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By J. H. Bassarear

Conventional crushing and grinding circuits are compared to semiautogenous circuits. Recent installations of each circuit are reviewed and seven methods of using autogenous or semi- autogenous techniques are described. Steel and power consmption data are reported and benefits of a dedicated digital computer are discussed.

Jan 1, 1981

By S. N. McIntosh

Column bioleaching was evaluated by the U.S. Bureau of Mines as a means of recovering manganese from a low-grade ore from the Three Kids deposit in Southern Nevada. Manganese was solubilized from the ore using indigenous heterotrophic microorganisms. Diluted molasses medium was provided as nutrient for the microorganisms. The medium was recirculated through the ore bed until the sugars were spent. Two methods were evaluated to recover manganese from the sugar depleted bioleaching solution: (1) adsorption with a weak cation exchange resin followed by stripping and precipitation techniques, and (2) direct precipitation of the manganese using ammonium carbonate. Both methods removed up to 95 pct of the solubilized manganese from the medium as a carbonate salt. After manganese removal, the medium was replenished with fresh molasses and recycled back through the column. More manganese was effectively leached. This process of manganese solubilization and recovery followed by replenishment and recycling of the medium was repeated until 98 pct manganese was extracted from the ore.

Jan 1, 1993

By R. A. Ynchausti

In January 1993, Pyramid Resources began implementation of a supervisory expert control system at a U.S Cu concentrator. The objective of this control system was to improve plant profitability through unit operation optimization and integration. This paper documents the key aspects of the project, including: economic and associated benefits, system architecture, concepts of implementation, process control strategies, practical aspects of implementation and conclusions. The implementation of expert control at this concentrator has resulted in an estimated benefit of $50,500 per day. This is a net result of improved tonnage, reduced reagent consumption, improved concentrate grade and reduced energy per ton produced.

Jan 1, 1995

By W. P. Diamond

The Bureau of Mines has been investigating several techniques, including the use of horizontal and vertical boreholes, to remove gas from coal in advance of mining. Horizontal boreholes drilled from underground workings as part of the mining cycle have been shown (Finfinger, 1980; Hagwood, 1983; Perry, 1978; Prosser, 1981; Thakur, 1980; VonSchonfeldt, 1982) to be very effective in providing short-term, immediate relief from high methane emissions. This technique has been widely accepted in the coal mining industry, but it does require close coordination to integrate the drilling and subsequent gas drainage and disposal into the projected mine development plan. Vertical boreholes can be placed several years in advance of mining to predrain gas from coalbeds over relatively large areas (Dunn, 1984; Elder, 1975; Lambert, 1980; Steidl, 1978; Stubbs, 1979). The vertical borehole technique has the additional advantage over horizontal boreholes of allowing work to be performed on the surface instead of in the more restrictive underground environment. However, except for the relatively large scale vertical borehole programs for both mine safety and commercial production in the Black Warrior Basin of Alabama (Dunn, 1984; Lambert, 1980; Stubbs, 1979), the technique has been underutilized. The primary reason for this seems to be a combination of the current economic climate in the coal industry, legal questions as to the ownership of coalbed gas, and potential roof damage from the stimulation treatments required to increase the characteristically low permeability of coalbeds to enhance gas production. The question of potential roof damage is the subject of this paper.

