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By L. P. Meade

The need to feed an established talc mill from a crude are source located closer to the mill prompted the drilling in 1986 of a previously mapped talc-carbonate deposit. This talc-bearing rock had never been considered as a potential source of crude talc are because of the high carbonate content and other deleterious minerals that were observed in outcrops. Selective mining, in-pit grade control and creative processing has allowed this deposit to be developed into an orebody. By definition, an orebody has to be a source of positive cash flow. With industrial minerals, this is determined as much by market acceptance as by are tenor.

Jan 1, 1992

By Emanuele Catelli, Paolo Vicentini, Manuel Petitat, Paolo Lanfranchi

"More than 800 million tons of material will be excavated during large underground projects such as tunnels, undergrounds and power plants by 2030 in Europe only. The raw material excavated is often classified as waste, which involves environmental impact and transport issues: landfill areas, CO2 emissions and noise. But how can such massive amounts of material be transported, processed and deposited? Using the example of the AlpTransit Ceneri Base Tunnel (15.4 km), we show that suitable excavated materials can be used sustainably as a primary resource for tunnel concrete. This requires careful planning of the installations and storage areas by the client, timely building of the processing plants and other handling facilities outside the tunnel and a continuous evaluation of the raw material quality. 1. INTRODUCTION Spoil management is a central element of large construction projects. The systematic reuse of suitable excavated material not only saves natural resources, reduces transport distances and landfill volume, but can also decrease overall construction costs. Ideally, all of the concrete needed for tunnel lining can be produced with this on-site material. Such a natural resource management concept was applied for the construction of the new Gotthard Base Tunnel (L = 57 km). Spoil management concepts are, how-ever, difficult to implement and call for innovative techniques, sophisticated logistics and organization. In the context of large projects, environmentally friendly transport, processing and storage of millions of tons of excavated loose material represent another logistics challenge (Simmen & Lieb, 2010). This paper shows key factors that led to the successful completion of spoil management at the Ceneri Base Tunnel, which constitutes a part of the AlpTransit Gotthard Project (Figure 1)."

Jan 1, 2016

A kinetic model for leaching of various metals with different lixiviants in a batch system has been developed. Material balances for reactants and products at the solid/liquid interface were formulated and solutions to these balances were obtained in view of practical conditions. Special emphasis has been given to examine mixed controlled reaction systems where both heterogenous reaction and mass transfer play important role on the overall rate expression. The resulting kinetic expressions for either powder or rotating disc are discussed in light of experimental findings for various metals. Examples of the metal dissolution systems considered in this study include cobalt, nickel, copper and gold in acid, cyanide or ammoniacal solutions.

Jan 1, 1992

By J. W. Hawkins, K. B. C. Brady, M. W. Smith

The Pennsylvania Department of Environmental Protection (PaDEP) has been issuing surface mining permits since 1984 that authorize remining in areas that will affect preexisting pollutional discharges. These permits require the mine operator to employ best management practices to reduce pollution loading from abandoned mine discharges. A total of 110 completed mining operations with 233 discharges were evaluated to determine the impact to water quality. Overall, acid loading from these discharges was reduced by 7, 200 kg (15, 900 lbs) per day or 61%. Metal loadings were also reduced. For acidity, 49% of discharges improved or were eliminated, 52% showed no significant change and fewer than 1 % got worse. Loading reductions resulted from a combination of reduced concentrations and lower flows.

