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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

By A. Zangooi

Frothers play major roles in flotation through interaction at the air/water interface. A method of determining frother adsorption density (coverage), i.e., the number of molecules per unit of interfacial area of bubble surface, is introduced. The technique is based on mass balancing the frother around a continuously operated bubble column. The mass balance requires collection of bubbles before they burst. The column design and operating procedure is reviewed, and some preliminary results discussed. Keywords: flotation, colorimetric frother analysis technique, frother mass balance, coverage

Sep 1, 2012

By Z. F. Dai

The Thompson Nickel Belt, located in Northern Manitoba, Canada, contains more than 400 million tonnes of ultramafic low-grade nickel mineralization in 9 deposits. One of these, the Pipe deposit, was mined between 1971 and 1983 producing a Ni concentrate of 9% to 11% grade at 73% recovery. The operation was terminated because the poor recovery, low Ni grade and high MgO con-tent of the concentrate made processing this ore uneconomical at the metal prices prevailing at that time. Vale Inco is now re-evaluating these deposits with the intent of providing a new source of concentrate for its Thompson integrated processing facility. It is known that serpentine slimes coating on the sulphide surfaces are responsible for the poor metallurgy. Various desliming methods were tested including settling, elutriating, tabling and hydrocycloning. Hydrocycloning has proven to be the most effective means of desliming. With a feed assaying 0.70% Ni and 33% MgO, a rougher flotation concentrate assaying 22.7% Ni and 4.8% MgO was produced at a Ni recovery of 62.5% (relative to the feed to grinding), with no utilization of slimes dispersants. Another 16.6% Ni recovery was achieved in scavenger flotation resulting in a total Ni recovery of 79.1%. Batch flotation tests using various flowsheet configurations to optimize the grinding, desliming, reagentizing and flotation conditions are in progress.

Jan 1, 2014

By S. Koca

Vast amount of fly ash, bottom ash and slags, are produced each year due to coal combustion in thermal power plants. These products consist of mainly unburned carbon and inorganic compound (such as: silica, alumina, iron oxides, magnesium oxide, phosphorus oxide etc.). These are valuable minerals and can be recycled or recovered if properly processed. One third of the material find application as an ingredient in cement and other construction products, the rest is held in dams or similar dumps, which results in a hazardous impact on the environment, polluting soil and ground water. The unproductive use of land, the associated long term financial burden maintenance and negative environmental impacts have led to realization that alternative uses for combustion by-products as a value added product beyond incorporation in construction materials are needed. At present, there is an intensive search to increase their uses. Other uses of coal combustion residues include as raw material in brick and ceramic tile fabrication, as filler in plastics and paints, extraction of valuable mineral materials, production of zeolites and soil and mine waste treatments. Separation of unburned carbon from bottom ashes by means of flotation was conducted in order to increase the possibility of the recycling of coal combustion wastes. In the flotation experiments collector, dispersant and frother amount, pulp density and pH were tested as variables. After first stage flotation experiments, at optimum conditions, the carbon content was reduced down to 5.58 % in the tailings fraction. This fraction meets the industrial specifications and can be utilized as a cement additive. At the same conditions the carbon content of the concentrate increased to 44.72 % at a carbon recovery of 65.81 %. After the cleaner stage flotation experiment the carbon content of the product is enhanced to 62.53 %. This fraction can be blended back into the coal feed to the power plant boilers.

Jan 1, 2014

By W. Rubarth

The kaolin losses in hydrocyclone classification are determined by the fines, which are discharged together with the water to the underflow. This paper presents an improved technique of water injection to the conical part of the cyclone applied especially for small cyclones in kaolin preparation. In small hydrocyclones water, injection is a sensitive process. Therefore, the process was stabilized by controlled water injection dependent on the measurement of the underflow shape. Three applications of this innovation are presented. In the first case, the water injection is applied for the separation stage in dilute suspension where the final product is produced in the overflow of a 50mm hydrocyclone. The underflow contains sand and residual kaolin. For a higher kaolin recovery, the underflow is usually treated downstream in washing cyclones. The wash water injection results in a 45 ? 50% - reduction of the kaolin fraction <25µm in the underflow. Thus, water injection to the classifying cyclone leads to a separation comparable with a downstream washing stage. An additional hydrocyclone stage can be deleted. The second application refers to a classification in dense suspension. Here, the underflow of the last hydrocyclone stage was directed to a washing in a 50mm hydrocyclone. The additional injection of 3L/min water in to the conical part of the cyclone reduced the kaolin losses by half.The third application was executed in the washing stage equipped with 75mm hydrocyclones where the underflow is directed to flotation. Using the water injection the kaolin recovery in this stage was increased by approximately 20%. Keywords: hydrocyclone, classification, kaolin beneficiation, water injection, underflow washing

