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By Dr. Jack M. Gillette

A system of models which simulate surface coal mining operations has been developed for use in mine planning and economic evaluations. Micromodels simulate individual mine operations for equipment selection and mine planning. Macromodels simulate all operations in the complete mine for economic evaluation of reserves. A cash flow analysis model makes a complete discounted cash flow analysis to deter-mine a required coal sales price or return on investment for evaluation of any mining project.

Jan 1, 1978

By M. D. Bath

Minproc Engineers Inc. (Minproc) recently completed the construction and start-up of a process facility to treat 14,000 t/d of gold-silver ore at Kori Kollo, Bolivia. The comminution circuit consists of crushing and SAG-ball mill grinding. Breakage characteristics of the ore were determined and a circuit model developed. This enabled variations of the circuit to be simulated, and evaluated in terms of predicted performance to provide the criteria for final engineering design. Subsequently, analysis of the operating circuit provided data for circuit model-fitting. The validity of the original model and circuit performance predictions are discussed.

Jan 1, 1994

A digital computer program has been developed to mathematically simulate the effect of limited changes in feed rate on the grinding circuit of an operating mill. The data on which the program is based was supplied by the staff of the mill in question. Samples taken around the complete grinding circuit were analyzed for solids content and particle size distribution for two feed rates. Matrix models were used to represent the grinding units: rod mill and pebble mills. Parameters for these models were computed using a method developed by Mular(l). Classifier parameters were computed by the Powell search method(2) for the Plitt model (3) . The simulation program, which permits the computing of the size distributions in the circuit resulting from the changes in feed rate between the two measured values, assumes that a linear relationship exists between the corresponding parameter coefficients. The program uses an iteration method to bring the simulated grinding circuit to a steady-state material balance for any specified' feed rate between those measured. The program is, in addition, extremely fast and economic in computing time. The results show that the simulations are not everywhere consistent with practice. For example, higher feed rates on simulation predict finer products. These errors are shown to be attributable to anomalies in data gathering techniques. An improved sampling procedure for grinding-circuit data gathering is suggested for future simulations of this type. It is concluded that the

Jan 1, 1971

By A. Haghighat, B. Lattimer

"Mine face ignition due to a high levels of methane is one of the most common fire incidents in underground coal mines. This work exams ignition scenarios in continuous miner headings. Depending on the magnitude of the ignition or resulting fire, the ventilation curtain in the continuous miner (CM) heading may be damaged or dislodged, affecting the ventilation into the area. A computational study was conducted to investigate the effects of different levels of damage to the ventilation curtain on the ventilation flow into the CM area. The computational fluid dynamics software Fire Dynamics Simulator (FDS), Version 6.0 was used to predict the conditions that develop due to a 200 kW fire in the coal mine face following a methane ignition with different levels of curtain damage. Smoke layer depth, temperatures and mass flow into the CM area were used to evaluate the impact of no damage to the curtain, partially dislodged curtain, and fully removed of the curtain. Partial removal of the curtain allowed more smoke to accumulate in the CM area and a reduction in ventilation into the CM area. With full removal of the curtain, the smoke accumulated through the entire depth of the CM area and flowed out the entrance to the CM area and the ventilation completely bypassed the region. INTRODUCTION Active working faces in underground coal mines are one the most hazardous locations in terms of fire events. According to Mine Safety and Health Administration (MSHA) data analysis, the highest number of non-fatal fire incidents was reported at mining faces, intersections and crosscut areas in comparison with other locations from 2000 to 2012. About 464 fires happened at active working faces from 2000 to 2012, most consisting of a methane ignition, in some cases followed by localized fire. These are high risk incidents due to the potential to raise float dust and damage ventilation systems, particularly auxiliary systems such as curtain or tubing. Depending on the magnitude of the ignition or fire, the ventilation curtain in the continuous miner (CM) area may be damaged or dislodged, affecting the ventilation into the area. Five computational fluid dynamics (CFD) scenarios were considered to investigate the smoke layer depth, temperature, visibility, mass flow rate, and the behavior of airflow in an entry with a continuous miner (CM) located in it. The state of the auxiliary ventilation was varied based on the assumption that as an ignition increases it magnitude it will affect ventilation curtain proportionally. Visibility and temperature along the height of the entry at different sections were investigated and the interface height at each section was determined. Also, the fresh air height was studied for tenability analysis in future. FDS, Version 6.0 was used to predict the conditions that develop due to a 200 kW fire on the coal mine face following a methane ignition with different levels of curtain damage. Smoke view software was used as the post processor to visualize and analyze methane fire behavior at the face. Most entry fires are reported as fuel-controlled fires as they are rarely restricted to air access (Ingason et al, 2014). The working face fire in the following models was assumed to be a fuel-controlled fire."