Jan 1, 2003

By R. H. Parker, B. A. Wills, D. G. Binns

Introduction With the increasing need to mine lower grade ores, high energy-related costs in comminution are of major concern. Very fine grinding is needed to liberate the fine mineral particles in these ores. Not only is this expensive, but it leads to greater losses in slimes. Gravity concentration techniques become unacceptably inefficient for particle treatment below 25 to 50 µm, and even flotation fails in the ultra-fine range. Ore from the South Crofty mine near Redruth, Cornwall, was subjected to thermal pretreatment in the hope that differential thermal expansion of the minerals would lead to intergranular cracking, and thus enhanced liberation. South Crofty ore contains about 1% tin as cassiterite associated with a complex assemblage of quartz, chlorite, tourmaline, and hema¬tite in granite and slate. Recovery of cassiterite can be as low as 70%, as overgrinding occurs during stage reduction of the material to 1 mm (primary grinding) and 180 µm (regrinding). Cassiterite is present in grain sizes ranging from submicroscopic to + 10 mm, the bulk being predominantly in the range of 50 µm to 3 mm. Experimental Flat polished sections of the ore were photographed in reflected light using a Vickers M17 microscope. The sections were then heated in a Carbolite LMF4 muffle furnace. The heating rate and temperature were monitored by a thermocouple immersed in the bed of particles. Previous work by Sherring (1981) on the same material showed that a 55% reduction in grinding resistance occurred when the material was rapidly heated and cooled through the quartz inversion tem¬perature (573°C), where a volumetric expansion of 0.86% occurs. The samples were therefore heated to 650°C at 26°/min, and were then water-quenched to room temperature. The effect of heat treatment on the mineralogy and fracture network was assessed by examining the same area after treatment. Results Most of the sections examined showed that extensive transgranular cracking occurred as a result of heat treatment. Such cracking, although weakening the rock and hence reducing the work index, would in no way enhance the liberation of the cassiterite from the host minerals. Intergranular cracking, which would lead to enhanced liberation, was difficult to discern under reflected light, but there was evidence of such cracking in some of the sections examined. Figures 1 and 2 are examples of typical sections before and after heat treatment. Figures la and lb - show cassiterite in hematite, Fig. lb, in normal incident illumination, illustrating clearly that after heat treatment, transgranular fracture is evident in the cassiterite. If any intergranular cracking has occurred, it is not evident in this photograph. Figures 2a and 2b show cassiterite in quartz before and after treatment. Fracturing in both minerals after treatment can clearly be seen, and there is evidence of intergranular fracturing. However, protruding "arms" of cassiterite are severed by transgranular fracture. Subgrains of quartz have also been isolated by trans¬granular fracture. There is major transgranular cracking across the wider sections of cassiterite. Discussion The effect of rapidly heating South Crofty tin ore to 650°C, followed by water-quenching to room temperature, has been studied by observing the fracture networks in mineral grains. The choice of 650°C as the heating temperature was influenced by the work of Sherring (1981), who found considerable reduction in grinding resistance after thermal pretreatment of the same ore. Scheding et al. (1981), however, have shown, by means of a crude calculation, that heat treatment cannot be justified solely on the basis of reduced grinding costs. The cost of heat treatment far out-weighs that of grinding, resulting in the combined costs for heat treatment being over six times that for grinding unheated material. The most economically attractive aspect of heat treatment is the possibility of enhanced liberation of the valuable mineral due to increased intergranular rather than transgranular fracture. Grinding costs would be greatly reduced by improved liberation at coarser sizes, and the costs of ancillary processes, such as dewatering and tailings disposal, would be reduced. The most significant economic effect, however, would be in improved metallurgical efficiency. Improved liberation would increase concentrate grades, and recoveries would be higher, particularly in the case of ores where high slime losses are produced due to the excessively fine grinding required to produce adequate liberation. Manser (1983) has shown that only a 1% increase in tin recovery, at the same concentrate grade, would be sufficient to offset heat treatment costs on South Crofty ore. Heavy liquid analysis and shaking table separation have been used to evaluate the effect of thermal treatment on processing (Binns, 1984; Scheding, 1981; Sherring, 1981). However, treatment of unheated and heated samples of South Crofty ore, ground to the same product size, by such methods have shown little evidence of improved metallurgical efficiency after thermal pretreatment. The large amount of transgranular fracturing revealed by reflected light studies helps to explain this lack of improvement. Nevertheless, from the evidence of some of the fracture work, it is surprising that no improvements in metallurgical

Jan 1, 1988

By R. G. Reddy

Spent potliner is generated in the electrolytic process of reducing alumina to make aluminum metal using molten fluoride electrolytes. Spent potliner (SPL), obtained at the end of the pots life contains a small amount of cyanide and fluoride which present environmental problems. SPL became a listed hazardous waste under RCRA (K088) in July, 1990. One of the possible uses of spent potliner is as a substitute for Calcium Fluoride (CaF2) as a fluidizer in iron-and steel making and in the glass industry. A low viscosity and a low melting point are prime requirements for accomplishing the above. In the present study, viscosity measurements were performed. Effect of various additives, such as sand, limestone, dicalcium silicate dust, and MgO baghouse dust on the viscosity of SPL was studied. The results showed that with the addition of sand and limestone, very high fluidity of SPL melt can be obtained at significantly low temperatures. The results suggest that spent potliner mixed with additives could potentially be used as a substitute fluidizer.

