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By Caitlyn J. McKinley, Ahmad Ghahreman, Maziar E. Sauber

Ever-growing global needs for critical metals, such as rare earth elements (REE), and base metals, such as copper and nickel, and their environmental impact motivated the pursuit of sustainable flowsheets. Regeneration of hydrochloric acid in chloride-based leaching flowsheets as a critical unit operation is an example of such endeavours. This study presents an efficient hydrochloric acid regeneration method from a magnesium chloride solution waste by addition of sulphuric acid in relatively low temperatures. The effects of temperature, initial magnesium chloride concentration, amount of sulphuric acid added, and airflow are examined. Experimental work are focused on temperatures between 80 and 95°C, initial magnesium chloride concentrations of 2 to 5 M, 100% to 220% stoichiometric sulphuric acid additions, and airflows between 200 to 600 mL/min. The developed technology recovers hydrochloric acid at a high rate and concentration with a relatively small environmental footprint. INTRODUCTION The mining and metals sector is under increasing environmental and economic pressure to make more efficient use of chemical reagents and energy in the production process. This affects several areas of process and flowsheet design such as the selection of the most appropriate unit operations and the overall design of the process steps paying heed to sustainability. Owing to the inherent inefficiencies of physical and chemical processes used in the mining industry, there will be materials and streams generated that are not a desirable part of the envisaged flowsheet. Thus, methods are implemented to recover and recycle such effluents. If the recovery and recycling are not economical, then procedures are followed to neutralize and dispose these effluents. In many cases, these effluents are potential contaminants or hazardous materials, and their disposal should be looked at in a much larger context. The safe management of the contaminants and hazardous effluents is a daunting problem in the mining industry and is fraught with technological, economic, social, and political challenges.

Jan 1, 2019

By L. Frost

"Since the late 1990s, increased prevalence of severe lung disease among US coal miners has been observed, particularly in central Appalachia where thin-seam mining is prevalent. While respirable silica exposures have been implicated in many cases, the available dust monitoring data from mines shows no explanatory trends. One possible factor could be differences in the relative toxicity of silica particles based on their surface condition. Previous research has indicated that particles with occluded surfaces (e.g., by a thin layer of clay) may be less toxic than those with non-occluded surfaces. However, this dust characteristic has not been investigated before now in central Appalachian mines. In the present study, 18 respirable dust samples from seven central Appalachian mines and two northern Appalachian mines were analyzed to assess the relative occurrence of surface-occluded silica. Results showed that the dust from central Appalachian mines actually had higher fractions of occluded silica, which may be due to extraction of large amounts of rock strata along with the coal. However, the central Appalachian mines also more silica particles overall (i.e., occluded + non-occluded) in terms of total number percentage of respirable particles.INTRODUCTIONResurgence of occupational lung disease among US coal miners, especially in the central Appalachian region, has been observed since the late 1990’s (Gibson, 2016; Zosky et al., 2016; Suarthana et al., 2011; Gamble et al., 2011; Antao et al., 2005; Attfield & Sexias, 1995). In addition to increased prevalence of simple Coal Workers’ Pneumoconiosis (CWP, or “black lung”), the prevalence of severe and rapidly progressive disease has risen dramatically (Almberg et al., 2018; Blackley et al., 2018a, 2018b, 2016, 2014; Graber et al., 2017; Cohen et al., 2016). While exposures to respirable silica have long been known to cause or play a role in diseases such as silicosis or progressive massive fibrosis (PMF), which is conventionally considered as the most advanced form of CWP, it is unclear whether silica is the only culprit in the recent outbreak of severe disease. Indeed, as disease rates have risen, both total respirable dust and silica concentrations generally appear to have declined since the late 1980s, based on regulatory monitoring data in the most affected mining districts (i.e., MSHA coal Districts 4, 5 and 12, which cover central WV, eastern KY and southwestern VA, and southern WV, respectively) (Figure 1). Of course, the latency of disease can vary and may be or more 10 years, but many of the most recent cases are likely to have resulted from exposures that occurred since the late 1980s."

Jan 1, 2019

By R. Dawes, B. R. Davis, T. LeBel, C. Pelow

Settling of copper, lead, and other metals in slags is an important part of overall recovery of metals, both in primary and secondary operations. The impact of slag reduction on settling is not well known. This is important since the cycle time for slag cleaning can be significantly changed with reduction of slag, through a decrease in slag viscosity and growth of metal/sulphide particles. KPM has worked with a number of primary and secondary recyclers to better understand how reduction of slag can improve overall operation. In this presentation, we describe the type of test work and analysis done and how this information can be used to guide improvements in metal recovery from slags. INTRODUCTION Typically, copper smelter slags contain about 1-2% copper, both in the form of copper and copper sulphide beads and dissolved copper oxide in the slag (converter slags are recycled to the smelter). With the average grade of world copper deposits close to 0.7%, it is practical to recovery copper from these slags. This is done routinely by one of two methods. The first method uses slow cooling in large ladles or beds to grow particles of copper sulphide. The slag is then crushed, milled, and floated for copper recovery. The slow cooling promotes precipitation and growing of the sulphide particles from the solution and then, the slag can then be milled to recover the copper through froth flotation. A consideration of this process includes the energy cost related to grinding, the use of water, capital cost for ladles, and the availability of tailing dumps. At the same time, the retreatment of the Cu concentrate produced in the mill will displace fresh concentrate, which ultimately results in a reduction of the throughput. The second method is the so-called “slag cleaning” and is based on the settling of copper and copper sulphides particles dispersed in the slag. This is achieved by decreasing its viscosity by increasing the slag temperature and reducing the iron spinel solid phases (magnetite) that increase the apparent viscosity of the slag. Typically, the reduction does not extend to the reduction of copper, and soluble copper (mainly as oxide) and fine matte particles remain at concentrations typically at or above 0.5% (Cardona et al., 2011; Cardona, 2011). This is an improvement on 20 years ago when slag was sent to dumps at 1% or less (Demetrio et al., 2000).

