Search Documents

By Chitombo GPF

The dilution of blasted ore with cemented backfill materials has been recognised as a significant factor influencing the economics of some underground metalliferous mining operations. Several mechanisms have heen identified as possible causes of fill failures. The purpose of this study was to determine the possibility of damage as the result of one mechanism, that of production blasting adjacent to bodies of cemented hydraulic fill (CHF). A vibration amplitude transfer function has been developed to model the transmission of blast vibrations from the source, through ore, across the ore to CHF interface and into the CHF mass. The model may be applied in the near field. The model has permitted estimation of vibration amplitude at a point in a CHF mass, to which damage criteria may be applied. A number of assumptions and simplifications have been made to render the problem relatively tractable. Ore and CHF material characteristics recorded by a number of authors were utilised to formulate preliminary damage estimations. A simple application of the amplitude transfer model indicated that a zone of plastically deformed CHF would be produced, and would extend to a distance of approximately 0.5 metres from the interface into the CHF. A sensitivity analysis was also conducted, that indicated that the zone of plastic deformation would be more extensive given appropriate conditions. Recommendations for further model development and future laboratory and field investigations have been made.

Jan 1, 1998

By A. Jahedsaravani, M. Massinaei, M. H. Marhaban, N. Mehrshad, M. I. Saripan

"It is well known that froth visual features reflect the operating conditions of the flotation process, so that being able to accurately obtain the froth properties is the most significant criteria to optimize and control this process. Froth segmentation is a useful procedure that can determine the bubble size distribution. Several algorithms have been proposed in this field, but marker-based watershed transform shows the best performance. In spite of this fact, the algorithm suffers from oversegmentation in cases when the flotation froth includes large bubbles along with small ones. In the paper, the marker-based watershed method is modified to prevent oversegmentation of large bubbles. The developed algorithm is validated using some froth images captured at different operating conditions, so the results indicate that the method can segment the mixture of big and small bubbles effectively.IntroductionFroth flotation is a widely used process for separating valuable from gangue minerals. Effective control of flotation circuits has a dramatic effect on overall performance of a mineral processing plant. In most flotation plants, process operators monitor the froth surface visually and make adjustments to process parameters based on their interpretation of the surface appearance and their idea of the appearance of an ideal froth. However, due to natural complexity of the flotation process, achieving optimal control is often not possible for human operators.In recent years, attempts have been made to control the flotation circuits using machine vision systems (Moolman et al., 1995; 1996a,b; Bartolacci et al., 2006; Kaartinen et al., 2006; Vanegas and Holtham, 2008; Aldrich et al., 2010). The froth bubble size distribution is the most significant control variable that reflects the operating conditions in a flotation machine. To date, a number of approaches have been proposed for bubble size measurement from froth images, including segmentation (Sadr-kazemi and Cilliers, 1997; Wang et al., 2003; Mehrshad and Massinaei, 2011), texture spectrum (Nguyen and Thornton, 1995), wavelet (Liu et al., 2005), an improved texture spectrum approach, a method based on binary images (Lin et al., 2008) and, finally, using interfacial morphological information (Yang et al., 2009)."

Jan 1, 2015

By Peter Moser, Mark Ganster, Radoslava Ivanova, Florian Bauer

Blasting accurately in underground drifts and creating a smooth contour requires proper drilling, knowledge about the apparent geology, a well designed blast pattern and ideally a smooth blasting product. These products are usually cartridged explosives with less energy and are charged in the contour holes in order to reduce the energy concentration and therefore the cracking into the surrounding rock. With the development of a new contour blasting system, a device can now be delivered to the industry that that avoids the additional storage of cartridged products when bulk explosives are used. The system consists of a foldable hose that is charged with bulk emulsion, in the same way as the rest of the blast, from the base to the collar of the hole. It centers automatically in the borehole and provides a decoupled charge. The paper describes the system in detail, gives background information on smooth blasting and presents the first successful field tests using the system in the drifts of an underground mine. It shows the advantages of blast results that produce more stable contours that reduce the amount, time and cost for support but also increase safety underground.

