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By K. Norrena

Grade control in open pit mining requires the specification of dig limits that account for mineral grades, economic costs, and selectivity of mining equipment. Visual identification of ore rock types is ideal, but this is not always possible in lower grade disseminated deposits where ore/waste contacts are not visually discernible. In this case, conventional grade control practice consists of a two-step procedure (1) create a map of mineral grades at some selective mining unit scale, and (2) determine practical ore-waste boundaries or dig limits on the basis of the gridded block grades or assay information. This procedure is laborious, depends on a subjective assessment of where the boundary should be, and may be economically sub-optimal. We pose the determination of dig limits as an optimization problem and solve that problem with the technique of simulated annealing. Simulated annealing has the unique advantage of being able to combine multiple non-linear constraints into a single objective function. We use maximum profitability and the ability of the equipment to mine the proposed dig limits as constraints in the determination of optimal dig limits. We require a map of expected profit for eah block. Geostatistical techniques are recommended, for mapping expected profit but not necessary. Geostatistics will provide a quantification of the uncertainty in the grades within rock types using all available blasthole samples and exploration drilling. Some variant of L-optimal estimation or kriging can be used to determine the block-by-block classification that is economically optimum. We also need the expected profit for each block. It is unrealistic to assume free selection, that is, each block cannot be extracted independently of its neighbors. The optimal balance of ''accepting dilution'' and ''wasting ore'' is achieved to maximize profit subject to equipment constraints.

Jan 1, 2001

By S. Christiansen, G. R. Winslow, R. W. Kobler

Todays End of Life vehicles are shredded and their metal components recovered and recycled by standard methods. The remaining non-metallic fraction is shredder residue, and contains vast amounts of high value engineering plastics. None are today recovered. Discussed are the developmental approaches used in the first process to recover these valuable plastics. Examined are initial laboratory studies, pilot plant design and construction, product development, results, and flowchart explanations.

Jan 1, 2001

By F. Burat

Large reserves of feldspar ore exist in the Aegean region of Turkey. The main colored impurities in these ores are iron- and titanium-bearing minerals such as anatase, rutile, sphene and ilmenite. In this study, a potassium feldspar ore containing mainly quartz and coloring impurities was subjected to beneficiation tests involving magnetic separation and flotation, which were applied either separately or in combination. Bench-scale flotation experiments using cationic collectors G-TAP and Flotigam V-4343 and using HF and H2SO4 as modifiers were employed to separate feldspar from quartz and to remove part of the titanium impurities. The best results were achieved with a combination of high-intensity wet magnetic separation and flotation. A feldspar concentrate containing 16.28% Al2O3, 10.75% K2O, 2.84% Na2O, 69.97% SiO2 and 0.16% Fe2O3 was produced. A quartz concentrate containing 2.30% Al2O3, 0.48% K2O, 0.42% Na2O, 0.07% Fe2O3 and 96.20% SiO2 was also obtained

Jan 1, 2007

By R. E. Scheffel

Most supergene copper heap leach operations today employ forced-aeration, irrespective of ore grade. Unfortunately, there is little published quantification of its benefit. There is a natural desire to strive for the ideal chemical kinetics. The reality, however, is that physical mechanisms control the commercial extraction rate. This paper presents the performance of a number of operations, their operating conditions and physical ore characteristics, which contribute to non-ideal solution distribution and variable extraction rate. Regardless whether one uses forced-aeration, commercial experience to date suggests it is prudent to design for longer leach cycle times to ensure the production target is met.

Jan 1, 2006

By Ching-Liu Wu, John Hawley, Andrew H. Liu, James Chai

The Hatch Mott MacDonald/Bechtel Joint Venture team is designer and construction manager for the 5.25-mile Tunnel Segment of the overall 16-mile Silicon ValleyRapid Transit Project, which extends the existing Bay Area Rapid Transit (BART) system southward from Fremont to San Jose. The Tunnel Segment includes twin boredtunnels, mined cross passages, and three deep station excavations situated in highlyvariable ground, high ground water table, and a dense urban setting with high-risebuildings adjacent to the largest excavation. This paper will discuss design challengesthat have arisen with the excavations and the proposed solutions.

