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By T. Scully

Since early days in coal mining, it has been known that some coals and the carbonaceous materials associated with them will heat and fire spontaneously. Many theories have been advanced to account for this phenomenon, but it is only within comparatively recent years that any scientific research has been carried out to determine the causes of this heating, the conditions which bring about its occurrence, and the reason why different coals heat with a varying degree of readiness. So far, this research has not cleared up these points entirely, but a great advance has been made in our knowledge of the matter. In general, any coal will fire spontaneously, although with a varying degree of readiness, provided conditions for its doing so are favourable enough. These conditions are that the coal must be in a fine state of division, that sufficient oxygen must be present for rapid oxidation, and that the air current passing must be so small that it is insufficient to carry off the heat produced by this oxidation. Many other minor factors, however, contribute to bring about spontaneous heating, either by producing initial heat themselves or by inducing the other major conditions.

Jan 1, 1931

By ?. S. Potokin

"In general the electric pulse treatment is composed from two processes – electric pulse grinding and electric explosive (electric discharging) activation. The electric pulse grinding with the effect of selective destruction refers to a major slag fraction, more that 2-5 mm, when a one can see a physical prerequisites for electrical breakdown of the slag particles. The electric pulse treatment of slag is considered as an additional operation in the technological scheme extraction of non-ferrous metals from copper smelting slags in addition with mechanical grinding, flotation enrichment and acid leaching. Studies of the reprocessability of pelletized slag have shown the possibility of higher extracting non-ferrous metals via flotation after electric pulse disintegration (EPD) treatment. By using EPD of slag pellets, it is possible to increase the non-ferrous metal yield to concentrate by 18-24%.INTRODUCTION The use of the explosive effect of the plasma discharge channel at electrical breakdown of a solid at a pulsed high voltage is the physical basis of the electric pulse method of destruction of geomaterials (Vorobiev et al., 1971; Andres, 1995; Semkin et al., 1995). The flowing of a pulsed current in the discharge channel is accompanied by a sharp increasing of plasma’s temperature and pressure, leading to a supersonic expanding of the discharge channel, the formation in the solid of intensive mechanical tension field, spreading of cracks, and eventually, to the destruction of the solid. Fragmentation and grinding of ore and mineral aggregates by electric pulse method due to a number of specific physical mechanisms of power load and crack formation, belonging only to this method, is different by high selectivity of destruction. This ensures better liberation of grains of individual minerals and their better preservation from destruction and less formation of a slurry output. These features creates the prerequisites for a more complete extraction of a useful mineral in the concentrate during ore dressing, to improve the quality of concentrate. In contradistinction to mechanical methods, electric pulse technology does not contaminate the product with instrumental metal, material of lining and grinding bodies. The possibility simply and in a wide range to change the dynamic load character allows to regulate the granulometric composition of the product of grinding, to obtain a narrower class of product size than is possible with mechanical grinding. The product of electric pulse grinding is characterized by less roundness and large specific surface area of grains due to the trait, that a new surface is formed in the process of splitting during the expanding of cracks. The degradation product has increased sorption and reactivity in chemical reactions. Liberation of the mineral inclusions particle better corresponds to their initial natural state in the rock and this is the great importance for the study of mineral raw materials."

Jan 1, 2018

By Adrian Dance

Newmont Ghana Gold Limited?s Ahafo operation have been working with Metso Process Technology & Innovation (PTI) since early 2009 to increase mill throughput from a combination of controlled blasting practices and optimised primary crusher and grinding circuit conditions. For such Mineto- Mill projects, PTI?s methodology is termed Process Integration & Optimisation (PIO). Ahafo operate a SAG mill, ball mill and pebble crusher (SABC) circuit that processes a range of primary ore of varying hardness from different pits which is blended with soft oxide material. The PTI study focussed on ball mill limited material from the Apensu open pit. Following a benchmarking study of all blasting, crushing and grinding practices in January 2009, PTI recommended changes in both blasting and crushing conditions in order to generate a finer feed size to the SAG mill. Additional operating changes in the grinding circuit were recommended. A series of trials were conducted in November 2009 where three blasts were fired using a different blast design (hole diameter and explosive type) in the same area of the Apensu pit as the benchmarked material in January 2009. Top and bottom benches (or flitches) from each blast were sent exclusively to the grinding circuit and the material was tracked using PTI?s SmartTag? system. The results from the six trials showed a significant increase in primary ore throughput at a reduced blend of oxide material. Ahafo have since standardised on these modified blasting conditions for all Apensu ore zones and have been able to sustain higher throughput compared to historical performance on similar material. This paper summarises the phases of the PIO project, the changes made in operating practices and the outcomes of the blasting trials that validated the predicted increase in mill throughput.

