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By G. J. C. Young

In 1986 the city of Johannesburg celebrates its first century of existence. The fact that the city was founded to exploit the gold deposits which underlaid it, prompts this review of the gold process development in the mining industry of South Africa. Clearly a complete history of, the gold recovery process to date is not called for and it is proposed therefore to outline the most significant developments which have taken place since the middle 1930's, that is to say the last 50 years or so. Prior to this period the industry had seen the development of comminution processes employing cone crushing in closed circuit with vibrating screens followed by grinding in rotating mills and the gradual disappearance of stamp mills. The all sliming process was well established as a viable route and continuous dewatering in thickeners, continuous leaching and filtration were serious rivals for the earlier batch processes. Continuous processes for gravity concentration had also been developed and the recovery of gold from pregnant solutions employed cementation on zinc dust as opposed to shavings. Thus at the beginning of the half century under review the industry had adopted, or started to adopt, many of the processes still accepted as modern practice. However in some areas little change was evident this was especially so in the smelthouse where some thirty more years were to elapse before the hand stoked coal fired calcine and reverbatory furnaces were replaced by more environmentally acceptable electric furnaces. The most significant feature in recent history has been the mining of progressively lower grades of ore and the retreatment of tailings from earlier operations, much of the latter comprising tailings only a decade or even less in age. Notable among these operations are those on the East Rand near Springs in the Transvaal, in the Orange Free State at Welkom and more recently, massive reclamation of tailings close to the city centre itself. The carbon in pulp (CIP) process has been much publicised in recent years and all new plants erected during the 1980's have adopted this route for gold recovery. However the major proportion of tonnage milled in the industry is still subjected to the more traditional process of liquid solids separation by vacuum filtration. The discussion that follows will centre largely on the developments in the traditional process route, which for the sake of completeness is listed below: Comminution Dewatering Leaching Liquid solids separation Gold recovery Smelting

Jan 1, 1985

By Charles B. Escapule

The first successful heap leach of silver ores in the State of Arizona has been under continuous operation since early 1976 at the State of Maine Mine, two miles southwest of Tombstone, Arizona. The silver produced from leaching old mine dumps at this property vas the first in the Tombstone mining district to achieve a 999+ purity. While cyanide leaching of silver and gold ores is a time-proven accepted practice, a relatively new method of treatment called "heap" leaching was employed. Heap leaching is a comparatively inexpensive fast way to recover precious metals from low grade material.

Jan 1, 1981

By B. K. Mishra, A. Datta

Estimating the power draw of a ball mill is of great importance from both operational and control standpoints. There are many factors that affect the power draw, and its prediction is particularly difficult in an operating plant. The important factors that affect power draw are the mill dimensions and operating parameters. Although mill dimensions remain the same for any given mill, the operational factors, such as ball load, mill filling and mill speed, may vary. This makes the modeling effort extremely cumbersome. It is for this reason that an artificial neural network is considered for the development of a black-box-type model to predict power draw. In this work, a total of 48 sets of plant data are used. Using these data, a neural network is built and trained. The trained network is used to predict power that is found to be in good agreement with operating mill power for many situations. In addition, the results of simulations are also com- pared to those obtained from a discrete-element method- based power-draw model.

Jan 1, 2000

By Qingqing Huang, Aaron Noble

The Mineral & Metallurgical Processing Division (MPD) of the Society for Mining, Metallurgy & Exploration held the first MPD Student Video Contest during the spring of 2021. The event showcased the work of 18 graduate and undergraduate students from several U.S. and international institutions. The contest began in January when students submitted a onepage abstract for judging. Over the next several months, they developed a three-minute video that further explained their research findings. Both the abstract and video were evaluated by a panel of judges, and the top-placing participant was recognized at an MPD virtual event held on June 10.

