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By A. R. MacPherson

The procedure to arrive at an energy efficient autogenous grinding plant is carried out in the following steps: First Step - Determine power requirements to grind a particular ore. This work carried out on small samples ground in a 450 mm diameter Aerofall Hill and the results are checked against a standard Bond Index test. Second Step - A bulk sample from the ore zone is ground in a 1.8 m diameter pilot mill. This work is carried on until the power objectives as indicated from the first step have been realized. Third Step - Correlate the pilot mill data, with the data from the numerous samples ground in the small 450 mm mill and arrive at design criteria for the commercial plant. Ensure commercial mill design will be suitable to obtain similar results as those obtained in the pilot mill.

Jan 1, 1981

By K. Kim, H. Gao

A site-characterization strategy formulated for the probabilistic assessment of rock mass properties is presented. The strategy, which takes into account the variability of rock properties and the stochastic nature of the rock-failure process, entails determining probability distributions of rock properties by utilizing extreme value statistics and Monte Carlo simulation. Laboratory and, field test data are analyzed and presented to illustrate the methodology. The results indicate that the distributive characteristics of rock mass can be estimated by using this proposed method. The results of the analysis can be incorporated into the design of underground structures. Then, the relative uncertainties of the failure probability of the structures can be assessed.

Jan 1, 1997

High pressure grinding rolls have found widespread acceptance for cement processing, and are now making their debut in the metalliferous minerals industry. Significant energy and wear material savings appear achievable in many applications. This paper re- views the technical literature on this important, emerging technology.

Jan 1, 1997

Simulation models were developed at the Julius kruttschnitt Mineral Research Centre to provide accurate estimates of power consumption for a wide range of equipment. With the models, a range of circuits and operating conditions can be compared by simulation for a particular ore type. Accurate models of classification allow for the interaction between classifier efficiency and target product size (e.g., P80 or percent passing 150 /an) to be considered. This paper considers a range of circuit types and overall energy efficiency in the context of case studies where different circuit types were treating similar ore types.

Jan 1, 1999

By Peter L. Siems

Humid tropical environments pose many problems for mineral exploration. The problems result from thick lateritic soils, dense vegetation, seasonally heavy rains, deep chemical weathering, few outcrops and thick saprolites. Although geochemical exploration should be potentially a useful technique in these environments, it appears from the scarcity of reports in the literature that insufficient attention has been paid to developing procedures that are specific to the needs of humid tropical areas. For this reason, the authors believe that this account of a geochemical study in a tropical coastal area on the edge of the Brazilian shield is of general interest and importance for potential geochemical exploration surveys in similar areas within the tropics. The objective of the geochemical study was to develop a practical technique of reconnaissance geochemical prospecting for copper deposits in Brazilian tropical coastal lowland areas. In order to achieve this objective, information concerning the secondary dispersion of copper in these areas was required. Consequently, an orientation survey was designed to provide this information. The present account contains details of the geochemical study and the information about the secondary dispersion of copper that was acquired during the course of the orientation survey. Location and Climate The field area is on the Atlantic coastal lowland of Brazil at latitude 13°S. It lies approximately 10 kilometers south of Maragojipe, a city of 15,000 inhabitants; this city is on the western side of the Bay de Todos os Santos about 45 airline kilo¬meters northwest of Salvador. (See Fig. 1) A good gravel road from Sao Felipe to Sao Roque do Paraguay crosses the southern part of the field area. The climate of the area is hot and moist, and is without prolonged dry periods. The mean annual rainfall is about 1600 mm (63 in.) and the greatest precipitation occurs during the winter months of May and June and the summer months of December

Jan 1, 1972

By W. E. Foreman, A. Hayatdavoudi, A. Ghalambor

The objective of this investigation was to determine the sensitivity of three selected input parameters in the operational control of continuous bottom fed thickeners used for the treatment of coal refuse slurries. The three variable parameters were "Feed Flow Rate," "Feed pH," and "Feed Solids Concentration." These three input parameters were studied under three cationic-anionic polymeric conditions. For each polymeric condition, two mathematical models were developed, one for overflow response and the other for underflow response. The combination polymers produced the best quality of overflow and underflow. For this polymeric condition, change in the feed solids concentration was the most sensitive factor in the maintenance of the overflow quality, and the feed pH was the most sensitive factor for the maintenance of underflow quality. The mathematical models generated a set of plots that would allow an operator to control and/or adjust any of the three variables to achieve optimum conditions.

