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By Richard R. Klimpel

Introduction Froth flotation is one of the most common unit engineering operations in use today. Its aim is to upgrade the quality of coal by removing ash/pyrite and separating selected minerals from undesired gangue materials. Flotation has been successfully practiced at the industrial scale for more than 50 years. Its use is increasing due to the ever decreasing feed grades of the coals and minerals being processed. Flotation has also shown itself to be a flexible process that lends itself well to many solid/solid separations. Thus, with surprisingly little equipment modification, separations can involve very different particle sizes and densities, and relative weight ratios of materials to be separated. In addition, the flotation process is economic, especially when compared to size reduction, its associated precursor process. Flotation also lends itself to continuous operations with a given equipment configuration. The operation must exhibit an ability to vary feed rate of solid to the process by as much as 50% without a total collapse of separating efficiency. In addition, the mechanical flotation cell is scaleable from 2.8 to 57 or 85 m3 (100 to 2000 or 3000 cu ft) with surprising ease relative to other unit engineering operations over the same relative size increase. The separating medium used is water. Most of the chemicals required - pH regulators, frothers, collectors, activators, and depressants - are all relatively inexpensive and common. They are not usually used in large quantities. Froth flotation is certainly one of the most versatile and forgiving unit operations in the chemical, mining, and agricultural industries. The problem with the industrial flotation process is that it is fairly easy to get reasonable results and relatively difficult to get excellent results. Why is it so difficult to fine tune the froth flotation process? There are some obvious reasons and a few not-so-obvious factors. The obvious category would certainly contain the tendency of natural feed materials (ores and raw coals) to have variable physical, metallurgical, and surface properties. This occurs even when special care is taken to minimize such differences with blending. There is another obvious reason for difficulty. An inherent broadness of the feed particle size range to flotation results from using any of the common industrial-scalefine grinding devices - ball-, rod-, or autogenous mills. Research has been done into the chemical reagent and equipment aspects of flotation. It has shown strong interactions (limitations) of chemical reagents and equipment on larger and smaller particles. The point is that current flotation practice works best on average- or medium-sized feed particles. The greater the amount of large or small particles, or of both large and small, the more difficult it is to achieve excellent flotation results. Other reasonably obvious factors include: • variations in mineral type and liberation sizes; • water chemistry variations such as those involving Ca", C03, or Fe", or various soluble metal cations; • the presence of stray organic materials such as returning soluble reagents or partially degraded reagents in reuse water; • the lack of reliable on-line instrumentation for monitoring and control; • frequent equipment malfunctions of all types; • excessive feed rates for installed plant capacity; • poor operator interaction with the process; and • poor reagent dosage control. There are less obvious, but real limitations to flotation. These are inherent in the design and operating characteristics of the most common cell design in use today - the mechanical flotation cell. Individual performance attributes of the chemical reagents used, along with their manner of use, also carry limitations. The bulk of this paper will deal with chemical reagents and their use. Chemical reagents In 1979, the author and his co-workers were asked to invent and implement, at the industrial scale, new flotation reagent chemistry. After reviewing some of the literature (Sutherland and Wark, 1955; Klassen and Mokrousov, 1959; M. Fuerstenau, 1962; D. Fuerstenau, 1976; and Leja, 1982), a series of carefully controlled plant scale tests were set up. These tests were designed to understand existing reagent scale-up from the laboratory to the plant. They were to quantify at the plant level the effect of some of the more important, controllable chemical reagent factors (frother and collector type, frother and collector dosage, pH effects). This is a learning experience that all researchers involved in flotation theory should experience. It quickly became apparent that: • because a factor is important

Jan 12, 1988

This paper discusses considerations to be made for the selection of rock tunnelling machines, as opposed to drilling and blasting. A systematic approach is presented in terms of utilizing data frcm site investigations to accurately forecast machine performance for estimating and planning purposes and to help minimise associated risks. Useful rock index properties are identified, and correlations for predicting advance rates for roadheader and full face machines are presented together with a simple method of characteristing rock mass conditions for estimating machine utilization and the savings to be gained in support costs. Finally considerations for tunnelling in adverse ground, for advance probing and for large sized tunnels are outlined.