Sep 13, 2021

By W. K. Utt

This report discusses U.S. Bureau of Mines' research involving modem vehicle position determination techniques in surface mining. The applications would include haul trucks, power shovels, and drilling rigs. Accurate position determination of these vehicles in near real-time is expected to result in safer and more efficient mining operations. The requirements for a vehicle position monitoring and warning system were determined. After screening several concepts, the global positioning system (GPS) and a radar positioning system were selected for further evaluation. A state-of-the-art GPS receiver was taken to a surface mine to assess the feasibility of receiving the satellite signals. A state-of-the-art radar positioning system was evaluated with regard to accuracy.

Jan 1, 1995

By I. M. Konduri

Theoretical investigation and laboratory experimentation have shown a great potential for jet fan ventilation in mines. Jet fans, also called induction fans due to the induction effect of the fluid jet to ventilate headings, may have particular application in remote-controlled production operations. This paper summarizes ongoing research using a scaled laboratory model. The model uses water as a fluid medium and simulates a typical 25m long heading of 1.5mx6m cross-section. The effects of various nozzle positions and designs have been investigated by using still photography as a tool for flow visualization. It is also found that the use of jets in combination with line curtains has enhanced the overall ventilating effect in the model entry.

Jan 1, 1996

By Kenny Lo

"SummaryFor more than a century, ground freezing has been a construction technique used in stabilization of ground by means of lowering the temperature of surrounding soil strata. This technique is used in circumstances where conventional grouting method is unable to achieve the degree of consolidation required to prevent settlement and water ingress during the execution of underground excavation. Whilst ground freezing is effective in imparting self-supporting characteristics to the excavation profile, it poses significant challenges when it comes to the New Austrian Tunneling Method (NATM) where sprayed concrete is used to support the freshly excavated ground. Sprayed concrete, if used in an appropriate manner, provides a fast, efficient and structurally-reliable means of supporting the structure, especially in underground construction. The evolvement in sprayed concrete technology is attributed to the development of concrete know-how, improvement of spraying technique with the use of automation spraying equipment, more in-depth understanding of sprayed concrete behavior and enhancement of materials used in production of high quality sprayed concrete Not only has this markedly escalated the prominence of sprayed concrete on wider perspective,. the positive development has also pushed sprayed concrete beyond its boundaries, enabling it to be embarked on area of application not considered possible decades ago. Nevertheless, sprayed concrete, for all its placement versatility, still depends largely on the technicality provision very similar to concrete to achieve the required quality. Parameters such as raw material grading composition, curing temperature and cement quality are some of the factors that can easily sway the quality of concrete from one extreme to another. Conducive ambient temperature is critical in ensuring optimum hydration of concrete. This is more important in sprayed concrete where temperature plays a pivotal role in influencing the early strength and long term strength development. The low temperature imposed by ground freezing is everything but ideal for competent hydration to take place. This paper outlines how the innovative use of sprayed concrete helps to overcome the adverse ambient temperature in the construction of a 110m underground pedestrian walkway utilizing ground freezing technique in Hong Kong."

Jan 1, 2016

By C. V. Deutsch, D. A. Silva

The geologic modeling of multiple domains is required for the prediction of mineral resources and reserves. In general, explicit methods have wide acceptance among modelers due to the ability to manually add deemed important trends and geological features into the models. As an alternative, implicit geologic modeling techniques are increasingly adopted to reduce professional time requirements. These methods aim for objective, repeatable and flexible models by replacing the manual time-consuming interpretation of sections with the interpolation of signed distance values. These techniques, however, have been developed for the binary case of two domains at a time. The current paper presents an algorithm that extends the binary case to multiple domains. The method is able to transfer large-scale geological features from data to geologic models. A case study illustrates the benefits of the algorithm and practical implementation considerations.