Jan 1, 1991

By Vojtech Gall

Pre-support measures for urban tunneling have seen a substantial development in the recent past. Ground improvement techniques, pipe-arch and spiling methods now allow for non-disruptive tunneling at very shallow depths under sensitive structures, rail tracks and roadways. The paper presents experience gained on national and international projects built over the past decade that represent case histories and therefore may be used as guidance for the development of similar solutions for future tunneling projects at shallow depths. Reference projects include tunnels for the Washington, DC Metro, London Underground, Dulles Inter-national Airport, Busway tunnels in Boston and the Ft. Canning Tunnel in Singapore.

Jan 1, 2008

By H. T. McAdams

The logic of regression analysis as an operations research tool is critically examined, and a formal basis for its application to mining problems is developed. The traditional view of regression analysis as a statistical discipline does not provide an adequate basis for evaluating a regression model in a specific area such as ore reserve calculation or process control. In particular, the validity of the residual-sum-of-squares criterion is questioned, and the need for a criterion based on interpolative features of the model is emphasized. Strictly speaking, a regression model is statistically supported only at points at which observations are available, yet inferences are drawn with regard to a continuum. When considered as a mathematical function, therefore, the model is observationally defined only on a domain consisting of a finite number of points. Extension of this domain to an interval of the real line must be based on physical rather than statistical argument. Vector space and function theory concepts useful as a logical framework for a physically oriented problem analysis are discussed and their usefulness demonstrated in a practical problem.

Jan 1, 1966

By D. Malhotra

This paper discusses the need for periodic auditing of mineral processing flowsheets and the potential benefits a company can gain from a study of this nature. A carefully designed flowsheet audit can have a significant impact on the metallurgical performance in the plant. Several case studies illustrating the potential benefits that can be attained from flowsheet auditing of mineral processing plants are discussed.

Jan 1, 1988

By E. Bakhtavar

It is considered that the most economical method for the exploitation of Gol-e-Gohar Area 3 iron ore mine is to combine open-pit and underground methods. In this regard, the most critical problem is the determination of optimal final pit depth. In this paper, a method which was recently introduced on the basis of economical block models of open-pit and underground is used to determine optimal final open-pit depth of Gol-e-Gohar Area 3 mine with due regards to the future underground mining option. Considering a low cost and productive underground method as a feasible alternative for extraction of the lower part of this deposit, room and pillar was selected. It is concluded that after the assessment and comparison of different values for depth, optimal final open-pit depth was determined to be equal to 285 m.

Jan 1, 2010

By J. C. Monette

Stripping of gold and silver from carbon is effected by means of two main processes (AARL and ZADRA ). The main rate-enhancing parameter in the stripping of gold and silver is temperature. A secondary rate-enhancing parameter is ionic strength. (1) Stripping is usually conducted within a solution containing sodium cyanide (0.1 -0.5% ) and caustic ( 1 -3%). The development of a chemistry that increases the rate of gold and silver stripping from carbon in a manner proportional to its concentration is described. Its use in atmospheric and pressure strips is also outlined.

Jan 1, 1992

By P. G. Semple

For the last four years, the Kilborn Group of Companies has been involved in several major projects in the Confederation of Independent States (CIS). These include the Kumtor project, the Kubaka gold project, the Kazgold project, the Aginskoe project and the Jerooy project. These projects are all in various stages of detailed engineering and construction. Western mining companies are pursuing mining opportunities throughout the world in search of ore bodies for development. The quest for profitable mining ventures has led mining companies to South America and Asia and, more recently, to the former Soviet Union. When considering the CIS, several factors should be considered. The most notable are geography, mining culture and previous mining production.

Jan 1, 1996

By T. C. Page, P. C. Gibson, M. A. Miller, J. D. Sell

[The Yarnell gold deposit in the Weaver mining district, Yavapai County, Arizona, occurs in a structurally controlled, hydrothermally altered zone in a 1700 Ma granodioritic intrusive. Both potassic and sericitically altered rocks around and above the low-angle, northeast striking Yarnell fault are known to host economic gold mineralization. A wider envelope of weakly-propylitic altered rock also occurs in this area. During mineralization, strong sericitization accompanied several stages of quartz (±adularia) veining, stockwork formation, localized silicification and potassic replacement, in association with deposition of specularite, pyrite (now oxidized) and gold. The footwall of the fault is also sericitically altered but poorly mineralized. Mineralization along the Yarnell fault continues both northeast and southwest from the main deposit, although the thickness of the zone and associated alter avian envelope diminish away from the orebody A sample of undo formed illite taken from the Yarnell fault zone was K/Ar dated at 69 + 1.6 Ma. This date reflects a minimum age for both mineralization and latest movement on the fault. Gold mineralization is accompanied by modest increases in Ag, As. Cu and Mo content. Both CO2- and H2O- rich fluid inclusions were studied and suggest mesothermal pressures and temperatures of formation for the deposit. Ninety-six reverse circulation holes and four diamond drill holes outline a bulk-minable mineral reserve of'4.1 million tons at 0.051 oz of Au per ton. An additional 2.7 million tons at 0.017 oz of Au per ton occurs in a low-grade zone above and subparallel to the main mineralized zone. Total calculated mineral inventory stands at 6.8 million tons at a grade of 0.038 oz of Au per ton, with a waste-to-ore ratio of 1.45:1. Column leach tests indicate that cyanide heap leach gold recoveries should exceed 70%.]

