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By Donald M. Keagy

How many times have you said or heard someone say, 'What are you doing right now?" And how many times have you heard the reply, "Breathing air!" Probably never, or at most only a few times in a facetious vein. Breathing air is absolutely necessary to sustain human life, and yet most of us take it completely for granted. Beginning ten to fifteen years ago there was growing concern on the part of the general public that pollution of the air is a threat to man's health and welfare. Concurrently much thought and effort was devoted to the task of defining and resolving the problem of air pollution. In the course of this effort it has become quite clear that our National policy in this regard should be founded upon three basic axioms: (1) Action should not be postponed until emergency conditions make it compulsory; (2) The air cannot be purified after it is polluted, and (3) Air pollution control cannot be accomplished without close cooperation among all levels of government, industry, and the public.

Jan 1, 1967

By J. Iannicelli

An entirely new level of magnetic filtration technology was put into full commercial production by the kaolin industry of Georgia, U.S.A. during 1973-1974. At present, four kaolin producers in Georgia are operating large magnetic filters each capable of processing over 1000 gallons of kaolin slurry per minute or over 65 tons of kaolin per hour on a dry basis. A fifth large filter will go on stream in August, 1975. Four of these units are 84" machines manufactured by the Pacific Electric Motor Company of Oakland, California. When operated at the maximum 1000 g, p. m. rate, these five large magnetic filters have a combined capacity approximating the entire waterwashed coating and filler kaolin produced in the U.S.

Jan 1, 1976

By B. R. Pothini, H. von Schonfeldt

In underground coal mining many excavated openings have a relatively short projected life span. To ensure safety for men and materials at a minimum cost over the projected operating life, only pillars for overburden support and roof bolts for support of the openings are used extensively. Mining activity constantly changes the geometry of the mine producing load changes on the structural support members of the openings that often induce unstable deformations which can lead to roof falls or pillar failures. The paper describes how simple deformation measurements can be used to design primary and supplementary roof supports and to predict roof falls and possibly pillar bumps. Specifically, bed separations in the roof measured directly with the help of borescopes and calculated from differential convergence data are used to optimize bolt links or support requirements for chemical stabilization of mine roofs. Roof falls are predicted on the basis of admissible values for cumulative convergence between roof and floor, convergence rate, and the change of the rate of convergence. The pillar extraction operations convergence anomalies detected from contouring identify bump prone pillars, while convergence and pillar dilation determine the yield zone in a pillar to verify pillar softening and de-stressing. Manuscript not received in time for publication.

Jan 1, 1983

By Dale C. Matthews

Pressure oxidation of refractory gold ores is becoming more popular in our environmentally sensitive society. This paper will discuss some specific process problems and solutions involved with starting up and operating an autoclave circuit.

Jan 1, 1991

By Adolph V. Mitterer

International Minerals and Chemical Corporation operates one of six potash mines in the Carlsbad potash basin. More than 90 percent of America's potash is produced at Carlsbad and IMC accounts for about one-fifth of that amount, Since the Company began operations in 1941 it has mined nearly 50 million tons of ore. Of the two types of ore mined at Carlsbad the principal tonnage is sylvinite in which sylvite-potassium chloride-is the ore mineral. It is produced by IMC as well as by all other mines in the area, In addition to sylvinite IMC is the exclusive producer of langbeinite ore--potassium-magnesium sulfate. From its two ores, International produces a spectrum of 8 high-quality agricultural and industrial chemical products.