Jan 1, 2016

By Christopher E. Dianora, Matthew Sorrell, Eileen Test

"Constructed between 1939 and 1945, the Rondout-West Branch Tunnel (RWBT) portion of the Delaware Aqueduct is 45 miles (72 km) long. The New York City Department of Environmental Protection (NYCDEP) first identified suspected areas of leakage from the RWBT in the 1990s. A $1 billion project is underway to mitigate the leakage through the construction of a bypass tunnel around the area of most severe deterioration, a 2.5-mile (4 km) section located beneath the Hudson River. Two shafts, 800 and 900 feet (244 and 274 m) below the ground surface, are being sunk to support the tunnel construction. The deep shafts will be subjected to high groundwater pressures and have been designed to accommodate multiple tunnel portals. This paper discusses the engineering decisions and analyses leading up to the final design. INTRODUCTION Project Background The New York City Department of Environmental Protection (NYCDEP) provides over 1 billion gallons (3.7 billion liters) of water to over 9 million residents of the City of New York and surrounding communities each day. This water is stored in upstate reservoirs and conveyed to the City via a system of aqueducts and tunnels. Water is delivered to the City almost completely by gravity and consists of three systems: the Croton, the Catskill, and the Delaware. The Delaware System is the largest of the three and supplies between 50% and 70% of the City’s daily water supply. In the 1990s, the NYCDEP discovered leaks in the central 45-mile-long (72 km) portion of the Delaware Aqueduct known as the Rondout-West Branch Tunnel (RWBT). The leaks release between 15 and 35 million gallons per day (MGD) (132.5 million liters per day) and are concentrated in two areas near Wawarsing and Roseton, New York. As part of the Rondout-West Branch Bypass Tunnel and Wawarsing Repairs Project (Bypass Tunnel Project), the leaks in the Wawarsing area will be repaired by grouting from inside the existing RWBT, and the leaks in the Roseton area will be mitigated by constructing a bypass tunnel parallel to and 1,750 feet (533 m) north of the leaking portion of the existing RWBT. Two deep shafts will be excavated on either side of the Hudson River: Shaft 5B in Newburgh and Shaft 6B in the Town of Wappinger."

Jan 1, 2016

By Chris Howell

PotashCorp?s Aurora phosphate mine, in Beaufort County, NC, operates four low pressure boilers and four high pressure boilers to meet its process steam requirements. Maintaining these boilers is critical to meeting production demands. Processing phosphate ore into phosphoric acid requires large amounts of sulfuric acid and steam. Ore is mined from the phosphate deposit with large bucket excavators after 9 to 30 m (30 to 100 ft) of overburden is removed. The phosphate ore is mixed with water to make a slurry that is pumped to the mill. Elemental sulfur is burned in the presence of air to make sulfuric acid. This process is highly exothermic and boilers produce steam while cooling the process. The phosphate ore is reacted with sulfuric acid and the resulting products are refined into different grades of phosphoric acid for fertilizers, feed stock and food additives. Plant operators at the mine were challenged with boiler feed water that was high in silica and other contaminants. As a result, boiler operations were experiencing difficult, labor-intensive operations and equipment deterioration. This resulted in higher operating costs and diminished processing performance. The facility was operating an aged boiler feedwater pretreatment system that included warm lime softening followed by pressure filtration and a cation/anion/mixed bed demineralizer system. The demineralizer required frequent regeneration and chemical usage was high and costs were difficult to predict. Depressurized well water (DPW water), used for plant utility water and boiler makeup, is very high in silica, in the range of 60-70 ppm. Silica can form scale at pressures below 600 psig. Above 600 psig, silica starts to volatize, carrying over with steam to potentially form deposits on downstream equipment and processes. Mine officials decided to upgrade the boiler feedwater pretreatment system to a state-of-the-art reverse osmosis (RO) membrane system. This new system, which started up in March 2009, has improved operating performance and reduced water consumption and overall operating expenditures.

Jan 1, 2011

By J. Y. Hwang

Coal cleaning with traditional magnetic separation usually yields unsatisfactory results because minerals associated with coal, such as quartz, clay, pyrite and calcite, are weak-or non-magnetic. Magnetic reagent technology is a new mineral processing technology with the capability to enhance the magnetic property of minerals selectively. This reagent can be adsorbed selectively on minerals through the control of surface chemistry and, thus, result in selective magnetic enhancement. The application of this technology on coal cleaning has been experimentally demonstrated. Good separation results can be obtained at low to medium magnetic field strength. Comparison with other processing technologies is included.