Jan 1, 2016

By K. Luxbacher, A. Haghighat, B. Lattimer

Mine face ignition due to high levels of methane is one of the most common fire incidents in underground coal mines. In continuous miner headings, depending on the magnitude of the ignition or resulting fire, auxiliary ventilation controls may be damaged or dislodged, affecting the ventilation into the area. A computational study was conducted to investigate the effects of different levels of damage to an exhausting ventilation curtain in a continuous miner heading, and the impact on ventilation to the face. The computational fluid dynamics software Fire Dynamics Simulator (FDS) Version 6.0 was used to predict the conditions that develop due to a 200-kW fire in the face following a methane ignition with different levels of assumed ventilation curtain damage. Smoke layer depth, temperature and mass flow inby the last open crosscut were used to evaluate the impact of no damage to the curtain, partially dislodged curtain, and fully removed curtain. As more of the ventilation curtain was damaged, smoke depth and temperature outby the fire increased. With the full removal of the curtain, the smoke accumulated from the last open crosscut to the face, with the ventilation completely bypassing the continuous miner region.

Jan 1, 2016

By Majid Ataeepour, Ernest Y. Baafi

High level programming languages such ass C, FORTRAN and BASIC have been used in the mining industry to simulate truck-shovel systems. In addition, some special languages for simulation such as GASP, GPSS, SLAM, PROOF and SIMAN are commonly used. The most recent simulation system ARENA uses graphical modelling approach as well as animation notion. In this paper, the main elements of ARENA required to perform a truck- shovel simulation and to view the simulation results by means of the model animation are presented. The layout of the haulage system including shovels, trucks and dump sites was generated using draw tool in ARENA. All the components of the haulage system were represented by graphical modules. Animation tool was used to depict the performance of the haulage system as the simulation progressed.

Jan 1, 1996

By A. Exikis

Simulating a ventilation network of an underground mine can help in solving complex ventilation systems with many features, selecting proper fan specifications, location and settings. Early computer systems running simple network simulations were able to provide solutions to the most common and immediate problems regarding underground mine airflow. The more advanced systems available today can perform more sophisticated modeling and simulation of a mine?s ventilation network and present their results in a more understandable and easy to communicate form. This paper presents a ventilation network case study from an underground mine. All aspects of mine ventilation network modeling and simulation are discussed as well as the results from the simulation process. The algorithms and techniques used are thoroughly explained. Some useful guidelines for the application of ventilation network software are also provided in the text.

Jan 1, 2006

By Arthur B. Steiker

Digital simulation was used to model a proposed underground' train system. The trains are to haul ore from numerous loading points beneath the production area of the mine to a central underground dump location, and then return to the mine. The purpose of the simulation was to aid mine engineers in studying various alternatives and configurations regarding track layout, crusher (dump point) specifications, dispatch procedures, fleet size, and train length, among others. The simulation' model can also be used to study the same aspects of existing haulage systems. To accommodate a wide and initially unknown range of system designs, a modular model structure was developed with major components devoted to track routing, train movement, loading process, dumping process, and dispatch. Key statistics tabulated were number of trains dumped during a simulated week, queueing delays in the mine and at the crusher, crusher utilization, cycle time, and percent of time for each: activity (loading, moving, dumping, etc.). The simulation results were instrumental in identifying a train system design which would reduce queueing delays and meet production goals with a minimum of trains and track mileage.

Jan 1, 1982

By Chen Ziming, A. Burkert, A. L. Mular

A mechanism has been proposed for autogenous grinding that involves three distinct types of breakage: self impact breakage, media breakage and abrasion. Based on this analysis a mathematical model and an autogenous grinding simulator have been developed. Using pilot plant data fitted to the model, the simulator was tested and employed to examine both the scale-up problem and the effect of feed size distribution on performance.