Jan 1, 2007

By J. E. Friant

Until 1956, drill and blast was the only way to excavate rock. In that year, a tunneling machine using disc type cutters economically bored a small Toronto tunnel. Its amazing 105 ft/day set a new world record and set the stage for a new industry. The Disc Cutter Role in Excavation Mechanical excavation of hard rock is by now deeply ensconced in the heavy civil construction industry. All over the world, from the Swiss Alp Melange to Hong Kong Granite, to New York Gneiss, huge Tunneling Boring Machines (TBMs) create transportation, water and sewer tunnels. Powerful machines, boasting as much as 6000 hp, bore through rock, excavating in excess of 1400 tons per hour. The tool that makes this tunneling phenomenon possible is the single blade, rolling disc cutter. These hardened steel discs, from 15 1/2 to 19 inches diameter are arranged on a rotating cutterhead, to cut concentric circles in the rock. As the machine is propelled forward under great pressure, rock below each cutter is crushed. But the efficiency of the cutterhead is derived from the science of cutter spacing (distance between cutter paths). The majority of the rock excavated is not crushed, but flakes off in chips and chunks. No pick, tooth, or drag type cutting tool can duplicate the performance of a disc cutter. The economic use of drag type tools is limited to as low as 5,000 psi UCS rock strength in massive formations. In weakly bonded, foliated rock, drag tools do better, but are still limited to rock generally less than 15,000 psi.

Jan 1, 2002

bauma 2004 will feature a couple of firsts for one of the world’s largest construction and building materials machinery exhibitions. The event is scheduled for March 29 through April 4 of next year at the New Munich Trade Fair Center in Munich, Germany. For the first time, bauma will feature an exhibition area dedicated to mining equipment and technology. Also for the first time, the Commonwealth of Independent States (CIS) will be a partner region of bauma.

Jan 1, 2003

By Edward Holloway

The basis for the selection of the ultimate pit for an open-pit mining operation is generally opaque. Some form of value-based analysis will generally guide the final decision; however, the value will often gradually plateau while the ultimate pit size continues to increase. There is no established framework to guide specialists in the selection of the ultimate pit, with such decisions regularly made on a somewhat arbitrary basis. The key component that is missing from the analyses typically used to select the size of the ultimate pit is risk. Once risk is quantified within the analysis framework, the decision-mak-ing range is significantly reduced and the process for select-ing the ultimate pit becomes more consistent, replicable and defensible. The technique outlined in this paper provides an approach to including risk in the process used to select the ultimate pit.

Jun 1, 2024

By Hasan Nizamoğlu, Z. Abidin Sarı, Aslıhan Demiraslan, M. Deniz Turan, Tolga Depci

In this study, recovery of copper from solid material (obtained by leaching of chalcopyrite with oxalic acid in the presence of hydrogen peroxide) with a copper oxalate structure was carried out selectively using HCl. The chemical composition of the solid was as 29.3%, 9.7%, and 13.3% for Cu, Fe, and S, respectively. Selective recovery of copper by degrading the copper oxalate structure with a low-solubility product (Ksp = 4.43 × 10−10) was performed by conventional leaching in the presence of HCl. The optimum leaching conditions were determined as 5 M of HCl concentration, 318 K of leaching temperature, 120 min of leaching time, 25 ml/g of liquid–solid ratio and 400 rpm of stirring speed. Under these conditions, approximately 77% of copper and 3% of iron were taken into the solution. According to the characterization of the leach residue that was obtained, the oxalate structure was degraded. Moreover, the results of XRD analysis showed that the sulfur (S) and cubanite (CuFe2S3) phases were mostly observed in leaching residues, and this was supported by the SEM-EDX data. Based on the results, it may be stated that selective copper extraction can be obtained from a chalcopyrite concentrate by a two-step leaching method using a conventional hydrometallurgical technique.

