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By Ravi Shah, Augusto Lucarelli, Daniele Peila

"In mechanized tunneling the annular gap between the segmental lining and the surrounding soil caused by tunnel driving, must be backfilled almost instantaneously with an adequate grouting mortar. The objective of this research is to perform a fully three dimensional modeled parametric study using FLAC 3D and evaluate the effects of backfill grouting on the tunneling performance. The research focuses on comparisons between different injection materials and state-of-the-art Bi-Component grout and their effects on the settlements on the surface. The research consists of testing a regular situation of tunnel excavation using a shielded machine with face under pressure. The tunnel dimensions and the soil properties are selected as close as possible to the reality and based on Turin Metro case. 1 INTRODUCTION Excavation of tunnels in urban areas can induce ground movements, which have negative effects on existing structures. In such scenarios, shield tunneling has become a well-accepted construction method in various ground conditions. It is characterized by relatively complex interactions between the soil, the tunnel boring machine (TBM) itself, the tunnel lining and the tail void grout. The problem to control the settlement depends on the face pressure, ground properties and back filling procedure and material of the tail void. The face pressure acts against the front to guarantee the face stability. In case of EPB TBMs the stability of the tunnel face is ensured through the excavated soil itself, which is conditioned and is maintained in compressed state within the excavation chamber. When excavating with TBMs a tail void is created between ground and the lining (Fig.1) after the TBM excavation and ring assembly that must be backfilled instantaneously by injecting the backfill material through the TBM’s tail shield. The process is of primary importance as it reduces the surface settlements and creates an immediate link between the ground and lining, sealing against ground water and leakage, reducing the differential movements between segments and providing long-term stability. The most used backfilling materials are: Inert mixtures that do not contain cement instead sometimes they are replaced by fly ash or other substitutes. A typical design of an inert mortar consists of sand, fly ash, bentonite and water. Pea gravel, which is constituted of granular materials with grain size ranging from 8 to 12 mm. This mixture is highly recommended for tunnels being constructed in rock mass with little deformation rates.Cement mortar is composed of cement, water, aggregates and sometimes bentonite. Cement controls the principle mechanical property of the mix, which can reach high values of 15-20 MPa in 28 days. The aggregates contribute towards the shear strength and reduce the pumpablity of the mix (Thewes and Budach, 2009). The reduced active systems have a cement content of 50-100 kg/m3, whereas the active system the binder component derives full hydration with cement content of over 200 kg/m3 ."

Jan 1, 2016

By T. Mudder

The objectives for closure of a hard rock mine include minimizing long term environmental liability, attaining regulatory compliance, and maintaining geotechnical stability, while closing as cost-effectively as possible. Proper planning for closure should come during the feasibility study, design and permitting phases, and during operations as updates. The lack of a proper or updated closure plan can result in severe environmental and economic consequences. Effective mine closure is the result of a combination of innovative concepts, long-term commitments, and multi-party cooperation. The purpose of this paper is to discuss concepts, commitments, and cooperation as they relate to an effective closure plan.

Jan 1, 1999

By Lester E. Sutton

The past three years have been the most difficult period in the modem history of the barge line industry. Having withstood the fuel cost run ups of the late 1970s and the imposition of inland waterways system user fees, the industry has struggled more recently with an overcapacity problem of unprecedented proportions. In responding to these challenges, the industry is undergoing important long-term structural changes, with the various individual barge lines pursuing an array of divergent long-term business strategies. This paper discusses these strategies in terms of their probable impact on the industry as a whole, and argues for the survival of a competitive number of large, national, independent barge lines as the outcome most in keeping with the long-term interests of the mining and minerals industry.

