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By Thomas E. Ban

The continuous sintering process was invented more than 60 years ago by two metallurgists, Arthur S. Dwight and Richard L. Lloyd, who saw a need for automation in mineral processing. Their specific objective was to beneficiate copper ore by desulfurizing and agglomerating it for copper blast furnace smelting at the Cananea plant in Mexico1. Since their early development the process expanded widely in scope, size, and application. The current worldwide sintering applications exceed 250 million tons per year for agglomerating ores of lead, manganese, zinc, and iron. Sintering is also widely used for production of sintered lightweight aggregate from clays, shales, and fly ash. The continuous sintering process took on wide expansion during the 1960's in foreign countries. Plants for production of approximately 135 million tons per year were built in these countries for sintering iron ore fines as shipped from new iron ore projects of Canada, Liberia, India, Brazil, and Australia. This expansion represented construction of approximately 80 new sintering plants, some as large as 15 thousand tons per day production on a single large sintering machine. Sized self-fluxing or highly fluxed sinter has become recognized as a premium blast furnace charge and has enabled blast furnaces of Japan and Europe to produce upwards of 10,000 tons of metal per day with coke rates less than 1,000 pounds per ton of metal. This coke requirement is practically 50 percent of the ordinary rates achieved during the early 1950's when the peak blast furnace production was less than 113 of the current records.

Jan 1, 1975

By GRANT COLLIGAN, BROCK O’KELLEY, Corby Anderson

With the world’s ever-expanding push to expand technological capabilities, the need for specialized materials including rare earth elements has exploded. One source found in the USA is bastnaesite, a rare earth bearing fluorocarbonate mineral, currently mined at the Mountain Pass Mine in California. To increase production, it is essential to optimize existing processes and create new ones to better utilize current resources. Therefore, a US Department of Energy Critical Materials Institute sponsored research program was carried out at the Kroll Institute for Extractive Metallurgy to expand the fundamental understanding of the industrial bastnaesite concentrate leaching system. With the help of prior knowledge, thermodynamic calculations and design of experimentation based lab testing, a novel single-stage hydrochloric leach system was created to optimize the rare earth extraction from bastnaesite. Historically, the existing industrial process has utilized a two-stage leach system involving a high-temperature hydrochloric acid leach with liquid solid separations followed by a caustic crack stage of the leach residues. A series of single-stage leach experiments were run by reacting locked cycle flotation concentrates with hydrochloric acid to test common leaching parameters. The results of these patent pending single-stage tests have shown rare earth recoveries significantly higher than reported recoveries of historic two-stage caustic crack processes, all while decreasing the equipment required and the type and amount of reagents needed.

Jan 31, 2022

By T. W. Camm

"We hear all the time about the value of hard work and perseverance, and the part they play in the professional life of successful people. What we do not hear so much about are the many professionals who work hard and persevere, yet never seem to quite reach the level of success they aim for. Some current authors are beginning to give more attention to the part luck/black swans/outliers play in success. This is not a new phenomenon, Machiavelli had a lot to say about it back in the Renaissance. So how can knowledge of this dynamic help in a modern organization? INTRODUCTION Work hard and you will succeed. Go to the right school, major in the right degree, study hard, and get a good job. Look at the lives of successful people, and do what they do. Be all that you can be. You can be anything you want to be. Really? Those who are successful always get attention, people want to know what they did to reach such a high position. Invariably, at least part of their narrative will include hard work, wise insight, taking advantage of opportunities, etc. If they are of a more generous nature, they might also allow that building the right friendships and collaborations also played a role. All of this may be true; what we do not often hear are the stories of those who did all of these very same things, but did not find success. An example from pop culture: The Voice. I have watched this show occasionally the past couple of years. One of the things I like about the show is that the initial screening of contestants is based solely on their singing voice (hence the name of the show), and not on their appearance. At the time of this writing (early November), the judges have just finished elimination rounds for their final teams to go on to the live shows. Here is my point—in almost every case the judges agonized over choosing who would go forward and who would be eliminated. And the reason is because all of them are really talented singers. It is impressive how gifted they are. At the end of each season, only one is declared a winner, out of that gifted pool of singers. When you hear their stories, they are all talented, hard-working individuals sacrificing for their art. And as far as I know, none of them has ever become a star. Hard work, dedication, sacrifice, talent—sometimes it is enough, sometimes not. I will be looking at the part uncertainty/luck/black swans play in our lives, but I want to make it clear at the beginning that I am not saying everything that happens to us is out of our hands or beyond our control. Taleb makes this same point (2007, p. 52): “This problem is chronic: if you tell people that the key to success is not always skills, they think that you are telling them that it is never skills, always luck.”"