Jan 1, 2019

By Nick Vayenas, Ming Cai, Hongbin Zhang Lorrie Fava, Enrique Acuña

"A hybrid methodology is proposed to improve the accuracy of Diesel Particulate Matter (DPM) concentrations simulated in a ventilation network model by using Computational Fluid Dynamics (CFD). DPM, as a primary concern for underground hard-rock mines, has been studied in two dominant numerical models, ventilation network solvers and computational fluid dynamics. Ventilation network solvers are efficient, but they are not able to provide three-dimensional DPM concentration contours and only accept area-average DPM data as input. CFD simulations are time-consuming, but generating DPM concentration results with high accuracy. Besides, both monitoring points and planes can be created in a CFD model, which can take both point data and area-average DPM data as input. The hybrid methodology is intended to combine the advantages of the two by using the CFD results to update the network model results at key locations. A field study was conducted in a dead-end heading in an underground gold mine in the United States. Real-time DPM monitors were used to collect data. A CFD model and a network model were built for the experiment area. The CFD model was calibrated to the experimental data. In the study presented here, results from a calibrated CFD model are converted to equivalent diesel emission rates in the ventilation network model at a shared outlet. The hybrid methodology is used to provide better input for the network model. INTRODUCTION Mine ventilation system is one of the most important parts for an underground mine. It not only provides fresh air to the personnel but also helps clear the contaminants generated from the diesel-powered equipment. For most underground metal and non-metal mines, diesel particulate matter is the main contaminant. It is also the focus of this paper."

Jan 1, 2019

By John O. Marsden

Technology development and innovation has played a crucial role in the copper industry throughout history. The effective development and implementation of new technologies allows mankind to produce copper at progressively lower cost of production at a given feed grade and mineral type. This progress serves to counteract cost escalation over time and, depending on the magnitude of the cost benefit, allows ore cut off grades to be reduced thereby improving the availability, accessibility and utilization of mineral resources. The development of step change technologies that can offer >$0.15/lb total cost benefits provides a significant opportunity for producers to achieve competitive advantage, but it has been argued that rapid dissemination of technology makes such competitive advantage unsustainable over time. This paper presents the results of a recent study that evaluates a number of historical and emerging step change technology case studies in the copper industry and quantifies the associated cost benefits for users, the impact on the production cost curve, and the duration of such cost benefits for various categories of implementers: first mover, fast follower, conservative followers and laggards. The results provide a compelling case for major, mid-tier and emerging copper producers to invest in technology development initiatives if they wish to achieve and sustain competitive advantage over the long term. INTRODUCTION AND BACKGROUND A key issue for mining companies is how much time, effort and cost to spend on research and technology development (R&TD). The economic drivers for technology development and implementation are poorly understood in our industry and the business case is clouded by some notable and well-publicized failures (McNulty, 1998). Mining companies are in business to deliver financial returns to investors. This means delivering short term results on a quarter-by-quarter reporting basis as well as sustaining and growing the company to retain and reward a sustainable longer term investor base. The cyclical nature of the commodity metal markets makes it challenging to maintain investment in research and step change technology development: Mining companies must manage through the highs and the lows of price cycles, typically ranging from 5-15 years in length. The discounted cash flow approach to investment evaluation results in weak financial justification for R&TD expenditures. A clear and compelling rationale to support longer term investment in research and step change technology implementation is required.

Jan 1, 2019

By M. Lahtinen, P. Latostenmaa, I. Kojo, E. Peuraniemi, M. Lindgren, S. Jyrkönen, M. Jåfs

The year 2019 marks the 70th anniversary of Flash Smelting. The technology was operated on industrial scale for the first time at the Outokumpu Harjavalta copper smelter in Finland in 1949. Since then Flash Smelting technology, now owned and developed by Outotec Oyj and the first plant, now owned by Boliden Harjavalta Oy, have been evolving throughout history by optimizing the process for various feeds and raw-materials, as well as through developing the equipment and operating practices. Even though sustainability was not a popular theme during the first days of Flash Smelting, it has still been the key principle in guiding the development. This is well proven by the wide adoption of Flash Smelting for the processing of copper and nickel concentrates, mostly due to its ability to fulfil the economic and resource efficiency criteria demanded by its operators. This paper describes the history and improvements of the Outotec® Flash Smelting process by looking into the early days of operation and how the development of the process and equipment has taken place over time as a joint effort between the technology provider and the users of the technology. INTRODUCTION In the 1940s, Outokumpu Oy refined the concentrate produced in the Outokumpu mine into metallic copper initially in Imatra, and later from 1945 to 1949 in Harjavalta, based on the most modern electrical melting process of the world at that time. After the war, Finland lost a significant part of its hydropower production, and due to the increasing use of electricity, the availability of electricity weakened, and the price rose. To maintain Outokumpu's profitability, it was forced to look for a melting solution that was not based on electricity.

