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By T. Bhambhani, O. Yavuzkan, D. R. Nagaraj

"The recovery of oxide Cu minerals by flotation is a longstanding challenge in the minerals industry, especially for high acid-consuming ores which would not be economical for direct acid leaching. Sulfidization (often using controlled potential sulfidization or CPS) using NaSH (or Na2S) followed by flotation using traditional sulfide collectors is the widely used technique. CPS has certain limitations: a) inability to recover certain oxide Cu minerals because they are refractory to sulfidization, b) high consumption of NaSH (or Na2S), and c) potential health and safety hazards associated with NaSH (and Na2S). Flotation of oxide copper minerals using alkyl hydroxamate (AHX) collector has been studied extensively. Investigations using single minerals and laboratory ore flotation have been conducted in the past to demonstrate the efficacy of alkyl hydroxamates. The technology has been used intermittently in plants. One of the main challenges in plant use has been quantifying the true potential for alkyl hydroxamates for recovery of various oxide Cu species in complex and variable ore systems and identifying the most suitable conditions for optimal use. Quantitative mineralogical analysis using QEMSCAN was used in this study to characterize flotation products lab flotation samples. Analysis of concentrates and tails from hydroxamate flotation and CPS flotation stages demonstrated that certain oxide Cu minerals respond exclusively to alkyl hydroxamates and not to CPS. The hierarchy of interaction of AHX with the various oxide Cu minerals could be inferred from these studies. Finally, these studies also allowed quantification of a group of minerals species, which (erroneously) report as part of the Acid-Soluble Cu [ASCu] but cannot be recovered by flotation, thereby facilitating an estimation of the true recovery potential for alkyl hydroxamate.INTRODUCTIONCopper that is economically recoverable occurs in three major types of ores, which are defined by the modal mineralogy of Cu. For sulfide ores, Cu occurs as sulfide minerals and is satisfactorily recovered by flotation using sulfide collectors. Non-sulfide ores, which contain Cu in the form of oxides, phosphates, carbonates and silicates, described in the industry as “oxide” ores (or ores containing “acid-soluble” Cu or ASCu), are currently treated using hydrometallurgy, which involves leaching with dilute sulfuric acid followed by solvent extraction and electrowinning, unless the ores contain acid consuming gangue minerals such as dolomite. For mixed sulfide-oxide ores (i.e. containing both sulfide and oxide Cu minerals) that do not contain acid consuming gangue minerals, Cu values are easily recovered by flotation of sulfide Cu minerals followed by leaching of oxides (only when a leach plant is available). However, when the ore contains acid consuming gangue minerals flotation is required to recover both sulfide and oxide Cu minerals."

Jan 1, 2018

Nowadays, the more successful plants are those who have adopted effective and efficient strategies to optimise their plant operation. As the ?heart of the plant? could be viewed as the mil-ling/grinding area, one of the key steps in plant optimisation is, therefore, ensuring the mill is operating properly. In the past, when primary, secondary and tertiary crushers fed material directly to large ball mills, the energy efficiency of the concentrator was determined for the most part by the ball mill operation, whereas now the energy efficiency of a plant often rests largely on the semiau-togenous grinding (SAG) mill operation. As a result, mines have shifted their emphasis in optimization from ball mills to SAG mills. The grinding mill?s energy efficiency essentially depends on ore characteristics and the discharge rate of broken particles, which in turn depends on how efficiently the discharge pump (grate and pulp lifters) operates. The essential function of pulp lifter being to transport the broken material and slurry out of the mill, its design optimization therefore affects the discharge capacity (or mill throughput) of AG and SAG grinding mills. This paper will discuss how the optimised design of the pulp lifter/ discharger has helped to eliminate material transport issues such as flow-back and carry-over of slurry and pebbles to in-crease the energy efficiency of SAG mill using the actual operational data.

