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By I. Baltov

The Chelopech Mine, located in Central Bulgaria, is one of Europe?s largest underground copper- gold mines, currently mines and processes approximately one million tonnes of ore per year. Copper concentrates containing gold and silver with significant arsenic content are produced and sold on the world markets. The operation was acquired by Dundee Precious Metals in 2003. A modernization program for the Mine and Plant has since been in progress to increase both production and mechanical reliability, and also to optimize metallurgical recoveries. Since then, mine output and plant throughput have doubled, plant availabilities and utilization have increased significantly, and overall metallurgical performance for copper and gold improved. The paper presents the systematic approach for obtaining and analyzing data, communicating it, and making suggestions for changes to the technological parameters and flowsheet in order to maximize metal recoveries. These studies have correlated the ore characteristics (particle size distributions, metal assays, and Cu and Au mineralogical and phase analyses) with the actual plant performance (kinetics, recoveries, and throughput). Cu recovery by size has been calculated from the mineralogical analyses of feed, concentrate and tails, with the most significant losses being identified in terms of fraction and phase recoveries. This has provided the recommendations (some of them tested in plant) for changes in the grinding and flotation circuits.

Jan 1, 2014

By D. Blackwell, W. R. Reed, G. Ross, S. Peters, M. Shahan

Dust collectors for roof bolting machines generally use a dry box to collect the roof bolting material. Recently, an underground mining operation converted a dry box dust collector to a wet box dust collector with a unique exception from MSHA for testing purposes. Water is routed to the roof bolter from the main water line of the continuous miner. The wet box utilizes a water spray to wet the incoming material. Testing was conducted comparing the two different collector types. Respirable dust concentrations surrounding the roof bolter with the different collection boxes were similar. The main difference in respirable dust concentrations occurred when cleaning the dust boxes. The average respirable dust concentration during cleaning of the wet box was 0.475 mg/m3, and during the cleaning of the dry box the average respirable dust concentration was 1.188 mg/m3. The silica content of the roof material was high, ranging from 28.9% to 52.7% during this study. The results from this study indicate that using the wet box as a collector reduced exposure to respirable dust up to 60%when cleaning the collector boxes. INTRODUCTION Currently, the dry vacuum dust collection system is the standard dust collector on roof bolters in underground coal mining. It has been proven to be an effective dust control to prevent roof bolter operators’ overexposure to coal mine respirable silica dust during roof bolting operations [Potts eta l, 2011 and Colinet, 2013]. The dry collection system works as follows: drill cuttings are vacuumed into the precleaner. The precleaner dumps oversized material onto the mine floor while undersized material enters the dust box via vacuum airflow produced by a blower. The cuttings entering the dust box are either deposited on the floor of the dust box or into a dust collector bag. The vacuum airflow leaves the dust box through a final filter which removes any small particles from the airflow. Figure 1 shows the internal view of two dry collection system boxes; one that does not use the dust collector bags and another that uses the dust collector bags. Dust collectors that use dust collector bags to contain material inside the dust collector box have been shown to provide better protection to roof bolter operators than dust collectors that do not use the bags [Listak and Beck 2008]. The dry collectors are very efficient at reducing respirable coal mine dust exposure from roof bolting activities. Recently, Blue Mountain Energy’s Deserado underground coal mining operation, outside Rangely, CO, made a modification to the dry collector system to convert it to a wet collector system with a unique exception from the Mine Safety and Health Administration (MSHA) for testing purposes. The wet collector system still uses a vacuum system to pull material from the vertical roof bolt hole, but incorporates a water spray nozzle located inside the dust box to wet the incoming material. The flow through the nozzle ranges from 1.9–7.6 lpm (0.5–2.0 gpm) at 0.69 MPa (100 psi). The conversion to the wet collector system removes the precleaner and the cyclones inside the dust box. The wet material (sludge) then empties through a specialized valve in the bottom of the box. The final filter is still used to prevent respirable dust from leaving the dust box through the exhaust. During operation, the wet collector dust box is opened and hosed clean after roof bolting every place. After every two entries the final filter is changed out. Figure 2 shows the inside of the wet collector box.

