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By Rolf Andreas Lauten, Yanhong Wang, Yongjun Peng

"In mineral flotation, bentonite as a kind of clay mineral imposes deleterious effects on the flotation of valuable minerals, possibly through its ability to increase the pulp viscosity. A higher viscosity lowers the amount of froth and affects the bubble-particle collision frequency. A previous study found that adding gypsum to a bentonite-ore mixture lowered the viscosity, possibly by inhibiting the formation of interconnected network structures. In this study, sulfate as an anion with different types of cations, Na+, K+, Mg2+ and Ca2+ were used to reduce bentonite viscosity and to improve flotation performance. It was found that at the same concentration, MgSO4 was the most effective salt in reducing bentonite suspension viscosity, while CaSO4 was not as effective likely due to the lower solubility of CaSO4. Na2SO4 and K2SO4 reduced bentonite suspension viscosity at high concentration. Flotation kinetics of ore blended with bentonite was increased with increasing the electrolytes concentration, which generally correlated with the reduction of bentonite viscosity. Meanwhile, significant discrepancies were found between flotation results and rheological measurements in the presence of monovalent ions. It is indicated that the morphology of bentonite aggregates in electrolytes solution is likely to influence the hydrodynamics in the froth zone.INTRODUCTIONClay is present in many ore bodies as a gangue mineral. Presence of clay presents several challenges in the processing of valuable minerals. They are soft compared to valuable minerals, which means that during grinding of the ore, clay particles are likely to obtain a smaller particle size than the valuable mineral. Often clay particles may be within the colloidal size domain (<20 µm). The smaller size increases the probability of entrainment in the concentrate. Another challenge is their anisotropic charge distribution, where depending upon the pH, edges (E) and faces (F) carry charges of opposite sign. This facilitates formation of aggregation structures that may impede percolation of bubbles through a froth, but also increase the viscosity more than expected from the mere change in volume fraction. In addition to lowering the froth mobility, a high slurry viscosity will have implications for the gas dispersion in the flotation column as it affects the dispersion of the suspended particles, and it modifies the bubble-particle collision rate and attachment efficiency (Bakker, Meyer, & Deglon, 2009; Shabalala, Harris, Leal Filho, & Deglon, 2011). A pragmatic approach to this problem is to blend high clay ore with ore of lower clay content, reducing the overall clay concentration. Alternatively, one may lower the solids content of the flotation slurry to counteract the viscosity-building properties of clay. While feasible, this approach has the disadvantage of increasing required flotation volume, and it also affects the properties of the froth. Thus, there are currently limited options in lowering the impact of clays and their tendencies to increase viscosity in flotation slurries."

Jan 1, 2016

By R. Heikkilä

The utilization of Building Information Modeling (BIM) and model based 3-D control of work machines have increased a lot in new road construction in Finland as well as in other Nordic Countries. Up today, much less attention has been paid into the development of maintenance and rehabilitation processes. As a part of a large research and development program RYM PRE Infra FIN BIM in Finland, a focused research project of the BIM with experiments in total five (5) pilot projects has been performed. A main idea of the new BIM based process has been to utilize mobile laser scanning method for initial data acquirement, the use of novel 3-D analyze and modelling methods for point cloud processing, the use of new type optimization method for the planning of geometric and structural improvements needed for the existing uneven road surfaces, and further, through the creation of 3-D machine control models apply the newest 3- D machine control systems for continuous 3-D control of practical construction work using milling machine and asphalt paver. Finally, an evaluation is made between the new process model and the traditional way of working.