Jan 1, 2019

By Xiao min Zhou, Yan Xu, Hongzhen Liang, Xiaonan He

"With the increase of shaft excavation depth, the thickness of the shaft lining increases sharply. It is difficult to reduce thickness of lining effectively by improving high-strength concrete performance. The concept of the New Austrian Tunneling Method (NATM) is that surrounding rock plays a certain role in tunnel support. The solution should be to find the correct relationship between shaft lining thickness and rock strength, which is related with the interaction between the surrounding rock and concrete lining. The plane strain mechanics model is introduced to calculate lining thickness. Shaft lining design of Cixi Colliery in China is completed with the mechanics-based method proposed in this study. The lining design is verified through numerical simulation and field monitoring. The simulation results show that the maximum mises stress is located at the inner edge of the shaft lining. The increase of lining thickness cannot effectively reduce concrete grade. The monitoring results indicate that a lining design thickness of 900mm with C60 concrete, is safe and reliable in the shaft over 1000metres.This analytical design method can well be referenced in similar deep shaft projects.INTRODUCTION The New Austrian Tunneling Method (NATM), thought to have helped revolutionize the modern tunneling method, is the most extensive design philosophy and construction principle in today's tunnel engineering. It began to attract attention in the 1960s based on the work of Ladislaus von Rabcewicz, Leopold Müller, and Franz Pacher in Austria[1]. NATM was originally developed for tunneling in depth and in high situ-stress conditions in the Alps. The history of sequential excavation was reviewed, which highlights the progress of tunnel design and construction in Europe after NATM[2]. Structural conditions were introduced into the equilibrium of tunnels in NATM, and the additional force was estimated to stabilize the excavation of the tunnel[3].From the perspective of applied mechanics, there was no accuracy theory to explain the interaction between the tunnel structure and the surrounding ground. Numerical calculation is an effective means to study the basic mechanism of tunnel excavation[4].Based on two-dimensional modeling approaches in the past, such as NATM and other derivatives, a three-dimensional model was studied to"

Jan 1, 2019

By F. Musuka, D. Jenkins, A. Keyes

BHP Olympic Dam operates a Direct-to-Blister copper flash smelting Furnace (DBF) and an Electric Slag Cleaning Furnace (ESCF). Tapping blister copper from these furnaces via tapholes is a routine task carried out by trained personnel. Blister tapping is a high-risk activity with personnel operating in close proximity to molten metal. BHP’s risk management framework has identified taphole integrity as key to managing the potential for loss of molten metal containment and molten metal – water steam explosion, both of which have the potential to cause multiple fatalities. As part of the focus on managing this risk, since 2017, a dedicated Taphole Development Team has been embedded in the operation to run an accelerated improvement program focused on safely and sustainably embedding an improved taphole design with greater integrity. The program of works includes selecting and testing of new materials as well as improving operating discipline by collaborating with tapping personnel to convert their knowledge into codified condition monitoring and operating strategies. Computational fluid dynamics (CFD) is being used to derive critical risk controls, and to develop live-alerts to infer excessive refractory insert wear. To date, improving DBF blister taphole mudgun clay has led to more consistent drilling depths and subsequently reduced oxygen lancing requirements, resulting in improvements in taphole insert service life. On the ESCF, insert performance testing and development of a new taphole condition monitoring strategy, is being used to increase taphole insert tonnages to more sustainable levels. Operations personnel have been closely involved in different phases of the change management, this has led to standardization of tapping practices for both furnaces, and improved ownership of the proposed changes. The paper discusses the maturity in taphole integrity risk management as a result of recent and ongoing developments. It then provides an overview of future taphole developments proposed at Olympic Dam. INTRODUCTION Tapping operations at Olympic Dam and learning from significant events The Direct-to-Blister furnace (DBF) at Olympic Dam was built with a conventional design blister taphole, which was designed for manual oxygen lancing and clay stopper bar plugging tapping operations (Campbell, 2005). Manual tapping is a high-risk activity, where personnel work in close proximity to molten metal, and molten metal personal protective clothing and equipment must be used. Opening tapholes by oxygen lancing is a skilled activity and unintentional damage to the taphole inserts can occur. Since 2008, a Mudgun and Drill unit has been developed and trialled and is now in use on the DBF blister tapholes, to remove personnel from the line of fire when opening and closing tapholes. This has the additional benefit of reducing lancing damage to taphole inserts. A new taphole design labelled the Modular Blister Taphole (MBTH) was developed at Olympic Dam for the Mudgun and Drill operation. The intent of the design was for mudgun clay to fill the entire tapping channel when plugging after a tap. The drill would then drill through this clay plug to open the taphole.

