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By M. Guo

Coal-based Direct Reduction in Interior-combustion Shaft Kiln (CDR/ISK) is a brand-new technique. Compared with the traditional Coal-based Direct Reduction (CDR) technique, its main character is to use Interior-combustion Shaft Kiln (ISK) as the reactor of direct reduction. After being crushed and grinded, iron ore is made into green pellet, which will be surface-coated by coal fines. Then, the surface-coated green pellet can be directly reduced in ISK. The pellet should not be too dry and should be charged from the top of ISK. Oxygen-contained air should be blasted into ISK to keep the temperature in it higher than 1000 degrees centigrade, at which iron oxide will start direct reduction. The reduced pellet will be discharged from the bottom of ISK and after de-surface-coated, spherical Direct Reduced Iron (DRI) can be gained. The volume of carbon monoxide in the off-gas discharged from ISK is less than one per cent. By using this technique to get one tonne DRI, the consumption of coal is about 300kg of fixed carbon, which is much lower than the energy consumption by using other CDR techniques. There is a lot of complex refractory iron ore in China, which remains unexploited. The iron-bearing minerals in this kind of the iron ore can not be beneficiated economically by present technique of gravity, magnetic, flotation or magnetic roasting because the iron minerals are too very finely disseminated to be liberated, or, the iron minerals are too similar to gangue to be separated each other. By using CDR/ISK, complex refractory iron ore can be directly reduced in lower temperature and all kinds of iron mineral can be turned into iron metal. As the grains of iron metal growing larger during direct reduction, magnetic separation can be used to separate iron metal from gangue mineral, thus high-grade iron metal fines can be gained. According to the experiments, the grade of iron metal fines is above 90 percent and the recovery of iron is higher than 90 percent. The consumption of coal to process one tonne of complex refractory iron ore is only about 90kg of fixed carbon.

Jan 1, 2014

By Jonas Addai-Mensah

Despite the fact that nickel (Ni) laterites accounts for about 60 % of the world?s nickel mineralization, commercial processing of complex, low grade Ni laterite ores by conventional beneficiation (e.g. magnetic, electrostatic and flotation separation) still presents intractable challenges, particularly in heap leaching. Invariably, low grade laterite ores require aggressive hydrometallurgical techniques (e.g., highly acidic lixiviant leaching at ambient or elevated temperatures) for Ni and cobalt (Co) extraction. As a precursor to heap leaching, agglomeration of the multi-mineral phase feed particles into robust and porous granules of 4-10 m permeable bed, is essential. In the present work, several basic and applied studies of the agglomeration behavior of real Ni laterite ores and selected oxides and clay minerals (hematite, quartz smectite and kaolinite) which constitute the predominant host gangue phases of typical laterite ores are performed. Isothermal, batch agglomeration tests involving sulphuric acid solution as a binder were carried out to produce coarse, narrow-sized (5 ? 40 mm) granules which were well characterized. The influential role of feed ore characteristics (e.g., mineralogy/chemistry and primary particle size distribution) and binder composition (30 vs. 44% w/w H2SO4) and dosage (15-25 wt.%) in agglomeration behavior and granule properties were examined through several characterization techniques including granule size, compressive strength, bed percolation and re-wetting stability and 3-dimensional micro-structure analyses. Links between feed mineralogy/chemistry and size, binder formulation, agglomeration behavior, curing conditions and final granule properties and structural characteristics are established. The implications of the findings to Ni laterite plant agglomeration for enhanced heap leaching are discussed. Keywords: nickel laterite, complex low-grade ores, agglomeration, heap leaching, micro-structure

