Search Documents

By V. R. Bovino

You have afforded me the challenge of saying something profound in 20 minutes that will stay with you for 20 years. My hope is that from this presentation you will extract ideas that will move you? out of your offices, into the mine to seize upon the concepts that we will discuss. Your challenge is to transform those concepts into action and give life to the ideas discussed here. The notion of achieving limitless productivity produces peak levels of enthusiasm in today's mining leaders. Highly-productive mines do not happen by chance --they are created by progressive leaders. The quest for productivity improvement, exclusively through capital investment and technological advances, is an incomplete process. Improvement, through capital and technology, is often not achieved because we fail to energize the true potential and commitment in our employees.

Jan 1, 1991

By M. A. Rodrigues da Silva Enríquez

One of the rare consensual points among different resource-based economic analytical approaches refers to the strategic role of rent from mineral extraction, as a decisive tool to ensure that the temporary wealth generated in the present can turn into permanent income in the future. For this reason, evaluation, distribution and use of mining rent plays a central role in the sustainable development of mining cities. Brazilian legislation provides for this at the municipal level by means of participation in the financial results of mineral extraction accomplished in these municipalities, with the Financial Compensation for Mineral Exploration (CFEM). CFEM is a type of ad valorem royalty, which charges taxes of up to 3% of the net revenue of mineral production. However, legislation does not establish how these resources should be used. Therefore, there is wide variation in the use of CFEM income among Brazilian mining cities. A study from a sample of the 15 largest mining cities in eight Brazilian states made possible identification of two main patterns with regards to the use of CFEM which were labeled "sustained use" and " the pitfall of the single treasury." In that regard, this article discusses the pressuring factors that contribute to these patterns, as well as the institutional arrangements which may be more favorable to inducing more sustained use of CFEM.

Jan 1, 2011

"Above ground, elevated belt conveyors that span more than 200 m (656 ft) between support points can cross valleys, rivers, forests and buildings with a minimal footprint. The cable bridge conveyor (CBC) is a new type of suspension bridge based belt conveyor system that has long spans between support points. It combines a typical belt conveyor and an improved simple suspension bridge to form a conveyor bridge. The improved simple suspension bridge places a widened bridge deck directly on suspended cables, without the need for high truss towers. The benefits include reduced cost and increase aerodynamic stability compared to conventional suspension bridges. The CBC’s compatibility with current belt conveyors allows versatility in application.A belt conveyor is a ubiquitous material handling system. Conveyors can be placed directly on ground or elevated above ground by support structures. Considerations of cost, design, environment, civil work, safety and process requirements are all factors in choosing the ground-based or elevated conveyors (Zhang, 2014). The ground-based conveyor has the lowest structural cost when the conveyor is placed on an existing road. Maintenance access is easy and straightforward. Compared to the groundbased conveyor, the elevated conveyor can cross existing buildings and structures, give passage to traffic beneath the conveyor, has a smaller footprint and requires less civil work to pass mountainous areas. The drawback of the elevated conveyor is higher structural cost, which can be compared with savings in civil work and other benefits. Conventional elevated conveyors are supported by rigid truss-type structures, with a typical span of 15 to 25 m (50 to 82 ft) between concrete support bents or steel trestles. Triangular truss, using steel pipes instead of hot rolled steel sections, is more efficient. The typical span of a triangular truss-supported conveyor is around 30 to 40 m (100 to 130 ft), while the weight is about 10 percent less than conventional box truss with a shorter span (Jennings, 2013).Long-span elevated structures based on suspension bridge is another step forward in increasing the distance between support bents, reaching 100 to 400 m (330 to 1,312 ft) and beyond. The wide distance between the support points of an elevated conveyor offers unique benefits. The conveyor can cross rivers, valleys, highways, forests and other obstacles with minimal footprint and reduced civil work. The versatility from long-span conveyors makes bulk material transportation over previously impossible terrains now a feasible option."

Jan 1, 2014

By James C. Conti

A surface charge sensor has been developed that responds to changes in the double layer properties of colloidal silica during the cationic flotation of silica from taconite ores. Sensor design allows for the measurement of two aspects of the electrical double layer surrounding all solids immersed in ionic solutions. One aspect responds to a flow induced change in the double layer properties of a solid. The other is a function of the chemical composition of the aqueous phase. Evaluation of sensor performance during froth flotation experiments has been encouraging. Process monitoring capabilities are indicated.