Jan 1, 2019

By W. Kempson

"Mining Companies have producing assets in increasingly diverse portions of the world. It is not uncommon that the owner, the design team, the mine contractors and the operators are all based in different countries. While these assets are always subject to the regulatory requirement of those countries there have not been international standards available to review and evaluate these assets. This becomes particularly important when considering safety critical items such as tailings dams, vertical shaft systems and autonomous vehicles to highlight a few. The work currently being completed in ISO ensures these standards will be available and will be generated by and subscribed to on an international basis, thus removing the potential for patriotic partisanship and ensuring safe and predictable systems are installed. This paper will discuss the benefits of the international standards, the structure of the teams and working groups who are generating these standards as well as the process by which the standards are generated. This will allow insight into the creation of the standard and will aim to demonstrate the “neutral” and technically strong manner in which the generation of these standards is achieved. In addition, the paper will discuss the standards which have been produced in the last five years as well as the current standards which are in place. The finale will discuss upcoming work and the timelines in which it is anticipated these will be completed. INTRODUCTION Mining Companies have producing assets in increasingly diverse portions of the world. While these assets are always subject to the regulatory requirement of those countries, there have not been international standards available to review and evaluate these assets. This becomes particularly important when considering safety critical areas such as vertical shaft systems, tailings dams and autonomous vehicles to highlight a couple. The work currently being completed in the International Organization for Standardization (ISO) ensure these standards will be available and will be generated by and subscribed to on an international basis, thus removing the potential for patriotic partisanship and ensuring safe and predictable systems are installed. The ISO/TC 82 – Mining was founded in 1955. This was an active committee until it was thought that the standards at the time were adequate and the Technical Committee was put on “Care and Maintenance”. In 2012 countries lobbied ISO to pull this committee from dormancy and restart it, this happened in in the same year."

Jan 1, 2019

By Y. M. Shneerson, I. V. Fomenko, M. A. Pleshkov, E. A. Ospanov, A. A. Shakhalov, S. S. Naboychenko

Low-grade copper concentrates (with copper content less than 20%) often contain impurities such as arsenic, zinc, lead, mercury, antimony and bismuth. The pyrometallurgical treatment of such concentrates is associated with several problems, which will ultimately affect the cost and the quality of copper cathodes as well as by-products. SRC Hydrometallurgy proposed a complex hydrometallurgical technology which allows the removal of impurities and the enrichment of low-grade copper concentrates to a quality which will be more suitable for pyrometallurgical processing. Laboratory batch tests and pilot plant results for the pressure leaching steps are shown in this paper. The key parameters of the leaching steps were determined and optimized. The quality of possible by-products were also determined. The developed flowsheet includes two pressure leaching steps: pressure oxidation (POX) and hydrothermal alteration (HTA). Both operations are carried out at 170°C with subsequent flotation of POX and HTA residues and recovery of copper, zinc and lead into separate concentrates for further processing. The development of the flowsheet was based on the Balkhash Zinc Plant (Balkhash, Kazakhstan), which had been non-operational since 2009. The developed flowsheet for processing of low-grade concentrates will utilize 80% of the existing equipment of the Balkhash Zinc Plant, thus leading to a significant reduction in required capital expenditure. INTRODUCTION As the age of copper mining operations advance, copper grades continue to diminish and impurity levels increase. Therefore, copper producers are forced to look for new innovative hydrometallurgical technologies which are able to handle low-grade raw materials and solve problems associated with impurities in an economically justifiable way. New technologies allow to extract valuable components selectively and to process low-grade concentrates which had previously been marked as non-technological and economically unviable. Hydrometallurgical technologies for processing of copper-containing materials can be divided into two main categories: chloride and sulfate (atmospheric, autoclave and bacterial) based technologies. Since the 1970s, many autoclave techniques for the processing of copper-containing materials have been developed and implemented (Naboichenko, 2002; Dreisinger, 2005; Habashi, 2009; Shneerson, 2011). The mineralogical composition of the ore (or concentrates), geographical location of the deposit, distance from industrial areas, availability of existing treatment facilities, availability of skilled labor, cost of electricity and cost of neutralization are some of the factors which are usually considered when the appropriate technology is selected (Halbe, 2002).

