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By T. W. Camm, J. C. Johnson, S. D. Rosenthal

"Most engineers are bright, hard-working, reliable and prefer to avoid conflict. An engineering curriculum tends to self-select these characteristics. By most standards, you would expect workers exhibiting these traits to require minimal supervision. But, is this true? Is this how most current engineering managers lead? Looking at some current theories on leadership combined with personal anecdotes, this article will look at some common misconceptions about leading engineers.Engineers are different. There, it has been said. From cartoons to movies to television shows and more, there is a reason stereotypes of engineers resonate. Yes, you can find a lot of individual variation among specific engineers that you may know, but they do not detract from some of the overarching commonalities that engineers are known for.Clash of culturesWhat distinguishes a professional? Raelin (1985), in his book Clash of Cultures, describes professionals as having superior intellectual training, maintaining their own standards of excellence and being supported by associations that maintain the quality of the profession. Engineers obviously fit all three of these ideas: an engineering degree is still regarded as one of the most difficult to attain. Standards are maintained both through peer review and in academia, through ABET accreditation and through professional associations like SME to promote the discipline and foster technical growth.Six characteristics representing professional status are described by Raelin (1985, p. 9):• Expertise — prolonged specialized training in a body of abstract knowledge.• Autonomy — the freedom to choose the means to solve a problem.• Commitment — primary interest is in pursuing the practice of one’s own chosen specialty.• Identification — identifying with the profession and with fellow professionals, both through formal associations and through peers external to the organization.• Ethics — providing service without concern for oneself or without becoming emotionally involved with the client.• Standards — committed to help in policing the conduct of fellow professionals."

Jan 1, 2018

By Ethan Steward, Robert Eades, Kyle Perry

Shock tubes, either gas or explosively driven, are often used for physical modeling of free field explosions or arena testing. The use of shock tubes often requires less setup time of subjects and smaller driving forces to create pressure versus time waveforms similar to that of arena testing. However, the effects of the shock tube cross sectional geometry on waveform properties is uncertain while free field explosion wave propagation and estimation is well studied.

Jan 1, 2018

By Petrus van Staden, Dragan Milanovic, Francisco Sánchez, Eero Kolehmainen, Carlos Frias

"Currently there is no economical and viable process for on-site metal extraction from Low Grade, Complex or Poly-metallic deposits, and even more, there is not any industrial process or technology able to deal with polymetallic or bulk concentrates containing Cu+Zn+Pb base metals and also precious metals. Traditionally, metals recovery from polymetallic sulfide deposits is performed by mining, selective flotation to separate Cu, Pb and Zn concentrates, and finally, smelting/refining of those concentrates to obtain the refined metals. In many cases, selective flotation of that kind of complex ores produces low metals recovery and low concentrate quality containing impurities such as Hg, As, Bi, etc., which results in high penalties in treatment and refining charges, and consequently, worsening the economy of the mining business. Recovery of the valuable metals from Polymetallic, Complex or Low Grade ores could then be maximised by producing bulk concentrates or middling flotation products to feed novel hydrometallurgical processes, like the integral metallurgical system that is currently under development within the INTMET project. For example, producing bulk concentrates would increase more than 100% Cu+ Zn+Pb cumulative recovery versus conventional selective flotation. Founded by the Horizon-2020 EU Programme, the INTMET Project was started in February 2016 and will be running over three years. The INTMET consortium is led by Cobre Las Cruces (Spain) and integrates twelve partners from seven EU countries, and including Serbia and South Africa as well. The INTMET project represents a challenging opportunity to develop suitable technological solutions to deal efficiently with difficult, polymetallic and complex sulphide ores that are abundant in Europe and worldwide. Main activities carried out during the first 18 months of the INTMET project development includes: (i) An atmospheric leaching pilot plant having a capacity of 300 kg/h bulk concentrate which has been installed and operated continuously for nine months at the Las Cruces mine; (ii) Pressure leaching test work developed by Outotec; (iii) Bioleaching test work performed by Mintek in collaboration with MMI Bor. Prior test work was applied on bulk concentrate samples supplied from Spain, Portugal and Serbia. Some of the results of these technological developments have been very positive and are presented in this paper."

