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By R. Asmatulu

According to Darcy's law, the rate of filtration should increase with increasing pressure drop across a filter cake. In centrifugal filtration, the driving pressure is created by the centrifugal forces applied in the free water on the surface of a filter cake. However, the pressure drop can become negative when the free water surface disappears, which makes it difficult to achieve low cake moistures. In hyperbaric centrifugal filtration, this problem is overcome using air pressure to restore the pressure differential. In the present work, various mineral and coal fines have been subjected to hyperbaric centrifugal filtration tests. The laboratory tests show that the moistures of various mineral fines, such as copper and zinc concentrates, phosphate, talc, kaolin clay, and precipitated calcium carbonate, can be reduced substantially below that achieved by conventional centrifuges. Similar promising results have also been obtained with various coal fines in laboratory and pilot-scale test programs and in full-scale plant demonstrations.

Jan 1, 2012

By R. R. Graham

Echo Bay Minerals operates a 650 tpd gravity float gold circuit at their Manhattan facility. The objective of this paper was to document the gold recovery by size distribution. This was accomplished by studying the material balance of each size fraction as it progressed through each gravity Circuit separator. It proved to be an impossible task. Figure I depicts the gravity circuit. The gravity cyclone underflow goes to two duplex Pan American type jigs. The jig overflow reports to the OK Flash Float Cell. The cyclone hutch product is reground and goes to a full size wilfly table. The rougher table concentrate reports to a pilot size Wi1fly cleaner table. The cleaner and rougher table tails circulate back to the jig feed. The gravity circuit was composite sampled for two to four hours per day for four days. Each sample was taken every 20 minutes. Each composite sample was filtered, dried, repu1ped, and screened through a wet/dry screening procedure. Each size fraction was checked for gold value by fire assay fussion technique. A material balance was run on each size fraction. The tables listing the results are enclosed.

Jan 1, 1989

By G. Southam

Bacterial populations play an active role in mineral weathering in subsurface and near-surface environments e.g., supergene enrichment of Cu at Morenci, AZ. An in vitro bacterial biofilm model was used to examine the interaction between Sporosarcina ureae and ionic gold (which is toxic) or amino acid-gold complexes in gold mobility. The immobilization of ionic gold was between 80-90% for 1 week but as the available, cellular reactive sites became saturated immobilization decreased to 14% within 2 weeks. In the asparagine-gold system, gold immobilization occurred at a high rate (80-90%) throughout the experiment with limited toxicity towards Sporosarcina ureae.

Jan 1, 1999

By M. J. Shields

There are numerous suggestions in the literature on methods of obtaining representative samples of waste rock or mill tailings. Some suggested methods would result in thousands of samples and very high costs for a large facility. There is no general rule that can (or should) be followed, such as collection of a given number of samples per mass of material, per acre of impoundment, or per foot of drillcore. Each site is different, and the adequacy of sampling must be tailored to the site. A logical approach is to let the variability at the site dictate the number of samples that should be collected and analyzed, and then to quantify and evaluate the results by means of standard statistical methods.

Jan 1, 1998

By Jeff Schwoebel, Dale Evans, Boyd Tangren

The Soldier Canyon Mine (the "Mine") degasification project demonstrates the ability to commercially recover coalbed gas to reduce overall mine costs associated with methane drainage. Gas is recovered from active and inactive areas of the Mine through an underground pipeline and surface compressors. Close inspection of gas quality is required due to potential contamination of air caused by excessive vacuum. Water must be removed routinely to enhance gas removal. This paper will review the operational and production procedures required to maximize gas recovery and insure safety at the Soldier Canyon Mine gas recovery project.

