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By X. W. Zhang

Mica plate is broadly used in electric industry, production of man-made mica paper plate is in-creasing. The problem coming with is that large quantities of leftover materials unable to be re-cycled are produced during cutting and molding of mica plate productions. The leftover materials are always abandoned as crabs, which not only pollute the environment but also waste our resources. The study intends to find a new measure to decompose and to reuse the mica plate leftover materials so as to create a new production process of mica plate, which is clean and does not produce crabs.

Jan 1, 2014

By P. A. Bepswa

A numerical study done to test the efficacy of heuristics developed for the design of measurement networks for high precision metallurgical accounting is presented in this paper. The heuristics considered were designed to maximise variance reduction of terminal stream measurements through data reconciliation for observable linear flow systems. A complex metallurgical process flow sheet from the mineral sands industry was used as a case study. Monte Carlo type simulations coupled with a non-linear programming based steady state data reconciliation algorithm were used as tools to investigate the heuristics. The results obtained suggested a close correlation between magnitudes of measured variances and the respective levels of variance reduction obtained through data reconciliation for both internal and terminal streams. It was observed that variance reduction through data reconciliation was maximised for terminal stream measurements in networks characterised by high precision measurement of internal streams and/or in flow sheets characterised by high ?stream to node ratios?. Terminal streams attached to highly interconnected parent nodes were observed to experience higher reductions in variance compared to terminal streams attached to less interconnected parent nodes. The results generally highlight the additional benefits of highly interconnected flow sheets and high precision internal stream measurement regimes on the maximisation of variance reduction of terminal stream measurements through data reconciliation. These findings are significant to metallurgical accounting and to process accounting applications in general in that they provide a conceptual basis for design decision making regarding the construction of measurement networks aimed at maximising variance reduction of targeted streams through data reconciliation.

Jan 1, 2014

By A. Shandilya

ACC ECOSAND is finely powdered crystalline silica, which can replace natural sand usage in concrete and plasters. ACC ECOSAND ensures a comparatively denser concrete than those made only with natural sand and / or quarry fines / Manufactured Sand (Artificial Sand). Moreover, there is a significant gain in compressive strength (10-15 %) & durability in concretes (Reduced chloride conductivity leads to increased durability). ECOSAND is a by-product of froth flotation of limestone. At ACC Madukkarai cement works, Coimbatore, Tamilnadu, full-fledged mineral beneficiation process is adopted to enhance the usage of flotation reject in concrete and plasters. Optimum level for usage of ECO-SAND is 50%. With 50% usage of natural sand+50% ECO-SAND in concrete mix, 1 day, 3 day, 7 day & 28 day compressive strength is increased by 30.1 %, 22.6 %, 15.1 % & 11.0 % respectively and with moderate chloride permeability as compare to 100% Natural Sand. Keywords: froth flotation process, beneficiation studies, Denver cell, ECOSAND, siliceous material, durability & compressive strength, RCPT

Sep 1, 2012

By Jacob Masliyah, Zhenghe Xu, Lujie Yan

"Understanding adsorption mechanism of polymeric organic process modifierssuch as carboxymethyl cellulose (CMC) on talc hasbeen a major challenge due to anisotropic nature of talc basal planes and edge surfaces. The main objective of this study is to investigate the adsorption of CMC on the basal planes and edge surfaces of talc.Smooth basal plane and edge surfaces of talc were prepared successfully by simple cleavage and sophisticated ultramicrotome cutting method, respectively. The prepared surfaces were characterized by atomic force microscope (AFM) imaging to be sufficiently smooth for colloidal probe force measurements using AFM. Anisotropic surface charge characteristics were determined,with the basal planes to carry a permanent negative surface charge and edge surfaces featuring a pH-dependent charge characteristic. The adsorption of CMC on talc basal plane and edge surfaces at pH 9 in KClaqueous solutions of various ionic strengths wasinvestigated by in situ AFM imaging technique. Themorphology of adsorbed CMC on talc basal planes and edge surfaces was found to be significantly different, due to different binding mechanisms involved. Interaction of CMC with the talc basal plane was found to bedominated by hydrophobic interactions while its binding with the talc edge surface was mainly through chemical complexation and hydrogen bond. The amount of CMC adsorbed on both talc basal planes and edge surfaces increased with increasing ionic strengthof solutions. The methodology developed in our study opens the door to probe polymer adsorption on anisotropic phyllosilicate surfaces, which can help us better understand the mechanism of polymer adsorption on specific mineral faces."

