Search Documents

By Wen L. Chen

The steam coal quality is less stringent than metallurgical coal quality. The steam coal is prepared either by cleaning full size range of raw coal or cleaning coarse coal only, leaving the fine coal raw. The latter scheme is more cost competitive. It is particularly applicable to U.S. eastern soft coal where low ash coal is concentrated in fine sizes. For raw coal size separation, a recently developed Rotating Probability Screen, developed by the British Coal Board, may be advantageously used for easy change of raw coal separating size and to avoid screen deck plugging when handling wet and clayey raw coals.

Jan 1, 1983

Strainburst phenomena, generally characterized by a sudden release of energy in a volume of highly stressed rock, are often encountered in such situations like crown pillar bursts in cut-and-fill mining, face bursts at development headings and floor bursts in deep shaft sinking. This paper describes a simple FE modeling approach which leads to the calculation of the energy release rate (ERR) and the total energy storage rate (TESR) in the rock mass around the openings. The merits of using such energy parameters in the analysis of strainburst problems to identify areas of high energy release/storage are discussed. However, much site-specific back analyses are needed to better understand how strainbursts and energy parameters are inter-related.

Jan 1, 1998

By Robin G. Adams

The market prices received by producers of internationally traded commodity metals have been, and continue to be remarkably volatile and unpredictable compared with most other traded goods and services. This volatility results in an erratic financial performance on the part of producing companies, disruptive and often inflationary cost changes for consumers, unreliable tax revenues and export earnings for host governments and severe social and economic pressures on local, sometimes remote, communities which are dependent on the activity in question. Generally speaking, price volatility appears to be associated with the inability of the metal producing side of the industry to regulate the volume of supply in a manner that is consistent with metal demand, which in turn reflects broad macroeconomic and industrial developments around the world. This statement does not purport to apply to all metals or to all instances of volatility of course. Price movements may occur as a result of pure speculation or even illegal manipulation of the commodity markets. Embargoes, boycotts and other politically induced supply changes may contribute. Threatened or actual strikes also cause artificial swings in sales volumes and prices. How- ever, most of these developments are of a short-term nature. Yet metals price cycles may last for several years, as demonstrated by the extended copper price trough from 1981 to 1986. This paper deals with price volatility which reflects long-term economic cycles and the adaptive processes that exist within the industry in response to such cycles. Special emphasis is placed on the role of forecasts and forecasters in these processes. It should be said at the outset that this reflects the personal experience of one forecaster working in private sector commercial consulting practices that are independent of producers, consumers and host governments. However, the experience does cover the entire period since 1973 and has involved working with a substantial majority of the major companies that supply high volume commodity metals. By way of background it should be stated that the post-1973 world economy has provided a challenging environment for forecasters. One cannot be precise about the forecasting record of either industry insiders or outside consultants, financial analysts and academic forecasters because comprehensive records have not been kept, or if they have the results are too embarrassing to be published. Institutions such as the World Bank have published forecasts of the prices of major commodities on a regular basis and these have, presumably, had some influence on financing decisions in the industry. This record along with our own experience and numerous discussions with metal producers, major consumers and host governments permits certain generalizations to be made. The most important of these is that during the early 1980s. from about 1980 through 1985/6, the forecasters system- atically and substantially over- estimated metal prices. While some fore- casters did correctly anticipate a recession in the early 1980s and some consequential decline in prices, the magnitude and duration of the decline was far greater than anyone foresaw. This systematic forecasting "failure" appears to have occurred independently of the forecasting methodology employed. Moreover, its extent cannot be explained by obvious factors such as incorrect macroeconomic assumptions. There appears to have been some kind of structural change in the world mining and metals industry over this period

Jan 1, 1989

By S. Frimpong

The coal mining industry is an important sector of Canada?s economy. The cost of mining and haulage of coal in Western Canada is a major focal point when compared to inexpensive coal from Australia. Spot coal price volatility affect contractual price arrangements and this creates pressure on companies? profit margins and their competitive edge. In order to alleviate this pressure, companies may have to take short-term drastic measures that may hurt their strategic positions in the long-term. Companies must also create a mix of their products to ensure effective maintenance of profit margins given various quantity and quality constraints. In this paper the authors provide extensive analysis based on detailed probabilistic production systems for coal extraction and haulage in Western Canada. An optimization model is formulated for typical coal mining operations, processing and haulage from mine sites to the Vancouver Ports using linear programming algorithm. A stochastic model is also formulated to analyze the associated risks and uncertainties. These models are validated using data from five operating mines in Western Canada with varying quantity and quality products and uncertainties. The results show that the five mines studied have to produce between 180,000 and 2.10 million tonnes of metallurgical coal and between 70,000 and 2.16 million tonnes of thermal coal to enhance their profitability given the underlying constraints. The average expected probability of success associated with production capacities from these mines is about 66%. This results in a failure probability of 36%, which is extremely high under contractual arrangements. The results also show that management?s profit expectation of $83 million can be achieved at a zero percent failure probability. With a higher risk of failure of 10%, this expectation increases by 21% to $100.3 million.