Jan 1, 2012

By A. L. Nunes, J. R. E. Garcia, G. Silva, U. Prasad, C. Rabe

"Drilling through the Guayabal shales, a gray calcareous shale, and the C1 to C100 formations, a well-cemented calcareous-sandstone in Corralillo field, Mexico, is a challenge due to severe wellbore instability problems. Additionally, there has been a history of ineffective reservoir stimulations by hydraulic fracturing. To predict and mitigate these subsurface issues, it is essential to characterize the mechanical properties and rocks strength for a better prediction of borehole stresses and collapse pressure during drilling. Various correlations can be used to estimate and/or determine the unconfined compressive strength but most of them are based on transit time and porosity.In this study, grain size distribution was combined with acoustic travel time, porosity and static Young’s modulus to develop a rock strength prediction model for the turbiditic sandstones of the Chicontepec basin. The main reason this combination of parameters was employed was because of the wide variations in rock strength estimated using traditional porosity-based correlations such as the McNally’s (1987), GMI-Jizba-E’s and Bradford’s (Bradford et al., 1987).To develop a new correlation, a geomechanical and microstructural campaign was initiated. Mineralogy by X-ray diffraction, pore and grain sizes by petrography, clay distribution by SEM and porosity by mercury intrusion porosimetry were measured. Static and dynamic Young’s moduli and Poisson’s ratios were acquired by triaxial and ultrasonic measurements on undisturbed sandstone samples from the Chicontepec basin. More than ten offset wells with wireline data, including transit time, porosity, density, resistivity and gamma ray, were used for reservoir and geomechanical characterizations.Our analyses lead us to propose a new correlation for predicting the uniaxial compressive strength (UCS) of sandstones of the Chicontepec Basin as a function of transit time and grain diameter, both of which can be derived independently from destructive laboratory tests. Our results also highlight the importance and value adding of a combined approach incorporating grain size analysis in the rock strength prediction. The UCS predicted using the transit-time and grain-size-based model presents a median value (P50) of 76 MPa, P10 of 55 MPa and P90 of 89 MPa."

Jan 1, 2015

By V. Vakiloroaya

The paper aims at developing a hybrid solar-assisted air conditioner system for performance enhancement and energy efficiency improvement. To increase sub-cooling of the refrigerant at partial loads, we propose a new discharge bypass line together with an inline solenoid valve, installed after the compressor to regulate the mass flow rate of the refrigerant vapour passing through a hot water storage tank. For control design, a lumped parameter model is first developed to describe the dynamics of the system in an explicit form of input-output relationship. The system has been fully-instrumented to examine its performance under different operation conditions. The system model is then validated by extensive experimental tests. The predictions from the models exhibit a good coincidence with experimental results, judging by an RMS error less than 15%. Based on the obtained dynamic model, a linear quadratic regulator (LQR) is applied to optimize a cost function of the output errors and control efforts. The key challenge is to regulate the refrigerant temperature entering the condenser by controlling the valve opening. The design approach is then tested in a transient simulation tool to predict the system performance in transient conditions. The experimental results obtained from implementation with PLC demonstrate that the proposed system delivers higher system efficiency owing to the higher refrigeration effect in the direct expansion evaporator. Thus, the novel development is promising for improvement of energy efficiency, enhancement of the system performance while fulfilling the cooling demand. Consequently, between 25 and 43% of monthly electricity can be saved on average.

Aug 1, 2013

By M. K. Mohanty, H. Akbari, L. A. Ackah

Dry separation was the predominant method of coal cleaning in the United States from the 1930s to 1980s. The application peak of dry separators for cleaning raw coal was in 1965, when about 23.1 Mt of cleaned bituminous coal was produced. The main advantage of dry coal cleaning is the elimination RIWKH GHZDWHULQJ VWDJHV DQG VLJQL¿FDQWO\ UHGXFHG moisture in comparison to wet processing. In addition, developed dust control systems have made dry cleaning method an environmentally friendly process. The largest air-based coal cleaning plant was built in Pennsylvania in 1968 and could clean 1,272 t/h of raw coal sized smaller than 19 mm. This was followed by a decline in dry coal cleaning to less than 3.6 Mt in 1988. Some of the main reasons that shifted coal operations IURPGU\WRZHWSURFHVVLQJZHUHWKHQHHGIRUPRUHHI¿FLHQW separations with lower density cuts, increase in raw coal surIDFHPRLVWXUHVSHFL¿FDOO\LQXQGHUJURXQGPLQLQJWRFRQWURO GXVW ¿QHUSDUWLFOHVL]HUHTXLUHPHQWV LQFUHDVHLQ¿QHVLQUDZ coal from underground mines, and health and safety concerns related to dust and noise (Arnold, Hervol and Leonard III, 1991; Miller, 2011).

