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By R. J. Gochin, G. D. Schena, R. Spencer

The impact of a mineral project in a developing country is evaluated in the broad context of its economy using input-output models. Minimum economic theory is used to develop simple numerical models. Sets of technical coefficients are exploited in the development of linear models of the productive element of an economy. The analysis allows assessment of the overall economic consequences of a mineral development in which issues broader in scope than financial objectives need to be incorporated in the evaluation. In part 1, the framework for the development of the input-output model is presented. The model is refined to incorporate country-specific behaviour. The increased flexibility of the enhanced semi-input-output model permits a more confident investigation of the economy-wide effects associated with a new project in the mineral sector of a developing country. The relevance of the models is illustrated using an example from Namibia

Sep 1, 1991

By Jayant Khambekar

In a typical mining operation, run-of-mine (ROM) ore is crushed and screened to achieve a desired particle size distribution and then fed to processing equipment for further refining. For an operation to be profit-able, the ore handling system from the mine face to final product loadout must be reliable. However, the handling system components do not always perform as expected and production problems related to material flow occur. These problems include flow stoppages, limited live storage capacities, uncontrollable flow, segregation, spillage and dust emissions. These result in lost production, excessive maintenance, safety and environmental issues, and even structural failures, in some cases. Flow patterns Flow problems and their solutions can be best understood by first learning how bulk solids flow. As bulk solids discharge by gravity from a storage system, primarily two types of flow patterns can develop: funnel flow and mass flow. Figure 1 shows a schematic of these two flow patterns. In funnel flow, only a portion of the material is in motion during discharge, which flows toward the outlet through a channel that forms within the stagnant material. Funnel flow occurs when a hopper is not sufficiently steep and smooth to ensure flow along the walls or when the outlet is not fully effective. In mass flow, all of the material is in motion whenever any is discharged ? there is no stagnant material. Mass flow occurs when the hopper is sufficiently steep and smooth to ensure flow along the hopper walls. Shallow valleys are not permitted and the outlet must be fully effective. A third type of flow pattern, called expanded flow, can develop when a mass flow hopper (or hoppers) is placed beneath a funnel flow hopper or bin. The mass flow hopper is designed to activate a sufficiently large flow channel in the funnel flow hopper to avoid flow problems due to a rathole. The flow pattern in which a bulk solid discharges from a storage system strongly influences the flow problems that may occur in that facility.

Jan 1, 2009

Jan 1, 1987

The study of gas emitted from face coal samples at the coal face is part of an investigation of instantaneous outbursts of coal and gas. Normally, seam gas essentially comprises methane of which the origin in the metamorphism of coal is undoubted. The origin of other gases sometimes occurring in high proportion in seam gas, particularly carbon dioxide, is more controversial. A simple meter for rapidly assessing gas in coal was developed. Tests with the meter enabled comparisons of seam gas in face coal at some outbursting and nonoutbursting mines, and under various working conditions. The varying results of widespread testing suggest certain trends, including some prospect of recognising outbursting potential at the coal face.INTRODUCTIONThe aim of this work is identification of differences in gas condition between coals subject to instantaneous outbursts and coals which have not outburst, and between faces of coals which will and which will not subsequently outburst. Any comparative test should be conducted right at the coal face on coal about to be worked and the results of testing should be available after a short period. Moreover, the method and the comparison of results should require no special skill, and be well within the capacity of junior mine officials. Any consistent relation between gas condition and subsequent mining conditions - outbursting or not might be valuable in prediction of outbursts.INSTANTANEOUS OUTBURSTSInstantaneous outbursts (Hargraves, 1958) , are largely unpredictable and unaccountable ejections of coal (up to 5,000 tons) and gas (up to 5,000,000 cu.ft.) from a standing coal face. Usually the gas is essentially methane (CH4 ) but may be essentially carbon dioxide (C02 ), or an intermediatemixture...

Jan 1, 1962

By S. Fawell, H. R. Manouchehri

The main electrophysical properties, i.e., dielectric constant and electrical conductivity, of pure calcite, quartz and wollastonite mineral samples were measured and their triboelectric charge attributes were investigated by contacting minerals particles with different tribochargers made from different materials. In addition the energetic work function values for mineral samples were estimated due to their acquisition charge. Besides, the behaviour of triboelectrically charged of different particle size fractions of mineral samples were inferred. Finally an attempt were made to translate the findings from single mineral systems to a real carbonate ore. The results exposed good prospects to beneficate the examined minerals by triboelectric separation.