Jan 1, 2011

By Mark E. Gershon

Conventional methods of drillhole site selection are reviewed briefly. Two approaches using geostatistics are then discussed, both of which have been shown to yield improved results. Finally, a branch and bound algorithm is described which will select the best locations for drilling from a user specified number of possible drill sites. Two options are discussed. First, the user can specify a maximum drilling investment or a maximum number of drillholes and the program will select the locations yielding the minimum estimation variance. This amounts to getting the most for a given investment. Alternatively, a maximum tolerable estimation variance can be specified and the program will select the number and location of the drillholes to obtain the desired information at a minimum cost. Another benefit of the approach is the quantification of the tradeoffs between investment and information obtained.

Jan 1, 1983

Thermal pretreatment can significantly improve industrial comminution operations by reducing energy requirements and increasing mineral liberation. The effect of pretreatment using conventional and dielectric heating followed by quenching on the fracture properties of a number single and multiphase brittle materials has been investigated. The reduction in the impact fracture energies and particle strengths with and without pretreatment has been measured in precise single-particle experiments using the Ultrafast Load Cell. Variations in the fragmentation pattern caused by different pretreatments were assessed by measurements of the progeny size distributions. The differences in the effect of thermal treatment on single and multiphase materials are discussed based on the experimental results.

Jan 1, 1995

By Gerald H. Luttrell

The determination of mass balances is the first step in analyzing the performance of processing circuits. Although conceptually very simple, the mathematics associated with mass balances can be cumbersome when conflicting data sets and/or complex circuits are evaluated. Fortunately, many of the spreadsheet programs available today include powerful search routines which can be adapted to solve common mass balance problems. To demonstrate these capabilities, a generalized mass balance program has been developed using the Microsoft Excel? spreadsheet. Compared to commercial programs, the spreadsheet format is user-friendly, more versatile and easier to customize. This paper reviews the mass balance problem and describes how spreadsheet tools can be used to reconcile conflicting data.

Jan 1, 1996

By N. R. Sainath

This paper discusses the results of a laboratory investigation carried out to study the microscale flow characteristics of copper ores and the variation in flow behavior resulting from flow of leach solution. Fractures in 1.5 and 4 inch diameter cores were mapped by visual inspection. The cores were stressed in a triaxial stress field representative of in situ conditions. The permeability of the samples to water was then estimated. The samples were exposed to 20 g/l sulfuric acid and the experiment repeated. The Permeability of unleached samples ranges from 10-1 to 10-19 m2 and it increases as leaching progresses. The porosity variation and the rate of recovery of copper from the specimen during leaching were also studied.

Jan 1, 1991

By Duk-Won Park

The stability problems of back- filled spoil banks became more important since the Federal Surface Mining Control and Reclamation Act of 1977 was enacted. The material properties of spoil banks were categorized as the first part of the study and spoil slope stability was evaluated using computer programs as a second part. Emphasis was placed on the effects of natural barriers, which is required in the federal law.

Jan 1, 1982

By Jon C. Yingling

A control system for reducing peak loads on mine conveyor networks is proposed. The system involves continuous monitoring of flows into the conveyor network and section feeders with variable discharge capability. The control strategy uses differences in material transit times from various production units to the transfer points in the network to forecast load levels that will be intersected by the discharge of the controlled feeders over future time intervals. Feeder setpoint adjustments are made to prevent excessive peaks in the combined flows at the transfer points, while maintaining adequate feeder throughflow to avoid production bottlenecks.

Jan 1, 1992

By Andrew J. Regis

Resource figures for bentonite clays are generally based on stratigraphic, sedimentary geologic data and drilling and sampling. Estimates of bentonite resources and/or reserves commonly found in the literature report on bentonite occurrences in specific localities or areas but none on any documented comprehensive estimates of bentonite resources. From 1974 thru 1977 the Bureau of Land Management conducted extensive studies of the resources of commercial grade bentonite in the three state region. These investigations consisted of: 1. Stratigraphic and geologic sampling with supplemental drilling data, followed by geostatistical analysis. 2. Data compiled from a systematic search of county and state records on mining locations, leases and acreage filed for bentonite. Estimates of resources of commercial grade bentonite using industry parameters were calculated from these data sources. It is concluded that there exists from 1.5 to 2.4 billion tons of in-place bentonite in Wyoming, Montana and South Dakota. Assuming a 5 percent annual growth rate for the industry, this would indicate a life of 62 to 73 years.