Sep 1, 2012

By G. Alfano

This investigation is concerned with the optimization of ultrafine grinding of solids. It is focused on a dynamic classifier for recovering the fine fraction, for automatic recycling of the oversize particles and for reducing power consumption. Power consumption plays a major role in these energy intensive processes and depends on several parameters such as nature of the solid, degree of fineness of the finished product and, above all, grain size of the feed. This study indicates the optimal conditions for a dynamic classifier, that is, geometric characteristics of the apparatus and its capacity, inlet air flow rate and dimensions of the classification circuit. It is also shown that a mean grain diameter (dm) of about 2.00 µm with top size (dmax) of 50 µm can be achieved with an imperfection value of below 0.40 and energy consumption of 215 kWht-1. Keywords: air classification, dynamic classifier, jet mill, energy

Sep 1, 2012

By D. Saramak

The proposal of the nip zone angle determination in HPGR crushing process is presented in the paper. Knowledge of the nip zone angle value, in turn, makes it possible to determine the real maximum pressing force in the high-pressure comminution. Two methods of determination of this maximum pressure were proposed and verified. The first method is based on the roll?s geometry, and the change of the HPGR chamber?s volume together with the roll rotation, while the second one considers the outlet gap width impact. Results of the nip zone angle calculations according to both methods are similar and show convergence with the real operating conditions. The verification was carried out in a piston-die press, and experimental results show that methodology of the nip zone angle determination presented in the paper has its practical confirmation. A proper determination of the nip zone border makes it possible to calculate the comminution probability of given type of material and is a basis for the HPGR crushing process modeling and optimization. Keywords: HPGR, comminution, nip zone, ore processing

Sep 1, 2012

By Gaom M. W.

The Mount Isa copper concentrator started operation in 1973. Its secondary grinding circuit consisted of two 5 meters diameter ball mills in closed circuit with 505 mm cyclones. At the design throughput of 800 t/h, the 80% passing size of the circuit product (P80) was about 140 µm. The then Mount Isa Mines Limited (?MIM?) installed two autogenous grinding (?AG?) mills in 1991 to replace two stages of crushing, a rod milling stage and one primary ball milling stage. One of the AG mills was later converted to semi-autogenous grinding (?SAG?) operation by the addition of a steel grinding medium to achieve the designed plant throughput of 800 t/h. The cyclone over-flow P80of the secondary ball mill circuit was reduced to 120 µm by the increased operating power in the AG/SAG mill circuits. The two secondary balls mills had a grinding power of 5.2 MW. A mineralogical study of the milled products indicated that half of this grinding power was sufficient for adequate chalcopyrite liberation. Eliminating one of the secondary ball mills could reduce energy and operating costs by more than A$2 million dollars per year. An optimisation project team was established to achieve the predicted power saving. Grinding circuit simulations were conducted for different circuit configurations. Ball mill parameters such as ball size, ball charge and feed slurry density were optimised. Cyclone body diameter, spigot and vortex finder sizes, and cyclone types were tested. The secondary ball mill circuit was redesigned and several proposed circuits were run as trial production campaigns to determine their operability and efficiency. The plant trials confirmed that one of the secondary ball mills could be decommissioned. Significant cost savings were achieved as a result. The success of the project demonstrates optimising grinding circuits can not only deliver the plant performance, but also a much lower unit operating cost through energy and maintenance savings.