Jan 1, 2018

By Lou Gaozhong, Guo Wenbing, Zhao Gaobo, Wang Shuren

"The height of a fractured zone due to high-intensity mining (HIM) plays a vital role in the safety analysis of coal mining under bodies of water. This paper described the characteristics of HIM. The processes of overburden failure transfer (OFT) are analyzed. The state of destruction transfers from a certain stratum to the upper stratum as face advance distance increases, and the processes of OFT are divided into two stages: transmission development stage and transmission termination stage. Through theoretical analysis, the limited suspension-distance and limited overhanging distance of each stratum are proposed to judge the damage of each layer. Based on this, the OFT criteria of fractured zone development are obtained. The mechanical model of strata suspended integrity and overhanging stability are established. Finally, a new method to predict the height of fractured zone due to HIM is put forward based on the processes of OFT, the limited suspension-distance, and the limited overhanging distance. Further, a HIM panel in the Datong coal mine is taken as an example. Theoretical methods are proposed, and engineering analogy is used to predict the height of the fractured zone, which is compared with in-situ measurements reported in the literature. The results show that the in-situ measurements for the height of the fractured zone are in close agreement with the theoretical calculation result. Therefore, the rationality and reliability of the theoretical method proposed to predict the height of fractured zone is verified.INTRODUCTIONThe height of the fractured zone (HFZ) due to the exploitation of coal is a key parameter for the safety analysis of coal mining under a body of water (Wenbing, Youfeng, and Hou, 2012). Accordingly, it is necessary to predict HFZ under the corresponding mining conditions before coal mining."

Jan 1, 2018

By Harold Gibson, Ulrich Schwarz-Schampera, Ralf Freitag, Hendrik Mueller

INTRODUCTION Germany has a long history in marine research in the Indian Ocean. The first German scientific cruise started in 1964, followed by a series of state-sponsored research cruises between 1983 and 1995 leading to the first finding of polymetallic sulfides in the Indian Ocean. The research included regional bathymetric, geological, structural, volcanological, petrological and hydrothermal investigations along the Carlsberg Ridge and the Central Indian Ridge (CIR). Early environmental base line studies covered oceanographic and sedimentology aspects. In 2010, BGR took the initiative for the preparation of a license application for the exploration of polymetallic sulfides with the International Seabed Authority (ISA), and prospecting started in 2011 along the southern Central (CIR) and the northern Southeast Indian Ridge (SEIR) in the southwestern Indian Ocean (cruises INDEX 2011 on board R/V Sonne), INDEX 2012 (R/V Fugro Gauss), INDEX 2013/1-2 (R/V Sonne) and INDEX 2014 (R/V Pelagia). After three years of resource-oriented and environmental base line studies, BGR, in order for the Federal Ministry for Economic Affairs and Energy (BMWi), applied for an exploration license which was approved by and subsequently signed with the ISA in 2015. The license gave permission to start a detailed exclusive resource-oriented exploration program in the license area. The program includes the outline of potential ore deposits and a resource assessment but also extensive and detailed base line studies for the sustainable protection of the marine environment in the license area. The license contract has a fifteen years lifetime and may allow the application for a subsequent mining license. The exploration aims at the identification of inactive polymetallic sulfide deposits, formed below former discharge zones of hot hydrothermal fluids on the ocean floor (“black smoker” systems), by advanced and modern exploration techniques.

Jan 1, 2018

By Elizabeth Holley, Meriel Young, Gabriel Walton

"The coal mine roof rating (CMRR) was developed by Chris Mark and Greg Molinda to bridge the gap between geological variation in underground coal mines and engineering design. The CMRR accounts for the compressive strength of the immediate roof, the shear strength and intensity of any discontinuities present, and the moisture sensitivity of the immediate roof. The CMRR has been widely used and validated in Eastern US coal mines, but it has seen limited application in the Western US.This study focuses on roof behavior at a Western coal mine. Mine A shows significant lateral geological variation, along with localized faulting and a laterally extensive sandstone channel network. The CMRR is not used to predict roof instability at the mine.It is, therefore, hypothesized that there are other factors that are correlated with roof instability in underground coal mines that could potentially also be included in the CMRR.This hypothesis was tested by collecting 30 CMRR measurements at Mine A. At each measurement location, a binary record of the roof condition (stable or unstable) was made along with parameters, such as depth of cover, thought to also correlate with roof stability. A statistical analysis of the data was performed to determine the parameters in addition to those included in the CMRR, which can be correlated to roof stability.INTRODUCTION AND BACKGROUNDRoof fall is one of the greatest hazards facing underground coal miners (Barczak et al., 2000). In 2017, 91 lost-time injuries occurred due to roof fall in US underground coal mines. A further 48 roof falls occurred with no lost days (MSHA, 2018).The coal mine roof rating (CMRR) classification was developed by Molinda and Mark (1994) to quantify the geological description of mine roof into a single value that could indicate mine roof stability and be used in engineering design. It is widely used in the Eastern US as an input for the analysis of longwall pillar stability (ALPS) in underground coal mines. It provides an excellent start; however, it is arguably not fully comprehensive, nor is it widely used in the Western US."