Jan 1, 2014

By M. Prasad

Growing concern over increased levels of atmospheric carbon dioxide has prompted new interests in development of materials and techniques for its sequestration. Various research and developmental work on different aspects of carbon capture technology are being extensively carried out worldwide. The main objective of the present work is to synthesize a HAS material having high capacity and robust ability for recycling to capture greenhouse gases with special reference to carbon dioxide (CO2) from the sources from where it is released to the atmosphere. Existing CO2 capture techniques involves the use of solid materials that lack sufficient stability for repeated use or liquid adsorbents that are expensive and require significant amounts of energy. Keywords: greenhouse gases, carbon capture, solid adsorbent, HAS material

Sep 1, 2012

By W. Z. Yin

With increasing of mining depth, many iron ores in Liaoning Province contain carbonates such as siderite and ankerite. The emergence of these carbonates in ores creates a fatal impact on the running producing process of anionic reverse flotation in Dong Anshan Sintering Plant, which leads to ?concentrate and tailing no separated?. And its reason is still unknown. Moreover, siderite, despite that its ferric theoretic grade is only 48.2%, however, do not affect the blast furnace utilization factor, therefore, can be used as raw materials in ironmaking. In order to solve the separate problem of iron ore containing carbonates, five pure minerals, martite, magnetite, quartz, siderite and ankerite, were selected for a series single flotation experiment. The aim was to discover the flotation difference of these minerals, furthermore, to explore a new flow sheet for the iron ore containing carbonates. The results of single mineral flotation experiment reveal that the combination regulators, starch and CaCl2, in different pH extent, can make these minerals taking on obvious flotation difference, which make it possible to process the iron ore containing carbonates. A new flow sheet, step-flotation, to process iron ore containing carbonates is explored, that is, first step, direct-flotation processing, is to eliminate the bad effect that the carbonates bring in flotation system by collecting carbonates under neutral condition; the second step, reverse?flotation processing, is to get qualified iron concentrate by collecting quartz under alkaline condition. Manual mixed ore sample were processed successfully through this new flowsheet under proper reagent system, which has absolute advantage compared with routine flowsheet. Actual ore sample of compound magnetic separation concentrate were processed successfully both open and closed circuit experiment through this new flowsheet. SEM and EDS were used to probe the reason why carbonates affect the regular processing. It is analyzed that moderate floatability of siderite and its coating on the surface of hematite and quartz make the phenomenon ?concentrate and tailing no separated?. This research provides a reasonable processing scheme for iron ores containing carbonates and can be used for reference in processing other complicated, refractory iron ore.

Jan 1, 2014

By Ying Gu

Automated mineralogy methods and tools, such as the Mineral Liberation Analyzer (MLA) and the QEMSCAN, are now widely used for ore characterization, process design and optimization. Several case studies published recently demonstrate that large gains can be obtained through grinding and flotation optimization guided by automated mineralogy data. However, since automated mineralogy can only provide the information pointing to where the process gains can be made, it does not directly impact the production gain. Thus, a question is often asked: how to value the contribution of automated mineralogy to process improvement of a particular plant. This appears to be a difficult question. On close examination however, it is found that this is essentially a question of the value of information and it is reasonably well documented in various other industries. Hubbard (2010), in chapter 7 ?Measuring the Value of Information?, dealt with exactly this type of problem. The value of information is the reduced risk of an investment and opportunity loss. The methods Hubbard developed can be applied to estimate the value of automated mineralogy, as well as metallurgical test work, which also produces information that reduces the risk of investment. This paper first introduces Hubbard?s theory on the value of information and how to measure it. It then applies his methods to estimate the value of automated mineralogy, using Anglo Platinum?s fine grinding project as an example. In this case, the value of automated mineralogy includes the reduction in investment risk worth US$ 62.5million, in project rejection worth US$197 million and in opportunity loss worth US$320 million. In the end, a general model is developed to allow the simulation of the value of automated mineralogy in different mining operations constrained by different parameters.

Sep 1, 2012

By Mingfei He, Xianyang Qiu, Hongling Wang, Yude Gao, Qingbo Meng, Xiaoping Xu, Hao Bu, Guosheng Wang