Jan 1, 2014

By V. Buddhiraju

Liberation of valuable minerals from low-grade ores is an important challenge faced by the minerals industry. It is necessary to grind the ore to extremely fine size in order to liberate the mineral from such ores. As it is generally difficult to produce ultra-fine particles of diameter less than 1-10 mm using traditional grinding equipment such as the ball mill and the rod mill, several new types of grinding equipment are being explored to produce ultra-fine particles. The planetary ball mill is promising in that it makes grinding to submicron sizes possible by imparting high energy to the ground powder. It consists of four pots mounted on a disc. The pots and the disc rotate in opposite directions. The high-speed rotation of the pots and the disc makes the grinding media move at high centrifugal velocities leading to high impact energy and thus improving the grinding performance. The planetary mill is currently being explored for its capability to produce ultra-fine particles on a large scale. In this context, there is a need to understand the dynamics of the ultra-fine grinding process within the planetary ball mill. Here, we address this need by studying the movement of media inside the pots and the grinding kinetics, employing both experimental and modeling techniques. The experiments were conducted on a laboratory scale planetary ball mill. The particle size distribution of the powder was monitored to allow an estimate of the grinding kinetics to be made while video images of the media profiles inside the pots were taken to allow quantification of the media movement as a function of process variables such as the media size, percent loading, etc. The population balance modeling (PBM) framework was used to simulate the kinetics of grinding while the discrete element modeling (DEM) approach was utilized to simulate the media motion. The parameters in the population balance model, namely, the specific breakage rate and the breakage distribution function were determined by fitting the batch grinding equation to the experimental data. The predicted powder size distributions were found to be in good agreement with the experimental data. The experimental results have shown that the mean size of product powder decreases as the size of the grinding media decreases. Keywords: population balance modeling, grinding, planetary mill, grinding media, grinding equation

Sep 1, 2012

By Smuts. E. M.

This paper describes a methodology used to develop a numerical model for the study of particulate suspension rheology. Initially, Computational Fluid Dynamics (CFD) models of different rheometer geometries were tested with both a Newtonian fluid (water), and a non-Newtonian Herschel-Bulkley slurry. Rheograms were reproduced from these models and compared to experimental values. Once a single-phase model had been validated, a coupled model combining CFD and the Discrete Element Method (DEM) was created. Two open source software packages were chosen. CFD is implemented using Open FOAM®, and DEM using LIGGGHTS. These two different codes were coupled via another program called CFDEM. This coupled model is currently capable of modeling spherical particles in a suspending liquid. DLVO forces have been included in some models to account for inter-particle forces due to the surface charge on the particles. The coupled model is currently being validated. Preliminary results show good qualitative behavior of the model. Keywords: rheology, cfd, dem, suspensions, modeling

