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By Alan Boughey

The world's largest grinding mill operates at the Cadia Hill Mine in Australia. Svedala Industries supplied the 12.2-m- (40-ft-) diam, 20-MW Cadia gearless, semiautogenous grinding mill (SAG). This was a leap of more than 40% above the largest operating SAG mill. This article reviews the significant items involved in the development, design, manufacture, installation and operation of this mill. Description of the Cadia project The Cadia Hill Mine is located 25 km (15 miles) southwest of Orange, in the Central Tablelands of New South Wales, Australia. The mining lease covers about 3,100 hm2 (7,660 acres) of the Cadia Valley. The Cadia deposit is a large, homogeneous, low-grade, porphyry-type, gold-copper resource. Current reserves stand at 202 Mt (222 million st), grading 0.73 g/t (0.02 oz/st) gold and 0.17% copper. They contain 146.2 t (4.7 million oz) of gold and 347 Kt (382,500 st) of copper. The operation consists of openpit mining and ore processing to produce gold bullion and a gold/copper concentrate. The operation processes 17 Mt/a (19 millon stpy) of ore to produce 91 kt/a (100,300 stpy) of concentrate and 9.1 t/a (293,000 oz/year) of gold. The plant operates two 12-hour shifts a day and had a targeted availability of 94%. The plant facilities include a copper concentrator, o water supply system, an openpit mine, tailings pipeline and dam, and a concentrate pipeline and dewatering facility located in Blayney, about 35 km (22 miles) from the concentrator. Significant features of the process plant include o primary crusher and stockpile, a reclaim conveyor system feeding, the Cadia SAG mill (Figs. 1 and 2) and two 6.7-m- (22-ft-) diam ball mills (Fig. 3). A portion of the gold is extracted in a gravity circuit. The balance is extracted with the copper in the flotation section of the plant. Concentrate is thickened and piped about 35 km (22 miles) to the filter plant and rail loadout facility located in Blayney. Tailings are pumped to a tailings dam and process water is reclaimed from the tailings dam. The water system is designed to control and capture available runoff from local creeks, and to store these waters in dams and weirs. In addition, a major portion of the water for the process plant is treated effluent from the city of Orange and a smaller portion from Blayney Mill selection. The low-grade ore posed a dilemma for Cadia. To achieve a satisfactory economic operation, large-scale processing was required. The selection of the mills, equal to the largest designed and operated at the time, gave a plant configuration consisting of two 11.1- x 5.8-m (36- x 19-ft) SAG mills and three 6.1- x 9.1-m (20 x 30-ft) ball mills. This configuration did not provide the most satisfactory economic model for the project. A review of the single line configuration indicated that a significant reduction in the overall capital cost of the plant could be achieved by increasing the size of the mills and reducing the quantity. Increasing the size of the mills,

Jan 1, 2001

By K. F. Clark

Some 30 years ago Stevenson (1940) underscored the fact that most of the world's molybdenite production came from the Cordillera that comprise the western part of North America, and that the northern extension of the Cordillera into British Columbia is not essentially dissimilar to the United States section. Therefore, in view of the successful development of molybdenite resources in the United States, he concluded that prospecting in the Canadian section f the Cordillera should be encouraged. However, as recently as seven years ago Schneider (1963) remarks that no large economic deposits have been brought into production in British Columbia, although one important property was being evaluated. World production f molybdenum ore was sporadic until 1900. Among the very early producing areas in North America were Arizona and New Mexico in the United States. World War I provided the stimulus that brought the Climax deposit into production, and in 1920 Questa, New Mexico followed, although the ore came from fissure vein deposits at that time. In the early part f this century high grade deposits in various parts f the world containing 5-20 percent MoS2 were exploited. In Canada most production during World War I came from Quebec and Ontario. With the build-up of world tension and the inception f hostilities in 1939, British demand was satisfied by United States producers (Schneider, 1963).

Jan 1, 1970

By Charles J. Johnson

The United States is totally dependent on imports for all primary chromite and most ferrochrome supplies. Although the United States imports chromite and ferrochrome from a number of countries, the long-term future of chromite supplies appears to lie in southern Africa (Republic of South Africa and Zimbabwe) where 88 percent of known world reserves exist. Floreover, low mining costs and the availability of low-cost electricity for ferrochrome production gives South Africa a comparative advantage over most other chromite and ferrochrome-producing nations. A well-known problem faced by the United States is that when viewed from a longer-term perspective, the major sources of supply of metallurgical grade chromite and ferrochrome may be subject to disruption. The three countries that have caused the greatest concern have been the Republic of South Africa, the Soviet Union, and Zimbabwe. South Africa presents a particularly difficult problem because it may be subject to internal political unrest and/or U. N, economic sanctions. South Africa has increased its share of world chromium production from about 30 percent in 1968 to 62 percent in 1978.1