Sep 1, 2012

By A. L. Hinde

The steady-state and dynamic behaviour of semi-autogenous grinding (SAG) mills are arguably best described using a population model that caters for the breakage kinetics and the material trans-port of rock and pulp inside the mill. Breakage kinetics are usually expressed in terms of a specific breakage rate function and a separate primary breakage distribution function. Material transport usually invokes the concept of a specific discharge rate function. Unfortunately, the breakage rate and breakage distribution functions for SAG mills are very difficult to estimate uniquely from plant data alone. Simplifying assumptions must be made to over-come this problem, which leads to many unresolved dilemmas with regard to whether or not the de-rived functions are accurate, precise, and reflect reality. For example, it is sometimes assumed that the breakage distribution function for a SAG mill treating run-of-mine ore can be derived from laboratory dropweight and tumbling tests on small rocks in narrow size ranges. Such tests hardly reflect the environmental conditions likely to be encountered in a pilot or production SAG mill where there is a wide spectrum of particle sizes. It is shown that the dilemmas associated with standard population balance models (models that utilise separate breakage rate and breakage distribution functions) can be overcome by expressing breakage behaviour inside a SAG mill in terms of a single function. This function is an energy-based cumulative breakage rate function defined as the fractional rate at which particles and rocks coarser than a given size break to below that size per unit specific energy input. A model for SAG milling is formulated, which invokes the concept of a cumulative breakage rate function. Comparisons are made between the mathematical structure of this ?simple model? and standard population balance models. Perhaps the most attractive feature of the ?simple model? is that the cumulative breakage rate function can be uniquely estimated from measurements of size distributions and mass flows of the feed and discharge streams together with the size distribution and holdup mass of the mill charge. Such measurement can easily be made at pilot scale. It is concluded that this simplified approach to SAG milling may turn out to be the quickest way to fully describe and quantify the performance of these very complex mills.

Jan 1, 2014

In this study, selective flocculating of diaspore using anion macromolecular reagent as flocculant was tested to separate diaspore from alum-silicate minerals. Firstly, the effect of pH on settling behavior of diaspore and kaolinite dispersions has been investigated. The results show that the maximum settling speed of diaspore and kaolinite appeared re-spectively at pH7 and pH3.33 which is close to the point of zero charge (PZC) of diaspore (6.8) and kaolinite(3.5). This result is in well agreement with the double electric layer theory. Secondly, the settling behavior of diaspore and kaolinite particles in different anion flocculant solution have been researched. The results indicate that flocculant solution concentration significantly affect the selectivity and the flocculating performance of anion molecular. In high concentration solution, both diaspore and kaolinite have faster settling rate compared to blank solution. How-ever, in low concentration solution, the anion macromolecular can enhance the settling rate of diaspore remarkably but has no apparent effect on the settling rate of kaolinite. This result suggests that the tested anion flocculant is a promising reagent for de-silica of diasporic bauxite. Lastly, FTIR method was employed to probe the adsorption mechanism of flocculant on diaspore and kaolinite. The results reveal that there are anion flocculant characteristic bands on the spectra of diaspore but no obvious characteristic bands of flocculant on the FTIR spectrum of kaolinite. This result is in good correspondence with settling test.

Jan 1, 2014

The objective of the paper is to develop a material balance calculation procedure for a production unit involving two plants separated by a pipeline. The case study is taken from the oil sands industry. The raw sands are first mixed with water in a conditioning plant, then transported through a pipeline to an oil extraction plant. The combination of pipeline dimensions and nominal throughput creates a significant variable time lag between the two plants. As usual, mass balance calculations required for the evaluation of plant performance indicators, such as bitumen recovery, are inaccurate due to measurement errors. In addition, in the present case study, the time lag of the pipe creates an additional source of uncertainty, which may lead to misinterpretations and wrong decisions. Raw data are usually reconciled through steady-state mass balancing, to correct for measurement errors. However, because of the significant pipeline dynamic lag, standard steady-state daily mass balance may fail at giving an appropriate picture of the operations. The proposed solution to the data reconciliation problem includes the use of a pipeline plug-flow model in the mass balance calculation. To fulfil the industrial constraint that current data reconciliation must not modify past reconciled values, while still satisfying dynamic constraints, a daily one-step method, i.e. a unitary filter-ing horizon, is recommended. The method is illustrated with simulation data, and the results com-pared to those of standard data reconciliation methods.

