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By Bror Nyman

Wide settlers are a way to decrease the linear velocities of advancing liquid phases. It has, however, been found unnecessary to risk a proper settler performance by building shallow settlers in order to avoid a so-called interface turbulence due to a too big difference between the linear velocities of the organic and the aqueous phase. This conclusion has been reached from tests using a large transparent settler model, where the behaviour of a clean interface between two advancing liquids has been investigated. Also in a more realistic case, making an organic in aqueous or an aqueous in organic dispersion to move between the liquid phases, no obstacle has been found to use a somewhat more deep and correspondingly ore slowly t10wing aqueous phase. Based on above findings, support can be given to a new trend to build the settlers slightly deeper than what has been typical for the so-called low-profile design. In this way, it is much easier to avoid an excessive air introduction and other severe difficulties, like those caused by crud moving from one stage to another. It is further shown, how gravity can be used to slow down and distribute a dispersion being fed into a settler of a VSF unit. Entrainment levels have been found to be reduced by a careful design of primary dispersion distributors and picket fences of the settler. Finally, it is demonstrated, how outlets from the side of the settler can be used to simplity interstage pumping and to decrease the rotation speed of any pumping device.

Jan 1, 1996

By W. F. McDermott

The Iron Ore Industry has perhaps seen more varied and drastic changes in its approach to crushing and grinding in the last 5 years than any of the other mineral industries, Multimillion ton per year plants have become common place. Centralized control and computers have become an established benefit. Autogenous grinding along with a variety of rod and ball grinding flowsheets are in use. This morning I will discuss a few of the more important and new concepts in the control of these crushing and grinding circuits.

Jan 1, 1970

By Raymond Mancha

"Conventional" coal dryers really do not exist. What we really mean to say is that there are many and varied kinds of coal dryers -- and the "air handling problem" is really the only portion of it which has been approached for solution by conventional methods. It now appears that these conventional methods need supplementing by some new, relatively unconventional apparatus. In order to approach this matter with mutual understanding, here is a quick survey of the coal drying art. Figure #1 shows a McNally Pittsburgh Pulso Dryer, In the McNally Pulso Dryer, the coal is fed-onto the screen by a rotary feeder assuring even distribution of the coal. As the coal travels forward due to the action of the screen, it is subjected to a controlled pulsating flow of hot gases. T ese originate below the deck and are directed up through the moving bed of coal. Fines sifting through the deck are dried in the hopper below the screen as they fall through the hot gases to an evacuation screw. The coal remaining on the screen is dried to the desired degree when it reaches the discharge end. At this point, it is directed down into the evacuation screw to combine with the fines, or it may be discharged as a separate product. As the coal travel down the screen, it is subjected to intermittent upward currents of hot gases. These first distend the bed allowing the gases to come into intimate contact with the coal particles for rapid and efficient heat transfer. Then, as the flow of gas is cut off, the bed settles and the extreme fines sift through the screen preventing their being carried away into the exhaust system.

Jan 1, 1958

By Eleanor Kentish, Nathan Bond, Edward Batty, Simon Webber, Alan Skarda

"Crossrail is Europe’s largest construction project — a new 100km rail route running through central London. A joint venture of BAM, Ferrovial and Kier (BFK) has constructed the tunnels and escalator shafts at the new Bond Street and Farringdon Stations. The recent trend in the UK industry towards sprayed secondary linings is driven by the potential for significant savings in cost and time. BFK is unique within Crossrail by constructing both sprayed and cast secondary linings. This paper presents a direct comparison between sprayed and traditional cast in situ secondary linings at Bond Street and Farringdon Crossrail Stations. An objective comparison is drawn between procurement and mobilisation periods, production rates, flexibility, tolerances and logistics in the tunnels. The technical challenges surrounding cast and sprayed secondary linings are explored, and recommendations are made of how each method could be improved for future use. INTRODUCTION It is well established that sprayed concrete offers a fast and effective method to seal the face of an excavation. In a relatively short space of time, sprayed concrete can be applied to an open face to support the short term ground loading on the tunnels during construction. Advances in sprayed concrete lining (SCL) technology — such as the use of wet mix processes, improved accelerators, fiber reinforcement, remotely controlled spraying robots, innovative surveying equipment and nozzleman competency schemes — have greatly increased the speed and safety of tunnel excavations using this technique. As a result, design engineers have become increasingly confident to use SCL primary linings as part of the permanent structural lining (Su 2014). Historically, long term ground and water pressure loads have been considered to be carried by the main structural or secondary lining, constructed using cast in situ concrete (Pickett 2014). However, the advances described above have made sprayed secondary linings a viable option, which has already been proven on the A3 Hindhead Tunnel (Arnold 2012). Sprayed concrete secondary linings offer potentially significant savings in cost and time during the construction process. The contractor does not need to procure a bespoke formwork system for each different sized tunnel — the SCL plant required is already on site for the primary lining. Each bay is sprayed with accelerated concrete, becoming self-supporting almost immediately — compared to moving and resetting the shutter, pumping concrete and waiting for it to cure. With sprayed concrete, working sequences and cross sections can easily be changed."