Jan 1, 1987

By Brain W. Lawrence

Sublevel stoping generally is a large-scale open stoping method. It sometimes is referred to as long-hole or blasthole stoping. This method usually is applied to strong ore bodies that require minimal support and are surrounded by strong country rock. The ore body should be fairly regular in shape and well-defined. The dip of the footwall normally should be sufficient to allow broken ore to gravitate freely, although the method has been adapted successfully to mine some of the flatter ore bodies. Sublevel stoping is not dependent on the width of the ore body. Widths of less than 6 m (20 ft), however, make the utilization of long-hole drilling techniques more difficult. The main criteria for sublevel open stoping are competent ore and stable host rock, regular ore boundaries, and a footwall dip that exceeds the angle of repose of broken ore. Basically, the method entails providing access to the ore body at various subintervals between the main haul- age levels in order to drill and blast the intervening ore. Stope drilling is carried out from drilling drifts on the sublevels, and the ore is blasted in slices towards an open face, which generally is vertical on the downholes and may be inclined towards the open face for the up holes. The blasted ore gravitates to the bottom of the stope and is collqcted through drawpoints. Fig. 1 illustrates a typical sublevel stoping mine. The method requires extensive ore body development with relatively high capital expenditures. How- ever, much of the development is in ore, and production costs are comparatively low. Productivity rates are in the 13.6 to 27.2 t (15 to 30 st)/manshift range. The drilling, blasting, and loading operations are performed independently, and equipment utilization is high. Large outputs can be obtained with few units and limited personnel. Dilution with waste rock may occur if ore boundaries are irregular or if caving occurs, but 100% of the ore within the stope usually is recovered. Pillar recovery sometimes is a problem. It is at this point that most of the waste dilution occurs. At the time data was gathered for this report (1973), the sublevel open stoping method was used by more than 21% of the metallic ore mines in the US (9 out of 42 mines producing 1088 + t/day (1200 + stpd) and provided more than 12% of the total metallic ore production from these mines. DEVELOPMENT Access to a sublevel open stope mine is gained by a slope or shaft that is normally sunk in the footwall of the ore zone, away from any possible effects from blasting or other production operations in the stoping process. Main level interval is selected and usually varies from 45.7 to 121.9 m (150 to 400 ft), depending on the vertical extent of the ore body, the number of drawpoints required to maintain output, and the eventual stope height. The main haulage drifts are located at the bottom of the stope horizon, either directly in ore or in the footwall, with access crosscuts at intervals. Raises are driven up through the ore to connect to the level above and provide access and ventilation to the sublevel drilling drifts, which are driven horizontally in the ore for the length of the stope. Depending on the drawpoint system to be used, the stope is either undercut by a raise-and-cone system, from a scram or slusher drift, or simply provided with a drilling drift from which access is made at intervals to the main haulage level. A raise driven either at the end or in the middle of the stope (if stope access is from both ends) provides a start for opening up a vertical slot across the stope to establish a free or open face for long-hole drilling and blasting. Sublevel stoping has proved to be a relatively safe and economical system.

Jan 1, 1982

By Bétournay. M. C.

Advantages ?Safety ?Health ?Rapid, continuous development, productivity ?Stope dilution reduction Disadvantages ?High cost and long time for equipment development ?Hard rock mining condition limitations ?Size of equipment ?Equipment set-up time, down time ?Performance does not meet financial return targets ?Drill and blast retains advantage in cost, productivity, capital investment, application flexibility ?Stress accumulation issues in deep mining, ground support and material handling issues in weaker rock

May 1, 2009

By M P. Sandy, R M. Stephenson

Portals to access underground mines are important infrastructure and their design requires careful consideration. Portals are generally expected to last for the life of the mine. Typically, the exposure of personnel and equipment is high, with many hundreds of movements through the portal per day. Consequently, the risk associated with geotechnical instability must be extremely low. Portals are often established from a boxcut. In areas where the weathering profile is well developed, the design and execution of the boxcut can involve significant effort, with the objective of minimizing the volume of the boxcut, whilst ensuring that conditions at the design depth are suitable for establishing a stable portal. Properly designed site investigations are a critical part of this process. Currently available portal design guidelines have not been updated for decades, however the equipment and ground support systems have changed significantly in recent years. Many mine portals have since been constructed in a relatively short time frame with success, often in challenging ground conditions using some of the more modern approaches to ground support. This is beneficial because delays in establishing a portal will generally delay other critical path activities, and lead to cost overruns.

