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By A. Noble, R. Q. Honaker, J. Werner

Recovery of rare earth elements (REE) from coal-related resources has recently received significant interest due to supply concerns and their key roles in critical industries and defense-related technologies. An integrated flowsheet consisting of sorting, crushing/grinding, physical separation, acid leaching, solvent extraction, and selective precipitation was designed to achieve continuous production of rare earth products from various coal-related resources such as coarse refuse and acid mine drainage. A pilot plant was constructed that enabled continuous testing of the circuitry on a range of different coal-based feedstocks. Despite achieving significant success in producing high-grade rare earth oxide products, low REE recovery values and high operational costs necessitated a re-evaluation of the process flowsheet. This article describes the circuitry improvements that were based on both laboratory and pilot plant test results. Roasting as a pre-leach treatment was found to significantly improve the leaching rate and overall REE recovery values. After roasting West Kentucky No. 13 and Fire Clay coal refuse materials at 600 °C, REE recovery increased by 60 and 40 absolute percentage points, respectively. Rare earth concentration in the pregnant leachate solution (PLS) was increased to around 700 ppm prior to solvent extraction using a staged precipitation method. REEs in the precipitate were re-dissolved, purified, and extracted from the PLS using solvent extraction and selective precipitation to values of around 80%. As a result of the improvements, chemical consumption in the acid leaching and solvent extraction processes was significantly reduced. A techno-economical assessment of the improved flowsheet indicated significant commercialization potential.

By Chen Lin

Tectonic stress is an important parameter for understanding the dynamics of underground engineering and for the exploitation of coalbed methane. Multiple-period structural features usually have complex spatial relationships in tectonic superposition areas, which provides evidence for identification of the sequence of the tectonic stress period. Conjugated joints and slickensides are used to reconstruct the tectonic stress of the No. 8 Mine in Pingdingshan. Based on the geological unit division and field measurements, data on hundreds of joints and slickensides are collected from 33 stations. The tectonic stress results indicated by the conjugated joints show that there are mainly four directions of tectonic stress: NEE-SWW, NW-SE, NE-SW, and NNESSW. The tectonic stress results of the slickensides indicate that there are mainly four directions of tectonic stress: NNE-SSW, NNW-SSE, NEE-SWW, and NW-SE. According to the systematic analysis of the joints and slickensides, this paper separates the superposed joint and slickenside sets and identifies the tectonic stress periods with their abutting relationships. Three tectonic stress periods are determined and the sequence of the tectonic stress periods is NE-SW, NW-SE, and NEE-SWW. The results are consistent with other tectonic stress measurements for both the region and the locality.

By Chen Lin

Tectonic stress is an important parameter for understanding the dynamics of underground engineering and for the exploitation of coalbed methane. Multiple-period structural features usually have complex spatial relationships in tectonic superposition areas, which provides evidence for identification of the sequence of the tectonic stress period. Conjugated joints and slickensides are used to reconstruct the tectonic stress of the No. 8 Mine in Pingdingshan. Based on the geological unit division and field measurements, data on hundreds of joints and slickensides are collected from 33 stations. The tectonic stress results indicated by the conjugated joints show that there are mainly four directions of tectonic stress: NEE-SWW, NW-SE, NE-SW, and NNESSW. The tectonic stress results of the slickensides indicate that there are mainly four directions of tectonic stress: NNE-SSW, NNW-SSE, NEE-SWW, and NW-SE. According to the systematic analysis of the joints and slickensides, this paper separates the superposed joint and slickenside sets and identifies the tectonic stress periods with their abutting relationships. Three tectonic stress periods are determined and the sequence of the tectonic stress periods is NE-SW, NW-SE, and NEE-SWW. The results are consistent with other tectonic stress measurements for both the region and the locality.

By K. Kohli

A case study involving a historic structure undermined by longwall mining is presented in this paper. The location of this study is in South Western-Pennsylvania; USA. The structure is 150-years old and subsided 4.5 feet. This paper discusses the mitigation measures taken to reduce the subsidence damage and its effectiveness.

Jan 1, 2002

By Wern-ping Chen

Technical and non-technical challenges exist in each mega infrastructure project. It?s no exception to the first US underground PPP Port of Miami Tunnel (POMT) project in Miami, FL. The POMT will connect two man-made islands, the Dodge and the Watson Islands, under the Biscayne Bay within highly porous limestone formation. Permeability as high as 0.1 cm/sec has been identified. Its 41-ft outside diameter, if constructed, is the largest precast segment lining in the US. Besides its geological and hydro geological challenges and risks, local community influence and impacts have controlled the fate of this project. This paper describes its tender design enhancements and the evolving of its slow advancement in resolving local community issues.

