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"A commercially available Through-the-Earth (TTE) communications system was evaluated at an active underground longwall mine in West Virginia. This TTE system uses electric field (E-field) sensing to send text based communications using two separate antenna arrays connected in parallel. Each antenna array is composed of interconnected, grounded metallic rods or other such structures. Two-way communication between subsurface locations was investigated in this study using various antenna configurations. This field study was conducted as a part of a larger multi-site evaluation of available TTE systems in an effort to determine their operational sensitivity. INTRODUCTION Wireless, Through-the-Earth (TTE) communication technology is designed to achieve point to point communication through solid strata using very low frequency (VLF) and ultra-low frequency (ULF) electromagnetic waves. This ability allows TTE communication to function without the need for intermediary communications infrastructure, such as repeaters. As a result, such communication systems have the potential to provide reliable, robust communications between surface and underground personnel. Exploration into the use of TTE technology for this purpose dates back to the 1920s (Jakosky and Zellers 1924; Pittman, Church and McLendon 1985), but U.S. permissibility requirements slowed the development of TTE equipment for widespread implementation (Durkin 1980; Pittman, Church and McLendon 1985). One of the primary challenges in producing wireless TTE communications is the counteraction of signal attenuation when propagating through solid strata (Barkand, Damiano and Shumaker 2006; Wadley 1949). The long wavelengths of TTE transmissions make them well-suited for reducing the rate of attenuation. However, even when operating within the VLF to ULF range, the performance of TTE systems is still affected by geologic and anthropogenic factors (Geyer 1973; Geyer and Keller 1976; Geyer, Keller and Ohya 1974; Jakosky and Zellers 1924; Large, Ball and Farstad 1973). Although commercially developed TTE systems have demonstrated the ability to communicate through a variety of conditions, their range and performance have been highly varied (Barkand, Damiano and Shumaker 2006; Geyer and Keller 1976; Geyer, Keller and Ohya 1974; Ilsley, Freeman and Zellers 1928; Jakosky and Zellers 1924; Yenchek et al. 2012)."

Jan 1, 2016

"INTRODUCTION Foam, unless intentionally created, in any industrial process presents operational problems, or at a minimum, is a nuisance. Some foam problems are unique to a given industry and others are common across many industries. A few problems foam presents to any particular industry are: (a) Poor Housekeeping, (b) Environmental impact, (c) Safety Hazards, (d) Slower Production Rates and, (e) Reduced quality of the end product. Defoamers address these issues. Sadly, the assumption in most industries is all defoamers are alike. In reality, a lot of chemistry is involved in the manufacture of even the simplest defoamer sold today and rarely are any two defoamers “just alike”. Today’s defoamers can include polymer chemistry, fatty esters, alkoxylated alcohols, silicone chemistry, silicone surfactants, ethoxylated and propoxylated block polymers, and a tremendous amount of emulsion chemistry just to name a few. This paper will discuss the various types of defoamers, defoaming mechanisms, the advantages and disadvantages of defoamer selections, and how to choose the proper defoamer for your application. Before a discussion of defoamer can be brought about, foam generation and composition must be discussed. WHAT IS FOAM? Foam is a colloidal suspension of a gas dispersed in a liquid. Most often foam consists of air dispersed in water. If a stream of air is introduced into a liquid, the bubbles produced assume a spherical shape. As the density of the bubble is less than the liquid the bubble rises. When the individual bubbles reach and pass through a surfactant free liquid they collapse. Air from the bubble dissipates and the liquid previously surrounding the bubble flows back.It should be noted a pure liquid will not foam. In the case of air dispersed in water a surfactant is necessary to make the water support a stable foam. A surfactant is a term used to describe a surface active agent; a compound with a hydrophilic end and a hydrophobic end on the same molecule."

Jan 1, 2016

By Stewart A. Silling, Dale S. Preece

The two key results of rock blasting are fragmentation and movement of geomaterials. Movement/flow of the blasted rock is often referred to as heave. Modeling the movement of full scale blasting is now possible with 3D distinct element models and parallel processing.

Jan 1, 2016

By Rob Farnfield, William Birch, Douglas A. Anderson

In the blasting industry, even to the most safety conscious shotfirer, misfires are a constant source of concern. In the United Kingdom, there are two types of misfire, as classified by the Health & Safety Executive. Type A occurs when testing a shot before firing reveals broken continuity that cannot be rectified. However, due to the fact that a majority of quarries use non-electric initiation [i.e. shock tube] that cannot be tested, this type of misfire is very unusual.