Jan 1, 2012

By Roger V. Pierce

IN the last few years, much study has been devoted to increasing stoping efficiency. The reasons for this are shortage of manpower, shorter working hours, operating regulations, and shortages of essential materials. More efficiency in mining methods is needed to offset these adverse factors. In the past, attention has been centred upon haulage, hoisting equipment, mill flow-sheets, etc., but recently the spotlight has been focused on the cost of stoping and the cost of handling materials. Scrapers and scraper hoists have thus assumed greater importance. In order to make it possible for certain orebodies to be mined at a profit, it has been necessary to apply assembly-line practices to the streamlining of mining methods. All cycles of the mining operation must balance, and the sooner broken ore is removed from the working face, the sooner another round can be started. Since the introduction of scraper hoists in metal mines more than thirty years ago, much progress has been made in their design and application. Alert operators are now constantly watching for methods in which to apply scrapers. The saving of manpower in development work and the changing of mining methods that once employed manual handling of materials are increasing vital wartime tonnages. Essential ores from newly discovered orebodies are moving rapidly from stopes to reduction plants-because it is now possible to develop an orebody and place it in production with a minimum of manpower and development work. Today, speed is one of the prime essentials o mining. Everywhere, there is a concentrated effort to use experienced miners in breaking rock, in timbering, and in carrying out the various phases of mining that require many months of training. Much effort is being made to mechanize the working places because experienced men naturally prefer to work where the majority of materials are handled mechanically. In line with this policy, many new men are being taught the details of scraper work, because even green men can quickly become acquainted with scrapers and thereby release older heads to perform the more skilled phases of mining.

Jan 1, 1943

"At the request of the Anthracite Institute, the United States Bureau of Mines during February, March, and April 1935, made a field survey of commercial anthracite shipped from collieries scattered throughout the Anthracite regions. In all, 268 samples were taken at 41 breakers from Carbondale at the northern end of the field to Pottsville at the south. These collieries ship approximately 50 percent of the industry’s total production. The geographical distribution of the breakers sampled was as nearly as practicable in proportion to the tonnage of the companies from each region cooperating in the plan.The following are the weighted average analyses, by sizes, of the samples taken in this survey;"

Jul 1, 1935

By M. Amick, G. Swan, R. Hill, C. Pritchard

Falconbridge is a major basemetal producer in the Sudbury Basin of Ontario, Canada. The company identified a need to find a safe and cost-effective replacement for the welded wire mesh used to support loose ground during underground nickel mining. Falconbridge took a methodical approach to the concept of a spray-on liner as a screen replacement, proving the strength characteristics of the liner as a safe, cost effective and suitable method of supporting ground Compact, hydraulic mixing and spraying equipment were developed and are now in use at the Fraser Mine. Tekflex has been approved as a wire mesh replacement and has been in use since November 1998.

Jan 1, 2002

By A. W. Fahrenwald

The purpose of screening is to separate a crushed or natural product into one or more products in which size of grain is constant, or within certain size limits. The ore dresser finds need for this operation in the laboratory, in the study of ore-dressing processes, and for various purposes in the plants. In the plant, for example, screens are employed in closed circuit with crushing devices such as rolls, and sometimes are used in closed circuit with ball mills. Screens are generally used to prepare jig feed where a sized feed is wanted. For any given sieve opening there is in any feed a certain percentage of grains that will pass through the sieve meshes only with difficulty and under favorable conditions. For example, cylindrical grains of length greater than the maximum dimension of the sieve mesh and of diameter less than the sieve opening pass the sieve only when the long axis of the grain is normal or nearly normal to the sieve. Whether such grains should actually be in the through's or the oversize of a screening operation--considered from the point of view of the subsequent treatment of the grains--can not be said. The grains that pass the sieve opening in a screening process only under-favorable conditions have been named "difficult" grains by R. K. Warner.4 In many ore-dressing flow-sheets it probably matters little whether these difficult grains show up in the screen through's or oversize. The main objection to them is that they are sieve-blinding.