Jan 1, 2014

By Teja Reddy, Narasimha Mangadoddy, Mandakini Padhi

"In mineral comminution circuits, the feed to hydrocyclone consists of a heterogeneous mixture having varied degrees of liberation and sizes leading to the multi-component particle system. The presence of multicomponent particles exhibits a significant change in the classification performance parameters. In this work, a numerical study is conducted with an artificial mixture of magnetite and silica of different proportions having similar particle size distribution to understand the multicomponent interaction in a laboratory scale hydrocyclone. The heterogeneous feed is injected tangentially would attain different settling rates under the influence of centrifugal, drag and turbulent dispersion forces. In this work, Large Eddy Simulation (LES) is used to resolve the continuous phase turbulence. Modified Algebraic Slip Mixture (ASM) model using the corrected Newtonian rheology of fines to simulate multi-density and multi-size particles of the mixture in a hydrocyclone. The influence of the multi-component particles on classification performance is extracted from the simulation in terms of the performance curve, i.e. recovery to underflow, volume fraction distribution and the key forces acting on each particle in the mixture. An interaction was observed between different components during the classification process, featuring accumulation of heavier particle at wall-side pushing the lighter particles into the inner locus of zero vertical velocity (LZVV) zone. The comparison of separation factors of different size particles presented the higher probability of the magnetite of same size reporting to wall region and hence to underflow. Hence, an increased component cut-size with the increased magnetite proportion, particularly a profound effect on lighter density component’s cut-size was observed. INTRODUCTION The multicomponent existence is found in naturally occurring ores, affecting the pure metal extraction, nonetheless also affects the comminution and classification processes. Among many another classifier, hydrocyclone is a vital equipment used vastly in many industries. The main advantages over other classifiers are a static body, low operating cost and maintenance, high throughput, low floor space requirement etc. A typical hydrocyclone consists of a cylindrical section with a central tube connected to a conical section with a discharge tube. The fluid is injected tangentially into hydrocyclone causes swirling and thus generates centrifugal force within the device. The multiphase interaction inside the hydrocyclone is extremely complex and mostly explained by theories based on hypothesis. In past years, many theoretical models were proposed like a balanced orbital model (Criner, 1950), the residence time model (Reitema, 1961) etc. Though these models give an estimation of the cut-size and other performance parameters, it cannot predict the accurate performance of the actual state of operation. Among these models, the balanced orbital theory is the most adapted concept, based on the force balances of the particle in the dual vortex flow of hydrocyclone. The finer particle is subjected to the inward drag force, generated from the outer vortex flow to the air core, and drags the particle towards the overflow. The larger particle with the higher mass have enhanced centrifugal force and falls into primary vortex near wall reporting to the underflow. Generally, the forces acting on the particle include the drag force, centrifugal force, pressure gradient force, added mass force, Saffman lift force, Magnus force and basset force (Kraipech, 2005). The major forces like a drag, centrifugal, pressure gradient are the function of the particle properties like the size and the density. Hence, the existence of the multi-size and the multi-density particle will affect the separation phenomenon, with the varied forces acting on it. The understanding of the multicomponent classification effect using ores has been only explored in few studi"

Jan 1, 2018

By C. A. Acuña

Extensive literature exists on the motion of single bubbles and the behaviour of swarms of bubbles. This contribution describes work to track and reveal the motion of individual bubbles in a swarm. The technique is based on high speed cinematography and tracking of multiple moving objects. Image processing algorithms were implemented in Matlab to isolate and measure geometric proper-ties of the bubbles in image sequences recorded at 2 ms interval; and these properties were compiled into a data structure. To track a bubble, the geometric properties and a matching criterion were applied on consecutive pictures to identify the bubble. The bubble trajectory was reconstructed from the data structure for the matched objects. The methodology is briefly described. The new technique was tested for bubbles produced at slot-type spargers (i.e., approximately 2-D swarms) in the presence of two frother types (&apos;strong&apos; and &apos;weak&apos;). Two observations are discussed: a) that bubble motion in a swarm describes a velocity-size relationship dictated by the dominant bubble size class; and b) that surfactant type influences bubble rise velocity for bubbles in the range 0.1 mm to 4 mm. The latter suggests surface viscosity rather than surface immobilization determines bubble rise velocity.