By Franco Oboni, Iain G. Bruce

The design of tailings containment structures relies on well-understood engineering methods being applied consistently. Unfortunately, not all facilities are designed or managed to the same level of competency. To standardize procedures, the Mining Association of Canada (MAC, 1998) prepared a “Guide to Tailings Management.” It recommended review of designs and an assessment of the risks associated with tailings impoundments be implemented during all phases of amine life. This paper describes how the quantitative risk assessment (QRA) process can be used to define risks associated with the design, construction and operation of a tailings management facility. And it discusses how, once the risk tolerability curves (RTC) are defined for a project, they can assist the risk management (RM) process.

Jan 1, 2002

By Andrea Koschinsky, Peter E. Halbach, Margret Halbach, Andreas Jahn

"Ferromanganese crusts contain hydrous Mn and Fe oxides as main metal compounds together with some economically interesting minor elements such as Co, Ni, Ti and Cu and trace metals such as Mo, W, Nb, Te, Ga, Pt, and REEs. Some of these metals or semimetals have a great future potential as innovative high-technology constituents. All of them are highly enriched in the crusts compared to seawater composition.The Mn in the crusts mainly originates from the O2 - minimum zone in the oceanic water column. The agent for Mn2+ oxidation is dissolved oxygen, transported upwards from colder deep water layers by turbulent eddy diffusion. The Mn itself descends from surface waters and is carried down to the O2-minimum zone by fecal pellet transport. In contrast, Fe is mainly supplied from carbonate dissolution of planktonic skeletons in the water column. These relationships result in the fact that the oceanic water depth strongly controls the metal composition of ferromanganese crusts: the Mn - group metals are more enriched in shallower water, whereas the concentration of the Fe - group metals increase with water depth. The REEs play a very important role with regard to the trace metal composition of the crusts: their concentrations increase with water depth mainly controlled by a decreasing Mn/Fe ratio.In seawater, REEs occur as carbonate complexes; preferably, the light rare earth elements (LREEs) form REECO3 +(aq) and the heavy Rare Earth Elements (HREEs) REE(CO3)2 (aq) complexes. The REEs are transition metals, their 6s orbital of the outermost shell is filled before the filling of lower 4f electron shells is completed, thus the configuration of the valence electrons is similar in all the REEs, and all REEs exhibit similar chemical behavior and exist, dominantly, as 3+ cations. The ionic radius decreases progressively from La3+ (1.18 Å) to Lu3+ (0.97 Å), this phenomenon is called "lanthanide contraction". Due to the fact that REEs in seawater form cationic and anionic carbonate complexes, the two main hydrogenetic constituents, hydrous !-MnO2 and Fe-oxyhydroxide, fractionate the group of REEs by surface absorption processes. According to the pHZPC-concept the ?- MnO2 phase has an electronegative surface, and Fe-oxyhydroxide a slightly positive surface charge at seawater pH. These relationships are the main reason for the observed REEs fractionation."

Sep 1, 2014

By A. Arik

An accurate estimation of mining block grades continues to be a challenging task for ore reserve practitioners. Two of the factors that affect the accuracy of the estimates are the estimation method used and the variability of the mineralization in the deposit. The objectives of the study are twofold: Firstly, to see how different estimation methods perform on a given deposit. Secondly, to determine the impact of particular nature of the mineralization on the results. The comparison of several estimation methods for the prediction accuracy is performed using the conditional simulation results as the basis.

Jan 1, 2000

By Debasis Deb

The first version of the longwall strata control and maintenance system (LSCMS) has been successfully developed by the Strata Control Re¬search Team at the University of Alabama. The system includes a software package designed to monitor shield leg pressure, interpret the data and predict the forthcoming roof loads and the existence of geological anomalies. It can also detect maintenance problems of the face equipment. The LSCMS was installed underground and connected to the surface terminals at Drummond's Shoal Creek Mine in Alabama. The system has proven to be a useful and practical system for improving safety and efficiency in coal-mining operation. The Shoal Creek Mine is a new, large coal mine operated by Drummond with two longwall panels. The Blue Creek seam is the primary source of coal production. It is located at a depth of 275 to 440 m (900 to 1,450 ft) below the surface with an approximate 2% southwest dip. Typical strata conditions are represented by two stratigraphic columns (Figs. la and b). A fireclay/dark shale parting (called Middleman) 0.2- 0.7-m- (1- to 2.5-ft-) thick exists between the Mary Lee and Blue Creek seams. Mining conditions vary from area to area. This mainly depends on the Blue Creek seam thickness that ranges from 0.9 to 2.9 m (3 to 9.5 ft). The thickness of the Mary Lee and the parting is relatively consistent with a to¬tal of 0.9 m (3 ft). They are mined when the Blue Creek seam becomes thinner. In most of the panels, the immediate roof is composed of sandy shale 1.5-

