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By David R. Kalasky

One of the primary areas of computer application in mine ventilation has been the analysis of mine ventilation networks. A variety of network analyzers that are aimed toward the solution of flows in a given network has been developed. These programs typically use the Hardy Cross or other iterative algorithm for solution of any network, even those that are complex. The computer software has become more efficient and sophisticated over time and has thus been widely adopted for ventilation network analysis. One of the shortcomings of these programs is that they have been developed with the idea of analyzing the ventilation requirements at a single point in the lifetime of a mine. This provides the ventilation engineer with an important tool for analysis but falls somewhat short of providing a convenient means to economically com- pare alternative methods for ventilating a mine. The program described in this paper provides such a tool. The principal concepts that were necessary for the completion of a computer program that analyzes ventilation alternatives is the capability of efficiently determining the ventilation requirements at a variety of times during the lifetime of the ventilation system and some method of analyzing the costs of the alternatives on a realistic comparative basis. To accomplish this task, the authors began using Penn State's mine ventilation simulator designated as PSU/MVS, Didyk et al. (1977a, 1977b) and added the necessary additional software to accommodate the need for multi-period, time-dependent analysis of the net- work. The software was then tested on a coal mine ventilation problem with a 23-year life. The problem points out the value of such a program for ventilation analysis.

Jan 1, 1986

By Steven J. Schatzel, Kayode M. Ajayi, Zoheir Khademian

The integrity of unconventional shale gas well casings positioned in the abutment pillar of a longwall mine could be jeopardized by longwall-induced deformations. Under such scenarios, the surrounding fracture networks could provide pathways for gas flow into the mine creating safety concerns. To provide recommendations for developing guidelines that ensure a safe co-existence of longwall mining and unconventional shale gas production, this study evaluates the impact of parameters that could affect potential shale gas flow into the mine in the event of a casing breach using a discrete fracture network (DFN) model. These parameters are evaluated using a conceptualized DFN realization that is representative of the fractured zone in the overburden, and the range of parameter variations is within values validated with field measurements. The results show that a decrease in fracture aperture (potentially due to longwall-induced stress in the likely vicinity of the breach location) reduces the potential gas flow to the mine by a significantly higher proportion. A 50% decrease in the aperture of the fracture that directly transports the gas from the casing breach location reduces the gas flow to the mine by over 70%. Similarly, changes in the fracture water saturation level significantly affect the gas flow. In all cases, the potential gas flow to the mine is higher if the casing breach occurs at an increased gas well pressure. These findings provide critical information regarding the impact of each of the parameters associated with gas flow in the event of a shale gas casing breach near a longwall mine and could help towards the development of guidelines to ensure a safe coexistence of both industries.

Sep 28, 2022

By F. W. Petersen

Slurry reactors are being used extensively throughout the chemical, biochemical and mineral processing industries. This paper describes the interaction between fine ore particles and granular porous adsorbents such as activated carbon and ion-exchange resins in a stirred tank reactor. Gold and silver cyanides were used as adsorbates to detect changes in the mass transfer characteristics of the adsorbents, which were ashed to determine the loading of ore particles. A simple kinetic model incorporating film diffusion, intrapanicle diffusion ~d the adsorption equilibrium, was used to interpret kinetic data and to estimate the effect of slurry conditions on the diffusion parameters. It was observed that the equilibrium loading of fines in the adsorbents was independent of their concentration in the slurry. Furthermore, the presence of these panicles inside an adsorbent decreases the effective diffusion of gold or silver cyanides into the adsorbent matrix. When fine suspended solids are present in the reactor, a decrease in the effective availability of the superficial surface of the pre-saturated adsorbent panicles for mass transfer from the liquid phase was observed. This newly defined surface availability factor was dependent on the concentration, panicle size, and the zeta potential of the fine particles in suspension.