Jan 1, 1985

By K. L. Lamb

At the Sierrita mine, 40 km (25 miles) south of Tucson, Arizona, Duval Corporation is rapidly gaining operating experience with its new Portable Crushing and Conveying System, (PCCS). As of November 23, 1983, over 4.5 million tons (5.0 million st) of ore have passed through the system. Mining cost per ton for the months of July, August and September was 83% below the average for the first five months of 1983. Although all the cost reductions experienced cannot be attributed to the Portable Crusher, it was a major contributing factor. The Sierrita ore deposit has several natural topographic and geologic conditions which are not favorable to mining. It is not a sidehill deposit and therefore no low-level exit points exist to facilitate truck haulage. The ore is very hard. Quartz diorite, hardest of the three major rock types, averages 172-207 MPa (25-30 000 psi) unconfined compressive strength and may run as high as 345 MPa (50 000 psi). Blasting in this rock produces oversize material which runs approximately 20% 51 centimeters (20 inches). The ore is low grade, averaging slightly better than .30% contained copper and .035% contained molybdenum, with small amounts of silver. These conditions, plus high design production tonnages, make the Portable Crushing and Conveying System (PCCS) practical for Sierrita. Without crushing and conveying, truck haulage would be prohibitively expensive. A typical, October, 1983, ore haul from the bottom of the pit would involve a vertical lift of 260 meters (850 ft) and a horizontal distance of 3 860 meters (12 200 ft) were not in-pit crushing and conveying available. The corresponding cycle time would be nearly 32 minutes.

Jan 1, 1984

By D. H. Lynch

Prompted by the need to conserve energy and reduce operating costs, Agrico Mining Company has made two significant improvements in the transportation of phosphate ore from the mine to the beneficiation plant. One improvement involves a change in a slurry pipeline system which substantially reduced pumping energy, and the other improvement is a major innovation for the phosphate mining industry which involves the transportation of the ore by railroad. This paper briefly describes these two projects.

Jan 1, 1981

By C-D. Johansson, B. Ögren, B. M. Ludvigsson, K-Å. Johansson, R. Lindh, G. Berg, M. Maliarik

This paper presents the High Current Density (HCD) Silver Electrorefining Process. A 25-year history of development of the silver electrorefining process as well as associated equipment is given. The process is simple and robust, but at the same time highly automated. With low operating costs and man power requirement it allows consistent production of 99.99 % quality cathode silver. The process ensures that no toxic gases are formed in the working environment. Silver Electrorefining is a heart of a Silver Refinery plant covering the complete range of processes from casting of silver Doré anodes to casting of the bars of refined silver or/and silver granulation. The process has been successfully applied at 11 installations world-wide with plant capacities ranging from 30 to 1500 tpa.

Jan 1, 2014

By L Lachance, F Flament, D Leroux, S Gariépy

The pervasiveness of poor sampling practices in and around mineral processing plants could seem intriguing in view of the various documented evidences both for causes and consequences. To this extent, this paper revisits the well-documented but lesser-known fact that failure to care sufficiently about how samples are selected and managed is the mother source of almost all sampling biases. The authors believe that the potentially huge leverage between causes and consequences as well as the diversity of people involved in sampling call for a globally integrated solution rather than for a point solution. Such a globally integrated solution has already been put forward by the AMIRA P754 Metal accounting – code of practice and guidelines (AMIRA, 2007) that inherently requires accuracy to be targeted, measured, reported and managed. Furthermore, always in order to avoid a point solution, several layers of protection against biases must be put in place with each one involving a different ownership whenever possible. This is exactly the role intended by the supervisory bias detection method described in this publication. It is based on the continuous monitoring of the expected value of reduced residuals obtained from statistical data reconciliation conducted in a metal accounting context. This supervisory bias detection method is developed in full details after which Monte Carlo simulations are done on a mineral processing plant example for showing how it can be successfully applied for detecting hidden biases.CITATION:Lachance, L, Leroux, D, Gariépy, S and Flament, F, 2014. Detecting sampling biases in metal accounting, in Proceedings Sampling 2014 , pp 109–120 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 29, 2014