Jan 1, 1992

By Rodolfo V. de la Cruz

The stresses in the materials surrounding an underground opening are dependent upon the virgin stress field, the geometry of the opening and changes in boundary conditions as mining progresses. For most underground openings especially in coal mines, roof bolts are installed to help stabilize the opening. While most parameters in roof bolt design and installation have been thoroughly investigated, the effects of the initial stress field on the effectiveness of roof bolts have not been recognized. This paper summarizes the results of investigation of the effect of the initial stress field on the performance of mine roof bolts. Roof bolt installations are duplicated in the laboratory utilizing conventional roof bolt frame, commercial roof bolts and shells, mine torque wrench and encapsulated rock specimens for anchorage. A special and primary feature of the laboratory set-up is the addition of a loading system for generating stresses at the anchorage specimens. For this preliminary study, different levels of hydrostatic stress fields were induced at the anchorage specimen, instrumented roof bolts were installed in the usual manner, and the bolt load loss-with-time observed. Statistical analysis of data showed that the stress field at the anchorage horizon has a considerable influence on the performance of mine roof bolts, i.e. the higher the stress field, the higher the anchorage efficiency. From this observation, methods of improving the performance of mine roof bolts utilizing new shell designs and methods of installing them are suggested.

Jan 1, 1978

By Philip Lindstrom

Retreat mining, using yielding steel friction props, over a seven-year period has been successful at a uranium mine operated by Hecla Mining Company in southeast Utah. The support system allow good roof control, maximum profit, complete extraction, and good ventilation. Unusual subsidence observations were made in that some of the surface was raised rather than lowered, Longwall mining, commonly practiced in European coal mines, has a potential of broader application because of mechanization possibilities and better roof control and ventilation at greater depths.

Jan 1, 1964

By Frank A. Aplan, Barbara J. Arnold

INTRODUCTION Coal flotation is a fine cleaning process usually present in all but the older preparation plants. It is typically used to clean either the -28 mesh (-500 pm) or - 100 mesh (- 150 pm) raw coal fines, and it is the only commonly used preparation method that can effectively recover coal particles finer than, say, -200 mesh (74 pm). To place coal flotation into its proper context, it should be noted that the bulk of the raw coal sent to preparation plants is treated by gravity concentration. On a worldwide basis, from 0 to 40% of the raw feed to a preparation plant is treated by flotation, while in the US only about 10% of the raw coal feed is floated. Roughly, 50% of US preparation plants use flotation to process at least a portion of the raw coal feed, although most of the newer plants incorporate flotation into their flowsheet. Historically, the process has only been used to treat the raw coal fines naturally occurring after mining and a minimal amount of crushing at the preparation plant. This is in sharp contrast to ore flotation where, typically, the entire tonnage is first ground and then floated. As a consequence, of the approximately 500 Mt of raw coal treated by preparation in the US yearly, it is estimated that only about 40 Mt are sent to the flotation circuits (producing -30 Mt of clean product).'O1 This small tonnage compares with about 400 Mt of ores treated annually in the US by flotation. By analogy to ore flotation, where it is an effective, large tonnage, low cost, easy to operate process, its potential in coal preparation should be great. Reasons why it has not achieved a greater potential in coal preparation have been attributed by Aplan 102 to: 1. Indifferent results in removing sulfur and ash. 2. Difficulty in floating low rank and oxidized coals. 3. Inability to make clean separations with the finer sizes. 4.Inability to clean slurries with a high percentage of clay. 5. Problems with water chemistry. 6. Competition with effective, gravity coarse-cleaning methods. 7. Low value of coal historically. 8. Dewatering problems. 9. Transportation and storage problems with coal fines. 10. Marketing problems with coal fines. 11. Inadequate attention to the process in the plant. 12. Inefficient use of capital and operating monies. Inadequate attention to procedures, machines, and processes.