Aug 1, 2013

By L. E. Young

"The Red Dog deposit of the western Brooks Range, Alaska was discovered in the 1970s. Two mineralized areas are present, the Main and Hilltop deposits. With indicated and inferred reserves of 77 million tonnes of 17.1% zinc, 5.0% lead and 82 g/ tonne silver, the Main deposit of Red Dog represents one of the world&apos;s largest zinc-lead deposit s. Since serious evaluation by Cominco commenced in 1980, a better understanding of deposit geology has been gained through 10 715m of diamond drilling and concurrent geologic, geophysical and geotechnical studies. The Red Dog deposit is of Mississippian to Pennsylvanian or Early Permian age, and straddles a redox transition in fine-grained and chemical sediments of the Red Dog structural sequence.The Main deposit has been modified by regional Mesozoic thrust faulting and isoclinal folding, resulting in complex interrelationships between silica rock, sulphide rock and barite. Multiple lines of evidence suggest the Main deposit contains both a syngenetic stratiform and a replacement component. Ore fluids were probably derived by regional lateral movement of brines through a coarse clastic footwall aquifer, then upwards along block faults to the site of the Red Dog deposit.Historical PerspectiveThe region in the vicinity of the Red Dog deposit (Fig. 1) was first prospected by J. W. Kelley in the late 1880s (Orth, 1967). The first coordinated inland exploration was conducted by the U.S. Geological Survey in 1910-1911 and 1923-1926 (Smith, 1913; Smith and Mertie, 1930). The earliest reports of zinc-lead mineralization in the region include reference to samples collected at unknown locales by Eskimo prospectors (Anderson, 1944). In 1955 stratiform pyrite was discovered 19 km west of Red Dog by I.L. Tailleur of the U.S. Geological Survey (Tailleur, 1970). The first reported visit to what is known as Red Dog was by I.L. Tailleur in 1968, who was field checking a colour anomaly noted by B. Baker, a local bush pilot (Tailleur, 1970; Moore et al., 1986) ."

Jan 1, 1989

By P. G. Dunn, J. Fitzgerald

ABSTRACT The scheduling of underground mining activities is a complex task that must simultaneously satisfy a large number of constraints. A schedule optimization tool (SOT) for underground mine planning is described, and its use for investigating strategic decisions is illustrated through a case study. The maincomponents of the SOT include (a) a genetic algorithm that searches for optimal schedules, (b) guidance for the application of heuristic rules, and (c) sliding, which implements just-in-time development. Findings indicated that preliminary scheduling performed before invoking the SOT, intended to provide a good starting point for the search, did not ultimately lead to higher value schedules.

Jan 1, 2010

By T. Marolt, J. Likar, E. Grøv, J. Žarn

"Underground structures are an integral part of the infrastructure of modern society and are used for a wide range of applications, including subways and railways, highways, not at least nuclear facilities. When the wider area is subject to earthquake activity, underground constructions should be analyzed on seismic and static loading. Observations showed that the underground structures have significantly less seismic risk than surface structures. Available methods allowed analyzing the magnitude of risk for different input parameters of seismic loads in different ground environment. Simulation of earthquake loading on underground structures, in the present paper is given the various aspects of analyzing the potential damage and instability of underground facilities. INTRODUCTIONThe development of methods and computing resources used for para-seismic engineering has finetuned the evaluation of the seismic strength of buildings and equipment. Reinforcements may therefore be decided, not simply on the basis of a reassessment of the hazard, which constitutes input data for the calculation of structures and equipment, but also on the basis of developments in para-seismic engineering. Underground facilities are an integral part of the infrastructure of modern society and are used for a wide range of applications, including subways and railways, highways, material storage, and sewage and water transport and not at least nuclear facilities. Although in the past showed that the underground structures are significantly less seismic risk than on the surface, the professional researches and their results are accessible. Seismic resistance of underground structures is analyzed from several aspects. The currently available methods allowed analyzing the magnitude of risk for different input parameters of seismic loads in different ground environment. For better interpretation of earthquake loading on underground structures, are given below the various aspects of analyzing the potential damage and instability of underground facilities in rock. One of the early studies which covered this are of investigation were prepared by Dowding and Rozen (1978). They grouped damages due to earthquakes in underground structures into three main categories:- damage from ground shaking- damage from fault dislocation- damage by earthquake-induced ground failures (e.g. liquefaction and landslides)."

Jan 1, 2015

By David S. Wong

With air emission limits for total particulates continually tightening, management of `potroom dust&apos; or airborne particulates from aluminium smelting potrooms is of increasing importance. To better understand how settled and airborne particulates are generated within a potroom, methodologies have been developed to sample and analyse the compositional signature of dust, in relation to its sources. During a smelter case study, these methods allowed tracking of mineralogical phases in dust across a range of potroom locations, showing that the mechanisms of dust generation do vary spatially and vertically in a potroom. Such methodologies may also be applicable to other metallurgical industries.