Jan 1, 1979

By Alessandro Navarra, Aldo Quelopana

For decades, open-pit mine planning algorithms have incorporated geological uncertainty and other elements or characteristics for increasingly realistic representations. Among these complexities is the detailing of downstream processes that occur inside processing plants. Previous studies have demonstrated that the strategic mine plan and mineral concentrator design are coupled, and should therefore be optimized simultaneously within the same quantitative framework. However, existing frameworks offer limited representation of operational modes. This work demonstrates an approach to resolving this gap, in an optimization based on a parallelized Variable Neighborhood Descent (VND). The resulting algorithm embeds mass-balancing linear programming (LP) using a DantzigWolfe decomposition. A case study of a Zn-Pb deposit is presented to show the performance reached.

Jun 25, 2023

By H. Salamanca

The electric operation and design features of the 11.000 H.P. variable speed SAG mill gearless drive is presented. The function of the frequency converter, control system drive and lubrication systems are described. An analysis of the harmonic characteristic in the Supply System and Motor is presented, and the dynamic development of the stator current, speed and the magnetic flux in the start-up process of the drive is evaluated. Besides, the most important aspects in the commissioning and maintenance of the drive are analyzed.

Jan 1, 1991

By John D. Rockaway

This report and accompanying engineering geologic map describe the generalized engineering geology of St. Louis County, Missouri for use in determining the most efficient, economical, and environmentally sound program for land development and urban growth. It includes an evaluation of such factors as the physical and engineering properties of soil and bedrock, surface stability, and subsurface geologic structure. The map and text are designed primarily for property owners, engineers, architects, real estate developers, and city planners involved in land-use planning. The geologic information and engineering interpretation must be considered as a general guide and not as a substitute for a complete on site investigation prior to initiation of any land-use project. The map scale, 1:63,360 (1 inch to a mile) is too small to include the detailed information normally provided on the 7 1/2-minute quadrangle series (1:24,000). The smaller scale is most useful at regional planning levels and was chosen to present information on the more significant engineering factors of the geologic environment for county-wide planning and development. A conventional geologic map deals primarily with the distribution and variation of bedrock formations, and a pedologic map presents information on the soil or natural medium for plant growth. Basic geologic maps and pedological maps are valuable tools that can be of assistance in studying the geologic environment, however, these maps do not provide all the information required for land-use planning. The engineering geologic maps are designed to provide this data. The engineering geologic map is related to both of these basic maps but emphasizes the engineering properties of the rock formations and soils rather than their age or origin. Some of the unit boundaries shown on the county map will closely follow some geologic formation and/or pedologic boundaries; others will transgress these conventional boundaries. Earth materials, bedrock and soil, that have similar engineering characteristics have been mapped as one unit without regard to their geologic or pedologic classifications. This is to assure that geological factors are recognized, adequately interpreted, and presented for use in engineering practice.

Jan 1, 1970

By Ratnakar Singh, Raj Kishore, Kisor Kumar Sahu, Ranjeet Kumar Singh, Ganesh Chalavadi

The Falcon concentrator is capable of separating minerals in fine size classes based on their differential density. Separation of mineral particles depends upon the fluid flow characteristics and relative movement of particles in a fluid. In the present study, a fluid flow characteristic inside the Falcon concentrator was established through experimentation and modeling. The Falcon concentrator has two fluid entry points: (a) Fluid entering through gravity assisted feeding system and (b) Fluid entering through the fluidized hole on the concentrator wall. In order to identify the role of fluid entering the concentrator, a tracer was injected into the system. As per the tracer based experimentation, it was established that fluid entering through the gravity based feeding system is responsible for thin flowing film formation in the stratification zone where particles are stratified based on their relative density. The momentum balance and continuity equations were simplified for a high centrifugal force field, and the fluid velocity profile was estimated inside the thin flowing film. Estimated fluid flow profiles will help to simulate the particle trajectories inside the Falcon concentrator. The influence of rotational speed, fluid flow rate, and cone angle on the fluid velocity profile were investigated. Fluid thickness over the concentrator wall is also estimated, and it is typically of the order of ~150–200 μm.