Jan 1, 2018

By Italo Onederra, Gary Cavanough, Ewan Sellers

Reactivity of ammonium nitrate based explosives is associated with the presence of iron sulfides in the ground reacting with explosive products and in some instances causing spontaneous reactions which can lead to detonation. The stability of explosive products can also be linked to in-hole density, which influences detonation efficiency, breakage performance and the potential generation of Nitrogen Oxide (NOx) fumes. Reactive ground testing involves detecting a temperature rise of a mixture of a bulk explosive product sample, a ground rock sample and some specific chemical agents. This paper describes improvements in reactive ground testing involving the use of time lapse video analysis and detection of NOX gas emissions from the sample. Reactivity is stored and linked to a using cloud based software to map of the mine showing the exact location of the sample. The location marker can be selected to allow quick access to the sample test results and video. In addition to reactivity, the stability and detonation performance of bulk product can also be influenced by depth. In this paper, a system that simulates product at depth and measures density changes and monitors the structure of bulk samples is described. Results from an explosive product are analyzed and detonation performance is assessed by the measurement of velocity of detonation and detonation pressure.

Jan 1, 2018

By S. Gomez, P. A. Bebswa, A. N. Mwale

"The research aimed at improving the way screen performance analysis is conducted using a model that accounts for most feed and design parameters in its formulation. Thus, the aim was to validate the fine screen model that was developed at the Centre for Minerals Research (CMR) unit at the University of Cape Town. Fine wet screening is increasingly becoming an important application in fine grinding operations. Minera Saucito, a lead-zinc Mexican mine has replaced hydrocyclones with eight stacks of five decker derrick screens to close the ball mill in their concentrator plant. The five decker stacks have improved the overall plant throughput by 20% and have had the ball mill circulating load reduced considerably. As a continuous plant optimization process, a number of surveys were carried out to assess the performance of the 75 µm panel aperture installed screens. The surveys were conducted at seven different feed rates to the entire nest of screens to collect performance data. Using the fine screen model to analyze the results, it is found that as the feed rate increase, the sharpness of separation reduces. The CMR fine screen model was fitted to these results. The model fits the plant data with good accuracy. Simulated results based on this model are also presented.INTRODUCTION The potential of high frequency vibrating screens has long been identified as an alternative to hydrocyclones in grinding applications (Rogers and Brame, 1985). However, high frequency vibrating screens have had two main disadvantages, low capacity and high wear rates (Kelley and Mckeon, 2005; Teknikk, 2009). Current vibrating screen technology overcomes these challenges by multiple deck screen design and use of wear resistant urethane materials for panel construction (Kelley, 2007; Valine and Wennen, 2002). For a example, the Derrick screen’s material of construction is a tensionable urethane that provide high open area ranging between 35 to 45% with considerably reduced blinding (Valine and Wennen, 2002). Thus, there has been an increased uptake by the mining industry in the use of wet fine vibrating screens closing the ball mill as the final classification stage in the comminution circuit (Barkhuysen et al., 2010; Frausto, Ballantyne et al. 2017; Pelevin and Lazebnaya, 2009; Teknikk, 2009). Even though there is a number of models in existence, none of these models adequately predict the performance of high frequency vibrating screens (Karra, 1979; Rogers, 1982; Subasinghe et al., 1990; Trumic and Magdalinovic, 2011). Recently Mwale et al., (2016) developed a model for predicting the performance of high frequency vibrating screens using the partition curve properties. The input parameters of the model include screen open area (??) in m2, tonnage feed rate (????) (tph) and the weight fraction of solids (??) in the feed for a given panel aperture size. The model was developed based on data collected from a single deck industrial size derrick screen, in a pilot setup. The work presented in this paper is an attempt to test this model using data collected from Minera Saucito concentrator, an industrial plant whose comminution circuit is shown in Figure."

