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It is crucial to reestablish a domestic rare earths minerals production industry to help secure the Nation's clean energy future, reduce the U.S. vulnerability to material shortages related to national defense, and to maintain our global technical and economic competitiveness. Given that the Chinese dominance of the rare earths market has adversely impacted supply stability and endangers the United States and its allies' assured access to key materials, rare earths should qualify as materials either strategic or critical to national security. Further, the U.S. government should facilitate the reintroduction of a globally competitive rare earth industry in the U.S. Realization of this objective requires: ? Developing domestic processing capability so that the U.S. is not primarily dependent on China as a source of rare earth ore, and almost exclusively dependent of China for processing of the ores. ? Providing a mechanism where access to Federal lands for rare earth exploration and extraction is possible, and ? Training engineers to design and operate rare earth ore processing facilities

Jan 1, 2011

The recovery of coarse particles has been widely recognized as being limited by the froth in mineral flotation. In response to this, FLSmidth has developed the Selective Froth Recovery (SFR) System. The SFR System is an extraction system that vacuums material from select locations within the froth and separates the recovered solids into coarse and fine fractions with a hydrocyclone. The SFR is supported and located by an actuator connected to the cell?s level control so that the suction heads are maintained at an offset distance from the slurry level. This can increase the recovery of coarse material by selectively recovering the material close to the bottom of the froth where drop-back of coarse particles typically takes place. The SFR System has been tested at two separate mine sites, and has been proven to increase the copper recovery in both trials. TEST RESULTS The SFR prototype was installed in a copper recovery circuit, on a rougher scavenger 160-m3 flotation cell. Figure 1, shows the SFR System, which consists of four conical skimmer heads that are plumbed together and share a common actuator. The SFR System, raised out of the froth prior to a test, can be seen in Figure 2. The SFR prototype was able to maintain a variety of set points using the level control to determine the slurry height.

Feb 27, 2013

By G. Montes-Atenas

Throughout the years, research studies have reached a consensus in acknowledging the relevancy of surface chemistry phenomena on minerals separation and metals extraction. Many techniques, and notably, scanning electron microscope-based technologies have revolutionised the entire mineral processing industry. Nevertheless, the comprehensive understanding on how surface chemistry properties influence the performance of many processes involving ores is still a challenge, a matter of controversy. The latter is mainly due to the fact that all interfacial processes do not necessarily require stoichiometric and well defined atomic structures. This is particularly true in the case of sulphide minerals which are well known to be superficially unstable in aerated media. When trying to measure any variable related to mineral-mineral or mineral-aqueous solution interfaces, there are too many unknowns regarding how sensitive the interface is when facing sampling protocols and sample handling. The aim of this research work is to make a case for improving future concentrators? survey protocols. It suggests a methodology to study effectively chemical changes at the outmost mineral surface layer at different stages of a mineral processing operation. The sampling protocol and sample handling is presented in details and it is applied to the regrinding stage of an industrial plant.

Feb 27, 2013

By Kenneth J. Hartman

Introduction The term kaolin is derived from kauling, a Chinese word meaning high ridge. This was the name of a hill in China where kaolin was first mined several hundred years ago (Murray, 1976). Other common names used for kaolin include clay and China Clay. Clay technically has a broader meaning and could refer to bentonite and ball clay as well as kaolin. China clay, as a descriptive term, apparently results from kaolin's origin. But it could also be due to a significant historical use in ceramic applications. The terms kaolin and clay will be used interchangeably in this analysis because of the common practice of using these terms in the paper industry. Major reasons for kaolin's wide-spread industrial usages center on kaolinite's physical features of good color, low viscosity, and inertness. Kaolin is described as a hydrous aluminum silicate with an approximate composition of 2H2O • A12O3 . 2SiO2. A new version of the product is calcined clay with modified hydration content. It is gaining widespread use. Components of any particular kaolin, in addition to alumina and silica, are viewed as impurities. The more values deposits and, hence, higher priced kaolin products are those of the highest purity. Kaolin is the most widely used mineral in paper manufacturing throughout the world. Key production centers are located in England and the US. Most of the Tatter's production is located in Georgia. The key markets for Georgia kaolin are paper markets - both paper coating and paper filling. These paper markets extend throughout the world, not just to domestic markets. In fact, export markets are second in size only to domestic paper markets for Georgia's producers of kaolin. Just as the paper markets are important for kaolin producers, kaolin is an important raw material for papermakers. Compared to the other three major pigments - titanium dioxide, calcium carbonate, and talc - kaolin's 1984 tonnage for papermaking represented 85% of the total. Even though titanium dioxide's unit value is much higher, kaolin's estimated total 1984 value still represented 51% of total dollars spent by papermakers for the four pigments. Kaolin grades- are briefly defined using particle size and brightness as principal means of classification. Likewise, grades of papers using kaolin are defined using the American Paper Institute's guidelines. From these definitions, associated kaolin grades used in particular grades of paper are reviewed. Special emphasis is placed on how qualities desired in certain papers are achieved through the use of specialized kaolin grades. World kaolin production World production statistics (Coope, 1979; Table 1) demonstrate that kaolin is produced in many areas of the world. About 60% of production is centered in the US and England (Fig. 1). Deleting Eastern Europe's produc-