Jan 1, 2017

By J. D. Grenia

The Buick Mine is a joint venture of American Metals Climax, Inc., and Homestake Mining Company located 120 miles by road southwest of St. Louis, near the village of Boss, in the 'New Missouri Lead Belt' (See Figure 1). Since start-up in 1969, over four million tons of lead-zinc ore have been mined and milled at Buick. Situated about 1,100 feet below the surface at an elevation 270 feet above sea level, the flat lying sinuous ore bodies are up to 250 feet wide, 85 feet high and several thousand feet long. Mineralization is galena, sphalerite and chalcopyrite in dolomite, Access to the mine is through two 18'Ø concrete lined vertical shafts - one for servicing and the other for hoisting ore (See Figure 2). The mine is being worked by a modified room and pillar method using both rubber tired equipment and a sub-level rail haulage. Ore is broken from first pass headings, back and bench faces and transported by load-haul-dump units to ore passes located on 900 foot centers. The ore is pulled from chutes on the sublevel 90 feet below into 15 ton bottom dump cars and delivered in 10 car lots by a 15 ton diesel locomotive to a 42" gyratory crusher (See Figure 3). A recent innovation has been the introduction of two 50 ton trucks with plans to haul up to 60% of the ore on the mining level to an ore pass feeding directly to the primary crusher (See Figure 4). Ventilation raises up to 16'Ø, which were originally planned for 900 foot centers, are now driven on 450 foot centers.

Jan 1, 1973

By A. E. Jack Swanson, Brian P. Micke

INTRODUCTION Nevada Goldfields began underground mining development at the Kingston Project in September, 1986, followed by mill start-up in March, 1987. The first gold pour in April followed three years of preparatory work in establishing a North American operational base for the production of precious metals by Golconda Minerals N.L., an Australian mining firm. GENERAL CORPORATE BACKGROUND The Golconda Group of companies was established in early 1983 in Australia. It began operations by successfully retreating tailings at several old gold mining sites throughout Australia. With the limited reserves available for tailings retreatment, Golconda began to look toward the future by conducting a gold exploration program in Australia. However, the continued high price of gold in Australia had limited the possibilities of acquiring good properties at a reasonable cost and consideration was given to looking outside Australia in addition to Golconda's domestic exploration activities. North America was favored because of the proven potential for substantial gold deposits, the established infrastructure which would allow for rapid and cost-effective development of new projects and the advantages of similar political and economic climates. In mid-1984, Golconda established an office in California and began an extensive study of over 100 prospects throughout the United States. Two prospects were identified as a result of this study whch showed merit; one was located at Empire, Colorado and the other at Aurora, Nevada. Negotiations were then successfully undertaken to acquire these two properties. Golconda's U.S. offices were moved to Reno, Nevada in early 1985 to facilitate management of its projects. To operate and manage these projects, a small Canadian company listed on the Vancouver Stock Exchange, Cannon Minerals, was acquired by Golconda and renamed Nevada Goldfields Corporation. The current structure of the company is shown below in Figure 1. A private placement of 2,575,000 shares of common stock at US54.00 per share was arranged by Jacksons Limited of Australia in association with W.I. Carr (U.K.) Limited of London. This placement resulted in US510.3 million being available in May, 1986 for the acquisition and initial development of the Aurora and Empire projects. While the financing was underway, project planning commenced on both the Aurora and Empire projects. The Aurora project was selected as the one to be initially developed because of its relatively advanced stage of development. The