Jan 1, 2018

By T. Yamazaki, T. Goto, R. Arai, N. Nakatani

The importance of cobalt-rich manganese crusts on the Pacific seamounts for possible future rare metal sources has been recognized these 30 years. The thin layer-type coverage and the micro-topographic undulation of basement affect not only the excavation efficiency but also the economy of mining venture. Because of these distribution characteristics, no economic feasibility has been recognized through the past economic analyses. On the basis of a recent geological study about seamount rocks, a possibility of by-product substrate recovery for phosphorous supply with cobalt-rich manganese crust mining has been highlighted. In the mining model, the substrate rocks are utilized as phosphates for agricultural and chemical usages. Under some preliminary technical and economic assumptions, the possibility of cobalt-rich manganese crust mining venture is examined. The results show a better economy of the venture including the substrate rock usage for phosphorous supply. Introduction Cobalt-rich Manganese Crusts and the Economic Feasibility Cobalt-rich manganese crusts on the Pacific seamounts received attention as potential sources for strategic metals such as Co, Ni, Cu, and Mn, due to their vast distribution and higher cobalt concentration than manganese nodules (Cronan, 1980; Halbach, 1982; Manheim, 1986). In the earlier stage, the geological distribution characteristics were reported (Cronan, 1984; Clark et al., 1984; Misawa et al., 1987; Pichocki and Hoffert, 1987) and a systematic feasibility of the mining was studied (Hawaii DPED, 1987).

Jan 1, 2018

By B. Gorain

"INTRODUCTION The last few decades have seen some remarkable advancement in information technology, but recently various digital technologies have resulted in several synergies to deliver innovation in diverse applications. The mining industry has been relatively slow in adopting these technologies compared to the other industries, but this scenario is changing fast. Keywords: Digital Transformation, Operational Intelligence, Gold Recovery, Mine to Mill integration, Planning and Execution strategy, Theory of Constraints. Challenges Mining companies globally are going through a series of challenges such as declining ore grades with complex metallurgy, increasing depth of ore bodies, high capital and operating costs, lower productivity, shortage of technical resources, significant pressure from stake-holders to deliver, along with growing environmental and corporate social responsibility issues. Improvement in profitability would need significant improvements in operational performance. Consequently, over the last few years, there has been a major focus amongst some mining companies to imbibe Operational Excellence. This has been only possible because of the replacement of a silos based approach by an integrated view of the organization. Such an integrated view is now possible via the evolving digital technologies. Even so, such a transformation calls for a change in culture, which, for most organization is not trivial. Attempts in the past to integrate functions such as through Mine-to-Mill initiatives in the mining industry have demonstrated significant benefits to many operations (McKee, 2013). Still, sustaining these benefits has clearly been a challenge due to manpower turn over and lack of proper systems and structures that integrate information between business functions within an operation and between operations and the corporate.Opportunities The advent of digital technology has opened-up opportunities to integrate inter-departmental information for a unified understanding of, and across, an entire organization. The advances in instrumentation, equipment control systems, supervisory control systems (SCADA/Historian) and industrial networks have helped in the direction of enterprise wide integration. The availability of real time information across an enterprise has given rise to numerous possibilities to improve organization performance. As suggested by Seshan & Gorain (2016), some of the potential opportunities are as follows:"

Jan 1, 2018

By T. Barryere, R. B. Pedersen, E. Reeves, A. Stensland, I. Thorseth, T. Baumberger

Venting on ultraslow spreading ridges is far more abundant then previously predicted, and the discrepancy between observed and predicted vent field density may imply that non-magmatic heat sources are common along these ridges (Baker and German, 2004; Escartin et al., 2008; Rona et al., 2010; German et al., 2016). In this study we have estimated the flux from two hydrothermal vent sites situated on the slow to ultraslow spreading Mohns Ridge at the Arctic Mid-Ocean Ridge system (AMOR). The flux estimates have been made using the primordial isotope 3He in the non-buoyant plume above the Loki’s Castle vent field at the northern termination of the Mohns Ridge, and from the Jan Mayen vent fields area situated close to the southern termination of the ridge. Primordial 3He enters the oceans through degassing and mixing with hydrothermal fluids eventually to be discharged at the ocean floor primarily at hydrothermal vent sites and submarine volcanic eruptions (e.g. Clarke et al., 1969; Lupton and Craig, 1981; Lupton, 1998). Once introduced into the water column the concentration will only decrease by dilution due to its conservative behavior in the water column. Water column samples were collected using a CTD (conductivity, temperature, depth) probe (911plus Seabird) with a Niskin water bottle rosette. The water column above the Jan Mayen vent fields (JMVF) was sampled in the years 2006, 2011, 2012 and 2013 (82 samples) and the water column above the Loki’s Castle vent field was sampled in the years 2007, 2008 and 2009 (116 samples).

