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By Fahimeh Dehghani, Louis Ackah, Tathagata Ghosh, Justin Godbold, Jia Liu, Meisam Peiravi, Manoj Mohanty, Azam Baharlouei

Primary economical deposits of rare-earth elements (REEs) are exhausting all over the world, and it has become necessary to find new sources and methods for their extraction. In addition, increasing the application of REEs in modern technological society has increased its demand globally. One of the important movements to compensate for the future shortages of critical metals is the recovery of REEs from recyclable materials. This paper presents a review of the classification and extraction methods, as well as general applications of REEs with emphasis on secondary sources such as coal and coal byproducts, iron ore tailings, apatite, and phosphate byproducts. An overview of the current state of knowledge on the various methods of REE beneficiation and extraction is covered. These methods include physical separation, as well as hydrometallurgical and bio-hydrometallurgical techniques. The application of these REE extraction techniques for enhanced recovery has been driven primarily by the unique industrial application of these important elements. This paper further explores the existing and potential environmental challenges associated with REE extraction. The authors have presented a wide array of literature, in-depth discussion of the subject, and a succinct summary of processes and relevant case studies.

Sep 23, 2020

By Ray Hutton, Darrell Liebno, Taro Nonaka

Background Population growth and increasingly stringent regulatory controls on water quality across North America have resulted in municipal governments investing heavily in infrastructure to control what are known as Combined Sewer Overflows (CSOs).These are events which occur when combined sewers exceed their conveyance capacity during periods of heavy rainfall or snowmelt. The city of Atlanta, Georgia is one such municipality; with a population of over450,000 within city limits and a sewer system servicing 1.2 million including adjacent jurisdictions, the City of Atlanta has a Combined Sewer System (CSS) encompassing approximately 15% of its total 3,540 km (2,200 miles) of sewers. Atlanta’s CSO discharges to local watercourses began to draw fire from environmental groups in the1980s. As a result, in the early 1990s, the City constructed a series of CSO control facilities which provided screening and chlorination at seven CSO discharge points across the CSS watershed. Unfortunately, these facilities were not capable of handling all of the overflows generated due to heavy storm events; frequently, untreated water was bypassed around the treatment facilities. The federal Environmental Protection Agency (EPA) deemed that water quality standards were being violated by these discharges, and a suit was brought against the City to force a higher standard of compliance. As a result, the City entered into a federal Consent Decree which would bring CSOs into compliance with federal standards by 2007. A critical component of this plan was the design and construction of the West Area CSO Tunnels and Pumping Station. In February 2003 the City’s Department of Watershed Management retained the services of Jordan Jones & Goulding/Hatch Mott MacDonald/Delon Hampton Associates (JDH Joint Venture) to design and provide construction management ser-vices for the project, which was designed to capture combined sewage from three of the City’s existing CSO facilities on the northern end of the CSS watershed. The design consisted of two connected tunnels which would convey the wastewater originating from the North Avenue, Clear Creek, and Tanyard Creek CSO facilities to a submersible wet well pumping station located at the R.M. Clayton Water Reclamation Center (WRC). Since the majority of the effluent stream consisted of storm water, the City elected to design and construct a separate treatment plant. This plant was designed under a separate contract, and is currently under construction.

Jan 1, 2007

By E. Bakhtavar

All parameters influencing the decision for selection of a suitable extraction method were first selected as the base of this study. Then these parameters were categorized in two main groups. The first group of the parameters includes ?geomechanical and inherent characteristics of the dimension stones? such as hardness, RQD, compressive strength, joints plane orientation and spacing, and water content. The second group was named ?technical and economical parameters associated with the investor?s objectives? like for example extraction capacity (production rate), blocks recovery, mechanization, capital investment and operational costs. Finally, the influences of all mentioned parameters on the selection of the most applicable extraction methods have been assessed and discussed.

