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By L. Gao, X. Gui

Fine coal obtained from Kailuan mine served as the processing object of this study. This material was difficult to separate. A flotation rate experiment was designed to investigate the process distribution characteristics of size and density during fine coal flotation. Size and density analyses of five clean were studied. The mineral morphology of flotation rate experiment cleaning was observed through scanning electron microscopy. The fractions -0.074+0.045 mm and -0.045 mm exhibited the best practical floatability and presented the highest combustible body recovery rates, but the selectivity and natural floatability of these two fractions were the worst. The - 0.074 mm fraction has contaminated the clean coal from the early stage of flotation, and the cumulative clean coal ash of -0.074 mm reached up to 17.20%. The low and middle-density classes displayed varying flotation behavior, but the flotation yield difference was only nearly 3%. The middle-density class caused the clean coal to have high ash content. The poor selectivity of fine coals, middle-density fraction, and fine mud resulted in high-ash clean coals during flotation. Thus, improving the selectivity of fine coal, restraining the flotation of fine mud, and grinding the coal to decrease the middle density mass fraction to liberate clean coals can yield high-quality clean coals through flotation.

Jan 1, 2014

A processing scheme is presented to use one single chemical that has multiple functions to re-duce the use of chemicals and achieve more efficient mineral flotation and solids dewatering. Sti mulisensitive polymers which display hydrophilic/hydrophobic transitions in response to changes in temperature or pH have been found to be useful as such multiple function reagents. They can cause the mineral particles to be either hydrophilic or hydrophobic at one stimuli condition and the opposite at the reverse stimuli condition. Therefore, both particle surface wettability and inter-particle interaction forces are reversibly controllable. When the surface is hydrophilic, particle dispersion is achieved by repulsive inter-particle forces whereas when the surface is hydrophobic, particle aggregation is induced by inter-particle hydrophobic attractive forces. In addition, the hydrophobic surface condition allows for the attachment of particles to bubbles. Flotation and solid settling tests have been conducted with a silica suspension treated with the temperature-sensitive polymer poly (N-isopropyl acrylamide) (PNIPAM). The results indicated that PNIPAM can be used to induce a transition between hydrophilic and hydrophobic surface character at temperature lower or higher than its critical solution temperature (CST around 32oC). Thus, both effective silica dispersion or hydrophobic aggregation and flotation without adding any additional collector have been demonstrated. In tailings treatment, rapid silica settling was obtained with hydrophobic aggregation at temperature above the CST and further sediment consolidation (and water release) occurred at temperature below the CST. Contact angle measurements confirmed the hydrophilic/hydrophobic transition induced by PNIPAM.

Jan 1, 2014

By M. S. Prithvi

Over the decades, mine and mineral processing plant operations for the most part, have been found to have had adverse impacts on the environment. At the same time, mineral processing and mining operations produce mineral products that are indispensable to modern society. Thus, the sector has desirable and undesirable attributes simultaneously. The situation presents itself as a contradiction (i.e.) the mineral processing and mining operations are wanted by society, and at the same time unwanted by society. The existing methods of addressing the issues raised above have evidently not been very successful in reducing the opposition to new projects and to the related activities such as land acquisition. This paper attempts to show the relevance and applicability of TRIZ for addressing the issue. TRIZ, or Teoriya Rezheniya Isobretatelski Zadach, is a Russian acronym meaning Theory of Inventive Problem Solving. TRIZ is a powerful tool that can be usefully applied to resolve such contradictions, using resources usually available within the system of interest. Accordingly, this paper introduces the issue background, followed by an introduction to some key concepts of TRIZ such as the 40 principles, separation principles and directed evolution. The paper goes on to apply the 40 principles to two case studies. The results show that TRIZ could be a useful tool to generate potentially innovative and sustainable approaches. Its most appropriate position would be as a supplement to current decision-making procedures, and as a validation tool to review existing solutions for possible improvements. Keywords: minerals, environment, TRIZ, contradiction, resources