Jan 1, 1993

By P. Karimi, A. Akcil, A. Amini, H. Abdollahi

"In this study, cyanidation experiments were carried out on a massive sulfide ore sample, whose grades of the precious metals gold and silver were found to be 4.2 g/t and 311.9 g/t, respectively. Other elements in the ore were arsenic with average grade of 1,751.6 g/t; antimony, 619.7 g/t; zinc, 781.4 g/t; copper, 454.6 g/t; lead, 101.8 g/t; mercury, 324.3 g/t; and bismuth, 0.6 g/t. The first objective of test work focused on determining the best conditions for extracting gold from the ore, ground to less than 75 microns. Different influential parameters such as particle size fraction, cyanide concentration, pH and leaching time were investigated. The optimum parameters were found to be particle size fraction of less than 25 microns, cyanide concentration of 2,000 mg/L, pH of 11 and cyanidation time of 24 hours. In these optimum conditions, the highest gold and silver leaching efficiencies were 76.88 and 59.63 percent, respectively. In addition, roasting as pretreatment at a temperature of 700°C over a period of two hours was evaluated. Cyanidation testing of the roasted ore in the optimum conditions found increases in the gold and silver leaching efficiencies to 85.97 and 67.57 percent, respectively. Moreover, antimony extraction rose to 43.10 percent, from 23.73 percent without roasting.IntroductionGenerally, gold ores can be classified as “free milling” or “refractory,” depending on how they respond to cyanide leaching (La Brooy et al., 1994; Celep et al., 2009). While high gold recoveries (> 90 percent) from free-milling gold ores can be readily achieved, refractory gold ores are often characterized by low gold recoveries (50-80 percent) within a conventional cyanide leaching process (Rubisov et al., 1996; Adams, 2005; Celep et al., 2009). The presence of preg-robber components such as carbonaceous matter, sulfide minerals and aluminosilicate can further decrease gold and silver dissolution rates and recoveries. With the negative effect of the presence of preg-robbers, gold dissolution is considerably diminished in solutions with high cyanide concentration (Tan et al., 2005). In such refractory gold ores, gold particles may sometimes be occluded or included in the sulfide minerals, and pretreatment becomes necessary to break down the mineral structure to liberate gold for subsequent recovery. These ores are usually pretreated with an oxidizing process, after which gold and silver can be recovered by a standard cyanidation process. The main oxidizing processes available for refractory gold ores are roasting (LaBrooy et al., 1994; Angelidis and Kydros, 1995; Li et al., 2009; Karimi et al., 2010; Kyle et al., 2012), biological oxidation (Lawrence and Bruynesteyn, 1983; Komnitsas and Pooley, 1990, 1991; Deng and Liao, 2002; Ciftci and Akcil, 2010, 2013) and pressure oxidation (Mason, 1990; Murthy et al., 1992; Qingcui et al., 2009). In addition, ultra-fine grinding is being used in some plants for the liberation of gold and silver particles that are interlocked in the sulfide or silicate minerals (Celep et al., 2011)"

Jan 1, 2015

By D. R. Spears

The U.S. Bureau of Mines has had an ongoing interest in developing new reagent schemes for floating Stillwater, MT, chromite ore. Previous reagent schemes have been unsuccessful in achieving complete separation, primarily because little is known about the surface chemistry of the minerals in this ore. In order to design a rational reagent scheme, a study of the binding of various functional groups (R = -H, -OH, -CO2H, -NH2) on the two components (chromite and forsterite) of the Stillwater chromite was undertaken. Electron Paramagnetic Resonance (EPR) Spectroscopy was used to determine the adsorption isotherm, from a cyclohexane solution, of spin-probes which contained the functional group of interest. This was complemented by studies of the saturation surface coverage of the spin probe on the two minerals. In each case, more sites existed on chromite than forsterite; however, the forsterite sites were more strongly binding for each functional group. The results are discussed in terms of their implications for flotation.

Jan 1, 1994

By Larry Diaz

A single stage ball mill-cyclone circuit was extensively tested for its reactions to step changes in three controllable variables: feed rate, water to cyclones, and water to the ball mill. A series of carefully designed tests are to be carried out in order to determine relationships between the various ball mill and cyclone parameters. Cyclone overflow particle size distribution is to be continuously monitored during the tests using an ultrasonic device. Other circuit variables that are to be measured and recorded are feed rate, ball mill mass flow, cyclone feed and overflow densities, cyclone feed sump level, water flows, etc. Once the circuit performance is defined, two types of grinding circuit control systems will be evaluated: (a) mass flow-based; (b) particle size- based. Results obtained by each approach in terms of feed rate and cyclone overflow size distributions are discussed. The high sensitivity of continuous particle size measurements to grinding circuit disturbances is emphasized.

