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By G. Granata, C. Tokoro, T. Kato

"The goal of this study was to evaluate the effectiveness of mechanochemical activation by planetary milling as method to enhance the recovery of cerium from rare earth ores. For this purpose, a weathered ore was first ground by planetary milling and then leached by sulfuric acid. The influence of planetary milling was investigated by assisting the experiments with X-ray absorption fine structure (XAFS) in cerium LIII-edge and inductively coupled plasma spectrometry to measure the concentration of cerium dissolved by leaching. Results showed that, by increasing the grinding time, although the particle size of the specimen increased due to agglomeration, the recovery of cerium significantly increased. This finding clearly indicated that a smaller particle size actually hinders the recovery of cerium. In particular, XAFS analysis revealed that the longer the grinding time, the more tetravalent cerium could be converted into trivalent cerium and such conversion, also called mechanochemical reaction was beneficial to the recovery of cerium. Based on the obtained results, it was confirmed that approximately 70% of cerium could be recovered by mechanochemically activated leaching of rare earth ores.INTRODUCTION Rare earth elements (REEs) are a group of 17 chemically similar metallic elements comprising lanthanides, scandium and yttrium. Since REEs have various unique physical and/or chemical properties, they have become essential materials for advanced application (Adachi, 2015). REEs used in industry are usually supplied as rare earth minerals. In the last decades, flotation, gravity separation, magnetic separation and leaching have been widely applied to recovery of REEs from rare earth minerals like monazite (Archana, Rekha, Manis, Jitendra, & Jin, 2015). Among these operations, leaching has been widely studied in the recent years to improve the state of the art (Archana, Rekha, Manis, Jitendra, & Jin, 2015; Xiao, Feng, Huang, Huang, Chen, Liu, Wang, & Long, 2016; Farzaneh, Fereshteh, & Ahmad, 2017). Aiming to enhance recovery of REEs from rare earth minerals, a possible advancement of leaching technology could be the mechanochemically activation of the ore by high-intensity milling (Alorro, 2016). In the mechanochemical activation, an improvement of the leaching performances can be achieved through high-intensity milling operations which result into a dramatic decrease of the mineral particle size with a consequent improvement of the physical kinetics of leaching. Furthermore, the high mechanical energy provided to the sample during milling can determine the rupture of the crystal structure of the mineral, thereby transforming it into a more leachable form."

Jan 1, 2017

By T. Avilez, D. Salari

"The economics of developing gold deposits containing elevated levels of cyanide soluble base metals is often challenged by high cyanide consumption and increased operating costs. SART is a chemical process that enables cyanide consumed by base metals to be recovered and recycled for gold leaching. The process also provides concurrent recovery of the base metal to generate incremental revenue from the sale of high-grade base metal sulphide concentrates. Although SART was developed and successfully piloted by Lakefield Research and Teck Corporation in the late 90’s and is now a public domain technology, the adoption of SART has been relatively slow due to concerns about implementation costs and the reliability of metallurgical performance. Through extensive experience in selective metal sulphide precipitation applied to mining wastewater since 2007, BQE Water has provided process know-how, design along with operations and maintenance experience to a number of projects involving the integration of SART into various metallurgical flowsheets on an industrial scale. This paper presents the commissioning experience and operating data from a SART plant treating up to 500 m3/hr of leach solution at a heap leach operation in Mexico. INTRODUCTION One of the current trends in the gold industry globally is the increasing importance of complex polymetallic gold deposits as discoveries of large Carlin type gold deposits become increasingly rare (Sceresini, 2005). The presence of cyanide soluble copper and zinc in complex gold deposits necessitates changes to the traditional gold extraction metallurgical flowsheet. A tool available to the industry to help manage the interference of cyanide-soluble base metals in gold extraction is the SART (sulphidization-acidification-recycling-thickening) process. SART breaks the weak acid dissociable (WAD) base metal-cyanide complexes, precipitates the metals as high-grade sulphide concentrates and makes the freed cyanide available for recycle."