Jan 1, 1991

By B. Cavender

Mining managers trying to rapidly reduce production costs tend to implement a traditional set of topdown managerial practices: reductions in production volume, employee layoffs, renegotiation of supplier contracts, cancellation of employee training, restrictions on travel, reductions in office supplies, and so forth. While these practices do reduce costs, the benefits are often limited in both magnitude and duration, and the workforce is usually left demoralized. Successful cost-cutters take a different approach. They make the continuous reduction of costs a priority for all members of the organization, whether managers or workers. The culture of these firms emphasizes the commitment, voluntarily given, of individuals and work groups to this goal. Cost-cutting practices often reject all of the traditional methods mentioned above, but are far more numerous, innovative and successful. This culture of cost reduction is the result of a set of leadership competencies that establish direction for the organization, align the organization's various constituencies with this direction, and motivate and inspire the organization. Cost reduction then becomes a routine task rather than a heroic achievement.

Jan 1, 2002

By L. Yuan, J. H. Rowland

"In 1995 and 2003, the U.S. Mine Safety and Health Administration (MSHA) conducted surveys to determine the number of atmospheric monitoring systems (AMS) that were being used in underground coal mines in the United States. The survey reports gave data for the different AMS manufacturers, the different types of equipment monitored, and the different types of gas sensors and their locations. Since the last survey in 2003, MSHA has changed the regulation requirements for early fire detection along belt haulage entries. As of Dec. 31, 2009, point-type heat sensors are prohibited for use for an early fire detection system. Instead, carbon monoxide (CO) sensors are now required. This report presents results from a new survey and examines how the regulation changes have had an impact on the use of CO sensors in underground coal mines in the United States. The locations and parameters monitored by AMS and CO systems are also discussed.IntroductionThe last survey conducted by the U.S. Mine Safety and Health Administration (MSHA) on atmospheric monitoring systems used in underground coal mines in the United States was in 2003 (Francart, 2005). A total of 146 active mines were surveyed. The survey report states that since 1995 there had been a steady increase in the use of atmospheric monitoring systems in underground coal mines as the technology of carbon monoxide (CO) sensors was improved by manufacturers. Atmospheric monitoring systems had become more reliable, and some CO sensors could be purchased with the capability to discriminate between the CO produced by a fire versus CO produced by diesel equipment. This increase in reliability had reduced the number of false alarms and the response time. The faster response time to a developing fire allowed miners to take the necessary action to put out the fire or exit the mine.At the time of the last MSHA survey, some mines still used point-type heat sensors to detect the presence of a fire on conveyor belts. This detection method works by measuring the temperature of the air around the sensor. As a fire starts to develop, smoke and hot gases are produced from the combustion process, and the air is heated up. Once the air and gases reach a designated temperature detected by the point-type heat sensor, a fire alarm signal is generated. Studies have shown that the response times for detecting the presence of a fire using CO sensors are much shorter than when using point-type heat sensors (Conti and Litton, 1995)."

Jan 2, 2018

By Stephen Stone, Kerby Dobbs, G. Richard Whittecar, W. Lee Daniels, Zach Agioutantis, Tess Thompson

A common result of Environmental Impact Assessments associated with mining projects is the construction of new wetlands in areas disturbed by mining operations. Where appropriate, this mitigation may be considered an integral part of the mine reclamation process under the principles of sustainable development in the minerals industry. Wetbud is a new tool for estimating wetland water budgets using available weather data and site-specific topographic, soil and geohydrologic data, coupled with mass balance mathematics. Wetbud is primarily intended as a planning tool for use in the design of created wetlands, but it can also be applied to native wetlands or wetland restoration sites where the required input parameters can be specified. Wetbud can be run in its basic form where wetland topography, soil parameters and groundwater flux are simplified, or in the advanced form, where these parameters are included in a more complex approach via integration of the MODFLOW package, a free 3D program that was developed by the United States Geological Survey. Both versions can also include overbank flow hydrology sources and the advanced form can also model sloping and irregular topography. The program downloads weather data from the nearest applicable station and selects appropriate wet-normal-dry (W-N-D) years following a modest user data clean-up step. Wetbud also has the ability to utilize existing short-term (e.g. 6 to 9 months) groundwater data from an up-gradient well to simulate longer-term groundwater level inputs for the selected W-N-D years. In addition, Wetbud features a “Wizard” version that comes pre-loaded with 14 pre-selected weather data sets for all areas of Virginia that can develop a simple monthly water budget in less than 15 minutes – a feature that could be expanded anywhere geographically with historic weather data.

