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By John S. Carman

Our industry is in trouble. Real trouble. It has never been an easy, secure business. But to-day it is engulfed in revolutionary currents. No longer can there be reliance upon the checks and balances of market forces. Supply and demand largely dictated the economics of business enterprise in simpler days. To-day politics, in particular nationalism become increasingly dominant. And as governments expand and put out tentacles of interference in the direction of the mining industry, far too little understanding is evidenced as to how that industry works. Then there is something which is relatively new -stagflation. As the prices of minerals falls, the capital investment required for new extractive facilities soars at rates which far outdistance those which are cited by governments to indicate the magnitude of inflation. To illustrate; 1) In 1971 it was calculated that $355 million would be required to bring the Cuajone property in Peru into production. Five years later that stage was reached at a cost of $680 million. 2) With the Caridad mine in Mexico, estimated capital investment doubled between 1971 and 1976. 3) The requirements calculated for Cerro Colorado in Panama have risen in two years from $560 to $800. 4) The budget of $240 million for Sar Chesmeh in Iran in 1971 had become $500 million by 1976.

Jan 1, 1977

By P. Samanta, Mohammed N. Azad, Gustad F. Taraporewalla, A. K. Mukherjee, Abhay S. Patra, D. Sachinraj

Beneficiation of coal is a water intensive process, and the water is recovered in downstream operations in the high rate thickener (HRT) and vacuum belt filtration (VBF). Clean coal particles entering the HRT have an inherent tendency to enter the overflow because they are extremely fine and hydrophobic. Hence, flocculants (polymers) are used to floc the ultrafine particles so that they settle and enter the underflow. Ultrafine coal particles (−37 μ), which are highly hydrophobic, if present in the stream, will not be efficiently captured by using flocculants alone. This is observed in the normal plant operation at one of the beneficiation plants in the Jharia region, Jharkhand, India. Approximately 6–7% of the feed to the HRT enters the over flow (supernatant water). Hence, this amount of clean coal particles is not recovered and account for production losses. A comprehensive settling and dewatering test work was conducted with clean coal slurry using several commercially available reagents. Studies were also done on different combinations of reagents, including coagulants and surfactants along with flocculants, to improve the settling behavior of the coal particles. The reagents were assessed based on their performance with respect to settling rates, overflow water clarity, and compaction of the underflow solids. Emphasis was given to the ability of the reagents in compacting thickener underflow to higher densities so that maximum water could be recovered from the thickener. Pretreatment of highly hydrophobic coal slurry with a combination of coagulant and surfactant followed by flocculation showed very good settling characteristics with clear overflow.

Sep 30, 2021

By C. L. McKenzie

American Girl Mine is located in the Cargo Muchacho Mountains in the southeastern Imperial Valley of Southern California. Production from the current open pit mine and heap leach recovery system began in early 1989. Previous mining and gold recovery took place commencing in 1987 at the Padre Madre site, situated adjacent to the American Girl site to the southwest. In mid-1990, a 790-tonne-per-day underground gold mine and mill went into production. Approximately 6,500 troy ounces of gold per month are recovered from the combined open pit underground mine operation. Copper in the form of Azurite [Cu3(CO3)2(OH)2] and Malachite [Cu2CO3(OH)2] are abundant in the mined ores (Henshaw, 1942). The high solubility of these minerals in caustic cyanide solutions has a negative impact on carbon adsorption and electrowin processes. This paper presents the results of monitoring programs, process chemistry, and control changes introduced at American Girl Mine to abate production complications in the refinery and measures taken to minimize solution gold losses in the adsorption circuit(s).