Jan 1, 1993

By A. H. Farazi, C. Quamruzzaman

The freezing and subsequent solidifying of unstable, weak (sands, silts and clays) and/or wet soil to form a desired-shape frozen barrier around a construction area are possibly the main features of the freezing method for shaft sinking. The barrier, along with strengthening the soil, provides a dry environment to ensure sustainable subsurface construction work before placing a permanent lining. The freezing method requires the installation of freezing pipes in boreholes around the construction area and the circulation of chilled salt water through these pipes and has long been a proven technique for dry shaft sinking through unstable and water-bearing seam around the world. As removing heat from the ground is the main feature of the method, an efficient thermal design of the freezing process is mandatory to ensure success of the shaft sinking operation. This applies to both the sustainability and economy of the intended structure. The design presented in this paper is aimed at figuring out the heat-removing ability and operating time of the refrigerative equipment using some simple formulae. The authors adopted a theoretical approach to determine the quantity of heat to be removed from the ground. The amount of energy for the equipment was found to be greater than that for freezing, which proved the validity of the design. The active freezing period was calculated to be 121 days. The authors followed the structural design of the freezing process they proposed in their previous work (Farazi and Quamruzzaman, 2013). Though the first coal seam in the coalfield was encountered at a depth of approximately 352 m in the subsurface, the target depth for cooling and freezing was decided to be 162 m. The formation demands extra care to nullify its risk of the temporary structure collapsing and water rushing in (Farazi et al., 2012). Discussion on the determination of refrigerative equipment parameters was excluded from the scope of this work.

Jan 1, 2014

By G. R. Hart

The expected 1990 Clean Air legislation is providing electric utilities with a series of challenges and decisions as the utilities prepare strategies to comply with the resulting regulations. This paper addresses the strategy development of a coal-based utility --the legislation, the process used, the fuel issues, the options available, and the decisions to be made.

Jan 1, 1991

By Risto Lindsberg

A wide concept of flotation equipment and technologies is presented in this paper. The basis for the presentation in Outokumpu's world-wide experience in mineral processing and other related areas, and continuing research and development work done in Finland as well as abroad by Outokumpu's subsidiaries (and customers). It is understood that flotation equipment selection for a certain process stage is becoming more complicated. It is obvious that flotation equipment in grinding circuit needs different design from a multistage cleaning process. In this paper, column flotation is compared with other flotation methods. Thus three areas of flotation are discussed in this paper: 1. Flotation in the grinding circuit, Skim-Air machines 2. Rougher-scavenger flotation, conventional cells vs columns 3. Cleaning flotation, columns

Jan 1, 1988

By Markus Thewes, Mario Galli

"INTRODUCTIONProject-related studies showed that lab tests are a helpful tool for the planning of EPB tunneling and soil conditioning in cohesionless soils. This type of ground commonly represents the extended application range for EPB shields, which demands for a treatment with additives. Considering soil conditioning with foam, so far, approaches exist for the investigation of the foam quality and of the conditioning behavior of soils (e.g. (EFNARC GUIDELINES 2001 2003)), but not any standards for testing procedures related to soil conditioning. State-of-the-art research on the topic is and was conducted for example in Bochum (Germany) cf. (Budach 2012; Maidl 1995), in Lyon (France) cf. (Quebaud et al. 1998), in Oxford and Cambridge (Great Britain) cf. (Borghi 2006; Peña Duarte 2007), in Delft (Netherlands) cf. (Bezuijen and Schaminée 2001), in Turin (Italy) cf. (Borio 2010; Peila et al. 2013; Vinai 2006), and in Aachen (Germany) cf. (Vennekötter 2012). Additionally, applied science is reported by the tunneling practice and suppliers of conditioning agents. Although the research focus in all these and further studies varied, similar test methods and test series were applied. A standardization of essential properties and testing methods (setup and procedures) however did not take place. The results from laboratory testing can only function as index values for practice because in the studies, production and application of the conditioning agents mainly takes place under atmospheric conditions. Nevertheless, the tests enable basic understanding of feasibility as well as processes and interactions going on during soil conditioning. For recommendations for standardized and reproducible testing see (Budach 2012; Budach and Thewes 2015).The most extensive investigations on the flow behavior of soil-foam mixtures have been performed by using the slump test from concrete engineering, cf. (DIN EN 12350-2 2009-08), which originally is applied on evaluating the workability of fresh concrete. Although this test does not describe the actual flow behavior, it rather represents an index on the workability, very much experience exists with this test method. Besides others, the workability – or flow behavior – of the EPB support medium certainly is a major factor of influence on the properties of the material in the excavation chamber and thus, for effective tunneling with EPB shields, cf. (Galli and Thewes 2014). For a summary of various investigations on the workability of conditioned soils using the slump test and resulting recommended slump ranges see (Budach 2012; Vinai 2006). Thereof, slumps between 10 and 20 cm have been reported as suitable workability for EPB applications. However, there is actually not much known about the real flow behavior of soil-foam mixtures related to rheological properties such as the viscosity (?) or potential yield stresses (t0). These physical values are necessary for a realistic determination of face pressure, for the design of required torques, and for an evaluation of the material flow at different locations in the excavation chamber, in the screw conveyor or on the conveyor belt. To generate a linear pressure distribution at the tunnel face, as it is assumed a priori, a low-viscosity fluid is favorable, whereas in the screw conveyor, a high-viscous fluid is needed for a controlled pressure decrease. On the conveyor belt, yield stress plays an important role preventing deliquescence and spilling from the belt. Attempts in characterizing the actual flowing of soil-foam mixtures have so far only been made by few researchers, the application of rheometry is rare."