Jan 4, 1987

By F. N. Kissell, C. D. Litton

This study predicts the level of smoke that miners might meet while trying to escape a coal mine fire and describes how smoke would impede their safe escape. For this study, the authors assumed that miners exit through an escapeway adjacent to the burning entry, that some air would leak from the burning entry to the escapeway. The following conclusions were made: • A very low amount of air leakage to the escapeway can produce a critical level of visual obscurity from smoke. This shows that intake airways may be as susceptible to smoke visibility problems as return airways. • This critical level of smoke obscurity is reached much before a critical level of carbon monoxide is reached. • Small fires can cause a severe sensory irritation that further limits vision. Thus, reliable eye protection is very important. These results show that methods to guide miners through dense smoke will contribute greatly to saving lives during mine fires.

Jan 1, 1993

By K. T. Lee, M. U. Ozbay, M. D. G. Salamon

Design of yielding chain pillars in deep coal longwall mines is not as well established due mainly to the lack of knowledge in the behavior of coal pillars in the post-peak regime. This study shows that two of the existing strain-softening models have the potential to provide an improved understanding of yielding and, therefore, could form a rational basis for yielding coal pillar design. Analytic and numerical modelings of a row of chain pillars in a two-entry development at a depth of nearly 700 m suggests that yielding pillars are feasible, but the design is very sensitive to the coal’s post-peak behavior.

Jan 1, 2001

By S. Strömberg, A. Jokilaakso

Two complex copper concentrates and one arsenical nickel concentrate were oxidized in simulated flash smelting conditions using a laminar-flow furnace. The concentrates contained tetrahedrite as Sb-bearing mineral and arsenopyrite and gersdorfite as As-bearing minerals. At high temperatures and low oxygen potentials, Sb tended to vaporize, but with high oxygen potentials it was captured in mixed oxide phases with copper and iron. Arsenic was found to follow antimony in copper concentrates, although with less sharp contrast between low and high oxygen potentials. In the nickel concentrate studied, arsenic was found to vaporize from the gersdorffite particles and, subsequently, condense on the other particles.

Jan 1, 1998

By J. M. Manka

American mining companies operate many drum hoists that hoist from various depths with varying payloads. This paper will review the procedure of selecting optimum wire rope constructions for these existing hoisting installations. Selection for proposed installations along with recommended hoisting parameters will also be presented. To achieve this optimum rope performance, preventative and corrective maintenance procedures will be reviewed along with examples of rope problems and their causes.

Jan 1, 1992

By K. Sasaki

Diffusion phenomena in mine airways are important to trace gas and dust introduced into mine ventilation flows. Authors have carried out tracer gas measurements to check mine ventilation using concentration-time curves measured in mine airways, however dispersion mechanism to enhance effective diffusion have not been cleared. A numerical model using discrete tracer points dosed into tube flow has been presented to simulate their movements in consideration of turbulent velocity profile and fluctuation. Numerical simulations have been carried out to predict distributions of dosed points in tube flows with turbulent velocity profile, turbulent intensity profile and Reynolds stress. The numerical simulation results show that a combination of turbulent velocity profile and fluctuation creates extremely large dispersion of points in longitudinal direction and concentration curve with long tail was observed. This dispersion by velocity profile and fluctuation contributes large effective diffusion coefficient compared with original diffusion coefficient dominating in uniform velocity fields. Furthermore, the effect of Reynolds stress on the concentration-time curves is discussed.