Jan 1, 1929

By Christopher Mark, Anthony T. Iannacchione

Falls of ground continue to be one of the most serious causes of injury to U.S. miners. Of the 256 fatal injuries that occurred in mining between 1996 and 1998, 59 (23%) were caused by falls of ground (Table 23.1). Falls of ground affect some sectors of the mining industry more severely than others. For instance, nearly 40% of the 98 coal mine fatalities between 1996 and 1998 were caused by falls of ground. Underground miners are at much greater risk than surface miners. Nearly half (45 out of 101) of underground mine fatalities were attributed to roof, rib, and face falls, while only 6% of the 155 surface fatalities were caused by falls of highwalls or slopes. The goal of this chapter is to provide guidance to safety professionals tasked with preventing ground fall injuries. This chapter combines an analysis of the Mine Safety and Health Administration's (MS HA) accident and injury data with a survey of industry "best practices" to safeguard miners from ground falls. Ultimately, this approach can help to form the basis of a sound, proactive ground control program for the mining industry. SOURCES OF DATA All the injury data examined in this study were derived from MSHA's fatal investigation reports and the MSHA accident database. Because falls of ground often result in serious injury, MSHA "Fatalgrams" and fatal investigation reports provide a useful snapshot of ground control issues in the mining industry. These reports are available to the public (on the M FHA Web site at www.msha.gov). Fatalgrams, are one-page summaries that are usually published within a month of an accident. They contain very basic information about the accident with a graphic and a short section on relevant best practices. Fatal investigation reports are the official accident investigation reports filed by MSHA personnel. These reports contain general information about the mine, a, description of the accident, physical factors involved in the accident, a conclusion, and enforcement actions, Enforcement actions typically identify citations and discuss violations to the Federal Mining Law. MSHA also maintains comprehensive statistical data on the mining industry's accident and injury record. The law requires that mines file a report on every reportable accident that occurs, containing information on the accident's location, severity, classification, activity, and nature of injury A short narrative is generally included as well. Accident reports can be searched by many of the above fields.

By K Kongolo, M K. Kalenga

It is well known that the electrochemical precipitation of metals from aqueous solutions is conducted by the electrochemical standard potential scale. This scale indicates the order of nobility of different metals. Consequently, the standard potential scale shows the nocivity of metals when they are present as impurities in aqueous solutions containing metals. In the hydrometallurgy of cobalt, nickel and zinc are co-deposited during cobalt electrodeposition. Nickel has almost the same chemical, physical and electrochemical properties as cobalt. Furthermore, the electrochemical potential of nickel is relatively higher than that of cobalt. For this reason nickel is preferentially reduced at the cathode in the presence of cobalt. The presence of small amounts of zinc in solution leads to contamination of cobalt electro won. In spite of its lower electrochemical potential in comparison to cobalt, zinc is reduced on the cathode because of its higher hydrogen-overvoltage. But, in the hydrometallurgy of zinc, small amounts of cobalt present into solution will contaminates the zinc reduced at the cathode. This is easily explained by the fact that cobalt is more electropositive than zinc. The co-deposition mechanism of sulphur at the cathode is not yet well understood. Great attention has to be paid to the mechanism of co-deposition of sulphur during cobalt electrolysis..This work aimed to investigate the influence of some parameters on the co-deposition of nickel, zinc and sulphur during cobalt electrowinning. The following parameters have been investigated : Co2+ concentration in the electrolyte, current density and ammonium sulphate (NH4)2SO4 additions. It has been established that important nickel, zinc and sulphur co-deposition takes place at relatively low Co2+ concentration in solution. The behaviour of these elements with regard to the cathodic phenomena has been established.

Jan 1, 2005

By T. C. Desollar

The group of iron-ore mines known as the Red Ore Mines, owned and operated by the Woodward Iron Co., is on Red Mountain approximately ten miles southwest of Birmingham, Ala. At the present time NO. 1 and No. 3 mines are active, No. 2 mines having been abandoned in 1928. Ore from this group of mines was first mined in 1882, and originally came from open cuts along the outcrop, but, when the "soft ore" (weathered hematite) was mined out and the harder ore was encountered, it became necessary to develop the orebody by means of slopes driven in the ore formation. The three mines to date have produced more than 22,000,000 tons, and the two operating mines now have a capacity of over 1,000,000 tons per year. Geology The U. S. Geological Survey has described the features of the district. It places the hematite of Red Mountain, commonly called "red ore," in the Clinton formation of the Silurian system. This formation varies from 200 to 300 ft. in thickness, and is composed largely of shale (slate) and sandstone. There are four iron orebeds in the formation, known as the Hickory Nut, Ida, Big Seam and the Irondale seams. The strike of the orebeds is northeast and southwest, and the dip is southeast, the outcrops being on the west side of the mountain. The two seams that have been worked at the Red Ore mines are the Big Seam and the Ida. The Big Seam, which is and has been the principal source of the ore mined, is approximately 20 ft. thick and consists of hematite and ferruginous bands of sandstone. It is separated into "upper" and "lower bench" ore by a slate parting that is about 30 in. thick. All present mining is confined to the "upper bench" ore, which is uniform in texture and drills and breaks fairly easily when the holes are placed so as to take full advantage of the face of the ore. Typical analyses are shown in Table 1. The presence of two water-bearing formations, the Fort Payne chert and the Hartselle sandstone, lying respectively 160 and 300 ft. above the Big Seam, make it essential that in mining the ore any movement of