Jan 1, 2012

By K. M. Mohamed, R. K. Zipf

The shear strength properties of generic cement foam material and cement foam/concrete interfaces were examined at three testing scales. In laboratory direct shear tests on specimens with average shearing area of 0.006 m2 (10 in.2), the cement foam material had average peak and residual shear strengths of 0.88 MPa (128 psi) and 0.39 MPa (56 psi), respectively. Depending on the concrete strength, the cement foam/concrete interfaces had peak and residual shear strengths ranging from 0.71 to 0.81 MPa (103 to 117 psi) and from 0.27 to 0.29 MPa (39 to 42 psi), respectively. In laboratory direct double shear tests on specimens with average shearing area of 0.084 m2 (130 in.2), the cement foam/concrete interfaces had average peak and residual shear strengths of 0.17 to 0.30 MPa (25 to 44 psi) and of 0.11 to 0.23 MPa (16 to 33 psi), respectively. In large shear tests of simulated cement foam seals with the Mine Roof Simulator (MRS) test frame, cement foam/concrete interfaces with shearing area of 1.486 m2 (2,304 in.2) had average shear strengths of about 0.08 and 0.16 MPa (11 and 23 psi) along the roof and floor interfaces, respectively. The average shear strength through the cement foam material was 0.38 MPa (55.3 psi). Finite element analysis of the large seal tests and the back analysis of the shear strength of full-scale cement foam seals conducted at the NIOSH Lake Lynn Laboratory confirmed shear strength of about 0.14 MPa (20 psi) along the seal/rock interfaces. The study concluded that the structural analysis of cement foam seals should be based on their residual shear strength determined from small laboratoryscale tests of the cement foam/concrete or rock interface and not be based on their peak strength.

Jan 1, 2014

By Keros Cartwright

Sanitary landfilling has become one of the most widely used methods of disposing of solid refuse. A principal concern of regulatory agencies and the public itself is that landfill operations do not degrade the physical environment, including water resources, and the ground-water reservoir in particular. Ground-water and engineering geology can guide landfill operations into suitable terranes or develop measures to compensate for any natural limitations at a particular site Experience and research in Illinois suggest four activities relating to landfill disposal that warrant attention by geologists and engineers: (1) Regional delineation of favorable and unfavorable hydrogeologic conditions to facilitate planning and preliminary screening of potential landfill sites. (2) Site evaluations, with considerations of geologic materials, topography, water levels, flow systems, and local occurrence and use of water resources. (3) Re- search on aspects of the hydrogeologic environment that control effects of, or are modified by, landfills. (4) Formulation of practices in the siting, construction, and operation of landfills that prevent, mitigate, or isolate deleterious effects. The first two activities are basically in the domain of earth science, requiring the application of fundamental concepts of geology and hydrology and conventional site-exploration methods. The third activity, research, requires contributions from geology as well as other disciplines, including soil physics, sanitary engineering, and chemistry. The fourth calls for policy decisions by regulatory agencies and elected officials, using the contributions of scientists and engineers.

Jan 1, 1970

By W. Burger

In underground mines worldwide, a large number of short and small diameter slot holes need to be excavated. Herrenknecht has developed and built a new boxholeboring machine based on the well-proven Microtunnellingpipe jacking technology. The innovative Boxhole Boring Machine significantly increases work safety and requires only minimal drift dimensions. The high and consistent production rates that can be achieved result in enormous time savings compared to conventional drill and blast excavations. GENERAL ASPECTS In gold, copper and ore mines ventilation shafts are required to prepare block caving operations, to discharge ore onto the transportation level and to provide evacuation shafts. A high level of occupational safety and efficiency is the main objective when drilling vertical or inclined shafts. The faster and more safely shafts can be constructed, the earlier the actual production in the mine can start or be continued. Mechanized or conventional methods (drill&blast) that have been used to date only partially meet the required safety standards and fail to provide the requested production rates.

Jan 1, 2012

By M. A. Raza

Cable shovels are capital-expensive and primary production equipment in many surface mines. The forces acting on the shovel dipper vary as the dipper moves through the muck-pile. The variations in the forces cause stress loading of the components of shovel and dipper resulting in unplanned downtimes, reduced shovel efficiency, and high mining costs. A potential solution to the above problems is the deployment of an intelligent shovel excavation (ISE) technology, with real-time formation identification, recording, and knowledge transmission capabilities. This research advances the ISE technology by developing dynamic model of cable shovel dipper using Newton-Euler techniques. The model includes the dynamic cutting and dynamic weight forces acting on the dipper as it moves through the muck-pile.