Jan 1, 1993

By T. E. Bernard

"Refuge alternatives provide shelter to miners trapped underground during a disaster. Manufacturers must demonstrate that their refuge alternatives meet the U.S. Mine Safety and Health Administration (MSHA) requirements for oxygen supply, carbon dioxide removal, and management of heat from the occupants and mechanical/chemical systems. In this study, miner size and activity level were used to determine the metabolic heat rate, oxygen requirements and carbon dioxide generation that are representative of miners in a refuge situation. A convenience sample of 198 male miners was used for the distribution of current U.S. coal miners, and the composite 95th percentile height and weight were determined to be 193 cm (76 in.) and 133 kg (293 lb). The resting metabolic rate (RMR) was determined to be representative of activity level in a refuge alternative. The highest likely metabolic heat generation ranged from 113 to 134 W, depending on occupancy. The highest required oxygen supply and carbon dioxide removal were estimated to be 23 L (0.81 cu ft) of oxygen per hour per person and 20 L (0.71 cu ft) of carbon dioxide per hour per person, which means the margin of safety is 50 percent or more compared with the MSHA requirements. The information on metabolic heat generation can be used to assess refuge alternative thermal environments by testing or simulation. The required oxygen supply and carbon dioxide removal can be used to assess refuge alternative requirements. IntroductionRefuge alternatives provide shelter to miners trapped underground during a disaster. Manufacturers must demonstrate that their refuge alternatives meet U.S. Mine Safety and Health Administration (MSHA) requirements for the supply of oxygen (O2), removal of carbon dioxide (CO2) and management of heat resulting from the refuge alternatives’ occupants and mechanical/ chemical systems (MSHA, 2008)."

Jan 8, 2018

By M. Werner

Mining in the Coeur d'Alene Mining District has been going on for over 100 years with a long- term continuation very likely. Mining is presently carried out at depths below the -5000' horizon. As mining continues at ever increasing depths, higher in-situ rock stresses and subsequent rock deformation is encountered making mining costly and hazardous. To provide access for men and materials in such areas, a wooden raise preparation structure is typically built. Although these structures provide adequate support and access, they have proved to be very costly to construct and maintain.

Jan 1, 1986

By W. A. Vine

Next year, in 1964, Butte will celebrate its Centennial. It was in May, 1864, that the first recorded mining activity took place. During that summer, several rich placers were found on Silver Bow Creek and its tributaries, and a gold rush followed. As placer mining proceeded in the creek beds, the quartz lodes on the hillsides were located and the veins were prospected. Mining in Butte entered its second phase when the rich silver mines, the Alice, Moulton, and Lexington, were opened. The silver boom lasted until the decline in the price of silver in the early 1890's forced the closure of many of the mines. An indication of the beginning of the copper mining era in Butte was in 1866 when it was noticed that green copper carbonate discolored some of the, lode material. It was not until ten years later, however, that the Anaconda and St. Lawrence claims were located by Michael and Ed Hickey. The claims were sold in 1880 to Marcus Daly and in 1881, Daly obtained financing and organized the Anaconda Silver Mining Company to exploit the vein The silver venture was a failure because of the predominance of copper which diluted the bullion to only 400 fine.

Jan 1, 1963

By C. I. Basilio

The mechanisms involved in the adsorption of modified thiol-type collectors on sulfide minerals have been investigated in the present work. These collectors belong to the broad classes of thionocarbamates, thioureas, thiophosphates and thiophosphinates. They differ significantly from the traditionally used thiol-type collectors, such as xanthates and dithiophosphates, in terms of structural features that involve either the introduction of an additional oxygen donor or the alteration of electron densities on donor atoms. Electrochemical studies suggest that the adsorption of these classes of collectors is probably the result of a coupled reaction of the EC-type, involving an initial electron transfer step (E), followed immediately by a chemical reaction (C). Thus, the overall adsorption process is controlled by both the E, and pK of the system. The role of structural features in changing the interaction of the donor atoms with sulfide minerals is also discussed.