Jan 1, 1959

By R. Cooper, K. De Wet, A. Janwong

"Horsehead Metal Products is a zinc refinery in Mooresboro NC treating crude Waelz Oxide (WOX) to produce Special High Grade Zinc by a hydrometallurgical process, comprising leaching, zinc solvent extraction/electrowinning (SX/EW), melting and casting and bleed treatment. Cadmium removal by zinc dust cementation plays an essential role in the bleed treatment circuit to prevent a build-up of cadmium in the circuit. Silica, although not present at significant levels in the WOX feed material (approximately 0.3%), had a significant impact on the efficiency of cadmium cementation with zinc dust, most likely due to the passivation of zinc dust particles with silica gel. Solid/liquid separation efficiency by filter press was also impacted. The silica levels were mapped throughout the circuit in an attempt to identify the source of the silica issues. Adjustments including using PLS as feed to cementation, pH control in WOX leaching and neutralization have been introduced to mitigate the issues created by silica gel in the circuit. INTRODUCTION Located in North Carolina, Horsehead Metal Products Inc. is a hydrometallurgical zinc refinery processing Waelz Oxide (WOX) to produce Special High Grade (SHG) zinc. The flowsheet, known as the Modified Zincex® process, consists of leaching, solvent extraction, electrowinning, melting and casting and bleed treatment as illustrated in Figure 1. Cadmium cementation, part of the bleed treatment process, provides an essential bleed of cadmium from the circuit, as metallic cement. The Cadmium cementation circuit consists of agitated cementation reactors, a zinc dust addition system, filter presses, agitated purification (releach) reactors and a cadmium concentrate filter press Silica can be found in several forms in acid leaching. The first form is fine silicate particles. The size of the particles can vary from one to twenty microns (1). Fine silicate particles can lead to the formation of crud in solvent extraction circuits (2, 3). At Mooresboro, crud has been observed in Depletion, which is part of the solvent extraction circuit. Silica content in the solution in this section is high. The second form of silica is monosilicic acid Si(OH)4, which begins to polymerize almost immediately upon being leached into solution. Monosilicic acid polymerizes to silica gel or a silica precipitate dependent primarily on supersaturation (5). Factors that influence the rate of polymerization include temperature, sulfuric acid concentration / pH, hydrofluoric acid concentration, seeding, and dissolved salts concentration such as zinc and aluminum in the solution (4, 5, 6). In sulfate systems, silica solubility is reported in the range of 150 to 450 ppm of SiO2 (3, 5, 7)."

Jan 1, 2016

By R. L. Lewis

The White Pine Mine is the second largest active underground copper mine in the United States, covering an area of approximately 34 km2 in the Upper Peninsula of Michigan. A numerical flow model of the White Pine Mine was constructed to evaluate engineering controls that would reduce the rate of mine water discharge after closure. Of the passive controls evaluated, the placement of low-flow bulkheads within the mine workings was predicted to offer the greatest benefit, reducing the rate of discharge by as much as 35 percent.

Jan 1, 1996

By Faruk Oksuz, Dave Schiemann, Matt Trotter, Mike Padilla, Miguel Sanchez, Carmen Scalise

"Chicago’s Tunnel and Reservoir Plan (TARP) is a nearly $4.0 billion and over 30 years long program and arguably the largest and longest combined sewer tunnel and reservoir system in the world. Recently, a massive tunnel construction is underway for connection of the McCook Reservoir to the existing TARP tunnel system. Once completed in two stages in 2017 and 2019, the reservoir will hold 38 billion-liters (10 billion-gallons) of combined sewer overflows (CSO) and flood waters from the city of Chicago and over 20 communities in Cook County, Illinois. McCook Main Tunnel will connect Chicago TARP’s Mainstream Tunnel to the McCook Reservoir. Connecting two 10-meter (33-ft) diameter tunnels at 92 meters (300 feet) underground has not been a simple task for the McCook Tunnel Project participants, the project owner U.S. Army Corps of Engineers (USACE), local sponsor Metropolitan Water Reclamation District (MWRD) of Greater Chicago, designer Black & Veatch, and the contractor, Kiewit Infrastructure Company (Kiewit). Yet alone excavating and lining massive size tunnels, the team is also challenged with live tunnel conditions in TARP Mainstream Tunnel that carries CSO and flood flows from city of Chicago which runs full during rain events and must remain in service at all times. The project is a noteworthy feat for engineering and construction with the upcoming installation of world’s largest underground wheel gates for flow control within the tunnel. In this paper, we describe one of its kind elements of this major tunnel system along with key design and construction considerations, specifically for the live tunnel connection which is a rare occurrence in the tunneling industry. INTRODUCTION The McCook Main Tunnel system consists of a 10 m (33 ft) finished diameter and 490 m (1,600 ft) long hard rock tunnel constructed from a 27.5 m (90 ft) diameter and 92 m (300 ft) deep main gate and tunnel construction access shaft. The gate shaft houses six high head 4.4 m by 9 m (14.5 ft by 29.5 ft) wheel gates to be installed in the bifurcated and steel lined section of the tunnel. The tunnel also includes portal and energy dissipation structures as it daylights into the reservoir."