Jan 1, 2011

By D. Hopkins, D. Türler, R. D. Giauque, W. B. Davis, M. Karaca

In a highly collaborative research and development project with mining and university partners, sensors and data-analysis tools are being developed for rock-mass characterization and real-time measurement of mineral content. Determining mineralogy prior to mucking in an open-pit mine is important for routing the material to the appropriate processing stream. A possible alternative to lab assay of dust and cuttings obtained from drill holes is continuous on-line sampling and real-time x-ray fluorescence (XRF) spectroscopy. Results presented demonstrate that statistical analyses combined with XRF data can be employed to identify minerals and, possibly, different rock types. The objective is to create a detailed three-dimensional mineralogical map in real time that would improve downstream process efficiency.

Jan 1, 2002

By M. E. Smith

Waste rock dumps, tailings impoundments and spent leach heaps are common features at mine sites. Many of these waste disposal facilities contain sulfide-rich minerals, which generate acid mine drainage (AMD) when they oxidize. Control of AMD can be achieved by removing one or more of the three essential components in the acid-generating process (sulfides, air, or water). One AMD prevention measure is to cap the waste with an engineered cover system to minimize the infiltration of water and diffusion of air into the system. Possible cover designs include: ? Earthen ?store-and-release? covers (also known as evapotranspiration (ET) or water balance covers), including capillary barriers. These covers require climate conditions where there is both modest to little rainfall and significantly greater evapotranspiration than precipitation, both annually and seasonally. ? Low-permeability compacted clay liners (CCLs) employing fine-grained soils typically compacted at wet of optimum water content. ? Geosynthetic composite covers, comprised of a geomembrane liner placed over and in direct contact with either a CCL or a geosynthetic clay liner (GCL). These systems have been commonly used for base liners for leach pads as well as covers and base liners at municipal solid waste (MSW) landfills in the US for more than 20 years. Comparisons of these different cover systems, both in terms of performance and cost, are presented later in this paper. First, however, a review of the typical mine closure approaches, and the possible rationale behind them, is warranted.

Feb 27, 2013

By G. L. Mowrey

One critical element of the U.S. Bureau of Mines (Bureau) autonomous mining research program is the development of a reliable coal interface detection (CID) system. Several candidate CID concepts currently being investigated by the Bureau include vibration, passive infrared, radar, and natural gamma radiation (NGR). To establish which CID sensor technologies need to be developed for a given seam, coal and adjacent rock samples (i.e., immediate roof and floor) are being collected from selected major coal seams in the U.S. and are being analyzed in terms of NGR and other geophysical measurements. Results of the NGR measurements indicate that, in general, all shale and shale-like materials (e.g., drawslate, slate, and fireclay) have higher NGR readings than the coal seam. Consequently the NGR method appears to be a potentially useful CID tool, provided that the immediate roof and floor are both composed of a high percentage of shale-type material.

Jan 1, 1990

By Brenton Cook, Nate Long, Larry Applegate, Aaron K. McCain

"The Northgate Link Extension project is the third phase of the Sound Transit master plan to extend light rail throughout the greater Seattle metropolitan area. When completed, the Northgate Link Extension will extend the existing light rail system north by about 7 km (4.3 miles) from the University of Washington to the Northgate neighborhood. A general overview of the project alignment is provided as Fig. 1. The project was funded by a combination of federal grants and allocations from local taxes. The general contractor on the project was JCM Northlink LLC (JCM), a joint venture between Jay Dee Contractors, Frank Coluccio Construction Company and Michels Corp. SoilFreeze, Inc. was retained as a subcontractor to provide ground freezing design and construction services.The project involved the construction of two parallel 5.5-m, 25-cm (18-ft, 10-in.) (inside) diameter tunnels using earth pressure balance (EPB) tunnel boring machines (TBM) and precast segmental concrete tunnel liners. The two tunnels maintained roughly the same elevation along the alignment and were spaced roughly 12 m (40 ft) apart (centerline to centerline). A total of 23 cross-passages connecting the two tunnels were included at approximate 244-m (800-ft) intervals. Cross passage excavations were elliptical in shape with dimensions of approximately 5.6 m (18.5 ft) in height and 5.3 m (17 ft) in width. The cross-passages were 5.8 to 6.1 m (19 to 20 ft) long as measured between the exterior of the tunnels at springline elevation. Cross passages were intentionally located directly beneath public right-of-ways thus avoiding buildings. Many of the cross passages were located beneath narrow roads in residential neighborhoods with mature vegetation, existing utility structures and piping and limited parking areas. Excavation and support for each cross passage was completed using the sequential excavation method (SEM).The subsurface soil and ground water conditions at the cross-passage locations were described in the Northgate Link Geotechnical Baseline Report (GBR) prepared by Jacobs Associates and the Northgate Link Geotechnical Data Report (GDR) prepared by Shannon and Wilson, Inc. Soils along the project alignment were glacially overridden and characterized as very dense or hard. Subsurface soils consisted of cohesionless sand and gravel (CSG), cohesionless silt and fine sand (CSF), cohesive clay and silt (CCS) and till and till-like deposits (TLD)."