Jan 1, 2002

By Alan A. Campoli

The U.S. Bureau of Mines evaluated two different conventionallongwall gate entry systems in the Southern Appalachian Basin, where mining and geologic conditions are conducive for coal pillar bumps. These gate entry systems were in a coal mine located in the Pocahontas No.3 Coalbed under approximately 2,000 ft of overburden and a massive quartzite sandstone member, and both employed a center abutment pillar flanked by yield pillars. The 8O-ft-square tailgate abutment pillars within the first study area began bumping 500 ft in advance of mining. This was accompanied by face bumps on the tailgate corner of the longwall face. The 120-by 180-ft tailgate abutment pillars within the second study area did not begin to bump until mining was approximately 100 ft past. Coalbed stress change and abutment pillar dilation data demonstrated that a 15-ft-wide perimeter of yielded coal surrounded a highly stressed core in both sizes of abutment pillars. The 62 pet more core area per foot of gate entry in the larger abutment pillars prevented excessive load transfer to the corner of the tailgate panel and eliminated the face bumps experienced with the original gate entry design.

Jan 1, 1990

With the proving of a mineable orebody at Orlando in May 1961, Peko Mines N.L. was faced with the decision of whether to mill the ore on site or to haul it 25 miles to central facilities at Peko. Orlando was a relatively small orebody, so that it was decided to haul, although no reliable assessment of possible ore haulage costs was available.The necessity for a good haul road was recognised from the beginning and a 17 mile, 12 ft wide, single seal bitumen road was constructed, to link the mine to the Stuart Highway and Peko. The initial selection of 20 ton capacity diesel-powered end-tipping ore carts was made, with the best information available at the time.Since then some 130,000 tons of ore have been carted over a period of 3 years, and this paper presents the experiences of this haulage operation and the lessons learned.A second mine has just been brought into operation at Ivanhoe, 19 miles from Peko. For this haul it was decided to use an ore haulage vehicle of the side tipping road train type, which would cart some 70 tons, or more than three times the load of the vehicles initially selected.Only about 5,000 tons had been hauled at the date of this paper, but preliminary figures indicate a cost 01 1· 65d./ton-mile as against 2·47d. for the smaller vehicles.It would appear that the road haulage of ore from small outlying mines to a central plant can be highly economical, if certain basic rules concerning haul roads and vehicle selection are followed. This paper does not try to determine the maximum tonnages and haul distances which would finally make road hauling uneconomical...

Jan 1, 1966

By John E. Kelley

A method for measuring the spark-shower radiance of metals when abraded on a grinding wheel was developed by the Bureau of Mines for evaluating the sparking tendency of metals. The radiance was measured in units of emissive power per solid angle per area of the detector. Over 100 metals were tested and rated relative to commercially pure iron. The metals tested included elemental metals, iron binary and ternary alloys, iron-carbon ternary alloys, commercial steels, nonferrous alloys, and a few hard-metal compounds. Some alloys were synthesized; others were obtained commercially. Alloys that possessed good strength properties were emphasized for selection. The results indicate that the spark-shower radiance of plain carbon steels and carbon alloy steels was greater than that of pure iron. Certain elements, particularly vanadium and chromium, reduced the sparking tendency of iron. Stainless steels and particularly nickel alloys displayed low spark-shower radiance. Some metallic elements had much lower radiance than iron; others, much greater. Plain carbon steels, heat treated to a variety of hardnesses, gave radiance values that generally increased with increasing hardness. The effect on sparking tendency of an increase in hardness of an alloy steel was studied. The sparking tendency increased with an increase in hardness to a maximum, then decreased with a further increase in hardness.

Jan 1, 1974

Open pit mine plans define the complex strategy of displacement of ore and waste over the mine life. Various mixed integer linear programming (MILP) formulations have been used for production scheduling of open pit mines. The main problem with these models is the inability to solve real size mining problems. We present a mixed integer linear programming formulation for the open pit long-term production scheduling problem. To reduce the number of binary integer variables in the formulation, we aggregate blocks into larger units referred to as mining-cuts. We present a semi-supervised clustering algorithm which aggregates smaller blocks based on rock types and grade ranges into mining-cuts without introducing an error in the grade estimated values. The cluster-based aggregation algorithm is fully integrated into an MILP mine production scheduling prototype software. We have implemented, verified, and validated our models. The efficiency of the new platform is evaluated through iron ore mine case study.

Dec 6, 2010

By D. D. Southworth

In 1981, 1982, and 1983, the Bureau of Mines examined the potential for lode deposits of platinum-group metals (PGM) in the Goodnews Bay ultramafic complex, Alaska. The complex consists of the Red Mountain, Suzie Mountain, and Smalls River ultramafic bodies and displays concentric zoning of rock types similar to complexes in southeast Alaska, British Columbia, and the Ural Mountains in the U.S.S.R. Results of the study indicate that platinum is preferentially associated with chromite and magnetite in the dunite core of the complex, and palladium is preferentidlly associated with sulfide minerals in the outer clinopyroxene-rich zones. the most promising targets for PGM lode deposits are the chromite-rich dunite at the heads of Fox Gulch and Squirrel Creek and iron-nickel and iron copper sulfide-bearing magnetite clinopyroxenite and hornblende-rich rocks outward of the dunite core, also in the Fox Gulch-Squirrel Creek area. Significant placer reserves are present in the unmined, deeply buried placer ground in the lower Salmon River Valley, and also in tailings from previous dredging.