Jan 1, 1982

By Adam Levy, Thomas Novak, Sampurna Arya, Joseph Sottile, Kozo Saito

The use of a woven wire-mesh screen as part of a flooded-bed dust-scrubbing system is popular in the underground coal mining industry. It is used in combination with a demister (mist eliminator) to remove dust from the dust-laden air. A study was conducted to measure the pressure drop across a flooded-bed, wire-mesh screen at different airflow rates in one-phase (dry) and two-phase (wet) conditions. Two empirical relationships between pressure drop and air velocity were developed for dry and wet conditions, respectively. In both cases, the form of the empirical relationships was found to be similar to relationships given by Sabri Ergun for high velocity, non-Darcy, single- and multi-phase flow through porous media. The experiments were repeated on a reduced-scale model of the wire-mesh screen, and the pressure-velocity relationships obtained from the full-scale prototype experiments were tested. The test results show validation of the full-scale empirical formulae on the small-scale model with an insignificant variation. This paper presents the empirical equations for pressure drop across the wire-mesh screen in dry and wet conditions. Researchers can use these equations as a tool to predict total pressure drops for wire-mesh screens of different scale sizes.

By R. Mensah-Biney

The kinetics of loading of gold from bromide solution onto an anion exchange resin, PAZ-4, were investigated in a batch stirred reactor. The initial loading rate was described mathematically by a first-order reaction rate equation. The effect of agitation speed, temperature, resin particle size, resin concentration, initial concentration of gold and bromine in solution on the rate was investigated. The model described fairly accurately the loading process in terms of the variables investigated. The rate constant for the initial loading ranged from 0.5 to 1.3 x10-3 sec-1 and the half-time was 9.3 to 56 minutes. The initial rate constant increased with increasing temperature with an activation energy of 15.7 kJ/mole (3.8 kcal/mole). The rate constant was directly proportional to the concentration of the resin in solution. The subsequent reduction reaction was also modeled by the first-order rate equation and the apparent rate constant was estimated to be 3.0 x 10-6 sec-1 with a half-time of about 44 hours.

Jan 1, 1994

By Yoginder P. Chugh

Physical mine modeling and computer simulation techniques were used to conduct technical feasibility and economic analyses of selected pit configurations for surface mining a single coal seam dipping at about 15 percent to a maximum depth of 150 feet. The pit orientations along the dip (dipline), strike (strikeline) and along an apparent dip were studied. Physical models of each pit configuration were prepared first to delineate potential operational problem areas, and also to furnish a data base-for the computer simulation models. A dragline micro- simulation model (Fluor), a shovel/truck simulation model and a cost analysis model were used to conduct the study. Sensitivity analyses were conducted on variables such as the pit width, block length, and angle of dip. The productivity (Cu.yds/hour) of the mining equipment (dragline or stripping shovel) under each set of conditions was used to optimize the pit configuration. Both block length and panel width were found to significantly affect the dragline productivity larger size trucks were preferable to smaller size trucks in the pit configuration along an apparent dip. The cost analysis results showed that the pit configuration along the seam dip was more economical than the pit along the strike or along an apparent dip.

Jan 1, 1984

The dissolution kinetics of cobalt in iodine/iodide solutions was investigated using a rotating disc technique. Variables studied here included temperature, rotating speed, concentration of lixiviants, and pH of the solution. The overall dissolution reaction was found to be limited by mass transfer of tri-iodide through the diffusion boundary layer with Arrhenius activation energy of less than 16.2 kJ/mol (4 kcal/mol) over the temperature range, 2-42°C. The pH of the solution had little effect as long as the pH of the solution was less than 8. However, when the pH of the solution became greater than 8, the dissolution rate decreased dramatically due to passivation. The rate of dissolution was in good agreement with the dissolution model developed by the authors earlier.

Jan 1, 1994

By R. J. Sweigard

Many states are considering the need to establish or modify policy relating to the disposal of coal ash. One of the primary concerns is the impact of leachate from the ash disposal sites upon groundwater and nearby bodies of surface water. A detailed site investigation was conducted at a coal ash disposal facility associated with a power generation station. The disposal site is situated alongside a major river. Monitoring wells were installed and soil samples were taken for characterization. Groundwater models were used to simulate migration of leachate from the disposal site toward the river. Such models could be used potentially to verify regulatory compliance. This paper addresses the validation and adaptability of these models to this case and their usefulness as possible tools to be used in future environmental audits.

