Search Documents

By David Smith, Bernie Martin

The Queens Bored Tunnels consist of 11,000 feet of 19'-6" inside diameter tunnels mined through rock, mixed face and dense glacial till, constructed with bolted gasketed one pass reinforced concrete liner. The tunnels are to be excavated with a pressurized face TBM, either EPB or slurry. The construction of the tunnels will require ground stabilization in the mixed face area, instrumentation and monitoring of railway infrastructure, underpinning of bridges, relocation and protection of utilities, demolition of some industrial buildings, construction of open-cut approach tunnels and emergency exits and vent plants. The purpose of this paper is to describe the scope of work, the suggested methodology and the proposed construction schedule.

Jan 1, 2005

By T. E. Wakefield

Over several decades in Southern Africa the advance rates when sinking vertical shafts have declined significantly. The upside has been a substantial improvement in shaft bottom conditions and a commensurately improved safety performance, with an increasing number of shafts being sunk without fatalities and disabling injuries. This paper briefly reviews historical sinking rates and matches changed sinking productivity to the introduction of new sinking methods that have been adopted to eliminate/mitigate safety risks. Meeting the challenge of returning to historical advance rates whilst progressing in the quest for zero harm by utilizing three dimensional animated computer modelling is described. Making use of commercial modelling software makes it easier to evaluate different methods, sequencing, in shaft barrel ergonomics, and stage and shaft bottom layouts before procuring project plant and equipment. Benefits accrue not only in better communicating methods and configurations for detailed planning and design, but also during crew training. The traditional engineering ?as-built? drawing practice has been extended to the concept of an ?as executed? sinking model which seeks to capture operational experience and learning for future best practice. The paper concludes with some of the organizational culture challenges being overcome as this non traditional approach to shaft sinking optimization is being introduced.

Jan 1, 2009

By J Belke

Murrin Murrin Operations have not had a successful beginning. Numerous reliability and operability issues, many of which are the result of design decisions, have been addressed through mechanical and operational changes and the CCD circuit is no exception. Four design aspects of the CCD circuit that have caused and continue to cause operational problems are: the inclusion of solution neutralisation gypsum in the CCD circuit feed which was designed solely for HPAL residue without proper investigation of its impact on the achievable underflow density and resulting wash efficiency; the decision to construct the thickener base from thickened solids; the lack of redundancy in the overflow, underflow and tailings pipe work; and the lack of thickener operational flexibility in the central rake-lift and feedwell dilution system. In November 2002, the lack of operational flexibility in the rake-lift and the feedwell dilution system was improved through mechanical modification as follows:CCD1 rake mechanism was modified to allow central vertical lift of 600 mm; and CCD1 changed to forced dilution using the Outokumpu TurbodilRântechnology by replacing the E-DucânRtechnology of Eimco. The installation and the results of the CCD1 rake-lift mechanism and feedwell dilution system changes are discussed in this paper.

Jan 1, 2004

By R B. Evans, M G. Townsend

In Northland, New Zealand, localised large deposits of halloysite clay have been produced by in-situ alteration of rhyolite volcanics of Pliocene or Pleistocene age, which were erupted through pre-Pliocene sedimentary strata and locally through Pleistocene basalt; and which were subsequently onlapped by further basalt flows. Alteration to clay has been a result of both hydrothermal and of meteoric processes, and decreases in intensity of alteration with increasing depth. The raw material is crushed and fractionated to produce a product of less than two micron particle size, which is of exceptional whiteness and brightness. The unique properties of the clays render them highly desirable for specialised ceramic purposes.

Jan 1, 1990

The maximum current density at which conventional copper electrowinning plants will result in satisfactory, adherent, and dendrite·free cathodes is determined by the thickness of the diffusion boundary layer. A decrease in the value of that thickness will permit an increase in the current density. This fact is utilized to develop a high current density cell in which the reduction of the boundary layer thickness is accomplished by means of a specially designed electrolyte circulation system. The high current density cell is used to determine the effect of current density on such process parameters as current efficiency, cell voltage, power consumption, and cathode purity. A number of empirical equations are developed for the purpose of estimating the magnitude of these effects.