Jan 1, 2011

By CH. Liu, H. X. Jiang, X. Xiao

"A study has been conducted to characterize the fatigue life in 7050-T7451 thick plate by the comparison between an experimental alloy and commercial alloy. The fracture origins were specified and their sizes were measured by scanning electron microscope (SEM). Additionally, the size, number density and spatial distribution of porosity in the experimental material and commercial material were characterized and compared, using X-ray Computed Tomography(XCT). The results showed that microporosity was the predominant site for crack nucleation and subsequent failure of the experimental alloy. However, as for the commercial alloy, fatigue cracks were found to originate from constituent particles. The presence of microporosity in 7050-T7451 thick plate reduced fatigue life of an order of magnitude or more compared to the commercial alloy. The relationships between size of origin and fatigue life were proposed. It was showed that the fatigue endurance was reduced when the size of porosity increased.INTRODUCTION 7xxx series aluminum alloys, due to their combination of high strength, high resistance to stress corrosion cracking, and good fracture toughness, are widely used in structural engineering applications where high-strength and low-density characteristics are fundamental design requirements (Williams& Starke, 2003). Every designer is striving to find an optimal combination of properties including strength, corrosion resistance and fatigue resistance (Wanget al., 2016). Based on the design principles of aircraft, a higher fatigue resistance of aluminum alloys are required. Thus, many investigations have been carried out on the microstructures and its effect on fatigue properties of the 7xxx series aluminum alloy (Robson, 2004; Schubbe, 2009).Microporosity, which is a common defect in casting materials, can lead to a significant deterioration of mechanical performance and fatigue resistance, especially in the high alloyed 7xxx aluminum alloys. The actual valid loading area decreases due to microporosity, which results in detrimental effect on the mechanical properties. Many experimental studies have been conducted in this research field. Mayer et al.(2003) investigated the fatigue properties of magnesium alloys produced by high-pressure die-casting. The results show that porosity in magnesium alloys greater than0.18mm diameter may be considered as the most important material defect for high cycle fatigue and fully reversed loading conditions. Nadot et al.(2004) found that the near surface defects are much more dangerous than the internal defects. Wang et al.(2001a) used the Weibull statistics method to analysis the influence of the microporosity, oxides and particles on the A356-T6 alloy fatigue life. The results show that, the porosity is more detrimental to fatigue life than oxide films and particles. With regard to fatigue resistance, although the deleterious effect of microporosity has been generally acknowledged, a quantitative understanding between casting microporosity and fatigue life in 7050-T7451 plate is not well established."

Jan 1, 2018

By N. Gharib, F. Hassani, P. Nekoovaght

"Novel rock breakage techniques are becoming more viable and attractive to industry. Microwave energy, as a thermal energy capable of inducing micro cracks through differential heating (therefore expansion) is a technology gaining considerable attention in mineral processing and ore comminution applications. Recently, the use of microwave radiation has been evaluated as a possible avenue for terrestrial and extra-terrestrial drilling applications as well as full face tunneling or rock breaking machines. As part of an overall research on use of microwave in rock breaking systems, the influence of microwave energy on the mechanical properties of common hard rock types as basalt has been investigated. The results revealed that microwave energy irradiation imposes micro and macro cracks to the surface of the rock being irradiated. In explosive free tunneling applications using TBM, jointed and cracked surface of rock eases the cutting process and increases penetration rate. The experimental setups have been simulated with the help of a multi-physics numerical modeling and the results have been compared with practical experiment. The wave propagation of microwave has been simulated and the distances where the power intensity is higher are identified. Experimental and simulation results underlined the potential impact of the use of microwave energy in underground or surface excavation applications such as mining and tunneling. This will also contribute economically when mine-to-mill operation is fully considered to improve the efficiency of rock crusher stages. INTRODUCTIONDuring hard rock breakage (i.e., separation of a piece of a rock from its parent deposit) in mining and civil applications, the performance of mechanical equipment such as tunnel boring machines (TBMs) is limited by high levels of bit wear and maintenance. Preweakening natural rock prior to breaking it by machine is one approach to lower bit wear and maintenance costs. Some preweakening methods apply heat directly or indirectly. For example, flame torch-assisted TBMs (Lauriello et al., 1974; Resource Technology, 1984) have been deemed economical in terms of equipment, but their feasibility is limited by high fuel consumption. Microwave energy could offer several advantages over the flame torch method: it does not produce emissions or increase fuel consumption (electricity source is available on the machine), and is easy to control (quick power on and off)."