Jan 1, 2016

By B. Y. Wong

In April 1989, Southern Company Services signed a 3.5 year contract with DOE-PETC for generic engineering development of an advanced physical fine coal cleaning technology known as selective agglomeration. This technology offers the potential for significantly higher pyritic sulfur removal (90% +) than conventional coal cleaning (30 to 50%) while maintaining high Btu recovery (90% +). Engineering development will include bench-scale process development; component development; adaption or modification of existing unit operations; proof-of-concept (POC) module design, fabrication, testing and evaluation; and small commercial facility conceptual design. The information obtained during POC operation will be sufficient to result in a technical and economic design base that can support construction and operation of a small commercial plant. The major goal of the research is to develop selective agglomeration technology to achieve 90% pyritic sulfur removal while operating at Btu recoveries above 90% based on run-of-mine quality coal. This objective will be accomplished in two phases: Phase 1 -bench-scale and component development, and Phase 2 -POC module operation and conceptual design of a small commercial plant. Currently, work is proceeding under Phase 1 (Tasks 1-7) of the project. A review of the status of Tasks 1-7 is presented in this paper.

Jan 1, 1991

By John E. Litz

Since the 1974 introduction of catalytic converters to automobiles in the United States, more than 150,000 kg (5,000,000 oz) of platinum, palladium, and rhodium have been used in the converters. An estimated 8 to 10 million converters are being used annually in the United States, each containing from $5 to $15 of PGM metals. In addition, use of converters is beginning in Europe which will significantly increase the quantity of PGM used. Two basic types of catalysts for converters are being used: pellet and monolithic. The pellets are small, discrete spheres or cylinders of gamma-alumina coated with platinum group metals, Figure 1. The monolithic are honeycombs of a cordierite, A13(Mg,Fe)2Si5AlO18, base coated with gamma-alumina and subsequently with platinum group metals, Figure 2. Pellet catalysts are being used by General Motors and American Motors; whereas Ford and Chrysler are using monolithic catalysts. The table below compares the PGM content and value of the catalysts.

Jan 1, 1986

By M. R. Shahan, W. R. Reed

A laboratory apparatus (shield dust simulator) was designed and constructed to simulate the dust generated during the advance of longwall hydraulic roof supports, or shields. The objective of the study was to develop a tool that could be used to test the hypothesis that foam applied to a mine roof prior to a shield advance could be used to reduce the respirable dust generated during shield advances. This paper will outline the design parameters for the development of the system, as well as describe baseline testing of coal and limestone dust. Results show the average instantaneous respirable dust concentrations that occurred during simulated shield advance. Confidence intervals were calculated from the instantaneous respirable dust data to determine the repeatability of the data produced by the device. INTRODUCTION During longwall mining, miners can be exposed to respirable dust that is generated during the advance of hydraulic roof supports or shields. National Institute for Occupational Safety and Health (NIOSH) researchers have conducted numerous surveys of longwall mining operations, benchmarking the operating practices and dust control measures in use. It has been determined that the shields are responsible for 27% of the respirable dust that is generated on the longwall face [1]. The dust generated by the shield advances ranks second, next to the longwall shearer which is accountable for 43% of the respirable dust generated on the longwall face. The respirable dust generated during the advance of the shields can be a significant contributor to the respirable dust exposure of the mining personnel operating at the longwall face, especially since some of this dust is generated in the walkway. Control systems designed to reduce the dust levels generated during the shield advance have the potential to greatly reduce the respirable dust exposures of the personnel downwind of these activities. One control technology to decrease the dust generated by the shield advances would be to apply a layer of foam to the forward shield-roof interface prior to the shield advance [2]. The blanketed layer of foam would interact with the material located on the top of the shield during the advance, preventing a portion of that dust from becoming entrained in the mine air. This layer of foam would be applied using a foaming nozzle located on the longwall shearer body that would spray foam on the roof surface as the shearer passed. Substantial laboratory work has been completed to determine the feasibility of this type of foam application. NIOSH engineers have classified the various characteristics of foaming agents, using foam expansion ratio and drainage as important properties, as well as developed the mechanical systems required to apply the foam safely to the mine roof [2, 3]. The construction of an apparatus that could simulate the mechanical interaction between the dust-laden shield top and mine roof was necessary to adequately test the hypothesis that foam could be an appropriate control. A team of engineers designed and constructed a shield dust simulator system allowing for in-house testing prior to a full-scale field investigation.