Jan 1, 1994

By P. A. Korpi

The angular spiral lining system reduces energy consumption and grinding media consumption in grate discharge ball mills. This paper discusses the effect of this lining system on mill product size distribution. Performance comparisons of a grinding circuit outfitted with angular spiral liners in the ball mills are made with respect to standard double-wave liner installations. The angular spiral lining system was developed by Waagner-Biro of Austria. The installation of this lining system at Magma Copper Company, San Manuel, Arizona, is the first of its kind in a grate discharge ball mill used for wet grinding.

Jan 1, 1979

By R. K. Rajamani, A. Datta

An appropriate scale-up methodology is very useful for ball mill design and optimization of the grinding circuit. To date, the scale-up is based on the selection and breakage function model using lab mill data. However, a major drawback of that approach is that the charge motion in a lab mill is vastly different from that in a large industrial mill. Therefore, in the methodology proposed here, first the energy of individual collision in the mill is computed employing the discrete element method (DEM). Then the breakage of particles as a function of collision energy is studied in a separate experiment. Together, this information constitutes what is known as collision energy based population balance model. The appropriateness of this model is shown for different batch grinding mills.

Jan 1, 1999

By C. D. Broadbent

Open pit blasting can be a low cost routine or a high cost bottleneck depending on geology, environment and the operator's ability to master site conditions. Because blasting is a repetitive operation, there should be ample opportunity to optimize the process; but ordinarily this optimization is rarely achieved and then only if conditions remain consistent and predictable. Often, however, and particularly with porphyry coppers, hidden differences in rock characteristics nullify the operator's best efforts. At a porphyry copper deposit being mined by Kennecott Copper Corporation, there are all of the following rock types: oxidized and fresh porphyry, altered and silicified limestone, explosion breccia, rhyolite, sandstone, shale and several others. The units can cover large areas or be limited to a few tens of feet in maximum dimension. They are rarely visible on the bench surface and often do not show up in the bench slope. Even though the blastability of these rocks varies substantially, a generally-uniform blasting pattern was formerly used with disappointing results. Secondary blasting was often required and high bottoms occurred frequently; overblasting wasted drilling time, and explosives caused excessive throw. Several possible methods for improving the blast design were considered and a geophysical method was chosen for testing. There had been reports in the journals that seismic methods were being used in Europe as aids for blasting design. A literature search turned up work by Haxby 1/ on use of a refraction seismograph for measuring pit bench rock strength. Using his work as a springboard, equipment was purchased and a program was planned and carried out for developing, evaluating and implementing the seismic method for routine mine use. Following are discussions of the development program and results.

Jan 1, 1974

By Karl C. Dean

The current emphasis on environmental problems has focused attention on the massive nationwide accumulations of mine, mill, and smelter wastes that represent potential air and water pollution hazards. The pollution hazards can be reduced or eliminated by utilization or stabilization of these wastes. The U.S. Bureau of Mines, since the inception of the Solid Waste Disposal Act of 1965, has been conducting research to determine the practicality of various utilization and stabilization procedures. Investigations include partial extractions of desirable waste components and full utilization of the wastes as simulated soils or in ceramic or other structural products. Chemical, vegetative, and combined chemical-vegetative methods of stabilization have been actively studied. This report updates information previously developed by the Salt Lake City Metallurgy Research Center and presents the current status of antipollution solid waste work 1/,2/.

