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By Hasan Nizamoğlu, Z. Abidin Sarı, Aslıhan Demiraslan, M. Deniz Turan, Tolga Depci

In this study, recovery of copper from solid material (obtained by leaching of chalcopyrite with oxalic acid in the presence of hydrogen peroxide) with a copper oxalate structure was carried out selectively using HCl. The chemical composition of the solid was as 29.3%, 9.7%, and 13.3% for Cu, Fe, and S, respectively. Selective recovery of copper by degrading the copper oxalate structure with a low-solubility product (Ksp = 4.43 × 10−10) was performed by conventional leaching in the presence of HCl. The optimum leaching conditions were determined as 5 M of HCl concentration, 318 K of leaching temperature, 120 min of leaching time, 25 ml/g of liquid–solid ratio and 400 rpm of stirring speed. Under these conditions, approximately 77% of copper and 3% of iron were taken into the solution. According to the characterization of the leach residue that was obtained, the oxalate structure was degraded. Moreover, the results of XRD analysis showed that the sulfur (S) and cubanite (CuFe2S3) phases were mostly observed in leaching residues, and this was supported by the SEM-EDX data. Based on the results, it may be stated that selective copper extraction can be obtained from a chalcopyrite concentrate by a two-step leaching method using a conventional hydrometallurgical technique.

By D. R. Wilburn

This summary of international mineral exploration activities for the year 2013 draws upon information from industry sources, published literature and U.S. Geological Survey (USGS) specialists. The summary provides data on exploration budgets by region and mineral commodity, identifies significant mineral discoveries and areas of mineral exploration, discusses government programs affecting the mineral exploration industry and presents analyses of exploration activities performed by the mineral industry. Three sources of information are reported and analyzed in this annual review of international exploration for the year 2013: 1) budgetary statistics expressed in U.S. nominal dollars provided by SNL Metals & Mining (SNL) of Halifax, NS, Canada (formerly Metals Economics Group (MEG); 2) regional and site-specific exploration activities that took place in 2013 as compiled by the USGS; and 3) regional events that affected exploration activities, including economic, social and political conditions, that were derived from published sources and unpublished discussions with USGS and industry specialists. Commodity and regional compilations are presented in this summary. Because multiple sources are used to develop commodity and regional compilations, reported statistics may vary depending on the source and type of data that are being reported. The SNL data summarize planned company budgets for worldwide exploration activities in 2013 for 20 nonfuel mineral commodities based on surveys returned by companies primarily focused on precious metals (gold, platinum-group metals and silver), base metals (cobalt, copper, lead, molybdenum, nickel, tin and zinc), bulk commodities (coal, iron ore, phosphate and potash), and specialty commodities (diamond, lithium, niobium, rare-earth elements, tantalum and uranium). Information on uranium exploration activities was included in the MEG overview for the first time in 2007. MEG included data on the commodities lithium, niobium, phosphate, potash, rare-earth elements and tantalum for the first time in 2010 because of the increased topical significance of these commodities. Since 1999, companies with exploration budgets of $100,000 and greater were included in the MEG and SNL compilations. SNL budget estimates exclude aluminum, coal, and oil and gas. Budget estimates for iron ore have been compiled since 2011 but reported separately. The post-1999 budget surveys by MEG and SNL cover at least 90 percent of world?s reported nonferrous, nonfuel mineral exploration budgets; the 2013 survey is reported by SNL to cover an estimated 95 percent of these budgets. The 5 percent that is not covered is accounted for by companies that chose not to participate in the SNL survey, private companies that do not publish their budget data, and government-funded exploration activities.

By K. E. Yassin, A. Yehia, M. Amar

Phosphate fines (size ≤ 45 μm), from the Red Sea Region, Egypt, were subjected to beneficiation process to recover the phosphorite grains from such fines. The sample is characterized by low P2O5 content (18.78%) associated with gangue minerals such as silica (22.77% SiO2) and carbonate (2.01% MgO) indicating its low grade. Phosphate pre-concentrate was prepared by gravity separation, using Falcon, where 63.37% of the phosphate, with 24.94% P2O5, 1.46% MgO, and 10.54% SiO2, was firstly recovered reducing the mass flow to the subsequent beneficiation process. However, the gravity tailing was the feed for the reverse phosphate flotation using bench scale column flotation where oleic acid was used as a carbonate gangue collector and amylase enzyme as a phosphate depressant. Under the appropriate flotation conditions (0.1% amylase, 5·10−4 mol/dm3 oleic acid, and temp. 30 °C), phospho-concentrate assaying 0.61% MgO, 13.14% SiO2, and 27.85% P2O5 with a P2O5 recovery of 55.45%, was finally obtained without the use of expensive depressants, e.g., phosphoric acid or sodium silicate. A tentative flow sheet for the whole process was postulated.