Jan 1, 2014

By S. Mohanta

In composite washeries optimization of operating parameters to achieve maximum clean coal yield at the desired clean coal ash level is a major problem. This problem is more acute in countries like India, which have predominant reserves of difficult-to-wash coals. The constrained operational parameters of washing for some equipments make it more severe. In addition to this, the dependence of separating performance of different equipments upon various variables aggravates the situation. Here an attempt is made to find a numerical solution to get maximum yield and minimize the difference between the actual and the theoretical yield. The solution is arrived through constrained non-linear optimization of a multivariable objective function that utilizes spreadsheet tools; the method accommodates any number of source coals or washing size fractions. By using a designed Ep value the predicted yield of composite clean coal has been calculated and the yield is optimized subject to constraints on both the ash and specific gravity. It is shown that operational constraints of different washeries in the composite plant that utilizes gravity separation methods can also be over-come. The technique offers the coal preparation engineer an effective and straightforward method for determining the optimum cut-points of separation for different coals or blended coals to obtain maximum product yield at a specified level of ash content.

Jan 1, 2014

By Diogo R. Prado, José Aurélio M. da Luz

Drying operation can have a major importance in a mineral processing undertaking. The proper sizing of dryers can ensure the specified dewatering level without energy wastage. However, often the sizing of fluidized bed is done disregarding the actual residence time distribution (RTD) of the particles inside the reactor. In this case it is usual to adopt the average residence time as a design criterion. In this work, we have quantified the effect of residence time distribution on drying, ensuring that a previously adopted fraction of the particles remains inside the reactor for the required time lapse needed for drying. Design criteria such as particulate flow rate and drying time, taking into account the statistical distribution of residence time was studied, matching the thermodynamic and fluid dynamic aspects of the drying process. Experimental tests carried out have confirmed the RTD for a teetering bed as the same for a canonical ideal mixing system. Although the fluidized bed volume using the proposed formulation was higher than that found for the average time based procedure, the efficiency gain in drying has proven advantageous.

Jan 1, 2014

By T. Lang

Clay sorbents from the North Bohemian Brown Coal Basin represent important but still some-what neglected accessory raw material. Submitted paper is concerned with relation between mineral structure, sorptive efficiency and reclamation exploitation of these rocks. Characters and localities of main clay sorbents from the North Bohemian Brown Coal Basin are shortly evaluated in an introduction. In next part, methodology of mineralogy survey for these accessory raw materials is stated, it is based on diffract analyse with D 5000 Siemens X-ray diffracto-meter. At the conclusion results are stated of mineralogy analyses from several clay sorbents. The determination of the zeolite and montmorillonite localities was accentuated. The paper presents also possibilities of practical clay sorbents utilization, especially by reclamation works.

Jan 1, 2014

By Lev Filippov, Vyacheslav Severov, Inna Filippova

"Reverse cationic flotation is a very efficient method of beneficiation of oxidized iron ores when you need to separate hematite and quartz. This method can be also applied to reduce silica content in the magnetite concentrates obtained by wet low-intensity magnetic separation. However, cationic flotation in this case is less effective due to the presence of Fe-Mg-Al-bearing silicates as amphiboles in magnetite ores. These silicates are concentrated in magnetic products and determine the difficulties of their separation from iron oxides when amines and starches are used as collectors and depressants, respectively. The recalculation of the results of the electron microprobe analysis of three calcic Fe-Mg-Al-bearing amphiboles used to characterize cation distributions in structural units and to obtain structural formulas in accord with stoichiometric limits was conducted. The Mössbauer spectroscopy was used to examine the validity of the empirical estimation of cation distributions in amphiboles. The studied samples are metamorphic pargasite and ferrotschermakite and volcanic magnesiohornblende. The crystallographic analyses of the amphibole samples exhibited their heterogeneous surfaces explaining worse floatability of amphiboles with dodecylamine at pH 10. The electrokinetic measurements showed that the position of the isoelectric point of amphiboles is related to a substitution of Al3+ for Si4+ in tetrahedral sites and to an amount of Mg2+ cations in octahedral sites. Thus, the dodecylamine adsorption onto amphiboles through electrostatic interactions is mainly affected by a distribution of these cations in tetrahedral and octahedral sites of amphiboles. In addition, the effect of starch on the depression of Fe-Mg-Al-bearing amphiboles during flotation can be attributed to the presence of metal ions on the amphibole surface, which are capable of forming strong chemical complexes with starch molecules."