Jan 1, 1986

By C. I. Walker

"Understanding the influence of slurry particle size on wear is essential to maximising the life of centrifugal pumps operating in mineral processing plants and for hydrotransport duties. Particle size influences not only the wear rate but also the wear pattern in pumps. Complicating the situation is the different relative wear rate for different pump parts depending on particle size. A simple Slurry Wear Type (SWT) number based on particle size and size distribution is proposed as a means for categorising slurry pump wear patterns and optimising pump application and material selection. INTRODUCTION The wear of centrifugal slurry pumps in mineral processing and hydrotransport can be quite severe and is one of the major cost concerns of plant operators. Some typical worn slurry pump parts made from high chrome white iron are shown in Figure 1. Erosion wear rates of up to 2 mm/day are not uncommon [1].Centrifugal slurry pumps are required to handle solid-liquid mixtures with a very wide range of particles extending from sub-micron size clay through to 200mm and larger cobbles. Particle size distribution can also vary widely from uniform and narrow (such as graded sand) through to very broad (such as grinding circuit slurries). Slurry particles may also undergo size change due to attrition during the pumping process. The major wearing parts in a slurry pump are the impeller, side liners and casing liner. These are shown with reference to a Warman® MC centrifugal pump in Figure 2. While many particle properties (including size, shape, hardness, density and concentration) influence pump wear, this work will consider only the effect of particle size as it is the major determinant of wear characteristics. Particle size influences the wear pattern, material performance and relative component wear rate in centrifugal slurry pumps. SLURRY WEAR TYPE (SWT) BASED ON PARTICLE SIZE Soil and grain size classification systems abound. Many have different limits to the ranges for a particular classification, albeit not too"

Jan 1, 2018

By James Douglas

For the past several years, inflation has placed increasing pressure on our economic system. The total effect of inflation is complex when combined with other factors which affect the economics of equipment. A mathematical model is described herein which can be programmed on a computer to determine the effect of inflation on economic life and profits after taxes. The computer output results in graphic plots which clearly show the relation of various percentages of inflation to life and profits. Inflation has become a common topic of conversation in the recent past. What is it and how can it be measured? What effect does increased inflation have on equipment policy? Research now in progress at the Construction Institute at Stanford University is beginning to unravel some of the mystery of inflation. As a start, let us answer the first question by defining the word inflation. The dictionary says that inflation is "an increase in the volume of money and credit relative to available goods resulting in a substantial and continuing rise in the general price level. It appears, in fact, that we are in an inflationary spiral which is "a continuous rise in prices that is sustained by the tendency of wage increases and cost increases to act on each other." 3 Inflation behaves just like compound interest. It takes more dollars of future years to buy an equal amount of a given commodity, be it a material or a service. Let us assume an annual inflation rate of 5 percent. Assume that 1Associate Professor of Civil Engineering, Stanford University, Stanford, California. 2Webster's Seventh New Collegiate Dictionary, Springfield, Mass., G. and C. Merriam Co., 1969. 3Ibid.

Jan 1, 1972

By James Wonneberg, William Edgerton

"Today’s underground construction megaprojects are tremendous feats of engineering on a massive scale, excavating through ground conditions once thought impossible, using new and innovative contracting practices. But one important truth remains unchanged; projects are built by people. What separates winning projects from the rest? Great people, working in great organizations. In straight-talk fashion this paper sets forth fundamental differences between good project leaders and bad ones, on topics ranging from client relations, design management, and scheduling, to use of the whiteboard, and everything in between. Broadly applicable to all corners of project delivery, this paper will resonate with project leaders from around the world and help identify skills necessary to succeed in the management of underground facilities. A NOTE FROM THE AUTHORS This is a training document, and not really a “paper” per se. We have attempted to tackle some big and potentially complex topics using bite-sized paragraphs, each of which are intended to promote thoughtful introspection and dialog. So please feel free to skip around, or even set this document down while you reflect on your own personal experiences, tactics, and philosophies. We have found that providing examples of “what not to do” is oftentimes more instructive than simply listing “what to do”, hence the Good/Bad format of this document. Please note that “PM” refers loosely to anyone on the project management team not just the “Project Manager”. We also wish to preface this with the following cautionary statements: • The authors do not pretend to be the “Good PM” in all cases. In fact, we’re almost certainly the “Bad PM” for some. We aim to improve on those areas. • It has been said that “The only real training for leadership is leadership.” (Antony Jay) We all started somewhere, and nobody has 20 years of experience on day one. • Converting this text into some sort of prescriptive checklist would be a disservice to the evolution of project management. Our world – and our awareness of it – is constantly changing. We must always be open minded to new ideas and different perspectives on project delivery."