Jan 1, 1934

By J. C. Draper

The Duquesne Light Company and GAI Consultants, Inc. conducted a demonstration program aimed at establishing permanent vegetative cover directly on acidic, deep coal mine refuse. Several plots were treated with formulas varying in soil amendment application rates and plant species. Periodic monitoring of refuse chemistry has indicated when maintenance applications of seed and soil amendments were required. To establish drainage control, the site had to be regraded. The most successful formula was applied to the entire site. Specific treatment for acidic spots has been initiated. Results of the program indicate that adequate permanent vegetation has been established.

Jan 1, 1983

By Issa S. AI-Kharusy

Oxidation/reduction (REDOX) alloy media, as used in wastewater treatment, is founded on the exchange of electrons. Because of this electron exchange, many contaminants are converted to harmless components which require no further treatment. Other types of contaminants are removed from the waste stream by electrochemically bonding to the alloy medium. This paper discusses the REDOX reactions, the role of the alloy medium in various treatment processes, and describes specific applications of REDOX alloy media for the removal and minimization of waste. The characteristics and handling of spent treatment media is also reviewed as a further consideration in waste minimization.

Jan 1, 1996

By Joseph M. Pugliese

This work was done by the Bureau of Mines to provide quarry operators with an uncomplicated, first-approximation method for designing blast patterns, considering geologic structure, and to show the valid use of the technique by comparing drill and blast pattern dimensions used in the quarry with those determined by the presented method. The author visited 12 limestone and dolomite quarries in Ohio (Adam, Crawford, and Highland Counties), Wisconsin (Milwaukee, Racine, and Waukesha Counties), and Minnesota (Fillmore, Olmsted, and Wabasha Counties); observed the blasting practices; studied the major geologic features; and after discussion with the quarry managers, foremen, and blasters, compared the quarry blasting patterns with those as calculated by the empirical formulas (after R. L. Ash), with geologic structural considerations. When geologic structure such as bedding, jointing, folding, and caves, as well as explosive properties and field performance characteristics are accounted for in a manner suggested by the research, the presented empirical formulas may be used as a good first approximation. The included steps in planning a blast design and generalized blast patterns should be of help to the quarry operator. Design changes are recommended for those quarries where problems are occurring.

Jan 1, 1972

By Kalliat T. Valsaraj, Louis J. Thibodeaux

A mathematical model is described for the transfer of hydrophobic compounds from aqueous to an immiscible organic phase using fine bubble aeration; the process otherwise known as "solvent sublation" an adsorptive bubble separation process. The limitations of the model are explored by simulating experimental results both for a batch scale process and a continuous process. The qualitative predictions of the model with respect to the influence of the organic layer (mineral oil) are tested by performing experiments using chloroform and 2,3,6-trichloroanisole as hydrophobic compounds in the aqueous phase. The continuous process is seen to be limited by the requirements of fine bubble generation and the ratio of influent feed rate to air flow rate.

Jan 1, 1989

By J. N. Stevens, M. Tulwin, P. J. Lawlor

All metals producers are on an unending search for a competitive advantage. They need to produce in the most cost effective way. Sometimes a new mill might be considered but in this paper we present examples of how this might not always be necessary. A detailed investigation by an equipment vendor who can consider the mill and or plant as a complete entity: mechanics, automation and process control can often find solutions that are both lower cost and can be implemented in shorter time frames.

Oct 1, 2019

By C. L. Berrien

BEFORE the present company was formed, in 1916, each group of mines comprising the old organizations made its detailed daily and monthly mine cost records along the lines used before the consolidation; that is, there was no attempt made to standardize and compare the stope costs of all mines. The general cost sheets for all mines, however, were standardized, and cumulative labor cost sheets were compiled in the general superintendent's office. At most of the mines, a daily record or distribution sheet for each working place was kept, showing the number of men, hours of drilling, hours of timbering, hours of tramming, cars of ore, cars of waste, sticks of powder and feet of fuse. This information was kept by each shift boss and entered on the distribution sheet by him or, at some mines, by a tram boss. The superintendent solved his own problems under the direction of the general superintendent, but without coming in touch with other superintendents, either through records or general conferences. Probably 95 per cent. of the stopes were square-set worked by day's pay; there were some back-filling and shrinkage stopes. Many of the development places, such as shaft sinking, station cutting, drifting and raises had always been run by contract. These contracts were given, for no definite period, at so much per linear foot and were measured monthly, or when completed; the men being paid monthly. In some cases, fairness to the employee, was not maintained. On the whole, there was no standardization. There were no stope contracts, because of the objections of the Western Federation of Miners to general contracting in the mines.