Jan 1, 1991

By ANDREW HOBERT, Maoming Fan

Low-cost and environment-friendly green froth flotation modifiers of plant origin, such as guar gum, carboxymethyl cellulose (CMC), and starch, have been used in flotation of some sulfide and non-sulfide minerals. Certain green modifiers may be used as dispersants, flocculants, depressants, or activators. The functions of green modifiers in froth flotation highly depend on their molecular composition, flotation slurry chemistry, hydrodynamic conditions, etc. This paper will discuss the fundamentals, current applications, and potential new applications of guar gum, CMC, and corn starch in valuable minerals (phosphate, potash, and iron ores) and the unwanted gangue minerals (silica and clay minerals) flotation. In this study, improved flotation performance was achieved using some green modifiers in flotation columns with the more plug-flow environments than in conventional flotation cells approaching perfectly mixed conditions. This is because the hydrodynamic cavitation-generated ultrafine bubbles could help bridge ultrafine particles to form aggregates, promote the formation of flocs, and increase the stability of flocs.

Jan 6, 2022

By M. Younis, E. Comis

"The success of a tunnel project relies on many factors, but one of the most important is also the most overlooked: coordination by all parties involved during the design stages. This is particularly true of segment design and TBM design. Tunnel lining with segmental rings is usually designed according to the standards of reinforced concrete construction based on a given GBR. However, for TBM tunneling, the determination of loads during ring erection, advance of the TBM, earth pressure, and bedding of the articulated ring are all part of the tunnel lining design as well. TBM design can be heavily affected by the segment arrangement, dimension, and weight, but these are usually given as a fixed input to the TBM manufacturer—a process that can cause unnecessary complications. The authors propose that the industry evaluate the process as it stands. In order to find the optimum balance between lining design and TBM cost and operational workflow, both designs should be finalized concurrently. This requires coordination between the TBM manufacturer and segment designer from the early stages. The aim of this paper is to evaluate the influence of the segment lining design on TBM cost and performance, and to provide commentary on existing design guidelines to optimize lining and TBM procurement. INTRODUCTION The conventional project setup for tunnel lining design and the design and manufacture of the tunnel boring machine (TBM) should be coordinated in a timelier manner. It is widely acknowledged that the design of segments must consider the forces exerted by TBM rams during tunnel construction, but other inputs are most frequently provided to the TBM manufacturer as fixed parameters to design around. This paper describes other important factors in TBM design that impact not only the interaction with the segments, but also the construction of the tunnel in terms of overall production and even safety. For example, the segment width and tapering have direct influence on shield body length and thrust cylinder size. Furthermore, TBM geometry can also affect the backup (trailing gear) layout and length."

Jan 1, 2016

By Edward A. Nowatzki

The purpose of this paper is to present an example of the application of a theoretically derived mathematical model for track-soil interaction to the evaluation of the mobility of large-scale mining equipment used in open pit operations. The model described by Karafiath and Nowatzki (1978) and presented in detail by Karafiath (1978) was used to predict the performance characteristics of four different bucket wheel excavators (BWEs) on rwo types of copper mill tailings at various moisture conditions. The BWEs considered In the analyses are two-and three-tracked continuous excavators. Most have boom-mounted rotating buckets and swinging side- or rear-discharge conveyors. The analyses were performed at the request of Dames and Moore for the Kennecott Corporation's proposed remining of selected tailings deposits at the McGill, Nevada, concentrator. The objectives of the analyses were to determine whether BWEs would have sufficient mobility In the tailings deposit to achieve satisfactory production rates, and TO compare the predicted performance of the various BWEs evaluated. Good qualitative agreement was obtained between the results of the theoretical analyses performed for the McGil1 operation and the actual performance of BWEs in two South African gold mine tailings impoundments.