Jan 1, 1995

By B. K. Mishra

The motion of the charge inside a grinding mill is of considerable practical importance. The dynamics of grinding mills have been the subject of study by a number of workers because it can accurately predict: i) the power drawn by the mill, ii) the distribution of forces inside the mill, and hence the wear rate of balls as well as the liners, and iii) mass transport of milled product through the porous ball charge. Some of the earlier analyses of the motion of a charge of particulate material in a tumbling mill were reported by White (1904), Davis (1919), and Dyer (1945) and have been reviewed by Rose and Sullivan (1958). In these works, frictional force at the wall of the mill and between the colliding balls, and the interaction of different ball trajectories, was not considered. Moreover, it was assumed that the profile of the tumbling charge is independent of the degree of filling, which is generally not true. However, all this work led to the identification of so-called "equilibrium surface" which is the plane that separates the rotating charge into two regions. The inner region is static; here there is no motion relative to the mill shell. The other region is a shear region where either the balls flow down the surface of the charge (cascading motion), or are projected out of the surface and follow approximately parabolic paths (cataracting motion).

Jan 1, 1990

By D. Vavadakis

Abandoned bauxite surface mines in the Parnassos area may be rehabilitated using bauxite residues as filler. The objective of this study was to estimate the percentage of precipitation that may infiltrate through the bauxite residues to the lower geological formations when they are disposed off in mine open pits. Two scenarios were investigated simulating: a) available field tests, and b) a demonstration test that was planned to be performed in an abandoned open pit close to the Aluminium of Greece plant. It was indicated that the annual infiltration from bauxite residues disposed off in the demonstration test for the most probable scenario is very low, equal to 13.17mm corresponding to 3.1% of the annual precipitation. Furthermore, it was estimated that the annual percolation from the field tests is approximately 4.4%, very close to the infiltration values measured in the field tests for the same period.

Jan 1, 2006

By Sylvain Duchesne, Claude Bazin, Robert Grant

Grinding simulators are now widely available to assist in the selection of circuit operating conditions or flowsheet designs that yield a given product size distribution. These simulators do not inform of the impact of the grinding product size distribution on subsequent flotation stages. This paper presents a method to predict the effect of fineness of grind on a flotation bank operation. Application of the method is illustrated with data from two Canadian concentrators.

Jan 1, 1995

By J. B. Rubinstein, V. J. Badenicov, S. T. Hall

A simulation technique of the flotation process and models for the solution of various problems are developed. A modular model of column flotation is constructed taking into account the kinetic relationship of the process and the hydrodynamic regime in the cell. Based on this, a technique of calculating the column parameters based on laboratory tests is developed (scaling-up), and applied for calcetest results is developed (scaling-up), and applied for calculating the design of commercial-scale columns.

Jan 1, 1996

By C. J. Barbee, P. J. Bethell, C. J. Wood

Heavy medium cyclones (HMCs) are commonly used to clean run-of-mine coal in the 50 x 0.5 mm size range. Unfortunately, field studies suggest that industrial HMC circuits are often poorly designed or improperly operated, resulting in significant losses of recoverable clean coal. To assist plant engineers in overcoming these problems, a spreadsheet-based simulation package has been developed to predict HMC performance based on mathematical expressions originally developed by Wood (1990). A case study is provided to illustrate the predictive capabilities of this simulation package for an industrial HMC.

Jan 1, 2004

By E. Topuz, M. J. McPherson, I. M. Konduri

The research is carried out to investigate the flow mechanics and effectiveness of face ventilation using induction fans, as an effort to provide a more efficient alternative to conventional auxiliary duct or brattice ventilation systems. The induction effects and plume longevity of fluid jets are being studied with the help of a plexi-glass model, using water as the fluid medium and creating a system that is dynamically similar to the flow in mine headings. This scaled model represents a typical 1.5m x 6m x 25m heading connecting to a crosscut. Reynolds Number criteria are used to obtain dynamic similarity of the flow in the designed model to simulate real mining conditions. The role of various parameters such as nozzle position in three dimensions, airway roughness, nozzle geometry, and flow rate in the jet are studied. During the laboratory tests, flow visualization techniques, coupled with still and video photography, were employed to identify the flow patterns. The results indicate that in typical coal mine headings, jet fans can produce effective face ventilation for distance up to 30 meters.