Jan 1, 2018

By T. G. Edgeworth

Some of the historical background of the industry is reviewed, with reference to the different types of reduction cells in use for aluminum smelting. Factors to be considered in cell des1gn involve capital, power, and operating costs. The trend is apparently toward larger cells. The industry is studying new construction materials for cell linings, as well as alternate electrolyte compositions and other design changes which will improve productivity and energy efficiency. The aluminum smelting activity in other countries is briefly reviewed. TODA Y'S industrial production of aluminum is still based on the simultaneous discoveries made in 1886 by Charles Martin Hall in Ohio, and Paul Heroult in France. Up to that date, only about 50 tons of aluminum had been produced in the world, and the price at that time was about $5 per pound. Sucl1 figures must be contrasted with the present world aluminum smelting capacity of over five mil-lion tons per year, and a price of about 25 cents per pound.

Jan 1, 1962

By D. K. Sarkar, J. Perron, J. D. Brassard

"Nearly perfect spherical shaped water drops rolling-off from the surface of lotus leaf is one of the beauties of nature. This kind of surface is called superhydrophobic, since the water does not like it. Physically, a superhydrophobic surface provides a contact angle (CA) of water over 150°. The combinations of both mico-nanostructure topography as well as low surface energy are essential to have such high CA on a surface. Nano-micro structured superhydrophobic surfaces have been developed in different methods. (i) Monodispersed fluorinated silica nanoparticles have been synthetized via Stöber Sol-Gel process and deposited on various surfaces, such as aluminium or glass, to obtain transparent superhydrophobic thin films. (ii) Similarly, zinc stearate nanocomposite coating has been fabricated by spray process on the same substrates. These thin films are found mechanically robust with drag reduction of coefficient 16% lower than as-received surfaces. (iii) By electrodepositing pure zinc on steel surfaces and further coating it with diluted room-temperature vulcanized silicone rubber, the surface become superhydrophobic. This superhydrophobic surface protects the steel against corrosion by increasing the polarization resistance from 1.5 k? on steel to 44.4 k?. This coating also reduced the ice adhesion on the steel surface 6.3 times as compared to bare steel substrates. Globally, these superhydrophobic surfaces have tremendous applications against corrosion reductions, drag reductions and ice adhesion reductions.INTRODUCTIONSuperhydrophobic coatings are increasingly attractive to the industry and academia due to their unique self-cleaning properties as a result of their water repelling characteristics. Fabrication of superhydrophobic coating is an inspiration from nature as water is seen to repel on many natural surfaces such as those of the lotus leaves, butterfly wings, water striders’ legs, and so on (Gao & Jiang, 2004; J. Huang, Wang & Wang, 2006; Neinhuis & Barthlott, 1997; Zheng, Gao & Jiang, 2007). This non-wetting phenomenon is well understood on lotus leaves, shown on the Figure 1 (a), and it is considered as the basis of the studies of superhydrophobicity. The existence of this binary structure on the surface of the lotus leaves allows a large amount of air entrapment and consequently reduces the contact area of water on it and the presence of low surface energy waxy components with reduced affinity to water together leads to the superhydrophobic properties. The phenomenon is shown on Figure 1 (b). Cassie and Baxter (Cassie & Baxter, 1944) as well as Wenzel (Wenzel, 1936) proposed two mathematical models to explain the wetting phenomena on rough surfaces that leads to superhydrophobic properties. By definition, superhydrophobic surfaces are characterized by a water contact angle value = 150° with the rolling off of water drops from the surfaces (Sarkar & Saleema, 2010). Superhydrophobic surfaces find tremendous importance in the technological world where it can applied in domains such as anti-corrosion, anti-biofouling, electrowetting, icephobic and even in drag reductions (Bushnell & Moore, 1991; Cao, Jones, Sikka, Wu & Gao, 2009; Carlborg & van der Wijngaart, 2010; Carré & Mittal, 2009; Y. Huang, Sarkar & Chen, 2010a; R. Karmouch, Coude, Abel & Ross, 2009). However, the most important challenge faced by industries is their feasibility large scale in an effective an economical manner."