Jan 1, 2016

By William E. Bruce

Percussive drill calibration experiments performed by the Bureau of Mines on two drills are described. The use of a linear velocity transducer to determine piston velocity, blow frequency, and piston stroke length is discussed. Data are presented on the relationships between maximum work rate and feed air pressure. Penetration rates in nine rock types were measured for the same two drills. Physical properties of the nine rock types are presented in tabular and graphical form to show relationships between penetration rates and physical properties. Finally, conclusions are drawn as to the potential use of these data to predict percussive drilling rates.

Jan 1, 1970

By J. Allen Hennessy

INTRODUCTION The increasing price of gold and silver over the past 10 years has caused increasing activity in the exploration, evaluation and development of precious metals projects. Many of these deposits are relatively low grade and short lived which makes them economically sensitive to the major project variables such as metal price, capital cost, operating cost and of course, tonnage and grade. These deposits often have a high variability (a coefficient of variation -- o/u -- of 2 to 5) and an intermixing of ore and waste, making ac- curate ore reserve estimation difficult, especially when using traditional estimation techniques. Often, the estimation errors are not the 10-20% that we see in base metal deposits, but the errors in grade and tonnage can be as high as 50%, which can obviously have a very substantial impact on project Recent developments in geostatistics when coupled with a sound geologic under- standing of the deposit can significantly improve reserve estimates of these variable precious metals deposits. Examples will be given of actual deposits where the traditional estimates were significantly different from the mining reality. An attempt will be made to explain the applicable geostatistical tools with a minimum of geostatistical jargon and without complicated formulas. The key to improving the reserve estimates is a clear understanding of the deposit geology and especially the structural controls, the use of local estimation techniques that recognize the intermixing of ore and waste and the effect of selective mining on recoverable reserves, and the use of a global reserve estimation technique to check the results of local estimation. Geologic Controls The vast majority of gold and silver deposits being mined or developed in the western United States would be classified as epithermal deposits. These are formed by hydrothermal fluids (hot water) flowing upward through the rocks and depositing the precious metals as the fluids cool or reach areas of lower pressure or favorable chemical sites. These environments are similar to present day hot springs-type environments with some deposits being clearly associated with surface hot springs such as the Homestake McLaughlin deposit in northern California. These hydrothermal deposits can occur in sedimentary rocks resulting in deposits such as those of the Carlin district or the Jerritt Canyon deposit or the hydrothermal systems can occur in volcanic rocks forming deposits such as Round Mountain, Manhattan or Paradise Peak. The mechanisms of formation were similar in either case with the solution flow controlled by geologic structure and precious metals deposited when the conditions of temperataure, pressure and chemical environment were favorable. The gold and silver hearing solutions travel through permeable faults and fracture systems depositing the metals along these channels. The grades are often highest in the central parts of these conduits (veins) with lower grades in the surrounding rocks. An understanding of the nature, distribution and orientation of these plumbing systems is important to a realistic reserve estimate. The point to be emphasized here is that, good, sound geology in the form of geologic mapping, logging of rotary chip samples and a few carefully logged core holes can signifi- cantly improve an ore reserve estimate.

Jan 1, 1987

Barrick Gold plans to have four new gold mines in production by 2006. Together, the mines would increase the company’s output by 40 percent. The projects include Veladero in Argentina, Alto Chicama in Peru, Cowal in Australia and Tulawaka in Tanzania. All of them are scheduled to begin production between the first quarter of 2005 and the first quarter of 2006. They are expected to drive Barrick Gold’s growth profile to a target of 211.5 to 217.7 t (6.8 million to 7 mil-lion oz) of gold production in 2007. The company’s projected output for 2004 is 152.4 to 155.5 t (4.9 million to 5million oz) in 2004. Overall, higher production and lower costs are expected in the early years from the new mines.