Jan 1, 2016

By Michael Loken, April Montera

"The process of blending consistent and predictable feed for the roasters is critical to optimizing product quality and controlling production costs. To assist in this process, Online PGNAA Slurry Analyzers have been installed and evaluated at a Sudbury Ontario smelter. They are used to measure 100% of the full process stream to obtain elemental composition data in real time. This paper explains the application details at Sudbury and the benefits achieved from their Full Stream, Elemental Slurry Analyzers.INTRODUCTIONSudbury Integrated Nickel Operations (Sudbury INO), a Glencore Company consists of two underground nickel/copper mines in Sudbury, Nickel Rim South and, Fraser, along with the Strathcona mill and the Sudbury smelter. The facilities are spread throughout the 60 kilometer-long, oval-shaped geological formation known as the Sudbury Basin (Figure 1). The company has been mining nickel-copper ores in the Sudbury area since 1929. Nickel and copper are the primary focus of operations at Nickel Rim South and Fraser. Other base metals such as cobalt and precious metals are also produced."

Jan 1, 2016

By Ramazan Comakli, Cemal Balci, Nuh Bilgin, Hanifi Copur, Can Polat, Deniz Tumac

"Application of mechanical excavators for rock excavation in both civil construction and mining engineering fields has increased significantly in recent years. Prediction of the excavation performance of any mechanical excavators – tunnel boring machines, roadheaders, impact hammers, continuous miners and shearers for any geological formation is one of the main concerns in determining the economics of a mechanized mining and/or tunneling operation. A new portable linear rock cutting (PLCM) device was developed in the Mining Engineering Department of Istanbul Technical University and supported by The Scientific and Technological Research Council of Turkey (TUBITAK-112M859). The PLCM is used for cutting small core or block rock samples by a real-life mini disc cutter. The results from the PLCM are compared with the results obtained from the full scale rock cutting tests and theoretical model. It is found that there is reliable correlation between test results obtained from both cutting tests and theoretical model. 1. INTRODUCTION Mechanical excavators are currently the only alternatives to drill and blast due to higher production rate, increased safety, uniform muck size, less roof support, easier ventilation, continuous rather than cyclical operation, and possibilities for automatic control. The most of large civil tunneling and some mining projects are now carried out by mechanical excavators rather than drill and blast methods. Mechanical excavators can be categorized into two main groups: full-face and partial-face machines. Full-face machines such as tunnel boring machines excavate the face in one mode at the size of the cutterhead. Due to their cutting mode, the shape of the face profile by the full-face machines can only be circular. As for partial-face machines, the cutterhead is attached at the end of a boom. The face profile excavated by the partial-face machines can be from circular to horseshoe shape due to the cutting mode of the boom."

Jan 1, 2016

By M. Hepokoski, M. Klein

"Mine refuge shelters are designed to protect mine workers from hazardous environmental conditions after a mine disaster, but high temperature and humidity levels inside these shelters may pose a significant safety risk. Due to the safety risks associated with human testing, detailed thermal models of shelters and human occupants have been developed using TAITherm simulation software. These models are used to predict the temperature and humidity within the shelter resulting from metabolic heating, evaporation due to sweat and respiration, moisture and heat from the shelter’s carbon dioxide scrubbing system, and heat transfer within the shelter. A detailed human thermoregulation model simulates the sensible and latent heat generated by the shelter occupants, and predicts the occupant’s body core temperature and moisture lost due to sweating and respiration. This information is used to assess the safety of the shelter. In this paper we will review technical details of the human thermal model, validation comparing the human model to human subject test data, and results of a mine shelter analysis. INTRODUCTION Portable mine refuge chambers are used in US coal mines to provide protection to mine workers from hazardous conditions following a traumatic event. Although these shelters are designed to supply clean air and sustenance for up to 96 hours, prolonged exposure to the mine shelter environment itself can pose a substantial risk to human safety. Heat generated by the shelter occupants combined with heat from the carbon dioxide (CO2) scrubbing system can raise the shelter interior temperatures and relative humidity to dangerous levels that can lead to heat stress in humans. Unfortunately, the thermal burden associated with mine shelter exposure is not well characterized due to potential hazards associated with underground human subject testing. In order to assess the thermal burden on people within a mine shelter environment, a detailed thermal model was created to accurately predict the temperatures and humidity within the shelter, as well as the impact of these environmental conditions on human occupants. The model consists of a mobile inflatable tent-type mine shelter, 23 humans, and also includes the surrounding mine environment. The thermal simulations were performed using ThermoAnalytics' validated commercial heat transfer prediction code, TAITherm (v12.0). Additionally, TAITherm's Human Thermal Module (HTM) provided the capability to simultaneously model the thermo-physiology of 23 unique humans contained within the mine shelter. The human thermal models accounted for the thermal interaction with the environment and also provided a core temperature response prediction, which can be used to evaluate survivability in heat stress situations [1]."