Jan 1, 2016

By W. Basuki, B. Setyotomo, L. Hakim, R. Hendrajaya

Due to high crack sensitivity of slab product of gas and oil line pipe application, its steel making process and alloy composition were evaluated and then improved to overcome its critical solidification process and reduced surface defects. The study was conducted at Slab Steel Plant Krakatau Steel. The purpose was to improve slab surface quality by reducing surface defects so that the slab surface doesn't need to be totally repaired. The method applied was by performing plant trial process, which the secondary process parameters such as alloying method and the casting parameters such as casting powder selection, metallurgical cooling, mould level control, and superheat were continuously monitored and then adjusted to the surface quality of the product. Based on the calculation of Ferrite potential of the steel, the chemical composition was designed to achieve optimum casting parameters in order to avoid high shrinkage during solidification. The results of the study are decreased surface defect quantity, and smooth casting process. The quantity of crack decreased by almost 90%. The slab surface repairing was significantly reduced from 85. % to less than 10%. These new casting parameters and developed alloy composition are then used and standardized for the mass production of the steel.

Jan 1, 2005

By J. H. Ambrose

Introduction The copper smelter of the Hudson Bay Mining and Smelting Company, Limited was constructed to handle the concentrates produced by the concentrator, the residues from the zinc plant, concentrates from Sherritt-Gordon Mines, Limited, and other custom material that might be available. Construction work was started in 1929 and the first concentrates were smelted in November, 1930. From that time until June, 1931, the operations were more or less of an experimental or tuning-up nature. In designing the smelter, it was believed the following tonnages would be available for smelting per day: Copper Tons Content H. B. M. & S. Co. concentrates 331 14.0 per cent H. B. M. & S. Co. zinc plant residues 77 2.5 per cent Sherritt-Gordon concentrates 200 20.0+ per cent Consideration was given to wet-smelting the charge, but, in order to give greater flexibility to the operation, it was finally decided to roast the concentrates before smelting. Briefly, the smelter equipment consists of three Nichols-Herreshoff roasters, one reverberatory furnace, two Peirce-Smith converters, a Walker casting wheel, and a four-unit Cottrell plant, two units' for the roaster gases and two for the converter gases. A general plan of the smelter is shown in Figure 1. Prior to the commencement of smelter operations, a stockpile of about 9,000 tons of concentrates had been built up by the concentrator and the old pilot-mill. The zinc plant was in operation, but the equipment for drying the residues at the smelter had not been completed. Sherritt-Gordon did not commence their shipments of concentrates until April, 1931. The only flux available was barren sand from a pit ten miles south of Flin Flon, adjacent to the railway. Several small deposits of metal-bearing siliceous ore had been discovered in the district, but none of these were sufficiently large to be considered as a source of smelter flux. At the beginning of March, 1931, the entire stockpile of concentrates had been consumed, and available tonnage for smelting was limited to the daily production of the concentrator.

Jan 1, 1935

By W. N. B. Armstrong

CORROSION of metals, for the purpose of this talk, may be divided into two general classes, namely, atmospheric and chemical. Atmospheric corrosion is caused by the natural agents -water, air, salt, and temperature -as well as by the agents arising from industrial operations which pollute the atmosphere. Chemical corrosion affects metals in refineries and chemical plants where severe conditions exist due to .acids, alkalies, salts, solvents, gases, ?steam, etc. A special condition is encountered on road equipment and motor vehicles due to the large amounts of corrosive salts which are used on our roads in the winter. Exposure to corrosive conditions such as those referred to above causes metal to be destroyed and, therefore, it has to be protected. The non-metallic or organic coatings used to protect the metal are themselves destroyed ultimately by these same conditions. Since all types of organic coatings do not have the same kind and degree of resistance to degradation, a particular kind of -coating must be used for a particular set of conditions in order to obtain the maximum benefit. In ?addition to the above mentioned agents, organic coatings are degraded ?by sun-light, which is probably the severest single factor in the breakdown of organic coatings exposed outdoors. We can divide organic coatings, in a general way, into the following classes: (1) Conventional coatings, and (2) Special coatings.