Jan 1, 1999

By C. E. Jordan

The Bureau of Mines investigated a simultaneous elutriation and flotation technique for separating polyethylene terephthalate (PET) from polyvinylchloride (PVC). The Tuscaloosa Research Center, through a cooperative agreement with a recycling company, devised an elutriation-flotation method for beneficiating the mixed heavy plastics portion of municipal solid wastes which is composed of polystyrene (PS), PET, and PVC. A sodium carbonate brine was used to remove the lighter PS from the heavier PET and PVC. Over 98 pct of the PS was recovered in a high purity PS concentrate containing 99.7 pct PS, The remaining PET and PVC mixture was washed to remove the brine salts that would be harmful to the flotation process. The clean PET and PVC mixture was conditioned in a solution of 45 g/t gelatine and floated in a short (l-m) column flotation cell in an upward flow of water. In a single flotation step, over 75 pct of the PET was recovered in a high purity product containing 99.8 pct PET. The bubbles attached to the PET lowered the effective density of the PET-bubble agglomerate and allowed successful separation of these agglomerates from the PVC plastic pieces. This method separated two-thirds of the mixed plastics fraction into high purity PS and PET products suitable for recycling and left only one-third of the plastics in the mixed plastics product.

Jan 1, 1992

By Jean-Michel Rendu

Accurate modeling of the semivariogram is an extremely important step in the geostatistical analysis of mineral deposits. Automatic fitting of a mathematical model is often possible but not necessarily desirable. Significant geologic and statistical information must be taken into account in the fitting process, which is not always available to the computer. Manual fitting of the model is, on the other hand, extremely time consuming. Interactive graphics are best suited to optimize the process. A number of interactive methods are described, which are adapted to the modeling of semivariograms in one-, two-, or three-dimensional environments.

Jan 1, 1982

By Harrison R. Cooper

The expanding use of digital control in the metallurgical industry is a significant recent development. From 1970 to 1975, approximately forty metallurgical plants throughout the world have adopted automation techniques based on digital controls (see Table 1). Several recent technical reports have described development of digital control systems in concentrator grinding control, 1,2 flotation,3 and smelter operations.4,5

Jan 1, 1975

By Thomas J. Wright

The evaluation and development of the Eastern North Carolina phosphate deposit resulted in one of the world's largest and most modern phosphate mines and fertilizer complexes at an investment in excess of $90,000,000. The resulting ore beneficiation process showed excellent correlation with pilot plant data. A number of variations from current industrial practices were introduced and projected from bench scale tests through pilot plant to production. Principal among these variations were the following: 1) removal of magnesium by classification, 2) simultaneous flotation of coarse and fine phosphate, 3) the use of saponified fatty acid, 4) utilization of filter wash water for deoiling, 5) utilization of a rougher concentrate for acidulation, 6) calcination of flotation concentrates, and 7) elimination of grinding prior to the manufacture of phosphoric acid.

Jan 1, 1971

By R. Raitani

Five kaolin crudes from the state of Georgia in the U.S. were investigated for processability with chemically enhanced magnetic separation (CEMS) technologies developed by Cytec. The technologies used magnetic reagent alone or in conjunction with specialty chemicals to selectively agglomerate and magnetize the desired minerals (impurities) to be removed by the conventional magnetic separation equipment. All crudes indicated treatability using CEMS. Results indicated that CEMS technology could be applied to different kaolin crudes to obtain a product with titanium impurities less than 0.6% TiO2 from individual crudes. The features and benefits of the technologies were also reviewed.