By F. C. Appleyard

A couple of miles southwest of the town of Saltville in the western tip of Virginia is a little village called Plasterco. Gypsum has been produced in this area since about the year 1815, being originally found as small outcrops at the surface. Production in the early days was very small, and the use of the mineral was limited to that of "land plaster" or ground gypsum which was spread on the land to sweeten the soil. In the late 1800's, a small calcining plant was constructed and the production of gypsum plaster began. About this same time, the surface rock was depleted and it became necessary to begin underground mining operations in order to maintain a continuous supply of raw material. The United States Gypsum Company became interested in this property in 1909, and has operated there ever since, having enlarged the calcining mill and built a plant for the manufacture of gypsum wall-board in the middle 1920's. Production of gypsum continues from underground' mining operations, and the present mine at Plasterco is now about 1,000 feet below the surface, making it the deepest gypsum mine' in the world.

Jan 1, 1965

By P. H. S. W. Kulatilake, T. Hudaverdi, C. Kuzu

Prediction of blast fragmentation plays a key role for overall productivity of mines. In this study, a new multivariate analysis procedure for prediction of blast fragmentation is presented. Several blasts performed in various mines and rock formations worldwide were brought together and evaluated. An extensive blast database was created. Blast design parameters, the modulus of elasticity and in-situ block size were considered to perform multivariate analysis. A complete multivariate analysis procedure was applied in three steps. First, a hierarchical cluster analysis was used to separate the blast data into different groups of similarity. Two different groups were formed based on the elasticity modulus values. In the second step, group memberships were checked by discriminant analysis. The dominant parameters of the occurrence of the groups were determined. Also, discriminant analysis was used to determine the group membership of the respective blasts. As the last step, the multivariate regression analysis was applied to develop prediction equations for estimation of the mean particle size of muckpiles. Two different prediction equations were developed based on the rock stiffness. Validation of the proposed equations on various mines was performed. Prediction capability of the proposed models was found to be strong. The models are not complex and are suitable for practical use at mines.

Jan 1, 2011

By L. M. Cenegy

Introduction The formation of scale is common in gold ore processing plants. A working definition of such scale is: "A hard, tightly adhering deposit formed in place by the precipitation of calcium-bearing mineral compounds from water." The most common scale found in gold processing plants is calcium carbonate (CaCO3) although calcium sulfate (CaSO4) is occasionally a problem. The problem of scale in carbon strip circuits Carbon strip circuits present a particularly challenging scale inhibition problem. Many of the factors that tend to promote scaling are present in these systems. For example, carbon strip circuits are run at high temperatures and high pH levels and require long batch cycle times. Tortuous paths are encountered by the strip solution circulating through heat exchangers, pipes and elbows, causing transient pressure drops throughout the system. Severe conditions such as these cause the water to possess a high scaling potential and may lead to the breakdown of some of common types of scale inhibitors. Formation of scale Natural waters contain dissolved minerals and gases that promote scaling. One of the contained gases, carbon dioxide (CO2), is an important factor in scale deposition. Carbon dioxide dissolves in water to yield carbonic acid according to the following reaction: [CO2 + H2O - H2CO3 (carbonic acid)] Carbonic acid rapidly dissociates to yield bicarbonate and carbonate ions depending on the pH of the system: [H2CO3 -s H+ + HCO-3 (pH range 6-10) HCO3 -a H+ + COO (pH range > 9)] In gold cyanidation processes, lime is added to raise the pH of the mill solution to 10 or above to promote cyanidation of the gold and to eliminate the possibility of hydrogen cyanide (HCN) formation. Lime contributes both hydroxyl ions (OH--) and calcium ions (Ca++) to the solution. The normal scale forming reactions in mill water systems were described by Beasley (1973) as: [HCO-3 + OH -s C03 + H2O Ca++ + C03 -a CaCO3] Factor affecting scale deposition According to Linke's (1958) solubility tables, the solubility of calcium carbonate in carbon-dioxide free water is only 13 mg/dm3 (13 mg/L) at 25° C (77° F). Scale deposition occurs when the concentration of calcium and carbonate ions in the solution exceeds the solubility of calcium carbonate. This occurs, in most cases, when the water has undergone some chemical or physical change. Some typical changes that might occur that lead to scale deposition are discussed below. Temperature An increase in temperature can greatly increase the tendency to form calcium carbonate scale. Studies by Miller (1952) have indicated that calcium carbonate is less soluble at higher temperatures. Hence, high temperatures promote scaling. For this reason, scale is often noticed on heat exchangers, autoclaves and other high temperature surfaces. Pressure A decrease in pressure may lead to an increase in the tendency to form calcium carbonate scale. Fulford's (1967) work has shown that scale is more soluble at high pressures. Hence, scale is likely to be prevalent in pump suction lines, elbows, baffles and other areas that produce turbulence and subsequent pressure drops. Change in pH Calcium carbonate scale is pH dependent and tends to form more readily at high pH. Any event that causes an increase in pH, such as the introduction of lime or caustic, would tend to initiate scale formation. Since most gold recovery operations are run at a pH above 10, the tendency to form calcium carbonate scale is always great. The use of scale inhibitors to prevent calcium carbonate scale Many products are commercially available to inhibit the formation of calcium carbonate scale. Some of the more effective types include phosphonates, as well as acrylate and maleate-based polymers and copolymers. Many of these products function by means of threshold