Jan 2, 1922

By J. W. Leonard

Gravity based coal/mineral preparation plants must be operated to yield products of a quality satisfactory to existing markets; but, because of historic control problems, recovery is frequently sacrificed to achieve quality resulting in losses of valuable product. Plant control has ranged from intuitive in-plant spot quality judgments made by various operators to gross methods involving such devices as density gauges, floats, grab-sample on-the-spot sink-float tests, etc. Millions of tons of quality coal/minerals are lost to refuse each year, because of the historic lack of a continuous and dependable control system. The result is both serious economic as well as environmental losses. While the economic losses are obvious, less obvious environmental losses, in the case of coal, result from the misplacement of more ignitable quality fuel to refuse banks. A control system capable of supplying a market-grade coal/mineral product, while continuously minimizing product losses to refuse, has until recently escaped technology.

Jan 1, 1991

By M. B. C. Brandt

Richter magnitudes for seismic events were calibrated for use as a Local magnitude scale in the West Rand (WR), Far West Rand (FWR), and Klerksdorp–Orkney–Stilfontein–Hartebeesfontein (KOSH) gold mining areas. Richter magnitudes are currently calculated from seismograms recorded by local surface cluster networks using tabulated calibration values for Southern California, published in 1958. The Richter (1958) model is incorrect for distances of less than 30 km and should be applied only to crustal earthquakes in regions with similar attenuation properties to those of Southern California. When compared to the South African National Seismograph Network (SANSN), the cluster networks, on average, overestimate seismic event magnitudes by approximately 0.1 of a magnitude unit. A calibrated Local magnitude scale was derived by means of a multiple regression analysis between the Local magnitudes reported by the SANSN and the largest zero-to-peak trace amplitudes measured on the cluster network horizontal seismograms, after modelling the attenuation of the seismic waves as these progress from the epicentre to the station position. Magnitudes reported by individual stations for the same event show a significant scatter around the average magnitude owing to the near-surface amplifications of the seismic waves at the recordings sites. Average magnitude should be estimated using as many magnitudes of individual stations as possible to ensure an accurate estimate. Larger event magnitudes should be compared with those recorded by the SANSN.

Nov 1, 2021

In the last four years, 2007~2010, 9 out of 24 metal/nonmetal underground mine fatalities were caused by ground fall across United States of America (Mine Safety & Health Administration, MSHA). To reduce or eliminate incidents/accidents caused by ground fall, this paper clarified how to design and select ground support based on different ground conditions, how to use mine ground support standards, what geotechnical engineers and underground operators should do to keep mine production free of ground failures.

Jan 1, 2012

By Carlos A. Aranda

The Smelting and Refining Department of Cerro de Pasco Corporation is located at La Oroya at an altitude of 3,720 meters (12,205 feet) in the Peruvian Andes. Producing lead, zinc and copper as well as twelve by-product metals and chemicals, the smelter is among the world's most complex. With the intake of high-bismuth ores in 1934, electrolytic lead refining by a modified Betts process was piloted and the plant went into commercial production in 1937 at a nominal capacity of 100 M.T. per day. After expansions in 1950 and 1963, nominal capacity has increased to 250 M.T. per day. Anodes spaced at 10.8 cm centre to centre and starting sheets are both set into the cells by overhead cranes. The asphalt-lined concrete cells are arranged in a Walker side-by-side configuration, and the electrolyte, circulating at 13 l/min./cell, is a solution of locally-produced hydrofluosilicic acid and lead fluosilicate. The corrosion cycle is limited to four days due to high impurity content of the bullion, which has successfully been treated at contents of up to 9% impurities. The cathodes are melted, drossed, and cast into blocks and pigs assaying 99.997 + % lead. The anodes with the blanket of slime adhering, are washed with electrolyte and condensate makeup water to remove the concentrated lead fluosilicate entrapped in the slimes. The slimes are then removed with high-pressure water sprays, centrifuged and sent to another plant for recovery of silver, gold, bismuth, selenium, tellurium, and antimony.

Jan 1, 1970