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By K. G. Correia

The replacement of the dry mining method at Guajú Mine by the dredging method was a means of ensuring its feasibility by maintaining the production levels. Dry mining increased the cost of the deposit with the distance and presented a limited mined volume, while the decreasing grade of the deposit led to a production drop. With the new methodology, there was a considerable reduction in unit cost of the mine and an increase in the production level of a deposit with low heavy minerals content.

Jan 1, 2005

Membrane technology has been available for over 36 years, but has been used sparingly in the general mining industry. However, recent developments in polymer chemistry, spiral wound element construction, pretreatment equipment and techniques and an expanded understanding of membrane fouling and cleaning techniques have dramatically improved the reliability and robustness of membrane based systems in the mining industry. Harrison Western has expanded the use of this “new” technology to enhance the use of membrane technologies to separate metals from large volume heap leach mining solutions containing copper, zinc, and iron, gold or silver. Moreover, membrane technologies are ideally suited to fractionations that add value to processing fluids from refineries like separating metals from acids or concentrating acids and producing high quality process fluids. Finally, wastewater from Acid Mine Drainage (AMD) or, as in the case of the Newmont Yanacocha Mine in Peru, the treatment of excess barren leach solution created during the rainy season, can be cost effectively processed to meet World Bank Standards for surface discharge. Polymeric membranes, specifically thin-film composites, have been developed that will purify, fractionate or concentrate gold, silver, copper, zinc or nickel. Recent applications have been developed for spiral wound modules that operate across the pH spectrum from 0 to 14. Systems using membranes have been constructed that operate on feed streams from 140° C to 300 centipoise. Opportunities exist to apply membrane technology to concentrate gold, silver, copper, zinc or nickel using thin film composite membranes. Engineered membrane types can operate across the spectrum from low pH (<2) acid applications to high pH > 10 cyanide applications. Incorporating HW EMS™ membrane technologies into current mining operations could allow one to increase production because the membrane technology would be used to pre-concentrate heap leach solutions, and therefore, increase utilization of existing extraction and refinery capabilities.

Jan 1, 2007

By K. Awuah-Offei

An aggregate plant may have difficulty balancing product stockpile inventories if hot mix asphalt (HMA) design engineers do not account for aggregate inventory during mix design. Yet HMA design engineers do not, often, take this into consideration during asphalt mix design. This is due to the lack of tools that enable the lab technician or engineer to optimize the mix for good performance while helping the aggregate plant manage its stockpile inventory levels and reducing the aggregate cost. This work presents a linear programming model of the asphalt mix design problem that helps aggregate plants manage their inventory levels while meeting HMA customer demands. The algorithm is implemented in MATLAB as an Asphalt Mix Design Optimization (AMIDO) program. The program is successfully validated with real-life data. The results show that AMIDO can be used to successfully produce any mix design while reducing the cost of aggregates by using the cheapest stockpile materials. The application of AMIDO will increase aggregate plant profitability when serving HMA customers and could potentially be modified for concrete aggregate customers too.

Jan 1, 2009

By D. Noon

Mine production crews and drill-and-blast crews may be exposed to unexpected movement of ground when working under pit slopes. Without specialist geotechnical advice and appropriate measurement systems, mine crews are faced with conducting risk assessments and relying on subsequent controls that may or may not be adequate to ensure their safety. Mine crews need an ?early warning? monitoring system to give them the confidence that they will have time to walk out of the danger zone if the pit slope begins to move. Slope stability radar technology is used by mine geotechnical engineers to assess overall slope stability over an extended period, typically days or weeks, and to critically monitor slopes that are actively moving and may become unsafe. The complexity of slope stability radar allows for geotechnical engineers to assess movement types and movement rates across multiple work areas of a mine from long ranges, with alarm capability to a central location. However there are many mine work areas where production and drill-and blast crews are not adequately covered or alarmed by slope stability radar systems. What is required is an easy-to-use, short-range, fast-scanning tool that can be operated directly by a work crew and can provide a local alarm with sufficient warning when a wall movement occurs within the work area. The Work Area Monitor (WAM) concept has been developed specifically to be operated by a mine production crew. The system comprises a sensitive, fast-scanning radar coupled with a high-resolution camera, built into a mine-standard light vehicle. The system has been designed specifically for ease of use with the output being a local area alarm to warn workers of slope movement in their vicinity, as opposed to the broader pit monitoring and long-term deformation measurements of the known slope stability radar systems.