Jan 1, 2014

By R. Paturi

Mill liners play an important role in the operation of a mineral concentrator influencing the throughput, availability, power drawn and the efficiency of the mill in the plant. Liners protect the shell and transfer energy to the grinding charge. Metso Technology Development has conceptualized, developed and successfully implemented physics based 3D DEM simulation techniques to predict charge motion, power drawn, energy spectra and wear over the life of the liner. This paper will present a case study of shell liner optimization for a 34? SAG mill including the input data requirements, and shell liner optimization methodology using the 3D simulations that eliminates the need for the traditional expensive and lengthy proto-type testing. These simulations will cover ball and particle movement, liner wear and mill power draw, and do not cover particle breakage and slurry flow. Even the liner manufacturers lack the ability to provide this type of qualitative and quantitative information on their products. The data from these simulations provides the plant engineers a scientific basis for their decision making and thus eliminates guess work. Keywords: liner, optimization, multi-physics, 3D-DEM

Sep 1, 2012

By B. P. Baruah

A good deposit of high sulphur coals of tertiary origin is existent in North eastern region of India. These coals are known to have indifferent characteristics in comparison to other Indian coals. The general Physico-chemical characteristics are low ash and high volatile matter, calorific value and sulphur content. Sulphur in these coals (70-95% of organic) is mostly affixed to the structure of the coal. Owing to the stringent environmental regulations, the utilization of these coals has severe limitations due to high sulphur content. In the present investigation, sulphur incorporation in to these coals has been discussed along with possible organic sulphur functionalities. The various desulphurization techniques carried out for removing sulphur from these coals have been discussed. Two step oxidative desulphurization processes has been found to be most efficient for organic sulphur removal along with mineral matter and potential toxic elements. Keywords: oxidative desulfurization, potential toxic elements, sulfur incorporation

Sep 1, 2012

By Evvie Chockalingam

Acid mine drainage (AMD) is a perennial problem particularly in abandoned mines, occurring due to the oxidation of sulphidic mine wastes. AMD is usually characterized by high concentration of dissolved metal ions, sulphate and low pH. The efficacies of substrates such as rice husk and the bark of Eucalyptus tereticornis (Sm.) are assessed for the removal of metal ions such as iron, zinc and copper from acid mine water obtained from an abandoned copper mine. Over 99 % of Fe, 98 % of Zn and 95 % of Cu removal could be achieved from acid mine water, with a concomitant increase in the pH value by three units using rice husk as an adsorbent. With respect to tree bark as an adsor-bent, about 96 % of Fe, 75 % of Zn and 92 % of Cu could be removed from the acid mine water with an attendant increase in the pH value by two units. The free energy of adsorption of the metal ions onto rice husk and tree bark is found to be negative in both the cases, while the adsorption process is endothermic in the case of rice husk and exothermic for tree bark. The adsorption process is found to adhere to the Lagergren pseudo-first order rate equation. The reduction of sulphate con-centration in the acid mine water is achieved using a typical sulphate reducing bacteria namely De-sulfotomaculum nigrificans. Desorption experiments indicate that about 88 % of Zn, 87% of Cu and over 77 % of Fe could be recovered from rice husk and over 70 % of Fe, 82 % of Zn and 77 % of Cu could be desorbed from the metal loaded tree bark using 5 M HCl. The possible mechanisms of metal ion and sulphate removal from acid mine water using rice husk and tree bark are discussed.