Jan 1, 2019

Grinding with an electrochemically inert grinding media (i.e. high chrome white iron, or Magotteaux’s Duromax® alloys) shifts the pulp potentials to more oxidising conditions, increases the dissolved oxygen content and reduces the EDTA extractable iron concentration when compared with milling with electrochemically active grinding media (forged steel). These changes in pulp chemistry produce cleaner particle surfaces, reduce reagent consumption and increase concentrate grades and recoveries. This paper presents a robust laboratory test program that is able to not only demonstrates these effects but also provide an indication of the magnitude of the improvements that are possible. While laboratory studies are interesting, the proof is in the pudding! So, the paper provides an overview of plant trials conducted at a number of operations around the world, including: Newcrest’s Cadia Operation, Oz Minerals’ Prominent Hill Mine and Glencore’s Ernest Henry Mine. These successful plant trials clearly demonstrate that selection of the right grinding media alloy will yield savings in grinding media consumption and reagent consumption as well as increases in revenue through improved copper, gold and molybdenum recoveries. INTRODUCTION The key to a successful separation in mineral processing is the preparation of particles with adequate liberation under the correct pulp chemical conditions. While the importance of liberation on flotation separations is generally understood and well documented in the literature (Johnson, 1987; Jackson, Sutherland, Gottlieb & Quittner, 1989; Young, Pease, Johnson, & Munro, 1997; Greet and Freeman, 2000), the importance of pulp chemistry is more nebulous, particularly with regard to the impact of grinding media. Extensive work examining the electrochemical interactions between grinding media and sulphide minerals has been completed (for example, Iwasaki, Reid, Lex & Smith, 1983; Natarajan and Iwasaki, 1984; Yelloji Rao and Natarajan, 1989(a); Yelloji Rao and Natarajan, 1989(b)). Broadly, these studies indicate that most sulphide minerals are more noble than the grinding media used during comminution, therefore a galvanic couple between the media and the sulphide mineral(s) exists, which increases the corrosion rate of the grinding media. The corrosion products of the grinding media, iron oxy-hydroxide species, invariably precipitate on to the surfaces of the sulphide minerals thereby affecting their floatability (Johnson, 2002).

Jan 1, 2019

By S. Eckert, M. Reuter, O. Keplinger, D. Obiso, N. Shevchenko, M. Akashi

We report on laboratory experiments focusing on bubbling phenomena arising from gas injection through a top submerged lance (TSL) in a liquid metal layer. The objective of this study is to reveal the characteristics of the formation and behaviour of the particular bubbles at different gas flow rates and submergence depths of lance. Visualization was performed in the eutectic alloy GaInSn using X-ray radiography. Argon bubbles were injected through the injection positions at three different submergence depths. Essential parameters such as the bubble size, bubble shape, detachment frequency and the two- dimensional gas distribution in the flat vessel were obtained by image processing. The results show that the deep position of the submerged lance causes an asymmetric large-scale circulation inside the fluid vessel. Bubble detachment frequencies were calculated by Fast Fourier Transformation from fluctuations of the image intensity in the vicinity of the nozzle injection point. This frequency does not show strong variations with respect to changes of the gas flow rate and the submergence depth of the nozzle. An increasing gas flow rate results in an increasing two-dimensional projected bubble area and the occurrence of a significant number of small bubbles being trapped by the strong fluid flow in the liquid metal layer. INTRODUCTION The Top Submerged Lance (TSL) process has been an essential component of the metallurgical industry since the emergence of first concepts about 50 years ago (Floyd, 2005). The process, which is characterized by blowing reactive gas through the submerged lance into a liquid bath, was developed mainly for improving the tin smelting process and has been applied for waste treatment or the production of several metals such as copper, lead, nickel and zinc. The productivity of the reactor is determined mainly by the efficiency of the chemical reaction between the gas or solid particles and the liquid. To achieve a high efficiency requires good exchange between the gas-liquid phase and therefore a large interface area. The efficiency changes greatly with the number and size of bubbles injected from the nozzle and the extent of splashing on the free surface. The degree of turbulence in the bath plays a decisive role here. For the reason, the design of an efficient TSL process requires a profound knowledge of the fluid dynamics especially for complex multiphase flows.

Jan 1, 2019

By M. Hashemzadeh

The efficiency of water use is a top priority for the global minerals industry, especially in regions with limited freshwater supplies. In these areas, the freshwater shortage has prompted mining companies to search for alternatives to freshwater sources. Seawater has been proven to be a potential water source for mineral beneficiation and metal extraction processes. This study compares chalcocite leaching behavior with ferric chloride to that with cupric chloride. We carried out leaching tests with a highly pure chalcocite sample in jacketed reactors under fully controlled pH and solution potential. The effect of chloride concentration, oxidant concentration, and temperature on copper extraction was quantified in both cupric and ferric chloride systems. In the ferric chloride system, increasing ferric concentration showed a positive effect on the first stage of chalcocite leaching. In the second stage, increasing temperature markedly enhanced copper extraction. In the cupric chloride system, chloride concentration presented a considerable effect on both the first and second stages of leaching, while temperature had a remarkable effect only on the second stage. The findings of this study would be beneficial to mine operations aiming to replace fresh water with seawater for heap leaching of chalcocite. INTRODUCTION Mineral processing operations/plants are normally operated adjacent to mines which are often located in remote and arid area, such as northern Chile, southern Peru and Australia with limited access to fresh water (Liu, Moran, & Vink, 2011, 2013). Water scarcity in these areas has prompted mining companies to invest in sustainable technologies to reduce the water use and/or increase the water use efficiency. One of the current sustainable approaches in mineral processing operations is to replace fresh water with seawater. Seawater is now being increasingly used for mineral beneficiation and metal extraction processes (Hernández et al., 2015). Another application of seawater could be for heap leaching of copper secondary sulfides, mainly chalcocite. However, the high concentration of chloride ion in seawater may significantly affect leaching kinetics of copper sulfide concentrates and ores (Watling et al., 2014). Therefore, it is essential to develop a fundamental understanding of the leaching of chalcocite in chloride media.