Sep 1, 2012

By S. V. Bogdanov, S. I. Grishaev

"The article presents the materials about the appropriateness of the use of rental indices to assess the effectiveness of the use of deposits of rare earth elements (REE). The authors suggest from the standpoint of rent payments to rate for the owner the possibility of using the anticipated rental income as the indicator for the analysis of preferences and economic significance of enrichment of extracted raw materials in the emerging field of rare earth metals (REE). Usually from ore mined at the fields, for flotation technology to produce concentrates with collective REE, then they are subjected to chemical-metallurgical processing of the received products are divided into pure oxides, chemical compounds or isolated from them pure metals and alloys. This commercial product is shipped to the buyer. REE were a non-renewable natural resources, so the calculations for determining differential and specific rent showed that during the development of the technologies of mineral processing of a specific field it is necessary to consider what the expected rental income depends on the magnitude of differential rent is related to the volume of production of REE for the whole planned period of exploitation of natural resources. This income is determined by the amount of stock field. For long-term exploitation of the deposit is observed in almost direct proportional dependence between the annual differential rent and the rental income. The decrease in rents in the long run is determined by the change in the composition of ores included in the extracted raw materials and the balance between light and heavy REE. The largest 70% reduction of the rent projected for ""cerium"" fields, while for ""yttrium"" these losses are considerably smaller. Tomtor, Chuktukon and Katuginskoye Russian deposits are characterized by a level of rent that is comparable to the mastered foreign sources of REE. Thus, the enrichment of minerals with REM in the domestic deposits is quite competitive at the world level. INTRODUCTION Deposits of rare earth metals (REE) are non-renewable resources that should be developed and used so that it would be possible to provide a reduction due to payment of appropriate resources for future generations. This compensation, due to the reduction of natural resources, can be carried out both in natural and in economic terms (1). When analyzing economic compensation options, particular attention should be paid to rental income in assessing the attractiveness of using different REE deposits. It is known that absolute and differential rents are summands when calculating the value of natural rents. The value of the absolute natural rent is proportional to the unit price of the product obtained from mineral raw materials and sold on the commodity market. Limitations, as well as the use in production processes and business, contribute to the gradual reduction of natural resources, which increases their consumer value and affects the price of commodity products from primary raw materials."

Jan 1, 2018

By R. L. Pascual, W. J. Whiten

"The froth flotation process is not well understood. Both flotation models, and the parameters used to describe the stream flows are not well defined. They in fact vary considerably in different applications. This creates difficulties is designing a simulation program suitable for use by plant personnel, consultants, and researchers. In addition to simulation, an effective simulation program can be expected to provide a range of other services.This paper shows how a process circuit simulator can be designed with sufficient flexibility to satisfy these needs, and discusses some of the additional services."

Jan 1, 2003

By S. H. Morar

Froth stability is widely recognized as a key driver of flotation selectivity. It is well known that froth stability is affected by the type and quantity of surface active reagents present (frothers), and the concentration and hydrophobicity of solid particles present. While some studies have been performed on the effect of frothers on froth stability in three-phase systems and the hydrophobicity of particles present, very little work has been performed on the effect of solids loading on froth stability. This may be due to insufficiently robust measurement techniques. This paper investigates the use of a new machine vision measurement to measure solids loading, and the relationship between this measurement, bubble size, and bubble burst rate on the froth surface. Keywords: froth flotation, machine vision, solids loading

Sep 1, 2012

By I. A. S. Brum

Brazil has large reserves of coal (7 billion tons) located predominantly in the south of the country. Despite the relative ease of exploitation, these resources have been underestimated as a source of energy. Currently the country's strategic planning aims to minimize the gap between coal and resources traditionally used in the Brazilian energy matrix. In this scenario, the processing of Brazilian coal in columns flotation appears as a promising alternative, having been successful in mineral systems containing fine particles. This paper aims to study the overall process of column flotation for a specific Brazilian coal. The material used in this study consists of fine coal that is usually discarded as waste and deposited in the tailings dams. The objective is to recover carbonaceous matter and reduce the ash and contaminants grade. The variables analyzed were the influence of size particle, solids concentration in the pulp, the concentration of surfactants and frothers to be used. The first results showed that it is possible, from a feed with around 65% of ashes, to obtain products with approximately 35% ashes with mass recoveries about 40%. Concentrations of frother (pine oil) ranged from 50 g/t to 300 g/t and the collector (diesel oil) of 50 g/t to 200 g/t. Keywords: column flotation, coal, tailings, negative bias