Mar 15, 2021

By Roger Keller, Jason Ryan

A number of studies have evaluated excavation methods for the construction of subsurface facilities for a potential deep geologic repository for the disposal of nuclear waste at Yucca Mountain, NV. Many of these studies suggest that where TBM (tunnel boring machine) methods are not applicable and alternative mechanical excavation methods can not efficiently excavate harder rock drill and blast methods may be the most efficient means of excavation. However, a number of concerns regarding drill and blast applications have been raised in these evaluations, most notably the affects of blasting on the surrounding perimeter, as isolation of the waste by the natural barrier of the surrounding rock is a key element in the concept of a deep geologic repository.

Jan 1, 2001

By F. T. Cawood

This article is a continuation of a series of publications by the authors on the international debate on resource nationalism, with specific reference to South Africa. Previous outcomes have shown that mine nationalization is not a solution for South Africa, and that maintaining stability of the current mineral and tax regimes is fundamental. It will not be wise to replace existing law and policy instruments until there is a better understanding of the distinction between fact and public perception about the impact of the current system. The new scheme of state custodianship linked to a mining royalty that effectively targets economic rents provides for effective resource use. The methodology in this article is to consider how South Africa's mineral tax regime can be tweaked to achieve optimal management and benefit from mineral extraction and associated rents by avoiding changes feared by investors. The major finding is that the current suite of instruments can be considered a suitable platform for optimal management of resource rents. However, it will be necessary to first investigate ways of improving the mineral beneficiation intent of the royalty structure, and secondly investigate whether the mineral rent portion of the royalty formula can be ring-fenced for the purpose of establishing a sovereign wealth fund.

Jan 1, 2013

By Susan G. Bilhorn

A number of studies have been conducted in active and inactive mine environments using continuous monitoring and data acquisition systems to detect various parameters. In addition to the information obtained for research purposes, these monitoring systems can provide a means to remotely collect required information (such as radon daughter concentrations and air velocity) and control various conditions (such as fan operation and air door position) in numerous working sections of an active mine. Selection of detector locations and placement, which are critical to obtain the information and control desired while not inhibiting mine operations and influencing the detector readings, are covered in this paper.

Jan 1, 1984

By Stephen C. Tadolini, Thomas E. Marshall, Cecil Banta, L. J. Prosser, Anthony T. Iannacchione

The Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) endeavors to provide national and world leadership in the prevention of work-related illness, injury, and death. This is accomplished by using a scientific approach to gather information, assemble and create knowledge, then translate the knowledge and results into products and services. These products and services are then delivered to all personnel who can effect prevention. Obviously, the development and use of instruments to monitor mine roof conditions provides an opportunity to execute that mission. In the late 1990’s, based on observations at a number of underground limestone mines, only a few used roof monitors. Subsequently, NIOSH introduced the Roof Monitoring Safety System (RMSS) as an aid to roof inspection beyond traditional visual and sounding techniques. Initial expectations were that by gaining roof movement information, ultimately roof sag rates could provide indications of eventual failure. During this investigation, RMSSs were installed in 13 underground limestone mines in six states and this paper analyzes the data obtained at three of these mines. This paper also provides an overview of the system, data, analysis, and applications relevant to the RMSS.

By Panagiotis (Takis) Katsabanis, Lyall Workman, Jack Eloranta

The reduction of metallic ores to concentrate consumes a great deal of electrical energy. In the past two decades, a number of case studies have demonstrated a beneficial relationship between powder factor and grindability. However, changes in mill performance cannot be attributed to changes in feed size alone. Blasting energy and the distribution of that energy appears to affect subsequent comminution beyond crushing. This experience has prompted researchers to attempt to duplicate and quantify the mechanisms involved. To date, published reports indicate a measure of success. However, the blast engineer and the mill engineer still lack the tools and basic understanding necessary for full drill to mill optimization.

Jan 1, 2015

By L. A. Hansen, D. L. Buffington, G. H. Beckwith

This paper reviews geotechnical engineering considerations in heap leach pad design, discusses design philosophy and provides design procedures. A brief discussion of surface water hydrology ground- water protection and other design considerations are also presented. Special emphasis is placed on projects in the arid and semiarid regions of the Western United States where annual evaporation exceeds rainfall, and where good foundation conditions are usually present.