By J. Gordon Scott

The Iron Ore Company of Canada has now been operating a computer for the grading or blending of direct shipping ores for two years. This paper deals with the computer application pertaining to the grading of direct shipping ore. It consists of five sections. The first part deals briefly with a description of the operation of the Iron Ore Company of Canada; the second with the source and flow of the various data required to grade or blend ore; the third briefly outlines the computer programs used in this application; the fourth illustrates the mathematical approach used to properly blend ore. The final section briefly describes other technical computer programs.

Jan 1, 1964

By Robert M. Cox

A thorough geological engineering investigation is required before surface lands overlying abandoned underground mines can be safely recommended as building sites. The major problems confronting the geological engineer are assembling accurate geologic and mining information and developing an accurate rock mechanics model of the situation. A successful investigation requires a combination of technical expertise in rock mechanics and engineering geology tempered with practical engineering judgment. The results of a good study are not always favorable to the prospective builder.

Jan 1, 1975

By Vasiliki Founta, Andrew J. Whittle

"This paper describes the development of a 3D finite element model for predicting ground movements caused by construction of 7.1 m diameter twin bored tunnels for the Crossrail project in London using Earth Pressure Balance (EPB) machines. The model uses the commercial FE code, Plaxis 3D, to represent the face pressure, conical shield, grouting process and activation of precast segmental concrete lining systems through a set of boundary conditions that advance through the soil mass along a prescribed trajectory. Soil behavior is described using the Mohr-Coulomb soil model with input parameters calibrated from laboratory element tests. The analyses focus on the performance of the EPB tunneling machines in greenfield conditions beneath Hyde Park, where the tunneling occurs within deep layers of relatively uniform London Clay. The model predictions are in good agreement with surface and sub-surface vertical settlements measured at a well-instrumented section, but tend to overestimate the measured lateral displacements towards the tunnel. Ongoing studies are focused on the role of soil behavior and the approximations in FE model predictions of tunnel-induced ground deformations. Introduction Since their introduction in the 1970’s, closed-face Earth Pressure Balance (EPB) machines have become widely used for soft ground tunnel construction. The EPB design relies on a screw conveyor system to regulate the pressure of the excavated soil/spoil within the head chamber and hence control stability at the face of the machine. One of the key design issues in the application of EPB machines is to establish how control parameters, including the advance rate, face pressure and grouting processes (used to compensate for the tail void at the rear of the shield and to infill gaps between the precast lining rings and surrounding soil) affect and/or control the far-field ground movements. For closed-face systems, short-term deformations are associated with ground losses at the face, overcutting and ploughing of the shield and poor control of grouting in the tail void; while long-term deformations can occur due to consolidation and creep within the surrounding soil (and are closely connected to the seepage boundary conditions;e.g., Laver & Soga, 2012). The control parameters for advancing the EPB machine can have a significant effect on the magnitude and distribution of the far-field deformations. Therefore, analyses of the ground response to tunneling require accurate modeling of the soil stratigraphy and constitutive behavior as well as the construction process. Finite element (FE) methods have been used to simulate tunnel construction since the early 1980s, but only a few studies involved three-dimensional modelling of mechanized tunneling (e.g., Finno and Clough 1985; Bernat and Cambou 1999; Swoboda and Abu-Krisha 1999; Dias et.al. 2000; Melis et.al. 2002; Kasper and Meschke 2004; Möller 2006). In order to get a better understanding of the effect of the construction process and soil properties on the development of the ground deformations more comprehensive models of tunnel excavation and tunnel support are required in order to capture the 3D nature of mechanized tunneling and the effect of construction parameters such as advance rate, face and grout pressure."

Jan 1, 2016

By J. P. De Carvalho, R. Dimitrakopoulos

An actor-critic reinforcement learning approach is presented to improve the production of an industrial mining complex by defining shovel allocation and adapting the short-term plan given grade-control decisions. Blasthole data updates the simulated orebody models, which are input into a stochastic grade-control method based on a spatially constrained clustering approach that minimizes the profit-loss function. These aspects are embedded in a discrete-event simulator that defines the material flow from faces to processors. A case study at a copper mining complex shows the methods’ ability to adapt to new information, improving the quality of the material feed and increasing cash flow by 23% compared to a baseline case.

Jun 25, 2023

By Darrell E. Young

This presentation will define what talc is, how it is mined and processed, and how talc is used in the paper industry. It will also give you some idea about who Luzenac America is and from where it came. Luzenac America was formed in July, 1992 as a result of the acquisition of the talc assets of Cyprus Minerals by RTZ of the United Kingdom. Cyprus Industrial Minerals was then merged with the other RTZ talc interests under the Luzenac name. Luzenac is a town in the Pyrenees of Southern France -and the home of Talc de Luzenac, RTZ's first talc acquisition. The Luzenac Group is the largest talc producer in the world.

Jan 1, 1993