Feb 1, 2012

By Musa D. Manzi, Raymond J. Durrheim, Richard T. Masethe

Large mining-induced seismic events and their aftershocks cause hazardous working conditions, damage infrastructure, delay production and pose a risk to miners in the deep-level gold mines of South Africa. Stress changes affecting pre-existing zones of weakness are the main drivers of large mining-induced seismic events, which are often followed by aftershocks triggered by quasi-static stress transfer within the rockmass. A better understanding of seismic source mechanisms is important if the seismic data is to be used more effectively for mine planning and to reduce the rockburst risk. Four large seismic events (ML≥2.0) associated with the mining of the Ventersdorp Contact Reef (VCR) at Kloof Gold Mine occurred on 13 June 2017. The events and their fore- and aftershocks were studied in detail to establish the circumstances and the cause of the incidents. The local magnitudes ranged from ML 2.3 to ML 3.0, the seismic moment from 0.69 to 2.25 x 1013 Nm and the source radius from 92 – 150 m. The main shocks were preceded by foreshock sequences, which were especially vigorous in the four hours before the main shock. Seismicity was recorded by in-mine arrays of three-component 4.5Hz geophones (detection threshold approx. ML -2.9). Following all four main seismic events, ML 2.3, ML 2.3, ML 2.9 and ML 3.0, the network detected a total number of 300 aftershocks ranging from ML -2.9 to ML 1.6 spread within a 1300 m radius from the centre of the seismic network. The statistical properties of the aftershocks were analysed using three scaling relationships: (i) Gutenberg–Richter frequency magnitude relationship; (ii) modified Omori’s law; and (iii) Båth’s law for the magnitude of the largest aftershock. The geological or mining feature that controlled the failure (e.g., fault, dyke, pillar, abutment) was determined by calculating the orientation of the nodal planes of the large seismic events using moment tensor analysis and studying the aftershock distributions.

Apr 26, 2022

By Daniel A. Payne

For many years underground mining in the Sydney Coalfield has suffered from the effects of high horizontal stresses. It is only in the last 15 years that they have come to be recognized, understood, predicted and even avoided. This paper relates experiences in three coal mines in three different seams in the Sydney Coalfield. The effect of the direction of the principal horizontal stress on the direction of drivage of gate roads, access roadways and longwalls is described. Results of a monitoring program to measure the change of magnitude and direction of the principal horizontal stress in the gate roads as a result of longwall mining are also presented as well as the effect of the direction of principal horizontal stress on the shape of sandstone/gas outburst cavities.

Jan 1, 1998

By R. A. Thomas, C. D. Litton

"The objective of this study was to develop a laboratory-scale method to rank the ignition and fire hazards of commonly used underground mine materials and to eliminate the need for expensive large-scale tests that are currently being used. A radiant panel apparatus was used to determine the relevant thermal characteristics of the materials: time to ignition, critical heat flux for ignition, heat of gasification, and mass loss rate. Three thermal parameters, TRP, TP1, and TP4, were derived from the data, then were developed and subsequently used to rank the combined ignition and fire hazards of the combustible materials from low hazard to high hazard. The results compared favorably with thermal and ignition hazards of similar materials reported in the literature and represent a simpler approach to quantifying these combustible hazards. INTRODUCTION The potential fire hazard from combustible mine materials is a major concern that can impact the safety of mine workers. Combustible materials tend to be solids and within this category there exist degrees of flammability and fire resistance. These materials may be readily ignitable or they may be able to withstand high temperatures and high heat fluxes. Presently, no simple methodology exists to assess these possible fire behaviors and quantify the resultant fire hazards. Thus, better knowledge of the thermal properties and chemical characteristics of combustible materials is of great importance to the safety of mine workers. Tewarson [1994] developed a methodology which he subsequently used to evaluate the ignition and fire resistant properties of combustible mine materials, but these efforts are more than 20 years old, and do not include many of the new materials used in mines today. The standard practice that has evolved for a combustible material to be approved by the Mine Safety and Health Administration for use in underground coal mines is to conduct extensive and costly large-scale experiments on each new material that is used in a particular mine operation. Results of such tests provide pass/fail answers to the questions of a material’s flammability or fire resistance, yet they provide little, if any, information that will lead to a better understanding of the basic mechanisms involved. Therefore, there is a need to quantify material flammability properties and to develop a methodology to rank the ignition and fire hazards of commonly used underground mine materials. During the heating and ignition stages of combustible materials, properties such as smolder susceptibility, minimum surface temperature for ignition, thermal conductivity, heat capacity, density, and heat of gasification are known to be important [Apte, 2006]. During the flaming stage, additional parameters, such as the heat of combustion, heat release rate, flame spread rate, yields of soot/smoke, and toxic gas production become more important as the flame is sustained and spreads. In very general terms, the heat flux incident on the surface of a solid combustible not only controls the rate of temperature increase of the local fuel surfaces, resulting in expulsion of fuel vapors that sustain the flaming process, but also the heating of other combustible surfaces that subsequently ignite and spread flame."