Jan 1, 1987

By William P. Lohden

INTRODUCTION It is recognized that, for a variety of reasons, some companies in the mineral industry today are by no means cash-rich and, in fact, are reporting a growing proportion of long-term debt in their capital structures. A review of recent balance sheets of small, medium-size, and some larger companies, indicates that a fair number still have substantial positions in cash equivalents such as U.S. government issues and other short-term money market instruments. In part, this paper concerns itself with companies which have sufficient cash and equivalents and/or cash generation to internally finance mining projects or expansions but which, for some reason, choose to borrow funds. Misconceptions which appear to frequently underlie so-called "leveraging" decisions are explored in this paper. Also considered arc' those circumstances under which any company, including one that is cash rich, should consider borrowing for a project in an amount beyond what would otherwise be necessary based upon its internal financing ability. I do not attempt to cover the raising of equity capital in public markets in this paper. OVERALL RETURN ON INVESTABLE CASH If you approach an individual with an investment which can be financed from savings, or by borrowing at a rate higher than one is earning on savings, that individual will quickly tell you that to pay interest at a rate higher than is being earned on savings would reduce overall income. Assuming that additional investment opportunities are not currently being considered, the individual concludes that a draw-down on savings, leaving a cushion for contingencies suited to individual circumstances, is the correct financial decision. For reasons discussed later, the simple mathematical logic leading to this conclusion tends to become obscured at the corporate level. When Leveraged Studies Are Inappropriate or Premature Surprisingly, I have heard of a number of companies that could afford to finance an investment solely with internal funds, which have made DCFROR (i.e. discounted-cash-flow rate-of-return) studies not only on a 100% equity basis but also on a leveraged basis. Certainly, a leveraged study would be appropriate if additional projects were competing for more capital than was available internally. Often, however, other projects are not far enough along to warrant a leveraged study and there is some danger that a project may be undertaken because it has an estimated acceptable rate of return, on a leveraged basis, that is not ultimately earned because some of the other projects are postponed or abandoned and borrowing is less than expected. For the above reasons, until it has been determined that (1) borrowing is a reasonable certainty for a particular project and (2) the timing and amount to be borrowed has been determined within a reasonable range of accuracy, I believe it is inappropriate and misleading to calculate DCFROR for a project other than on a 100% equity basis. Even when there are several projects currently competing for funds and borrowing will be required to finance one or more of them, using the common yardstick of calculating DCFROR on a 100% equity basis is a safer method to initially evaluate and compare the attractiveness of the projects. Many companies, whether they would have to borrow or not, will reject projects that on a 100% equity basis do not meet their minimum rate of return standards. Some companies which have to borrow will undertake a project provided the project's DCFROR on a leveraged basis meets its minimum return standards. The danger of this approach is that even moderate shrinkages of estimated cash flows could plunge return below

Jan 1, 1985

By William P. Lohden

INTRODUCTION It is recognized that, for a variety of reasons, some companies in the mineral industry today are by no means cash-rich and, in fact, are reporting a growing proportion of long-term debt in their capital structures. A review of recent balance sheets of small, medium-size, and some larger companies, indicates that a fair number still have substantial positions in cash equivalents such as U.S. government issues and other short-term money market instruments. In part, this paper concerns itself with companies which have sufficient cash and equivalents and/or cash generation to internally finance mining projects or expansions but which, for some reason, choose to borrow funds. Misconceptions which appear to frequently underlie so-called "leveraging" decisions are explored in this paper. Also considered are those circumstances under which any company, including one that is cash-rich, should consider borrowing for a project in an amount beyond what would otherwise be necessary based upon its internal financing ability. I do not 'attempt to cover the raising of equity capital in public markets in this paper. OVERALL RETURN ON TOTAL POOL OF INVESTABLE CASH SHOULD INFLUENCE FINANCING DECISIONS If you approach an individual with an investment which can be financed from his savings, or by borrowing at a rate higher than he is earning on his savings, he will quickly tell you that to pay interest at a rate higher than he is earning would reduce his overall income. Assuming he is not currently considering any additional investment

Jan 1, 1977

By J Lyall Workman, Peter N. Calder

"Presplitting is a technique mines and quarries may use to produce high quality final pitwalls. Damage from backbreak can be minimized, thereby insuring the final pit walls standat the designed angle. Thus costly excess waste removal is avoided. Safety in the pit isenhanced. Control blasting is an essential component of procedures to maintain the stabilityof final pit walls prone to failure."