Jan 1, 1972

By L. R. Plitt, A. A. Turak, B. C. Flintoff

"Since the publication of empirical cyclone models by Lynch and Rao in 1975 and by Plitt in 1976, the technical literature on this subject has consisted primarily of reports of applications, with only a few articles discussing basic modifications or enhancements in model form. In fact, most of the modelling eff ort in this period has been concerned with theoretical models based on the hydrodynamics of multiphase flow. (Preliminary resutls have been encouraging, however, it will be some time before this approach reaches the practical application stage.) This paper presents a review of empirical cyclone modelling technology, with an emphasis on developments since the mid 1970s. The topics addressed include homogeneous and heterogeneous ores, parameter estimation techniques, parameter confidence intervals, and the introduction of a new conceptual model of cyclone operation.IntroductionSince their first reported application in the mineral industry by Driessen (1939), cyclones have become a common unit operation in all of the process industries. The widespread use of the cyclone stems from its relative low cost and its versatility. It can be employed to carry out liquid-liquid, solid-liquid and solid-solid separations. It is the area of solid-solid separation which is of greatest interest to a mineral processing engineer. Historically, this area was divided into two application categories: (I) Separation according to density, the cyclone washer, and, (2) Classification according to particle size, the cyclone ciassifier. (When water is the carrier fluid, the cyclone is more often called the hydrocyclone. For the purposes of this paper the two names are used interchangeably). Classification is the principal application in mineral processing circuit s. Within this category, the cyclone is most commonly employed to provide some positive control over the size distribution of product from a grinding circuit. Other uses include sand-slime separation prior to froth flotation and mill tailings treatment, either for dam construction or in backfill preparation."

Jan 1, 1987

By Chen-Luh Lin, Jan D. Miller, Sindhoora Puvvada

The depletion of good-quality phosphate resources, coupled by a need to supply acceptable products at a rapid rate, while meeting the specifications of fertilizer chemical plants, is of significant concern to the phosphate industry, particularly the production of concentrates with tolerable dolomite content. Tremendous efforts have been made in the past to develop an efficient and economical process that can effectively reject dolomite. However, dolomite removal continues to plague the phosphate industry due to several process-specific challenges being encountered with various beneficiation technologies. In this regard, detailed characterization of phosphate reserves is crucial to understand textural limitations and help design appropriate strategies to achieve quality products. In this paper, the development of procedures to establish dolomite rejection/francolite recovery curves for gravity preconcentration of pebble phosphate from Central Florida is described using high-speed X-ray computed tomography (HSXCT). The developed procedure is illustrated with the analysis of high MgO pebble phosphate samples (10.39 mm × 1 mm) received from South Pasture and Four Corners locations operated by the Mosaic company. The rejection/recovery curves were calculated for each sample for five different particle size classes to observe the trend in rejection/recovery with variation in particle size. In order to evaluate the reliability of the HSXCT data, analysis using the high-resolution X-ray computed tomography (HRXCT) technique was performed on one particular sample (FC-3-1). Finally, to assess the separation efficiency, the HSXCT and HRXCT rejection/recovery curves obtained were compared to experimental gravity preconcentration results reported in the literature. In this way, liberation limitations for gravity preconcentration in the processing of pebble phosphate have been established based on X-ray computed tomography analysis.

By Y. Nakamura, T. H. Okabe, S. A. Sunkar, K. Nose

Ruthenium (Ru) is known as a platinum group element with a very small production volume. In fact, the worldwide annual production of primary Ru metal is only about 20-30 tons, and it depends on the amount of Pt produced, since Ru is a byproduct from Pt smelting. The primary uses of Ru are as a material for resistors, as a catalyst for electrode materials, and as a sputtering target for hard disk memory storage. In order to recover Ru from the spent sand-blasting abrasive media generated during the cleaning of the apparatus used for Ru sputtering, a hydrometallurgical recovery process using hypochlorite solution has been investigated. In this study, various types of recycling processes that are presently under development are also introduced, and their features and differences are discussed. The advantages and disadvantages of the new recycling processes are evaluated, and the possibility of establishing new recycling processes in the future is discussed from a multilateral perspective.