Jan 1, 2016

By D. A. Knight

The property is located in the Porgera Valley 600 Km North West of Port Moresby. The remote location is 2500 m above sea level. The mine area has 3,600 mm of annual rainfall and a temperate climate with temperatures ranging from 10" C to 22° C throughout the year. Alluvial gold was reported in the Porgera area in 1938 and has been an important source of revenue for the area for many years. Intermittent exploration was carried out until the 1960's when Placer (PNG) Pty. Ltd. with Mt. Isa Mines commenced an extensive exploration program. The property was brought to production in 1990 by the Porgera Joint Venture group consisting of Mount Isa Mines Ltd, Rennison Goldfield Consolidated Ltd. and Placer Dome Inc, each with a 30% ownership and the Government of Papua New Guinea with a 10% share. Placer Dome Inc. is the manager of the property with construction under the direction of the Placer Dome Technical Services group.

Jan 1, 1992

By L. E. Bowman

Efficient filtration of fine kaolin particles plays a crucial role in processing of raw kaolin to a marketable product. Oftentimes, filtration Is the rate controlling step of the whole process. As a consequence, plant production is dependent, to a great extent, on the rates being achieved In filtration. In order to alleviate the bottleneck in production, Nalco Chemical Company initiated a reagent development program to chemically enhance the performance of the filtration units. Filler aids of different classes were synthesized for evaluation. These include reagents whose primary mode of functionality were: coagulation, flocculation, thickening, and combinations of the preceding. All reagents that were synthesized and tested were listed under the appropriate Food and Drug Administration sections of the Code of Federal Regulations. This paper discusses the development and application of a new reagent that Improves the filter production rate with minimal Impact on filter solids. The results of laboratory filter studies along with plant data are presented and discussed. Plant data indicate that this reagent is capable of increasing production rates by as much as 35% on various clays of coarse particles to the finest fractions, as well as clays that are calcined. The reagent's Impact on solids content, re-slurrying characteristics, Brookfield and Hercules viscosity, and drying is within the standards set by plants who have evaluated and now use this product.

Jan 1, 1993

By A. Jolly, A. R. Kumar, T. Novak

"Coal dust in an underground mining environment has always been a health and safety issue, especially with longwall faces. Efforts to integrate a flooded bed scrubber within a longwall shearer are underway at the University of Kentucky (UK) in order to reduce worker exposure. Small scale physical modeling, along with numerical modeling and full-scale experimentation, are engineering tools being used by the authors for simulating operating conditions underground. Recent advances in affordable 3D printers offer a means for fabricating accurate, scale models for obtaining timely insights prior to building large, expensive test setups. Comparing scale-model results with those of numerical modeling, such as computational fluid dynamics (CFD), lends guidance and confidence in a proposed design. This paper discusses the small scale physical modeling of a longwall shearer with an incorporated flooded-bed dust scrubber in its operating environment. A tracer gas was used in the model in lieu of dust to measure dust-capture efficiency. Results obtained from the physical model are presented and compared with those of CFD model. The small scale model and the CFD results demonstrate good agreement. Dust capture results show the usefulness of the approach in advance of actual design implementation. INTRODUCTION Dust generation is an undesirable, but innate, byproduct of all mining processes. It is particularly problematic in underground coal mining, where coal dust poses potential hazards from two fronts – health and safety. Coal workers’ pneumoconiosis (CWP), commonly referred to as black lung, is a chronic lung disease that results from the long-term overexposure to respirable coal dust. Although the prevalence of CWP has steadily and significantly declined over the three decades following the Federal Coal Mine Health and Safety Act of 1969, a study by the National Institute for Occupational Safety and Health (NIOSH, 2008) indicates that significant health hazards associated with respirable dust still exist within the coal mining industry. In addition to being a health hazard, coal dust can also create a potentially catastrophic safety hazard. Dust that is not captured or removed at its source is suspended and transported throughout a mine by the ventilation airstream. This float dust is subsequently deposited on all mine surfaces along its travel path. Without adequate application of rock dust to these surfaces, forces from a localized methane ignition can reintroduce settled coal dust into the airstream creating an explosive mixture. Therefore, capturing and removing coal dust at its source mitigates the probability of two major hazards that continue to plague the mining industry."