Jan 1, 2015

By K D. Conroy

For the past year, Lowphos Ore Ltd. has been operating two desliming hydroseparators on a fully automatic basis. Automatic operation is achieved by sensing the position of the silica-magnetite interface and automatically controlling the jet water addition to maintain a desired interface position. The system further provides automatic control of the underflow pump speed in order to assist in maintaining interface position when an <Ore change occurs. Interface position is maintained at 12 inches below the surface and is -controlled within plus or minus one inch. Metallurgical unit recovery is held above 98.5 per cent, and a 10 to 12 per cent increase in concentrate grade is normally achieved.

Jan 1, 1963

By R. Hans

Removal of toxic anions from aqueous solution was studied using a Magnetic Ion Exchange (MIEX) resin which is a polyacrylic, strong base resin. Gravity based settling is made more efficient due to the magnetic nature of the resin which is advantageous over conventional ion exchange resins. In addition, the magnetic microspheres of MIEX have larger surface area in comparison to conventional ion exchange resins. Over the years MIEX has been successfully used and has gained significant popularity for efficiently removing dissolved organic matter from wastewater and groundwater. In the present study the efficiency of the MIEX resin was tested for the removal of chromium(VI), molybdenium(VI), vanadium(V) and arsenic(V) anions. Effects of pH (2-10) and temperature (25oC-55oC) were examined. In general, low solution pH values were favorable for anion uptake by MIEX. Except for chromium(VI), the metal ion uptake was significantly increased by the increase in solution temperature. The adsorption data were analysed on the basis of chemical speciation and heterogeneous kinetic models.

Jan 1, 2014

By Z. Luo, China University of Mining & Technology, C. Duan

"The magnetic separation removal rate of pyrite could be improved effectively by increasing the susceptibility of pyrite. The electromagnetic characteristics and absorption response performance of high-sulfur fine coal were studied in strengthening the susceptibility of pyrite. In the process of treating the sample through the microwave, electromagnetic energy could be converted into heat energy due to dielectric loss and magnetic loss. The RL(dB) was evaluate the performance of absorption response of coal. The microwave improved the susceptibility was in ultra-high frequency region, which is the most natural resonance. The absorption fine coal to microwave was strengthened and microwave energy was improved by adding the magnetite powder with double loss characteristics as the microwave absorber. The dielectric properties and permeability characteristics of the fine coal trend were investigated by maxing magnetite powder. The microwave absorption in different coal thickness was surveyed through the reflection of energy loss.INTRODUCTIONMicrowave desulfurization is one of the most important research directions (Haque, 1999; Makul, Rattanadecho, & Agrawal, 2014; Su, Tang, Zhang, Jing, & Bai, 2014). The working principle of microwave absorption response can be briefly described as the interaction of the sample with microwave energy, which will result in the microwave energy converting into heat energy loss (Keangin & Rattanadecho, 2013). For specific samples, the polarization effect includes multiple polarization mechanisms(Meikap, Purohit, & Mahadevan, 2005). Different polarization mechanisms have different occurrence time and dominant mechanisms. Meantime, energy consumption will be occurred during the process of polarization effect (Chelgani & Jorjani, 2011; Rowson & Rice, 1990) . The absorption of microwave energy in the fine coal is a process of electromagnetic response (Znamenácková, Lovás, Mockovciaková, Jakabský, & Briancin, 2005). Microwave transfers the electromagnetic waves into the heat energy by microwave dielectric loss and magnetic loss for achieving the absorption of microwave energy in the treatment of samples (Lee, Kim, Kim, Chung, & Kim, 2004). The additive magnetic medium is Fe3O4 belonging to microwave energy absorber of double loss medium (Uslu, Atalay, & Arol, 2003)."