The trend for using larger equipment in open pit mining to achieve cost effectiveness raises the question about the optimum economic point of scale in the current world of globalization. The present paper treats this question through the prism of a new methodology of assessing the impact of the size of production equipment on the economic outcomes of coal mining ventures. The methodology incorporates a production scheduling optimization model that implements both principles of mine planning, coal quality optimization and waste deferment. The implementation of the waste deferment principle dealing with the spatial and time aspects of the mine sequence arrangement allows the adequate modeling of the optimality of production equipment scale through the use of mine investment parameters, such as, purchase and ownership costs and discounted cash flows analysis. A case study is provided to illustrate the applicability of the new methodology.

Jan 1, 2004

By O. Noirot, H. C. Owens, P. D. Rao, D. E. Walsh, J. R. Mokka

Over a period of seven years (1989-1996) the Mineral Industry Research Laboratory (MIRL) University of Alaska Fairbanks, has investigated the effects of temperature, residence time, and particle size on the degree of low-rank coal (LRC) upgrading for a non-evaporative, hydrothermal drying process, also known as hot water drying (HWD). Three Alaskan LRCs were used in this study: Usibelli coal (Seam No. 4) from the Nenana Coal Field, Little Tonzona coal from near McGrath, and Beluga coal from the Beluga-Yentna field on the west side of Cook Inlet. Replicated, factorial tests were conducted. Experimental results indicate that most of the low-rank coal upgrading via HWD occurs rapidly within the first 10-20 minutes of residence time. Thereafter, the upgrading process slows down and over 100 minutes of additional residence time are required to produce similar percentage increases in coal properties to those achieved in the first 10- 20 minutes. The properties of the hot water dried products were very sensitive to process temperature. Calorific value, carbon and oxygen contents, equilibrium moisture levels and Hardgrove gindabilities all appear to change linearly with temperature within the 275°C to 325°C range.

Feb 24, 1997

By Yi Luo, Jeremy Slagley, Arunkumar Rai, Steve Guffey, Syd S. Peng

Research was conducted to study the characteristics of longwall mining machine noises and to develop engineering controls for the reduction of noise exposure at longwall faces. Time-motion noise dosimeter data was analyzed and compared with existing databases. Experiments were conducted above ground on a stage loader/crusher to explore the potential of using active noise control (noise cancellation) in reducing the noise levels. A 5-7 dBA reduction in recorded stage loader noise was achieved. This paper presents the equipment, procedure and results of the noise surveys, as well as the active noise control experiments.

Jan 1, 2005

By P. D. Rao, D. E. Walsh

Chemical and physical properties of typical low-rank coal (LRC) ash are significantly different than bituminous coal ash. With the exception of extraneous ash, which is incorporated during mining or is due to ash partings within or between coal seams, LRC ash consists primarily of inherent ash that is bonded into the coal's organic matrix or finely disseminated mineral matter. This paper reviews the nature of LRC ash, both inherit and extraneous, and how this impacts the prospects of washing and utilizing LRCs. A literature review, as well as washability data, proximate and ultimate analyses and ash analysis of 25 Alaskan LRC seams are used as a basis for this discussion. The authors' remit research into the nature and distribution of phosphorous in an Alaskan LRC is also discussed

Feb 24, 1997

By F. L. Pirkle

A heavy-mineral deposit about 1.6 kilometers (I mile) in length and averaging about three meters (10 feet) in thickness is exposed approximately130 kilometers (80 miles) east of Denver, along Interstate 70, in Elbert County, Colorado near the town of Limon. The deposit is exposed in a geomorphic feature known locally as Titanium Ridge. The dominant heavy minerals, accounting for about 70% of the total heavy mineral suite by weight, are ilmenite, garnet, and zircon. The mineralized zone appears in a series of visually interpretable facies that are stacked vertically and represent subtidal, forebeach, backbeach, washover fan, and aeolian depositional environments. These paleoenvironments are analogous to depositional environments represented by a modern heavy-mineral bearing facies tract on St. Catherines Island, Georgia. Thus, Titanium Ridge provides evidence that heavy-mineral accumulation models for late Cenozoic deposits in the Georgia and Florida coastal plains are applicable to heavy-mineral deposits of the Western Interior subsurface and, by implication, the Western Interior Seaway, extending from Mexico to the Canadian Arctic.