By I. M. Ahmed, R. S. Hassan, M. I. Aly

Extraction and separation of La, Sm and Dy ions from acidic sulfate-phosphate solutions was investigated using a cation exchange extractant, bis(2,4,4-trimethylpentyl) phosphinic acid, CYANEX 272, in kerosene. The influence of shaking time, equilibrium pH, extractant, sulfate and phosphate ion concentrations, diluent type and temperature was studied. The extraction was found to be pH-dependent, and increasing the phosphate ion concentration inhibited the extraction which was found to be endothermic. The stoichiometry of the extracted metal species was found to be MOH.H2OHSO4H2A.A2. Aliphatic diluents were found to enhance the extraction compared to aromatic diluents. The results showed that there was a separation mode between the metal ions when varying the hydrogen ion and sulfate ion concentrations, under the used experimental conditions. The investigated process was used for the recovery of La, Sm and Dy from the acid solution resulting from the leaching of low-grade monazite.

By Maurício Covcevich Bagatini, Maycon Athayde

Water consumption reduction in pellet feed operation is of paramount importance. Compared with traditional ball mills, high-pressure grinding rolls (HPGR) play an important role in Blaine surface area (BSA) generation to improve agglomeration properties, although stability is still a challenge. Grindability improvement of existing operation has a direct impact on the performance of the filtering and pelletizing operation. The results of this study, as a pregrinding operation, can be applied not only in new operations but also in existing ones, helping the operator control process variation in a more effective way while ore hardness increases. 

By G. A. Christie

This paper presents a vision system capable of providing an accurate estimate for the volume of stockpiles using 2D images. By imaging a stockpile from multiple viewpoints with a two-camera system, a 3D point cloud of known scale is generated using image-based 3D reconstructions. With a small amount of user interaction, the points that correspond to the surface of the stockpile are extracted and used to measure the volume. The hardware required for the two-camera system is light enough to be carried by a small unmanned aircraft and is a cheaper alternative to LiDAR while still being competitive in terms of accuracy. When testing the volume measurement algorithm on a stockpile of known volume, the measured output was found to have less than a 3% error from the ground truth.

By Fengyu Ren, Ruslan Puscasu, Kunpeng Yu, Gideon Chitombo, Liangliang Kang

Weak rock mass and poor flow of material can cause excessive ore loss and dilution in sublevel caving. This paper proposes a method to establish design parameters for an inclined deposit within a weak rock mass and evaluates its effectiveness through a case study. In order to solve the problem of low production capacity and poor safety conditions of sublevel caving mining at the Yingfangzi silver mine in China and to ensure a smooth production from the refractory ore body, it is necessary to select appropriate stope structure parameters. Based on random medium theory of gravity flow and the improved equation of ore discharge in random medium, an end wall drawing experiment is carried out to determine the optimum design and flow parameters. It was observed from the experiment that, due to the influence of the randomness of particle movement, there is a mismatch in the flow parameter measurement. The flow characteristics and distribution of the marker particles are different from that of the tested particles resulting in large drawbody shape distortion. The study finds that the flow parameters obtained by the new method are more practical and account for drawpoint width and recommends that the new method for determining the sublevel stope height is used when the drawbody is a non-standard ellipsoid. The outcomes have shown a significant reduction in the dilution and improvement in the recovery rates, and the safety and efficiency of mining have been greatly improved.