Jan 1, 1987

By R. C. Gilmore, S. A. Lolon, G. E. Bogin, S. A. Saki, J. F. Brune, J. W. Grubb

"Gob ventilation boreholes (GVBs) are widely used in underground coal mines for longwall gob degasification purposes. GVBs are often drilled within 10 to 30 m above the top of the coal bed into the fractured zone, completed with 20 cm (8 in.) diameter casing and 60 m of slotted pipe at the bottom. The purpose of this completion strategy is to create a pressure sink to capture the emissions before they can enter into the underground workplace. For GVBs to work effectively, they must be drilled close enough to the working areas to capture methane from the fractured zone while the setting depth must be kept above the caved zone to minimize the amount of ventilation air that is drawn into the GVBs. Well completion parameters are important for creating safe working conditions. In this paper, computational fluid dynamics (CFD) studies will be presented to analyze the effect of different practices for GVBs completion parameters for methane extraction, formation of explosive gas zones in the gob and methane concentrations at the longwall face and tailgate. Authors have identified the optimum completion parameters for GVBs, which can maximize the benefit and minimize fire and explosion risk. INTRODUCTION Coal mines may be considered gassy based on the presence of CH4. Gas from the mined coalbed or from rider seams above or below the mined coalbed can migrate into the gob and then potentially move towards the working areas. In longwall coal mines with high methane emissions, sufficient ventilation and additional methane control measures are usually required to reduce the methane concentration in working areas to below statutory levels. Several techniques or combinations of techniques are available to control the methane hazard. These may include mine face ventilation to dilute methane, coal bed degasification, nitrogen injection into the gob to render a methane atmosphere inert and the use of gob ventilation boreholes (GVBs). Longwall face ventilation and dilution alone can only handle methane emissions up to a certain amount. When methane emissions exceed the face ventilation capacity, additional control measures are required. Drilling horizontal or vertical methane drainage holes into the coal seams as well as gob ventilation boreholes from the surface into the gob area to extract methane are common practices. GVBs are usually drilled from the surface above the longwall panel ahead of mining. When the face moves outby the GVBs and the gob begins to form, methane production starts from the boreholes. It is important to control the performance of GVBs to maintain a safe working environment in the mine. The performance of GVBs depends on multiple factors, including borehole location, length and diameter of slotted casing, setting depth of casing above the coal seam being mined, wellhead vacuum pressure, and permeability of caved-fractured zones."

Jan 1, 2016

By Sean Cassady, Jason Liu, Sanja Zlatanic, Taehyun Moon, Chris Devery

"For the Hollywood International Airport Runway Expansion Project at Fort Lauderdale, Florida, the structural fire durability analysis was completed for a series of tunnels formed by roadway and railroad cells located under the runway structure. A systematic design approach was developed to mitigate structural damage during a fire event and arrive at a practical method to structural fire engineering that is compliant to NFPA 502. To ensure the NFPA 502 requirements are satisfied, the performance based approach was implemented and the engineering analyses were performed for the adopted design fire event. The analyses considered the facility’s unique features including its fire safety systems to determine applicable design fire curves for structural durability analyses. The paper also outlines the process of defining the project specific fire curves for a specific design fire scenario and summarizes the results of heat transfer and structural fire durability analyses. This approach was aimed to assist the owner and Authority Having Jurisdiction to achieve practical decisions to the tunnel facility fireproofing.INTRODUCTIONFort Lauderdale–Hollywood International Airport (FLL) in Broward County, Florida is a major hub facility serving more than 23 million passengers annually. As part of the Airport Expansion Program, the South Runway (9R-27L) Expansion project aimed to meet ever increasing service demands via an increase to runway lengths. This necessitated the placement of one of the reconstructed runways on bridge structures over the existing U.S. Route 1 (US 1), a major north–south U.S. Highway that serves the East Coast of the United States, and the Florida East Coast (FEC) Railway, thus effectively creating multiple tunnel cells beneath the subject runway. For this project, HNTB suggested a tunnel fire damage mitigation system that would protect the runway major structural elements from the design fire event that may happen within the tunnel cells. This paper addresses the issues related to the fire event originating within the tunnel encompassing the US1 highway only, and deals with requirements of NFPA 502 [5] exclusively. Therefore, while approaching the structural fire protection issues for the specific tunnel cells beneath the runway structure, the requirements of the American National Standard NFPA 502 (Standard for Road Tunnels, Bridges, and Other Limited Access Highways, 2008 edition) were followed. Per this standard, regardless of tunnel length, all primary structural concrete and steel elements shall be protected in order to:"