Jan 1, 2019

By W. A. Krivsky, R. Schumann

Relaxation calculations were made to find the temperature distribution in the refractory wall surrounding a tuyere pipe. One set of boundary conditions approxiwated those of a standard copper converter while a second set represented a hypothetical,thermally insulated tuyere pipe. The pvonounced cooling effect of the tuyere is related to the problem of tuyere accretions and tuyere bunching. PARTICULARLY severe service conditions are encountered in the tuyere zone of a basic copper converter during the matte blow. High-temperature gradients result from the juxtaposition of the hot charge and the tuyere pipe carrying cold air. Refractory temperatures near the tuyere mouth vary rapidly with time when the blast is turned on or off. One of the most serious problems is the formation of magnetite accretions around the tuyere mouth, which occurs very rapidly under some operating conditions. As a result, continual punching of the tuyeres is necessary to maintain a satisfactory rate of converting. Thus, if some means could be devised for keeping the tuyere pipes fully open without necessity for punching, a considerable saving should result from reduction in labor cost, maintenance of full capacity operation, and reduction in refractory costs. Recent quantitative studies of the FeO-Fe,O,-SiO, system1 have shown that the solubility of magnetite in iron-silicate slags decreases rapidly with de- creasing temperature in the range of copper converting temperatures. Data taken from the previous work are shown in Fig. 1. Thus the formation of "horns" and accretions around the tuyere mouth can result simply from the freezing out of magnetite on the cooler areas of refractory immediately adjacent to the tuyere pipes. One might expect to find a correlation between the severity of magnetite formation and the area of refractory surface which is cooled below the freezing point of the slag (corresponding to magnetite precipitation). Magnetite itself has a very high melting point (1597°C) so that the accretions are for all practical purposes infusible. The accretions might be dissolved by increasing the silica content of the slag and at the same time raising the temperature, but this approach is not feasible because it results in rapid corrosion of the basic refractory lining of the converter as a whole. In order to understand better the problems involved in tuyere design and operation, it seems essential to have at least a semiquantitative idea of the thermal conditions in the tuyere zone. Accordingly, this paper presents results of thermal calculations for an idealized copper converter tuyere. These calculations follow the so-called relaxation

Jan 1, 1960

By William C. Peters

The frustration encountered by exploration crews in connection with land acquisition could be graphed to show a correlation with the natural law that everything tends to become more so. Figure I shows a rather common, situation. The combinations of ingredients are almost limitless and the resulting brew is often poisonous to an exploration man. A single step, that of taking a series of deep soil samples is often delayed until some sense can be made from "floating" unpatented claims which are obscure in orientation as well as position, placer claims overlapping lode claims, location posts with empty Prince Albert cans, and claims with no apparent assessment work for ten years. Add to this some patented claims with¬out monuments, a state or federal withdrawal area which may or may not invalidate pre-existing claims, a loosely defined tunnel site, and some ranchers who understandably resent the separation of surface rights from mineral rights. The picture is familiar to exploration men. One approach to such problems is to ignore them until someone voices an objection -- but then an even more chaotic situation is likely to develop. Another practice is to stake new claims to cover all ground that is "open" at first glance and then find out if there are conflicts so that the new claims can be adjusted accordingly.

Jan 1, 1970

By William F. Hahn

It is a pleasure to speak to this group about special crusher installations which are in the bauxite and phosphate rock processing industries. The installations to be discussed demonstrate the variety of conditions, materials, and results desired which must be evaluated before a selection is made from the specialized crusher technology available today. Those of you who are closely involved with phosphate rock and phosphate products processing will find some of this information a bit interesting and perhaps alien to your own descriptions or every day references. It is given from a "crusher" manufacturer's viewpoint and therefore is infused With our flair and language. General features of six (6) different crushers will be shown in cross-section With slides and will be discussed in the same order.

Jan 1, 1978

By Messervey, J. P.

NOVA SCOTIA is sharing in the rapid advance of the mining industry that is one of the remark- able features of Canada's recent progress. The production of coal and gypsum has increased rapidly, and there has also been a marked development in the mining of gold, salt, zinc, copper and other minerals. Coal, the basis of the principal mining industry in the Province, was discovered by the early explorers on the shore of Cape Breton Island, and used by the garrison at Halifax as early as 1749. The first government record shows total annual sales amounting to 1668 long tons in the year 1785, while last year production was 6,643,000 long tons. The principal mines are discussed in a separate paper by Alexander L. Hay1.

Jan 1, 1928

By K. Hausmann, W. Whelchel

The properties of ethylene Ionomer resins for the inner layer of non-electric shock tubes will be discussed in detail, and opportunities for property enhancement will be pointed out. A stiffness program for prediction of shock tube stiffness, as determined by the stiffness of the individual layers, will be presented and discussed.