Jan 1, 2016

By D. Gaboury

Most hydrothermal gold deposits contain quartz with fluid inclusions that record composition and temperature of the mineralizing event. Quartz has strong chemical and mechanical resistances to weathering and abrasion. Hence, quartz fragments occurring on weathered surfaces or in till cover have the potential to be used for gold exploration as far as we know what is the signification of the volatile content of the fluid inclusions for gold mineralization. In this perspective, fluid inclusions were analyzed in pure quartz by solid-probe mass spectrometry from gold deposits hosted in the Archean Abitibi (Canada) and Paleoproterozoic Birimian (Western Africa) belts. This approach provides the relative abundance of volatiles from families of fluid inclusions decrepitating at specific temperatures (Td). Fluids in gold deposits are aqueous-dominated with CO2 and minor H2S in accordance with their fundamental role as gold-ligands (H2S) and for pH-buffering (CO2) of the gold-bisulfide solubility. However, there is no correlation between CO2 and H2S contents of fluid inclusions with the gold grade of the samples. This suggests that trapped fluids represent a marginal portion of the fluid history recorded by the veins. However, in barren quartz veins away from known mineralization CO2 or H2S are commonly absent. Wide ranges in H2O Td from 250 to 450°C and CO2-H2O Td offsets are common, indicating phase separation. The content of other volatiles seems to be more dependent on the geological setting. Helium content may suggest proximity to a crustal-rooted fault, a critical parameter for gold mineralization. Methane and especially C2H6 appear to be indicative of fluid buffering by organic-rich material such as graphitic-shale. These rocks may provide an important primary gold reservoir from sedimentary metal-rich pyrite. Nitrogen-bearing fluids may be related to a magmatic component but can also be derived from organic-rich sedimentary rocks. For gold exploration, quartz containing CO2- H2S-bearing fluid inclusions and having H2O-CO2-Td offsets within 250 - 450°C has strong vectoring potential.

Jan 1, 2011

By J. Jankovic

Numerous advantages have been recognized for solid oxide fuel cells (SOFCs) operating at temperatures of 500-700°C. However, there are several issues related to low temperature SOFCs, such as high electrolyte resistance and high electrode polarization. One of the routes to enhance the electrode performance, particularly for the cathode, is to use new materials with optimized microstructure. In this work, the plasma-spraying technique, recognized to have several advantages over presently used deposition techniques, was used to deposit cathode materials onto ceramic and stainless steel substrates to obtain highly porous structures. Cathode materials with composition of Lao 6Sr0.4Co02Fe0 8O3 (LSCF) were employed in the powder form. The LSCF was prepared from powder precursors with different pore formers and binder levels, or from already produced, single-phase LSCF. The (La0.8Sr0.2)0.98MnO3 (LSM) cathode material was also processed for comparison purposes. The deposition process was developed to obtain coatings with good bond strength, porosity, film thickness and residual stresses. The phase and microstructure of deposited materials were characterized using XRD and SEM.