Jan 1, 2017

By William P. Shell

An important part of process control engineering is the implementation of the basic control system design through commissioning to routine operation. This is a period when basic concepts can be reviewed and improvements either implemented or recorded for application in future systems. The experience of commissioning the process control systems in the Homer City coal cleaning plant are described and discussed. The current level of operating control performance in individual sections and the overall system are also reported and discussed.

Jan 1, 1983

By P. W. Conrad, C. Todd, N. A. Degerstrom, N. West, R. Kramer

"Surface subsidence caused by underground room-and-pillar mining operations and by solution mining operations have been studied separately but never in combination. In 2008, FMC Minerals began using solution mining at its Westvaco Mine as a secondary extraction method in an area that had been previously mined using the room-and-pillar mining method. Mining regulations require that subsidence associated with underground mining activities be monitored and measured annually. Using Salt_Subsid, a subsidence software package from the Solution Mining Research Institute, and ArcGIS, Esri's mapping platform, researchers at Montana Tech were able to develop a relationship between measured surface mine subsidence and solution mining that can be used at the Westvaco Mine to estimate the production of trona from solution mining operations. Project backgroundFMC Minerals has increased the production of trona from its Westvaco Mine near Green River, WY, using solution mining as a secondary extraction method in an area previously mined using the room-and-pillar method. The area of interest was mined until 2001 with the use of a borer miner at a depth of approximately 488 m (1,600 ft). Currently, FMC determines the amount of trona produced using its solution mining operations by measuring the dissolved solids pumped from the mine. This approach, however, does not account for the location from which the trona was removed.The location from which the trona is removed and the size of the cavern created by the solution mining operations are important to FMC’s mine planning. FMC believed that with proper investigation of the subsidence at the Westvaco test site, a correlation might be found between surface subsidence measurements and the amount and location of trona production from the solution mining activities. The primary goal of this project, conducted by Montana Tech, was to find relationships between the measured subsidence and the solution mining activities. The project attempted to develop an equation that could be used to predict solution trona production based on measured subsidence. The project attempted to model the relationship between the measured surface subsidence and solution mining production using Salt_Subsid, an existing subsidence software package from the Solution Mining Research Institute (SMRI, Clarks Summit, PA) to estimate the location, size and shape of the solution mining cavern. This study would determine the program’s usefulness for locating and developing the cavern created by secondary solution mining activities. The subsidence and production data sets used in this study were collected over a seven-year period from 2008 through 2014."

Jan 4, 2018

By A. Warren Wilson, Hugh R. Wilson

This paper describes the evolution of the Waste Management Program at the Lupin Mine through the years 1982 - 1986. Echo Bay Mines' Lupin Mine is located on the western shore of Contwoyto Lake in Canada's Northwest Territories about 80 km. south of the Arctic Circle. The gold mine commenced production in 1982 and the Waste Management Program was based originally on the total containment concept. Due to an expansion of the mill circuitry and increased throughput, it was apparent that total containment was no longer applicable and therefore studies were undertaken to characterize the tailings, to evaluate the effectiveness of natural degradation of contaminants in the tailings pond and to determine what additional treatment steps would be necessary to meet the requirements of the mine's Water Licence. These studies indicated that arsenic and cyanide concentrations in the tailings pond decant water would not meet Water Licence discharge limits unless certain measures were under taken. As a result of this work, in late 1984 a decision was made to create a two-ponds-in-series system and the necessary civil work was started in 1985. In addition, a series of dykes were constructed to contain the solids portion of the mill tailings in a confined area of the first pond. To remove cyanide, the ponds are operated in a sequential fill and decant mode to take maximum advantage of natural degradation. For arsenic removal, a chemical feed system was constructed for iron salt addition to the decant stream from the first to the second pond. Decanting of the ponds is accomplished by means of a series of 500 mm (20 inch) Sclairpipe syphons.

Jan 1, 1987