Jan 1, 2016

By F. Schreiter

"One method to increase the exploitation rate of a mine is the use of backfill with residual materials in exploited areas. The backfilled material is meant to support both, the walls of galleries and pillars as well as the roof of mining openings. With increasing depth, the exploitation rate diminishes fast, thus the application of backfill in order to change the layout of the mine is crucial for economic success. In result of using backfill, it is possible to change the layout of the working area with a higher ratio to excavated areas and less area occupied by pillars. Thus it is possible to boost the output of a mine by using backfill. Setting the criteria for the selection of the best possible materials and whose improvement, it is useful to know about their qualities and handicaps. The Mining Department at TU Bergakademie Freiberg is analyzing the parameters of residues from different processing methods, accrued in plants of different potash mines and blending different residues for optimization of material attributes. These were significantly characterized by basically parameters like the size and the distribution of different diameters of the grain material. INTRODUCTION The chair for underground mining methods at TU Bergakademie Freiberg is tasked with the sufficient and sustainable supply of economics with raw materials. The steady high demand, the rising prices and the finiteness of the deposits are reasons for the need of an optimized economic utilization of natural deposits, a continuous improvement of mining technics and technology. From an ecological and economical position the best possible utilization of the resources has to be achieved. Many mining operations are by reasons of the deposit not able to haul valuable minerals only, they have to haul a mixture of valuable minerals and waste rock. This hauled combination is given into the processing plant for separation and enrichment of the valuable mineral. The residuals of the processing are commonly dumped to a waste rock pile. For minimizing the size of such a waste rock pile and also minimizing the ecological footprint of a mining operation the only way is minimizing the quantity of accruing waste rock material. Both, optimization of economic utilization and also minimization of waste rock dumps can be realized in one by backfill with processing waste rock material in mined out areas. Especially in mines, mined by room and pillar method, smaller dimension of the pillars are sufficient for safety and stability. By the way less valuable minerals have to be leaved back in the mine and the mine outcome is increasing."

Jan 1, 2015

By Kim McKnight

Dupont has successfully incorporated a Floatex Density Separator into its wet-gravity operations for the recovery of zircon from titanium tailings. Results indicate that the Floatex achieved a zircon recovery of approximately 95% while rejecting similar amounts of quartz and other gangue minerals. Additionally, a unit capacity approaching 16 tonnes/hr/m2 was achieved. Results also show that the alumino-silicates can be separated into other product streams that will further improve process economics and minimize waste material. The improved plant feed grade provided by the Floatex has allowed for either an increase in overall plant capacity and/or final product grade. This paper will present the findings from the in-plant study.