Jan 1, 1992

By L. M. Cenegy

The formation of scale is common in gold ore processing plants. A working definition of scale, applicable to the various scaling conditions found in gold ore processing plants, would be: "a hard, tightly adhering deposit formed in place by the precipitation of calcium-bearing mineral compounds from water". The most common scale found in gold processing plants is calcium carbonate (CaCO3) although calcium sulfate (CaSO4) is occasionally a problem.

Jan 1, 1990

By M. S. Shishvan, J. Sattarvand, R. S. H. Meij

Navigating miners during an evacuation using a smart evacuation technology can significantly decrease the evacuation time of an underground mine in case of an emergency. This paper presents a mathematical programming model to calculate the most efficient escape path for each miner as a critical component of the smart evacuation technology. In this model, the total evacuation distance of the crew is minimised and scenarios with blocked pathways, and stamina categories for the miners are simulated. It was found that all the tested scenarios are technically feasible. Using the feature that filters out blocked pathways has no downsides, as safer routes are calculated, and there is no penalty in the computation time. The paper also discusses the social and technical issues that need to be overcome before the algorithm can be implemented as an actual escape solution.

Sep 1, 2021

By J. D. Robertson

An in situ water sampling device has been developed to measure biologically-available or “labile” metals in natural waters and effluents. The active mechanism involves the use of a polyacrylamide gel layer to quantitatively control metal transfer to a trace-metal-adsorbing, gel-imbedded resin. Because the resin only adsorbs free metal ions (the gel sampler methodology is a kinetic speciation technique), and because metal bioavailability is related to the free-ion activity, the device provides a direct measure of the biological-availability of metals in the environment sampled. The prototype consists of a layer of ion-permeable polyacrylamide gel which separates the solution to be sampled from an ion exchange resin. Because approximately 90% of the polyacrylamide gel is water, mass transport through the gel is diffusion-controlled, and is therefore well defined. Metal ions are rapidly bound by the resin, creating a steep concentration gradient in the gel. The amount of labile trace metal that accumulates on the resin can be related directly to the concentration of the metal in solution, the exposure time and the molecular diffusion coefficient of the labile species. In addition, the passive nature of this device affords it the potential to address many of the limitations presented by conventional sampling methods, such as sample contamination introduced during collection or filtration and changes in trace metal speciation prior to analysis. Laboratory studies and limited field trials indicate that the sampler behaves as anticipated and illustrate that biologically- available metal concentrations in many environments are a small fraction of the total concentrations and often significantly less than the dissolved concentration. The implications of this on regulatory criteria are discussed. Additional field trials and correlation with bioassays are currently underway.

