cakes are studied. Limitations of available empirical correlations for cake dewatering characteristics are presented. The mechanisms of air displacement dewatering are delineated as no-air-flow and air-flow dewatering regimes, and new nondimensional groups combining the pertinent parameters in each regime are proposed for correlating the equilibrium saturation. On the basis of the capillary flow dynamics, a nondimensional group is formulated for the correlation of dewatering kinetics in the absence of air flow rate data. The correlations are verified with the experimental data obtained from the filtration of hematite slurries and an empirical equation based on the same data is suggested for equilibrium saturation predictions.
Batch experiments were carried out on the dry ball milling of commonly used ceramic raw materials... more Batch experiments were carried out on the dry ball milling of commonly used ceramic raw materials quartz, kaolin and feldspar, singly and as ternary mixtures. The modified form of the Charles energy-size reduction equation was used to calculate the energy consumed by each of the components in the mixture. The results confirmed the validity of the mass fraction hypothesis for energy split between the components that had been defined and verified for the binary mixtures of equal-density minerals. The distribution and size module of the minerals remained the same whether they were ground separately or in a ternary mixture.
Conventional drum pelletization circuits exhibit undesirable surging behavior that is known to re... more Conventional drum pelletization circuits exhibit undesirable surging behavior that is known to result from uncontrolled occurrence of the mechanisms of nucleation, coalescence and layering. This study was undertaken to investigate the mechanism of pellet growth by layering. Several laboratory experiments were carried out to delineate the effect of feed moisture content and feed quantity. This paper presents an analysis of the experimental results and a simple model to describe the layering process.
Mineral Processing and Extractive Metallurgy Review, 2015
ABSTRACT The use of high-pressure grinding rolls (HPGR) prior to ball mills has become a common p... more ABSTRACT The use of high-pressure grinding rolls (HPGR) prior to ball mills has become a common practice in cement clinker grinding due to significant energy savings in comparison to ball milling alone. The energy savings has been attributed to higher energy efficiency of the HPGR at low reduction ratios, smaller particle top sizes in the ball mill feed, and the weakening of particles resulting from compression of particle bed by HPGR. This study attempts to show how the weakening effect changes the kinetic breakage parameters of HPGR-treated clinker. For this purpose, batch ball mill experiments were conducted with three narrow-size fractions (−3.35 + 2.36 mm, −1.70 + 1.18 mm, and −0.85 + 0.60 mm) of the feed and product samples of an industrial HPGR, and the breakage rate and breakage distribution parameters of the samples were compared. The results show that the weakening effect leads to non-linear breakage rates for all sizes, coupled with abnormal breakage at the two coarsest sizes. The weakening effect leads to increased breakage rates of the HPGR product relative to particles of the HPGR feed. The increased breakages rates are accompanied by coarser progeny distributions for the two coarsest size ranges relative to that of the HPGR feed. The progeny distribution of the finest size of the HPGR product, however, is finer than that of the HPGR feed. Ball milling of size-distributed feeds prepared from the HPGR product and feed samples for the same grind time produces self-similar size distributions when the size is normalized with respect to the median size.
Flocculation behavior of two clay rock samples with different dolomite and clay mineral (smectite... more Flocculation behavior of two clay rock samples with different dolomite and clay mineral (smectite) contents was examined using a non-conventional, medium-anionic polyacrylamide-based flocculant in borax solutions. The samples were representative of two major types of gangue material discarded from the borax processing plant at Kirka/Turkey as borax-saturated tailings stream which present serious disposal problems from technical and environmental points of view. The effect of the dissolved borax concentration by itself, and the effects of Ca 2+ and Mg 2+ ions at a constant borax concentration of 3% w/v were investigated with dispersions flocculated at the buffered pH 9.4. Flocculation efficiency was mainly assessed by the supernatant turbidity. Increasing the borax concentration decreased the supernatant turbidity. The effect was attributed to the reduced negative electric field around the dolomite and clay mineral particles due to the high ionic strength and the adsorption of sodium cations on the surfaces of the clay mineral particles, facilitating the hydrogen bonding of the amide groups of the flocculant. Ca 2+ ions were essential for improving the floc formation and obtaining clear supernatants, but Mg 2+ ions were detrimental to floc formation and turbidity removal. Positively-charged adsorbed calcium-hydroxo species on the particles should have promoted stronger salt linkages with the negative pendant groups of the flocculant. The adverse effect of Mg 2+ was attributed to its higher hydration energy and the likely precipitation of Mg(OH) 2 on particle surfaces. FTIR studies provided some supporting evidence for the suggested mechanisms of flocculant adsorption.
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