Jan 1, 2016

By J. Lorengo, C. H. Bucknam

"Standardization of the Inductively Coupled Plasma Mass Spectrometry (ICPMS) method for gold in cyanide solutions was undertaken to provide a more sensitive method to quantify the gold content than the atomic absorption method standardized in 1994 (E1600). The gold concentration range covered is from 0.001 mg/L Au - 0.3 mg/L Au (0.00005 toz/t Au – 0.009 toz/t Au). Interlaboratory testing was carried out with the assistance of the American Society of Testing and Materials (ASTM) International on two committees to determine the within laboratory and between laboratory reproducibility. Three barren solutions from metallurgical operations were measured in triplicate to satisfy statistical requirements for Committee E1 on Analytical Chemistry of Metals, Ores and Related Materials. A synthetically prepared matrix representing the metallurgical processing solutions was used to prepare Youden pairs to satisfy the requirements of Committee D19 on Water. Results of the standardization program are presented. INTRODUCTION Analysis of process solutions for gold concentration requires accurate and sensitive analytical methods in order to manage process control and metallurgical accounting. Flame atomic absorption spectrophotometry (FAAS) has been the work horse of the assay lab for this duty for decades. In 1994 the FAAS standard method was approved by the American Society for Testing and Materials (ASTM) (1). Six process solutions were collected and preserved by measuring the pH and adjusting to greater than pH 10, if necessary. Duplicate solutions were provided to eight laboratories in random order for analysis by FAAS covering the gold concentration range of 0.19 µg/mL (0.006 toz/t.) to 10.7 µg/mL (0.312 toz/t). A high precision method was used, which involved bracketing the sample with the higher and lower standards nearest to its concentration repeating readings three times and averaging the results. The optimum precision for the FAAS gold method was found to be at the 1.00 µg/mL (0.029 toz/t) and lower scope limit 0.3 µg/mL (0.009 toz/t) gold concentration. Since tailings solutions typically have concentrations below the lower scope limit, use of ICPMS was developed at Newmont USA Limited (Newmont) to assay the lower range solutions."

Jan 1, 2016

By Maciej Wrobel, Joerg Hammerschmidt, Dana Nurgaliyeva, Alexandros Charitos, Jochen Guentner

"Smelting of copper concentrates in the flash smelter generates a flue dust stream that contains a substantial amount of copper and accumulates more than half of the arsenic input to the smelter. In view of its high copper content flue dust recirculation to the flash smelter is common practice. Globally traded copper concentrates are affected by ever increasing arsenic contents and cause an increasing circulating arsenic load in flash smelter operation. Control of the arsenic level in the smelter slag becomes a challenge. This interaction of arsenic loaded copper feedstock, need for flue dust recirculation and slag quality control call for possibilities to reduce the arsenic load of the recirculated flue dust stream.The technology of partial roasting is known from pre-treatment of copper concentrates before smelting, and gold concentrates before cyanide leaching, to remove the harmful element arsenic. The partial roasting technology can be adapted for use in the purification of the flue dust. A major challenge for flue dust treatment is its extremely fine particle size compared to usual concentrates. For this reason Outotec developed a new process, which allows handling of such fine flue dust. This process solution provides an efficient possibility to reduce the arsenic burden in copper smelter operations.The suggested process aims at reducing the arsenic load to the smelter by treating the flue dust prior to recirculation to the smelter. The presented results are based on test work in the Outotec R&D-centre in Frankfurt. It is possible to remove 80-85% of the contained arsenic and to collect it in an arsenic trioxide residue with a concentration above 90%. The final off gas contains SO2 from decomposition of sulphates that are contained in the flue dust. The off gas stream is relatively small. We assume that it is possible to combine the off gas stream with other smelter process gas streams and to treat it in an existing sulphuric acid plant. Coal is used as fuel and as reductant to reduce pentavalent arsenate to trivalent arsenite. Arsenite can be kept in gas form at temperatures above 450°C. This permits separation of a calcine stream with arsenic levels of 0.2 – 0.3%, which is recirculated to the furnace.Outotec has a wide range of roasting testing facilities from lab-scale to pilot-scale. Outotec has both capability to modify and adapt technology to specific ore or concentrate requirements, but also the necessary infrastructure in its research centers in Frankfurt and Pori to do appropriate validation tests in lab and pilot scale size plants."