Jan 1, 2004

By Masahiro Lnoue, Kenichi Uchino

Airflow velocity vectors by a forcing auxiliary fan at a heading face were measured in an actual size model gallery and an actual mine. The location of an outlet of ventilation duct gives significant effects on the airflow at the heading in the gallery. It was also found that there were several stagnated regions which may have danger of methane accumulation. The flow were also examined using the visualization technique by laser light in a reduced scale model. The flow in reduced scale model showed similar behavior to those observed in actual size galleries. The air velocity at the outlet has no significant effect on the airflow. It was found that a region to be ventilated by the direct flow of the exhaust fan is limited to a relatively short distance but a secondary flow region is generated near the heading face. CFD ( Computational Fluid Dynamics ) method was also developed to examine the airflow. The calculated results coincides with those measured by actual and reduced scale models. It is concluded that the CFD is useful tool for the analysis of ventilation at the headings.

Jan 1, 1997

By N. N. Manu

In the Central African Copper Belt, sulfidization flotation is the standard practice for dolomitic copper oxide ores. It is a delicate process, and its plant application requires close control of the reagent addition. This paper presents the results of a thorough laboratory investigation. It features the monitoring, during sulfidization, of the pulp pH, the residual sulfide ion concentration and redox potential. Variables examined during the process were: retention times, sulfidizer additions, pH, collector type, dispersant dosage and reducing agent addition. Implications of the findings for plant application and process control are also briefly examined.

Jan 1, 1994

By Peter J. Lawson, John A. Rideout, Gregory W. Dicinoski

A considerable body of literature directed towards optimising the efficiency of gold and silver extraction from cyanide leach liquors has appeared in recent years. A few examples from dissolution to solvent extraction to adsorption in carbon-in-pulp (CIP) and resin-in-pulp (RIP) operations follow. Selective leaching of gold from copper-gold ores using ammonia-cyanide mixtures extends the % copper which may be tolerated in ores (Ruane, 1991, LaBrooy et al., 1991, Costello, 1991). The removal of copper and recycling of cyanide from high copper ores is another important development (Sceresini and Staunton, 1991). Solvent extraction of alkaline cyanide liquors (Riveros, 1990, Mooiman & Miller, 1991) and solvent aided elution in CIP (Muir, et al., 1985) look promising. Recent definitive papers on the mechanism of adsorption of aurocyanide by activated carbon should lead to more efficient use of CIP (Adams and Fleming, 1989, Klauber, 1991). Strong and mixed weak-strong base resins have been applied in RIP for aurocyanide extraction in Russian Plants since the 1970's (see for example Borovskii et al., 1985, and references cited in Fleming, 1988a). Fundamental studies on applications of commercial weak and strong base resins-in-pulp (Fleming & Cromberge, 1984a, b, Fleming 1988a, Hosking 1984, Riveros and Cooper 1987) have generated much interest in RIP. Detailed comparisons of CIP vs RIP efficiencies at Mintek in South Africa (Fleming et al., 1988b), and the inefficiency of CIP in contact with clay led to the commissioning of the strong base RIP Golden Jubilee plant in 1988. Its operation and improvements have been reported (Seymore and Fleming, 1989, Fleming & Seymore, 1990). The use of anion exchange membranes for aurocyanide extraction shows some promise (Mauthoor et al., 1991). However, the development of new gold specific resins at Mintek (Green et al., 1984, 1986, 1990, Johns and Green, 1991) and elsewhere (Asker et al., 1987, Wilson et al., 1987, Harris et al., 1992) should improve the viability of RIP processes. The polydiallylamine gold specific resins (Hodgkin & Eibl, 1988, Fawell et al., 1992a, b) have high capacities for auro cyanide recovery from high concentration liquors. The use of guanidine based liquid and solid ion exchange extractants for gold was recently reported by the Henkel Corporation (Kordosky., et. al., 1993). Such specific resins tailor made for gold and/or silver cyanide extraction should lower overall cost by improving metallurgical efficiency. In the case of strong base resins this selectivity largely eliminates the problems of poor base metal elution and/or poisoning. The work reported here outlines the approach taken at the University of Central Queensland to synthesize sterically hindered strong base anion exchange resins which are designed to have high selectivity for auro- and argentocyanide complexes. It summarises selectivity tests on low grade cyanide leach liquors from several mines. It also examines an RIP vs CIP comparison, and investigates the elution properties and cycling of one such promising resin.