Jan 1, 2005

By L. Vinnett, I. Panire, J. Yianatos, F. Ruiz

"The effect of operating variables on the flotation performance at steady-state has been extensively used for modelling and simulation of separation processes. However, the dynamic characterization of key variables such as gas dispersion (Sauter mean diameter of bubbles, D32, and bubble surface area flux, SB) and froth discharge rate is rather scarce. In this paper, an experimental design allowed identifying the dynamic response of the flotation process in a laboratory scale flotation cell, using a two-phase system, airwater. The installation included automatic control for the superficial gas rate, JG, and the pulp level. Gas dispersion was evaluated in terms of the Sauter mean diameter of a bubble population and the bubble surface area flux, SB = 6·JG/D32. The D32 was measured using the McGill Bubble Size Analyzer (MBSA) along with a semiautomated algorithm. In addition, the froth discharge velocity was measured in real-time using a Visiofroth system. The control variables were the superficial gas rate and the frother concentration (Teefroth). The dynamic characterization of the flotation process is useful to design algorithms that allow the direct or indirect control of metallurgical variables such as flotation rate, concentrate grade and mineral recovery.INTRODUCTIONGas dispersion indicates the way the gas entering a flotation machine is dispersed throughout the volume of the equipment (Schwarz & Alexander, 2006). The gas dispersion is typically characterized in terms of the bubble size (dB), gas holdup (eG), superficial gas rate (JG), and bubble surface area flux (SB =6·JG/dB) (Finch et al., 2000). All these variables have significant impact on the metallurgical performance of flotation machines. For example, Perez-Garibay et al. (2014) investigated the effect of the particle size, bubble size distribution, superficial gas rate and collector dosage on the flotation performance, for the separation of a sphalerite mineral. The authors observed that recovery increased with the superficial gas rate ranging from JG = 0.04 to JG = 0.08 cm/s and also a maximum recovery was obtained for bubble size close to 300 µm. Gorain et al. (1998) reported a strong correlation between the flotation rate constant and the bubble surface area flux in a zinc cleaner circuit. Both variables were directly proportional at three froth depths in the range of hF =7 - 45 cm. Dobby & Finch (1986) incorporated the effect of the superficial gas rate and the bubble size on the flotation efficiency by means of a kinetic model for the rate constants. Yianatos & Contreras (2010) developed a model to estimate the carrying capacity in large flotation cells by including the bubble surface area flux."

Jan 1, 2016

By Ltd. (CYMCO) Technology Center Yunnan Metallurgical Group Co., S. Jian, T. Song, J. D. Miller

"As sulfide zinc ore deposits become exhausted, nonsulfide zinc ore deposits become the other resource for zinc production. However, flotation for zinc recovery from nonsulfide deposits is much more difficult than the flotation of sphalerite from sulfide deposits and may become an option for zinc production only if a suitable processing technology is developed. In this regard, research efforts are being devoted to the flotation of nonsulfide zinc oxide minerals. Some common methods which have been used for the flotation of zinc oxide minerals include sulfidization-flotation, activation, and direct flotation with anionic and cationic collectors. The traditional flotation techniques have low efficiency and difficulty in separation and recovery of the zinc minerals from gangue minerals, for example, smithsonite (ZnCO3) from other carbonate gangue minerals and hemimorphite (Zn4Si2O7 (OH)2·H2O) from silicate gangue minerals. In this study potassium lauryl phosphate was evaluated as a collector for the flotation of nonsulfide zinc minerals. Results from contact angle and microflotation experiments at pH 6–9 show that hemimorphite (Zn4Si2O7 (OH)2·H2O) can be floated from quartz and that smithsonite (ZnCO3) can be floated from calcite. However, when dodecylamine, which is a common collector reported in literature for the flotation of nonsulfide zinc minerals, was used as collector, no significant difference between nonsulfide zinc minerals and gangue minerals was observed at any pH value. Initial evaluation suggests that potassium lauryl phosphate is effective at low concentration and may be a promising collector for zinc oxide mineral flotation.INTRODUCTIONBefore the twentieth century, zinc was mainly produced from nonsulfide ores (Large, 2001; Gilg, Boni, & Cook, 2008). With the development of differential flotation processes in the late 19th century major production switched from nonsulfide zinc sources to sulfide zinc ores (Hitzman, Reynolds, Sangster, Allen, & Carman, 2003; Gilg et al., 2008). However, as it is becoming more difficult to find new sulfide ores, recovery from nonsulfide deposits is being considered. Nonsulfide flotation for zinc recovery is much more difficult than the flotation recovery of sphalerite from sulfide deposits and may become an option for zinc production if a suitable technology is developed. Zinc and lead oxide ores are difficult to beneficiate ores due to their similar floatability with gangue, high solubility in water, and the influence of slimes (Fa, Miller, Tao, & Li, 2005). In order to improve the performance of oxidized minerals, lots of effort is being devoted to this field of study (Ejtemaei & Mahdi, 2014)."