Jan 1, 1980

By J. D. Miller, C. L. Lin

"The use of 3D X-ray tomography analysis for plant-site characterization of coarse particles at a sampling rate of about 3 kg/min for particles ranging in size from 150 mm to 1 mm at a voxel resolution of about 150 µm is now possible. This is quite a significant advance in X-ray tomography technology and promises to be useful for plant-site coarse particle characterization—size, shape, composition, density, texture, grain exposure and mineral liberation—with a response time of minutes after receiving the sample. This paper discusses applications in the mineral industries, including the coal industry, aggregates industry, metal mining and the processing of industrial minerals.IntroductionPlant-site characterization of coarse particles at coal preparation plants, crushed stone/aggregate plants and mineral processing plants is needed to improve plant capacity, product quality and/or process efficiency. Not much online coarse particle characterization is being done at these plants. Only some limited information regarding particle size is obtained online from reflected light images using analyzers such as the OPSA, Split and WipFrag™ analyzers. Even the laboratory analysis of coarse particles has been difficult because of the large amount of sample required to ensure statistical significance of the results. During the past several decades, laboratory 3D characterization of particles from energy and mineral resources by X-ray tomography has been demonstrated and used to good advantage (Miller and Lin, 2004, 2009).Three-dimensional X-ray tomographic analysis has its origins in the medical services industry, where it is used to provide internal images of the human body. It has since been developed for nonmedical applications as well (Banholzer et al., 1987). Figure 1 shows a schematic diagram of the cone-beam geometry micro-CT system. In our case, X-rays from a microfocus X-ray generator are partially attenuated by the sample (a packed bed of particles) that is made to rotate in equal steps in a full circle about a single axis of the particle sample. At each rotational position, the surviving X-ray photons are detected by a planar two-dimensional array (image intensifier) large enough to contain the shadow of the specimen. These two-dimensional projection images are collected using conventional video technology. The video signal for each projection is then converted to a two-dimensional digital array by an image processing system. Finally, a threedimensional image is reconstructed from the collected set of projection images."

Jan 1, 2016

By Albert Ruiz

The 2,250-MW, coal-fired Navajo Generating Station located in Page, AZ draws water from Lake Powell using submersible pumps installed in five inclined shafts. Drought threatens to lower the reservoir to below the existing intakes. A system of new steel-lined intake shafts located on the same site was required for uninterrupted plant operation. The small size of the site, and the need to keep the existing system in operation, required detailed designs and placed significant limitations on construction equipment and activities. The Navajo Sandstone that forms the near vertical shoreline of the reservoir is 98 percent very fine grained quartz, highly abrasive and contains highly fractured intervals that presented numerous challenges to drilling the new 152-m (500-ft) deep, 109-cm (43-in.) diameter intake shafts inclined 23° to 26° from vertical. Spatial constraints, submersible pump design and operational criteria required that each shaft have a unique inclination and orientation and hit a small breakout target located 76 m (250 ft) under water. Sophisticated drilling equipment and techniques as well as state of the practice downhole survey technology and methods were used to make adjustments and maintain drilling accuracy with less than 1 percent deviation. Environmental requirements mandated water as the drilling fluid and grout was not allowed in to the lake under any circumstances. The shafts were videotaped and the breakout locations were examined using an underwater remotely operated vehicle (ROV) to verify shaft locations and rock conditions, and to guide placement of pneumatic packers to ensure grout did not transmit to the lake during the steel liner installation. In anticipation of the invasion of quagga mussels, the shaft design included an allowance for a chemical dosing system and a copper-rich alloy at the exposed portions of the steel liner.

Jan 1, 2011

By J. A. Herbst

In spite of potential theoretical and economic advantages of large-diameter ball mills, many manufacturers elect not to build these mills owing to what is perceived as an excessively large design risk. This risk results from the fact that traditional predictions for mill-scale-up to large diameters are not always accurate. It is apparent that alternative methods of analysis and scale-up are required. Recent studies have shown that detailed population balance models which account for important grinding subprocesses, i.e., grinding kinetics, material transport, and classification, are capable of predicting the performance of small- and intermediate diameter mills (up to 4.3 m (14 ft)) from small-scale batch tests. These same models are used in the current study to predict the performance of a "borderline" large ball mill (4.7x5.5 m) at Asarco's Sacaton operation, a ball mill (5.0x5.8 m) at Kennecott's Chino operation, and one of the world's largest ball mills (5.5x6.1 m), at Cities Service Pinto Valley operation. Model parameters required for scale-up have been estimated in a 380-mm diameter batch mill. Predictions are compared with the results of detailed plant sampling in the three plants. For the Sacaton and Chino operations, the error of the predictions was found to be less than 2.5%, while the corresponding error for the Pinto Valley operation was less than 2.7%. It is concluded that proper representation of the major subprocesses of grinding in the model equation is the key to achieving accurate scale-up. Of special importance is the need to account for the size distribution of the grinding media and the influence of the size distribution environment in the mill on grinding kinetics.