"By the “HGMS-gravity separation-Flotation” combined technology, a Ta-Nb-Sn concentrates with the grades of Ta2O5 10.00%, Nb2O5 9.13% and Sn 42.62% at the recovery of 44.73% , 9.13% and 14.62% respectively , a Li concentrate with Li2O 3.11% at the recovery of 51.83% and a feldspar product are obtained. All the value elements are recovered. INTRODUCTION Tantalum and niobium widely used in electronics, atomic energy, aerospace and chemical industries with the advantages of high melting point, good ductility, low vapor pressure, strong corrosion resistance and high thermal conductivity are important strategic resources which occupy a special position in rare metals (Crockettand, 1993; GAO and Zou, 2004; LI and HUANG, 2012). China's tantalum and niobium resources are poor, and most of them are low grade, fine grain size, complex composition, and polymetallic associated with refractory mineral resources (GAO and Qiu,2013; Liang and Li, 2016). The Yifeng Lion Ore containing lithium and other rare metals (tantalum, niobium and tin) is an important lithium polymetallic deposit in China Jangxi province. While extensive previous studies have settled on the recovery of lithium minerals by flotation only for the extremely low grade of Ta, Nb and Sn. The regular gravity concentration is used, and the recovery of tantalum niobium is low. This paper sets out to investigate a combined flowsheet of “high gradient magnetic separation (HGMS),-gravity separation-flotation” to effectively comprehensively recover the Li, Ta, Nb, Sn and the feldspar resources in the Yifeng Lion Ore.ORE PROPERTIES Chemical analysis The run of mine comes from Jiangxi Yifeng Lion ore. The main elements of the ore chemical analysis results shows in Table 1. From Table 1, the grades of lithium and rubidium are relatively high, but the grades of tantalum and niobium are lower than the industrial grade; feldspar with high content of potassium and sodium and low content of iron can be used as high-quality ceramic raw materials."

Jan 1, 2018

By S. Z. Shafaei

An experimental investigation has been carried out using a laboratory scale Denver flotation cell. For evaluation of cokeable coal of Alborze Sharghi coal washing plant, the full factorial method was used to statistically design and analyse the experiments. The 2 factorial interaction model were developed for combustible recovery and ash content as response and diesel dosage, conditioning time, feed percent solids and rotor speed as factors. Model validation and residual analysis were con-ducted and results indicated that the fitness, predictability power and residual distributions of models were good. The effect of parameters and interactions were examined and it has been demonstrated that rotor speed, solid percent and interaction between diesel dosage and solid percent were more important terms of all responses. A product with approximately 78% combustible recovery and 10% ash content was obtained at 4000gr/ton diesel fuel oil (high level), 30 sec conditioning time (low level), feed percent solids of 15% (low level) and 800 rpm rotor speed in appropriate condition.

Jan 1, 2014

By Georges Delemontex, Nigel Grigg

"Pre-concentration of precious metal and base metal ore types is becoming more relevant with the discovery, development and operation of many lower grade deposits around the world. The fluctuations in metal prices and currencies expose many mines to risks especially dealing with low and variable ore grades. Pre-concentration, the process of concentrating the valuable metal into a smaller mass yield, effectively results in the introduction of higher feed grades to milling circuits. Gangue rejection, the removal of lower S.G. waste rock from the circuit, not only results in higher downstream grades but also potentially removes harder, non-valuable mineral, providing significant power savings within the circuit. The pre-concentration or ‘gangue rejection’ process offers a number of benefits when considering the treatment of marginal ore deposits, especially if it can be performed at a coarse crush size; these benefits include a reduction of the operating costs and the feed of more metal units to the mill. Gekko Systems has effectively utilized the Inline Pressure Jig (IPJ) to pre-concentrate the valuable metal, achieving high primary recoveries into a range of mass yields resulting in upgrade ratios between 2 and 10 times. This paper explores: the benefits of pre-concentrating ‘marginal’ ore deposits prior to the milling circuit; the selective rejection of ore types that may affect either the recovery or comminution process; and also looks into the potential to effectively reduce the ‘cut-off’ grade when considering the mine planning process. Case studies of projects using the IPJ to pre-concentrate and reject gangue are also included. Pre-concentration and gangue rejection provide the potential to develop marginal ore deposits, thus providing higher grades, less gangue and more metal at a lower operating cost to producers."