Dec 1, 2018

By Frank H. Buchella

Principal factors influencing equipment selection can be grouped into five basic categories. Tonnage Requirements, Ore and Waste Loading, transporting, and ground preparation equipment are largely determined by tonnage requirements. Generally, the greater the tonnage requirements, the larger the equipment size selected. Large size equipment is appropriate for a production of about six million tons (total) per month, medium size for three mil- lion tons, and small size for one million tons or less.

Jan 1, 1973

By J. D. Miller

Contact time during bubble/particle collision is calculated by taking into considera¬tion the effect of bubble and particle motion, buoyant force, bubble size, and particle size and specific gravity density for different cases of collision. From this motion analysis approach for the prediction of contact times and from bubble attachment-time measurements,, fundamental aspects of flotation such as flotability, kinetics, and separation can be explained and are discussed with respect to the effects of bubble/particle motion, bubble size, particle size, and attachment time.

Jan 1, 1987

By Mehmet Guney

Acceptable working environments in production areas and service openings of Mindola Mine on the Zambian Copperbelt are currently maintained with an air volume of 1000 cu m/s and 5500 kW of installed refrigeration plant. It is planned to open up additional deeper areas of the mine for future production. Temperature problems, due to the increased heat generation from various underground sources are recognized as potential hinderances to efficient production. Findings of research work indicate that the present total heat output of 58,000 kW will inevitably increase by the second five-year period of the deepening program to 52,900 kW and by the fifth five-year period to 63,200 k\V. Estimated WB and DB temperatures, representing the total heat generation in stope faces and development headings during these same periods are predicted to increase to 53.8/40.2 °C and 35.5/42.1 °C respectively. It is assessed that the nominal refrigeration capacity needs to be progressively increased to 9,000 k\V This paper deals with the thermal problems in Mindola Mine, current heat output calculations, future prediction of temperature and heat load in various working areas of the mine with the application of computer programs and interpretation of data in order to find the effective solution for long-term planning of ventilation and air-conditioning.

Jan 1, 1982

By Choon K. Quan

Subsidence is a surface manifestation of the underground development and exploitation of minerals, and its impact on the environment is becoming of increased concern, particularly in the face of an accelerating demand for energy and minerals. In the United States, the state-of-the-art in subsidence prediction, control, and prevention and in subsidence-related damage abatement has not progressed to the level achieved in other countries. To bridge this gap, the Bureau of Mines, through its Mining Environmental Research program, is pursuing a comprehensive subsidence investigation, specifically designed to address major problems on the local, regional, and national level.