By I. B. Tulu, M. M. Sears

In 2015, 40 longwall mines provided nearly 60% of the US coal production from underground mining methods. This represents a substantial yet gradual increase from just under 50% over the last 5 years. As a result of this increased production share, the percentage of ground-fall-related fatalities in longwall mines has also increased when compared to all US underground coal mines. Additionally, about 80% of ground-fall-related fatalities have occurred in areas where the roof was supported. In an attempt to better understand the status quo of current US longwall support practices, a sample of 25 longwall mines were visited representing nearly 50% of the currently active longwall mines representing all of the major US longwall-producing regions. The resulting data was obtained from a wide variety of overburden depths, geologic conditions, mining heights, ground conditions, support practices, and gateroad configurations. The data collected is reported using both qualitative and quantitative methods. Results from the research update previous efforts in classifying mining accidents and injuries as well as current support practices presented by this author at the 2017 Society for Mining, Metallurgy, & Exploration Annual Meeting. This data provides a necessary background for future research aimed at further reduction of ground fall accidents and injuries.

By C. K. C. K. Gupta

The rare earths in elemental form are required for a variety of scientific and technological purposes. They are not easily obtained in this form, due to the great chemical stability of the rare-earth compounds and the strong tendency of elemental metals to react with everything they come in to contact with, especially at high temperatures. Beginning in the 1950s, when sufficient quantities of separated rare earths became available, as the result of intense research and development, three processing routes were developed to accomplish the preparation of all 16 naturally occurring rare-earth elements. They are chemical reduction of the halide intermediates, the oxides and electrochemical reduction of chlorides and oxide-fluoride mixtures. Not all the processes are effective with all the rare earths. In spite of the celebrated similarity of trivalent rare earths, the physical properties of individual rare-earth elements are sufficiently different that a variety of techniques are required for their preparation. The development of reduction processes for the rare-earth metals are covered in this paper, with focus on the oxide reduction routes. The strong reliance of effective reduction processes on the fundamental science of reduction reactions is highlighted.

By Jean Habimana

Complex and distinct geological units spread along the 7-mile long 30-ft inside diameter Upper Rouge Tunnel CSO Control Project in Detroit, Michigan. Its construction is divided in two tunnel construction packages: The South Tunnel, to be driven in finely laminated weak TG Limy Shale, will be excavated by a shielded TBM with precast concrete segmental lining, while the North tunnel, predominantly in a relatively more competent geologic formation Antrim Shale, will be excavated by a main beam TBM with a two-pass lining system. The adits and deaeration chambers will be excavated by sequential excavation method. This paper addresses the process of selecting excavation methods and lining systems for shafts, tunnels, connecting adits, and deaeration chambers.

By William H. Hansmire

The Modified Detroit River Outfall No. 2 (MOD DRO-2) will discharge treated wastewater to the Detroit River. Construction of a 6.4-m-diameter, 1.9-km-long tunnel was halted in 2003 by flooding during tunneling with an open face hard rock TBM. A new design for a higher rock tunnel, a ?Modified? design, was completed in 2007 and Notice to Proceed to the tunnel contractor was given in November 2008. Project duration is four years for completion of tunneling and start of outfall tunnel operation. This tunneling project has high groundwater pressure (5 bar), pervious limestone rock of up to 140 MPa (20,000 psi) strength, and hydrogen sulphide in the groundwater. The new tunnel will be connecting to access shafts and outfall diffuser riser shafts previously built for the now-abandoned tunnel. The new tunnel design construction contract, and initial planning to use a pressurized-face (slurry) hard rock TBM are presented.

By Gerald H. Luttrell, Seyed Hassan Amini, Aaron Noble

Single-unit separations in mineral processing are typically not able to meet the strict purity requirements for consumer markets. As a result, multistage separation circuits are often employed. Because these circuits represent a large and inflexible capital investment, process engineers are careful to ensure that the circuit is optimally designed to meet the desired objectives. The set of interdependent decisions that constitute the circuit design may involve the selection of different unit operations, different equipment specifications, different operational parameters, and different unit interconnections. To assist circuit designers in assessing these options, researchers have attempted to establish standard design methodologies that involve various techniques and tools.