Jan 1, 2014

By D. R. Spears

As part of its mission to develop technology to assure a continuing supply of minerals, the US Bureau of Mines has investigated the flocculation of a Stillwater, MT, chromite ore. The ore was flocculated at different solids contents and at different stirring speeds to determine the importance and effect of hydrodynamic factors. In acidic and basic pH, the chromite ore was flocculated with high molecular weight polyacrylamides differing in the degree of hydrolysis. Polyacrylamides were found to bind to chromite ore particles through hydrogen bonding. The anionicity of the polymer and the pH affected the degree of polymer-particle interaction, which in turn affected polymer conformation at the surface. A polymer conformation with many loops and tails was used to explain high flocculation efficiency. It was found that such a conformation could compensate for poor hydrodynamic conditions.

Jan 1, 1992

By Don Welch

Pressures for change ?Land use constraints ?Project financing ?Local communities ?Environmental issues ?Sustainability requirements ?Stricter regulatory procedures ?Technical excellence ?Reduce risk ?Impacts of failure & non-compliance

May 1, 2010

By Zhibao Li, Kunming Zhai, Yan Zhang

The hydration kinetics of MgO, namely magnesia or magnesium oxide, obtained by calcination of magnesite MgCO3 or synthetic MgCO3·3H2O has been studied. Nesquehonite (MgCO3·3H2O) was prepared by the reaction of MgCl2 with Na2CO3 in a mixed-suspension mixed-product removal (MSMPR) crystallizer at 40 °C. Three magnesium oxide samples were obtained by calcination of magnesite MgCO3 or synthetic MgCO3·3H2O in muffle furnace at 900, 1100 and 1300 °C for 3 h, respectively. The hydration experiments of MgO samples were investigated at 25, 35 and 45 °C for 24 h in a stirred batch reactor. The hydration results indicate that the rate and extent of hydration of magnesia decreased remarkably with hydration temperature and increased with decreasing calcination temperature at a constant hydration temperature. The whole hydration reaction of magnesia was supposed to experience the promotive period and declining period. An empirical kinetic model ( k t p -?ln(1-??) ??) and a modification of the classical shrinking core model for diffusion control ( k t b d -?-?3 2 ????1 [1 (1 ??) ] ) have been applied to fit the experimental data of hydration in two stages, respectively. The values of kinetic parameters ( p k and d k ) were obtained by regression analysis and the activation energy of the sample at 900 °C was estimated to be 34.23 kJ/mol. The comparison between MgO from calcination of synthetic MgCO3·3H2O and a commercial MgO used in silicon steel production was carried out, indicating that special silicon steel grade MgO can be obtained by calcination of MgCO3·3H2O below 900 °C.

Jan 1, 2014

By James Westfield

Drilling for roof bolting has created a new dust problem for the coal-mining industry. Drilling is inherently dusty, and control of dust produced by drilling vertical or nearly vertical holes is much more difficult than control of that produced by drilling flat or down holes.4/ Also, the dust produced by roof drilling differs in composition from that produced by drill-fur, or cutting the coal face because it contains a significantly greater amount of free silica and therefore presents a greater potential hazard of silicosis. Roof bolting has been practiced successfully in the mines of the St. Joseph Lead Co. in southeastern Missouri for over 20 years, but it was not until 1947 and 1948 that large-scale roof-bolting experiments were conducted in coal mines.5/ Although the need for dust control in conjunction with roof drilling was recognized from the beginning, the development and acceptance of roof bolting progressed so rapidly during 1949 and 1950 that solution of the dust problem lagged behind other engineering phases of the technique.

Jan 1, 1951

By Frederick Felder

The paper point out the Angostura deposit is located in Colombia. The Angostura deposit, located within the Eastern Cordillera of Colombia is hosted by Triassic-Jurassic quartz monzonite and quartz diorite porphyries emplaced into Precambrian gneisses of the Bucaramanga Group. Silicification, pyritization, sericitization, alunite and pyrophyllite and other alteration and indicator minerals suggest a high sulfidation origin for the strong hydrothermal alteration. Major faults and shear zones occur in the area with NE, E-NE, E-W, WNW, NW and N-S directions. Analysis of geological results and structural modeling has also demonstrated that there is potential for additional high-grade ore shoots within the presently known mineralized structures. Delineating these structures should result in an increase of overall grade and contained ounces.