Jan 1, 1983

By Ken Fucik, Jorge Briceno, Bjorn Bjorkman

In 1993, a lawsuit was filed on behalf ofnative groups in Ecuador against Texaco for environmental damage resulting from petrole­um production activities which had occurred many years earlier. The basis of the lawsuit at the time was that Texaco had failed to perform its foreign activities in the same manner that it operated in the U.S. No environmental regulations were in existence in Ecuador at the time of Texaco's operations. Also in 1993, a lawsuit for over $3 billion Australian was filed on behalf of native New Guineans for alleged environ­mental damages and health impacts that occurred as a result of BHP's operations at its Ok Tedi Mine. Since then, Royal Dutch Shell has been subjected to major criticism for environmental damage caused by its operations in Nigeria. A more recent report has criticized Shell for groundwater contamination of an aquifer in Turkey. Southern Peru Copper is now defending against a lawsuit filed by citizens exposed to air emissions from smelter operations in Peru. In all of these cases, much of the alleged damages occurred many years previous. A defense com­monly made by the companies has been that operations were conducted according to the standards in place at the time. This has not limited the lawsuits nor minimized the international publicity which has followed. While such lawsuits have been common in the U.S. for many years, their appearance in other nations have pointed out a growing sense of worldwide concern with regard to the impacts of industrial operations. Of particular concern is the fact that lawsuits have been filed in countries that have up to now had few, if any, environmental regulations. The regulatory environment has been a part of most U.S. business operations since the early 1970's. Now, however, envi­ronmental regulations are starting to be implemented in many less developed nations. This has led to the formulation of a myriad of standards and approaches to environmental regulation around the world. For multinational companies, the challenge becomes one of anticipating the level of compliance that will be required to minimize liabilities not only for the present but also in the future. The purpose of this paper is to provide some guid­ance with regards to choosing a level of compliance, particular­ly as it applies to water quality.

Jan 1, 1996

By R. B. Elver

The St Lawrence Seaway, a deep-water canal system between Montreal and Lake Ontario, was opened for navigation on April 25, 1959. Prior to the opening of the new Seaway, small boats known as canalers and a few deep-sea carriers, primarily from Norway since World War II, were the only ships able to journey past Montreal into Lake Ontario through the old Canadian St. Lawrence canal system. Thus it was necessary for many tons of bulk and general cargo to be shipped all-rail to and from Atlantic ports or to be transhipped to and from canalers. With the opening of the new Seaway, large Great Lakes bulk carriers and a much larger percentage of the world's shipping fleet are now able to sail directly from the sea to the heart of industrial North America. In this paper, the historical events leading up to the construction of the Seaway and the physical nature of the Great Lakes transportation system are briefly reviewed. Following this, an attempt is made to evaluate the effects of the new Seaway on Canada's mineral industry. Because the Seaway has been in operation for only one season, this paper must be considered only an interim report. Because of the importance of the Seaway to iron ore, this commodity will be dealt with in detail, although the effect on other mineral commodities such as coal, petroleum, nonferrous ores, iron and steel will be mentioned. At this time the author wishes to thank the various company and government officials who provided both factual information and critical opinions.

Jan 1, 1960

By Shi Wang, Hongbin Liu, Meiliang Wei, Wu Liu, Xiaojun Wang, Yuxian Ke, Xuepeng Song, Tiejun Tao

The study investigates the influence of water migration on the fluidity of fresh cemented paste backfill (CPB) with and without flocculant under variable shear rates. The research utilizes nuclear magnetic resonance (NMR), rheological tests, and scanning electron microscopy (SEM) to analyze water migration, rheological properties, and microstructure evolution. The findings reveal that water migrates to more stable states as shear rate increases, and the addition of flocculant enhances water migration and increases shear stress and apparent viscosity. The study establishes relationships between water content and rheological parameters, providing insights into the flow characteristics of fresh CPB for pipeline transportation.