Jan 1, 2009

By Enrique Hermana, Raymond F. Dalton, Raymond Price, Barry Hoffman

Introduction Chloride leaching of sulfidic ores has been known about for 100 years. It is recognized as a highly efficient process to produce concentrated leach solutions. Despite this, chloride leaching found little practical application until recently because of the highly corrosive nature of concentrated chloride solutions. This situation changed with the advent of modern construction materials such as GRP, polypropylene, butyl rubber, etc. And in the past 20 years, research has burgeoned in the area of chloride hydrometallurgy. The research impetus stemmed from the belief that chloride leaching can provide an alternative to smelters for treating conventional copper concentrates. In addition, chloride leaching was thought to be suitable for on-site refining of copper at small tonnage operations located in remote areas. And chloride leaching was seen as a logical choice for treating unusual or complex concentrates that smelters could not handle. Underpinning these beliefs is the attraction of chloride-based hydrometallurgical processes for sulfidic ores. Sulfur is liberated in the environmentally acceptable elemental form rather than as sulfur dioxide. Consequently, sulfidic copper ores have received much attention. A review of Edmiston in 1984 describes 12 chloride-based processes. All managed to progress past the "laboratory beaker" stage of evaluation. In nine of these processes, copper is recovered electrolytically. Key features of these processes are summarized in Table 1. Table 1 shows that the processes must include a copper solvent-extraction step. Only these processes produce a clean copper electrolyte capable, with no further refining, of directly producing high quality cathode copper. The ICI/Elkem process is the exception here. The rest of these processes use o-hydroxyaryloxime reagents for the solvent extraction of copper and are constrained by the performance of these reagents. This is governed by hydrogen ion concentration (Equation 1). The practical result is that only relatively dilute copper solutions can be treated (Canmet, Phelps Dodge), or careful pH control or adjustment is necessary (Minimet Recherche, B.H.A.S.). This negates one of the attractive features of chloride leaching - its ability to produce very concentrated copper solutions, up to 40-45 gl-1. [ ] In all four processes using o¬hydroxyaryloxime extractants, solvent extraction transfers the copper from the chloride to the sulfate medium. To minimize cross-contamination of the two anions, the loaded organic solvent has to be scrubbed to remove the chloride ion. This represents an additional complication in the solvent extraction circuit. And it

Jan 1, 1988

By George Watson, Gu Quanzhong, S. Gerard Sawyer

Bulkheads, also known as hydraulic seals, are used to seal abandoned workings and protect adjacent active mines from explosion and control unwanted inflows of water from poorly sealed shafts, water-bearing strata, and abandoned mine areas or gobs (1). At coal seam outcrops, bulkheads have typically been used to prevent access and to control acid mine drainage. Bulkheads have also been installed at outcrop openings located within the footprint of an embankment dam, or within the reservoir of an impoundment, to prevent stored water or slurry waste from flowing into active or inactive underground mine workings (2). Components of MICON Bulkhead Seal MICON bulkhead seals in mining applications refer to seals designed to impound liquids or slurry. The MICON bulkhead seal is comprised of two concrete block walls set in the front and back and a polyurethane/aggregate core (Figure 1). The two walls are usually dry-stacked, surface-bonded walls constructed with solid load-bearing concrete blocks (ASTM C90) or concrete building brick (ASTM C55). The surface bonding material used in the wall construction must be MSHA-approved. The type of stone, if any, used to fill the space between the walls is not essential. However, MICON generally uses No. 57 limestone in 50 lb. bags, specified to moisture control, shrink-wrapped and palletized. The polyurethane foam used in the construction of the bulkhead seal is engineering specified and formulated by density based on the optimization of cost, seal core thickness, required adhesive strength, the use of stone filler and other required physical properties.

Jan 1, 2005

By E. Topuz, C. Patrick

Longwall face-to-face transfers can cost more than $100 per minute in lost production potential and $100,000 for personnel and supplies. Such high costs make extensive planning and control of the transfer process a critical necessity for the economic feasibility of longwall operations. Operations research techniques are used for the analysis and modeling of longwall face-to-face transfers. Transfer data has been collected from companies who operate, over 35%, of the total US longwall faces. Comprehensive sequence networks of existing longwall transfers were developed; simulation was used to generate models of transfers under Carving conditions; and the economic feasibility of tine-cost tradeoffs in the transfer procedure was investigated.

Jan 1, 1994

By Ma. X.

Passive seismic imaging is applied in underground mining to analyze the stress redistribution after the occurrence of a major seismic event. The velocity model is established to be utilized in velocity inversion. By comparing the images from velocity tomography on two different time scales, the average velocity of a mining area decreases significantly after the major event. It is highly likely that the stored energy level drops due to the occurrence of a major event. Also, total energy stored in micro-seismic events for each day is summed up and the energy change trend is plotted to illustrate the correlation of energy with a major event.

Feb 27, 2013

By Clay Haynes

While the Kansas River Tunnel is a relatively short, small diameter tunnel, the shaft excavation methods implemented were long and large on innovation and use of reverse circulation drilling equipment. ATS Drilling, L.P. used mechanical excavation techniques for both soil and rock segments of the 42.7 m (140 feet) and 38.1 m (125 feet) deep shafts that were 2.9 m (9.5 feet) and 4.1m (13.5 feet) diameter, respectively.