Sep 1, 2012

By Al Cropp, Julie Hunt, Will Goodall, Ron Berry, Dee Bradshaw

Geometallurgy aids the understanding of ore body variability but has the most value if the data is easily available along the entire mining value chain. This requires cross-discipline communication and collaboration across traditional silos, and an organizational culture that encourages that to flourish. Data that are collected by the numerous groups (i.e. mining, geology, milling, processing, refining, smelting, marketing, environmental etc.) involved in the mining process may have relevance to other stakeholders; mineralogical and textural data for example has value to all these groups. Data required for modeling comminution or identifying acid potential from waste rock may already exist, however it needs to be made available to all the relevant stakeholders in the right format at the right time. As part of the GeM (AMIRA P843 & P843A) project the opportunity has been taken during the sponsor meetings, short courses, case studies etc. to ask the question: ‚What information do you want from further up the chain?? For example, to metallurgists ‚What information would you like from the geology group before the ore enters the mill?? The geology group may already have information important to mineral processing but not know it is of interest. This could, for example, be in the form of a geometallurgical drill core log that contains quantitative measured values. This paper focuses on the interaction between the mining, geology, mineral processing and environmental groups, using ore properties resulting from geological alteration to identify potential impacts throughout the mining process and discusses how a cross discipline approach can benefit all.

Jan 1, 2014

By Kwang Soon Moon

Liquid ? liquid reactions such as solvent extraction in hydrometallurgy and BTX extraction in petrochemical industry has long suffered from the long retention time mainly due to the limited interfacial area caused by the immiscibility between water and oil phase, requiring typically very large perfect mixer type reactors and tall adsorption towers. A novel spray reactor for immiscible liquids; that is the KISEI Nozzle Reactor (KNR) was introduced, enabling the drastic increase in the interfacial area between the reacting immiscible liquids. Various spray mechanisms were applied in materials processing, e.g. spray drying, powder metallurgy, and aerosol industry, but not in hydrometallurgy. The KISEI Nozzle Reactor(KNR) was fully developed and used in production of biodiesel from the immiscible triglycerides and methanol. An experience with a full production plant facility is briefly discussed in the current paper. With the fog-like methanol spray in oil medium, the trans esterification reaction was almost instantaneous, and transformed the traditional batch trans esterification process into a continuous production process. And above all, with no moving parts in the KISEI Nozzle Reactor (KNR), the process requires minimal operation and maintenance costs. Keywords: immiscible liquids reaction, nozzle spray reactor, continuous biodiesel reactor, hydrometallurgy, organic extraction, micro emulsion

Sep 1, 2012

By Robert Snow, Shibo Zheng, Wenyi Song, Xiaoqing Ma, Patrick Zhang

Numerous phosphate mineral depressants have been reported in the literature for use during anionic flotation of dolomite from carbonate fluorapatite in slightly acid circuits. In one part of this research, laboratory flotation experiments were conducted to compare the effectiveness of phosphate depressants to process ground, deslimed high-MgO Florida phosphate pebbles. Ten potential phosphate depressants were evaluated during laboratory anionic flotation of dolomite from phosphate in a slightly acid circuit using a sulfonated oleic acid soap plus oil as the dolomite collector. Eight of the depressants have been used by various investigators with foreign and domestic carbonate-phosphate ores. Four of the depressants were found to be reasonably effective during the current flotation study, namely: sodium tripolyphosphate (STPP), sodium hexametaphosphate (SHMP), tetrasodium pyrophosphate (TSPP) and diphosphonic acid (DPA). Without depressants, the sulfonate collector required to produce cell underflow phosphate products containing <0.80% MgO and MgO/ P2O5 ratio <.033 was 1.13 kg/ton of flotation feed at a flotation pH range = 5.5-6.0. Using this collector level with 0.91 - 1.36 kg/ton of feed of STPP, SHMP or TSPP yielded phosphate products analyzing 0.73-0.92% MgO and MgO/ P2O5 ratios = .027-.034 at 90.0-96.8% P2O5 recovery. Similar grade phosphate products were obtained using DPA as the phosphate depressant at 84.1-87.5% P2O5 recovery. When no depressant was used, a similar grade phosphate product was obtained at only 65.9% P2O5 recovery. Another part of the research aimed at reducing MgO content in the final concentrate from Florida phosphate plants by conducting dolomite flotation on the final concentrate. Numerous phosphate depressants were tested for this purpose, including acidic, neutral and alkaline reagents. The most effective phosphate depressant was found to be phosphoric acid, giving both high grade and recovery.