Jan 1, 2014

Large quantities of electrical and electronic equipments are discarded at the end-of-life (EOL) in different industries and house hold applications. Their disposal is creating a challenging environmental problem due to the presence of hazardous metals and non-metallic materials such as epoxy resins and plastics including brominated flame retardants etc particularly in printed circuit boards (PCBs). The recovery valuable metals and separation of hazardous materials from discarded PCBs will not only conserve the resources but also mitigate the environmental pollution. From a recycling point of view for a sustainable society, the studies have been carried out for the recovery of metal values from EOL-PCBs of DVD video players (DVD-PCBs) and vacuum cleaners (VC-PCBs) using physical beneficiation techniques. The concentration of the metals was found to be 43 wt.% and 30 wt.% in DVD-PCBs and VC-PCBs, respectively. Both the PCBs samples were ground in a hammer mill after cutting and their size analysis was carried out. The liberation of the metallic and non-metallic fractions was investigated under the microscope for different size fractions. Subsequently, froth flotation and pneumatic air separation studied were carried out to enrich the metallic constituents. The studies showed the enrichment of metals in coarser particles (-1000 +150 µm) and non-metals in the finer particles -150 µm following mechanical recycling process. A grade of 90 % with 75% recovery was achieved by froth flotation, but lower grade and recovery of 75% and 65% respectively were obtained by pneumatic separation with -1500 µm powders for DVD-PCBs. A grade of 86% metal was obtained by froth flotation with 76% recovery in the case of VC-PCBs. The lower grade of 65% with almost same recovery was achieved during pneumatic separation studies due to lower concentration of metals in VC-PCBs. The studies also showed that the froth flotation is an efficient process for enrichment of metals from both the samples. The process is environmental friendly as no chemicals are employed during entire processing. The higher recovery and grade of metal is expected to be obtained on a large scale beneficiation process.

Sep 1, 2012

By H. Kasaini

Batch wise adsorption tests for platinum (Pt) on the surface of activated carbon pellets (Norit RO 0.8 BET surface area 1100 mg/g) were carried out in mixed chloride solution. The purpose of this study was to assess and compare the adsorption performance of amine-treated activated carbons (AACs) and native activated carbons (NACs) in terms of adsorption capacity and selectivity. The effect of pH and temperature on adsorption capacity and selectivity was established. The amine- treated ACs were prepared by anchoring the amino groups (butyl amines) on the surface of AC pellets in aqueous media and the UV-Vis was used to determine the amount of amine sequestered from solution by ACs. The dosage of butyl amine on the surface of ACs averaged 0.15 g/g, carbon. The adsorption mechanism was described by the ionization and complexation model whereby interaction between the protonated AAC surface and the anionic chlorocomplex ions (PtCl5 [H2O]-, PtCl62-) proceeded by either electrostatic attraction or/and by covalent bonding [(NH3)2PtCl6 or (CH2COO)2PtCl6]. By comparison, the adsorption capacities of Pt on amine-treated ACs and native ACs were 53.8 mg/g and 33.03 mg/g, respectively which highlight the benefits of anchoring functional molecules on ACs. The selectivity of AACs was influenced by solution pH. Pt adsorbed selectively on the surface of amine-treated ACs at pH<1.5. The highest separation factor that was recoded pertained to Pt and Fe species (ßPt/Fe = 90) then followed by Pt and Ni species (ßPt/Ni = 30) or Pt and Cu species (ßPt/Cu = 15). The lowest separation factor was recorded for Pt and Cr ions (ßPt/N= 5). Adsorption kinetics of Pt on amine-treated AC surfaces, according to the first and second order reactions, were investigated and results showed that rates were in the order 10= 5). -4 min-1 and 102 g?min/mg, respectively. The pseudo 1st order kinetics predicted the adsorption capacity of 51.81 mg/g which was almost similar to the experimental value (53.8 mg/g) while the second order rate equation predicted Pt adsorption capacity of 40.1 mg/g. Both The Langmuir and Toth isotherm fitted the Pt adsorption at pH < 1.0. The Freundlich isotherm tended to underestimate the adsorption capacity of AACs.

Jan 1, 2014

By R. Venugopal

Hydrocyclones have been used extensively for more than 100 years to classify mineral slurries for recirculation in grinding circuits. Sometimes hydrocyclone classification is carried out in more than one stage to improve the efficiency of classification. Factors affecting separation efficiency include fluid velocity, density, and viscosity as well as the mass, size, and density of the particles. The geometric configuration also affects its efficiency; it includes parameters like cyclone diameter, underflow and overflow diameter, position of vortex finder, height of the cyclone, feed inlet geometry, and diameter etc. Besides changes in the basic parameters some modifications in cyclone has also been introduced from time to time which have affected its efficiency, some of these are :-(i).Introduction of magnetic force along with the centrifugal and drag force to control the flow of the magnetic particles inside the chamber.(ii). Introduction of sparger, air is introduced in the chamber in the form of bubbles, to control the flow of fine particles and hydrophobic particles. (iii). Introduction of dilution technologies for the dilution of thickened underflow. (iv).Introduction of new model. In spite of wide use and simple geometry, the real working principle of hydrocyclone chamber is extremely complex because of the swirling turbulent flow inside the device. In order to get more knowledge about hydrocyclones and to increase its efficiency, past 10-15 years simulation techniques are being developed. The simulation models also enabled a deeper insight into the static and dynamic behavior of hydrocyclones. Therefore, more emphasis on simulations by methods like Computational Fluid Dynamics (CFD), Finite Element method (FEM) is given. Overall, a status review of the work carried out on the analysis of hydrocyclone performance, modeling approaches and its contribution in the efficiency of mineral processing operation is highlighted.