Jan 1, 2016

By Joseph Nawrocki, Margaret Hettinger, Dr. Catherine Johnson

"Optimized rock fragmentation is essential for minimizing downstream costs to mining operations.Photographic fragmentation analysis, vibration monitoring, and high-speed video all providemeasurements of blast effectiveness and supply data that allows operations to modify blasts to achieve downstream goals."

Jan 1, 2016

By Gabriele Eccher, Michele Caponero, Paolo Cucino, Roberto D’Angelis

"This paper describes the optic fiber structural monitoring system implemented for Pavoncelli Bis tunnel. The paper highlights the optic fiber sensors customization capabilities, how they smoothly fit precast concrete lining processes and TBM operations, and how a lifelong service monitoring can be achieved. An overview of readings’ evolution during excavation concludes the paper.INTRODUCTIONPavoncelli Bis is a 10 km hydraulic tunnel designed to by-pass the existing Pavoncelli tunnel which experienced severe damages during the 1980 Irpino-Lucano earthquake, in south of Italy (Barla 2009). Pavoncelli Bis excavation work commenced in 1988-90, however, when excavation approached pk. 0+583 in 1992, water percolations became more and more consistent and resulted in work suspension. The tunnel was eventually sealed at pk. 0+383, leaving a flooded section between pk. 0.383 and pk. 0+583. Work resumed in 2012 where EPB-TBM excavation was adopted to cross the flooded section and to overcome complex hydro-geological conditions in various lito-types and, in particular, in the Varicolori Clay-shales area (Figure 1).Consequently, stress evolution monitoring is extremely important during construction and during the service life of tunnel lining in clay-shales and in faults areas. In particular, the paper focuses on the monitoring system proposed for the newly EPB-TBM excavated portion from pk 0+583 onwards where optic fiber sensing technology was chosen for its reading stability and reliability in presence of water and its ability to be connected in series and remotely interrogated at kilometers of distance. FBGS OPTICAL FIBER SENSOR TECHNOLOGYFiber Bragg Grating Sensors (FBGS) are gaining increasing attention in the field of experimental stress analysis. Basically, Fiber Optic Bragg Sensors are strain-measuring devices and therefore provide many of the advantages of the well-known metal foil strain gages (Kreuzer 2007).Bragg gratings are written into so called single-mode fibers. These fibers consist of a very small inner core of 4 to 9 µm diameter and an outer part (cladding) of pure glass (SiO2) of 125 µm diameter. The difference of refraction indexes between inner core and cladding causes the light to propagate only inside the small core."

Jan 1, 2016

By Darryel Boucher, Thomas W. Leadbeater, Raymond Langlois, Joshua Sovechles, McGill University, Zhoutong Deng

"Spiral concentrators are used to upgrade ore based on the density difference between their component minerals. This simple flowing film gravity separator is of interest for the processing of large amounts of material, as found in the iron ore industry. Addition of wash water at different points on the trough of the spiral affects the grade and recovery of the valuable concentrate by affecting the flow of particles within the thin slurry film. This paper shows how radiolabelled hematite (-355+300 µm) and quartz (–1,180+1,000 µm) tracers were used to determine the particles’ behaviour within the slurry film with and without the addition of wash water. The results presented provide a detailed particle flow pattern around a wash water addition point and its effect on the trajectory and velocity of the particles. This information is of interest in building knowledge about spiral wash water injection parameters such as injection location, direction, flow rate and nozzle orifice type (affecting jet shape and velocity).INTRODUCTIONSpiral concentrators are density based separation devices. They are extensively used in the upgrading of iron ore, fine coal and minerals sands (sources of ilmenite, rutile, zircon and monazite) (Wills & Finch, 2016). A spiral unit is composed of a channel of specific profile formed as a helix of 3 to 7 turns around a central structural post. The feed pulp is composed of 15 to 45% solids with particle size from 75 µm to 3000 µm (Wills & Finch, 2016). Throughput of a single spiraling trough can be up to 8 ton per hour and multiple trough unit (up to four trough) can process up to 30 ton per hour for a footprint of around 0.7 m2 (Palmers & Vadeikis, 2010). They are low cost concentrators considering manufacturing of their trough via polymer reverse molding. The energy intensity of a spiral plan is notably small considering the throughput and is mostly related to pulp pumping and final concentrate dewatering."