Jan 1, 1981

By Giovanni Barla

The stress-relief method for the determination of the ground stress tensor is a common procedure in rock mechanics. In particular, the method of applying gauges to the end of a borehole is a well-established technique. Investigations, both experimental and theoretical, indicate that large discrepancies can exist in the determination of the ground stress tensor when the rock substance is not the ideal elastically isotropic material assumed for the reduction of data. The purpose of this paper is to extend the analysis of strain gauges applied to the end of a borehole to rock material more closely approximate to an orthotropic substance.

Jan 1, 1969

By Z. Yu

The effect of particle size on coal dewatering has been well recognized However, there are no systematic studies on ultrafine coal dewatering. The results discussed last year revealed the effect of flocculant type and coal wettability on the filtration of ultrafine coal In this paper, the differences in dewatering between -25 µ m ultrafine and -500 µ m fine coal with addition of flocculants, surfactants and oil-emulsions in vacuum filtration are further investigated Significant differences were observed in the reduction of the cake moisture. The utilized emulsions were found to be very powerful and promising filtration aids for both ultrafine and fine fractions of hydrophobic and hydrophilic coal

Jan 1, 1995

By Julián Ortiz C., Clayton V. Deutsch

Indicator simulation allows specification of different continuity of high and low values through the use of grade thresholds. The sequential implementation of indicator simulation has been widely used, but the problem of order relation deviations remains a significant drawback. A new procedure for "Hierarchical Indicator Simulation" is introduced that avoids order relations and offers greater flexibility than the conventional sequential approach. The new implementation simulates all locations at the largest threshold and then considers decreasing thresholds in turn. All nodes with grades that are above the previous threshold are excluded from the domain of the current threshold and therefore, they are not used as conditioning data. The probability of being above or below the threshold is calculated using simple indicator kriging using all conditioning data in the domain, thus the covariance structure is preserved. The theoretical framework of this new approach is fully developed. Practical implementation details are discussed. Application to a copper deposit shows the advantages and drawbacks of the method. Finally, the possibility of incorporating multiple-point statistics is discussed.

Jan 1, 2002

By J. F. Stenebråten, W. P. Johnson

Carbonaceous material (CM) from the Barrick Goldstrike Mines, NV, was characterized with respect to its gold sorption (preg-robbing) and gold recovery behavior. The breadth of graphite peaks measured by X-ray diffraction were used to calculate crystallite dimensions (002) of the CM. The (002) dimension was found to vary inversely with preg-robbing activity and directly with gold-recovery behavior, indicating that the degree of graphitization (maturation) experienced by the carbonaceous material is correlated with gold-loss during ore processing. The inverse correlation of preg-robbing activity was improved when percent preg-robbing was regressed against (002) crystallite size and carbon content. The (101) crystallite dimensions of all samples were calculated from laser Raman analysis, and were not found to correlate with preg-robbing behavior of the CM. BET surface area and micropore size distribution results were affected by grinding history, negating comparison of these characteristics between samples.

Jan 1, 2000

By S. K. Sharma, D. A. Stanley

The US Bureau of Mines is investigating the fundamentals of the flocculation process. The objective of this study was to determine the effects of various physico-chemical parameters, namely, shear rate, polymer dosage, and polymer concentration, on floc growth and to determine the applicability of a model for predicting polymer flocculation behavior. A rapid in-line particle size analyzer was used to follow the progress of both the floc growth and the breakage as a function of time. A genetic algorithm (GA) was used to determine the unknown parameters in the model and to fit a curve to the experimental data. The results showed that the model reproduces the experimental data with only reasonable accuracy and that it was relatively insensitive to the parameters. Results of the flocculation study showed that increases in the polymer dosage had a greater effect on the time required to reach the maximum floc size than on the floc size itself: It was also determined that, given all the above parameters, the degree of slurry mixing during the flocculation process had the greatest bearing on floc growth.