Jan 1, 2010

By Timothy J. Matthews, Timothy J. Batchler, Daniel J. McElhinney

The National Institute for Occupational Safety and Health’s (NIOSH) Mine Roof Simulator (MRS) at the Pittsburgh Mining Research Division was commissioned for operation in 1981. The MRS was originally designed for longwall shield research and was the only hydraulic press in the world with the capability to apply biaxial loads to these large structures. The results of this forty-year research program have contributed to improved performance and increased knowledge of longwall shields, mobile roof supports and hydraulic cylinders in the mining industry. Also, considerable research and development have been conducted to develop standing support technologies for the mining industry. The Support Technology Optimization Program (STOP) was developed to evaluate how these various technologies can impact and improve both ground control conditions and mine safety. Additional MRS research has included the performance of ventilation stopping walls including the development of a new testing protocol to evaluate the transverse loading capabilities under arching load conditions and evaluating the performance characteristics of welded wire screen as used in underground mine roof surface control. The NIOSH Mine Roof Simulator has been a reliable and valuable tool for the past forty years for the evaluation of safety structures used in mining, and this research has contributed significantly to the advancement toward safer mines. This paper will summarize those research results and provide a glimpse of planned future activities.

By Thomas W. Smelser

A full-scale geotechnical model of a 15-foot (4.6 m) wide coal mine entry in correlation with computer finite-element analysis (FEA) is being employed at the Bureau of Mines Spokane Research Center for basic research on roof-bolt support systems. Physical and computer modeling of various coal mine roof-bolt reinforcement systems will increase our basic knowledge of how roof supports function. This information, in correlation with computer FEA and underground verification tests, will provide a basis for establishing safer, more cost- effective roof control plans and help establish guidelines for employing fully grouted and conventional bolting systems. The basic rationale for the research, research approach, methods and equipment employed, results to date, and future research plans are described in this paper.

Jan 1, 1982

By L. George Imperato

The Blocked Iron Corporation has been active for many years in the development of mineral agglomeration processes by cold chemical induration. Millions of tons of iron ore fines agglomerated by their methods have been consumed in open hearth steel making furnaces. Some of you may remember these open hearth agglomerates as the carbonate-bonded cylindrical block shown in figure 1. With the realization that iron making would create the greatest demand for agglomerates our research efforts were directed to the production of carbonate- bonded (C-B) pellets containing iron ore, flux and carbon, shown in figure 2.

Jan 1, 1968

By H. R. Pierce

A gas well has a certain definite capacity to deliver gas from the gas sand through the producing string of pipe. This capacity depends upon the pressures in the sand; that is, a well will deliver gas at a rate of flow which is determined by the formation or "shut-inn pressure in the sand and the back pressure at the face of the sand in the well. The three factors, rate of flow, formation or "shut-in" pressure, and the back pressure, for a given well, can be written into a fundamental relation which is strictly applicable only to that well. This relation can be used to determine the capacity of the well to deliver gas from any formation pressure against any back pressure held at the f ace of the sand in the well. Studies have been made of the deliveries of 400 gas wells operating under different conditions of pressure, Most of the wells which have been studied are in Osage County, Okla.; however, several representative studies have been made on wells in southern Louisiana, southern Texas, the Texas Panhandle, and West Virginia.

Jan 1, 1929

By John P. Carter

The U.S. Bureau of Mines conducted research to determine suitable construction materials for use in brine and steam environments produced from high-salinity geothermal brines. The high-temperature, high-salinity geothermal brines in the Salton Sea Known Geothermal Resources Area (KGRA) are a valuable source of energy and mineral values. The brine and steam produced from them are corrosive and cause early failure of many common materials of construction. Mass-loss and electrochemical corrosion measurements were conducted on over 60 metal alloys in brine and steam environments produced from geothermal well Magmamax No.1, located at the Salton Sea KGRA, at temperatures from 1800 to 2150 C, and in synthetic Magmamax brine at 105° and 232° C. General corrosion, crevice and pitting corrosion, and stress corrosion were examined along with the effects of dissolved gases. The alloys with the most acceptable corrosion performance in high-temperature, high-salinity geothermal environments were the high-chromium ferritic stainless steels, the Inconels and Hastelloys, and the titanium alloys. Specific alloys that performed well in wellhead brine included Fe29Cr4Mo, E-Brite 26-1, stabilized Fe26Cr1Mo, 6X, Inconel 625, Hastelloy C-276, Hastelloy S, Hastelloy G, Ti5OA, TiO.2Pd, and TiCode 12.