Jan 1, 2014

By P. Somasundaran

Treatment of mineral surfaces with appropriate surfactants plays an important role in mineral processing operations such as flotation, flocculation and dewatering. Recently biosurfactants, in particular, have received a considerable amount of attention because of their unique surface active properties and biodegradability. In this work we examined the performance of biosurfactants, sugar based alkyl glycosides and sophorolipid esters as reagents to control the hydrophobicity of minerals with selectivity of adsorption on mineral surfaces for flotation applications. It was discovered that n-dodecyl-ß-D-maltoside adsorbs on alumina, titania and hematite but, interestingly, not on silica. The hydrophobicity obtained is governed both by the surface coverage as well as the nanostructure of the adsorbed layer in terms of orientation of the adsorbed species. Surprisingly, even though the above surfactants are non-ionic, their adsorption was pH-dependent. We have correlated this pH dependence to the type of species on the mineral surface. Also it is shown that mixing of these surfactants with traditional ones can help reduce the carbon footprint due to synergy between the reagents and help selectivity due to antagonism. The experimental results were analyzed to get information on optimal pH and dosage conditions, for mineral surface modification. The study provides guidance for mineral treatments using biosurfactants and the potential use of these next generation reagents in mineral processing.

Jan 1, 2014

By Y. Rama Murthy

Around 90% of the chromite resources of India are concentrated in the Boula-Nuasahi Sukinda belt of Orissa state. In order to conserve these valuable ore resources strategically, several companies established chrome ore beneficiation plants in this region. The general beneficiation process in these plants consists of gravity unit operations such as Floatex density separator, spiral, wet shaking table etc. Most of these gravity circuits suffer huge losses of valuable minerals in the tailing. Any attempt towards decreasing these losses would not only increase the limited reserves in India but also make the economics of the operations more attractive. Apart from the liberation phenomena, in many of the operating plants considerable quantity of values are lost in the tailings, due to inconsistent feed quality, inappropriate selection of operating and design parameters. Mineral engineers in this regard have to play a proactive and continuous role to improve the performance of all separating units by modifying even small changes based on tests conducted in laboratory under controlled conditions followed by attempts to make necessary changes in the plant. For such improvements, accurate data collection and proper data interpretation followed by making necessary change which is implementable in an operating plant play a very critical role in performance of the circuit. Databank collected over a period of time under various conditions would also help in overcoming the future problems related to either variation in the feed characteristics or specific demand by metallurgical industries. The above concept was adopted in one of the operating chromite beneficiation plant at Sukinda. The approach adopted and practical problems encountered during the study were reported in this paper. The result of trial campaign has shown that, an overall product assaying 30.2% Cr2O3 from the feed (18% Cr2O3 ) can be produced to in single stage. The final discards of the process contain 12% Cr2O3. Keywords: chromite, chromite beneficiation, chromite losses, gravity concentration techniques, plant operating data bank