Jan 1, 1997

Oil sands processing generates huge volumes of slurry, known as tailings, that is being stored in tailings ponds. The volume of produced tailings is a very important factor in oil sands surface mine planning, because the available area for dam construction is limited to the lease areas. On the other hand, oil sands operators cannot leave mine sites without reclaiming the tailings ponds. Since most of the reclamation material is generated in either oil sands mining or processing, it is reasonable to include reclamation material requirement as part of long-term mine planning. In this paper, an integrated optimization framework is proposed to maximize the net present value (NPV) of the produced oil sands, with respect to tailings capacity constraints and reclamation material requirements. A mixed integer linear programming (MILP) model is developed to find the optimal solution for long-term mine planning problem. A sample bitumen processing flow sheet is used to formulate the volume of produced tailings, based on Clark hot water extraction method. To verify the proposed model, it is coded in Matlab and run using CPLEX. Run results for real-case oil sands dataset show that the optimal production schedule meets material requirements for reclamation, tailings volume is within tailings capacity range in all periods and the production schedule follows the predetermined horizontal direction.

Feb 27, 2013

By Takuji Yamamoto

High-speed TBM excavation requires rapid ground assessment ahead of excavation, particularly in complex grounds. The Tunnel Reflector Tracing technology (TRT) developed by authors, uses seismic reflections to produce volumetric images of ground anomalies. To further minimize interruption in the TBM excavation the authors modified surveying technique switching from cable (wired) to radio (wireless) data acquisition system. This paper presents the outline of the Wireless TRT system, and compares the results for the wired and the wireless surveys. The comparison shows that the wireless system offers high precision data, is more efficient and economical and significantly less intrusive in tunneling operations.

By Luke Erickson

San Francisco Public Utilities Commission is planning to replace 5 miles of pipeline under San Francisco Bay. The tunnel will be constructed using an Earth Pressure Balance (EPB) TBM and will be the first TBM-driven tunnel under the Bay. The alignment passes under environmentally sensitive habitats, through interbedded layers of sands and clays, and through a buried bedrock ridge. This paper discusses the geotechnical characterization and anticipated tunneling conditions and presents the analysis of various construction methods that resulted in the selection of an EPB TBM. Considerations related to tunneling with an EPB TBM are described in detail, including ground conditioners, TBM cutterhead wear, muck control, and squeezing ground.

Jan 1, 2008

By L. Yuan, A. Smith

In order to provide insights for the optimization of ventilation systems for U. S. underground coal mines facing both methane control and spontaneous combustion issues, a computational fluid dynamics (CFD) study was conducted to model the potential for spontaneous heating in longwall gob areas. A two longwall panel district using a bleeder ventilation system was simulated. The permeability and porosity profiles for the longwall gob were generated from a geotechnical model and were used as inputs for the CFD modeling. In this study the effect of methane emissions from the mined coal seam, including the longwall face and overlying rider seam reservoirs on the gob gas distribution was considered. The spontaneous heating is modeled as the low-temperature oxidation of coal in the gob using kinetic data obtained from previous laboratory-scale spontaneous combustion studies. Unsteady state simulations were conducted and the effects of the coal’s apparent activation energy and reaction surface area on the spontaneous heating process were also examined. Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.

Jan 1, 2007

By D. W. Partridge, W. Lamb, A. E. Lamb, S. Bird

Due to the constant need to improve SAG mill performance and efficiency, extensive research into all aspects of SAG mill optimization has been performed. This paper will review the current evolution of SAG mill shell liner design and their performance at the Copperton Concentrator. The effect of these liner design changes will be discussed with respect to: • Liner configurations • Mill operating performance, i.e., throughput, power draw, mill control • Mill mechanical performance, i.e., liner wear profiles, liner life, liner breakage, liner hardness • Foundry manufacturing considerations • Economic evaluation of throughput versus liner life This paper will discuss the results of Kennecott Utah Copper’s (KUC) and ME International’s (MEI) test work, providing an insight into the past, present and potential future opportunities of SAG mill liner design.

Jan 1, 2002

By Evangelos Petrakis, Kostas Komnitsas

This study investigates the evolution of dimensional properties of grinding products, namely, the mass, the surface area, the length, and the number of particle distributions with the energy input in a ball mill. The size analysis of the mill products enables the calculation of the mass distribution of each material at predetermined size classes and then the determination of the other dimensional properties by taking into consideration the geometry of the particles. Based on the distribution of dimensional properties, an effort was made to determine whether the grinding products are fractal in nature. The effect of material type and grinding conditions on the relationship between the dimensional properties and the specific energy input was also investigated. Special importance was assigned to the study of the specific surface area and the surface area production rate, both during the initial grinding stages and at higher energy levels. The determination of the surface area production rate allows the identification of the grinding limit and the maximum specific surface area which could theoretically be achieved. This approach has as ultimate objective the maximization of energy efficiency and subsequently the minimization of the high grinding cost.