By J. E. Harris

By elimination of other possible nucleation processes, it has been demonstrated, for commercially pure magnesium and a Mg-Al alloy, that at stresses less than that necessary for triple-point cracking creep cavities are most probably nucleated heterogeneously at second-phase particles. Evidence for the existence of such particles is presented and the role of grain boundary sliding in the nucleation process is examined quantitatively. DURING creep deformation of polycrystalline magnesium and its dilute alloys in the temperature range 0.45 to 0.7 Tm (Tm = absolute melting temperature) cavities form mainly along grain boundaries oriented normal to the stress axis and failure eventually occurs by their growth and impingement.' The possibility of low-ductility creep failure of magnesium-alloy reactor cans during service has prompted a number of studies of cavity formation in these materials.2-5 In this paper divergent theories of cavity nucleation6-10 are examined critically and conclusions drawn regarding the most probable mechanism of formation of cavities in magnesium. The paper is divided into two parts. The first section consists of the review and quantitative assessment of the possible role of grain boundary sliding in the nucleation process. In the second part an experimental program is described where an electron-microscope technique has been used to determine if second-phase particles exist in as-received commercially pure magnesium and in a magnesium alloy 1) THEORETICAL REVIEW Possible nucleation sites for creep cavities are: a) high-angle grain boundary triple points,11-14 b) subboundary/grain boundary intersections,15-18 c) ledges in the grain boundary, 19-25 d) second-phase particles. 9,26-30 Each of these possibilities is now considered with special reference to deformation of magnesium. 1.1) Triple-Point Cracking. The stroh31 condition to nucleate fracture is: " > vr [1] where ss = applied shear stress, ? = surface energy, C = shear modulus, L = length of sliding interface. This relationship is independent of the nature of the interface and it is possible to calculate the stress concentration at the end of a sliding high-angle grain boundary and thus deduce, approximately,* the minimum applied stress necessary to nucleate triple-point cracking. Such theoretical predictions for Nimonic alloys have been made by McLean13 and found to agree quite closely with the minimum stress determined by experiment. Stresses capable of nucleating triple-point cracking should also be sufficient to nucleate fracture at a grain boundary due to intragranular slip, for the lengths of sliding interface in the two cases are approximately equal. Thus the minimum stress for triple-point cracking should represent a demarcation between failure due to general "cracking" and that due to cavitation. Hauser, Landon, and Dorn32 have demonstrated that for polycrystalline magnesium in the temperature range 78° to 298°K the fracture stress is inversely proportional to the square root of the mean grain diameter. As pointed out by stroh31 this result indicates that Eq. [I] describes the fracture characteristics of magnesium at low temperatures. Heal3 has reported that for rapid deformation (112 pct hr-1) of polycrystalline magnesium the transition from cracking to cavitation occurs in the temperature range 175" to 275°C. He also presented the fracture-stress values for the same material tested under similar conditions. From Eq. [I] taking G = 1.3 x 10" dynes , ? = 600 ergs . cm-2,33 and L = 0.017 cm, a Stroh-McLean13,31 tensile stress of -266 kg. cm-2 is calculated, corresponding to a transition temperature of -190°C; this is in

Jan 1, 1965

Efficient project planning during the detailed feasibility to final engineering stages of a project requires not only the accurate prediction of the grade, tonnes and recovery, but their degree of variability as well. An understanding of the major parameters involved in the grade and tonnage estimates is essential, and the communication to those receiving the results is most important. The personnel involved in the project require more than just a global reserves classification. Quality parameters other than grade should be evaluated as carefully as the estimate itself. This paper does not present any novel ideas to overcome or enhance any of this. Rather, it takes a step back and tries to look at the global picture of requirements for proper project planning.

Jan 1, 1987

By P. Spolaore

In the frame of Bioshale FP6 project, the bioprocessing of a polymetallic and polymineral concentrate produced in an industrial operation in Lubin, Poland, was assessed. Following successful batch culture tests, processing in continuous conditions was tested to determine the main specifications for the application of the stirred-tank technology to this sulphide concentrate from black shale ores. The experimental work was carried out in a laboratory-scale unit consisting of 3 stirred tanks (50L or 20L) using an acidophilic and moderate thermophilic bacterial population. Different configurations of the unit and key operating parameters were tested (nutrient medium composition, solids concentration, rates of agitation and aeration). Scientific and technical approaches, such as bacterial community structure and mineralogical analysis were implemented in order to better understand the chemical and biochemical reactions occurring in the system. Using the data produced during the continuous operation, downstream processing assessment for both copper and silver recovery was also carried out. The best copper recovery obtained in the continuous operation was 92% and a hot brine leaching of the bioleach residue (PLINT process) allowed to recover 92% of the silver. A preliminary tech-no-economic evaluation of Lubin concentrate bioprocessing including bioleaching, copper and silver recoveries demonstrated the potential economic feasibility. Recovery of silver plays an important role in the economy of the process. This study presents promising values to further investigate this bioprocessing option.