Jan 1, 1958

By K. Adham, T. Buchholz

"Significant capacity increases to meet new production demands can often be fulfilled through debottlenecking of an existing production facility, rather than the more expensive option of building new plants and facing new environmental and infrastructure challenges. To achieve that goal, it is important to model and calculate the existing ultimate capacity of each processing plant area, and that of each key equipment sector within the plant areas. This paper describes a methodology of how process modeling tools can be used to simulate the processing steps, how to estimate their existing and ultimate capacities, and how to determine the sweet-spots (minimum cost points) for a plant expansion – leading to a road map of the subsequent debottlenecking project implementation.The debottlenecking technique is presented through a generic work-flow narrative which can be applied to different mineral processing studies, starting with establishment of heat-and-mass balances, drawing a bottleneck diagram, brainstorming capacity increase options, and preparing a cost-capacity curve. Hatch has successfully applied this technique to a number of plant capacity studies, with great benefits to our industrial clients.INTRODUCTIONWith the softening of the metals and minerals prices, and the escalated costs of building new processing plants, it is now economically more viable to improve and debottleneck the existing facilities, rather than build new ones. However, spending new money on old plants requires careful considerations, in order to identify the most economically advantageous incremental steps of improvement and the best potential returns on investment. Process modeling, hand in hand with plant measurements, can identify the best scenarios to balance the three aspects of plant capacity (nameplate, utilization and yield), both at the global and the individual system and subsystem levels."

Jan 1, 2016

By H. B. Gillis

THE following pages c9ntain a brief description of the processes involved in the manufacture of silica brick at the Sydney plant of the Dominion Steel & Coal Corporation. Silica brick manufacture was commenced at Sydney in 1918, for the purpose of supplying the requirements of the steel plant, where about three million silica bricks were used annually. Previous to that date, all silica refractories were brought to Sydney from American sources and were subject to a freight cost of nine dollars per ton, or about twenty-seven dollars per thousand. As a preliminary step to manufacture, a thorough investigation of all possible sources of silica in the vicinity of Sydney was carried on during 1916 and 1917. ?Eighteen separate deposits were examined. Of this number, only four were found suitable for brick making, and the Leitches Creek silica, being the nearest of these four deposits to Sydney, was selected as the raw material for the proposed plant. CRYSTAL MODIFICATIONS OF SILICA A brief review of the silica minerals may serve to indicate why careful investigation of sources of supply is necessary before actual brick-making is attempted. The crystal modifications of silica, i.e., quartz, tridymite, and cristobalite, all possessing alpha and beta phases, play a most important part in determining the suitability or otherwise of the resulting brick. By heat treatment, any one of these forms of silica may be converted to either of the others. The inversion temperatures (after Fenner) in degrees Centigrade are shown on rage 160.

Jan 1, 1938

By A. Saigal

The effect of temperature on the cutting forces during machining of alumina reinforced aluminum composites was investigated, Aluminum 6061, 10% Al2O3 reinforced composite and 20% Al2O3 reinforced composite were tested, A 5/8-inch diameter high-speed steel end mill, a Micro 100 TiN coated single edge endmill cutter and a two-fluted solid carbide insert cutter were used for tooling, The results, in general, showed an increase in the cutting forces as the temperature of the material increased, From the raw data, there are temperatures ranges in which the force data did decrease but they were insignificant with regards to predicting a downward trend. A regression analysis was used to understand which variables had the greatest affect on the forces being generated, The correlation and regression analysis showed that at 600 rpm (velocity: HSS- 98,2 sfpm, Micro 100 cutter - 78,5 sfpm, solid carbide cutter - 192,4 sfpm) the tooling, the workpiece material, built up edge, and temperature were statistically significant factors in the test, Tooling was a significant variable in all testing, The smallest forces recorded during machining were generated with the solid carbide two-fluted endmill cutter, Visually, the solid carbide tooling produced a better surface finish during the testing which made it the tool of choice, In addition, the force data proved that as the cutting speeds were increased, the cutting forces decreased.

Jan 1, 2005

By E. H. Kranck

Introduction Baffin Island is still too in-accessible to be of interest to the mining industry. However, twenty years ago few people dreamed of mining iron ?ore in Labrador. A journey by air to the most remote places in the Arctic is today no more remarkable than a trip to Europe, and the technical difficulties of mining minerals of high value are not insurmountable. Some ?observations concerning the geology and mineral possibilities of Baffin Island, the largest of the Arctic islands, may therefore interest the members of the Institute, in spite of problematic practical value of the subject. The following short account is mainly based on observations made during the Baird Expedition of the Arctic Institute of North America last summer 1950), and on information available from earlier expeditions. Early Work Baffin Island was one of the first parts of Canada to attract prospectors. Frobisher sent a shipload of rocks, which he believed contained precious metals, from Baffin Island to England. This attempt, however, was a failure and no further serious prospecting work has, so far as I know, been done. During the past few years geological mapping has been carried out by the Geological Survey of Canada (Fortier. Davison, 1949-1950) in the southern parts ?of the island, along the coast of Hudson strait. In 1942, Weeks mapped the coast from Pangnirtung to the head of Cumberland fiord, and Netteling river up to Netteling lake. In the northern parts of the island, only scattered observations have been made ?by Bell, Watkins, Baird, and others.