Jan 1, 2019

By P. Taskinen, D. Lindberg, H. Viitala

The formation of copper chlorides in flue dust or deposits in heat recovery boiler of copper smelters or waste-fired boilers may lead to formation of corrosive partially molten deposits on walls and heat exchangers of the boilers. These deposits can contain various other metals, such as alkalis, Fe, Zn, Pb together with oxides and sulfates. In the present study, a thermodynamic model for copper-containing binary and ternary metal chloride systems within multicomponent CuCl-CuCl2-FeCl2-FeCl3- PbCl2-ZnCl2 system has been assessed and optimized based on own experimental phase equilibrium data, as well as literature data. The thermodynamic properties of the liquid phase was modelled using the quasichemical quadruplet model and a thermodynamic database was optimized to predict all available experimental data within the experimental error limits. The thermodynamic database allows for more accurate predictions of potential corrosion-related issues in various heat recovery boilers and waste-fired boilers due to formation of copper chlorides. INTRODUCTION In the copper flash smelting, flue dust can cause severe problems in the gas train, used for separating dust from the SO2-rich off gas, by forming corroding accretions on the walls of the heat recovery boiler. Formation of dust build-ups in the boiler need to be cleaned regularly and potential corrosion damage checked, requiring costly and unscheduled shutdowns of the flash smelting process. Compounds of copper and zinc among other elements having high vapour pressures may volatilize during the smelting of the copper concentrate, forming dust when the process gas cools down. Also, particles of solid or liquid iron oxides originating from the ore get transported with process gas to the heat recovery boiler as a result of entrainment in the flue gas (Miettinen, 2008) The dust deposit build-ups on the boiler walls are formed partly by direct impact of particles and partly by vapour condensation on the boiler walls. The initial deposition takes place by the condensation of vapours that contain zinc, lead, arsenic and other metals having high vapour pressures. Also, low melting point eutectic components of alkali salts such as chlorides and sulphates can act as sticky cohesive particles attaching to the boiler walls. The fine particles landing on the surface of the porous dust deposit layer react in the SO2-rich atmosphere of the boiler to sulphates. The process gas within the boiler contains SO2, O2, SO3, H2O and N2 that diffuse into the porous accretions to form a stagnant gas layer within the dust deposit structure. The composition of this gas layer may differ greatly from the composition of the process gas that is flowing on the surface of the accretion layer. Locally HCl and H2SO4 are formed and even a reducing atmosphere may exist within the dust deposit layer, allowing new reactions to take place. The local micro-atmosphere may enable metal sulphates to be reduced to secondary sulphides and even metallic components. Within the accretion layer, components may be formed that would not be stable in the gas atmosphere inside the boiler (Miettinen, 2008). This may be the mechanism by which for instance chlorides of Cu, Fe and Zn are formed within the deposit layer.

Jan 1, 2019

By T. Schepp, T. Friedrich

"The natural stage of deep mines operation is a closure of unnecessary shafts. It is extremely important to ensure a proper shaft closure to avoid stability loss and the associated damage to surface facilities in the future. For the still active shafts, it can be done by a dedicated shaft closure design, but even then, depending on the shaft closure method, it may be necessary to perform regular shaft inspections. The paper presents a short overview of shaft closure methods and available tools and devices developed in the last time for such shaft inspections. INTRODUCTION The natural stage of deep mines operation, commonly occurring after depletion of the reserves of mined materials, is a closure of unnecessary shafts. All over the world, the number of liquidated shafts grows continuously and the problem of shafts disposal is especially critical for deep shafts. The typical depth of 600 m of currently liquidated shafts in Poland may already be seen as a challenging task. The greater is the challenge of shaft closure in Germany where the last active coal mines for shafts with a depth of up to 1,300 m have been recently closed. It is therefore extremely important to ensure a proper shaft closure to avoid stability loss and the associated damage to surface facilities in the future. For the still active shafts, it can be done by a dedicated shaft closure design, but even then, depending on the shaft closure method, it may be necessary to perform regular shaft inspections. In many cases, it is more important to inspect old, abandoned shafts, where the wall stability or even liner type are not fully known. SHAFT CLOSURE METHODS Abandoning a shaft is a complicated task, as shafts, being the link between the surface and an underground network of workings, disturb hydrogeological and gaseous conditions in the rock mass (Sztelak, 1991). Closure procedures at older mine sites have been carried out in accordance with earlier legislative requirements. For very old shafts (+100 years), it means in many cases only a sealing of the shaft entrances by means of timber or concrete slabs. In the 20th century, the shafts were also closed by means of filling with grainy materials, but even then the retrospective activities at abandoned mine sites were extremely limited and in most cases no further monitoring measures were performed. The possible consequence of an improper shaft closure and lack of monitoring is presented in Figure 1."