Jan 1, 2014

By Georg Petersen

El presente texto describe la historia del primer centenario de la industria petrolera peruana (1863 -1963). La revisión va desde la historia temprana del petróleo en la primera mitad del siglo XIX, desarrollo de la industria moderna del petróleo en el Perú hasta el estado actual de este.

Jan 1, 1964

By Matthew Preedy, Anthony Pooley, Mike Wongkaew, Dirk Bakker, Raghu Bhargava

Sound Transit’s ST3 program will add 62 miles of light rail to the Puget Sound area, including connections to the neighborhoods of West Seattle currently anticipated by 2031 and Ballard by 2036. These connections include considerations for both elevated and tunnel alternatives, as well as a new downtown tunnel for which different configurations are being considered with potentially very different construction logistics and risk profiles. This paper describes the latest developments in the ongoing evaluation process that will inform the consideration of different tunnel and station construction methods, technical and operational challenges and contracting methodologies, including construction of deep stations in dense urban environments.

Jun 13, 2021

By R. Pixler

Arch Mineral Corporation and Rocky Mountain Energy's Medicine Bow Mine in Wyoming presented an interesting challenge to the concept of mining a multiple-seam, dipping coal in the Hanna Basin. The 3362 and 2962 pits at MBCC were designed in a multiple seam coal consisting of 4 (and in some areas 5) bands of coal; these coal beds are all in the Ferris formation. The area was subject to some localized faulting and a major fault caused a physical restraint that we mined up against in our final cut. Using a 1570 dragline as the principal stripping machine, the concept of developing a bench for stripping the lower seams from the low-wall side of the pit was initiated. The results of this method of stripping were very satisfying for this pit through the completion of pit life and prompted us to use it in other areas at MBCC and at our other operations. Mining a dipping coal presents a small twist to conventional "flat" coal stripping. The spoil has a tendency to continually try to slide into the pit and the increased overburden on each cut as you mine down the dip creates spoil problems unless adequate design provisions are made prior to stripping.

Jan 1, 1986

John Eliot Allen has been made acting head, dept. of geology, New Mexico Institute of Mining and Technology, Socorro, N. Mex. He had been associate professor of geology. Robert B. Anderson has accepted a position with the U. S. Steel Co., Gary, W. Va., as assistant to the superintendent, No. 2 mine. [ ] Donald L. Archibald has joined the sales dept. of the Ellicott Machine Corp., Baltimore. He formerly had been associated with the Joy Mfg. Co., St. Louis. J. C. Boswell has been appointed manager of the Fairbanks dept., United Smelting Refining & Mining Co. J. B. Metcalfe has been appointed assistant to the president. G. Howard LeFevre was elected vice-president and general manager of metal sales and R. N. Hunt, vice-president and chief geologist was elected a director. R. B. Earling, vice-president and general manager of Alaskan operations, has retired but. will con¬tinue to serve on the board of directors. J. D. Crawford has been appointed general manager of Alaskan operations.

Jan 1, 1952

By R. V. Ramani

In this report, the application of the Open Pit Materials Handling Simulator (OPMHS) to a mine located in Ohio using a large stripping dragline, and truck and front-end loader (FEL) is described. The specific objective of the study is to demonstrate the application of the simulator to mine planning and coal production. On the basis of the simulations, it was concluded that the production from the haulback operation should be increased to accommodate improvements in both the stripping dragline's availability and mean cycle time. Several alternatives were studied for the best use of equipment if the present operating parameters could not be improved upon. No economic analysis of these proposals were made.