Jan 1, 1951

Presentation Outline ERM ? corporate profile Background to sustainability reporting GRI G3 Guidelines (Oct 2006) Best practice examples Contact information ERM ? corporate profile Over 35 years of experience World?s largest all-environmental consultancy* 130+ offices in 40+ countries; 3,200+ professional staff Worked with >50% of the Global Fortune 500 (FY07) Annual turnover > US$500 M (FY07) 2008 Environmental Advisor of Year** Offices/Staff ? Canada (5/50) and US (65/1,350) *Source: Engineering News Record: July 2, 2007 ** Source: Acquisitions Monthly: December 2007

May 1, 2008

By T. Thriveni, Ji Whan Ahn

"The current advanced technologies for the manufacture of light weight metals processing significantly increasing and attributes to the safety, performance, recyclability and economy. Still lack of technologies developed for light weight metals processing waste utilization and application. Environmentally friendly methods need to develop for better understanding the processing waste utilization. Alumina and aluminium processing creates a wide range of waste products, the most significant being is red mud. Bauxite residue is a high volume hazardous waste and nearly 3 billion tons have been dumped worldwide. Approximately, 120 Million tons/yr of red mud being produced without any environmental sustainable solution. Currently the most significant technology is waste utilization. The bauxite residue is suitable for road base construction, golf bunker sand, back fill and, general fill. Sustainable recycling technologies are necessary for the bauxite residue utilization for the recovery of rare earth elements and cement materials. Carbonation or CO2 sequestration of carbon dioxide is a method pioneered for the bauxite residue is modified to reduce alkalinity. The carbonation of alkaline material is an inexpensive and safe process that leads to the formation of thermodynamically stable products. The use of the carbonation can be an advantageous solution for environmental climate change and sustainability problems in the new century.INTRODUCTIONIn 2014, bauxite consumption was estimated to be 9.6 million tons, nearly all of which was imported, worth an estimated 269 million dollars. More than 95% of the bauxite was converted to alumina, and the remaining 5% went to non-metallurgical products, such as abrasives, chemicals, proppants, and refractories. Global aluminum demand is growing steadily spurred by growth in India and China (RBCAluminum Market Outlook, 2013) (Figure 1). Aluminum consumption is expected to rise 5% annually through the end of the decade, reaching 67 million tons per year by 2020. Global bauxite production decreased by 17% from that of 2013, principally owing to lower production in Indonesia. In response to a Government ban on exporting bauxite and other unprocessed mineral ores that took effect on January 12, 2014, bauxite mines throughout Indonesia shut down and production decreased from 55.7 million tons in 2013 to an estimated 500,000 tons in 2014. The ban was part of a mining law that was instituted in 2009 to increase development of downstream processing facilities in Indonesia."

Jan 1, 2016

By R. K. Collings

Mineral wastes from the mining, metallurgical and chemical processing industries in Canada amount to about 800 million tonnes annually. Such wastes often are largely non-metallic in composition and are of interest for traditional non-metallic mineral uses and applications. Mineral waste disposal and maintenance are costly; furthermore, these wastes may pollute groundwater, rivers and lakes. These factors and an increased appreciation of the potential utility of some mineral wastes have stimulated research in this area.