Jan 1, 2011

By S. Cotten

The regulations for current coal mine refuge alternative (RAs) require that there be sufficient life support to sustain survival of the maximum number of RA occupants for a minimum of 96 hours. This minimum duration assumes that rescuers can access the RA through the mine within four (4) days of the onset of the mine emergency. But what if mine rescue teams cannot reach the miners within the RA before the RA air supply is severely limited or exhausted? What could be done to extend the duration of the RA life support capability into the 97th hour and beyond? In addition, what might be done to enable more rapid rescue of the miners if they could not be reached through the mine in a timely manner? This paper describes a systems approach to address the potential need to extend the duration of RA life support beyond current design limits. New capabilities that need to be developed in advance of such a dire need include more reliable emergency communications, highly mobile and efficient drilling rigs, enhanced directional drilling techniques, and a standardized RA external life support interface along with RA internal design modifications to accommodate use of an external supply. The following sections describe the need, intent, and technology gaps associated with each of these capabilities. Government agencies and the mining industry should consider initiation of a program to investigate, design, and develop effective means of extending the current 96-hour time restriction on coal mine refuge alternative life support. The development process should begin with a focused study to refine the overall operational concept, investigate the current state-of-the art of critical technologies, identify specific technology development priorities, and make recommendations for a development program to provide in an organized, efficient, and timely manner a solution for extended refuge alternative life support and occupant rescue.

Jan 1, 2011

By H. Antrekowitsch

Nowadays, the pyrometallurgical treatment in copper smelters is the common process for the recycling of metals from the electronic scrap. Furthermore the European Directive on the Waste from Electrical and Electronic Equipment (WEEE) and the Directive on the Restriction of Hazardous Substances (RoHS), increase the importance of electronic scrap recycling. Besides these a high amount of plastic and inert components in these materials leads to problems at the processing. An optimisation concerning the internal recovery and the high amount of plastic is necessary to reach the recycling quota of the European directive. The majority of the scrap is treated mechanically in order to separate in a first step plastics from metals, iron from nonferrous metals and harmful substances from valuable materials. But the quality of the different fraction often rather low and further treatment leads to higher costs. Therefore an interaction between mechanical treatment and metallurgical processing should be realised. The Christian Doppler Laboratory for Secondary Metallurgy of Nonferrous Metals at the Institute of Nonferrous Metallurgy at the University of Leoben carried out investigations concerning the optimisation of the metallurgical recycling and the treatment of the input materials especially of printed circuit boards.

Jan 1, 2006

By Yi Luo

In dealing with various subsidence cases, accurate predictions of mining induced subsidence are the basis for correct assessment of subsidence influences and subsequent mitigation efforts. There is a good demand for a reliable tool to perform the subsidence predictions and related tasks. A comprehensive and integrated subsidence prediction model, CISPM, developed by the senior authors in the later 1980?s and early 1990?s (Peng and Luo, 1992) is one of such tools. Built on solid mathematical models and calibrated by a large number of collected subsidence cases, CISPM provides a rich set of features needed in subsidence engineering and research works. Its reliability and usefulness have been proven by numerous field applications. This upgrade of CISPM will not only preserve its original features and reliability but also provide some new needed features and a more user-friendly working environment.

Jan 1, 2008

By G. W. Jones

The results presented in this report deal with the elimination of explosion hazards of ether-oxygen mixtures by the addition of helium. The method is based upon the fact that every combustible gas, vapor, or dust will not burn or explode when the oxygen content of the mixture is reduced below certain definite values. These critical oxygen values are usually different for each combustible, varying with the percentage of the combustible present in the mixture and also with the inert gaseous material used to reduce the oxygen content of the mixture.

Jan 1, 1941

In a previous paper the author showed that silver considerably delayed the recrystallisation of lead after cold work. The effect of antimony on the rate of recrystallisation of distorted lead was studied next, and the experiments performed, and the results obtained, are described in this paper. Electrolytic lead was used as a standard of comparison.It was also used to make the lead antimony alloys.This electrolytic lead contained 0.0005% total impurities.It was prepared from commercial lead by fire refining, followed by electrolysis and finally by vacuum casting. The process was described in the previous paper and the description need not be repeated here. PREPARATION OF LEAD - ANTIMONY ALLOYS.The steps taken to procure pure antimony are outlined in the appendix. To make the lead antimony alloys a mother alloy was prepared thus:-A quantity of the antimony (it was received in the powdered form) was placed in a pyrex glass tube, which was closed at one end. The antimony was washed with hot hydrochloric acid (1: 1), then with more dilute acid, then with distilled water, and finally with absolute alcohol; it was dried by warming and evacu,ating the tube. This should leave the antimony more nearly free from surface oxides.The amount of antimony was determined by weighing quickly; the appropriate amount of vacuum-cast electrolytic *Research Fellow, Dept. of Metallurgy, University of Melbourne.