Jan 1, 2018

By G. V. Kalabin

"The paper supports applicability of satellite imagery at regional and local level for rapid quantitative assessment of natural environment in zones of activity of mining complex enterprises. Exacerbation of environmental problems during mineral mining and processing associated with their scale and geography of field distribution through the vast territory of our country requires constant monitoring of natural environment status, which necessitates engagement of space surveillance nowadays. It is proposed to use the monitoring of land cover and land use at regional and local level for the environmental assessment of a particular production or complex productions. You must establish the dependence of NDVI change trend with the magnitude of anthropogenic impact on the source or multiple sources of environmental pollution a particular area.. We present the results of studies of vegetation remote sensing methods in a number of territories placing mining enterprises. INTRODUCTION Ensuring a healthy environment is necessary both in untouched areas and disturbed. The condition of the developed territories should be monitored with particular attention, since the restoration of the disturbed territories requires great efforts and financial costs. More narrowly, the health of the environment (Zakharov V.M. and etc.,2001) means its quality ensuring the health of man and other species of living organisms, which includes two aspects (Zakharov V.M. and etc, 2000): - ensuring an environment conducive to human health as a biological species: - maintaining the health of the natural environment, i.e. its constituent species of living organisms and plants. The consequence is the disturbance of natural ecosystems, which determines the quality of the environment, favorable for human habitation and the state of health of the population in total determine the status of the territories where enterprises for the development of georesources are located and allow them to be ranked according to the degree of environmental danger. Without knowledge of the trajectory of ecosystem successions, it is impossible to offer adequate requirements for the technologies used to ensure the implementation of the preserved natural potential after the removal or reduction of man-made stress."

Jan 1, 2018

By I. Yu. Rasskazov, A. V. Rasskazova, N. M. Litvinova, N. A. Lavrik, V. G. Kryukov

The possibility of the intensification of the gravity processing of complex iron-manganese ore, which contains the finely dispersed inclusions of gold and platinum is shown. Clear mineral fractions of precious metals were sorted out of the different types of ores (quartz-braunite and carbonate- magnetite ore, ferruginous quartzite, carbon-containing shale, breccia-limestone and dolomite breccia). Composition and structures of precious-metals particles was detailed. The industrial content of platinum and gold was found. Precious-metals mineralization is character for all types of ores. High content of platinum is indicated in the carbonate-magnetite (up to 11.3 mg/kg) and quartz –braunite (up to 10 mg/kg) types of ore. Gold is presented in the ferruginous quartzite (up to 1.29 mg/kg) according to the data of the reduced mineralogical analysis. The composition of native platinum depends on the type of the ores: 1) quartz-braunite type contains isoferroplatinum (Pt3Fe) with Cu, Rh, Ir, Ru; 2) carbonate-magnetite type contains isoferroplatinum with Cu, Sn, Ni, Rh, Ir, Os; 3) pyritic-carbon ore contains isoferroplatinum with Sn, Ni; 4) ferruginous quartzite contains isoferroplatinum without admixtures. The ultrasonic treatment of mineral aggregates (P = 41.5 Watt, I = 15 W/cm2) made possible the liberation of fine particles of precious metals. Smooth-shaped or crystalline mineral aggregates are effectively liberated after acoustic treatment. Their surface is freed from impurities. The aggregates with the complex form and structure, which consist of the numerous plates and the grains, are not effectively liberated from impurities. It is shown that the ultrasonic treatment of aggregates with the fine inclusions of precious metals contributes to the liberation of the particles of platinum and gold and intensification of the gravity processing of refractory ore. This approach contributes the increase of the raw-material base of precious metals.

Jan 1, 2018

By M. Holuszko, I. Mikhalev

"Previous studies described by Galvin et al. (2017) have shown that for Australian bituminous coal fines, both in batch and in continuous process, the new improved oil agglomeration procedure based on the use of high-internal-phase (HIP) emulsions, as compared to the conventional “pure oil” agglomeration process, enables a significant reduction in the amount of oil while reaching a high yield of clean coal (approximately 90% of agglomerates greater than 355 µm in size) in a significantly shorter time. The HIP emulsion used in these experiments comprised up to 95% vol. aqueous solution of sodium chloride (3% wt. concentration) and for the rest, a mixture of kerosene (oil) and sorbitan monooleate (SMO emulsifier) in a 1:1 ratio as a binder. This study evaluates the applicability of the new HIP-oil agglomeration process to treat Canadian bituminous ultra-fine coal and Russian sub-bituminous coal fines and compares results from agglomeration to the flotation response of both coals. Oil agglomeration is known to be sensitive to surface properties of coal. Since surface properties of coals depend not only on the rank of coal but also on their origin (depositional environment) and mineralogical composition, both the applicability of this new improved agglomeration process to the non-Australian coals and its efficiency became the motivation for this study. To evaluate the applicability of the new process to both Canadian bituminous and Russian sub-bituminous coals, a series of bench-scale tests were carried out under conditions similar to those described by van Netten et al. (2016) for the Australian coals. Based on the results obtained in this research, new boundary conditions for the application of the HIP emulsion-based oil agglomeration process have been outlined and conclusions on the viability of the new process to treat ultra-fine coal from Western Canada and Russian sub-bituminous coal fines have been reached.INTRODUCTION In most cases, to meet the market requirements, the mined coal has to be processed to reduce the ash content by the removal of mineral matter and thus to increase the quality of the coal products (van Netten et al., 2016). Generally, flotation is used for processing fines from high rank coals; however, there are high losses of very fine coal due to the inefficiency of this process. Furthermore, difficulty in dewatering the fine coal results in excessive moisture levels causing coal handleability issues, which increases costs in the coal-cleaning industry (Capes & Darcovich, 1984). Much of the development that has occurred in fine coal cleaning has taken place with higher-value coal, often metallurgical (Klima et al., 2012). If the fine coal is deemed to be too difficult or expensive to process, it may be discarded as waste (van Netten et al, 2014). Such disposal not only creates an environmental liability but may also result in the loss of a valuable, high quality product that is better liberated than the coarser fractions of coal."