Jan 1, 2011

By M. Valdebenito, J. Rajala

An OCS Expert control system was implemented by Svedala Cisa at the Minera Maricunga Refugio Crush-Leach Operation near Copiapo, Chile. The purpose of the Expert system was to maximize production through the primary and secondary crushing circuits and help balance crusher usage between each stage to maximize total plant production. Interesting aspects of the control strategies are discussed. Benefits of the control were verified through a randomized On/Off test program. Tonnage increases ranged from 5% to approximately 20% at good confidence intervals. Benefits analysis results are discussed. The crushing plant at Refugio is very remote and is located at approximately 15,500 ft. This poses many challenges. The effect of altitude and remote location on plant operation are discussed.

Jan 1, 2002

By Mutombo Nombe, Avimanyu Das, Rick Honaker

Enhanced gravity separators (EGS) provide a more efficient separation than froth flotation when cleaning coal in the 150 x 25 µm particle size range. To improve the performance of an EGS unit, air bubbles were injected into the feed stream in an attempt to decrease the apparent density of the coal particles due to the formation of bubble-coal particle agglomerates. Air injection had a significant impact on operating characteristics and separation performance. Coal recovery was increased by 10 to 20 absolute percentage points while a 2 percentage point drop in the minimum product ash content was also achieved.

Jan 1, 2005

By Joseph J. Feiler

Fires in underground coal mines are persistent problems anywhere in the world that coal is mined. Coal fires pose safety and health hazards in the form of mine subsidence, loss of energy reserves, destruction of property and surface improvements, and air pollution. In 1995, the US Bureau of Mines (US-BM), in cooperation with the Colorado Division of Minerals and Geology (CDMG),entered into a contract with Goodson & Associates Inc. (GAI) to design and field test the effectiveness of a new foamed grout technology called ThermoCell. GAI is a Lakewood, CO geotechnical and mining reclamation engineering firm. The company developed ThermoCell to control and extinguish underground coal fires. The viability of the special grout and the technology of application were established during a full-scale field demonstration at the abandoned IHI Coal Mine fire, near Rifle, CO. Following acquisition of additional funding by CDMG in 1999, Goodson returned to the site in April to continue the grouting to fully extinguish the IHI fire.