Jan 1, 2014

By ?. Kostadinov

Theoretical study of the behavior of grinding medium presented by TBP (tetraballpebs) was conducted by computer modeling of the position of grinding medium at different speeds and different drum fill factor. For the modeling were used known equations of motion derived for the ball load. Algorithm was created by SolidWorks software, allowing determination of center of gravity of the load in the mill and energy for grinding. These results were compared with similar results obtained by ball grinding medium. The capabilities of both grinding media are demonstrated by graphics under the following conditions: 1.Equal dimensions of the experimental model of the mill; 2.Equal mass of the grinding loads; 3.Comparison of grinding bodies with the same number, mass and density. Keywords: simulation, behavior, grinding medium, balls, tetraballpebs

Sep 1, 2012

By G. Unland

The sizing of crushers depends on the expected crushing forces. However, the crushing forces develop differently with every individual rock while it is compressed by the working surfaces of the crusher. For sizing, this compression process has to be characterized by the maximum crushing force. The maximum crushing force depends on the strength, shape and size of the rock, the amount and velocity of the imposed displacement of the working surfaces of the crusher on the rock and the conditions of the contact surfaces. From experience it is known that the strength of the material and, therefore, the crushing forces depend on the size of the specimen. This dependence is the so called size effect. The determination is based on compression tests. The force development is recorded during the compression of the specimen and for every individual test the maximum force is determined. The occurring maximum crushing forces of several rocks with the same diameter comminuted under the same conditions can be assessed by a mean value and a variance. The relationship between the mean values of the cross section related maximum crushing forces FAmax and the corresponding sizes d of the specimens can then be described by mathematical functions. They are derived from different approaches (phenomenological, statistical and statistical-physical methods). The phenomenological methods are subjective and yield functions depending on the assumptions of a person, whereas the statistical and statistical-physical methods are based on an evaluated function and the optimization of the parameters.

Jan 1, 2014

By P. Altinkaya, O. Celep, H. Deveci, E. Y. Yazici

"Copper-bearing gold ores have proved difficult to treat in conventional cyanide leaching process owing to prohibitively high consumption of cyanide by readily soluble copper minerals interfering with gold extraction. Cyanide leaching of gold from copper-rich ores can be improved by intensive cyanidation or application of physical and chemical pre-treatment methods (e.g., ultra-fine grinding, roasting and leaching). In this study, nitric acid leaching of a copper-bearing pyritic concentrate (0.3% Cu, 62 g/t Au and 110 g/t Ag) as pre-treatment prior to cyanidation was investigated. The mineralogical analysis of the concentrate has revealed that it is composed of mainly quartz (25%), pyrite (32.7%), sphalerite (5.37 %), galena (2.12 wt %) and anglesite (1.13 %). Arsenopyrite, chalcopyrite, covellite and bournonite were also detected as minor phases present. Previous studies carried out by the authors showed that direct cyanidation (1.5 g/L NaCN) of the as-received concentrate (d80: 80 µm) produced low gold (45% Au) and silver (46% Ag) extractions. Nitric acid pretreatment of the as-received concentrate was performed for 5 hours at 1-5 M HNO3 and 80oC. In these tests, 65% Cu/Pb and 94% Zn were leached. The nitric acid pre-treatment improved the extraction of gold and silver in subsequent cyanide leaching (1.5 g/L NaCN) to 82% Au and 87.5% Ag with a concomitant decrease (up to 54%) in cyanide consumption. It can be inferred from these findings that the removal of copper from the concentrate and the liberation of the occluded gold by nitric acid leaching as pretreatments can be appropriately employed for the treatment of the copper-bearing pyritic concentrate with high gold/silver content. INTRODUCTION Refractory ores are often characterized by their low amenability to cyanide leaching resulting low (often <80%) Au/Ag extractions (Bhappu, 1990; Celep et al., 2009; Marsden and House, 2006). One of the most common causes of refractoriness is the physical or chemical encapsulation of submicroscopic or fine-grained gold in sulphide minerals such as arsenopyrite and pyrite (La Brooy et al., 1994; Vaughan, 2004). To render refractory gold ores/concentrates amenable to cyanide leaching, the decomposition of sulphide minerals within a pre-treatment process to expose the encapsulated gold grains to the action of cyanide is required. In this regard, roasting, pressure oxidation and biooxidation are commercially used processes for pretreatment of arsenopyrite/pyrite gold ores/concentrates ahead of cyanide leaching (La Brooy et al., 1994). Presence of cyanide-soluble copper minerals in the ore leads to low gold recoveries and high cyanide consumptions under conventional cyanide leaching conditions. High cyanide concentrations (CN:Cu>4) should be employed to achieve high gold recoveries from copper-rich gold ores/concentrates. This may require recovery of cyanide from effluents. In this regard, SART Process (sulphidisation-acidification-recycling-thickening) employed industrially for recovery of cyanide and copper as a by-product. This process simply relies on the addition of sulphide (as Na2S, NaSH or H2S) to the leach solution prior to the acidification to pH 4-5. This results in the precipitation of copper as Cu2S and occurrence of free cyanide which is recycled to the leaching circuit after S/L separation (Dai et al., 2012)."