Jan 1, 2015

Little knowledge is available that considers the effects of continuous miner position on the possible respirable dust exposure of the remote mining machine operator. Such information could be very useful for increasing the awareness of the remote operator as to those parts of an extended cut that generate higher levels of respirable dust. This data could be used to develop guidelines for positioning the remote operator to reduce his potential exposure. This work details the effects of continuous miner position on dust levels measured on the machine and at the remote continuous miner operator location.

Jan 1, 1998

By V. Rastogi

Acid rock drainage is the result of exposure of sulfidic materials, such as pyrites and sulfidic ores, to air and water. The oxidation of these sulfides is catalyzed by more than a million times by the bacteria Thiobacillus jerrooxidans and close families. Inhibition of these bacteria can mitigate 98% or more of the acid loading generated. This can be achieved by the use of certain surfactants that are selectively bactericidal to the lithotropic acidophilic bacteria. Bactericides are used in two ways. As periodic or continuous treatments for prevention of acidification of material actively handled and moved, and in controlled release form for reclamation where treatment sets up a change in site microbiology to replace Thiobacillus jerrooxidans with heterotrophic bacteria and creates a stable site without need for further treatments. Use of bactericides begins with laboratory testing of the site material to qualify the site for bactericide treatment and dosage determination. Site specific treatments are designed for active sites and reclamation. Once acid production is controlled, solubilization of metals is correspondingly reduced. Results and economics of use from active and reclamation sites are presented.

Jan 1, 1995

By J. Astier

The idea of using only one strand for both sintering and cooling of the sinter is not new. In 1952, in the U.S.A. a sintering plant was built at Benson Mine (Star Lake, N.Y.), including : - 68 m2 or 735 sqft (8 wind boxes) for sintering, - 22 m2 or 237 sqft (3 wind boxes) for cooling. In the USSR, a large number of machines have been built allowing for cooling of the sinter on the strand, especially the 4 m (about 13 ft) machines, with : 252 m2 sintering grate area 60 m2 cooling grate area 312 m2 total grate area. However, such ventures did not prove very successful, and the IRSID embarked many years ago on a research program to discover : - what are the problems associated with cooling on a sintering strand ; - what are the possible solutions for industrial plants.

Jan 1, 1974

Dynamic permeability is a significant hydrologic condition associated with in-situ leaching at the Cyprus Casa Grande operations. Several factors contribute to changes in the permeability conditions. They are: 1) hydraulically induced fracture development, 2) geochemical changes during leaching in the rock matrix, and 3) changes in the relative degree of saturation of the deposit. Dynamic permeability conditions were evaluated using available pressure and flow rates from the 58 injection and recovery wells obtained over one year period. A finite element, 2-D hydrologic model called INVERT which is designed to estimate aquifer parameters under transient and steady state flow conditions was used for the investigation. The permeability conditions during 7 different steady state intervals throughout the one year time frame were determined. The results confirm that big changes in permeability occur as a function of time as well as a function of injection pressure condition.

Jan 1, 1991

By M. W. Harmer

Laboratory test work, pilot plant testing and plant experience with wet, fine mesh screens is discussed. High frequency, low amplitude, fine mesh, wet screens were installed on the 6th cleaner concentrate stream. These screens produce a 60% oversize recovery split of the molybdenite concentrate that is of leached equivalent quality. The undersize stream is leached with 'hot ferric chloride to remove Pb and Cu contaminates before roasting or shipment to sulfide customers. This plant modification is a good example of using existing technology in an unconventional flow sheet to yield significant cost savings.

Jan 1, 1990

By T. Gouri Charan

Indian coals, which are of Gondwana origin, contain high amounts of mineral matter, wherein the extraneous material was intimately mixed in the coal matrix during the formation stage, causing a high level of impurity in the run-of-mine (ROM) material. These coals possess difficult to very difficult washability characteristics. Beneficiation of high-ash non-coking coals of India has become the prerequisite for improving the overall economics and efficiency of power generation. The use of dry cleaning systems in India for beneficiation of non-coking coals has gaining renewed interest recently. The benefit of the dry beneficiation process is to exploit the given resources while providing a more reliable and consistent quality fuel with a low operating cost. M/S Allmineral has introduced a technique for the dry beneficiation of coal, which is being tried in India for the treatment of high-ash non-coking coals. The first commercial air jig of 50 t/hr capacity was installed and commissioned to beneficiate high-ash coals of 40 x 5 mm feed with an ash content of 40%; a clean coal product of 33% ash was produced and is being used for a sponge iron plant.

Jan 1, 2011