Jan 1, 2019

By R. C. Bunge

The success of a mineral separation is commonly assessed from the separation curve, a graph of the recoveries achieved versus the corresponding separator settings. Two values characterize the curve, first the "splitpoint" which is the separator setting that produces a recovery of 50%, and second a measure for the separation sharpness. The splitpoint represents the "mean" while the measure for the separation sharpness represents the "scatter". In modelling the performance of crossflow separations the mean particle behavior is calculated from the force equilibrium that determines the particle trajectory which leads to a deterministic model. The scatter is then represented by a stochastic model. This presentation discusses the modeling of a crossflow separation and some implications with separation theory. The model is shown to successfully predict the performance of a magnetogravimetric separator.

Jan 1, 1992

By Ehsan Alavi, Sanjeer Yogendran, Savreet Singh

The Don River & Central Waterfront Coxwell Sanitary Bypass Tunnel Project in Toronto extends approximately 10.5 km from Ashbridges Bay Treatment Plant west under Lake Shore Boulevard, north under Bayview Avenue and east through the Don River park area to the Coxwell Ravine Park. This project includes the installation of five intake shafts connected by 10.5 km of 6.3 m internal diameter tunnel and eleven drop shafts and vent shafts, connected to the tunnel by a series of adits. During the excavation of one of five intake shafts (20 m in diameter and 52 m deep), significant volumes of free phase oil and hydrocarbons were encountered. Due to the heavy inflows of the contaminants, excavation was stopped at the transition depth. The initial support of excavation needed to be redesigned, shaft had to be backfilled with CDF and installation of deeper secant piles are in progress to cut off contaminants. This paper outlines the initial plan for excavation as well as the design changes to the plan. The current status of the shaft excavation and lessons learned will be discussed.

Jun 13, 2021

By Matthew Preedy, Anthony Pooley, Mike Wongkaew, Dirk Bakker, Raghu Bhargava

Sound Transit’s ST3 program will add 62 miles of light rail to the Puget Sound area, including connections to the neighborhoods of West Seattle currently anticipated by 2031 and Ballard by 2036. These connections include considerations for both elevated and tunnel alternatives, as well as a new downtown tunnel for which different configurations are being considered with potentially very different construction logistics and risk profiles. This paper describes the latest developments in the ongoing evaluation process that will inform the consideration of different tunnel and station construction methods, technical and operational challenges and contracting methodologies, including construction of deep stations in dense urban environments.

Jun 13, 2021

By L. Yuan, J. Soles, D. Bahrami, W. Tang, R. Thomas

Mine equipment fires remain as one of the most concerning safety issues in the mining industry, and most equipment fires were caused by hot surface ignitions. Detailed experimental investigations were conducted at the NIOSH Pittsburgh Mining Research Division on hot surface ignition of liquid fuels under ventilation in a mining environment. Three types of metal surface materials (stainless steel, cast iron, carbon steel), three types of liquids (diesel fuel, hydraulic fluid, engine oil), four air ventilation speeds (0, 0.5, 1.5, 3 m/s) were used to study the hot surface ignition probability under these conditions. Visual observation and thermocouples attached on the metal surface were used to indicate the hot surface ignition from the measured temperatures. Results show that the type of metal has a noticeable effect on the hot surface ignition, while ventilation speed has a mixed influence on ignition. Different types of liquid fuels also show different ranges of ignition temperature. Results from this work can be used to help understand equipment mine fires and develop mitigation strategies.