Jan 1, 1984

By S. Kobayashi, N. Ohara, T. Aoki, S. Sakurai, M. Iwano, M. Shimo, I. Otsuka

"This project is the upgrading of a commuter line of approximately 76 km to improve the railway system in Istanbul metropolitan area. Railway tracks have been connected between Asia and Europe through a tunnel under the Bosphorus Strait. The length of these underground structures sums up 13.6 km. In this paper, the observational construction management based on field measurement performed at large scale underground railway station (Sirkeci station) constructed by means of New Austrian Tunneling Method (NATM) is described and the mechanism for generation of ground surface settlement above this station is discussed.Buildings above Sirkeci station are overcrowded. About 60% of the buildings are made of reinforced-concrete (RC) and others are of brick. Based on the investigation into the predicted settlement and inclination, necessary actions such as structural reinforcement and soil improvement have been conducted for dilapidated buildings.Rock mass around Sirkeci station consists of alternative strata of sandstone and mudstone. It is overall soft rock with an elastic modulus of 150 MPa, partly including fractured zones. Overburden is about 30 to 40 m. The thickness of unconsolidated sand layer distributed on the bedrock is about 10 m. As a result of in-situ permeability tests, the coefficient of permeability of the sand layer is about 1.0x10-3 cm/s. Fill layer of about 10 to 25 m in thickness covers the sand layer at the ground surface. The fill layer contains a lot of artificial waste like splinters of wood, brick chips and mortar chips, etc. in addition to gravel, sand, silt and shells. The coefficient of permeability of fill layer is estimated to be 1.0 x10-2 cm/s, which is one-order greater than that of the sand layer. Fill layer consists of ancient city ruins of ages respectively from the Eastern Roman Empire, the Byzantine Empire and the Ottoman Empire and has a lot of gaps.The underground part of the Sirkeci station was excavated through a ventilation shaft. Ground surface settlement occurred more than predicted. Therefore, back analyses were performed in order to precisely predict the next-step settlement. However, back analyses with elasto-plastic models could not simulate the actual phenomena and hence, an anisotropic-damage-parameter model developed by Sakurai (1999) was adopted for the back analysis. Furthermore, as the excavation of tunnel proceeded, the ground surface settlement exceeded the predicted value again. Based on the monitoring results, it seemed that pore water pressure decreased by the tunnel excavation resulted in the soft rock and soil to be contracted due to the increase in the effective confining pressure. A coupled hydraulic-mechanical analysis was applied to explain the relationship between decreased pore water pressure and ground surface settlement. The settlement due to drainage from tunnel wall was well-estimated in the coupled hydraulic-mechanical analysis.However, further settlement occurred more than predicted again and again. Though it was very difficult to clarify the reason of the large settlement, it was recognized that the unexpected ground surface settlement resulted from the existence of the large gaps in the fill layer that was greatly compressed. The final settlement reached up to 327 mm."

Jan 1, 2015

By E. Eccleston, E. Gardner, F. Letarte, R. Schonewille

"In 2005, after nearly a decade of process development and feasibility work, the commercialization of the Falconbridge Nickel Smelting Technology (NST) began in earnest with the design and construction of a grassroots ferronickel plant at Koniambo Nickel in New Caledonia. The NST process was developed as an alternative to the conventional Rotary Kiln-Electric Furnace (RKEF) process for production of ferronickel from saprolitic nickel laterite ores. The NST process promised environmental and energy efficiency advantages over the conventional route. A key step of the NST process involves fluidized bed pre-reduction of calcined laterite ore using direct injection of pulverized coal as the reductant. Two parallel fluidized bed reduction roasters (FBRs) were installed at Koniambo Nickel, each designed for a maximum capacity of 4,200 MTPD of calcined nickel laterite ore. This paper describes the process development and scale-up of the fluidized bed pre-reduction process, the design challenges associated with the prototype commercial units, and the current status of the FBR operation at Konaimbo.INTRODUCTION In the mid-1990s, Falconbridge began to develop a new flowsheet for production of ferronickel from nickel laterite ores. The process that developed came to be known as the Falconbridge Nickel Smelting Technology (NST). The flowsheet, which is particularly appropriate for saprolitic ores, involves several major unit operations, including: drying in a hammer mill-flash dryer, calcination and preheating in a flash calciner, pre-reduction in a fluidized bed reactor, and smelting in a DC arc furnace to produce the ferronickel product. This paper focuses on the fluidized bed pre-reduction step of the process and provides an overview of the process chemistry, laboratory and pilot plant development work, scale-up and commercialization of the pre-reduction step, and the results obtained in the prototype commercial units."