Jan 1, 1971

By José Luis Lee Moreno

This paper presents a preliminary phase of a study being conducted by the Department of Geochemistry of the Consejo de Recursos Naturales No Renovables in the vicinity of the Pachuca-Real del Monte Mining District. This district is located in central Mexico, about 100 km northeast of Mexico City. It has been in operation for the past 450 years and has produced about 38 million kg of silver and about 190 thousand kg of gold. At the present it is being worked by the state owned mining company of Real del Monte and Pachuca. The rocks of the area consist mainly of Tertiary volcanics, ranging in age from early Oligocene to late Pliocene. Ore bodies are recognized as epithermal, vein type fracture fillings. The main ore minerals are argentite and acanthite normally accompanied by base metal sulphides, Gold is present in small amounts as native gold and in other minerals. Orientation geochemical studies performed on soil and rocks over known veins in the district, showed zinc to be the best indicator. Lead and silver anomalies are restricted to the immediate vicinity of the veins, mercury shows the mineralized structures only when the "C" horizon is sampled, while antimony gave erratic values. The El Chico area is about 10 km north of the Pachuca-Real del Monte district and covers approximately 400 sq km. Geological evidence indicated the possibility of an extension of the Pachuca ore bodies in this area. Results obtained from soil and rock samples from El Chico, showed several anomalous area. Detailed investigations proved these anomalies to be related to faults and fractures which in several cases have been found to be mineralized. Drilling is planned with preliminary results expected by late 1974.

Jan 1, 1974

By Norbert Patzelt, Johann Knecht

Future ore reserves of major gold producers in North America and elsewhere will consist of refractory gold ores. About 60 % of the current U.S. gold production is mined in Nevada. Several of the large gold operations in this state indicate that 40 to 90 % of their future ore feeds will contain refractory gold. To com­pound problems, average head grades for refractory U.S. gold ores had fallen from 8 - 9 g/mt to about 4 g/mt by 1991. In Latin America, 52 % of the gold operations will require milling for optimal recovery. Deeper reserves are, like in North America, refractory. Therefore a special treatment process is needed in order to allow for the gold ore to be leached downstream in a conven­tional cyanidation process for a high gold recovery. There are several options available for this oxidation process like treat­ment of the gold bearing ore in pressure oxidation, in a biooxi­dation or in a roasting plant depending on the reason for the refractoriness. If organic carbonaceous matters and sulfides are the prima­ry reasons for the refractoriness, whole ore roasting is a pre­ferred method for the treatment of this type of ore. Since dry ore is to feed to the roaster, a dry grinding mill is advantageous. For the dry grinding system, the moisture content and the ore char­acteristic is of importance. Those parameters decide the mode of the grinding system. For autoclave systems common wet grind­ing systems can be applied. This paper deals with technical aspects for dry grinding plants and gives an outlook on and pos­sibilities for new grinding systems.

Jan 1, 1996

By Eberhard Stolarski, Michael Tacke

When the oxidized surface gold deposits are mined out, the underlying refractory gold ores become the challenge of treat­ment systems. The size and value ofrefractory gold ore reserves are a function of recovery efficiency and operating cost. The start-up of LURGI's gold roasters at NEWMONT's Carlin site has established whole ore gold roasters as a key to high gold recoveries. The ores from several deposits of the Carlin trend are roast­ed utilizing LURGI / NEWMONT technology, which has achieved gold recoveries approaching 95%. This is in dramatic contrast to the traditional perception that roasting is limited to gold recoveries in the mid 80's. Extensive investigation in pilot scale is required to achieve stable high gold recoveries for most variables in the ore body. The key question for all pilot tests is the classic question of (ROM) run of mine ore roasting or concentrate roasting. All variables are dominated by the leaching/ recovery char­acteristics of the natural ores. The degree ofrecovery improve­ment by roasting / calcining establishes the frame of the eco­nomical conditions. The full range of flexibility is required for the design of the plant to allow for ore variations in heat values, combustible con­tents, agglomeration behavior and off-gas composition. The variables in the ore body influence, therefore, the price of the plant proportionally to its flexibility. Concentrates are usually fairly stable in composition, com­bustion behavior, heat values and particle size since they are a product of the very selective flotation process. Flotation is not the successful process step when the tailings remain high in refractory gold contents.