Jan 1, 1993

By C. Cunningham

The process of initiating opencast blasts through long cables is onerous. An obvious alternative is to replace these with radio controlled firing apparatus. Such devices appear from time to time and with the advance of telecommunications, more are likely to appear. However, there are two crucial and seemingly intractable obstacles to overcome: firstly, the problem of malfunction of the system, which can either fire prematurely or go into a state of suspense in which it is unknown whether firing might unexpectedly occur, and secondly, the problem of terrorism, as such a system could provide the capability for an off the shelf remote bomb. The issues of accessibility and electronic reliability when linked to explosives in a mining environment have to be demonstrated to be adequately covered before serious consideration should be given to these systems, up to now largely confined to military applications.

Jan 1, 2003

By W. M. Colwell

When it comes to the analysis of gold bearing ore, there are literally dozens of variables that contribute to the final "true value" of a given sample. Initial sample selection, splitting size and method, inherent nugget gold, pulverization method, and analytical method variations are but a few. However, it seems that the inherent nugget gold particle is targeted as the primary reason for intra and inter-laboratory variations in assay. The following study will show that this is not always the case. A series of tests were undertaken for the Aurora Partnership-Aurora Project to solve inter-laboratory variations in the analyses of blasthole cuttings. Initial concern was centered on the probability that free gold occurrence was resulting in erratic results for the mine's cyanide shake assays and outside laboratory fire assays. Comparison of fire assay and cyanide shake assay was sporadically consistent with previously demonstrated extraction percentage for the cyanide method. The goal was to delineate the factors that ensure consistency in analyses; implement, where needed, Good Laboratory Practices; and reestablish acceptable analytical method correlation.

Jan 1, 1993

By Robert J. Russell

The importance of grinding as a unit operation in all industry has caused much effort to be expended toward improving the facility with which grinding can be done. Endeavor has continued nearly 100 years to formulate laws governing crushing and grinding. This has not been without controversy. However, grinding is an experimental science and our useful knowledge originates in experience. The recorded experience is grinding history. Today, many types of size reduction equipment, each with variations, are available to industry. Frequently, more than one type of grinding equipment will meet a requirement of grinding. However, an economic evaluation of installation and operating costs generally indicates a preferred type. The selection of grinding equipment requires' a consideration of the purpose in grinding, the characteristics of the material to be ground, equipment available for grinding, and the manner in which it can be applied best.

Jan 1, 1960

By Earl M. Frizzell

This paper addresses considerations for the use of artificial support of pit walls in surface mines, a new project of the Bureau of Mines. Results to date indicate that a polymer-coated cable with embedded grit could provide good anchorage for stabilizing benches and highwalls, and an electronic method of recording discontinuities in the field is being reviewed and developed for application to mining. The objectives of the work in progress are to define the engineering parameters and evaluate the concepts for artificial supports in order to provide safe working environments when pit slopes are steepened to increase ore recovery and reduce overburden handling.

Jan 1, 1986

By R. P. H. Willis, A. G. du Plessis, R. B. Wilson

This paper reviews issues to be considered in choosing primary access and transportation options for platinum and other mines. It proposes appropriate criteria and a methodology for deciding on the optimum primary access option for any particular orebody. Also included are generic parameters that can be used to facilitate the process of choosing the optimal access option.

Jan 1, 2004

By C. L. de Jongh

The number and scale of backfilling operations in the South African gold mining industry have grown rapidly in recent years. The application of backfilling as a means of stope support in a wide range of geological conditions and mining systems has resulted in the development of a variety of alternative fill systems. Experience gained in the evaluation of operating fill systems has contributed to a knowledge of the essential concepts to be considered in their design. This knowledge can also influence management's perception of what is expected of a backfilling system. The factors to be assessed in stating and satisfying these objectives are examined. The areas of investigation cover the selection of a suitable material, its preparation, distribution and placement, and the engineering logistics involved in the management of such a system. Finally, the integration of a filling system with an existing mining operation is examined.

Jan 1, 1988