Sep 1, 2012

By Pramila Misra, Jibardhan Meher, Debadutta Das

The concentrated coal-water slurry has been receiving considerable attention recently due its ability to replace fossil fuels. Attainment of stable and concentrated slurry has been succeeded so far through several physical and chemical techniques. The present article reports the formulation and stabilization of a highly concentrated coal-water slurry formed from five varieties of non-coking coals with variable ash contents obtained from Eastern part of India, employing three varieties of starch esters, such as starch benzoate, starch formate, and starch carbamate as dispersant. The apparent viscosity of the modified coal-water slurry has been measured by varying coal loading, dispersant percentage, pH, temperature, etc. The apparent viscosity of the slurry has been found to be decreased substantially on addition of 0.8% of adsorbate in the slurry. The particle-particle interaction has been considerably decreased and stable concentrated coal-water slurry containing high weight fraction of coal (61.5-63.5%) has been achieved in each case. The slurries stay in a non-settling form for about a month with viscosity in a permissible low range. The coal-water slurry has been found to behave as a non-Newtonian liquid. Comparison of the zeta potentials of the naked and modified coals evidences that adsorption of the dispersants at coal-water interface results in inhibition of the agglomeration of coal particles through mostly steric repulsions.

Jan 1, 2014

By Yimin Zhu, Dezhou Wei, Haijun Liang, Zhifu Zhou

It has been fairly well established by many experiments that Thiobacillus ferrooxidans (T. ferrooxidans), also named Acidithiobacillus ferrooxidans(Kelly and Wood, 2000),can depress the floatability of pyrite. However, the mechanisms governing the process have not been known completely. In the present investigation, wettability and electrokinetic studies were carried out to examine the surface chemical changes on pyrite before and after interaction with T. ferrooxidans or its secretions. Attachment of T. ferrooxidans to pyrite was observed using a scanning electron microscope. The results of experiments showed that, under certain conditions, T. ferrooxidans and its secretions would obviously change the surface electricity of pyrite and result in the iso-electric point of pyrite shifting notably. However, the surface wettability of pyrite hardly changed and its hydrophobicity increased little after interaction with T. ferrooxidans and its secretions. Based on the results of the present investigation it can be reasoned that the depression of floatability of pyrite is due to the reduction of surface free energy, rather than the increase of surface hydrophilicity of pyrite. The decrease of surface free energy weakens the attachment of collector to pyrite; during the process bacterial protein plays the most important role and the bacterial chemotaxis strengthens the effect.

Jan 1, 2003

By Kamalendu Bhunia

With the progressive depletion of known resources of good quality coal and minerals as well as the increasing demand of these minerals by different user industries, the emphasis has been shifted all over the world from selective mining to bulk mining followed by up- gradation to obtain the required quality of concentrate. The column flotation cell is one of the alternatives to reduce the gangue content of fines because of its inherent characteristics viz. easier to operate, low space required, no moving parts etc. A laboratory flotation column is used to conduct experiment. Present work has been undertaken to observe the effect of process variables (gas flow rate, feed/slurry flow rate, and frother concentration) on gas dispersion parameters (gas holdup, bubble surface area flux) in collection zone and to explore the effect of feed (slurry) inlet orientations and gas flow rate on column?s metallurgical performance. The effects of solid particle concentration, size and type (hydrophobic and hydrophilic) of solid on gas dispersion parameters have also been investigated. Test work has been performed in a continuously operating Perspex column (10 cm in diameter and 168 cm in height) using coal, sphalerite and dolomite as solid. Gas hold-up has been measured by phase separation method and mean bubble sizes are estimated from a drift flux analysis. The influence of operating parameters on bubble surface area flux has been discussed. It is observed that gas holdup in collection zone is affected by air as well as feed flow rates and also solid?s type. It is also found that addition of solid decreases the gas holdup and rate of decrease in gas holdup increases when solid concentration increases and particle size increases. Increase in gas flow rate increases recovery in collection zone due to increase in number of bubbles per unit volume of the column. From the experimental results it is evident that cross-current orientation of feed inlet shows slightly better metallurgical performance compared to other orientations. Keywords: column flotation, gas holdup, drifts flux, bubble size, bubble surface area flux, hydrophobicity, and recovery