Apr 22, 2003

By K Belanger, J. Mclachlan, F. Stober, G. Norval, B. Snider, A. Munsch, T. Koehler, E. Piantino, J. Carlos Queiroz

The project to rebuild the smelting furnaces at the Anglo American - Barro Alto ferronickel smelter, located in Goias, Brasil, was initiated in September 2013. To optimize the capital cost, while maximizing furnace integrity and robustness, a design basis giving flexibility to ore composition variation was developed in order to ensure sustained nameplate production. The resulting capital efficient, fasttracked project execution was accomplished through the creation of an integrated project team of Anglo American and Hatch through FEL 3 and FEL 4 phases of the project. The integrated team addressed the project challenges through a cooperative and versatile approach, created by access to knowledge, experience and systems in both Anglo American and Hatch. The team could operate at an optimized speed of execution, as demonstrated in the FEL 3 and FEL 4 completion durations, as well as efficiently mitigating any risks of increasing cost or delaying schedule by utilizing lessons learned and team knowledge from Anglo American on the original green-field project and Platinum smelters and Hatch on similar reference ferronickel furnace rebuilds. Other critical drivers of project cost minimization and revenue loss/generation (considering production revenue of each furnace) are scheduled durations for construction, commissioning and ramp-up. The integrated team commenced construction, commission and ramp-up planning almost one year in advance of the shutdown and this paper will discuss the strategies developed to reduce risks and optimize the construction schedule to mitigate revenue loss and optimize ramp-up time to sustained operation at nameplate capacity.

Jan 1, 2015

OWING to two large falls of ground which resulted in serious accidents occurring towards the end of 1908, it became evident that the "open chamber" system then in use was unsuitable for the conditions existing in the Mount lVIorgan mine. It will be admitted that in all mining operation, the first consideration is the economy of the system adopted, combined with its safety and ability to give the desired output. A sectional system with square sets has been introduced into the mine, in which due attention has been paid to these factors. In this paper a brief description of this system will be given. An outline of those previously used will be ineluded, as it is necessary to understand the eonditions which existed in the mine at the initiation of the sectional system. Outside the actual mining methods employed, various points that might prove of interest will be touched on.The square set system of mining has been in use throughout the stopes in the gold ore in the upper levels of the mine since underground operations were started in Mount Morgan.

Jan 1, 1910

By Mark Sanders

This report compares a proposed 10/60 "piggyback" 02 generating self-rescue unit to the standard CO self-rescue unit with respect to work task interference. A simulated low seam coal mine was constructed and subjects performed locomotion, shoveling, cart pushing, and timbering tasks with the 10/60 or self-rescuer attached to their belts. Task completion time was longer on all tasks when wearing the 10/60 unit, although only locomotion was statistically significant. The 10/60 unit was bumped over 100% more often than the standard self-rescuer. Implications for design of the proposed 10/60 container are: 1) unit?s container must be extra durable to withstand the added abuse it is likely to receive by low coal miners; and 2) extra consideration must be given to preventing the device from slipping on the belt while working, especially in low coal.