Jan 1, 2017

By S. Dominguez, E. Gebrehiwot, S. Richardson, S. Sandoval

Copper electrowinning/electrorefining (EW/ER) is powered by direct current (DC) rectifiers that typically generate 30,000 to 70,000 amps and a bus-bus voltage of 200 to 500 volts DC. Tankhouses are designed so that DC current flows through “cell lines” which contain individual EW/ER cells electrically connected in series. Electrolyte composed of copper sulfate and sulfuric acid in water forms the “liquid conductor” that connects the metallic conductors in this circuit. In this setting, stray current is a DC current that strays from and therefore bypasses the tankhouse circuit by finding a path to ground, often through the electrolyte in pipelines that feed into and discharge from the cells, or through dried electrolyte (i.e. sulfate), which is also electrically conductive. Tankhouse workers can be exposed to shock hazards if they become part of a stray current path to ground. This presentation details examples of stray current shock hazards in electrolytic tankhouses and provides voltage and amperage measurements associated with stray current in these examples. A review of critical safety controls in EW/ER tankhouses that will mitigate the risk of employee shock from stray current is also provided. INTRODUCTION Electrolytic tankhouses are designed to deliver relatively large amperages of DC current to a series of electrolytic cells in which copper is plated out of solution using the classic anode-cathode pair geometry within each cell. Electrolyte is the “liquid conductor” that transfers current in between the metallic conductors of the cell. The metallic conductors include inter-cell copper bus bars and the anodes and cathodes themselves. It is sometimes forgotten that electrolyte as a conductor is capable of delivering DC current outside the designed circuit of a tankhouse. Stray current is a DC current that strays from the tankhouse electrical circuit by finding a path to follow other than the designed path. Safety becomes a concern when there is a risk of an employee becoming part of an accidental stray current path, thereby suffering an electrical shock. In 2016, Freeport-McMoRan (FMI) suffered a fatality at one of its copper electrowinning tankhouses. The forensic analysis concluded that stray current from the tankhouse rectifier contributed to the fatality. An employee accidentally fell into contact with a metal flange at the end of an HDPE pipe that was collecting cell overflow electrolyte from the tankhouse. DC current passed through the employee to ground, creating a shock that was judged to contribute to his death. The situation was exasperated because the employee was unconscious, and therefore was exposed to the stray current for several minutes before being found. In addition, the employee’s clothing was saturated with liquid, and the employee was found kneeling in puddled liquid on the ground. FMI immediately began an investigation into the root cause of the stray current that was measured at the scene. Sufficient electrolyte had accumulated in the HDPE pipe such that a continuous path was formed between it and electrolyte that was continuously overflowing from energized electrowinning cells. The metal flange on the pipe was the metallic conductor that carried the current to the employee from the electrolyte inside the pipe. Current then flowed through the employee to ground. Because of this incident, FMI undertook an extensive review of the hazards of stray current in EW/ER. FMI’s tankhouse workforce received a Tankhouse Electrical Safety training course developed in- house to insure worker understanding of stray current hazards. Tankhouse design changes were implemented to better insulate workers from stray current. Personal protective equipment (PPE) standards were also reviewed and changes made.

Jan 1, 2019

By M. Pötsch, A. Kluckner, P. Söllner, W. Schubert

"The in situ block size is a key parameter in the geomechanical characterization of rock masses. It describes the fracturing of the rock mass and thus is a measure for the degradation of the rock mass strength. Several classification systems use the in situ block size. For instance, the Geological Strength Index (GSI) requires the “blockiness” and joint surface condition factor as key input parameters. The “blockiness” has recently been related to the in situ block volume (Cai et al., 2004). Due to the limited information about the internals of a rock mass, it is not possible to determine the in situ block size directly. Currently, the in situ block size is determined by calculations using oversimplified models, vague estimations or, due to the lack of relevant information, it is neglected. As remote measurement systems have become available for rock mass characterization, a more comprehensive record of discontinuities can take place. Measurements can be performed on exposed rock outcrops and in particular on tunnel faces and walls, delivering the location, orientation, spacing and persistence of discontinuities at an arbitrary number and locations. An estimation of the in situ block size at the same level of sophistication is still not available. This paper aims at examining the relationship between visible and measureable information at the rock surface, and the in situ block size. Three-dimensional block model simulations were performed using the block model engine of the distinct element code 3DEC. Initial investigations focussed on the minimally required observation area in order to obtain reliable block size distributions. Based on a representative volume element, a reference distribution of the block area at the observation area for a specific discontinuity system was determined. Subsequently, the size of the observation area was decreased stepwise and each new distribution was compared to the reference distribution. For all analyzed systems, it turned out that the mean block area must be smaller than 1% of the observation area to achieve a reliable block size distribution. Further simulations focussed on discontinuity systems with three non-persistent sets. The results were compared to the formula proposed by Cai et al. (2004). A transformation factor T was introduced which replaces the persistence terms in Cai et al.’s proposed formula. The factor describes the correlation between block volumes generated by persistent and corresponding non-persistent discontinuity sets. The simulations included the variation of the discontinuity set spacing, persistence, and orientation. The mean and additionally the 25%-, 50%- and 75%-quantiles of the block size distribution were analyzed. Examining all values for the transformation factor the distribution can be described by a power function with a negative exponent. The function depends on the persistence only. Finally, the results of random simulations were compared to the analytical formula using the transformation factor. The predicted mean and selected quantiles show a good agreement with the simulation results. It gives a comprehensive picture about the block size distribution in discontinuity systems with three non-persistent sets."