May 4, 2022

By H. Huang, R. N. Gow

"The reactivity of an enargite mineral electrode was investigated spectroelectrochemically under conditions typically found in alkaline sulfide leach solutions, with pH 11-13 and Na2S additions of 50 and 250 gL-1. A bulk enargite electrode was cycled between 0 and -1,000 mV for each set of solution conditions. Raman spectroscopy was used to determine and compare surface formations against species in mass-balanced EH-pH diagrams generated using STABCAL. Previously, it was determined that arsenic could be selectively leached under alkaline conditions at an average solution potential of -300mV, across the pH range 11-13. Operating under such conditions allowed for the selective leaching of arsenic with elemental sulfur formation. From several of the voltammograms obtained during this current testing, the formation of elemental sulfur appeared at increasingly reducing conditions with increasing sulfide concentration. At high concentrations, copper started to dissolve, possibly as a bisulfide complex, reducing the selectivity of the leach, unlike previous studies. However, the presence of the higher sulfide concentration is also anticipated to prevent passivation by consuming any surface formation of elemental sulfur. This study provides insight into the operating parameters of alkaline sulfide leaching in regards to the selectivity of arsenic leaching, as well as guidance for control of reagents and solution potential and, of course, the need for water treatment afterwards.IntroductionEnvironmental limitations on the pyrometallurgical processing of arsenic-bearing concentrates have forced operations to consider other solutions. Attempts to hydrometallurgically process enargite (Cu3AsS4) fall into two categories: the co-dissolution of arsenic and copper under acidic conditions, and the selective leaching of arsenic under basic conditions. The authors believe that the selective leaching of arsenic is more amenable because it produces a solid copper phase, preferably chalcocite (Cu2S) or covellite (CuS) that could then be processed using conventional methods already in place in the copper and gold industries. Potential leaching methods include alkaline sulfide leaching (Achimovicovica et al., 1999; Anderson and Twidwell, 2008a,b; Tongamp et al., 2009 and 2010), hypochlorite leaching (Vinals et al., 2003; Curreli et al., 2005; Mihaljovic et al., 2007), ammoniacal leaching (Gajam and Raghavan, 1983), and acid leaching (Gow et al., 2014b) with or without fine grinding to mechanically activate the enargite surface and increase normally slow leach reaction kinetics (Achimovicova et al., 1999; Balaz et al., 2000; Balaz and Achimovicova, 2006). In this study, the reactivity of enargite under alkaline sulfide leach conditions was examined."

Jan 1, 2015

According to the Balandin's (1) "multiplet theory of catalysis", adsorption can occur only if atoms of the reactant molecules are congruent with surface atoms of the catalyst. Such a condition calls for certain definite geometrical relationships between the reactant molecules and the atoms at the surface of the catalyst. If such a match or geometrical 'fit' is not provided, the surface reaction will not take place. An appropriate analogy to this may be the lock and key theory that enzymes should fit a substrate just as a key fits a lock. Similar geometrical considerations in adsorption studies were made in connection with the flotation of minerals. Gaudin(2) and Gaudin and Preller (3) proposed that if the dimensions of collector ions are in registry with the mineral lattice, an ordered layer of adsorbed species is formed. They explained that the structural fit is one reason for good flotation of galena with xanthate. In another study, Bachmann (4) attributed the selective flotation of KC1 from NaCl with amine to the fact that the lattice parameter of the amine collector is closer to that of KC1. Schubert(5) investigated the flotation of various nonmetallic minerals with amine and pyridine, and related the dimensions of the collector ions with the anion distances of the mineral surface. He concluded that good flotation is obtained when the tolerance is within 20%. The geometrical theory has also been used by Groszek (6) to explain the preferential adsorption of n-paraffin onto the basal plane of graphite. The geometrical theory has thus been found useful in explaining adsorptive properties of an adsorbate relative to the substrate structure. The purpose of the present work is to examine the possibilities of a geometrical fit between sodium dodecyl sulfate and Cu(OH)2 surface, and to construct a crystallographic model of the surface compound.