Sep 1, 2012

By V. E. Vigdergauz

Possibilities of the analysis of potential energy of bubble-particle interaction on the basis of extended DLVO theory are discussed. Interaction energies of mineral silica, coal and pyrite particles with contact angles from 20 to 100 degrees and air bubbles in neutral and alkaline solutions are analyzed. It is shown that for hydrophilic silica, the formation of particle-bubble complexes (either in the area of primary or secondary potential minima) is impossible due to the high potential barriers (from 6000 to 140000 kT)and low values of the attraction force. There is shown that for coal and pyrite particles the energy of interaction vs. particle-bubble distance strongly depends on pH value. Improvement of floatability of minerals by the hydrophobization of their surface by collectors leads to the eliminating of potential barriers and the formation of the stable complexes of minerals and air bubbles in the area of primary potential minimum. In addition, due to hydrophobization of coal and pyrite changing pH has practically no influence on the energy of interaction. There are discussed results of the numerical calculations of normalized interaction forces in particle-bubble systems on the nanometer distances for pyrite, sphalerite, and chalcopyrite at contact angles up to 85° in comparison with the experimental data. The values of adhesion force for hydrophobized particles of coal and pyrite to air bubbles are about 10-5 N, that indicates stability of the formed flotation complexes. Examples of using the long-range and high-energy effect of hydrophobic interactions for improving minerals floatability are discussed. There are illustrated minerals wettability changes induced by the adsorption of thiol collector and hydrophobic polymer. Possibilities of flocculation and flotation of mineral slimes due the polymer-collector hydrophobic interactions are shown. Keywords: bubble-particle interaction, contact angle, extended DLVO theory, floatability

Sep 1, 2012

By M. F. He

The depression of pyrite in marmatite flotation by a new depressant Sodium Glycerine-xanthate (SGX) has been investigated through microflotation, zeta potential, and adsorption measurements in systems open to the atmosphere. The flotation tests of single mineral show that in the presence of SGX, marmatite can be activated by Cu2+ and shows good flotability, while pyrite can?t be activated and therefore shows poor flotability, as a result these two minerals can be separated using butyl xanthate as the collector. The depression mechanism of SGX on sulfide minerals is discussed based on Zeta potential and adsorption isotherm. Zeta potential experiments demonstrate that at the presence of Cu2+, SGX can strongly adsorb on the surface of pyrite, while it can?t adsorb on the surface of marmatite, thus the results are in accordance with those of flotation experiments; the results of adsorption isotherms show that the adsorption density of SGX on pyrite is greater.

Jan 1, 2014

By Elisabeth Schmidt

The conventional Canadian oil sand processing, the Clark Rowe process, is associated with many risks for the environment and high energy costs. To recover the bitumen from the oil sand (tar sand), large quantities of water have to be heated up and mixed with caustic soda and the oil sand. During this process, tailings with stabilized clay colloids are formed and dumped in tailings ponds. To avoid these disadvantages, a new, non-aqueous extraction process is to be established. Organic solvents are used instead of water and caustic soda to mobilize the bitumen from the sand-clay mixture. Pressure filtration, washing and steam pressure filtration are part of the new concept. A mixture of organic solvents and the oil sand is first pressure filtrated in a nutsch filter until a saturation level of one is obtained. After the cake has been formed, the filter cake is washed with organic solvent to flush the bitumen loaded solvent out of the cake. The following steam pressure filtration mechanically and thermally removes the remaining volatile components of the solvents from the filter cake. The filtrates from the pressure filtration, the washing phase and partly from steam pressure filtration are subsequently thermally treated to recover the organic solvents and obtain a higher bitumen concentration in the mixture. This mixture is then lead to an upgrader to win synthetic crude oil (SCO). The recovery of bitumen in the conventional hot water extraction process based on the Clark Rowe process can, in highly optimized plants, achieve between 88 and 92 %. Variation of oil sand properties leads to an actual range of between 80 and 90 % of bitumen recovery. With the alternative process based on organic solvents, the bitumen recovery exceeds the recovery of the conventional process by up to 16 percentage points. The composition of the two organic solvents in the first step of forming a suspension with the oil sand is important. The aromatic component is crucial for liberating and solving the asphaltenes, which tend to flocculate. The order of the two components of organic solvents is also important in the washing step. The paraffinic component is essential to achieve successful steam pressure filtration with respect to fast steam breakthrough and a filter cake free from organic compounds, as a result of its lower boiling point. Keywords: oil sand, filtration, organic solvents, pressure filtration, steam pressure filtration, filter cake washing