Sep 1, 2012

By A. A. Lavrinenko, N. I. Gluhova, L. M. Sarkisova, D. V. Makarov

"The purpose of the study is to study the feasibility of using sodium diisobutyl dithiophosphinate (DDP) to enhance the recovery of platinum group elements from low-grade refractory copper-nickel ores characterized by a portion of nickel and platinum group elements (PGEs) locked in the dominant sulfide mineral — pyrrhotite. These ore characteristics dictate the need to produce a bulk PGE-containing sulfide concentrate due to the difficulties of producing selective concentrates without a significant loss of the metals.New data on the adsorption and flotation performance of DDP-containing collectors were obtained by measuring the electrode potential, hydrophobicity of the sulfide mineral surfaces and by means of extraction spectrophotometry and flotation studies. The interaction between DDP, pyrrhotite, and pentlandite leads to the formation of surface hydrophobic layers consisting mainly of disulfide and a small amount of metal compounds. These adsorption layers are formed by the reaction with butyl xanthate. In the case of cooperite, DDP reacts with the surface, forming not only disulfide, as in the case of butyl xanthate, but also a complex platinum compound. DDP-containing agents demonstrate stronger collecting properties with respect to sulfide minerals of copper-nickel ores compared to butyl xanthate, which is explained by a stronger hydrophobizing effect and foaming properties.The addition of a combination of DDP-containing agents and butyl xanthate at a ratio of 3:1 for the recovery of sulfides and PGEs in the bulk flotation of copper-nickel ore made it possible to improve the recovery of Ni, Pt, and Pd by 13.6, 9.2, and 9.4%, respectively, relative to the recovery achieved in flotation with butyl xanthate.Bulk flotation with the addition of a composition of DDP-containing agents and butyl xanthate allows the most complete recovery of all valuable elements and is the only technologically feasible method for processing of lowgrade ores, when it is impossible to produce without loss high-grade selective concentrates suitable for smelting."

Jan 1, 2018

By Robin B. Batterham

"Since the 1970?s we have seen a marked corporate response in terms of the environment. In part this has come from regulation but it has largely come from stakeholders and the community. Rising expectations have in general been met. We now see a similar trend towards sustainability. At the same time, the importance of mining to the share market has decreased drastically and with that decrease has come the requirement for the mining sector to show returns similar in manner to other sectors. While rationalisation can achieve some progress towards these goals, the long-term requirement is for innovation, as it always has been. This paper looks to the logical goal of innovation within a sustainable mining framework and targets the removal of the desired metal values with minimal environmental footprint. It is suggested that broad ranging alliances will be necessary, particularly amongst the R&D suppliers, to achieve this goal. Industry will need to take an active role given the recent global restructuring.THE MARCH TO SUSTAINABILITYSince the 1970?s there has been an increasing corporate response on environmental matters. We have moved from matters environmental being issues relevant only to minority groups through a series of attitudinal changes by management. Whilst there have always been examples of excellent environmental performance, for many in the 70?s spending money on improving the environment beyond some minimal level was seen as a distraction from production or treated in a similar way to donations to the community. There is little of that attitude these days, as most mining companies have long since regarded the environment as a core business direction. Indeed, for some years one could note an escalation in matters of environmental reporting to the extent that the environmental performance of companies is now very public. In some cases, NGOs have even been invited to help certify and audit the reporting standards. Similarly with health & safety.There is now a rising expectation on the part of the community that social matters will also be given the same level of support as health, safety and the environment. This time around it would appear that the mining industry is at the leading edge of sustainability. The Global Mining Initiative (Global Mining, 2002) and the contributions to the Rio World Summit on Sustainable Development (Rio +10, 2002) suggest that sustainability is being taken very seriously by the mining industry. For sustainability it is convenient to use the Brundtland (1987) definition. This definition has widespread acceptance with governments, industry, environmental groups, financial institutions and individuals as a direction against which our activities and plans can be measured."