Jan 1, 2016

By Lynn B. Hales

The Supervisory Computer System at Cities Service copper mine and concentrator at Miami, Arizona was installed at Pinto Valley in the spring of 1975. Design and specification [l] of the digital system was initiated jointly by key plant personnel at Pinto Valley and staff of Cities Service Research and Development Company. The Pinto Valley digital system [2] may be classified as a supervisory control system of hierarchical design. There are three fully independent satellite computers which retrieve and reduce the raw plant data from each of the three main operating areas - the primary crushing plant, the fine crushing plant, and the grinding and flotation plant. While the three satellite computers are core resident systems, the master computer is a disc-based operating system which also interfaces with a computer controlled on-stream x-ray analyzer system. Figure 1 illustrates the basic system configuration [3]. The software systems required to support a large system are quite diverse and vary greatly in function. The philosophy followed in dividing the software into three categories was designed to: 1) fully utilize existing process knowledge of technical staff; 2) delegate certain software tasks to outside sources already skilled and trained in software development; and 3) maintain final control over the design and operation of each system.

Jan 1, 1976

By T. McCallum, B. Wellbrook, T. Ratnaweera

"Pressure oxidation (POX) leaching of copper (Cu) concentrates continues to be explored as the next generation of leaching processes to sustain existing Cu Solvent Extraction/Electrowinning (SX/EW) operations as easily leachable ores become scarcer. The leach liquors produced, particularly from total pressure oxidation, contain elevated concentrations of Cu and acid, making solvent extraction processing more challenging. Addressing this challenge will require innovative processing techniques and continuous improvement to be successful in achieving satisfactory physical and metallurgical performance in the SX plant. The ability to efficiently process these feeds via SX plays an important role in the continued success of POX technology. Characteristics of a concentrate leach pregnant leach solution (PLS) are discussed, along with best practices that should be considered for processing by SX. Findings discussed in this paper will shed light on ways to reduce process risk and bring additional improvement to the industry with minimal change to the SX plant. INTRODUCTION Hydrometallurgical processing of copper concentrates continues to gain interest from the industry. Treatment by smelting and electro refining continues to dominate, accounting for ~80% of global copper production, but is faced with its own challenges. The case for increased hydrometallurgical processing has been discussed as high grade ore deposits are diminishing, capital costs for smelting are high, and the environmental aspects present challenges for sustainable practice. The hydromet copper industry is also turning a corner as easily leachable copper oxide deposits are depleting, and excess SX-EW capacity exists in certain regions. The transition to hydrometallurgical processing of copper concentrates will take a bit of effort as leaching of copper sulfides is difficult and byproduct credits must be considered. Various POX leaching processes have been studied and proposed to the industry as viable practices. Of the many processes, commercial use has been practiced with the Mount Gordon Copper Process, total and partial pressure oxidation by Freeport-McMoRan at their Bagdad and Morenci, Arizona complexes, the Sepon Copper Process in Laos, and the bioleach BIOCOP™ process in Chile. The experience related to the current paper centers around Cu concentrate leaching performed by Freeport McMoRan (known as CLP). The patented process was developed as an alternative to smelting and refining in 1998. The technology applies to both molybdenum and copper concentrates. Commercial CLP research and development began with Phelps Dodge in 1999 to 2001. The first commercial plant was commissioned in 2003 at the Bagdad operation. Initial operating conditions of the Bagdad CLP were under high temperature conditions before converting in 2005 to medium temperature conditions. In 2007-2009, the CLP technology was commissioned in Morenci, operating medium temperature and high temperature lite conditions until shutting down due to the economic downturn. The Morenci CLP restarted operation in April 2015 due to acid production benefits for the Morenci leach operations. Renewed solvent extraction test work initiated well before restart and has been an ongoing focus for further SX plant optimization."

Jan 1, 2018

By Enrique Fernandez

The success of the excavation of a sewage tunnel in a very extreme geological conditions, from river deposits and sandy layers to hard dolomite, and several meters below the estuary under the sea water influence, shows that the choice of a right equipment together with the use of chemical products like foam and polymers enable to dig tunnels in unexpected areas and give solution to the environmental problems. The paper describes the excavation and support process as well as the adopted solutions in every material and during the cross through the intermediate shafts, also under sea influence.