Jan 1, 1979

By Julian Prada

Tunneling requirements are presenting designers with greater challenges. The design and construction of the 2000-ft long unidirectional twin highway tunnels for the approach to one of two bridges of the Louisville-Southern Indiana Ohio River Bridges (LSIORB) Project is no exception. Excavation under low cover, beneath an historic site, with each tunnel of 70-feet wide and 50-feet high dimensions will set precedents for US highway tunnel excavation size. To investigate ground conditions to supplement final design of the highway tunnels, an exploratory tunnel excavated through karstic limestone and shale will be located within the confines of the proposed final alignment. With the LSIORB Project, Jefferson County, Kentucky and Clark County, Indiana will have improved cross-river mobility between them. The Indiana Department of Transportation (INDOT) and the Kentucky Transportation Cabinet (KYTC) are developing the LSIORB Project jointly, in coordination with the Federal Highway Administration (FHWA). Section 4, one of six sections, as shown in Figure 1 is the East End Kentucky Approach and Connections to I-265. Key elements of Section 4 are the twin three-lane highway tunnels under the historic Drumanard Estate. The property is located on the north side of US Highway 42 (US 42) at the intersection with the Gene Snyder Freeway (also KY841) as shown in Figure 2. One aspect of the project consists of the excavation of an Exploratory Tunnel along the southbound alignment tunnel. At the time of preparation of this paper, KYTC has not awarded the Exploratory Tunnel Contract. This paper will focus on the planned geotechnical investigation program that will occur during excavation of the exploratory tunnel and how the design of the twin highway tunnels will incorporate the findings to achieve an innovative and efficient configuration.

Jan 1, 2008

By Paul Bartos

Operations at the Sweet Home Mine transformed the mineral specimen industry, not only in the development of new innovative extraction techniques, but also in the fields of sample preparation and marketing. Principally as a result of the activities at the Sweet Home Mine, there is now a better appreciation of minerals and the market they encompass. Individual Sweet Home rhodochrosite specimens have been sold for more than $1 million, with many more in the five- and six-figure dollar range. This article is a review of the Sweet Home operation, with emphasis on its extraction techniques. District history The Sweet Home Mine is located within the Alma mining district in the Mosquito Range of central Colorado, approximately 6 km (3.7 mile) northwest of the town of Alma at the base of the Red Amphitheatre in Buckskin Gulch at an elevation of 3,440 m (11,286 ft). Other nearby mining districts include Climax, Leadville, Breckenridge and London. All are considered part of central portion of the Colorado Mineral Belt (Fig. 1).

Jan 1, 2007

In the dimension stone industry, workers in processing shops may be exposed to harmful levels of respirable silica dust when conducting the different tasks in stone preparation, which include cutting, grinding, polishing, and thermaling. To protect workers from this health hazard, operators sometimes ventilate processing shops using fan-powered dust collectors to capture and filter dust. To investigate this issue, NIOSH, Pittsburgh Research Laboratory, in cooperation with a dimension stone operation, upgraded an off-the-shelf dust collector the operator was utilizing in a polishing/cutting shop. Initial dust surveys showed that the unit was under-designed for the amount of dust being generated in the shop. The objective of the research was to cost-effectively increase the air cleaning volume and improve dust capture efficiency of the unit with a larger motor and blower. The unit?s original stock 0.56 kw motor and blower was replaced with a 2.24 kw motor and matching blower to increase airflow. The unit was evaluated both in the laboratory and the shop before and after the retrofit to determine the improvement of the upgrade. The study showed that the 2.24 kw upgrade improved the performance over the original 0.56 kw motor resulting in more dust being cleaned from the ambient air in the shop. The 2.24 kw unit cleaned 19% more air and captured 32% more respirable dust than the 0.56 kw unit.

Jan 1, 2009

By B. J. Sauer

Variable frequency drives (VFD’s), or adjustable frequency controls (AFC’s) as they are more precisely identified, have been available to the mining industry for over 20 years. However, in recent years as the push to cut production costs has become ever so crucial, AFC usage has become more widespread. This paper seeks to provide professionals in mineral processing plant design and operation with an introduction to AFC’s, insight as to why AFC control for AC induction motors can be advantageous, and specification and design considerations.

Jan 1, 2002

By M. Deul

For the first half of the 21st Century the USA will rely on the same mix of fuels as for the past 50 years: Petroleum will cost more and availability will decline as developing nations modernize. Increased use of natural gas for electric power generation will result in severe stress on gas supply. Coal will be the fuel of last resort. More than half the petroleum used is imported, about the same amount as used for transportation. Only coal can provide relief by fueling railroads through electrification while encouraging ‘piggy-back’ trailer haulage, co-generation for manufacturing and expanded passenger service.

Jan 1, 2002