Jan 1, 2003

By N. Schreithofer

Varying flow regimes, particle populations and consequently different types of bubble-particle interactions characterize the different zones of a flotation cell. The understanding of the role of the different zones of turbulent intensity on the particle-bubble interactions is of primary importance to optimization and scale-up of flotation processes and machinery. In order to study particle-bubble interaction in turbulent flow a completely new approach was taken. A laboratory scale stationary turbulence device was developed and built. The set-up allows the observation of particle-bubble interactions in various turbulence intensities, particle and bubble sizes and surfactant concentrations. The experimental set-up consists of a transparent, specially designed tank in which liquid flows between carefully designed and placed obstacles that create different turbulent flow fields. Bubble-particle aggregates are introduced into this turbulent zone. The behaviour of the aggregates, such as attachment /detachment of particles to/from air bubbles is recorded by a High Speed Imaging (HSI) system (5400 fps). The images are then analysed and the dependence of attachment/detachment process is described as a function of turbulent intensity in different conditions for different surfactant concentrations. This paper introduces this method to study particle-bubble interactions in turbulent flow and correlation to Computational Fluid Dynamics (CFD) simulation. CFD modelling is validated for two and three phase systems; liquid-gas with liquid and solid tracers respectively. The CFD simulations using the RANS k-S turbulence model showed good correlation to the experimental data and the experimental method is a promising tool for investigation of particle-bubble interaction in turbulent flow.

Jan 1, 2014

By S. Castro, L. Gutierrez

"Mining operations are often located in remote arid environments with limited access to fresh water. Shortage of fresh water in such cases makes it necessary to use seawater in mineral processing plants. Such plants treating Cu- Mo sulfide ores in seawater have been fully operational in Chile (e.g. Las Luces, Centinela). In many cases process waters used in commercial flotation plants (e.g. Mt Keith in Western Australia) are even more concentrated electrolyte solutions than seawater. This paper is an attempt at classification of the flotation operations carried out in process waters that are concentrated electrolyte solutions.INTRODUCTIONAccording to Gleick (1966), of the total Earth’ water resources 97.5% is in the oceans and ice caps, and thus only about 2.5% is fresh water. Shortage of fresh water in many parts of the world makes it necessary to use seawater in mineral processing operations. The existing commercial operations using seawater as well as recent research projects that deal not only with sulfide ores but also with apatite ores provide a lot of information that can now be generalized. The progress that has been made in this area is reviewed and based on this information an attempt is being made at classifying the flotation operations carried out in highly concentrated electrolyte process waters.SALT FLOTATIONFlotation in highly concentrated electrolyte solutions was studied by Klassen (Klassen, 1963). He reported that hydrophobic, bituminous coals, could float in salt solutions without addition of any other flotation agents. The process is referred to as salt flotation. Other inherently hyhrophobic minerals (e.g. talc, graphite, sulfur, etc.) were shown to behave similarly (Klassen and Mokrousov, 1963)As Figure 1 shows, some coals float quite well in solutions of Na2SO4, NaCl and NaNO3 (Klassen, 1963). While there are differences between the tested salts (explained by different foamabilities of these solutions) all the tests indicate that only bituminous coals float well in concentrated electrolyte solutions. 0.3 M solutions are quite sufficient to initiate a good and very fast flotation. If wettability of various coals is compared it becomes obvious that these well floating coals are very hydrophobic bituminous coals (Figure 2)."

Jan 1, 2018

By A. K. Suri

India plans to increase the nuclear power share in overall energy-mix to about 30% by 2032 using both indigenous and imported reactor technologies. In the immediate time-frame, it is envisaged to generate 10000 MW electricity by PHWR technology by 2020 using indigenous uranium resources. This necessitates setting-up of new uranium mills and augmenting the existing resource, mining and milling capacities. This paper describes the current status and future R & D needs towards achieving the targeted demand of yellow-cake. Keywords: uranium, hydrometallurgy, leaching, yellow cake