Jan 1, 1995

By B. K. Mishra, R. K. Rajamani, A. D. Joshi

The liners are the most important part in the SAG mill operation. Hence, the liners and their design parameters are primarily studied to see its effect on SAG mill operations. Effective liner designs are directed to reduce downtimes, which is needed for the replacement of worn liners. There exists constant chance of improvement in the capacity of mill by studying the effect of liner design on the charge motion inside the mill. This need is satisfied by three-dimensional discrete element code "Millsoft", which uses Discrete Element Method (DEM) to analyze the motion of charge. This simulation of SAG mill keeps track of all the moving bodies like ball and rock and observes its interaction with liners and lifters. The recent work done on this software helps generating mill to more reality by putting conical wall at feed and discharge end, over the earlier flat walls. Millsoft is an effective tool to watch the change in the motion of the charge due to different types of lifter bars and different design parameters. It was concluded that by simply increasing chord length between the lifters and increasing the face angle of the lifters, capacity of the mill could be increased. On the other hand, this software can also be used to get power draft at the respective mill design.

Jan 1, 2002

By J. T. Ryan, Wayne H. Griffin

Solutions to typical leaky ventilation circuits such as multiple entry headings and ventilation tube or brattice face ventilation are obtained using the discrete continuous simulation language SLAM II. While the continuous aspect of the language allows exact numerical solution of leaky systems, the particular discrete-continuous interface of this language is easily adapted to space varying geometry and flow parameters encountered in mine ventilation. The ease with which this simulation system is adapted to ventilation problems and the availability on personal computers encourage its wider application in the field.

Jan 1, 1987

By Yi Zheng

Under normal circumstances, methane released along a longwall face represents only 10%-20% of the total me- thane emitted from the entire longwall panel. However, there might be a sudden surge of methane at the face which may cause a potential problem because the friction from shearer cutting, support movement, and scraper conveyor dragging can be ready ignition sources. Therefore, to predict the distribution of methane will be critical to prevent possible explosions. In this paper, methane dispersion patterns along a lognwall face are simulated under normal and abnormal conditions. With the simulation of methane released from the face, around shearer drum, and from the broken coal on the conveyor, places with possible high methane content can be identified by different phases of working process and shearer positions. Local ventilation measures are evaluated so precautionary measures can be planned ahead.

Jan 1, 2012

By Alejandro Gutiérrez, David Ahues, Paola Merino, Felipe González

The semiautogenous grinding (SAG) mill is one of the most important pieces of equipment in the comminution of materials. Its objective is to reduce the size of the ore until the ore can be released and continue on its transformation process. Although it is a simple process that involves impact, abrasion and attrition, its energy consumption is extremely high and inefficient, with no more of 17 percent of the energy supplied going toward size reduction. This gives rise to an important challenge because any improvement generates great economic benefits.

By Alejandro Gutiérrez, David Ahues, Paola Merino, Felipe González

A Discrete Elements Method (DEM) study of load movement within a SAG mill 12,192 × 7620 (40′ × 25′) in normal operating conditions is performed. The purpose is to determine how the geometry of the lifters affects the kinetics of the load inside the mill. Specifically, the changes produced by the incorporation of inclined lifters and spiral or helicoidal pulp lifters to the kinetics are evaluated. Four study cases are identified: first, the base case corresponds to a conventional geometry; the second case corresponds to inclined lifters incorporation; third case corresponds to a mill with helicoidal discharge; and the fourth case corresponds to a mill with inclined lifters and helicoidal pulp lifters. To save computational resources, the water that enters the mill has been modeled by varying the coefficient of restitution. The results of a series of experiments are presented to determine how this coefficient varies when having impacts on surfaces with different liquid levels. A comparative analysis is made of the following variables: mean transport speed and material flow, for normal operating conditions. Taking as reference the mill with straight lifters and radial pulp lifters (case 1), the case with the inclined lifters and radial pulp lifters increases the material discharge flow less to 76 mm of size by 5.1%, and this value increases even more when the helicoidal pulp lifters are incorporated reaching a 58.6%. The most significant change is seen in the flow through the grates and the pulp lifters discharge, which can increase substantially improving the operation.