Jan 1, 2014

By S. Carsten, S. Subramanian, R. Vasant Kumar, S. Vimalnath

"The effect of EPS components namely protein, polysaccharide and biosurfactant purified from Pseudomonas fluorescens was investigated for the bioremediation of Pb(II) ions in aqueous solution. Two parameters, namely the amount of EPS component and the concentration of Pb(II) ions were optimized for maximum Pb(II) ions uptake. The EPS components interacted with Pb(II) ions were characterized using energy dispersive X-ray analysis (EDAX) to ascertain the presence of Pb and by attenuated total reflection-Fourier transform infrared spectroscopy (ATR–FTIR) to reveal the functional groups involved in Pb(II) binding. The maximum Pb(II) binding capacities of protein, polysaccharide and biosurfactant were found to be 11.4, 0.55 and 0.11 mg mg-1 respectively. The biosorption processes followed the Langmuir model. The Gibbs free energy (?G0) values of -23.6, -20.9 and -23.2 kJ mol-1 for Pb(II) biosorption by protein, polysaccharide and biosurfactant respectively, attested to spontaneous, chemisorption processes. The ATR–FTIR results revealed the presence and involvement of amino, hydroxyl, carboxyl, phosphate, and methyl functional groups in Pb(II) binding and EDAX analysis confirmed the interaction of Pb with EPS components. The Pb(II) binding mechanisms of EPS have been discussed. The results demonstrate the potential of the purified EPS components of P. fluorescens for removal of Pb(II) ions from aqueous solution INTRODUCTION Waste water containing toxic metals from various industries pose a serious threat to human health and ecosystem. For treating such waste water, conventional methods like chemical precipitation, coagulation, evaporative recovery, electrodialysis, floatation, flocculation, ion exchange, reverse osmosis, nanofiltration, ultrafiltration are used (Lakherwal et al., 2014). These methods have some disadvantages like toxic sludge generation, incomplete metal removal and high cost (Singh and Gadi, 2012), necessitating the search for cheaper and efficient alternative methods. Bioremediation is one of the emerging alternatives where bacteria, fungi, yeast, algae and other biological substances are used as sorbents to remove toxic heavy metals (Vijayaraghavan, et al., 2015). Recently, the bioremediation potential of extracellular polymeric substances (EPS) of microbial origin has attracted attention. However, for Pb(II) removal, there is a paucity of literature focusing on EPS."

Jan 1, 2018

By R. M. Zhao

The process conditions and mineral characters of cleaning separation stage in magnetite concentration plant are studied in the paper, and the affecting factors and the methods to increase the concentrate grade are analysed and given. The BKJ cleaning special drum magnetic separator is developed specially for the cleaning stage according to process conditions and mineral character. The separation mechanism, structure characters, separation process and excellent adaptability of BKJ special magnetic separator are described. The results in Zhangjiawa Concentration Plant show that the BKJ special drum magnetite separators play an important role in increasing the concentrate grade and improving the economic benefit.

Jan 1, 2014

By N. Vasumathi

Most of the Iron ore washing plants set up in India in the earlier days consist of sizing of the ore by dry / wet screening, washing and classification by screw classifiers. In this classical approach, iron values were lost in the form of fines and ultrafine into the tailing ponds as they had little commercial value in those days and accumulated in huge quantities over the years. As the high grade deposits are getting exhausted and the demand for high grade finer material for pellet making is ever increasing, focus is shifting towards recovering the values from the erstwhile tailing ponds by column flotation. This is also supposed to mitigate to a certain extent the environmental problems caused by the ever expanding and unmanageable tailing dams. A case study is presented wherein a composite sample is prepared from samples drawn systematically from multi - locations in a sprawling tailing dam. Laboratory scale column flotation tests on this composite tailings sample, basically originating from two operating iron ore beneficiation plants of JSW Steel Ltd., one of the leading producers of steel in India are found to be encouraging. Desliming followed by reverse and cationic flotation tests using flotation column resulted in the concentrate of 61.88% Fe, 4.81% SiO2, 2.52% Al2O3 and 3.30% loss on ignition (LOI) from the tailings analyzing 57.86% Fe, 7.10% SiO2, 3.52% Al2O3 and 6.14% LOI with 52% weight recovery. The causes for the quality improvement could be attributed to desliming of un-liberated ultra fines of kaoline and hydrated iron oxides and their further reduction by efficient flotation process. The process and the cationic collector developed for this purpose are adopted in the new flotation plant created to treat these tailings. Keywords: iron ore, washing, ultra fines, tailings pond, column flotation

Sep 1, 2012

With rapid development of Chinese iron & steel industry, it is of significance to intensify the utilization of domestic complex iron ore resources. The tin, zinc-bearing complex iron ores are typical polymetallic and intractable ones because of the complicated intergrowth relations among the multi-elements, and they have not been efficiently utilized, presently. Based on the thermodynamic analysis of iron, tin and zinc oxides reduction by CO, the technological conditions of tin and zinc recovery and pellets preparation from tin, zinc-containing iron concentrates by selective reduction roasting are studied and a new comprehensive utilization process is developed in this investigation. Under the optimum conditions, the tin and zinc volatilization is respectively in excess of 80% and 70%, and the compression strength of roasted pellet is more than 2500 N/P. Moreover, the residual tin and zinc in the finished pellets is below 0.06%. The finished pellets can be used as high quality iron-making burdens for large-scale blast furnace.