Jan 1, 2016

The National Institute for Occupational Safety and Health (NIOSH) conducted field tests to evaluate the effectiveness of a wet head continuous mining machine for reducing dust exposure for continuous miner operators. Wet head technology delivers water via sprays to the continuous miner's cutter head as opposed to traditional standard sprays located on the boom and body of the mining machine. The sprays, positioned directly behind each bit on the cutter head, deliver water at the point of attack, serving to cool the bits during mining to reduce the potential for frictional ignitions. The sprays also flood the coal with water to potentially suppress dust generation. Dust surveys were conducted at several mines to evaluate the wet head's effectiveness to control respirable dust exposure at the continuous miner operator location and in the immediate return. Results show that the wet head miner improved air quality at both locations to varying degrees in some cases and not in others when compared to a continuous miner with a standard spray system.

Jan 1, 2010

By L. Michael Kaas

Any increasing number of restrictions are being placed on mining management's ability to pursue profit. Raw materials pricing, the cost of capital equipment, labor cost, and overhead costs, are becoming more difficult to control. Cost reduction is one of the few remaining areas in which management may still exercise its profit making ability. Equipment maintenance is an area where mine and mill management can readily reduce costs and increase profits. Why is this possible? First, maintenance costs comprise a large portion of total operating cost. Thirty to sixty percent of the operating cost dollar is not unusual. Even a relatively small percentage reduction in this cost represents a very sizeable increase to mining profitability.

Jan 1, 1967

By T. S. Govindan

The first step in energy conservation in any industrial plant involves implementing many of the day-to-day "house-keeping" items such as fixing leaks, turning out lights, etc. When this step has been accomplished, additional opportunities require a detailed analysis of the energy systems, evaluation of risks and costs, and assignment of priorities. Examples of conservation schemes drawn from the experience of Du pont's Energy Management Consulting Services will be discussed. The utility of heat balances for kilns and dryers in minerals processing will be outlined. The inputs needed from Management for the success of conservation efforts will be discussed.

Jan 1, 1978

By J. Perlacia

Introduction The Bulk Handling Technology has already started its transformation to the Industry 4.0. Having some of the harshest working and environmental conditions of the industry, the possibility of remote analysis and maintenance of the components seems a perfect target to focus on. The most important and expensive tools have been adapted to the digital era during last years, from remotely controlled haul trucks to monitored conveyor belts. However, these big parts of the installations rely in smaller parts that have been left aside for a while, mainly due to the difficulty to adapt them to IoT (Internet of Things). The paradigmatic example is the lack of monitored rollers whereas all the other components of the conveyor belt installations (the belt itself, motors, drums etc.) were monitored some time ago. The main problem is that a failure of a single roller can cause the stop of the whole conveyor, due to the possible damages to the belt, thus the implementation of an integral monitoring system of all the components of the conveyor is a must. The R&D Department of ULMA Conveyor Components, has been working since early 2012 on the development of Monitored Rollers, facing all the problems until its final installation in very different demanding conveyors, from the Australian extreme heat to the freezing cold Norway. All the tests done under actual working conditions, in real installations, have given a valuable knowledge in the identification of problems, their solution and the final advantages of a roller monitoring system. Background and Current State The malfunction of a single roller in certain conveyor belts can suppose the standstill of the whole installation until its replacement, due to the risk of greater and more expensive failures like the rip of the belt. In the case of a bulk handling installation where a continuous supply of material is necessary, an unexpected stop of one hour could entail huge economical losses. What’s more, many conveyor belts are several kilometers long or the access to some parts of them is very complicated. Due to these difficulties the inspection and maintenance operations can become expensive and hard going, with staff going over the whole area checking the correct condition of the conveyor and rollers, which means a dangerous activity. As in many other industry products, the condition of rollers can be recognized measuring key parameters like the temperature of the bearings, the vibration level etc. The traditional way is to use the characteristic noise of a failing bearing, but this method usually implies to change several rollers because the maintenance team is not able to identify a single source of the noise. In recent years different attempts to measure the temperature of the bearings have been made, but the result is not accurate enough due to the proximity of the rollers in the idlers