Jan 1, 2003

By K. W. Morris

Of the fossil fuels used for power generation coal is by far the most variable and complex in its properties. A thorough review of the characteristics of the coal to be fired is essential before boiler design can begin. Major parameters such as heating value, moisture content and ash properties will determine not only the boiler size and configuration, but also the performance of the unit with respect to the thermal efficiency, particulate and gaseous emissions, and unit availability and reliability. An example of a review completed on a large low-rank coal deposit for a power plant will be described.

Jan 1, 1983

By Dirk van Zyl

It can systematically assess if the control and management systems designed for protection of sensitive ecosystems are adequate. The results of the assessment can help to identify key elements in the project that pose higher risks due to uncertainties in design. These assessments can then be used to make recommendations to further manage and reduce risks as the project is developed. QUALITATIVE RISK ASSESSMENT The general principles of a risk assessment are well summarized by Kaplan and Garrick (1981): "In analyzing risk we are attempting to envision how the future will turn out if we undertake a certain course of action (or inaction)." Fundamentally, therefore a risk analysis consists of an answer to the following three questions: What can happen? (i.e. what can go wrong?) How likely is it that that will happen? If it does happen what are the consequences?" Risk assessments can be performed using various levels of sophistication depending on the amount and accuracy of data available. A qualitative risk assessment uses descriptors throughout to express the level of risk. The definitions of the descriptors are presented in terms of the magnitude or concentration of contaminants. The results of a qualitative risk assessment can be used to: a)Document the evaluation and decisionmaking process. Although differences of opinion may exist about the definitions of the descriptors, the process is well-documented; b)Express the relative risk associated with specific activities or design elements; and, c)Select those failure modes or release mechanisms that may result in significant risks. These mechanisms can then be further developed in quantitative risk assessments. A qualitative risk assessment can be performed in a systematic approach using four steps (Van Zyl, 1987): A qualitative environmental risk assessment can be used to describe the risks associated with the development of a new mine and to make an evaluation of the adequacy of its design for environmental protection. The relative magnitude of risk associated with selected failure modes and exposure/consequence scenario assessments is the final result of a qualitative risk assessment. These failure modes are based on site specific areas and components, and mining and construction phases. The four steps of a risk assessment (hazard assessment, exposure assessment, consequence assessment, and risk characterization) are used in the development of a qualitative risk assessment. Relative magnitudes (using a five point scale of negligible to high) for each step, can be quantified in a qualitative risk assessment. Development of the descriptors for the relative magnitudes in each step is a very important part of a qualitative risk assessment. The success of a qualitative risk assessment depends on the adequacy of the information base and the subjective judgements made in each step. The quality of the risk assessment is, therefore, dependent on the experience of the assessors. A mining project in a sensitive coastal environment is presented as an example to demonstrate the application of a qualitative risk assessment. INTRODUCTION Environmental impacts from mining operations have been a significant factor in the last century. This was especially the case prior to the development of a better understanding of environmental processes and the potential impacts of acid rock drainage (ARD), and associated heavy metals, or the uncontrolled disposal of tailings and waste rock (Smith, 1987). Much care has been exercised over the last two decades in designing and operating mines to limit the environmental impacts as far as possible. All new mines are specifically designed with mitigative methods to manage such potential environmental impacts. Attention is directed to ARD impacts, safe disposal of mine waste rock and tailings, transportation and storage of chemicals and fuels, and final reclamation. A qualitative risk assessment can be used to address all project systems and activities that may potentially pose a risk to the environment.

Jan 1, 1992

By Ihsan Berk Tulu, Deniz Tuncay, DYKE MARK ALEXANDER VAN, Ted M. Klemetti

Bleeder entries are critically important to longwall mining for the moving of supplies and miners as well as the dilution of mine air contaminants and must stay open for many years. In this study, standing supports in moderate cover bleeder entries were observed, numerically modeled and instrumented by researchers at the U.S. National Institute for Occupational Safety and Health (NIOSH). The measurements of the installed borehole pressure cells (BPCs), standing support load cells and convergence meters, and roof extensometers are presented in addition to the numerical modeling results and visual observations made by the NIOSH researchers in the bleeder entries. The results include the effects of multiple panels being extracted in close proximity to the instrumented site as well as over one and a half years of aging. As expected, standing supports closer to the longwall gob showed the greatest load and convergence. The roof sag appeared generally independent of the proximity to the longwall gob. The BPC readings were driven by both the proximity to the gob and the depth into the pillar. The results of this study demonstrated that the entry roof can respond independently of the pillar and standing support loading. In addition, the rear abutment stress experienced by this bleeder entry design was minimal. The closer the mine development, pillar or supports are to the gob, the greater the applied load due to rear abutment stress.