Jan 1, 2018

By M. C. Harris

"In the flotation process the contact angle is an important indicator of the hydrophobicity of a mineral particle. There is considerable literature showing that the contact angle increases when the chain length of the alkyl group associated with the collector molecule used to render the valuable mineral particle hydrophobic increases. The extent to which an alkyl group interacts with surrounding water molecules is quantified thermodynamically by the excess Gibbs energy. In the present paper it is shown that there exists generally a strong linear relationship between the excess Gibbs energy of the alkyl group associated with the collector and the contact angle. The structure-activity of such alkyl groups is in turn related to the total surface area, molecular volume, the molar volume, molecular weight of the functional groups in the molecule and interaction energies. It is proposed that the demonstrated relationship is indicative of the role which the alkyl group component of the collector, which is attached to the mineral particle, plays in increasing the extent to which water molecules at the surface of the mineral are rejected from the surface thus increasing the contact angle. The relationship between excess Gibbs energy and surface tension is further explored with a view to relating the observations quantitatively to the parameters in the Young equation.INTRODUCTIONThe issue of wettability of materials is of great importance to many industrial applications. Wettability studies usually involve the measurement of contact angles which indicate the degree of wetting when a solid and liquid interact. As is well known the contact angle (O) is the angle between planes tangent to the surfaces of the solid and the liquid at the wetting perimeter which is the zone where the air, water and solid phase merge. When the air bubble attaches to the solid surface there is an increase in the air/solid interface area and a decrease in the solid/water interface area. For attachment to occur the cosine of the contact angle should be less than 1 and this will be promoted if the interfacial surface tension between the air and the solid (? SV) is low. Classically the relationship between these parameters has been expressed through the Young equation (1) for a perfectly flat surface:"

Jan 1, 2018

By P. Knüpfer, B. Babel, M. Rudolph, F. Perez Maldonado, U. A. Peuker, L. Ditscherlein

"In heterocoagulation processes for the separation of mineral particles, the most famous being froth flotation, the main characteristic of separation is a differing wettability of the constituents to be separated. This most crucial property in the economically important process of flotation is often only and incompletely, quantitatively described in terms of contact angles against water. A water contact angle larger than 90° is referred to as hydrophobic and hydrophilic vice versa. Looking at Young’s equation shows that it is actually the surface energy of the solid in interaction with the surrounding phases and their surface energies (or surface tensions for liquids) which describes whether there will be hydrophobic/hydrophilic hydration interactions leading to attraction or repulsion. This, we have previously published for various more or less hydrophobic minerals in correlation to their flotation response, i.e. flotability (c.f. Rudolph & Hartmann, Coll.Surf.A 513, 380-388). In the same paper we also discussed the heterogeneity of wettabilities as assessed with the novel method of inverse gas chromatography. Furthermore we have also reported on hydrophobic force distributions as assessed with atomic force microscopy which are as well due to wettability heterogeneities (c.f. Fritzsche et al., Coll.Surf.A 459, 166-171).In this paper we present wettability distributions of different substrates and particles with various surface roughnesses/shapes and degrees of hydrophobization as assessed with iGC, AFM and dynamic sessile drop analyses. We are putting the results in context in unifying models and present methodologies helpful to make use of the fundamental information and their impact on the actual industrial separation process in fundamental process models. Besides froth flotation we also emphasize the impact on selective hydrophobic flocculation process."