Jan 1, 1996

By C. Sun

Due to unfavorable geological condition, excessive deformation of mine drifts occurred in a large underground copper and nickel mine. In searching for a solution, a comprehensive underground monitoring program was implemented and the opening convergence and the surrounding rock deformation were monitored. A large number of field data were collected and thoroughly analyzed. The convergence and deformation as function of time and depth were determined and a rock stability index was proposed. Based on the deformation-time and deformation-depth relations, critical deformation times and locations were identified and defined as characteristic values to be used for mine opening and support designs. The characteristic values are critical in the application of two-step supporting system, and the determination of support parameters. The application of the method developed in this study has demonstrated that this practical approach in support design and installation is effective. With the two-step supporting system, a long-term drift stability can be achieved in the mine.

Jan 1, 1998

By L. Bomvisinho

As a result of today?s requirements for larger mills with higher power demand, and in order to cope with maximizing throughput, and optimize grinding efficiency, the minerals industry is increasingly relying on the robust Gearless Mill Drive (GMD) solution. This paper describes the new features introduced with the revolutionary ABB drive controller for Gearless Mills, and explains the benefits this can bring to the operation. Extensive surveys have been performed with GMD users to gather suggestions and understand the market wishes. As a result the new driver controller capabilities and functionalities focus on safety, high availability, operational flexibility and remote diagnostics.

Jan 1, 2010

By J. M. Ekenes, C. A. Caro

"New approaches that increase hydrometallurgical recovery from refractory minerals in below mill cutoff -grade sulfide copper ore can add significant value, improve profitability and increase ore reserves. This paper describes the development and implementation of an engineered heap (EH) approach to leaching low-grade, chalcopyritebearing ore at Freeport-McMoRan’s mine in Morenci, AZ. The technical evolution of the engineered heap concept is described together with the challenges and benefits following implementation. Introduction The Morenci ore deposit, located in eastern Arizona, has been mined for copper for 140 years. Mineralization in the Morenci district consists of sulfides and oxides. To process these ores, Morenci operates concentrator and leaching circuits. Leaching accounts for two-thirds of the copper produced in Morenci. More than one-half of this leaching-derived copper production comes from run-of-mine (ROM) stockpiles. The largest category of material moved in Morenci is destined for ROM stockpiles and waste dumps. Materials that are not economic to mill or leach are designated “waste.” However, this designation can change based on improvements in extraction technology and commodity prices. Chalcopyrite does not leach well due to its refractory nature. For predominant chalcopyrite mineralized ore, copper recovery during a typical leaching cycle may be as low as 5%. For this reason, chalcopyritedominant ores below mill cutoff grade have historically been classified as waste. By incorporating advanced leaching technology to improve metal recovery from previously leach-resistant ore types such as chalcopyrite, the Morenci Mine has been able to reclassify substantial amounts of this “waste” to “ore.” Process chemistry Chalcopyrite copper extraction is temperature, oxygen and ferric dependent. The temperature is achieved primarily by pyrite oxidation (Eq. (1)) and secondarily by oxidation of chalcopyrite itself (Eq. (2)). The regeneration of ferric in solution can be enhanced by providing the appropriate acid and oxygen levels according to Eq. (3). In the absence of microorganisms, this reaction is very slow."