Jan 1, 2019

By Rita Aiello, Stan Mack, Peter Werth, Joseph McCarney, Jozef Stachulak

"Johnson Matthey has developed the first diesel particulate filter (DPF) for underground mining that controls particulate matter (PM) at the same time as maintaining emissions of NO2 at or below engine baseline levels. DPF technology is critical for controlling PM which is classified as a carcinogen, but passively regenerating systems rely on the use of oxidation catalysts that can potentially increase NO2 emissions. This paper reviews the development of low-NO2 PM control technology and the results from testing this technology underground on diesel mining equipment. KEYWORDS Decomposition catalyst, Diesel particulate filter (DPF), Diesel particulate matter, Mining Continuously Regenerating Trap (CRT®), NO2, SCR INTRODUCTION The introduction of diesel particulate filter (DPF) technology on heavy duty diesel (HDD) engines has been an important step towards addressing the clean air and health concerns for mining companies. Control of diesel particulate matter (PM) emitted from diesel engines is already being implemented for on- and off-road vehicles, and similar legislation is being prepared for mining equipment. In addition to PM, the diesel emission control strategies (DECS) also reduce carbon monoxide (CO) and hydrocarbons (HC). Some DECS control oxides of nitrogen, or NOx, which is composed of NO and NO2. Johnson Matthey has led the development of emission control technologies for diesel engines for almost 30 years. Over the last ten years alone JM has supplied over 3 million Continuously Regenerating Trap (CRT®) DPF systems for on-road vehicles, and over 200,000 systems for off-road vehicles. The patented CRT technology combines a diesel oxidation catalyst (DOC) with a DPF to effectively trap harmful PM from diesel exhaust, while removing CO and HC. The DOC converts part of the engine NOx to NO2, which reacts with the trapped soot to regenerate the filter. As engines become more fuel efficient, less waste heat enters the exhaust. This can be a disadvantage for after-treatment systems as it leads to lower catalyst operating temperatures. The CRT system regenerates passively, without addition of heat, at temperatures that are typical of diesel engine exhaust. JM recently launched the Mining CRT system which integrates CRT technology with NO2 abatement to reduce PM and tailpipe NO2 from underground diesel mining equipment. This is the first technology proven to control both PM and NO2 emissions for a cleaner, healthier working environment. The Mining CRT is also cost-effective compared to other technologies."

Jan 1, 2019

By T. Holmes

Investigations reveal that the throughput difference between a perfect production day and the average is often on the order of 40%, and that bulk solids handling system deficiencies are the largest (>50%) class of lost opportunities. Root causes for underperformance of elements in material handling systems can often be traced back to the detailed design and even study-stage oversights. To reduce or eliminate bulk solids handling problems in an existing system requires an analysis of troublesome handling equipment – for example, a concentrate transfer chute that experiences plugging, poor flow to the furnace, unacceptable dust generation, and spillage. These problems often lead to significant maintenance costs related to downtime and personnel time. Understanding the cause and cost of flow issues is the first step in troubleshooting the problem. Next, measuring the material’s flow properties is critical to providing design data required to develop a comprehensive scientific solution. In the case of a new installation, the design data is required to properly design the system right first time and prevent flow problems from occurring so that the new equipment works correctly from start-up. This paper highlights the cost of material handling problems and discusses the best approach to evaluate material handling system deficiencies. A case study is given of how Anglo American's operation in Barro Alto Brazil enjoyed a 5-month payback from a bulk solid transfer chute debottleneck project. INTRODUCTION When operating a plant or designing a greenfield or brownfield operation, the intent is to have perfect production days (PPD) each and every day. Money is made by moving material through the plant in a controlled manner to produce the desired product. Mining operations and copper concentration processes are at the most basic level a practice in bulk solids handling (BSH). Unfortunately, many of the project planning steps are overlooked, particularly related to BSH. Investigations reveal that the throughput difference between a PPD and the actual average is often on the order of 40%, and that BSH system deficiencies are the largest (>50%) class of lost opportunities (Wellwood, 2017). Root causes for underperformance of elements in material handling systems can often be traced back to the detailed design and even study-stage oversights. BSH issues are essentially baked into the fabricated plant and left to operations to accept the deficiencies and deal with them for the life of the mine. These deficiencies then become part of the normal operation of the mine and plant.