Jan 1, 1996

By M. Board, C. Alexander, M. Ramström, W. Johnson

"Hecla - Lucky Friday is an underground mine that has been in operation for 75 years and produces from depths over 2.3 kilometers (7,500 ft) below the surface. Technical issues at this depth include high rock temperature and seismicity. The use of new innovative mechanization is being examined for ore production. Principal advantages of mechanization are the reduced exposure of personnel, reduced seismic triggers, and increased efficiency. Lucky Friday has partnered with Atlas Copco to design, build, test, and deploy a mechanical miner for primary ore production. We will discuss the background, concept, development and deployment strategy for a mechanical miner. BACKGROUND The Coeur d’Alene mining district in northern Idaho was first discovered over 130 years ago and has been the most prolific silver producer in the US. The Lucky Friday mine of Hecla Mining Company (Figure 1) is the oldest (76 years) and deepest mine in the district, producing approximately 725 tonne per day (800 tons per day) from narrow, vertical lead-zinc-silver veins. Cut and fill stoping is currently employed at depths to about 2.3 km (7,500 ft) below ground surface, making it one of the three deepest mines in the western hemisphere. The #4 Shaft, a winze collared at approximately 1.8 km (5,900 ft) below surface and extending to a depth of nearly 2.9 km (9,600 ft), was recently completed to exploit the high-grade 30 Vein, whose resource has been identified to at least 3 km (9,700 ft) in depth.As with other deep mines worldwide, a number of challenging engineering issues occur, including: high in situ rock stress, squeezing ground, seismicity, high in situ rock temperature that requires refrigeration, diesel equipment that generates diesel particulate matter (DPM) requiring high ventilation airflow rates, and long travel times for worker transport to mining areas."

Jan 1, 2018

By M. Wasel

The Gross Rosebel gold deposits are located in the Guiana Shield of north central Suriname. Initial discovery of surficial gold in 1880 by local artisanal miners preceded small-scale mechanized mining from 1885 to 1939. The first systematic exploration program was carried out by Placer Development from 1974 to 1977. In May 1992 Golden Star Resources optioned the property. Initial shallow reconnaissance diamond drilling of the extensive surface geochemical anomalies intersected sporadic gold mineralization with no apparent continuity between drill sections. Successive deep augering, trenching and systematic grid drilling based on information from surface mapping allowed development of a preliminary geological model. Further drilling of specific structural-lithologic targets and more complete synthesis of geological data from the trenching and deep auger sampling added to the geological model and defined the multiple controls of gold mineralization. Carefully planned infill drilling on a tighter grid spacing resulted in progressive definition of reserves within six discrete gold deposits. In a complex geological setting, the key to success at Gross Rosebel was persistent, systematic exploration, detailed mapping, careful core logging and perceptive geological interpretation. Reserves now stand at 48.6 Mt at 1.6 glt Au, or 2.4 million ounces of gold. The purpose of this paper is to describe the progression of exploration activity that led to the definition of substantial gold reserves and to summarize the geology of the deposits.