Jan 1, 1995

By S. C. Libby

The amount of fine material (minus 60 Tyler mesh) generated during calcination and/or handling of calcined abrasive grade bauxite from Alcoa's operations at Moengo, Suriname, has recently increased relative to past production experience. Bulk samples of raw abrasive grade bauxite from three deposits in the Moengo area have been studied in order to determine the factors controlling the generation of fine material samples from the Jones IC and Tapira deposits, which generate excessive amounts of fine material, have been compared with reference samples from the Begi Gado deposit, which does not generate excessive fine material. Additional type samples of abrasive grade and marginal abrasive grade bauxite from deposits in the Moengo area which represent different bauxite textures found in the Jones IC, Jones I, and Begi Gado deposits have also been studied. Field observations in the Moengo area have indicated that abrasive grade bauxites with a dull, earthy appearance generally do not generate excessive fines. On the other hand, excessive fines are generally associated with coarsely crystalline bauxite in which the gibbsite crystals appear to sparkle in sunlight.

Jan 1, 1980

The Ernest Henry copper-gold project is located in North West Queensland, Australia and commenced production in late August 1997. Utilizing a philosophy of selecting the biggest proven equipment available Ernest Henry at full production ¥ill treat 9 Mtpa through a single grinding line over a 15 year mine life. 350.000 tonnes of concentrate a year will be produced, containing 95,000 tonnes of copper and 120,000 ounces of gold. The two mills recently commissioned at the Ernest Henry Copper/Gold Mine are a 10.4m x 5.1m (34 ft x 16.75 ft) SAG Mill and a 6.1m x 8.4m (20 ft x 27.5 ft) ball mill. The mills have a power draw of 11 MW (14745 hp) and 5.5 MW (7373 hp) respectively. While the SAG Mill is not the largest SAG Mill in the world, it is the largest shell-supported SAG Mill in the world. The Ernest Henry mills epitomize the new standard design of large grinding mills. The design was introduced more than 20 years ago and has been further developed from extensive experience with grinding mills, and the need to produce a design, which overcomes the recognized problems of large mills. The result is a design with the potential to be used for mills up to the largest for which machine tools can be found to fabricate and machine them, currently approximately 15m (48') overall diameter.

Jan 1, 1999

By Robert M. Mann

The Ag/S specific ion electrode has been evaluated for analysis of both free and total cyanide. Metal cyanide solutions were prepared from reagent grade compounds and by stoichiometric fixture of the metal with a potassium cyanide solution. Solutions containing Cu+1, Ni+2, Fe+2, Fe+3 and Zn+2 complexes were analyzed prior to and following EDTA pre treatment. This effort provides an understanding of the effect of each metal cyanide complex on the SIE analysis of free and "total" cyanide.

Jan 1, 1981

By J. A. Harrison

Most coal being used in the United States has been subjected to one or' more processes of coal preparation. The physical and chemical characteristics of a coal have a marked influence on the ultimate uses that coal may have. The selection of the proper preparation processes may similarly be important in producing the best practical coal product for any particular use. The physical composition and distribution of physical constituents in the coal will partially determine the efficiency of the preparation process chosen and conversely distribution and concentration of coal macerals will, to a degree, be controlled by the preparation process. A number of preparation processes have been evaluated to determine this interrelation. If a coal having' certain specifications is desired, these evaluations trill assist in providing information needed for the production of this coal.

Jan 1, 1962

By William E. Wallace, Larry Grayson, Thomas Simonyi, Joel C. Harrison

Application of an SEM-based methodology suggests a reason for past contradictory results on the relationship between quartz and coal workers' pneumoconiosis (CWP). Results indicate that coal seams with the same bulk analysis of quartz have different amounts of surface-available quartz. Our research shows that the amounts of pure and surface-available quartz in a respirable dust vary directly with the rank of a coal seam, except in the case where rock materials are mined. The estimated amount of surface- available quartz therefore provides a measure of the quartz-related fibrogenic potential of a respirable dust.