Jan 1, 2019

By B. Catalano, D. Ifrim

The Annacis Island Outfall Project includes two TBM bored tunnels with face pressures above 3.5 bar, with an internal diameter of 4.2 metres. This paper discusses the innovative approach to TBM tunnelling and TBM design at the Annacis Outfall Project. The TBM custom design includes a 3.6 m OD core machine manufactured by Herrenknecht and a 5.0 m add-on by the Contractor (Bessac), acting as an extension kit, with optimized gantry design to accommodate for short tunnel drives and quicker launches. This novel design approach produced safety improvement, cost and schedule savings while streamlining logistics of TBM retrieval.

Dec 1, 2022

By Katerina Adam

During wet grinding the electrochemical interactions between grinding media and pyrrhotite not only accelerate the media wear but also adversely affect the flotation response of the sulfide mineral. A possibility of remedying the adverse effect on its floatability by applying electric potentials to grinding media was examined. Flotation tests, Auger electron spectroscopy and x-ray photoelectron spectroscopy were used to study the surface properties of pyrrhotite. Although anodic polarization of the steels increased the metal loss by corrosion, the flotation recovery of pyrrhotite was increased. In the case of cathodic polarization, the flotation recovery improved in a narrow range of overpotentials. At higher cathodic overpotentials, however, the floatability of the mineral was progressively lowered although the corrosive wear of grinding media might be reduced.

Jan 1, 1984

By David E. Siskind

The Bureau of Mines has studied the problem of cracking in residential structure walls from vibrations produced by blasting in surface mines. Direct observations were made of blasting damage consisting primarily of cosmetic cracking in plaster and gypsum board walls. Measurements of structure response and also application of the response spectra analysis single-degree-of-freedom model were used to quantify the frequency dependence of the safe level criteria. An overall summary analysis was performed using the new Bureau of Mines damage observations and data obtained from nine previous studies, including the three analyzed earlier by the BuMines for Bulletin 656, published in 1971. Separate analysis of the high- and low-frequency damage cases, structural response, and two types of construction resulted in the establishment of safe vibration levels ranging from 12 mm/sec to 50 mm/sec (0.5 in/sec to 2.0 in/sec).

Jan 1, 1980

By A. G. Ulsoy

In recent years there has been an Increasing Interest In the application of automatic control theory to mineral processing systems, and numerous applications of mineral process control have appeared in the literature. A general approach to the synthesis of mineral process control systems is presented. The first phase of the control system design consists of specifying the control objectives, process variables and their interactions; these topics will be discussed with specific reference to mineral processing. The second phase Is con¬cerned with selection of control strategies algorithms, instrumenta¬tion, and other components of the control system and is discussed at length. These concepts are then illustrated by a flotation control case study.