Jan 1, 2016

By Lawrence Melis

Fission Uranium Corp.’s Triple R Uranium Deposit at its Patterson Lake South Project is located in northwest Saskatchewan in Canada’s Athabasca Basin. As part of pre-feasibility studies for the project a detailed metallurgical test program was completed to provide process design criteria. The testwork program encompassed preparation and analysis of test composites, comminution testing, uranium acid leaching, liquid-solid separation, solvent extraction of uranium, precipitation of uranium yellowcake products, tailings and effluent treatment, tailings physical and chemical characterization, and environmental testing of prepared tailings, as well as investigations of gold and silver recovery from the mineralization. The paper provides mineralogical information, testwork methodologies and test results which were used to arrive at process design criteria and the selection of the process flowsheet for the project.

Jan 1, 2020

By Hong Zhong, Shuai Wang, Fangxu Li, Guangyi Liu

"The flotation performances and adsorption mechanisms of a-hydroxyoctyl phosphinic acid (HPA) to malachite, cassiterite and wolframite were investigated by micro-flotation tests and X-ray photoelectron spectroscopy (XPS) analyses. The micro-flotation results indicated that compared with styrene phosphonic acid (SPA), diphosphonic acid (DPA), benzohydroxamic acid (BHA) and salicylhydroxamic acid (SHA), HPA exhibited excellent collecting power to the three oxide ores. In addition, HPA showed superior selectivity against hematite, tourmaline, feldspar and quartz. The results of XPS analysis demonstrated that HPA reacts with active species (M) on metal oxide by formation of P-O-M or P-M bonds.INTRODUCTIONIn mineral processing, flotation has been the main process for separation and recovery of valuable minerals from complex ores (Mei, 2013; Zhou, 2014). One of the key requirements in flotation process is to increase selectively the surface hydrophobicity of the targeted minerals by surfactant (known as collector in flotation) adsorption so that these mineral particles can preferably attach air bubbles in a slurry or pulp (Bai, 2004; Hankins, 2004). To anchor a solid surface selectively, special functional group are designed to adjust the interaction between the surfactant and the active sites of solid surfaces (Wu, 2006; Huang, 2014).Organic phosphorous compounds have strong affinity toward metals or metal oxides because they form more stable metal complexes than metal carboxylates (Pazik, 2001; Zheng, 1998). In mineral engineering, phosphorous compounds have been exploited as metal extractants and flotation collectors (Alguacil, 2002; Sun, 2008). Ni (2012) and Zhang (1998) introduced diphosphonic acid (DPA) as an effective collector for flotation of fersmite and niobite. Liu (1999) found styryl phosphonic acid (SPA) was a superior collector for flotation recovery of finely disseminated rutile ores. Gruner and Bilsing (1992) thought SPA was one of the best collectors for flotation recovery of cassiterite which could obtain a high-grade concentrates of more than 40% with high recovery values. Bulatovic (1999) investigated the flotation performances of phosphoric acid ester (PAE) to perovskite, ilmenite and rutile and found that PAE was an impactful collector for selective flotation of titanium minerals from complex ores in the presence of petroleum sulfate. However, a-hydroxyoctyl phosphinic acid (HPA) as a flotation collector for recovery of titanium ores were hardly reported in the previous literatures."