Jan 1, 2018

By B. Gorain, O. A. Bascur

"The advent of digital revolution has now enabled us with numerous tools that could be leveraged to transform our operational data into actionable insights. Key opportunities with digitization include better visualization, transparency, integrated planning and execution for value-chain optimization, that results in smarter production, intelligent response to changes in ore, process and equipment conditions, reduce energy and waste along with prevention of asset breakdown, safety and environmental issues. It is important to realize that these digital tools have limited value, from a metallurgical operational context, if we cannot bring-in the appropriate domain expertise along with getting the basics right. The focus within Barrick is to ensure that there is adequate depth of different disciplines built into our platforms along with breadth to integrate other disciplines such as geology and mining for an effective Mine-to-Mill integration. A gold recovery improvement strategy based on optimal Gaudin size distribution, leaching performance monitoring and guidance via feed grade maps is discussed. Simultaneous identification of process and equipment constraints enable finding the best overall conditions for Gold recovery. This paper discusses the methodology, findings, and challenges in the ongoing journey of implementing a Metallurgy Analytics platform that evolves from being retrospectively descriptive to anticipatively prescriptive.INTRODUCTION The last few decades have seen some remarkable advancement in information technology, but recently various digital technologies have resulted in several synergies to deliver innovation in diverse applications. The mining industry has been relatively slow in adopting these technologies compared to the other industries, but this scenario is changing fast. Mining companies globally are going through a series of challenges such as declining ore grades with complex metallurgy, increasing depth of ore bodies, high capital and operating costs, lower productivity, shortage of technical resources, significant pressure from stakeholders to deliver, along with growing environmental and corporate social responsibility issues. Improvement in profitability would need significant improvements in operational performance."

Jan 1, 2018

By Yuexin Han

The wet preconcentration of haematite, comminuted by high-pressure grinding roller was studied, using the cylindrical ferromagnetic medium. The effects of various factors including rod diameter, rod gap and background magnetic field intensity (BMFI) on the performances of preconcentration for different size fractions and the force analysis of single mineral particles with different diameter in the separation zone were emphatically investigated. The results showed that as the rod diameter increased, the rod gap decreased, and the BMFI increased the tailings grade and the tailings yield reduced while the concentrates recovery raised that was regardless of variations in feed size distribution. For the -3.2+0.18mm size fraction preconcentration, the magnetic medium with a rod diameter of 4 mm and a rod gap of 7 mm at BMFI of 454kA/m is used to get a higher performance. For -0.18mm size fraction preconcentration, the magnetic medium with a rod diameter of 4 mm and a rod gap of 4 mm at BMFI of 263kA/m is used to get a higher performance. After the classifying preconcentration, at the optimum condition, the overall concentrate grade increases by 9.56 percentage points and the concentrate recovery is up to the 82.67% with a tailing grade of 10.68% and a tailing yield of 40.31%. The magnetic force, exerted on weekly magnetic minerals was proportional, to the specific susceptibility and square of BMFI. For the same BMFI, the magnetic capturing force on coarse particles increased, and that on fine particles decreased with the increasing of rod diameter. For the lean locked-particles, considering the gravity and viscous resistance of particles, rods with a big diameter were beneficial to the capture of coarse particles and had no influence on the capture of fine particles, while rods with a small diameter were good for the capture of fine particles and not suitable for the capture of coarse particles of lean locked-particles. Keywords: low grade haematite, high-pressure grinding roller, high intensity magnetic separation, pre-concentration