Jan 1, 2016

By F. Roemer, D. Goldmann, T. Elwert

Tantalum is an important minor metal for the production of high performance capacitors. Approximately 60% of the annual tantalum production is used in this application. Despite its high price of 298 US$/kg (average price 2010–2014), at the moment, no recycling from end-of-life products takes place. In the established recycling processes of waste electrical and electronic equipment (WEEE), tantalum is lost in the slags of copper smelting, where it is highly diluted. An economic recovery is not possible at that point. Although tantalum must therefore be extracted from the WEEE stream before it enters smelting, no industrial recycling processes exist. The main reasons are its low concentration in the WEEE stream, lack of information about tantalum bearing devices, technical difficulties of extraction, and conflicts of interests regarding the recycling of other valuable metals in WEEE. In this paper, the results of a cooperation research project are presented. The aforementioned challenges are addressed and a novel tantalum recycling process is developed. Small pilot scale experiments show that a mechanical processing route can produce marketable tantalum-concentrates of 30% tantalum with yields between 60 and 70%. This is reached through a manual pre-sorting of potentially tantalum bearing products followed by a combination of an optimized comminution, sieving, air classifying, eddy-current (EC), and two stage magnetic separation. Key to the implementation of this process was a detailed survey of the tantalum concentrations in different products carried out by the industrial partner.

Jan 1, 2016

By C. R. Kato, G. Proulx

"Within the continuous scenario of reduced aluminium price and plants production costs increase, the energy consumption optimization in the aluminum electrolytic pots continues as the main focus for the producers. Energy consumption was chosen as a key performance indicator to drive the efforts and actions for improvements. Alcoa improved the energy consumption by approximately 3% from 2005 to 2015. This improvement was a result of best practices implementation, new technologies introduction, strategic actions with plant curtailments and management practices. The main objective of this paper is to highlight the importance of the management practices for planning and operational improvements beyond the technology changes. About 10 years ago, Alcoa reorganized its approach to retain knowledge in the Smelters by using a Best Practices format. For each specific subject, a skilled team defined the minimum requirements and the Best Practices for several aspects of operation and maintenance, which affect the environment, safety, cost, customers and performance. These Best Practices were deployed to all Smelters combined with training sessions to process and operation professionals. We will describe how the Best Practices were organized, the deployment strategy used, and the approach to measure the plants’ success. We will describe the management approach that includes Manufacturing Analyses focused on 3-year potential, annual planning, and weekly monitoring of plant stability. A manufacturing analysis is organized at select plants with cross-functional participation of specialists from technical, operational, procurement and finance. The output of a manufacturing analysis includes a roadmap of enablers to improve energy efficiency. A quarterly follow-up of enabler deployment is held with the plant and resources that participated in the analysis. Annually, there is a Planning Process where energy consumption enablers are selected to be implemented during the next 3 years for each plant. A monthly critical analysis is made by the plants with regional best practice support. On a weekly basis, key performance indicators are reviewed with determination of a stability index for each plant. Any deviation signal of unstable condition is alerted and supporting resources are diverted to the plant to reverse trend with countermeasures.INTRODUCTIONDue to factors like excess aluminum in the market and lower consumption in China, the LME price is declining along the last years, as showed in Figure 1. In 2011, the price peaked at US$ 2,400/ton and since then, continues to trend down and approaching the lowest level at US$ 1,500/ton in the last 5 years."