By I. B. Tulu, M. M. Sears

In 2015, 40 longwall mines provided nearly 60% of the US coal production from underground mining methods. This represents a substantial yet gradual increase from just under 50% over the last 5 years. As a result of this increased production share, the percentage of ground-fall-related fatalities in longwall mines has also increased when compared to all US underground coal mines. Additionally, about 80% of ground-fall-related fatalities have occurred in areas where the roof was supported. In an attempt to better understand the status quo of current US longwall support practices, a sample of 25 longwall mines were visited representing nearly 50% of the currently active longwall mines representing all of the major US longwall-producing regions. The resulting data was obtained from a wide variety of overburden depths, geologic conditions, mining heights, ground conditions, support practices, and gateroad configurations. The data collected is reported using both qualitative and quantitative methods. Results from the research update previous efforts in classifying mining accidents and injuries as well as current support practices presented by this author at the 2017 Society for Mining, Metallurgy, & Exploration Annual Meeting. This data provides a necessary background for future research aimed at further reduction of ground fall accidents and injuries.

This review provides a new and comprehensive summary on studying colloidal interactions encountered in mineral processing with representative examples for critical information, which are of great scientific and practical importance. Colloidal interactions play a vital role in mineral processing, including grinding, physical separation (particularly flotation), dewatering and tailings management (Fig. 1). Despite great energy input in comminution to liberate valuables from gangues, hetero-coagulation between valuables and gangues would prevent the separation of valuables from gangues. On the other hand, selective coagulation/flocculation to increase the size of desired fine particles could enhance physical separation and dewatering, while dispersion is needed for fine grinding. The importance of colloidal interactions is becoming increasingly significant as we process ever more finely disseminated low-grade ores as a result of inevitable depletion of high-grade ore deposits. To control the state of colloidal dispersions by creating favorable conditions, it is of paramount importance to study colloidal interactions in a relevant system and understand underlying mechanisms. 

By Michael J. Lehnen

Slurry diaphragm walls are commonly used as both temporary excavation support walls, and permanent structural walls, for circular shafts and long rectangular structures (such as underground subway stations); however, they are not commonly used for more compact rectangular or square shafts. In these instances, a second wall is typically cast inside the slurry walls to form the permanent structure. This paper discusses the approach used on the Silicon Valley Rapid Transit Project in California to analyze these compact rectangular types of structures for static and seismic loading, and to determine whether or not slurry walls can be confidently used as both the temporary and permanent walls for two tunnel ventilation shafts.

By Mahmut Altiner

This study aimed to produce magnesium oxide (MgO) particles with different properties from dolomite ore using an experimental procedure comprising four stages: sample preparation (S1), HCl leaching (S2), precipitation (S3), and calcination (S4). Three different base sources (NaOH, KOH, and NH4OH) were used as precipitant in the third stage to obtain magnesium hydroxide [Mg(OH)2] from a leachate solution, which was obtained in the second stage. Next, Mg(OH)2 particles generated by different alkali sources were calcined at various temperatures from 600–1000 °C for different durations (1–5 h). The effect of these base types on the properties of each product was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), atomic force microscopy (AFM), and wet chemical analyses. The experimental results indicated that each product was identified as periclase (MgO) mineral, which was produced with a specific surface area (SSA) of 4.49–44.54 m2 /g depending on the production conditions. The surface roughness of the MgO particles increased with increasing calcination temperature. SEM analyses showed that MgO particles produced at a temperature of 600 or 800 °C were amorphous, indicating that the process was not influenced by the base type, but MgO crystals were smooth when the calcination temperature was 1000 °C. Finally, it was determined from all experimental findings that MgO particles produced via the addition of NaOH have superior properties (such as higher SSA and lower surface roughness) compared with MgO particles produced with KOH or NH4OH as the alkali source. These properties led to great improvement of its usability in industry.

By Jue Kou, Lei Yu, Bern Klein, Lusheng Zhou, Chunbao Sun, Genzhuang Li, Reem Roufail, Amit Kumar