Jan 1, 2000

By E. Petrakis, K. Komnitsas

The main objective of batch grinding modeling is the estimation of the product particle size distribution over time or specific energy input to the mill. So far, the developed analytical methods require often complicated calculations which are timeconsuming. Thus, more simple approaches that allow the reliable prediction of the complete product size distribution need to be developed. In the present paper, an approach, based on the population balance model (PBM), that reliably predicts the product size distribution is proposed. In order to enable this, the simplified form of the fundamental batch grinding equation was transformed into the well-known Rosin–Rammler (R-R) distribution, thus allowing the determination of the breakage rate for each grinding period. A time-dependent breakage rate framework was developed where the traditional linear theory of the PBM is considered a partial case. This approach allows the deviations from the linear theory to be categorized and the degree of the acceleration-deceleration of the breakage rate to be predicted. Modeling results were validated by laboratory grinding studies using two homogeneous materials, quartz and marble, and one heterogeneous, a limonitic laterite. The experimental data revealed that grinding exhibits non-first-order behavior and the degree of deviation from the linear theory depends on the tested material. The reliability of the proposed model was validated with the use of the distribution modulus n, the a value of the breakage rate parameter, and the optimum n values that minimize the sum of the differences between the experimental and estimated particle size distributions.

Feb 8, 2021

By Eduardo Poltronieri Trés, Anderson Denadai Thomazini, Rodrigo Boyer Fernandes, Francisco de Assis Dutra Macedo, Gilvandro Bueno, Maycon Athayde, Rossano Augusto Pilon Nunes

The fundamental importance of comminution by high-pressure grinding roll (HPGR) technology to efficiently increase the particle surface area lies in lower energy and water consumptions for iron ore pellet feed production. This study compared the ball wet milling process with the innovative HPGR processing technology for hematite-goethite ores. Green-pellet balling and induration processes were simulated on the bench and pilot scales.

By Eduardo Poltronieri Trés, Anderson Denadai Thomazini, Rodrigo Boyer Fernandes, Francisco de Assis Dutra Macedo, Gilvandro Bueno, Maycon Athayde, Rossano Augusto Pilon Nunes

The earliest industrial application of high pressure grinding rolls (HPGR) at comminution was in 1984 in the cement industry. Since then, the equipment has been widely applied in mining activities. Despite the rapid spread across the industry, several challenges are still present in the equipment’s application, especially considering the complex ore breakage behaviour reported for this process. The pellet feed’s HPGR comminution was recognized as fundamental to efficiently increase the particle surface area (e.g., blaine specific area, BSA) at a lower energy and water consumption level (Chapman et al. in J Southern Afr Instit Mining Metall 113:407–413, 2013). The present study considers a novel milling process applying only HPGR as a re-regrind stage after concentration. The amount of successive ground product recirculation into the machine to achieve the required particle size for the pelletizing process was investigated. The study compared the ball wet milling process with the innovative processing technology for hematite–goethite ores. Green pellet balling and induration processes were simulated in bench and pilot scale. The milling results showed a considerably steep increase in BSA after each recirculation step into the HPGR, although compared with the ball-milled product the size fraction <45 μm% increased a modest five percentage points after three recirculation cycles, remaining steady until the last recirculation step. As a result, the green pellet generated presented higher concentration of pellets between 10 and 16 mm (%10-16 mm), with a higher drop number than typically observed when produced with ball-milled feedstock. Consequently, on the induration process, a higher pellet deformation was observed during the pot grate loading. Despite that, the fired pellets still presented an outstanding performance in cold crush strength (CSS) considered suitable to an industrial application.