Sep 1, 2012

By B. McFadzean, P. E. Ngoepe, P. P. Mkhonto

"The theoretical technique of computational modeling and the experimental determination of the enthalpy of adsorption of a ligand molecule onto a mineral surface deliver the same output parameters and, therefore, complement each other in investigating the affinity of different ligand types for mineral surfaces.This study ran parallel experimental tests and computational calculations to determine the enthalpy of adsorption of a series of increasing chain length xanthates onto a pyrite surface. The outcomes showed that, while the absolute energy values were different, the trends were similar. Both computational and experimental approaches showed that the extent of the interaction of the xanthate molecule increases with increasing carbon chain length. The computational values were larger than the experimental values, which could be explained, in part, by the addition of water to the computational system, which resulted in a decrease in the heat of adsorption on the (100) surface, compared to the adsorption of the collector in a vacuum. The computational method showed that, in the case of the pyrite (100) surface, the most exothermic reaction was obtained when the two xanthate sulfur atoms bridged two pyrite 5-coordinated iron atoms. The (111) surface was found to be more reactive and different adsorption mechanisms were predicted for each of the C2, C3, C4 and C5 chain length xanthates.The experimentally determined exothermic increase in heat of adsorption for the addition of each CH2 group was found to be -8.17 kJ/mol. The contribution of the thiol head group was -34.9 kJ/mol. Previous studies on self-assembled monolayers have shown that these values are compatible with lateral interactions between CH2 groups and the exclusion of water. This study provides a rigorous experimental and computational approach which is intended to afford confidence in modelled data for the screening of new ligands for flotation processes.INTRODUCTIONComputational modelling is a fast and cost-effective method of screening collector molecules for the efficacy of their adsorption onto mineral surfaces. However, it is desirable to measure the computational outputs against experimental outputs to check for congruency. Computational modelling and experimental microcalorimetry both deliver the same output parameter: the energy of adsorption of the molecule onto the solid surface. These techniques are therefore ideally suited to complement one another in investigating the affinity of the interaction between collector molecules and mineral surfaces."

Jan 1, 2018

By B. Y. M. Bueno

Biosorption of heavy metals can be an effective process for the removal of heavy metals ions from aqueous solutions. In this study, the adsorption properties of Rhodococcus opacus biomass for Pb(II) and Cu(II) ions was investigated. The effects of initial pH, initial metal concentration and biomass concentration on biosorption efficiency were studied in a batch system. Results showed that the initial pH would play an important role in the Pb(II) and Cu(II) ions removal by R. opacus and affected the zeta potential of R. opacus. The equilibrium adsorption was reached with 60 min. The Langmuir and Freundlich models were used for describing of adsorption isotherm data. The maxi-mum adsorption capacities of biomass were determined as 94.3mgg-1 and 32.2 mgg-1 for the Pb(II) and Cu(II) ions, respectively. The experimental data fitted to pseudo second order kinetic model. Adsorption capacity of Pb(II) ions was found to be reduced by the presence of the other competing metal ions in the system. The FT-IR results of R. opacus biomass showed that biomass has different functional groups and these groups are able to react with metal ions in aqueous solution.

Jan 1, 2014

By Hossein Zarei, Masoud Kashani, Mehdi Safari

The feed of flotation unit in Angouran mine, as a part of Iranian Lead and Zinc National Corporation, contains about 34.26% zinc (about 12% Zn sulphide) and 10.14% lead (about 2% Pb sulphide). The grade of Pb and Zn in the final concentrate (rougher+scavenger), under optimal conditions (200 g/ton PEX, 500 g/ton zinc sulfate, 30 g/ton MIBC and pH = 7.5), was 63.18% and 13.01%, respectively, and the total Pb (sulphide-oxide) recovery was about 19% which included 95% Pb sulphide. The grade of Pb and Zn in rougher concentrate step was about 71.86% and 5.97%, respectively, when PEX (Potassium Ethyl Xanthate) was used as collector. While in the presence of PAX (Potassium Amyl Xanthate), the grade of Pb and Zn in rougher concentrate step was 66.8% and 10%, respectively. Tailing of the galena flotation (with 8.48% Pb grade and 34.92% Zn grade under the optimal conditions) was used as a feed for sphalerite and oxide section flotation.