Mar 2, 2022

By Nathaniel Herz, R. J. Adamson, C. M. Romanowitz, Frank W. Jr. McQuiston, C. D. Hoyt, Robert S. Shoemaker, P. H. O’Neil

1. INTRODUCTION In this section, precious metals are defined as gold, silver, and the platinum group metals comprised of platinum, palladium, iridium, osmium, and rhodium. If the first three years of the 1970's are the criteria, gold, silver, and platinum seem destined for a bright future. Gold advanced in price from the historic figure of $35 established in 1934 to over $100 per oz (1973). For the five years 1966 to 1970, silver consumption exceeded production by about 50%. The silver price appears to be definitely on the uptrend, and a price of over $3 per oz seems probable. On this basis (at 1964 costs) the United States has an estimated 5 billion oz of unmined silver. The fresh burst of interest in platinum with a surge of renewed price strength (end of 1972) is due to the activity in the automobile emission control area, where platinum re¬mains the front runner in the catalyst area. Some international financial experts believe that governments will not rush into reform of the monetary system, and "Special Drawing Rights" (SDR's) will gain increased standing as international mone¬tary reserve assets. Gold will continue to be reviewed as the ultimate store of value and will remain the global monetary base. Devaluation of the U.S. dollar caused by imbalance of import payments over ex¬ports is the basic reason that the price of gold will likely remain above the $90 per oz figure for the balance of the 1970's. Gold and silver usually occur intimately associated, and recovery methods are often closely related; however, they were assigned sepa¬rate chapters, because the major production of each metal is from ore deposits classified as either gold or silver. For example, the gold ore occurrences in South Africa, the world's leading gold producer, have a ratio of gold to silver of approximately 10 to 1. The ores at the Homestake Mine, Lead, S.D., the largest U.S. gold producer, are predominantly gold with a ratio to silver of approximately 5 to 1. Silver in each example is a byproduct. By this same classification, the largest U.S. silver producers are the silver ores of the Sunshine, Galena, and Lucky Friday mines in the Coeur d'Alene district, Idaho. However, the largest single-mine silver producer in the Free World is the Kidd Creek Mine at Timmins, Ont., where the occurrence is with sulfides of copper, lead, and zinc. Thus, the major gold production of the world is derived from those ores classified as gold ores; whereas, less than one-half of the silver production is from silver ores, and only a small percentage of the silver production is from gold ores. 2. GOLD Gold, the noblest of metals, has been mined for thousands of years. Its chemical symbol, Au, is derived from the Latin "aurum," meaning "shining dawn." A precious substance because it is one of the rarest metals, it has unique physical properties: it does not tarnish; it exceeds all other metals or alloys in malleability and ductility; it is a good conductor of electricity and is one of the most nonreactive metals. Its greatest strength is its indestructibility. It is the only metal mined at depths exceeding 10,000 ft. Since the early 1800s, its chief role has been as a medium of exchange, providing the basis for interna¬tional trade. In the past 15 years, however, gold has emerged as a useful industrial commodity. This role has been fortified by the estab¬lishment of a two-tier pricing system which maintains monetary gold prices at an established U.S. Government price, with industrial gold being priced higher by the free-market system. Occurrences and Production Native gold furnishes most of the world's production, since gold forms stable natural compounds with few other elements. Neverthe¬less, the metal is widespread with traces of it found in seawater and in the ashes of plants and animal material. Next to the native metal, the tellurides have been the most important gold-bearing minerals; these include calaverite, krennerite, slyvanite, hessite, and nagyagite. Native gold is invariably alloyed with more or less silver, but it is exceptional to find any other metal in the alloy. It is found in veins associated with quartz, calcite, alunite, other gangue minerals, and with various sulfides. Sulfide minerals in order of frequent associa¬tion are: pyrite, galena, chalcopyrite, sphalerite, arsenopyrite, tetrahe¬drite, and pyrrhotite. Small amounts of metallic gold are commonly disseminated through such sulfides. When considerable amounts of silver occur in gold, the mineral electrum is formed. In a few deposits, gold and mercury form natural amalgam. Native mercury is formed by weathering from cinnabar and other mercury minerals. Among the minerals sometimes mistaken for gold, pyrite, marcasite, and especially chalcopyrite may be men¬tioned. The flakes of biotite and other micas, especially when partially oxidized, also may imitate it closely. World gold reserves never have been estimated carefully. Esti¬mates indicate that present world reserves approximate I billion oz, of which about 60% occurs in South Africa and 20% in the USSR. World gold output is dominated by South Africa which produces two-thirds of the world's production from reserves that are adequate to maintain existing output levels. South African gold output comes from approximately 50 large underground operations that mine and mill 70 to 80 million tons of ore annually to recover 30 to 32 million oz of gold. The USSR is the second largest gold producer, followed by Canada and the United States (see Table 1). Gold production in the United States and Canada rose to high levels in the 1930's, following the increase in price from $20.67 to $35 per oz and with an abundance of good labor due to depression in other industries. Production of over 10 million oz in 1940 was behind only that of South Africa. World War II caused a precipitous drop in gold output due to the imposition of War Production Board Limitation Order L-208 issued in October 1942, which caused over 9,000 gold mines in the United States to shut down, most of which never reopened. The U.S. Treasury, which suspended purchases of newly mined gold in 1968, had been the sole buyer of U.S. produced gold since 1934. This created the two-tier pricing system, and in March 1972 the President signed into law a bill authorizing a $3 increase in the official price of gold to $38 per oz. In February 1973 the President ordered a second devaluation of the dollar, amounting to about 10% which raised the official price to $42.22 per oz. The erratic development of the gold market, which has seen the