Jan 1, 2010

By Richard H. Sillitoe

Gold is an important byproduct and, locally, coproduct of porphyry copper deposits, and possesses potential for discovery as the major metal in porphyry deposits in either island arcs or Cordilleran belts. Tungsten and tin occur as major components of several potentially bulk-minable porphyry deposits, as well as being byproducts from the Climax porphyry molybdenum deposit. Whereas porphyry tin systems are localized in Cordilleran back-arc settings, their tungsten counterparts appear to span a range of geotectonic settings, from Cordilleran principal arcs through back-arcs to rifts. Although silver is a common byproduct of porphyry copper deposits, it tends to be preferentially concentrated with lead and zinc on the fringes of all types of porphyry deposits and/or as late-stage superpositions; the latter situation could be of some interest in the higher parts of porphyry systems. As byproducts, rhenium, uranium, platinoids and magnetite are exploited occasionally, and rutile and the rare metals, such as tantalum and niobium, have merited consideration.

Jan 1, 1982

By Irving Hartmann

At the 9th International Conference of Directors of Safety in Mines Research a paper6/ was presented describing the initial phases of research by the Safety in Mines Research Establishment at Buxton, England, on the remote control of timber fires with high-expansion foam plugs in a rock tunnel. The work received extensive publicity, and great interest was aroused by the implied possibility that the method might be used successfully to control coal-mine fires, which for various reasons cannot be approached and attacked by standard fire fighting measures and frequently require sealing extensive, valuable coal properties and lead to loss of production and coal reserves and occasionally loss of lives. To investigate the practicability of the foam-plug technique under American min¬ing conditions, with room-and-pillar-type extraction and multiple entries, the Bureau of Mines in 1957 began an investigation at its Experimental Coal Mine, Bruceton, Pa, In preparation for this work it was necessary to rehabilitate and reinforce an elliptical tunnel in the mine where studies had been made, many years ago, leading to development of a ventilation system used in the Holland Tunnels between New York and New Jersey, and in many other vehicular tunnels.

Jan 1, 1958

By Sherif Elfass, Gary Norris

Bi-directional load testing of drilled shafts has been widely adopted as a means to evaluate their load carrying capacity. However, in order to reach failure, most of these tests are carried out on sacrificial shafts using expensive sacrificial elements such as hydraulic jacks. A proposed low-cost bi-directional testing technique is discussed. It mechanically loads the end bearing soil below a drilled shaft, against its side shear resistance. The technique was originally established as an alternative to post-grouting to reliably account for the forfeited end bearing resistance. However, since it loads the shaft in a manner similar to conventional bi-directional tests, it can be used to not only load test sacrificial shafts, but production shafts as well. Furthermore, unlike conventional bi-directional load tests, the load is applied through surface jacks. These jacks, along with other load test components, are movable and can be reused to load test all the shafts of the project thus presenting an economic benefit. The concept of this technique has received favorable feedback from a few consulted departments of transportation, and while promising, has not been field tested to date. A U.S. patent was issued for the tip loading module and the loading technique described.

Sep 8, 2021

By Sheng Zhang

The compressive strength of coal in Yanlong mine area of China is less than 3 MPa. Basically, it is powdery. The roof and floor rocks are mudstone. Therefore this coal seam is a typical ?three soft? coal seam. Roof bolting cannot be used due to the very soft strata. When the conventional U-steel support was used, roadways deformation exceeded 30% of its original dimensions in some sections one half month after development. The required repair work was huge, seriously affecting the daily mine production. This paper describes how to support the soft coal roadways. The deformation characteristics of soft coal roadway were investigated. The conventional U-steel support is not subjected to uniform load, so the whole supporting structure must be strengthened. In addition, drilling holes in the coal seam can transfer high stress from near the ribs to the deeper parts of the surrounding strata, which is beneficial to the stability of the roadway. This new support method is to combine the strengthened U-steel support with pressure-relieving drill holes, providing an economic and efficient way to support the very soft coal roadways.