Jan 1, 2016

By L. A. Cornish, J. W. van der Merwe

"The hydrofluoric acid (HF) industry in South Africa uses normalized mild steel (SA 516 Gr 70) for the storage and distribution of its technical-grade product (70% HF). The technical-grade acid is split from the anhydrous hydrogen fluoride (AHF) product during distillation just after HF is produced, in a stainless-steel-lined kiln, from the reaction of calcium fluoride (CaF2) with sulphuric acid (H2SO4). Uniform corrosion of the storage tanks is mitigated during commissioning by contacting the steel with 70% HF. A corrosive reaction takes place (2H+ + 2F- + Fe - H2 + FeF2) to form scale inside the tank which diminishes the attack of the steel by fresh HF, thus prolonging the service life expectancy of the vessels. This iron fluoride scale in the vessel grows continually, resulting in corrosion of the vessels continuing at a predictable rate (approx.0.5 mm/a) since the first commissioning of the tanks at Necsa in 1993. In early 2012, an increase in the average corrosion rate of the tanks to 3 mm/a measured at and below the liquid band in the storage vessels was noted. Three months later the corrosion rate had increased to 30 mm/a, just before the first leak from the tank was detected. The tanks were decommissioned shortly afterwards and an investigation revealed that the rapid corrosion was due to the presence of increased levels (>50 ppm) of nitric acid (HNO3) in the tanks, which attacked the fluoride layer protecting the steel.The oxidation characteristics of high concentrations of HNO3 with low concentrations of HF on stainless steel surface treatment are well documented. The effects of low levels of nitric acid on the corrosion of steels in sulphuric acid are also known, but no suitable published data currently exists on corrosion by high HF concentrations with low HNO3 concentrations. Establishing the rate and mechanism of corrosion by HNO3 (0.1 to 1%) in 70% HF is currently a high priority for the HF industry in South Africa and will become increasingly important in the near future due to depleting fluorite reserves and cheaper, but less efficient, processes producing H2SO4 with higher impurity levels, which were not anticipated in the original plant design. The aim of this study is to simulate the corrosion conditions in the plant on a laboratory scale in order to establish the corrosion characteristics of the steels used in the HF plant, which are increasingly exposed to the HNO3 impurities that tend to concentrate in the final technical-grade HF acid product."

Jan 1, 2016

By L. Rudolphy, P. Tähkiö

"The cPlant is a modular flotation plant which has been designed to minimize capital expenditure and risk. The plant is based on a number of standard modules, for both flotation and ancillary equipment, which can be configured to give the required flowsheet for the ore being treated. All of these modules can be rapidly deployed and erected onsite, minimizing not only engineering time and site preparation but reducing the time taken to get the plant up and generating revenue. Given the paradigm shift in flotation circuit design that has been employed in the cPlant it may allow smaller, previously uneconomic deposits to be exploited and create a more cost efficient upgrade route for existing plants. This paper introduces the cPlant and presents a case study comparing EPC cost and development timing of a cPlant against a traditional flotation circuit design. INTRODUCTION In the development of any mining project the cost associated with process plant engineering, equipment procurement and installation can affect the financial viability of a project. This is of special significance for smaller scale mining projects which perhaps don’t have the mine-life or revenue generation to justify the payback on a modern processing facility. Listening to customer feedback and understanding the challenges that small to mid-sized projects can face lead Outotec to the development of the cPlant. Modularization of mineral processing plants isn’t a new idea with a number of examples being reported in literature for gravity gold (Cabot, Trudel and Cabot, 2001; Gray et al., 2006), dense medium separation (September and Abate, 2006) and even hydrometallurgy (Saario et al., 2013). All these plants have been developed to try to improve on the traditional economics associated with fixed processing plants. Using standardized modules to construct a plant reduces engineering time and design costs which can both be beneficial to the outcome of a project. In addition the modular nature of the plant lends itself to transport to remote sites and rapid installation with only minimal site preparation required. A plant of modular design also has several other advantages over its conventional cousins. Firstly it is relatively easy to expand by duplicating existing modules. Secondly the modules can be treated as building blocks for the process and rearranged if a change in conditions requires flowsheet adjustment. Thirdly, there is potential to disassemble and remove the modular units at the end of the mine life. The ability to easily disassemble, re-pack and transport the plant to a new location not only is important to the long term environmental footprint of an operation but can also be seen as a bonus to an operator that has a number of small ore deposits. If applied in this way modular plants have the potential to create a whole new operating model for previously unviable ore deposits."

Jan 1, 2016

By Pedro C. Carneiro, Luiz G. I. Maciel

"This article presents data of advance and excavation rates in tunnelling works, and how theseactivities interact with the duration and cost of a contract. These key parameters, after analysis andsynthesis, will be used in coming works to ensure the evolution and adaptation of the method created by the Norwegian University of Science and Technology - the NTNU Method - to Brazilianconditions, which will be reflected in the duration and cost of underground drill and blast tunnellingworks."