Jan 1, 1992

By J. C. Judd

The U.S. Department of the Interior, Bureau of Mines investigated solvent extraction methods for recovering gallium from filtrates produced from sulfuric acid leaching of hydrometallurgical zinc residues. These filtrates typically had pH values of 0 to 0.5, too high an acid content for effective gallium recovery by traditional extractants. Of the nine extractants studied in batch tests, 0.3M octyl phenyl acid phosphate (OPAP) in a kerosene diluent was the most effective extractant for gallium recovery, extracting up to 99.9 pct of the gallium. This high extraction was possible when the iron in solution was maintained in the reduced ferrous state. Batch tests also showed that a 1.5M-H2SO4 strip liquor recovered 98 pct of the gallium from the loaded OPAP. A continuous solvent extraction system was designed and operated based on McCabe-Thiele analyses of equilibrium loading and stripping isotherms. When 12 L of leach filtrate containing 0.32 giL Ga and 20 giL Fe were pumped through the system in 32 hr, results showed that 95 pct of the gallium was extracted in four stages at an A:O ratio of 1:1. Stripping the loaded solvent with a 1.5M-H2S04 liquor recovered 94 pct of the gallium in four stages at an A:O ratio of 1:4. A two-stage, 50-pct-phosphoric acid strip successfully removed ferric iron from the OPAP, allowing high gallium extractions to be maintained.

Jan 1, 1990

By K. N. Han

Coal is becoming increasingly important as a major energy source in the face of the world's depleting energy mainly based on oil reserves. Coal is by far the most abundant fossil fuel both in the United States and abroad. Currently, because of increased mine mechanization, the fineness of preparation plant feed is increasing. Further, in the future as the grade of coal diminishes and the sulfur content increases, upgrading preparation of coal is very important. Because the density of coal is less than that of rock materials that occur as impurities, coal is separated from such waste largely by gravity-controlled processes for particle size between 5 inches and 28 mesh. If the size of coal particles is below 28 mesh, froth flotation is a good method for upgrading fine coal. Previously, numerous investigators have tried to upgrade coal values by froth flotation(1-16) and have achieved moderate success. However, the recovery and grade of coals in the concentrates are not always satisfactory, especially when the particle size is small. In general, when the size of coal is below 100 mesh, the above methods suffer from poor grade and low recovery. The reason for this is that as size decreases, the effects of gravity diminish, and other forces take effect.

Jan 1, 1985

By J. C. Norman

The United States was the world’s largest producer and consumer of boron compounds during 1995. According to estimates from the US Geological Survey(USGS), boron mineral concentrate and chemical production in the United States totaled an estimated 1.1 Mt(1.2 million st) yielding 602 kt (663,000 st) of B2O3 for an estimated value of $462 million. This level of production exceeded 1994 revised production figures by about 9%. The United States continued to provide nearly all its own boron supply while maintaining a strong position as a source of sodium borate products and boric acid to foreign markets. During 1995, about 900 people worked in domestic boron mines and plants, about the same as in1994. USGS estimated total world production of boron during 1995 to be about 3 Mt (3.3 million st), yielding about 1.6 Mt (1.8 million st) of B2O3. World production in 1995 was about equal to revised 1994 levels.

Jan 1, 1996

By R. S. Olson

The operation of a series wash thickener-two stage filtration circuit determines the soluble loss in many hydrometallurgical operations A study of this circuit yielded expressions which permit calculation of soluble loss for almost any condition of operation. The soluble loss over a range of the circuit variables is presented to illustrate and evaluate circuit performance, The interrelation of factors affecting filter performance and some of the wash circuit, variables are quantatively described. Filter wash, which is governed by wash zone size, filter pulp level and filter feed pulp density, has the greatest affect on soluble loss. Excepting clothing blinding and flocculation the factors which decrease filter capacity also decrease soluble loss. Repulping with water, under some circumstances, can bean important means of soluble loss reduction. Water for primary filter wash, leach pulp density repulp density and wash thickener underflow density have little effect on soluble loss. The dilution of both o the filter pulps with wash solutions is suggested as a means of reducing soluble loss, and at the same, time, controlling the performance of the filters. Blowback and filter cloth blinding seriously increase soluble loss.

Jan 1, 1962

Like the Summer Olympics and U.S. presidental elections, MINExpo comes along once every four years. More than 35,000 people attended the last MINExpo and there is talk that there will be more this time. Just about every company that has anything to do with mining, 1,822 to be exact, will exhibit their wares at the show, but it is the ones rolling in the massive equipment that make MINExpo the show that it is. The following is a glimpse at some of the companies and equipment that you can expect to see at this year?s MINExpo.