Jan 1, 2015

By F. Doxey

Introduction In order to improve outputs and to reduce or hold mining costs, many attempts have been made to mechanize the getting and loading of coal in the major coal producing countries, and machines of various kinds and sizes have been designed and manufactured. Some of the most important are: Joy Continuous Miner Joy Coal Auger Goodman Mining Machine Lee-Norse Koal-Master Jeffrey Colmol Cardox Hordsecg Recovery Drill German Coal Plough British Coal Plough with agitated blades M. & C. Samson Stripper AB Meco-Moore Cutter Loader Joy Gloucester Getter The three last named are the chief longwall machines in use and the AB Meco-Moore and the Samson Stripper are doing a good job in their respective applications. It is understood that the Gloucester Getter recently installed in a British colliery also shows reasonable promise. It was felt, however, that to meet the conditions of the mines in Nova Scotia, any machine developed must have certain distinctive characteristics. It must: ( 1) Be able to cut and deliver coal in quantity and of the right sizes ( 2) Be easily manoeuvrable ( 3) Be suitable for longwall operations ( 4) Not interfere with timbers already set ( 5) Cut its own stable (6) Work on reasonably heavy gradients

Jan 1, 1951

By Frank D. Shepherd

THE Gunnar Gold Mines property is on the west shore of Beresford lake, in the Rice Lake mining division, southeastern Manitoba. Gold was first discovered in place in the Rice-Beresford Lakes area in 1911 on the Gabrielle claim, now included in the San Antonio Mines property at Rice lake. Following an eastward trend of favourable prospecting ground, promising showings were next staked in the vicinity of Long lake during the years 1915 and 1916. At that time, William Walton and associates, among them Gilbert LaBine, staked the Eldorado vein, north of Long lake, and Eldorado Gold Mines, Limited, was formed to develop the property a Company that, later, was to become widely known through successful operation of its radium-silver mine at Great Bear lake, Northwest Territories. Continuing eastward from Long lake, Walton and his partners, Gunnar Berg, Leo Seaberg, and Wm. Quesnel, staked claims during the years 1920-24 in the vicinity of Beresford lake which, later, were to become incorporated into the Gunnar Gold Mines property. The presence of gold-bearing quartz on these claims had been known from the time they were staked, but an opportunity to consolidate them into a group was not forth-coming until early in the year 1933. Although promising gold showings had been disclosed during the performance of assessment work on individual claims, no continuous mineralization having mine-making possibilities was discovered until after the consolidation of the entire group. From this stage onward, progress was rapid. Active exploration was begun on August 1st, 1933, and late in October James Houston reported favourably on the property. On October 27th, Gunnar Gold Mines, Limited, was incorporated in the Province of Ontario to develop and operate the property. The Company is also registered in Manitoba. The authorized capitalization is 3,000,000 shares of $1.00 par value. Gilbert LaBine was appointed president of the Company, with James Houston as mine manager. Following completion of a diamond-drilling programme, planned in 1933, it was decided to install a mine plant capable of carrying development to a depth of 1,000 feet. A transmission line, 5 miles in length, was built to the Great Falls-Central Manitoba line of the Manitoba Power Company, Limited.

Jan 1, 1939