Jan 1, 2013

By W. J. Reagan

The problem of increasing output and decreasing percentage of rejections is a vital one in the manufacture of steel of any kind. The making of basic open-hearth steel for use in rolled steel wheels, tires for locomotive and car wheels, and forgings of various kinds, is a highly specialized industry. The increase in weight of railway rolling stock of all kinds, and the high speed that the public demands of transportation facilities, make it imperative that steel for use in this class of material shall be of the highest quality obtainable. During the past few years it has been the writer's good fortune to have opportunity to study the defects in basic open-hearth steel, and also the results obtained by various changes in open-hearth practice, on such defects. The opportunity for study and the details available are rarely found in the manufacture of steel of any kind. It seems reasonable to assume that many of the results determined here can be applied to the production of steel of other types with a decided improvement in quality, a decrease in the percentage of rejections and an increase in output. All of the material described is basic open-hearth steel with the following range of analysis: carbon, 0.50 to 0.85 per cent.; phosphorus and sulfur, 0.04 max.; silicon, 0.15 to 0.35; manganese, 0.50 to 0.75. All of this material is bottom-cast, therefore tapping and pouring temperatures are higher than in top-cast production. Ingots used in this type of work are of standard length with varying diameters. The ingot is known as duodecagonal, or twelve-sided. The standard body length is 88 in. and the hot top length, 14 in. Fig. 1 shows a typical ingot of this type. The diameter varies from 13 to 30 in. Ingots for special forgings, which cannot be made in molds of standard size, are made in molds of various sizes and designs. These ingots are sliced cold, into blocks of various lengths, depending upon the weight of the forging to be made. Fig. 2 shows the ingot after coming from the slicing lathe. Jusf sufficient metal remains between blocks to hold the ingot in one piece while it is being removed from the lathe; then steel wedges are inserted between the blocks and the blocks are broken apart. This affords abundant opportunity for inspection, as the interior of the

Jan 1, 1930

By William R. Chedsey

IN the last two years the E.C.P.D. committees having to do with the inspection of engineering schools for possible accrediting have been concerned with the engineering content of some of the mineral industries courses. Originally the discussion arose with regard to engineering geology, or geological engineering, afterward broadening to metallurgical engineering, ceramic engineering, agricultural engineering, and other branches not pertinent to this discussion. Some members of visiting committees took the attitude that they probably would have to accredit these types of training as included in the engineering group if they met the average standard set by the mining schools, though they questioned -whether they were really engineering.

Jan 1, 1939

By W. J. Reagan

THE problem of increasing output and decreasing percentage of rejections is a vital one in the manufacture of steel of any kind. The making of basic open-hearth steel for use in rolled steel wheels, tires for locomotive and car wheels, and forgings of various kinds, is a highly specialized industry. The increase in weight of railway rolling stock of all kinds, and the high speed that the public demands of transportation facilities, make it imperative that steel for use in this class of material shall be of the highest quality obtainable. During the past few years it has been the writer's good fortune to have opportunity-to study the defects in basic open-hearth steel, and also the results obtained by various changes in open-hearth practice, on such defects. The opportunity for study and the details available are rarely found in the manufacture of steel of any kind. It seems reasonable to assume that many of the results determined here can be applied to the production of steel of other types with a decided improvement in quality, a decrease in the percentage of rejections and an increase in output. All of the material described is basic open-hearth steel with the following range of analysis: carbon, 0.50 to 0.85 per cent.; phosphorus and sulfur, 0.04 coax.; silicon, 0.15 to 0.35; manganese, 0.50 to 0.75. All of this material is bottom-cast, therefore tapping and pouring temperatures are higher than in top-cast production. Ingots used in this type of work are of standard length with varying diameters. The ingot is known as duodecagonal, or twelve-sided. The standard body length is 88 in. and the hot top length, 14 in. Fig. 1 shows a typical ingot of this type. The diameter varies from 13 to 30 in. Ingots for special forgings, which cannot be made in molds of standard size, are made in molds of various sizes and designs. These ingots are sliced cold, into blocks of various lengths, depending upon the weight of the forging to be made. Fig. 2 shows the ingot-after coming from the slicing lathe. Just sufficient metal remains between blocks to hold the ingot in one piece while it is being removed from the lathe; then steel wedges are inserted between the blocks and the blocks are broken apart. This affords abundant opportunity for inspection, as the interior of the

Jan 1, 1930

By P. D. R. Maltby

This paper describes the background and markets for calcium carbonate and silica sand in Canada, as well as the results of recent test work carried out at the Ontario Research Foundation. Tests on sericite, tremolite, vermiculite, barite and graphite are also mentioned.

Jan 1, 1979