Jan 1, 2012

By G. G. Gold

A leach pad’s fluid flow characteristics greatly affect the recovery of metals from heap leaching. However, because there are other factors such as particle size distribution, application rate and method, and chemical reactions to consider, mining companies often overlook potential problems associated with fluid flow until it is too late. In an effort to better understand the dynamics of fluid flow in leach pads, a series of experiments were preformed using temperature probes. A model leach pad was set up using a particle size distribution, fluid application rate, and application method common to modern leaching methods. Variable water temperatures were applied in succession and data gathered from the three dimensional grid of temperature probes built in to the model. Current work is analyzing these data along with visual observations of the model, computer simulations, past mining experiences, and other related research, in an attempt to develop a low cost test that could be performed prior to large scale leaching to determine the fluid flow characteristics of a particular ore. This paper will summarize the work and findings to this point as well as suggest areas of additional related research.

Jan 1, 2004

By Z. Konstantinovic, M. Ahrens

Due to the large installed electrical power and the large number of electric drives in minerals and mining plants power factor compensation and harmonic filtering has always been an important issue. For the design of harmonic filter and power factor compensation installations several approaches can be taken. The paper describes different concepts and their advantages and analyzes special requirements and design considerations for minerals and mining plants. It also highlights areas where problems can occur and which points need to be addressed carefully. Optimized designs and solutions are discussed in case studies and the resulting energy savings and benefits for the plant operation are shown.

Jan 1, 2007

By D. G. Klaren

Self-cleaning fluidized bed heat exchangers are conquering the world for reason that they are able to solve any severe fouling problem in indirect heat transfer due to the circulation of cleaning particles through the tubes of vertical shell and tube exchangers. In most cases, these particles consist of chopped metal wire. Moreover, self-cleaning fluidized bed heat exchangers perform with excellent heat transfer at very low liquid velocities, which makes completely new designs of shell and tube configurations possible. Further, self-cleaning fluidized bed heat exchangers show a strong shear thinning effect in non-Newtonian liquids. All the above characteristics make the self-cleaning fluidized bed heat exchanger an ideal tool for the indirect heating of laterite nickel slurry in High-Pressure-Acid-Leach (HPAL) plants. Preliminary tests and evaluations of these heat exchangers have shown that the performance and price of these heat exchangers used for the production of nickel and cobalt from a laterite slurry, cannot be matched by existing conventional heat exchange systems. This article explains the principle, design, lay-out and enormous advantages of the self-cleaning fluidized bed heat exchange technology in a plant suitable for an annual production of approx. 45,000 ton nickel and 4,500 ton cobalt from laterite slurry through high pressure&apos;acid leaching.

Jan 1, 2002

By Y. P. Chugh

A novel dry and wet air dust filter concept was conceived and demonstrated successfully at two mines. A steel-wool and a fiberglass filter, suitable for underground use were identified through laboratory testing and demonstrated in the mine. The steel wool filter was operated with and without water sprays while the fiberglass filter was only operated in the dry mode. The dry steel wool filter provided a dust capture of 37% at a negligible pressure drop. When fine misting water sprays were used on the steel wool filter, the dust capture increased to 51% again with a negligible pressure drop. The filter screen also remained clean and no change in air flow characteristics was observed as a function of time. The dry fiberglass filter however did not perform as well achieving only 11% dust capture while introducing a significant resistance to air flow. This technology is seen to have several applications in underground coal mines.

Jan 1, 2009

By Fernando Humberto Muge

One of the problems that arises in the early stages of the mine planning before the determination of the mining exploitation method is to predict what will be the recoverable ore reserves in tonnage, grade and metal quantity, if the select ion is based upon block grades. The estimation of these recuperation or recoverable functions can act as an important planning tool in what concerns the appraisal of the consequences of ore-waste discrimination of individual blocks in a selective mining operation. Estimation methods of all these functions are discussed together with cross validation tests using the available information concerning a preliminary drilling campaign accomplished during the exploration stage of an iron orebody located in the North of Portugal (Moncorvo Orebody).