Jan 1, 2019

By H. Staton, V. Suontaka, E. Sharifi

"Flotation circuits are typically controlled using on-line elemental assays obtained from the slurry lines. In base metal applications, X-ray fluorescence (XRF) analyzers are the most common instruments for elemental analysis of the slurries. Eagle Mine has been utilizing a Courier XRF Analyzer since 2014. Typically, in XRF analysis, the sampling rate is 10-25 minutes which is good enough for manual process control. In 2018, Eagle Mine upgraded the Courier XRF analyzer with the Rapid Measurement module that is based on reflectance spectroscopy. This option reduces the sampling rate to 10-15 seconds, while maintaining the superior accuracy of the XRF analyzer. This paper presents the results from implementation of Rapid Measurement at Eagle Mine.INTRODUCTION Eagle mine is an underground mine producing nickel and copper concentrates. Eagle Mine is owned by Lundin mining and located in the Upper Peninsula of Michigan, USA. The Humboldt Mill, previously an iron ore processing facility, was refurbished in 2014 and is used to process the ore and produce separate nickel and copper concentrates. Approximately 2,000 metric tonnes of ore is milled per day. Ore is processed using a conventional crushing followed by single stage ball mill and flotation. Nickel and copper concentrate are transported to facilities in North America via rail car. A bulk copper-nickel concentrate is produced by separating the copper and nickel minerals from gangue material by flotation. The copper-nickel bulk concentrate is reground, followed by one stage of cleaning to reject further gangue minerals. The bulk cleaner concentrate is then subjected to a final flotation stage where the copper and nickel minerals are separated from one another through the addition of lime. Final concentrate grades are 14% Ni and 2% Cu in the nickel concentrate and 31% Cu and 0.8% Ni in copper concentrate."

Jan 1, 2019

By D. R. Murray

"In 2017, Nutrien Allan Potash remediated a portion of the concrete liner in the production shaft. A set of underslung work platforms and collection boxes were used in conjunction with hydraulic splitters, jackleg drills and hand chippers to excavate and remove the broken concrete. New concrete was placed with the original pressure relief design, using a shaft slip form. Shortly after excavating, it was found that the estimated breaking rate and amount of original concrete in-situ was under estimated. Fifteen feet of excavated concrete (2719cu.ft) and ten feet (of replaced concrete was completed on April 28, 2017, and operation of the production shaft was returned to mine operations. During February 2019, Nutrien Allan Potash began remediation of a portion of the concrete liner in the service shaft. The project is different than the 2017 project, as the remediation has occurred during normal running operations and occurred only on night shift. Rather than hydraulic splitters and hand chippers, the new method includes a concrete saw and mechanical excavator from a working platform. The selected method is based on the lessons learned from the 2017 project in the production shaft. The service shaft project was scheduled to be completed in July, 2019. INTRODUCTION Nutrien Allan Potash is located approximated 75 km east of the city of Saskatoon, Saskatchewan, Canada. There are currently two shafts at Nutrien Allan Potash: the Production Shaft and the Service Shaft, transporting people and material from surface to a depth of 3,335 ft. The Production Shaft was completed in 1967, with one section of grey cast iron tubbing installed in the Blairmore formation between the 1605 and 2037 ft Levels. A second set of cast iron tubbing was installed in the Duperow formation between 2203 and 2463 ft Levels in 1999. The remainder of the concrete as of todays standards is designed as a pressure relief liner. The Service Shaft was completed in 1968, with one section of grey cast iron tubbing installed in the Blairmore formation between the 1600 and 2048 ft Levels. A second set of cast iron tubbing was installed in 1981, with 169 ft installed through the Duperow formation. The remainder of the concrete as of todays standards is designed as a pressure relief liner. PRODUCTION SHAFT REMEDIATION During the second quarter of 2015, the Mine Engineering team were notified of an area of concern in the production shaft. The shaft specialists of Golder Associates Ltd (Golder, formerly Alan Auld Canada) were contacted to complete an inspection of the production shaft liner with emphasis on the area of concern. Based on the inspection and documentation review, it was determined that the concrete at the 2804 foot elevation had been broken out for some time and was retained with #8 rebar bolts with resin encapsulation. The broken concrete was encroaching on the clearance to the conveyance."

Jan 1, 2019

By E. McLaren, J. Sanftenberg, C. Cameron, H. Dello Sbarba

"A Ventilation on Demand (VOD) system has been optimized and maintained at Glencore’s Nickel Rim South Mine (NRS) in Sudbury, Ontario, Canada for the past seven years. The system monitors and controls air quality and quantity through real-time, dynamic automation of primary fans, secondary fans, automated airflow regulators, and air monitoring instrumentation with VentSim™ CONTROL, a VOD software. This paper will focus on the implementation of testing procedures and system maintenance methods. Overall, the results show a consistent reduction in energy usage.INTRODUCTIONThe Ventilation on Demand (VOD) system at Glencore’s Nickel Rim South (NRS) mine in Sudbury, Ontario, Canada, involves the control of two 2,980 kW centrifugal surface exhaust fans with Variable Frequency Drives (VFDs), three 335 kW vane-axial surface intake fans with VFDs, 21 automated airflow regulators, six automated dampers, seven automatic doors and 198 underground auxiliary fans with ON/OFF starters. Additionally, the system monitors airflow at 48 locations, carbon monoxide (CO) at 40 locations, nitrogen dioxide (NO2) at 21 locations, and dry bulb and wet bulb temperature at 21 locations. The VOD system is also integrated with a tagging and tracking system to modulate the ventilation system automatically and in real time according to the presence and position of the personnel and vehicles. The tracking system comprises of 75 vehicle tags with diesel status and hydraulic status (ON or OFF), 440 personnel tags, and 200 tracking zones. Finally, it also involves the configuration and updating of 55 level plan and interactive procedures and 24 daily scheduled events. NRS currently uses VentSim™ CONTROL, Ekahau Tracking and PI Datalink to control, monitor, and configure their VOD system."

Jan 1, 2019