Jan 1, 2014

By Francisco Vicuña, Miguel Becerra, Gonzalo Montes-Atenas

"The optimization of the copper recovery from smelting slag by a process of comminution / flotation has been a widely discussed topic during the last few decades. Several studies covering the characterization of different types of slag, the impact of the slag cooling rate and of different flotation operating conditions on the flotation performance have been widely published. Currently, at El Soldado mine site (Angloamerican), there are large copper bearing slag deposits that can be a profitable alternative for the concentrator with capacity to treat this material. Under this process schema, the optimization of the flotation process to obtain better copper recoveries is a relevant topic of study. The aim of this study is to assess the efficiency of a sulfidation stage of a slag and to correlate that process with copper recoveries results in a flotation circuit. This article presents a detailed examination at both laboratory and plant scales of the slag sulfidation on the recovery of copper in the flotation process. The experimental methodology involves studying the effect of the sulfidation agent dosage, the pH, the particle size distribution of the flotation feed and the conditioning time. Furthermore, the performance of the sulfidation stage was analysed through the XPS analytical technique. It was observed that the sulfidation of particles in floatable size fractions correlated well with the increase in copper recovery. The results indicated that it is possible to increase between 2 to 4 points the total copper recovery with a sulfidation process implemented appropriately."

Jan 1, 2014

By M. R. Hosseini

Among all gravity concentration methods, Shaking-table is the most effective one from the metallurgical point of view. In this study, Shaking-table was used for concentrating a manganese ore sample from Ghasem Abad area in Kerman, Iran. Experiments were designed by using L8Taguchi design with five variables and each variable in two levels. The influence of each variable and their interactions on the operation of the device was studied. The variables under investigation were: table slope, table frequency, water flowrate, feed rate, and particle size. The manganese concentrate grade and recovery were used as response variables. It was shown that water flowrate, table slope, feed rate, and particle size are the significant variable on concentrate grade; while, all the variables influence manganese recovery.

Jan 1, 2014

By L. C. Zhou

The floatability of andalusite and associated minerals are studied and their action mechanisms of andalusite and associated minerals with collector alkyl benzene sulphonate are also studied. Through the mensuration of electrical potential and the infrared spectroscopy, as well as desorption tests, it is confirmed that the interaction of andalusite with sodium dodecyl benzene sulphonate (SDBS), is in addition to physical adsorption, but also is chemical adsorption. The study results of the pure minerals are used for the flotation of actual andalusite mineral. By flotation from contain-ing 45.68% andalusite ore, the fine andalusite concentrate is gained which Andalusite grade is 85.88%, containing Al2O355.29% and Fe2O3 less than 1.5%.

Jan 1, 2014

Micro-fine disseminated molybdenite was ground in a laboratory stirred mill using steel media and zirconium media respectively. The floatability of ground molybdenite and slurry chemistry was investigated. It was found that the total recovery of ground molybdenite using zirconium media was higher while the pH and Eh of the slurry are lower than that using steel media. When steel media was used, iron oxy-hydroxides had been generated coated on the surface of molybdenite, and decreased the floatability of molybdenite, especially of the -10µm particles. The iron and lead oxy-hydroxides was generated by the reaction between steel media with pyrite and galena associated with molybdenite. It was also found that changing the grinding media to inert can benefit the flotation of molybdenite. Keywords: stirred mill, grinding environment, floatability, micro-fine disseminated molybdenite, fine grinding

Sep 1, 2012

By Kazutoshi Haga, Ryo Kawarabuki, Atsushi Shibayama, Masato Kosugi, Masanobu Kawata, Refilwe S. Magwaneng, Kohei Mitsuhashi, Altansukh Batnasan