By Evangelos Petrakis, Kostas Komnitsas

This study investigates the evolution of dimensional properties of grinding products, namely, the mass, the surface area, the length, and the number of particle distributions with the energy input in a ball mill. The size analysis of the mill products enables the calculation of the mass distribution of each material at predetermined size classes and then the determination of the other dimensional properties by taking into consideration the geometry of the particles. Based on the distribution of dimensional properties, an effort was made to determine whether the grinding products are fractal in nature. The effect of material type and grinding conditions on the relationship between the dimensional properties and the specific energy input was also investigated. Special importance was assigned to the study of the specific surface area and the surface area production rate, both during the initial grinding stages and at higher energy levels. The determination of the surface area production rate allows the identification of the grinding limit and the maximum specific surface area which could theoretically be achieved. This approach has as ultimate objective the maximization of energy efficiency and subsequently the minimization of the high grinding cost.

By Paul D. Tomlingson

During the next several months, SME’s E-Newsletter will feature 15 articles on maintenance management. The articles may be read online or downloaded and distributed within your organization. They will address maintenance management topics, offer guidelines to mining managers and provide techniques that the maintenance manager can use. The articles will stress equipment management, a strategy that the mining industry has accepted as a modern replacement for outdated maintenance practices. Equipment management is the mutually supportive interaction of all mine departments as they establish equipment needs, procure equipment, test, commission, operate, maintain, modify and eventually replace equipment. The successful application of equipment management principles can quickly and reliably produce cost reduction and performance improvement results while providing a dependable way of sustaining them. Equipment management embraces modern management techniques. These include reliability-centered maintenance, life-cycle costing, capital performance, the effective use of information and productive organizational models.

Jan 1, 2003

This study was conducted to establish the effects of a diesel particulate filter (DPF) system with sintered metal substrate on the concentrations and size distributions of nano and ultrafine aerosols and concentrations of nitric oxides in underground mine air. The study focused on the formation and transformation of nucleation mode particles in mine air under prevailing test conditions. Experimental work was conducted in the NIOSH Diesel Laboratory at the Lake Lynn Laboratory experimental mine, a facility developed to allow evaluation of control technologies directly in underground conditions. The DPF system was examined for four repeatable steady-state engine modes using a naturally aspirated mechanically controlled Isuzu C240 diesel engine fueled with ultralow sulfur fuel. The engine coupled to an eddy-current dynamometer was operated in the underground drift with tightly controlled ventilation. Measurements upwind and downwind of the exhaust system discharge were used to quantify the effects of the DPF system on the mine air. A baseline was established using a standard muffler. The study showed that sintered metal DPF systems reduced the total mass of aerosols in the mine air by more than ten-fold when compared to a muffler. The nucleation mode aerosols (50dem<40 nm) in mine air were found to be strongly influenced by engine operating mode. The concentration of nucleation mode aerosols was found to be significantly higher for high-load modes than for low-load modes. The muffler and DPF system resulted in comparable total nitrogen oxides (NOx) concentrations. However, the nitrogen dioxide (NO2) fraction of the total NOx was found to be substantially higher for both systems for low-load modes than for high-load modes.

Jan 1, 2009

By Steve Kral

Worker safety is an issue that transcends industries, whether it be mining, construction, manufacturing or even general office work. In the mining industry, safety and training are particularly important because mining is a dangerous occupation. Throughout the years, federal and state safety regulations have been written and revised to keep up with the changing technologies. And mine operators have installed their own safety and training programs. They have come to realize that a safe and healthy workforce has positive effects on productivity and profitability —not to mention avoiding the high costs of injury-related absenteeism.

Jan 1, 2003

By M. T. Ansari

"This article explains the ways in which investment on mining infrastructure is a geopolitical issue. It discusses the effect of installing sufficient infra structure to get the product to the world market, and argues that there is a risk involved in depending on traditional suppliers who wish to invest in the infrastructure. It explains how to make a distinction between dedicated purpose infrastructure and general use infrastructure by examining the positions of the main actors in mining projects. It argues that these positions can not be understood as analogous to projects in developed countries. To conclude, infrastructure is a crucial link in the supply chain to market but the relative size of such projects in relation to the economy means that investors decisions in developing countries have quite different implications from those in developed countries."

Jan 1, 2011