Sep 1, 2012

By E. Hulthén

Cone crushers are used in the mineral, mining, and aggregate industry for fragmentation of rock materials. Control systems for cone crusher settings are widely used to compensate for wear and to protect the machines. The eccentric speed in a cone crusher affects the number of compressions the material is exposed to and thus the particle size distribution of the product. Eccentric speed also affects crusher capacity. However, the speed of the crusher is mostly fixed, because speed changes must be made by shifting pulleys, a process which is quite time-consuming. By applying a frequency converter, which has decreased in cost during recent years, it has become possible to adjust the speed continuously. By also applying mass-flow sensors to the process, the crusher can be run optimally to yield the most sellable products in a given moment. Existing systems normally only protect the machine. The sensors can be mass-flow meters, e.g., conveyor-belt scales. To analyze data from the process and calculate the appropriate value for the speed, an algorithm has been developed. The developed algorithm was tested and evolved at a crushing plant for aggregates that produces around 350 kton a year. The algorithm was implemented in a computer that could communicate with the frequency controller, retrieve data from four mass-flow meters, and also interact with the opera-tor. The computer was reachable over the Internet for the researchers at Chalmers and the algorithm was tuned and improved on-line. The result is a crushing stage that consistently and maximally produces the most desirable product. The performance (yield of required products) increased by 4%. As a bonus, the lifetime of the mantles increased 27% on the evaluated crusher.

Jan 1, 2014

By P. Spolaore

In the frame of Bioshale FP6 project, the bioprocessing of a polymetallic and polymineral concentrate produced in an industrial operation in Lubin, Poland, was assessed. Following successful batch culture tests, processing in continuous conditions was tested to determine the main specifications for the application of the stirred-tank technology to this sulphide concentrate from black shale ores. The experimental work was carried out in a laboratory-scale unit consisting of 3 stirred tanks (50L or 20L) using an acidophilic and moderate thermophilic bacterial population. Different configurations of the unit and key operating parameters were tested (nutrient medium composition, solids concentration, rates of agitation and aeration). Scientific and technical approaches, such as bacterial community structure and mineralogical analysis were implemented in order to better understand the chemical and biochemical reactions occurring in the system. Using the data produced during the continuous operation, downstream processing assessment for both copper and silver recovery was also carried out. The best copper recovery obtained in the continuous operation was 92% and a hot brine leaching of the bioleach residue (PLINT process) allowed to recover 92% of the silver. A preliminary tech-no-economic evaluation of Lubin concentrate bioprocessing including bioleaching, copper and silver recoveries demonstrated the potential economic feasibility. Recovery of silver plays an important role in the economy of the process. This study presents promising values to further investigate this bioprocessing option.

Jan 1, 2014

By Avishan Atrafi, Marek Pawlik

"Gas dispersion properties of sodium salts of 6, 12 and 18-carbon fatty acids (hexanoic, lauric and oleic acid) were investigated as a function of pH. A strong effect of pH was observed on gas dispersion properties of fatty acids. At high pH for 12 and 18 carbon fatty acids, at which these surfactants formed a true solution, the gas dispersion properties were similar to those of MIBC. In the case of sodium hexanoate, which has a much higher solubility than the longer chain fatty acids and therefore does not form precipitates, the gas dispersion properties of this surfactant were strongly enhanced in the acidic pH range, where hexanoic acid was fully associated. This result is an indication that undissociated hexanoic acid is much more surface-active than anionic hexanoate. Only a small effect of the surfactant chain length on gas dispersion properties of the tested reagents was observed. The measured critical coalescence concentration (CCC95) values increase slightly by decreasing chain length and range from 5.8 x 10-5 mol/L (17.7 mg/L) for sodium oleate to 7.2 x 10-5 mol/L (16 mg/L) for sodium laurate at pH 10 and 1.9 x 10-4 mol/L (26 mg/L) for sodium hexanoate at pH 3.7. These are compared to CCC95 of MIBC, which is measured to be 8 x 10-5 mol/L (8 mg/L). The soluble molecular species were recognized as the most effective species in preventing bubble coalescence."