Jan 1, 2016

By B. Damjanac, S. Maxwell, D. Chorney, M. Grob, F. Zhang, J. Hazzard

"A hybrid discrete-continuum numerical scheme is developed to study the behavior of hydraulic fractures crossing natural fractures. The fully coupled hybrid scheme utilizes a discrete element model for a core domain, within which the hydraulic fracture propagates and interacts with natural fractures, and a surrounding continuum domain to better approximate boundary effects. The results show that the behavior of hydraulic fractures crossing natural fractures is affected by a combination of factors. Nevertheless, three fundamental crossing scenarios can be identified from all of the simulations: no crossing, partial crossing, and direct crossing. Each crossing scenario has a distinct injection pressure history which may suggest guidelines for interpreting field hydraulic fracture injection data. Additionally, the capability for these models to generate synthetic microseismicity makes them appealing for the integration of microseismic field data with the reservoir geomechanics for ultimately providing a practical engineering tool for improvement of well completion and stimulation. The model is capable of examining and verifying four different shear deformation mechanisms associated with a propagating hydraulic fracture. The natural fracture can fail solely due to the stress perturbation of the passing hydraulic fracture or it can fail due to a combination of stress and pore pressure changes across different types of interaction scenarios. The simulations also illustrate that the level of fracturing complexity increases as the number and extent of the natural fractures increase. INTRODUCTIONAlthough hydraulic fracturing technique has been applied extensively as a reservoir stimulation technique in the oil and gas industry for over 60 years (Economides & Nolte, 2000), it is one of the key factors promoting the shale gas boom in the past decade (King, 2010; International Energy Agency, 2014). The hydraulic fracturing of shales can be differentiated from hydraulic fracturing of conventional reservoirs by the fact that shale formations often have a pre-existing discrete fracture networks which greatly impact the hydraulic fracture propagation. Based upon field production data as well as microseismic observations, it is believed that so called “fracture complexity” may result from interactions between a created hydraulic fracture and pre-existing natural fractures and planes of weakness (Warpinski, 2009; Maxwell & Cipolla, 2011)."

Jan 1, 2015

By J. A. C. Ross

Introduction To enlighten those who may be wondering where anyone could find sufficient data to write a paper on underground concrete work, the author would like to explain that, at Copper Mountain, we have found it necessary to line numerous headings with a layer of concrete in order to keep them in a safe and serviceable condition. The majority of these headings are scram drifts and ore-pass raises. This paper will therefore deal, in the main, with the methods of and reasons for placing concrete in these headings. During recent years, radical changes have been made in the methods of mining ore at the Copper Mountain mine. After considerable experimenting, a mining system has been developed making use of diamond drills for primary breaking and transfering such broken ore through scram drifts with slusher hoists. With the advent of scram drifts, it soon became apparent that some substantial means of reinforcement and protection for the scram drifts themselves would be necessary. Since the orebodies in this mine are cut by numerous dykes or faults, and often both, it was anticipated that some means of support would be required where headings necessarily passed through these incompetent zones. Further, as experience was gained, scram drifts were driven into pillars and in close proximity to old workings so as to recover the maximum amount of ore. In such places, the ground is often severely fractured, either as a result of previous mining or from the effect of excessive rock pressures.

Jan 1, 1950

By Ye Chen, Jianhua Chen, Xianhao Long, Qingxia Liu, Zhenghe Xu

"It is crucial to understand the mechanism of the collector interacting with the mineral surface in the presence of water molecules, which could influence the relaxation and electronic properties of sulphide mineral surface due to the proximity effect for narrow band gap of semiconductors. The adsorptions of three typical collector molecules (xanthate, dithiocarbamate and dithiophosphate) on the sulphide mineral surfaces in the absence and presence of water molecule have been simulated by density-functional theory (DFT). The calculated results show that the adsorptions of collectors on clean mineral surface in vacuum are not in agreement with the observed flotation behaviours. The presence of water molecules has a great influence on the adsorption of collectors. The analysis of density of states of the mineral surface atom suggests that the adsorption of water molecules could influence the electronic properties of mineral surface and consequently influence the adsorption between the surface and the collector molecule.INTRODUCTIONIn the separation of multi-metal sulphide ores, the selectivity of a collector is a key factor for the efficient recovery of the aimed mineral. Xanthate, dithiocarbamate (DTC) and dithiophosphate (DTP) are the most common collectors used in the flotation of sulfide minerals. Generally, xanthate exhibits powerful collecting property but lack of selectivity. While dithiophosphate and dithiocarbamate show the good selectivity in the lead and copper sulphide mineral flotation. The mechanisms of these collectors interacting with the sulphide mineral had been attracted many attentions and several mechanism based on experimental results had been reported (Chander & Fuerstenau, 1974; Fuerstenau, 1990; Raju & Forsling, 1991; Crozier, 1991; Bradshaw, Cruywagen & O’Connor, 1995; Guler, Hicyilmaz, Gokagac & Emekci, 2006). However, the micro-mechanisms of the selectivity of these three thiol collectors on different sulphide mineral surfaces are not fully understood."

Jan 1, 2016