Jan 1, 1982

By S. Kittel, P. Galleguillos, H. E. Urtubia

The rougher flotation at Escondida consists of 80 cells of 100 m3 each, with injected air. Escondida has developed a system of automatic control of the rougher flotation using video cameras, which have been operating since 1997 for remote monitoring and manual control. Since 1999, an image processing software and a group of rules have allowed implementation of an expert system. To date, the expert system controls the superficial speed of each cell by adjusting the air flow and the froth depth of the flotation bank. Preliminary tests of the expert control on two of the eight rows gave 1.2% higher rougher recovery at a 92% degree of confidence. The proven benefits are already sufficient to move towards a complete plant implementation.

Jan 1, 2001

By Jeffrey A. Pontius

The Cresson gold deposit is in the southcentral portion of the Cripple Creek mining district in central Colorado (Fig. 1). The deposit is hosted by a series of 32 Ma (Kelley, 1995) felsic to mafic, alkaline volcanic rocks that were deposited in a diatremal environment. Mineralization in the Cresson deposit is structurally con-trolled. It occurs as disseminated and vein type. Gold deposition is closely associated with potassium-pyrite metasomatism and quartz-telluride vein development(Pontius, 1992). The Cresson deposit is owned by the Cripple Creek and Victor Gold Mining Co. (CC&V), a joint venture between Pikes Peak Mining (67%) and Golden CycleGold (33%).

Jan 1, 1996

By E. Arioglu

Discussion by E. Arioglu Y. Luo and S.S. Peng are to be congratulated for their outstanding paper providing new results from surface subsidence monitoring over longwall panels under different conditions. This writer found the authors&apos; paper very interesting. In reference to this paper, the following contributions are offered: • In the paper, the maximum possible subsidence [(ASmax)] induced by chain pillar convergence has been related to a parameter (h/1- p) by linear regression. (Notations are expressed in this discussion&apos;s Fig. 1 (b).) It is a well-known fact that in a goaf the roof lowers onto broken material that gradually compacts. Then the physical behavior of goat may closely follow the compaction characteristics of broken materials. In light of this assumption, a mathematical means (Fig. 1(a)) of defining the expected compaction (i.e. surface subsidence) represents an exponential expression between [ASmax/m vs. h/1-p]. This is based on Luo and Peng&apos;s field observations from the Appalachian, Illinois and Alabama coal fields. (The coefficient of regression "r" under consideration was computed to be 0.883). • According to Wardell&apos;s (1969) findings for board and pillar mining, the maximum possible subsidence can be expressed in terms of maximum pillar loading (depth, ratio of extraction) and the height-to-width ratio of the pillars left. Using Luo and Peng&apos;s 1991 results, this writer discovered a regression equation between the above-mentioned factors. As displayed in Fig. 1(b), the functional expression approximates as closely as possible the observed subsidence data. It may be noted here that Wardell&apos;s approach (1969) can be successfully utilized for longwall panels having chain pillars. Reference Wardell, K., 1969, "Ground surface and control," Mining Congress Journal, January, pp. 1-7.

Jan 1, 1993

In practice, frothers are selected following general guidenlies and verification by laboratory and/or plant flotation tests. The terms “powerful” or “selective,” which are commonly used to characetrize frothers, have intuitive rather than scientific meaning. A research program has been set out to study fundamental properties of the flotation frothers and to identify the tests which can provide information needed to characterize and classify such flotation agents.

Jan 1, 2004

By Günther M. Volkmann

Continuous developments in tunneling require knowledge transfer between designers and suppliers to optimize the application of support systems. This collaboration allows the designer access to the latest research results, technical innovations, and support specific measurement techniques as well as the supplier?s experiences on recent projects. Project specific requirements determine the information that can be used to increase support system efficiency, advance rate, degree of safety, or decrease costs. This cooperative effort results in not only an unambiguous tender document, but also an optimized design with reduced risk that is coordinated with safe and high performance construction techniques. This paper will address the benefits of an early collaboration to both the design and the specifications in the tender document by using the A3 Hindhead project (UK) as an example.