"The recovery of copper and iron from carbonaceous sulfide ore is of economic and environmental interest despite its processing difficulty. Hydrometallurgical methods can be used to concentrate sulfide metals of these hard-to treat ores in a simple and eco-friendly manner. In this study, high pressure acid leaching process was comprehensively studied to dissolve metals from an ore with organic carbon and carbonaceous gangue material using autoclave equipment. The sample used for the experiment was reduced to an average particle size of 75 µm after undergoing flotation to reduce carbonaceous gangue minerals. A comparative study on two leaching reagents of sulfuric acid and iron sulfate and their dosage was used to observe dissolution of copper and iron. Other parameters of temperature (90-170 0C), solid-liquid ratio (1:10, 1:5, 1:3 and 1:1) were investigated through kinetic studies to access the influence of organic carbon and carbonaceous material on recovery of copper and iron. Materials balancing analysis was used to evaluate the efficiency of metal dissolution. The effects of parameters on leaching rate and concentration was demonstrated. Results obtained from the experiment indicated low concentrations of copper and iron in pregnant leached solutions, which was attributed to acid consumption by organic carbon and carbonaceous material in feed. However, the high efficiency rates of 92.4% and 86.3 % for copper and iron respectively in sulfuric acid can be concluded that leaching of concentrates of carbonaceous ore is possible provided system control on type of acid, pH and temperature. The purpose of this research is important in understanding mechanism involved in dissolution of copper and iron in concentrates of carbonaceous ore and marks an improvement in leaching of highly contaminated ores."

Jan 1, 2018

By Benoit Clermont, Jan Lux

"Magotteaux and Anglo Platinum started a co-operation program with the main aim of establishing the optimum milling configuration measured in terms of throughput, fineness and energy consumption.For this purpose, a fully instrumented pilot milling plant, supplied by Magotteaux (Pty) Ltd, and equipped with a 0.9 x 1.0 m ball mill, was erected at Frank concentrator (Merensky Pt ore). The primary ball mills at Frank concentrator were surveyed in order to set the conditions for the base case. This data was then replicated in the pilot mill under the same configuration. Thereafter, a series of different parameters were varied in order to attempt to optimize the milling system.Some of the grinding parameters that have been studied are:•,Gate versus overflow discharge•,Open versus closed circuit•,Different filling degrees•,Different shell liner profilesOnly grate versus overflow discharge and open versus closed circuit will be discussed in this paper.It should be noted that this paper does not attempt to give a universal solution as to what milling configuration is optimum in all cases. The conclusions apply for this particular case and probably most others, but it would be advisable to consider each case on its own."

Jan 1, 2003

By Peter Scales, Ricardo Jeldres, Fernando Concha, Pedro Toledo, Shane Usher, Anthony Stickland

The impact of several electrolytes present in seawater on the rheological properties of flocculated mineral suspensions was assessed using the creep test. Flocculated suspensions were obtained by adding polymer flocculant to a cylinder of mineral suspension and aggregating the suspension using the plunger method. The suspension was allowed to sediment and the supernatant liquid decanted prior to tests for the viscoelastic properties of the resulting sediment. The solid used was alumina AKP-30 both, below and above the isoelectric point. The polymer used was AN934SH, an anionic flocculant with high molecular weight. Salts analyzed were MgCl2, CaCl2 and NaCl, known as water structure makers, and KI and KCl, known as water structure breakers. A high salt concentration of 0.5 M was used to approach the ionic strength of seawater. For both pH’s studied, the sediments demonstrated a viscoelastic non-linear behavior observed as a non-linear relationship between yield strain and applied stress. In the absence of flocculant, it was observed that the viscosity and yield stress of a suspension increase in the presence of structure maker salts for the case of both silica suspensions and alumina suspensions. These results were explained using hypernetted chain statistical mechanics models describing the interaction of ions with solvated surfaces. In contrast, with the presence of flocculant, the shear yield strain of alumina suspensions increases with the breaker character of the salts, however, this result has been explained by an extension of the results from the models. The work has significant implications for the flocculation of mineral suspensions in the presence of seawater.

Jan 1, 2014

Coal preparation plants usually operate with water in a closed circuit mode. In this practice, large quantities of water is continuously being recycled. To compensate the natural losses, only small quantity of fresh make up water is added into the circuit. As a result, a gradual build up of residual concentrations of flotation reagents (frothers, collectors, coagulates etc.) take place in the water and the concentration levels of the contaminants increase. Besides, the recycled water accumulates higher amounts of total dissolved components (1600 ppm) and hardness (740 ppm) than the fresh water. Nearly 80 ? 85% of the process water used in a coal preparation plant is utilized in treating the coal fines in flotation circuit. The presence of certain alkali earth metal ions (e.g., Ca++, Mg++) may adversely affect the flotation performance as they precipitate sparingly soluble hydroxyl complexes on the coal surface and change its surface charge. These studies showed that the use of recycled water in flotation has a significant effect on the selectivity and kinetics of the flotation process because, the dissolved compounds, both inorganic and organic, alter the chemistry radically. By treating the recycled water through a softening process, the concentrations of alkali earth metals and hardness were reduced significantly. The concentration of alkali earth metals and hardness were reduced to 10 ppm and 35 ppm respectively in the softened recycle water. From the selectivity studies, it has been observed that the flotation yield and recoveries increased by four to seven units by softening the recycled water. The kinetic studies indicated that the clean coal particles followed first-order kinetics. The kinetic parameters namely, flotation rate constant (k) and maximum recoveries (R8) of flotation, were found higher with softened recycle water than the recycled water. This reduces the residence time in the flotation cell and thereby, increases its productivity. Keywords: coal flotation, hardness of water, water chemistry, softening process, selectivity, kinetics, flotation rate constant and maximum recovery