Jan 1, 2016

By Alexandre Passos, Giorgio De Tomi, Tatiane Marin, Dennis Cremonese, Jacopo Seccatore

"In the mining industry, rock excavation is the first phase of the comminution process. Downstreamoperations such as secondary breaking, crushing and milling terminate the process, reducing the size of the grains down to the desired particle distribution. In such a cascade process, every process upstream heavily influences all the downstream operations. When rock excavation is carried out by drilling and blasting, a very economic source of energy (the explosive) is used at the utmost upstream; a more expensive source of energy (electricity) is employed for all the downstream phases. This means that managing the correct employ of the explosive energy is a form of managing the whole process, controlling the operational costs and therefore the profitability of the whole business. We simulated this cascade behavior, using as a starting point the experimental data obtained from small-scale block blasting, evaluating the influence of blasting on the grindability of the blasted material. This study showed the reduction in visible (particle size) and invisible fracturing (micro-cracking, resulting in a reduction of the Work Index WI). The particle size distribution for full-scale blasts was estimated by means of algorithm simulation, then we simulated the behavior of the comminution plant fed with the material possessing the characteristics previously estimated. All the costs (drilling, blasting, electric energy for the engines of the crushers and mill) were calculated and charted. The results show a clear curve that allows to estimate the minimum operating expenditure (OPEX) for the whole mine+plant framework. Being the WI dependent on the output on the blast, one can manage the performance and the expenditure of the whole comminution process by adjusting drilling and blasting parameters For any given mine, it is possible to perform a simulation and encounter the minimum OPEX scenario for the comminution process and managerial choices can be oriented accordingly. In a cascade productive chain as mining is, responsible strategic choices must be taken looking at the entire production framework. Compartmentalized managerial staff and budgets for separated production areas are not acceptable anymore. Somehow higher costs upstream can lead to effective decrease in costs and increase in efficiency and productivity of the processes downstream."

Jan 1, 2016

By A T. Spathis, M G. Wheatly

Some preliminary dynamic pressure data were obtained from several charges detonated in a tunnel situated in massive granite rock. The context of the work is the potential for desensitisation of explosives, failure of detonators, and sympathetic detonation due to the close proximity of inter-hole and inter-deck explosive charges to each other. Dynamic pressures were measured using piezoelectric gauges in water-filled 45 mm diameter holes adjacent to the charges. Some of the first arrival peak pressures were noisy, and although not fully resolved, may be due to reflections and the physical arrangement of the transducers and their size with respect to the monitoring holes. The estimated peak pressures were between 0.1 to 8.7 MPa at approximate distances of 2.8 to 0.8 m, respectively. Further work is planned with gauges that are disposable, have a higher pressure range, and can be used within a few borehole diameters rather than the piezoelectric gauges used in the present work.

Jan 1, 2016

By Per Hedvall, Jan-Eric Ståhl

"The main objective of this study is to introduce the new Sandvik’s production cost-model within Crushing & Screening (C&S) technology. So far, there have been different ways of determining different production costs in the industry, however, the previously published and presented methods have not been very efficient in calculating the costs per product and metric ton. Accordingly, the current study has been planned and started in collaboration with Lund University to provide an accurate and easy to implement cost estimation program to determine the costs for crushing and screening plants worldwide.The proposed model has been adapted to fit the C&S processes of different rocks/ores fractions. The result is presented as cost per ton of the end product(s).Within this paper the cost estimation results for 3 different crushing and screening plants are presented based on the information obtained from the following sources: a) documents at Sandvik SRP, b) Sandvik’s crushing & screening internal/external machines/plants data and information, c) literature studies, including the use of Sandvik’s internal/external simulation and software programs, d), visiting the crushing and screening plants ,e) interviews, information systems’ data, and, f) testing and observations by ourselves.In order to improve the level of accuracy and the validity of the attained results, simplistic Monte-Carlo simulations have been used, where needed. The achieved results, so far, have proven the reliability of the model. The calculated cost estimations have shown an accuracy over 80% when they compared with real cost data obtained from plant practices.The current cost calculation model, will offer the possibility of:•,Calculating the production costs in proposed and/or existing C&S plant.•,Making detailed cost analyses for the end product(s) in proposed and/or existing C&S plants.•,Determining the profitability of each finished product when it’s required.•,Cost optimization by potentially cutting the cost for part of C&S plant with an existing plant practice"

Jan 1, 2016