Jan 1, 2014

By Kwan Ho Kim

The beneficiation study of low quality pyrophyllite is conducted to enhance the value of it by selective grinding. In mining stage, the main gangue mineral is quartz, and the content of quartz in ore has an adverse effect on the quality of pyrophyllite. Using the huge difference in hardness between quartz and pyrophyllite, the selective grinding is accomplished using stirred ball mill. As a result, a finer pyrophyllite particle can be easily separated from coarser quartz particle by simple size classification, and the content of Al2O3 of fine particle smaller than 45um increased largely. It means that the pyrophyllite particle is ground selectively compared to the quartz particle, and the quality of pyrophyllite is enhanced.

Sep 1, 2012

By Venkataramana Runkana, Aditya Pareek, Vishnu Masampally, Nagaravi Kumar Varma Nadimpalli

"Recovery and grade of the ore produced are two important metrics, which define the profitability of a mineral processing plant. Achieving high grade and high recovery at the same time in a mineral processing plant is difficult due to conflicting nature of the two objectives. To explore the operability limits of the plant operations and find the set of operating conditions that can help achieve the best possible recovery and grade, there is a need to solve a multi-objective optimization (MOO) problem. Past research focused on building a plant-wide simulation model or on optimization of individual units or a part of a mineral processing plant like grinding circuit, crushing circuit, etc. However, it is necessary to consider optimization of the complete plant in order to optimize the plant performance. Here, we have formulated the mineral processing plant performance optimization as a MOO problem. We have applied machine-learning algorithms such as random forest to build models to predict the recovery and grade of the ore. A non-dominated sorting-based multi-objective evolutionary algorithm called NSGA-II (Non-dominated Sorting Genetic Algorithm II) was employed to solve the MOO problem. Since the number of parameters that influence recovery and grade are quite large, we have applied machine-learning algorithms for feature selection or identification of key process variables. Pareto optimal conditions were determined for manipulated variables like grinding mill throughput, speed ratio at SAG mill, speed of centrifugal pump, water addition at different locations etc. The results obtained are useful in identifying the operability of a mineral processing plant to achieve the optimum grade and recovery for a given feed grade and the processing circuit. INTRODUCTION Copper is majorly mined or extracted as copper sulfides from large open pit mines in porphyry copper deposits. Among all the available ores, sulfides are the most commercial ores, especially chalcopyrite (Greenwood and Alan, 1997). Copper grade in these ores generally lies between 0.4 to 1.0%. In order to perform smelting operation, the grade of copper has to be improved to around 30% (Biswas et al. 2013). This targeted copper grade is achieved through two stages of mineral processing. Firstly, the copper in the ore has to be liberated by crushing the mineral rock. Secondly, the liberated copper in the crushed ore is then physically separated from other minerals like nickel by froth flotation techniques."

Jan 1, 2018

By N. Dhawan

In the last decades, High Pressure Grinding Roll (HPGR) has gained significant importance in hard rock processing due to numerous metallurgical benefits such as energy savings, particle weakening, preferential damage of coarse particles, and preferential comminution-liberation. There are a limited numbers of lab-scale HPGR units throughout the world. The laboratory-scale HPGR machine at the University of Utah is first-ever lab-scale machine designed by late Dr Klaus Schönert, the inventor of HPGR. This HPGR is constructed with two counter-rotating hardened tool steel rolls, each 200 mm in diameter and 100 mm in width. The HPGR unit is equipped with eight sensors and a robust control system, which serves as an ideal system for fundamental studies and lab-scale testing. In HPGR operation, throughput, energy and product size distribution are intricately linked to specific grinding pressure, roll gap and rolls speed. The nip angle existing during the operation determines the volume of feed material above the rolls that is pulled into rolls without slip. In this paper, scale-up factors and some of the existing models have been reviewed. A number of experiments have been carried out with limestone and a slag material. The influence of operating variables and their complex relationship has been studied.

Sep 1, 2012