Jan 1, 1981

By N. S. Tanious

The need to provide better mine roof support and control in longwall tailgate entries prompted the Bureau of mines to search for a replacement product for wood cribs. Their search isolated steel-fiber-reinforced concrete (SFC) as the most effective replacement. Through successful laboratory and underground mine tests, handmade SFC cribs proved to be a viable and more effective roof support system. However, to ensure wider usage, U. S. Steel Mining Co. initiated a joint development and evaluation program with Burrell Construction Company in order to mass produce SFC blocks of reasonable dimension, weight, and cost. Small specimens and full-size cribs were evaluated during this program to determine their compressive strength and post failure characteristics. After considerable testing and adjusting of various concrete mixtures, a final formulation for the SFC crib blocks was selected. That formulation permitted the construction of SFC cribs possessing a nominal crib strength of 3200 psi (22.1 x 106 Pa) and a nominal modulus of elasticity of 1.0 x 106 psi (6894.76 x 106 Pa). These SFC cribs can support from 3.5 to 14.5 times as much load as a wood crib, depending on the size of the wood crib being replaced. Both laboratory and limited mine tests, conducted by U. S. Steel Mining Co. have shown the SFC crib to be an economical and effective means of roof control.

Jan 1, 1984

By B. P. Atkin, D. W. Brown

The handleability monitor has been specifically designed to provide a simple, rapid and on-site assessment of the whole or part consignment of a coal blend in its ‘as-received’ condition. Evaluation has been carried out at a number of coal-handling plants, on both metallurgical and power station coals from a variety of sources world-wide. The results which are used to predict which coals could routinely pass through a handling plant at line capacity, without causing blockage or delay, have also been correlated with moisture, ash and size analyses of the coal to develop a predictive model of handleability.

Jan 1, 2000

By J. A. Herbst, H. R. Cooper, R. J. Brison, R. W. Harper, K. P. Ananthapadmanabhan, W. C. Hellyer, B. H. Bergstorm, D. M. Hopstock, H. Rush Spedden, W. C. Hellyner