By J. C. Cawley

This National Institute for Occupational Safety and Health study was conducted to focus future research on the most significant electrical problems in the mining industry. Data from 1,926 mine electrical accidents (including 75 fatalities) that occurred between 1990 and 1999 were studied. Coal and metal-nonmetal operator- and contractor-reported data are presented. All data used in this analysis were MSHA closeout data, except 1999, which were preliminary data. Electricity was the 4th leading cause of death reported in mining despite being the 14th leading cause of injuries. Electrical shock, not electrical burns, caused 70 of the 75 electrical fatalities reported. About one-half of mine electrical accidents and fatalities occurred during electrical maintenance. Suggestions for mitigating electrical hazards are proposed.

Jan 1, 2002

By K Timtner

As shown in former publications there are problems in load sharing of backstops in multiple drives of conveyors. Therefore, detailed calculation methods and design recommendations are required. In this paper various designs of load sharing methods are described and a dynamic torque calculation method will be presented. With this method the loadsharing properties for low and high speed backstops are calculated and compared. These properties depend on the spring characteristic of the drive train between backstop and load. Furthermore, the properties depend on the method of torquearm support and shock absorber configuration. Remarkable differences for external and internal backstops are shown

Jan 1, 1998

By William R. Yernberg

The Fifth International Conference on acid rock drainage (ICARD 2000) was held May 21-24, 2000, in Denver, CO. The three-day conference consisted of about 150 oral presentations and poster sessions that described the state-of-the-art of acid-rock-drainage (ARD) science and technology. The conference also featured a trade show. It included representatives from consulting companies and government agencies with interests in ARD, as well as other environmental issues related to mining. The conference also included field trips to ARD treatment sites and short courses on acid rock drainage issues. ICARD 2000 was planned and promoted by the ICARD 2000 Organizing Committee and the Society for Mining, Metallurgy, and Exploration, Inc. (SME). Financial support was provided by Barrick Gold, BHP Copper, Homestake Mining, Noranda, Phelps Dodge, PlacerDome, the US Bureau of Land Management, the USEnvironmental Protection Agency and the US Geological Survey. Since the original ICARD was held in Roros, Norway, in 1988, knowledge has improved of the behavior of mine wastes as have methods of environmental mitigation. The ICARD 2000 presented the latest advancements in the field of acid drainage.

Jan 1, 2000

By E. A. Metz

It has been approximately four years since IARC reclassified crystalline silica as a “Group One” substance. Since that time, crystalline silica has been considered a human carcinogen. Silicosis is a preventable disease and several aggressive campaigns have been developed to increase awareness of silica dust related problems in the industrial environment. New analytical techniques are being developed to determine quantitatively the amount of crystalline silica in materials. Yet, still much is to be learned about the surface properties of silica and the way in which the disease progresses into full-blown silicosis. This paper will discuss the interaction of free radicals generated by the mineral particles and lung tissue. It is the cell injury and DNA damage that progresses to fibrogenesis. Freshly fractured surfaces of silica contain free radicals. These free radicals play an important role in the stimulation of the alveolar macrophage and the development of the inflammatory reactions leading to the fibrotic response caused by silica. Engineers, scientists, and physicians need to discuss the mineralogy of silica and the technical issues concerning the development of silicosis.

Jan 1, 2000

German manufacturer DBT signed a contract to supply a sixth automated-plow long-wall system to Shenyang Coal in Liaoning province in northeastern China. This most recent order occurred just weeks after DBT signed a contract to deliver a fifth automated-plow longwall system to Datong Coal in Shanxi province. The plow will go into service at Shenyang Coal’s Hongyang Mine. Mining conditions at the mine, coupled with DBT’s advanced automated-plow technology, means that the system has the potential to become one of the world’s most productive thin-seam longwalls.

Jan 1, 2004

By R. D. Peterson

As underground mine operations expand, the ventilation systems supporting them become complex. Complexity increases with periodic ventilation changes. New diagonal connections require a rebalance of resistance to maintain airflow in affected splits in the system. Incidents of mine fires and explosions have occurred in U.S. coal mines when diagonal connections resulting from ventilation changes have resulted in changing airflow directions. MSHA regulations prohibit the reversal of airflow and poor ventilation practice in general, but regulations cannot stipulate or recommend proactive preventative measures because every situation is different. This paper discusses the phenomenon of diagonal branches and recommends practical precautionary measures that can be taken to prevent airflow reversal in planned ventilation changes.

Jan 1, 2012