Jan 1, 1970

By Joseph J. Zaluski, J. Steven Gardner, Marco M. Rajkovich

The telephone rings at 3:20 a.m. An exasperated voice on the other end says, “There has been a mine explosion at Mine No. 5 and we have not heard from three units of men.” Twenty-three minutes later, the phone rings again and another panicked voice says, “There is something wrong at the slurry impoundment, the pool level has just dropped five feet and we are trying to figure out what is wrong” Thirty minutes later, the mobile phone rings. An excited security guard says, “We have reports of thick black water running down the right fork and left fork of Straight Creek and both seem to be rising in the banks.” If this is not enough excitement, the mobile phone rings again. A stressed company official says, “I just heard a report that black slurry is running out of the portals of XYZ Co. No. 2 Mine, which is adjacent to our No. 5 Mine.” Is this all some kind of dream or nightmare? More importantly, though, if this happens, what do you do? Most people think: “It can’t happen to me.” But mine explosions do happen, slurry impoundments can rupture and creeks can flood with black water causing damage to others, including competitors. A mine’s response must be quick, cool-headed, calculated and effective. This article examines the issues, concerns and ramifications of this hypothetical disaster. The authors then present a systematic crisis-management response.

Jan 1, 2004

By A. M. McKim

6, 7.3 meter diameter autogenous mills at Wabush Mines are undergoing conversion from a radial configuration of pulp discharger to a curved design. Improved discharging efficiency has effectively lowered the pulp level in the mill. The low level operation enhances the grinding efficiency netting a 12% power reduction. Significant reductions to rate of wear has been a spin off benefit. The design incorporates features for holding the assembly solidly in place thus eliminating bolt hole damage and leakers. Preliminary work in one 11 meter mill at Hibbing Taconite did not indicate that all the same advantages were available in their process.

Jan 1, 1982

By Gary Beerkirkcher

INTRODUCTION The mine hoisting equipment that is selected and installed at a mine is for the lifetime of the mine and, therefore, it is extremely important that a proper choice be made. Several types of mine hoist designs, including double drum hoists, single drum hoists, friction hoists, and various special designs of these, are available to¬day. Each has advantages and disadvantages and they should only be used in suitable applications. Drive systems for mine hoists must be evaluated together with the mechanical systems for each hoist application. It does not make sense to properly select the hoist mechanical system and then choose a drive system that turns out to be a bottleneck. MINE HOIST TYPES There are two basic types of mine hoists available in the world today: the drum hoist, on which the hoist rope is actually stored during the hoisting cycle, and the friction (Koepe) hoist, which merely passes the rope over the wheel during the hoisting process. Drum Hoists Single Drum Hoist: A single drum hoist (shown diagrammatically in Fig. 1) can be used as a service or production hoist with the cage or skip in balance with a counterweight (Figs. 2 and 3). It can efficiently service one or more levels, since the location of the counterweight at any time is not important. As a pro¬duction hoist with skips in balance, the single drum hoist is best used for single level hoisting. All rope adjustments for proper spotting must be done manually for the single drum hoist. This has to be done periodi¬cally to compensate for rope stretch. A variation of the single drum hoist is the divided drum hoist. If multilayer winding is necessary, the single drum hoist must have a divider to allow a sep¬arate compartment for each rope. If a counterweight is used with a divided drum application, the counter¬ weight rope can be wound on a smaller diameter (Fig. 4). Consequently, it moves a lesser distance than the main conveyance and rope adjustment problems are re¬duced. Double Drum Hoist: A double drum hoist in oper¬ation is shown in Fig. 5. Double Drum Hoist With One Drum Clutched: As a service hoist with cage and counterweight, a double drum hoist with one drum clutched (Fig. 6) can serve several levels efficiently. The advantage of having the clutched drum is that it allows rapid adjustment of ropes due to initial stretch. Some users may prefer the single drum hoist with manual rope adjustment, while others consider the added expense of the second drum and clutch is justified to make rope adjustments quickly. The value of this feature for a particular application should be discussed with the hoist manufacturer. As a production hoist with skips in balance for a multi¬level operation, the clutch can be adjusted for efficient hoisting from any level. Double Drum Hoists with Both Drums Clutched: There are also double drum hoists that have both drums clutched (Fig. 7). The main advantage claimed for this type of hoist is that if something happens in one of the two compartments, the hoist can operate in the other compartment to raise and lower men and sup¬plies. This feature is particularly favorable if there is only one shaft entrance to the mine. Multiple Drum Hoist: The multiple drum hoist, a South African innovation, is a type of drum hoist about which everyone should be aware. Basically, it uses two hoist ropes per conveyance which at great depths per¬mits use of smaller ropes and smaller drums. There are none in use in the United States today. However, they should be considered in very deep mines. Friction (Koepe) Hoists This hoist (Fig. 8) was introduced to the mining world by Frederick Koepe in 1877. The basic prin¬ciple of the friction hoist is that the hoist rope passing

Jan 1, 1982