Jan 1, 1998

By Cory Dippold, Michael Mett, Jérôme Steinkühler, Kristi Latimer

For decades, tunnels of all types have been a significant part of our infrastructure. In particular, water tunnels carry millions of gallons of fresh water every day to major metropolitan areas and surrounding communities. As a critical piece of public health infrastructure, it is important to inspect the condition of these tunnels regularly to ensure reliable and continuous operation. A specific challenge with water infrastructure is that it’s often difficult or impossible to shut down the system for long periods of time to perform the needed inspections. The latest method of tunnel condition assessment is the use of hybrid reality 3-D scan data. Photogrammetric and LiDAR based 3-D data ensure a reliable and objective view of tunnel conditions. The data can be used to support a detailed digital inspection including the compilation of databases that consist of a wide variety of deficiencies such as cracks and spalls within the structure. Mott MacDonald, a design engineer company worked closely with Dibit, used a 360-degree scanning system to collect high-resolution photogrammetric and LiDAR data on a recent project involving a water tunnel. The allows for full 360-degree coverage of the tunnel surface including a water covered invert. It operates at walking speed and ensures a fast and reliable data acquisition which can reduce the time of tunnel shutdowns. Several allocated inspection weeks can reduce to few days, with the final work product being a higher quality and more complete deliverable than traditional inspection methods would have provided. The true-color 3D-model has a photo resolution of 1 × 1 mm (0.039 × 0.039 inches) which makes cracks visible with a width of down to 0.3 mm (0.011 inches). The assessment of water tunnels, its technical challenges and the results of the 3D-tunnel inspection case study are illustrated and described in this publication.

Dec 1, 2022

By W. M. Houston

The phosphate formations of the Pliocene epoch were deposited along the coastal shelf of the eastern seaboard. The deposition of the phosphate is thought to be somewhat contiguous along the early shoreline, and the deposit can be more or less traced over an 800 to 930 mile path from the Florida Gulf Coast, near Ft. Myers, to the Pamlico Sound of North Carolina. This is illustrated in Figure 1. Three areas of commercial importance are currently being exploited from this extensive known deposit: 1 - The so-called ?Bone valley? in Central Florida (multiple operations) 2 - Hamilton County in North Florida (Occidental Corporation operation) 3 - Beaufort County in North Carolina (Texas Gulf Sulphur operation)

Jan 1, 1966

By D. J. Shalanski

In 1962 a computerized data processing system was first installed and programmed for the grading of direct-shipping iron ore from the Sept-Iles terminal of the Iron Ore Company of Canada. Over the years several changes and improvements have been incorporated into this system. It is the purpose of this paper to describe its present operation and features. Sept-Iles is located on the north shore of the St. Lawrence River, 500 miles north east of Montreal. The direct-shipping ore is received by railroad from Schefferville, 320 miles to the north in the Knob Lake Iron Range of New Quebec and Labrador. The shipping season extends from mid-March to December. The maximum tonnage handled in this period being 13,045,000 long tons in 1959. Crude ore receipts for 1974 amounted to 6,568,000 tons of direct-shipping and 4,700,000 tons of plant feed material from Schefferville. This was augmented by 4,447,000 tons of concentrate and 7,572,000 tons of pellets from Labrador City 200 miles north of Sept-Iles. The direct-shipping ore has come from as many as ten mines, and grade variations, even-within the same mines, have been sufficient to require blending for uniform, acceptable cargos. Shipments of low phosphorous, non bessemer and manganiforous iron ore are made, to Canada, the United States, Europe and Japan with grade variations to meet customers requirements.

Jan 1, 1975

By R. W. Waytulonis

This paper is an update of the activities of the U.S. Bureau of Mines, other government agencies, and the automotive and truck industry concerning diesel emission control. Enacted and proposed regulations from the U.S. Mine Safety and Health Administration (MSHA) and developments in diesel emission control are presented in terms of their impact on underground coal, metal, and nonmetal mines. Mine air quality regulations proposed by MSHA may require the underground mining industry to comply with new standards. Some mines may be required to take additional actions to meet new diesel particulate and lower nitrogen dioxide exposure standards; however, the mining industry is in a position to benefit from emission controls developed for the on-highway diesel engine market. The U.S. Environmental Protection Agency (EPA) has enacted regulations to reduce emissions from on-highway diesel trucks and buses. Engine manufacturers have responded by developing cleaner burning engines. Fuel producers have responded by providing cleaner burning reformulated diesel fuel, and exhaust aftertreatment devices have been developed to provide additional emissions reductions. Bureau research and development projects seek to determine the advantages of using modern engines and fuels, and to evaluate the efficacy of new exhaust control devices on mining machines. It appears that the diesel engine will continue to be a practical power source for use in confined environments because no other available power source is as mobile and efficient.