Jan 1, 2018

"Mining used to be a business primarily focused on the technical aspects of getting valuable ore out of the ground and extracting the minerals efficiently. Without denying the importance of these skills, a narrow focus on technical issues is no longer enough to guarantee success when it comes to exploiting rare earth element (REE) deposits. Molycorp failed to enter the global REE market in a successful manner, while none of the many REE exploration projects has turned into an active mine so far and none is expected to commence operations in the near future. Accordingly, the world of REE is far more complex compared to other commodities. This paper looks into the REE industry to identify the factors that can connect potential U.S. REE mines to the market. The ability to break free from past thinking and become future-focused is a key driver. Mining of REE is pointless without a corresponding value-adding chain, while developing a value chain without first establishing an uninterruptible source of REE is also senseless. The mining sector must be based on the REE value chain and vice versa, along with the establishment of a market channel for the REE products that come out of the mine. INTRODUCTION It has been seven years since rare earth elements became the subjects of front-page headlines. It was when the controversial Chinese export policy for these critical commodities was epitomised in a maritime border dispute with Japan in September 2010 that resulted in the big REE crisis and price spike of 2011 (Barakos et al, 2016c; Mancheri, 2015). The world was dismayed, especially in REE-importing countries, such as the United States that was and is still totally dependent on Chinese production and exports (Barakos et al, 2016c; Kennedy, 2015). The short-lived alarm initiated a treasure hunt by way of exploration for REE deposits all over the world. The continuously growing demand on the one hand and the Chinese sovereignty of the REE-market on the other, led the rest of the world to explore their own REE resources. In just a few years, more than 400 projects were initiated to explore REE deposits outside of China (ERECON, 2015; Goodenough, 2016). The prices of REE, however, dropped rapidly and at the moment of writing this paper are in 6-year lows, at the level of the price average before the 2011 crisis (Barakos, 2017). The viability of even major established producers is being challenged, not to mention the development prospects of potential REE-market entrants (Barakos et al, 2016b; Rollat et al, 2016). Production cutbacks and industry consolidation in China impel REE market experts to forecast that prices have already reached their lowest point and have nowhere to go but up (Adamas, 2015; Roskill 2015). Yet, expectations for increased REE prices are limited and drastic changes are unlikely to happen in the near future, as there is still excess supply in the overall REE market (Barakos, 2017). Nevertheless, the low prices of rare earths are not the only reason that potential producers are struggling to enter the global REE market. Among other parameters, the separation of the individual elements seems to be the most important factor, as it is technically challenging and expensive to build and to operate."

Jan 1, 2018

By J. Starkey

A comminution circuit in recent history, is one of the most difficult parts of a mineral processing plant to design with confidence. It is usually the most costly part of a plant to build, and it can consume up to half or more of the energy used on a mine site. To suggest that comminution energy usage is sustainable in the long term is not possible at this time. What we have to choose from today, based on more than 50 years of experience, does include the best available technology, and the best way to design it. There is controversy in the industry as to how to properly approach the subject of comminution design, with many of the optional solutions requiring a level of training and expertise beyond the ability of a non-specialist engineer. Semi-autogenous grinding technology in particular, has not been properly appreciated because of many recent mistakes in its application and design, which have blurred the positive perception about what SAG technology is, how it can be used, and how it needs to be designed and built. In order to change this, mine owners and senior managers need to take responsibility for, and learn to understand the fundamental challenges that a comminution circuit poses to the project, to the design process, to the operators who use the equipment, and to the resulting metallurgy. This address is intended to summarize these challenges and offer fundamental engineering solutions, which are clear, specific and in a format which is directly applicable to the mining and mineral engineering community.

Jan 1, 2018

By Edgar Schach, Tom Leistner, Markus Buchmann, Urs A. Peuker, Martin Rudolph, Marius Kern