Scope of Section The physical characterization of an ore or mineral mixture in such detail that mineral processing may be effectively applied to create more useful products is one part of the technology of sampling and testing. In addition, the evaluation of the multitude of separation processes, both physical and chemical, combined with ancillary opera¬tions and performed on samples at a laboratory scale, is another part of the testing procedure. Although analytical techniques provid¬ing quantitative determinations of elemental compositions are an im¬portant and necessary supplement to any testing program, that field of endeavor is a well-developed, separate entity beyond the scope of this Section. Sampling procedures cover the practice of selecting representative quantities of test materials in the field to evaluate mineral deposits, and extend to techniques of obtaining process samples in slurry and bulk ore as part of process evaluation. The same techniques are appli¬cable, of course, to standardized methods of metallurgical accounting. Sampling is also an important facet of successful on-line measurement of slurry properties such as assays and particle size in the practice of automation. However, the sampling methods in this case can be different from those needed for precise testing and accounting pur¬poses. Sampling was well defined in Taggart's Handbook as "the opera¬tion of removing a part convenient in size for testing, from a whole which is of much greater bulk, in such a way that the proportion and distribution of the quality to be tested (e.g., specific gravity, metal content, recoverability) are the same in both the whole and the part removed (SAMPLE). The conditions of the more stringent definition, that the sample shall be completely representative of the whole as regards all aspects save bulk, are practically never fulfilled when heterogenous mineral mixtures are sampled." Taggart's Handbook of Mineral Dressing, Section 19, "Sampling and Testing," continues to be a very useful compendium of principles and techniques, particularly as applied to manual methods for han¬dling samples. In the intervening years since its last revision, substan¬tial progress has been made in both the theory and the techniques; thus, this current contribution is designed to be an extension of the earlier work, yet complete enough to provide procedural guidelines to methods of continuing validity. Although basic principles of testing remain unchanged, the meth¬ods of applying those principles have undergone great change. New testing equipment has become available, yielding a greater precision of results. Testing methods have been refined which, in many cases, allows for a valid scale up of flowsheet designs without the necessity of costly pilot or prototype plant development. Justification for a Sampling and Testing Program* The proper evaluation of a mineral property is a complicated process. It often is done on a team basis with the exploration geologist, mining engineer, mineral process engineer (extractive metallurgist), economist, and product utilizer (ceramist, chemical engineer, chemist, metallurgist, etc.) all represented. The mineral processing engineer is a key member because he can provide a go no-go answer to the question, "Can this ore be processed economically?" In addition, his judgment on the response of even the initial sample to processing can be an invaluable guide to the proposed process and its mutations. Since the capital investment and operating costs are so sensitive to the type of process used, the judgment of the mineral processing engineer forms an important part of the early evaluation of the profitability of a new mining venture. This early estimation of the processing approach is all the more important since, for some metalliferous ores, the capital investment for mill, smelter, water supply, and tailings disposal exceeds the cost of the mine. At present, for commodities such as coal, the reverse is true. There is a smaller capital investment for the coal preparation plant than for the mine. In general, both the capital and operating costs escalate very rapidly in the following order: gravity concentration of alluvial deposits (e.g., dredging), gravity concentration of lode ores, flotation, simple hydrometallurgical processes, and complicated hydrometallurgical and pyrometallurgical processes. The latter two processes may cost 100 to 1,000 times more per ton treated than processing of a simple alluvial deposit. This dictates that the valuable mineral be concentrated as much as possible to minimize the total tonnage treated in the more expensive operations. Within each of these ore-processing categories there is a wide range of process sophistication and hence of capital and operating costs. Perhaps the greatest variations are in the chemical processing of ores. These range from the simple leaching of a copper waste dump to very sophisticated hydrometallurgical processing of ores in increasing order of cost. Because the overall cost of a mining venture is so sensitive to the process selected, it is essential that the mineral¬ processing engineer evaluate the ore in the initial stages of the development of an ore body. As better samples become available, he must continually revise his estimate of the process to be employed. The sampling and testing process must be a necessary and continuing activity throughout the life of a project. One fundamental aspect of nearly all mineral deposits is the inherent variability of the mineral assemblage and composition. A utopian goal of any processing plant is to have the process so flexible and so well-defined that an automatic process control system can optimize the economic recovery at all times. Since this is rarely possible, a continuing or at least a periodic testing program is desirable. Variables to be considered are: 1) Ore body inconsistencies. 2) Zonal variations. 3) Feed variations from mining plan or methods. 4) Variable performance of processing units due to wear. 5) Seasonal or other changes affecting processing conditions such as water quality, temperature, etc. 6) Changing market conditions for product quality or byproducts. 7) Technological advances in processing methods or equipment. 8) Increasing demands for environmental control. 9) Changing economics of competitive processes, of supplies, of capital investment vs. labor costs, etc. Sampling Procedures Preliminary Guidelines for Sampling Ore Deposit Studies. t At a very early stage, it is essential that the mineral processing engineer receive a sample of the ore. This may be a portion of the diamond drill core or a split from the trench, pit, churn drill, channel, or sheet sample. Even a grab sample may have some value, but it should be selected by the mining engineer or exploration geologist to be as representative of the ore body as possible within his best judgment. The sample delivered to the process engineer should have been subjected to as little prior crushing as is practical since fine sizes are difficult to concentrate. In addition, finely ground ores are readily oxidized and thus may give misleading test results. Furthermore, ground samples may make it impossible to eval¬uate either the comminution or the coarse-gravity concentration pro¬cesses. For an initial evaluation, a good deal may often be learned from a sample of only a few pounds if that is all that is available. To obtain the maximum information from a sample, its selection should be carefully discussed with the mineral processing engineer. In addi¬tion to being as representative as possible, the mineralogically distinct samples should be carefully segregated rather than composited. Since drastically different processes are often needed to process samples of differing mineralogy, considerable care and time must be exercised during this sample collection step. The segregation of samples showing gross mineralogical differences, such as the oxide caping on a sulfide deposit or a laterized zone, is easy. It is the more subtle changes in mineralogy that can often elude the field man. Yet these differences are often sufficient to dictate that an entirely different type of process be used. Obviously, the selection of these initial samples for ore testing and mineralogical studies requires that it be done by a man of consider¬able experience and judgment. While the mining engineer or field geologist is collecting these samples, he should also note and convey to the processing engineer such details as water quality and availabil¬ity, terrain, potential mill location, tailings-disposal areas, case of transportation, etc. As the property is developed with additional drill holes, adits, etc., larger and more representative samples will be required to develop the ore-processing flowsheet more adequately. If pilot-plant studies are required, a very large sample may be necessary. Though the type and amount of sample collected for flowsheet development investigations vary widely, gathering a representative sample of the ore body is a prime requisite for any process development effort. The process developed for any given ore body is only as reliable as the sample on which the flowsheet was based¬