By V. S. Tadsen

Today, man is able to probe space because of technological advancements including the ability to control certain combustion reactions very precisely. The recent adjustment of the attitude of Skylab by radio command from earth is an excellent example of such control. It is strange, and indeed unfortunate, that very little is known about the mechanism of combustion of pulverized coal, the primary fuel for rotary kilns. The selection of a coal for direct pulverized firing of a rotary lime kiln may be determined by trial and error, persistence of sales personnel, proximate analyses, grindability, or apparent BTU cost. Occasionally, the only question asked is, "How much lime will it make?" To study the behavior of a particle of coal in the combustion stream of a rotary kiln is most difficult. We must, therefore, discuss the general mechanism of combustion of pulverized coal, and relate this mechanism to the selection of a proper coal for a rotary kiln. The classic three T's -time, temperature, turbulence -must be enlarged upon for a better understanding of the problem. Pulverized coal occupies only 0.01 per cent of the volume of air required for its combustion. This mixture behaves like a gas and the general laws governing the movement of solid particles in gasses are in effect. The differential velocity between air and coal particles depends on forced and natural convection, diffusion, and the length of time each particle is in the combustion space. As a particle of coal absorbs heat from its surroundings, it begins to give off volatiles". These gasses ignite as their kindling temperature is reached, and burn readily because of the excess oxygen immediately available. Combustion proceeds at this stage by the outward diffusion of gas from the coal particle into the surrounding oxygen-rich envelope. We could say combustion at this stage represents a small coal particle surrounded by an envelope of volatiles burning at their point of contact with sufficient oxygen. This release or expulsion of gasses from the coal may result in exfoliation or disintegration of the coal particle. If this occurs, and it is desirable that it should, it will accelerate the final stages of combustion. The escape of volatile material from the particle of coal and its subsequent combustion will cause increased turbulence around that individual particle. Ignition is maintained by radiation from gasses and solids in the combustion system, and most importantly, re-radiation from the kiln refractories and the process load.

Jan 1, 1978

By Richard W. Patton

With the advent of the Clean Air Act and the installation of flue gas desulfurization (FGD) equipment (scrubbers) on coal fired power plants, the management of solid wastes has taken on added importance. Aside from the large amounts of fly ash and bottom ash usually generated, large quantities of liquids in the form of scrubber sludge are also produced. These wastes must be disposed of within the constraints of land and water quality regulations. This paper describes the practices adopted by the electric utility industry in denting with this problem, including methods of generation and treatment, quantities and characteristics of the materials, and transportation and disposal practices. The paper also briefly describes final product characteristics and several applications for commercial utilization and land reclamation.

Jan 1, 1983

By Kristian E. Waters, Hao Ma, Haibei Wang

Heavy metal ions exist in waste effluents including mining tailings, manufacturing discharges, and smelting and metal plating process wastes. Various methods are available to treat industrial effluents containing high levels of metal ions, but when confronted with wastewater that has low metal ion concentration below 500 mg/L, most techniques suffer from low removal or separation efficiency as well as high operating cost. ELM-based techniques can be used to solve these problems.

Apr 1, 2023

By Keith S. Olsen

Any discussion of barite mining is virtually impossible without considering, almost in the same breath, the many other variables, such as beneficiation, transportation, infrastructure and location that impact the economics of a particular barite orebody. My comments will be limited to just the mining aspects of barite orebodies and these observations must be considered in proper context with all other parameters affecting exploitation of a barite property prior to final decision on economic feasibility. In many instances low-cost mining situations are more than offset by high-cost beneficiation requirements. Likewise, there are cases of relatively high-cost mining associated with no or low-cost beneficiation requirements thus permitting economic exploitation. Barite orebodies and occurrences are almost as varied as the number of occurrences. As in most mining situations, the design of a mine plan and implementation of a proper exploitation program must be approached on a case by case basis. Proper and sufficient geologic control of a barite orebody must precede the development of a mine plan. Generally speaking, barite orebodies can and, at many times, do "strange" things; pinch with depth; almost never increase in size with depth, overturn, fault-off, change grade, etc. Due to the extreme variable nature of most barite orebodies, a mine plan and its implementation must be as flexible as possible. The ability to quickly adapt to variable conditions will greatly enhance the economics within a particular barite mining environment.