Jan 1, 1993

By G. R. Marchant

The nonferrous industry has for many years maintained monitoring stations in agricultural areas in the vicinity of smelters to collect data concerning impact of smelter emission on agricultural crop production (Thomas and Cross, 1928). However, in 1967, the United States Congress passed the Clean Air Act which was amended in 1970 (Marchant, et al., 1977). The interpretation of this act by the Environmental Protection Agency (EPA) made it necessary for the industry to install extensive real-time ambient sulfur dioxide (SO,) monitoring systems. This was only the tip of the iceberg. Since that time as a result of additional laws and agency directives, it is now necessary to monitor concentrations of a number of substances -in both air and water. And unless there is a major change in government thinking, this trend will continue during the decade of the eighties. It is difficult to estimate the full impact of these laws. Nevertheless, the impact is large and affects every person in the United States today (Anon., 1972; Rockefeller, 1971; Nelson, Yeager, and Guptill, 1973; and Anon., 1975). It prohibits the burning of trash and paper in most areas of the country. It increases the cost of transportation and the price of motor vehicles. It increases the, cost of nearly everything that is manufactured. In industries which compete in the international market, it reduces their competitive position. In some industries the environmental impact is felt on costs of goods sold in the vicinity of 25% of the total production costs. The major portion of these costs is not due to the monitoring systems but instead is due to the increased cost of production facilities, equipment, and raw materials in industries that are required to comply with environmental regulations.

Jan 1, 1979

By J. M. Rotter, R. A. Lohnes, J. Y. Ooi

Reliable prediction of wall pressures in a coal silo demands careful characterization of the stress-strain properties of the coal. This paper describes the results of triaxial compression tests on a typical fine-ground coal used in power generation and describes the fitting of several different constitutive models to the data. The fitted parameters for the constitutive models are well suited to application infinite element analyses. The different models are used to give the reader flexibility in choosing a model and to show the shortcomings of some models. To explore the quality of the fitting process, the fitted results are compared with finite element predictions of the triaxial test itself.

Jan 1, 1998

By Ken A. Pfaff, Ray Daigh

This paper will discuss state-of-the-art applications of GPS automation in mobile conveying systems. Robotic mobile conveying systems increase profitability, optimize stacking and reclaiming operations, and control complex interfaces more accurately than other systems. We will also discuss the application process in machine-to-machine coordination, selection of the appropriate GPS system, and Ethernet considerations. As the leading supplier of GPS-controlled mobile conveying systems, we'll draw on our experience at Morenci, Radomiro Tomic, Zaldivar, El Abra (Figure 1), and El Tesoro mines in the US and South America to demonstrate system reliability and the lessons we've learned through analysis of these projects.

Jan 1, 2002

By V. F. Hollister

Epithermal gold deposits occur in and near the marginal fault that circumscribes the Goldfield, Nevada, Tertiary caldera. The gold occurs disseminated in alunite, pyrite, and kaolin- bearing silicified zones that are controlled by the circular faults. Other Tertiary calderas (i.e., Summitville and Red Mountain No. 3) have epithermal disseminated gold deposits located in and near their marginal circular faults in settings that resemble the Goldfield example. These additional caldera- controlled epithermal gold deposits are also characterized by alunite, pyrite, and kaolin-bearing silicified rock that act as hosts for the gold disseminations. The Goldfield District is therefore an exploration model for those seeking disseminated epithermal gold deposits in a caldera setting.

Jan 1, 1986

By Robert Harris, David Duncan

The Samira Hill gold mine represents the first commercial gold project for the landlocked country of Niger in West Africa. It began production in October 2004 as the result of over 10 years of exploration and development work. There were several administrative, social and technical challenges that had to be overcome to realize the successful development of the project. The Samira mine is located on the geological structure known as the ‘Samira Horizon’ which is developing as a promising district for additional discoveries and other mine developments.

Jan 1, 2005