Magnetic liners can improve the performance of ball mills by increasing grinding efficiency, extending service life, and reducing maintenance costs. Despite their importance, the fundamental understanding and the quantitative investigation on the effects of the magnetic liners has not been addressed in the literature. This paper addresses this gap by studying charge motion, and how the use of a magnetic liner affects the breakage mechanism of the mill, using discrete element method (DEM) modeling and the Hertz-Mindlin contact model with relative velocity dependent (RVD) rolling friction. Charge motion was modeled under different mill speeds. Compared to conventional steel and rubber liners, the charge motion in the magnetic liner mill was predominantly cascading. Quantitative analysis of the energy dissipation within the mill was conducted to investigate mill breakage. Regardless of speed, over 50% of the total energy dissipation in the magnetic liner mill was in the form of abrasion and attrition. The results highlighted the appeal of magnetic liners in secondary and regrinding application, where abrasion and attrition are considered more efficient in the fine material breakage, and where impact is ideally minimized to reduce mill wear. A number of experiments were conducted to assess the effect of different model parameters on the performance of the magnetic liner mill. The highest abrasion/attrition intensity was observed with high values of the model parameters namely the restitution coefficient, static friction coefficient, and rolling friction coefficient.

By Manuel Pérez-Tello, María M. Salazar-Campoy, Óscar Rodríguez-Hoyos

A common problem during the operation of the Kaldo furnace is the formation of accretions and blockage of the injection lance due to splashing. This typically occurs during the processing of anodic slimes for the production of doré. In this work, a 1:7 scale model of the Kaldo furnace currently in operation at Metalúrgica de Cobre, Mexico, was built in transparent acrylic plastic. Water and colored oil were used to represent the doré and slag, respectively. The model was used to determine the maximum penetration distance of the injection lance under a variety of experimental conditions at room temperature. Input variables included two types of oil, rotation speed, inclination angle, and the fraction of the vessel volume occupied by the liquids (φ). A mathematical correlation for the dimensionless maximum penetration distance of the injection lance d ∗ as a function of φ, the Froude number of the liquids in the vessel (Fr), the Reynolds number of the gas jet (Re), and the oil-to-water kinematic viscosity ratio (η)was developed. Reasonable agreement between the calculated and experimental values was obtained. Digital images showed that splashing was caused by the turbulent gas jet impinging upon the free surface of the liquids, whereas the cascade effect was negligible. The results of this work have been useful to improve the operation of an industrial Kaldo reactor.

By Robin J. Batterham, Dave J. Robinson

The most significant trend in flotation has been the ever-increasing scale of operations. There is, however, doubt that this ongoing trend is enough to maintain the economics against trends such as falling grades, increasing mining costs, pressure on water supply and demand, rising energy demands needed for mineral processing, and a focus on whole of life value and mine legacy issues. We comment on the ramifications of broader uptake of more sustainable mining for mineral processing methods and address the specific question of whether recent progress in in-place recovery will lead to a timely breakthrough. The answer proposed is that this is possible in the next 10 to 20 years, but in the meantime the focus is just as likely to be on removal of waste (beneficiation) much earlier in circuits. Either way, mineral processing and flotation as we know it will change significantly. 

By Chinmay Shingote, Robert Visintainer, Renjie Ke, Jaikrishnan R. Kadambi, John Furlan

Hydrocyclone separators are widely used in various industrial applications in the oil and mining industries to sort, classify, and separate solid particles or liquid droplets within liquid suspensions, which are considered to be multiphase systems. Numerous valuable studies have been conducted in recent years to investigate the flow fields inside hydrocyclones. However, much of the information regarding the performance of cyclones in the literature has limitations and much of it cannot be considered as completely applicable to most real-world applications; many of the studies investigated the flow fields within extremely simplified hydraulic designs that are not representative of the complex geometries or large sizes which are typical in industry. Therefore, in this study, the two-phase flow system inside the actual hydraulic geometry of a milling circuit hydrocyclone is explored with the aid of both computational and experimental techniques (particle image velocimetry (PIV)). More specifically, the flow field with an air core has been investigated. In addition, the air-liquid two phases flow in a hydrocyclone might cause some challenges on both the computational and experimental sides. Two turbulence models are utilized in the numerical calculations: the Reynolds stress model and large eddy simulation. The computational studies are mainly focused on the local flow behavior and the prediction of the dimensions and shape of the air core. Different section planes of hydrocyclone are selected as planes of interest and divided into several fields of view (FOV) for PIV measurements. Two-dimensional experimental velocity vector maps are obtained in each of the fields of view. The computational results are validated globally using pressure and flow rate readings at the boundaries and locally by comparison to the PIV velocity vector maps and profiles.