Jan 1, 1980

By Donald P. Tuchman, Emanuele G. Cauda, Steven E. Mischler, Elaine N. Rubinstein, Jay F. Colinet

The PDM3600 and PDM3700 are two closely related person-wearable dust monitors manufactured by Thermo Fisher Scientific. Both are based on tapered element oscillating microbalance technology and provide nearly real-time, mass-based readings of respirable dust concentrations. From a monitoring perspective, the primary difference between the models is the PDM3600 has an integrated cap lamp with attached inlet, while the PDM3700 has no cap lamp and a revised inlet attaches to the worker’s lapel. Using coals of varied origin and employing a wide range of concentrations, side-by-side measurements from these instruments were collected under controlled laboratory conditions and then compared. By use of ordinary least squares and weighted least squares regression methods, followed by mixed model analysis, results suggest there is no statistically significant or practical difference in instrument performance. The two monitors are equivalent for the field dust concentration measurements for which they were designed.

Feb 28, 2024

By Taehong Kim, Changsoo (Kevin) Moon, Anil Parikh

"This paper presents an overview and performance evaluation for a reconditioned decades aged open type hard rock TBM utilized for the twin running tunnel excavations of the Second Avenue Subway Project in Manhattan, New York. The TBM tunnel lengths are approximately 2,370 m (7,800 ft, east TBM Tunnel) and 2,190 m (7,200 ft, west TBM Tunnel) with a 6.7 m (22 ft) bored diameter. This “senior” TBM mined through metamorphic rocks consisting of schist, granofels, and pegmatite, and encountered various adverse geological structures, including some relatively heavy groundwater inflows. The ground support was generally pattern friction rock bolts, and steel sets were used in poor ground. This paper presents TBM characteristics and the subsequent performance, such as machine utilization, downtime, cutter consumption rate, net penetration rate, and daily advance rate. Machine operating parameters including thrust, torque, gripping force, and cutterhead RPM, are compared with various accompanying ground conditions. The performance changes between the adjacent tunnel sections are also presented. INTRODUCTION Project Overview The Metropolitan Transportation Authority Capital Construction (MTACC)’s Second Avenue Subway (SAS) Program consists of four (4) phases from 125th Street to Manhattan Battery Park along the 2nd Avenue (see Figure 1) in Manhattan New York. As a part of Phase 1, Contract 1 was awarded to S3 JV (Skanska/Schiavone/Shea) to build a TBM launch box and subsequent twin TBM tunnels from 92nd Street to 63rd Street under 2nd Avenue. Contract 1 was one of the key contracts in Phase 1 to pre-excavate through the footprint of the follow-on underground stations (72nd St. Station, 86th St. Station, and 96th St. Station) by hard rock TBM excavation. The project team included Client MTACC, S3 Tunnel Constructors, Designer, Aecom-Arup JV, and Consultant Construction Manager, Parsons Brinckerhoff. The major elements of Contract 1 included construction of TBM Launch Box supported by secant pile and slurry walls and mining of twin TBM tunnels with a combined tunnel length of approximately 4,560 m (15,000 ft). The dimension of the TBM launch box was approximately 247 m (810 ft) long from 92nd Street to 95th Street, 21 m (70 ft) to 24 m (80ft) wide along the 2nd Avenue, and 18 m (60 ft) to 21 m (70 ft) deep from the ground surface. The launch box was later used for the follow-on 96th Street Station."

Jan 1, 2016

By Hal McVey

There are thousands of industrial minerals occurrences in the world. The existence or nonexistence of a market for the minerals from these deposits dictates whether or not they will be developed. Therefore, a market srudy is an integral part of the evaluation and development of an industrial minerals property. Some of the factors to be considered in a valid market study are: Supply & Demand; Transportation; Specifications; Competition; Substitutes E Alternatives; Price and Market Structure. Of these, Transportation and Specifications are of particular importance to market evaluations in the field of industrial minerals. The market researcher, working closely with technical personnel in geology, mining and processing, can determine the technical and economic acceptability of the product to be produced from the prospective property and can often create areas of opportunity for marketing of industrial minerals.

Jan 1, 1980