Jan 1, 1977

By Sergey Ulianov, Arkady Senchenko, Alexey Shvets, Arkady Bakotin

"This paper contains description of research results of technology development for copper recovery from weathered tails of iron processing plant. The predominant host mineral that contains valuable component is chalcopyrite occurring in its free form and in associations with ore and rock-forming minerals. Copper grade is 0.26-0.30%. Emulsion inclusions of chalcopyrite in pyrite and sphalerite were noted. Major problem is low copper recovery (30-35%) by flotation. When studying chalcopyrite in primary concentrate it was determined that the surfaces of many chalcopyrite grains are covered with oxide films which prevented collector attachment onto them. Second issue was deep association of chalcopyrite with pyrite and sphalerite. Sulfidizing reagent addition did not help to reach the required level of copper recovery to concentrate. In the result of research performed the technological flowsheet was developed including preliminary treatment of head material in a special unit aiming at oxide films removal, followed by copper rougher flotation on head size tails, crude concentrate regrinding and a number of cleaner flotation operations. After the treatment of weathered tails according to the flowsheet developed, copper recovery to flotation concentrate became 71.53%, at 23.46% copper grade. The suggested technology allows one to solve the issue with treatment of technology-related copper-containing stockpile material, as well as to include the ores where copper is represented by sulfide minerals covered with oxide films into processing."

Jan 1, 2014

It was shown previously that chalcopyrite could be floated without using a collector when the ore samples were treated with small amounts of sodium sulfide (Na2S). The role of this reducing agent was considered to be one of a cleaning agent to remove the hydrophilic surface oxidation products. It was later found, however, that the collectorless flotation could be obtained only under slightly oxidizing conditions. This might suggest that collectorless flotation is not due to the clean surface but to the elemental sulfur which may be present as an incipient oxidation product. Therefore, a search for the presence of elemental sulfur has been made by means of ESCA, mass spectrometry, and solvent extraction followed by W spectrophotometric analysis. On the basis of these results, the mechanisms of collectorless flotation are discussed.

Jan 1, 1983

By G. E. Bobeck

The first year's work of a proposed three-year study of the effects of the exposure of coal mine roof rocks to the mine atmosphere has been completed. The project has been terminated. The goal of the project was to determine if possible the mechanism or mechanisms by which coal mine roof rocks interact with the mine atmosphere and weaken, and coupled with mechanical stresses, ultimately fail. The scope of the study was limited to the effects of environmental factors on the deterioration of the rocks. While mechanical stresses may play an important role in the interaction of environmental factors, stress effects were excluded from the study. In order to study the effects of environment on coal mine roof rocks, samples were obtained from several coal mines in the western states. The rocks forming the roofs of most of the mines visited were shales of varying composition. These shales were subjected to numerous tests to determine how the rocks changed with time after exposure. In addition, the identity of the minerals present in the shales was determined by x-ray diffraction analysis and by thermal analysis as well as by optical microscopy

Jan 1, 1973

By R. M. Campoy

Mexico's mineral wealth has long been recognised and indeed has played a historically significant role on a world scale. The dynamics of the Mexican mineral industry have experienced a dramatic transformation especially over the last two decades. This transformation has mainly been instigated by the high growth rates and industrialisation of the Mexican economy since the 1960's. This paper focuses on the base metals sector of the industry which represents one of the major contributors to this transformation. The objective is to present a brief base metals review and to discuss some recent occurrences which pertain to this sector of the industry. This is followed by a discussion of mining's relevance in the current economic situation in Mexico. With this overview as background, the investment climate, primarily from a domestic investor's perspective and secondly in terms of foreign investment, is discussed. Finally, some recent government initiatives, including tax and accounting changes, are outlined. Any one of the sections of this paper can easily be developed into an extensive and indepth analysis; however, the intention of this paper is to provide the reader with a broad overview of the topics discussed.

Jan 1, 1985