Sep 1, 2012

By I. N. Gridasov, T. V. Ignatova, E. V. Shelepov

"Mikhailovskoye Deposit is comprised of oxidized ferruginous quartzites among other minerals with the former widely spread across the ore field and mined along with unoxidized ferruginous quartzites. PJSC Mikhailovsky GOK strategic development is aimed at iron ore product output expansion. The most critical item of the strategic development road map is process design for separation and concentration of hematite contained in oxidized ferruginous quartzites mined as the by-product in the open pit. Laboratory and semi-industrial tests run to design cost-effective, reliable and environmentally friendly process for Mikhailovskoye deposit oxide quartzites processing included the following processes: - pilot tests of reverse anionic flotation which produced concentrate with Fe60.1-62.9% total iron content and 66-69%Fe recovery rate; - combined magnetic separation and flotation (Marubeni Company, 1982) including slime removal, reverse anionic and cationic flotation and high gradient magnetic separation resulting in 48.9% yield, Fe55-57.5%, up to Fe60.5% hematite concentration ( Fe64.1% being the best result achieved),76.2% recovery. - magnetic separation and flotation, including separation in low gradient (1400 Oe) and high gradient (up to 17000-18000 Oe) magnetic field. The results of these pilots tests were the following: 57-59%Fe concentrate, 70%Fe recovery (Mekhanobrchermet, MGOK, 1982-1988): - magnetic roasting in pilot plant of TSGOK (Krivoy Rog) which produced 61.1%Fe concentrate with 81.5% recovery. Major disadvantage of the method is high generation of dust equal to 20% of the initial feed. Based on third-party studies flotation of oxidized ferruginous quartzites process embracing best processing methods was designed by Metalloinvest Management Company LLC and PJSC Mikhailovsky GOK engineers. This paper discusses analysis of studies aimed at intensification of separation processes with application of mechanical slurry agitation (MSA), addition of alkali (NaOH) and elutriation of initial feed. The paper also provides a design solution to implement a lab-scale MSA plant. It includes feasibility evaluation of MSA inclusion in flotation of oxidized ferruginous quartzites process to enable higher yield and hematite recovery in resultant concentrate. Outcomes of the discussed work have significant value for prospective engineering of OFQ concentration process."

Jan 1, 2018

By V. Hema

Granular materials are widely used in process industries, such as chemical, pharmaceutical, cement, food, detergents, and fertilizers. Mixing, blending, calcining, reduction, heating, and granulation of these materials are frequently carried out in rotating cylinders. In all of these processes, the mixing and segregation of these granular materials is important as this controls the secondary phenomena in the rotating kiln such as heat transfer to the material. A significant amount of work is available in the literature but to date these efforts have not been able to capture the important parameters affecting the mixing and segregation in rotating kilns. In addition, the range of parameter values studied so far is rather limited. Simulations of granular materials are based on either discrete elements or continuum models. The discrete element methods (DEM) combine semi-empirical models for the inter particle interactions with the equations of motion from classical mechanics to simulate the explicit paths of all granules in a rotary kiln, thus yielding realistic predictions of the mixing process. This approach is very demanding computationally, which strongly limits the number of granules and the number of revolutions in a simulation. Continuum models dispense with the discrete particles and can therefore be scaled up more easily. But the constitutive relations that serve as the foundation for continuum modeling are difficult to come by, and often only applicable to specific systems and conditions. Here we have chosen DEM simulation for investigating the mixing and segregation behavior of granular materials in a rotating cylinder. This work is directed towards demonstrating the capability of the prediction of the mixing and segregation behavior of granular materials in a horizontal rotating cylinder through discrete element simulation. Further the effect of particle size and rotational velocity on the mixing and segregation behavior is investigated. The simulation results are quantified in terms of mixing index, mixing rate, segregation index and percolation index. Keywords: DEM simulation, granular mixing

Sep 1, 2012