Jan 1, 2012

By J. M. Mutmansky

This paper outlines the results of a study of opinions of practicing engineers concerning the value of environmental engineering courses in a mining engineering curriculum. One hundred engineers with significant experience in mining-related engineering work were carefully chosen. Of the sixty-seven responses received, about half were from mining engineers and half from environmental engineers. The results of the survey are outlined in detail. The number and type of courses recommended by the respondents are summarized as well as the specific topics recommended for inclusion in a mining engineering curriculum. The survey form also asked for the stages in the mine life when environmental experts were needed and the percentage of environmental engineering performed by outside experts for many mining-related environmental tasks. The results of this line of questions are provided. Finally, the paper offers a comparison of the results for environmental engineers and mining engineers and analyzes the differences.

Jan 1, 2001

By Robert L. Grayson

An application of goal programming (GP) in evaluation of proposed purchases of major mining machinery is presented. It incorporates historical operating data compiled on mechanical delays to production time. The goal programming technique, which is an extension of integer programming, is used to maximize an objective function. The objective function combines the capital budgeting evaluation methods of net present value, payback period, profitability index, and total net earnings as goals weighted according to a management preference. The GP method gives an optimal solution to a multiple-goal problem. A sensitivity analysis is performed to determine the effect of an increased production forecast or a tightened budget on proposal selection.

Jan 1, 1982

By M. R. Yalamanchili

Recently, noequilbrium electrokinetic measurements using laser-Doppler electrophoresis were reported by Miller et al. (1992) for alkali halides and the sign of their surface charge thus determined. These results are generally as expected from simplified lattice ion hydration theory with KCI, under normal circumstances, being the most significant exception. In this regard, lattice defects (F centers and oxygen imperfections) have been found to influence the surface charge of KCI and its electrophoretic mobility. In particular, the presence of oxygen defect states in the crystal lattice has been found to be responsible for KCI's unexpected behavior. The concentration of oxygen defect states in KCI, as characterized by UV/Vis absorption, was varied in order to study their influence on the electrokinetic behavior and subsequently on the flotation response of KCl. At low oxygen contents « 60 ppm) KCI is positively charged as expected from lattice ion hydration theory. However, typically, KCI contains substantial oxygen (>300 ppm) sufficient to impart a negative surface charge which accounts for the selective flotation of KCI from NaCl by hetero-coagulation with oppositely charged alkyl amine hydrochloride collector colloids.

Jan 1, 1994

By S. A. Diatchkov

There is a misconception that mineral-project economic evaluations in the former Soviet Union are either nonexistent or very limited. This is not the case. In fact, there are at least two basic methods that can be utilized to evaluate the vast mineral resources of the Commonwealth of Independent States (CIS). Evaluation procedures are based either on a comparison to known projects, which may rely on limited available data, or on potential-profit calculations, which generally uses more extensive databases. Significant philosophical differences between these systems and those utilized in the Western world include the following: •Under the centralized-government system, the economic evaluation of a mineral project was based on artificially determined mineral prices and costs. Every ten to 12 years, prices for concentrates and metals were established by the Council of Ministers and remained unchanged until the next reconsideration of prices .

Jan 1, 1995

By N. O. Lotter

Studies investigating the evaluation errors in laboratory scale flotation tests for platinum-bearing Merensky Reef in the Bushveld Complex, South Africa, have constructed a quality control model to assure a 95% confidence in the attested data. Specialized knowledge of the mineralogy of the platinum-group elements (PGE), together with acquaintance of evaluation models, validate a systematic checking of the sub-processes of the testwork. These include determination of minimum mill feed sample size, assay head reference distribution, mass balance checks, and specialized sample preparation of flotation test products prior to analysis. A flow schematic of this quality control model is proposed, with an example of test data that produce an error in the metal balance of 0,2% after rejection of outlier data.

Jan 1, 1995

By V. A. Shea-Albin

Sandstone escarpments surrounding western coal-bearing plateaus serve as critical habitat for animal species. Effects of mining subsidence on escarpment stability are not well documented; therefore, regulatory agencies may limit extraction of coal reserves underlying escarpments. Because millions of tons of this coal exist on Federal Lands, associated public revenues from Federal royalties, and valuable coal reserves, risk being lost. The U. S. Bureau of Mines is using numerical modeling techniques to analyze effects of subsidence on escarpment stability. Finite element models that incorporate bedding plane slip, gob formation, and movement along joints simulate escarpment subsidence observed in the field.

Jan 1, 1994

By S. Vivek

An atomic force microscope (AFM) was used to measure the surface forces between silica plate and glass sphere in sodium oleate solutions. Hydrophobic forces were observed when the two surfaces were activated by CaOH+ or MgOH+ ions. The force measurements conducted in the absence of the surfactant showed that the activated silica surfaces do not exhibit the primary hydration forces that have been observed between unactivated surfaces. The activation mechanism was studied by calculating the contributions from electrostatic and chemical interactions to the total free energy change. The results suggest that the adsorption of the hydroxo-complexes is controlled mainly by the lateral interactions between the adsorbed species on the silica surface.

Jan 1, 1999