By N. Verbaan, E. Bourricaudy, M. Dry

"Starfield Resources is developing a novel circuit for the recovery of nickel, copper, cobalt, iron oxide, sulphuric acid and precious metals from the Ferguson Lake deposit in Nunavut, Canada. In this deposit, pentlandite is too finely disseminated in pyrrhotite for the production of a smelter-grade nickel concentrate at an acceptable nickel recovery, so established technology is not applicable and a novel chloride-based circuit is under development. The enabling aspect of this circuit is the hydrolysis of ferric chloride to hematite, releasing gaseous hydrochloric acid that is recycled. Conventional steps are used for separating and recovering the valuable metals from the chloride solution generated. This paper briefly outlines the circuit and presents the results of experimental work on the enabling steps, viz. the oxidation and hydrolysis of iron chloride to hematite and gaseous hydrochloric acid.IntroductionThe Ferguson Lake bulk sulphide ore body in Nunavut, Canada, owned by Starfield Resources Inc., contains significant amounts of base and precious metals but its mineralogy is such that it is not amenable to conventional processing. Pentlandite, for example, is too finely disseminated in pyrhhotite for even modem techniques such as fine grinding and improved flotation reagents to be effective [ 1] and extracting the value requires processing the entire bulk sulphide, including the pyrrhotite. To give the project a total green footprint, in terms of both carbon emissions and acid rock drainage, Starfield imposed the following requirements:• No reactive tailings to generate acid rock drainage.• No gaseous emissions other than normal atmospheric constituents.• No liquid effluents.• No regular consumption of fossil fuel.• High recoveries of all the valuable metals."

Jan 1, 2011

By Kazusuke Sato, Takahiro Uno, Koji Hoshino

"A novel Ni coating technique of Ni(OH)2 powders was developed to improve the positive-electrode performance· of the Ni-MH batteries. It was found out that Ni(OH)2 powder was reduced by N2H4 without any catalysts in an alkaline - solution at high temperatures. In result of observation of pH and potential changes in the solution during the reaction, it was found that the reduced species was HNio2- ion dissociated from Ni(OH)2 in the alkaline solution. The molar fraction of reduced Ni of the Ni(OH)2 was increased in proportion to the amount of added N2H4. At the small Ni fraction, a porous Ni layer was formed on the surface of Ni(OH)2 powder. Open cell tests were carried out with the paste type electrodes made of either the Ni coated Ni(OH)2 powder or non-coat powder, and cell performances were compared. In result, it was found that the Ni coating technique is effective on improvement in the utilization of Ni(OH); as a positive-electrode active material under high current densities.IntroductionNi-MH rechargeable battery is generally used for the power source of portable machines and electric vehicles because of its good performance at high energy density and. long term cyclical life as well as cleanness and good safety. Cell component materials have been improved respectively, and as concerns ·the positive-electrode reducing 'the internal resistance is a principal problem to improve the discharging performance at higher current densities.In recent years, improved Ni(OH)2 powders coated with conductive materials as NI. or CoOOH have been developed for the· positive-electrode active materials in order to· reduce the internal resistance of the electrode1)· 2) The Ni coated Ni(OH)2, however, is costly because it is fabricated by .the -non-electrode plate technique which needs a expensive precious ·metal catalyst as PdC12We found that Ni(OH)2 powder was reduced by N2H4 without any cryatalysts in an alkaline solution at high temperatures. After the treatment, Ni(OH)2 powder become gray color like Ni powder from light-green color; and. turned into a magnetic. In this study, the mechanism of the -reducing reaction was investigated to apply the reactions .to a novel Ni coating technique of Ni(OH)2 powders, · and the performance of the Ni coated Ni(OH)2 powder obtained by the reducing process was evaluated as an -positive-electrode active material of Ni-MH batteries."

Jan 1, 2000

By D. Weijie, S. Kai, Y. Hu, X. Ning, M. Shiyi, W. Junpeng, Z. Guihong, L. Xianjie

Flotation is one of the most important processes in the copper production industry. The copper grade in the concentrate is a pivotal indicator of the flotation process performance. However, it is difficult to achieve real-time measurement through hardware sensors. Based on the production data provided by an industrial operation, a novel soft sensor based on multi-layer perceptron (MLP) is proposed for effective monitoring of this pivotal indicator. The proposed soft sensor uses the nonnegative garrote (NNG) to perform global variable selection for MLP, while a local search (LS) approach is incorporated to improve the model presented by NNG. Simulation results show that the proposed algorithm has higher prediction accuracy and better model simplicity than other algorithms. Furthermore, the variables selected are consistent with the field experience, and the developed model can provide reference of feedback control for the optimisation of the process. Keywords: Flotation process of copper ore, nonnegative garrote, local search, soft sensor, multi-layer perceptron