Jan 1, 1974

By J. Kretschmann

According to the model of product life cycles, the global coal mining industry is in the stagnation phase. The coal demand of the main consumer, China, has peaked in 2013 and is slowly declining. The Norwegian sovereign wealth fund, the world´s largest, has excluded coal-related companies for ethical reasons. Important players like the UN or the EU have already begun to describe pathways towards de-carbonization. Increasing competition between coal mining companies and the mining regions can be expected worldwide if companies want to keep their positions on the global and national coal markets. Companies will focus on the best deposits. European countries like France, Spain or Germany are only forerunners of this development - their centuries of coal production have been finished. The concept of Sustainable Development (SD) is fundamentally based on a model of progress where ecological, economic and social dimensions should be developed equally and positively. But without the idea of competition, the concept of SD is incomplete. Questions arise, such as: How can SD be realized on stagnating or declining markets without guarantees for companies “to live forever”? How can SD be a corporate goal in a phase of decline? How can declining mining regions sustainably progress into a better future? The German hard coal mining industry´s lifecycle has ended in 2018 after 60 years of stagnation and decline. As of 2019, all hard coal consumed in Germany will be imported, especially from Colombia, Russia and South Africa. What has been done in Germany to handle the coal decline in a sustainable way and the lessons learned from this process is described in this paper. It may be useful for mining regions who will face a similar future sooner or later. INTRODUCTION Principally, mining natural resources is a finite business that reaches its limits once the deposits mined are depleted, the resources can no longer be mined in an economically profitable way, or substitutes are pushing the mined products out of the market. An example for the latter is the increasing replacement of coal with natural gas and renewables in power generation in the USA. (Kok 2017) According to the model of the product lifecycle, the global mining hard coal mining industry has reached the stagnation phase. (Kretschmann 2000) Although the coal mining business is more a multi-regional than a global business the trend is obvious. The peak of coal use is behind us, especially because the coal demand of China is slowly decreasing since 2013. (Shell 2018) China´s government has announced investing $360 billion in renewable energy by 2020 and scrap plans to build 85 coal-fired power plants. In March 2018, Chinese authorities reported that the country was already exceeding official targets for energy efficiency, carbon intensity, and the share of clean energy sources. China’s energy regulator, the National Energy Administration, rolled out new measures to reduce the country’s dependence on coal. (Kejun and Woetzel 2017) Coal consumption in the US is facing a 16 % decline in five years from 800 to 670 million short tons between 2015 and 2019 and - according to the EIA – will not rise again. (EIA 2018) The decline is attributed to complex market dynamics from low gas prices because of the “shale gas revolution” (Kok 2017, p. 3) to federal environmental regulation like the Clean Power Plan. The United Nations´ UNEP Finance Initiative is cooperating with the Portfolio Decarbonization Coalition of institutional investors to implement decarbonization strategies across their portfolio. Amongst these investors is the New York State Common Retirement Fund, the third largest public pension plan in the USA. (UNEP 2017) The European Union has already begun to de-scribe pathways to decarbonization. (European Union 2018) The Norwegian sovereign wealth fund, the world´s largest, excluded coal-related companies for ethical reasons. The oil giants Total S.A. and Royal Dutch Shell, tradi

Jan 1, 2019

By Madhu G. Ranade

A statistically designed pot grate- kiln test program was conducted to determine the agglomeration process variables necessary for increasing the low temperature disintegration resistance (LTD) and reducibility (R40) of magnetite-based Empire acid pellets. The ASTM tumble index and compression strength were to be maintained at an acceptable level. Six process variables, bentonite addition level, preheat time and temperature, firing time and temperature, and cooling rate, were investigated within the constraints of the Empire plant. The bentonite addition level and firing temperature had the largest effect on pellet properties. The results of this program were verified during a pl ant trial. The target firing temperature at the Empire Plant has been decreased for increasing the LTD and R40 of commercially produced Empire pellets

Jan 1, 1985