Jan 1, 1992

By Kevin J. Ashley

Coal is deposited at a mine site in several thin seams which outcrop in rolling hills and dip at about 8° to the northeast. The deposit is located in the northeast area of the State of New Mexico in the Southwest of the United States. A drilling program was undertaken and was quite irregular. Not all of the seams appear in all of the drill holes. Some of the holes did not go deep enough, while others were drilled below the outcrop of some seams. Occasionally a seam would pinch out and not be seen in a drill hole. Also, the outcrops of the seams are buried in many places by several feet of alluvium. All of these factors make correlation of the seams between drill holes difficult. The drawing of cross sections in three directions and at many locations across the mining area have been necessary to assure the accuracy of the input data.

Jan 1, 1982

By Jose Agapito

Roofbolts with expansion anchors have been used at White Pine for more than twelve years, but always with an understanding that their performance was not entirely satisfactory. Some bolts fell out, some were obviously loose, and, when roof failures did occur, very few bolts actually broke. Obviously, there was an anchorage problem. A program was started in May, 1967, to define the problem and to solve it. This paper describes briefly those parts of the program which led to the development of a roofbolt assembly which performs much better in the medium-hard rocks at White Pine. As a result of the changes, significant improvements were found in the torque:tension, tension loss, and pull tests.

Jan 1, 1970

By A. Tew

The Ernest Henry copper-gold project is located in North West Queensland, Australia and commenced production in late August 1997. Utilising a philosophy of selecting the biggest proven equipment available Ernest Henry at full production will treat 9 Mtpa through a single grinding line over a 15 year mine life. 350.000 tonnes of concentrate a year will be produced, containing 95,000 tonnes of copper and 120,000ounces of gold. The two mills recently commissioned at the Ernest Henry Copper/Gold Mine are a 10.4m x 5.1m (34 ft x 16.75 ft) SAG Mill and a 6.1m x 8.4m (20 ft x 27.5 ft) ball mill. The mills have a power draw of 11 MW (14745 hp) and 5.5 MW (7373hp) respectively. While the SAG Mill is not the largest SAG Mill in the world, it is the largest shell-supported SAG Mill in the world. The Ernest Henry mills epitomise the new standard design of large grinding mills. The design was introduced more than 20years ago and has been further developed from extensive experience with grinding mills and the need to produce a design, which overcomes the recognised problems of large mills. The result is a design with the potential to be used for mills up to the largest for which machine tools can be found to fabricate and machine them. currently approximately 15m (48')overall diameter.

Jan 1, 1999

By S. D. F. Rocha

The influence of surfactants on the crystallization of calcium sulfate was investigated in both hatch and continuous systems. The investigation was per formed at the following conditions. 343 °K, 28% P205 and with a sulfate level of 2.0%. At concentrations of 5 and 200 µgig, respectively, dodecylbenzene sulfonic acid (DBSH) and sodium diisooctil sulosuccinate (SSNa) promoted both an increase in the size and a reduction in the length/width (L/W) ratio of the calcium sulfate hydrates produced in the hatch and continuous crystallizers. Unique effects were observed in the batch system at higher DBSH concentrations. At 10 µg/g, the precipitation of hemihydrate crystals with a distinct morphology and texture occurred under conditions where dihydrate precipitation was expected. Above 50 µg/g, the precipitation of calcium sulfate hydrates was completely inhibited.

Jan 1, 1996

By R. G. Reddy, A. E. Torma

Bio-treatment of uranium contaminated soils from Fernald using the bacterium Thiobacillus ferrooxidans was investigated. The experimental results showed that extraction of uranium upto 99 percent from soils were obtained with 10 percent pulp density suspension and with addition of iron (3000 mg/l) after bio-remediation time of seven days. Application of the results to industrial practices is discussed.

Jan 1, 1995

By A. V. Glembotsky, N. A. Greshnova, V. P. Seregin, V. A. Glinkin

Based on a new alternative depressant of zinc sulphide - dimethyldithiocarbamate- modern technology has been developed for the treatment of complex polymetallic ores. In addition to its general function (depression of sphalerite and iron sulphides to some extent), this double-acting reagent is a promoter for galena and silver minerals. Laboratory and plant tests, as well as industrial experience have all shown consistently higher silver recovery to the lead concentrate as compared with sodium cyanide, resulting in less pollution and a safer environment

Jan 1, 1995