Sep 1, 2012

By Xiao Ni

Alkyl hydroxamic acid was shown to be a suitable collector for the flotation of pyrochlore from carbonatite niobium oxide ores. In the direct batch rougher flotation from the ore without desliming, over 85% of the pyrochlore can be recovered at about 30% mass pull. Cleaner flotation tests showed that the rougher concentrate can be upgraded. The adsorption mechanisms of octyl hydroxamic acid (OHA) were studied by using high purity pyrochlore and calcite mineral samples and employing analytical measurements such as Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and UV/VIS spectroscopy. FTIR showed a shift of the vibrational frequencies of the carbonyl group in hydroxamic acid after adsorption on pyrochlore and calcite, and the shift was more pronounced on pyrochlore. XPS results indicated a lowering of the binding energies (chemical shift) of Nb3d5/2 and Ca2p3/2 electrons on pyrochlore, and the lowering of the binding energies of Ca2p3/2 electrons on calcite, again with the shift being more pronounced on pyrochlore. The results indicated hydroxamic acid formed stronger complexes with pyrochlore than with calcite. Adsorption isotherms indicated that OHA adsorbed more on pyrochlore than on calcite at low concentration. At high concentrations, the adsorption densities on both minerals were similar. All results explained the observed selectivity of the reagents in the flotation of the carbonatite niobium oxide ores.

Sep 1, 2012

By J. K. Afidenyo

Microbial pretreatment of a double refractory gold ore was investigated using a white rot fungus, Coriolus versicolor (ATTC 20869) to improve gold extraction. A series of preliminary tests were conducted to determine the amenability of the ore to fungus degradation. Pulp density, temperature, pH and retention times were the process variables considered. Both a single. Stage and two-step processes were studied to establish process conditions. During the single stage process, the ore was contacted with the fungus culture (biotic) for 3weeks at 30°C and pH 10.0. For the two-step process, the first step involves ore contact with the culture medium (abiotic) at 45°C and pH 10.0 followed by fungal contact (biotic) at 30°C. Results indicated that carbonaceous matter is not degraded but passivated by the fungus; as preg-robbing activities dropped significantly from 18.1% to below 1.0%. The single stage process resulted in higher gold recovery than the two-step process Gold ex-traction by cyanidation of the pretreated ore was 78.9% for the single stage compared with 15.0% for the untreated ore. In the two-step process, only 73.3% gold extraction was achieved. Application of the two step process conditions to a high grade flotation concentrate, resulted in 93.3% gold ex-traction as against untreated concentrate of 30.5%. The results show that the microbial pretreatment process degraded sulfide sulfur, passivated carbonaceous matter and enhanced gold extraction from double refractory gold ore and concentrate.

Jan 1, 2014

By John A. Herbst

The Mineral Processing Industry needs accurate Production Simulators for the design of future plants and expansions. To achieve this, these simulators should not only provide an accurate portrayal of the dynamics of individual pieces of equipment they should include the impact of discrete stochastic events such as scheduled and unscheduled maintenance so the relationships between availability, equipment sizes, and plant capacity are understood. To provide such a tool accurate dynamic Population Balance Models need to be combined with solid discrete event modeling. The current paper provides a description of how these two disparate modeling techniques were combined and the associated benefits from this combination. Keywords: dynamic plant simulation, population balance models, discrete event models, prefeasibility and feasibility studies, plant design and expansion

Sep 1, 2012