Jan 1, 1985

By Kal V. S. Sastry

Mathematical and expert system models are being used extensively for mineral process engineering. There exist no standardized methodologies for their computer implementation. In meeting this need, this paper introduces the concept of a process software model, or simply a software model and presents a two-step methodology for its development involving software model specification and development. The software model specification is to be performed after extensive discussions with the ultimate users of process software based on which the software model is developed. These software models provide a formal basis for the design and construction of software objects corresponding to the real world process objects.

Jan 1, 1994

By T. E. Wilson

In conjunction with experiments to improve the particle size preparation of coal bore cores prior to washability testing, discrete-event breakage of coal, shale and homogeneous low-strength concrete cores was studied. Breakage of individual size classes by drop-shatter and by incremental tumbling in an end-over-end hand-driven tumbling cylinder revealed systematic changes in the breakage function, namely, that breakage in any size class diminishes as the number of events increases. The effect of the fines removal enhances the breakage of harder material (having lower grindability indices), but appears to have less effect for softer material.

Jan 1, 1998

By K. V. Raj, A. Miller

"Workers at mineral processing facilities are often exposed to high levels of dust generated when ores are processed. Crushing, grinding, screening, and other processes generate large quantities of dust, which can exceed the threshold VALUES (prescribed by the Mine Safety and Health Administration (MSHA). Many ores contain quartz (silica), which has been known to cause serious health problems in workers over time. Given the structure of mineral processing plants, the airflow regime is not coherent inside the building, which may lead to multiple recirculation zones. These recirculation zones can trap dust, and concentrations of dust can then rise over time. Therefore, there is a need to understand the airflow phenomenon that occur inside of mineral processing facilities and how these occurrences interact with the dust generation processes to identify zones of potentially high dust concentration. Computational fluid dynamics (CFD) modeling can give a better understanding of the airflow and help recommend designs and methods to mitigate the high dust concentrations in a mineral processing plant. This paper presents the CFD modeling of airflow inside of a mill building to demonstrate airflow patterns that will affect the generation and subsequent dispersion of dust due to crushing, grinding, and other activities. This study was conducted by researchers from the National Institute for Occupational Safety and Health (NIOSH). INTRODUCTION In a mineral processing facility, minerals go through various mechanical processes in order to reduce their size for separation of economic minerals from gangue minerals to produce a final marketable product. This research, conducted by the National Institute for Occupational Safety and Health (NIOSH), focuses on ore mills in metal and nonmetal mining (MNM) operations, but the applicability of the approach will be valid for any large structure where workers are exposed to airborne contaminants. The processes of crushing, grinding, cleaning, drying, and product sizing in these facilities generate a large amount of dust, creating hazardous conditions for the workers in these facilities. This is highlighted by the fact that MSHA sampling data for the years 1997–2012 indicate that 12.3% and 15.9% of the gathered samples were over 100 µg/m3 for silica for metal and nonmetal mills, respectively [1]. Mineral processing operations typically use some type of engineering control to address their most significant dust sources. Engineering controls include such approaches as bag-house-type dust collectors, scrubbers, and electrostatic precipitation [2]."

Jan 1, 2018