Jan 1, 2020

By Baruch Grinbaum, Edwin Bwalya, Robert Minango, Deogratias Bukunkwe

Solvent extraction of Cu from acidic leach, using an oxime extractant, e.g. LIX 984 or Acorga is a well known and established process. As the process advances, Cu is extracted to the solvent and is replaced by H+ in the aqueous phase. At high acidity the distribution coefficient of Cu between the solvent and the aqueous phase decreases, and eventually relatively high concentration of Cu remains in the raffinate, regardless of the number of equilibrium stages. In many processes this phenomenon is immaterial, as the raffinate returns to the leaching and no copper is lost. But when the copper raffinate is used for processing of additional metals, minimal concentration of Cu in the raffinate is essential for an effective process. The recommended process includes three steps: 1. SX-1: Standard extraction of Cu with oxime. The resulting raffinate contains about 6-8 g/L Cu and 50 g/L H2SO4. 2. SX-N: Extraction of most of the acid into an amine-based solvent, and stripping it with a base, e.g. aqueous ammonia, caustic, Na2CO3 etc. The extraction removes no metals, but decreases the concentration of acid from 50 to 10 g/L. 3. SX-2: Extraction of the neutralized solution once more with oxime, to remove the residual copper. Such a process enables one to get down to 100-150 ppm Cu in the final raffinate. This process was developed and tested in the R&D facility in Chambishi Metals plc, by a joint team of Chambishi & Bateman, using Cognis LIX 984N and real solutions from the plant. In the laboratory scale, the equilibrium isotherms for SX-1, SX-2 and the neutralization were developed. Computer simulation of the results showed that the optimal configuration is two stages for both extraction and stripping for SX-1. For SX-2 2-3 stages of extraction and two stages of stripping are needed. The stripping stages may be common to both SX-1 and SX-2. The neutralization of SX1 raffinate was tested both by conventional precipitation with lime and by extraction with Alamine based solvent extraction and stripping with a solution of 10% NaOH. For the SX-N only one stage was needed for both the extraction and stripping. The bench scale pilot plant was run for both SX-1 & SX-2. The results were very similar to the simulated ones, and the configuration of 2E2S for SX-1 and 3E=2S for SX-2 delivered the required raffinate with less than 150 ppm Cu.

Jan 1, 2005

By R. Minango

Solvent extraction of Cu from acidic leach, using an oxime extractant, e.g. LIX 984 or Acorga is a well-known and establishedprocess. As the process advances, Cu is extracted to the solvent and is replaced by H+in the aqueous phase. At high acidity the distribution coefficient of Cu between the solvent and the aqueous phase decreases, and eventually a relatively high concentration of Cu remains in the raffinate, regardless of the number of equilibrium stages. In many processes this phenomenon is immaterial, as the raffinate returns to the leaching and no copper is lost. But when the copper raffinate is used for processing of additional metals, minimal concentration of Cu in the raffinate is essential for an effective process. The recommended process includes three steps: SX-1?standard extraction of Cu with oxime. The resulting raffinate contains about 6?8 g/lCu and 50 g/lH2SO4. SX-N?Extraction of most of the acid into an amine-based solvent, and stripping it with a base, e.g. aqueous ammonia, caustic, Na2CO3etc. The extraction removes no metals, but decreases the concentration of acid from 50 to10 g/l. SX-2?Extraction of the neutralized solution once more with oxime, to remove the residual copper. Such a process enables one to get down to 100?150 ppm Cu in the final raffinate. This process was developed and tested in the R&D facility at Chambishi Metals plc, by a joint team of Chambishi & Bateman, using Cognis LIX 984N and real solutions from the plant. In the laboratory the equilibrium isotherms for SX-1, SX-2 and the neutralization were developed. Computer simulation of the results showed that the optimal configuration is two stages for both extraction and stripping for SX-1. For SX2, 2?3 stages of extraction and two stages of stripping are needed. The stripping stages may be common to both SX-1 and SX-2. The neutralization of SX1 raffinate was tested both by conventional precipitation with lime and by extraction with alamine-based solvent extraction and stripping with a solution of 10% NaOH. For the SX-N only one stage was needed for both the extraction and stripping. The bench scale pilot plant was run for both SX-1 and SX-2. The results were very similar to the simulated ones, and the configuration of 2E2S for SX-1 and 3E2S for SX 2 delivered the required raffinate with less than 150 ppm Cu.

Jan 1, 2005