Jan 1, 1936

By A Giblett, R Dunne, D Appelhans

There are a number of hurdles that must be negotiated in order to design an effective gold ore treatment facility such that the expectations forming the basis of project economics are valid and can be achieved in practice. Selecting samples based on geometallurgical context, performing and interpreting testwork relevant to the selected process flowsheet are essential considerations towards achieving this aim. This paper discusses recent experiences in process development for free milling gold ores giving consideration to frequently encountered challenges of this nature.CITATION:Giblett, A, Appelhans, D and Dunne, R, 2013. Considerations for effective gold process development, in Proceedings MetPlant 2013 , pp 445-454 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By Michael J. Beus

This Bureau of Mines report describes a tunnel stress relaxation gage (TSR) developed to measure initial radial displacement around full-sized underground openings. The TSR technique was shown to be a valid concept in previous field verification tests. Sensitivity has been improved by employing a titanium alloy cantilever in the transducer head, which also permits a deeper sensor location. Use of improved fabrication methods such as stainless steel bellows and sputtering techniques and use of an environmental chamber for testing greatly increased overall reliability. A miniature data acquisition system (DAS) was interfaced directly to the transducer for increased versatility and containment entirely within a borehole. The present TSR system is suitable for use around full-size underground excavations, particularly machine-bored openings. Field evaluation of the improved instrumentation verified the design goals.

Jan 1, 1978

By G. W. Jones

The results presented in this report deal with the elimination of explosion hazards of ether-oxygen mixtures by the addition of helium. The method is based upon the fact that every combustible gas, vapor, or dust will not burn or explode when the oxygen content of the mixture is reduced below certain definite values. These critical oxygen values are usually different for each combustible, varying with the percentage of the combustible present in the mixture and also with the inert gaseous material used to reduce the oxygen content of the mixture.

Jan 1, 1941

By R. C. Burton

One of the major problems encountered with recirculatory breathing apparatus presently used by mine rescue teams is that the inspired air becomes uncomfortably, and often dangerously, hot. This is also true with self-rescuers. It is well known that man can tolerate very high dry-bulb temperatures if the wet-bulb temperature is low, but not vice- versa. The maximum tolerable, wet-bulb temperature is about 42 °C (108 °F). A continuously inhaled wet-bulb temperature above this value can cause irreversible damage to the throat and lung tissue, and wet-bulb temperatures close to it cause extreme discomfort (1) and seriously retard the capability of the man to perform useful work. A theoretical analysis, combined with experimental results, has shown that it is the carbon dioxide absorbent that is the major cause of high wet-bulb temperatures of the inspired air in the Siebe Gorman Proto 4, and in the Draeger BG 174 apparatus, both of which are used by rescue teams on South African mines (2). In the Proto 4 apparatus, the absorbent for the carbon dioxide is soda lime (calcium hydroxide). The German Draeger BG 174 also uses this absorbent but under arduous conditions such as in hot environments (50 °C, 122 °F), the use of an alkali absorbent cartridge is recommended which consists mainly of caustic soda (sodium hydroxide). Lithium hydroxide is used in some apparatus in the United States. It is clear that different absorbents will produce different quantities of heat and moisture for a given rate of absorption of carbon dioxide. The proportion of this heat and moisture which is transferred to the user depends upon how much can be removed from the recirculating air between the absorbent and the mouthpiece. This paper discusses the present methods of heat removal and describes the design and test results of a prototype evaporative cooler.

Jan 1, 1980

By Wils L. Cooley

Several aspects of coal mine safety-ground system operation are studied. Evaluations of two sophisticated ground-wire monitors are presented, along with a detailed report of development work on a modular ground-wire monitor. A portion of the report covers stray current flow in the safety-ground system, analyzing in detail conditions surrounding the generation of both dc and ac ground wire current. Considerable detail is provided concerning studies of mine ground beds. Additional progress is reported in the development of a. continuous ground-bed monitor, and new techniques are developed for the design of ground beds and their resistance measurement. New methods of accurately measuring electrical parameters of finite layered conducting structures are also reported. The effects of stray currents in ground beds is included. Touch-and step-potentials associated with mining equipment are analyzed, and methods are presented for determining earth voltage gradients around structures contacting earth. Instrumentation to determine gradients easily is suggested. Finally, an extensive effort is described dealing with lightning transients on open-pit coal mine ground systems. The nature of the transients, their expected frequency of occurrence, and the ways in which they damage equipment are analyzed in detail.

Jan 1, 1977