Jan 1, 2014

By M. Saghaeian, R. Hejazi, H. Abedini

Vertical ring and Pulsating Wet High Intensity Magnetic Separator (VP-WHIMS) is widely used for week magnetic mineral beneficiation or ferrous impurity removal from non-metallic minerals. Because of the complexity of this machine, mathematical modelling of its process is complicated and time consuming. In this paper, artificial neural network (ANN) and response surface methodology (RSM) were applied to evaluate the VP-WHIMS performance and optimize its main operating parameters in beneficiating of the Chadormalu hematite sample. The operational parameters of this magnetic separator are considered as: magnetic field intensity (2500-8500 gauss), pulsating frequency (20-100 %max), ring rotation speed (0.6-4.6 r/min) and slurry concentration (15-35 w/w %). Concentrate grade and recoveries (weight and Fe) are monitored as responses. Centre composite design (CCD) was used for experimental study. Four process variables were set using small CCD. Eight star points (a=±1), eight axial points (a=±2) and five replicates at the centre point (a=0) were chosen as experimental points. In ANN system, the best network topology was obtained as (4-5-3). The weights connection and biases were obtained using batch back propagation (BBP) method for 21 experimental data points. The results indicate that ANN

Jan 1, 2014

By I. S. M. K. Ilankoon

In heap leaching the transport of the acid from the drippers to the surface of the ore particles is a major factor in the overall performance of a heap. This flow behavior is complex as the flow is unsaturated and occurs along a tortuous set of inter-particle channels and connections. Previous modeling of this system has used equations from oil and ground water flow to model these systems, but the applicability of these models with the larger particles found in typical heaps is suspect as these systems are not necessarily capillary dominated. In particular, as the characteristic particle size goes from below to above a few centimeters, the flow changes from capillary to gravity dominated. This means that typical heap leaching heaps cover this interesting, but complex, transitional fluid flow regime. In this paper a set of experimental studies of this flow, including PEPT (positron emission particle tracking) based tracer experiments, highly accurate liquid holdup measurements and axial dispersion experiments using salt tracers will be presented. In this study, flow through mono-dispersed particle beds was carried out. In particular, the hysteresis in the liquid holdup as the liquid flow rate into the particle bed is varied is investigated, since this hysteresis means that the relationship between flow rate and holdup is history dependent, an effect not included in models currently used to describe fluid flow in heaps. A theoretical model that describes this hysteresis will also be presented. Keywords: heap leaching, hydrometallurgy, modeling

Sep 1, 2012

By Janne Kytökari

Controlling a wide range of minerals processes with single control system is an ordinary way to operate in mines all over the world these days. However the potential of these systems is not yet fully recognized nor utilized. The key issue is to manage the information in a way that enables automating the day-to-day tasks, quality control and safety functions. At the same time it provides means for optimization and constant improvement of processes creating a working environment where the system helps employees to do their key tasks instead of searching, modifying, and transmitting the huge number of information arising every day. The distribution of control system nodes enables the other processes to run heedless of a problem occurring in one of the sub-processes. Also the control room can be in remote location such as in large city removing the need to travel substantially long distances to plant sites every day. When all essential information is brought to the same place there is less risk for a mishap to happen due to information breaks that are often the cause of them. One of the biggest single reasons that result in production losses are break downs of machinery usually caused by normal wear, misuse, incorrect utilization rate etc. For this reason it is important to measure the condition of machines using vibration measurement and diagnostics. By moving from failure or time-based maintenance towards predictive or performance maintenance generates eventually a steady and predictable process but also results in significant long term savings. The mineral process at Talvivaara mine is based on bioheapleaching, whereby metals are leached from ore as a result of bacterial action. Bioleaching is a fairly new technology used in metals recovery. Therefore it is important for the mine to collect and analyze data from different stages of the minerals process. Talvivaara mine?s Metso DNA system has integrated machine condition monitoring and information management. These are not only necessary but also crucial in environmental conditions where the outside temperature can drop below -35°C, where ice and snow dominate the landscape and impact the equipment for four months a year and where distances between equipment can be up to 7.5 kilometers. Keywords: DCS, analyzer, machine condition monitoring, automation, remote communications, optimization, mining, metso DNA, Talvivaara

Sep 1, 2012