Sep 1, 2012

By F. J. Sotiuo

Variability of the quality of phosphate ore feed to the flotation plant has been of great concern for the industry. This variability sometimes resulted in 10% to 50% decrease of P2O5 recovery, a reduction of P2O5 concentrate grade and/or both due to depression of the system. For this investigation, samples of refractory ore and easy-to-float ore were obtained from the same mining area in Central Florida; and then submitted to bench flotation tests using fatty acids (FA). To understand the cause of difference in flotation behavior of these apparently similar ores (grade, mineralogy, and physical appearance), bulk and surface characterization studies were conducted. Based on the results of characterization studies and bench flotation tests on both refractory and easy-to-float samples, it was possible to determine FA surface coverage. It was found that the surface coverage for the refractory ore was between 6.9% and 9.8%, corresponding to 0% and 80% recovery, respectively; whereas the easy-to-float ore showed surface coverage of 17.2% (89% recovery) to 24.6% (98% recovery). Since size analysis, surface area and pore size measurements showed small differences, it was thought that the surface coverage differences could be caused by the ad-sorption of natural compounds onto the phosphate ore surfaces, depressing the system. SEM, EDS, and Leaching and Solvent Extraction (LSX) studies were performed on the phosphate ores to demonstrate the proposed mechanism. This paper summarized our characterization studies, flotation results, and findings. The study showed that the new identified compounds were responsible for the flotation behaviors of the Florida refractory phosphate ores.

Jan 1, 2014

By E. Scheepers

The process under investigation is the large-scale production of phosphorus. Gravity delivers the feed, consisting of pelletised apatite, coke and silica (in the form of gravel), to a submerged arc furnace through ten, evenly distributed feed chutes ensuring constant packed bed volume. Within this packed bed, solid-gas reactions are dominant in generating the gaseous product. These reactions, as well as the packed bed itself, were the main focus in the development of a fully three-dimensional CFD model in which fluid flow and energy distribution are represented as functions of chemical reactions, heating and melting of material and heat losses. The associated complex process interactions necessitated the creation of two process-specific, user-developed models that integrates accurate, thermodynamical data with computational fluid dynamics calculations, as well as reaction kinetics. The boundary conditions are provided by industrial measurements, and the key model parameters of reaction kinetics were obtained by laboratory experiments for different feed mixtures. Thirteen temperature probes installed inside the refractory lining of the furnace especially for this project allowed parameter fitting and validation to be guided within the constraints of real measurements. Simulation results reveal a thin, dome-shaped, reductive zone where conditions are optimum for maximum phosphorus recovery, as well as evidence of a thermal reserve zone similar to an ironmaking blast furnace located above this reduction zone. When compared to actual operating data, the CFD model can successfully predict the specific power consumption, the phosphorus in the slag and gaseous product flowrate under given operating conditions. This CFD model forms part of a larger project that aims to create a Dynamic-CFD hybrid control model.

Jan 1, 2014

By T. Kumaresan

The Bayer process used for refining bauxite to smelting grade Alumina serves as the linchpin of the Aluminum production industry worldwide. Even though the process is well established, the presence of impurities in the liquor affects the quality of product and imposes a major economic cost on the industry. This review article focuses on the issues pertaining to Gibbsitic (Al2O3.3H2O) precipitation circuit. The comprehensive review provides a basic understanding of the aluminum trihydrate precipitation and agglomeration phenomena. Crystal growth rate and agglomeration play a significant role in determining the output PSD of agglomerates. Hence, the effect of certain thermodynamic and hydrodynamic parameters along with the impact of impurities (oxalates, aldols, acids etc.) and additives on hydrate growth has been reviewed.

Sep 1, 2012

By E. Burdukova

This paper explores the relationship between the rheological behaviour and mineralogical nature of three different natural ore types. Rheological measurements performed here on Platreef, Kimber-lite and Norseman-Wiluna ores are correlated with the variation of phylosilicate mineral content in these ores and the corresponding physical properties of selected phylosilicate mineral groups. Preliminary results show that the clay mineral group (talc) has the least effect on both Bingham yield stress and viscosity of the three ore slurries tested, whereas the serpentine mineral group has a dramatic increasing effect on the Bingham yield stress especially at very low solid volume fractions. The Bingham viscosity of the mineral slurry appears to be the most influenced by the presence of the swelling clay mineral group (smectite). Significant increases in either Bingham yield stress or viscosity due to elevated contents of these problematic phylosilicate mineral groups are likely to cause negative effects on the processing and manageability of mineral slurries but it is unclear which is likely to have a more detrimental effect.

Jan 1, 2014