Jan 1, 1985

By W. S. Hannan

History Leaching of sulfide ore was first attempted by the Phelps Dodge Corporation about 1900 at Bisbee, Arizona, when Dr. James Douglas conducted experiments in an attempt to apply the leaching techniques then in use at Rio Tinto, Spain. Although this initital attempt was unsuccessful, research work was continued which culminated in successful leaching operations at Tyrone, New Mexico, in 1917 and at Bisbee beginning in 1920. Leaching has continued intermittently since that date, with material from the Lavender Pit being leached today. The Lavender Pit Leach Dump Stripping for the Lavender Pit was started in 1951, with mining operations on stream in 1954 and continuing to the present. All material removed from the pit has been classified as waste, leach material, milling ore, or direct smelting ore, depending upon grade and degree of oxidation. Lavender Pit leach material has been stockpiled in a single dump, called No. 7 Dump. This dump covers an area of approximately 135 acres and average about 300 feet in height. The dump has been deposited over a period of 20 years by truck haulage and contains several layers, each of which has a permeable boulder layer at the bottom and a compacted layer at the top. Leaching of Lavender Pit material was started in 1956 and has proceeded simultaneously with dump construction. Former leach pond areas and haulage surfaces have been ripped with D-9 tractors before deposition of succeeding layers of ore.

Jan 1, 1972

By Richard C. Corson

The objective of blending materials in a bedding pile is to reduce the variation in successive samples taken from the materials to be blended. In designing a bedding and reclaiming operation, several mechanisms are available to effect the reduction of variability, or increase in homogeneity, of the materials. These mechanisms can act before stacking, in the stacking process, in reclaiming and after reclaiming. In evaluating alternative methods of stacking and reclaiming, the potential user must judge each method on the basis of certain criteria; the capital cost of the equipment, the allowable absolute variability of the reclaimed product and the effectiveness of blending. Several stacking and reclaiming methods have been tested using a computer simulation. Based on the results of this program, factors were developed to describe the effectiveness of blending for chevron stacking of discrete materials and preblended materials, bucket wheel reclaiming and drum reclaiming. From these factors, the total effectiveness of a combined stacking and reclaiming system can be determined.

Jan 1, 1985

By H. E. Rutherford

Monterey Coal Company has begun a geologic monitoring program in order to better understand our in-mine geologic conditions and to apply the knowledge gained to our mining operations. Two methods are used to collect information. The first is a monthly examination of conditions throughout the mine using a rapid mapping technique. The second is the detailed mapping of specific events encountered during mining such as faults and roof falls. The data gathered from both methods is correlated with operational statistics to create a geologic/production database. From the database, a monthly evaluation of mining conditions is made. Also, the database has proved useful in such areas as forecasting roof conditions and examining how faulting has affected mining operations.