Jan 1, 1980

By Terrence M. Carroll, Chu E. Ho, Dimitrios Niarchos

"Construction of the new extension to Terminal 4 at John F Kennedy International Airport in Queens, New York involved the application of tapered piles for foundation support. Initial design based on past load testing experience had indicated that a pile depth of 65 feet was necessary to achieve a capacity of 394 tons. However, piles with a single length of 62 feet were ordered and installed, which led to marginal performance of the piles. This paper presents the technical considerations for mitigating the situation based on a systematic review of three preliminary pile load tests and dynamic capacity measurements on the shorter piles. Consideration was given to the long term gain in capacity of tapered piles due to set up in the Glacial Sand. The observational approach to the evaluation of piling performance adopted on this project resulted in salvaging many piles which failed to comply with the specified driving criteria. It was acknowledged that a more prudent course of action was for the Contractor to have ordered more appropriate pile lengths that allowed for potential variation in soil conditions across the site. The 4.6% saving in pile material did not warrant the effort that was required to mitigate the 39% of installed piles that did not meet the specified driving criterion.INTRODUCTIONAn expansion project at John F. Kennedy International Airport in Queens, New York involved the Phase 2 extension of Concourse B at Terminal 4. The site consists of 4 to 5 feet of pavement over about 10 feet of hydraulically placed sandy fill. Below this is a layer of marsh deposit, comprising of soft organic clay and peat, up to about 11 feet thick. Beneath the marsh deposits is a deep layer of glacial sand which extends to well over 100 feet below ground. Figure 1 shows the typical subsurface profile at the site. The new structures were supported on 223 steel tapered piles. The piles consisted of a straight steel pipe 18 inches in diameter and 0.375 inches thick, with a 25 feet long tapered bottom section (diameter varying from 18 inches down to 8 inches at the pile toe). The piles were first driven to the founding depth and subsequently in-filled with concrete. The concrete strength (fc) specified was 4,500 psi and the yield strength of the steel piles (fy) was 50 ksi. Initial pile design, based on earlier experience with static pile load testing for Phase 1 development at the same terminal, indicated that a pile length of 65 feet was necessary. However, piles with a single length of 62 feet were ordered and installed by the Contractor, leading to marginal performance of the piles. This paper presents the technical considerations for the adoption of alternative pile driving criteria, based on a systematic review of the preliminary static load test results for the present site and PDA measurements obtained during pile installation, in order to accommodate the capacity of the shorter piles."

Jan 1, 2017

By Collin L. Stewart

The high cost and limited flexibility of modern longwall systems has resulted in the need for mine engineers and geologists to predict possible adverse mining areas ahead of mining and to then design and implement suitable ground control solutions in a timely and cost effective manner. Therefore, over the last 30 years, geo-technical evaluations for coal mine planning and development have advanced from a minor afterthought to an important part of today?s successful, high capacity, longwall mining operations. The latest iteration in this progression of improved analysis for predicting future mining conditions is a computer-based Stability Mapping System developed by West Virginia University. This system is designed to allow the mining engineer and geologist to effectively combine the mine geologic characteristics, stress influences, and structural features into an integrated stability map for use in mine planning and support design. This paper details the application of the stability mapping system to Bowie Resources, LLC, Bowie No. 3, multiple-seam longwall coal mine. At this mine, the prediction of adverse mining conditions using the stability mapping system allowed management to accurately adjust their support densities and operational procedures, and to successfully mine through difficult conditions safely and successfully.

Jan 1, 2006

By S. Al-Hassan

The deposit has been exploited for Mn oxide and carbonate since 1916. Known reserves of MnO, however, are almost depleted and the survival of the mine will depend on the exploitation of the carbonate. Kriging, inverse distance weighting (IDW) and cross-sectional methods have been applied to the evaluation of the carbonate resources and reconciliation of the estimates obtained shows that kriging and IDW give almost identical block values. A comparison using conditional probability indicates that there is virtually no difference between the global reserve estimates derived from the cross-sectional and kriging methods. The physical causes of these similarities are highlighted and the problems of dealing with multimodal distributions are discussed together with the difficulties of semi-variogram modelling

Jun 19, 1905

By L. M. Lowe, D. G. Feasby, J. R. Goode

"Rare earth resources usually contain minor amounts of radioactive elements. The most widely recognised sources of radioactivity are associated with thorium and uranium. However, also present in the resources are isotopes of rare earth elements (REE) that are themselves radioactive, including lanthanum (La-138), lutetium (Lu-176) and samarium (Sm-147). These radioisotopes, as well as remnants of the natural thorium (Th-232) and uranium (U-238, U-235) decay series, can contribute to significant levels of radioactivity in mixed REE concentrates and in separated products. Levels such as these can present challenges for transport, transboundary movement, product storage, workers’ health and safety, as well as waste management issues at the facilities that separate out the individual REE’s. These are discussed in this paper. A particularly challenging radioactive isotope is Ac-227 (a decay product in the U-235 decay series). Actinium behaves chemically similar to lanthanides and hence normally concentrates with REE multi-element composites. Reliable analysis of Ac-227 is not widely available and the methodology required to deal with this challenge is briefly described. A principle reason for minimization of radioactive content throughout REE processing is restrictive specifications by concentrate purchasers in order to reduce waste management challenges. Approaches to the minimization of radioisotope content in REE concentrates and separated products are outlined in this paper."

Jan 1, 2014