Jan 1, 1993

By L. B. Rothfeld

In anticipation of RCRA reauthorization and subsequent rulemakings, the Bureau of Mines is studying potential economic impacts of RCRA on mining. For U.S. copper heap and dump leaching operations in a variety of terrains, the cost of liners and closure caps to comply with RCRA Subtitle D ranges from $55 million to $158 million per site, or about $500,000 per hectare ($200,000 per acre). If RCRA technology requirements and financial assurance had been required on current operations, 27 to 100% of production from heap and dump leaching would have been non-competitive at market prices between $2,310 and $1,650 per metric ton ($1.047 and $0.75 per pound) copper. This result is based on an analysis that considers return on capital, corporate overhead, marketing, and freight costs as well as operating and maintenance costs at the mine. Over the same price range, economic analysis using the IMPLAN input-output model on one-or two-county regions indicates potential net job losses of about 570 to 2,700 jobs. Total economic output of those counties could be reduced by about $180 million to $360 million.

Jan 1, 1994

By Harry Asche

Tunnels are frequently specified by owners to be designed to a structural code, often a bridge code. In the USA, AASHTO have created a tunnel code, based on structural principles, the AASHTO LRFD Tunnel Design Specification. The Load Resistance Factor Design method (LRFD) described in the AASHTO title is an approximation to the probabilistic design of structures, based on the independence of load and resistance. This methodology is well known to be problematic in geotechnical design, but it is widely used. The paper considers the difficulties of this approach and describes alternative approaches that would result in more appropriate designs for tunnels.

Jun 13, 2021

By J. M. Marek

The determination of the proper cutoff grade for an open pit metal mine is based on economic criteria and the operating philosophy of the mining company. Previous papers have dealt with the balance of a fixed mine production capacity versus economic return. Mine production capacity is often controlled by the amount of mining equipment and the working area in the pit. A complete cutoff grade strategy is a balance of economic return of mining higher grade material versus the capital costs of additional production capacity and the operating cost of moving the waste and low grade material to assure proper ore release. An approach to the problem is presented which is based in part on work by previous authors and provides guidelines to proper cutoff grade strategy encompassing the time value of money and variable commodity prices.

Jan 1, 1985

By G. H. Kuhnhausen

The Bear Creek Uranium Mill was designed in 1975 to process 909 tonnes per day (1000 STPD) of low-grade uranium ore from the Powder River Basin in Wyoming. The mill was expanded to 1818 tonnes per day (2000 STPD) in 1979. The Bear Creek Uranium Project is owned by the Bear Creek Uranium Company, a partnership of Rocky Mountain Energy Company and Mono Power Company. The original mill design contemplated processing ores from Bear Creek Uranium Company properties exclusively. The expanded capacity has been utilized for tolling ores from Kerr McGee Nuclear Corp. and other mining companies in the region. This paper describes the process of designing the original mill, the lessons learned from operation, and the design of the process modifications required for expansion. The project background, design philosophy, design basis, design criteria, actual flowsheet, special design considerations, and a comparison of assumed operating conditions and actual operating results will be presented. Bear Creek Uranium Company wishes to thank and acknowledge the help granted by the many operating companies who provided invaluable information, insight, and critique of the Bear Creek design through all the various stages and were instrumental in the successful completion and start-up of the mill. Without their contributions, the design philosophy used at Bear Creek would not have been possible and the results obtained would surely have been less satisfactory.

Jan 1, 1979

By A. Wallace Mitchell

Barite deposits in Nevada occur as bedded and vein-types along a north-northeastern -trending zone which parallels the Antler orogenic belt The bedded deposits of Nevada are the most significant economically. They are presently supplying eighty-five percent of the domestic barite production which is used primarily as a weighting agent in the petroleum drilling industry. The ore bodies are controlled both structurally and stratigraphically, occurring along regional and local structural breaks in siliceous eugeosynclinal rocks of mid-Paleozoic age. Evidence for origin of the barite includes sedimentary and hydrothermal features indicating that localization probably took place along fractures in the seafloor.

Jan 1, 1980