Jan 1, 1984

By C. Hendricks

This paper is based upon field studies conducted in a western Canadian open pit coal mine. This work has involved the adaptation of microprocessor-based instrumentation to monitor various operating parameters on-board blasthole drills and mining shovels. A review of instrumentation and monitoring methodology will first be presented. Based upon experience from field-based studies, the paper will subsequently focus on the application of monitoring technology within the framework of an integrated Equipment Monitoring System. Such a system will permit the real-time performance evaluation of key equipment involved in surface mille production.

Jan 1, 1991

By Dwight K. Smith

Fly ash as an additive for oil well cement was introduced to the oil industry by the Halliburton Company in 1949. Since its early usage in the Illinois area of the U. S., the total amount of fly ash pumped into wells has exceeded 30 million sacks, The advantages of using fly ash-portland cement mixtures in wells are fundamentally the same as for concrete except the conditions of placement and curing are variable and the nomenclature of properties are expressed somewhat differently. In some instances deep wells have been cemented with mixtures of fly ash and hydrated lime together with an activator which functions as a catalyst for setting. This fly ash-lime formula has many advantages for high temperature-pressure conditions found in wells.

Jan 1, 1968

By John C. Stankus, Xiaoting Li

"Underground structures such as square/arch steel sets, king beam structure, etc. are widely used for the roof support in underground mines. In designing and calculating the required carrying capacities of these underground structures, how to identify the potential rock loads on the structures over long term is a challenging question for ground control engineers. Based on design practices of both surface and underground structures, the authors have designed and applied appropriate load factors in underground structural design projects to accommodate different rock types, entry/intersection dimensions, roof geologic conditions, availability of roof bolts and water, etc. Classification of load (reduction) factors for large-span underground intersections are presented for reference. Success of designed underground structures in effectively controlling roof stability over years indicates the applicability of the load factor concept for underground structural design, and its same significance as of the load factor specifications in ASCE/SEI 7-10, ANSI/AWC NDS (2015), and AASHTO LRFD Bridge Design Specifications (2012). The load factor concept will facilitate ground control engineers to appropriately utilize popular structural design software, such as RISA-3D or -2D to efficiently design and analyze underground structures.LOAD FACTORS IN STRUCTURE DESIGN APPLICATIONSIn structures, loads cause stresses, deformations, and displacements. Assessment of their effects is carried out by the methods of structural analysis with the help of load factors. Loads can be increased or decreased by load factors to meet the requirement that design strength be higher than maximum loads. For example, in designing a staircase, a dead load factor may be 1.2 times the weight of the structure, and a live load factor may be 1.6 times the maximum expected live load based on the Load and Resistance Factor Design (LRFD) method. These two “factored loads” are combined (added) to determine the “required strength” of the staircase. Some typical load (adjustment) factors used for structural design are as follows:"

Jan 1, 2019

The capability for on-line measurement of the quality characteristics of conveyed coal now enables mine operators to take advantage of the inherent heterogeneity of those streams and split them into wash and no-wash stocks. Relative to processing the entire stream, this reduces the amount of coal that must be washed at the mine and thereby reduces processing costs, recovery losses, and refuse generation levels. In this paper, new approaches for optimal control of the segregation process, using time series models and empirical distributions, are presented and demonstrated using field data.

Jan 1, 1998

By H. Akgun

Design of plugs for abandonment of boreholes and shafts may be governed by the bond strength between the plug and host rock. This paper presents the results of push-out tests on cement grout plugs in salt. Two expandable cement grouts have been tested. The average interface shear strengths ranged from 2 to 12 MPa. Peak shear stresses at failure, assuming an elastic stress distribution along the interface, were up to eight times higher. Standard deviations commonly reached 20%. Dissolution along the interface was observed, and may have been enhanced by clay inclusions in the salt. This dissolution appears to have reduced bond strengths. Application of the results to the design of plugs for larger openings (e.g. shafts, drifts, or boreholes) is discussed.

Jan 1, 1991