Jan 1, 2015

By Fabiola Espinoza Carmona, Elena Chiriotti, Edoardo Misano

"INTRODUCTION Ganntas Tunnel is part of the modernization project of the railway between Alger and Oran, in Algeria. In order to double and rectify the existing line between El Affroun and Khémis Miliana, the alignment foresees the excavation of a 7 km-long twin tunnel. The excavation works started in June 2011 with the contractor CCECC, under the supervision of SYSTRA. Excavation is driven in conventional method by hydraulic hammer simultaneously on 8 different faces since excavation was started also from a junction window towards the middle of the tunnel. The minimum longitudinal distance to be respected between two contiguous tunnel faces has been set to 30 m. The tunnel cross-section is a 70 m² oval shaped profile, temporary support consists of shotcrete, bolts and steel ribs. A 30 to 50 cm thick cast in situ concrete final lining has been provided as well. When the tunnel reached a fault zone in soft clayey marls extreme squeezing occurred, works were stopped and re-profiling operations were carried out along more than 100 m. To date, works proceed at slow rate since high convergences are still monitored and completion of works is not expected before December 2016.GEOLOGY The project is located within the Tellian Atlas mountain area, including in particular the Djebel Ganntas massif in between Mitidja and Chleff plains. Djebel Ganntas is characterized by an extensive massif aligned in East-West direction with smooth slopes made of soft clays that emerge in multiple cliffs and ravines. On the top of it, along the edge, a more recent sandstone formation is found. The existing data on the geology did not allow to establish an accurate geological model at tender stage. In-situ investigations allowed at design stage to identify a Quaternary alluvial cover of clays and gravel, followed by a Miocene stratum divided in a sandy top layer and a lower clayey layer. From a structural point of view, geological maps suggest a north direction dip of layers, but the in situ surveys showed that layers were highly folded. The lack of information at tender stage on the structure of the geological series should have triggered an extensive investigation campaign at detailed design stage which did not take place causing serious consequences on costs and time at construction stage."

Jan 1, 2016

By QU Hong-lue, YANG Lin-han

Aiming at the subjective impact caused by subjective weighting method in the establishment of rockburst risk attribute identification and prediction model, the combined weighting method was introduced to eliminate the influence of unreasonable weight of each index. Eight discriminant indexes affecting the risk of rockburst were selected. Through the literature review, relevant rockburst cases were collected and 8 index rockburst sample sets were established. A variety of machine learning methods were used to analyze the feature importance of discriminant indexes in the samples, and then to determine the objective weight values of different methods. Combined with the subjective weights determined by the Analytic Hierarchy Process, the combination of weights were successively carried out. Based on the attribute recognition theory, the combination weights with different objective weight methods were established to identify the rockburst risk attributes, and verified by the confidence criterion. The results show that the objective weight value determined by the feature importance analysis of machine learning reduces the subjectivity of the weight of Analytic Hierarchy Process method, improves the prediction accuracy, and makes the prediction result closer to the fact.

Apr 26, 2022

By F. Warnaars

Historically, this area produced gold and silver from many well-known vein deposits, like Tayoltita, Topia, and San Jose de Gracia. Modern exploration identified three categories of deposits: 1) low grade porphyry golds in shallow level dacite porphyries; 2) batholith-related deposits; and 3) those formed in volcanic sequences of Late Cretaceous to Late Tertiary. At least four porphyry golds have been identified, of which Metates is best known. These are formed by and within dacite porphyries, associated hydrothermal breccias and sometimes within surrounding metasediments. Their ages are from mid-Cretaceous to Early Tertiary. Precious metal deposits associated with batholiths occur as veins, contact haloes in metasediments or volcanics, skarns, tectonic breccias, hydrothermal tourmaline breccias, dacite dikes or as disseminated or stockwork deposits such as La Fortuna. Several new gold discoveries were made in older Early Tertiary Volcanic Sequences and in the younger Tertiary volcanics within prominent structures exceeding 3 to 5 km in lengths. Some of these are open-pittable but most have to be mined by underground methods.

Jan 1, 1999

By J. M. Hird

By blending phosphogypsum with thickened mill clays, Texasgulf has successfully resolved the problems of gypsum disposal and reclamation of mined-over areas. In the process, clays are thickened to 10% solids through high rate thickeners, mixed with gypsum from a drained gypsum pile (75%) and a direct discharge from belt filters (25%), then pumped to mined-over areas. The blending of clays and the low pH gypsum yield a mixture with a pH of about 7. Dewatering is rapid to 40-45% solids within 3 months. The material spreads with very shallow slopes and within a year desiccation by high flotation ditching equipment is possible. The artificial soil is classified as a silty loam in texture, lacking only in nitrogenous nutrients. The soil material has proven to support many field crops including small grain, corn, alfalfa, and grasses. Sycamore, green ash, sweetgum and bald cypress have done well in 3 years of growth. The nitrogen source for tree growth will be made up through an alfalfa cover.

Jan 1, 1993