"In this study, the flotation characteristics of a cassiterite-bearing fine-grained and complex skarn ore from a deposit in the Ore Mountains is investigated. The tests are performed using an oil-assisted column flotation approach to process very fine ore fractions and avoid losses of cassiterite into the tailings. First, process parameters are obtained for a finely ground artificial mixture of quartz, magnetite and cassiterite, simulating the real ore. Thereby, magnetite is used, as iron oxides can have a detrimental effect on the flotation due to a similar flotation behavior. In addition, they can act as a source of multivalent ions, which are known to reduce the concentration of collector molecules, active for flotation. Based on the results, selected parameters are further tested for cassiterite skarn ore from the Hämmerlein deposit including a pre-conditioning and a water exchange step to remove ionic contaminants. The process response is analyzed in detail by XRF (X-ray fluorescence) and MLA (mineral liberation analysis) to get a better understanding of the behavior of the single ore components. Sulfosuccinamate type surfactant is utilized as the collector, emulsifier and to reduce the froth destabilization through nonpolar oil. Sodium hexafluorosilicate is added as the depressant.INTRODUCTION Complex skarn ore deposits containing considerable amounts of tin, indium and other metals are located in the Ore Mountains region (Germany). In this study, a skarn ore from the Hämmerlein deposit was investigated. Due to the finely disseminated nature of this ore, past beneficiation attempts failed, and the ore was considered economically unprocessable. However, increasing resource demands brings it back into focus (Schuppan and Hiller, 2012). Cassiterite is the main tin bearing mineral in this ore. Due to its high density (~7 g/cm³), the predominant beneficiation technique is gravity separation (Angadi et al., 2015). Tin ores from disseminated deposits have to be extensively comminuted to reach a sufficient degree of liberation of the cassiterite grains. As cassiterite has a brittle nature, it is preferable enriched in small size fractions, during comminution (Angadi et al., 2015). Gravity separation methods become more and more inefficient for particles smaller 40 µm (Falcon, 1982), causing tin losses of up to 30 to 40wt.-% (Angadi et al., 2015). Thus, froth flotation of cassiterite was first utilized in Altenberg in the Ore Mountains as an additional processing step to reduce the cassiterite losses into gravity separation tailings (Bulatovic, 2010; Gruner and Bilsing, 1992). Although the reported lower size limits for an effective cassiterite floatability are often smaller compared to other minerals, the flotation performance is in general decreasing for small particle sizes < 10 µm (Trahar and Warren, 1976). Therefore, different approaches have been already investigated for the flotation of such fine cassiterite fractions to overcome the limits in particle size. Bilgen et al. investigated the shear flocculation of cassiterite with a sulfosuccinamate collector (Bilgen et al., 1994). The agglomeration flotation of cassiterite has been tested by Schubert et al. (Schubert et al., 1966), in which the selective coagulation of fine hydrophobic particles and oil droplets leads to an increase of the effective particle size. Recently, Leistner at al. investigated an oil-assisted agglomeration flotation for ultra-fine cassiterite ore fractions (Leistner et al., 2016). However, a poor response due to an increased concentration of Fe and Ca ions, unselective oil/gangue coagulation and froth instability, that is caused by oil/frother interactions, has been observed."

Jan 1, 2018

By J. A. Dos Santos

"INTRODUCTION Dramatic reduction in energy use and environmental impact can be achieved with sandwich belt high angle conveyors that serve as the vital link in any IPCC (In-pit Crushing and Conveying) system. These high angle conveyors are not new at all, but have not found wide use in IPCC systems where they can realize the greatest advantage. Reduced energy consumption and environmental impact, with IPCC systems, was already realized in the 1970s. With the bulk material haulage limited to conventional open trough conveyors the most direct path out of the open pit was precluded, requiring low angle spiral ramps and/or deep slots and/or tunnels through the high wall of the open pit. These excavations, to accommodate the low angle limitations, represented undesirable impact on cost and on the environment. Against this backdrop, a major study in 1979 sought to develop high angle conveying systems that could continuously haul the mined bulk material directly out of the pit, along the high wall – the shortest distance between the two end points. Between 1979 and 1982, that study developed sandwich belt high angle conveying systems that utilized all conventional conveyor equipment including smooth surfaced rubber belts that could be continuously scraped clean. These systems had all of the positive features of conventional conveyors but overcame the angle limitation. By hugging the bulk material between two belts, the material’s internal friction could be developed to facilitate conveying at any high angle up to 90 degrees (vertical). After an intense testing period (about one year) on the first large scale prototype system, commercialization began in 1983 with the installation of a 60 degree incline system at a western United States coal mine, elevating 2000 t/h of coal to a train load out system. It did not take a long period of scrutiny and acceptance before this high angle conveyor found use in the most rugged requirements of an IPCC system. This was only the second commercial sale, and after more than 150 commercial installations, it remains arguably the most significant high angle conveying system. In 1984, a copper mine in Serbia, already using pit perimeter crushing and conveying, decided to move their primary crusher deep into the pit and to use a sandwich belt high angle conveying system to elevate the ore continuously, directly out of the pit, along the high wall to the pit perimeter where it then transferred to a conventional conveyor for the remaining haul to the plant. The system had significant features including 2000mm wide belts that elevated 250mm coarse ore, at 4000 t/h, over six 15-meter high benches for a total 90 meters of net lift. The system was able to reduce the truck haulage fleet by ten 200 ton trucks realizing great cost savings, zero emissions to the air and greatly reduced traffic congestion in the pit. The system operated successfully until 2002 when the mine shut down. Many successful sandwich belt high angle conveyors followed with the current count of commercial installations at more than 150. Despite the great success with this system, its use has not been repeated as part of an IPCC system."

Jan 1, 2018