Jan 1, 2000

By G. Coombs, L. Meade, J. Welshimer

Industrial Minerals commodity profiles are continued from May's Annual Review issue. Diatomite G. Coombs, Manville Sales Corp. Growth in US diatomite production continued to lag in 1986. The US Bureau of Mines estimated that 580 kt (640,000 st) were produced last year. This is a 1%0 growth over 1985. The cumulative growth from the 1982 low point is 4.4%. Present production, though, is still only 90% of the high tonnage of 1979. The industry will see increased competitive activity with the start-ups of two new mines and production facilities in California and Oregon. US production has come primarily from Lompoc, CA, Bassalt, Clark Station, and Lovelock, NV, and Quincy, WA. New production, probably with capacities of 45 kt/a (50,000 stpy) each, have started near Burney, CA, and Vale, OR. Eagle Picher's new, full-line filter aid and filler plant at Celatom, Vale, OR, was dedicated in August. The plant uses diatomite from the Celatom mining district in Juntura, OR. Grefco's new filter aid and filler plant near Burney, CA, was ready in July. It produced flux calcined products through a single kiln and can handle both bag and bulk shipments. The operations are in Shata County with the plant and mine at the same site. Manville Specialties Group is moving its Filtration and Minerals Division headquarters and research staffs to Lompoc, CA. The move is intended to strengthen response and performance by locating research, marketing, and production close together. Diatomite is processed in three methods: natural, calcined, and flux calcined. The natural is dried to remove water and is particle size classified. Calcined or straight calcined products have been sintered to modify particle size or permeability. Flux calcination, or flux sintering, has a stronger influence on permeability and also benefits color. The unique structure of diatomite is used in a range of particle sizes from fine paint fillers, to coarser filter aids, to granular aggregates. Dimension stone L. Meade, Geomapping Associates Ltd. 1986 was another good year for dimension stone production. The trend toward using marble, granite, limestone, sandstone, and slate has created an increasing demand. According to US Bureau of Mines 1986 estimates, 1.1 Mt (1.2 million st) of dimension stone, with a value of $173 million, was produced by 200 companies. This is an increase from 1985, where 220 companies produced 1 Mt (1.12 million st) valued at $172 million. The increased production volume and decreased unit value is due to the competition from imports. The net import reliance in 1986 was 68% compared to 62% in 1985. The value of imports was $374 million in 1986 versus $295 million the year before. In an effort to maintain their market share, domestic finishers, particularly in the granite industry, continued to upgrade plants and machinery during 1986. In addition, offshore dollars have financed a number of fabricating facilities in North America that will finish imported rough stock. It is hoped that this increased domestic production capability will capitalize on a devalued US dollar. The trend has been for growth in stone usage and market. This trend is continuing with increased public awareness and desire for natural stone in buildings. The area of greatest market growth is expected to be in residential and interior decorative stone usage. Use of sophisticated, automated equipment has made the cost more affordable. Now lobbies, foyers, and specialty rooms are being clad in stone. Dolomite J. Welshimer, National Lime & Stone Co. About three-quarters of dolomite production is used as construction aggregates and 10% to 20% is sold or used as an industrial mineral. Total limestone and dolomite consumed for chemical and metallurgical purposes is about 136 Mt/a (150 million stpy). Sales of industrial dolomitic products were somewhat stronger in 1986 than levels recorded in the early 1980s. Some of the sales' strength, however, can be attributed to reductions in the number of active mining and processing operations. The industry will probably undergo further consolidation by the end of this decade. This will be due primarily to the continued softening in demand by the steel industry. Dolomitic limestone deposits being mined for raw materials for the steel, glass, and refractory in¬dustries are generally 54% calcium carbonate and 45% magnesium carbonate by weight. Impurities composed of silicon, aluminum, iron, sulfur, and phosphorous, represent less than 1%. The heaviest concentration of high purity, surface mineable dolomite in the US is in northwestern Ohio. Crushed and sized dolomitic limestone is a basic raw material for the iron and steel industry. It is also used as feed stone or lime kilns. Soft-burned lime is a popular raw material for BOF steel production. It is also used extensively in insulating glass fiber manufacturing. A related material, hydrated

Jan 6, 1987

By David Kress

Mill crushing drive systems are essential to cement producers. With the increased emphasis on operating efficiency, it is vital that these systems be dependable and reliable. No one needs the costs or headaches associated with unscheduled downtime or inefficient machinery operation. A reliable drive system starts with the proper selection of the ring, or girth, gear and continues through proper maintenance. Ideally, selecting the right girth gear brings together the gear manufacturer, the system designer and the end user. The gear manufacturer must know the details of the application, the demands that will be placed on the gear and the nature of the equipment to be driven. Similarly, the user and the system designer must be familiar with the variables that affect gear drive performance and service. For example, an application that places a torque load on the drive in excess of its rated capacity will result in gear tooth distress and, in severe cases, breakage.

Jan 1, 2000

By W. J. Spat

Political risk is an integral part of the mining business in Northern Andean countries. Peru, Ecuador, Colombia, and Venezuela all have a higher than average political risk compared with other South American countries. Successful operations in such contexts require: 1. Good political risk information; 2. A thoroughgoing political risk management plan; and 3. A strategy to deal with political risk perception on the part of the investing public. Obtaining quality political risk information, developing a political risk management plan, and addressing political risk perception are the foci of this work.

Jan 1, 1999