Jan 1, 2008

By R. C. Richardson

Barite Worldwide barite production for 1985 decreased 1.3%, while US barite production increased 1.4%, according to US Bureau of Mines statistics. The increase in US production is attributed to heavy demand for oil and gas drilling during the first quarter and an unrealized heavy expected demand in oil and gas markets for the last quarter. Nevada accounted for 82.1% of the 807 kt (890,000 st) of barite produced in the US last year, according to the Bureau. Other producing states were California, Georgia, Illinois, Missouri, Montana, Tennessee, and Washington. In 1985, the US imported 1.8 Mt (2 million st) of crude barite and 64 kt (71,000 st) of ground barite. China led the way with 43.3% of the total. Imports from India accounted for 21.6%; Morocco, 15.5%; and Thailand, 5.6%. The 1.8 Mt (2 million st) of crude barite imported is an 18.8% increase over 1984. Apparent consumption of barite for 1985 was about 2.6 Mt (2.9 million st), a 15.7% increase from 1984. Due to very low drilling rig activity during the last quarter of 1985, actual consumption is probably less as crude barite inventories at mines and plants increased. According to the Bureau, 90% of barite consumed in 1985 was for the oil and gas market. Paints, rubber, glass, and other chemical uses consumed the other 10%. With the price of oil falling dramatically early in 1986, the outlook for oil and gas drilling looks to be significantly lower than 1985. This lower demand for barite, coupled with the high year-end inventories, should lower both imports and domestic production. Significant lower prices on imported barite are expected, especially from China, Morocco, and India. This also could further lower US production of barite this year.

Jan 5, 1986

By M. Oliverio

The Cigar Lake uranium deposit was discovered in 1981 at the south western end of Waterbury Lake, approximately 660 km north of Saskatoon in the province of Saskatchewan (see Figure 1). It is the largest undeveloped high grade uranium deposit in the world. It contains proven and probable reserves of more than 226 million pounds U3O8 at an average grade of 20.7%. The world average grade is less than 1% U3O8. [ ] The ore body is located about 450 m below surface at the interface between sandstone above and basement rock below (see Figure 2). The sandstone is fractured rock and saturated with water. This makes water inflow a real hazard at the mine. In fact there have already been two significant mine inflow events. The first of these occurred in October 2006 and resulted in the flooding of the mine. The second occurred in August, 2008 during mine recovery activities.

Jan 1, 2011

By M. Moats

Copper electrowinning operations have dramatically improved their ability to produce high quality copper at low costs over the past several decades. Even so, some fundamental understandings are still lacking, which could allow operates to run more efficiently. For example, a rule of thumb exists that estimates a current efficiency loss of 2-3% per gram per liter of iron in the electrolyte. While several laboratory studies have been performed that demonstrate this rule of thumb is likely true, no definitive relationship exists. In this paper, the first steps in developing a definitive relationship are presented. The effective diffusivity of ferric ions in synthetic copper electrowinning solutions was measured using chronoamperometry and the Cottrell equation. The effective diffusivity of ferric ion was determined as a function of electrolyte concentration and temperature. Synthetic electrolytes were then used in laboratory scaled copper electrowinning experiments where relationships were found under stagnant conditions between current efficiency and solution composition.

Jan 1, 2009

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 M. E. Kuchta

Research is currently being conducted at the Colorado School of Mines in the use of high-pressure water for scaling down loose rocks in underground mine openings. In addition to improved miner safety, the adhesion strength of shotcrete applied to rock surfaces treated with high-pressure water is also increased significantly resulting in improved overall support capabilities of the shotcrete layer. Test results show an increase in adhesion strength by a factor of four on a concrete test wall cleaned with water at 21 Mpa (3000 psi) as compared to a surface cleaned at 0.7 Mpa (100 psi).

Jan 1, 2002

By John H. Raymer

Groundwater inflow into hard rock tunnels is strongly affected by recharge and drawdown of the water table. Previous analytical and empirical methods for estimating inflow have generally not accounted for these factors in an accurate or systematic way, resulting is wrong conclusions about inflow and the effects of the tunnel on the surrounding environment. This paper discusses these issues and provides some simple analytical equations to estimate inflow and water table drawdown around the tunnel. Examples from tunnels in the Atlanta area are provided.

Jan 1, 2005